Valves, Piping And Pipelines Handbook, Third Edition

Valves, Piping and Pipelines Handbook 3rd Edition

Valves, Piping and Pipelines Handbook 3rd Edition

T. Christopher Dick:enson F .I. Mgt.

ELSEVIER ADVAN CE D TECHNOLOGY

UK USA JAPAN

Elsevier Science Ltd, The Boulevard, Langford Lane. Kidlington, Oxford OX5 1GB, UK Elsevier Science Inc .. 665 Avenue of the Americas, New York, NY 10010, USA Elsevier Science Japan. Tsunashima Building Annex, 3-20-12 Yushima, Bunkyo-ku, Tokyo 113. Japan

Copyright ©1999 Elsevier Science Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical. photocopying, recording or otherwise, without permission in writing from the publishers. Third eclition 1999 Library of Congress Cataloging-in-Publication Data Dickenson , T. Christopher. Valves, piping. and pipelines handbook IT. Christopher Dickenson.- 3rd ed. p.cm ISBN 1-85617-252-X (he) 1. Valves Handbooks, manuals, etc. 2. Piping Handbooks, manuals, etc. 3. Pipelines Handbooks, manuals, etc. I. Title.

TS277.D53 1999 621.8'4-dc21

99-26575 CIP

British Library Cataloguing in Publication Data A catalogue record for this title is available from the British Library. ISBN 1 85617 252X No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods , products, instructions or ideas contained in the material herein. Published by Elsevier Advanced Technology, The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK Tel.: +44(0) 1865 843000 Fax: +44(0) 1865 843971 Printed and bound in Great Britain by Cambridge University Press

Preface 11

A Vital Contribution to Modern Industry"

Over recent years, a number of significant developments in the application of valves have taken place: the increasing use of actuator devices, the introduction of more valve designs capable of reliable operation in difficult fluid handling situations; low noise technology and most importantly, the increasing attention being paid to product safety and reliability. Digital technology is making an impact on this market with manufacturers developing intelligent (smart) control valves incorporating control functions and interfaces. Computer Integrated Processing is now a fact of life. New metallic materials and coatings available make it possible to improve application ranges and reliability. New and improved polymers, plastic composite materials and ceramics are all playing their part. Fibre-reinforced plastic pipe systems, glass-reinforced epoxy pipe systems and the traditional low-cost polyester pipe systems have all undergone sophisticated design and manufacturing technology changes. The potential for growth and expansion of the industry is huge. The 3rd Edition of the Valves, Pipirzo and Pipelines Handbook salutes these developments and provides the engineer with a timely first source of reference for the selection and application of valves and pipes. It would not have been possible to provide so much information and data in this Handbook without the co-operation given by the individuals and companies listed overleaf, as well as the manufacturers who supplied information and data. Their contribution is graterully acknowledged. This is the decade of the customer, and the Valves, Piping and Pipelines Handbook 3rd Edition is intended to provide essential, practical product information and reference data where and when they are needed most. T. Christopher Dickenson F.I.Mgt. September 1999

vii

CONTENTS

Section 1.

Section 2.

Section 3.

Fundamentals Classification of Valves Basic Valve Nomenclature Valve Selection Guides Pipes and Pipelines-Definitions and Explanations

3 11 14 27

Valve Types Design and Construction Plug Valves (Cocks) Ball Valves Ball Float Valves Butterfly Valves Rotary Disc/ Rotor Valves Globe Valves Gate Valves Needle Valves Pinch Valves Diaphragm Valves Slide Valves Screw-down Valves Spool Valves Solenoid Valves Swing Check (Flap) Valves Penstocks Miscellaneous Valves

41 47 63 67 85 91 98 107 110 118 127 133 138 146 164 168 172

Pressure Valves and Services Check Valves Safety and Relief Valves Self-Acting Reducing Valves Air Relief Valves Foot Valves

185 200 225 236 243

O V ER A HUNDR ED YEAR S' EXP ERI ENCE HJ GONE INTO PERFEC TI NG A PRODUCT RAt\ A N D SERVICE TH AT IS WAY OUT IN FRO N .

.....J

0

With over I00 years of manufacturing experience, Hattersley know that the differenc between success and failure can be a fine balancing act. It's knowing business trends can change at any time, that has helped Hattersley to stay at the forefront of the valve industry, by developing and manufacturing hundreds of different valves for a multitude of industrial and HEVAC

r-

z

0 u

applications. So for a combination of experience and the latest in technical know-how, rely on Hattersley to deliver every time.

Hattersley have the largest selection of quality vJives available: • Bronze Gate Valves • Cast Iron and Ductile Iron Gate Valves • Knife Gat • Bronze. Cast Iron. Ductile Iron and Steel Globe Valves • Bronze. Cast Iron and Ductile Iron Check Valves • Bronze Rad1ator Vatvcs - Drain Taps -1 • Bronze Ball Valves • Bronze Plug and Gland Cocks • Commissioning Valves • Autoflow Bronze and Ductile Iron Automatic Balan em • Cast Iron Lubricated Plug Valves • Eccentric Plug Valves • Cast Iron Non-lub1·icated J-way PlugValves • Butterfly Valves • Pop Safety Valves - Reli1 • Diaphragm Valves • Equilibrium Ball Valves • GroovEnd Ductile Iron Valves FOR FURTHER INFORMATION CALL OUR SALES TEAM ON THE NUMBER BELOW QuALITY RELIABILITY

&

SERVI CE

Ass

Hatters ley Newman Hender Ltd Ormskirk Lancashire L39 2XG Telephone: 01695 577199 Facsimile: 01695 Em a iI: u ksa [email protected]. uk export@ hatters Iey-va lves .co.uk Web site: http://www. ha ttersley-val ve'

ix

Section 4.

Control and Automation

Valve Actuators Control Valves Float Control Valves Temperature Control Valves Regulators Section 5.

Pipes

Iron and Steel Pipes Fibre-Reinforced Plastic (FRP) Pipe Thermoplastic Pipe Pipe Joints and Couplings Expansion and Con traction Joints Corrosion and Cathodic Protection Corrosion of Stainless Steel Valve Corrosion Protective Coatings and Linings Section 6.

479 497 511 522

Performance and Calculations

Flow of Liquids through Pipes Flow of Mixtures through Pipes Compressible Flow in Pipes Losses in Bends and Fittings Strength ofPipes (Calculations) Buried Pipes Collapsing Pressure for Pipes and Tubes Boiler-Feed Calculations Steam Flow Calculations Cavitation Noise Control Balancing ofHydronic Systems Section 8.

325 339 356 396 427 443 457 462 465

Pipelines/Pipework

Pipeline Cleaning Pipe Cutting and Bending Pipeline Inspection and Evaluation Jacketing and Dual Containment Section 7.

249 280 301 306 314

533 556 572 584 601 610 628 637 645 658 667 682

Duties and Services

Water Services Hygienic Services Steam Services Fire-Safe Valves Fire Hydrant Valves

693 718 728 743 754

X

Marine Services Vacuum Services Cryogenic Valves Nuclear Services High Pressure Services Section 9.

759 763 768 775 784

Engineering Data

Glossary Standards and Designations Section 10. Author's Acknowledgements

793 800 851

Section 11. Buyers' Guide to Valves and Pipes

Classified Index by Product Category Alphabetical List of Manufacturers Trade Names Index Editorial Index Advertisers Index

855 863 865 867 872

AcknowledgementsIllustrations and Tables

Page Number

Company

Page Number

Company

3

Neles-Jamesbury Neles-)amesbury Neles-Jamesbury B F Goodrich Biwater Industries Serck Audco Valves Johnson Valves Serck Audco Valves International H wash en Corporation Fortune Manufacturing Co Worcester Controls Worcester Controls Neles-Jamesbury Orbit-Harwin Vi:!lves Flow Safe. Inc Tyco Valves and Controls Argus Argus Neles-Jamesbu.ry Neles-jamesbury Neles-Jamesbury Argus Worcester Controls Argus Neles-jamesbury Argus Guest and Chrimes Guest and Chrimes Guest: and Chrimes KSB Armaturen GmbH KSB Armaturen GmbH Neles-Jamesbury KSB Armaturen GmbH Neles-Jamesbury Neles-)amesbury l3aronshire Engineering Ltd KSB Armaturen GmbH Wouter Witzel GmbH

74 Figure 6 75 76 Figure 7 77 Figure 8 77 Figure 9 79 Figure 10 81 top 81 bottom 82 Figure 12 8 7 Figure 5 88 Figure 6 89 top 89 Figure 7 93 bottom left 93 bottom right 94 Figure 3 95 top 95 Figure 4 95 Figure 5

Neles-Jamesbury Guest and Chrimes Tyco Valves nnd Controls Posi-Flate Posi-Flate Neles-Jamesbury Tyco Valves and Controls Tyco Valves and Controls Charles Winn (Valves) Ltd Quality Controls Inc Quality Controls Inc Quality Controls Inc Nu-Con Equipment OMBSpA ASAHl/America Hitachi Valve OMBSpA KSB Armaturen GmbH KSB Armaturen GmbH Brooksbank Valves Ltd KSB Armaturen GmbH KSB Armaturen GmbH johnson Valves Guest and Chrimes OMBSpA OMBSpA m..mspA OMBSpA Johnson Valves Red Valve Company inc Red Valve Company Inc Crane •u Resistoflex Crane·'~ Resistoflex Crane •"!> Resistoflex Humphrey Products Kemutcc Powder Technology Kemutec Powder Technology Hopkinsons Ltd Hopkinsons Ltd

8 top 8 bottom 28 29 42 top 45 46 Figure ()(a and b) 47 48 Figure 1 49 top 49 bottom 50 top 50 Figure 2 52 top 52 bottom 53 Figure 4 54 55 figureS 55 Figure 6 56Figurc7 56 Figure 8 57 top 57 Figure 9 59 Figure 10 60Figure 11 63 64 64 Figure 1

67 68 69 Figure 1 70 top 70 Figure 2 71 Figure 3 71 Figure 4 72 73 Figure 5

98 99 bottom 102 top I 02 bottom 103 bottom I 04 Figure 5 I 04 Figure 6 l 04 Figure 7 lOS 108 bottom lll Figure 2 112 Figure 4 115 Figure 10 116 Figure 11 116Figure 12 122 Figure 3 124 Figure 6 l25Figure7 129Figure3 130 Figure 5

xii

Page Number

Company

Page Number

Company

131 Figure 6 134 135 136 137 146 147 figure l 148 Figure 2 149 Figure 3 150 Figure 4 151 Figure 5 152 Figure (i (a and b) 1 52top 15 3 Figure 7 (a and b) 1 53 FigureR (a and b) 154 Figure 9 154 Figure 10 155 156 Figure J 1 156 Figure 12 158 top left 15 8 top right 164 Figure I 165 bottom 16n figure 3

Bush-Wilton Grasso Spir
192

Durabla Fluid Technology Jnc Durabla Pluid Technology Joe Dur<~b la Pluid Techno logy Inc Abocus Valves Manufacturing Ltd Ba rons hire Engineer ing Ltd Spimx Sa reo Durabla Fluid Tech nology Inc Kepner Products Compnny Kepner Products Company Spirax Sarco IMI Bai ley Birkett Ltd Realm !MI Bailey Birkett Ltd Crosby Va lve Inc !Ml Bailey Birkett Lld Crosby Valve Inc Crosby Valve Inc Crosby Valve Inc IMt Bailey Birkett Ltd !MI Bailey Birkett Ltd IMI Bailey Birkett Ltd Plast-0-Malic VCJ lves Inc Port Valve Inc. Circle Seal Co nt rols Inc Circle Sea l Controls Inc Crosby Va lve Inc Crosby Valve Inc Flow Sofe Inc. Spirax Sarco Anderson. Greenwood-Co Crosby Va lve Inc Spir<1x Sa reo IMt Bailey 13irkett Ltd Spirax Sa reo Spirax Sarco Spirax Sarco Spirax Sa reo Spirax Sa reo Spirax Sarco Guest and Chrimes Guest a nd Cbrimes Guest and Chrimes SOCLA Dan foss Water Va lves SOCLA Dan foss Water Valves SOCLA Dan foss Water Valves SOCLA Dan foss \Vater Valves SOCLA Dan foss Water Valves SOCLA Dan foss Water Valves SOCLA Dan foss Water Valves Sounders Va lve Co Neles-jamcsbury Neles-jamesbu ry KSB Armaturen Gm bH KSB Arm a ture n Gm bH Neles-Jamesbury Rotork Controls Ltd

167Fip,ure4 1 70 Figure 3 171 Figure 4 171 Figure 5 172 Figure 1 174 Figure 2 175 Figure 3 176 Figure 5 177 Figure 6 1 78 Figure 8 1 78 Figure 9 179 Figure 10 179 Figure 1 1 1 79 Figure 1 2 180 Figure l2 180 Figure 13 185 186 top 186 figure 1 188 Figure 3 188 bottom left 188 bottom righ t 189figure5 190 Figure 6 190 Figure 7 191 Figu re 8 19 1 Figure 9

193 1 94 Figure 10 195 Figure ll 19 5 top 19 6 Figure 12 19 7 19 8 Figurel3 19 8 Pigure 14 2 01 Figure 1 202 Figure 2 202 Figure 3 2 0 2 figure4 204-206 Table 1 207 Figure 5 208 Figure 6 209 Figure 7 210 Figure 8 211 Figure 9 212 Figure 10 2 1 2Figure ll 213 Figure 12 213 Pigure 13 214 Figure 14 2 14 Figure IS 2 1 5 Figure 16 2 1 nFig ure 17 217 top 2 1 7 bottom 2 18 Figure 18 2 18figure 1 9 2 18 Figure 20 2 1 9 Figure 2 1 22fi Figure 1 227 Figure 2 227Figu re3 233 Figure 5 233 Figure 6 235 figure 8 238 top left 238toprighl 24 0 243 Figure 3 244 to p 244 Figurt' 2 245 Figu re 3 24 5 figure 4 245 Figure 5 246 Figure 6 249 2.52 25 3 2.54 255 256 257

xiii

Page Number

Company

Page Number

Company

258 260 Figure J 260 Figure 2 261 Figure 3 262 figure . 4 263 Figure 5 264 Figure 6 265 267 Figure 7 268 Figure 8 268 Figure 9 2o9 figure 10 2 70 Figure 11 271 Figure 12 27 3 Figure 1 3 274 Figure 14

Shafer Valve Co KSB Armaturen GmbH KSB Armaturen GmbH Neles-jamesbury Shafer Valve Co Shafer Valve Co Bel Valves KSB Armaturen GmbH Rotork Controls Ltd Hitachi Valve Rotork Controls Ltd Rotork Controls Ltd Rotork Con trois Ltd Rotork Controls Ltd Rotork Controls Ltd Dreamo Electro-Mechanik GmbH Dream9 Electro-Mechanik GmbH Rotork Controls Ltd El-0-Matic International Tyco Valves and Controls Exeeco Ltd Spirax Sarco Spirax Sarco Dewrik. a division ofSPX Plast-0-Matic Valves Inc Severn Glocon Guest and Chrimes Spirax Sarco Spirax Sarco Dezurik. a division ofSPX Spirax Sarco Spirax Sarco Spirax Sarco Spirax Sarco Spirax Sarco Spirax Sarco APV / In vensys APV /Iovensys APV /lnvensys K. Controls Ltd Realm Osmonics Gemi.i Valves Ltd SOCLA Dan foss Water Valves SOCLA Daofoss Water Valves Emile Egger-Co. AG Emile Egger-Co. AG Asco Joucomatic Ltd Asco joucomatic Ltd Asco joucomatic Ltd Cmtis Wright Control Flow Corporation Spirax Sarco Spirax Sa reo Spirax Sarco Spirax Si'lrco Spirax S<~rco Spirax Sarco

31 5 top left 315 top right 316 Figure 3 316 figure 3 317Figure4 317 bottom 318 Figure 6 319 figure 7 325 326 327 328 329Tablel 330 l:igure 1 3 30 [:'ig ure 2 330Table2 331 Table 3 3 31 Table 5 333 Figure 3 334

Oycon Oyna m ic Con trois Dycon Dynamic Controls Apco Controls Fisher Rosemount. Fisher Rosemount Fisher Rosemount Circle Seal Controls Inc Circle Seal Con trois Inc Griffin Pipe Products Co. Hitachi Valve Biwater Industries Griffin Pipe Products Co. Biwater Industries Biwat:er Industries Biwaler lodustries Biwater Industries Biwater Industries Biwater fndustries Griffin Pipe Products Co. Rath Manu[acturing Company Inc Special Metals Corporation Dow Chemical Co Dow Chemical Co Crane George Fischer George Pischer George l:ischer George Fischer George Fischer George Fischer Harvel Plastics George l:ischer Upnor Ltd Agru Company George Fischer George Fischer ASAHI/ America ASAHI/ America ASAH!/America Wiik and Hoeglund George Fischer George fischer George Fischer George Fischer George Fischer George Fischer Harvel Plastics Griffin Pipe Products Co. Griffin Pipe Products Co. Griffin Pipe Products Co. Biwater Industries Victualic Victualic Victualic Victualic Harvel Plastics Griffin Pipe Products Co. Biwater Industries

275 Figure 14 276 277 Figure 16 2 77 top 278l:igurel7 280 Figure 1 281 top 281 bottom 282 bottom right 282 top left 282 top right 284 Figure 2 284 Figure 3 285 figure4 286 Figure 5 287 Figure 6 287Pigure7 288 Figure 8 288 Figure 9 288 Figure 10 289 Figure 11 2 90 Figure 12 291 Figure 13 292 Figure 14 293 Figure 15 294 top 294 Figure 16 295 296 297 Figure 17 297 Figure 18 298 l:igure 19 298 Figure 20 299Figure21 299 Figure 22 304 Figure (i 305 Figure 7 307 Figure 2 308 Figure 3 310 Figure 5 310 Figure 6

335 Table 7 336 337 338 Figure 4 339 Figure J 340 Figure 2 341 3 56 Table 1 357 3 58 Figure 1 359 top 360 361 368 369 3 70 top 3 70 bottom 371 372 3 74 Figure 4 378 379 380 384Table 6 391 top 393 Table 7 395 396 400-401 Figure 1 402 403 Figure 2 403 figure 3 404 Figure 4 405 Figure 5 405 bottom 406 Figure 6 407 408 Figure 8

xiv Page Number

Company

Page Number

Company

410 top 411 412 Figure 13 413 Figure 14 414 top 422 Figure 15 422bottom 423 425 top

Biwater Industries Biwater Industries APV /Invensys 3X Engineering France 3X Engineering France George Fischer George Fisc her George Fischer International Hwashen Corporation George Fischer Victualic Metal Samples Metal Samples Metal Samples Pi Conversion Engineering Ltd Pi Conversion Engineering Ltd Plascoat International Dow Chemical Co Dow Chemical Co Biwater Industries Dow Chemical Co Dow Chemical Co Dow Chemical Co T. D. Williamson. lnc .'lj) I.S.T. Molchtechnik GmbH T. D. Williamson. lnc.QJ) T. D. WiUiamson, Inc. 1' T. D. Williamson. Inc. 1 T. D. Williamson. Inc. 1 E. H. Wachs Co E. H. Wachs Co E. H. Wachs Co Tubelar Engineering E. H. Wachs Co T. D. Williamson . Inc. 1' T. D. Williamson. Inc. 11 T. D. Williamson. Inc.'1' T. D. Williamson . Inc. 1 ' ' T. D. \1\'illiamson. Inc.m> Radiodetection Oyno-Rod Dyno-Rod Cabletime Systems Ltd Radiodet.ection Sharer Valve Co Controls Southeast I oc Controls Southeast Inc Controls Southeast Inc Controls Southeast Inc Controls Southeast Inc International Plastic Systems Ltd Enfield Industrial Corporatioo Spirax Sarco Weir Pumps Weir Pumps

656Table2 661 Figure 5 665 668 670 Figure 1 670 Figure 2 671Figure3 672 Figure4 672 Figure 5 673 Figure 6 673 Figure 7 674 Figure 8 674 Figure 9 675 Figure 10

Spirax Sarco Kent Process Control Dresser Valve Division Neles-Jamesbury Neles-Jamesbury Fisher Rosemount Fisher Rosemount Fisher Rosemount Fisher Rosemount Fisher Rosemount Fisher Rosemount Neles-Jumesbury Neles-Jamesbury Neles-J amesbury Crosby Valve Inc Engineering Applications Ltd Engineering Applications Ltd Engineering Applications Ltd Engineering Applications Ltd Tour+ Andersson AB SOCLA Dan foss Water Valves Spirax Sarco APV / lnvensys Dezurik, a division ofSPX KSB Armaturen GmbH Guest and Chrimes Wouter Witzel GmbH Dezurik. a division ofSPX Guest and Chrimes Adams Brooksbank Valves Ltd Johnson Valves SOCLA Dan foss Water Valves Lancashire Fittings Ltd Delta Capillary Products Ltd IMI Bailey Birkett Ltd IMI Bailey Birkett Ltd Realm Realm Bray Valves+ Cootrols (UK) Quality Controls Inc GSR VentiltechnikGmbH Dresser Valve Division Schott lndustrietl Glass Harvel Plastics Spirax Sarco Spirax Sarco Spirax Sarco J. G. Black Polymers Ltd Crosby Valve Inc Crosby Valve Inc Spirax Sarco B.T.G. Spirax Sarco Solvent+ Pratt Hindle Cock burns Ltd OMBSpA Solvent+ Pratt Solvent+ Pratt OMBSpA

441 Figure 13 445 top 449 Figure 4 450 top 450 Figure 5 454 Figure 7 454 Figure 8 467 468 top 468 bottom 472 Tuble 2 474 4 75 top 475 bottom 483 Table 3 484 top 484 Figure 2 486-487 f-igure 3 488-489 Figure 4 492 Table 5 497 498 499 top 499 bottom 501 top 507 508 top 508 bottom 509 510 514 515 Figure l 516 Figure 2 517 Figure 3 519 520 522 Figure 1 523 Figure 2 523 Figure 3 525 Table 1 526 Figure 4 528 Figure 5 529 Figure 6 638 640 641

677Te~blel

6 79 Figure 12 6 79 Figure 13 680 Figure 14 fi80 f-igure 15 684 694 695 Table 1 697 Figure 3 698 Figure 4 699 Figure 5 699 right 700 Figure 6 701 Figure 7 702 703 bottom 703 top 7 04 707 708 top 708 bottom 716 Figure 8 716Figure9 719 720 721 Figure 1 721 Figure 2 722 Figure4 723 Figure 5 725 f-igure 8 726 729 Figure 1 730 Figure 2 731 Figure 3 733 bottom 733 top 734 bottom 735 Figure4 739 f-igure 5 739 figure 6 746 Table 1 748 f-igure 3 749 bottom 749 Figure 4 750Table 3 753

XV

Page Number

Company

Page Number

Company

754 755 Figure 1 75 5 top 756 Table 1 757 Figure 2 759 761 bottom 761 top 764 bottom 764 Figure 2 765 Figure 1 766 Figure 4 768 769 770 Figure l

Brooksbank Valves Ltd Guest and Cbrimes Brooksbank Valves Ltd Guest and Chrimes IMI Bailey Birkett Ltd Brooksbank Valves Ltd KSB Armaturen GmbH Blakeborough Valves Neles-Jnmcsbury Neles-Jamcsbury Neles-Ja mcsbu ry Circle Seal Controls Inc Reiss Engineering Co. Ltd Solvent+ Pratt Tyco Valws and Controls

771 Figure 2 772 Figure 3 773 top 773 Figure 4 775 776 777 Figure 2 778 Figure 3 782

Tyco Valves and Controls Neles-Jamesbury IMf Bailey Birkett Ltd Circle Seal Controls Inc Worcester Controls Vanatome CraneQ!) Resistoflex EDF Mannesmannrohren-Werke AG Neles-Jamesbury GSR Ventiltechnik GmbH Adams Kepner Products Company Adams

784 786 788 Figure 6 788 middle 789

Note: Figures from T . D. Williamson. Inc. 0'; : Reproduced with the permission ofT. D. Williamson. Inc.\!<'' Registered Trademarks ofT. D. Williamson. Inc. in the United State~ and in foreign countries.

SECTION 1 Fundamentals

Classification of Valves Basic Valve Nomenclature Valve Selection Guides Pipes and Pipelines-Definitions and Explanations

Classi-fication of Valves Valves may be classified in a number of ways, e.g. by category (general type), specHic type, purpose or name: or by flow characteristics (e.g. straight-through, full-flow or throttled-flow). Descriptions can also differ slightly in different countries although the main type names are established internationally (with some exceptions). Classification of valves by category is given in Table 1. This follows British Standards and general practice adopted by British manufacturers. but is also generally applicable to American practice. One major difference in this respect is that the important class of ball valves is considered as a type of plug valve in the tabular summary, whereas American practice would favour regarding it as a separate category. The baH valve is, in fact, a major type in its own right.

Modular ball valve based on standardised components.

4

Fundame11tals

Table 1. Classification of valves ------------.-------------------~--------------------------

Category

Patterns

Types of construction

Remarks

Cock

1. Plug

Tapered plug Plug retained by gland or packing Packing between plug face and body seat Stuffing box in cover

Also parallel plug.

1. Taper plug 2. Parallel plug 3. Ball plug

Passage through port in rotatable. plug supported or mounted to reduce friction.

2. Gland 3. Packed cock 4. Compound gland

Plug valve

l. Plain 2. Lubricated

Screwdown stop valve

1. Inside screw

---2. Outside screw

- -

1. Globe vnlve 2. Angle 3. Oblique 4. Others

Gate VCIIve (wedge gate valve)

1. Inside screw 2. Outside screw 3. Lever (a) Sliding stem (b) Rotary stem

.l. Wedge (gate)

(a} Solid wedge or

2. Sluice (valve) 3. Double disc

(b) Split wedge. Solid wedge gate valve. Gate composed of parallel sliding discs or slides.

l. Swing (check) 2. Lift (a) Disc (b) Piston (c) Ball 3. Foot (valve)

Hinged flap check mechanism.

Gate valve (slide valve) Check valve

l. Horizontal 2. Vertical 3. Angle

----f-

Butterfly valve

Spherical body. Spherical body with ends at righl angles. Spherical body. stem axis oblique. Usually described by type (e.g. needle valve) or geometry of body (e.g. tee valve). ------Closure effected by wedge action .

-----------------

Disc check mechanism. Disc plus piston check mechanism. Ball check. Check valve fitted to bottom of a suction pipe.

l--

l. Double flanged 2. Water (a) Single Oange (b) Flangeless

Each flange is individually bolted. Primarily designed for insertion between pipe flanges

Based on rotatable disc valve.

------~-------------------4-----------------------

Diaphragm

Flexible diaphragm mounted over a weir.

valve

Ball (float valve)

1. Single beat

2. Double beat

1. Direct (lever)operated 2. Pressure-operated 3. Droptight 4. Non-droptigbt

Single beCJt--flow through single seating ring. Double beat-flow through two seating rings.

Classification of Valves

5

Table 1 (ronlinued)

Types of construction

Category

Patterns

Safety valve

I. Direct spring-loaded 2. Direct weight-loaded ~.Lever and spring-loaded 4.Leverand weight-loaded

Also designated by: l . High-lift valve. 2. Pnll-lift va lve.

5. Ten sion spr ing-loaded 6. Torsion ba r

4. Electrically-assisted va lve.

I. Direct spring-loaded 2. Direct weight-loaded

Also designated by: 1. High-lift (reliel) valve. 2. Pilot-operated (relieO valve.

-

Relief valve

-Pressure control valve

1. Self-contained 2. Spring-loaded 3. Weight-loaded 4. Pressure-loaded 5. Externally-piped 6. Tight-closing 7. Non-tight-closi ng 8. Relay-operated

3. Pilot-ope rated valve.

1. Pressure-reducing 2. Pressure-retaining 3. Indirect

-

-

Air relief valve

1. Single-orifice LP 2. Single-orifice HP 3. Single-orifice with integral isolating va lve 4. Double-orifice with integral isolating valve

Turbine valve

1. Regulating 2. Quick-closing 3. Starting 4. Exhaust 5. Guarding

Free disch a rge valve

1. Needle-type 2. Hollow jet-type 3. Sleeve-type

Remarks

-

-

--

-

I

Valves are classified and described by specific type in Section 2, which also include a number of individual designs best categorised as miscellaneous. Some other valve types are given in Table 2. Descriptions of various valve types may also differ and Table 3 lists some other descriptions, standard terminology in this case being based on that adopted for Table 1. This is by no means complete, but is offered as a general guide.

6

Fundamentals

Table 2. Some other valve types

Category

Description

Flow-regulating valve Temperature-regulating valve Automatic process-control valve

For controlling rate of flow in a system. For controlling fluid temperature level in a system. For controlling rate of flow relative to value of a command system. An automatic type of air valve for the prevention of the formation of vacuum or the release of vacuum in large bore pipelines. A valve which is used for cleaning sludge and other foreign matter from a boiler. A gate valve. A valve in which a ball, free to rotate in any direction. is moved at 90° to the flow stream from a position removed from the flow stream until finally rolling into a circular orifice for shut off. A fire prevention valve which has a weighted lever held open by a wire and fusibl e link which melts at an increase in room temperature. A control valve for either water, oil. or hydraulic systems. A valve incorporating an element by virtue of which the energy within the emitting jet: is dissipated. A single-faced type of valve consisting of an open lrame and door. and used in terminal positions only: usually located in tanks or channels as a means of controlling flow into a pipe. A gate valve incorporating a sluicing effect. A valve for controlling the flow of water through a radiator. A valve in which rotation of internal parts regulates flovv by opening or closing a series of segmental ports. A spherical-plug valve in which the plug, which rotates through 90°, is provided with a circular waterway to match the body and ports. A valve operated by an electrical solenoid. A type of parallel slide valve in which the 'spectacle gate' has one 'lens' of circular waterway and the other of solid section. A valve which combines temperature selection and flow control in the same body. A non-tight-closing butterfly valve with a centrally-hinged !lap which can be locked in any desired position.

Anti-vacuum valve

Blow-down valve Bulkhead valve Free-ball valve

Fusible-link or fire valve

Hydraulic valve Jet-dispersal valve Penstock

Plate valve Radiator valve Rotary-slide valve Rotary valve

Solenoid valve Spectacle-eye valve Thermostatic mixing valve Throttle valve

Classification of valves by function yields the following general list where any individual type of valve may be capable of performing one or more of these functions. Excluded from this list are specific functions or specialised services for which special designs of valves are normally employed. On-off service. (ii) Throttling or flow control. (iii) Preventing of reverse flow. (i)

Classification of Valves

7

Table 3. Terminology

General or 'popular' description

Standard terminology

Back-pressure valve Block and bleed valve Clack valve Conduit valve Controllable check valve Controllable non-return valve Dash pot valve Excess-flow valve Excess- or minimum-pressure valve Flap valve Follower-ring valve FuJI way valve Governor valve Non-return self-closing valve Parallel-gate valve Proportional-flow valve Reflux valve Retention valve Screw-down non-return and flood valve Wheel valve Y-type valve

Check valve Gate valve Check valve Gate valve with full-bore aperture Screw-down stop and check valve Screw-down stop and check valve Check valve (piston-check disc-type) Flow-regulating valve Flow-regulating valve Check valve (swing-type) Gate valve Gate valve Pressure-control valve Check valve Safety valve (direct spring-loaded) Flow-regulating valve Check valve Check valve Screw-down stop and check valve Screw-down stop valve Oblique valve

-- - - - - - - - - - - -

(iv) (v) (vi) (vii)

Pressure control. Directional flow control. Sampling. Flow limiting.

Valves classified by duty or the service they are intended to perform are described in Section 3. Necessarily these embrace types already described under specific types and the relevant chapters can be studied together where appropriate. A further source of reference and information in this respect is the chapter on Valve Selection Guides. Industrial valves operate under many different situations and temperatures which range from the cryogenic to high-temperature applications and with different materials including grit, sludge, corrosive chemicals, gases and liquids. In general, valve technology is mature. There are two main divisions in the industry: control valves giving precise control of flow and on/off valves which may be further subdivided into linear (multi-turn) and rotary (quarter-turn). Actuators which control the movement of a valve can be manual or automatic and are a major ancillary item for valves. Valves can be purchased as standard products (commodity valves) or as engineered units, purpose-built for a specific application. The emphasis today is on providing solutions to problems and automation wherever possible.

8

Fundamentals

High-performance butterfly valve with sectioned spring-diaphragm actuator for modulaLi11g control.

Rotary segrnent-control valve with noisl'-control trinr .

Classification of Valves

9

Processes are required to be more economical and run uninterrupted for longer periods. The intervals between production shut-downs for plant maintenance are growing longer and environmental protection legislation is becoming more stringent. Intelligent valves, based on digital control technology and incorporating control functions and communication interfaces are already making an impact and computer integrated processing (CIP) is a reality. The most striking changes in valve technology appear to be in the field of materials of constructions with new metals, ceramics and composites being explored. Valve connections

Valves are normally designed to take either threaded pipe ends, or with flanges for flanged connection. Threaded connections are simpler and cheaper to produce and more easily installed. However, it can prove difficult to remove valves so mounted without dismantling a considerable portion of the piping unless a number of extra fittings. such as unions, are incorporated.

db db 9P 9[? etaill fac e

Ruised fuce

l.ar~ c

nude and ./t'lllllle

/11(1/('

Small ond ( £'111111£'

/ . IIIX('

1011g11e

und groo t "l '

dq Small

Ring joint

!OIIg_lll' 1111d g r o O t "t'

Fig uri' I. Flangl'd ends.

10

Fundamentals

Flanged ends make a stronger. tighter and more leak-proof connection. Where heavy viscous media are to be controlled, as in refineries. process and chemical plants. etc., flanged-end valves are normally used. The initial cost is higher, not only because of the extra metal but because the flanges must be carefully and accurately machined. Also the installation cost is greater because companion flanges, to which the valve-end flanges are bolted, as well as gaskets, bolts and nuts must be provided. All flat faces are commonly termed plain faces. Bronze and iron flat faces can have a machined finish. Cast iron raised faces may be smooth finished or have a serrated finish (preferably with no fewer than 16 serrations per inch) which may be spiral or concentric. Steel flat faces and raised faces should have a serrated finish of approximately 32 serrations per inch. The serrations may be either spiral or concentric. Steel male and female and tongue-and-grooved faces should have a smooth finish. Steel ring-joint faces should have smooth finished grooves. If spiralwound gaskets are used on flange faces, the flanges should have a smooth finish. Examples of flanged ends are shown in Figure l. Socket or butt-welded ends are used on all-welded pipeline systems. For specific services valves are also to permit connection to pipes by soldering or brazing. In the latter case the valve may be supplied with integral preformed brazing-material inserts.

Basic Valve Nomenclature Most valves consist of a body containing a flow control element (discs, plug, gate, etc.) attached to and operated by rotation of a stem. (There are exceptions: e.g. swing check and pinch valves have no stem.) The stem, together with any stem seals. is enclosed within a bonnet. The top of the stem is fitted with a hand wheel (or lever) for rotation of the stem (although some stems may have a sliding operation for quick action). With threaded stems (giving a screw-down, screw-up motion) the threaded portion may be fully enclosed by the bonnet, known as inside screw; or exposed beyond the bonnet, known as outside screw. The former obviously provides maximum protection for the screw thread. Outside screws have the advantage of being easier to lubricate. With rising-stem valves the handwheel and stem move together, giving a visual indication of the degree of valve opening. With a non-rising stem the handwheel does not rise (or fall) with the turning movement. The advantage of this type is that it can be installed in situations providing only minimum headroom above the hand wheel. Various types of bonnet may be used, e.g. screw-in, screw-on, union-style and bolted or flanged bonnet. Screw-in or screw-on bonnets are the simplest and cheapest, but largely limited to smaller valves used on low-pressure services. Union bonnets generally provide tighter sealing and are particularly suitable for valves which are dismantled frequently for servicing. Plain (flat) flange and male- and female-flanged bonnets are generally preferred for high-temperature or high-pressure valves, and also larger sizes of valves. An alternative type for high-pressure and/or high-temperature services is the breech-lock bonnet. Valve trim

Trim is the term used to describe the parts of a valve which are replaceable, i.e. normally those parts likely to be subject to wear or degradation. The following parts are considered as trim: Gate valves-stem, seat ring, wedge. back-seat bushing. Globe and angle valves-stem, seat ring, disc. disc nut, back-seat bushing.

12

Fundamentals

Screwed bonne!.

Union bonner.

Bolted flanged bonnet.

Disc valve-disc, disc nut, back-seat bushing. Swing-check valves-disc, disc holder, disc nut, side plug. carrier pin. disc-holder pin, disc-nut pin. seat rings. Lift-check valves-disc, disc guide. seat rings . Stem seals and other internal seals (tl\rhere fitted) are arguably included under the definition of trim. but are not normally used in describing trim materials. Standard abbreviations

The following abbreviations are used to describe or designate valve parts. features, etc.: All iron All bronze BB CWp DD DW FE FF

IBBM IPS ISNRS ISRS NRS

RP RS SIB

all parts of iron construction. all parts of bronze construction. bolted (flanged) bonnet. cold working pressure. double disc. double wedge. flanged end (connection). flat flange . iron body bronze-mounted. iron pipe size. inside screw non-rising stem. inside screw rising-stem. non-rising stem. raised flange. rising stem. screwed bonnet.

Basic Valve Nomenclature

sw SintorintS S ren or ren S OS&Y WOG

13

solid wedge. internal seat. renewable seat. outside screw and yoke. water. oil. gas pressure rating.

Nomenclature covering the individual parts of various different types of valves is included in Section 2 .

Valve Selec-tion Guides

The main parameters concerned in selecting a valve or valves for a typical general service are: Fluid to be handled-this will affect both type of valve and material choice for valve construction. (ii) Functional requirements-mainly affecting choice of type of valve. (iii) Operating conditions-affecting both choice of valve type and constructional materials. (iv) Flow characteristics and frictional loss-where not already covered by (ii), or setting additional specific or desirable requirements. (v) Size of valve-this again can affect choice of type of valve (e.g. very large sizes are only available in a limited range of types): and avaiJability (matching sizes may not be available as standard production in a particular type). (vi) Any special requirements- e.g. quick-opening. free-draining, etc. (i)

In the case of specific services, choice of valve type may be somewhat simplified, e.g. by following established practice or selecting from valves specifically produced for that particular service. On a broad basis, Table 1 summarises the applications of the main types of general purpose valves. It has only limited use as a selection guide, i.e. can be regarded as a starting point. Table 2 carries general selection a stage further in listing valve types normally used for specific services. Table 3 is a particularly useful expansion of the same theme relating the suitability of different valve types to specific functional requirements. Normally, for general services (and for many specific services), several valve types may appear as possible choices. These may then need evaluating individually, and comparing on the basis of the flow characteristics they offer. Even more important, calculations may be necessary to establish a suitable size of valve to meet a specific performance requirement, e.g. a maximum acceptance pressure drop or head loss through the valve.

Valve Selection Guides

Table 1.

15

Valve types-typical applications

Vu lve cutq:ory

Gen(•ral app lication(~)

Screw-down

Shut-otT or regulation ofllow of liquids! } Handwheel ( i) Electric motor and gases (e .g. steam). ( ii) hydrau lic systems actuat r ( v) Hydraulic actuator ( •) Air motor

c:tuatinn

Rt'marks

- -stop valve

-

Cock

l sually manual

Low-prt'sst 1re service on cle<Jn. cold

(a) Limited application for low-

pressure/low-volume systems becilusc of relatively high cost. (b) Limited suitability for handling viscous or contaminated fluids. Limited application for steam services.

fluids (e.~.'vilter. oils. etc. ). Gi!te valve

1

Normally u sed eit her fully open or fully closed for on-on· regulati on

( i)

on wnt.er. o il. gas. steam and other fluid services.

( v) Hydraulic actuator

()

Electric motor ( ii) hydruulic systems aetna or ( )

Parallel-slide vulve

Regulation of flow. purtic ulrtrly in m~in servk:·es in process industries andsteilm power pla nt.

Butt·rrny \'alve

Shu t-off an d regulation in large

Handwheel

(a) Not recommended for use as throttling valve. (b) Solid wedge gale is free from 'chatkr' and jamming.

Air motor (a) OtTers unrestricted bore at full opening. (b) Can incorporate venturi bore to reduce operating torque.

()

Hand wheel

( i)

Electric motor Industries. petrochemical industries. ( ii ) hydraulic systems actua or hydroclectrir power stat ions and ( v) H ydrmwc actuator ( ) Air motor thermal po wer stiltions. pipelines in waterworks. process

Diaphragm

Wide range of applications in all

()

Handwbeel

valve

services for flow regul<Jtiou.

( i)

Electric motor

( ii} hydraulic systems aclu u or

Relatively simple construction. (b) Readily produced in very large sizes

(il)

(e.g. up to 18ft or more).

(a) Can handle all types of fluids. including slurries. sludges. etc ..

( v) Hydraulic actuator l Air motor

and con taminated nuids. (b) Limited for steilm services by temperature and pressure rating of diaphragm .

Hand wheel ( i) Electric motor ( ii) hydraulic systems actua <Jr ( v) Hydraulic actuator

(a) Unrestricted bore at full opening. (b) Can handle all types of fluids. (c) Low operating torque. (d) Not normally used as a throttling

(

Bill! valve

Wide range of applications for all sizes.lnclu dlng very large sizc.s in oil pipelines. etc.

()

valve. Piuch valve

() Mechanical Particular! y suitable for handling corrosive 10 cdia. solids in suspemion ( i) Electric motor slurries. etc ( ii) hydraulic systems actua o r ( v) Hydraulic actuator

(a) Unrestricted bore at full opening.

(b) Com handle all typesofnui ds. (c) Simple serv icing. (d) Limited maximum pressu re rating.

( • ) l'luid pressure

(modified design) Automatic processcontrol

Desi);ned to meet pnrticular service con dition~.

'1 o m eet particular s ~rvice

cooditions

Mos t commonly of single or double beat-globe valve con figuration.

valve Air-relief valve

t:se
Turbine valve

Desi!lncd to m cc.t requirements of steam and water turbines in mdustrial. mari ne and power

'I o m~ct parUrular

s ·rvice conditions

Provides guaranteed control over maximum and minimum turbine speeds and power in ilSsociation

16

Fundamentals

Table 2. Valve types for specific services

Service

Main

Gases

Butterfly valves Check valves Diaphragm valves Lubricated plug valves Screw-down stop valves

Liquids, clear up to sludges and sewage

Butterfly valves Screw-down stop valves Gate valves Lubricated plug valves Diaphragm valves Pinch valves

Slurries and liquids heavily contaminated with solids

Butterfly valves Pinch valves Gate valves Screw-down stop valves Lubricated plug valves

Steam

Secondary

-

Butterfly valves Gate valves Screw-down stop valves Turbine valves

Pressure-control valves Pressure-relief valves Pressure-reducing valves Safety valves Relief valves

--

Check valves Pressure-control valves Pre-superheated valves Safety and relief valves

-

Valve coefficients and flow values

The valve coefficient is a convenient method of relating flow rates to pressure drop through valves and, in fact. is sometimes called a flow value. This coefiicient can only be determined empirically for a specific type of valve as it will be influenced by detail design and construction. It will also vary with the physical size of the valve and the degree of opening in the valve. Valve coefficient values are normally quoted for 100% opening (full open), with individual valves for each size. Some confusion can arise from the fact that the coefficient quoted for a valve can have three different values depending on the basic units on which it was computed. Normally these are apparent from the designation of the valve coefficient, viz: in units of US gal/min, lbf/in 2 in units of l/min, bar in Imperial units oflmp gal/min. 1 bf/ in 2 The following conversions apply: Kv Kv Cv f

Cv 14.28

0.07 0.0589

0.83 57

f

17.0t) 1.1 t)6()

17

Valve Selection Guides

Table 3. Typical valve suitability chart

Valve type

Service or function

0..

~

0

t::

c;:l

Oil

t:: -;::: .....

a:: 0

t::

!:3

....


1.1) 1.1)

·;:::;

0 ....

I

0

u


Oil

~

0 ....

0.... .....

:>

'-

0....

.....

t::

1.1) 1.1)


0...

....

Oil

t::

·a

::I

....

::::l

"'

"'"' o.oc t::

~

::0"' c ::I

1.1)


....

'"0

.~ ::I


....

·~

...!.<:

-:9c: -o._ o


t::

0.. 0

....

u ~

cOil

0

::::l

....

v-~....

1.1)

'"0



·- 0..

cc

t:: 0

...t::

E-<

i5

~

0..

~

s

M

s

-

-

-

-

s

-

s

LS

s

-

-

-

s

-

s

s

s

s

M

-

-

-

-

-

M

M

-

s

0

....

0

0 .....J

t:.t..

1.1)

tr:: .=: -

Ball Butterfly

--

s

-

Diaphragm

s

Gate

s

-

-

-

-

-

-

s

s

s

-

Globe

s

M

-

-

-

M

-

-

-

-

-

Plug

s

M

s

-

-

M

-

s

s

s

LS

Oblique (Y)

s

M

-

-

-

M

-

-

-

-

-

s

s

s

s

Pinch

-

- --·,. -

-

-

s

-

-

s

-

-

f--

M

s

s

s

-

-

-

s

-

-

-

-

·-

s

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

s s

-

-

-

-

-

-

-

-

-

-

-

-

s

-

-

-

-

-

-

-

-

s

-

-

-

-

-

-

Sampling

s

-

-

-

-

-

-

-

-

-

-

Needle

-

s

-

-

-

-

-

-

-

-

-

-

M

-

-

-

Swing-check

-

-

-

s

Tilting-disc

-

-

-

Lift-check

-

-

Piston -check

-

Butterfly-check

M

-

-

-

s

-

-

s

-

-

-

-

Pressure-relief

s

Pressure-reducing

SliM

-

Key: S = Suitable choice M =May be suitable in modified form

LS = Limited suitabi lity

-

-

18

Fundamentals

Typical flow coefficient equations can be shown as follows: For liquids

{M

Q= Cv

v~

where

Q = flow, gallons per minute Cv = flow coefficient ~p = pressure drop, psi s.g. = specific gravity (water=1) For gases (non-critical flow):

Q = 16.07 Cv

Z(Pi - P~) T x (s.g.)

where

Q

= flow, SCFM Cv = flow coefficient P 1 = upstream pressure. psia P 2 = downstream pressure, psi a Z = compressibility factor T = absolute temperature (°F+460) s.g. = specific gravity (air= 1) For gases (critical flow): P2/P1

= R,

and

;-z-() VTXTsi:J

Q = 16.07 CvP1J

where Rand Jare functions of the specific heat ratio 'r' as follows :

-

r

R

J

1.20 1.22 1.24 1.26 1.28 1.30 1.32 1.34

0.564 0.561 0.557 0.553 0.549 0.546 0.542 0.539

0.825 0.828 0.831 0.833 0.836 0.838 0.840 0.843

-

-

r

R

J

1.36 1.38 1.40 1.42 1.44 1.46 1.48 1.50

0.535 0.532 0.528 0.524 0.521 0.528 0.515 0.512

0.845 0.847 0.849 0.851 0.853 0.855 0.857 0.859

-

Valve Selection Guides

19

Combining flow coefficients (1) Flow in parallel: Cv=Cvl +Cv2+Cv3+ ... (2) Flow in series: (

~y = ( c~

J' c\) \ (c~J \ +(

Flow characteristics of valves

Where the flow characteristics through the valve are of significance, the following notes can be useful. Plug valves (Figure 1) offer a straightway passage through the ports with a minimum of turbulence. Flow can be in either direction and a quarter-turn will fully open or fully close the valve. Similar comment applies to ball valves. Gate valves (Figure 2) present a substantially straightway flow through the ports in the full-open position since the wedge or 'gate' is lifted clear of the flow passage. Turbulence and pressure drop are low. Again flow can be in either direction. Globe valves (Figure 3) are normally installed so that pressure is under the disc, assisting operation and eliminating a certain amount of erosive action. Turbulence and pressure drop are higher than with straightway valves. Angle valves (Figure 4) have similar characteristics to globe valves, with flow directed through 90°. Again flow is normally directed under the disc. Reverse flow may be used in the case of high-temperature steam. Ball, globe and angle valves are suitable for throttling.

Figure 1. Plug valve.

Figure 2. Gate valve.

22

Fundamentals

, ......

100

Nominal Size

90

KviOO

8

41

1

80 70

95

0

80

180 327 484 725 1130 1700

#.

50

:G 0

40

30

~

20

?;

1()

u 0

u::

/

,

v

100

Nominal Soze

1/ ,_ -

I

-

49

0

77

#. 60

3;4

146 437

,

70

'h

1V.

'I'

80

3fs

:L60

I

0

8

1

-

J

90

Kv)OO

/

~ 40

~ 20 30

~

10

u::

f-

~,

-I-

~

0

10 20 30 40 50 80 70 80 90 100

0

10 20 30 40 50 60 70 80 90100

%open

%open

Gate

Lubricated plug

,.

100

Nomonal Size

'Is '14

3fe '12 3;~

1 1'Ia 1'1:! 2 3 4

·oo •I-- c---

KviOO

8 22 32 71 185 350 700 1000 1600 3100 6500 11000

81

I

'

> "' 0

I

"'

"' 40

~

v--

30

u

u::

/2

3;.

'lC'

~ ~0

90

Kv lOO

1

l _

fil )

§

Nominal Size

I

-"

?/?.

~

'0 0

- " ~ r-

1- 1-

-

10

?0

·~

:w "

11/4 ,...-

1'h 2 3

'

0

>O

%open

4

,/

80 70

63 121

'Q

GO

~

&0

187 332 416 704 1700 2700

"'"'

40

su

I I

II

~

30

~

20

~

10

u::

I ~

0

10 lO 30 40 60 60 70 80 90 tOO

%open

Diaphragm

'

·-

Kv l OO

/

- : - I--

. '

3

1500 3000

4

5000

5 6

8000 12000

8

17000

2~

8

l

Ball

Nominal Size

1/

I

60

0

v

0 0

II

'

·-

,_

r-

-

1--

I

" " ~

-----'---~

-

;::;:; ;>""

"

lr

1'

~

!

% open

/

r1,1

-

1--

-

1-- -

lj

J

~

.,

-

..

"

Butterfly

Figure 8. Examples offlow values Kv.

The Kv table for angle-seat valves gives a Kv 100 factor of 3 2 7 for size 1 in, 484 for size 1 1 I 4 in and 72 5 for size 1 1 h in. In this example the correct size to use is 1 1 I 4 in (See also Table 5 ). Example 2 (Figures 9 and 10)

(i)

(ii)

What is the Kv factor for a 1 1 I 4 in water pipeline with a flow of 300 I/min, an inlet pressure of 0. 5 bar and an outlet pressure of 0 bar? If a valve has to be fitted and the minimum acceptable flow rate in the pipeline is 250 llmin, which type of valve should be used?

Valve Selection Guides

23

Table 4. Typicai'K' values and pressure drops for various 150 mm (6 in) bore valves Pressure drop* Service

K value

bar

lbf/in 2

0.59

8.5

-

Globe

-txJ-

5.0

Swing-check

-{*

3.5

0.40

5.9

Y-pattern

M

2.9

0.34

4.9

Angle (globe)

~

2.2

0.25

3.7

Venturi parallel-slide (witb eyepiece)

~

1.1

0.13

1.9

Butterfly

1><1-

1.0

0.12

1.7

Parallel-slide without eyepiece

{X}-

0.15

0.021

0.3

0.05

0.007

0.1

0.05

0.007

0.1

0.045

0.005

0.075

Parallel-slide with eyepiece

M

Ball (full bore) Straight pipe (the length of an average 6 in bore valve)

*Flow 40 m/s (140 ft/s) at 24 bar (350 lbf/ in 2 ) saturated steam.

Solution to (i) (Figure 9)

Calculate the Kv for the pipeline (Kvp)·

Figure 9.

Given: Q y ~p

300 1/min 1 kg/dm 3 P 1 -P 2 =0.5-0=0.5 bar

24

Fundamentals

of£

Then: Kvp

-Kvp

=

300a 424

Table 5. Typical sizes and operating ranges of valves

Valve

Size Min.

Pressure range Max.

mm(in) Ball

6

erd 50 (2) 25 (1) 3

Butterfly

6

e 14)

(6)

6

Gate

e ls ) 3

Globe

(1 I sl 6

(114) 6

Plug. non-lubricated

e14) 6

Swing-check

(114) Swing-check. Y-type

50

250 (10) 760

(2)

(30)

3

3

610 (24) 760 (30) 1900 ( 7 5) 305 ( 12) 25

( 1 1~;)

(1)

Lift-check

( t I 4)

Tilting-disc Diaphragm

el/3)

3

Y (oblique) (

Slide Pinch Needle

Key: A = Atmospheric V =Vacuum.

1

I sl

50 (2) 25 ( 1)

Max.

A

v A

v v A A

525 (7500) 84 (1200) 84 (1200) 700 (10.000) 700 (10.000) 350 (5000) 210 (3000)

A A A

A

v v A

v

v

175 (2 500) 175 (2500) 175 (2500) 84 (1200) 21 ( 3 ()()) 175 (2500) 28 (400) 21 (300) 700 (10.000)

Max.

Min.

bar (lbl in 2 )

(72)

1830 (72) 1220 (48) 760 (30) 760 (30) 406 (16) 610 (24) 150

Butterfly-check

Plug, lubricated

1220 (48) 1830

Min.

Temperature range

"' C (oF)

-55 (-65) -30 ( -20) -18 (0) -277 (-455) -272 (-455) -40 (-40) -75 ( - 100) -18 (0) - 18 (0) - 18 (0) -260 (-450) -50

300 (575) 538 (1000) 260 ( 500) 675 (1250) 540 (1000)

315

-272 ( 45 5) -18

(600) 220 (425) 540 (1200) 540 (1200) 540 (1200) 590 (1100) 230 (450) 540 (1000) 650

(0)

(1200)

-75 ( -100) -78 ( -100)

260 (500) 260 (500)

(-60)

Valve Selection Guides

25

Solution to (iiJ (Figure 10)

First it is necessary to calculate the Kv factor for the total system (Kvt) .

Figure IO.

Given:

Q

--

y

--

~p

--

Kvt

--

oflp

--

250/ls

--

354

2 50 1/ min 1 kg/dm 3 P 1 - P 2 = 0.5-0 = 0 .5 bar

Then:

Kvl

The Kv factor for the valve (Kvv) can now be established by subtracting the Kv factor for the pipeline (Kvp) from the kv factor for the total system (Kvt). For this purpose, the formula for calculating the flow factors in series should be used, which is: 1 1 1 1 - 2-

Kvx

= - 2-

Kv 1

+-

2-

Kv2

thus:

1

1

1

+ ... -2Kvn

26

Fundamentals

1 2 Kvv

1 -

1

354 2 -424 2

= 7.98

X

10- 6

= 2.42

X

10- 6

K, = =

J

2.42

-

5.56

X

10- 6

~ 10-'

643

The calculation shows that the valve used must be one with a minimum Kv 100 factor of 640. From the Kv tables it can be seen that a 1 1 I 4 in ball valve has a Kv too factor of 1000 and a 1 1 I 4 in diaphragm valve has a Kv 100 factor of 3 32. Therefore only the 1 1 I 4 in ball valve can be used .

Pipes and Pipelines-De·finitions and Explanations According to the Oxford Dictionary, a pipe is a tube whereas a tube is a long, hollow cylinder. Neither is of any help in establishing true definitions, for there are recognised differences between pipes and tubes-but not those the dictionary gives. The more obvious distinction is that 'a pipe is a big tube, and a tube is a small pipe'-which is not far from the truth in application. But we are also concerned with differences in usage of terms in different industries-and in different countries. Taking the big tube/small pipe premise as substantially correct, we can further comment that pipes which may run up to several metres or feet in diameter are cast, spun, welded up or otherwise fabricated, depending on the materials and sizes involved. Nobody could logically visualise producing very small sizes of pipes-e.g. under 25 mm (1 in) diameter-by such time consuming methods. It is much quicker and cheaper to produce them by extrusion. Hence tubes are basically (but not exclusively) extruded products, involving reduction in size during manufacture in the case of metal tubes, and a moulding process in the case of plastic tubes. Just to confuse the issue, some tubes are produced by rolling to shape and seam welding or seam jointing; and large-size plastic tubes, which then become pipes. are produced by the same methods as small plastic tubes. But ignore that for the moment. A main difference does emerge from the two different methods of manufacture. Inherently, tubes have a smooth bore as manufactured. Pipes will have a varying degree of bore roughness, depending both on the material involved and the actual fabrication method. Once you extend tubemanufacturing process to pipe production, then these pipes also have a smooth bore (e.g. plastic pipes). Pipes produced by pipe-manufacturing methods normally require specific after-treatment to render them smooth bore. With this difference (and there are exceptions to the rule), we can further differentiate between the two by size ranges and terminology adopted by different industries. One of the main users of smooth-bore small-diameter tubes is the hydraulic industry where line sizes may range from 3 mm (1 / 8 in) bore up to 3 2 mm ( 13 in) bore, or larger in low-pressure hydraulic systems-and

28

Fundamentals

CPVC pipes and tubes.

Pipes and Pipelines-Definitions and Explanations

29

we have called them lines, not pipes or tubes. The industry itself may call them hydraulic pipes. hydraulic tubes or hydraulic lines; and larger hydraulic tubes (pipe sizes!) are produced for cylinder tubes. Industries and applications concerned with the conveyance of fluid products almost invariably refer to their tubular products as pipes or piping. Again. sizes may range dov,rn into tube sizes (and even be drawn or extruded products or true tubes)-e.g. gas pipes and small-bore water service pipes. But they are still pipes or piping. And the system they provide is a pipeline. Hopefully this has established a satisfactory definition and explanation of \•Vhy the title of this handbook is specifically concerned with pipes and pipelines, for these are the areas mainly covered. And those who work in these areas call

Ductile iron pipe for drinking water applications.

30

Fundamentals

Summary of pipe materials-metallic Material

Manufacturing process

Size range

Typica l applicalioos

Remarks

Cryo~cnir

and chemical pipelines: lightweight hydraulic pipes.

Low weight and good corrosion resistance.

Mainly smaU bore tubes

Marine application s. Hot water services (domestic).

Resistant to corrosion but costly.

Spi nning

Up to600mm (24 in}

Gas and water distribution systems.

Stronger than cast iron.

Grey cast iron

Casting

Up to 1200 mm (48 in}

Gas. water and drainage syste1ns.

Brittle matcri;~l .

Malleable iron Steel

Heat-treated casting Vadous

1\•lainly u sed for small fittings. Gas and oi l pipelines.

l ess brittle than cast iron. Available io a witle range of tensile st.renglhs.

Stainless steel

Va rious

Aluminium

Drawing or rolling (seamless tube)

Copper

Drawing or rolling (seamless tubing)

Ductile iron

Tungsten

Extrusion

Upto4000mm (l60in)

Cryogenic anrl chemical pipelin es. Stainless steel tubing for d omestic water supplies. plumbing and healiog. Mainly small bore tubes

Marine applications. Specialised hydra ulic systems.

Corros i o n -rc·s i ~lunt.

but

high cost.

Corrosion-resistant. n on-sparki ug mulcrial.

their tubular products pipes, but tubes are mentioned and described where appropriate. There remains one distinction between British and American practice to clarify. In the UK the handling and installation of pipes, performance calculations, etc., embracing the complete system are commonly referred to as pipework, e.g. pipework installations, pipework calculations, etc. In the USA the word 'pipework' does not appear to be accepted and is seldom. if ever. used. In the interest of rationalisation, this handbook uses the single description pipeline. It means the same as pipework. It is to be regretted that similar rationalisation is not possible between British and American and metric units and standards. This leads to differences in values of 'flow loss· coefficients for pipe bends, valves, etc .. the British/ American coefficient being based on m 3 /hat 1 bar pressure loss. Equally, pipe sizes are standard in both millimetre and inch sizes, together with match fittings and valves. There are no exact equivalents. You work in standard manufactured sizes, either in millimetres or inches. To give equivalent sizes in tabular data for either would be meaningless. With rare exceptions. the exact equivalent size is just not obtainable. That is a problem, too, which complicates the presentation of working formulae. We have attempted, within reason. to cover most possibilities in the case of the main formulae for flow-performance calculation in other forms embracing all the units most likely to be used, both in metric and Imperial units. Here. in fact. Imperial units are often less rational than their metric equivalents, with volumes expressed in cubic inches, US gallons. Imperial

Pipes and Pipelines-Definitions and Explanations Sum mary of pipe materia Is-non-meta II ic Corrosion

Mnteri a l

size range

Asbestos cement Clay

50 t o lOSOmm 12 to 42 in)

Concrete

ISO to1950mm Very good in most (6 to 76 io) soil s. Good resistance to sulphate auack and sewer gas.

Spun concrete

Prc-str<'~sed

concrete Pitcb/fibre

Plastic pipes ABS

rcslst~ncc

Very good in most soils. Very good.

Typical applications l3uricd water pipelines and drainnge system~ . Drainage pipelines <~nd ducts.

-

DraJnage pipelines. Sewerage. drainage. etc.

Large water and dr~inage pipelines. Small drainnge pipelines.

l2t o 150mm

Corrosion-free but lower chemical resistance than PVC. Corrosion-frce.

Alternative to PVC where better mechanical pipelines required.

Suitable [or solvent jointing.

Large water and drainage pipelines.

Thermoset material. Also available In other reinforced-plastic miltrix. (RPM) construct.ions. Disadvantage: high cost. Unplasticised PVC. Suitable for solvent welding. Widely avnilablc. Rigid PVC.

Upt o4800mm ( 190 in)

Polyvinyl chloride UPVC

llpt o 1050 m.m (42 iol

Corro sion-free.

General pu rpose pipelines suitable for n wide variety of exterior nnd interior applications.

Polyvinyl chloride CPVC Polypropylene (PPl

Upto 360mm ()4 inl

Corrosion-free.

Cold and hot water services. domestic plumbing. etc.

Upt o )000nun (40 inl [UK sizes up to tnt n] Uplo300mm (12 in)

Similar toPE. but superior for resista J1Ce to detergents.

Applications requiring good combined temperature/pressure pipelines. e.g. efiJuent. pulp mills. etc.

Jligh chemical-

Polypropylene (PVDFl

Upt o f>OOmm

(24 in)

Polytheoc (PEJ (PELl Polythene (PEMJ

Up t o 200mm (8 iJ u lip t o '500 mm (20 In)

Polythenc (PEHl

Up to t800 mm (70 in)

Polythcne

{Jp t o 1200mm (48 in)

(H,\IIW-PEHJ

PEX

Fluoroc;Jrbon (FEP. PFA. I'TI'E)

Brittle mnterial. Normally salt-glazed. Produced in unreinforced and rein forced forms. Smooth. conce ntric bore. Smooth external fioisb. High-density, steelreinforced. Suitable for very la rge diameters.

Ver)' good in most soils. Very good in most soils.

GRP

Polybutylcnc (PBl

Brittle material.

Up t o 3000 m.m (12!liol 50 to 225 mm (2to 9inJ

(lh to(> in)

Polypropylene

Remarks

Subject to embrittlement at low temperatu res.

Copolymer ofPP with bett.er resistance. Fusion-jointed.

Specialised applications: higher resistance. including: St!rvice temperatures thao possible <Jcids. alkalis aod with. other thermoplastic pipes. hydrocarbons. Hot-water applications- suititble Cheaper than PEX. better for temperatures up to llO"C abrasion resistance than (230°F). PEH (particularly at elevated temperatures). Cannot be solvent-welded. Corrosion-free. Agriculture and irri gation. Low-density polythene: l?ressures to 6 bar. Gas distribution. Gener11l purpose Medium-density Corrosion-free. pipelines for exterior and polythene: fusion -jointed ioterior applications. or mechanit·
31

w N "Tj

1::

§. 3

<:">

::s

s

~

Equivalent specifications for stainless and high-resistant steels I

Description

BS970 EN no.

12/1 4% chromium Low carbon

331S42 (56A)

12/ 14% chromium 15% carbon

420S29 (568)

12/ 14% chromium 35%carbon

(560)

18/ 20% chromium 2°/,, nickel

431S29 (57)

18% chromium

I

Swedish

I

AISI type

Avesta

Fagersta

410

393

R.R.J.10

410

393H

420

739H

431

249EH

French Nyby

Sandvikan

Uddeholm

Government

Ugine

Krupps

1410

2.C.27

S/S.1

Z.12.C.13

FIA/ FIB

Vl3F

R.R.J.l1

1415

4.C.27

S/ S.31

FIU12

VSM

R.R.S.72

1435

7.C.27

S/S.6

Z.36.C.13

S12

V3M

4N2C36

S/S.22

Z.15.CN

I

l

430

18% chromium 8 % nickel 0.08% carbon

VIM

I

249

R.R.M.20

1710

I.C. 36

S/S.2 2.C.34

453E

R.R.V.62

27-4

I.R.8

S/S.45

V.2.A. Supra Special V.8.A. Supra Special

F17

I

I

12%chromium 12% nickel

German

18-02

26% chromium 5% nickel 260.<. chromium 5% nickel 1.5% molybdenum

I

I

I 453S

R.R.V.64

27-SMO

I.R.lO

S/S.44

832P

R.R.N.J.39

14-12

2.R.l.

SjS.33

832M

R.l.M.291

18-8EL

O.R.2

S/S.3.M.M.

I

I

(58 0)

I

301Sl5 (58 3 /~J

304

I

I

I

Z.S.CN. 18-08

I

Vl7F Extra

Inoxargent

V. l2.A . Supra

N.S.22.S.

V.2.A. Supra

18%chromium 8% nickel

320S25 (58A)

302

832

18% chromium 8% nickel Free machining

303S21 (58M)

303

832C

I

18% chromium 10% nickel 1.5% molybdenum

I

18%chromiu m 8 % nickel 1.5% molybdenum

I

18% chromium 8/10% nickel 1.5% molybdenum

I

I

18- 08

T

2.R.2.

S/ $.3

2.R.2.A.

S/ S.43

832SV

31SS16 (58H)

832S

R.R.N.J.41

O.R.3

18- 8EMO

I I

V.2.A Norma l

Z.lO.CN. 18- 08

~

I

~

315$16 (58H)

321S12 (58 B)

R.R.N.J.32

S/ S.4.M.M.

'

I

I R.R.N.j.40

1 8- 8 1MO

2.R.3

S/S.4

I 321

8321'

R.R.N.J.51

1 8-81'

I.R.4

S/ S. 53

V.8.A. Normal

I Z. 10 .CNT. 18-08

N.S.2 0C

V.2.A. Extra

l

18% chromium 10/12% nickel 1 % niobium

347S17 (58 G)

347

8321'

17% chromium 20% nickel

254

25% chromium 20% nickel

I R.R.T.80

20-20

310

254E

R.R.T.83

25- 20

316

832SK

R.R.N.J.44

18-20MO

<'>

"' !:)

I.R.41

~

s::... 'i;l

2.R .6.

I

'i:)

-s·

3.R.9.

I

~

S/ S.l5

~

S/ S.2 5

Z.20.CNS 25/ 20

N.$ .30

S/ S.24

Z. 8 .CND. 18-08

N.S.M.C.

N.C.T. 3

"'"' I

t::J

~ ~

18% chromium 10% nickel 2.5% molybdenum

304Sl5 (SSE) I

I

O.R. ll

V.4 .A. Supra

~

c;· ~

"' ::s

!:)

s::...

lt'l ;..:

~

;::;..... c;·

::: !:)

::s

"'

w

w

34

Fundamentals

gallons or barrels, for example, depending on the industry or application involved. In other more specialised cases, solutions and formulae are presented in one set of units only, being those most generally used. or in which the original solutions were derived. In that case conversion tables will be necessary if you want to use these with different units entered. As a final comment here, do remember that g or gravitational acceleration is the same in Imperial or metric units-32 .2ft/s 2 = 9.81 m/s 2 =g. The following table lists ASTM (American) pipe specifications and grades with British Standard equivalents and basic material descriptions.

Pipe specifications: American and British Standards

ASTM A120 A53 Gr.A A53Gr.B Al06 Gr.A AP[ SL Gr. A A106 Gr.B API SLGr.B A333 Gr.l A333Gr.3 A335 Gr.Pl A335 Gr.Pl2 A335 Gr.Pll A335 Gr.P22 A33 5 Gr.PS A335 Gr.P7 A335 Gr.P9 A312 Gr.Tp304 A312 Gr.Tp304L A312 Gr.Tp316 A312 Gr.Tp316L

A312 Gr.Tp321 A312 Gr.Tp347

Material Carbon steel Carbon steel Carbon steel Carbon steel Carbon steel Carbon steel Carbon steel Killed carbon steel 3.5%nickel 1

/.~ %molybdenum

l%Cr 1I 1 %Mo 1 1 I 4 %Cr 1 /2 'Jfo Mo 2 1I 4 %Cr 1% Mo So/oCr 112 % Mo 7%Cr 1h %Mo 9%Crl%Mo Austenitic chromium nickel Austenitic chromium nickel (extra low carbon) Austenitic chromium nickel molybdenum bearing Austenitic chromium nickel molybdenum bearing (extra low carbon) Austenitic chromium nickel titanium stabilised Austenitic chromium nickel niobium stabilised

BS equivalent

1387 3601 / 23 3601127 3602/ 23 3602/ 27 3602127 3602/ 27 3603/ LTSO 3603/ 503LT100 36041240 3604/ 620 3604/621 3604/ 622 36041625 3604/ 62 7 3604/ 629 3605/304Sl8 (ENS8E) 3605/304 Sl4 3605/316 Sl8 (EN58J) 3605/ 316Sl4

36051321 Sl8 (EN58B) 3605/347 Sl8 (EN SSG)

Pipes and Pipelines-Definitions and Explanations

35

British. American and German equivalent steel specifications BS 970

Type or steel

070 M 20

'20' C steel (hot rolled or normalised)

080 M 30

'30'Cstcel

'40" C steel

070M 55

'55' C steel

AIS!

1020

-

Cl020

-·

l03S

Cl030

DIN

Cl035

C22

OS01

C3S

OS03

ClOSS

C4S

--

f-

Cl040

10S5

0402

1-

-

1040

-

Werkstoff

- -

1030

Bright C steel 080 A40

SAE

-

-

0503

C45

0601

C60

-

-

--

S26 M 60

'60' C- Cr steel

5160

51f>O

8161

58 Cr-V4

150M 28

C- Mn steel

30Mn 4

1% Cr steel 1% Cr steel 1'Yo Cr steel 1% Cr steel 1% Cr-Mo steel Cr-Mo steel J% Cr-Mo steel

Cl027 1330 5140 5132 5135 5140 4140 4140 4140

5066

530A40 530 A 32 530 A 36 5301\40 709 fv140 708 M 40 708 A 42

1027 1330 5140 5132 Sl35 5140 4140 4140 4140

7035 7035 7034 703S 7220 7225 7225

41 Cr 4 34 Cr4 37 Cr4 41 Cr4 34 Cr- Mo 4 42 Cr-Mo 4 42 Cr- Mo4

653M3! 817 M 40

3% Ni-Cr steel

5755

22 (31 ) Ni-Cr41

6582

34 Cr-Ni-Mo 6

---

-

1.5% Ni- Cr- Mo steel

4340

Cr-rust-resisting steel

Sl410

-

1-

4340

-

410 s 21

-- 420 s 29

x 20Crn

51420

420

4021

C 20 Cr 13

')1420

420

4034 -- 4024

x 40 Cr l3

6582

34 Cr- Ni- Mo 6

420S37

Cr-rust-resisti ng steel

420545

Cr-rust-resisting steel

420S2l

Cr-rust-resisting steel

-

- f-

5141 (~

416

51416 Se (Sl416 Se)

416Se

-

-Low Ni-Cr Mo steel

-

816 M 40

-

-

4021

51410

--

x 10 Cr 13

4006

-

410

Cr-rust-resisli ng steel

-

410

-

--

-

- -

- --

x 20 Cr 1 ~

f-

-

-

Colour codes for pipeline identification

Originally pipes or sections of pipes were painted in colours for identification. Identification colours are now more commonly applied with bands of self adhesive tapes, with colour-fast resistance to washing down, heat, etc. Colour coding employed in UK practice is based on BS 1710: 1960, BS 1710: 1971 and BS 1710: 1975. British Standard colours are shown with colour specifications in accordance with BS 4800.

36

Fundamentals

BS 1710: 1984 Optional colour code indications for general building services Pipe contents

Water Drinking Cooling (primary) Boiler feed Condensate Chilled Central heating (Ioooc Central heating <100°C Cold down services Hot-water supply Hydraulic power Sea. river, untreated Fire extinguishing Oils Diesel fuel Furnace fuel Lubricating Hydraulic power Transformer Other suggestions Natural gas Compressed air Vacuum Steam Drainage Electrical conduits and ventilation ducts Acid and alkalis

Basic colour

Green Green Green Green Green Green Green Green Green Green Green Brown Brown Brown Brown

Yellow ochre Light blue

Colour code indication

Auxiliary blue White Crimson/ white/ crimson Crimson/ emerald green/crimson White/ emerald green/white Blue/ crimson/blue Crimson/blue/crimson White/blue/white White/crimson/ white Salmon pink Green Red White Brown Emerald green Salmon pink Crimson Yellow Light blue White Silver grey Black Orange Violet

Pipes and Pipelines-Definitions and Explanations

37

Standard service codes Letter symbols are also used to identify pipes and pipelines. fittings. etc. The following summarises British practice. Water (various) Cooling water Hot (domestic) water Steam Treated water Wastewater Boiler-feed water Brine Cold water Mains Down service Drinking Flushing Pressurised Cold-water down supply Chilled water Fire fighting Pire extinguisher Fire hydrant

CLW HWS

s

TvV

ww BFW B

MWS

cws

DWS FWS PWS CWDS CHW

PE FH

Gases Town Oxygen Nitrous oxide

02 N20

Heating Low-pressure water Medium-pressure water High-pressure water

LPHW MPHW HPHW

Valves Air-release Air Auto air Ball Gate Lockshield Non-return Pressure-reduction Safety Sluice Wheel Sewers Foul water Surface water Drains Foul water Surface water Pipes Discharge pipe Rainwater pip<:: Vent pipe Effiuents Foul water Radio-active water Rainwater Surface water

G

ARV AV AAV

BV GV LSV NRV PRY

sv sv

wv FWS

sws

FWD SWD DP RWP

VP FW RAW RW

sw

Fittings Bath Bidet Wash basin Shower Urinal Flushing cistern Sink Drinking fountain Water closet Manholes, etc. Back drop Invert Inspection chamber Manhole Fresh air inlet

b bt wb sh u fc s df we BD

lNV

rc

MH FAI

Position High level Low level Prom below To below Prom above To above Flow Return

HL LL FB TB FA TA F R

Gullies Access Back inlet. Grease trap Road Sealed Yard

AG BIG GT RG SG YG

Miscellaneous Half-round channel Rainwater head Condensate Fuel Vacuum Cold feed Feed and expansion Plug cock Access points Access cover Cleaning eye Dry-weather flow Pire hydrant Compressed air Refrigerants (identified by symbol for particular gas) Draw-off point Open vent Stop cock

HRC RWH

c

F

v CF F&E

PC

A/C CE DWF FH CA Ro DO

ov

sc

38

Fundamentals

Basic identification colours BS 1710: 1984 Pipe contents

Basic colour names

Water Steam Oils-mineral. vegetable or animal; combustible liquids Gases in either gaseous or liquefied condition (except air) Acids and alkalis Air Other liquids Electrical services and ventilation ducts

BS identification colour reference BS 4800

Green Silver grey Brown

lOA03 06 c 39

Yellow ochre

08

c 3.5

Violet Light blue Black Orange

22

c 37

12D45

20 E 51 00£53 06 E 51

Safety colours Red 04 E 53 Yellow 08 E 51 Auxiliary blue 18 E 53

Reference colours (if other than s••fety colours) Crimson Emerald green Salmon pink Yellow Blue

04D45 14E.53

04C 33 10 E 53 18 E 51

SECTION 2 Valve Types Design and Construction

Plug Valves (Cocks) Ball Valves Ball Float Valves Butterfly Valves Rotary Disc/ Rotor Valves Globe Valves Gate Valves Needle Valves Pinch Valves Diaphragm Valves Slide Valves Screw-down Valves Spool Valves Solenoid Valves Swing-Check (Flap) Valves Penstocks Miscellaneous Valves

Plug Valves (Cocks) The description 'plug valve' or 'cock valve' is given to the simplest form of valve comprising a body with a tapered or, less frequently, a parallel seating into which a plug fits. The plug is formed with a through-port. the relative position of the port controlling the amount of opening through the valve (Figure 1). A 90° rotation of the plug fully opens or closes the fluid tlow . Greek and Roman periods saw the development of the plug cock valve and it remained virtually unchanged until the 19th century. The development of the steam engine from the early l Rth century led to further valve improvements including the introduction by Timothy Hackworth of adjustable springs instead of weights to the steam safety valve. The groove-packed plug cock was introduced by Dewarance & Co in 18 7 5, making a valve ·which was easier to operate and more suitable for steam. In 1886, Joseph Hopkinson introduced the parallel slide valve where the sealing of the valve was produced by line pressure on the disc. This system is still manufactured today . Plug cock valves are not as efficient as ball valves and can only operate fully open or closed.

Figure I.

42

Valve Types Design arzd Construction

High-performance pressure-balanced plug valve.

The simple plug valve is generally suitable for low-pressure, low-temperature applications, and can be made in quite large sizes: 250 to 300 mm (10 to 12 in) bore is quite common in some applications. Its main limitation is that if wide variations in fluid temperature are involved, differential expansion is inevitable, leading either to undue stiffness of operation or loss of pressure-tightness. This can be overcome to some extent by employing a packed gland on which the plug rides (Figure 2). The packing is commonly graphited asbestos. In the smaller range, the sleeve-packed cock represents a distinct step forward in cock design (Figure 3 ). Not only does this have a perfectly cylindrical plug, more economical to p~oduce than a tapered one, but the resilience afforded by the asbestos fabric sleeve longitudinally compressed by the two plugs screwed

Figure 2.

Plug Valves(Cocks)

43

Handle Nut Handle Neck Bush Plug _"rl--

Body Eyelet Packing Sleeve Tightening Nut

Figure 3.

into both top and bottom of the body provides for temperature variations and thereby prevents binding. In the UK, the description ' plug valve' is specifically given to a cock which incorporates special design features to reduce the friction between the plug face and the body seat. The plug itself may be tapered or parallel and the movement plain or lubricated (Figure 4). There is also a further variation known as a ball-plug valve. where the plug element is spherical. with circular ports rotating between circular seats of concave section (Figure 5 ). 0

A B C D

Ground-plug cock with nut and washer base. Ground-plug cock gland packed. Groove-packed plug cock with gland and holding-dovm plate. Lubricated-plug cock gland packed.

Figure 4.

Figure S.

44

Valve Types Design and Construction

Plug valves may be further categorised by pattern: Round opening-with rull-bore round ports in both plug and body. Rectangular (rectangular opening) with rectangular or similar shaped ports of substantially full-bore section. (iii) Standard opening-where the area through the valve is less than the area of standard pipe. (i v) Diamond port-where the opening through the valve is diamondshaped. Such valves are also normally of venturi design. (v) Multi-port-with three or more pipe connections. used mainly for transfer or diverting services. (vi) Venturi design-with reduced-area porting (down to 40%) and featuring venturi flow through the body. (vii) Short-with reduced-area ports and/or reduced face-to-face dimensions. (viii) Vertical-with reduced-area seating ports and the plug passages reduced in section to form a throat. (i) (ii)

·l· Pon 2 Positions

T PORT 4 Posrtions

c

Position 1 Pon 'A' feeds both Pons

Position 2 Pon "A' feeds Pon

·c·

Pon

·s· closed

Posllion 3 Pon ·c· fe~s Pon Port 'A' closed

·s· and ·c·

·s· or vice versa

,; A I Posrtron 2 Pon "A' feeds Pon

t~ 'l

·c·

only

Position 4 Pon 'A ' feeds Pon ·s· only Pori ·c· closed

Operation of three-way cocks with 'L' and "f' ports.

3-way2-port

3-way 3-port

4-way 4-port

Examples of nw/ti-porl. arrangemrnts.

Transflo plug

Plug Vnlves(Cocks)

Taper-plug vnll'e (lubricated) 1. Body 2. Plug 3. Lubricant grains 4. Cover 5. Lubricant check valve 6. Gland follo\·ver

Parallel-plug valve 1. Body 2. Bottom cover

Ball-plug valve

3. 4. 5. 6.

3. Seal 4. Bonnet

Plug port Plug Lubricant grains Lubricantscrew

45

1. Body 2. Ball

5. Spundle 6. Handle

Materials

Cocks and plug valves are produced in a variety of metals and plastics and also include lined types. Metals most commonly used are brass, bronze, steel and stainless steel. Basic design proportions

A rectangular- or trapezoid-section port is commonly preferred as this can be accommodated in a plug of smaller diameter than that required for a circular port of the same area. The width of the port is then often made less than half or the bore to provide an effective positive lap for sealing. The length of port is then given by d/2, where dis the pipe diameter. In practice a small addition is usually made to this length to allow for radiusing the corners of the opening. In the case of multi-port cocks or plug valves, negative lap may be called for to ensure that there is no complete shut-off during the transition of ports. This applies particularly when connected to a positive displacement pump (i.e. to prevent the pump pumping against a closed outlet). See also the chapter on Ball Valves. Pressure-balanced taper-plug valves

In larger taper-plug valves. pressure-balanced plugs are fitted for pressure pulsing or very high static pressure applications. \.Vith a non-pressure

46

Valve Types Design and Construction

Figure 6( a). Non-pressure balanced taper plug.

Figure 6( b). Pressure-balanced taper plug.

balanced plug. line pressure in an open valve can find its way into the large end chamber which exists below the plug. Under these conditions a resultant force exists tending to push the plug into its tapered seat with the danger or taper locking causing a seized valve, as shown in Figure 6(a) . This resultant force persists whether the line pressure subsequently remains high or is reduced. The development of an out-of-balance force on the plug is not an inevitable event with ordinary taper-plug valves. as there is normally sealant pressure acting on the small end of the plug. Nevertheless it can occur and can cause valve seizure. With a pressure-balanced valve, the live-line pressure is used to replace sealant pressure by allowing the line to pressurize the small end chamber. A balancing force is produced which prevents taper lock without the need for sealant pressure. Figure 6(b) shows how a more balanced position is reached when line pressure is allowed to equalise the pressure acting on the end of the plug. The pressure-balance system consists of two holes in the plug connecting chambers at each end of the plug with the line pressure. The hole in the small end of the plug contains a non-return valve. This enables sealant pressure to be built up if necessary, while allowing access of the line pressure to the small end chamber. Thus the pressure in the large end chamber always equals line pressure and the pressure in the small end chamber is always equal to. or greater than, the line pressure.

Ball Valves The ball valve, or spherical-plug valve as it is sometimes known. was developed around 19 3 6. although the idea of a ball valve dates back to ancient times. Modern ball valves, depending on type and pressure class, should be designed in conformity with international standards, e.g. BS 53 51. API 60 and AN SIB 16.34. Normally, ball valves have polymer-based seals. Ball valves are among the least expensive but most widely used of all valve types, as well as being available in an extremely wide range of sizes. Basic geometry involves a spherical ball located by two resilient sealing rings in a simple body form (Figure 1 ). The ball has a hole through one axis, connecting inlet to outlet with full-bore flow when aligned with the axis of the valve. Rotating the ball through 90°

A Lypicnl range of ball vnlves.

48

Valve Types Design and Construction

1----- --

£

1

Materials list: No. 1

2 3 4

5 6 7 8 9

10 11 12 13

Part Body

In screwed seat retainer Seat: Ball Stem Stem packing Thrust washer Gland Stem was her Handle nut Handle Handle cover Gasket

Specification ASTM A351-CF8M(3J 6) ASTM A351-CF8l\11(316) R.TFE ASTM A351-CF8M(316) ASTM A276-316 PTFE PTFE AISI 304 AISI 304 AISI 304 AISI 304 Plastic PTFE

Quantity ]

l 2 1 ]

1 1

1 1 l

1 1 1

Figure 1. Standard ball valvt>.

completely closes the flow passage with positive sealing via the sealing rings . Sealing is equally effective in both directions. Body forms and matching ball hole may provide straight-through (full-bore parallel), reduced flow, or venturi flow. Ends can be flanged or threaded . The ball itself may be free floating. in which case the squared oif or splined end of the stem fits into a matching recess in the top of the ball. On larger valves the ball may be trunnion-mounted. Trunnion mounting reduces operating torque to about two-thirds that of the floating ball (Figure 2). Ball valves are produced in top-entry and split-body forms for assembly and for renewal of the seals and ball. They are also produced in multi-port configurations. thus normally requiring a larger size of ball to accommodate multi-port drillings. These ports can be proportioned to give positive lap or negative lap as required (see also Figure 3 ).

Ball Valves

49

Cut-away section ofa rnulti-port valve.

Section view clearly illustrating how a characterised 'V' seat allows for precise flow coni rol in a rnodu/ating ball valve.

50

Valve Types Design and Construction

Plangedfull-bore ball valve.

Figure 2. Trunnion-mounted ball valve.

Full operating movement is 90° rotation of the ba] I. Steps may be incorporated to limit movement of the operating lever. or continuous rotation may be possible. In either case the lever position is in line with the axis of the valve in the open position and at right angles to it in the closed position. Larger ball valves may be operated by handwheels through reduction gearing, or by powered actuators. In all cases opening/ closing torque is low because the only friction forces involved are those of the ball rotating against its seals and the friction offered by the stem gland. The latter can range from 0-rings to glands

Ball Valves

51

3way L-PORT

0

~ ~~i~ ~ Form- /

Form -]

/-'(11111 -.l

0 Form-..J

........_

3way T-PORT

0

~ ~~L~ ~ 0 Form - /

Form-2

,..orm -3

'-----

Form -..J

Figure 3. Three-way ball valve. Oval Handle with Locking Device

Combination of Flexible and Braided Graphite Packing for Flresafe Applications

Predrllled and Tapped Mounting Pads

Double-Sealed End Plug

BlowoutProof Stem

Low-Friction Engineered Seat Design

Positive-Stop End Piece

One-piece ( unibody) ball valve.

fitted with die-formed packing rings. In some ball valves the ball is held against the seat by the cam action of a specially shaped stem. By turning the valve hand wheel the ball is pulled away from th e seat before being rotated . A precision spira l groove turns the stem and ball 90°, without ball-to-seat friction. to full-straight through-flow when open. The reverse action lowers the stem, turning the ball to the closed position, and the final hand·w heel turn tilts the ball and mechani cally wedges it against the seat to seal the valve closed.

52

Valve Types Design and Constmction

Predrilled and Tapped Mounting Pads

Split-Body Construction

Full-Bore Design

Low-Friction Engineered Seat Design Graded Body Bolts and Nuts

Two-piece (split body) jla11ged ball valve.

Full-port iligh-prc>ssure ball valve.

Historically. ball valves have been produced with soft, not metal seats because generally soft seats have covered most applications satisfactorily. Many valves of this type have seals made from PTFE, compounded with graphite, glass or steel powder to improve the material properties. However, abrasive media, high pressures and high temperatures can severely stress the polymeric seals normally used and lead to damage (Figure 4).

Ball Valves

53

Figure 4. Tllis ball was taken from a valve that had seen 3 years service in a ce111ent works. The polymer sea/in{] rings /rave been destroyed. tire /mil and the body srverely da111aged. Nletal/ic seals can prevent such problen1s.

For nominal diameters of# DN 50 PTFE. seals can only be loaded to a full pressure ofPNl 00 up to a temperature of approximately 1 00°C; with nominal diameters above DN80. the operating pressure is limited to 50 bar. Only gradual improvements can be made if highly resistant polymers such as POM are used. Upper temperature limits are 2 50°C with huge restrictions on pressure/ load capacity. Metal-seated ball valves

Metal-seated ball valves first came to prominence in the 1960s. They offer a number of advantages including: tight shut-off, smooth control, no jamming, low torque, wide temperature range, good corrosion and wear resistance and stability under pressure. The greatest risk to metal-seated ball valves is posed by corrosion through pitting, fretting corrosion. intercrysta lline corrosion and stress corrosion cracking. Media that contain even low quantities of aggressive substances are capable of causing corrosion. Metal seals do not bed in as easily as soft seals under pressure. It is therefore important for the ball and sealing rings to be machined precisely and have both hard- and low-friction coatings appJied to the base material.

54

Valve Types Design and Construction

Ball valves with metallic seals are suitable for use in high-solids abrasive media. for /Jigh nnd low temperatures,for extreme operating pressures. and for frequent operation. Even with critical media. they can be used for flow regulation. This pneumatically-activatPCI ball valve is an ideal con1ponent for increasing plant safety. In the event offailure of the compressed-air supply Llze spring-loaded. pnwmatic drive closes the valve autonzatical/y, rapidly and reliably.

Metallic seats tend to employ both nickel- and cobalt-based alloys and elements such as chrome and tungsten. However, the trend appears to be towards the use of different surface coatings for ball and sealing rings and choosing between them to suit the various circumstances. With the seat-supported ball valve (Figure 5). the valve seals on the downstream side. The upstream pressure pushes the ball against the downstream seat. closing it tightly. In the trunnion-mounted ball valve with a bellows seat (Figure 6), the valve seals on the upstream side. The internal pressure expands the bellows axially , pushing the seat against the ball. The seat is pressure-assisted and springenergised. The bellows seat acts as the seating component. This type of ball valve is suitable for the most demanding on-off services. The special control seat shown in Figure 7 works like a normal pressureassisted seat in trunnion-mounted ball valves. The upstream pressure is led through the hole behind the seat, pushing it against the ball. The seat is spring-energised to ensure low-pressure tightness. In control. the high-velocity flow passes through the restriction point of the partly open

Ball Valves

55

Back seal

Ball

Valve body

.

+-------_J Figure S. The metal seating principle in a typical seat-supported ball valve.

I

Ball

I

+---1- __

Seat ring

_ _ 1-----· _

_

--t-

va_lv_e_b_od: _ _ _

Bellows

Figure 6. Th e !Jellows seat for a typical trunnion-mounted ball valve.

valve. The high velocity creates low pressure, which is led behind the ball seat through the hole located in the vena contracta. The seat will thus be unloaded. The sealing principle of the floating-ball valve example shown in Figure 8 is effected at the downstream seat where the baH is pressed against the opposite seat by the medium pressure. In doing so the seat rings have a double function. They seal off and at the same time serve as a bearing. The seal at the upstream seat can be relieved in order to avoid a build-up of pressure. The sealing principle of the fixed-ball valve example shown in Figure 9 is one where the sealing is effected at the upstream seat where the springsupported seat is pressed against the fixed ball by the medium pressure. The ball itself can be fixed by bearing pads in the body, by trunnions or by bearing stems. A pressure build-up is prevented by the spring-supported seats in connection with the fixed ball . To summarise, effective sealing depends on: • • • •

the contact pressure the contact surface or the seat the accuracy of the surrace finish on the ball and ball seat the sealing design and the sealing material

56

Valve Types Design and Construction

\

- - - .L.:--

....._____ _ _

~

---

In control

Pvc< P2

P1 Back seal

r,

Flow

port

Seat nrtg

Body cavity

__P - =2 l_ T1ght shut-off

Figure 7. The special control sent.

clown-stre;"n

up-stre<J n>

Figure 8. The sealing principle of tile floating ball.

Ba//Valves

Lantern Ring

57

Gland plate loaded by self-compensating ...------- disc springs Stacked chevron packing stem

Purg-¥roonitoring port ---~

Diagram showing tire dual-stem sealing arrangement in a high-integrity ball valve.

down-stream

up-stream

Figure 9. Tl1e sraling principle of thefixed ball.

Generally, ball valves are sealed by applying a load to a soft seating material between the valve body and ball to create localised yielding. Seals of plastic material usually depend on localised yield to achieve bubbletight sealing. The problem with a jam seat is that increasing the shut-off pressure can increase plastic deformation. As long as pressure remains at a

58

Valve Types Design and Construction

high level this is not a problem; leakage may occur if the shut-off pressure is decreased. A jam seat has no pressure compensation. Another area to consider about jam seats is temperature swings. With increasing temperatures, metallic ball and valve casings expand. PTFE valve seats expand at a much higher rate and if the temperature change is high enough, the jam seat will tend to generate a 'self stress' above its yield strength and deform plastically beyond its initial state. When the valve is cooled, shrinkage of the additionaJly deformed seat may result in leakage. A possible way of overcoming this is to employ valves with flexible lip seats (Figure 1 0) or seats that incorporate a separate double block and bleed design. Another aspect to consider with soft-seated ball valves is built-in body-cavity pressure relief. Ordinary water trapped in a valve cavity without air will increase in pressure by about 100 lb/ in 2 . The pressure/ temperature relationships of most common liquids are in the orderof90-110 lb/in2 per°F (11.2-13 . 7 bar per °C). The cavity area created by the two soft seats of a ball valve is a typical area for pressure increases. While the valve is open, any pressure in the cavity zone created by the ball. seat and body can be vented via a hole from the bottom of the stem slot to the ball waterway. In the closed position, relieving cavity pressure is more difficult. Some valves have a vent hole in the ball. Cavity-pressure increases derive from the differential thermal expansion rates of incompressible fluids and typically a venting of one hundredth of a cc of trapped liquid will bring cavity pressure back to normal. The key to ball-valve performance is the sealing (seating) structure. regardless of whether the seats are metal or plastic. Pressure-temperature ratings

The pressure-temperature ratings of soft-seated ball valves are determined not only by the valve body materials, but also by the sealing material used for ball seats. Sealing materials for seats may be PTFE, lS'.Yo or 25% glass-filled PTFE, FPM, Celastic, N.R.G., POM, Lyton and steel. New and improved polymers are being developed all the time for coating and sealing and the use of ceramics is becoming widespread. It is very difficult to pre-determine exact pressure-temperature ratings for all kinds of media under all imaginable conditions. The chart shown in Figure 11 gives a typical general overview. Pressure-temperature seat ratings indicated by the solid lines on the chart are based on differential pressure with the ball in fully-closed position and refer only to seats. The dotted lines indicate the maximum working pressures for carbon-steel valve bodies made from TstE 3 5 SN (equal to ASTM A3 50 LF2). For ratings of other body materials refer to ANSI B 16.34. Pressure-temperature seat ratings for metal-seated valves are the same as the body ratings.

Ball Valves

59

16 9 15

16

~50

®-

e-

g.-

2

70

18

~ 7

~- · , 0 :25

(SOCKET WELD 0~ BUTTWELD ONLY)

6

2

Standard parts list Body material

Item no. Part name Carbon steel

Stainless steel ASTM A812 F 3 16. ASTM A351 CP8M orBS970S316 ASTMA812F316L ASTM t\351 CF8M/CF3 M orBS970S316

1

Body

ASTM Al05N. ASTM A216 WCB (0.25 % C Max) or BS970 070 M20

2

Body cap

ASTM A105N. ASTM A216 WCB (0.2 5% C Mac) or BS970 070 M20

3 4 5 6 7 8 9

15 16 18 19

Ba ll Stem Seat Body seal Gland packing Stem-thrust bearing Stem-tab washer Stem-thrust seal Handle Stem nut Gland Nut

20

Body bolt/stud

316 stainless steel 316 stainless steel or 17-4 PH stainless steel PTFE (1'). filled PTFE (M) or acetal resin (R) (Delrio"') Spiral-wound 316 sta inless steel and graphite PTFE Cnrbon-filled PTFE or acetal resin Stainles~ steel Graphite Stainless steel with PVC sleeve 316 stain less steel 316 stai nless steel ASTM A 194 grade 2!-l ASTM Al94 grade 8B. 8Cb. 8TB or ASTM Al94 grade 2HM. 7M or ASTM A453 grade 660 ASTM A 193 grade B7 ASTM A 19 3 grade B8 . B8 C. B8T or ASTM A 193 grade B7M. L7M class 2 o r ASTM A45 3 grade 660

25 29 30 50 70

Weld warning tag ldenlification plate Drive pin Stem-tab washer Anti-static spring

13

Sta in less steel Stainless steel Stainle~s steel Stainless steel

Figure 10. Soft-seated ball valve, exploded view.

60

Valve Types Design and Construction

3600

250

psi

bar

2880

200

----ANSI C L 1500 body rating

-- -- -- -POM

w

a:

::J (/)

- - - -

(/)

ANSI CL 900 body rat1ng

w

2160 a: Q. 150 _j

~

i=

z

LU

----

a:

w

ANSI CL 600 body rating

u. u.

1440 i5 100

ON 50

-- - ANSI CL 300 body ra11ng

720

50

275

20

ANSI CL 150 body rilt,ng

-50 - 58

0

32

50 120

100 '

150

200

:?!iO C

21?.

302

392

<1fl2 f·

I CMPERATURE

Figure 11. Pressure-temperature ratings.

Flow data

Typical flow data is shown in Table l. The flow rates were determined for ball valves in fully-open position and a water temperature of l5 °C (59 °F). Typical major application areas for ball valves include: Refineries • shut-off and isolation valves for tower bottom lines and thermal-cracking units with coke problems • gas/oil separation • gas distribution includin g measuring, metering and pressure regulation stations • controlling oil loading • pumping and compressor stations • emergency shut-down • refining units

Bn/IValves

61

Table 1. Flow data

Full bore Nominal flow rate Nominal size

Cv US gallons per min

19.4 45 .6 71.5 170 275 905 1414 3674 7155 12,500 20.780 3 7.000 70.700

22.6 53.2 83.4 198 321 1056 1650 4288 8350 14,590 24,250 43.100 82.500

in

mm

15x15x 15 20 x 20 x 20 25 x 25x25 40 x 40 x 40 50x50x50 80x80x80 lOO x lOO x lOO 150 x 150 x l50 200 x 200 x200 250 x 250 x 250 300 x 300 x 300 400 x 400x400 SOOxSOOxSOO

Kv m 3/ h

l / 2 x l /2x l /2 ~ / 4 x 3/4x 3/4 lxl x l ll / 2 x ll/2xl1/2 2x2 x 2 3x3x3 4 x 4 x4 6x 6x6 8x8 x S lO x lO x 10 12 x 12x 12 16x1ox16 20 x 20x20

Reduced bore Nominal flow rate Nominal size mm

20 x l 5x 20 25 x20x25 40 x 32 x 40 50x40 x 50 80x65 x 80 100 x 80 x 100 150 x l00 x l50 200 x 150 x 200 250 x 200 x 250 300x250 x 300 4()() X 3()() X 4()0 S00x400x 500

m 3 /h

Cv US gallons per min

14.3 40.1 89.8 146 484 800 728 3.5 77 6933 11.392 1600 33 ,333

16.7 46.8 105 170 564 934 850 4175 8090 ] 3,294 1.8.672 38.900

Kv in

3/4 X l/2 X 3/4 1x3/4xl 11/2x11/ 4 x 11/ 2 2 x 11/ 2 x 2 3 x 2 l / 2x3 4 x 3x4 6x4 x 6 8x6x8 10 x 8 x l0 12 x l0 x12 16x12 x l6 20xl6 x20 --

Kv value is the full-capacity flow rate through the ball valve in cubic metres per hour (m 3/ h) with a pressure drop ofl bar. Cv value is the full-capacity flow rate through the ball valve in US gallons/min of water at 60°F with a pressure drop ofl psi.

62

Valve Types Design and Construction

Chemical and petrochemical complexes • low differential pressure control • emission control • handling highly viscous fluids. abrasive slurries or corrosives as well as non-corrosives in processes and storing facilities Power industry • boiler feed water control • control and shut-off for steam • burner trip valves • sluicing valves for feeding coal into pressurised combustors and for extracting fly ash Gas and oil production • subsea isolation and shut-down • well-head isolation • pipeline surge control • secondary and enhanced oil recovery • processing separation • transmission and distribution • storage Pulp and paper industry • pulp mill digesters • shut-off valves • batch-digester blow service • liquor fill and circulation • lime mud (slurry) flow control • dilution water control Other common areas for the application of ball valves include: food industry. water supply and transport, marine and solids transport.

Ball Float Valves The typical ball float valve consists of a control valve of the piston and disc-type operated by a floating ball and lever mechanism adjusted to open the valve at a predetermined liquid level. It is thus essentially a level-control valve and is used mainly for controlling the supply of make-up water (e.g. in cisterns. \1\rater tanks, etc.) The most effective type is the equilibrium ball float valve (Figure 1). so called because the upward and downward pressure forces are nearly balanced out (leaving just enough unbalance to eliminate hunting). The basic type finds widespread application. The body is usually of angle pattern with the inlet flanged and bolted to the inlet pipe flange with the tank wall sandwiched between. Design geometry calculation

Design geometry calculations for ball float valves can be tedious. As far as fluid forces are concerned there is an upward force at the valve position due to mains pressure tending to force the float downwards, which will normally be resisted by the displacement force generated by the float under equilibrium conditions (Figure 2 ). These equilibrium conditions correspond to the valve being held closed by a surplus of 'displacement' force. (In the event of the water level falling , of course, the valve will open to allow inflow of water until equilibrium conditions are restored.)

A typical ball float valve.

64

Valve Types Design and Construction

140

I I

130

I

120

I I

110

I

I

100

1 1 I

90 L

.c:::.

80

~ 70 I

(l)

E' 60 ro

800

1 700 600

.~ 50

500

0

/

40

/

/ 400

~~

r

300

~

/ 200

/

I

l

I

/

/

/

30

~

/

,/

~

100

10 0

.,../

I

.c.

20

I

I

900

50

65

80

100

12 5

150

200

(7)

(9")

250

300

Valve inlet bore

Headloss approximately l. 5 m angular and 4. 5 m straight t·hrough.

Typical ballfloat valve capacity chart.

Specifically, the valve force (V F) effective at the ball is given by:

Vr

= 0.7854 PN x d 2 2 L

-

d

1

2

where P N L d1 d2

= supply water pressure = fulcrum, distance from valve

= fulcrum, distance from ball float = outside diameter of valve-sealing face = diameter of valve piston.

The displacement force (Of) is governed by the volume of the ball float (or diameter in the usual case of a circular float) and its depth of immersion. It is usual in the case of spherical-ball floats to design for socyo immersion, when :

Dp

=

0.01 D3 (to a close approximation)

where Dis the float diameter.

Ball Float Valves

F

65

dia H x L length

~

G To top w~t~ \~vel TWL

K

C

Approx float trav•l

B A

ftem description

l Body (beaded outlet) 2 Body (flanged outlet) 3 Cover 4 Fulcrum and retaining r ing

5 Valve 6 Keep plate 7 Split pins and washers

8 Nut 9 10 ll 12 l3 14 15 16 17 18 19

20 21 22 23

Pins to links Pins to fulcrum Spindle Links Liner Winged-valve plate Seat ring Keep ring Lever Studsandnuts Cup washers Cover joint Body joint Seat \-\'as her Float

Figure I. Angular-pattem ballfloat valve.

Thus the basic relationship is modified by: (i)

(ii)

The necessity of maintaining a positive closing force on the valve for fluid tightness. An empirical figure here is to make Dp equal to 1.2 5 x VF· Additional movements introduced by the weight of the lever on both sides of the fulcrum or pivot point and the weight of the float. These can be calculated or eliminated by counterbalancing.

66

Valve Types Design and Construction

N

L

Figure 2. Ball float valve displacement force generated by the float.

(iii) Frictional resistance of the pivot and rising part(s) of the valve. This

will call for an additional increase in displacement force. i.e. float size. It is difficult to establish required values except on empirical lines as frictional forces may be subject to change with age.

It may be further necessary to evaluate the displacement force with the float fully submerged (when OF= 0.02 D3 ) and the resulting loading on the fulcrum pin. Design should allow adequate sheer strength on the pin to allow for this contingency, particularly in ball float systems used with level controls in large tanks and/ or inaccessible positions.

Butterfly Valves Since it was first introduced well over one hundred years ago, the butterfly valve has come through many development stages to become one of the most successful high-performance valves in use today. The first butterfly valve was used by James Watt, the Scottish engineer, for his steam engine. It was also used in the Mercedes motor car in 1901 for the fuel intake linked to the accelerator pedal. Initially, butterfly valves were limited to low pressure drop applications and sizes that were about six inches or more. They also tended not to seal too well.

Butterfly valves for ir1dustrial applications.

68

Valve Types Df.sign and Construction

In basic terms, a butterfly valve uses a flat disc in which the closure device rotates about an axis regulating the flm.v of liquids with off-centre or in-line sealing. Smaller sizes usually have manual operation, but much larger devices such as penstock control valves are usually motorised. Butterfly valves can offer attractive cost savings and operating benefits over conventional globe valves. With high flow capacities, butterfly valves enable the use of smaller units ·which reduces cost, weight and space requirements. With only two wetted parts and a range of valve linings, butterfly valves isolate the body from the media, thus eliminating the need for expensive exotic materials. The smooth contoured, crevice-free disc produces lower torques. while the butterfly valve design makes it easy to install, maintain and service. The two main groupings are general purpose butterfly valves and highperformance butterfly valves. Butterfly valves have the disadvantage that they restrict the flow through the pipe and solids catching on the disc can cause a blockage or prevent the valve from closing. Butterfly valves are used in high-temperature, high-pressure applications or those involving toxic or corrosive fluids. Modern butterfly valves are normally of wafer design , fitting

Butterfly valvef or the che111ical industry .

Butterfly Valves

69

directly between pipeline flanges. Double-eccentric (offset) design butterfly valves have the sealing plane of the disc offset from the axis of rotation to create an interrupted sealing surface and the axis of the disc is laterally displaced from the true centre of the disc so that the disc will 'cam' away from the seat as the valve is cycled open. Butterfly valve movement is simple and straightforward . requiring only 90° rotation of the butterfly for full movement (or somewhat less in most designs) . The main technologically significant features of a butterfly valve are the designs of the disc and the seat. Nearly all modern high-performance butterfly valves incorporate some form of double-offset design as previously described. The two offsets in a typical butterfly disc are shown in Figure 1. Body construction is normally cast iron, ductile iron, cast steel, bronze and epoxy. Various other materials may be used depending on size and application. vVelded materials (e.g. steel, stainless steel and titanium) may be used for certain valves and in particular where percolation of gases through cast components is to be prevented. Discs are also usually of cast iron, although again alternative materials may be specified for particular services. Profile shapes vary, most having some form of convex streamline shape to minimise head loss. Valve seats

The seat (closure member) of the butterfly valve is an area where there are as many designs as there are manufacturers of butterfly valves. A single-piece

First o ffset

Sealing plane

Shaft cente rline

Figure 1. The two offsets in a butterfly disc.

Second offset

70

Valve Types Design and Construction

Butterfly valve for tile water industry.

Pressure

Insert

Disc

Body

Seat

C learance for flex1bility

Figure 2. Wafer-sphere sealing principle with tlzr disc downstremn of the seat.

Butterfly Valves

Insert Clearance for flexibility

Disc L - - - 1 ' - - --

Seat suppor1ed by insert

Body

t t t t Pressure

Figure 3. Wafer-sphere sealing principle with tfle seat downstream of the disc.

o-9

9-s

I Body cartridges 2 Top adaptor 3 Seat 4 Disc/Stem 5 Centre bush 6 Top bush 7 Bottom bush

8 Plus 9 '0-ring' 10 Body securing screws 11 Top adaptor securing screws 12 Notch plate 13 Lever 14 Notch plate fixings

Figure4. A wafer-type butterfly valve.

71

72

Valve Types Design and Construction

flexible PTFE seat has proved to be a popular choice, with thick cross-sections throughout the seat. pre-compression of the seat for low-pressure sealing and clearances surrounding the seat to allow flexibility . The significance of the single-piece seat is that there are no 0-rings or metallic springs to limit the temperature or corrosive conditions that the PTFE seat can be exposed to. A typical example of PTFE seat design is shown in Figure 2 where the disc is downstream of the seat. As line pressure is applied. the full cross-section of the seat is pressurised . which causes the seat to follow the natural deflections of the disc under pressure. Pressure activation of the seat enhances sealing with increasing line pressure. despite the fact that the disc is moving away from the seat due to the same pressure. With the flow in the opposite direction, with the seat downstream of the disc, the seat is supported by the seat retainer (Figure 3). The disc is deflected by pressure into the seat. enhancing the sealing as the pressure increases. A wafer-type butterfly valve is shown in Figure 4 . Typically the valve consists of a stainless steel disc/ stem in a polymer seat. fastened by two half-body cartridges. This particular valve has three side thrust-absorbing bushes, one top and bottom and one directly above the seat with a secondary 0-ring sea t adjacent.

Elastomer-lined centred-disc buttrr!ly valvP for water supply.

Buue~{ly

Valves

73

Fully rubber-lined butterfly valves , similar to the type shown in Figure 5, incorporate a rubber lining that is bonded and integral with the valve body. The main advantage here is that there is little or no deformation of the lining or corrosion to the body. Ebonite-lined butterfly valves are designed for use in systems which carry seawater and other moderately aggressive liquids. Ebonite is a hard natural or synthetic rubber. Ceramic- and fluoropolymer-lined valves are gaining in popularity for controlling highly corrosive and abrasive liquids, gases, slurries and powders. Another basic arrangement is a corrosion-resistant seat (e.g. bronze or stainless steel), into which a continuous rubber-ring seal is fitted. Others include flexible metal-seal rings (for high-temperature services) (Figure 6). Detail design may provide automatic adjustment to any eccentric motion of the disc and/ or automatic compensation for seal wear. Drop-tight closure of

Shof1 SQuiJre

Topflongc ISO 52 11

Shah (ccnccn1uc)

C:enHtC Vi)iVO diSC

VnlvR

Figure 5. Fully rubber-lined butterfly valve.

74

Valve Types Design and Construction

any butterfly valve is normal and can be retained for a considerable time before seal replacement is necessary. Metal seats in butterfly valves have particular advantages and should incorporate the following: • • • • • • • •

good tightness-to ANSI B 16.104 Class V and higher nojamming smooth control-low- and constant-friction load in the control position low torque high cycle service wide temperature range good corrosion resistance low cavity relief

The metal-to-metal seated valve shown in Figure 7 is designed for bi-directional zero-leakage service. A double-offset (eccentric) shaft together with an offset conical seat achieves the 'camming' action of the disc into the seat. This keeps the sealing ring clear of the seat except in the final shut-off position and provides for non-rubbing rotation.

SEATING PRINCIPLE The d1s~ of the valve IS rnach1ned to close tolerances to (.reate an elhpt•cal shapr ~lm~<ar lo an oblique slice ldken ffom a sol;d metal conc. \Nhen the v~lve s closed, the elhpt1cal d1sc at the maJOr ax1s d S· places the sea: nng outwdrd. causu1~ trc seal nng to ronldct the disc at the minor ax1s. \J\Ihen the v;
Figure 6. Metal-seated wafer-type lmtLcrfly valve.

Butterfly Valves

75

ENLARGED VIEW OF SEAT RING AREA

TOP OF OIS( PATH Of DOOR

STAINUII ITHL \(AIRING

ITAIHUIIITEH

/

/

Uii'I
Stainless steel-seated butterfly valve.

The cone angle allows the seal ring to touch the seat ·with a contact angle that is uniform and allows a slight amount of wedging. This type of valve is particularly suited for process and steam duties from cryogenic to high-temperature applications. Another novel butterfly valve is shown in Figure 8. This valve is designed specifically for dry solids processing. The valve has an inflatable seat that has only 'casual' contact with the valve disc during opening and closing. In operation. air and electric controls operate the valve. They automatically inflate and deflate the seat. allowing a single control input to operate the valve. When supplied with air, the control assembly moves the disc to the closed position and then automatically inflates the seat. When the control signal is received, the seat is instantly deflated and the valve disc moves to the open position. When the control signal is dropped, the assembly returns the disc to the closed position and automatically inflates the seat (Figure 9).

76

Valve Types Design and Construction

Actuation

All types of control mechanisms can be used to operate butterfly valvesmanual by lever or handwheel with reduction gear, electrical by actuator or reduction gear. hydraulic actuator or pneumatic actuator. Choice largely

Offset 1 Achu:ved by placlJJg the >haft bchrnd the ccntnlinc of the >o.:a.lrng

surface

Offset 2 Achieved by placing the shaft off.<et 10 on<..: side of tht: pipe :Lnd valve cenrerline ('he purpose of theM: offsets is to reduce

ruhbing bctwn:n scat

~mel ~cal

during

vai\'C travel.

Offset 3 Pro,•itk~

the

~cornetry

to disengage the scJt

ami seJ l U>Olpk:tcly upon any valve: travel. The unique combination of these: offsets

allows caroming, and completely eliminates

ruhhing. An)' chances of associated wear and lca.k:lge bet wecn thc scat and disc-mounted seal ring during tr:wcl are non-existent

Figure 7. Triple-offset metal-seat butterfly valve.

Butterfly Valves

77

depends on the size of the valve and the specific application. Special control systems can also be used for automatic closing, e.g. see Table 1. Fieldbus control

Butterfly valves have now become a viable alternative to conventional control valves due to development in sophisticated controls instrumentation and communications technology. A major milestone in flow control is the introduction of fi.eldbus control systems. Fieldbus systems take advantage of developments in low-cost microchip technology, allowing intelligence to be built into each device in the loop. Each device communicates via a protocol developed for rapid control information, with the ability to adjust a valve's position and enable the speed of the valve stroke to be altered using programmable, menu-driven communications devices.

Closed

Closed, inflated

Open, deflated Figure 8.

Figure 9.

Valve Types Design and Construction

78

The diagnostic role of a field bus system means it can give advance warning of potential problem areas so that corrective action can be taken. This instrumentation technology has resulted in a new breed of valve controls instrumentation. See also the chapter on Valve Actuators. Inherent flow characteristic

The inherent flow characteristic of a valve has been defined so as to keep the differential pressure across the valve constant. When the differential pressure across the valve is constant, the flow rate (q) through the valve is proportional to the valve flow coefficient (Cv). Because the valve flow coefficient (Cv) reflects the effective flow cross-section of the valve, the valve inherent flow characteristic

Table 1. Selection table for automatic-closing butterfly valves

No Is power available? ... During emergency closing? ... Any voluntary remote control?

--

Yes -

1-

·--~

'--

__i l -~-- i

•

Electrically motorised valve

--

--

Hydraulic jack Counterweight

<1)

u

·:;

Oleopneumatic accumulator

-

• • ----

- --

--

• • • • • • •- • • - - --

-

<1)

'"0

0!-.< ....,

c 0 u

Mechanical locking Manual resetting Automatic resetting

• •

• • • • • • •

Automatic leakage recovery Motorised pump Hand pump

o..... -roc !-.<

COil

u0 ·-rn

Defect transmission Mechanica L Electrical Optional Electrical remote control

•

•

•

•

•

• • • -• • • • • •

Butterfly Valves

79

shows how the effective flow cross-section changes as a function of the relative travel (h). Figure 10 shows the most common valve inherent flow characteristics as a function of the relative flow coefficient (N) and the relative travel (h). Valve sizing

The size of butterfly valves to be used for control purposes should not be dictated by the nominal diameter of the pipe, but should be calculated on the basis of the operating characteristics in order to achieve the correct control characteristics. To determine the size of a control valve, the opening angle characteristics need to be considered. Typically, some butterfly valves are designed with approximately equal percentage characteristics over an opening of 60°. The example in Figure 11 shows how to calculate the Kv (flow coefficient) from liquids and gases. Pressure/temperature ratings

The maximum working capability of a valve is either the body rating or the seat shut-off capability, whichever is the lower.

1.0

0.9 0.8 0.7 -&

c


0.6

2

/]

0 ;..=

Qj 0 v

0.5

3 _g 0.4
>

"_.3

"'

Qi 0:::

/

0.3 0.2

4

0.1

0 ~~=-~~~~~~~----~----~ 0

0.1

0.2

0.3

04

0.5

0.6

0.7

0.8

0.9

1.0

Relative travel h 1 quick opening 2 linear(~= h)

3 equal percentage 4 hyperbolic

(~=

4>o • exp (c*h))

Figure 10. Valve inherent flow characteristics.

1 ...

METHOD

I

co

0 Where

Calculate the Kv ( flow coefficient) from:


Kv =

a) Liquids

I

a

Kv = Flow coeffic ient (Metric Units) Cv = Flow co eff icient (Imperial Units) Q = Max. Flow volume in m3/ h = Specific weight in Kg/dm3 y F = Cross sec tion of pipe in cm2 6p = Pressure drop in bar Vn = Max flow volume in Nm3/h G = Specific weight in Kg/Nm3 T = Absolute Temperature in oK P1 Absolute pressure upstream in bar P2 Absolute pressure downstream in bar

y

6p Liquid sizing formula is o nly applicable for subcritica l f low

51';) ~ p.P2

I

50 65 80 100 125 150 200 250 300 350 400 4 50 500

of pipe in <m2

19.6 33.2

50. 3 78.5 123 177 31'491 707 962 1257 1590 1963

6~ '-- ~2_7 -

Kv

111 170 256 470 96 1 1666 2777 4273 6L.l0 85lo7 10 683 14957 18803 ]_2 393 1

90'

Cv

Kv

130 19 8

299 548 112 1 1944 32L.O 4986 7Lo80 9973 12466 17453 21940 27924

89 136 205 405 854 141 0 .2329 3675 5170 6923 9230 11965 14957 20512

so•

Cv

10lo 159 239 473 996 16lo5 2718 4288 6033 8078 10770 13961 17453 28955

"'""\::l

"'""

~·

;::,

:::

J::l.. (J 0

:::

"':;;::..........,

"'c;·...... :::!

Having calculated the Kv, the figure obtained should be compared with these below and the normal diameter determined.

Gas formul a o nly applicable 1f the r atiO :\p to P 1 (ups tream pressure absolute) is less than 0. 10

Cross- sec[ion

ON

">::::

= =

Kv=Vn_~

b) Gases

~

'-3 t!::

O pening Ang le

Kv

75'

Cv

76 89 111 130 175 20Lo 34 1 398 709 an 11 53 13'•5 1880 2194 3076 3589 4273 4986 5726 6681 7692 8975 10256 11967 12820 14959 17521 204lo5

Kv

70'

Cv

Kv

45 59 69 104 I 70 89 106 136 159 260 303 200 534 418 623 880 1027 683 1111 1495 1744 183 7 2350 2742 3L.61 4039 2649 4358 5085 3504 43 58 5555 6482 7863 91 75 6068 9829 11469 74 35 14 102 16455 1 100L.2

60'

Cv

Kv

53 82

12lo 233 488 797 1296 21 44 3091 4089 5085 708 1 8676 16455

50'

40'

Cv

Kv

23

27

35 53 102 213 350 598 982 1367 1880 2264 3162 3931 5213

41 62 119 249 408

1lo 22

16 26

32

37

62 132 2 13 358 572 854 1111 1452 1965 2393 3247

72 15lo 249 1< 18 667 996 1296 1694 2293 2792 3789

698 11 46 1595 2194 2642 3690 458 7 6083

Figw·e 11. Example methodjor calcu latingflow coefficients Kv!Cv.

Cv

Kv 7

12 18 35 75 123 213 333 470

30'

25'

Cv

Kv

8 14 21

8

9

12 23 51 83 145 222 324 lo27 555 769 961 1282

14 27 60 97 169 259 378 498 6lo8 897 11 21 1496

lol

88 144 249 389 S lo B

748 6-41 769 897 1068 1246 1367 1595 1880 2194

s

Cv

6 !

Butterfly Valves

81

Ceramic-lined butterfly valves have provided a long-term, low-maintenance solution to controlling abrasive and acidic titanium dioxide slurry flows.

High-performance butterfly valve.

82

Valve Types Design and Construction

In Figure 12 the seat ratings shown are based on data from API 609 and the body ratings shown are from ANSI B16.5/BS 1560 part 2. Butterfly check valves

Butterfly check valves differ from conventional butterfly valves in employing a hinged instead of a pivoted disc, with a sealing ring around the edge of the disc (Figure 13). With forward flow, the two halves of the disc are swung together to trail downstream. With reverse flow, the two halves open to approximately 45° each, sealing the bore. With this mode of working, a butterfly check valve is, in fact, another form of flap valve. It has the advantage of rapid action with a resilient seal. Butterfly check valves (Figure 14) require only a short length of body which can virtually be a length of standard pipe flanged at both ends (or threaded or plain ends in smaller sizes). It is also produced in wafer form for clamping between two pipe flanges . In this case the body length only needs to be sufficient to accommodate the hinge post and the two valve plates in their closed position.

ANSI 300, CARBON STEEL

ANSI 300.3 16 SS

SOOPSI

a

V3 c.. "-' <1)

..... :::1

400PSI

"'"'..... <1)

c..

_Body and Metal Seat Rat1ngs

300PSI

-Soft Seat Rat1ngs

200PSI

lOOPS!

300°F

tsooc

400"F

SOOoF

600"F

700oF

800"F

200°C

260°C

315°C

370°C

400°C

Temperature Of

oc

Figure 12. Typicalpressure/temperature ratings.

Butterfly Valves

83

Figure 13 . Butterfly check valve.

Figure 14. Butterfly check valve.

Advantages of butterfly valves

• • • • •

Butterfly valves are compact, require less space, less weight, less raw materia] and are generally less costly than other valve types. Butterfly valves are quarter-turn valves, easy to operate by lever, gearbox or actuator. They have excellent gland integrity. Butterfly valves have few parts and are generally easy to maintain . Butterfly valves are suitable for control purposes with linear flow characteristics between 30° and 70° of opening. Butterfly valves offer excellent rangeability from 30:1 to 100:1.

84

Valve Types Design and Construction

Typical major areas of application for butterfly valves include: liquids, gases, steam, cryogenics, pulpstocks both on control and shut-off services in chemical processing, waterworks duties. oil and gas processing, pulp and paper manufacture, the power industry, refineries and food and beverage processing. Properly selected and integrated with the latest controls and communications technology, butterfly valves can provide an economical, long-term solution to flow control in large process plants.

Rotary Disc/Rotor Valves

The rotary valve is an obvious configuration, although not widely used . It can be classified as a type of spool valve where the ports run axially instead of circumferentially (Figure 1 ). Sealing in the closed position, valves are a close fit over a restricted area only. Also friction can be high. In these respects , it is inferior to a conventional spool valve or even a plug valve. A somewhat better configuration is to employ a 'solid spool' with drilledthrough ports (Figure 2); or the rotary plate valve (see the chapter on Spool Valves). Geometric design is simplified to a degree with these latter types of valves , and both can readily be produced with overlap or underlap as required, e.g. by enlarging the circumferential length of the rotation or stationary port, respectively. This type of valve is known as a disc valve or rotary disc valve. A third basic configuration is shown in Figure 3. where a spindle or shaft rotates in a stationary housing. The shart is drilled axially and also vertically at the blind end to form a port whose position matches the inlet port in the Pressure

Exhaust ~

Pressure

Figure 1.

86

Valve Types Design and Construction

Ro tating disc

Fi.qure 2.

Figure 3.

stationary member. Again, the port opening(s) can be modified in length to provide overlap or underlap as required. A feature of both rotary valve types shown in Figures 2 and 3 is that they are capable of providing exact timing of port opening with continuous rotation of the rotary element. The design of rotary valve shown in Figure 4 overcomes the problem of friction and leakage by using shear seal rings in each port and a thrust bearing between rotor and housing. The shear seal rings are grooved to retain 0-ring seals and are spring-loaded onto the smooth rotor face by individual disc springs. The flow passages through the valve are made as clear as possible to reduce the pressure drop through the valve. Rotor valves

This type of valve differs from the typical rotary valve in that the valve design allows for transitional flow to occur when changing valve positions . Transitional flow eliminates dead-heading problems associated with positive displacement pumps . Typically the rotor valve (Figure 5) consists of four flow types with many flow-pattern combinations and 'piggable' versions. The stem and rotor are

Rotary Disc/ Rotor Valves

Mmirnum turbulence = Minimum pressure drop

Figure 4.

2-Way Tri-Ciamp

3-Way CherryBurrell 1-Line

Carbon Steel 4-Way 150# Flange

Figurr 5. Examples of rotor valves.

87

88

Valve Types Design and Construction

usually of a one-piece construction that can eliminate the source of wear and repair common to the typical ball valve design . Full-port diameter reduces the pressure drop across the valve, thereby increasing the flow. An independent leaf seal design eliminates the large cavities common to the ball valve and also the need for cavity fillers, which still create stagnant seams for product to enter.

VALVE FLOW PATTERN COMBINATIONS PORTING

Position 1

Position 2

2-WAY

3-WAY

S-

L-

4-WAY T-

··s-

LL

..T-

**L-

~ ~~~~~ ~ ~ ~~~~~ 0 ~ ~~~~~ ·~ ~ ~~~~~

0

C

c

B

C

B

c

c

8

C

B

**

Position 3

c

Position 4

c

c

8

C

B

C

B

c

B

5-WAY 8- (with special porting)

PORTING

B-

BS

BL

BT A,B,C&E

Position 1

Position 2

Position 3

Position 4

~~~~ ~ ~ ICIAJ cf}. ~ ~ ~ lj~ ljJ ~ ~ ~~~~ c®

~

8

C

E

B

c

®

c

B

C

B

C

B

C

B

®

c

8

C

B

C

~

c

8

~

8

C

~

B

c

8

A,C&E

A,B&E

~ j Ci; ~ 'I ~ ~ ~ ~ fJ I ~; c

c

Figure 6. Valve flow-pattern combinations.

Rotary Disc/Rotor Valves

89

Rotor valves of this type are favoured by a number of industries including:

food and beverage. pharmaceutical. chemical, petrochemical. refining, paper and paint and particularly where quick-couple fittings for sanitary systems are preferred. Typical flow-pattern combinations are shown in Figure 6.

Typical Parts 120• Ported "Piggable" 3-way Valve (2'h " Valve Size Shown) l 2. 3 4.

Valve body Roto r Top co ver Hat1dk 5. Washer

6. Hex nut

0 120° ported piggable 3 -way valve.

Fiaure 7. De-matmtaiJ/e rotary valve.

7 Hex head bo lt 8 Ported seal 9. Bod y o-ring 10. Stem o-nng Bono m roto r washer ll (not shown) 12. To p rotor washer 13. Co ver o-ring 14 . Sea l o-nng 15. Solid seal (no t shown) 19. Bo ttom co ver

90

Valve Types Design a11d Construction

De-mountable rotary valves (Figure 7) are mainly used Cor sanitary duties in dairy, food, pharmaceutical and chemical applications with powder or granular product. This type of valve is usually produced in 316 stainless steel with the rotor end-plate and shaft seals easily disassembled without tools and the unit capable of being cleaned in place (CIP). Capacities up to 1500 cubic ft/ hr in either drop-through or convey-through configurations are common.

[C.:.:~~~~JI ISO-~~OlQualityAssurance

([@~~)~ STAINLESS STEEUCARBON STEEL VALVES .. .

- -~ Certifted Factory

& FITTINGS MANUFACTURE

FIRE SAFE API&o7 VALVES

AUTOMAnON VALVES

MOUNT DIRECT VALVE

JOHN-VALVE MFG. FACTORY CO., LTD. 1149-11, Bee San Rd., Tsao Tun Town, Nan-Tou Hsien, Taiwan. Office/Tel: 886-4-3780078 (6 Lines) Fax: 886-4-3754978 E-mail: johnvalv@msl3. hine t.ne t http://johnvalve .com .tw

Globe Valves Over the last 60 years, globe valves have been re-appraised in the light of new materials available for use. They are popular as industrial valves because they have fine adjustment and permit unobstructed opening through pipelines. The globe valve is characterised by a baffle or partition separating the two halves of the body. with an interconnecting part at the centre opened and closed by a screw-down/screw-up disc or plug mounted at right angles to the body (Figure l ). The name derives from the fact that original body shapes were spherical, the more usual modern form being semi-spherical or even substantially parallel-sided. The globe valve offers good regulation characteristics but high resistance because of the tortuous flow path. This can be reduced to some extent by making the throat area equivalent to that of the pipe (calling for a more bulbous body),

4

~--2

l. Body. 2. Bonnet 3.Cover. 4.Giand packing.

5.Stem. 6. Handwheel.

I

I

u Figure I. Screw-down globe valve.

92

Valve Types Design and Construction

Bronze globe valve.

rounding the partition to smooth flow or inclining it to the flow (Figure 2) . Reduction of head loss by such treatment is generally minimal and so rightangled partitions are commonly used. Globe valves are produced with a variety of discs or plugs and seals. Discs provide line contact with the seat which can be broken by solid deposits forming on the seat. They are thus mainly suited only for clean fluids . Disc valves. too. are not as effective as plugs for throttling duties and so are normally used only on shut-off valves. Another limitation of the disc is that it does not provide positive shut-off for air and gases, unless made of a resilient material. Plugs are used in a variety of configurations, ranging from needle shapes to semi-discs. The plug contour also governs the throttling characteristics, e.g. equal-percentage plugs (percentage flow proportional to valve lift), etc. Needle plugs provide the finest flow control. Globe valves fitted with this latter type of plug are normally referred to as needle valves. Needle valves are normally made only in small sizes.

Figure 2.

Globe Valves

Cutaway ofglobe valve.

For{Jed-steelgloiJe valve.

Plastic globe valves.

93

94

Valve Types Design and Construction

Seats

Globe valve seats may be cast integral with the body or take the form of screwed-in, pressed-in, or spot-welded rings. A variety of materials may be used for seats, depending on the application, including coated seat rings with plastic inserts. Normally only screwed-in seat rings are replaceable. Stems

Possible stem assemblies include inside screw and outside screw (both rising stem) and sliding stem. Inside stem rising screw is usual. A stem seal (stem gland) is necessary to eliminate leakage. This is normally a gland-type packing or gland rings. A diaphragm bonnet seal or bellows bonnet seal may also be used on globe valves, the former isolating the working parts of the valve from the fluid as well as preventing leakage to the atmosphere. Metallic bellows seals are often used on valves intended for high-vacuum duties. The valve shown in Figure 3 is manufactured from malleable iron. This valve is widely used on standard pipelines for steam, oil and water.

No. l

PART NAME BODY

MATERIAL Malleable Iron

2 BONNET

Malleable Iron

3 BODY SEAT RING

13 Cr Stainless Steel

-------------------------2 1 I /' "'4" Carbon Steel

L Hard Facing Part

-

No.@@

--i

Spot Weld Nom mal Size 4 ·· Above

4 DISC

Carbon Steel

5 DISC STEM RING

13 Cr Stainless Steel

6 BONNET BUSH

13 Cr Stainless Steel+ H350

7 PACKING BUSH

13 Cr Stainless Steel

8 STEM

13 Cr Stainless Steel

9 BONNET BOLT

Carbon Steel

lO NUT

Carbon Steel

11 GLAND BOLT

Carbon Steel

12 NUT

Carbon Steel

l3 GLAND FLANGE

Malleable Iron

14 YOKE SLEEVE

High Tension Brass

15 SET PIN

Brass

Figure 3. Malleable-iron glob(• valve.

Globe Valves

'Y '-pattern globe valve: bellows seal. inside screw and yoke.

----

Adjustable Jilt stop • AIIHI dOSing. disc can reach 11s 1ni1ia1 DOSfft()(l

Locking device • Protecho:l !(Qm W11r\lent100al

acluat•on

- ·-

Vibration-damped thronle disc • LOW-flOiSO UO'N f:GiliWI

pos.s•ble

Cone " ·,th Pl Fl ·<;p sket, ON 15·2m

RQiil:i cone I rom ON 200 onwards

Lead - s~alabte

Figure 4 . Globe valve with metallic seat.

C.:l P

95

96

Valve Types Design and Construction

Malleable iron provides a high yield point, a more important property than tensile strength for valve materials. It is also stable against temperature change. Low-pressure valves of this type generally have PTFE seats. Valves for use at higher pressures have the valve disc and body seat ring made from hard-faced stainless steel. The hard face is an alloy containing cobalt, chromium and tungsten. Valves of this type can also be fitted with replaceable PTFE discs when used with liquefied petroleum gases. The gland packings are usually of a synthetic rubber of butadiene-acryl-nitrile polymer V packing design to provide for good oil and wear resistance. Over time, the V packing will harden: tell-tale signs are: a friction sound when the valve is opened and

Non-rising handwheel of glassfibre reinforced polyamide • tdeal in confined spaces • Reduced handwheel temperature

Cap with position indicator outside the Insulation • Position of valve can be checked any time

Non-rotating stem, protected external thread • High operational reliability

Pressure retaining body in one piece • Hermetically sealed • No cover bolts to re-tighten • No spare part costs for bolts and cover gasket • Suitable tor full and easy insulation in compliance with the German heat1ng systems regulations

Low weight body with short face-to-face length • Saves transport costs • Easy to install • Space-saving

Body of favourable hydraulic design • Minimal pressure loss • Lower investment and operating costs

Figure 5. Globe valve with high-temperature soft seat.

Globe Valves

97

Figure 6. Oblique or 'Y' valve.

closed; the opening and closing operation becomes difficult to operate; and the gland actually leaking. The packing must then be replaced. An example of a standard globe valve for use in hot- and warm-water heating and boiler installations is shown in Figure 4. This particular valve has a metallic seat. The temperature range is from -1 ooc up to + 3 50°C, with pressures up top= 2 5 bar. The valve illustrated in Figure 5 is fitted with a soft seat for high-temperature operation from -1 ooc to + 200°C. Typical applications included hot-water heating systems, district heating plants and low-pressure steam plants. The valve has a short face-to-face length which makes it particularly compact. Globe valves are a traditional standard solution for many control applications because of the ability to modify the trim design for different throttling purposes. Oblique valves

The oblique valve or Y-valve is a hybrid globe valve characterised by the stem being angled (Figure 6 ). As a consequence the flow path is less tortuous, with reduced pressure drop compared with a conventional globe valve. It retains the same good throttling characteristics as a globe valve and can be fitted with similar types of plugs. Construction is basically the same as globe valves with the option of integral or fitted seat rings, stem options and stem seal gland treatment.

Gate Valves The main feature that distinguishes a gate valve is the flat face or vertical disc or wedge that slides in a track or seat which can be lifted in a direction at right angles to the valve until clear of the flow path. Generally gate valves are used for on- off non throttling service, i.e. they are intended to be either fully open. when they offer little resistance to flow, or fully closed . For this reason , they are the principal valves used in bulk pumping practice. Large gate valves tend to be power operated. Throughout the water industry. for example, automation with actuated valves has been introduced in response to the requirement for lower manning levels. Gate valves are divided into a number of classes, depending on the design of the 'gate' and its seating faces.

Gate vnlves.

Gate Valves 8

6 IH-7'' ----

5

I. Body . 2.Bonnct. }. Wedge. 4.Scat ring. S.G iand packing. o.G iand follower . 7.Stem.

3

~. H r.~ n d wh eel.

~~~L3 . -t -- -+- 2 ~wJ)~~L1

4 Solid wedge gate valve.

! .Body. 2. Di sc. J .Spring. 4.Bonnet. 5.Giand. 6.Stem. 7. Y okc. 8. H andwheel.

Parallel slide gate valve.

r---

Non-rising handwheel • Favourable in confined spaces

Threaded bush with cylindrical thrust roller bearings • Easy actuatton

....________ Sturdy yoke head • Easy retrolitting ol actuators without dismantling pressure retainmg parts

Pressure seal bonnet

Movable wedges • Precise adaptation body seats • Wedges are easy to replace

Wedge holder guide (lorged in the body) • Serves as anti-twist lock • Reduces bendmg forces acttng on the stem

• Htgh reltability • Long life

rail~/ \~""~I,_'j Sl=~~- ~ 1 1

t•

\

'- -

- - •_

~

_ .•

Gate val vi' with press ure seal bonnet.

99

100

Valve Types Design and Construction

Wedge~gate

valves

The gate is wedge-shaped and seals on corresponding faces in the faces of the valve body. Wedges and seats can be made of, or coated with, resistant material or faced with plastic such as PTFE. The plastic is often contained in a groove to prevent it spreading. Figure 1 shows a wedge-gate valve with external screw, and Figure 2 one with internal screw. Flexible-wedge valves and split-wedge valves are similar to the aforementioned . but with provision for slight seat misalignment. Wedge-gate valves can be further described as inside-screw or outside-screw patterns (see Figure 3). They are widely used for oil, gas and air services. and also for handling slurries, etc. Double-disc valves

In these valves the gate is in the form of two discs which a re forced apart against parallel seats by a spring. This provides tight sealing without relying on fluid pressure, making this type of valve particularly suitable for steam duties as well as handling gases and light oils. Parallel-slide valves

In 18 8 6, Joseph Hopkinson introduced the parallel-slide valve where sealing of the valve relies on the upstream pressure acting on a flat parallel gate valve. H a nJwhecl

Thrust rlate

"'-llo.o:-~"'""

Sea ting) W edge

Figure 1. External scre w.

Figure 2. lnternal screw.

ga te

Gate Valves

Wedge gate sluice va lve inside screw pattern

Wedge gate sluice valve outside screw pattern Figure 3.

HANDWHl( L

STUFFING BOX

BONNET

GASKET

W EDGE NUl SEATS

WE OG (

Inside-screw gate valve.

101

102

Valve Types Design and Construction

F fanged and butt-welded gnt.e valves.

Bronze dol.l/Jle-disc lever gnte vnlve.

The system is still popular today and the simplest (and probably most effective) layout employs two discs as valve members initially separated by a spring (see Figure 4). The function of the spring is to prevent the discs from rattling and to encourage a wiping action on the downstream disc when under pressure and on both discs when there is virtually no pressure in the line. This is to avoid-as far as is possible-grit or scale becoming trapped between the vulnerable seating faces which might impair their sealing properties. Parallel-slide valves are used extensively in the pulp and paper industry. Sluice valves

This is a name applied to solid-wedge valves for waterworks.

GateValves

Parallel slide valve inside <;crew pattern

Parallel slide valve outside screw pattern Figure4.

Metnl-sentecl gate valve.

103

104

Valve Types Design and Construction

Bellows seal-gate valves

Environmental protection is a major concern and the bellows seal valve is designed to minimise exposure to dangerous or harmful substances through valve-stem leakage.

_____L r -~'"1. --r-~---

Figure 5.

Figure 6.

Figure 7. Construction details.

Gate Valves

105

The bellows is a metallic device capable of sealing between the valve stem and the bonnet to prevent escape of the system fluid to the atmosphere. The bellows take the form of convolutions that can move linearly. A hermetic seal is achieved by welding the bellows to the valve stem at one end and to the BELLOWS SEAL VALVES ....---~~

GATE, CLASS 800, 1f2''

r

GLOBE, CLASS 800, 3/4"

Bellows seal valves.

GATE, CLASS 1500, 2"

106

Valve Types Design and Construction

bonnet at the other end (Figure 5). The structural shape of the bellows provides resistance to high pressure, even with thin wall thicknesses (Figure 6 ). In operation, the bellows eliminates a leak path to atmosphere. The stem/ packing area is sealed from the medium being processed and the bellows becomes the primary seal since the bellows assembly is welded to the stem and to the bonnet as shown in Figure 7. Replaceable bellows are gaining popularity with valve users in process plants. In replaceable bellows valves, the bellows is not welded to the bonnet; instead, it is welded to a transition piece that is clamped between the body with standard gaskets to seal the joint. The lower end of the bellows assembly is welded to the disc which is attached to the stem by a threaded connection . The gasket on the media side is generally a spiral-wound gasket. The gasket at the top of the bellows assembly only comes into operation if the belJows fails. Where maintenance is difficult, the welded bonnet valve may be the better choice. Gate valves are used mainly in general industry. power stations, process engineering, pulp and paper and marine engineering for water. steam, gas, oil and non-aggressive media. Actuation

Manual actuation of gate valves is invariably by screw and handwheel. The screw mechanism may be exposed or protected and the screw 'rising' or 'non-rising'. A variety of materials for the working parts is offered by some makers. Power actuators are very often fitted, especially where valves are difficult to access and are operated frequently . Automation and semi-automation control schemes also make extensive use of actuators. See also the chapter on Slide Valves.

Needle Valves Small sizes of globe valves fitted with a finely tapered plug are known as needle valves. This description also applies to any type of valve incorporating a tapered needle having axial movement relative to the axis of a concentric orifice and thus controlling the effective opening of the orifice. Three basic configurations are shown in Figure 1: (A) is a simple screwdown valve; (B) is an oblique version, offering a more direct flow path: (C) is another form where the controlled outlet flow is at right angles to the main flow (and may be distributed through one or more passages). In these basic

d l

[

I

c A Figure I.

NeedlP valve with interchangeable stlm!.

D

I

108

Valve Types Design and Construction

Oblique and 'T'-type needle valves typically used for process duties.

Pan

BS

H a ndwheel N ut

Cou bon Steel

1760

'"i ilnd w h eel

Malleable hon

309

Sterr"

Stau1lcss

Gl ond Nul

Carbon Srecl

1506 I ll

Gl and

Caroon Steel

1506·1 11

P ackmg

V al v .1~ .. ~a nd

Sl~t!l

1506 713

A STM

A l82 G R F6

Piastr e

N o 1: M c r.,ILt Stecf P ac:..rnq Rrng

Mdd S1ecl

970 ENIA

Bonne(

Carbo n S1e c1

150() 11 1

U·1 · 1et

Bo d y

Gasket

Am'K O Iro n

Caf bon Steer Forqrng

Typical needle-type meter valve.

1501 161 G R J2

At 05 G A 2

Needle Valves

109

versions a threaded needle is shown, the thread itself acting as a seal to eliminate leakage past the needle. This is normally quite satisfactory in very small sizes or needle, although a more leak-tight arrangement is to mount the needle in an externally threaded end piece [Figure 1 (D)]. This end piece can also act as a grip for adjustment of the needle. Sealing in this case can be further improved if necessary by incorporating an internal seal. such as an 0-ring. The other common form of needle valve is the float-controlled, carburettor-type valve. See also the chapter on Globe Valves.

Pinch Valves The 'working' element of a pinch valve, also known as a clamp valve, is an elastomeric tube or sleeve which can be squeezed at its mid-section by some mechanical system until ultimately the tube walls are pinched or clamped together producing full closure of the flow path. In its simplest form it can consist merely of a length of elastomeric tube fitted with a pinch bar mechanism incorporating a closure stop to prevent over-pinching of the tube. More usually the moulded rubber tube is housed in a metal body which also incorporates the pinching mechanism (Figure 1 ). This can be a simple scre\r\r-operated mechanism. where the pinch is applied only to one side of the tube, or a differential scre·w controlling two pinching mechanisms working in vertical opposition . The latter produces lower-stress working of the tube. Other types of pinch valves dispose with mechanical mechanisms entirely, the tube being squeezed shut by air or hydraulic pressure injected directly into the body of the valve (Figure 2). With a regulated fluid pressure the valve may

2

I .Bouy . 2 Flexible tulle . 3. U ppe r pinch bar

4. Lowe r pinch S. Spimlk .

oar

6. H andwhc c l.

Figr.tre I. Pinch vnlw-bnsiccompolli'nls.

Pinch Valves

l.ll

capability of sealing with entrapped solids.

Figure 2. Hydraulic prpssure-operated pinch valve.

be used for throttling as well as shut-off (full closure) (Figure 3 ). The particular advantage of the fluid-operated pinch valve is that it will still close tight over entrapped solids (making it particularly suitable for handling products with solids in suspension). Also, because the tube is flexed under uniformly distributed pressure, its life should be much longer than that or a similar tube working with a mechanical pinching system. In common with the diaphragm valve, the operating mechanism is not in contact with the working fluid at any time, and nor is the body. In this respect, pinch valves have the advantage over diaphragm valves, unless the latter are ru bber-lined or otherwise surface-protected. This exclusion of the working fl uid from all parts excepting the sleeve itself makes it ideal for the handling of aggressive fluids and those which readily attack metal; and its straight-through characteristics mean it is suitable for the handling of slurries, pastes and semi-fluids generally, even those containing sizeable solid lumps in suspension.

J

OPEN

A1r lnlel

THROTTLING

Fig1u·e 3.

~

Aor lnlel

CLOSED

112

Valve Types Design and Construction

Pinch valves with mechanical pinching mechanisms are normally operated by a handwheel and screw mechanism. but may equally well be driven by a powered actuator in larger sizes. Bodies are normally split horizontally to facilitate changing the tube when necessary without removing the complete valve from the pipeline. Flow pattern

The flow pattern of a pinch valve is streamline and laminar. The non turbulent flow pattern even in the wide-open position means that wear on the valve sleeve is minimised. The linear characteristics of some control pinch valves result in flow rates which are directly proportional to the amount of sleeve travel throughout the stroke of the valve while under constant-pressure and pressure-drop conditions. Typical valve sleeves are shown in Figure 4. These include standard, double wall for very abrasive conditions, cone sleeve for throttling control and variable orifice sleeve for improved flow characteristics where a high pressure drop is required. Another form of pinch valve is shown in Figure 5. In addition to a resilient sleeve this also incorporates a streamlined core on to which the sleeve closes to seal. This valve can be operated in a variety of modes. In mode 1, the valve

Standard Sleeve

Double Wall Sleeve

Cone Sleeve

Variable Orifice Sleeve

Figure 4 . Typical control pinch valve sleeves.

Pinch Valves

113

Control port Control space

V c\IVC housing Supporting beam Core

Resilient sleeve

Figure 6.

FigureS.

remains closed when no pressure is present, due to the resilience of the sleeve (Figure 6 ). In the presence of pressure in the pipeline, the valve opens and remains open (Figure 7). It closes again in the absence of flow pressure. Line pressure of about 1 bar (14 lbf/ in 2 ) is sufficient to hold the valve in the fully open position. In mode 2, inlet pressure is tapped and fed to the control space between the sleeve and body, closing the valve. The valve opens when the operating pressure is relieved from the control space (Figure 8). At extremely low line pressures, circa 0.5 bar (7 lbf/in 2 ), the valve remains closed and drop-tight, even when operating pressure is relieved from the control space. In mode 3, the operating principle is the same. except that the control space is pressurised from an independent source, e.g. compressed air or a hydraulic supply. In mode 4, the flow is tapped to feed the control space which is only partially filled and then isolated, holding the sleeve in a partially closed position (Figure 9). In this mode the valve operates as a throttling valve or pressure-regulation valve. Various low-hardness, high-tensile elastomeric compounds are used for the tubes, choice being made on chemical resistance and/ or abrasion resistance required and service temperature. Typical materials used are:

Figure 7.

114

Valve Types Design and Construction

Figure 8.

Figure 9.

GRS Bun aN Neoprene* Butyl

Hypalon* PTFE

Silicone

FDA EPDM

exce1lent abrasion resistance. good resistance to solvents and hydrocarbons. good chemical and hydrocarbon resistance; in white compound also suitable for fast and dry application. good combination of chemical and temperature resistance: in white compound has good resistance to animal and vegetable oils. excellent chemical and temperature resistance. outstanding chemical and high-temperature resistance. good combination of high- and [ow-temperature resistance. excellent abrasion resistance; suitable for many foods and dairy applications. excellent heat and chemical resistance.

*Neoprene and Hypalon are registered trademarks of DuPont Dow Elastomers.

Pinch Valves

115

Fluid performance

A pinch valve presents full-bore flow in the open position, with a straight, uninterrupted flow passage. Pressure drop or head loss under such conditions is thus minimal, related only to flow velocity and tube length. for a given fluid. There is no slamming when the valve closes against back pressure and the elastic nature of the tube tends to eliminate hammer (although this feature is absent in a hydraulically-operated pinch valve). Vacuum services

Pinch valves tend to have limited suitability for vacuum services because of the tendency for the tube to collapse inwards. This is particularly true in the case of pinch valves with simple exposed tubes. Where the tube is enclosed in a body it is possible to adapt the valve for vacuum duties by applying a vacuum within the casing to balance the internal (vacuum) pressure. Sizes and ratings

Sizes commonly available range up to 300 mm (12 in), with standard bodies suitable for pressures up to 14 bar (200 lbf/ in 2 ), or steel or stainless-steel HANDWHEEL POSITION INDICATOR Slatnless Steel SHEAR PIN Sta1nlcss Steel POSITI VE STOP COLLAR Stain less Steel

BO DY Duclile Iron

STEM Sta•nless Steel YOKE Ductile Iron

A NSI CLASS 150 FLANC.f S COMPRESSOR Ductile Iron

LIFT FO RK STUD Stainless Steel

TFE TUBE

LINK S Stamless Steel TFE REINFO RCING JACKET RADIU S CLAMP Stamless Steel

Figure 10. Clamp valve.

116

Valve Types Design and Consiructiorr

bodies for pressures up to 28 bar (400 lbf/in 2 ). Larger sizes are also available, those over 600 mm (24 in) diameter usually being individually made with fabricated steel bodies. Clamp valves

This type of pinch valve (Figure 10) consists of a flexible tube and clamp. The flexible tube has a heat-shrunk reinforcing jacket with both made from virgin TFE fluorocarbon resin. The clamping mechanism consists of a compressor which travels down a stem with rotation of a handwheel or power operator. and a yoke which travels up the stem at the same time. Lift forks pull open

•

Lrnkage system pulls inward

•

• Actions of valve mechanisms when ope ning Figure I 1.

Compressor clamps closed Linkage system pushes outward

•

Yoke clamps closed

Actions of valve mechanisms when closmg F i[fure 12.

Pinch Valves

117

Radius clamps are connected to the yoke and to the compressor by means of links and pins. Working together, they provide a 'scissor-jack' action which pushes the tube element inward during the opening cycle and pulls it outward during closing. The actions of the valve mechanism are shown in Figures 11 and 12. Pinch valves are ideal for use in many industrial applications including: • • • •

Chemical plants- where there are corrosive chemicals and for pump isolation. Power industry-FGD systems, ash handling and wet lime scrubbers. Mining industry-centrifuge control, solids separation, tailings systems. coal washing. Waste water treatment-flow equalisation, polymer feed systems, sludge control, grit systems, carbon slurry and raw sewage.

Diaphragm Valves The distinguishing feature of a diaphragm valve is the closure device. This is usually an elastomeric diaphragm or tube which acts as a flexible seal when compressed against a ridge in the valve body. The diaphragm valve handles corrosive and erosive materials. Diaphragm valves fall into two main types-weir valves and straightthrough valves. In the former geometry (Figure 1 ). the body has a dividing weir, above which is mounted an elastomeric diaphragm. In the closed position the diaphragm sits on the weir. In the open position, it is fitted to provide a streamlined flow through the valve body. The amount of lifting is variable, so the valve can act both as a flow controller or a stop valve. The straight-through diaphragm valve (Figure 2) may have a parallel. top-tapered or venturi-pattern body with closure provided by a wedge-shaped projection of the diaphragm. Because of the full-bore opening. it offers minimum resistance to flow in the open position. can pass suspended solids, and is capable of being rodded through for clearing any blockage. Because the diaphragm isolates the moving parts. these valves are particularly suitable for handling aggressive ~uids, as well as for 'clean fluid '

1. Body Weir Diaphragm Diaphragm movement Bonnet Spindle 7. Handwheel

2. 3. 4. 5. 6.

Figure 1. Weir-type diaphragm valve.

Diaphragm Valves

119

Figure 2. Straight-through diaphragm valve.

2. Operating mechanism, protected from line fluid corrosion; permanently lubricated bonnet neck

Flexi ble, reinforced diaphragm supported in all positions. (With a rubber diaphragm, any small solids present in the fluid and trapped on closure between the valve weir and diaphragm, just embed themselves in the pliable material of the latter until the valve is opened, when they are released).

3. Compressor guide fingers in the bonnet of finger plate. (Finger plate in DN 40-50 only). Fully support d iaphragm in all positions to give long diaphragm life. 4. Weir or seat on which the diaphragm beds down.

5. Clean, streamline passage without pockets.

Sta11dard diaphragm valve.

applications, the type of elastomer being chosen accordingly. The body itself can also be lined for corrosive duties. Particular advantages of the diaphragm valve are the glandless construction and absence of seating problems. Its main limitation is that the maximum service temperature and pressure are limited by the temperature/ pressure rating of the elastomeric material. Typical body materials are cast iron, malleable iron, bronze, gun-metal and stainless steel. Lined diaphragm valves normally have cast-iron bodies lined with rubber, neoprene, polypropylene, PTFE or glass. Typical diaphragm materials and their main uses are summarised in Table 1. Reinforced diaphragm materials may be used for more arduous duties and are virtually standard for vacuum services. Typical flow coefficients for weir-type and straight-through diaphragm valves are given in Tables 2A and 2B.

120

Valve Types Design and Construction

Table 1. Diaphragm materials Material

Size mm

Temperature

Main uses

in

Butyl rubber

15 to 350

0.6 to 14

-30 to 90

-22 to 134

Acids and alkalis

Nitrile rubber

1 5 to 3 50

0. 6 to 14

-1 0 to 9 0

+ l4 to 134

Oils. fats and fuel s

Neoprene

1 5 to 3 50

0. 6 to 14

- 2 0 to 9 0

-4 to 134

Oils. greases. air and radioactive fluids

Natural/ synthetic rubber

15to350

0.6to14

-40to90

-40 to 134

Abrasives. brewing and dilute minera l acids

White natural rubber

15tol25

0.6to5

-3 5to90

-3ltol34

Foodsaodpharmacenticals White diaphr<Jgm

White butyl

15to150

0.6to6

-30tol00

-22to212

Naturalcolour.foodstuffs plasticisers and pharmaceuticals

Vi ton*

15 to 350

0.6 to 14

+5 to 140

+41 to 284

Hydrocarbon acids. sulphuric and chlorine applications

Hypalon*

l 5 to 3 50

0. 6 to 14

0 to 9 0

+32to 134

Acid-andozone-resistant

Butyl rubber

15 to 350

0.6 to l4

-20 to 120

-4 to 248

Hot water and intermittent steam services. sugar refining

*Du Pont Dow Elastomers Registered Trademark.

Operation

Of the standard forms of manual operation available, the handwheel is preferred for most purposes. The design of handwheel and operating mechanism (spindle, compressor, bush or nut) varies according to the size and type of valve. Various-shaped handwheels are also available. This facility. for instance, greatly assists the operator in identification in dark conditions or where the handwheel becomes slippery. Various bonnets are applicable to handwheel-operated valves. Extended spindle valves are readily available but existing valves can be simply converted by use of adaptor and extension. Other variants of bonnet assembly can be substituted for the hand wheel-operated design. Normal bonnet assembly material is cast iron but alternative materials are offered by most manufacturers, e.g.: All iron and steel construction (for handling acetylene, ammonia and other similar fluids). (ii) All stainless steel (where there is severe atmospheric-corrosion conditions). (iii) Gun-metal (for medical oxygen, turbine oils and certain water services). (iv) Cast steel with rising spindle fitting (mainly used in oil refineries) . (i)

Diaphragm Valves

Table 2A.

Typical flow coefficients for weir-type valves

Valve size

Cast iron

Rubber-lined

Halav / glass-lined

ON

C,.

Kv

Cv

Kv

Cv

Kv

15 20 25 32 40 50 65 80 100 125 150 200 225 250 300 350

5.8 11.5 17.4 26.5 4.3 84 126 180 320 420 600 1260 1630 1990 2580 3840

1.6 3.2 5 7.5 12.2 21.4 30.5 44.4 77.7 108 147 305 388 500 625 833

1.3 9.4 14.5 22 35 70 102 147 264 348 504 996 1320 1620 2088 3060

4.4 2.6 4 6 9.8 17 24.4 35.5 62 86.4 117.6 244 .310 400 500 666

6

1.7 3.4 5.6 8 12.8 22.5 32 46.6 81.6

Table 2B.

121

12 18 28 45.5 88 132 185 336 444 630 1320 1680 2076 2700 4020

113

154 320 407 525 656 875 .7

Flow coefficients for typical stra.lght-through valves

Valve size

Cast iron

Rubber-lined

ON

Cv

Kv

15 20 25 32 40 50 65 80 100 125 ISO 200 250 300 350

8.6

1.8

3 7.8 55.8 75 128 238 330 588 924 1680 2580 4020 6060 .10.300

7.9 12.5

20 34 68 90 150 235 385 789 1050 1510 2800

Cv

30.6 45.6 66 107 195 264 480 720 1260 2196 3420 4884 9950

Kv

6.5 10.1 18 28 55 73 123 184 293 665 900 1221 2360

Halav / glass-lined

Cv

Kv

9

1.9

39 58.2 79 138 254 342 618 960 1800 2724 4296 6204

8.2 12.9 21

36 72 92 158 274 545 825 1100 1550

(v) Silicon aluminium (for lightness and low temperature). (vi) A variety of plastic materials (for general corrosion resistance). (vii) Epoxy-coated cast iron (for corrosion resistance, attractive appearance). For quick closure and/ or opening, lever-action valves can be used. A quarter-turn movement is preferred when the liner can also act as a valve

12 2

Valve Types Design and Construction

position indicator, e.g. parallel with the pipeline in the fully open position and at right angles to the pipeline in the fully closed position. Diaphragm valves are particularly suited for rapid closure/ opening because the cushioning action of the flexible diaphragm minimizes the shock throughout the pipeline, compared with equally rapid but less resilient types of valve movement. Double-diaphragm valves

A double-diaphragm valve is a basically simple design consisting of two flexing diaphragms on an axial stem. There is no metal-to-metal contact. 0-rings or sliding seals, making lubrication unnecessary, as shown in Figure 3. The valve requires no special filtration and is tolerant to dirt-laden media as well as scrubbed instrument air. Designed for compressed air and inert gases. the self-purging non-lubricated design is also suitable for vacuum applications. A cartridge-insert version is manufactured for direct integration into finished products. Typical areas of application include food processing and medical equipment. In fact. a doublediaphragm air valve has performed over two billion cumulative cycles. an equivalent of 50 years of human life, in various heart systems. The valves are located in the mechanical control system. which is attached to the patient by plastic tubes, and control the flow of compressed air through the tubes to the artificial heart, causing it to pump.

Figure 3 . Double-diaphragm air valve.

123

Diaphragm Valves

Plastic diaphragm valves (Figure 3) are becoming increasingly popular. Manufactured from PVC-U, PVC-C. ABS, PP and PVDF plastics, the main advantages are lightweight and compact construction, corrosion resistance and a long maintenance-free working life. Typical pressure-temperature charts are shown in Figures 4 and 5. Miniature air-operated diaphragm valves are designed for pressure applications for PVC-U, PVC-C, ABS 16

-

-

15

1-

14

-

1-

,-·r

--

I

<

-

IJ 1-II

10

K

f'I.C-lJ f'N 101 \

9

~

8

\\ \

P\C-Uf"'l7)1 \

I'\ f'l.<

U L)

"~~~

0..~'\' \

1-

Area of application

h

DK1phrour" vulvPS ON 15 100 DJC•phroum volv<-'s DN 150

0 -40 -30

-20

-10

0

10

20

30

40

f

r~

~

-- -

PIIC l

r\_

~

:t J.I'

50

-

- 1--- -

I~

PVC.U, PVC C. ABS. PVC-U

-

-1--~

f'I.C C ~ IOf

MSrNlOJ'

-~-

t

--r-·

12

60

70

Tempero lure in

80

- --f- --

90

100

I

-

110

I

120

I.JO

140

oc

Figure 4. and 5. Typical pressure-temperature diagrams for diaphragm valves. PVC-U, PVC-C, ABS

-

16 IS

~

-

14

-

13

-

ABSJ'N 1ol

1 -

10

-

1-

" I"

PIICU~Il' '\(

-10

o

10

~

20

30

1-

\

~~

-•o~r -30 -20

--·

\\

r\ \. 1\\ ABS I" f'I.< U£\

Area of application

0

i

~

I

-

PVC-U. PVC -C. ABS Doopnrogm valves DN I 5-100 ~ PVCU Doaphrogm valves DN 150

t- -:-

PIIC-ca"' '01 PIIC-U.fN ~~

9

1

- t - _I_ -

12 11

-+-

-- -

40

50

~ PIIC r

'

60

Tempero ture in

I

-

=-r

--- -

~10

so

r

90

I 100

oc

Fiqun: 4. and 5. Typical pressure- temperature diagrams for diaphragm valves.

).

no

-

120

I 1JO

140

124

Valve Types Design and Construction

Figur£' 6. Iris-type dinp!lrngm valve.

Dinpf!ragm V nlves

12 5

highly corrosive or ultra-pure liquids, when space is critical. This type of valve has numerous applications in the electronics/semiconductor industry for use with concentrated etchants and ultra-pure water. Generally, the valves open with air pressure and close with a return spring. Diaphragm valves play a significant role in air-pulse jet-dust control equipment and valve performance has a great influence on the cleaning efficiency of the generated air pulse. Air-pulse diaphragm valves need to open and close very rapidly at high flows. Fluttering of the diaphragm during opening and closing increases air consumption and will affect valve performance. The opening time of the pulse valve must be as short as possible, i.e. between 8 and 14 ms to achieve best performance. Long closing times increase air consumption. Iris-type diaphragm valves

The diaphragm valve shown in Figure 6 is designed specifically to control the flow of dry bulk solids and is used for food, chemical pharmaceutical and general processes. Essentially the valve consists or a tube of flexible material, fixed rigidly at each end . This tube is held in a mechanism which rotates one end through 180° relative to the other. vVhen twisted in this way, the tube closes completely, creating a diaphragm visually resembling the iris of a camera. Iris-type diaphragm valves have a variable area concentric orifice so that the flow can be accurately controlled. They can open or close irrespective of size to the smallest of orifice sizes, regulating the flow of even the finest of powders. Power-operated models can open or close to pre-set "dribble-feed" positions.

Fig11re 7. lris-type diaphragm valve m embranes.

126

Valve Types Design and Construction

Central to the performance of the iris-type diaphragm valve is the correct selection of diaphragms. The diaphragms are usually made from either (i) elastomers~natural and synthetic, (ii) fabrics and (iii) coated fabrics (Figure 7). Typical applications include discharge valve to cake-mix mixer, discharge valve for rail tankers carrying bulk sugar, packing herbs and spices, controlling the flow of finished tablets and capsules, general purpose flow-control valves for silos and hoppers, filling fertilizers into 1 tonne bags, gland around telephone cable to remove excess grease. valve on salt silo for motorway gritting, weighing out of abrasive ingredients, and controlling the flow of pigments.

Slide Valves Slide valves are one of the many variations of the gate-type valve and were originally designed for use in the pulp and paper industry to overcome the problems in handling wet and dry fluidized solids in pipelines. The slide valve, or knife or plate valve as it is sometimes called, in its original form was a simple rattle-fit plate in a fabricated body. Opening or closing was achieved by pushing or pulling the plate to give a crude shut-off. Although design improvements have been made, this simple form of valve is still commonly used as a diverter or hopper outlet valve on dry powders or solids where a pressure seal is not required. In such applic ations the body of the valve will probably be of square or rectangular bore to suit the hopper outlet or duct on which it is fitted . The logical advancement from this design was the fitting of resilient seals and an operating screw and handwheel to open and close the slide. With the improvement in sealing that this gives, the slide valve is suitable for a much wider range of services and can handle solids suspended in liquids or gases. Although they are simple valves, there are a variety of designs on the market all sharing, to a greater or lesser degree. the following advantages: (a) (b} (c) (d) (e) (f)

(g) (h) (i)

short overa II length no wedging action thin closing member to cut through solids in the line substantially full-round bore lightweight easy to power-operate stem/slide connection not in contact with line fluid slide exposed for visual inspection when valve is open good regulating characteristics when fitted with specia lly-shaped slide and/or body bore

The resilient seals. which can be fitted in the body or on the slide depending on individual design, are available in various materials to suit the fluid being handled. For most applications they will be in rubber, e.g. Nitrile or Vi ton*. *Dupont Dow Elas tomers registered Trade Ma rk.

128

Valve Types Design and Construction

but for higher temperatures or in the food and chemical industries it may be necessary to specify PTFE or other special elastomers. There are many individual designs of slide valve on the market. In some ways, this is advantageous as it gives the valve user more scope for finding a valve specifically designed to overcome a unique problem. Generally speaking, slide valves are used on services such as: viscous media dry powder (iii) dry solids of small and large particle size (iv) slurries and sludges (i) (ii)

These applications are commonly found in the waterworks, sewage, mining, chemical. power generation. food, cement, brewing and other process industries as well as the pulp and paper industry for which the valve was originally designed. But this does not necessarily mean that slide valves are only used on difficult applications. They are equally successful when put on less arduous duties where the benefits of leak-tightness, space-saving, price, etc., need to be considered. Figure 1 shows a typical design of slide valve. It will be noted that the bore is clear of obstructions and that there are no pockets in which solids can collect,

5

!.Stainless ~tecl stem. 2.Cast body . J.Gate guides and jams. 4. Raised face nanges. S. Handwheel. 6. Yoke. 7. Pa<:k in g. l'\.Full round port. 9.Stainless steel gate. Ill. Welded on steel flanges .

'------10 Fig uri' 1. Knife-edge slid!' valve.

Slide Valves

129

in addition to which the seal is housed in the body of the valve and shrouded by the body to avoid damage from solids in the line. [n this design the seal seats on the edges of the slide, which means that the valve will seal equally well with flow in either direction and the slide has a chamfered leading edge which enables it to slice through any obstruction and seat effectively against the body seal (Figure 2). These features ensure bubble-tight shut-off against pressure or vacuum.

Figure 2. Features of the slide vnlve shown in Figure l. l. Built-in horizontal seal; 2. internal seal located in vahw body; 3. valve slide with chmnfered end: 4. intl'rnal contours designed to ensure that deposits arefhtshed into tlwflow.

0: Bearing~ in bridge for ease of operation.

Stop ( crosshead) e xternal to pressure ----- • envelope, limits travel a nd gives position indication Spindle and ~eating components are free to adjust dimensionally in response to thermal ---_ changes within the ---pressure envelope

Bonnet pressure sealed (as shown) on valves to Class 900/PN 150 and above . Bolted on Class 600/PN 100 valve~ Back scat , / Belt eye j Seat pressed-in (as shown) on carbon steel valve~ welded-in on alloy steel valves

.~--=JJ Figure 3. Venturi pnrnllel-slide valve.

130

Valve Types Design and Construction

Unlike conventional gate valves, the slide passes through the body and a standard gland packing cannot therefore be used . In the design shown here. profiled transverse seals are employed. These comprise two lengths ofV-section rubber with the open sides of the V facing each other. During assembly, the diamond-shaped opening is filled with an oiled-fibre packing which is forced

Valve closed

Valve open

Fluid pressure (indicated by arrows) holds disc on outlet side in contact with seat.

Gives unobstructed flow. 'Eye-piece' bridges gap to complete venturi form passage and protect seat faces.

Figure 4 . Parallel-slide action .

Figure> S. Para/Id-s/ide valve>.

Slide Valves

131

in and pushes the lips of the transverse seals into contact with the body and the slide. In this way. leakage to atmosphere is prevented. Also. by removing the screws on the sides of the body, more packing can be inserted at a later date to maintain a tight seal even if the valve is on-stream and under pressure or vacuum. An optional extra on this design of valve is a set of scraper blades set below the transverse seals. During the opening phase, this enables the slide faces to be scraped clean over their whole width before they are drawn through the transverse seals, and damage to the seals is thereby prevented. This is particularly important when handling sugar, sticky media such as honey, chocolate compound. glues, tenacious powders. etc. A venturi parallel-slide valve is shown in sectioned form in Figure 3. This valve incorporates a pressure-sealed bonnet design and is used as a general purpose stop valve for main steam and feedwater isolation on power sta tion boiler plant. The parallel-slide action is shown in Figure 4. A cutaway view of the internal cross-section of the valve is shown in Figure 5. When power operation is required, slide valves are particularly easy to operate pneumatically as the pneumatic cylinder can be mounted directly on

Figurf 6. Slide valves used in (top left ) brewi11g. ( top right ) food processing rmd (bottom) dust control.

13 2

Valve Types Design and Construction

the valve pillars and the end of the piston rod connected direct to the valve slide. Electric actuation is also widely used on slide valves and, to a lesser extent, hydraulic actuation. In addition, a very useful alternative to hand wheel operation is the lever-operated slide valve which gives a very quick open/ close operation. When powders and granular materials are stored in silos or conveyed by belt and screw conveyors, actuated rectangular valves are often required, as shown in Figure 6. This is particularly true for pulverised fuels. ash and grain . as well as brewing, food processing and dust control. See also the chapter on Gate Valves.

Screw-down Valves The general classification "screw-down valve" is taken to refer to all types of valves sealing by a disc or p.lug. etc., and in which the sealing element is lifted from and lowered on to the valve seat by rotation of a threaded stem, the axis of which is perpendicular to the valve seat. Mainly this embraces various types of stop valves , e.g. globe valves, oblique or Y-valves, gate valves, lift-type plug valves and angle valves. Much of this has been covered in other chapters. It also includes certain types of throttling valves, i.e. needle valves in particular. Screw-down valves are also categorised as: (i) (ii)

Inside screw, where the threaded portion of the stem is fully enclosed within the bonnet. Outside screw, where the threaded portion of the stem is exterior to the bonnet and (usually) carried in a yoke (see Figure 1). Handwheel

Handwheel

Bridge

Gland

Yoke sleeve Stem Pillars Gland

Bonnet Bridge Stem

Bonnet

Gasket

Gasket

Wedge nut

Stem nut

Seats

Seats Wedge

Body· - - --

lnside screw

Figure I. Outside-and inside-screw gate valves.

Outside screw

134

Valve Types Design and Construction

A further distinction is made between: (a) (b)

Rising-stem valves. where the stem moves in or out of the bonnet as the stem is rotated by a hand wheel. lever or actuator. Non-rising stem valves, where there is no displacement of the stem along its axis when rotated.

Both inside-screw and outside-screw valves can be of rising-stem or nonrising-stem type. Principal differences between these categories are: (i)

(ii)

Inside-screw valves have the threaded length of the stem protected from dirt, etc. However. the stem is fully exposed to the fluid being handled. Also it is more difficult to provide lubrication for the thread where the fluid handled is not itself a lubricant. Outside-screw valves have the threaded length fully exposed to the surroundings. hence they can readily collect dirt and/or be subject to corrosion. Lubrication is easier because the threaded length is fully

Inside screw-down val vi'.

Screw-down Valves

135

6 10

9 8 7

5

No Part 1 Body Valve Seat 2 3 Valve 4 Locknut 5 Bonnet 6 Stem Y2" - 1" 1 Jj.,"- 2"

4

3 2

Operating range u 0

~

~

ro

260

~:;

-

200

~

~

(i) 0.

E 100

~team

Saturation

(j)

f-

[;.;'{·:;.:,.:,;::=:. :i·)()";.:;

r---

Curve I

0 0

5

10

15

20 25 Pressure bar g

~

L....___j The product must not be used in this region.

Typical industry standard stop vnlve.

7 8 9 10 11 12

Washer Gland Packing Gland Packing Nut Handwheel Handwheel Nut

136

ValvP Types Design and Construction

N0Part --·--- 1

2

3 4

5 6 7 8 9 10

Body Bonnet Seat Disc/Plug Bellows Stem Handwheel Stem Packing Bonnet Studs Bonnet Nuts Body/ Bonnet Gasket

Operating range

(ANSIJOO)

u 0 Q)

::>

Q;

a. i1l E

~

20o~hd--~q===mllfl Steam -f"C-----+---Saturation --+-----+-t----=~~ Curve 10

E:'.:~::(.'./]

20

30

This product must not be used 1n this region .

ANSI bellows-sea.led stop vnlve.

Screw-down Valves

13 7

Outside-screw rising-stem stop valve.

accessible, but again lubricant will promote collection of dirt on the threads. The threaded length of the stem is isolated from the fluid being handled by the stem glands. hence this type is more suitable for handling corrosive media , slurries, etc. (a)

(b)

Rising-stem valves provide a visual indication of the position of the valve disc or gate and thus the degree of valve opening. On the other hand. adequate clearance is needed above the valve to accommodate the rising-stem movement. Non-rising-stem valves have the advantage that they can be installed in positions where headroom is limited. Stem wear is also minimised, although there may be increased wear on the threaded length which lifts and lowers the valve disc or gate.

For corrosive duties, stem protection may be provided by a bellows seal applied either to an inside screw (usually) or an outside screw.

Spool Valves Spool valves embody two basic elements: a cylindrical barrel in which slides a plunger or spool. Port blocking is provided by glands or full diameter sections on the spool, with intervening waist sections which provide portinterconnection through the barrel. This makes it easy to provide multi-way and multi-position switching. Sliding-spool valves are generally used in hydraulic and pneumatic fluid power systems for directional and flow-control purposes. There must be an annular clearance between the spool and the body, so there is always some leakage flow across the spool and this must be taken into consideration. Spool valves are relatively simple and economic to manufacture, although for adequate sealing a fine surface finish is required on both the spool and the barrel bore. with close tolerances to ensure practical minimum clearances. Glandless spool valves thus normally require a lapped fit between spool and body. Pneumatic-spool valves with static seals offer simpler construction in this respect and also rather more flexibility in design with seals positioned between valve spaces so that a seal is situated between each subsequent port and one seal on the outside of each of the two outer ports (see Figure 1). Spool valves operate on a sliding principle, so design normally follows the basic requirement of all slide valves, i.e.: Pressure-balanced ports are required so that there is no net pressure force acting axially on the spool. The valve diameter should be a minimum consistent with suitable stiffness.

(i)

(ii)

2 2

3

4

1

5 4-way va lve

3-way valve

Figure I. 3-way and 4-way spool valves.

Spool Valves

139

(iii) The valve body or sleeve must have adequate rigidity.

(iv) Friction forces must be minimised and are largely controlled by material selection for rubbing/ sliding parts. (v) Annular flow should be symmetricalin order to avoid radial unbalanced forces which could increase friction . (vi) Bernoulli forces. arising from changes in fluid momentum. must be minimised. Parameters (v) and (vi) are largely controlled by the detail design of the spool. Spool-cushioning passages can be built into the valve as shown in Figure 2. These equalise hydraulic forces on the ends of the spool and cushion the spool shift. v\lhen the spool is shifted. the fluid displaced from one end of the spool is transferred to the other end through the passage which is designed to provide a cushioning effect and balance the spool. Forces may also be set up due to the changes in fluid momentum through the valve, generally described as Bernoulli forces. Thus, typically, there may be a reduction in pressure on the valve spool at the controlling edge, leading to a force being generated producing unbalance or tending to close the valve. At the same time, if backlash is also present in the system, Bernoulli forces may produce high frequency 'chatter' of the valve spool. The hydraulic unbalancing effects of fluid momentum between the cylinder and tank ports of a vale can be minimised by contouring the spool shape as shown in Figure 3. Flow forces that are developed at the conventional square land orifice lP to B) are partially compensated for by the force-balancing contour on the outer spool lands (A toT). Accurate sequencing of land opening and closing also provides maximum axial stability. as shown in Figure 4. In this example, it is important that flow path A toT is opened before the path P to B to prevent pressure intensification which could upset axial balance and limit valve function. The spool can be moved manually, mechanically, by pilot pressure or by an electric solenoid. Directional-control valves usually have finite spool positioning to change the direction of flow from one port to another.

... Figure 2.

140

Valve Types Design and Construction

Pigure 4.

Figure3 .

Proportional-control valves and servo-valves have infinitely controllable spool positioning so that the flow rate of the fluid as well as the direction of flow is controlled. Servo-valves

A servo-valve is capable of providing continuously variable flow with changing input signal. The latter is normally a n electric signal to a torque motor. but feedback signals may also be derived hydraulically or mechanically. The simplest form of spool valve to control both the direction of flow and flow rate is the three-way valve, but this will control the flow to only one side of the load and a differential-area spool must be used . A more common design. shown in Figure 5, is the four-way valve whose symmetry results in improved linearity. However, there are three critical axial dimensions of the spool and the sleeve. To reduce some of the manufacturing difficulties , designers have used the following different designs.

I .Surply. 2. Ex hilust . 1 .T orque moto r . C l il nd C2 to load.

Fiyure 5. Spool-type valve.

Spool Valves

141

Split-spool valves

To reduce the number of critical axial dimensions of the four-way valve, two separate three-way valves may be linked together, as shown in Figure 6, and a means of zero adjustment can be provided in the links. Although manufacturing problems associated with porting are reduced, further difficulties are introduced in that two parallel bores have to be made, and there may be additional backlash in the linkage. Furthermore, its weight is usually more than that of the simple four-way valve . A design in which manufacturing difficulties associated with axial tolerances are eliminated is the Elliott adjustable lap valve. This is a split, three-way valve in which the two spools are mounted back-to-back and are actuated by a central ram against restraint. The correct valve lap is obtained after assembly by axial adjustment or the sleeves. Sliding-plate valves

This design . shown in Figure 7. may be likened to an unwrapped spool (that is, two-dimensional). or even to the original D-type steam valve. It overcomes the difficulties associated with the manufacture of the bores in spool valves, and hole-and-plug porting techniques may be used. However, some manufacturers consider. the difficulties associated with the production of flat and parallel plates greater than those or making spools and sleeves. Various methods are used to reduce friction forces; in some valves the sliding member is suspended on spring plates to prevent metallic contact, and others achieve hydrostatic pressure balance. Rotary-plate va lves

An alternative form of the plate valve is the rotary type shown in Figure 8. Reaction-force compensation may be fairly easily introduced by the use of deflector vanes which have the added advantage of being adjustable.

!. Supply . 2. Exhau~t. 3.Torque motor Cl and C2 to load .

Figure 6. Split-spool valve.

142

Valve Types Design and Construction

! .Input. 2.Exhamt. 3. Torque motor. CI anJ ('2 to load.

Figure 7. Sliding-plate valve.

!.Input. 2. Exhaust. 3.Torquc motor.

C! and ('2 to load .

Figure 8. Rotary-plate valw.

Askania-type valves

The main advantages claimed for this type or valve, sho·wn in Figure 9. are that it is less susceptible to contamination clogging, and the ease or rna n u facture . Although it has been fairly extensively used [or control purposes in lowpressure applications, its design for medium- and high-pressure systems presents a far more difficult problem because it is based on empirical methods. A comment has been made that large reaction forces leading to serious instability can occur, although the reasons for this are not known. This valve, whose action depends upon the conversion of kinetic energy of the jet into static pressure at the spool or ram, is referred to in the United States as the 'jet-pipe' design. However, it is probably preferable to avoid this term to prevent confusion with other nozzle or jet designs used in two-stage valves. Two-stage valves

Two-stage valves were designed to overcome the practical limitations of power and response of single-stage valves. Any of the previously mentioned

144

Valve Types Design and Construction 4

6

--oo-c- - - - - - - - - - - - - - - - ----, I

I

----~----------,

II I

I I

I I

+I

!.Supply. 2. [xhausl. }.Torque motor 4. 1nput force. 5 First stage 6 .SeconJ stage posit1on feedback. 7. SeconJ stage. I( Restrict or C I and C2 to loild.

I I

I -

t

2

- - __ j

t

C! C2 ~~--------------------~

Figure 11. Two-stage valve: IIOzzle-flapper spool.

4

6

---------------------,

I

I I

I

• I

I

I I

I __ JI

! .Supply . 2. Exhaust. 3.Torque motor 4.Jnput force. :'i. First stage. 6.Sccond stage position feedback. C! and C2 to load.

Figure 12. Two-stage valve: double rwzzlf-flapper spool.

causes an increase in the pressure in the chamber between the nozzle and the restrictor which causes the second stage spool to move and thus deliver oil to the load. Movement of the flapper in the other direction will reduce the chamber pressure, causing the spool to move in the opposite direction and produce reverse motion of the load. Thus the nozzle and flapper act as a variable impedence, and a variable percentage of the supply pressure acts on the right-hand end of the second stage spool. Double nozzl~flapper spool valves

Representing a further development of the design previously described, this valve is shown in Figure 12. The flapper and nozzle control the pressure at

Spool Valves

145

I. DLtncing roll . 2. Lever

3. Driver roll or in-winder. 4.Servo-valvc . ."i.Boost pump.

Figurl' 13. Corrtrolli11g weiJ tension wit/1 hydraulic servo-operated variable delivery pump and hydraulic motor drive.

both ends of the second stage spool and thus the operation of the first stage may be likened to that of the four-way valve. Although a fairly high quiescent flow is inevitable with this design, the power loss is not significant for most applications. The introduction of the nozzle-flapper device as the first stage. with its low inertia and short stroke, was a major contribution in the field of two-stage valve design. The design shown in Figure 13 is basically one of the earliest of a family of valves having nozzle- flapper as the first stage. For more detailed information on spool valves, refer to the Pneumatic Handbook also published by Elsevier Science Limited.

Solenoid Valves A solenoid valve is basically a valve operated by a built-in actuator in the form of an electrical coil (or solenoid) and a plunger. The valve is thus opened or closed by an electrical signal. being returned to its original position (usually by a spring) when the signal is removed. Solenoid valves are produced in two modes-normallyopen or normally-closed (referring to the state when the solenoid is not energised). The solenoid itself may be operated by d.c. or a.c. A d.c. supply may be provided by a battery, d.c. generator or through a rectifier. An a.c. supply is normally taken from a.c. mains voltage, through a transformer if necessary. Valve types and classifications

Basically there are nine different valve types to be distinguished, as shown in Figure 1. Solenoid valves are also classified by type as follows:

So /maid valves.

Solenoid Vnlves

SLIDE DISC

CORE DISC

FLAPPER DISC

IJ FLOATING DIAPHRAGM

LEVER

HUNG DIAPHRAGM

POPPET

PISTON SPOOL

Figure I. Solenoid vnlve types.

14 7

148

Valve Types Design and Construction

2/2 (2-way valves)

T·wo-way valves have one inlet and one outlet pipe connection (see Figure 2). They are of either • •

normally-closed construction-valve is closed when de-energised and open when energised, or normally-open construction- valve is closed when energised and open when de-energised.

+

Figure 2. 2 / 2 ( 2-way valves).

Solenoid Valves

149

3/2 (3-way valves)

Three-way solenoid vales have three pipe connections and two orifices (when one is open the other is closed and vice versa). They are commonly used alternately to apply pressure to and exhaust pressure from a diaphragm valve or single acting cylinder (see Figure 3 ). Three modes of operation are available. •

•

•

Normally-closed construction-with the valve de-energised, the pressure port is closed and the exhaust port is connected to the cylinder port. With the valve energised, the pressure port is connected to the cylinder port and the exhaust port is closed. Normally-open construction-when the valve is de-energised the pressure port is connected to the cylinder port and the exhaust port is closed. When the valve is energised, the pressure port is closed and the cylinder port is connected to the exhaust port. Universal construction-this allows the valve to be connected in either the normally-closed or normally-open position. In addition, the valve may be connected to select one or two ports (selection) or to divert flow from one port to another (diversion).

...

2

.. 3

Figure 3. 3/2 ( 3-way valves).

150

Valve Types Design and Construction

4/2 and 5/2 (4-way valves)

Four-way solenoid valves are generally used to operate double-acting cylinders. These have four or five pipe connections-one pressure. two cylinder and one or two exhausts (Figure 4). In one valve position, pressure is connected to one cylinder port; the other is connected to the exhaust. In the other valve position, pressure and exhaust are reversed at the cylinder connections. Single-solenoid and dual-solenoid types are commonplace. Manual reset valves

Manual reset valves must be manually latched into position and will return to their original position only when the solenoid has been energised or de-energised depending on construction (Figure 5 ). Four modes of operation are possible: • • • •

electrically tripped-latched open electrically tripped-latched closed no voltage release-normally-closed no voltage release- normally-open

Valve classifications

•

•

General purpose valve-a normally-open or normally-closed valve intended to control the flow of a fluid but not depended upon to act as a safety valve. Safety shut-off valve-a normally-closed valve of the 'on' or 'off' type. intended to be actuated by a safety control or emergency device to prevent unsafe fluid delivery. It may also be used as a general purpose valve. A multiple-port valve may be designated as a safety shut-off valve only with respect to its normally-closed port.

Figure4. 4/2 and 5/2 (4-way valves).

SolenoidValves

Figure 5.

•

Ma~rual-resct

151

valves.

Process-control valve- an approved valve (FM) to control flammable gases. but not to be relied upon as a safety shut-off valve.

Direct-acting valves

When the solenoid is energised in a direct-acting valve, the core directly opens the orifice of a normally-closed valve or closes the orifice of a normally-open valve (Figures 6a and 6b ). The force needed to open the valves is proportional to the orifice size and fluid pressure. As the orifice size increases, so does the force required. To open large orifices while keeping the solenoid size small, internal pilots are used. Pilot-operated valve

This type of solenoid valve is equipped with a pilot and (smaller) (bleed) orifice and utilises the line pressure for operation. When the solenoid is energised. the pilot orifice is opened and releases pressure from the top of the valve piston or diaphragm to the outlet of the valve.

15 2

Valve Types Design and Construction

Solenoid coil

Bonnet

Hung spring

Body

Disc

Direct-acting i111ng-diap!Jragm solenoid valve component parts.

FLON

FLON . .

Df·EIIERGIZED

o+

EIIERCliZfD

Figures 6a and 6b. Direct-acting solenoid valves.

This results in an unbalanced pressure which forces the line pressure to lift the piston or diaphragm off the main orifice and open the va lve. When the solenoid is de-energised, the pilot orifice is closed and full line pressure is applied to the top of the piston or diaphragm through the bleed orifice. producing a sealing force for tight closure. There are two common types of construction:

Solenoid Valves

(i)

(ii)

153

floating diaphragm or piston which requires a minimum pressure drop to remain in the open position (Figures 7a and 7b ); hung-type diaphragm or piston which is mechanically held open by the solenoid core and operates from zero to the maximum pressure rating (Figures Sa and 8b ).

Pressure-operated valve

This is a diaphragm- or piston-operated valve equipped with a 3- or 4-way solenoid pilot which alternatively applies a separate operating pressure to or from the diaphragm or piston to open or close the main valve (Figures 9 and 1 0).

OUTLET

DE·ENEROIZED

ENERGIZED

Figures 7a and 7/J. lrrt('rrwl pilot-operntedfloaUng-diaphragm valve.

FLOW-

FLOW-

DE-ENERGIZED

ENERGIZED

Figures Sa and 8b. Internal pilot-operated hung-diaphragm valve.

154

Valve Types Design and Construction

Pressurr-opernted diaphragm solr11oid valws.

Air-operated solenoid valves

An-air operated solenoid valve has two basic functional units: (i) (ii)

an operator with a diaphragm or piston assembly which when pressurised develops a force to operates: a valve containing an orifice in ·w hich a disc or plug is positioned to stop or allow Aow.

Low and instrument air-pressure range operators usually have a diaphragm for operation and for pneumatic operation the operator is generally a piston.

+

Figure 9. Pressure-opPrated diaphragm valve.

Figurr 10. Prcssure-operatl'd pist.on vaiw'.

Solenoid Valves

155

4 / 2. 5/ 2 direci pilot-operated solenoid valves.

In dual-acting valves the operator stem is moved by the diaphragm or piston and directly opens or closes the orifice. In internal pilot-operated valves, the valve is equipped with a pilot and bleed orifice and utilises the line pressure for operation. Figure 11 shows a direct-acting valve flow diagram and Figure 12 an internal pilot-operated valve flow diagram. Return-spring effect

vVith a two-way normally-closed valve, both the spring force and the fluid inlet pressure act to close the valve. As a consequence, the return spring can be made relatively weak, and in some designs eliminated entirely. The latter would require mounting the valve so that the solenoid was vertical. return action being by gravity plus fluid pressure. \!\lith a two-way normally-open valve, the spring holds the valve open, assisted by fluid pressure. The solenoid force must be sufficient to overcome both spring pressure and inlet pressure to close the valve. Three-way valves require an upper and a lower spring. The lower spring presses the valve against its seal opened by inlet pressure. The upper spring acts in a direction to force the valve open. The following are the combination of spring strengths required: Three-way normally-closed Three-way normally-open Mixer valve Divider valve

Lower spring Strong vVeak Medium Strong

Upper spring Weak Strong Medium Weak

15 6

Valve Types Design and Construction

Normally Closed

e;;;;E~~~

Operator Exhausted

Operator Pressurized

Figure II. Flowdiagram:direct-acting valve.

Normally Closed

Operator Exhausted

Operator Pressurized

Figure I2. Flow diagram: pilot-operoteri valve.

Solenoid enclosures

Various types of enclosures may be used for solenoid coils, ranging from general purpose enclosures to protect from indirect splashing and dust. through dust and watertight enclosures to full explosion-proof enclosures. Requirements in this respect are specific to the application and selected accordingly. Glandless solenoid valves

By arranging the solenoid armature to work in a sealed tube with the solenoid coil enveloping it, the sealing glands can be dispensed with, so simp lifying the construction and eliminating one possible point ofleakage. This principle has been applied extensively to smaller valves. A typical type is shown in Figure 13. This valve is T-shaped with two ports opposite each other. while the third is at right angles to them. The plunger, usually of a corrosion-resistant ferrous material, is spring-biased so that when unenergised it closes the lower orifice while leaving the other open . When energised. the plunger is pulled up so that the lower orifice is opened and the upper closed. rr desired. the spring can be arranged to bias the plunger in one direction. The plunger is provided with plastic valve discs, usually of synthetic rubber or nylon. Because the plunger is unbalanced. the force due to the pressure must be limited and the size of orifice, and therefore the flow and pressure drop, is usually related to the pressure.

Solenoid Valves

1 57

T

!.Plunger. 2.Synlhetic seats. 3.Sieeve . 4.Coil. A. Cylinder. B. Pressure. T.Exhaust.

Figure 13. Glandless solenoid valve.

The maximum pressure is also related to the type of valve and may be as high as 210 bar (3000 lbf/in 2 ) with an 0.85 mm 32 in) orifice. Flow depends on the allowable pressure drop and this in turn depends on the orifice size and the fluid. Sealing is normally 'bubble-tight' but this is to some extent dependent on the cleanliness of the fluid . Lubrication is not essential but if used with air the valve life is increased by air-line lubrication. Glandless valves can be installed in any position and will withstand appreciable shock loads. Response time is extremely short, 5 ms on a.c. and 10 to 15 ms on d.c. and it is said that speeds of up to several hundred cycles per minute are possible. For hazardous atmospheres, most manufacturers supply explosion-proof materials which are slightly heavier and bulkier than the standard type. Although these valves were originally developed for aircraft and missile application, there is no doubt that they have many uses in hydraulics, both as main valves for low-power systems and as pilot valves. Where pressures do not exceed 17.5 bar (2 50 lbf/ in 2 ), a 1. 6 mm 16 in) diameter orifice is suitable and this gives a flow of 2.31l/min (0.50 gal/min) for 3.5 bar (SO lbf/ in 2 ) pressure drop. On a 50.8 mm (2in) diameter cylinder, this would give a piston speed of 760 mm (30 in) per minute, while when used as a pilot valve for 2 5.4 mm (1 in) diameter spool with 12.7 mm (2 in) movement. the operating time is about half a second. When acting as pilot valve, the actual flow would almost certainly be greater than that for a 3 .5 bar (50 lbf/ in 2 ) pressure drop, as for a large part of the time the pressure drop will be nearer 14 bar (200 lbf/ in 2 ), until the resistance to piston or spool builds up .

e/-

e/

158

Valve Types Design and Construction

Spool-type solenoid control vnlves.

Piston-type opl'rator solenoid control valvPs.

Most of the manufacturers of these valves also supply pilot-operated valves incorporating the basic glandless valve; four-way valves, and two- and threeway valves for larger flows, are made in this way. These valves may prove useful in acting as pilots to larger valves when the 'pressure release' principle is adopted. Figure 14 shows this applied to a differential-area spool valve. Normally the larger area keeps the spool to the right, with the solenoid valve SC closed. Opening the solenoid valve causes the pressure to drop in the left-hand chamber and the spring, with the excess pressure, causes the spool to move to the left. A two-position springless valve could also be operated in the same way. with jets and solenoid valves at each end. Glandless solenoid

valves~pool

type

The construction of a four-way spring-centred closed-centre double-solenoid valve is shown in Figure 15. It has push solenoids with a spool movement of 1 mm (0.040 in) either side of the centre. It is suitable for pressures up to 140 A

B

Figure 14. Small solenoid valve used as pilot. employing pr£'ssure-reiease prirtcip/P.

Solenoid Valves

159

Figure 1 S. Glandless solenoid spool valve.

1. \Vet solenoid. Encapsulated units. Plug a nd socket connectors. Valve body. Spoo l. 6. 0-ring sea ls. 7. Mounting s urfa ce.

2. 3. 4. 5.

Figure I 6. Wet-type solenoid valve.

bar (2000 lbf/ in 2 ) and has a flow of9ljmin (2 gal/min) for a pressure drop of 2 bar (30 lbf/ in 2 ) on light hydraulic oil at 2 7 to 38°C (80 to 100°F). It is gasketmounted and when used as a pilot valve is bolted on top of the main valve. Another example of a glandless valve with a 'wet' armature is shown in Figure 16. All seals are static 0-rings. Selection

A number or operating and physic a1 parameters must be considered when selecting a solenoid valve. The operating parameters include: •

Pressures Maximum operating pressure differential (MOPD). i.e. the pressure the electrical solenoid has to overcome to open the valve and allow flow to occur.

Minimum operating-pressure differential (MinOPD) , i.e. the minimum pressure drop that will exist across the valve when it is flowing.

160

Valve Types Design and Construction

Safe static pressure, i.e. the maximum pressure the valve can be subjected to in normal service. Proof pressure, i.e. 5 times the safe working pressure. •

Temperatures Normal ambient temperature Maximum ambient temperature Minimum ambient temperature Maximum fluid temperature

•

Viscosity Viscosity is greatly dependent on temperature and to know the actual viscosity of a fluid, the real temperature of the fluid must be considered. Oil grades-both hydraulic and fuel oils are classified relative to viscosity and are roughly distinguished in heavy and light oils.

•

Response time This is the time lapse after energising (or de-energising) a solenoid valve and depends on the valve size and operating mode, the kind of electrical supply, a.c. or d.c., fluids handled by the valve, temperature, inlet pressure and pressure drop.

Approximate values for a.c. valves on air service under average conditions are: Small direct-acting valves: 5-10 ms Large direct-acting valves: 20-40 ms Internal pilot-operated valves: (a) (b) (c) (d)

small diaphragm-type 15-60 ms large diaphragm-type 40-120 ms small piston-type 75-100 ms large piston-type 100-1000 ms

Operation on liquid media generally has little effect, i.e. (a) small direct-acting valves: 20-30% higher (b) large direct-acting valves: 50-150% higher Response time on d.c. valves is approximately 50-60% higher than on a.c. operation. •

Valve seat tightness Valve-seat tightness or leakage depends on the type of valve used. sealing materials, trim and medium.

Solenoid Valves

161

Valve sizing

It is essential to size a valve properly because both undersizing and oversizing

have undesirable effects. Undersizing may result in: (1) (2) (3) (4)

Inability to pass desired flow requirements Flashing of liquids to vapours on the outlet side of the valve Lowering the outlet pressure Creating a substantial pressure loss in a piping system

Oversizing may result in: (1) (2) (3) (4) (5)

Unnecessary cost in oversized equipment Variable flow through the valve or erratic control of the flow Shorter life of some valve designs through oscillating of internal parts Erratic operation of some designs such as failure to shift position due to lack of required flow in 3- and 4-way valves Erosion of wire drawing of seats in some designs because they operate at nearly-closed position

The Kv (Cv) method of valve sizing reduces all variables to a common denominator called flow coefficient. Most, if not all. manufacturers provide extensive information and reference data for estimating Kv (Cv) and accurate sizing of solenoid valves. To summarise, the basic factors in valve sizing include: • • •

Maximum and minimum flows to be controlled Maximum and minimum pressure differentials across the valve Specific gravity. temperature and viscosity of fluids being controlled

Table 1 gives details of problems, possible causes and solutions in relation to the operation of solenoid valves. It is recommended that manufacturers' data is referred to and followed carefully when problems occur. It is advisable that the manufacturer is consulted in cases of difficulty.

...... 0\

Table 1. Troubleshooting guide

N

Problem

Possible cause

Probable solution

Valve will not operate when valve circuit is energised (direct-acting valve)

Low voltage or no voltage to solenoid coil

Check voltage at coil: for most valves. voltage should be at least 8 5% of name plate rating.

Burned out coil

See ·coil failure· below.

Excessive foreign matter jamming core in core tube

Clean valve: install strainer close to val\·e inlet.

Binding core or damaged core tube

Replace parts.

Excessive fluid pressure Valve will not operate when valve circuit is energised (pilot-operated valve)

Valve will not close or shift when valve circuit is de-energised (direct-acting valve)

Reduce pressure to valve nameplate pressure rating or install suitable valve.

~

"''"" "'"' ~

CJ

::;

~

0

c :::: .... "'.... ~ .... :::

Low pressure drop across valve

Valve might be oversized: replace valve with one having a smaller orifice. lncrease pressure if possible.

Ruptured diaphragm or piston ring

Replace damaged parts.

Plugged or restricted pilot orifice

Clean valve and pilot orifice.

Coil not de-energised

Check electrical control circuit.

Excessive foreign matter jamming core in core tube

Clean valve: install strainer close to valve inlet.

Damaged disc or seat causing internal leakage

Replace with nevv parts.

Binding core or damaged core tube

Valve will not close or shift when valve circuit is de-energised (pilot-operated valve)

"'

~

c;·

Same causes and solution as for direct-acting \'alve. plus:

Damaged spring

<:::l

=:.. <::;

Replace with new spring. Never elongate or shorten.

Same ca uses and solution as for direct-acting valve. plus: Plugged bleed orifice

Clean orifice.

Damaged pilot seat or pilot disc

Replace with new parts.

Damaged diaphragm or piston

Replace with n ew parts.

Damaged pilot spring

Replace with new spring. Never elongate or shorten spring.

Insufficient pressure drop across the valve

Valve might be oversized: replace valve with one having a smaller orifice. Increase pressure if possible.

Wire drawing

Dirt or foreign matter is lodged on seat

Replace valve body or install new valve; install suitable strainer close to inlet or valve.

Coil failure

Overvoltage

Check voltage at coil: voltage must conform to nameplate rating.

Damaged core or core tube causing inrush current to be drawn continuously

Check for damaged core and core tube. or damaged spring. Check for scale or foreign matter on the core or inside the core tube. Clean thoroughly. and replace any damaged parts.

Excessive foreign matter jamming core in core tube and causing inrush current to be drawn continuously

Check for damaged core and core tube. or damaged spring. Check for scale or foreign matter on the core or inside the core tube. Clean thoroughly. and replace any damaged parts.

Excessive fluid pressure causing inrush current to be drawn continuously

Reduce pressure or install suitable valve.

Excessive ambient or fluid temperature

Class A coils are limited to ambient temperatures of 77°F. For temperatures up to 16JOF. use Class F coils: for temperatures up to 2l2°F. use Class H.

Missing solenoid parts

Install missing solenoid housing and other metal parts or properly install incorrectly assembled metal parts. The housing and other metal parts form part of the magnetic circuit and are required to provide the impedance needed to limit current draw.

Moisture inside solenoid enclosure

Waterproof the entrance conduit to prevent entry of moisture. If va lve is mounted outdoors. check to see that enclosure is weatherproof and that gaskets are in good condition: use appropriate sealant where required . If general purpose enclosure is used in a damp or humid atmosphere. use watertight. moulded coils.

' [n explosion-proof solenoids. a binding core. high-input voltage. or excessive ambient or fluid temperature may cause the solenoid's non-resettable thermal fuse to open. If this occurs. the solenoid must be replaced.

V:J 0

~

:::;

0

~

~

~

~

I-'

0'

w

Swing Check (Flap) Valves 'Swing check' valves is the preferred description for non-return valves consisting of a hinged disc, although they are also commonly called flap valves because of their geometric action. Their mode of working is obvious. With flow in one direction the disc hinges upwards to permit flow through the valve. With reverse flow the disc is held closed. Equally, spring pressure or mass effect normally holds the disc closed in the absence of flow. In some cases closure is also assisted by the use of a weighted lever. Small-size swing check valves for low-pressure services may use an elastomeric disc with a square end clamped in position, eliminating any need for a separate hinge. A back-up plate is added to assist closure and also provide rigidity to the unsupported area of elastomer when the valve is closed. Without this the disc would tend to collapse and extrude through the port. Larger versions of flexible (elastomeric) flap valves are made in sizes up to 1500 mm ( 60 in). Larger swing check valves are more usually made with discs or flaps of metal or composite materials, hinged at the top and sealing on a metal seal. The sealing surface is inclined at a small angle to the vertical to assist opening. provide more positive sealing under back pressure and reduce shock when closing under high pressure. A typical valve design is shown in Figure 1. In

1. Body in ductile iron FGS 500-7 epoxy coating 250 microns inside/outside 2. Cover in ductile iron FGS 500·7 epoxy coating 250 microns inside/outside. 3. Bolts in dip galvanised steel. 4. Closing disc: ON 65 mm to 150 mm: ducti le iron FGS 500-7 DN 200 m m: steel. 5. Drain plug : dip galvanised steel. 6. Disc coating : NBR {Nitrile). 7. Gasket: NBR (Nitrile). 8. Disc shaft: brass BS.2874 NBR coated.

Figure 1. 1'ypical standard swing check valve.

Swing Check ( Plap) \1a.lves

16 5

larger valves the disc or flap may be double hung. Flap shapes are normally (but not necessarily) circular. Swing check valves present relatively high resistance to flow in the open position as well as creating turbulence , because the flap 'floats' in the fluid stream. They may also tend to chatter in systems having frequent flow reversals. Swing check valves are normally used in horizontal pipelines. They can also be used in sectional pipelines with upward flow. They are not suitable for use in systems with pulsating flows. However, weight added to the flap or disc

Standard series swing check valve.

Door hinge bracket

Door

Anchor bolt

Lifting handle

Flexible seal

Large flexible-flap valve.

166

Valve Types Design and Construction

(or spring-loading) can control the opening pressure as well as assisting closure under back pressure. Commonly the body shape incorporates a 'dead' volume in which fluid can be trapped downstream of the flap once the valve is closed . If necessary, a drain can be incorporated at this point, e.g. when it is desirable to drain a system completely on shut-down. The double-plate check valve shown in Figure 2 is particularly suitable for pumping and general industry applications such as water treatment, irrigation, general circuits and indus trial processes.

FigurP 2. Double-plate swing check val vi'.

01

L Fiyure 3. Sprung swing check valve.

Swing Check (Flap) Valves

16 7

Figure 4. Tl1reP-piece construction swing check valve.

The valve is mounted between flanges and is suited to installations where space is limited. The swing check valve shown in Figure 3 has only one moving part and is of the sprung type. It has a tight shut-off and is capable of working in temperatures up to 600°C and pressures up to 100 bar. The spring mechanism is usually made from Iconel-X. titanium or Hastelloy. Swing check (flap) valves are also produced in a three-piece construction similar to that used in ball valve design (Figure 4) . The straight-through flow makes it particularly suitable for hydrocarbon and chemical process lines. For maintenance purposes, the valve body swings outward to allo·w access to the check and seats. Materials

Body materials used for swing check valves include cast iron. bronze. cast steel, forged steel, stainless steel. high-duty alloys and also plastics . Valve discs may be in similar materials or composites. Applications

Main application areas for swing check valves are the water industry, including pumping and water treatment, irrigation, and the petrochemical industry including hydrocarbons and industrial processes. Other applications can be found in air conditioning and general industry.

Penstocks A penstock is a single-faced valve consisting of an open frame and a door. This form of valve is normally located in tanks or channels as a means of controlling flow into a pipe. Many types are available to suit particular requirements and operating conditions. The main ones are: Penstocks for operating against pressure , i.e. pressure forcing the door onto the frame. (ii) Penstocks for operating against off-seating pressure, i.e. pressure forcing the door away from the frame. (iii) Penstocks designed to accommodate both seating and off-sea ting pressures. (i)

Seating pressure can be accommodated by the use of side wedges only. Off-seating pressure requires the use of bottom wedges or top and bottom wedges (see Figure 1). Penstocks subject to sealing pressure normally seal tighter than penstocks for off-sealing pressure duties. Both types can be made virtually drop-tight with correct installation, distortion of the gate frame at

-

I Ill

DO•

~

...

Sid e Wedg es

• t-

'== F=

=· Sid e. Bo tt o m an d To p W edges

Figure I . Penstocks showing tile location of wedges.

Penstocks

169

IM---+11------ SEALING FACES

Figure 2 . Typical penstock.

the time of installa tion being the determining factor as far as leakage is concerned . Penstock frames may be circular or rectangular. In the latter case a preferred proportion of width to depth is 2:3 for vertical form, and 4 :3 for horizontal form. Frames and gates are commonly made of cast iron, although plastic materials (usually reinforced steel) are also used for gates operating in aluminium. stainless steel or epoxy-coated frames for corrosive applications. Frames may be for channel or wall-mounted application (Figure 3 ). Sealing faces in suitable materials are embedded into both the frame and door surfaces. Handwheel operation of the gate is normal, using a rising stem supported by a suitable headstock or bracket. The advantage of a rising stem is that the screw thread at the bottom of the stem is not usually immersed and is readily accessible for lubrication. A non-rising stem eliminates the need for a headstock and merely rotates through a nut in the penstock door (see Figure 2). The threaded portion at the bottom is then usually immersed in the product being handled . Different systems for raising and lowerin g the gate may be employed on modulating penstocks used for flow-control purposes (Figures 4 and 5).

170

Valve Types Design and Construction

Spindle

/

Gusset Door lifting bracket

Adjustable seal

/ /

Chased-Invert Type.

Fixed top seal Door wedge Frame Concreto

wall Anchor bolt Reinforcing

gusset

/

/

Spindle

__. Gusset /'

Door lifting bracket

fiKed top seal Door

Flush-Invert Type.

Frome

Figure 3. Wall-mounted penstocks.

Discharge through penstocks

A penstock when opened represents a partial obstruction in an open channel over which liquid accelerates with a free liquid surface. Its performance is thus essentially similar to that of a weir where !low rate Q is proportional to width and velocity head. Working formulae are:

Q (Imp gal/min) Q (US gal/min) 3

Q (m /s)

0.13 x area (ft 2 ) 0.158 x area (ft 0.7xarea(m 2 )

2

)

x x x

J2 g x head (ft) J2 g x head (ft) J2 g x head (m)

Penstocks Fixed seal

pindle

Adjustable seal

Anchor bolt /

Concrete wall

Figure 4. Weir pwstock.

Door

lifting bracket Adjustable seal Frame End cap Fixed

vertical seal /

Door Shroud

/

angle

/

Flexible /

seal

Figure 5. Chnnnelpenstock.

171

Miscellaneous Valves Where processes or storage applications require continuous safety. the three-way changeover valve allows the user to cross over from one relief-valve system to another. The design permits two valves on a single riser. This arrangement protects the system with one active valve while the other valve is either in reserve or being serviced. Construction details are shown in Figure 1. The valve works with many general and specialised applications and can incorporate an interlock system that allows either valve to be discharged into Vent valve (not shown) • Vents cavity between rsolated crossover valve seat and relief valve • Provides port(s) lor in situ testing

Stop plate Provides posrlion adjustment and posrtive stop lockrng locatron

Integral handle • No tools • Fast operation • Short operatrng stroke (76°) • Rotary motion • Highly vrsible posrtron indicator • Green ·safety indicator" shows operator proper alignment

Balance valve For balancing pressure i!c.ross closed seat to provide low actuation torque

Locking arrangement • Cannot be locked until all components are transferrea and properly aligned • Tamper-proof handle and locking mechanism Load ring Provides controlled seat loading at assembly

Closure member • Partrally sphencal closure member • Three-ported/two-way ball • Flow path never completely closes • High Cv values • Overpressure protection at all times

Figure 1. Til reP-way changeover valve.

Spool seats • Spnng-loaded. floatrng seats provrde easy marntenance, and are pressureactuated for rn srtu testrng • Cannot be overloaded by operator • Seats protected from media

Miscellaneous Valves

1 73

Quick cross three-way changeover valve.

a single header. One valve mounts on the riser, the other on the outlets of the relief valves. The valves are operated simultaneously through a simple linkage. This type of valve can also be adapted for remote actuation, still maintaining the single movement rotary change-over action. Typical areas where the valve is used include chemical plants, fertilizer plants, offshore platforms, refineries, pulp and paper mills, gas distribution systems, toxic service, environmental protection. chlorine storage tanks, refrigeration, dual filtration and process systems. Pneumatic piston controlled on-off valve

Typically, this type of valve is best suited for controlling the flow of fluids , gases, steam and other substances apart from explosive substances (Figure 2). The valve is equipped with a position indicator. Generally the material of construction is either AISI 316, bronze or brass. Although the valve can be fitted in almost any position, it must be fitted so that the direction of flow is opposite to the plunger-closing position, otherwise water hammer can result. Tunnel diverter valve

This valve is designed for use in pressure or vacuum systems to divert or converge pellets: granules, fine powders or abrasive materials. Two types of sea ls are

174

Valve Types Design and Construction

Figure 2. Piston-controlled Oil-off valve.

used: 0-ring seals for applications conveying pellets and granular materials. and air-assisted seals for conveying powdered or abrasive materials ·where three air inlets introduce compressed air into the diverter-valve housing. An unusual design of check valve is shown in Figure 3 . This features a lipped elastomeric membrane as the working element, offering virtually unrestricted flow in the open position with a capability of passing suspended solids up to the full bore diameter. The membrane itself is held open to a full circular form by the flow. the circumference of the membrane in this condition being D. Loss of head is thus minimal (e.g. directly comparable with that of a swing check valve). With reverse flow. the membrane assumes a closed position ·with the lips in mating contact (Figure 4), i.e. the natural 'unloaded' form of the membrane. Closure is further assisted and maintained by the reverse flow impinging on the sides of the now wedge-shaped membrane. The length of seal in this case is rc.D/2, or substantially half that of a conventional check valve (i.e. the potential leakage path is reduced by half). The membrane itself is not subject to elastic deformation. merely flexure. and thus has a long life. particularly if the fluid does not contain abrasive solids in suspension. When servicing is required, replacement of the membrane

Miscellaneous Valves

Fig 11rr 3. Membrane check valve.

1TD

~I I I I

I

OPEN POSITION

Figurr4.

CLOSED POSITION

1 75

176

Valve Types Design and Construct.ion

is a simple operation. No other servicing is necessary. The membrane elastomer is selected according to the product to be handled. Because of the elastic nature of the closure, this type of check valve cannot water hammer and is also noiseless in that it has no hinge or spring which can be excited into vibration in either the open or closed position. Currently this valve is made in threaded form for water pipes up to 50 mm (2 in) diameter and flanged for water pipes from 50 to 400 mm ( 2 to 16 in) diameter. Valve sizes up to 12 5 mm ( 5 in) have a single passage. Larger valves have several passages, each with its individual membrane (Figure 5 ). This solution of dividing the total flow into partial flows with smaller flow rates which never open or close strictly eliminates water hammer in these larger valve sizes with higher flow rates. Eccentric valves

The description 'eccentric valve' is applied to plug valves having an eccentric motion against a resilient facing. i.e. as the eccentric plug rotates 90° from open to closed, it moves into a raised eccentric seat. The complete action can be followed from Figure 6. In the open position, the segmented plug is out of the flow path. Flow is straight-through, flow capacity is high. As the plug closes, it moves towards the seat without scraping the seat or body walls so there is no plug binding or wear. Flow is still straight-through. In the closed position, the plug makes contact with the seat. When furnished with a resilient facing, the plug is pressed firmly into the seat for dead-tight shut-off. The eccentric plug and seat provide lasting shut-off because the plug continues to be pressed against the seat until firm contact is made.

Figure 5.

Miscellaneous Valves

177

Figure 6. Eccentric valve: complete action.

Throttling characteristics of a valve of this type are generally excellent (Figure 7), and shut-off in the closed position is positive with air and gases as weH as liquids. The valve shown in Figures 8 and 9 has been specifically intended for applications such as tanker truck loading, portable tanks, intermediate bulk containers (IBCs) bulk transfer stations, and agricultural and aviation duties. The unit is designed to avoid accidental spills and cannot be disconnected in the 'open' position. A handle prevents this and poppets automatically stop the flow from both directions when the unit is disconnected. Maximum working pressure is 150 lb/in 2 . The valve must not be opened or closed when the pressure is in excess of 60 lb/ in 2 .

100

80 3:

0_.J

...... 2

:::> ~

x<X:

~

...... 0

~

20

60 VALVE% OPEN

Figure 7. Throttling characteristics.

80

100

17 8

Valve Types Design and Construction

Open Position

Figure 8. Dry disco11nect valv~: cutaway view.

Figurl' 9. Dry disconnect valve.

Polymer valves

Polymer valves are used to drain feed, changeover, sample, inject. distribute and control polyester (including PET), nylon, PVC, PP, PU, HOPE. LDPE and related polymers. The difi'erent types of valves used in the polymer processes include: •

•

Feeding valves-disc valves are better suited than ram valves for feeding low viscosity feedstocks into reactors (Figure 10). Typical feeding valves are used to regulate the flow of polyester into esterification and polymerization reactors. For vacuum service. bellows are generally used. These should be of the external type due to the possibility of failure in a crystallising environment. Discharge valves-ram and disc-type bottom outlet valves are used to drain reactors or control access to the transfer lines between reactors and crystallisers (Figure 11).

Miscellaneous Valves

179

Figure 10 . Feeding valve.

•

Injection and stripping (deodourising) valve-in many processes, unwanted impurities or remnants, such as unpolymerized monomers in PVC and polyurethanes or solvents in paints and coating suspensions, are stripped from the batch at the end of the process by the injection of saturated steam. The ram tip of the valve is adapted to each vessel as well as the required flow conditions to optimise the spray pattern and prevent product reflux during the operating cycle and in the closed position.

Rather than emptying the reactor when an exothermic reaction goes out of control, the injection and stripping valve (Figure 12) injects a stopper. Another injection valve injects protective colloids. This type of valve is a lso used to inject steam to heat a reactor.

Figure 11 . Discharge valve.

180

Valve Types Design and Construction

Figure 12. Injection anc/ stripping ( desodorising) valves.

•

• •

Spray rinse valves-typically used to rinse polymer reactors. especially in the production of PVC where the dome and bottom pad are the parts most in need of cleaning. Valves can be used with water or steam at up to 40 bar. Sampling valves- for drain and sampling and flush or purge. Polymer additives injection valve-these valves allow small amounts of additives and catalysts such as titanium dioxide to be injected into the line and distributed evenly through the polymer (Figure 13 ). Different types are available.

Figure 13 . Polymer additives injectio11 valve.

Miscellan eolts Valves

•

•

•

•

181

Multipart diverter valves-these eliminate multiple in-line valves with associated distributor 'T' pieces and piping. Main lines can be divided up to six lines with the valves having up to seven inlets and outlets. Filter switching valves-usually two valves are involved for switching duplex filters in high-viscosity polymer plants. The inlet valve diverts the flow to one of the duplex filters and the outlet valve guides the flow back to the main line. Piston diverter valves and rotating disc valves are used for this process. Both types of valves can also incorporate particular features and modes of operation. In-line valves- these are used to control and shut off the flow of polymer through the piping system. Ball valves and globe vaJves are not suitable for this duty. Y-globe valves are used in both manual on/ off and automatic control versions with polyester. As an alternative, gate valves are used in low pressure and vacuum applications. Dye head valves-these valves combine a bottom outlet piston or an end of line Y-globe valve with a stranding dye head, the one used in polyester and nylon polymerization plants.

SECTION 3 Pressure Valves and Services

Check Valves Safety and Relief Valves Self-Acting Reducing Valves Air Relief Valves Foot Valves

Check Valves In general terms. check valves are intended to prevent reverse flow in a line e.g. after a pump has stopped and to prevent water hammer. They are also known as non-return valves. reflux valves, flap valves. retention valves and foot valves in different services. The basic principle of the valve is to only allow flow in one direction only and with non-return valves, the check valve is self actuating when flow is reversed. Discs, wafers or membrane diaphragms are used in this type of valve. There are numerous types of closing systems in check valves but basically the check valve can be categorised as follows : (i)

S·wing- or plate-type valves (swing/ plate check valves)-Figure 1, where the check mechanism is a hinged plate or flap, or disc-see chapter on Flap Valves, Section 2. The butterfly check valve is a variant on this principle-see chapter on Butterfly Valves, Section 2.

Q{-1o 2

2

Swing check valve, (exploded view).

!.Body. 2.Body connector 3.Seat housing. 4.Retaining plate . 5.Ciack. 6.Seat. 7.Bodyseal. 8.0rientation pin. 9. Body connector bolt. IO.Body connector nut. ll.Optional clock spring . 12. Body label. 13. Identification label.

18 6

Pressure Falves and Services

Swing check valves.

Buttweldmg End

Figure 1. Bolted cover swing check valvr.

CheckValves

187

(ii)

Tilting disc check valves, similar to swing-type check valves but with a profiled disc. (iii) Guided or lift-type valves where the check mechanism incorporates an element which lifts along an axis in line with the axis of the body seat. These may be further sub-divided into: (a) disc check valves. (b) piston check valves. (c) ball check valves. (iv) Foot valves: specifically check valves fitted to the bottom of a suction pipe. (v) Spring-loaded check valves. (vi) \t\lafer check valves: includes swing-type, sprung disc twin plate. (vii) Check and surge-suppressor valves: including multi-door check valves for larger pipelines. and electrically- and pneumatically-operated surge-suppressor valves. (viii) Hydraulic and pneumatic check valves. Tilting disc check valves

The basis of the tilting disc check valve is a 'lifting' section disc. pivoted in front of its centre of pressure and counterweighted and/ or spring-loaded to assume a normal closed position. With flow in one direction the disc lifts and 'floats' in the stream. offering minimum resistance to flow. The balance of the disc is such that as flow decreases the disc will pivot towards its closed position, reaching this before flow has actually ceased, sealing before reverse flow commences. With reverse-flow, reverse-flow pressure and the counterweight system hold the disc closed (Figure 2). Operation is smooth and silent under all conditions. Valves of this type normally have resilient sealing rings mounted on a metal face. Metal seals may be used for high-temperature applications. Guided or lift-type disc valves

Lift-type disc valves are similar in configuration to globe valves except that the disc or plug is automatically operated, i.e. is capable of floating in its seat. The

Full flow

Low flow

Figure 2. Ti!Ungdisccheck valve.

Reverse flow

18 8

Pressure Valws and Services

Figure 3. Standard guided 11011-retrm1 check valve.

disc or plug is lifted by flow in one direction, permitting through flow. With reverse flow the disc or plug is held on its seat by reverse-flow pressure. giving shut-off. A typical standard check valve is shown in Figure 3. Valves of this type are further categorised by geometric configuration, i.e. horizontal. angle (oblique) and vertical. Piston check valves

The piston-type lift check valve incorporates a dashpot applied to the check mechanism (Figure 4), otherwise it is basically similar to a lift-type disc valve. The advantage of the dash pot is that it provides a damping effect during operation. Lift-type piston check valves are commonly used in conjunction with globe and angle valves on piping systems subject to surge pressures or frequent changes in flow direction.

Check valve for high-duty pressure wat.er systems.

Horizorrta/lift check valve.

CheckValves

lit-~+---.-

""'*~~

2

189

l.Body.

2. Disc. 3.Disc holder . 4.Cover.

Figr.trf 4. Piston check valve.

Ball check valves

The check element in a lift-type ball valve is a spherical ball, suitably restrained but capable of floating off and onto a seat. With forward flow the ball is forced away from the seat. opening the valve. With reverse .flow the ball is forced onto the seat to produce a seal and shut-off. A particular advantage of ball check valves is that they can prove more suitable for use with viscous fluids than other types (Figure 5). Ball check valves may be of all-metal construction, metal ball with resilient seat. mixed construction (metal or plastic ball), or all-plastic construction. Foot valves

Foot valves, which often include a strainer, are fitted to the end of a suction pipe and prevent a pump emptying when it stops and therefore not needing priming when restarting. They should have a minimum resistance to flow, with the

Figrtre 5. Ball rlrl'ck valve. The closing system is a ball lifted up by thefluid and guided ton lateral housing.

190

Pressure Valves and Services

Figure 6. Foot valve for p11mping installations with substantia/flow.

Figure 7. Menrbrane foot valve for irrigation and drainage pumps.

actual valve element or flap as light as possible if the risk of cavitation is to be avoided. The valves may be of the single flap (Figures 6 and 7) or multiple flat-type , membrane, guided or ball-operating systems. See chapter on Foot Valves. Spring~loaded check valves

Lift-type check valves may be spring-loaded for more positive shut-off action, particularly as regards more rapid-response cessation of flow. i.e. they can be adjusted to close before flow has fully ceased rather than having to rely on reverse-flow pressure. They can be of disc, plug or ball-type and can work in any position. i.e. horizontal, inclined, upward or downward flow (Figure 8 ). Spring-loaded check valves can be made in the widest variety of materials with stainless steel or high-duty alloy springs as necessary. Opening characteristics are governed by the spring rate. In-line spring assisted valves

The advantages of valves of this type are that they can be installed in the line in any orientation and typically they do not rely on gravity or reverse flow to close. Instead, as the forward velocity of the fluid slows, the spring assist starts to close the disc. Due to the spring assist and short travel distance of the disc, by the time forward velocity has decreased to zero, the valve disk has reached the seat and the valve is closed. With reverse flow eliminated, the forces necessary to produce water hammer on both upstream and downstream sides of the valve are substantially reduced.

CheckValves

191

Figure 8. Spring-loaded check valve for protecting drinking water nPtworks.

In-line check valves of this type are probably among the most popular types and are used in many industries including chemical, food and beverage. mining, oil and gas. pulp and paper, building services and general industry duties . A basic in-line check valve is shown in Figure 9. A list of typical applications for spring-assisted in-line check valves is shown in Table 1 . Water hammer

This is the generation and effect of high-pressure shock waves (transients) in relatively incompressible fluids. \.Vater hammer is caused by the shock waves that are generated when a liquid is stopped abruptly in a pipe by an object such as a valve disc. Symptoms include noise. vibration and hammering pipe

DISC

BODY SEAL "O"AING

Figure 9. Spring-assisted in-lim' check valve.

19 2

Pressure Valves and Services

In-line check valves.

sounds which can result in flange breakage, equipment damage, ruptured piping and damage to pipe supports. vVhenever incompressible fluids exist in a piping system, the potential exists for water hammer. The risks or water hammer developing are particularly high when the velocity of the fluid is high, there is a large mass of fluid moving and/ or when there are large elevation changes within the piping systems. The check valve shown in Figure 10 is specially designed for use on the discharge side of reciprocating air or gas compressors. It includes a pulse damping chamber to maintain the disc in the open position during the momentary reductions in flow associated with each cycle of a reciprocating compressor and to protect against premature seat wear. Restrictor check valves are generally used for applications that require higher cracking pressures to open the check valve. They should not be considered a substitute for a pressure-relief valve. A general check valve trouble shooting guide is given in Table 2. The operation of in-line check valves is not normally affected by their proximity to elbows, 'Ts' control valves, etc. It is not good practice to install

CileckValves

193

Table 1. In-line check valves

Applications

Building maintenance Compressor discharge Condensate lines Pump discharge Steam lines Water lines Chemical processing Boiler feed and discharge Compressor discharge Condensate lines Cooling towers Cryogenics Evaporators Metering pumps Mineral dewatering Nitrogen purge Process lines Pump discharge Steam lines Vacuum lines and breakers Water treatment Food, beverage and drug Autoclaves Boiler feed and discharge Chemical lines Compressor discharge Condensate lines Cookers Evaporators Metering pumps Pump discharge Refrigeration (hot gas defrost} Steam lines Vacuum lines and breakers

Petroleum production and refining Pump discharge Steam lines Vacuum lines and breakers Water treatment Power generation Boiler feed and discharge Compressor discharge Cooling towers Evaporators Fly ash system Pump discharge Steam lines Vacuum system Water lines Primary metals Chemical lines Compressor discharge Condensate lines Evaporators Extrusion equipment Hydraulic lines Presses- water inlet and outlet Pump discharge Steam lines Water lines Water treatment

Mining Boiler feed and discharge Mine dewatering

Pulp and paper Boiler feed and discharge Chemica\ lines Condensate lines Generator inlet and discharge Metering pumps Pump discharge Steam lines (digester and paper machines) Water treatment

Petroleum production and refining Boiler feed and discharge Compressor discharge Condensate lines Cooling towers Crude and refined product lines Evaporators Generator iolet and discharge

Textiles Boiler feed and discharge Chemical dye lines Compressor discharge Condensate lines Metering pumps Pump discharge Steam lines

194

Pressure Valves and Services

SPA ING ___,~_-f,:.q2::::;:......_.~ RETAINER

NUT

Fig11re I 0. Check valve for reciprocating compressors.

in-line check valves directly to the outlet of such devices as it can result in decreased life due to turbulence caused by the fitting. Some manufacturers recommend that in-line check valves be installed a minimum of five pipediameters downstream of any fitting that would cause turbulence. The flow arrow on the body casing, if shown, must be pointed in the direction of the flow . Wafer check valves

Typically wafer-style-design check valves are used as an effective solution for the prevention of reverse flow in pipes carrying most types of liquids, steam gases, and vapours. They are usually designed to fit between two pipeline flanges . The valves are opened by the flow pressure of the fluid and closed by a spring when flow ceases and before reverse flow can occur (Figure 11 ). Typical applications include: • • • •

Steam boiler flooding protection Pipeline fitting protection Prevention of reverse flow Vacuum breaker

A typical wafer check valve with its pressure-loss diagram is shown in Figure 12.

Check Valves

19 5

Water-type cfll'ck valve.

01

DO

Fig11re 1 7. Spring disc wafrr clzeck valve.

Hydraulic and pneumatic check valves

Check valves employed in hydraulic and pneumatic applications are more comprehensively covered in the Hydraulic Handbook and the Pneumatic Handbook both published by Elsevier Science Limited. These valves are generally used where high pressures (up to 10,000 lb/ in 2 ) in standard form where positive leak-tight sealing is required.

196

PressureValvesandServices

Pressure loss diagram 200

100 70

~ ~

50 30

Q)

20

E

·= ~ 3:

~ \<JIJ

2.-~~

/ .L'

10 7 5

0

c;:

.....

2

3"'

50 30 20

~

I--'

~ ...

..... I

,

j_

3

2

/

1 0.7

~co<J I"'

~ v v ~v v ~~~

L--'

lLr"

~\':>

~

~

v--

s

5

~

3 2

2.....

....

L--'

...-'

--

= Q)

I'

..t!.

~~~ ........


........

10 1--"

~~:;..;-

if"

~ v ,;'"",..

......

3:

Q)

-<;;;

:s::

~

0.5 0.2

0.01

0.02

0.05

0.1

0.2

0.5

Pressure loss rn bar

Pressure loss diagram with open valve at 20'C The values indicated are applicable to spring loaded valves with horizontal flow. With vertical flow, insignificant deviations occur only within the range of partial opening. The curves given in the chart are valid for water at 20'C. To determine the pressure drop for other fluids the equivalent water volume flowrate must be calculated and used in the graph.

Vw-~

xV

Vw = Equivalent water volume flow in 1/s or m3/h Q V

= =

Density of fluid kg/m 3 Volume of fluid 1/s or rn3/h

Figure 12. Typical wrifer-type check valve and pressure loss diagra111.

CileckValves

197

Table 2. Check valve trouble-shooting guide Symptom

Cause

Solutions

Water hammer. loud noise, vibration, ruptured piping. equipment damage.

Slow-closing check valve.

In-line spring assisted check valve.

Low flow. pulsating flow, improper sizing.

Custom sizing of the check valve intervals. PDC for reciproca ting air or gas medium.

Excessive seat leakage (greater than MSS-SP61).

Dirt. trash. foreign substance in the valve.

Clean out the valve. Install strainers if it is a recurring problem. Install a soft seat if bubble tightshut-offis required.

Noise. clicking. tapping.

Low flow . pulsating flow , improper sizing.

Custom sizing of the check valve internals. PDC fo r reciprocating air or gas medium.

Steam wear (pointed stem). elongated seat guide. bushing wear.

-

Reverse flow.

-

Component breakage. valve failure.

-

Slow-closing check valve.

In-line spring-assisted check valve.

Reciprocating compressor.

PDC for reciprocating air or gas medium.

Valve not full open. pulsing flow, improper sizing.

Custom sizing of the check valve internals. PDC for reciprocating air or gas medium.

-Missing internals.

Various types of hydraulic and pneumatic check valves are shown in Figure 13. The distinguishing feature of these valves is their zero leakage achieved by a flexible seal seat (Figure 14). The flexible seal seat design allows the poppet in the check valve to impact only slightly on the '0' ring in the closed position. The metal-to-metal contact between the poppet and the end cap serves as a mechanical seat. Under reverse pressure, the '0' ring flexes only as much as is needed to seal around the nose of the poppet and to expel any foreign particles. As a result the '0' rings are protected from excessive wear. Five flow holes drilled into the poppet core are positioned to provide a streamlined flow path through the valve. The combined area of these holes is greater than the area of either the inlet or outlet parts. The flow is directed through the centre of the spring. Typically, hydraulic and pneumatic check valves incorporate ball-type, poppet, cartridge shuttle and split-flange designs and are used in a wide variety

198

Pressure Valves a.nd Services

ZERO PRESSURE NO FLOW Relaxed seal rong an d gentle seal-to· poppet contact guarantees low pres· su re sea1 1ng and ellm 1nates va l ve c ha tter.

HIGH PRESSURE FULL FLOW Seal flexes to close ott all external leakage around end cap Enclosure protects seal ring. prevents s.:a l displacement.

HIGH PRESSURE REVERS E FLOW CH EC KE D Seal Still hold1ng external leakage now cJiso tlexC's arouno poppet. H 1gner PI<)SSurcs t1ghten th e seal. l eakage Zero.

Figure 13. Hydraulic and pneumatic check valve 1vithjlexiblP spa [ seat. design.* Flexible sC'al sl'at.

Figure I 4. Hydrau lic and pnertmn.tic check and relief valvrs. *Flexible seal seat.

Check Valves

199

of industries including agriculture, aerospace, road equipment, robotics. industrial machinery. medical equipment instrumentation and controls, chemical processing and handling. Check valves are commonly used in combination with flow control valves. the type and operating characteristics of which can influence the choice of check valve type. Suitable combinations are: Swing check valve-used with ball. plug, gate or diaphragm control valves. Lift check valve-used with globe or angle valves. Piston check valve-used with globe or angle valves. Butterfly check valve-used with ball. plug, butterfly, diaphragm or pinch valves. Spring-loaded check valves-used with globe or angle valves. The exception is the foot valve, normally associated with a pump (i.e. there is no other valve positioned between the foot valve and the pump). See also chapters on Swing check/Flap valves, Non-return valves , Water services.

Safety and Relief Valves Valves that are vital for the protection of people and plant are termed Safety and Relief Valves. These valves operate automatically when a predetermined pressure level is exceeded by releasing an adjustable spring which holds a valve disc against a valve seat. There are. however, distinctions between safety valves and relief valves that lead to the following definitions and terminology. •

Safety Valve-A valve which automatically discharges gases and vapours so as to prevent a pre-determined safe pressure being exceeded . It is characterised by a rapid full-opening action and used for steam, gases or vapour service (Figure 1 ).

Safety valves can be further categorised as follows: Low-Lift Safety Valve-A low-lift valve in which the disc lifts automatically such that the actual discharge area is determined by the position of the disc. (ii) Full-Lift Safety Valve--A valve in which the disc lifts automatically such that the actual discharge area is not determined by the position of the disc. (iii) Pilot-Operated Safety Valve-A safety valve, the operation of which is initiated and controlled by the fluid discharged from a pilot valve which is itself a direct loaded safety valve.

(i)

•

•

Relief Valve-A valve which automatically discharges fluid, usually liquid when a pre-determined upstream pressure is exceeded (Figure 2). It may be provided with an enclosed spring housing suitable for closed discharge system application. Pressure Relief Valve-A safety device designed to protect a pressurised vessel or system during an overpressure event, by relieving excess pressure, and to reclose and prevent the further flow of fluid after normal conditions have been restored. It is characterised by a rapid opening pop action or by opening generally proportional to the increase in pressure over the opening pressure (Figure 3 ).

Safety and Relief Valves

201

Materials of construction Item I -?-3 4 5 6

Component Ma1enat · SV 57 7 SV54 S00y________________G ~G~G _·_ 40~t~~ ~G7S~C~·25 Seat 1.4507Bonnet GG G-4 0.~GS-C25 Cap GGG-40.3 DISC _________________::_ I 4SOi

----... D~ ISC:-:9::-:U:-:;I d: .. : : - - - - - - Sk1rt

GGG-40 3 t.4031 s----~ sp~~n~d~ te----------------------,~.4~0~ 34

7

9 Body Botts DIN-931 5.6 ZNIOIN-933 CK-35 10 _ sgnng washers CK 45 -1-t Retatner ung t 4034 t2 Guide steeve t .403 t Sprtng adjustment screw 1.4034 13 --:1-i4- - - -, L'-'oc =k--"n'-u·t Carbon steel DIN 1651 95 Mn 36 -Zp 15 Sprtng Carbon Steel DIN 17225 so crv4--:1i6 ------7c<':::a~ p .:: bolt OIN-931 5.6 ZN 17 Collar Carbon steel Zlnc 18 Lever GGG 40.3 Ptn 19 Carbon steel Zmc ciiCiip DIN-4 71 Carbon steel ~ -21 P1n OIN-7343 l'l SSPDra1n Role 22 1.4034 23 Sp1ndle Bail Alum1mum ldeniiilcatton plate ~ 25 Cock1ng Screw OIN-913 A~ OIN-t48t 26 Rmg ptn Lever stem 1.4034 GGG-40.3 28 Cam l'ack1ng Grapfitte 29 1.4305 30 Gland i51N-t471 Nut 31 1.4031 32 0 - 1'\mg relatner O - l'i1ng Accordmg 10 SeiVICC 33 C. steel 34 Gland nut Gasket ! rellel only ) Asbestos lree 35 -36 Asbestos lree Gasket ( rehel o~

v-

9

34

30 29

28

27

Packed easing lever

Gas light cap

32

33 31 --~=-~~~--~ 0-rlng seal

Figure I . Safety valve suitable for steam, gas and liquid service.

•

•

Pilot-Operated Pressure Relief Valve--A second type of pressure relief valve in which the major relieving device is combined with and is controlled by a self-actuated auxiliary pressure relief valve. Safety Relief Valve--A valve which will automatically discharge gases, vapours or liquids so as to prevent a pre-determined safe pressure being exceeded. It is characterised by a rapid full-opening action or by opening in proportion to the increase in pressure over the opening pressure, depending on the application, and may be used either for liquid or compressible fluid (Figure 4).

202

Pressure Valves and Services

I

toOY

~ o~

T

J

GUIDE

.~-- ---·o· ~

5

- -SPIIING - PIAU SPIIING COVlR

S"NOU -

12 13

ADJU$11NG SCRIW - IOCKHUI-

OOMt NAMEPLAU RlNEWAIU SEAl

D

L

VALVE INLET

•

Figure 2. Liquid relief valve.

Figure 3. Pressure rdiefvnlvl'.

Figure 4 . Filii-lift. safety reliljvalve.

Safety and Relief Valves

203

A safety relief valve can be further categorised as: (i)

(ii)

A Conventional Safety Relief Valve-A valve which has a spring housing vented to the discharge side of the valve. The operational characteristics (open and closing pressure and relieving capacity) are directly affected by changes of the back pressure on the valve. A Balanced Safety Relief Valve-A valve which incorporates means of minimising the effect of back pressure on the operational characteristics (opening and closing pressure and relieving capacity).

Since all of these types of valves are safety devices, there are many codes and standards throughout the world written to control their design and application. Some of these codes and standards are shown in Table 1. Among the most widely used is the ASME Boiler and Pressure Vessel Code, commonly referred to as the ASME Code. More specific information may be found by referring to this code, various published standards and by consulting literature published by safety and relief valve manufacturers. Safety Valves

Typical operating parameters for safety valves are given in Table 2. Safety valve set pressure and temperature limits are governed by a number of factors and may not always coincide with manufacturers' published limits for the applicable materials and flange ratings. Particular limits may be based on spring limitations. specific material selection or other design considerations. With boiler applications, for example, set pressures and total capacity requirements for safety valves are usually established by the design agent or boiler manufacturer. Safety valves are intended to open and close within a narrow pressure range; therefore, valve installations require careful and accurate design, both as to inlet and discharge piping. The higher the operating pressure and the greater the valve capacity. the more critical becomes the need for proper design of the installation. Safety valves should always be mounted in a vertical position directly on nozzles having a well rounded approach that provides smooth, unobstructed flow from the vessel or line to the valve. A safety valve should never be installed on a nozzle having an inside diameter smaller than the inlet connection to the valve, or on excessively long nozzles. The pressure drop occurring in the inlet piping should be calculated at actual flow of the valve. Where safety valves are installed to protect piping systems, as on the low pressure side of a reducing valve or on a turbine by-pass, the pipe or header must be or sufficient size to maintain flow under the safety valve while it is discharging . A typical design of a pop-type safety valve is shown in Figure 5.

204

Pressure Valves and Services

Table 1. Codes and standards

Regulatory body

Codes and standards

All ami Energerhkai es Energiabiztonsagtechnikai Felugyelet (AEEF) (State Authority for Energy. Management and Safety) Budapest VIII Koztarsasag ter 7. Hungary

Safety Valves 22/1969/Vl.l2 (mod) 29/1960/VI. 7 (orig)

American National Standards Institute 1430 Broadway New York, NY 10018. USA

816.34 Steel Valves. Flanged and Buttwelded Ends 816.5 Steel Pipe Flanges and Flanged Fittings B3l.l Power Piping 831.3 Chemica IPlant and Petroleum Refinery Piping B31.4 Liquid Petroleum Transportation Piping Systems 89 5.1 Terminology lor Pressure ReliefDevices ANS[/ ASME PTC 25.3 Performance Test Code. Safety and Relief Valves

American Petroleum Institute 2101 LStreetNorthwest Washington, DC 2003 7. USA

API RP 510 Pressure Vessel Inspection Code API RP 520 Recommended Practice for the Design and Installation of Pressure Relieving Systems in Refineries: Part 1- Design; Part II- Installation API RP 521 Guide for Pressure Relief and Depressuring Systems API Standard 526 Flanged Steel Safety Relief Valves API Standard 52 7 Commercial Seat Tightness of Safety Relief Valves with Metal to Meta l Seats API 2000 Venting Atmospheric and Low Pressure Storage Tanks API Guide for Inspection of Refinery Equipment Chapter XVI-Pressure Relieving Devices

The American Society of Mechanical Engineers United Engineering Center 34 5 East 47th Street New York . NY 10017, USA

Boiler and Pressure Vessel Code Section 1- Power Boilers Section li- Materials Section IV- Heating Boilers Section VII- Care ofPower Boilers Section VIII-Pressure Vessels Section IX- Welding and Brazing Qualification s

Safety and Relief Valves

20 5

Table 1 (co11Unued)

- -

-----~

Regulatory body

-,---

Codes and standards -~--

---------------------------

Association Francaise de Normalisation Tour Europe Cedex 7 F-9 2049 Paris La Defence. France

NFE 2 9-410 to 420

Australian Standards Association No. 1 The Crescent Home bush New South Wales 2140. Australia

AS12 71 Safety Valves, Other Valves. Liquid Level Gages and Other Fittings for Boilers and Unfired Pressure Vessels 1990 Edition AS121 0 Unfired Pressure Vessels (EAA Unfired Pressure Vessel Code) 1989 Edition AS1200 Pressure Equipment 1994 Edition

British Standards Institute 389 Cbiswick High Road London W4 4AL. England

BS6759 Parts l. 2 and 3 Safety Valves

Canadian Standards Association 178 Rexdale Boulevard Toronto. Ontario M9W 1R3, Canada

CSA 2299.2.85 (Rl991)-Quality Assurance Program-Category 1 CSA 2299.3.85 (Rl991 )-Quality Assurance Program-Category 3 CSA 2299.4.85 (R1991)-Quality Assurance Program-Category 4

Chlorine Institute lnc. 2001 L Street. NW Washington. DC 20036, USA

Pamphlet Type 1-1/2" JQ Pamphlet41 Type4" JQ

CCNASTHOL Shenogina Street 123007 Moscow, Russia

GOST R Certification System

Deutsche lnstitut Fur Normung Burggrafenstrasse 6 D-10787 Berlin. Germany

DIN 50049 Materials Testing Certificates

Comite Europeen de Normalisation (European Committee de Standardisation) rue de Stassart 3 6 B-1050 Brussels, Belgium

CEN Standards for Safety Valves Pressure Equipment Directive

Heal Exchange Institute. [nc. 1300 Sumner Avenue Cleveland. OH 44115. USA

HEI Standards for Closed Feed water Heaters

International Organisation for Standardisation Case Posta le 56 CH-1211 Geneve 20, Switzerland

fS0-900 Quality System IS0-4126 Safety Valves--General Requirements

206

Pressure Valves and Services

Table 1 (continued)

Regulatory body

Codes and standards

I.S.C.I.R. Central Bucuresti Frumoasa nr. 26. Romania

Romanian Pressure Vessel Standard

Japanese Industrial Standard Committee Japanese Standards Association 1-24, Akasaka 4-chome. Minato-k u Tokyo 107 Japan

JIS 882 .l 0 Spring Loaded Safety Valves for Steam Boile rs and Pressure Vessels

Manufacturers' Standardization Society of the Valve and Fitting Industry 1815 North Fort Myer Drive Arlington. VA 22209. USA

SP-6

Ministerie Van Sociale Zaken En Werkgelegenheid Direcl:oraat Generaal Van De Arbeid Dienst Voor Het Stoomwezen 251 7 KLGravenhage Bisenhowerlaan 102. The Netherlands

Stoomwezen Specification Al301

National Association of Corrosion Engineers P.O. Box 1499 Housto n, TX 77001. USA

NACEMR01 7 5

Finishes ofContactfaces of Connecting End Flanges SP-9 MSS Spot Facing Standard SP-55 Quality Standa rd for Steel Castings

-----National Board of Boiler and Pressure Vessel inspectors 1055 Crupper Avenue Columbus. OH 43229, USA

NB-25 National Boa rd In spectors Code NB-65 National Board Authorization to Repair ASME and National Board Stamped Safety Valves and ReliefV a lves

National Fire Protection Association Batterymarc-Pa rk Quincy. MA02269 . USA

NFPA 10 FlammableandCombustibleLiquids Code

Schweizerisher Verein fur Druckbehalteruberwachung (SDVB) Postfach 35 8030 Zurich. Sw itzerland

Specifications 602- Safety Valves fo r Boilers and Pressure Vessels

Den Norske Trykkbe holderkomite (TBK) Norsk Verkstedsindustris Standardiseringssentral Oscarsgate 20, Oslo. Norway

TBK General Rules for Pressure Vessels

Verband derTechnischen Ubenvachungs-Vereine e. V (TlJV) KurfurstenstraEe 56 4300 Essen 1. Germ any

TRD 421 AD-Merkblatt A2

Safety and Relief Valves

207

Table 2. Safety valve operating parameters --

Parameter

Definition

Set pressure (also known as crack pressure)

(i)

(ii)

Uquid services: iolet pressure at which valve starts to discharge under serv ice conditions. Gas or steam services: inlet pressure at which the valve pops under service conditions.

Differeo tia I set pressure

Difference between set pressure and back pressure (where present).

Overpressure

Pressure increase over the set pressure of the va lve or relief device.

Blowdown

Differen ce between the set pressure and resetting pressure expressed either as a specific pressure or percentage of the set pressure.

Back pressure

Any pressure on the discharge side of a pressure-relief va lve .

Accumulation

Pressure increase over maximum allowable working pressure of a vessel or system during discharge throu gh the pressu re relief va lve.

Operating pressure

Normal allowable working pressure of the system or vessel.

No 1 2 3 4

PART SEAT VALVE DISC BODY SPINDLE 5 SPRING END PLATE 6 SPRING 7 ADJUSTING SCREW 8 LOCK NUT 9 LEVER 10 DOME 11 SLOWDOWN RING 12 SETTING SCREW 13 BALL

Figure 5. Typica l pop-type safety valve.

MATERIAL GUN METAL GUN METAL GUN METAL H.T.BRASS BRASS STEEL·ZINC PLATED BRASS BRASS BRONZE GUN METAL GUN METAL H.T.BRASS STAINLESS STEEL

208

Pressure Valves and Services

The discharge piping from safety valves should be equal in size to, or larger than, the nominal valve outlet and should be as simple and direct as possible. Good practices must be observed with discharge manifold lines. All discharge piping in the discharge system must be vented to a safe disposal area to prevent personnel injury when the valve discharges. The valve shown in Figure 6a is typically used for steam generators and steam systems. It is a high capacity reaction-type valve designed specifically for saturated steam service on boiler drums having design pressures above 103 bar(l500lb/in 2 ). A typical valve operating cycle (Figure 6b) is as follows: As pressure in, say, a boiler increases to the safety valve set point the valve will pop open. After the valve opens steam passes through a series of annular flow passages (A) and (B) which control the pressure developed in chambers (C) and (D) . The excess steam is exhausted through guide ring openings (E) to the valve body bowl (F). As pressure in the boiler decays, the dynamic forces on the lower face of the disc holder assembly are reduced and the safety valve disc begins to close. Assisted by pressure in chambers (C) and {D), the valve at this point closes sharply and tightly.

Figure 6A. Safet.y valve for sat urated steam applications.

Figure 6 B. Safety valve opera ling pri11ciple.

Safety and Relief Valves

209

Figure 7 shows a safety valve frequently used in process applications. The valve has a closed bonnet that contains the process fluid within the safety valve preventing any release to atmosphere. In Figure 8. the safety valve incorporates a balanced bellows to provide satisfactory safety valve performance when the developed back pressure becomes excessive. Balanced bellows ensure that safety valve characteristics such as lift and relieving capacity, opening and closing pressure and stability are not unduly influenced by static pressure in the discharge manifold. Balanced safety valves must be installed when the percentage build-up back pressure in the exhaust system is allowed to exceed the percentage overpressure applicable to the safety valve. Valves that vent to the atmosphere, either directly or through short vent stacks. are not subjected to elevated back pressure conditions. Valves installed in a closed system, i.e. on corrosive, toxic or valuable recoverable fluids, or when a long vent pipe is used. may develop high back pressure. Back pressure which may occur in the downstream system while the safety valve is closed is called superimposed back pressure. Back pressure which may occur after the valve is open and flowing is called dynamic or built-up back pressure. Figure 9 shows a double-spring high-lift sarety valve that combines a top guided design to provide an unobstructed seat bore with a floating disc.

Figure 7. Basic safety valve for process applications (closed bonnet type).

210

Pressure Valves and Services

Figure 8. Safety valve for process applications ( /Jalanced /Jdlows type).

Relief Valve

A basic difference between the design of spring-loaded safety valves and relief valves is that, in safety valves. the poppet or disc overhangs the seat to promote faster lift whereas, in a relief valve, the area exposed to overpressure is the same whether the valve is open or closed. As a consequence, a safety valve pops open while a relief valve lifts gradually with increasing pressure until it reaches its fully open position. The relief valve shown in Figure 10 is a standard type suitable for relieving excess pressures of water oil, air, gases or steam where high discharge rates are not required. Duties include the protection of pipelines against overpressure and protection against thermal expansion. It is filtered in the upright position. A spring-loaded side-discharge version is shown in Figure 11. Other spring relief valves have cartridge-type assemblies for easy cleaning. They are usually suitable for use with positive displacement pumps of the rotary or reciprocating type. They can also be used as combined relief and by-pass valves. The relief valve (Figure 12) is manufactured from plastic -PVC, PVDF and CPVC with solid Teflon'!{)* shaft, intended as a chemical-resistant relief valve for corrosive and pure liquids . The relieving pressures can be adjusted by screwing the adjusting bolt up or down to decrease or increase the pressure setting. This type of valve is not a pop safety-type valve. "'Dupont registered trade mark.

Safety and ReliefValves

1 Body 2 Cover

3 Valve Disc Holder 4 V<:~lve Disc 5 Seat Ring 6 Guide 7 Spindle

S Blow Do1.-vn Ring 9 Setting Screw 10 Valve Disc Ball

11 12 13 14 l4a 15 16 17 18/19 20

Spindle Ball Spring Steel Easing Lever

Dome Screwed Dome

Dome Cap Adjusting Screw Locknut Spring Plate Disc Retaining Clip

211

21 Body Gasget 2 2 Locking Pin 23 SeatSecurring Pin 2 5 Padlock 26 Body Stud 2 7 Body Stud Nut 28 Nameplate

29 Nameplate Screw 30 Locknut

Figltre 9. Double-spring high-lift safety valve.

Emergency relief valves of the type shown in Figure 13 are designed to meet the stringent conditions of container, rail, road and static tanks for emergency venting under total fire engulfment conditions. Usually manufactured from 316 stainless steel, these types of valves can incorporate a manually operated vacuum vent button. The type of relief valves shown in Figure 14 is ideally suited for air, acetylene, ammonia, freon 12 and 22. hydrogen, carbon dioxide, oxygen, aromatic fuels, synthetic oils, tetrachloride and toluene, at operating pressures up to 2400 lb/in 2 . It can be mounted in horizontal and vertical positions. In closed operation, the spring load is carried by a metal-to-metal seat. An 0-ring provides a tight seal and the sealing efficiency increases as the pressure increases up to cracking pressure. At cracking pressure the ports in the poppet open fully and eliminate the rapid increase in pressure. Flow is throttled between the poppet shoulder and seat and a regularly increasing flow area is

212

Pressure Valves and Services

Figure 10. Standard spring-operated relief valve.

/

/

'

[1]

1 2 3 4 5 6

7 8 9 10 lOa

Seat Valve Disc Body Spindle Spring End Plate Spring Sheradized Adjusting Screw Lock Nut Lever Lever Dome Leak ProorDome

Figure 11. Spring-loaded side-discharge relief valve.

Gun metal Gun metal Gun metal H.T. Brass Brass Brass Brass Bronze Plastic Gun metal

Safety and ReliefValves

213

provided with increasing flow rates. When fully open, the inline construction and full flow ports permit maximum flow with minimum increase in system pressure (see Figure 15). High pressure variants operate at pressures up to 10,500 lb/ in 2 .

ADJUSTING

ADJUSTING ..,..-- BOLT

DOLT~

----

LOCK NUT

PLUNGER__

(

.

~-

SPRING ~ PLUNGER

r -- § VENT "U" CUP SEALS (3)

VALVE SEAT

TEFLON SHAFT

INLET

VALVE SEAT

RESILIENT SEAT

FigHre 12. Chemical-resistant relief valves.

Figure I 3. Emerging relief valves.

214

Pressure Valves and Services

Pressure Relief Valves

The basic spring-loaded pressure relief valve (Figure 16) has been developed to provide overpressure protection. • • •

Overpressure may be defined as a pressure increase over the set pressure of a pressure relief valve, usually expressed as a percentage of set pressure. Set pressure is the pressure measured at the valve inlet at which a pressure relief valve should commence to lift under service conditions. Popping pressure is the value of increasing static pressure at which the disc moves in the opening direction at a faster rate as compared with corresponding movement at higher or lower pressures.

Figure 14. High-pressure relief valve.

CLOSED

CRACKING

OPEN Figure l S. High-pressure relief valve method of operatio11.

Safety and Relief Valves

215

The valve shown in Figure 16 consists of a valve inlet or nozzle mounted on the pressurised system, a disc held against the nozzle to prevent flow under normal system operating conditions, a spring to hold the disc closed. and a body or bonnet to contain the operating elements. The spring load is adjustable to vary the pressure at which the valve will open. The sole source of power for the pressure relief valve is the process fluid. The pressure relief valve must open at a pre-determined set pressure and close when the system pressure has returned to a single safe level. Pressure relief valves must be designed with materials compatible with many process fluids from simple air and water to the most corrosive media. This type of valve is required to remain on systems for long periods of time and must have the ability to maintain tight shut-off. Most manufacturers recommend that system operating pressures not exceed 9 5% of set pressure to achieve and maintain proper seat tightness integrity. Examples of spring-loaded pressure relief valves are given in Figure 17. A rupture disk device (Figure 18) is a non-reclosing pressure relief device actuated by inlet static pressure and designed to function by the bursting of a pressure containing disk. A rupture disk is the pressure containing and pressure sensitive element of a rupture disk device. These products provide full opening with instantaneous pressure relief in the event of system upset. Application of rupture disk devices to liquid service should be carefully evaluated, especially if used in combination with a safety or safety relief valve.

;:s::GPS~- SPRING ~~ ~- BONNET VENT

PLUGGED

DISC

Figure 16. Standard spring-loaded pressure relief valve.

216

Pressure Valves and Services

r ..1

Figure I 7. Pressure relief valves: top left- standard valve: top right- screwed valve with single tr im: lower-sanitary valve for foodst.uffs and plumnnceuticnls.

Pilot-Operated Pressure Relief Valve

This type of valve consists of a main valve with a piston- or diaphragmoperated disc and a pilot. Under normal conditions the pilot allows system pressure into the piston chamber. Since the piston area is greater than the disc seat seal area, the disc is held closed. \1\lhen the set pressure is reached. the pilot actuates to shut off system fluid to the piston chamber and simultaneously vents the piston chamber. This causes the disc to open (Figure 19). Another version of a pilot-operated pressure reducing valve is shown in Figure 20. Other constructions have integral porting, eliminating the need for tubing to activate the valve and relieve the system pressure, as all pressurisation is performed through porting machined into the main valve and the mating pilot valves.

Safety and Relief Valves

217

Higil-pressurepilot-operated safety reliefvalve.

Two pilots combined on the nwin body of a pressure-reducil1fJ valve.

Pilot-operated relief valves have several advantages. As the system pressure increases, the force holding the disc in the closed position increases. This allows the system operating pressure to be increased to values within 5% of set pressure ·w ithout danger of increased leakage in the main valve. Valves can be set fully open at the set pressure and closed with a very short blowdown. A reducing valve will modulate from its maximum capacity down to zero load when it will shut. However, if the valve is to work under low load conditions for much of its life. there may be a good case for fitting two smaller valves in parallel.

218

Pressure llalves and Services

PILOT

MAIN VALVE

Figure 18. Rupture disk device.

Figure 19. Snap-acting pilot-operated pressure relief valve.

~ Control sp11ng

Pilot dtaphragm

-/

/

Downstream externa: sensing p;pe connection

Flow_.

Mam ~~._- diaphragm

Figure 20. Standard pilot-operated pressure-reducing valve(or steam. air and industrial gases.

Modulating pilot valve designs limit fluid loss and system shock. However. this type of valve is generally only recommended for clean service and is found in a broad range of applications and industries including steam. air and industrial gases, petroleum-refining offshore applications, chemical processing, pulp and paper mills and general manufacturing. There are numerous styles and designs available from many manufacturers.

Safety and Rdie.fValves

219

Safety Relief Valve

The purpose of a safety relief valve is to discharge a given amount of vapour, gas or liquid. whilst preventing the pressure increase exceeding a pre-determined level. The safety relief valve should close with the smallest drop in pressure consistent with tight closure, and it should remain pressure-tight up to the time of the next response to an overpressure situation. A standard safety relief valve is shown in Figure 21. The valve must be reliable so that the action is always a repeat of the previous action. A safety relief valve should be used on any closed vessel or system in which the pressure can be other than atmospheric and where, under any circumstances, the design pressure of the system can be exceeded. In most instances the discharge pipework is direct to atmosphere, but when the medium is toxic, inflammable or otherwise objectionable, complex-type discharge pipe\1\rork systems are used and, frequently, more than one valve discharges into the system, resulting in a variable back pressure at the safety relief valve.

~ [@]

@]

@]

~0

8

[I]

~ OJ]

OJ

[I]~

0

~

[2] .

r•~•••••· •-••• .. t '

l

2

3 3a 4 5 6

Body Seat ResiJJent Disc Disc Spindle Spring Cap Spring

...

' -...... .

;

' ....... ....... ........... . ··--.......

Gun metal Gun metal Brass-EPDM/ Viton Brass Brass Brass Chrome Vanadium or Stainless Steel

7 8 9 10 11 12 13 14

·---·· ·········-····· ...

Adjusting Screw Locking Ring Dome Lever Ball Padlock Bush Pinning Screw

Figure 21. Typical certified safety relief valve.

Brass Brass Plastic Brass Stainless Steel Brass P.T.F.E Steel

220

Pressure Valves and Services

When such a discharge system is adopted, the safety relief valve must be designed in such a way that the effects of the variable back pressure on the set pressure are minimised. This requires the use of a balanced bellows valve. The safety relief valve should be as maintenance-free as possible. Sizing Safety and Relief Valves

Proper sizing and selection of safety and relief valves is critical. The first step in applying overpressure protection to a vessel or system is to determine the type of fluid, set pressure. back pressure, allowable overpressure and required relieving capacity; the next step is to establish inlet temperature, compressibility factor, gas constant or isentropic coefficient, molecular weight, specific weight, specific gravity and viscosity. Sizing equations are available from manufactures and regulatory bodies. e.g. British Standards BS 6759. American Standards to ASME Code Section VIII and European Standards A.D. Merkblatt A2. All capacities can be calculated in accordance with the internationally accepted sizing equations using the certified coefficients of discharge. Typical sizing equations in accordance with specific standards are, for example: In accordance with BS 6759: 1984

Modified for the effects of set pressure below [ 3.0 bar, back pressure and superheated steam

For steam: A=

E 0.52 5 P.Kdr.Fp.Fb.FsH

or

E = 0.525 P.A.Kdr.Fp.Fb.FsH

For compressed air: A=

Ql

fi8s 0 .193 P.Kdr.Fp.Fb.y r

[288

= 0.193 P.A.Kdr.Fp.Fb .v T

or

Ql

or

Q2 = P.A.C.Kdr.Fp.F b.v ZT

or

Q2

For gases: A=

For liquids: A=

Q2

P.C.Kdr.Fp.Fb.[f~

Q2

1.61 Kdr.Fv.Fw ..JPXP

,{M

= 1.61 A.Kdr.Fv.Fw.V{JM

For hot water: A=

Q3 0.329 Kdr.P.Hws.

or

Q3

= 0 .329 A.Kdr.P.Hws. V{JM

l

Safety and ReliefValves

221

Key to equations

=

Office area = Required capacity of steam = Required capacity of compressed air Required capacity of gas/liquid Required capacity of hotwater Absolute inlet pressure (set pressure+ overpressure+ 1.013) = Relieving pressure- Back pressure (set pressure + overpressure- back pressure) Inletten1perature = Liquid density Molecular weight = Compressibility factor = 10 5 P.V.M. R.T.

= = =

T p

M

z

= =

mm 2 kg/hr ljs kg/hr

kW bar abs bar gauge oK (°C + 2 73) kg/m 3 kg/kmol

z

where R V C

=

K

=

Universal gas constant-8314 N.m./ krnol.k = Specific volume of gas at STP conditions = Gas constant Use the following formula

rr

Isen tropic exponent at the relieving in let conditions. the value of K is not avai Iable at these conditions the value at 1.013 5 bar abs and l5°Cshould be used

Capacity correction factors =

rp Fb Fv Fw

= =

Fsh Fdr Hws

= = =

=

Capacity correction factor for the effects of low set pressure Capacity correction factor for the effects of back pressure (balanced bellows valves only) Capacity correction factor for the effects of viscosity (liquids only) Capacity correction factor for the effects of back pressure (liquids only; balanced bellows valves only) Capacity correction foetor for the effects of superheat De-rated coefficient of discharge. Select Kdr appropriate to the fluid Hotwater correction for vented system (0. 5 if vented/ 1 if pressurised)

In accordance with A.S.M.E. Code Section VIII and API RP 520

Modified for the effects of set pressure below ] [ 3.0 bar, back pressure and superheated steam

Note:- When sizing valves in accordance with ASME Code Section VII, the certified capacity may only be calculated at 10% overpressure or 3 psig, whichever is the greater and without the use of correction factors Fp, Fb, Fv, Fw and Fsh. Set pressures below 15.0 psig may not be ASME stamped.

222

Pressure Valves and Services

For steam:

w 51.5 Pg.Kdr.Fp.Fb.FsH

or

W = 51.5 Pg.A 1 .Kdr.Fp.Fb.FsH

or

Q = 1.175 Pg.Cg.At.Kdr.Fp.Fb JG.Tg.Z

For air/ gases: Al

Q.JG.Tg.Z 1.17 5 Pg.Cg.Kdr.Fp.Fb

= ~--------

For liquids: 3 8v'3]\ Kdr.Fv.Fw

or

v," --

38A 1 )PLKdr.Fv.Fw

---------==-- - -

JG

Key to equations

AI

Q

w VL

Pg ~pL

Tg G

= = =

= = = =

z

= =

Cg

=

Office area Required capacity of air/gases Required capacity of steam Required capacity of liquid Absolute inlet pressure (set pressure+ overpressure+ 14. 7) Relieving pressure- Back pressure (set pressure+ overpressure - back pressure) Tnlet temperature Specific gravity Compressibility factor for the gas or vapour at PorT conditions (if not given use Z = 1) Imperial gas constant. Use the following formula Cg

K

=

=

in 2 SCFM lb/ hr usgpm psia psig

OR (° F + 460)

K( K+l 2 )W

Isentropic exponent at the relieving inlet conditions. If the value of K is not available at these conditions the value at 14.7 psi abs and 59°F should be used

Capacity correction factors

Pp Fb Fv

F'w Fsh Kdr

= Capacity correction factor for the effects of low set pressure = Capacity correction factor for the effects of back pressure (balanced bellows va Ives only) Capacity correction factor for the effects of viscosity (liquids only) = Capacity correction factor for the effects of back pressure (liquids only: balanced bellows valves only) = Capacity correction factor for the effects of superheat = De-rated coefficient of discharge. Select Kdr appropriate to the fluid

=

Safety and RPliefValves

In accordance with A.D. MERKBLATT A2

For steam:

223

Modified for the effects of set pressure below ] [ 3.0 bar, back pressure and superheated steam

Qm.x

Qm

=

Ao.Kdr.P.Fb.Fp

Ao = --------,-Kdr.P.Fb.Fp

or

0.1791 Qm Ao = - - -- - - - l/!Kdr.P.If/r Fp.Fb

or

Om =

or

Ao.Kdr.J/]XP Fv.Fw Qm- - -- - - - - 0 .6211

X

For air/ gases:

-

Ao.ljrKdr.P.If/r Fp.Fb

_ __ ____:___ __

0.1791

For liquids:

0.6211 Qm Ao = -----===--Kdr.J/]XP Fv.Fw

Key to equations

Ao Qm P fl.P

T p M K

1/1

x

= Office area mm 1 Required capacity of steam. air, gases or liquids kg/hr = Absolute set pressure (set pressure+ 1.013) bar abs = Relieving pressure- Back pressure (set pressure- back pressure) bar gauge = Inlettemperature °K(°C+273) = Liquid density kg/ m 3 = Molecular vve ight kg/ kmol = Isentropic exponent at the relieving inlet conditions. If the value ofK is not available at these conditions the value at 1.01 3 5 bar abs and l5°C should be used A.D. Merkblatt outtlow function for air and gases = A.D. Merkblatt pressure medium coefficient for steam

=

=

= O.fi2ll JPV 1/1 V =Specific volume in m 3 /kg for supercritical pressure relief

Capacity correction factors

Fp

Fb Fv

=

=

Fw

= =

Kdr

=

Capacity correction factor for the effects of low set press ure Capacity correction factor for the effects of back pressure (balanced bellows valves only) Capacity correction factor for the effects of viscosity (liquids only) Capacity correction factor for the effects of back pressure (liquids only: balanced bellows valves only) De-rated coefficient of discharge. Select Kdr appropriate to the tluid

224

Pressure Valves and Services

Manufacturers' engineering support information and technical data are essential if the correct valve is to be selected for the job. Some manufacturers supply rull details on a computer program. Generally the program is easy to use with many features including: quick and accurate calculations, user-selected units, selection of valve size and style, valve data storage, printed reports, specification sheets and dimensional drawings . There is no substitute for qualified engineering analysis, and the application of safety and relief valves of any type or make should be assigned only to fully trained personnel and be in strict compliance with rules provided by the governing codes and standards. Selection of safety and relief valves should not be based on arbitrarily assumed conditions or incomplete information . Valve selection and sizing is the responsibility of the system engineer and the user of the equipment to be protected. Testing Safety Valves

Safety valves should be tested regularly to ensure that they have retained their capability of operating at design lift-off pressure. Two basic methods of testing are: On-line testing by deliberate overpressure of the system to determine the actual pressure at which the valve lifts off its seat. Off-line testing by removal of the valve from its line or position and determination of active lift-offby hydraulic test. It is also possible to apply a hydraulic test for on-line testing using a portable hydraulic test pack.

Self-Acting Reducing Valves Self-acting reducing valves generally fall into two main categories: (i) directacting valves and (ii) relay- or pilot-operated types. An example of a direct-acting pressure reducing valve for steam, compressed air and other gases is shown in Figure 1. The valve is designed for point-of-use installations. On start-up, the upstream pressure, aided by a return spring. holds the valve head against the seat in the closed position. Downstream pressure is set by rotating a handwheel in a clockwise direction which compresses the control spring and extends the bello·ws. This downward movement is transmitted via a push rod which causes the main valve to open . Liquid then passes through the open valve into the downstream pipework and also surrounds the bellows. As downstream pressure increases, it acts through the bellows to counteract the spring force and closes the main valve when the set pressure is reached. The main valve modulates to give constant downstream_pressure. Materials used for the bellows include phosphor bronze and stainless steel with nitrile main valve. Other diaphragms used include rubber, synthetic rubbers, stainless steel and phosphor bronze materials. The direct-acting reducing valve shown in Figure 2 is designed for use with liquids and incorporates a balanced piston design providing accura te control of pressure under stable load conditions. The valve is installed in a horizontal pipeline. Typical applications include laundry equipment and reducing pressure at the point of use on Injection Moulding machines. Pressure reduction in water systems aids both the efficient design of the piping network and protects consumers from excessive noise from high velocity within buildings. high-pressure discharge at taps and other outlets, and climbing overnight pressures when the distribution network is lightly loaded. The ability to control water-entry pressures ensures a balanced distribution network and also limits the maximum supply volume and so reduces water waste. Cost-effective steam distribution depends on keeping pipe sizes to the minimum and having the highest acceptable distribution pressure between the boilerhouse and the areas of steam usage. then dropping pressure at the working area to the levels for the highest heat transfer, efficiency and safety.

226

Pressure Valves and Services

16- -

16

2 --

6

- 6 - 9 - 17 -10 - - - -12 - 11

-

-13

- - - - t4 - - - - - - t5

No. Part Materoal 1 Spnng Housing Alumilllufll - Epoxy coattld LM 24 2 Adjustment Hand Wheel Mineral ReonlorCOld Nylon 3 Top Spring Plate Cast Iron DIN 1691 GG 20 4 Pressure Adjustment Srhcon Chrome BS 2603 685 ASS Spnng Spnng Steel Range 2 5 Bellows Assembly Stainless Steel 3t6Ti/J16L Option Phosphor Bronze/Brass S Bellows AssemblyG asket Slainless Steel Reinforced -=-..--c-----,-;----,----;;-;:-- - ,E ;;,cxlolia led Graphite 7 Spring Housing Bolts Steel- - Z,nc plated BS 3692 Gr 6.6 M6 x 25mm 8 Body Screwed SG Iron DIN t693 GGG 40 3 Flanged SG Iron DIN t 69J GGG 40.3 Graphite lilled PTFE 9 Guide Bush tO Pushrod Staonless Steel A STM A276 316L Staonless Staal BS 9/0 431 529 11 Valve Seat 12 Valve Seal Gasket - -Stamless Steel BS 1449 316 S1t 13 Valve AISI420 Staontess Steel 14 Valve Return Sprmg Staontess Steel BS 20056 316 542 Staonless Steel -BS 1449 316 SH 15 Straoner Screen 16 Spring Range ldenlilicalion Disc Polypropylene Staonles"-: s'-;; S':-: to-=el; - - - - -316 L 17 BulkheHd Plate :,.I:;.:. Id""Steel · Copper Plated 18 Tamperproof Prn - --'M Iac.:n;:; kir:.:119c.:,P~Iu:.:,g.:.__;__ _-cS;;:I= a,~ nl.ess Steel BS97()43 I S29 7. 19~B;20 Compressoon Frt1on9_

Brass

Figure I. Direct-acting pressure reducing valve.

A relay- or pilot-operated reducing valve for steam services is shown in Figure 3. It comprises: (a) (b)

The valve body, which contains the main valve and seat piston assembly. The control head, which houses the pilot valve assembly with its associated diaphragm and main adjusting spring.

This type of valve works by balancing the downstream pressure against a control spring. This modulates a small valve plug over a seat (the pilot). The flow through this seat is directed in turn to the main valve diaphragm (phosphor bronze or stainless steel), where it modulates the main valve.

Sel(-AcLing Reducing Valves Materials No 1 2 3 4

Par1 Mateml Spnng housing --:-:-:-::--=-~~7 A;I~-=m:in u ='"o~ um =--"e:::p-::-ox:::y-:-c::o:::a::1ed :-:;-;L--;M-.--;;-24 Ad1us1men1 Hand Wheel PlastiC - Polypropylene Top Spring Plate Cast Iron DIN 1691 GG 20 Pressure Adjustment Silicon Chrome BS 2803 685 ASS Spring Spnng Steel Range 2 5 Bellows Assembly Phosphor bronze/brass - - BS2872 CZt22 (Siainless Steel oplional 31 6Ti/ 316L) 6 Bellows Assembly GaSket Reinforced Exloloated Graphofe Steel - Zone plated 7 Sprong Housong Bolts BS 3692 Gr 8.8 MS x 2Smm - 8- Body Gunme1a1 BS 1400 LG2 9 Guode 7-;B ;;;-u- s7h_ _ _ Graphite lolled PTF E 10 Pushrod ------;:S,.-ta~onless Sleel ASTM A276 3 1Gl 11 va·:-,v-o-;:: Sc :-,a - :t, - - S1ainless Steel BS 970 43 I S29

12

Valve Seal Gasket i3"Pi5ton 14 Valve Ht>ad tS Poston Retur-n--=s=-p_n_n_g __

16

Straoner Screen ~Cap Cap Gasket t9 Spnng Range 10 Plale

-;a20 21

Bulkhead Plate Tamperproof Pin

Staonless Steel BS t449 3t6 S1 I Staonless Steel BS970 431529 Notnle Rubber Stainless-;; S,.-te-e71--=B=-=s=-=20=s-=-6-::G:-:: r302 S26 Staonless Steel BS t449 304 Sttf Brass BS 2872 Cf122 Reonforced Expholoaled Graphote Polypropylene

----sliiiniOSs Steel 316 L Mild Steel - Copper Plated _ _

Figure 2. Direct-acting pressure reducing valve for liquids.

Pressure adjustment - - -""",~......._

..... control spnng Pilot diaphragm Downstream external sensing _ p1pe connection Pilot valve ------

Control

C+ - t- - port

Main - diaphragm ~~-~-"'

Pi{Jltre 3. Pilot-opl'rated press lire reducing valve.

22 7

228

Pressure Valves and Services

Under stable load conditions, the pressure under the pilot diaphragm balances the force set on the adjustment spring. This settles the pilot valve, allowing a constant flow across the main diaphragm. This ensures that the main valve is also settled to give a stable downstream pressure. When the downstream pressure rises, the pilot valve closes and pressure is released from the main valve diaphragm through the control orifice, to close the main valve. Any variations in load or pressure will immediately be sensed on the pilot diaphragm which will act to adjust the position of the main valve. ensuring a constant downstream pressure. In order to achieve the most stable operating conditions an external pressure sensing pipe is used. This becomes more important as the valve is used near its maximum capacity or under critical flow conditions. A solenoid will provide for remote on/off control and a fully adjustable set point is possible using an air-driven pilot. The set point can then be adjusted via a compressed air regulator situated away from the valve. For example, the valve may be high up in a pipeline but adjustment can be made from an air regulator at ground level. The characteristics of both pilot-operated and direct-operated reducing valves are shown in Figure 4. Both curves are shown for 25 mm (l in) valves reducing from 10 to 3.5 bar (150 to 509lbf/ in 2 ). It should be noted that in the case of the direct-acting valves (including those with balance pistons) the outlet pressure falls as the flow through the valve increases. Thus if the valve is set at a no-flow setting of 3. 5 bar (50 lbf/ in 2 ), the outlet pressure falls by about 0.35 to 3.15 bar (5 to 45 lbf/ in 2 ) when

Values given arc for I inch valves re ducing from 100 !o 50 lb/in'g 55

50

5

I

I

Dead en d seuing .....

_Jlbflin pressure drop_. _

PILOT-OPERATED VALVE

~

!

. , pressure I d rop 5 lbf/tn'

~

f""o

I

I D,l?

I

I

~0:-1

l

I

~IJV,

i

~-

5

200

I

362 400

600

BOO

' ...

I

'...

...

'

I I

i

I

!'...

Th1s corTc<ponds to the average now through a 1 in bore pipe at 100 lbflin2

30

I I !

i

I

Cv

i"

... ...

I ... ...

...

I

...

- r----

I

I M axomum capaci1y o 1 • pil01 -opcrated

Lt 1000

1200

VALVE CAPACITY lbfhr

Figure4. Se{(-acting reducing valves.

1400 1500 1600

valve

1800

Self-Acting Reducing Valves

229

passing an average flow for this type of valve. The direct-acting valve is usually made equal in size to the inlet pipe. In the case of the pilot-operated valve it will be seen that apart from an initial pressure drop of 0.03 5 bar (2 lbf/ in 2 ) from the dead-end setting of 3. 5 bar (50 lbf/in 2 ) the outlet pressure remains constant until maximum-rated capacity is reached. It should also be noted that. in the examples shown, the 2 5 mm (1 in) pilotoperated valve is capable of passing a flow of more than four times that of the direct-acting valve, and with only 0.035 bar (2 lbf/in 2 ) pressure drop as compared with a drop of0.35 bar (5 lbf/ in 2 ). Applications of reducing valves

Reducing valves are used for reducing one pressure to another. control being via throttling of the fluid through the valve and its seat. Reducing valves should never be deliberately oversized as if the valve is too big then the lift of the valve will be small and wire drawing or erosion of the valve and seat can result. Additionally, small variations in valve opening cause large changes in flow which at small flow demands can lead to pulsating pressure being generated in the downstream flow. The following notes designate the main fields of application of self-acting reducing valves. Air or gases

This application includes all compressed air systems for use with power tools, pneumatic control systems, etc., and control valves for the storage and distribution of industrial gases. etc. Both direct-acting and pilot-operated reducing valves may be used for these duties and are selected according to the accuracy of control required and whether or not the valves are intended to give a dead tight shut-off under no-flow conditions. Water

Reducing valves are extensively used in industrial and domestic water distribution, fire protection systems and the limitation of water pressures in high buildings, etc. Direct-acting valves with piston valves are generally used for these duties . As a general rule, reducing valves are used mainly as pressure limiting devices in water-distribution systems. Because of high peak demands at times of heavy industrial usage. water authorities usually have great difficulty in maintaining pressures in the systems, although high pressures are usually available at the source of distribution. such as at reservoirs or main pumping stations. Very large pressure drops are

230

Pressure ValvesandServices

experienced in the system during high demands and as a result there is a tendency for the pressure to be below normal at the point of usage. However, when the total demand in the system drops, much higher pressures are experienced in the distribution system and these are frequently in excess of the normal pressure ratings for the equipment being used. This can give rise to burst mains or excessively high discharge rates from domestic fittings, such as water closets. wash basins. etc. or storage tanks. It is therefore common practice to fit a reducing valve in the line which. under high flow conditions, normally operates in the wide open position and presents only a nominal resistance to flow (such as would be experienced with an ordinary globe stop valve). However, at periods of low demand and high pressure, the reducing valve becomes effective and reduces the pressure in the downstream mains to an acceptable limit. It is important in such applications that the outlet pressure is not affected by inlet pressure variations and for this reason the direct-acting valves with piston balance are admirably suited to this application. Other liquids

In this field, reducing valves are used for such applications as: controlling ram pressures on hydraulic presses; bearing lubrication systems in rolling mills and heavy industrial equipment; and for pressure control in fuel-oil systems. Again valves are normally used for these applications. In many applications the flow is relatively constant and the outlet pressure from the reducing valve therefore remains constant. In fuel-oil systems the flow variations are normally of the order of 50 to 100%, in which case the outlet pressure variation would probably be of the order of0.14 to 0.21 bar (2 to 31bf/in 2 ), depending on the size of valve used. The variation would be in the order of 0 .3 5 bar (5 lbf/ in 2 ) between full and no-flow conditions. Steam

This particular category covers by far the majority of reducing valve applications and in general there are two broad sections. Power

Reducing valves are only occasionally used on power installations involving steam, i.e. direct steam supply, steam engines and turbines, etc. In these cases the general principles of application still apply, although special problems do sometimes arise in the case of reciprocating machinery which may give rise to pulsations in the pipework system, and these can be amplified by the reducing valve itself. This is normally overcome by providing adequate pipe volume both upstream and downstream of the reducing valve to act as a 'steam accumulator'.

Self-Acting Reducing Valves

2 31

Process

\t\fith saturated steam, temperatures and pressures are strictly related and,

because of this, it is frequently found convenient to control temperature by controlling the steam pressure. Applications in the process field includes space heating, kitchen equipment, sterilizing equipment, curing processes in the rubber and plastics industries, etc., industrial cooking equipment, etc. In fact, anywhere steam is used as a heat-transfer medium, reducing valves will invariably be installed. In general. only low pressure steam. usually below 3. 5 bar (50 lbf/ in 2 ), is used for process purposes. At such low pressures the latent heat content of the steam is relatively high and is easily transferred from the steam to the product being processed. Size of pipes and fittings

The inlet and outlet pipes should be sized to suit the maximum steam demands of the system, e.g. see Table 1. Pipe sizes should always be determined in terms of pressure drop and not by such rules as arbitrary steam velocities. Correct sizing ofpipework and fittings associated with all valves is extremely important in order to obtain the best possible operation. Specifically: (i)

Strainers should always be equal in size to the inlet pipe. (ii) When globe valves are used as inlet and outlet stop valves , these should also be equal in size to the respective pipe, into which they are fitted. (iii) When parallel slide valves are used as stop valves, these can be fitted equal in size to the reducing valve for reduced pressures between 30 and 70% of the inlet pressure. They should be equal in size to the respective pipe when the pressure difference between the inlet and outlet is 2 bar (30 lbf/ in 2 ) or less. When they are connected directly to the reducing valve the length of distance pieces between value and fitting should not exceed three pipe diameters. (iv) In order to provide a streamlined flow at the approach to the reducing valve , a straight length of pipe equal to 10 pipe diameters should be provided between the fitting and the reducing valve (this does not apply to parallel slide valves) . Typical reducing valve layouts are shown in Figures 5 and 6.

Reducing valves in parallel

As already mentioned, two reducing valves in parallel should be considered when the minimum flow through the system is less than 10% of the maximum capacity of a single reducing valve , or when the valves are expected to work for long periods on 'no-flow' or 'dead-end' conditions. or working in partially completed plant systems. A typical layout is shown in Figure 7.

232

Pressure Valves and Services

Table 1. Steam pipe capacities (lb/hr dry saturated)

Pressure lbf/in 2

Pipe size in inches

]h

>;4

1

12 32

63

1 1 /4 1 1h

2

2 1 /2

3

4

5

6

8

10

bar 5 0.35 10

0.09 20

1.38

106 163 320 536 0.4 0.4 0.4 0.4

813

1560

2550

3820

6180

100.000

0.4 0.4 0.4

0.4

0.4

0.4

0.3

0.3

0.3

15 40

113 206 404 676

1055

1962 0. 5

3220

8000

12.950

0. 5

4810 0. 5

0.4

0.4

2680 0.7

4390 0.7

6550 0.7

11 .300 0.6

lS.nSO 0. s

14.700 0.8

22.300

8000 12.000 2] .450 7.3 1.3 1.2

33.400

79

0.5 0.5 0.5

0.5

0.5

0.5

0.5

18 '54 107 182 300 586 980 0.6 0.7 0.7 0.7 0.8 0.8 0.8

0.5 1400

0.7

-

30

2.07 50

3.45 75

5. I 7 90

6.21 -

100

6.90

-

-

24 69 137 245 377 740 1240 1880 0.9 I.() 1.0 1.0 0.9

2600

5900

8810

0.9

0.9

0.9

35 98 203 357 582 11401910 2640 1.2 1.3 1.4 1.5 1.6 1.6 1.6 1.4

4880

47 136 284 495 780 149 3 2500 3800 1.6 1.8 2.0 2. I 2.2 2.1 2. I 2.1

7100 11.600 16.900 30.600 48.400

53 157 332 581 896 1755 2940 4460 2.5 2.5 2. 5 2.5 2.5

8280 13,57019.450 35.400

0.8 0.9 0.9

1.8 2.1 2.4

1.3 2.0 2.4

2.0 2.4

1.9

2.2

1.8 2.1

-t--

59 173 362 615 984 1928 3220 4840 2.0 2.3 2.6 2.6 2.8 2.8 2.8 2.7

9040 14.820 21.800 38.900

2.6

2.6

2.5

2.3

0.7 1.1 7.7 54.500 1.9

fil. 500

2.2 -

120

73.000

8.27

68 204 431 75 5 1182 2320 3900 5710 10.920 17.910 26.000 46.900 2.9 2.3 2.8 3.2 3.4 3.5 3.5 3.5 3.3 3.3 3.3 3.1

ISO 10.34

83 252 539 945 1420 2900 4770 7100 13.600 22.300 32.500 59.100

2.8 3.5 4.1

93.000 3.6

180

12.41 200

13.79

-

4.4

4.5

4.4

4.2

4.2 --

4.2

4.2

4.0

3.8

2.7

--

96 296 642 11311748 3440 5890 8750 16.680 27.300 40.000 71.500 112.000 3.3 4.2 5.0 5.3 5.4 5.5 5.7 5..5 5.4 4.8 4. 5 5.4 5.2 107 324 708 123 8 1942 3880 6530 9750 18.880 31,000 44.300 80,000 126.000 3.7 4.6 5.6 5.9 6. I 6.3 6.4 6.4 6.3 6.3 5.8 5.5 5.2 -

220

l5. I 7 250

17.24 300

20.69

116 354 770 1350 2120 4200 7150 10.850 20.800 34.000 49.000 90.000 141.000 4.0 5.0 6.0 6.4 6.6 6.8 7.0 7.0 7.0 7.0 6.5 6.3 5.9 133408 871 1525 238 5 4760 8100 12.360 23.800 39,000 57.000 105.000 J 68.000 4,5 5.7 6.7 7.1 7.3 7.6 7.8 8.0 7.0 7.6 7.8 8.0 8.0 15749610251798 2800 5160 955014,760 28.400 46.500 68,900125.900 202.000 5.3 7.2 7.8 8.3 8.5 8.9 9.2 9.6 9.4 9.1 9.6 9.6 8.9

Note: Figures in italic show pressure drops (lbf/ in 2) for equivalent lengths equal to 360 pipe

diameters. When u sing this table. allowance should be made for the effects of bends and fittings in the pipeline.

Self-Acting Reducing Valves

Figurr 5. Control ofwalerdistrilmtion.

Figure 6. Control ofstenm distribution.

Reducing valve at)() lb/in -'

SCI

Relief valve set at 57 lh!in 2

Reducing Valve set at 52 lb/in 1

Fig11re 7. Parallel arrangement of reducing valves.

Steam trap

233

234

Pressure Valves and Services

In order that the valves can deal effectively with minimum capacity variations of less than 10%, two unequally sized reducing valves having a maximum capacity equal to the required capacity should be connected in parallel with the outlet pressure of the smaller valve set 0.14 to 0.21 bar (2 to 3 lbf/ in 2 ) higher than that of the large valve. In this way the larger valve would shut at low demands leaving the smaller valve to handle the low flows. As the demand increases the larger valve will open automatically as the reduced pressure falls. and share the load with the small valve. By this method capacity ratios of up to 100:1 can be obtained. Superheated steam

Superheated steam is less dense than saturated steam and, therefore, for the same pressure drop the reducing valve will have slightly smaller capacity. The reduction in capacity is dependent on the amount of superheat. Capacity figures quoted in manufacturers' catalogues are normally for dry saturated steam. vVhen steam is superheated above 2 8°C ( 50°F) before it enters the reducing valve. dry steam capacities should be multiplied by the following factors: 56 to 83°C (100 to 150°F) ofsuperheat-0 .8 9 83 to 111 oc (150 to 200°F) ofsuperheat-0.86 111 to 16 7°C (200 to 300°F) ofsuperheat-0.82 Steam traps

Whenever possible. pilot-operated reducing valves should be sited at some point in the pipeline where they cannot become flooded with condensate during periods of low flow or prolonged shutdown. If this is not possible then steam traps (and, if possible, dirt pockets) should be fitted to both the inlet and outlet pipework to remove any condensate which may accumulate in the vicinity of the reducing valve. Condensate can be trapped between the piston and pilot valve when the steam flow is resumed and this prevents the main valve from closing as the reduced pressure may continue to rise above the setting and eventually cause the relief valve to blow. The thermodynamic steam trap shown in Figure 8 is suitable for use in condensate removal from high pressure steam mains and for turbine casing drainage. On start up, incoming pressure raises the disc and cooled condensate plus air is immediately discharged (A). Hot condensate flowing through the trap releases flash steam. High velocity creates a low pressure area under the disc and draws it towards the seat (B). At the same time there is a pressure build-up of flash steam in the chamber above the disc, which forces it down again st the

Self-Acting Reducing Valves

A

B

c

23 5

D

Figure' H. Th ermodynamic steam trap-operating sequence.

pressure of the incoming condensate until it seats on the inner ring and closes the inlet. The disc also seats on the outer ring and traps pressure in the chamber (C). Pressure in the chamber is decreased by condensation of the flash steam and the disc is raised by the incoming pressure. The cycle is then repeated (D). Fitting of balance pipes

It is strongly recommended that a balance pipe should be fitted when the reduced pressure is 10% or less of the inlet pressure. The purpose of this pipe is to improve the performance of the reducing valve when working under difficult downstream conditions. It will also help to counteract any pressure drops in downstream pipework caused by undersized pipe fittings , etc., providing they are not excessive. A stop valve should be fitted in the balance pipe to allow complete isolation of the reducing valve from the steam flow (particularly when a bypass line is fitted). The balance pipe should be arranged to fall to allow it to drain into the downstream pipe. The tapping into the downstream pipe should be made at a point where smooth flow occurs preferably downstream of the relief valve. The downstream pressure gauge should be fitted as near to this point as possible.

Air Relief Valves Air or gas trapped in a pipeline carrying a liquid can cause problems. e.g. reduce the effective flow, aggravate the effects of surge. and cause pump cavitation. Possible causes of air/ gas entrainment are: (i)

The pipeline was fully charged with air/ gas when empty. (ii) Air is entrained at pump suction. (iii) Air is drawn in through faulty joints or glands. (iv) Air/gas is trapped in pockets during pipeline filling. (v) Air/ gas in solution is released due to changes in pressure and temperature. The problem of dealing with air/ gas entrainment is not usually a demanding one. Entrained air/ gas will tend to collect at high points in the system . It can then be removed by introducing air release valves at these points. These may be simple, manually-operated valves (bleed valves), or fully automatic. In the latter case the valve should perform the following functions : (a) (b) (c) (d)

release of air/gas accumulating in pipeline during normal pressurised operation, to prevent restriction to fluid flow retention of the fluid in the pipeline without loss under all operating conditions release of air/gas during pipeline filling at a volume rate sufficient to prevent back pressure restricting the fiHing rate admission of air to the pipeline during emptying at a rate sufficient to prevent excessive vacuum pressure in the pipe.

Single orifice valves (Figure 1) are capable of performing functions (a) and (b). They are normally used where only relatively small volumes of air/ gas are to be released, or where it is desirable to provide additional ventilation at operating pressures. Dual-orifice valves are capable of performing all four functions. They can normally provide complete protection against air/gas entrainment under all system-operating conditions. The type of fluid product being handled also affects the design requirements or the air release valve (especially automatic valves) . With sewage or industrial

Air Relief Valves

23 7

Cowl

Orifice bracket Sealing

face Fulc pin Float and I

Figure I. Single-orifice air relief valve.

effluent. for example. the solids content may block the release passage(s) periodically. causing unreliable operation . This can be overcome by using large-volume auxiliary float chambers to contain the fluid under all operating conditions so that it can never come into contact with the air valve elements. An example of a dual-orifice air valve suitable for water systems is shown in Figure 2. The valve combines small and large orifices. The small-orifice valve comprises a composite float a nd lever assembly sealing off a small-orifice vent. When the Components Large Oriflce Sedhng Rmg Small Onhc e

S:lldll O ri hcc LC'v t> r Air Valve F'loJ t T uppet

A!r Valve Unll

Ele v ato r Guide Sleeve

Mam Cov e r Float Chamb er Opcrahng Float

Figure 2. Dual-orifice air relief valve.

238

Pressure Valves and Services

Underpressure air reln rse valve.

Dual-orificr air valve.

I

I

Air valve with VNRV

Tank I

Point of Ouid separation

~----'*',' ~~~

Pump house /'--'~ ,,_-

,,"

---•- -... ---- --------

_, , , "

t

~

~

I

,'

Transient pressure wave

.-

Example of patented air relief valve with vented non-return valve for performing additional function of surge suppression.

Vent regulating valve

Air relief valve.

Vented non-return valve

1

Air Relief Valves

239

float chamber is fiJling with water, the orifice is closed initially by the float working through a lever ratio of 5:1. When the chamber is filled with water under pressure. the orifice is held closed by the combined upthrust of the float and the differential pressure over the orifice area. On air accumulated in the system entering the chamber under working pressure. the water level in the chamber is depressed until it reaches a point \•vhen the weight of the float is sufficient to uncover the orifice and exhaust air. Air is expelled until the water level rises again and causes the float to close the orifice. The large-orifice valve consists of a float sealing off a large-orifice vent to the atmosphere. The float is held at a predetermined height in its casing by a ribbed cage which also guides the float onto the seat. During the pipeline filling or emptying, the 'aerokinetic' feature holds the float off the seat and keeps it completely stable under all air outflow or inflO\v conditions. The valve cannot close prematurely during outflow. It closes only when water enters the casing and raises the float onto the seat. An example of the working of dual-orifice air relief valves designed for handling sewage and similar effluent is shown in Figure 3. When the pipeline

>I Sealing

5 Pressurisation

6 Re lteving

Figure ). Operational sequerrce of a dual-orifice air relief valve.

240

Pressure Valves and Services

Double-acting sewage air valve.

is empty, the spherical operating float is suspended from the elevator within the main chamber and the cylindrical float element of the air valve is supported by the guide cage. The operating lever of the small-orifice valve is held open by a tappet on the elevator. Air/gas having been inhaled or expelled from the pipelines is able to flow freely through both orifices. the design of the valve being such that the air flow creates a positive down force to hold the cylindrical float element stable within the guide cage. As the air/gas is exhausted from the pipeline, liquid enters the main chamber and the operating float then rises with the liquid. The elevator. raised by the float, releases the small-orifice valve and engages the base of the cylindrical element, which rises until seated on the rubber face of the large orifice. At this point air/gas outflow ceases and further inflow of liquid to the main chamber under pipeline pressure compresses the air/gas until maximum working pressure is reached. The proportions of the main chamber are such that the fluid level will not rise above the bottom face of the main chamber cover. When the pipeline is emptied and pressure falls. the valve main chamber will drain into the pipeline and the operating float. following the liquid level. releases the cylindrical float to allow the large orifice to open. As the pipeline pressure falls to atmospheric, it opens the small-orifice valve. The pipeline is then able to ventilate freely and sub-atmospheric pressure conditions are avoided.

Air Relief Valves

241

During normal operating conditions. air/gas will be released from the liquid and will collect under pressure in the main chamber, depressing the liquid level. The operating float falls with the liquid but system pressure will hold the cylindrical valve element on the large-orifice seat. As the operating float approaches the limit of its travel, the tappet on the elevator opens the small-orifice valve, releasing the accumulated air/gas under pressure. This in turn allows the liquid level to rise again and the small-orifice valve to close. thus completing a cycle. Positioning of air relief valves

In systems handling water, air relief valves would normally be placed at all high points, i.e. where a rising section changes to a falling section. In systems handling sewage or industrial effluent, rather more extensive treatment is necessary. as illustrated in Figure 4. Where the fluid is pumped through the pipeline it is desirable that a dualorifice valve (valve A) be located just downstream of the pump-delivery valves. Dual-orifice-type valves are also required at all peak points which are defined relative to the hydraulic gradient and not necessarily to the horizontal. In practice a peak may be considered as any pipe section which slopes up towards the hydraulic gradient or runs parallel to it. In the latter case the

Rising section

-~

-----

--- ----

Hydraulic

---

gradie nt

E

E

Datum line

Falling section

c

D a tum line

fi gure 4 . Typ iral sewage air valve location poin ts.

242

Pressure Valves and Services

minimum requirement is a dual air valve at each end of the section (valve B); any additional valves may be of a single-orifice type. Positions where an increase in down slope occurs will require ventilation by a small orifice valve which should also be installed at points of decrease in up slopes (valve D) . Pipeline sections of uniform profile also require ventilation and dual-orifice units should be installed at about 800 m (2500 ft) intervals on these sections (valves E).

I

Foot Valves A foot valve is basically a check valve fitted to the end of a suction pipe leading to a pump. Its purpose is to keep fluid trapped in the suction pipe when the pump stops. thus maintaining a suitable prime for the pump. When the pump restarts. the suction created opens the valve, giving full flow to the pump inlet. (Foot valves are unnecessary on self-priming pumps.) Foot valves may be of a simple flap-type, or more usually lift-check or ballcheck valves. They are commonly combined with an integral strainer. Some examples follow. Poppet lift foot valve

In the example shown in Figure 1, the poppet assembly consists of a plastic tripod which can be displaced along a bore above the seat valve. The travel of the poppet is controlled by a stop on the end of the poppet legs acting as supports for the return spring shouldered onto a washer. This spring ensures that the valve will work in any position. The main characteristics of this design are low head losses with good sealing provided by a nitrile rubber 0-ring.

Figure 1. Foot valve with plastic tripod.

244

Pressure Valves and Services

Figure 2 shows a design with the tripod in cast iron and with a cast-iron poppet head with streamlined tripod hub. Sealing is provided by a flat gasket shouldered by the poppet head and placed on a collar-type seat. This is a simple and robust design suitable for general applications.

Poppet-tlJpefoot valve with strainer.

Figure 2 . Foot valve with tripod and poppet head in mst iron.

FooL Valves

Figure 3. Foot valve with all metal poppet and profiled head.

245

Figure 4. Ball foot va.lve.

Figure 3 shows a further design where the all-metal poppet with profiled head is guided by three legs and restrained by a downstream stop. Sealing is by a flat seal on a flat bearing surface. Valve travel is limited by the stop. A spring can be added to ensure that the valve will operate in any position. Ball foot valve

An example of this type is shown in Figure 4. This is a simple ball valve guided by an inclined cylindrical chamber and seating on an 0-ring. Note that the ball is displaced laterally along its chamber with inward flow , but it runs down

SUCTION

FLOW STOPS

Figure 5. Membranefoot valve.

246

Pressure Valves and Services

Fig11re 6. A selection of membrane foot valves.

the chamber onto its seat when the flow rate decreases. [t is particularly suitable for use with contaminated waters or more viscous fluids. All examples illustrated are of the type with integral strainer. Membrane foot valves

Membrane foot valves consist of a cylindrical rubber membrane fitted inside a steel strainer. When there is a suction developed at the strainer, the membrane is displaced to allow fluid to flow through the valve. When back-flow conditions exist, the cylindrical membrane closes the apertures in the valve strainer, thus closing the valve, (see Figure 5 ). A selection of membrane foot valves is shown in Figure 6. The lever fitted to one valve enables the valve to be drained by physically displacing the membrane when the lever is lifted. See also the chapter on Check Va lves.

SECTION 4 Control and Automation

Valve Actuators Control Valves Float Control Valves Temperature Control Valves Regulators

Valve Actuators Numerous types of devices exist for the remote operation of valves. These range from simple gearboxes to highly sophisticated motorised valves with automatic control. programmable logic controllers. microcomputers and field communications networks. In basic terms, an actuator can be described as ' A device supplying force and motion to the closure member (ball. disc. plug, etc.) of a valve'. There is a distinction between the actual requirements but, in general, the vast majority of applications are concerned with the opening and closing of

Bushes inserted

t.r~m i'!S!C!~

cvJ.!'!.der

Standard-type pneumatic valve actuator.

2 50

Control and Automation

valves. Certain systems may call for continuous modulating control which can set limits on the usefulness of both mechanical and energy systems. In 1992, the world's first non-intrusive 'intelligent' enclosed actuator. that could be commissioned and interrogated without removing electrical covers, was launched. All actuator settings and diagnostics are made through a sealed indication window using an infra-red setting tool, avoiding the use of penetrating shafts. Solid-state torque and limit measurement is used throughout, eliminating the use of springs. switches or levers. The separation of the setting tool from the actuator provides a most effective method of security of the settings. Multi-turn actuators-on-off duty

The general design principle of a multi-turn actuator is to turn a multiple of 3 60° at its output drive. The resulting rounds-by-stroke relationship can be from 2 to more than 1450. Within this range, position-indicating devices, such as limit switches, and electronic position transducers can be adjusted . Initially, multi-turn actuators fitted to valves transform the cycle movement of the output drive to linear movement according to the demands of the valve. Multi-turn actuators for on- off duty (short-time operation 10-15 min) mostly operate valves with only a few number of opening and closing periods a month. Part-turn actuators-on-off duty

There is another type of multi-turn actuator for operating ball or butterfly valves or dampers, for example. with a movement of less than 3 60° for opening and closing. Normally. the internal gear of the part-turn actuator is designed for a turn of 90°, although 120° and 180° are commonplace. Thrust actuators-on-off duty

Thrust actuators may be fitted to valves requiring linear movement. They transform the torque of a multi-turn actuator into an axial thrust force by means of an attached thrust unit. Linear actuators are mainly used with globe valves or similar and, when indirectly mounted, may be used to operate butterfly valves, flap valves or dampers. Multi-turn actuators-modulating duty

The requirements of modulating service (operation of control valves) on actuators are different from the 'normal' on- off duty.

ValveActuators

251

Part-turn actuators-modulating duty

Typically, a part-turn actuator for operating a control valve consists of a combination of a multi-turn actuator with a worm gear, the connection between the two being achieved via the output drive. It is probably more appropriate to deal with the overall subject of actuators under three main headings: main types of valve actuators (ii) choice of energy systems (iii) electric/electronic controls (i)

Main types of valve actuators

The main types of actuators used are: (a) (b) (c) (d) (e)

manual operators cylinder actuators (pneumatic or hydraulic) vane actuators electric solenoid diaphragm actuators (f) electric motor actuators

All have their particular virtues and uses. Manual operators

Apart from the obvious job of providing a means whereby a person can open or close a valve. the requirements of a manual valve actuator may encompass any or all of the following: Convert motion from linear to rotar}'

Valves of the gate. globe, diaphragm and pinch type utilise linear motion of the obturating members to achieve a seal. Handwheel operation implies rotary motion, and conversion is generally by nut-and-screw, which may be part of the valve or of a separate manual actuator. Withstand thrust

When the threaded nut forms part of the manual actuator, it will have to withstand the operating thrust developed and incorporate suitable thrust bearings.

2 52

Control and Automation

Lock the valve in position between operations

For valves operated by linear screw thread, position locking is achieved by use of an irreversible, (i.e. low-efficiency) thread. Butterfly valves must also be restrained against self-operation as a result of dynamic flow, and again this is customarily ensured by using irreversible, low-efficiency, gearing such as worm and wheel between valve stem and hand wheel. In each case the efficiency must be Io·w enough so that the valve does not move from an intermediate position if pressure is applied to the stationary valve, and it will also stay in position if manually-operated with flow present. There have been many occasions when valve slamming has occurred under high-flow conditions with a gear ratio which was thought to be irreversible, but proved not to be when the handwheel was started under heavy-flow conditions and the valve took over. This dynamic effect is less of a problem with plug and ball valves which have a higher ratio of static friction to dynamic torque and, in any case, are not suited in standard form to flow regulation. Whatever manual means is adopted for the operation of valves, the main constraint is always the human muscle power available. It is difficult for a person to exert more than about 75 vV (1 / 10 hp) continuously for any length of time by hand. Size and type of valve. line pressure and other factors will determine the power required. For larger valves, this will nearly always mean the introduction of an intermediate gearbox with a handwheel capable of operating the valve comfortably with a human's strength-i.e. with a rim pull below 2 7 kg (60 lb). The average male can exert up to three times this force momentarily. by pulling his weight on a handwheel, so that the extra force required to seat or unseat a valve is not a problem if the gearing is adequate. However. the

Manual gear actuators.

Valve Actuators

2 53

fundamental principle of gearing to reduce input torque inevitably means that the number of turns required of the handwheel increases. For large valves and pressures. the number of turns is such that manual operating time may be measured in hours rather than minutes. There is no way, therefore. that emergency manual operation can be quick. The alternative philosophy is to accept that large valves are difficult to operate and require at least two people, or a team in an emergency, operating a larger handwheel with far fewer turns. There is no ready solution to this dilemma other than power operation. Another reason for utilising reduction gearing is to reduce the torque to be transmitted via shafts and couplings to a remote operating point, e.g. spur gearing of a gate valve to a pedestal, say, on a floor above. A side handwheel is generally more convenient than one with a vertical shaft. Bevel gear actuators are therefore widely used to reduce the operating torque of gate valves and bring their handwheel to a particular side for access. The use of worm gearboxes and equivalent nut-and-screw scotch yoke actuators for quarter-turn valves automatically turns the drive through a right-angle, which may therefore be oriented in the right direction. Additional

HANDWHEEL EXTENSION

CHAIN SPROCKET

RIGHT-ANGLE DRIVE

Manual operators.

2 54

Control and Automation

gearing for torque reduction is then usually provided by spur gears. although a further change of direction via a bevel gear may sometimes be needed. Hypocycloidal gear-train manual actuators have been especially developed for the operation of centred-disc butterfly valves mainly used in the heating. ventilation and air conditioning industry (HVAC). Other manual actuators with worm wheel and screw kinematics are used with 1 / 4 -turn valves including centred or double-eccentric disc butterfly valves. ball valves, etc. They are designed to deliver a constant output torque. Signalling

A problem with manually-operated valves- especially in plants with centralised control-is the absence, usually, of any standard means of signalling the valve status, or of confirming that a required operation has been carried out. If this is necessary, special provision has to be made. Often this is done by attaching some form of external limit-switching mechanism, using switch boxes that meet environmental and safety requirements (see the section on Limit switches below). Handwheel drives for powered actuators

All the aforementioned points apply to auxiliary manual drives for power actuators. However. the fact that the drive is auxiliary only and not the main Visual pointer protected by a tranparent cap

Handwheel in zinc-aluminium alloy with open and clos1ng direction and symbols

Gear casing 1n zinc·alumm1um alloy with ISO 5211 mounting plate Satellite gears m steel Driving dev1ce in zinc-alumin1um alloy

Interchangeable insert

Hupocycloidnl gear-train kinematics.

Valve Actuators

2 55

means of operation may make design compromises in the interests of economy more acceptable than they would be if manual operation were the regular and only means. Cylinder actuators

This type has an actuator using a piston moving inside a cylinder by pneumatic or hydraulic pressure. It can be single-acting, i.e. equipped with a return spring, or double-acting, using air or oil pressure for movement in both directions . The piston and cylinder can be practically any length or diameter and readily converts pneumatic or hydraulic pressure into linear force. This can be further converted to part-turn operation by rack-and-pinion or linkage, i.e. scotch yoke . Pneumatic actuators for industrial valves are predominantly applied in continuous processes. WhiJe one actuator may pass through hundreds of cycles, 24 hours a day. another may open and close just once a month. Pneumatic actuators can be applied to ball valves. plug valves and butterfly valves. Vane actuators

A vane actuator is a pneumatically or hydraulically operated actuator used with rotary valves. Typically. the actuator has a paddle-like vane in a sectorshaped pressure casing giving a 90° rotary motion to the vane shaft connected to the valve stem. Vane actuators can be double-acting, i.e. operated in both directions by air or gas pressure, or single-acting with a return spring.

Pneumatic spring-return actuator.

2 56

Control and Automation

Electric solenoid

The electric solenoid tends to be limited to very small powers, i.e. to pilot duty rather than actuation duties for other than the smallest valves. Diaphragm actuators

This can be described as a pneumatically operated actuator where the air chamber is sealed by a flexible diaphragm, with most of its flat area supported by a plate at the end of an actuator stem. Variable air pressure flexes the diaphragm and positions the stem with the assistance of a return spring. Spring-diaphragm actuators are designed for both proportional and on-off control of rotary valves. They may be operated by air, gas, water, oil or other supply media compatible with the diaphragm and its case. Other types of spring-diaphragm pneumatic linear actuators are designed for operation with linear control valves. The action can be direct-acting, where the stem extends with increased air pressure, or reverse-acting. where the stem retracts with increased air pressure. Electric-motor actuators

Stringent demands are made of electric actuators for industrial valves. Extreme temperature fluctuations and aggressive media that affect the actuator's resistance to chemicals are just two of them. Microcomputers are being increasingly used to achieve more accurate and finer controls and adjustments. They are installed not only in large facilities but also in individual equipment. The trend will intensify with price reductions

Spring-diaphragm actuator.

Valve Actuators

2 57

in microcomputers and with the desire to trace system hazards quickly. These factors have caused an acute need for automatic controls for entire piping systems. Generally. electric-motor actuators are designed for use on baH valves. gate valves. butterfly valves, plug valves and any mechanical equipment calling for 90° rotational control. including dampers and ventilation grids. etc. The development of the smart valve accessible by a digital communications link means that commands can initiate a stroke check of the valve. recording pressure versus valve travel as the valve is stroked. With an additional sensor for stem and shaft position, the data can then be used to evaluate the condition of the actuator and accessories under various parameters based on an investigation of the valve's stored history. Digital communications to the valve can measure input signal, pneumatic pressure and valve travel. comparing the data with stored expected value's and recommending corrective action. The electric motor will become a serious challenge to pneumatic power when its inertia matches that of a piston or a diaphragm and when gears have zero backlash. It must also rid itself of thermal overloads. limit switches, cams, heaters and thermostats, duty-cycle limitations and explosion-proofhousings. The trend. though. is definitely towards electronics and micro-electronics and for the future there is the possibility of an actuator that emulates a biological muscle-a fast. powerful mechanism that uses stored chemical energy and is controlled by weak electrical pulses. This device might consist of polymer strands that contract on signal and take their energy from a chemical bath that is recharged electrically, as needed by a continuously connected power source. The electric-motor actuator is particularly suited where the stroke is long, because a motor with gearbox has unlimited stroke. However, there are different mechanical virtues between the electric motor and the piston and cylinder. As

Intelligent communication and control.

2 58

Control and Automation

mentioned earlier, the piston can be kept continuously pressurised, whereas the electric motor cannot; a piston can maintain its position, but the drive of a motor must be mechanically self-locking in order to maintain its position when switched off. The motor does, however, have the virtue of kinetic energy-the ability to take a 'running jump' . Kinetic energy, however, places mechanical constraints on the use of motor actuators as the energy must be controlled and not misapplied. In certain circumstances, electric-motor actuators are not very efficient. For example, when driving through a worm gear and nut-and-screw, e.g. on a gate valve, up to 90% of the motive power is trying to wear itself out and only 10% is useful. This is acceptable for intermittent valve operation, but it is one of the reasons why geared motor actuators are not well suited to continuous modulating or positioning control via stem nuts or self-locking gears. Multi-turn electric modulating actuators with linear output drives may be a better solution. Position indicator with protective cover. ~

~

Isolation valve w1th male quick disconnect for purging actuator with hydraulic fluid. '

Actuator purge ports also serve as secondary hydraulic power ports.

Isolation valves with male quick disconnects on primary open and close hydraulic power ports.

By-pass valve for initial commissioning and purging of the umbilical.

Isolation valve with male quick disconnect for filling and purging spool cavity with -.. . hydraulic fluid .

'· Actuator body.

~l::=:Pf--r-1r----'-'~

Isolation valve with male quick disconnect for purging spool cavity . ~

Relief valve for spool cavity.

..........

'--1'-------- --__J ............,

----~·l

Rotary-vane subsea act11ator.

.

- Upper mount1ng spool.

Lower mounting spool.

Valve Act11ntors

2 59

Choice of energy system

Clearly the selection of the energy system for a particular valve-operating duty is not something that can be made in isolation. Overall design considerations. safety requirements, availability of supplies and total installed initial cost and subsequent maintenance costs all need to be considered. No single type of control valve actuator is best for all applications. Demands for power, speed, stiffness and precision vary and cost considerations are always present. For some applications, there is no actuator that performs adequately. Sometimes practical valve or environmental needs dictate the use of a specific type of actuator, in which case the energy source is predetermined. Sometimes the non-availability of an energy source-or the prohibitive cost of providing it-will rule out certain actuator options. What follows. therefore. is only a brief resume of the basic systems available, and the practical and economic pros and cons of each for various duties. This must, of course, be related to the foregoing section on actuator types and their performance capabilities. Advice is readily available from most actuator manufacturers on the choice, sizing, adaption. installation and commissioning of valve-control systems. For the unwary or inexperienced specifier, there may be some risk of bias in such advice from manufacturers of particular types of actuator. This is rare among leading suppliers whose own reputation must stand or fall on the soundness of advice in terms of performance and reliability. Pneumatic systems [f the

operation is to be within the confines of a plant where compressed air is available, the cheapest method of valve actuation is a pneumatic piston and cylinder. Pneumatic operation over a distance is, however. limited entirely by the high cost or making adequate compressed air available over long distances, ease of storage of compressed air facilities and fail-safe operation under electric-power failure conditions. The major limitation of pneumatics is available force due to practical pressure limitation-6 to 8 bar (80 to 100 lbf/in 2 ) being the normal maximum. Ninety percent of modulating control valve actuators are still pneumatic. There are many variations of pneumatic actuator available today with output torques up to 12,000 Nm (9000 ft.lbs). The actuator shown in Figure 1 is of the double-acting rack-and-pinion type and is particularly suitable for the automation of a quarter-turn valves (butterfly snd ball valves). This type of actuator may also be fitted with an electronic integrated instrumentation unit to ensure the direct control and supervisory functions encountered in all modern processes and, more particularly. in communication by fieldbus. The pneumatic actuator shown in Figure 2 is a double-acting type incorporating scotch yoke drive.

260

Control and Automation

Figure 1. Double-acting rack-and-pinion prwwnatic actuator.

Figure 2. Double-acting pneumatic actuator with scotclr yoke drivr.

Valve Actuators

261

This actuator develops a variable torque and is well suited for the operation of larger size quarter-turn valves (butterfly and ball valves) when a significant torque is needed near the closed position or near the open position. A typical standard type of double-acting and spring-return piston-type actuator is shown in Figure 3. This style of pneumatic actuator also employs a self-contained spring cartridge to protect against failure in either the open or closed position. Actuators of this type offer an extremely long cycle life and are well suited to operate almost any rotary valve in both modulating control and on-off service. Most actuators of this type are located in fully-closed housings, sealed against humidity and dust, and should not need regular maintenance. Another versatile unit is the positioner-actuator which consists of a double or single actuator, a pneumatic or I/P positioner and conventional or inductive limit switches. This is mainly used with small. segmented ball valves. Normal operation of pneumatic actuators is generally accomplished by pressurising the appropriate supply ports by means of an air-control valve. Most solenoid and control valves perform better on lubricated air which may be added with an air line lubricator. Clean, dry air extends the life of pneumatic actuators and, if this is not available, an in-line filter should be used. Before hook-up, air lines should be purged to remove scale and other particles which could damage the control valve, positioner and actuator seals.

Figure 3. Standard-type double-acting and spring-return pneumatic actuator.

2 62

Control and Automation

Vane systems

Rotary-vane valve actuators are used for quarter-turn valves in critical applications, especially on natural gas pipelines where the actuators are typically powered by natural gas using gas over oil tanks. Other applications include: • • • • • •

quarter-turn valve control on crude-oil products pipelines with the actuators powered hydraulically or by nitrogen-storage vessels high-vibration applications including slurry-pipeline valves, pumping station valves and compressor-station valves offshore platform applications cryogenic or extremely low-temperature applications subsea-valve control high-speed applications with stroking times as fast as 250 ms

A typical rotary-vane actuator is shown in Figure 4. The general principle of operation of this type of actuator is that opposite chambers in the actuator are corrected by pressure-equalising passages in the upper and lower heads. In this manner, the actuator produces a balanced torque as hydraulic force simultaneously pushes both of the rotor valves away from the stationary shoes.

Pressure equalizing passages in the upper and lower heads.

Carbon Steel Upper Head

Vane Seal

Bronze Rotor Bearing

Shoe Seal

Bronze Wear Pads

Cast Iron Stationary Shoe ·

Adjustable Travel Stop ...

Carbon Steel Rotor/Vane Module Carbon Steel Body

Carbon Steel Lower Head

Figure 4. Rotary-vane actuator: schl.:'matic.

Valve Actuators

263

Torque output of the rotary-valve actuator remains constant throughout the ru II rotation of the valve. Constant torque output is an especially important feature in high-flow applications, plug-valve applications and for valves which have rotating seats. Constant torque output insures that the specified safety factor will not diminish at various positions during the valve stroke. The rotary-vane actuator has often been described as the complete actuator for high-pressure duties. Regulators, pressure-reducing valves or relief valves SEQUENCE 1

The actuator may be powered by a hydraulic power unit, stored gas pressure or by natural gas pressure from a pipeline. In this illustration, the actuator is fitted with gas hydraulic tanks and is powered by gas pressure. In the first sequence, the actuator is in the open position. There is no pressure in the actuator or tanks.

SEQUENCE 2

The actuator control system is used to admit high pressure gas into the closing gas hydraulic tank. The pressurized gas in the tank forces hydraulic fluid into the actuators closing port. Pressure equalizing passages allow both closing quadrants to be pressurized simultaneously providing balanced torque as the vanes push away from the stationary shoes. The actuator is rotating clockwise.

SEQUENCE 3

When the actuator reaches the fully closed position, the control system will allow all remaining pressure in the tank to vent to atmosphere, thus neutralizing the pressure in the tank and actuator.

High Pressure Gas •

Pressurized Hydraulic Fluid Non-Pressurized Hydraulic Fluid

Figure 5. Rotnry-vn}ve actuator: operating sequence.

264

ControlandAuwmation

are generally not required in the power supply circuit. The operating sequence of a typical rotary-valve actuator is described in Figure 5. Hydraulic systems

Hydraulic systems are the natural choice if an exceptional duty requires a large amount of stored power (Figure 6 ). The forces available, and the speed

6. 1 5.000 lv!in 2 down control panel. Figure

COII(fuiL-gate valve with hydrarliu spring-return

acwawr and emergency shut-

Valve Actuators

265

and control of the hydraulic actuator are virtually unlimited, i.e. the only method of operating a large valve in seconds is to pump up a hydraulic accumulator first. Unless these particular virtues are needed. the system is uneconomical and. for this reason, is not commonplace. Furthermore. the hydraulic system is very expensive for operation over long distances. A pneumatically-operated valve is vented to atmosphere but, with the hydraulic system. the hydraulic fluid has to be returned through a line of greater suction to avoid pressure drop. For some special situations. such as tanker-cargo valves, however, hydraulics provide the only acceptable means of centralised control. Hydraulic systems are still used for fail-safe and standby duties. Combined pneumatic/hydraulic systems (air-oil cylinder)

There are some specialised applications where the combination of pneumatics and hydraulics can meet particular operational, fail-safe and other needs. Usually, the principle involved is to use a plant's existing compressed-air supply to drive a hydraulic pump which, in turn, is used as the regular valve-actuator energy source, but which also tops up an accumulator for standby emergency use. Such systems can be devised to cater for virtually any supply-failure conditions. A typical application is for self-powered actuators in gas pipelines from which the live gas can pressurise a hydraulic accumulator system for emergency isolating valves. Live gas is also used to operate the actuator directly. as previously described.

Hydraulic actuntors will? output torque valves to 2000 Nm.

2 66

Control and Automation

Electric systems

There are two main factors to be considered here: an electric motor as the power source, and electricity for the control system. Undoubtedly , full electric operation and control offers the greatest flexibility. and best suitability. to centralised automatic control. Remote indication by electrical position feedback and provision for stand-by manual operation are inherent if the system is totally electric. Electric control

Much of the development in industry today is in the direction of centralised control, which in turn involves remote electrical control of valves, so a close look at electric valve actuators and their control systems is justified. Electric valve actuation continues to evolve with astonishing speed. Among the leaders in the field, this evolution has resulted in very advanced, sophisticated designs suitable for instant adaptation to practically any kind of valve, in any environment, in any part of the world. The weakness of electrical equipment is that electricity and water do not mix. However, electric actuators are required to operate in a wide variety· of environments: high temperatures, steamy atmospheres, adverse weather conditions, mud, sand, flooding and so on. Thus the primary problem for the designer is not the mechanical duty-that is negligible-but to keep the environment out. For example, a plant operating 5 days a week, 50 weeks a year, with a motorised valve of 1 minute stroke time, opening in the morning and closing in the evening, would demand a total actuator working life of only 7 days in 20 years. Thus. proper environmental sealing to enable an actuator to do nothing with complete reliability is paramount. A minimum requirement is that it should be watertight and flood-proof. As a further safeguard to exclude the environment. the terminal areawhich has to be exposed for wiring on site- should be separately sealed from the rest of the equipment, to prevent the ingress of dirt or water during installation, the most vulnerable period in an actuator's life. Single-phase, watertight electric actuators are a simple and cost effective way of controlling small quarter-turn valves and dampers . They are suitable for use in many areas where an IP68 (NEMA 6) enclosure is required . The example shown in Figure 7 is suitable for simple open-close duties where on-off control is required. This is achieved without the need for reversing contactors. The structural components of a typical standard electric valve actuator for use with cast-iron and stainless-steel ball valves and butterfly valves, including also motor-operated control valves and rotary control valves, are shown in Figure 8 . One example ofhO\"-' solid-state technology is being applied to electric motor controlled actuators is shown in Figure 9.

Valve Actuators

267

Figure 7. Single-phase Plectric actuator.

The actuator consists of a motor controlled by an integral solid-state control assembly driving through two stages of worm and wheel gearing to a quarterturn output assembly giving clockwise-to-close output. The solid-state assembly consists of two elements, the transformer rectifier providing DC power via thyristors to the motor and the CMOS gate array which controls and monitors the actuator functions and interfaces with remote controls. The logic circuits are protected from high-voltage transients which may appear at the actuator terminal by opto isolators. A schematic (Figure 10) shows the circuitry. Electrically operated/electronically controlled

Intelligent, non-intrusive, three-phase electric valve actuators incorporate the latest electronic techniques and combine them with tried and tested motor and gearing technology (Figure 11 ).

268

Control and Automation

Figure 8. Electric valvPactuator: st rue lura/ co111ponerzts.

Figure 9. Elrctric quart.er-t11rn actuator for }itlly-modulat.irlg duty.

Vnlve Actuators

269

Thermostat ConiJguration swuches

Monllor Motor relay runn1ng

The rmostat 1r1p AC illput DC oower sup ply

n emcte inputs Open

Stop CtoSA

AAA-

Opto ISolators

Reversing relays

.,;

Swilch,ng conftgurauon 0 0

l imit SWIIChes

~

CMOS

0

logiC c rcut

~

0

A-

Local

Translorrr<:r

I t

I I

Jnputs

AClose 6Open

Torque lflp

Local/ ~ Stop/ cr o Remote

Soli star~-~ Opllonal hm1t SVIIICh lflP

Figure 10. Circuitry of c>lcctric actuator shown in Figure 9.

Essentially, the non-intrusive actuator makes it unnecessary to remove electrical covers during motorised valve commissioning by providing local controls that do not penetrate the electrical enclosure. The actuator consists of a self-contained unit for intermittent valve operation and comprises a three-phase motor, reduction gearing, reversing contactor starter with local controls and monitoring facilities, all based in a doublesealed, watertight enclosure to IP68 NEMA 4 and 6. All torque and turn settings and configuration of the indication contacts are effected using a non-intrusive, handheld infra-red setting tool. Infra-red setting

The infra-red programming and setting device is a handheld setting tool that allows the valve actuator to be configured, interrogated and commissioned in a completely non-intrusive way. This allows, for example. the possibility of making adjustments to a 'live' actuator within hazardous and wet areas (operational conditions permitting). A liquid crystal display on the actuator shows its status digitally. LEDs also show, for example: green-fully closed, yellow-any intermediate position and red-fully open. The handheld infra-red setting tool can confirm torque settings and perform simple diagnostic procedures to reveal why an actuator may not be functioning correctly. Power-supply faults, interlocks and other interruptions can be identified. Torque levels, limit settings and the configuration of the actuator may also be changed. Each time the actuator is powered up, it automatically tests its operational circuit's memory devices.

N 'l

0 (")

c

::s

~

-

cs

!::>

::

~

:;t.

~

3 phase induction motor

~

a· ::s

Position limits

Set position limits

~ .... I~

Flux

Torque Current

Fig1.1re 11. Electrically-operated. electronicnlly-controlled intelligent actuator.

Va/veAcLuators

271

Handheld interrogation computers allow actuators to be assessed via an infra-red link which is connected to the handheld computer and attached to the actuator indication window (Figure 12 ). This unit carries out all the functions previously described and downloads them for analysis. Historical information such as operator actions and output torque profiles can also be downloaded for analysis and to provide a view of operating events that can be viewed in groups or as traces. Details of a valve's last opening/closing cycle profile and its historical average opening/ closing profile are also captured. From these, the latest profile could be compared with the average, giving an idea of changes in the valve torque requirement. Communication and supervisory control

The major milestone in flow-control development and technology has been the introduction of field bus control systems. Modern facilities require up-to-date communications right down to plant level. Fieldbus systems take advantage or the latest developments in low-cost micro-chip technology, allowing intelligence to be built into each device in the loop. This intelligence allows the rapid development of networks of intelligent control devices. each communicating with each other over a common medium.

Figure 12. Handheld computer gives acress to valve-actuator diag11ostics and configuration.

2 72

Control and Automation

The 'peer-to-peer' control allows operators accurately to position a valve and thus achieve the optimum process parameters, including temperature levels. pressure and other critical variables. Each control device communicates via a protocol that has been specially developed for the reliable and quick transmission or control information. with guaranteed transmission times for high-priority messages. Fieldbus systems promise greater process control coupled with increased accuracy, efficiency, cost savings and plant reliability. The diagnostic role of fieldbus means that it can also give advance warning of potential problem areas, thus enabling preventative action to be taken. Two-wire loop systems

Two-wire communication systems provide the link between valve actuator and supervisory control. Systems generally have three essential elementsfield units, the 2-wire loop and a master station. Field control units are typically mounted within the actuator's housing. Variable parameters such as the field unit address and baud rate are set non-intrusively using an infra-red communications link. Changes to the parameters can usually only be made when the field unit is in 'loopback' mode. An EEPROM holds the address and communication speed data, and a detector senses the loop current. The field unit does not interfere with the actuator local controls which remain operable in the event of field-unit rna \function. The 2-wire loop carries a current loop signal which is modulated by a master station to send and receive data from field control units. The cable is a single twisted pair with an overall protective screen. The loop is capable of being installed in an electrically hostile environment where large surge currents can induce transient currents in the cables (i.e. lightning storms). The use of a 2-wire system greatly reduces the number of cable cores to transfer signals from the actuator to the control centre. The two wires are connected to, and taken from, each field control unit in turn. They originate from and return to the master station to create a single twisted-pair, 2-wire loop. As each device may be accessed from either direction. a redundant communications path is available. The integrity of the 2-wire cable is continuously checked whilst the system is running. Should communication fail, the master station ceases transmission and every field unit asserts its 'loopback' circuit. After a short period, the master station begins communication to each field unit in turn, extending the current loop until the fault location is revealed. The master station is typically equipped with two processors, one to control the loop data and the other to handle the host communications, screen display and keypad. All messages passed over the network are under the control of the master station. A field unit may not transmit any data unless it receives a

Valve Actuators

Figurt' 1 3. Advanced 2-wire loop-network communication system.

273

2 74

Control nnd Automation

request from the master station. The host system may be a DCS, PLC or SCAD A system. The information is typically passed using a universally accepted fieldbus communicator standard, e.g. Mod bus, HART, INTER BUS, etc., protocol. Information is continuously gathered by the master station from the field units, so ensuring that information requests by the host system are serviced with an intermediate reply from the internal data base. Command instructions from the host have priority and are processed immediately by passing the message to the field unit concerned. Advances in this technology also provide for high levels of system safety and security, including hot standby, cable fault protection and field unit failure protection, as well as logic and sequencing capabilities of a PLC. and Direct Operator Panels where operatives require push buttons and indicators for valve positions and graphical interfaces to the valves and plant using mimic diagrams to show the plant layout. Any valve may be controlled and navigation through the application is by mouse control. Systems ofthis type can operate with a single network covering 240 devices over a 20 km loop length, without restriction on inter-node distances. Some examples of layouts showing the control of actuators by Bus system are shown in Figures 14 and 15 . Electronic controllers have reached a high stage of development and sources within industry consider that the Field bus specification may be too complex in attempting an all-embracing standard. Problems are possible in migration between Fieldbus variants and integration with distributed control systems.

DJ

1/)

(.)

....I

Q.

=t::::~

(_

~

ch. :J

llllii

~~

,_ ........J

....... . .. -

....,_.......,.II __________ .......... 3

DREHMO-Mat•c I

3 ph AC power supply. e.g . 400 V/50 Hz

-------....~::.....;.;........;.;;.._~----.

3

3

DREHMO-Mat1C I

Fig 1.1re 14. Controlling the actcw tors IJy BUS system: In terlms-S.

Valve Actuators

2 75

Distributor box 3 ph AC power SUPply. e.g. 400 Vi50 Hz

3

OREHMO-Malic I

DREHMO-Mai1C!

PiyurP 15. Controlling the actuators by BUS system: Profilms.

This is important where a transparent interface between the intelligent 'smart' valve and the Distributed Control System is required. There is also concern that lightning strikes could cause failure of the microprocessors in the positioner. Manufacturers are actively working in this area developing their own intelligent electronics systems such as Fieldview, Starpak, Smart Valve Interface, Pakscan, ISMO, TZID, Keydig and Matic. Valve positioning

There are two basic requirements in the opening and closing of valves: when closing. to be sure that the valve is properly and tightly seated, yet without excessive force being applied; when opening, to be certain that the valve is fully opened without excessive overrun or strain on the backseating. A positioner is a device for varying and maintaining an actuator position in control valve applications. The positioner compares the actual actuator position with respect to the given input signal and adjusts the pressure applied on the actuator until the desired position is attained. Positioners can be pneumatic or electropneumatic, single- or double-acting and capable of being used on both rotary and linear actuators. Typically. a pneumatic positioner is a single-stage, force-balance device that can regulate virtually any actuator step less from 0 to 100%. In basic form it consists of a flapper and nozzle, spool

276

ControlandAutomation

pilot valve, an adjustable range and reversing mechanical feedback. Generally, the electropneumatic positioner's action is based on the principle of analogue electronic comparison. More advanced electropneumatic positioners are low-powered high-flow switching devices. Using menu-driven button control pads or remote communications devices, the operator selects from a wide range of pre-set or automated control characteristics. User configuration enables adjustments to be made manually so that parameters can match specific process conditions. Certain systems have the ability to adjust the valve's position using a static or dynamic option. Static setting allows the fixed adjustment of the actuator's upper and lower limits, while the dynamic option enables the valve position to be altered to match the individual installation requirements. The valve positioner shown in Figure 16 is an intelligent digital device that combines micro-processor technology with a piezo-electric interface. The instrument can be connected to 2-, 3- or 4-wire systems and checks to establish what it is connected to and what is required of it, then calibrates the basic settings accordingly. Some positioners incorporate or can accommodate a gauge block directly onto the positioner for a continuous indication of the input and output air pressure of the actuator and the positioner.

Electric modulating actuator for control valves a.nrl damper applicat.ions.

Valvulctuntors

Programmable positioner for quarter-turn actuators.

FigHre I 6. Electropneumatic valve positioner incorporating digital technology.

277

278

Control and Automation

Limit switches

A limit switch is a device connected to an actuator or valve that transmits a signal when the valve reaches a pre-established position. A typical limit-switch box for pneumatic actuators is fitted with two switches. These are activated by two adjustable cams mounted on the drive shaft. A direct coupling with the actuator drive shaft provides an exact indication of the valve 's position. The switches can normally be set independently of each other to provide an open/closed signal of the drive shaft and thus the position of the valve to the control room. Gear operators

There are three main types of gear operators. These are of worm gear. bevel gear and spur gear design. Gear operators are generally suitable for both manual and motorised use (Figure 17). Input reducer Motorised input flange

IW4 I IR1

(70:1 I 4:1) 280:1

Baseplate

Worm quadrant Thrust bearing Worm

Figure 17. Quarter-tum worm-gc:nr operator.

Va/veActuators

279

Worm-gear operators tend to be used with butterfly and ball valves and dampers, as well as other applications where keyed shafts are used to operate equipment. Spur, bevel and multi-turn worm-gear operators are for use on gate. globe. sluice and penstock valves, as well as other applications where screwed or keyed shafts are used to operate equipment. Applications include low and high temperatures. submersible duties, buried service, marinised duty, water works specification and special indication. Efficiency

It has been said already that some valve motor drives are mechanically inefficient-giving only 10% useful energy when, for instance, they are driving through a worm gear and the nut-and-screw of. say, a gate valve, and not much higher when driving a butterfly valve through self-locking gears. Wearing of inefficient gears or stem nuts is the primary limitation on frequency and continuity of operation of such drives, and this also limits the practical speed of operation of large screw-operated valves and penstocks. Nevertheless, the many advantages of control, power source. interfacing with supervisory control and instrumentation and so on compensate for the mechanical inefficiency, provided the actuator duty is properly considered. Portable valve actuators

Portable valve actuators or valve wrenches can be used to provide portable turning power to replace manual effort in opening or closing valves on pipeline systems not fitted with permanent valve actuators. For example, water distribution piping systems generally have no permanent actuators installed, opening and closing of valves, when required, being by manpower. An advantage of portable valve actuators is that they permit implementation of valve-exercising programmes designed to service and operate valves in order to keep them in good condition, e.g. eliminate 'valve seizure' problems ·which can arise when valves are left in one position for long periods. This applies particularly in water systems. Portable valve actuators and valve wrenches may be designed for operation by electricity (i.e. powered by electric motors), compressed air or hydraulic power, and are normally adaptable for fitting a wide range of standard valves. The best designs provide operation 'feel', as well as speed control, reversibility and the ability to make instant stops and starts and reverses needed to free up sluggish gate valves, hydrants and sluice gates, etc. Typically, speeds of up to 20 to 2 5 r/min may be provided. with operating torques up to 13 60 Nm (1 000 lbf/ft)for handling valves in the size range 152 to 15 24 mm ( 6 to 60 in) . The majority of such models are readily portable, i.e. weigh less than 18 to 23 kg (40 to 50 Ib). Larger. heavier models may be trolley- or truck-mounted.

Control Valves In general terms, a control valve may be described as a power-actuated valve, capable of throttling or modulating the flow, and used as a final control element in a control loop. Control valves operate automatically, receiving signals from an external controller. They may incorporate several different types of valve including globe, butterfly. ball and diaphragm (Figure 1 ). Their operation can be vacuum, pneumatic, electromagnetic and hydraulic. Within the area of control valves, most developments have taken place with the internal components such as the trim , which may well be or the cage type (hollow cylindrical trim), with retained seat, instead of contoured plugs with threaded seats. Development in control valves has been driven by a demand for higher temperatures and pressures within the chemical, oil and power industries. Transcontinental pipelines, offshore oil and gas platforms and under-sea modules have been important driving forces. Developments for control valves point to electronic packages located on valves which can be called up for remote interrogation. 'Smart valves' accessible by a

Butterfly

Ball

Cv

Segment ball or rotary plug Globe

Rating

Figure I. Control valve types.

Control Valves

Control valve.

Rotary control valve.

281

2 82

Control and A utornation

_____ ..,.

DIRECTION OF FLOW

Pressure control valve.

Severe-service control valve for oil and gas duties.

Flow control valve.

digital link receive and transmit commands that can indicate a stroke check of the valve, recording pressure vs valve travel as the valve is stroked. With an additional sensor for stem and shaft position, the data can be used to evaluate the condition of the actuator and accessories under various parameters based on an investigation of the valve's stored history. Digital communications to the valve can measure input signal, pneumatic pressure and valve travel, comparing the data with stored, expected values and recommending corrective action. Current difficulties arise over the fieldbus communications standard . While the concept of valve intelligence does not depend on digital communications. the reality is that some form of digita l field bus is essential. Control valve sizing

A number of valve manufacturers have produced control valve sizing programs that can be u sed to select a control valve with optimum controllability and control accuracy for each process application. Typically. these programs are based on the flow characteristic curve a nd gain curve of the installed valve.

Control Valves

28 3

Inherent and installed flow characteristics

The selection of a control valve of optimum size and type begins with the valve's flow characteristic. This has been defined as the curve relating percentage of flow to percentage of valve travel. i.e. rotation of the ball or the butterfly disc or linear movement of the globe valve disc . 'Inherent flow characteristic' applies to situations when constant pressure drop is maintained across the valve. 'Installed flow characteristic' takes into account the variations in the pressure drop caused by conditions in the system where the valve is installed. There are two common flow characteristics for control valves. In the equal percentage characteristic, a given fraction of valve opening changes flow by a certain percentage of previous flow. In the linear characteristic, a given fraction of opening changes flow by the same fraction of maximum flow. Figure 2 shows the most common valve inherent flow characteristics as a function of the relative flow coefficient (¢)and the relative travel (h). A typical installed flow characteristic curve for a butterfly valve in a process application is illustrated in Figure 3. Overshoot

An important function of control valve performance is 'overshoot'. As the control valve responds to a step change in signal, overshoot is the amount of travel beyond the final steady-state position. While in most systems it is important that a control valve responds quickly to changes in signal, it is equally important that this response does not destabilise the operation. Excessive overshoot can contribute to loop nonlinearity. as well as increase loop instability and affect control-loop performance. With a signal of 5%, a control valve with zero overshoot will travel directly to the required position. A valve with up to 20% overshoot will pass beyond the proper position by 1% and require time for adjustment to the new position. A control valve with the least amount of overshoot will provide the system with the best opportunity to respond to changes in process demands. Percentage overshoot should be less than or equal to 2 0 % of the step magnitude for steps ranging from 10% of travel down to steps equal to the backlash / stiction limit + 1%. Speed of response needs to be viewed in conjunction with how accurately the control valve responds to a change in input signal and the percentage of valve overshoot. Quick response by itself without a high level of accuracy and with too much overshoot will destabilise system performance. Control valve speed of response is typically determined by four major criteria: • •

Dead time (Td)-the time it takes to respond after the signal is initiated. It is measured in fractions of a second . T63-the time it takes the valve to reach 63% of its new position. It is measured in seconds or fractions of a second.

284

Control and A11tomation 1.0 0.9 0.8

I

0.7 ~

..... c

0.6

<1)

2

u

~0 0.5 u

~ 0

0.4

;:;::::

3

<1)

>

~

0.3

·~

"'

Q)

a::

0.2

4

0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Relative travel h

1 quick opening

2

linear(~=

h)

3 equal percentage 4 hyperbolic

(~= ~o

,.., exp (c->.:h))

Figure 2. Valve inhenmtjlowcharact.eristics.

INSTALLED FLOW CHARACTERISTICS Q = percent of fully open flow rate

NELSIZE 100 %--.---

- - - - - - - - - - - - - - - - - - -------., 0

0

0

Trim: S1C Size: 150 0

Q

0

Fully open flow:

0

[m 3/h) 363.8 0

Specified Q max. flow: 96 % min. flow: 22 %

0

0

relative travel h

100 %

Figure 3. Typical installed ]low characteristic for a butterfly-control valve.

Contro/Valves

• •

285

T98-the time it takes the valve to reach 98% of its new position. It is measured in seconds or fractions of a second. Band width-the frequency at which the plug position amplitude is diminished by 6 dB (difficult to verify).

The control valve shown in Figure 4 has been designed for highly erosive services and with simple maintenance procedures without special tools . The valve can be used with sodium chlorate, wet chlorine, terepthalic and hot acetic acid because it has a tiodyed titanium seat and plug, a ceramic-coated titanium shaft and titanium bearings with Kalrez H•* seals. The plug and seat are self-aligning and bi-directional flow capability helps to prolong valve life. The valve operates over a 90° range of motion and can

Figure' 4. Rotary control valve for highly erosive services. *Dupont registered trade mark.

286

Control and Automat.ion

withstand high pressure drops. Typical products being handled include digester gas off, Kaolin slurry, Ely-ash slurry, titanium dioxide slurry and steam. Segment control valve

This type of valve may be considered to be a special category of single-seated control valve (Figure 5). Segment valves have a concentric V-shaped trim on the side of a rotary baJl segment (Figure 6). They are typically designed as high-capacity, general-purpose valves with equal percentage flow characteristic. An almost linear characteristic can be obtained using the non-V-shaped cheek of the ball. The metal-seated butterfly control valve shown in Figure 7 is equipped with a flow-balancing trim. The trim is located on the downstream side of the valve body and is effectively a perforated plate partially covering the valve outlet to reduce noise and cavitation, stabilise the flow pattern and reduce dynamic torque on the disc. Valve sizes range from DN 150 to DN 100 ( 6 in to 40 in). The concept of this design is to transfer fluid forces out of the disc to the body. Figures 8 and 9 illustrate flow treatments with a concentric-type, conventional butterfly valve compared with a valve fitted with a flow-balancing trim. Figure 10 shows the seating principle of this butterfly control valve. The disc of the valve is machined to close tolerances to create an elliptica l shape similar to an oblique slice taken from a solid metal cone. When the valve is closed, the elliptical disc at the major axis displaces the seat ring outwards, causing the seat ring to contact the disc at the min or axis.

FigurP S. Segmented control valve .

ControlVnlvc>s

Fig ure 6. Conce11tric ·v'-slwperl trim on side of rotary ball segment.

Figure 7. ;'vlctal-senterl butterfly-control valve withflow-balnrzcing trim.

287

288

Control and Automation

When the valve is opened. the contact is released and the seat ring returns to its original circular shape. Double-seat valves

This type of valve (Figure 11) employs two seats with an optimally dimensioned leakage chamber between them so that any seal leakage drains directly to atmosphere.

Figure 8. Conventional concentric-type valve flow treatment.

Figure 9. S-DJSCjlow treatment.

Figure 10. Seating principle.

Control Valves

289

The valve is pneumatically operated and suited for applications in brewing, beverage, dairy, food, pharmaceutical and chemical plants. The method of operation is shown in Figure 12. The valve is designed for cleaning in place (CIP), as outlined in Figure 13. Double-seat valves typically allow for the design of 'totally contained flow systems', eliminating the need for manual swing bends for product and cleaning lines. thereby simplifying the processes of flow automation.

Figure 11. Double-seat-type control valve.

2 90

Control and Automation

Double Seat Valve Operation lower valve stem upper valve stem

upper seat closed

VALVE IN Cl.OSED POSITION. Upper and lower valve seats are closed and separated by the leakage chamber open to atmosphere In th ts positton, two flutd streams (pipeline A and pipeline 8) may pass through the valve without a chance of tntermixing.

upper valve stem

seal between upper and tower valve stem c loses off leakage chamber

leakage outlet

VALVE IN OPEN POSITION. Upper valve stem moves down towards the lower one and presses it from its seat. At the same time tts seal closes off the leakage chamber and separates it safely from the product area. In this posttton, fluid streams (pipeline A and pipeline B) are open to each other. Figurel2 .

Control Valves

Double Seat Valve Cleaning upper valve stem

pipeline A (cleaning solution) upper seat open

leakage chamber between the seats

pipeline B (product)

leakage outlet

UPPER VALVE SEAT AREA.

The upper valve stem is momentarily opened by the seat lift actuator. Cleaning solution is allowed to flush the upper seal and seat area as well as the leakage chamber. lower valve stem upper valve stem

lower seat open pipeline B (cleaning solution)

WWER VALVE SEAT AREA.

The lower valve stem 1s momentarily opened by the seat lift actuator. This allows cleaning solutton to flush the lower seal and seat area as well as the leakage chamber.

Figure I 3.

2 91

2 92

Control and Automation Top cap !Of p<essure to close (fyPe P.C.) - -Dust cap tor p<essure 10 open (fype P.O.)

---.

Lift spring titled o n -----... P.C. Valves.

Inlet

Figure I 4. Piston-operated control valve.

Piston-operated control valves

The piston-operated control valve shown in Figure 14 is another valve developed to meet the needs of the processing industries. Power is applied through integral piston operators and the operating source can be pneumatic, hydraulic or line pressure itself, depending on the application. The valve is non-concussive in operation and suitable for controlling water. gases and other liquids compatible with the valve materials. Modulating control valves

Control valves of this type are generally available with a comprehensive range of options. They have a vertical pneumatic piston-type actuator with integral electronic controller/positioner housed in the head. The control head consists of an electronic processor that enables the valve to operate in either a 'positioner' or 'controller' mode (Figure 1 5). Curve characteristics and signal scaling are set by means of dip switches. The electronic controller's built-in software generates an adoptive response to changing process conditions, reducing hunting and overrunning. The pneumatic-diaphragm type provides conventional mechanical control. Control valves are used for a multitude of applications, e.g.:

Control Valves

FigurP 15. Modulating electronic control valve.

•

Pressure control, including Controlling Downstream reducing and stabilising Upstream sustaining Holding a differential pressure Backflow prevention Double direction flow if upstream pressure< downstream pressure. Full opening at a present upstream pressure

•

Flow and level control, including Controlling Maintaining a maximum flow Reducing and stabilising flow downstream Controlling the upper level Back flow prevention

•

Tank and reservoir control. including Controlling Not controlling (fully open or fully closed) Controlling the upper level Opens at lower level. closes at upper level

293

294

Control and Automation

Diaphraam control valves fo r softening and.filter applicntio11s.

Figure 16. Act11ated plasLic-rliapl!ragm control valve.

Control Valves

•

29 5

Protection and control. including Against \•Vater hammer Against electrical failure Pump protection Electrical/electronic monitoring Against downstream pipe failure Against 'overspeed flow·

Pressure-reducing valves and pressure-relief valves are also used as control valves and are covered in their specific chapters. Trim designs include metal-seat ring and cage, soft seat and cage, balanced and unbalanced plug. soft-seated plug and bonnet types including bellows-seat bonnet. The valve shown in Figure 16 is an actuated plastic-diaphragm control valve. Utilising a threaded spindle which operates as a helical gear, it is possible to regulate the minimum flow (fully closed or fully open). The stroke limiter in the upper part of the actuator is also adjustable. The internal gear operates as stroke limiter which provides for restriction as it rotates and thus provides stroke limitation from fully open to fully closed across its complete movement. Typical applications include water treatment, water supply. and the chemical industry. Iris-type control valves are used where it is difficult to control and regulate viscous or charged liquids as well as gaseous media, particularly if very small

1. 2.

3. 4. 5.

Membrane: reinforced nitrile. Position indicator with purge: brass and stainless steel. High-pressure valve head (pressure setting 2 5): cast iron epoxy coating. Nuts a nd bolts: stainless steel. Replaceable streamlined seat: bronze.

6. Body drain plug: brass. 7. Reversible seat seal: nitrile. 8. High-pressure valve housing: cast iron epoxy coating (pressure setting 2 5 ). 9. Pressure relief holes. 10. Pressure relief holes.

~t\fatrr imfustry control

valve.

296

Control and Automation

quantities are involved. Conventional flow control valves with slot-type, sickle-shaped or elongated flow apertures will not generally permit fluctuationfree regulation. Other control valves tend to have greater head losses that can result in increased energy costs. A typical iris-design control valve is shown in Figure 17. It will be seen from Figure 18 that the flow aperture is almost continuously variable, making it suitable for use in sugar centrifugals, sewage treatment stations, paper and paper board processes, etc. Pneumatic control valves

Pressure-operated and solenoid air poppet and spool valves are extensively covered in the 'Pneumatic Handbook', also published by Elsevier Science Limited, which should be referred to for information on this subject. The valves covered include 2- and 3-port. direct and pilot-operated and pressureoperated valves as well as 4- and S-port solenoid air-operated valves.

Progressive opening and closing altitude valve.

Pump protection control valve.

Upstream/downstream control valve.

Examples of water industry standard control val \II' S.

Control Valves

297

Pressure- and solenoid-operated air control valves (Figure 19) are used in general and specialist services including steam. combustion gases. cryogenics. vacuum. dust collector systems, engineering. proportional. and explosive atmospheres, etc. Figure 20 shows how pneumatic-distribution spool-valve islands can be connected with a PLC or PC control system through a multi wire cable or with a fieldbus through a communications protocol. These systems meet the needs for automated installations and allow the transmission of any control signal to the spool valves and any information signal from the position detections. A typical connection structure is shown in Figure 21. See also the chapter on Actuators. Electromagnetic control valves

Typically, electromagnetic control valves are solenoid-actuated and employ a pilot disc to assist operation. They do not use any stem. packing or bellows and there are few moving parts.

Figure I 7. Iris-type diaphragm control valve.

Figurt> 18. Iris-type diaphragm control valve: openir1g sequence.

2 98

Control and Automation

Figure I 9. Solenoid air poppet and spool valves.

( 1) (2) (5) (6) (8) (9) (13}

-

lnterbus-S input lnterbus-S output Pressure supply 1 Exhausts 3 and 5 Ports 2 and 4 Detector ports 24V DC supply

Fig11re J.O. Spool-valve island wil.hjieldlms connection to PLC or PC control systl'ln.

Control Valves

PLC -

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124 VDC ~ I I

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Figure 21. Typicnllnterbus-S connection structure.

Figure 2 2. Electromaqnetir control valve- 'equivalent to pipe·.

299

300

Control and Automation

Two basic designs are on-off isolation valves and modulating control valves. Operation of the valve occurs when the solenoid is energised to develop a magnetic field. This lifts the plunger and pulls a pilot off its seat to open an internal vent port. vVhen the differential pressure between the top and bottom surfaces of the main disc changes sufficiently, the main disc follows in servo motion to the pilot and allows the fluid at the inlet to flow. In modulatory designs, an electronic positioner controls electrical power to the solenoid to match disc position with desired flow. An electromagnetic control valve is shown in Figure 22. Typical applications include storage and handling of hydrocarbons. The increasing use of rotary valves proceeds hand in hand with the widening application range, improved reliability and cost-effectiveness of control valves. It is also becoming standard practice to combine globe valves in small sizes with rotary valves in larger sizes. In on-off applications, the rotary types are used throughout the size range. The availability ofmanufacturers' software programs for sizing control valves provides a valuable tool (or the engineer who needs to evaluate the true performance of the control. valve. It can also give information on how to program the controller to achieve the required control characteristic and thus to improve control accuracy and overall process-cost efficiency.

490

Pipelines/ Pipework

Modern pigging systems now operate with a 'captive pig' and the pipeline is opened up only occasionally to check on the condition of the pig. At all other times, the pig is shuttled up and down the pipeline at the end of each transfer, for example. Today's pigging systems can also be operated by a Programmable Logic Controller (PLC) or other computer-based control system. System types

Pigging systems usually comprise one or more of the following types: 1. Open system: where the pigs are forced into and expelled from the system whenever necessary. The system works on a one-way principle. 2. Closed system: the pigs remain 'captive' in the system for their entire operational life and do not need to be forced into and expelled from the pipe. 3. Single-pig system: has only one pig in the pipe which goes into action when. for example, product residue needs to be cleared out of the line. This can be a cost-effective answer for simple tasks. 4. Two-pig system: probably the pigging system chosen most often. It has two pigs in a pig launching and receiving station. \1\lhen the pumping process begins, the first pig is pushed into the line and the product then pumped in after it. The second pig pushes the product out of the pipe, cleaning any residue from the pipe as it moves along. Smart pigs

Smart pigs are generally deemed to be any series of pigs used for internal inspection of a pipeline. Smart pigs can detect bends, dents and other reductions. inspect for corrosion and other damage and photograph the internal walls of a pipeline. Sophisticated electronics and computers in sealed containers take and record various internal measurements. Enhanced cleaning pigs

These pigs are specially designed to be more aggressive than standard cleaning pigs. Typically. there are three types: • •

Magnetic cleaning pig for dealing with loose debris in both gas and liquid lines. Pin wheel-type pig for removing hard scale and wax deposits adhering to the pipe wall , usually in liquid lines.

Pipeline Cleaning

•

491

Brush wheel pig which is run after a line has been enhanced and cleaned using a magnetic cleaning pig, a pin-wheel pig, or a combination of both.

Enhanced cleaning pigs can be set up for various levels of aggressiveness, ranging from very low to very high. This gives the advantage of implementing controlled and gradual increases in aggressiveness to prevent over-cleaning, which could lead to a blocked pipeline. Foam pigs are made of polyether or polyurethane foam from 32 to 144 kg/ 3 m (2 to 9 lbf/ft 3 ) density, chamfered on the leading edge and with a sealing disc on the rear pressure face. On some types the outside surface is coated with elastomeric polyurethane to increase the resistance to abrasion from the pipe wall. Abrasive foam pigs, in addition. have bands of abrasive grit around the circumference to improve the cleaning action. While normally made with a circular cross-section, foam pigs can be fabricated with other profiles for cleaning ductwork. Steel pigs are, in comparison, relatively complex, consisting of a steel frame which seals against the pipe wall by means of two or more elastomeric cup seals. Except in the case of gauging and bi-directional pigs, cleaning is achieved by a series of scrapers or brushes arranged around the outside of the frame. Gauging pigs consist simply of the frame and seals, while the seals of bi-directional steel pigs are placed in opposition to each other to enable the pig to be driven in either direction. Table 4 summarises the principal applications of each type and Table 5 gives recommendations for certain pigs in a given application.

Table 4. Type of pig

Principal u ses

Example

Foam

Swabbing: removal of thin, soft or liquid films

Sludge or water in air lines; to avoid damaging pipe surfaces.

Coated foam

Removal of films and heavy sludges

Oily deposits.

Abrasive foam

Removal of h eavy or h ard deposits

Rust; slag; hard sca le in water: effl uent and hydrocarbon lines .

Cleaning (brush)

Removal of miscellaneou s superficial materials

Light rust and scale; pre-commission cleaning.

Scraper

Removal of h ard or strongly ad h ered film s and deposits

Corrosion; wax in effluent and hydrocarbon lines.

Gauging

Proving minimum bore prior to commissioning

Bi-directional

Plugging pipeline during hydrostatic testing

49 2

Pipelines/ Pipework

Table 5. Pigging application Pipeline application

Pig choices

Geometry survey. e.g. proving that the inside diameter of the line has a minimum clear bore

Gauging or calipe(' pig.

Removal of rust. scale. and hard deposits

Brush cleaning pig.

Removal of wax-type deposits

Urethane-bladed cle<ming pig.

Chemical swabbing

Spheres: multi-cupped pig.

Water filling/air removal

Bi-directional pig: foam pig: multi-cupped batching pig.

Dewatering Higher cost: maximum dewatering Lowe(' cost: less dewatering

Cup swabbing, bi-directional foam pigs.

Product ('emoval

Multi-cupped pig; foam pig: spheres.

Intemally-coated lines

Foam pig; urethane brush pig.

Product separation

Spheres; multi-cupped batching pig.

Meter proving

Spheres.

Corrosion/material defect

Corrosion-detect ion pig.

On-stream liquid removal

Spheres; multi-cupped pigs.

Valves

Full-bore, full-opening valves in accordance with API-6D standards are required for safe pig passage. Reduced port valves usually cannot be pigged. Some cmnmon piggable valves include: through-conduit gate valves. wedge-type gate valves, ball valves and check valves. Wedge gate valves can sometimes present problems for pigs, e.g. those that are gapped between seat ring spacings. Generally. ball valves are the best type for use in pipelines that will be pigged. Optimum cleaning methods

Careful selection of equipment is essential if a pigging operation is to be successful, and this depends upon possessing adequate information on the following factors: • •

internal pipe diameter bend radii

Pipeline Cleaning

493

• location and type ofbranches, valves, flow meters and other obstructions • location of access points • material of construction • pressure rating of pipelines • constraints on propellant type • physical properties of material to be removed • distribution and thickness of material to be removed • · health hazards Nominal pipe bore. actual bore and bend radii are of crucial significance in selecting the sizes and types of pigs to be used. Very tight bends or changes in direction can be negotiated only by foam pigs. vVhere there is a possibility of the pig becoming stuck. it is necessary to use a bi-directional pig so that it can be withdrawn from the blockage. The physical properties and distributions of the material to be removed influence the type of cleaning action required and hence the choice of pig. In many cases, a range of different pigs will be used in succession to provide the optimum cleaning action at each stage of the operation. Unfortunately, it is often difficult to determine in advance which pigs will be needed, and it is sometimes necessary to make the choice of pig types as the operation proceeds. It is essential to identify berorehand all intersections of pipe runs, change of bore and obstructions in the bore from valves, pumps and monitoring equipment. and to plan the pigging operations carefully. ln complex process pipework it may be necessary to break the operation into separation sections. On long pipelines there is no reason, however, why a pig should not be sent many kilometres (miles). If desired it can be followed electrically or magnetically by the use of tracking equipment. Applications

Pigging as a technique is suitable for cleaning the walls of pipes and removing sediment from the invert. It is particularly suitable for long runs of pipework having many bends and few access points, which cannot easily be cleaned by

Table 6. Pig type

Range or actual bore D(mm)

Foam

12-1220

Steel

50-1420

Minimwn bend radius

Uni/bi-directional

/ r48

No limits

Bi-directional

2- 56

1 1h D-SD

Either

D (in) 1

494

Pipelines/Pipework

any other method. Pigging is not suitable for unblocking pipes which are completely closed. With the correct choice of pigs and equipment, pigging can be successful in dealing with a wide variety of materials of which the following are examples: Removal of: weld and nodular scale slag rust and corrosion lime scale ochre cement powder wax waste liquid sedimentation contamination

Special applications: gauging hydrostatic testing swabbing (disinfectants, etc.)

Typical locations in which these commonly occur are: Pipelines: crude oil natural gas refined hydrocarbons chemical water effluent dewatering slurry

Process pipework: refined hydrocarbons petrochemicals general chemical cooling water food and brewing

High-pressure water jetting

With high-pressure water-jetting techniques, deposits and blockages in pipes are broken up by the action of fine, high-velocity jets of water directed on to them from suitably shaped nozzles , and the resulting debris is washed out of the pipe by the flow of spent water. Pressures of up to 1400 bar (20,000 lbf/in 2 ), or in some cases higher, and a wide range of flow rates are used, depending on the nature of the material to be removed. Water is delivered to the nozzle through lances for cleaning small-bore pipes and tubes, and through flexible, self-propelling hoses for cleaning larger pipes. With lances. straight pipes of 16 to 150 mm ( 5 / 8 to 6 in) bore can be cleaned for a distance of up to 6 m (20 ft) from access points. Hoses are capable of cleaning pipes of 50 to 1020 mm (2 to 42 in) bore (up to 1.5 m (60 in) with attachments) for a distance of up to 120m (400ft) from access points, and they may also negotiate a number of bends.

Pipeline Cleaning

49 5

Equipment

A conventional pump assembly consists of a diesel or electric power unit, high-pressure water pump, header tank. control valves and instrumentation, all mounted on either a skid, trailer or vehicle. Fully flame-proofed versions are available for use in hazardous environments. The choice of pump is determined by the pressure and flow requirements of the pipe to be cleaned. Pumps are usually of the triple plunger type, enabling a range of pressures and flow regimes to be selected by changing plungers. The alternative diaphragm type of pump, often used in low-power applications. may also be used over an extended range of pressures, although this can only be achieved efficiently by a change of pump heads. The power requirements of the pump are determined primarily by the pressure and flow rate. A useful rule of thumb is that, within the limits of flow and pressures for a given pump, the product of available flow rate and pressure are approximately constant. The majority of high-pressure water-jetting pumps are rated at between 2 5 and 200 hp. going up to 500 hp. A typical specification for a 100 hp pump, for example, would be to deliver 45 I/ min at 690 bar (10 gal/min at 10,000 lbf/in 2 ) . Hoses are selected to withstand the maximum operating pressure with an acceptable margin of safety, and to transmit the required flow rate with the minimum of pressure drop along lengths of up to 120m (400ft). A primary consideration in the selection of lances for use in small pipes is the bore of the pipe, as sufficient clearance must be left around the outside of the lance without restricting the flow through the bore. Maximum lance length is 6 m (20ft). A range of nozzles is available to suit the application with a choice of the number and orientation of jets. and materials of construction. High-pressure water is extremely dangerous. All pressure devices must be able to withstand the operating conditions, and must be properly maintained. Similarly, all operators must be correctly equipped with protective clothing. Optimum cleaning methods

Careful selection of pressures, flow rates and nozzle configurations is an essential step if pipes are to be cleaned efficiently, and this depends upon possessing adequate information on the following factors: • • • • • • •

internal pipe diameter distance from access points number and location of bends and branches location of valves and other obstructions physical properties of material to be removed distribution and thickness of material to be removed health hazards

496

Pipelines/ Pipework

Table 7.

Pressure range

Example

Upto275bar (4000 lbf/ in 2 )

Grease, paraffin wax, crude residues algae. pulp. asbestos. PVA. food residues.loose masonry. clay. mud. silt.

275-550 bar (4000-8000 lbf/in 2 )

Boiler scale, carbon. potas h. asphalt, cement. plaster. mastic. PVC. unbonded paint. rust, oils.

550-1380 bar (8000-20,000 lbf/in 2 )

Polymer. bonded paint. resin s. plastics, synthetic rubber. coke, concrete, silicates, mill scale.

The physical properties of the material to be removed form the principal factor in determining the pressure required. Table illustrates cutting abilities of various pressures, although there can be considerable variations in practice. Increasing flow rate has the general effect of increasing the rate at which material is cut. When large quantities of contamination have to be removed from a pipe, and particularly when it is completely blocked, high flow rates are essential. This is also true in the case of large-diameter pipes when sufficient cleansing flow must be maintained in the bottom of the pipe to keep debris in suspension. The distribution of the material within the pipe influences the configuration of nozzle jets which are required, forward-facing nozzles being used to clear blockages, and rear-facing nozzles for flushing out loose material. Applications

Water jetting is particularly suitable for removing large amounts of unwanted materials from pipes, including the cleaning of long lengths of totally blocked pipes. It offers advantages in plant downtime, cost and, very often, effectiveness of cleaning.

Pipe Cutting and Bending Large-diameter iron and steel pipes are normally cut by mechanical saws or oxygen (flame) cutters in the manufacturer's shop. Special cutting machines are used for accurate production of profiles for pipe branch'"-'Ork, saddles and square cuts. Pipe-cutting machines and tools for genera l or on-site use range in size from powered tools capable of handling the largest sizes of pipes down to handoperated cutters. The actual cutters may be circular saws (or cutting discs), reciprocating saws. wheels or knife edges. Hacksaws may also be used for hand cutting smaller pipes. A power-driven abrasive disc is one of the most widely used method s for cutting ductile-iron pipe of all sizes. Circular-saw cutters are usually robust bench- or stand-mounted machines. but differ appreciably in detail design. Some employ milling cutter wheels, others conventional circular-saw blades. The majority encircle the pipe to be cut in a se lf-centring vice, but some are designed to travel around the pipe as they make the cut.

Power-driven a/Jrnsive disc cutter used for cutting ductile-iron pipe.

498

Pipelines/Pipework

Reciprocating saw cutters range from simple machines with minimal guidance to guillotine saws where the tool is clamped to the pipe and the horizontal saw blade is fully guided to ensure a square cut. Wheel or 'knife-edge' cutters are designed to encircle the pipe and hold it concentrically as the cutter is rotated around the pipe. On larger. power-operated machines of this type, the actual cutters are symmetrically positioned on a ring which is rotated by power. Each cutter is held in a tool box which automatically increases the depth of cut with rotation of the carrier ring and is profiled to remove equal amounts from the cut simultaneously. Manually-operated cutters normally employ cutting wheels rather than knife-edges, with a similar working principle (i.e. the tool is rotated around the pipe to produce the cut). The number of wheels employed may range from one to four. Cutter advance is by rotation of the handle (i.e. is not automatic). The other major difference is that the cutter does not have to be rotated continuously but can be 'rocked' backwards and forwards to make the cut if it incorporates three or four cutting wheels. This is a distinct advantage for close field work as only a relatively small clearance is then needed around the pipe being cut.

Guillotine pipe saw.

Pipe Cutting and Bending

Pipe-cutting and machining t.ool.

Electric pipe-cutting rnttchine.

499

500

Pipe/ines/Pipework

Pipe bends

Large-diameter pipes are bent in the manufacturer's pipe-bending shops using various types of bending tables and furnaces (for hot bending). Three main types of bends are used: plain bending, crease bending and corrugated bending. The former two may require the pipes to be filled with sand. Corrugated bends are produced with the pipe first corrugated in the straight on a corrugating machine with local heating and are then bent empty ,.v ith each corrugation heated separately (e.g. by portable furnaces).

Semi-rotnry wheel wtter.

Rotnry pipe cutter.

Pipe Cutting and Bending

501

Plain pipes from 12 to 300 mm (2 to 12 in) may be bent cold on hydraulically-operated cold-bending machines, with bends up to 180° possible on radii depending on the pipe diameter and wall thickness. Plain pipes up to 900 mm (36 in) diameter or more can be bent hot, depending on the furnace capacity. Temperatures up to 1100°C (2000°F) may be used and heating time depends on the pipe size, type of bend and pipe material. For bending, the heated pipe is pegged to the bending table at one end and the other end pulled by a winch.

Orbital pipe cutter.

Hydraulically-operated pipe-bending machine.

502

Pipelines/Pipework

The bending operator. who works to a curved template conforming accurately to the shape of the bend taken directly from a floor drawing, controls the rate of bending and the contour by using a coolant on the exterior of the pipe to control the heat spread. Water is normally used for low carbon steels, but is not recommended for alloy steels. Alternatively, stop pegs are used for control instead of a coolant; these are removable pegs inserted into holes in the bending table as required during the pulling operation. After bending and allowing to cool, the pipe is emptied of sand, dressed and examined, and then checked on a surface table against a full-scale drawing. In all instances of hot bending, a great deal depends upon the skill of the pipe bender; movement may take place during cooling which must be predicted and allowed for. and the whole procedure of hot bending a large pipe calls for many years of accumulated experience for which there is no substitute. With thinner pipes. subsequent dressing with a flatter may be necessary to take care of slight rippling while the possible ovality of a pipe caused in bending is always under careful control. Sometimes, a resetting may be necessary to correct an error, for which gas-fired portable furnaces using premixed gas and air supplies are used. Tube bending

Pipe bending by hand is only practicable in the smaller sizes of tubes. and then is not always satisfactory. On larger sizes, or with tubing with thin walls. it is

Bevel-grinding machine for pipes.

Pipe Cutting and Bending

503

difficult to prevent local collapse of the inner wall unless a pipe bender or filler is used. Provided the tube material is reasonably ductile, all such bends are made cold. The general rule for a minimum radius of bend is that this should not be smaller than three times the o.d. of the tube. A more generous figure is to be preferred. particularly in the case of the smaller sizes which are usually hand bent. Bent radii larger than the minimum values should always be used as far as possible because these produce less frictional loss and are less liable to result in deformation of the pipe section through wrinkling or stretching or introducing ovality. The latter is a common fault, even with pipe benders, unless extreme care is taken, and can materially reduce the working strength of the tube at the bend. The four basic methods of machine bending are: (i)

Press bending-particularly adapted to the bending of heavy gauge wall tubing up to six times the tube o.d. radii with included bend angles of 120° maximum. It can also be used with wing dies to achieve a minimum bend radius of three times the tube o.d. (ii) Roll bending-also suitable for heavy-gauge wall tubing and capable of achieving a satisfactory bend radius down to six times the tube o.d. The bend angle is unlimited because by using three power-driven rolls the tube can be fed continuously through the machine to produce complete coils. Four-roll bending machines are capable of producing true arcs right to the extreme end of the tube. (iii) Stationary die-a simple and popular method of bending smaller diameter sizes, usually up to ,about 16 mm ( 5 I 8 in) o.d. The tube is simply wrapped or 'whipped' around a grooved bending die. Both circular and non-circular bends can be produced, also bends in two planes (using special dies). This method is, therefore. extremely versatile. (iv) Revolving die-in this case the die is rotated while the bending shoe remains stationary. The particular advantage of this method is that the tubing can be entirely confined internally and externally at the point of bend, thus minimising the risk of distortion. The revolving die machine is particularly suited to handling thin-walJed tubing. Proprietary pipe benders are usually based on one or other of these methods. All aim at producing the bends down to a specified minimum radius with minimum distortion of the tube material. Many, it will be appreciated, involve a 'wiping' or rubbing action over the outer surface of the tube and in such cases lubrication is important. Light rn.ineral oil is a satisfactory lubricant for bending steel tubes. Some designs of pipe benders are designed to compensate for 'thinning' effects on the outside wall of the formed bend so that the distribution of material over the cross-section remains unaltered. Others may produce appreciable thinning.

504

Pipelines/ Pipework

Instead of pipe benders, filler may be used to support the inside of pipes and tubes for manual manipulation, or even be used with pipe benders to prevent distortion. The best type of filler for the pllrpose is a low melting point alloy which can be removed by gently heating after the bend is completed. The use of low melting point metallic fillers is not, however, generally recommended for bending hydraulic tubes as it is difficult to remove completely all traces of the metal. The only effective way of ensuring complete removal is usually to blow through the pipes with steam. Sand is not generally used as a filler as it is difficult to ensure its complete removal after forming, unless elaborate pressure-cleaning methods are used. The quality of the bend produced, whether manipulated by hand or machine, is very much dependent on the operator. Jerky or irregular actions may produce kinks or wrinkles. Wrinkling may also occur on the inside of the bend due to the compression of the material in this region, unless the machine compensates for this by applying tension to the inner radius. Thickness of bends

The minimum thickness (tb) of a straight pipe from which a pipe bend to a radius in accordance with Table 1 is to be made shall be determined from Table 1. Minimum bending radii for pipes of thickness determined by BS formulae

Radii measured to centre line of pipe ---

o.d. mm 26.9 33.7 42.4 48.3 60.3 76.1 88.9 101.6 114.3 139.7 168.3 193.7 219.1 244.5 27 3.0 323 .9 355.6 406.4 457.0

- --

tb = 1.12 5 tf all thicknesses

tb = l.l tf tb = 3 5 mm or above

mm

mm

65 75 100 115 150 190 230 265 305 380 460 630 710 810 1020 1220 1500 1730 2030

1140 1270

1520 1780

2030 2080

Pipe Cutting and Bending

505

equation (i) or equation (ii), except where it can be demonstrated that the use of a thickness less than tb would not reduce the thickness below tf at any point after qending. For pipes 219.1 mm o.d. and below. and for pipes above 219.1 mm o.d. bent to the radii specified in the table. column 2: tb = 1.125 tf

(i)

For pipes above 219 .1 rnm o.d. where tf is 3 2 mm or more. bent to the radii specified in the table, column 3: tb = 1.1 tf

(ii)

The value of tb is the minimum thickness and provision shall be made for minus tolerances. Manufacturing considerations may make it necessary for pipes thicker than this minimum to be used . Radii of bends

Pipes complying with the requirements ofBS 1387 andES 3601 shall not be bent to radii less than those given in Table l. Other pipes of a thickness determined by BS formulae shall not be bent to radii less than those given in Table 1 unless: (a) It can be demonstrated that the use of this thickness will not reduce the thickness at any point after bending to below tf, and (b) where the design tempe~ature of the piping is higher than 430°C in the case of alloy steels and the radius is less than three times the i.d. it can be additionally demonstrated that the thickness at the internal radius of the bend is not less than resulting from the following: 2R- r 2R- 2r

ti > tf - - -

where ti is the thickness at internal radius (mm); R is the radius of the bend (mm); r is the mean radius of the pipe (mm). In general it will be necessary to increase the thickness above that determined by BS formulae in order to meet the aforementioned requirements. There is a minimum thickness for each size of pipe, depending on bending procedure, below which the allowance for thinning will be exceeded and , in such cases, the radius given in Table 1 should be increased where necessary to ensure that the thickness is not below tf at any point after bending.

506

Pipelines/Pipework

Rigid thermoplastic pipe

Rigid PVC and CPVC plastic pipe can be readily cut with an ordinary hacksm·v or power saw. A cutting speed of 6000 r/min using ordinary hand pressure is recommended. With band saws, a cutting speed of 3600 ft/min using hand pressure is recommended. Under some circumstances a lathe can be used. Best results are obtained with fine-toothed saw blades (16-18 teeth per inch) and little or no set (max 0.02 5 in). Cuts should be square and smooth, particularly if the pipe is to be threaded . A mitre box or similar guide should be used when cutting by hand . The cut ends can be bevelled with a hand file and the interior deburred with a regular tool or knife. Dust and chips should be removed to prevent fluid-stream contamination. The pipe should be well supported during cutting and protected from nicks and scratches by wrapping in canvas or similar material. Use of wheel-type pipe cutters is not generally recommended since they tend to generate heat and can produce a raised bead or ridge which increases the bevelling effort required. Bending may sometimes be advantageous in fabricating PVC and CPVC pipelines. However, bending should be limited to non-critical applications at room temperature or lower where maximum operating pressures are not utilised. With the procedure normally used in bending, some stresses from bending are retained in the material in addition to those caused by the pressure of the medium. If bending has to be done, the pipe should be heated from 120 to 135°C (250 to 2 7 5° F) by use of a flame less hot-gas torch, hot-air oven, or by immersion in hot oil. Uniform heat distribution is required and localised overheating must be avoided. Care should be taken to avoid holding the pipe at bending temperature for too long as the pipe may lose its form. The pipe should be bent around a regular pipe bending form of the required radius. grooved to the proper diameter and having a radius at bend not less than five times the pipe outside diameter (to prevent flattening). Other proven methods include filling the pipe with sand or the insertion of a coiled pipe spring before bending. Because of the recovery characteristics of the pipe. it should be bent slightly beyond the desired radius and allowed to spring back, then quickly cooled in water or with air. It is recommended that the pipe manufacturer or supplier be consulted regarding the bending suitability of plastic pipe. Thermoplastic piping is a general term applied to a variety of different plastics. Hot tapping and plugging

Hot tapping is the procedure for cutting an opening into cast-iron. ductileiron and steel pipe which is carrying a product under pressure. A fi tting is welded or mechanically attached to the line and a valve is attached to the fitting . A tapping machine is installed and the tap made through the valve.

Pipe Cutting and Bending

507

After the tapping is made, the cutter is withdrawn and the valve closed. If a completion plug is to be installed in the fitting, the valve can then be removed. In the petrochemical industry, for example. it is often necessary to isolate a section of piping without interrupting the service the line provides. Lines must be kept in service to avoid the shutdown of an entire unit. Hot tapping and plugging equipment is designed to meet these requirements. Plugging occurs after the tap is made. Typically a STOPPLETM plugging machine is installed on the valve and a plugging head inserted into the line. The plugging head serves as a block valve and seals the line retaining the pipeline pressure. [f two plugging machines are used, or one plugging machine and an existing in-line valve. a section of pipe can be isolated and drained, making possible necessary repairs or modifications in the isolated section. A bypass can be installed around the isolated section. keeping the line in service. If a new section of line is being installed, it is possible to use the new section for a bypass while the old section is being removed. When all repairs have been made. the job is completed by installing a completion plug in the fitting. The plugging head is removed, restoring service through the line. The tapping machine is then fitted with the completion plug, inserted and locked into the fitting to provide the seal. The tapping machine, bypass and tapping valve are removed and a blind flange installed on the fitting. In most cases the blind flange can be removed and the line re-entered at a future date after the completion plug has been removed. One of the most common hot tapping and plugging applications is used when a valve in a piping system no longer works properly or is damaged. WELD FITTINGS

MAKE TAPS

~

d /

2·· THREAD-0-RING ~~ -::,....Purge & EqualizatJOn-:>1 !l ..- "' Frtlrngs / /.-- _,

~--:/

-~-
Tapping Machine

? '

Fit1ing

B~ass

Fr rn

A PLUG LINE

·

B

SANDWICH Valve

\ '/----------------~~ RECOVER VALVES g-/ /

c Hot tapping a11d plugging sequencr.

D

508

Pipelines/ Pipework

If it is not necessary to keep the line in service, the line can be tapped and plugged upstream of the valve using only one plugging machine. Where it is necessary to keep the line in service while repairs are made, two plugging machines are set, isolating the faulty valve. The use of a three-way T or an adapter with a side outlet eliminates the need for additional tops. In plugging many types of product lines, slight seepage across the plugging head can sometimes occur. In the case of hazardous products. a better seal must be obtained with the plugging head before the work is commenced. Folding plugging head

This concept is used on low-pressure lines (maximum 150 lb/ in 2 depending on the size of the line) to plug a line through a reduced branch fitting . The folding plugging head involves a flexible sealing element which is attached to a plugging head with hinged leaves. Depending on the size. the leaves are opened in the line either hydraulically or mechanically.

Typical completion plugs.

High-pressure STOPPLE"f"" ami tappingfittings.

Pipe C11tUng and Bending

f-irst. two STOPPI..F." Fillings arc installed on the pipe.

The plugging heads arc lowered into sealing position. diverting now through the temporary bypass.

6

fhe tempor'df)' bypa" is in,talkd and pressure tested.

With all now divcncd through the byp:L~S. workers cut and remove the isolated section.

7

The tapi)ing mm:hinc makes taps through bmh STOPPLE Filling>.

4 Once the new section is tied in, the plugging hemls are retracted. returning full flow to the main.

8

The ST OPPLECI<' Pluggi ng Machi nes arc installt:d.

The plugging machines and bypass Jines arc removed.

9

Completion plugs are s<:t in the STOPPLF. Fillings and the SANOWI\Hw Valves and spools are recovered , completing the job.

Typical example ofa t.apping and pluggiltg application using n temporary bypass to maintain flow.

509

510

Pipelines/ Pipework

Tile 96-in plugging head. in its folded position. is retracted into tlze 60-in housing. It is lowerrd tlrrougll the tapped hole into the pipe. When the guide wheel. shown at the top. toudws the !Jottom of thr pipe. the plugging head opens cmd the elastomer sealing element smls agai11st tile wall of tile pipe. assisted by differential pressr1re.

Welded fitlings

Extreme care must be taken when welding onto an in-service pipeline. Two major concerns are: l. Burn-through-where the pipe wall is penetrated allowing the contents to

escape. 2. Hydrogen cracking-as a result of high hardness levels from the accelerated cooling rate associated with the ability of the flowing pipeline contents to remove heat from the pipe wall. A thorough understanding of factors related to welding and, in particular, to welding on in-service pipelines is required to ensure safe operating procedures and sound welded joints. For some applications, the heat input required to avoid cracking may be greater than the heat input allowed to avoid burn-through, making welding prohibitive. In addition to hot tapping and plugging cast-iron, ductile-iron and internally-coated steel pipe, it is also possible for tapping and plugging to be accomplished on most reinforced-concrete pipe, provided it is done within the pressure limits required when the steel shell is exposed to mount the fitting.

Pipeline Inspection and Evaluation Pipelines are normally surveyed for one of the following reasons: To investigate repeated or isolated blockages. (ii) To check: on structural integrity, for connections from new sites, or expected working life for maintenance expenditure budgets. (iii) To determine exact location or pipelines, branches and connections to update drawings or carry out maintenance work. (iv) To inspect installations prior to hand-over. (v) To check on scale or corrosion build-up on industrial heating or process pipelines. (vi) To detect and locate leaks in buried pipelines. (vii) To carry out interior inspection of welded joints on long rungs of metal pipe (e.g. gas or oil lines). (viii) To test individual components, e.g. safety and relief valves on line. (i)

Techniques used obviously vary with individual industries and installations, size of pipes. etc. Defects in pipelines cannot be effectively evaluated thoroughly without some form of inspection. both internal and external, being undertaken. Many systems have been engineered and developed for this purpose. Public authorities and municipalities have been recording video tapes of the activity in their pipelines for over 30 years, together with corresponding inspection logs which have caused massive retrieval problems. Hardware and software is now available to catalogue and reduce mountains of material into a highly effective data collection and information retrieval system. Inspection data normally include four basic materials: video tape, inspection log. defect classification/ cataloguing and picture capture. Video tapes provide a good visual picture of a pipeline's overall condition. Defects, though, will only generally represent a few seconds in a tape lasting from one to one and a half hours. If an inspection log is available. the user can fast-forward the video tape to the exact point of the tape. If no inspection log is available. then the tape has to be scanned continuously to locate the defect.

512

Pipelines/ Pipework

Inspection logs can vary considerably in their content. A good log should be identified to a corresponding video tape, with both tapes and logs indexed and referenced as to exact location. Some logs contain much more information than just defect data and location. More sophisticated logs incorporate contract information, line location, pipe size, pipe type, line gradient (or slope) and other conditions. Logs are typically stored on a reproducible medium such as a floppy disc. Software is available to classify and catalogue defects by type and severity of defect. These programs allow the automatic sorting of defects in order of severity and rehabilitation requirements. This information then serves for scheduling repairs and budgeting projected costs. For a classification program to be effective, continuity in defect classification is mandatory. When a single operator performs defect classification. there is less of a problem than when different crews, operators or contractors perform inspections and defect classification. Photographs of each defect or problem should be taken and, if possible, this should be carried out using digital equipment to avoid the possibility of picture degradation due to ageing. A digital picture will not fade or degrade with age, humidity or temperature and can undergo enhancement and reproduction without much limitation, using a standard computer and ink-jet or similar colour printer. Stand-alone inspection vehicles are particularly useful with municipal waste-water collection systems. They typically have a data system that will measure the pipeline gradient (slope), label a defect, insert its distance location (distance from entry) and label an operator-selected defect classification . This alphanumeric data will display simultaneously on the video monitor and be recorded on the video tape and stored on a magnetic disk. The addition of a graphics computer and picture-capture software makes it possible to store a still-frame digital picture of a defect or other significant item simultaneously on a magnetic disk. It is possible to copy all the data including the captured photograph to a removable disk for integration into a master database or geographical information system (GIS). Inspection reports and hardcopy photographs of captured defects should be placed in a master defect log book. Information and data from each collection vehicle or base should then be ultimately stored in a central library to provide easy access to all available historical data. Geographical information systems

Geographical information systems (GIS) are used to collect and store information on pipelines and tunnels over large area networks. GIS databases now contain information on pipeline inspections and surveys using CCTV equipment. When a survey is completed for a particular pipeline or section of pipeline. the information is stored in the database where it can be accessed quickly and assessed via on-line/ off-line multi-media tools.

Pipeline Inspection and Evaluation

513

TV surveying

Control is the key to inspection systems and TV surveying is a particularly versatile method of pipeline inspection, generally applicable to pipes ranging in size from 50 mm to over 1m (2 in to over 4ft) in diameter. Such systems can also be designed to function under widely varying conditions. The following will be required: video camera, umbilical cable, a control unit, lighting leads, a video signal recorder (e.g. videotape) , power supply and ancillary equipment. Video camera units may range from as small as 25 mm (1 in) diameter upwards. (Small units are obviously n ecessary to survey small-diameter pipelines and negotiate bends.) A normal 2 5 mm (1 in) diameter camera. for example. can be expected to negotiate goo bends in 100 mm (4 in) diameter pipelines. Solid-state mini-cameras can now inspect pipe as small as 25 mm with goo bends. Sizes vary but, typically, camera heads the size of a golf ball have high intensity LED (light-emitting diode) bulbs and a lens with a 2 70° rotational viewing angle.

514

Pipelirzes/ Pipework

Built-in sondes transmit radio signals from within even cast-iron pipes to provide accurate location of the camera in the pipeline. Sewer camera systems generally comprise a choice of camera size, 60. 90 or 120 m of flexible rod wound onto a rotating frame, a high-resolution VCR monitor and a locator. Power for the system is usually mains supply or 12 v d.c. for remote operation. Various lighting attachments may be used for illumination of pipes of different diameters, including the use of a rotating mirror in front of the lens at

Typical pipeline ii!Spl'ction system.

Pipeline Inspection and Evaluation

515

90° to the line of the pipe so that ports and branch lines can be screened circumferentially. An umbilical cable of suitable length connects the camera to the control console. This carries lighting power, rotating-mirror power and vision signal; it is stored on a 12-\•vay slipring drum or similar device that contains a trip-measuring device plus an electronic pulsing unit which relays back to the monitor the distance the camera has travelled down any one line. This distance can be zeroed or preset to any measurement at any one time. The control unit. which is basically the power unit for the camera, controls lighting intensity, remote focusing capability, and rotating-mirror positioning. Lighting heads are normally low-voltage lamps of different sizes and wattages housed in intrinsically-safe. glass-fronted housings for attachment to the front of the camera. Various items and relevant information need to be shown on the monitor screen during a survey. such as: site address, date, pipe diameter, run number, location and description or faults. etc. The equipment used to produce the characters shown on the screen can come in various shapes and sizes with differing capabilities. but it is normally known as a word processor or screen writer. Ancillary equipment carried by the unit may include: generator, winches, steel rods. drain stoppers, lifeline, harness, hydrant stand pipe. hoses and key, extension leads, gas detector, road cones, cable rollers, field telephone set with up to 365m (400 yd) of cable float lines. etc. Survey methods

A tried and tested method used to carry out a TV survey is that shown in Figure 1, whereby a line is passed through the run and a camera is towed by a winch from chamber 'A' to chamber 'B' . \,Yinch 'A' is purely a safeguard, so that if the run being surveyed is damaged to such a degree that camera progress is impeded, the camera can be retrieved by winching back on a steel WINCH METHOD CABLE DRUM

SKID CAMERA

Figure 1.

516

Pipelines/Pipework

band instead of pulling on the umbilical cable. As previously stated, as the camera and umbilical cable are pulled down the run, the measuring wheel on the drum transmits back to the monitor the distance the camera has travelled from the beginning of the run for location purposes. Runs are normally surveyed in the direction of the fall of the drain. The reason for this is that if the camera is pulled against the flow it can create a bow wave, causing droplets of water to splash on to the camera lens, so distorting vision. Waste matter can also be deposited on the lens which could obliterate vision completely. Surveying against the fall is only possible if the run is 'dry' during the survey. A landline telephone system may be used for communications between vision controller and winchman, so that the camera can be stopped anywhere along the run to focus on any problem area. When the survey is completed the camera and skid are detached from the umbilical cord and safety winch cable. The two cables are then wound back to chamber 'A'. Other methods of transporting the TV camera are by rodding (shown in Figure 2) and self-propelled traction units. Duct tractors are capable of providing a vehicle for tasks as varied as simple draw-line installation, the positioning of remote inspection devices such as sensors, as well as closed-circuit TV surveillance applications. One system uses a self-propelled small-bore pipe crawler with traction being created by the deformation of counteracting diaphragms on the internal walls of the pipe. This method of traction allows the tool to operate along pipes running at various inclines, including vertical limbs of up to 100m (328ft). The crawler can also traverse holes in the pipe wall of up to 75% of the pipe diameter and, in the straight pipe condition, over holes of up to 100% of the pipe diameter, i.e. inverted equal-T junctions. The energy source is compressed air or an inert gas, depending on environmental conditions, delivered at the appropriate pressure along an PUSH METHOD RODDING EYE

RODDING REEL WITH INTERGRAL POWER LEAD

Figure 2.

1

~

Pipeline Inspection and Evaluation

517

umbilical supply line. The crawler is designed to operate in most dry, commercially available ductways with the exception of PTFE-Hned pipes. In general, the rougher the traction surface the more satisfactory the operation. The vehicle will also travel at reduced speed through a pipe which at any point contains up to 20% non-viscous liquid, e.g. water. Figure 3 shows a duct tractor unit complete with trailed pneumatic logic carriage, umbilical interface carriage and 50 m (164ft) reel of drive supply line on drum. long pipelines and tunnels

Several techniques are used for inspection of long pipelines and tunnels. Varieties of autonomous underwater vehicles (AUV), ranging from the dumb pig swept through by water flow to smarter systems capable of recording their progress and the state of the pipeline or tunnel as they pass, operate with variable success rates. The problem has always been whether to have freeswimming vehicles in the pipeline or tunnel. Remotely operated vehicles (ROV) are a viable proposition if cable drag can be kept within acceptable limits. Good cable needs to be neutrally buoyant and carry sufficient copper and fibre-optic links. It also should be under 15 mm in diameter with a polyethylene outer jacket to provide a low coefficient of function. ROVs operate on tethers of 10 km without problem. Remotely operated vehicles have

Figure 3 . Remotely-controlled duct tractor capable of tackling severe bends in small-diameter pipes.

518

Pipelines/Pipework

anumberofthrusters, (usually 12, eight forward and two each for vertical and lateral movement). Control software typically includes the standard diagnostic features and the unit is capable of handling up to four video cameras. In addition to those used for inspection work, one usually faces rearward to help vehicle retrieval. Sonar fitted to the vehicle are used for collision avoidance and scanning (e.g. short-range profiling). As the vehicle progresses down the pipeline or tunnel, it rotates and scans a helical path. The sonar screen displays the tunnel cross-section. Flattening at the bottom indicates sediment build-up and features elsewhere show either wall corrosion or a build-up of mineral deposits, usually around flanges. Two forward-looking cameras look at abnormalities thrown up by the sonar. The biggest problem usually encountered by ROVs is the amount of debris in the water in spite of trash rakes and sieves. Plastic-material debris can snag the propellers in the thrusters and plastic bags or similar objects can become wrapped around the sonar head, for example. The chances of traversing a 10 km tunnel or pipeline without encountering any obstruction are probably very small. Position surveys

Metal detection can be used to trace the path or buried metal pipelines, and also plastic pipelines where a metalised identification strip has been buried with the pipe. Simple hand-held units of this type are efi'ective up to depths of 2 m (6ft) . More powerful units may be used for detection at greater depth, and also for surveying wrapped or coated pipes. In the latter case the instrument may also be capable of detecting flaws or breaks in the pipe wrap. Such instruments may work in the inductive or conductive mode. In the inductive mode, a linear or circular aerial is used as a 'direction finder' to establish a small signal which identifies the exact location of the pipeline run relative to the aerial. With conductive mode operation, no aerial is used and direct contact is made with the pipe to be traced to feed the signal directly into it. Cable-avoiding tools (CAT) and transmitters offer advantages in terms of accuracy and speed for pipe and cable location equipment. This type of equipment can be used in all weather conditions. An innovative plastic water pipe tracing tool operates by connecting a 'transonde' transmitter to a running tap or stand pipe. The pressure-wave signal produced in the pipe can be located on the surface using a hand-held receiver. Battery-operated versions are used for tracing service pipes. Leak detection

Water-leak detectors are an essential inspection tool for pinpointing leaks cost-effectively and quickly. Typical apparatus is based on the H 2 method where a low concentration of hydrogen is 'injected' into the leaking pipe and

Pipeline Inspection and Evaluation

519

the escaping gas is then located using a specially designed hydrogen-gas detector. The gas can permeate through most materials. It is a 5% mixture in nitrogen and therefore non-explosive in this diluted state. Line protection

Line protection systems are pipeline monitoring and line-break detection devices controlled by a dedicated microcomputer. The system is normally located at a pipeline valve site to provide supervisory control of the valve and actuator. Line protection systems continuously monitor the pipeline pressure at a point near the valve site. Once armed, and when abnormal pressure conditions are sensed, the protection system strokes the valve to a fail-safe position. The system operates in various modes including: Data collection mode-pressure is sampled at 32 second intervals and 30 minutes of pressure history is stored in a temporary rolling memory. Memory capacities are usually quite large. Valve control mode-pipeline pressure is sampled every 8 seconds. The pressure magnitude and rate of drop are continuously compared to the userset values. When pre-set values are exceeded for the specified time duration, the control will cause the valve to stroke the fail-safe position. Internal relay contacts interfaced with telemetry or SCADA systems send a warning signal back to pipeline operations personnel. Communications mode-used when the system is connected to a portable computer.

Water leak detector.

520

Pipelines/ Pipework

location of sub-marine pipelines

Four different methods can be used to locate sub-marine pipelines: echo-sounding, magnetometers, sonar-scanning (and similar acoustic methods), and seismic profiling. Echo-sounding and acoustic methods can only be used to detect sub-marine pipes which are exposed above the seabed. Magnetometers and seismic systems can detect buried sub-marine pipelines. The most common method of locating exposed sub-marine pipelines is by side-scan sonar, using a towed 'fish' with laterally-directed transducers generating acoustic pulses of frequencies of the order of 100 kHz. Various techniques are used depending on the depth of water involved, the length of pipeline, etc., and the feasibility of employing underwater acoustic transporters. In shallow waters. suitable results may be achieved more simply and economically using transit sonar, when the sonar transducer is mounted on the hull of the running vessel, or conventional high-resolution echo sounders. The application of a magnetometer or seismic profiler for the detection of buried sub-marine pipelines requires the use of detectors towed behind the survey vessel which then performs a series of transverses to intersect the expected pipeline axis. Magnetometers measure the strength of the earth's magnetic field, which is affected by the presence of a steel pipeline. Essentially, then, a magnetometer detects the presence of such a buried pipeline by its anomalous magnetic effect. This magnetic effect is usually proportional to the centre of the distance

Linebreak protection system.

Pipeline Inspection and Evaluation

521

between the magnetometer sensor and the object (pipeline). For this reason it is necessary to lower the magnetometer 'fish' as close as possible to the seabed. With a seismic profiler, a piezoelectric transducer or 'pinger' emits pulses of acoustic energy with single frequencies in the range 1.25 to 1.4 kHz at a high pulse rate. The 'fish' is towed at a height of 5 to 10 m ( 15 to 30 ft) above the seabed, concentrating the downward-directed energy beam over a small area or seabed. A proportion of acoustic energy penetrating the seabed is reflected back by the lined pipeline, producing a characteristic deflection on a graphic recorder.

Jacketing and Dual Containment Even the most engineered piping system is subject to temperature-control and containment problems. Process industries require higher and more precise temperature control for efficient operation. A range of thermal-jacketed products are available for organic and inorganic chemical processors. pharmaceutical plants, polymer producers. petrochemical plants and food processors. These products cover a broad range of processing components including pipes, valves, strainers. fittings and pumps. Generally, jacketing that has been specifically fabricated falls into one of three broad categories: standard, swaged and hybrid systems. Standard jacketing

Typically, this system provides uniform application of heat by covering the pipe or valve (core) from the flange. The jacket is welded to the back of the flange so oversize valves must be used to accommodate bolts. Figure 1 shows the standard jacketing system.

Process

Jacket-Size Flange

Figure I. Standard jacketed pipe.

Jacketing and Dual Containment

523

Swaged jacketing

Also referred to as capped or partial jacketing, this system is often used where protection against cross-contamination is required and where temperature discontinuities at flanges can be tolerated. Swaged jacketing can be less expensive than standard jacketing because small in-line flanges can be used (Figure 2). Hybrid jacketing

This method utilises a combination of both swaged and standard jacketing systems as well as removal and special jacketing. Straight-line piping may use swaged jacketing while valves and fittings employ standard or removable jacketing to eliminate temperature discontinuities at critical flow areas (Figure 3 ).

Figure 2. Swaged jacketPCI pipe spool with stainless core and carbon jacket. The jacket has an integral staittless expansion joint to relieve cyclic heaL sl.ress.

LINE-SIZE FLANGE

\c

SWAGED JACKETIN G REMOVABLE JACKETING

Figure 3. Typical f1ybrid jacketing.

524

Pipelines/ Pipework

Jacketed system design

Very little information is readily available regarding design considerations and recommendations for jacketed piping systems. Fabricated jacket equipment manufacturers are the best placed to provide the information as a result of their manufacturing and fabricating experience and accepted practices within the processing industries. A typical manufacturer's recommendation to be considered in overall system design is given here: 1. Design for uniform temperature control throughout the system. Chill spots, even in moderate temperature systems (120-180°C; 250-350°F), are the problems most frequently encountered. Temperature discontinuities at flanged connections, valves or fittings may cause product build-up and solidification at critical points. 2. Design for uniform heat stress. This is particularly important where temperatures are over 120°C (250°F) and in batch-type service where the piping is subject to frequent heat cycles. Under these conditions the core and the jacket should be of the same material or have very similar coefficients of expansion. 3. Lengths of straight-jacketed pipe should be a maximum of 6 m (20 ft) for ease of installation. 4. Spacers between the core and the jacket on pipes should have a nominal clearance ofl.58 mm (1h 6 in) to restrict core sag while allowing differential motion caused by heat stress. 5. The slope of installed jacket pipe should be gradual, about 3 mm per 300 mm (1/ 8 in per foot) to eliminate pockets and facilitate drainage of the heating fluid from the jacket. 6. Heated fluid should flow counter-current to the process to promote the most uniform application of heat. 7. The length of jacketed runs or the number of spools per single supply of heating fluid should be carefully analysed. Almost every single application will have widely varying parameters. 8. Jacket jumpovers, depending on the size of the jacketed pipe and the heating throughput required, should be 25, 19 or 12 mm (1, 3/ 4 or 1h in). Flexible metal-hose jumpovers can be used with both vapour and liquid heating media. System pressures determine whether the hose should be braided or unbraided. In certain high-temperature, high-pressure applications, pre-formed metal tubing may be preferred to metal hose. 9. Metal selection for jacketed piping usually has two major considerations: performance and cost or performance versus cost. The most frequently used jacketed-piping systems by the chemical process industry is standard weight carbon steel (SA 53) for both the core and jacket. Food and pharmaceutical processors generally specify stainless on stainless construction for service above 120°C (250°F), and carbon on stainless construction for lower-temperature services.

jacketing and Dual Containment

52 5

Fabricated jacketed assemblies

Fabricated assemblies provide considerable savings on material costs and save on installation time. The assemblies are easier to insulate, with few jumpovers and fewer flanges. Table 1 compares a conventional jacketed-piping construction with a piping construction utilising jacketed assemblies, both using the same piping section. jacketed valves

Practically all types of valves can be fully jacketed by fabricating techniques, including many valves not available with integrally-cast jackets (Figure 4). Standard fabrication includes modifying the valve to accept oversize flanges. extending the body as necessary to ANSI standard. then adding the Table 1. Conventional jacketed-piping construction versus jacketed assemblies

2

Piping construction utilizing .jacketed assemblies.

52 6

Pipelines/ Pipework

full jacket ensuring that the interior tolerances remain the same as the original unjacketed valve. Typically, there are four basic types of jacketed valve: 1. Partially jacketed valve for low-temperature non-critical processes. 2. Fully jacketed valve with oversize flanges. This jacket provides uniform temperature control and is used mainly for high-temperature processes. 3. Fully jacketed valve with standard flanges. This is only used with components or piping having swaged jackets or special bolting facilities. 4. Fully jacketed valve having oversize flanges and the face-to-race dimension of an unjacketed valve. This construction should be used with caution. It is not recommended for new installations. Advantages and disadvantages

Integrally-jacketed piping systems and components have long been the preferred method used with processes that require elevated temperatures for efficient in-plant transfer or product. Advantages of integral jacketing include: • • •

unit construction high rates of heat transfer from the heating medium to the process ability to maintain processing temperatures within close tolerances

Figure 4. Typicnl t.wo-piece Cont roHeat valve jacket.

Jacketing and Dual Containment

52 7

Like many systems, they have their disadvantages; these include: • • •

the limited selections available for jacketed components relatively long deliveries for these components inconsistencies of quality of the jacketed components due to the lack of industry-wide fabrication standards

An alternative to integrally-jacketed piping systems is the clamp-on heating system comprising bolt-on jackets for valves and heat-tracing elements for piping. Practically any piece of equipment can be heated with a clamp-on jacket. However, the cost of the clamp-on system can increase as the required temperature of the process approaches the temperature of the heating fluid. Component programs using finite element modelling have been produced by jacketed-piping fabricators to assist end-users in determining the right system or product for their application. Typically, these programs consider the thermal conductivities of the system components, film coefficients of both the processes and the heating fluid, a detailed temperature profile of the piping system. and the heat lost to the atmosphere through the insulation and the net beat input to the process. Dual-containment piping

Dual- or double-containment piping is by no means a new concept to process piping applications. Systems using a carrier pipe with secondary containment have been installed using metal pipes for many years. Applications have included systems for the nuclear and chemical process industries where hazardous or highly toxic materials have been transported. Dual-containment piping is all about employee safety and environmental damage caused by chemical spills and leaks. It is widely accepted that pollution of the soil due to chemical leaks eventually leads to groundwater contamination which has become a major world-wide problem. One proven method of avoiding serious leaks from piping conveying hazardous or highly toxic materials is to utilise a primary pipe contained within a protective outer casing, combined with a leak-detection system to pinpoint leaks and simultaneously raise an alarm. Systems of this type have often proven to be complex. labour intensive and costly. Polypropylene and PVDF piping are now widely and successfully used for transporting chemical waste and toxic and other hazardous materials (Figure 5). Typically. the design uses a twin-wall pipe which is extruded as a single homogeneous structure. The fittings are often moulded as a one-piece item, with both inner and outer walls fixed in place. The pipes and fittings may be joined with standard butt welding with a single weld simultaneously joining both the inner and outer walls.

528

Pipelines/Pipework

Figure 5 . Polypropylene dual-containm('llt piping.

Black polypropylene is preferred as it is resistant to weathering and can be safely used in exposed situations. It is important that pipe and fitting brands should not be mixed. Polypropylene dual-containment piping systems can also be particularly useful for conveying chemical waste in underground systems under gravity flow conditions. Typically, the method of jointing is to use primary and secondary couplings, each manufactured with an integral chrome/ nickel/ alloy resistance wire moulded in place. The wire is electrically heated using a microprocessorcontrolled fusion unit that enables uniform jointing to be made in minutes. Both primary and secondary joints can be assembled in the trench or above ground local to the trench, depending on the site conditions. Polypropylene pipe is characterised by its outstanding chemical resistance, high thermal

Jacketing and Dual Containmmt

52 9

Figure 6. Underground doub le-containment acid-waste pipin,q.

resistance and good fatigue strength. Polyvinylidene fluoride (PVDF) is resistant to most inorganic acids as well as to alphatic and aromatic hydrocarbons, organic acids, alcohols and halogenated solvents. It is not resistant to alkaline amines, alkalis and alkaline metals. Strongly polarised solvents, such as ketones and organic acid esters, swell PVDF slightly. It has an exceptional resistance to UV radiation and a wide pressure/temperature range.

SECTION 7 Performance and Calculations

Flow of Liquids through Pipes Flow of Mixtures through Pipes Compressible Flow in Pipes Losses in Bends and Fittings Strength of Pipes (Calculations) Buried Pipes Collapsing Pressures for Pipes Boiler-Feed Calculations Steam Flow Calculations Cavitation Noise Control Balancing of Hydronic Systems

Flow of Liquids through Pipes Liquids pumped or discharged through pipes under conventional pressure behave as incompressible fluids. Flow is assumed to fill the pipe section: basic flow rate (Q) and flow velocity (V) are directly related, viz: Q = V x pipe bore area (in consistent units) Flow velocity

Flow velocity is defined as the mean or average velocity at a given crosssection. Due to frictional effects (and the fact that all real fluids possess viscosity), a velocity gradient will exist across a pipe section, ranging from zero at the point of contact with the pipe wall to a maximum at the centre line (Figure 1). The actual velocity profile may be smooth or irregular, depending on whether the flow is laminar or turbulent, respectively (see the section Laminar and turbulent flow below).

ZZZZZZZ(?.ZZZZZZZZZZ?Zt

--.

r-

Temporal mean profile"

Figure 1.

5 34

Performance and Calwlations

The basic formula relating Q, V and pipeline diameter (d) is: Q =~XV 4

X

d2

In engineering units this becomes:

Q = kV

X

d2

where k is a constant, depending on the units employed (see Table 1 ). Transposed forms of this equation are also useful for direct solutions for V and d. viz:

Q V = k X d2 Flow velocity Vis not necessarily a significant parameter except that it governs frictional losses. For general design work. arbitrary flow-velocity limits are normally assumed, e.g. for water supplies normal design flow velocities are: General services Water supplies Boiler feed

1.2 to 3m/ sec (4 to 10ft/sec) up to 2m/sec (up to 7ft/ sec) 2.5 to 4.5 m/sec (8 to 15ft/sec)

Gallon=277in 3 One day= 86,400 sec Barrel= 3 5 Imp gal / min 42 US gal/min m 3 = 6.28 barrels

Table 1. Flow velocity bycalculaHon Flow rate (Q) unit

Flow velocity

Pipe bore (d) unit

ft/ sec

m/ sec

Cubic in/sec

Q/10d 2

0 .03 Qj d 2 20.8 Q/ d 2

in mm

Cubic in/ min

0 .00177 Q/ d2

0.00054 ()/ d 2 0.348 Q/ d 2

in mm

0.49 Q/ d2

O. l5Q/ d 2 9 7 Q/ d2

in mm

2 Qjd 2 1 2 7 5 Q/ d 2

in mm

0 .1250Q/ d 2 80 Q/d 2

in

mm

1 5 Q/d 2 14.7 5 Q/ d 2

mm

0 .0036 Q/d2 2.3 5 Q/d 1

in mm

Gallons per minute Lit res per minute US gallons per minute Ton s of water per day Cubic metres of water per day US barrels per day

0 .408 Q/d 2 49 Q/ d 2

0.012 Q/ d2

in

Flow ofLiquids through Pipes

53 5

Example: 7 in pipe: 0.267 ft 2 , 1000 gal/min. 16.7 gal /sec/ 6. 24 = 2.6 7 cusec/0.26 7 = 10ft/sec

°·

49 Ve 1= 10 ft1sec= 4g x 1 ooo ga I/ min= 1 o ['t Isec d 2 = 1 million Area= 0.785 m 2

Coefficient= 0 .49 1 day= 86.400 sec Pipe 1000 mm diameter

1 million m 3 /day /86,400 = 11.55 m 3 /sec/0. 78 5 = 14. 7 5 m/sec rr/ 4=0.785(1Mm 3 / d 2 ) x 14.75 PipelOOOmmdia=d. Pipe sizing

Rather greater attention to limiting flow velocities is normally required on the suction side or pumps. AJso, frictional losses are proportional to fluid viscosity as well as flow velocity. More specific recommendations for flow velocities are given in Tables 2A and 2B. Again, these are largely arbitrary figures based on providing suitable hydraulic conditions in suction pipes or generally acceptable levels of friction loss in delivery pipes (see also Table 3 ). Accepting arbitrary valves for flow velocities, the corresponding pipe size (d) required for a specific delivery (Q) follows from simple formula calculation. In the case of water. a general formula often used is: pipe diameter (in)

gal/min 10

=

Table 2A. Recommended suction-flow velocities Pipe bore

\Nater

Light oils

Boiling liquids

Viscous liquids

mrn

in

m/sec

ft/sec

m/sec

ft/sec

m/sec

ft/sec

m/sec

ft/sec

25

1

0.50 0.50 0.50

0.300 0.330 0.375

1.0

1.5 1.6

0.300 0.300 0.300

1.0

2

1.5 1.6 1.7

1.5

50 75 100 150 200 250

0.50 0.50 0.50 0.55

l.8

0.60

2.0

0.55 0.60

1.8 2.0

0.300 0.350

8

0.75

0.70

2.3

10

0.90

2.5 3.0

0.90

12 over 12*

1.40

4.5 5.0

0.90

3.0 3.0

300

3 4 6

1.50

*General formula : pipe diameter (in) -

J -gal/min . 10

1.0 1.0 1.0

1.1 1.2 1.3

1.1

0.400 0.425

1.4

0.375

1.2

0.450

l.S

0.450 0.450

1.5 1.5

0.500 0.500

1.7 1. 7

53 6

Performance and Calculations

In high-pressure systems, e.g. hydraulic circuits using small-bore pipes, pipe sizing is more critical and normally determined directly from a specified or nominal figure for pressure drop. This involves working an appropriate pressure-drop formula as a solution for pipe bore. The same technique may also be applied to fluid transport systems. especially if high pressures are involved or working conditions are critical. In this case, Table 28. Recommended delivery-flow velocities

Pipe bore

Water

Light oils

Boiling liquids

Viscous liquids

mm

in

m/sec

ft/sec

m/sec

ft/sec

m/sec

ft/sec

m/sec

ft/sec

25

1

1.00

3.5

1.00

3.5

1.00

1.00

3.5

50

2

1.10

3.6

1.10

3.6

1.10

3.5 3.6

1.10

3.6

75

3

1.15

3.8

1.15

3.8

3.8

1.10

100

4

1.25

1.25

4.0

4.0

1.15

3.7 3.8

150

6

1.50

4.7

1.50

4.7

1.20

3.9

200 250

8

1.50 1.75

4.0 4.7

1.15 1.25

5.5

2.00 2.65 3.00

1. 75 2.00 2.00

5.5

10 12 over 12*

1. 75 2.00

1.20 ].30

4.0 4.5

1.40

4.5

300

5.5 6.5 8.5 10.0

2.00

*General formula: pipe diameter {in) = .j

6.5 6.5

6.5 6.5

gal/min . 20

Table 3. Pipe bore size for given velocity

Flow velocity

Pipe bore (mm) for flow rate in

Pipe bore {in) for flow rate in

ft/sec

1/ rrtin

gal / min

0.3 0.5

1

8.4.jQ

0.7 .jQ

0.6 0.9

2

6.5 .jQ 6.0.jQ

0.5.jQ

m/sec

1.0 1.1 1.2 1.5 1.8

3

2.75 3.0

0.4.jQ

4.4.jQ 4

4.2.jQ

0.35.jQ

5 6

3.8.jQ 3.4.jQ

0.3 .jQ 0.28.jQ

7

3.3.jQ 3.2 .jQ 3.0.jQ

0.265 .jQ 0.2 5 .jQ

2.0 2.1 2.4 2.5

4.9.jQ 4.6.jQ

8

2 .9 .jQ 9

2.8.jQ

10

2.6.jQ

0.23.jQ 0.22.jQ

FlowofLiquids through Pipes

53 7

since relatively larger pipe sizes are normally involved, recommendations are commonly based on flow rates only, viz: Suction lines: pressure drop 0.0115 to 0.23 bar per 100m (0.05 to 1lbf/in 2 per 100ft) depending on the available NPSH. Delivery lines: 0.115 to 1.38 bar per 100m (0.5 to 6 lbf/in 2 per 100ft) depending on the flow rate, viz: (a) 0.46 to 1.4 per 100m for flow rates up to 450 lfmin (2 to 6 lbf/in 2 per 100ft for flow rates up to 100 gal/min) (b) 0.33 to 1.15 bar per 100m for flow rates from 450 to 900 l/min (1.5 to 5 lbf/in 2 per 100ft for flow rates from 100 to 200 gal/min) (c) 0.23 to 0.92 bar per 1200 m for flow rates from 900 to 2250 lfmin (1 to 4lbf/in 2 per 100ft for flow rates from 200 to 500 gal/min) (d) 0.11 to 0.46 bar per 100 m for flow rates above 2250 lfmin (0.5 to 2 lbf/in 2 per 100ft for flow rates above 500 gal/min).

Pipe sizing by specific gravity of fluid

The size of delivery lines on centrifugal pumps is sometimes based on economic flow velocity related both to the specific gravity (SG) of the fluid being handled and the type of driver. This is realistic in the sense that the power input required, and thus the cost of pumping, is directly proportional to fluid specific gravity, and economic flow velocity varies inversely to pump speed. Recommended flow velocities are given in Table 4.

Table 4. Recommended flow velocities based on fluids SG

Pipe diameter

Power-driven pumps SG = l.O

mm

in

m/sec

ft/s<:c

SG = 0.75

m/sec

Turbine-driven pumps SG = 0.5

ft/sec

m/sec

ft/sec

SG

=1.0

SG=0.75

m/sec fl}sec

m/scc

ft/sec

SG == 0.5

m/sec

ft/sec

50

2

1.80

6.00

2.10

7.00

2.30

7.5

1.50

5.00

1.70

5.50

1.80

6.00

75

3

2.10

7.00

2.40

8.00

2.60

8.5

1.70

5.50

1.80

6.00

2.00

6.50

100

4

2.40

8.00

2.75

9.00

3.00

10.0

1.80

6.00

2.00

6.50

2.15

7.00

150

6

2.75

9.00

3.00

l 0.00

3.65

11.0

2.00

6.50

2.15

7.00

2.40

8.00

200

8

3.00

10.00

3.40

11.25

4.00

13.0

2. 10

6.75

2 ..30

7.50

2.60

8.50

250

10

3.25

l 1. 00

3.65

12.00

4.20

14.0

2.15

7.00

2.35

7.75

2.75

9.00

300

12

3.50

11 .50

3.80

12.50

4.40

14.5

2.15

7.00

2.40

8.00

2.80

9.25

350

14

3.60

11.75

4.00

13.00

4.50

15.0

2.15

7 .00

2.40

8.00

2.90

9.50

400

16

3.65

12.00

4.00

13.00

4.60 15.0 and over

2.15

7.00

2.40

8.00

2.90

9.50

Performance and Calculations

53 8

Critical flow velocity

Flow velocity is 'critical' in the sense that it is a major factor in determining the frictional losses of the flow. This is not necessarily significant for fluid transport applications involving flow velocities within the recommended ranges. Flow velocity can, however, be a critical factor in practical applications involving the transport of solids in suspension in a fluid. The flow velocity will largely govern whether the solids are transported in suspension (homogeneous flow). or whether the solids tend to settle out forming sliding layers over a settled bed (heterogeneous flow). To produce homogeneous flow it is necessary that the flow velocity should be greater than the fall velocity of the solids in the fluid. This sets critical or minimum flow-velocity requirements for the handling of fluids containing solids in suspension, which can only be determined satisfactorily on empirical lines. Some specific recommendations are given in Table 5. See also the chapter on Flow of Mixtures through Pipes. laminar and turbulent flow

Flow through pipes can be either laminar or turbulent, the flow condition being significant in affecting both the velocity gradient and the frictional losses. With laminar flow, frictional losses are due to viscous drag and are independent of the condition of the pipe bore. With turbulent flow, viscous shear forces predominate and the condition of the boundary surface can materially affect the total friction. The actual flow condition can be established by reference to a non-dimensional parameter, the Reynolds number (Re), determined as: dV Re = V

where d =pipe bore V =velocity of flow v =kinematic viscosity of the fluid (in consistent units) Note: The Reynolds number itself is dimensionless. Table 5. Minimum flow velocities for slurries

Flow velocity Type

Size of solids (mesh no.) ft/ sec

m/ sec

Fines

Over 200

3- S

1.00-1.50

Sands

200- 20

5-7

l. 50-2.00

Coarse

20-4

7-11 11-14

2.00-3.25

Sludge

3.25-4.25

Flow of Liquids through Pipes

539

In engineering units:

Re

= 7740dV where

Re = 930dV v

or

v

dis in inches Vis in ft/sec vis in centistokes

where dis in em Vis in m/sec v is in cen tistokes

In the case or clean cold water: Re = 7740 dV when d is in inches, V in ftjsec

= 9 30 dV when d is in em, V in

mjsec.

Also, see Table 6. The same formulae apply for the calculation of Reynolds numbers for flow in non-circular pipes, substituting the equivalent hydraulic diameter for the circular diameter, viz: cross-sectional flow area) Equivalent hydraulic diameter = 4 x ( d wette parameter The quantity contained in the brackets is the hydraulic radius of a non-circular pipe. The flow is laminar at Reynolds numbers up to 2000; and turbulent at Reynolds numbers above approximately 4000. In the transitional range (Re = 2000-4000), flow can vary from laminar to turbulent and flow conditions are indeterminate. In the case of laminar flow the velocity gradient will be linear. Maximum velocity at the centre of the bore will be of the order of 1. 5 times the mean flow velocity. With turbulent flow there is no clearly defined velocity profile. The temporal mean profile will be of the form shown in Figure 2, the actual profile varying with the Reynolds number. At low Reynolds numbers the maximum flow velocity (at the centre of the bore) will be of the order of 2.0 times the mean velocity, reducing to about 1.2 5 times the mean velocity at higher Reynolds numbers. Table 6. Reynolds number for clean cold water Pipe bore mm (in)

25

40

100

1 50

200

(ll h_ )

50 (2)

75

( 1)

(3)

(4)

(f))

(8)

250 (10)

(12)

450 (18)

Per 11/mio*

835

550

420

280

210

140

105

85

70

46

3800

2500

1900

1270

950

630

475

380

120

210

Per l gal/min*

*Multiply by actual numerica I value in either unit to give Reynolds number.

300

VALUES OF (vd) FOR WATER AT 60 °F (VELOCITY IN FT/SEC X DIAMETER IN INCHES) ~

~

8 10

; ;-,

JC

f.O

80: 100

) Uv

.oOO

600

~"'"'

80V .._.

, ...

r!>"'

·~

1.

### 'b · ,~

lo

V1

i-1>0

'"'0

I ~

.07

~· -t-t-

f

t- m·-tt 1t 1t t

r r 1 11!

I I I I I II I

""<::> '

~

3 :::,

1, 1 1111

~ 4

;:s

+-+-++H-1 , , H -

r,

""

T

.06

:::, ;:s

' ' '

s::...

Q

;:;-

OS

;::;-

·-~~~-~ -

'"" c;· ;::

.04

""

J Friction factor= hL

(

~) ~

03 075

~

__ L

·r I

I

.OZ

-)'-..

=~~~~ ~ 1(}'

ffftlllllill f=fl l l~mlf:: : ::: ::: ::~, , . . .

a.k

2

3 4 5 6 8 10'

?

3 1 ) 6 8 10

'

' ' ' ""

'"N

3 4 ) 6 8 10'

Re - Reynolds number =

Dvp

Jle Figure 2. Frictionfactorsfor pipes. Example:frictionfactor for pipe with relative roughness 0.001 at flow Reynolds number of 30.000 =0.026.

FlowofLiquids through Pipes

541

The velocity profile is primarily of significance where a pilot tube or similar flow-measuring device is inserted in the pipe as this will be subject to position error. In the cross-section with turbulent flow there is no point where the local velocity is likely to be constant and fully predictable. This factor is not necessarily significant where measurements or calculations are based on flow rate, or mean flow velocity, the latter being determined directly from the flow rate and pipe bore. Frictional losses

Frictional losses are calculated in terms of pressure drop or, alternatively, head loss. Figures for frictional losses are normally reduced to (friction) head equivalent perm (ft) or per 100m (ft) of pipe and are then directly applicable to any length or aggregate length of straight run of pipe of the sizes concerned. Such data are available and presented both in graphical and tabular form for a wide range of pipe sizes, for water, oils and fluids. Agreement is not always good between such data originating from different sources. Many, particularly for w a ter flow through pipes, are based on formulae more than half a century old and have a limited range of accuracy. Others are based on quite widely differing empirical coefficients, with similar limitations. If the reliability of the data available is suspect. or shows inconsistencies, more accurate solutions will be arrived at by working from basic principles. In the case of laminar flow, the D' Arcy- Weisbach formula can be applied in the form: LpV 2 .6.p = f- 2Dg where .6.P = pressure drop in lbf/ in 2 L = length of pipe in feet V = flow velocity D = bore of pipe in inches p = mass density of fluid ' f f I = a riction actor = ld64 b Reyno s num er In the case oflarger pipes (e.g. 25 mm (1 in) bore and above), and expressed in terms of flow rate (Q) rather than flow velocity (V), the following simplified formulae can be used: .6.P =

Q2L r-

-5 X

KtD

specific gravity of nuid

where K 1 is a constant dependent on the units adopted for Q, Land D.

542

Performance and Calwlations

The corresponding formula for head loss (~H) is: Q2L

~H = fK2Ds

It must be noted that before these formulae can be used the Reynolds number must be determined to: (i) Establish that the flow is laminar (Re

~

2000)

(ii) Calculate the friction factor for the formula

(r = 64Re ).

With laminar flow, friction loss (pressure drop or head loss) is not affected by the roughness of the pipe bore (unless this appreciably modifies the effective bore size). The formulae are thus directly applicable to laminar flow in all types, construction and ages of circular pipes and non-circular pipes (the latter with Rc computed on the basis of their hydraulic radius). Turbulent flow

In a majority of practical cases of pumped fluids, flow is turbulent (i.e. Rc > 4000) and simple calculation of flow losses no longer applies. Basically. the D' Arcy formula can be used. but with a different friction factor (fturb). the value of which is dependent both on the Reynolds number and the surface roughness of the pipe bore. Specifically, when the Reynolds number of flow exceeds 2000 there is a critical zone into which laminar flow may extend (but flow conditions are unpredictable and may change from laminar to turbulent, and vice versa), followed by a region of developing turbulent flow where the friction factor decreases with increasing Reynolds number but increases with increasing bore-surface roughness. Finally. full turbulent flow is established. when the friction factor is a constant regardless of increase in the Reynolds number and is dependent only on surface roughness. For smooth-bore pipes, the following formulae can be used to calculate the friction factor directly: 0.3164 fturb = Re 0 _25 for Re values between 4000 and 10,000 ' lturb

=

0.0032

0.221

+ Re 0 .237

for Revalues over 10,000

Working data for friction factors for turbulent flow are usually presented in chart form (Figure 3) where these zones are clearly seen. Effectively. turbulent flow friction factors are bonded by a lower curve, representing the friction factor for smooth-bore pipes, surmounted by a series of curves for pipes with increasing surface roughness. Roughness is defined in terms of relative roughness or E/0.

543

FlowofLiqLiids through Pipes

Pipe diameter, in feet - D

.l

.US .04

.2

I

" r"-

"

"' '

.008

......

' ''

.006 "\.. ,"-. 005 ...... ~ 004 ~ '

""' " '

.003

1--

.OlJ2

l1J

"""

.001 .0008

I

~

'

'

2 .0004 (I)

-~

"'

0::

t"\

"'I' ~~

'"'~ "' ~' ' "

0-1'\.1'\..

' "'>- ~ . . . ·~G'-1~

'

"

I'

·-

~

~0 (' -?0~' 1-

.s~

"""

.OOGU3

0

~~ ~.,

',

"~

\

~

~

.....

['\

' :-....

4

'~

""~

'

::l 0

.... c

~ .D

.... :::s

OJ& ~
a. .._,014

E c ~ 0

Ll-

1

"

012

'~ »~ ~ , ,, oo ~~ ~(<'-....(I"

' I'\.. .01 ""'~ "io0on-........ -........

'x , "' ' '

i\.: ~

....

~

1-- .

009

oo

['\,

~

5 6

1--

' !"-

~ ,, 1\..·o

~,r

3

~

-....:. ,,

~ ["\

'

lJl8

x,,

' ~ '' "'~ '~ ""

!>I)

(_)

N0"'

["\ ~

..c

C).

'

~

~0

2

0.

1'-.t-.Oi'

' 1'1

""

Ro

.0000 1 .000008 .000006 .000005 1

'

',

['.

"'0. C)

'r"\..

I'\.

~~

.00002

~

'r-..

~

~

-

G25

N'u>

:

~

"~<

V,-

'-«-,, --..,.o/.

01- , r"'

S:'- >-

.000 1 .00008

' ''

~"'>- ,.., '~

~

" I'\.

~

'

r-- :!< .>-~~~'

r-

. 00006 00005 .00004

' '

"'-<>,y .,-). :"\..

1'\.

- .03

~

,~,'1'.

['.

'

I'

"'

U4

035

"'

~-,..

........

. 0002

!"-

~ "-. li>o~ '

'

'

-

'

'

-~" ~

!'..

h

.

--

~~

~

~

I

'~

!

'\

~

-

a:;

' r-~,-

TAVE

~

.

.0003

N RE E

I

'

' ' t\ "'

WOOD

~r-.

......

T CD ST Eo.EL

''

-~

r'\

'

'

'

R~ V

f'-

0005

f- . 05

r.......

1'-1'. ['.

~

r"r-.

" ,.__ '

-. (j6

"'

~,

'

' "K

"' ;g"' .0006

~

r'\.

[..-

~~

~

I o. I

""

........

2U 25

I

["\..

~

.01 ~

4 5 6 1 ~ 110

3

~

!"..

"' r-...

2

I

1'.

~

-

.e 1 1

1

1'-

.03 "\..

02

5 .6

.4

.3

8 10 20 30 4G 50 60 80 100 Pipe diameter, in inches- d

.008

i"\..

200 30u

Figure 3. Frictionfactors and relative roughness for commercial pipes wit.hfully turbulentj]ow (based on ASTVIJ:: dat.a originated by L. F'. Moody). Example: for 10 in diamPter cast-iron pipe, relati ve roughrwss ( r=/ D) =0 .0008 5. Friction factor= 0.0196.

544

Performance and Calculations

where E is absolute roughness. or effective height of pipe-wall irregularities, and D the pipe bore. in the same units. An alternative form of chart is shown in Figure 4, together with typical values of E for different pipe materials, from which factors for turbulent flow can be read directly. It must be appreciated that the relative roughness of pipes is increased by corrosion, and also by age, due to encrustations. Data given in Figures 3 and 4 apply to new pipes in clean condition. Basic formulae then applicable are:

pV 2 2Dw

.6-HP

- - = fturb X - -

L

where pis the fluid density w is the fluid specific weight. Practical formulae for calculations: Reynolds number (R e):

w

Re = 0.482 Q ~J.l-SG

Re=6.3ldJ.l,

for Q in ft 3 / hr din inches Jl in centipoise

for Win lb/hr din inches Jl in centipoise

Energy grad,enr . Hydraulic gradient

6 h

~-++---+-V 22 ~-----.j.d---J-- 2 g

p2

Horizontal datum

Figure 4. Simplified energy and pressure gradients.

Flow of Liquids through Pipes

Re=

dV

Re = 7740 dV v

~

v

for din inches V in ft/ sec v in centistokes

for din ft V in ft/min v in ft 2 /sec Q Re = 1,419,000 dv

Q

Re = 3160 dv for Q in ft 3 / hr din inches v in centistokes

for Q in ft 3 / sec din inches v in centistokes

wv

Re = 394 dv

for Win lb/hr V(specific volume) in ft 3 j ib din inches v in centistokes

Re=2274~

Re = 92 .9 dV v

for Q in mm 3 / hr dinmm v in centistokes

for din millimetres V in mm/sec v in centistokes

Flow velocity (V):

v=

Q 183.3 d2

v=

for Q in ft 3 /sec din inches

v=

0.00389

Q X SG d2 p.

for Q in ft 3 / hr pin lb/ ft 3 din inches SG =specific gravity

Q 0.408 d2 for Q in US gal/min din inches

v=

Q 0.340 d2

for Q in Imperial gal/min din inches

545

546

Performance and Calculations

v=

Q 3350d2 for Q in m 3 /hr dinmm

Head loss (laminar flow):

HL (ft)

LV~-t

= 0.09 62 d2 p

HL (ft) = 0.03 93

for Lin ft V in ft/sec Min ceo tipoise din inches pin lb/ ft 3 LW~-t

for Lin ft Q in US gal/min 1-t in ceo ti poise din inches pinlb/ ft 3 LQJ.-L HL (ft) = 0.0328 d4p

HL (ft) = 0.0049 d4 p2

for Lin ft vV in lb/ hr JJ- in centipoise din inches pinlb/ft 3

HL (m)

~?~

LVJJ,

for Lin ft Q in Imperial gal/ min 1-t in centipoise din inches pin lb/ [t 3 LQJ.-L Ht (m) = 2670 d4 p

= 107 d 2 p

for Lin inches Vin mm/sec J.-L in centipoise pin tonnes/ m 3 din milli-inches

for Lin inches Qinmm 3 /bar dinmm pin tonnes/m 3

Pressured rap (laminar flow): .

LVM

~p (Ib/in 2 ) = 0.000668 (f2

for Lin ft V in ft/ sec J.1 in centipoise din inches

~p (lbjin 2 )

LQJ.L

= 0.1225d4

l'or Lin ft Q in ft 3 /sec J.-L in centipoise din inches

FlowofLiquids through Pipes

LWJ.J~p (lb/in 2 ) = 0.000034 d4 P

547

LQ/1-

~p (lbjin 2 ) = 0 .0002 73 d4

for Lin ft Winlb/ hr 11- in centipoise din inches pin lb/ft 3

for Lin ft Q in US gal/min J.J- in centipoise din inches

~P

(lb/in 2 ) = 0.00022 75

u;:

for Lin ft Q in Imperial gal/min din inches

~P (bar)

LVJ.1

= o.030 crz

~p (bar)

for Lin inches Win in/sec din milli-inches

LQJ.J-

= 9.05 d4 for Lin inches Q in 1/ min din milli-inches

Head Joss (turbulent flow):

HL (ft) = 0.1863 f

LV 2

d

where f= friction factor Lis in rt V is in ft/ sec dis in inches

HL (ft)

= 0.0311 f

102

d

lvhere f= friction factor Lis in ft Q is in US gal/min dis in inches

LQ2

HL (ft) = 62 60 [ (IS

where f =friction factor Lis in ft Q is in ft 3 / sec dis in inches

LQ2

HL (ft)

= 0.02 6 f (IS

where f =friction factor Lis in ft Q is in Imperial gal/ min dis in inches

548

Performance and Calculations

HL (ft)

= 0.000483 f

LW 2 V2

d

HL (rt)

5

where f= friction factor Lis in ft W is in lb/ hr V(specific volume) is in ft 3 / lb d is in inches

HL (m) = 0.041 f

LB 2

= 0.01524 [ (f5

where f =friction factor Lis in ft B is in barrels (42 US gal)/hr d is in inches d is in inches 2

LV 2

d

HL (m) = 641,2 70 f Ldq

where f= friction factor Lis in m Q is in I/min dis in mm

where f= friction factor Lis in m Q is in m/sec disinmm

Note: These formulae may be used for both laminar flow and turbulent flow. with appropriate friction factors.

Pressure drop (turbulent flow):

~P (lbf/in 2 )

2

= 0.001294 f Lp;

where f= friction factor Lis in ft pis in lb/ ft 3 Vis in ft/ sec dis in inches

~p (lbf/in

2

) =

0.000216 f

where f =friction factor Lis in ft pis in lb/ ft 3 Q is in ft 3 /sec dis in inches

L~~

2

where f =friction factor Lis in ft pis in lb/ ft 3 Q is in US gal/min dis in inches

~p (lbf/in

where

2

= 0.00000336 f d 5

r=friction factor Lis in ft

) =

0.00018 f

L~~

2

where f =friction factor Lis in ft pis in lb/ ft 3 Q is in Imperial gal / min dis in inches LV\72 V

)

~p (lbf/in

2

~p (lbf/in

2

)

= 0.0001058 f

where f =friction factor Lis in ft

L 82

~5

Flow of Liquids through Pipes

W is in lb/ hr V(specific volume) is in ft 3 / lb dis in inches

Ty2 L

.6.P (bar)= 0.000001125 f where f =friction factor Lis in m Vis in m/sec dis in mm pis in tonnes/ m 3

549

pisinlb/hr B is in barrels (42 US gal) ph d is in inches LpQ2 .6.P (bar)= 0.1613 f (f5

where f =friction factor Lis in m pis in tonnesj m 3 Qis in 1/mm dis in milli-inches

Note: These formulae may be used for both laminar flow and turbulent flow, with appropriate friction factors . Other formulae

Other charts or friction factor data may show substantially different values of friction factor for similar values of relative roughness. This is because the general formula is one of the form: .6.H Q2 L=fxkDS which includes the Reynolds number as a factor. The value of the friction factor (f) derived is thus adjusted accordingly. Colebrook-White equation

The Colebrook-White equation for transitional flow is extensively used for determining the hydraulic performance of sewage, drainage and effluent systems. The general form of the equation is: - 1 = -2log 10

JJ:

( --+ ks -2.51) 3. 7D ReVJ:

2gDi where A.= friction coefficient ~

ks =linear measure of effective roughness (m) D =pipe internal diameter (m) VD Re =Reynolds number, v

5 50

Performance and Calculations

The equation expressed in engineering terms is: V = -2

V(2gDl. log10

ks 3.

?D +

(

2. 51 V ) ~ Dy (2gDI

where V =velocity (m/sec) g =gravitational acceleration (9. 81 m / sec 2 ) i =hydraulic gradient v =kinematic viscosity of fluid (m 2 / sec). The Hydraulic Research Paper No. 4 recommends values for the linear measure of effective roughness for the commonly used pipeline materials in various conditions. The values appropriate to ductile-iron pipelines are given in Table 7. Generally, there is no significant deterioration with time of the linear measure of effective roughness ks where cement mortar-lined or bitumenlined pipes are conveying treated potable waters. However. conveying certain raw waters can lead to a build-up of slime in the bores of all pipes and this will cause an increase in the value of k 5 • The formation of these slime deposits is not deleterious to the linings, and periodic cleaning of this type of main will restore the hydraulic performance virtually to that of the pipeline in its new condition. The empirical Hazen-Williams formula has the advantage of simplicity and, for determining the flow of raw or potable water at normal temperatures, it can be relied upon to give results of sufficient accuracy for all practical purposes. It is widely used for calculating flow in raw- and potable-water pipelines. The formula can be conveniently expressed as :

v=

0.4 s 7 x 1 o- 5 cD0 ·6 3 i 0

54

or

where V =velocity (m/ sec) Q =quantity (1/sec) D =pipe internal diameter (mm) i =hydraulic gradient (dimensionless) C =Hazen-Williams friction coefficient (dimensionless). By selecting the appropriate value for the coefficient 'C', the Hazen-Williams formula can be used for all types of pipe materials. Table 8 gives values of 'C' for ductile-iron pipelines. The values shovvn are based on case studies and consequently account is automatically taken of losses due to irregularities at the joints.

FlowofLit]uids through Pipes

5 51

The same comments about the linear measure of effective roughness ks apply equally to the friction coefficient 'C'. The values of 'C' as given in Table 8 are approximately correct at a velocity of 1m/sec. At other velocities the approximate corrections are given in Table 9. Effect of inclined flow

Pressure drop (or equivalent head loss) due to flow is the same in straight pipes whether the pipe run is horizontal, vertical or inclined. With vertical or inclined flow, however, pressure drop is modified by the difference in actual head involved. Here, the Bernoulli theorem applies in defining the total energy at any particular point above any arbitrary horizontal datum plane. Total energy is equal to the sum of the elevation head, the pressure head and the velocity bead, i.e.: p vz Total head = 2 + - + p 2g The total head (H) will be a constant for any point. Thus. if the friction loss between points 2 1 and 2 2 on an inclined run (Figure 5) is expressed as a head loss ~H : H at point 2 1 = H at point 22. Thus:

.,

21

P1

Vt 2

PI

2g

+ - + - =2z

Vz 2 + - +-+~H P2 2g

P2

Confusion can be caused by reference to hydraulic gradient rather than head or pressure loss. Fundamentally, steady flow conditions through a system can be analysed in terms of a series of Bernoulli equations appropriate to specific lengths of the system. from which may be derived energy curves and pressure curves, as shown simply in Figure 5. The energy curve, normally referred to as the energy gradient. shows the total energy at any point in the system. The pressure curve. normally referred to as the hydraulic gradient, shm".rs the (pressure) head at any point in the system. The energy gradient will always drop in the direction of flow in the discharge side of the energy into potential energy, e.g. at a sudden expansion. Over a section not subject to changes, e.g. a straight length of pipe, the hydraulic gradient effectively represents the friction head loss and may be referred to as such. The term is rarely used in practical engineering calculations, however. Water hammer

'Water hammer ' is the name given to the distinctive 'knocking' noise which can develop in a closed pipe system when the flow velocity is suddenly changed,

Performance and Calc11lations

55 2

e.g. by the sudden opening or closure of a tap, valve or other flow-control device.lt can also be produced by other factors causing abrupt changes in flow velocity, e.g. sudden starting or stopping of a pump, or abrupt changes in speed of a pump feeding the system.

Pressure sensor

1

~1-LI==¢;;;33~==~==~¢~~80========;::::::=_~~~ :l~~~fct\~'~ ~w:· F

-

-

~

wutc r towers a nd including a lateral.

Length of lateral 300 m Pressure at end o f

la~e ral

Satu rday 5/1

101 145

P.ba r

-

I

8

v """ '-

A

"

10s

L- -

~

.........

_,

~

v- v

...........

, - ._....

Saturday 511

v

i :+-

I

t

Press ure at e nd of lateral

...,s_,..._ 4

I

I I I

--

L"'\.

'-../

l0H30

P .bar 8

~

~

v v "-

t..-.

~

~

-

1ft.

·rv \I

..,...............

..,.,., -

J'

vM f-

10s

6

.A.

'1'\

-

-

_2 _, I - -

t Pressure a t e nd of lateral

0

Friday 4/1

12H

P .bar 8

-1

I/'\

/"'

\l

,...~ lM.. ....,- / \ ""' "V 'v \i \/ I'V I'

.-. I¥""

\)

~

\I

§...

A

"'

'V

-

t

Fig11re 5. Typical recording of pressure at e11d of lateral.

~

4

-- ~ 1_(5

v

r4 '

0

rl

Flow of Liquids through Pipes

55 3

The cause of the 'hammer' is a sudden pressure rise in the liquid, caused by the rapid acceleration or deceleration imparted to it, which travels as a pressure wave along the length of pipe, and is reflected backwards and forwards . In addition to generating knocking noises or 'hammer', if the pressure rise is excessive it can cause damage to the piping or system components. The pressure. velocity and time for the pressure wave to travel from one end of the pipe to the other can be determined from first principles, viz: ' 4660 Velocity ol pressure wave (v) = ( I) 1 + 1(0 t where 0 =pipe diameter t =pipe-wall thickness in same units elastic modulus for liquid elastic modulus for pipe material

K = - - - - -- - - - -- - -

Values ofK for water and common pipe materials are: Pipe material Steel Wrought iron Cast iron Asbestos/ cement

K 0 .010 0.0107 0 .025 0.088

Pressure rise, expressed as Head (H): V!:::.V H =g where !:::. V =reduction in liquid velocity Time for pressure wave to travel length L: 2L t= sec !:::.V Note that L is the length from the appliance concerned (producing the velocity change) to the ends of the pipe. There are various methods of reducing the intensity of the pressure wave and thus the shock or degree of hammer. The magnitude of the pressure wave is directly proportional to reduction in flow velocity. so it follows that: (i)

(ii)

Lowering the flow velocity will be effective, i.e. reducing the How rate for a given size of pipe or increasing the pipe size for a given flow rate, because!:::. V must then be less. Decreasing the rate of closure will have a similar effect if the flow stopping time is increased to several times the value oft (times of travel

5 54

Performance and Calculations

of pressure wave corresponding to instant closure). Surge compressor valves are usually designed on these lines. Other methods which can provide a cure for water hammer. rather than designing for the system parameters to avoid hammer. are: (i) (ii)

air-injection, and introducing a flexible element into the system.

Air aspiration is mainly applicable to larger pipelines, the entrained air so supplied acting as a cushion to absorb pressure surges. Air-relief valves can also be installed to relieve air and water during a surge. Chatter

'Chatter' is rather like water hammer in characteristics but is the result of elasticity in the fluid system. Such elasticity may be introduced by aeration of air entrainment. Under certain conditions. axial oscillation of the fluid column may then develop in the system. In the case of high-pressure systems, chatter may also arise from a mechanical fault, e.g. seal chatter. Surge-prone pipe systems

Calculation programs using mathematical models can simulate the most characteristic types of phenomena which give rise to pressure surges and can provide a theoretical determination of the range of over-pressures which are likely to affect pipelines. In practice, while such calculations are available for individual pipes and simple pipe systems. it is difficult to make assumptions covering all possible cases for complex networks. These may contain distribution points, pumps. valves, etc., in which there may be interference, simultaneous or otherwise. between the various situations caused by the different components. Furthermore, the attenuation of such phenomena in both time and space may only be imperfectly known. The typical recording shown in Figure 6 was made at the end of one of the laterals of a small municipal distribution system. In view of the complexity of the problem, it may be worthwhile carrying out a diagnosis of the system during operation by locating pressure gauges at various points to detect and record over fairly long periods all the dangerous pressure variations. The recording can then be analysed in order to determine whether a given sector is subjected to over-pressure or depressurisation problems, and to assess the frequency and importance of such anomalies. Assumptions can be made, by studying the shape of the pressure versus time curves. concerning the type of component or operation which gives rise to such occurrences.

Flow of Liquids through Pipes

55 5

Diagnostic systems have been developed consisting of a suitable number of sensors indicating the values of the various characteristics parameters selected, and a micro-computer acting as a central measurement system. The micro-computer can take readings from the pressure sensor at a frequency of 1000 readings per second. The other sensors operate at longer time intervals which can be varied according to requirements. The system has been designed to operate either as a controller or as a central measurement unit. In the latter operating mode, suitable software enables the micro-computer to provide operating personnel with information about the internal behaviour of the system. Operators can thus take measurements at various points in the network and gain vital information enabling them to ascertain: (i)

Unknown sources of possible damage to the pipelines caused by equipment items, and the cause of certain malfunctions. (ii) Risk of contaminating the mains water supply by ingress of pollution as a result of depressurisation. (iii) In certain cases, the nuisance factor experienced by consumers owing to pressure surges caused by local users.

Flow of Mixtures through Pipes Standard formulae for pipeline performance calculations (e.g. pressure drop or head loss) incorporate fluid viscosity as a constant parameter, i.e. as a specific value dependent on the working temperature of the fluid involved. Such calculations are valid only for Newtonian fluids where viscosity remains constant with agitation or change in shear rate. Typical Newtonian fluids include water, aqueous solutions. mineral oils. hydrocarbons, syrups and some resins. Various other types of fluid are essentially non-Newtonian in characteristics, when the viscosity value under any specific conditions is an apparent one rather than a true one. Such fluids may be categorised as follows: (i) (ii}

Fluids containing solids in suspension, further categorised as slurries, sludges and pulps (paper stock). Thixotropic fluids, where viscosity decreases as agitation or shear rate is increased. Thixotropic fluid s exhibit a hysteresis effect in that their apparent or instantaneous viscosity is dependent on the previous history of the fluid. Figure l is a typical rheogram for a thixotropic fluid under laminar flow. Turbulent flow will tend to change the structure of the fluid, which will recover if left standing for a sufficient time. Fluids of this type include greases, soaps. starches, vegetable oils, varnishes, some resins , tars. asphalts , glues and some inks.

Laminar flow of thi xotropic fluid

t

SHEAR RATE -

Figure 1.

Flow of Mixtures through Pipes

55 7

(iii) Colloidal fluids which behave like thixotropic fluids but will not recover their original viscosity when agitation is stopped. Fluids of this type include colloidal solutions of soaps in water. and oils, lotions, shampoos and gelatinous compounds. (iv) Dilatent fluids where viscosity increases as agitation or shear rate is increased. Fluids of this type include clays and some slurries. (v) Rheopectic fluids where viscosity increases with increasing agitation in shear rate up to a maximum value at any constant rate of agitation. (vi) Plastic and pseudo-plastic fluids where viscosity increases with increasing shear rate. but initial viscosity may be so high as to prevent start of flow in a normal pumping system. These are also known as Bingham fluids. Strictly speaking, only plastic fluids are true Bingham fluids and include such products as drilling muds. thick mineral slurries and sewage sludge. Pseudo-plastic fluids exhibit a different shear rate-shear stress relationship. Fluids in this category include paper stock, detergent slurries, some paints and lacquers, some mineral slurries, mayonnaise, and cellulose acetate in acetone. A further sub-category or such fluids is known as yield pseudo-plastic, typical products orthis type being clay-water suspensions and polymer solutions. Complex mixture flow

Complex mixture flow may be homogeneous, pseudo-homogeneous, heterogeneous or complex, according to the phase(s) involved and the size of the solids involved (see Figure 2). Homogeneous flow applies only in pure liquid flow. Simple mixtures involve two-phase flows. complex mixtures multi-phase flows. In pseudo-homogeneous flow the solids are present in finely divided,

SINGLE-PHASE I GAS OR LIQUID)

HOMOGENEOUS

MULTI-PHASE fGAS-UQUID. GAS-GAS. LIQUID-LIQUJn. SOLID-GAS. SOLID-LIQUID)

FINE DISPERSIONS

COARSE DISPERSIONS

PSEUDO-HOMOGENEOUS

HETEROGENEOUS

~COMPLEX

0-HETEROGENEOUS

Figure 2. Regimes for homogeneous and heterogeneous flow.

'""

5 58

Performance and Calculations

highly dispersed form with almost uniform dispension in the carrier phase. The whole mixture then tends to behave as a single-phase fluid. With increasing size and/or quantity of solids, dispersion is coarser. yielding hetergeneous behaviour, i.e. with a pronounced solids concentration gradient along the vertical axis of the pipe. The actual velocity of flo'"' then becomes a critical parameter. With complex flow, some of the solids content behaves heterogeneously in pseudo-homogeneous flow, i.e. the flow can be described as homo-heterogeneous. These are thus two separate sources of friction and pressure drop . Figure 3 shows the likely regimes for heterogeneous and homogeneous flow with typical slurries related to particle size and solids specific gravity for flow velocities in the range 1.2 to 2.6 mjsec (4 to 8ft/sec). Homogeneous flow

Common practice with slurries is to use the Fanning friction factor to estimate frictional losses. This is a quarter the value of the D' Arcy-Weisbuck friction factor . However. this straightforward approach does not take into account the fact that solids present have the effect of suppressing turbulence which can reduce the actual friction factor by up to 15%, depending on the type of slurry. Empirical formulae can thus be more realistic. Pseudo-homogeneous flow

Pseudo-homogeneous flow is considered to exist where there is no measurable solids concentration gradient along the vertical axis of the pipe. For any given mixture this is related to the flow velocity. Below the critical velocity. flow will be heterogeneous; above the critical velocity. flow will be pseudo-homogeneous. Specifically. the flow condition can be expressed in terms of the C/CA ratio where Cis the solids concentration measured at an arbitrary part near the top of the pipe (usually 8% of the pipe diameter). and CA is the solids concentration at the centre of the pipe. If these two values are equal (i.e. C/ CA = 1). flow wil.l be homogeneous. Progressively lower values represent pseudo-homogeneous flow. degenerating into heterogeneous flow. The actual value of C/CA is influenced by particle size and concentration, as well as flow velocity. In a mixture of solids, finer particles will have a high C/CA and coarser particles a low C/ CA. As a general guideline, a C/CA of 0 . 8 or greater is necessary to maintain pseudohomogeneous flow. Heterogeneous flow

\!\lith C/CA values below 0.8 .flow will be a mixture of pseudo-homogeneous and heterogeneous, e.g. fewer particles remaining in suspense with coarser

Flow ofM ixtures through Pipes

559

particles tending to settle out. Flow will be fully heterogeneous at C/ CA values of 0 .l or less. V\lith heterogeneous flow, inertia effects are far more significant than viscous effects. Also. there may be several different flow patterns ranging from symmetric suspension through asymmetric suspension to sliding bed (solids sliding along the bottom of the tube), then stationary bed, finally leading to plugging (pipe blockage) .

PA RTICLE DIAMETE R (Largest 5 %. )

TYLF.R MESH IN CH ES MICRONS

( Ve locit y - -l to 7 !t/s)

~====~===~====l====~

HOOO :::j 10000

;-------~--------+--------+------~

p 250

-l

0 1H5

-+-------lf-----+-----+------t

oOOO

41)()() +--------+

HETEROG ENEOUS

4~""'"---+-----f-----t------t

21Xl0

\

"""

' ....

HOO 1----..l'""'"'--+-----1-------t------1

600

+------~'":-------+------+-------1

1·.

'

-+-•.::..;•::----+--......::~~

400

Based ton thick s lurries _ wtth fmc (IU25 m esh) -+--··'"':-·--f--'~vehicle -

~

'

~

'•••••

200 -+----"~'r.·.:-.-+----+----'""'1111..:::~-------j

C'OMPLEX~,...,.---..._...._-1

•.. '···

··~

I 00

HO

Based o n th in slurrie" o r s lurries with g raded

~====t==='~part icle. • ·~ size ••••

-

- ==:::::!

n'nr':':':"~-:-----1

'· · ••u u n u...&.uJ

~~-------+------~~------+-------~

40 -+-----+-----+-----r------t

20 -+-------+- HOMOGEN EO US

I' I 0 +-----1----+------T--------1 I .0

2.0

3.0

4 .0

SOLIDS SPECIFIC GRAVITY

Pig11re 3. Regimes for lwmogeneous and l~eterogeneousjlo w.

5. 0

5 60

Performance and Calculatio11s

Friction losses for heterogeneous flow are commonly based on the Durand formula. although empirical formulae are also used (see later). The Durand formula for the friction factor (fh) for heterogeneous flow is:

~h = fl1 where f, D V p1 pS C0 Sv Sv

(l + lSODg) (pS-pl pl) (-1-) V Jet; 2

312

x Sv

= = = = = =

friction factor for liquid (dimensionless) pipe diameter (ft) flow velocity (ft/sec) density of liquid (lb/ft 3 ) density of solids (lb/ft 3 ) drag coefficient (dimensionless) = volume friction of solids (dimensionless) = volume fraction of solids (dimensionless)

Homo-heterogeneous flow

With homo-heterogeneous flow, some of the solids behave heterogeneously in a homogeneous vehicle. This is a condition commonly encountered in practice where the carrier fluid contains a mixture of particle sizes. To determine friction losses in this case, it is necessary to split the solids content into fractions of different size and into homogeneous and heterogeneous portions. i.e. based on the respective C/ CA ratios. Thus, taking each sign fraction in turn and determining its C/CA ratio. multiplying this by volume concentration for that friction will give the proportion of that fraction having homogeneous flow . The remainder will be heterogeneous flow. Each fraction is split into homogeneous and heterogeneous flow in a similar manner. Friction losses are then calculated for each flow . Transition velocity

Normally. all slurry pipeline systems operate with turbulent flow. Operating under laminar-flow conditions will allow some settlement which in time can lead to unstable flow conditions, or even blockage. Flow velocities must therefore be above the transition velocity, determined by the critical Reynolds number. Transition velocities for Bingham plastic fluids are conveniently related to a dimensionless Hedstrom number (NHr). where: NHI = Reynolds number x plastic number

Flow of Mixtures through Pipes

where p = slurry density (lb/ft 3 ) V = flow velocity (ft/sec) D = pipe diameter (ft)

561

To = yield spec (lb/ft 2 ) g - acceleration of gravity 17 coefficient of rigidity (lb/ft sec)

The relationship between critical Reynolds number and Hedstrom number is shown in Figure 4 and is closely followed by most slurries. Mud and clay slurries can be the exception. Critical deposition velocity

The critical deposition velocity relative to heterogeneous flow is given by Durand as:

. _ K 2gD(Ps - Pt)

Vcnt

-

112

Pl

where K is an empirical constant g = acceleration of gravity D = pipe diameter (ft) Ps = density of solids (lb/ ft 3 ) Pt = density of liquid (lb/ ft 3 ) In all such cases. performance calculations can be based on a pseudo-viscosity or equivalent Newtonian viscosity.

~ 10'.-------~--------------~------------------------------, v

a:: z a:: lJ..I

co ~

:::)

z

LEGEND: o Cement rock slurry C> River mud slurries o Clay slurry ell Sewage sludge • Th02 slurries • Lime slurry

(/)

g 10~ 0

z

>lJ..I

0

0:: ..J

4:

u

f=

a::

u 10 1 +----.-~~.,.......................-.---.................,..........,.......,............~...,---------.......,......~...,....,.....,....,---.......,......---~~-.--J 10~ 105 lcf 10' HEDSTROM NUMBER (NHe)

Figure 4. Variation ofNxe.- with NHe for Binghamflow in pipes.

562

Performance and Calculations

Slurries

Slurries are liquids (usually water) containing abrasive solids in suspension, resulting in an increase in specific gravity over the carrier fluid. Slurries are categorised by the size o[ the solids as fines, sands and coarse. Slurries behave as non-Newtonian fluids with an apparent viscosity depending on the degree of suspension, which in turn is dependent on the flow rate. This may be generally related to a fall velocity or the minimum flow rate necessary to maintain the solids in suspension and prevent them from settling out. This, in turn, depends on the size of the solids. and also their concentration. Approximate flow velocities to retain solids in suspension in water for various classes of slurries are: Fines (particle size 7 5 J.Lm or less) Sands (particle size 7 5 to 8 50 J.Lm) Coarse (particle size 8 50 to 5000 ~tm)

0.9 m/ sec l. 5 m/ sec 2.1 m/sec

(3ft/ sec) ( 5ft/sec) (7ft/sec)

These empirical figures are based on a solids content of 30 to 3 5% by weight and solids of specific gravity 2.5 to 3 .0 (see also Table 1 and Figure 5).

I (,/') (,/')

I.I.J c::t:::

f-

(,/')

c::t:::

«

I.I.J

:::r:

(,/')

VELOCITY GRADIENT- dU/dr

Figure 5. Fluid classification ofslurries.

Flow of Mixtures through Pipes

563

Table 1. Some typical slurries Slurry

Proportion of solids by weight

Alumina Crushed chalk Clay Coke fines Gravel Lime Magnetite Sand

Soda ash

up to 50% up to 68% up to 60% up to 55% up to 25 % up to 65 % up to 60% up to 60% up to 60'Yo

Solids which form an intimate mixture yield a homogeneous fluid. in which case the pump performance is largely determined by the specific gravity and viscosity of the homogeneous mixture, which behaves as a normal fluid . Solids in suspension. however. form non-homogeneous mixtures and flow is then heterogeneous. with particles tending to slide at the surface of a 'bed' of solids. This 'bed' is only carried fully suspended if the fluid velocity is greater than the settling velocity of the solids involved. At lower fluid velocities there will be a corresponding degree of settlement producing a sliding rather than a suspended 'bed·. The quantity of water required to deliver a specific quantity of solids when pumping slurries can be determined from: Water quantity = K x T (W + ~) R sgo where T - weight of dry solids/ hr W = percentage of water R - percentage of dry solids For water quantity in litres and Tin metric tonnes K = 1.06 For ,,vater quantity in Imperial gallons and Tin Imperial tons K = 3. 7 5 For water quantity in US gallons and Tin US tons K = 4.02 sg 0 = specific gravity of dry solids Specific gravity figures for suspensions of solids in water are given in Table 2. Frictional losses

There is no complete agreement on the method of calculating the frictional losses in pipes carrying fluids with solids in suspension. Generalised data can give extremely inconsistent results when applied to individual systems. particularly if localised areas exist where the fluid velocity may be less than the minimum needed to keep the solids in suspension. It can thus prove

Vl

Table 2.

0'1

Specific gravity of suspensions of solids in water

Percentage by weight of solids

Ratio water tosolids

~

~

Specific gravity of dry solids

..;, 0 ~

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.5

4.0

4 .5

5.0

::3

:::. :::!

C")

<'>

:::.

Specific gravity of solution 10

9.1

1.05

1.05

1.06

1.06

1.06 1.06

1.06 1.07

1.0 7 1.0 7

1.0 7

:::! !:l..

1.07

1.07

1.07 1.08

1.08

1.09

1.09

~

(';"

.s::

15

5.66:1

1.08

1.08 1.09

1.09

1.09

1.10 1.10 1.10 1.11

1.11

1.11

1.11

1.11

20

4:1

1.11

1.11

1.12

1.12

1.13

1.14

25

3:1

1.14

1.15

1.15

1.16

30

2.33:1

1.17

1.18

1.19

35

1.87:1

1.21

1.22

40

1.5:1

1.25

45

1.22:1

50

1.12

1.12

1.13

1.13

1.14

1.14 1.14

1.15

1. 15

1.15

1.1 6

1.16 1.1 6

1. 1 7 1.18

1.19

1.19

1.17 1.18

1.18

1.19

1.19

1.19

1.20

1.20

1.21

1.21

1.22

1.23

1.24

1.2 5

1.20

1.21

1.22

1.23

1.23

1.24 1.24

1.25

1.25

1.26

1.26

1.2 7

1.29

1.31

1.31

1.23

1.25

1.26

1.27

1.28

1.28

1.29 1.30

1.30

1.31

1.32

1.32

1.33

1.35

1.37

1.39

1.26

1.28

1.29

1.30 1.32

1.33

1.34

1.35

1.36

1.36

1.3 7

1.38

1. 39

1.40

1. 43

1.45

1.47

1.29

1.30

1. 32

1. 34 1.36

1.37

1.38

1.40

1.41

1.42

1.43

1.44

1.45

1.4 6

1.47

1.51

1.54

1.56

1:1

1.33

1.35

1.37 1.39

1.41

1.43

1.44

1.46

1.47 1.49

1.50

1.51

1.52

1.53

1. 55

1. 60

1.63

1.67

55

0.91:1

1.3 7

1.38

1.41

1.43

1.44

1.49

1.51

1.53

1.5 5

1.56 1.58

1.59

1.61

1.62

1.65

1. 70

1. 75

1.79

60

0.67:1

1.43

1.46

1.48

1.51

1.54 1.56

1.5 8

1.61

1.63

1. 65

1.6 7 1.68

1.70 1.72

1. 75

1.82

1.87 1.92

65

0.54:1

1.48

1.51

1.55

1.58

1.61

1.64

1.6 7

1.69

1.72

1. 74

1. 76

1. 79

1.81

1.83

1.8 7 1.95

70

0.43:1

1.54 1.57

1.62

1.65

1.69

1. 72

1.75

1.79

1.82

1.85

1.88

1.90

1.93

1.95

2.00

75

0.33:1

1.60

1.69

1.73

1. 78

1.82

1.86 1.90

1.93

1.97

2.00

2.03

2.06

2.09

2.1 5 2.29

1.65

2.03

2.08

2.10 2.20

2.27

2.40

2.50

[

o· :::! ""

Flowoflvlixtures through Pipes

565

difficult to estimate for centrifugal pumps the total head to be supplied by the pump and thus to determine the most efficient working point. A general formula which can be used is: .6-Ps

---1 ~Pw

= KCv

D(sg- 1) x Vs jd(sg - 1) x y2

where the constant K is determined from emperical data where .6-Ps = pressure drop when transporting solids ~Pw = pressure drop for water concentration of solids by volume Cv - pipe diameter 0 d = mean particle diameter sg - specific gravity of solids settling velocity of solids (in still water) Vs - flow velocity v Output

Typically, the output from a slurry pump will follow the characteristics shown in Figure 6. with the output curve consisting of three zones: (i) delivery distance, (ii) delivery distance within the normal working range of the pump, (iii) loss of output over any further delivery distance.

~ «l ..... ~

0~

C<~>

11):::::

.....

Output (solids)

6..

'--'

::l

;(

~

':1

E

600

::l

0..

2

II)

.:::.

u

.... .......
::l

400

3

..... 0

g_..o::

~

~ 0

1: c:

c:

.2

(;

.....

c:

II)

u c: 0

<.>

',~I

200

;:; 0.. ::l

0

0

900 1200 600 Delivery pipeline length in m

0

>

I. Delivery distance. 2 . Delivery distance within the normal working range of the pump.

Figure 6.

3. Loss of output over any further delivery distance.

5 66

Performance and Calculations

The first zone is critical in that it determines the suction conditions. At a high flowrate, when the upper limit is reached. the vacuum becomes critical. i.e. the flowrate at the attainable mean specific gravity of the mixture is so high that the corresponding vacuum on the suction side of the pump installation is equal to the critical vacuum, which may not be exceeded and thus constitutes the limit of the attainable vacuum . Figure 7 shows the critical vacuum applying to a delivery pipeline length 1 1 . The critical vacuum is reached at working point P 1. If the critical vacuum is exceeded, e.g. as a result of shortening the delivery pipeline. with the result that a lower resistance curve applies (see 1 2 in Figure 7), cavitation ensues. If it is desired to operate with a shorter delivery pipeline, the speed n 1 of the pump must be reduced to the point where the intersection of the corresponding pump characteristic and that of the shorter pipleline falls within the normal working range of the pump. This implies that the point of intersection (working point P 3 ) must coincide with a flowrate at which the vacuum is slightly below the critical level corresponding to the lower pump speed. This is shown in Figure 7. The two working points P 1 and P 3 have a virtually equal flowrate . If the delivery distance is less and the specific gravity of the mixture remains virtually unchanged, the output at these (too) short delivery distances will also remain virtually constant, as shown by the horizontal section 1 of the output group (Figure 6 ). I Hman

40 0

~ E c::

30

20

-

_1----.....

_:----r- --'

r--

PJ

Pump speed~._ n2 < n 1 • / P2

~p,

Pump speed n 1'

I

Pipeline length L2 <

v

/

c:

"'E

Pipeline lengt

10

··-

-

0

Vacuum

8 0 ~

4

E

2

u

<'l

>

I

I

I

__-_

Decisive vacuuml 6 at speed n,: /

E c:: :::l :::l

I

Decisive vacuum at speed n~ : \.

0

. .v

/

~"-· p2 PI

-f-

/

500 I0000 1500 Flowrate (lis)

Figure 7.

2000

L,

Flow of Mixtures through Pipes

56 7

Critical velocity

If the delivery pipeline is lengthened. the specific gravity of the mixture to be pumped must be reduced as soon as the critical velocity (the second bend in the output curve) is reached. This is necessary to avoid a subcritical situation, leading to sedimentation. At what is in effect an excessive delivery distance, pumping a mixture of such specific gravity as to cause sedimentation in the pipeline is to risk total blockage. In practice. this danger can be averted by admitting more water. The specific gravity must be reduced just sufficiently to restore a supercritical situation. In approximate terms. it can be stated that the critical flowrate of a soil/ water mixture at the reduced specific gravity differs little from the critical flowrate at the highest attainable mean specific gravity This implies that, when delivering into pipelines that are too long, the specific gravity must be reduced when a certain flowrate. which is virtually constant, is reached. This is the flowrate corresponding to the critical velocity. Increasing the delivery distance will therefore result in a lower output of solids. When pumping mixtures of vvater and fine sand (less than 7 5 :m), or clay, e.g. soil and silt, or combinations of these materials , the critical velocity in the delivery pipe will be very low. Moreover, the resistance offered by the pipeline is less than would be the case during the transport of mixtures of water and coarser sand under comparable circumstances. As a result. the bend in the output curve, between line section 2 (the actual working range of the pump) and section 3 (the area relating to delivery distances that are too long), will coincide with an extremely high delivery-distance value, or will be missing altogether. The output curve will then be as shown in Figure 8 and consist of only two sections. Sludge

Sludge is defined as a liquid (usually water) containing large solids with a particle size of 6 mm I 4 in) or greater, the solids being soft rather than abrasive in nature . These solids may be further describes as 'stringy', 'clogging', etc., although a more useful classification would be 'soft' and 'hard' sludges because the solids may be hard and abrasive in some cases. Sludges may also contain a proportion of smaller solids or sand which could have an abrasive effect, affecting pump material choice, clearances. etc. Thus, sludges may have some of the characteristics of slurries. Sewage, on the other hand, mostly involves soft solids.

e

Frictional factor

Frictional losses involved in th e transport of sludges and sewage are difficult to evaluate other than on empirical lines. However, where the mixture is

Performance and Calculations

5 68

reasonably homogeneous. a friction factor may be calculated on the basis of a pseudo-Reynolds number. This takes the form:

R - AQ e-

cxdY

where Q is the flow rate A is an empirical factor Cis the consistency of the mixture dis the solids' diameter Values of the exponentials x and y are determined empirically for different fluids. Typical values for pulps are x = 1.15 7 andy= 1. 79 5. The friction factor, for insertion in standard function formulae. is then determined as: K

fs

= (Rez)

where K is a constant for a particular sludge. The value of the exponential z also varies with the type of sludge, but is typically of the order of 1.63.

~

Mixture nowrate

1200

L.

I'· .................

~

~:? 1000

.........

~v

~

800

----

'-....... ~ ......

600 c:

.2 ~

...

20

c: Cl) u c:

10

0 u

Vol.
-

-

0

0

> .... ;:l

Output in clay material

I

600

0

............

..c:

.-, 6.. E E 400

c: ·-

'5

I

I

P--i

-------1--~

;:l

0.. Cl)

I

i I

i

!.Delivery distance. 2. Delivery distance within the normal working range of the pump.

o...:!

; t>

0~

200

--

Cl)

..... Cl)

0..

0

800

1600 2400

320

4000

4800

Delivery pipeline length in m

Figure 8.

Flow of Mixtures through Pipes

569

Table 3. Head-capacity factors for stock

Stock consistency (%)

Head factor (Hp)

Capacity factor

Head-capacity factor

(Qfl

(H p/Qp)

1.00 1.00 1.00 1.00 0.99 0.98 0.97 0.95 0.93 0.90 0.87 0.83

0.99 0.99 0.98 0.97 0 .96 0.92 0.87 0.80 0.72 0.62 0.52 0.42

0.99 0.99 0.98 0.97 0.95 0.90 0.85 0.76 0 .67 0.56 0.45 0.35

l.O 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

6.0 6.5 7.0

100

........;;

ex: ol){)

0 < ~

!"... ..........

80

r

(a)

--

F:: ......... r-- ....._

1---

-r-- ....._ ....._

...........

..........

0 < 70 0..

..........

..........

<(

60

<(

u

z

UJ

r--r--

5

r

~

Vl

z

u

0

3 ~ 4 >-

0

"'

u ~ u

.......... ~ ......

0

61;;

UJ

::r: .)-o 0

40 120 80 100 20 60 % WATE R CAPACITY AT MAXIMUM EFFICIENCY

100

i"""r-...

ex:

0

t;90

t--........

3

<( !J...

~ 80

(b)

-r---

t--

r-- r-- 1---

r-..r-..

0 < 0.. 70 < u

-r---..

0

~

>-

-

u 5 ~ rVl

1---.t---.....

zVl 0 u ~

4

6

u 0

o·o

!;;

<(>

UJ

::r: 50 t)

20

40

60

80

100

120

% WATER CAPACITY AT MAXIMUM EFFICIENCY

figurP 9. Deterrninat.ion of head-capacity correction factors: (a) chemical stock; (b) mechanical and reclaimed stock.

Perfo rmance and Calcr.tlations

5 70

.,., 2 ~

,

_......,

I--'

1..--

1.5

~

,... .......

l.,...--' ~

_,.,.,.

l.--- ......

ll"'v L.. ~

0. 1

~

1--"j..-

~ l,..oo

lo--""

......

--~

~ ~

,... L..oo

_..,

...

-"""'~

---~

~

~ .....

,..

,..i--

.....

~

~

...

~ ~

ioo""'

~

... ....

~

,.....

3.75

~"""' 3. 5

1.---'

.J'

..,.I'""

,

3.25

~

3

L,..o

......

~"""

....... p

::l

.;'

'"j" 0. 05

....

...,.,.

(/} (/}

0

.....l

0 0.04 .........

,..... ....... ,... '-"""

,.

~

,......

,.

-

~

lo-""

<(

.........

!..""

U)

,....

::r::

I--'~

0.03 ~

v

p

ioo" 1,.

-

0

~

>u z

~

c;.,;.;;;

~

..... ~""""

l.,...--' ~

~

,...

UJ

1-(/')

"""

(/")

z

0

u ::,t

u

L..

,.....__ '--

0 f(/")

l,..oo

~ ~

0.0 15

0 .0 1 200

~

300

400

2

lo-""

- ~"'

;..."'

0.02

~

I"""'

l.,...--'

"""""

........

.....

,

2.5

, ... ~

,.... ,....

.,

4

~

~~ ~

~

~

...... ~

~

~

4.25

L..oo

~~ ~

_.., ~

........

,....

..,.,.....

....

_..!--"'

[....; ~ lo-"""

4.5

.... ~

L...... ~

~~

5

.... ~

~

........ v

..,.,.,., , ,~ ,..,.. ,. ,.. ~ ~ ~""' ,.,., ...... .... I"' _.., , ~ ~ L c ..,.,.,., ,.,., p ....... ,... ;;;;; P" I"' ...... v ~ 0.06 ,...... 7 ...... ....... ,.,., ...... L,...-o ""',...., ... / ,. ....~ ,.... ~ ,...... ...... ..,.,. ~ ....... 0 OR

,.... [/

..,,.,., ,... .......""" ~

........ ~

~

~

, ..,.

I--"

5 .}

~~

~

~

~.,.,

P'

0.09 l.,...--'

,..,. 1--"

,

l.,...--' ~

....... 7

~

""

~~

.... 1.---'

"""""

....... ~ I"'

,. v ,..

--

, ,,

3

6

500

600

700 800 900 10000

Gal/ min

Figure 10 . Friction loss with pulp stock: 12-in pipe.

15000

2000

Flow of Mixtures through Pipes

5 71

Paper stock (pulp)

Paper stock is basically in the form of sludge with a specific type of solids (paper pulp). With low consistencies (i.e. less than 1% pulp by weight), flow and friction losses can be calculated as for water. With higher consistencies there is an increasing derating or pump performance (see Table 3 ). Frictional losses increase rapidly with stock consistencies above about 2% by \veight. A rriction [actor can be determined based on a pseudo-Reynolds number. viz:

where K = an empirical constant, dependent on the type of pulp Rc = pseudo-Reynolds number K 1 = a constant depending on the units employed C = stock consistency% D = pipe diameter x. y and z are exponents with the typical values: X = 1.63 y = 1.16 z = 1.8. For Q in gal/min and Din ft

K1 = 17.2 For Q in I/ min and Din em

K1 = 8.18 (see also Figures 9 and 10).

Compressible Flow in Pipes Air, steam and gases are all compressible fluids and the D' Arcy equation used for determining pressure and head losses with liquid flow is no longer applicable because the density of gases and vapours changes considerably with changes of pressure. However, for simplified general engineering calculations not requiring great accuracy, liquid D' Arcy flow formulae may be used if the pressure drop involved is less than 10% of the inlet pressure. Use of such formulae is also sometimes extended to pressure drops up to 40% of the inlet pressure. provided in this case the specific volume is taken as the average of the upstream and downstream conditions. The real flow of a pressurised gas through pipes differs appreciably in a number of important characteristics from the flow of liquids in pipes. Pressure. for example, drops at an increasing rate along the pipe, rather than with a constant pressure gradient. At the same time, velocity tends to increase up to a maximum defined by V = %kgRT for air. but subject to a limiting or maximum length, which must correspond to the end of the pipe. At this point the pressure gradient in infinite, i.e. the pipe is effectively closed. In this equation, k is the ratio of specific heats at constant pressure to constant volume. R the individual gas constant, and T the absolute temperature (degrees Rankine). An alternative formula isM= 1 %k (=0.845 for air), where M is the Mach number. The general equation may be written in the same form as the D' Arcy equation for fluid flm.v, but with the addition of an extra term representing the pressure drop required to increase the flow momentum: 6P f pV 2 - dV L = D X 2 + ,BpQ dL where 6P is the pressure drop Lis the pipe length fis a constant friction (but dependent on surface roughness) Dis the pipe diameter pis the gas density Q is the specific volume or gas dV /dL is the velocity gradient

Compressible Flow in Pipes

5 73

fJ is a factor of the order of unity and normally taken as 1.0 (i.e. can be eliminated from the equation). Actual flow conditions may range from adiabatic to isothermal. Adiabatic conditions are only likely to apply in short, well-insulated pipes where no appreciable heat is transferred to or from the pipe. Isothermal flow, or flow at constant temperature, is commonly assumed as more consistent with normal practice, especially for long pipes. In fact, most practical pipelines will generate polytropic flow conditions, which are virtually impossible to analyse. The assumption of isothermal flow is thus a practical compromise. Isothermal flow

With isothermal flow, a formula developed from basic principles is: f pV 2 L'lP D X 2 kM2 - 1 L The friction factor is dependent on the Reynolds number of flow and pipe roughness. It can be assumed independent of Mach number. The Reynolds number will be constant for isothermal flow, but may vary with adiabatic or isentropic flow (and certainly with diabatic flow), in which case a mean value can be assumed. The Reynolds number is a dimensionless quantity, given arithmetically by: pVD

Re = - 1-L

VD

v where p = the mass density f.L = viscosity v = kinematic viscosity

in units consistent with velocity (V) and { pipe diameter (D)

For air at standard temperature v = 1. 5 68 Thus Re

= =

X

1 o- 4 ft 2 /sec.

531.5 VD 530 VD (with sufficient practical accuracy).

where Vis in ft/ sec Dis in inches. The friction factor (f) is common for all fluids (i.e. gases and liquids) and is normally determined from empirical charts. For laminar flow, the friction factor is dependent only on Reynolds number and is numerically equal to 64/ Re,

57 4

Performance and Calculations

laminar flow being defined by the Reynolds number not exceeding 2000. For turbulent flow and smooth-bore pipes, the Reynolds number can be calculated from the following empirical formula: f = 0.3164 Re0.25

As the Mach number (M) approaches 0, the denominator in this equation comes closer and closer to unity, reducing the equation to the same as that for liquid flow. There is some justification for using the D' Arcy formula for compressible-flow calculations (as mentioned initially) as M60 (i.e. consistent with short lengths of pipes with resulting low pressure drops). This also implies that at very low Mach numbers, compressible flow can be treated as incompressible. Pressure gradients (~P /L) will. in fact, be ,within 5% of incompressible flow values at Mach numbers up to about 0.18 for air. A complete working formula for isothermal flow, expressed in terms of mass flow rate (Qm) is:

144gA 2

pl) D P2

- it ( Vt-+ 2\og-

where A = g = V1 = L = f = D = P1 = P2 =

cross-sectional area of pipe (ft 2 ) acceleration of gravity= 32.2 (ft/sec 2 ) specific volume of gas (ft) jib) length of pipe (ft) friction factor pipe bore (ft) absolute pressure (entry) absolute pressure (exit)

For long gas pipelines (where velocity gradient can be ignored) this reduces to: 2

Qm 2 = (144gDA VrfxL

x

)

(Pi-P~) P1

Or expressed in terms of volume flow rate (Qv) in ft 3 /sec:

Ov = 114.2

P~ - P~ x o ( fLT sg

5)

X

where Tis the absolute temperature (degrees Rankine) sg is the specific gravity of the gas.

Compressible Flow in Pipes

57 5

Other working formulae of similar derivation are:

Weymouth formula :

Ov

=

28.0D2.on7

( Pf - P~) Lsg

520 T

Panhandle formula : Qv = 36.8ED2.6182

p 21 _L p-_)7 ) o. s3 94 (

where E is an efii.ciency factor, normally taken as 0.92 for average conditions. The Panhandle formula is widely used for natural gas pipelines from 6 to 24 in diameter. Limiting values

Maximum possible velocity (V"' ) in a pipe is source velocity (M = ] ), given directly by: v~ = 12)kgPVv

where V"' is in ft/ sec k is the ratio of specific heats of the gas Pis the absolute pressure (lbf/ in 2 ) Vv is the specific volume of gas (ft 3 /lb)

Maximum pressure (P*) can be determined on the basis of continuity, viz:

Hence

P* = Vt = M1 = M Jk 1 P1 V* M•· where the suffix 1 refers to initial concentration . Hence (and because the velocity of sound is constant under isothermal conditions) :

57 6

Performance and Calculations

Unity Length (L"') can be determined from the general equation:

i- 1)

fLO* = (kMl

1 -loge kM2 l

or

L'= ~ ( (k~I ~ 1) ~ log,k~I) The implication of this is that velocity of gas flow can go on increasing in a pipe up to a maximum Mach number ofl/Vk. This increase ceases at a limiting length ofpipe (L*). which must be at the end of the pipe. If the actual length of pipe is greater than L*, initial conditions will have to be adjustecf to reduce M 1 so that the actual pipe length is less than, or equal to, L*. At the same time, the limiting pressure ratio (P*/ P t) and limiting length (L *) are dependent only on initial velocity (Mach number) and the k value of the gas. Pressures and lengths between two sections of a pipeline can thus be expressed as follows (if the Mach numbers at each section are known) : P2 M1

fL

D

Adiabatic flow

Similar treatment applies for adiabatic flow, although the corresponding formulae are more complicated and may require working as a series of approximations in order to reach real values in particular cases. In general, the pressure, temperature and velocity will always be slightly less than those for isothermal flow, but the limiting length will be similar. The di1rerences are usually small enough to be negligible, except at higher Mach numbers, and thus, for simplification of calculations, isothermal formulae can be used for subsonic adiabatic flow. Limiting velocity:

This is given directly by: , . - - -- - - -

V*

1

2(1+ k; 1Mi) k+ l

Compressible Flow in Pipes

57 7

Limiting temperature:

2(1 +~Mf) k+l Limiting length:

L* = D (l - Mi) F kM 2 1

+

k+ 11 2k

(k+ l)Mi

oge

Limiting pressure:

2( l

k- l +-Mf ) 2

k+l

Stagnation state

Flow is possible between two extremes. At one extreme, velocity is zero and temperature is a maximum because all the kinetic energy is converted to enthalpy. The speed of sound is also a maximum (stagnation point or stagnation state). At the other extreme, the velocity is a maximum and the temperature falls to absolute zero, all the enthalpy being converted into kinetic energy. The speed of sound ls then zero (zero temperature state). Between these extremes the practical flow may be subsonic, transonic or supersonic (Figure l) although the zero temperature state can never be reached (i.e. it is a hypothetical condition). At the stagnation state: 02 vz - + ho=-+h

2

2

or ho=

vz 2 +h

57 8

Performance and Calculations - - M
I

I w

I

""0

c

.2

::J

..0

0

"' ....v I

'Jl

'-

0

O..J

>,

u

52 v

;>

M =-I OR V::: c ---...M> I

E

I ·~

g

.c

81 ..:=, q

ro ~

Supcrson ic

I I

..J

Hypersonic

vu

Velocity V-+

Figure 1.

From the general gas relationship it follows that the stagnation temperature (T 0 ) is given by:

v2

To= T + 2 sp where sp =specific heat at constant pressure. Alternatively, To= 1 + k- 1 x M2 T 2

v

where M =Mach number= - . c The stagnation pressure can be derived as: k

~o = (i't

_L

=

(l+k 1M')'' 2

This may be expanded in the form: 2

pV { Po=P+2

2

l

M 2- k 4 +-+--M 4 24

+ ... }

This can be compared with the equation for incompressible flow: pV2 Po= P+l The difference between these two equations represents the effect of increased gas density due to compressibility, generally termed the compressibility factor. Values of the compressibility factor range from unity at very low Mach

Compressible Flow in Pipes

5 79

numbers (where there are no compressibility effects), up to 1. 2 76 as the Mach number approaches 1 (velocity approaches the speed of sound in the gas) . Besides increasing the dynamic pressure of compressible flow, compared with incompressible Aow, the rising value of the compressibility factor can also affect the flow velocity through ducts with varying area . The relationship between area and velocity changes is, in fact. a function of the local Mach number, and can be rendered in the form: dA A - = - (M 2 -1) dV V With subsonic flow . a decrease in area produces an increase in flow velocity and vice versa (similar to incompressible flow), i.e. area and Mach number changes are opposite. The flow velocity may be sonic only at a constant section. V\lith supersonic flow, a decrease in flow area produces a decrease in flow velocity and vice versa, i.e. area and Mach number changes are the same. Flow from stagnation conditions

Gas compressed and stored in a reservoir is essentially under stagnation conditions, where velocity is zero and the pressure and temperature are known (or can be determined). Where the reservoir is used as a supply, the velocity. temperature and pressure at any other section of flow are determined basically from the following relationships:

Velocity at any arbitrary section:

V=

2spT0

p) .\ ( 1 - Po

Alternatively. for adiabatic flow, the velocity at any section can be determined from the temperature at that section:

Flow rate Flow rate can be determined as the mass flow, i.e. mass flow = VAp. or directly as the product ofV and A in numerically consistent units: Dimensions are

L

T x L2 =

llow rate

L3

=T

5 80

Performance and Calculations

Pressure at any arbitrary section: Po p =

2)--r ( l+TxM k-1

k

1

Temperature at any section: T=

To

l+k-lxM2 2

At any (constant) section where the flow is sonic, the flow conditions are described as critical, yielding a critical temperature (T*) and a critical pressure (P*). where: T*

2

To

k+1

(adiabatic or isentropic flow) k

Po* -_ (k +2 1) n P

(isentropic flow only)

Note: For air, where k = 1.4, the value of critical pressure is

(_2__) b·: = 2.4

0.52 8.

That is, the critical pressure is 52.8% of P 0 . Similarly, the critical temperature can be calculated as 83.3% ol'T0 .

Critical area: The relationship between the critical area (A*) or throat area where and the area of any other section (A) is given by:

f.1.. =

1

A A* 2 =

-1 (1

M

+ 0.2M 1.2

3

2 )

for a1r. .

Nozzle flow

Flow at the throat or a nozzle, supplied by a reservoir or similar source under stagnation conditions, will be sonic if the critical pressure is greater than the receiver pressure (Figure 2a). This means that the flow will be critical. The flow velocity follows from calculating the critical temperature, from which: Flow velocity c

= 49 Jr ftjsec

Compressible Flow in Pipes

Reservoir

Reservoir

p• > Po

Po To

Po To

V 0 =0

Y 0 =0

5 81

*Po < Po

Figure 2.

(The velocity of sound in air - c = 49T ft/ sec where T is the absolute temperature in degrees Rankine.) If the critical pressure is less than the receiver pressure, then the flow cannot be critical (Figure 2b ). In this case the flow will be subsonic and the exit pressure will equal the receiver pressure. The temperature can be calculated from the general formula, or from: p ¥ =

T,

To(r~)

The velocity is likewise calculated from the general formula. Similar analysis applies where the nozzle is of convergent-divergent form (Figure 3). In this case it is necessary to establish whether the flow is critical or not (at the throat). The throat velocity can be determined accordingly, and from this the final exit velocity from the divergent section. Flow through a nozzle can also be rendered directly in terms of flow rate and a discharge coefficient, this being a convention for engineering calculations. The complete nozzle formula is: Mass flow = Ax Ec x

ox d 2 Jh yiP;7T

where A - a constant depending on the units employed E - coefficient for the velocity of approach 1

where m =

cross-sectional area of nozzle cross-sectional area upstream

A2 A1

c - nozzle coeffi.cien t o = expansibility factor allowing for the change in air density which occurs during acceleration through the nozzle Reservo ir

Po To Yo = 0

Figure 3.

58 2

Performance and Calculations

d = h = P2 = T =

1 - 0.07h f l or va ues of circa 0.16 1 3 . 6 p2 (and h in inches wg and P 2 in inches of mercury) diameter of nozzle pressure drop across nozzle absolute pressure on downstream side of nozzle absolute temperature on downstream side of nozzle.

If Tis in oR. P 2 in inches of mercury, h is in inches wg and d is in inches. a value of A= 0.1148 gives the mass flow in units oflbj sec. For a specific nozzle profile, the formula can be simplified by the use of a nozzle constant appropriate to that particularly geometry and nozzle size. Rendered as a solution for conventional flow rate (Q): ' Q = K(Tl/Pt)Vh JP2/T2

where K = T1 = T2 = P1 = P2 = h =

nozzle constant absolute temperature at specified inlet point absolute temperature at nozzle or specified point downstream absolute pressure at specified inlet point absolute pressure at nozzle or specified point downstream pressure drop across nozzle.

Simplified orifice formulae

An orifice is a simple form of nozzle. formed by a circular hole cut in a thin flat plate. Flow can again be determined with reference to an empirical discharge coefficient or orifice coefficient. This will be much lower than for nozzles because of the less streamlined flow but, owing to the simpler form of the nozzle. will be Jess subject to variation. Thus nozzle coefficients may vary between 0.90 (or less) and 0.995, depending on size and geometry, whereas an orifice coefficient can be expected to be of the order of 0. 61, regardless of size, and differing only if the orifice has a well-rounded, as opposed to a sharp, entry. Very much simplified formulae can therefore be applied to assess the discharge of air through orifices, and the following are generally satisfactory for straightforward engineering calculations: (1) For upstream pressures above 14. 7lbf/in 2 g

218xAxPu v'460+T

0 (ft 3 /min) for sharp-edged orifice= -~~==::::---

-

or

172

X

d2

X

Pu

J460 + T

(a)

Compressible Flow in Pipes

3

Q (ft /min) for rounded-entrance

orifice~

417

X

A X Pu

J460 +T

58 3

(b)

or

(2) For upstream pressures below 14. 7lbf/in 2 g 210

X

A

X

Pu

Q (ft 3 /min) for sharp-edged orifice=---;::::::::.~=~

(c)

J460+T

166xd2 xPu

or

J460+T 3

Q (ft /min) for rounded-entrance

A

X

Pu

X

d2

X

Pu

,. . ., -J-;=4===6O:::=+====:::c:T-

where A = Pu = d = T =

(b)

X

J460 + T

255

or

l. (a)

324

orifice~---;::::::::.~=~

orifice area (in 2 ) upstream pressure (lbf/in 2 g) orifice diameter (in) upstream air temperature (°F)

Q (ft 3 / min) or Q (ft 3 / min) or ·

= 11.9 Ax Pu = 9.4d 2 Pu ~ 18.3 A x P u ~ 14.4 d 2 Pu

2. (c)

Q (ft 3 / min) = 11.5 A x Pu or = 9.05 d 2 Pu

(d)

Q(ft 3 /min) ""17.7 A X Pu or ~ 13.92 d 2 Pu

(d)

Losses in Bends and Fittings Pressure losses in a piping system due to changes in the shape of the flow path or changes in cross-section as produced by bends, valves, fittings. etc., can be evaluated in three different ways: (i) as a resistance coefficient (K) for the component involved (ii) as an equivalent length (L/D) (iii) as a flow coefficient (Cv).

Resistance coefficients

Specifically because a bend, valve or fitting, etc .. presents additional resistance to flow, there is a velocity head loss at that point which can be expressed directly as:

where HL is the velocity head loss K is the resistance coefficient for the component involved. Table 1 gives a range of worked out values. Pressure drop ( 6P) can also be calculated directly from resistance coefficient: KV 2 w 6P=-2g where w is the specific weight of the fluid. For clean water: 6P (lbf/in 2 )

=

0.00673 KV 2

when v is in rtjsec 6P (bar)

= 0.000044

where V is in mjsec

KV 2

Losses in Bends and Fittings

585

Table 1. Head loss io [eet from resistance coefficient'

...,

~

Flow velocity- ft/sec (m/sec)

u c c ..., ro ·u

....,

·-

V)

...,

Q.)

0

.~ !:::

a::

u

0.05 0.1 0.2 0. 3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 l.l

1.2 1.3 L.4 1.5 1.6 1.7 1.8 1. 9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.1) 3.0 3.1 3.2 .U

3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.l 5.2 ').3 5.4 5.5

l (0.3)

2 (0.6)

3 (0.9)

4 ( 1.2)

(I. 5)

6 (1.8)

7 (2.1)

8 (2 .4)

(2.75)

10 (3.0)

0.00080 0.00200 0.00300 0.00500 0.00600 0.00800 0.00900 0.01100 0.01200 O.tH400 0.01600 0.01710 0.01860 0.02020 0.021 70 0.02330 0.02480 0.02640 0.02800 0.02950 0.03106 0.03261 0.03416 0.03571 0.0.3726 0.03881 0.04036 ().04191 0.04346 0.04501 0.04659 0.04814 0.04969 0.05124 0.05279 0.05434 0.05589 0.05744 0.05899 0.06054 0.06212 0 .06367 ().()6 522 0.06677 0 .06832 0.06987 0.07142 0.07297 0.07452 ().07607 0.07765 0.07920 0 .080 75 0.08230 0.08 38S 0.08543

0.003 0.006 0.012 0.019 0.()25 0.031 0.037 0.044 0.050 0.056 0.06 2 0.068 0.074 0.081 0.087 0.093 0.099 0.106 0.112 0.1.18 0.124

0.007 0.014 0.028 0.042 0.056 0.070 0.084 0.098 0.112 0 .125 0.140 0.154 0.168 0.182 0.196 0.210 0.224 0.238 0.252 o.26o 0.280 0.294 0.308 0.322 0.336 0.350 0.364 0.378 0.392 0.406 0.419 0.433 0.447 0.461 0.475 0.489 0.503 0.517 0.531 0.545 0.559 0.573 0.587 0.601 0.6] 5 0.629 0.643 0.657 0.671 0.685 0.69R 0.71 2 0.726 0.740 0.755 0.769

0.013 0.025 0.050 0.075 0.100 0.12 5 0.149 0.174 0.199 0.214 0.249 0.274 0.299 0.324 0.349 0.374 0.398 0.423 0.448 0.473 0.497 0.522 0.547 0.572 0.597 0.621 0.646 0.671 0.696 0.721 0.746 0.771 0 .796 0.821 0.845 0.870 0 .895 0.920 0.945 0.9 70 0.994 1.019 1.044 1.069 1.093 1.118 1.143 1.168 1.19 3 1.2 J H 1.243 1.268 1.293 1.3 J 8 1.342 l.367

0.019 0.039 0.078 0.117 0.155 0.194 0.233 0.271 0.311 0.349 0.388 0.427 0.466 0.505 0.544 0. 583 0.621 0.660 0.699 0.738 0.776 0.815 0.854 0.893 0.932 0.971 1.009 1.048 1.08 7 1.126 1.165 1.204 1.243 1.282 1.321 1.360 1.398 1.437 1.476 1.514 1.553 1.592 1.631 1.670 1.709 1.748 1.786 1.825 1.864 1.903 1.942 1.981 2.020 2.058 2.097 2.136

0.030 0.060 0.112 0.168 0.224 0.280 0.335 0.391 0.447 0.503 0.559 0.615 0.671 0.727 0.783 0.839 0.895 0.951 1.007 1.063 1.118 1.174 1.230 1.286 1.341 1.397 1.45 3 1.509 1.565 1.621 1.677 l. 733 1.789 1.845 1.901 1.957 2.013 2.069 2.125 2.181 2.236 2.292 2.348 2.404 2.460 2.5 16 2.572 2.628 2.684 2.740 2.795 2.85 1 2.907 2.%3 3.019 3.075

0.039 0.071) 0.1 52 0.228 0.304 0.381 0.457 0.533 0.609 0.685 0.761 0.837 0.913 0.989 1.065 1.141 1.217 !.293 1.369 1.445 1.522 1.598 1.674 1.750 1.826 1.902 1.978 2.054 2.130 2.206 2.283 2 .359 2.435 2.511 2.587 2.663 2.739 2.8 15 2.891 2.967 3.044 3.120 3.196 3.272 3.348 3.424 3 .500 3.576 3.652 3.728 3.806 3.882 3.958 4 .034 4.110 4.186

0.050 0.100 0.199 0.299 0.398 0.497 0.597 0.696 0.796 0.895 0.995 1.090 1.190 1.290 1.390 1.490 1.590 1.690 1.790 1.890 1.990 2.090 2.190 2.290 2.390 2.490 2.590 2.690 2.790 2.890 2.990 3.090 3.190 3.290 3.390 3.490 3 .590 3.680 3.780 3.880 3.980 4.080 4.180 4.280 4.380 4.480 4.580 4.680 4.770 4.870 4.97 5.07 5.1 7 5.27 5.37 5.47

0.063 0.126 0.252 0.377 0.503 0.629 0.755 0.880 1.006 1.132 1.25 8 1.380 1.510 1.630 1.760 1.890 2.020 2.140 2.270 2.390 2.520 2.650 2.780 2.900 3.030 3.150 3.280 3.400 3.530 3.650 3.770 3.900 4.030 4.150 4.280 4.400 4.530 4.650 4.780 4.900 5.030 5.160 5.290 5.410 5.540 5.660 5.790 5.9 10 6.040 6.160 6.29 6.41 6.54 6.(i6 6.79 6.9l

0.077 0.155 0.310 0.470 0.620 0.780 0.930 1.090 L.240 1.400 1.550 1.710 1.860 2.020 2.170 2.330 2.480 2.640 2.800 2.950 3.110 3.260 3.420 3.570 3.730 3.880 4.040 4.190 4.350 4.500 4.f:>60 4.810 4.970 5.120 5.280 5.430 5.590 5.740 5.900 6.050 6.210 6.370 f:>.520 6.680 6.830 6.990 7.140 7.300 7.4SO 7.600 7.77 7.92 8.08 8.23 8.39 8.54

0.130

0.1 36 0.143 0.141) 0.155 0.161 0.168 0. L74 0.180 0.186 0.192 0.198 0.205 0.211 0.217 0.223 \ 0.230 0.2 36 0.242 0.248 0.254 0.260 0.26 7 0.273 0.279 0.285 0 .2 92 0.298 0. 304 0.311 0 .3 17 0.323 0. 3 30 0.3.36 0.342

5

9

586

Performance and Calwlations

Table 1 (continued) ~

- -- - - -

~

Flow velocity- ft/ sec (m/sec)

u t: t:: ~

~

.~

"' ~

~

·;::;

E

1

u

(0.3)

2 (O.n)

3 (0.9)

4 (1.2)

5 (1.5)

0.08698 0.08853 0.09008 0.09163 0.09318 0.09473 0.09628 0.09783 0.09938 0.10093 0.10248 0.10403 0.10558 0.10713 0.10871 0.11026 O.ll181 0.11336 0.11491 0.11646 0.11801 0.11956 0.12111 0.1226fi 0.12424 0.12579 0.12734 0.12889 0.13044 0.13199 0.13354 0.13509 0.1361)4 0.1381':) 0.13977 0.14132 0.14287 0.14442 0.14597 0.14752 0.14907 0.150()2 0.15217 0.15372 0.15530 0.17083 0.18636 0.20189 0.21742 0.23295 0.24848 0.26401 0.27954 0.29507 0. 3 I OoO

0.348 0.355 0.361 0.367 0.373 0.379 0.385 0.392 0.398 0.404 0.410 0.417 0.423 0.429 0.435 0.441 0.447 0.454 0.460 0.466 0.472 0.479 0.485 0.491 0.497 0.503 0.509 0.516 0.522 0.528 0.534 0.541 0.547 0.553 0.559 0.565 0.571 0.578 0.584 0 .5 90 0.590 0.603 0 .609 0.615 0.621 0.68 0.74 0.81 0.87 0.93 0.99 1.06 1.12 1.18 1.24

0.783 0.797 0.811 0.825 0.839 0.853 0.867 0.881 0.895 0.909 0.923 0.937 0.951 0.965 0.979 0.993 1.007 1.021 1.035 1.049 1.063 1.077 1.091 1.105 1.118 1.132 1.146 1.1 fiO 1.174 1.188 1.202 1.216 1.230 1.244 1.258 1.272 l.28h 1.300 1.314 1. 328 1.342 1.356 1.370 1.384 1.398 1.54 1.68 1.82 1.96 2.10 2.24 2.38 2.52 2.66 2.80

1.392 1.417 1.442 1.467 1.491 1.516 1.541 1.566 1.590 1.615 1.640 1.665 1.690 l. 71 5 1.740 1.765 1.790 1.814 1.839 ] .864 1.888 1.913 1.938 1.963 1.988 2.013 2.038 2.063 2.087 2.112 2.13 7 2.162 2.1.87 2.212 2.237 2.262 2.287 2.312 2.336 2.361 2.386 2.411 2.43 5 2.4fi0 2.485 2.74 2.99 3.24 3.49 3.74 3.98 4.23 4.48 4. 73 4.97

2.175 2.213 2.252 2.290 2.329

~ 0

5.6 5.7 5.8 5.9 6.0 6.1 6.2 6.3 6.4 6.5 n.6 6.7 6.8 o.9 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 10.0 ll

12

13 14 15 16 17 18 ]9 20

'For head loss in metres. rae tor by 0. 3.

2.3(~8

2.407 2.446 2.485 2. 524 2.562 2.601 2.fi40 2.679 2.717 2.756 2.795 2.834 2.87~

2.912 2. 9 50 2.989 3.028 3.066 3.105 3.144 3.183 3.221 3.260 3.299 3.338 3.377 3.416 3.455 3.493 3.532 3.571 3.609 3.648 3.687 3.726 3.765 3.804 3.843 3.882 4.2 7 4 ,()() 5.05 5.44 5.83 6.21 6.60 6.99 7.38 7.76

(1.8)

7 (2.1)

8 (2.4)

9 (2.75)

10 (3.0)

3.131 3.187 3.243 3.299 3.354 3.4] 0 3.461) 3.522 3. 572 3.634 3.690 3.746 3.802 3.85H 3.913 3.969 4.025 4.081 4.137 4.19 3 4.249 4.305 4.361 4.417 4.472 4.528 4.584 4.040 4.6% 4.752 4.808 4.864 4.920 4.97o 5.031 5.087 5.143 5.199 5.2 55 5. 31.1 5. 367 5.423 5.479 5. 534 5. 589 6.15 6.71 7.27 7.83 8.39 8.95 9. 51 l().()7 10.63 11.1 8

4.2 1)2 4.338 4.414 4.490 4.5n7 4.643 4.719 4.795 4 .871 4.947 5.023 5.099 5.175 5.251 5.328 5.404 5.480 5.5 56 5.632 5.708 5.784 5.860 5.9 36 6.012 6.089 6.165 6.241 6.317 6.393 6.4fi9 6.545 ().621 6.697 n.773 6.850 6.926 7.002 7.078 7.154 7.230 7.306 7.382 7.458 7.534 7.612 8.37 Y.l 3 9.89 10.h5 I 1 .41 12.17 12.9 3 1 3 .n9 14.45 15 .22

5.57 5.67 5.77 5.87 5.97 ().07 6.17 6.27 6.37 6.47 6.57 6.67' 6.76 6.8n 6.96 7.0o 7.16 7 .26 7.36 7.46 7.S6 7.66 7.7o 7.86 7.96

7.04 7.17 7.30 7.42 7. 55 7.68 7.81 7.93 8.06 8.18 8.31 8.4 3 8.56 s.os 8.80 8.93 9.06 9.18 9. 3 I 9.43 9.56 9.fi8 9.81 9.93 I 0.06 LO. 19 10.32 10.44 I 0.57 10.69 10.81 10.94 1 1.07 11.19 11.32 11.45 11.58 11. 7() I 1.8 3 11.9 5 12.08 12.20 12.3.3 1 2.4 5 12.58 H.8 J 5.1

8.70 8.85 9.01 9.1 f) 9. 32 9.47 9.63 9.78 9.94 10.09 10.25 10.40 10.56 10.71 10.87 11.03 11.18 11.34 J 1.49 1 1.65 11.80 11.% 12.11 12.27 12.42 12.58 12.73 12.89 13.04 13.20 I 3. .3 5 13.51 13.66 13.82 1 3. 98 14 . .1 j 14.29 14.44

6

8.06

8. 16 8.26 8.36 8.4 6 8. 55 8.65 8.75 8.85 8.95 9.05 9.15 9.25 9.35 9.45 9.55 Y.65 9.75 9.85 9.94 10.9 1 l. 9 12.9 13.l) 14.9 15.9 16.9 17.9 lil .9 19.9

16.3

17.6 18.9 20.2 21.4 22.7 2 3.9 2 5.2

14.60

14. 7 5 14.91 15.06 15.22 J 5. 3 7 1 'i. 53 17.08 J 8.64 20. I 9 21.74 2 3. 30 24.8S 2 6.40 27.9') 29.5 1 31.0()

Losses in Bends and Fittings

58 7

The value of K for a given component is independent of friction factor or Reynolds number and is constant for all conditions of flow. including laminar flow. Equally. in theory at least. it should be the same for all sizes of a given component with similar geometry. In practice this is not so. Resistance coefficients are necessarily determined empirically, and can vary widely with pipe size. Some typical values are summarised in Table 2. Equivalent length LID

Equating velocity head loss derived from the D'Arcy formula with that derived from the resistance coefficient formula: (f

v2

X

L/d) - = K 2g

v2 X -

2g

It follows that: K= f

X

L/D

UK is a constant for all conditions of flow (but modified by geometric dissimilarities in different sizes, as above). the value of L/D for any given component must vary inversely with the change in friction factor for the different flow conditions. This rules out the effect of geometric dissimilarities in the sizes of valves. fittings, etc., of the same basic geometry.ln other words, the equivalent length of L/0 value for any particular valves. fittings, etc., is a constant for the same flow conditions. and is valid for all sizes of that particular component (see Figure 1 and Tables 3 and 4). Flow coefficient Cv

For valves (and , particularly control valves). it is often more convenient to express the capacity and flow characteristics in terms of a flow coefficient (Cv). defined as the flow or water at 60°F in US gal/min at a pressure drop of llbf/ in 2 across the valve. Note: This definition of Cv based on the US gallon and pressure drop in lbf/in 2 is used both in countries employing Imperial units and those normally employing metric units. The metric 'equivalent' is called the flow factor. designated Kv and defined as the number of cubic metres per hour of water at 20°C which will flow with a pressure drop of 1 kg/ cm 2 ( 1 bar). This gives somewhat different values for the same condition. Equivalents are: Kv = 0.853 Cv

Cv

= 1.16

Kv

588

Performance and Calculations

Table 2. Resistance coefficient of fittings Fitting

Pipe diameter-in lmm) 3

IR

1 /2

1

j / 4.

(10) (12.5) (20) Integral pipe bend

(25)

l 1/4 (35)

1 1/2 (40)

(50)

3 (7"i)

4 5 (100) ( 125)

1.25

1.15

1..00

0.80

0.70

0.55

0.40

0.38

0.34

0. 32

0.30

0.60

0. so

0.30

0.34

0.40 0 ..30

0.25 0.21

0.20 0.18

0.34 0. 32

0.32

0.30

0.29

0.27

0.31

0.29

0.28

0.28 0.2 7 0.19

0.18

0. L8

0.17

2

Approximately 0.04 (all sizes)

(turbulent flow) bend 3 xD Integral pipe bend

Approximately 0.025 (all sizes)

(turbulent flow) bend 4 x D Integral pipe bend

Approximately 0.1 (all size~)

(laminar flow) bend 3 x D Integral pipe bend

Approximately 0.06 (all sizes)

(laminar flow) bend 5 x D Integral pipe bend

Approximately 0.04 (
(laminarflow)bend lOxD Standard 90° elbow (screwed)

2.40

2.10

1.70

1.50

1.0

0.90 0.36

0.35

0.34

0.33

Standard 900 elbow (flanged)

0.45

Large-radius 90° elbow (screwed)

0.75

Large-radius 90° elbow (flanged)

0.40

Standard 45° elbow (screwed)

0 . .39

0.37

Stnndard 4 soelbow (flanged)

0.37

0.35

0.25

Large-radius 45° elbow (screwed)

0.24

0.23

0.22

0.21

Large-radius 45° elbow (flanged)

0.22

0.21

0.20

0.20 ().] 8

0.26

1..50

1.38

0.21 1.25

0.96

0.78

0.68

0.58

Return bend 180° (flanged)

0.43

0.40

0.37

0 .34

0.32

().3()

0.28

Large-radius return bend

0.80

0.70

0.60

0.50

0.40

0 ..35

0 . .30

0.42

0.39

0.36

0.30

0.25

0 .22

0.20

0.26

0.24

0.22

0.18

0.16

0.14

0.1.3

1.80

1.60

1.50

1.40

1.20

l.l ()

0. 90

0.80

0.72

0.64

l.OO 0.62

Return bend 180° (screwed)

2.40

2.10

l.70

180° (screwed) Large-radius return bend

L80° (flanged) T-line flow (screwed)

Approximately 0.9 (all sizes)

T-line flow (flanged) T-bnmch flow (screwed)

2.50

2.40

2.00

T -branch flow (flanged)

L.OO

Screw-down valve (straight)

12.00

10.00

s.oo

7.00

6.00

5.00

Screw-down valve (right-angle flow)

6.00

5.00

4.00

3. 50

3.00

2.50

0.17

0.15

0.13

0.11

0.30

0.23

0.15

0.13

0.2.3

Gate valve (typical) (screwed) Gate v<1lve (typical) (flanged) Gate valve: J /.rclosed Gate valve:

1/

Gate valve:

3

2 -closed

I 4 -c!osed

0.20

0.8-0.2 this range 4.0-0.8 this nmge 16.0-2.0 this range 15.0

12.50 12.50

8.50 8.50

7.50 7.50

6 . 50 6 . 50

6.00 6.00

Swing c heck valve (screwed)

5.0

3.00

2.00

2.00

2 .00

2.00

Swing check valve (flanged)

Typically 2.0 (all sizes)

Globe valve (screwed) Globe valve (flanged)

Foot valve

Typically 0.8 (all sizes)

Basket strainer

Typically I. 5-1.0 this range

Losses in Bends and Fittings

589

In terms ofD'Arcy equation:

c v-

29.9d 2 Jr x L/D

29.9d 2

JK

The flow through a valve handling liquids with a reasonably similar viscosity to that of water can then be determined as: Q = Cv

v

~ £). P

=

---;;-

7. 9Cv

v(M --;i

or

where w is the specific weight of the fluid (lb/ ft 3 ) sg is the specific gravity of the fluid f).p is the pressure drop across the valve. VISCOSITY CORRECTION TABLE

8

Gl\lhC

v~ lve

EQUIVALENT LENGTH OF PIPE FOR VISCOSITY RANGE (CP\ OF

o pen

Gate valve J;, closed 1 12 closed 'I• dosed Fully o pen

®

500

/

Standard elbow o r run o f tce reduced 1!1

~rru

Medium sweep elbow o r run of tee reduced 1/ •

~ tOt

Lo ng sweep elbow o r run of standard tee

nso

1 sao

150

7000

I SOO

I 000

sao

1000

750

sao

250

500

375

250

12S

100

50

30

200

LP·

"'"j

~(OJ-

3000

r300

Borda e ntran ce

tee

'

I I

rr3-

:;; 100 ...

a.

·c.. so .<:~ ~

I LP'_,J ' '

e ntrance

5

c

§!)

c:

-;;; -~

"0" Ul '''

I~

c:

ISO

100

75

50

37.5

25

12.5

30

22.5

15

7.5

20

IS

10

5

tO

7.5

5

2.5

2

1

r-so

a. 14

·c.. ~

E

00

3',

Sudden contraction t d!D- 'IJ d/D-'12 0.5 d!D-Jf,

u

c:...

.r:::.

200

20

.,

~

0

20

il-

.,.,

.s::

"' "' 0... .,

v;

30

1 Sudden enlargement d D-lf• 10 __;.., d D- 112 d D-Y• '

..,Ordinary

100 000

CP

2 000

~

/

\0

10000

CP

3 000

Sq uare elbow bend

?0 000

IV

CP

CP

I 000

2 000

50

[?'

Close return

'"'""•" "d'

•oo

CP

Standard tec

@ S t~ ndard

•o

20

Angle valve open

([]

?00 •o ' 000

lO \0

10

'0

c: :;;

., "'

'0

(,j c:

.E 0 z

''

., 0

..<:: u

=

6

'0

25

s 4' '

r-

f.4

3''

2''

,.,

t-

2

1.5

1

.s

l

.75

.s

f- .25

.375

.25

.125

.075

t--05

.025

o.s

0.3

0.3

0.2

0.2

., O. t

0.1 05

Figure l. Friction loss in valves and.fittings.

590

Performance and Calculations

Table 3. Equivalent straight lengths of fittings in feet

Fitting

Pipe diameter - in (mm) 8 10 12 l4 111 18 20 24 3h (150) (200) (250) (300) (350) (400) (450) (500) (hOD) (900)

6

Welded 90° L-benrls R/D. where R = bend radius D =pipe diameter 0.5 1.0 1.5 2.0 3.0

8 7

28 17 12 10 9

44 20 14 12

16 16

20

9

12

3

4

19 8 6 4 4

25 11 8 6 6

12 12

11

50 23 16 14 13

56 26 18 16 15

24

28

32

36

40

48

72

15

18

21

24

27

30

36

55

5

6

7

8

9

10

12

18

3.3 62

4

4. 5

5.5

6

h.S

8

12

73 70 350 36 23

80 400 42 27

90 440 46 30

100 480 52 34

120 570 63 40

.1 80 850 94 60

32 14 10

Standard 90° elbow (screwed) Standard 90° elbow (flanged) Large-radius 90" elbow (screwed) Large-radius 90° elbow (flanged) Standard 4 so elbow (screwed) Standard 45° elbow l[hmged) Large-radius 4 so elbow (screwed) Large-radius 4 so elbow (11anged) Return bend 180° Large-radius return bend 180° T-line flow T-branch flow Cast elbow (90°) standard Cast elbow (90°) large radius

2.5 47 19 26 30 40 150 200 Hi 20 14 ll

50 250 26 17

39 60 300 32 20

Screw-down valve (straight) Screw-down valve (right-angled run) Gate v
156 75 3.5 19 100 400 160

208 100 4.5 26 130 540 214

260 125 5.7 33 160 700 267

310 150 6.7 39 190 800 320

363 175 8.0

415 200 9.0

467 225 10.2

519 250 12 .0

622 300 14.0

934 450 20.0

373

427

480

534

640

960

40 12 11

53 16 14

67 20 16

80 24 18

93 28 21

107

120

240

36 30

134 40 35

HiO

32

48

72

16 11 3

20 15 4

26 18 6

3.1 22 7

36 25 H

42 29 10

6 9

8 12

10 l5

12 18

14 21

H1

18

24

3 (1

24

27

20 30

Swing check valve (screwed) Swing check valve (!langed) Foot valve (typical) Basket strainer (typical)

2

Jh

33

24

Sudden enlargement d/D= d/D

1

/4

= l/2 d/D = 3 /4

Sudden contraction d/ D =- 1h Entrance (typical) d, smaller pipe diameter. D. larger pipe diameter.

Table 4. Equivalent straight lengths of pipe in metres

fitting diameter-mm

1 <;

1000

800

600

500

400

300

200

150

100

80

fiS

50

40

32

25

~

6

5

4

3

2.7

2.2

1.5

1

0.7

0.5

0.43

0.35

0.27

0.2

0.18

-G-

110200

90170

70130

60110

5090

3570

2550

2035

1325

1020

8-15

6-12

5-9

4.7

3.6

2.4

Screw-down valve

~

300

250

200

1110

130

100

70

50

35

28

22

17

13

10

8

s

Screw-down valve. rightangled

-eool}

150

130

90

80

60

50

32

25

16

13

10

8

7

s

4

2.5

~

18

15

12

10

8

6

4

3

2

1.7

1.4

l

0.8

0.6

0.5

0.3

~

25

20

15

13

10

8

5

4

2.8

2

1.8

1.5

1

0.8

0.7

0.4

~

12

10

7

6

5

4

2.5

2

1.5

1

0.9

0.7

0.5

0.4

0.3

0.2

30

25

18

15

13

10

6.5

5

3.2

2.5

2

1.8

1.4

1

0.8

0.5

fitting Gate valve

Non-return flap va lve

Bends and elbows

a ~

-

0.1

t-< 0

"'"' "'"' 5

OJ

"';:s "';:ss:::.

~

75

60

50

40

33

25

17

13

8

6.5

5.5

4

3.2

2.6

2

1.4

~

~ ,...

.....

s· "'

<:!::>

Vl

1.0 f-.'

T fittings

~

~

a

100

70

80

58

60

45

50

35

40

30

30

24

20

15

15

12

10

8

8

6

7

5

5

4

4

3

3.2

2.5

2.7

2

1.7

l.2

U1

\.0 N

'\:l

"'

~ 0:::.

....

~ :.:::,

18

15

12

10

8

6

4

3

2

1.7

1.4

1

0.8

0.6

0.5

:s

0.3

"'::.':s"'

0.4

::.

~

(")

Taper connectors

5.5

2.5

~-Y4

25

~OjO=

30

25

20

16

13

10

7

5

3.5

2.8

2.2

1.7

1.4

1

0.8

0.5

60

50

40

35

28

20

14

10

7

5.5

4.4

5

3

2

1.8

1

~d/!J"

6

5

4

3.5

3

2

1.5

1

0.7

0.6

0.5

0.37

0.3

0.24

0.18

0.11

~%~

13

10

8

7

5

4

3

2

1.5

1.2

0.9

0.7

0.55

0.45

0.35

0.2

10

8

6

5

4

3.2

2.2

1.6

l.J

0.9

0.7

0.55

0.45

0.35

0.27

0.17

ct;.z L-~b-

30

25

20

16

13

10

7

5

3.5

2.8

2.2

1.7

1.4

1

0.8

0.5

_r-~~ ..,_..,:: '[) '2

15

13

10

9

7

5.5

3.5

3

2

1.5

1.3

0.9

0.7

0.6

0.5

0.3

-----...

15

13

10

8

7

5

3.5

2.5

1.8

1.5

1.2

0.9

0.7

0.5

0.4

0.25

20

16

14

11

8

4

3

2

1.5

1.3

0.9

0.7

c:;

s::: ~ .._

c;·

=

Abrupt 90° bend

Abrupt changes of section

1f2

t&J ~-3

~sh ~'[) __r-

L_

~

:s

"'

Losses in Bends and Fittings

59 3

The pressure drop across a valve can be determined from the same formulae rearranged: w

LlP = 62.4

(Q) 2 sg (Q)2 Cv Cv =

Working formulae

These formulae are expressed in terms of the resistance coefficient (K) where

K = fL

D

Head loss through valves and fittings

K0 2

HL (ft) = 522 d~

where Q is in ft 3 / sec d is in inches KB 2

HL (ft) = 0.0012 7 d4

where B is in barrels (42 US gal/ hr) d is in inches

Hr.. ( m)

=

KQ2

1, 8 7 7, 19 7 d4

where Q is in m 3 / sec dis in mm

KQ2

Hr.. (ft) where Q is in I/ min d isinmm

HL (ft)

= 0 .00216

= 0 .00259d4

where Q is in US gal/min d is in inches

K0 2 d~

where Q is in Imperial gal/ min dis in inches

where W is in lb/ bar V(specific volume) is in ft 3 / lb

Pressure drop through valves and fittings (using resistance coefficient K)

LlP (lbfjin 2 )

= 0.0001078kpV 2

where pis in lb/ ft 3 Vis in ft/sec

LlP (lbfjin 2 )

= 3.62

Kp0 2 d4-

where pis in lb/ ft 3 Q is in ft 3 / sec d is in inches

Performance and Calculations

594

~p (lbfjin 2 )

= 0.00000882

K~~

2

where pis in lb/ ft 3 B is in barrels (42 US gal/hr) dis in inches

~p

KpQ2 (bar)= 0.1729d4

~P (lbf/in

)

= 0.000018

= 0.000000112 KpV 2

where pis in tonnes/ m 3 Vis in m/sec

~p (lbf/in 2 ) = 0.00000003 KpV 2

where pis in tonnes/ m 3 Q is in l/min dis in mm

2

~p (bar)

where pis in lb/ ft 3 Vis in ft/ rrtin

K~~

2

where pis in lb/ ft 3 Q is in US gal/min dis in inches

~p (lbf/in

2

) =

0.000015

Pressure drop through valves and fittings (using flow coefficient Cv)

m

2)

=

2

pQ

62 .4Cv2

where Q is in lb/ ft 3 p is in 1bI ft 3 Q is in US gal/ min

~p

(lbfj'

m

2)

=

pQl

90Cv 2

where pis in lb/ ft 3 Q is in Imperial gal / min

d<

where pis in lb/ ft 3 Q is in Imperial gal / min d is in inches

where W is in lb/bar V(specific volume) is in ft 3 / lb

~p (lbf/'

Kp0 2

pQ2

~p (bar) = 223Cv where pis in tonnes/m 3 Q is in l/ min

Losses;, Bends a11d Fittings

59 5

Discharge through pipes and fittings

Q (ft 3 /s) = 0.0438 d 2 ~ = 0.525d 2

Q (US galjmin) = 19 6 5 d 2

.

ft5:P VI
-

where dis in inches He is in ft ~pis in lbf/ in 2 pis in lb/ ft 3

Q (Imperial galjmin) -

Q (lb/h) -

{EP

VKP

where dis in inches HLisinft ~pis in lbf/in 2 pis in lb/ft 3

16.375d 2 ~

= 19 7 d 2

where

236d 2

(fh VI<

ft5:P VI
dis in inches HL is in ft ~p is in lbf/ in 2 pis in lb/ ft 3

197.6pd2 ~

Q (lj min) - 0.1357

= 6.06 d 2

where dis in inches HL is in ft ~pis in lbf/ in 2 pis in lb/ ft 3

d2 ~ fM5

VT
where dis in mm HLis in m ~pis in bar pis in tonnes/ m 3

None or these formulae is strictly valid for predicting valve performance with viscous fluids or compressible fluids (i.e. air or gases). Losses in bends

Losses in bends are difficult to evaluate other than on purely empirical lines. Attempts to rationalise resistance coefficients in terms of relative radius (ratio of bend radius to internal pipe diameter) are generally unsuccessful, but values are fairly well established for standard bends, including mitre bends.

59 6

Performance and Calculations

Alternative data are presented in terms of equivalent length or L/0 (see Tables 3 and 4 and Figure 1). Contractions and enlargements

Flow through gradual changes in pipe sections (contractions or enlargements) can be analysed from first principles using the Bernoulli equation (Bernoulli constant), with the subsequent introduction of an empirical coefficient to take into account frictional losses introduced with a real fluid.ln problems involving closed circuits, the potential head can normally be ignored in view of the inherently higher value of velocity and frictional head so that the original equation can be reduced to: P v2 - +- = a constant 2g

p

This is often more convenient to use in the form: V2

2Pg

+ - p- = a

constant

Applying this condensed equation to steady frictionless flow along a length of horizontal pipe which contracts in cross-section, the following applies: 2Prg V 2P2g V 21 + --= 22 +-p p i.e.:

PI -

p2

=

p ( 2 2g v2 -

v 2) 1

This form of equation also shows that a steadily contracting section followed by a widening section can be used as a principle for flow velocity measurement by measuring the difference in pressure at two extreme sections, as in the venturi (Figure 2). If X expresses the ratio A 2 /A 1 • it follows that the volume of flow is the same at both sections that V1 = X x V2 . Hence, rearranging the equation above and rewriting (P 1 -P 2 ) as ~P:

Vl= -

2g~P

p

x2 X --~ (1- x 2 )

Figure 2.

Losses in Bends and Fittings

59 7

This is the basic formula for the theoretical design of a venturi velocity meter. In practice. the formula is modified by the introduction of a calibration coefficient to take into account frictional losses, etc., neglected in the Bernoulli equation. Sudden enlargements (Figure 3)

Again , flow conditions can be analysed from first principles, although for engineering calculations it is only necessary to determine the velocity head loss from the corresponding resistance coefficient K 1 . This can be determined as:

where d 1 = i.d. of smaller pipe d 2 = i.d. of larger pipe. This formula is also quoted in the form: Kl = (1- [32)2

Sudden contractions (Figure 4)

In this case, resistance coefficient is one half that for a sudden enlargement, viz:

or

Figure].

59 8

Performance and Calculations

Figure 4. Enlargement/contraction coefficients

e ~ 4 5o

Ce

= 2. 6 sin ~

Coefficients for gradual contractions, derived by Crane, are:

e < 4 5o

. e

Cc = 1. 6 s m 2

where eis the angle of divergence. These formulae can also be expressed in terms of the larger pipe and have been extended to define resistance coefficients (K 3) for both sudden and gradual enlargements and contractions, viz: Enlargement

(1 - {32)2 KJ =

f34 2.6 sin~ (l - {3 2 ) 2

K3

2

=

f34

Contraction

J~ (1 -

fJ 2 ) K3 = ------'----,---0.5 sin

[34

0.8sin~(l- {3 2 ) K 3 = - ---= {3-4 - - -

Losses in Bends and F'itl.ings

599

Resistance coefficients and equivalent straight lengths applicable to changes of cross-section are given in Tables SA, Band C. Flow through orifices

Flow through a sharp-edged orifice is particularly significant as this has a number of practical applications, e.g. an orifice plate can be used as an indicating flow meter. though normally restricted in application of pipes of relatively large diameter, say over SO mm (2 in). Orifices are. in fact, principally used to meter rate of flow. They are also used to restrict flow or reduce pressure. vVith liquid flow, several orifices may be Table SA. Change of cross-section: equivalent straight lengths mm

25

so

1

2

3

4

5

6

8

10

12

14

16

18

20

24

3

6 4 1

8 6 2

11 7 2

14 9

16 12

20 15

4

36 25 8

42 29 10

l2

55 46 15

65

3

31 22 7

48 34

3

26 18 6

2

3

3

4

6

tl

10

12

14

16

18

20

26

75 100 125

150 200 250 300 350 400 450 500 600

Pipe size (d) in Expansion d/D 0.25 0.5 0 .25 Con traction d/D 0.5

=

2 5

=

52 20

d. smaller pipe diameter. D. larger pipe diameter.

Table 58. Change of cross-section: resistance coefficient Ratio of smaller pipe diameter to larger pipe diameter (d/D) Change of section 0.1 10° taper 200 taper Sudden expansion Sudden contraction

2.0 0.5

0.2

0.3

0.4

0.5

0.6

0.35 0.15

0.25 0.12

0.20 0.10

0.45

0.45

0.4

Inlet:

Abrupt Gradual Projecting tube Outlet: Abrupt Gradual

0.8

0.3

0.2

0.9

0.15 0.45

0.45

Table 5C. [nlets and outlets: resistance coefficient Ch<mge of section

0.7

Typical value 0.5 Not less than 0.5 1.0

l.O Not less than 0.12

600

Performance and Calculations

FigureS .

used in sequence to reduce pressure in gradual steps, thus minimising the risk of cavitation occurring. Simple analysis is restricted to streamlined flow, the flow p~ttern being of the form shown in Figure 5. The streamlines converge on approaching the orifice and continue to converge after passing through the orifice, reaching a minimum cross-sectional area, known as the vena contracta, downstream of the orifice before diverging again. For small circular orifices. the downstream position of the vena contracta is of the order of half the diameter of the orifice. At the vena contracta, all the streamlines are perpendicular to the plane of the orifice.

Strength of Pipes (Calculations) In the case of homogeneous tubes (e.g. drawn tubes), a suitable pressure rating can be determined directly in terms of the D/ t ratio by assuming a uniform distribution of stress through the tube wall, when: 2St P=D where D -- outside diameter t -- wall thickness p -- internal pressure s -- material stress This can be rendered in terms of a working pressure rating Pw where: 2Sma.xt Pw = V where Smax = the maximum permissible material stress for the material used. This is generally taken as one third the ultimate material stress (see Table 1 ). Written as a solution for tube-wall thickness: PwD t=-2Smax Provided the maximum material stress figure is taken within the limit of proportionality of the material, this simple formula is valid. It does not hold true for higher stress values, and thus will not accurately predict bursting pressures, e.g. using Snit in place of Smax· It is also not valid where the ratio D/t is 16:1 or less, as stress is then no longer uniformly distributed through the wall thicknesses, but ranges from a maximum at the inner surface to a minimum at the outer surface. The simple formula is thus restricted to thinwalled tubes (D/t greater than 16:1). It will over-estimate the pressure rating for thick-walled tubes (D/ t 16:1 or less), and in such cases an alternative formula must be used. An alternative

602

Performance and Calculations

Table 1. Maximum permissible stress for tube calculations (Minimum UTS divided by 3) Pmax

Material

Condition

Low carbon steel

As drawn Drawn and polished* As drawn Annealed Half-hard Hard As drawn Annealed Half-hard Hard Annealed Precipitation hardened

20-ton steel Stainless (304) steel

Light alloy 61S-T6 Copper

Tungum

bar

lbf/in 2

1280 2000 1000 2350 2800 3500 1000 480 630 800 1550 1550

18.300 28.000 15.000 3 3.300 40.000 50.000 15.000 68001 9ooot

uoo

Titanium llS/125 Titanium 150/160

2100

u.Joot 22.000 22.000 18.500 30.000

*Cylinder tubes. tup to 65.5°C (150°P) only.

formula which can be applied in the case ofthick-waUed tubes and homogeneous metal pipes is:

Smax = P

X

RT

R~ _ RT X

)

(R~ RT + 1

where Ri = inner radius of tube R 0 = outer radius of tube. Alternative formulae, written as a solution for wall thickness required, are: t =

t

D (JsS-P+ P- 1) 2

=D 2

(J

3S + P _ 1 ) 3S- 4P

where S - Smax the corresponding value ofP is Pw s Sutt the corresponding value ofP is the bursting pressure. Modified formulae are used in the case of non-homogeneous tubes and also for non-metallic tubes. (i)

In the case of welded tubes, a correction factor may be introduced or. alternatively, a higher divisor may be used to establish P max from

Strength ofPipes (Calculations)

603

the ultimate tensile strength of the material. This is not necessarily the invariable rule, as welded tubes can have the same working strength as drawn tubes. Corrections may be applied to tubes with welded connections on a similar basis, however. (ii) In the case of cast tubes, a nominal (and substantially lower) value may be adopted for Pmax· Cast tubes are associated with older hydraulic systems and Large pipe sizes, where pressure rating is established on empirical lines. permitting fairly large tolerances in wall thicknesses. (iii) In the case of copper pipes and tubes intended for brazed or soldered connections, the standard thin-walled formula is de-rated: Pw

=

2Smaxt D- 0.8t

(iv) In the case of metallic tubes intended for threaded connections, an allowance is made for the reduction in tube strength due to threading. The following formula can then be used for thin-walled tubes:

Pw

(v)

=

2Smax(t- C) D - 0. 8 (t - C)

where Cis taken as equal to the depth of thread cut, with a minimum value of 1.2 5 mm (0.05 in). In the case of plastic tubes, an allowance is made for the higher elastic moduli of such materials, when a suitable formula is:

Pw

=

2Smax t D- t

Pipe-wall thickness according to British Standards '

Two British Standards are applicable for the calculation of pipe-wall thickness: BS 806: 1975 BS 3 3 51: 19 71

Specification for ferrous pipes and piping installations for and in connection with land boilers. Specification for piping systems for petroleum refineries and petrochemical plants.

Design to BS 806

Minimum pipe-wall thickness where the outside diameter (D) is used as a basis for calculation .

604

Performance and Calculations

Table 2. Design stresses for ferrous pipes (BS 3351) Values ofS for metal tcmper<Jtures in oc not exceeding• Materi
Notes -200 to +50

50

100

150

200

250

300

350

400

425

450

(N/ rrun 1 )

BS3601HFS. CDS. steel22

125.5

114.5

103.9

99.3

94.5

89.7

8'i.O

75 .0

fiS.7

56.9

BS3fi01HFS. CDS. steel 2 7

154.5

141.3

127.5

121.7

114.2

110.0

104.0

87.7

75 .8

fi2 .0

APlSLGradeA. seamless: steels open hearth, electric furnace and basic oxygen

122.5

111.9

101.3

95.8

91.3

86.5

82.0

7L1

64.8

55.8

APJSLGrndeB. seamless: submerged arc. spiral weld: steels open hearth. electric furnace and basic oxygen

153.0

139.8

126.5

119.0

113.8

108.5

102.5

89.3

7'i .5

62.0

BS 3602 CDS. HFSandEHW. steel 25

2

130.0

125.5

120.6

11 7.3

111.5

96.5

88.9

78.2

6 7. 9

5 7.7

BS 1602 CDS. HfSand ERW. steel 27

2

154.5

143.0

132.0

12 7.0

11':1.0

1J 0.0

104.2

89. 7

75 .9

62 .3

BS 3fi02 EfW Grade 28 13

2. 3

123.5

116.5

109.6

104.0

95 .2

90.4

8 7.0

n.s

62 .0

50 .3

BS 3603 HFS. CDS. steel 27 LT-30

4.5

1 54. 5

143.3

132.0

126.5

119.0

BS 3fi03 HFS. CDS. steel 27 LT-50

4. 5

154.5

143.3

132.0

126.5

119.0

BS 3603 HfS. CDS.stcel 503 LT-1 00

4. 5

1 59.0

14 7. 8

13 5.3

1 29.3

12 1.9

166.5

144.2

144.0

139.0

l24.5

114.0

109.5

104.()

101.5

':n\.5

BS 3604 620 HFS. CDS. steel2 7

-----------------------------------------------------------------------BS 3604 fi21 144.5 144. 2 144.0 13 9.0 124.5 11 5.5 110. 5 106.0 103 .8

100.0

HFS. CDS. steel 2 7 'Inte rmediate values may be obtained by linea r interpolfltion. (1) Limited application (see Section 3 of BS 3351). (2) The design stress values for pipe with a longit udinal or spiral weld seam inrorporflk weld-joint factors as follows: API 5L submerged arc welded: 1.0: API SLS Grade B: 1.0: BS 3602 ERW with Appendix A: 1.0: BS 3602 EFW: 0.8. (3) The values for BS 3602 EFWare based on material to BS 1501.151 or 161. Grade 2813 (certified or hot-tested). Por temperatures over 400°C. 161 material should be used. (4) The BS 3603 pipes listed are impact-tested <Jnd intended for use in low-temperature service. (5) Up to 250cc to cover 'steaming out' find flexibility Cfllculations. (6) The llgures in parentheses illongside the grades are equivalent AlSI types. There is no AlSI equivalent of 845T

Strength of Pipes (Calculations)

605

Values ofS for metal temperatures in °C not exceeding•

475

500

525

550

575

600

47.5

35.8

48.6

35.8

39.3

24.8

92.3

Sl.O

62.8

43.8

28.9

17.2

92 .8

81.2

64.3

49.3

34.2

14.4

650

675

700

725

750

775

800

825

606

Performance and Calculations

Table 2. Continued Values ofS for metal temperatures in ° C not. exceeding• Material

Notes

-200 to

50

100

150

200

2 50 (N/ mm 2 )

300

3 50

400

425

450

144.5

134.2

129.6

125.0

120.5

115.5

111.0

106.0

103.8

101.0

BS3604622 HFS.CDS. steel 31

164.0

164.0

164.0

164.0

156.S

150.5

144.0

1 37.2

134.0

130.2

BS 3604 660

172.0

172 .0

167.0

164.0

156.5

150. 5

144.0

137.2

134.0

130.2

137.0

131.0

125.5

ll9.5

114.0

108.5

103.0

97.0

92.8

86.5

126.0

113.5

103.5

95.0

R7.5

81.9

76.3

7 l. 7

(>13.'J

66.8

106.8

102 .8

90.3

76.5

68.2

h3.3

60.0

5 7 .2

55 .8

6

129.3

127.5

117.0

lOlLS

105.5

102.8

102.0

101 .3

100. 5

99.0

6

129.3

128.2

123.5

120.6

118. 7

118.0

11 7. 5

1 16.5

11 5.5

1 14.0

6

107.5

106.2

100.0

83.4

79.3

74.3

66.9

62 3

60.7

58.6

+50 BS 3604 622 HFS. CDS.

steel 2 7

CDS. HFS

BS 3604 625 HFS BS 3605 Grade 801 (304 )

6

BS 3605 Grade 811 (304H)

6

BS 3605 Grade 80 l L (304 L) BS 3605 Grade 822T (321)

BS 3605 Grade 832T (321H)

BS 3605 Grade845 (316)and Grade 845T and Grade 846 (3J 7)

BS 3605 Grade 8451 (316L)

*Intermediate values may be obtained by linear interpol<~tion . (1) Limited application (see Section 3 of BS 3351). (2) The design stress values for pipe with a lon gitud inal or spiral weld seam incorporate weld-joint factors as follows: APf SL submerged arc welded: J.O: API SLS Grade B: 1.0: BS 3602 ERW with Appendix A: 1.0: BS 3602 EP\N: 0.8. (3) The values for BS 3602 EPWare based on material to BS 1501.151 or 161. Grade 288 (certified or ho t-tested). For temperatures over 400°C.161 material should be used. (4) The BS 3603 pipes listed are impact- tested and intended for use in !ow-temperature service. (5) Up to 250°C to cover 'steaming out' and flexibility calculations. (6) The figures in parentheses alongside the grades are equ.ivalent AISltypes. There is noAISJ equivalent of845T.

Strength of Pipes (Calculations)

607

Values ofS for metal temperatures in •c not exceeding•

475

500

525

550

575

600

92.5

ll2 .8

63.8

47.5

36.2

26.8

107.5

82 .8

63.8

47.5

36.2

26.8

127.5

115.6

79.9

53.7

36.9

81.0

72.4

59.0

43.8

31.3

21.1

64.8

63.3

61.3

59.7

55 .8

48.0

625 (N / mm 2 )

()50

675

700

725

750

775

800

825

37.6

30.7

22.4

17.6

13.4

10.3

7.9

6.2

4.5

-- - ---------------------------------------------------------------97 .5

111.5

96.0

106.0

94.0

<J9.3

91.7

88.5

75.8

51.3

34.5

25.5

19.6

15.2

11.8

9.3

7.6

6.5

90.3

79.3

67.6

56.2

46.6

36.8

28 .3

22.0

17.6

14.4

11.8

9.6

608

Performance and Calculations

Pd mm- 2fe- P

t.

~ --­

where tmin P D d f e

e e

= = = = -

the minimum thickness (mm) the internal design pressure (N/ mm 2 ) the outside diameter (mm) the inside diameter (mm) the maximum permissible design stress as specified in Table 2 (N/mm 2 ) - 1.0 for seamless and for electric resistance wel.ded-steel pipes and for electric fusion welded steel pipes complying with the requirements ofBS 3602 in which the weld is fully radiographed or ultrasonically tested. = 0. 9 5 for electric fusion welded pipes complying with the requirements ofBS 3602. - 0.90 for pipes complying with the requirements ofBS 3601 other than electric resistance welded pipes.

The value of tmin is the minimum thickness for straight pipes and provision shall be made for any minus tolerance. Manufacturing considerations may make it necessary for pipes thicker than this minimum to be used . PD

t=---

20S

where t

--

p

--

D

--

s

--

+P

internal pressure design thickness (mm) internal design pressure (bar) outside diameter of pipe (mm) design stress (N/ mm 2 ) (shall be obtained from and shall not exceed those given in Table 2 for the design temperatures indicated therein). Linear interpolation for intermediate design temperatures is permitted.

Pipes with t equal to or greater than D/ 4 require special consideration. Mitred bends

Although smooth bends are more common, mitred bends are widely used in industry. Typical applica tions include large-diameter pipelines or ducting in chemical complexes, de-salination plants and nuclear power stations, where the manufacture of smooth bends may be either impra ctica l or uneconomical. To sa tisfy requirements within the high-pressure pipeline industry in the UK, the BSI has produced recommendations on the design and application of gusseted or mitred bends. This is published in Amendment No . AMD 3 545 to

Strength of Pipes (Calculations)

609

BS 806. A feature of the recommendations is that they are to be used in conjunction with BS 806 stress limits, and thus complement the BS 806 smooth bend design assessment procedure. Finite element methods have been used to analyse the stresses in single mitre pipe bends to verify experimental results. Tee junctions and intersections

Pipelines used in the power generation industry, either in conventional or nuclear power stations, are subjected to complex loading. The pipelines from the boiler to the turbine can weigh up to 400 tons. and have to be stressed as a structure loaded by its own weight, as well as a pressure vessel at high temperature. Tee branch pipe intersections are therefore subjected to both internal pressure and external moment loadings arising as a result of deadweight. thermal expansion, cold pull or seismic effects. The following design codes are used for the calculation of stresses and the determination of stress concentration and flexibility factors: BS 806: 1975

Specification for ferrous pipes and piping installations for and in connection with land boilers. Specification for unfired fusion welded pressure vessels.

BS 5500: 1982 ANSI/ASME Power piping 8.31.1:1980 ASME 111: 19 8 3 Boiler and pressure vessel code: nuclear power plant components. Finite element analysis methods have been used to compare the results obtained from the different codes with experimental results, and these have been published by the Institution ofMechanical Engineers in the United Kingdom. See also standards EN 545, EN598 and ISO 25321 as well as British Standard Code of Practice for Pipelines 8010 Section 2 .1.

Buried Pipes In designing rigid buried pipelines. the determination of the external load due to backfill and surface loadings is conventionally based on the methods and formulae established by Marston and Spangler. These involve lengthy and tedious calculations but are readily adapted to CAD (computer-aided design). For general calculation, simplified tables are available, notably those by Young and Smith (Building Research Station Report. 1970), corresponding to normal practice with concrete pipes and incorporating corrections for differences in external diameter. The latter can be a significant feature in the case of cement pipes because of the smaller external diameter reducing the load which it has to carry. Further simplified tables have been computed on this basis. Rigid metal pipes (e.g. cast iron) and pipes in flexible materials (e.g. reinforced glass fibre) need somewhat different treatment. The former can be laid at any depth with 7 5 to 600 mm ( 3 to 24 in) of cover under buildings; and with not less than 300 mm ( 12 in) under roads and yards subject to normal usage. Elsewhere in good ground. such pipes will only need extra protection where subject to special loadings or abuse. In the latter case, design is usually based on traditional empirical data; recommendations based on experience or derived from experimental data evaluating specific structural protection requirements. \tVith flexible pipe materials, due allowance must be given to the diametrical deflection produced by soil load. e.g. using Spangler's formula.

Cement-buried pipelines

The following covers the use of simplified tables for the design of cement-buried pipelines. Metric units are employed throughout, consistent with current British and European practice. General assumptions are: (i) Backfill density of2000 kg/m 3 (125lbf/ft 3 ) (ii) Frictional values KJJ. between 0.13 and 0.19 (iii) rsctP values of 0.5 and 0. 7 as indicated.

Buried Pipes

611

Appropriate conversions are:

1 mm - 0.0394 in 1m 2 - 10.76ft2 1 kg - 2.20461b 1m - 3.2008 ft

1 kg/ m 3 1N 1 N/mm 2 1 kN/m

= 0.0624lbf/ ft 3 = 0.2248lbf = 1 MPa = 145 lbf/in 2 - 68.52lb/ft

Notation

Be Be~

Fm

Fs H Y KJ.L rsdp \!1/e WT

Outside diameter of pipe barrel. Trench width, measured at the level of the top of the pipe. Marston bedding factor, the value of which depends on the bedding method employed. Design factor of safety (1.25). The height of soil cover. measured from the top of the pipe barrel to the ground or road surface. Soil density in kg/m 3 (2000). Product of the Rankine coefficient for the soil (K) and coefficient of internal friction of the soil (J.L). Product of p, the proportion of the pipe diameter that projects above the bedding, and rsd, the 'settlement ratio'. Total vertical external load imposed on the buried pipe (kgf/m). Minimum ultimate crush load of asbestos cement pipe (kgr/ m).

Application of the tables

Tables 1-3 are based on assumptions that will be safe for a wide range of site conditions. The equivalent water loads are included in these tables. By separating the concentrated surcharge loads, Table 4 enables the designer to vary the calculation of the backfill load to suit individual circumstances, but here the water load must be added from Table 5 for pipes of 600 mm and over. Pipes laid under verges should be designed for the full-vehicle loads. Buried pipes must not be exposed to excessive loads from heavy equipment during construction. Choice of the appropriate loading category for a given location is a matter for the engineer's judgement, with due regard to possible future changes. The tables are not appropriate for flexible pipes (pitch fibre, plastics, steel. etc.), nor for rigid pipes supported on piles. Design method

For safe design, the minimum ultimate crush load (Wr) which the pipe is designed to withstand must be greater than or equal to the computed external load (We multiplied by a factor of safety of 1 .2 5 and divided by the bedding factor Fm. 1.2 SWe WT > - - -

-

Fm

612

Performance and CalculaUons

I

l

'"'i/IJIS< """.....,.,..,IWI/;~ -

I

Bd

-

-

-

::::::_------:::__ -=::::....-

---------------------------

H

Class 8 Bedding Factor= 1.9

Class A Bedding Factor = 2 .6

Od

Od

1-0WM~~~=======~~-

. '10"'-'

H

II

2 1-·

l_'4

JOOmm

mm

--

\050Bc\

mon Class C Bedding Factor = 1.5

1. Lightly compacted fill. 2. Loose fill. 3. 20.5 N/mm 2 at 28 days concrete wellpacked under pipe. 4. Selected granular material well-tamped unde r and alongside the pipe. 5. Selected material well-tamped by h and in 7 5- 150 rom layers. 6. Selected materi a l lightly tamped by ha nd in 150 mm layers. 7. Normalfill. 8 . Lightly compacted by h a nd.

Class D Bedding Factor = 1. I

Bd =Width of tren ch at crow n of pipe. H = Depth of cover over crown of pipe . Be = Outside diameter of pipe. Bedding fac tor Type ofbcddlng

Bedding class

A (RCl A (Plain) B [l

c [)

I 20' reinforced concrete cradle 120° plain concrete nad le .l60- l:(ranul<Jr bedding 120' ~ranular bedding Hand-shaped lrt>nch bnttoru Hand-trinunl'lf flat boll om

Figure 1. Bedding factors for pipes in trenches.

F,, 3.4 2.6 2.2 1.9 1.5 l.l

Buried Pipes

613

Table 1. (Metric units. kgf/m): main roads Nominal Outside Assumed diameter diometer trench width (mm) (mm) (m)

100 150 175 200 225 250 300 375 450 525 600 675 750 825 900 975 1050

125 182 208 232 260 288 339 423 504 587 671 756 837 921 1007 1075 1157

0.60 O.oO

0.70 0.70 0.70 0.75 1.00 1.05 1.15 1.20 1.35 1.45 1.50 1.60 1.85 1.90

H= 0.9

1432 2047 2328 2587 2888 3190 3738 4585 5443 6320 7415 8372 9282 10.230 11.220 12.000 12.950

1.2

1.5

1.8

2.4

1352 1326 1332 1408 1946 1913 1926 2040 2216 2181 2197 2328 2465 2428 2446 2593 2756 2715 2737 2903 3046 3003 3028 3212 3574 3526 3556 3754 4368 4292 4547 4312 5190 5101 5127 5591 6031 5930 5901 6291 7089 6977 7012 7273 8009 7882 7924 8352 8883 8745 8793 9082 9796 9646 9650 9826 10.747 10.526 10.424 10.586 11.498 11.324 11.387 12.000 12.405 12.220 12 .290 12.750

3.0

4.6

6.1

7.6

1535 2228 2543 2834 3174 3288 3841 4951 5894 6672 7546 8743 9479 10.223 11.013 12.613 13.380

2003 2743 2784 3342 3385 3429 4058 5930 6666 7416 8367 9819 10.676 11.507 12.371 14.574 15.365

2202 2829 2856 3500 3528 3556 4257 6451 7272 8126 9190 10.935 11.876 12.831 13.907 16.545 17.520

2212 2881 2899 3565 3585 3604 4369 6797 7733 8680 9848 11.797 12.913 14.041 15.190 18.307 19.450

3.0

4.6

Table 2. (Metric units. kgf/m): light roads Nominal Outside diameter diameter (mm)

(mm)

100 150 175 200 225 250 300 375 450 525 f>OO 675 750 825 900 975 1050

125 182 208 232 260 288 339 423 504 587 671 756 837 921 1007 1075 1157

Assumed trench width (m)

0~60

0.60 0.70 0.70 0.70 0.75 1.00 1.05 1.15 1.20 1.35 1.45 1.50 1.60 1.85 1.90

H=

0.9

1.2

1.5

1335 1850 2085 2302 2554 2806 3265 3966 4681 5412 6360 7166 7934 8737 9576 10.236 11.037

1122 1585 1796 1991 2217 2444 2816 3458 4095 4745 5612 6837 7026 7746 8502 9097 9818

1053 1503 1708 1897 2117 2337 2737 3301 3915 4544 5388 6088 6756 7455 8128 8762 9460

1.8

2.4

6.1

7.6

1052 1152 1316 1863 2105 2144 1512 1667 1909 2540 2690 2782 1721 1901 2180 2552 2697 2785 1914 2117 2429 3083 3324 3440 2139 2369 2719 3096 3331 3445 2364 2621 2784 3109 3338 3449 2772 3056 3248 3683 4002 4188 3330 3677 4213 5462 6134 6572 3955 4552 5014 6110 6895 7465 4593 5082 5647 6768 7687 8370 5447 5890 6375 7628 8689 9493 6158 6793 7424 8987 10.370 11.400 6836 7357 8019 9755 11.250 12.470 7495 7927 8617 10.494 12.150 13.550 8067 8510 9257 11.264 13.160 14.660 8870 9782 10.738 13,36f> 15.750 17.740 9579 10.352 11,364 14.094 16.660 18.84 0

614

Performance and Calculations

True values ofFm are considerably dependent upon standards of workmanship and good compaction of the side fill. Those tabulated assume properly maintained and supervised standards. Method of use for Tables 1-3

Select the table appropriate to the type of surface loading. From the pipe diameter and the cover depth, the external load is read off directly. Use the given bedding factor to calculate the minimum value ofWr, and find the class of pipe required from Table 4. If a pipe of sufficient strength is not available a better class of bedding may be specified. In general. the cover depth will vary along the main, andl:he pipe strength and bedding class must be selected to meet the maximum cover-depth condition. With pipelines having considerable variation in cover depths, it may be worth specifying different classes of pipe and/or bedding for different sections of the main. Alternatively, the tables may be used to find the limits of permissible cover depths for the different pipe and bedding classes available. Method of use for Table 4

Where the trench conditions and backfill density deviate from the norm. Table 4 may be used to obtain the most economical design.

Table 3. (Metric units. kgf/ m): fields. etc. Nominal diameter (rom)

(mm)

Assumed treoch width (m)

100 150 175 200 225 250 300 375 450 525 600 67.5 750 825 900 975 1050

125 182 208 232 260 288 339 423 504 587 671 756 837 921 1007 1075 1157

0.60 0.60 0.70 0.70 0.70 0.75 1.00 1.05 1.1.5 1.20 1.35 1.45 1.50 1.60 1.85 1.90

Outside diameter

\11,1c

H=

0.9

1.2

792 1150 1313 1463 1638 1813 2131 2578 306(1 3564 4276 4843 .5384 5950 6547 7211 701() 7795 7586

809 1174 1341 1494 1673 1852 2176 2655 3157 3670 4397 4979 5535 6117 6729

1.5

1.8

825 1198 1368 1525 1707 1889 2221 2671 3177 3693 4423 5009 5567 6152 6709 7252 7839

886 l288 1470 1639 1835 2031 2388 2859 3401 3954 4722 5345 5940 6513 6998 7731 8.355

2.4

3.0

1054 12 53 1532 1821 1750 2080 1951 2319 2185 2598 2418 2650 2820 3090 3389 4021 4212 4786 4689 5384 5442 6076 6292 7089 h803 7649 7320 8210 7848 8814 9077 10.266 9605 10.856

4.6

6.1

7.6

183 7 2502 2509 3035 3043 3051 3nl5 5.3/R nOll 6654 7497 8841 9593 10.316 11.070 13.159 13.872

2091 2670 2674 3297 3302 3306 3964 n087 6840 7623 8616 10.290 11.163 12.046 13.049 15.630 16.53 3

2769 2771 3424 3427 3429 4164 6543 7431 8329 9448 1l.34n 12.414 13.492 14.591 17.668 18.766

2133

f3uried Pipes

615

The method of use is: Step 1 Step 2 Step 3 Step 4

Knowing the pipe diameter and cover depth, obtain the vehicle load and the wide-trench load. Knowing the trench width, read off also the narrow-trench load. Adopt the lesser of the two backfill loads. If the soil density y differs from 2000 kg/m 3 (125lb/ ft 3 ), correct the backfill load by y/ 2000 ( yj 12 5). Add the backfill. vehicle loads and equivalent water load for pipes over 600 mm to obtain We·

With We determined, the class of pipe and bedding required may be worked out as in Method of use for Tables 1-3 above. Example

Determine the strength classes and bedding required through a length of 600 mm nominal diameter asbestos-cement pipeline laid under fields at cover depth ranging from 1.2 to 6.4 m (narrow-trench conditions). Consider the use of Class B (F m = 1. 9) bedding or, if ground conditions permit, a Class D (Fm = 1.1) bedding. The maximum permissible external load can now be found by using the equation shown under Design method: . I.e.

We~

or We~

1.1 x Wr 1. 25 1.9 x Wr 1. 25

= 0 .88Wr = l.52Wr

The values ofWr for the different classes of pipe can be found in Table 4 . Wr for 600 mm diameter Class L pipes= 4300 kgf/ m. Wr for 600 mm diameter Class M pipes= 5800 kgf/m . The permissible depths of cover can now be found from Table 4. Table 4A.

W,. (kgf/m)

Class L

M

Depth of cover (m)

---

Fm=l.l

Fm = 1.9

Fm=l.l

Frn =l.9

3784 5104

6536 8816

0.6- 2.1

0.6-3.7 0.6- 7.0

A 600 mm Class L pipe, on a Class B bed, can be laid from 0.6 to 3.4 m; from 3.4 to 6.4 m, a Class M pipe laid on a Class B bed would be needed. If ground conditions permit, a 600 mm Class M pipe can be flat bedded from 0.6 to 2.1 m, and laid on a Class B bed from 2.1 to 6.4 m.

616

Pe1jormance and Calculations

Table 4. Class of pipe required Nominal internal diameter (mm) 100

150

175

200

225

250

300

37'5

450

525

600

675

750

Outside Trench diameter width Bd Be (m} (mm) 125

182

208

232

260

288

339

423

504

587

671

756

837

Type of load Narrow Wide(0.7) Main road Light road Fields. etc.

0.60 Narrow Wide(0.7l Main road Light road Fields. etc. 0.60 Narrow Wide(0.7) Main road Light road fields. etc. 0.70 Narrow Wlde{0.7) Maio ro«d Light road Fields. etc. 0.70 Narrow Wide(0.7) Main road Light road Fields. etc. 0.70 Narrow Wide(0.7) Main road Light road Fields. etc. 0.75 Narrow Wide{0.7) Main road Llgbt road Fields. etc. 1.00 Narrow Wide(0.5) Maio road Light road l'ields. etc. 1.05 Narrow Wide(0.5) Main road Light road Fields. etc. 1.15 Narrow Widc(0.5) Main road Light road Fields. etc. 1.20 Narrow Wide(0. 5) Main road Light road Fields. etc. 1.35 Narrow \>Vide !0. 5) Main road Light road Fields. etc. 1.4 5 Narrow Wide(0.5) Main road Light road fields. etc.

Tow I design load We in kilograms pe( metre of pipe length for covt'r depth 1-1 in met(CS H=

0.6

0.9

1.2

15

1.8

2.1

2.4

2.7

3 .0

3.4

233

350 1083 985 459

468 887 656 324

585 743 468 239

703 631 350 183

1173 364 144 79

680 1268 907 470

1370 851 1065 653 347

1550 1022 906 491 265

938 471 215 116 1840 1364 677 303 11iH

1056 413 174 95

508 154l 1343 666

821 543 271 144 1710 1193 780 381 209

1960 1536 59 3 246 1..17

2080 1707 523 203 114

1330 311 ll4 63 2J 70 1935 446 lli 1 91

580 1750 1506 761

776 1442 1021 537

1370 971 1211 737 397

1550 1167 1031 555 303

1710 1363 888 431 238

1840 1960 1559 ' 1754 771 675 343 279 19 1 157

2080 1950 595 231 130

2170 2211 508

646 1942 1656 848

864 1603 1127 599

1590 !083 134 7 815 442

1810 1301 1147 614 338

2010 1519 987 478 265

2190 1737 858 381 213

2340 1956 751 309 174

2470 2174 662 256 ]45

2600 2465 564 203 116

723 2167 1832 950

968 1790 1251 671

1590 1212 1505 906 495

1810 1457 1282 683 378

2010 1701 1104

2190 1946 959 424 239

2340 1191 840 345 195

2470 2435 740 285 162

2600 2761 632 226 130

799 2392 2008 1052

1070 1977 1374 743

1590 1341 161>3 997 548

1810 1612 1417 752 419

2010 1883 1220 586 329

2190 2154

2340 2425 n8 380 216

2600 3058 699 249 14 3

938 2801 2328 1238

1257 2319 1559 873

2060 1895 1663 878 492

l4S9 2881 1969 1089

2300 2214 1432 6R4 387 3230 2624 1781 847 482

2510 2533 1244 546 310 l570 3002 1547 676 387

3030 3596 820 292 168

1111 3476 2855 1544

1810 1576 1952 1162 645 2480 1867 2426 1434 804

2470 2690 8 18 3 14 180 2880 3171 961 368 21 I 4150 3758 1195 456 263

4420 4262 1020 362 210

1318 4126 3363 1839

.l769 3423 2327 1297

27 JO 2220 2884 1697 957

3540 3120 2118 1003 574

3911) 3751 1840 801 461

3870 3380 13 55 551 316 4260 4022 1611 653 377

4580 4473 1421 541 313

48RO 5073 1213 429 249

1529 4792 3883 2 J 41

2054 3979 2692 1510

2940 2579 3353 1966 llJ4

3420 3104 2859 1490 851

3860 3628 2463 668

4260 4153 2140 930 536

4650 4678 1874 758 438

5020 5203 1652 627 364

5350 5902 1410 498 290

1740 '5467 4410 2447

2340 4540 3063 1726

3170 2940 3827 223H 1273

4180 4 140 2812 1326 763

4620 4740 2443 1060 612

2629 5110 3438 1944

3630 3304 4308 2514 1434

4800 4956 3165 1490 859

5332 2750 I 191 690

5050 5340 2139 864 501 S850 6008 2408 971

5450 5940 J88h 71':> 416

1953 6149 4943 2757

3690 3540 3264 1698 972 4240 3980 3674 1908 1095

5830 6740 1610 568 332 6800 7585 1812 639

2901 5652 3795 2152

3850 3650 4765 2776 1587

4500 4398 4065 2108 1212

5120 5146 3501 1647 9'il

689 337 1002 384 1145 428 1276 478 1430 529 1584 619 1863 733 2324 868 2769 1004 3224 1141 3685 1277 4151 1405 4596

2153 6799 5451 3052

2870 2246 201i8 1086 6 14 H40 2(,7()

2459 1286 731

532

297

1164

1060

467 264

~350

5710 5895 W42

1317 7nl

2700 28 52 1089 445 254

(,~50

5b4

6hS4 2123 804 4(,9

&270 6642 2664 1073 624

6800 739 1 2.349 889 519

183

104

3 74

7280 8389 2005 706 413

Buried Pipes

617

Total design load W c in kilogn1ms per metre or pipe length for cover depth H in metres H=

3. 7

4.0

4.3

4.6

4.9

5.2

5.5

5.8

6.1

6.4

6.7

7.0

7.3

7.6

1448 278 97 54

1566 250 83 47

I 1)83 226 72 41

1801 205 63 3h

1918

2154 156 44 25

2271 143 39 23

2389 1 32 35 21

2506 122 32

2624 113 29

32

2036 170 49 28

19

17

2742 105 27 16

2977 92 22 13

2260 2 107 399 137 78

2340 2278 359 118 67

2390 2449 324 102 59

2450 2620 293 90 52

2500 279 1 267 79 46

2540 2963 244 70 41

2580

2620 3305 206 56 33

2640 3476 189 50 30

2660 3648 I 75 46 27

2690 3819 162 41 24

2710 3':190 151 38 22

2859 98 24 14 2730 4 161 140 35 20

2450 2994 334 102 59 2970 3338 372 I I3 65

2500 3189 104 52

2540 1385 278 80 46

2580 3581 254 71 41

2620 3776 234 64 37

2640 3972 216 57 34

2660 4168 199 52 3l

2690 4364 185 47 28

2710 4559 I 71 43 25

2730 4755 160 39 23

2750 4951 149 36 21

3040 355(, 338 100 58

3100 3775 309 88 52

3160 3993 283 79 46

3210 4211 260 71 41

3260 4430 240 64 37

noo

3330 4866 205 52 31

3360 5084 191 48 28

3390

4648 221 58 34

5303 177 44 26

3400 5521 165 40 24

2970 3740 415 126 73 2l)70 4141 459 139 81

3040 3985 378 111 65

3100 4229 345 99 58 3100 4583 381 JOY

3160 4474 316 88 52

3210 4718 290 79 46 32 [() 5225 321 87 51

3260 4963 268 71 42

3300 5208 247 6':1 .38

3330 5452 229 58 35

3360 'i697 213 53 32

3390 5942 196 49 29

3400 6186 185 45 27

3260 5496 296 78 46

3300 5767 273 71 42

3330 6038 253 64 311

3360 6309 235 59 35

3390 6580 219 54 32

3400 6851 204 49 29

3950 6786 321 S3 49

4010 7105 297 75 45

4050 7424 276 69 41.

4090 7743 257 63 38

6140 8044 398 103 61

6250 8422 369 94 56

6340 8801 343 85 51

6440 9179 319 78 47

4130 8061 239 58 34 6500 9575 297

2260 2407 4 54 156 89

2340 2602 408 134 77

2390 279/l 369 116 67

27 10 2683 505 173 99

2810 2902 454 14 9 86

2900 3120 410 129 75

2710 3006 565 193 1I 1

2810 32 51 508 166 96

2900

2710 l328 624 21.3 123

2810 3'i99 'i61 18.3 !Of>

3180 3915 7.l3 249 144

3300 4234 658

4fi50 4641

34'))

4 ~~~

144 83 2900 3879 506 159

U!6

sn

'JO

3040 4412 418 123

3134

224 62 36

72

64

3160 4954 349 97 57

3700 5510 447 127 7'i

3780 5829 410 114 67

3830 6148 376 102 60

3910 6467 347

95

3610 5191 490 144 84

5080 5397 739 231 135

5260 5775 fi70 202 Ill:!

5440 61H b09 178 105

'i600 fi532

5750 6910 509

6020 7666

5650 (>42 5 871l 274 160

5870 6876 796 240 141

6080 7326 724 211 124

6270 7777 661 188 1I 1

83 644() 8228 605 167 99

5900 7288 468 126 75

366 214

62.30 74'77 1021 318 187

6490 8002 926 278 164

6720 8256 842 246 145

f>950 9051 768 218 129

7150 9576 704 194 115

6190 7340 Hl9 485 284

6500 7940 1292 417 245

6820 RS 39 l16f> 363 213

7100 9139 1()<; 7 118 11!7

7230 826 1 J(i20 545 319

7630 8937 14 ~s 4hY 276

7750 9137 1792 603 35.3

8190 9885 lli09 519 305

92

3520 4872 '>38 163

124

3420 4553 594 186 108

30S 179

4870 5019 819 26(, 155

5160 5524 1084

5410 5'J75 974

3(,(,

315

213 S660 6427 1260 425 248

184

912

214

59'i0 6952 I 132

556

158 93

7390 7630 97l9 I 0.33l) 961 877 280 248 147 165 8720 9040 8010 8360 9613 10.289 10.965 I 1. 540 9S7 I 313 II S9 1082 408 357 3I 5 279 2I1 240 186 165 8620 9030 9400 9760 10.634 I J. 38 2 12.130 12.R79 1452 11 97 l316 1092 415 395 348 309 20f> 266 233 183

141

92

54

431

114 67

2750 4333 131 32 19

72

43

6610 8678

6760 6900 7040 7150 7260 7380 9579 10.030 10.480 10.931 11.382 9129 556 407 379 353 473 512 438 135 122 101 85 111 150 93 73 66 60 51 89 80 55 7340 7530 7700 7850 IWOO 8140 8270 10,101 10.626 11.150 U.675 12.200 12.725 13.250 647 596 550 4 73 440 410 510 I 74 15 7 142 129 99 118 108 103 85 64 93 77 59 70

7X60 8090 9020 9170 1>300 8500 8680 8870 10.939 11.539 12. I 39 12.739 13.339 1 3.938 14.538 15.138 738 628 582 540 502 468 803 680 222 179 162 147 134 123 113 199 13) 1I8 106 96 88 80 73 68 9340 9640 9900 10.200 10.400 10.600 10.800 11.000 12.316 12.992 13.668 14.344 15.020 15.696 16.3 72 17.048 904 707 654 565 527 765 831 607 202 249 224 182 166 151 138 127 148 13 3 120 109 99 90 83 76 10.100 10.400 10.700 11.000 11.300 11.500 11.800 12.000 l3.f>27 14.375 1 'i.J 24 15.872 16.620 17.369 18.1 17 18.865 919 782 1000 846 724 672 625 583 276 247 223 202 141 183 167 153 16 3 14 7 120 91 133 109 100 84

618 Table

Performance and Calculations

s.•

Nominal diameter (mm)

Equivalent load (kgf/m)

210

600

270

675 750 825

330 400 490 560 650

900

975 1050

·when a pipe is running full. its contents are equivalent to an external load of 75 1Yo of the weight of water in the pipe. '

Buried flexible pipes

The following are guidelines for calculations involving buried flexible pipes. Notation

Symbol

Definition Deflection lag factor Mean diameter of pipe Reduction in vertical diameter Elastic modulus for soil as determined at overburden pressure in tri-axial test Stiffness factor for pipe Sub grade modulus Bending strain Tensile strain Height of cover above pipe spring line Deflection coefiicient dependent upon bedding angle Meyerhof's constant for granular materials (taken as 1.63 N/mm 2 j m depth) Total external pressure on pipe External pressure on pipe used in buckling strength calculations External pressure on pipe used in deflection calculations Critical buckling pressure External pressure on pipe due to backfill Internal pressure External pressure on pipe due to surcharge loading

Unit

mm mm 2

N/mm N/m 2 2 N/ mm /mm

m

)

N/mm2

N/ mm N/mm 2

N/mm 2 N/mm

2

619

Buried Pipes

External pressure on pipe due to traffic loading Internal vacuum pressure Pipe-wall thickness

Loads Traffic loads (P1)

Traffic loading may be taken rrom the appropriate charts, e.g. as given in NBS Special Report No. 3 7.

Table 6. Turnall pipes: size range and classification

Nominal diameter

Class L

ClassM

Class H

Minimum ultimate crushing load

Minimum ultimate crushing load (W.r)

Minimum ultimate crushing load

(WT)

kN/m

mm

kfg/ m

kN/ m

(WT)

kfg/ m

kN/m

kfg/ m

3570 3940 4460 4840 5800 6550 7000 7600 8930 9670 10.120

37.95 3 7.95 37.95 37.95 37.95 37.95 46.68 52.56 58.35 65.70 77.47 86.10 91.88 100.71 107.87 116. 70 124.05

3870 3870 3870 3870 3870 3870 4760 5360 5950 6700 7900 8780 9370 10.270 11.000 11.900 12.650

~--

100 150 175 200 225 250 300 375 450 525 600 6 75 750 825 900 975 1050

37.95 42.16 48.05 51.00 55.40 58.35 62.76 ' 6 5. 70

35.00 38.63 43.73 47.46 56.87 64.23 68.64 74.53 85.57 94.82 99.24

3870 4300 4900 5200 5650 59.50 6400 6700

Table 7. Dept h 11 1 (mm) corresponding to bedding angle a Nominal di <Jmeter

200

225

250

300

350

400

450

500

600

700

7'i0

(rnm )

Bedding angle

lr 1 (mm)

a.

t100 90°

25 50

120°

f--- - -- - 100

-

- --

---7 f - -- - -

50 - - - - - - - + 100 200

~ ~

7 5 -----+ 150 -----+

~ 250 - - - - - - t

620

Performance and Calculations

For main road traffic loading, normally use either HA or 45 units of HB loading in accordance with BS 153: Part 3A, depending upon the quantity and type of vehicles expected. Surcharge loads (P5 )

Include here long-term loads. Backfill (P e)

Normally use the full weight of the soil above the crown of the pipe. For buckling resistance, where ground-water level is above the pipe, ma1<e allowance for buoyancy and add water pressure at crown (at invert if pipe can be empty). Vacuum (P)

Include this if there is a possibility of full or partial vacuum inside the pipe. Internal pressure (p)

This is used in strength calculations to assess the quantity of glass reinforcement necessary to resist bursting. Normally use maximum working pressure including an allowance for surges, and check using test pressure with a reduced factor of safety. Total external pressure on pipe (P0 )

For deflection calculations Pod= 2Pt + P s + Pe· For strength calculations P ob = P t + P s + P e + P v· Note: Transient loads, e.g. traffic loads, have less effect in deflecting a flexible pipe than do permanent soil loads and surcharges. Therefore. when considering deflection only. a reduction factor of 0. 5 may be applied to Pt. Deflection

Spangler's formula for the deflection of flexible pipes can be written thus: ~_ D

d-

1

K x

8 El 106 x d 3

Pod

+ 90.031 e.d.

where 8 - reduction in vertical diameter d - mean diameter of pipe e = subgrade modulus

Buried Pipes

El d3 -

621

pipe stiffness factor

D 1 = deflection lag factor This is introduced to make allowances for the slow increase in deformation of some soils under sustained lateral pressure. Typical values are in the range 1.0-1. 5 for non-pressure pipes. For pressure pipes where internal pressure just balances external load. use D1 = 1. For pipes where high internal pressure is likely to cause re-rounding use values between 0.25 and l, typically 0.5 . k = 0.100 for 60 bedding angle Meyerhof and Fisher, based on Terzaghi, have shown that: Es e= - -0 . 75 X d where Es = modulus or elasticity or the soil at overburden pressure, as determined in a tri-axial test. If no test results are available, use 4000-10,000 kN/mm 2 in good ground above water table, according to compaction; 2000 to 5000 kN/m 2 in poor ground, or in good ground below water table. Alternatively, in good ground Es may be assessed by the following relationships: Es = ksH x if backfill is dry granular material Es

d = ksH x 1.7 . if backfill is saturate granular material 2 7

where ks (Meyerhof) is taken in the range 1.09-3.2 5 N/mm 2 / m depth, a value of 1.63 N/mm 2 / m depth being commonly used. H = height of cover above pipe spring line With flexible pipes, the effect of the pipe stiffness on the deformation of the composite pipe/ soil system is small and can usually be neglected. The Spangler formula then reduces to: ~ _ D 2.4Poct

d-

1

Es

The long-term deflection calculated as previously should not exceed 5% of the diameter. If necessary. better quality surround material, and/ or higher compaction should be specified. Allowable initial deflection will depend upon the engineer's assessment of D 1 but, as a guide, this should be limited to a maximum or 3%.

62 2

Performance and Calculations

Buckling strength

Based on Meyerhof and Baikie. the critical buckling pressure on a buried pipe (P c) is given by the following equation:

El 1 Es x d3 x 10n

Pc = 4.6

Therefore. permissible buckling pressure (P ob) is as follows: 1

p ob

FS

=

X

4. 6 Es

X

El d3

1 X

Cf

X

1 on '

where FS = factor of safety against buckling for which a value of 2 is used Cf = creep factor typicallly in the range 2-3 depending upon the long-term elastic properties of the pipe-wall material

El

d3

-

pipe stiffness factor (initial)

Bursting strength

Bursting is resisted by glass-reinforced layers acting in hoop tension. The thickness of glass-reinforced layers provided is such that at working pressure there is an initial factor of safety against bursting of between 6 and 7. At test pressure, a factor of safety of at least 4 is normally available. Crushing strength

Certain pipes have a crushing strength in excess of 80 MN/ m 2 . Crushing stress is not normally critical. though. Longitudinal strength

Pipes should have longitudinal strength in excess of the requirements of BS 54 8 0 Part 1 : 1 9 7 7. Strain

Bending strain £6

If the pipe deformed a s a n eclipse, the strain in the pipe w a ll due to bendin g would be : 38 t Eb = - X d d where t = thickness of pipe wall.

Buried Pipes

62 3

Tests by Molin showed that bedding irregularities caused deviations from this theoretical value which were dependent upon pipe stiffness, i.e.:

where 3 ~ d ~ 6: d tends towards 3 for stiffer pipes which are less affected by bedding irregularities and hence, for a particular deflection, are subject to correspondingly lower levels of bending strain . In non-pressure pipes, bending strain should be limited to 0.3 5%. For pressure pipes, bending strain is generally limited to 0 .2%. Circumferential tensile strain E1

Circumferential tensile strain in pressure pipes should normally be limited to an initial maximum value of 0.2% at working pressure. Note: In pressure pipe design , the effects of bending and internal pressure are not additive and may, therefore, be considered separately. Summary of design criteria

Long-term deflection shall be limited by the allowable bending strains listed or to 5%, whichever is the lesser. Bending strain, 0.3 5% (non-pressure); 0.20% (pressure). Circumferential tensile strain, 0.2%. Trenching

The preparation of the trench bottom to give an even bedding for the barrel of the pipe, and proper alignment of pipes, is of primary importance. In rocky ground the trench should be extended to at least 100 mm deeper than required and then made up to the required level by introduction of well rammed compactible material of a type which will not be washed away; alternatively, the pipe may be embedded in a layer of freshly mixed concrete. The trench should not normally be opened up more than a few pipe lengths ahead of the point where laying is taking place. Width of trench

The trench width will depend to some extent on the ground conditions and depth of laying but should be kept to the practical minimum. Minimum widths for normal conditions. as used in the preparation of external loading charts, are based on standard bucket sizes wherever possible and give at least 150 and

624

Performance and Calculations

200 mm clearances on each side of the pipe for diameters in the ranges 200-3 SO and 400-7 SO mm, respectively. In narrow-trench conditions, the backfill load is a function of the depth of cover and width of trench (B) as measured at the level of the crown of the pipe. Thus the backfill loads will be the same for any of the trench sections shown in Figure 2. Where a particular width has been specified, it should not be significantly exceeded without reference to the pipeline designer. Depth of trench

The depths at which a pipeline is to be laid will normally have been determined by the pipeline designer to whom reference should be made if, for any reason, the depths specified for a particular application require to be exceeded by a significant amount. The minimum depth of cover will depend on considerations such as frost , traffic loadings, size and class of pipeline and, as regards adequacy of anchorage, the type and compatibility of the fill material. Preparation of trench bedding

Class C bedding

In Class C bedding where the pipe barrel is to be in more or less continuous contact with the foundation soil, the initial excavation should be marginally less than the required depth in order that final levelling and preparation of the bedding may be carried out manually. Any high spots should be removed. If overdigging accidentally occurs, the correct level must be regained by introduction of selected material, well-compacted. This preparatory work can be aided by use of a wooden straight-edge. of length not less than that of the

The effecrive rrench widrh (B) in lhe lhree exa mples shown is as measured all he level correspo nding 10 rhe u own o f I he pipe.

t

t

H

... .. . :-::·· . ..:. .· ·.

-8-+--~

H

...·

:- ·-::·

;~(:.::;:::

.. ::-:·:·:-::·

Figure 2.

..... ·:-:.:·

::- .·.-... ·.·..·.... ..··....·.·. . .

·.

Buried Pipes

625

pipes. One end of the straight edge should be notched. Allowance can be made for slight initial settlement due to the weight of the pipe. Class B bedding

In Class B bedding itis necessary to overdig the trench by an amount equivalent to the required depth of granular overlay between the pipe and the foundation ground. The straight-edge technique can again be used to obtain the gradient and approximate level of the granular bedding. For both Class B and Class C bedding it is necessary to excavate a joint hole of sufficient length and depth to give clearance for the coupling to ensure that the pipes rest on the trench bed and not on the coupling. Backfilling

Backfilling should be carried out in accordance with the requirements specified for the particular pipeline and can take place as soon as the joints have been made. rr it is desired to leave joints uncovered until completion of pressure testing, the trench should be backfilled only over the barrel portion of each pipe. In such cases it is necessary to ensure that an adequate depth of compacted backfill is applied over the crown of the pipe to prevent the pipeline lifting when the test pressure is applied. For Class C bedding selected backfill is compacted to a suitable depth h 1 , which corresponds to the bedding angles as selected for the particular nominal diameter of pipe. The backfill between levels is ordinary soil, free from lumps and large stones. Compaction will normally be required and should be carried out in stages with layers of 150-300 mm in thickness. The remainder of the excavated material can be used for the top level of backfill, the extent of compaction required depending on local factors. For Class B bedding the pipe will have been laid on a prepared granular bed, which should not be less than 100 mm for all sizes of pipe where laid in uniform soils. Where laid in rock or mixed soils containing rock bands, boulders. large stones or other irregular hard spots, dimension h should not be less than 200 mm. To complete the granular bedding, a further layerofsuitable depth (according to pipe diameter and bedding angle (a) as selected) should be added and compacted. Selected backfill. free from lumps or large stones, is then compacted in layers of 150-300 mm to a height of 300 mm above the crown of the pipe. Ordinary backfill material can be used for the remainder, the extent of compaction depending on local requirements. Joint holes should be backfilled with selected material and properly compacted.

626

Performance and Calculations

Large stones should be kept well away from the sides or the trench to avoid the possibility of their being accidentally dropped on the pipes which have been laid. Thermoplastic pipes

CPVC piping is usually selected for its higher temperature characteristics, i.e. 48-94°C (120-200°F). Expansion and contraction could become excessive at the higher ranges with intermittent flow in buried lines. Expansion joints are recommended for use in suitable pits for the upper temperature limits. In this case, the line should not be 'snaked'. Snaking the pipe with as many loops as possible per 30m (100ft) should prove satisfactory for normal conditions for PVC and for temperature ranges up to 60°C (l40°F) for CPVC. Sun heat or hot water flow to bring the pipe to 38-44°C (10011 0°F) surface temperature is recommended prior to preliminary backfill of the snaked line. Care should be used to make the best possible solvent-cement joint. Threading should be avoided. \,Yhere the thermoplastic pipe is joined to metal. use or a metal flange with a flexible gasket is suggested. Cement cure times in excess of those normally recommended are suggested prior to running at the elevated temperature. vVhen thermoplastic pipe is installed underground in trenches, the trench bottom should be smooth and rree or rocks and debris. Trenches should never be used as repositories for rubbish. H the trench is dug in ledge rock, hard pan or where boulders and rocks are not removed, the trench bottom must be padded out with sand or compacted with fine-grain soils. The trench should be wide enough to provide adequate room for : (1) joining the pipe in the trench, (2) snaking the pipe from side to side in the trench to provide slack for future contraction or expansion, and (3) placing and compacting side fills. Trench width may be minimised by joining the pipe outside of the trench and lowering it into the trench with levelling supports. Trench depth is determined by intended service. national standards and recommendations as well as local conditions. Thermoplastic pipe should be installed at least below frost level. Pipe for conveying liquids susceptible to freezing should be buried no less than 300 mm (12 in) below the maximum frost level. Permanent lines subjected to heavy traffk'should have a minimum cover of 600 mm (24 in). For light traffic 300-450 mm (12-18 in) is normally sufficient for small diameter and small diameter-to-thickness ratio pipe. \,Yith larger sizes or larger diameter-tothickness ratio pipe, bearing stresses should be calculated to determine cover required.

BuriedPipes

627

As well as local and national codes, reliability and safety should always be paramount. Bedding and backfilling thermoplastic pipe

vVith a smooth uniform trench bottom. the pipe will be supported over its entire length on firm, stable material. Blocking should never be used to change pipe grade or to provide intermittent support over low sections in the trench . Because subsoil conditions vary greatly throughout the world, different pipe-bedding problems will be encountered in various localities. In general, subsoil should be stable and should provide physical protection for the pipe. The pipe should be surrounded with backfill materials having a particle size of 13 mm I 2 in} or less. Backfilling should be carried out in layers with each layer compacted sufficiently so that lateral pressure soil forces are developed uniformly. Under certain conditions, it may be advisable to have the pipe under pressure during the backfilling operation. When compacting sand or gravels. vibratory methods are recommended. If water flooding is used, the initial backfill should be sufficient to ensure complete coverage of the pipe. Additional backfill should not be added until the waterflooded backfill is firm enough to walk on. Precautions should be taken to stop the pipe flo a ting. In all instances, the trench should be filled completely, and rolling equipment or heavy tampers should be used only to consolidate the final backfill. With regard to thermoplastic pipe, rererence should also be made to ASTM D2 774 'Underground Installation of Thermoplastic Pressure Piping' and ASTM D2321 'Underground Installation of Flexible Thermoplastic Sewer Pipe'. See also the Chapter on Thermoplastic Pipe.

e

Collapsing Pressure for Pipes and Tubes In the general case of pipes where the length is eight or more times the diameter, the uniformly applied pressure to produce collapse is given by: p

=

2E 1- a 2

where P

--

E

--

(_!_)

3

D

external pressure modulus of elasticity of pipe material a -- Poisson's ratio for pipe material t = pipe-wall thickness D = outside diameter

The upper limit for the collapsing pressure is given when the compressive stress produced is equal to the compressive yield strength of the pipe material. Buried pipes

Buried pipes are subject to both internal and external loading. the general theory stating that the magnitude of internal pressure which a rigid pipe can withstand varies inversely with the magnitude of simultaneously applied external loading. The net effect on the combined load-bearing strength of the pipe can be determined mathematically from the Schlick formula, as follows:

pi p+ -(~Tr] =

which may also be written as:

Collapsing Pressure for Pipes arrd Tubes

where P 1

-

P2 F1

-

WT

=

629

internal hydrostatic pressure (kN/m 2 ) which will fracture the pipe when acting in combination with some external load F. applied in two-edge bearing internal hydrostatic pressure (kN/ m 2 ) which will burst the pipe in the absence of any external load external load (kN/ m) applied in two-edge bearing which will fracture the pipe when combined with some internal pressure P 1 two-edge bearing load (kN/m) which will crush the pipe in the absence of any internal pressure.

Figure 1 shows a 'combined loading' curve for a pipe which would burst at some internal pressure, P 2 , or crush under some external load, WT, if either were acting alone. If, however, some lesser internal pressure, P 1 • is acting on the pipe in combination with an external loading, F 1 • the magnitude ofF 1 at which fracture will occur can be determined by means of ordinates drawn to intersect at a point X on the curve. Combined loading

The potential working envelope of a buried pipe is represented by a curve describing maximum internal pressure combined with a curve describing maximum external load (crushing pressure). Thus, because of the interdependence of the two parameters. boundaries are curves rather than straight lines and take the form shown in Figure 2. Practical curves of this form, known as combined loading charts, can be devised for each particular size and class of pipe and incorporate suitable safety factors against bursting or crushing. Such a chart will indicate maximum working limits, e.g. for any given pressure limit a corresponding safe working crushing strength, or safe working pressure limit.

Q) L. ~

~

Q)

p.

'-

a.

C'J

c .... Q)

c P2 X

WT y

F, External load Figure I.

630

Performance and Calculations /pressure limit curve

crush limit curve

Safe working two -edge crushing strength of pipe F( =~:} k Figure 2.

Basically, such loading charts are modified Schlick curves, taking into account suitable safety factors, e.g.: Pw =

~

[1 - (

~J]

where Pw = maximum sustained operating (or static) pressure (kN/ m 2 ) X = factor of safety against bursting when an in tern a! pressure. Pw· is applied together with an external load (see Table 1) F 1 = external load (kN/m) applied in two-edge bearing which will fracture the pipe when combined with some internal pressure. Pw F = safe working two-edge crush strength of pipe (kN/m) y = factor of safety against crushing when an external load, W c• is applied together with an internal pressure P 1 = internal pressure (kN/m 2 ) which will fracture the pipe when acting in combination with some external load, F1 , applied in two-edge bearing P 2 =internal hydrostatic pressure (kN/m 2 ) which will burst the pipe in the absence of any external load. External loading

From preceding considerations it is evident that the safe working two-edge crushing strength, F, corresponding to a particular maximum sustained operating (or static) pressure, Pw• must be compared with the total external load acting on the pipe due to backfill and any other superimposed loading.

Collapsing Pressure for Pipes and Tubes 16·0 ~----------------------------------------------------------------,

.. £!.

14·0

class 25 maxomum sustaoned pressure

~

Q_

~

"

t---------

12·0

:::.,

r----

a. ~ 10·0

~

0;

u

0 "0

~

8 ·0

§

"'

"'E"

" E

..

6·0

;;

.,E !:

o;

4·0

u

0.

2·0

0 0

10

20

"'

Workmg 2 -edge crush strength F

40

30

=( wke) kN/m

50

60

70

80

200 mm nominal diameter

Chart 1. Example of combined loading chart: 200 mm dianreter. 16·0

14·0 ~

8. ~

Q_ Q)

:; "'"' !'!

12·0

0.

g' .10·0

.,~u 0

.,

u c:

8·0

§

"'::>

"'E

" .,E"'

6·0

.~ )(

!: 'ii u 0.

4 ·0

2·0

0 0

10

20

Work1ng 2 -edge crush strength F

30 = (

40

~e

) kN/m

50

60

70

250 mm nomina l diameter

Chart 2. Example ofcombined loading chart: 250 mm diameter.

80

631

632

Performance and Calculations

16-0r------------------------------------------------------------------, 14·0

'"

8.

class 25 maximum sustained pressure

~

~

~

"'"'" P!

0.

"' ·= ~

.. ..

a. 0

"0

c

5...

"'"

E " 6.

..E .

-~

.E

~a.

10 Wor1<~ng

20

30

2 ·edge crush strength

F

40 = ( ~e

60

50

) kN/m

70

80

350 mm nominal diameter

Chart 3. Example of combined loading chart: 3 50 mm diameter.

16-or--------------------------------------------------------------------------. 14·0~------------------------------------------------

E

6·0

"

E ;c

.. ..

E c

4·0

~ o. 2·0

0

10

20

Workong 2-edge crush strength

30

F

50

60

70

450 mm nominal diameter

Chart 4. Example ofcombined loading chart: 4 50 mrn diameter.

80

90

'

Collapsing Pressure for Pipes and Tubes

6 33

16-o r--------------------------------------------------------------------------, :.

14·0

£

"' 1 2·0 class 25 m aXImum ~

susta•ned pressure

"'"'c. ~"' .1 ~

O·O c;;; 20mawrmum su~ta•ned pressure

., 0

~

8·0

'"

~

class 1 5 max•mum susta•ned pressure

E

E

.. ..

6·o

;;

E

~

4·0

"a. 2·0

O L-----------------------------~----------------~--------------------~ 40 70 10 20 50· 60 80 90 0 30

Work ing 2 · edg e c rus h streng th F (=~) k N / m l

650 mm nominal diameter

Chart 5. Example of combined loading chart: 6 50 mm diameter.

16-o r--------------------------------------------------------------------------, 14-0 r---------------------------------------------class

.,., c

25 maxtmum sustamed pressuro

class I 5 maxrmum 8·0 sus!
~

.. ..E :I

E

6-<>

:I

;;

E

2·0

0

10

20

30

W or'K ing 2 · edge c ru sh strength F (=~) kN / m

80

90

750 mm nominal diameter

Chart 6. Example of combined loading chart: 7 50 mm diameter.

110

120

634

Performance and Calwlations

Table 1. factors of safety (combined loading)

Nom ina! diameter of pipe mm

200 and 225

250-500 600-750

in

X

y

7.9 and 8.9 9.8-19.7 2 3.6- 29.5

3.5 3.0

2.5

2.5

2.5

2.5

Table 2. Bedding factors-Class 'C' bedding

Bedding factors (k) in different laying and backfill conditions Trench and negative projection Bedding angle CJ.

Positive projection

Ordinary backfill compacted between XX and YY

Ordinary backfill non-compacted between XX and YY

Ordinary compaction

1.3 1.5 1.7 1.7

1.1 1.2 1.3 1.3

1.4 1.7 1.9 1.9

Table 3. Bedding factors-Cla ss 'B' bedding

Bedding factors (k) in different laying and backfHI conditions Trench and negative projection Bedding angle ex

90° 120°

Positive projection

High compaction

Ordinary compaction

Ordinary compaction

2.6

1.9 2.2

2.3 2.5

3.0

·At least 90% of maximum possible at the optimum moisture content (90% standard Proctor). Notes: 1. The above factors of safety include allowance for surge provided that the maximum sustained operating, or static. pressure plus surge (i.e. pipeline design pressure) does not exceed the maximum allowable sustained pressure for the class of pipe by more than 10%. 2. For pipe sizes up to 150 mm (6 in) diameter. combined loading may not need to be considered a3'. in this range. pressure pipes are designed on the basis of beam strength and consequently have bursting and crushing strengths in excess of practical needs.

Collapsing Pressure for Pipes and Tubes

63 5

~

F is defined in terms of a two-edge strength, so the following relationship is applicable:

kF =We

or

F = We k

where We = total external loading acting on the buried pipe (kN/m) k - bedding factor (see Tables 2 and 3 ). The magnitude of We can be calculated from the appropriate Marston formulae and coefficient according to the type of soil and whether laid in trench ('narrow' or 'wide') or embankment conditions.

Table 4A. Modulus of soil reaction for pipes to EN 545

DN K (2cx:) -

-

--

{3=0. 75 E' =0

E' = 1000 =2000 E' = 5000 {3= 1.50 E' =0 E' =1000 E' =2000 E' = 5000 E'

80- 300

350- 450

500- 1000

() .11 () (20°)

0.105(45°)

0.103 (60°)

0 .3-10.5 0.3-11.0 0.3-12.0 0.3-14.0 0.3- 10.5 0.3- 11.0 (>.3- 11. 5 0.3- 14.0

0.3-7.5 0.3-8.5 0.3-9.0 0.3-12.0 0.4- 7.0 0.4-8.0 0 .3- 9.0 0.3-1 2. 0

0.5-2.0 0.3-3.5 0.3-4.5 0.3-8.5

~

See note 1

0.6-3.0 0.5- 4. 5 0.3-8.0

Note 1: Only a specific calculation for each case can provide an adequate a nswer. Note 2: The values given for the heights of cover have been established for the class K9: they are also valid for classes K ~ 10.

Table 48. Modulus of soil reaction for pipes to EN 598

DN

100-300

350-450

500- 1000

0.110 (20°)

0.105 (45°)

0.103 (60°)

0.3-5.0 0.3-6.0 0.3- 6.5 0.3- 8.5 0.6-5.0 0.5-5. 5 0.5-6.5 0.4-8.5

0.5-3.0 0.4-4.0 0.3- 5.0 0.3- 8.05

0.5- 2.0 0.4-3 . .5 0.3- 4.5 0.3-8.0

See note

See note

0.7-3.51 0.6- 5.0 0.4-8.0

0.8-3.0 0.6-4.5 0.4-7. 5

-

K (2cx:)

/3=0. 75 E' = 0 E' =1000 E' =2000 E' = 5000 /3= 1. 5 E' =0 E' = 1000 E' = 2000 E' = 5000

---

Note: Only a specific calculation for each case can provide a n adequate answer.

63 6

Performance and Calculations

Trench beddings

Wherever soil and other related conditions permit. it has been widely adopted practice over many years to lay concrete pressure pipes on the well-levelled and prepared natural bottom of the trench. Selected backfill is introduced in layers not exceeding 300 mm (12 in), and properly compacted up to a level of 300 mm (12 in), approximately above the crown of the pipe. In the International Standard. beddings of this type are designated Class 'C'. This bedding embraces the Class 'C' and Class 'D' beddings described in National Building Studies Special Report No. 35. Consult EN545: 1994 and EN598 : 1995 . See also the chapter on Buried Pipes.

Boiler-Feed Calculations Boiler-feed pumps have to deliver hot water at temperatures exceeding 1 oooc from closed feed tanks, with a steam cushion of a minimum saturated vapour pressure at a given temperature of the feed water. A typical layout is shown in Figure 1, when the geodetic positive suction lift is given by: Hgs = 6.Hc + h;:s where 6.Hc = cavitation margin hzs = pressure losses in suction pipe The positive suction lift (h) must be equal to or greater than Hgs· In smaller-size boiler feed pumps, the calculated Hgs value will usually be increased by the difference of saturated vapour pressure at trnax and tkmax from the balancing device. When planning larger boiler feed pumps, check calculations of the intake piping are recommended, particularly with regard to the positive suction lift. This is mainly to be done in the operation of the so-called stepping deaeration powers.

K N VTOI 2 3 4 5

-

Pp

-

Ps

-

Pv

-

Hgv Hgs -

Figure 1. Layout diagram ofa boiler-feed pump.

steam boiler feed water tank . high pressure heater . inlet piping discharge p iping. let~ k -o ff.

balancing piping from balancing device. discharge from balancing device. saturated steam pressure of feed water at respect ive temperature. suction branch manometric pressure . fina l resultant pressure of boilerfeed pump in discharge branch. geodetic delivery head . geodetic suction head .

63 8

Performance and Calculations

To meet potential requirements in individual projects regarding small positive suction lifts. a so-called 'booster pump' is installed before the boiler-feed pump. The positive suction lift of the booster pump is determined in the same way as for the boiler-feed pump. Minimum pressure in the suction branch (Ps) of the boiler-feed pump and/or the booster pump is given by the relation: Ps

=

Pp

+

(h- Hzs)Y lO

(bar)

where Pp = vapour tension pressure at a given temperature (bar) y = specific weight of water at a given temperature (kg/dm 3 )

_

Ps- Pp

+ (h-148 Hzs)Y

(Jbr;· 2)

m

Air vent

Condensate Boiler blowdown heat recovery ~

Temperature control

Drain

Injector Level probe protection tube

Feed tank desi!]n.

Boiler-Feed Calculations

639

·where hand Hzs are in fee t y is in lb/ft 3 Pressure in the discharge branch (Pv) is given by: Pv=Pk+

h zv X Y · (bar) 10

where Pk = steam generator (boiler) pressure (bar) h zv = pressure losses in delivery piping from the boiler-feed pump branch as far as the boiler (m wg) Pv = Pk +

hzv X Y

148

2

(lbf/in )

wh ere h zv is in feet y is in lb/ ft 3 Boiler-feed pump head

The head to be generated by the boiler-feed pump should be calculated from the required pressure in the discharge branch of the boiler-feed pump using the following relation:

_ (m wg ) H = Pv - Ps x lO y H = Pv - Ps x 1 7 s·5 (.In wg ) y where pressures are in lbf/ in 2 yin lb/ ft 3 However , the project engineer s hould take into account that the pump head in (m wg) will change its characteristics consistently, regardless of the feed-water temperature. The specific weight of the water will change with its temperature. If a booster pump is to be ins talled before the boiler-feed pump, the same relation should be applied for calculating the pump head as that used for the calculation of the pump head when no booster is involved. so that: H = Pv - Ps x 1 O ( m wg ) y

H = Pv - Ps y

X

17 55 (in wg)

640

Performance and Calculations

DUPLEX BRANCH CASING IMPELLERS

PUMP

STUFFING BOX BUSH

STUFFING BOX BUSH PUMP SHAFT

BALANCE DRUM

RESTRICTION BUSH

RING SECTION ASSEMBLY

Compensated boiler-feed pump.

The only difference will be in establishing the magnitude of pressure in the inlet branch of the boiler-feed pump which can be calculated by the relation:

Ps = Pvn -

hzp X y

10

(bar)

where Pvn = discharge branch pressure of booster pump (bar) h~P = head losses in the piping between the booster pump and boiler-feed pump (m) Ps = Pvn-

hzp X Y ) (lbf/in-) 148

for hzp in feet yin lb/ ft 3 Pump delivery

The boiler-feed pump delivery may be expressed as (l/hr) in project documents. The pumps are, however. tested in the manufacturer's test shops with cold • water. In European practice, pump delivery is given in (1/ min) and/or (I/sec).

Boiler-Feed Calculations

BARREL CASING

IMPELLERS I

z

0

E

DISCHARGE COVER

::J

(f)

BALANCE DRUM

STUFFING BOX BUSH

STUFFING BOX BUSH

PUMP SHAFT

Barrel-casing boiler-feed pump.

The relation between these deliveries will be: Q(l/ hr)

=

y X 60

1000

Q(l/min) X

Similarly, for Q in gal/ min: Q (ga ljhr) = 0(gal/min) X

60

Shaft input power required is given by:

N = Q X (Pv - Ps)

X

0 .02 723 (kW)

y X l}

where Q = pump delivery in (l/hr) Pv = discharge branch pressure (bar) Ps = inlet branch pressure (bar) y feed water specific weight (kg/dm 3 ) 17 = boiler-feed pump efficiency at a calculated point(%)

641

642

Performance and Calculations

In English units: N=

=

(Pv- Ps) y x ry

X

0.00932 5 (kW)

(Pv- Ps) yxry

X

0.0125 (hp)

(Pv- Ps) y x ry

X

0 .00777 (kW)

Ql X

Ql X

= Q2

X

= Q2 X (Pv - Ps) X 0.010 (hp)

yxry where Q1 is in UK gal/min Q2 is in US gal/ min Pv and Ps are in lbf/ in 2 yisinlb/ft 3 . The pump shaft input of a boiler-feed pump should be given by the manufacturer in the consistent units given later and calculated by the following equation:

N=

QX H 102

where Q H

X

60

X

= Nu

Y X

fJ

(kW)

fJ

= pump delivery (1/ min) = head (m wg)

Nu = pump useful capacity (kW) y = feed-water specific gravity (kg/ m 3 )

In English units (head His in wg):

N

= Ql

H X y (kW) 51,500xry X

Q] X

H

X

38,420

N

y

Q x Hx

y

X

fJ

2 = ----.42,920

Q2 X

H

3200

(hp)

X 1]

X

y

X YJ

(kW)

(hp)

Boiler-Feed Calculatio11s

643

Por the slection of the driving machine. a planning margin in its output should be considered owing to the inaccuracies in calculations of the whole system and unpredictable conditions. This is why the driving machine output (NM) will be obtained by the following relation:

NM

= ( 1.08 - 1.2)N

When speed-increasing gear boxes (speed-reducing gear boxes for booster pumps) and hydraulic couplings are to be set, then efficiency should also be taken into account for calculating the pump shaft input so that: Qx Hx y

N = -- - -- - - - 1 02

60

X

X

11 X 7']p X l7sp

where 7'Jp = gear box efficiency 7'J sp - hydraulic coupling efficiency

If the pump was tested with a cold-water supply then the followin g recalculations of the pump efficiency should be carried out if pumping hot water. l7p = '7ip

=

17m

yp where17ip = l -( l - 7'Ji) x - x 0.1 y

7'J i

= _!}_-efficiency after subtracting bearing losses YJrn

7'] 111 = m echanical efficiency y = kinematic viscosity of water at the test shop Yp = -kinematic viscosity of warm water leak-off

The whole of the pump sh a ft input. N, is not utilised in the pump for increasing the energy o f the liquid , as part of the input that corresponds to all losses within the pump will be converted into heat. This means that the water temperature in the boiler-feed pump increases proportionally to the losses within the pump. The temperature will then be:

where

0 = delivery (1 / hr) Qk = amount o f water flow throught the balancing device (l/ hr) N = pump sh a ft input (kW)

644

Performance and Calculations

If the amount of the feed-water flow through the balancing device is introduced before the boiler-feed pump, the temperature of water entering the boiler-feed pump increases to the value:

t _ (Qto I -

+ Ok)tk

Q + Qk

where t 0 = water temperature in the inlet branch less the effect of water from the balancing device (°C) tk = water temperature after the balancing device (°C). A temperature rise of approximately 1 ooc is permissible in small- and medium-sized boiler-feed pumps. At this point, a device discharging this leakoff delivery (from the piping placed after the boiler-feed pump) should come into operation automatically. In high-pressure boiler-feed pumps, more detailed analysis should be made of the leak-off amount (i.y. minimum delivery) at which the leak-off device must start to open automatically.

Steam Flow Calculations \,Yater freezes at ooc (32°F) and boils at lOOoc (212°F) under normal atmospheric pressure. ooc (32 °F) is the reference phase for zero heat content. Because the actual boiling point is dependent on ambient pressure, this can be designated t 1 . The heat required to raise the temperature of water from ooc (32 °F) to tlt marking the onset of vaporisation, is known as the sensible heat (h). At atmospheric pressure, the sensible heat of water is 349.3 kJ/ kg (150.17 Btu/ lb ). If heat continues to be applied to the water, the process of vaporisation (boiling) goes on until all the water has been transformed to steam (AB in Figure 1). During this period the temperature remains constant. The heat absorbed is called the latent heat of vaporisation (L), so that at point B: Total heat absorbed (H)

= h+L

D

c

A tl

I I I I

I I 0

oc (32

°F)

~

I h

.'.

I

I

7

L

Figure I .

+·

I Cp(t2

~I - t 1)

646

Performance and Calculations

Again, at atmospheric pressure, L = 2259.7 kJ/ kg (970.3 Btu/lb) so that:

H = 349 .3

+ 2259.7

H = 2609 kJ/kg or H = 150.17 + 970.3

H

= 1150.5 Btu/lb

At any intermediate point (C) between A and B. the stage of vaporisation can be expressed as the dryness fraction (q), or ratio of latent heat at that point to that necessary to produce a state of dry saturation (point B): Thus at any point C: H = h

+ qL

If, after point B, more heat is added to the dry saturated steam, the steam is said to be superheated. Provided the steam is subject to unrestricted expansion, the pressure remains the same, but the temperature rises to t 2 . The degree of superheat is then CP (t 2 - t 1 ). The approximate value of Cp is 0.48 . Specific values are obtained from steam tables. Steam can thus exist in three forms: dry saturated steam free of any water particles in suspension. wet saturated steam containing water particles in suspension , and superheated steam. The higher the degree of superheat the steam possesses, the more closely its characteristics resemble those of a perfect gas. Steam flow through pipes

The original (Babcock) formula for determining the quantity of steam able to pass through a particular pipe with a specified pressure drop is:

w = 87.5 where W = D = P1 = P2 = d L =

D(P1 - P2)d 5 L(l + 3.6/d)

quantity of steam (lb/ min) density of steam (lb/ft 3 ) initial pressure of steam (lbf/ in 2 ) final pressure of steam at end of pipe (lbf/ in 2 ) inside diameter of pipe (in) length of pipe (ft)

Steam Flow Calculations 212

259

266

307

)23

0

20

40

60

60

336

350

361

371

380

368 OF

140

160

180

200

64 7

PSIG 100

2600 2600

1 20 J

TOTAL HEAT OF STEAM

~

1100

-

2400 2200

-

...._

~

2000 1800

kJ/kg

1200

J

r--

1000

~

900

LATENT HEAT AVAILABLE AT DIFFERENT PRESSURESI

600

1600

700

1400

600

1200

500

Btu lib

1000 400

-

HEAT IN CONDENSATE AT STEAM TEMPERATURE

BOO

.--

-

..~

600 400

300 200

HEAT IN CONDENSATE AT ATMOSPHERIC PRESSURE I I I I I i i I I I

200

100

0

0 0

2

3

4

5

6

8

9

10

11

12

13

14

bar gauge

100120 134 144 152 159 165170175 180 184188192 195198

oc

Changes irr amounts of heat required for the two stages ofsteam production.

The formula can also be rewritten as a solution for pressure drop:

These formulae are applicable to both saturated steam and superheated steam. A further formula derived from these gives the size of pipe required for a specific mean velocity of steam:

d =usJv~D where V = steam velocity (ft/sec) Typical values ofV are: 20 to 30 m/s (70-100 ft/sec) for exhaust steam 30 to 45 m/s (100-150 ft/sec) for saturated steam 40 to 60 m/s ( 130-200 ft/sec) for superheated steam.

64 8

Performance and Calculations

Such formulae may still be used for simplified (approximate) calculations, but modifications of the D'Arcy equation are now normally employed, viz:

(PI-P,)= ,;p = _

- W

2

w' (o.oo~s336f) x V

(3 3, 6oor) dS

X

v-

X

l0

_9

where W is the flow rate (lb/hr) Vis the specific volume (ft 3 /lb) fis the friction factor appropriate to the pipe and flow velocity. Working is further simplified by calculating a discharge factor (C 1 ):

c1 = W2 x Io- 9

and a size factor (C 2 ):

c -

33 ,600f

d5

2 -

(Tabular data are available for determining C2 .) Then: ~P

-

= c1c2v

c1c2 p

where pis the mass density of the steam (lb/ft 3 ) and isdependenton temperature and pressure. W

= Jc1

X IQ-9

35,600f

c2

w Q = 4 .8 where Q ::: flow rate (ft 3 /min at STP) Sizing of condensate-return lines

Basic considerations

.

The diameter of the pipeline between the heat exchanger and steam trap is normally chosen to fit the nominal size of the trap .

Steam Flow Calculations

649

vVhen choosing the diameter of the condensate line downstream of the trap ,

flashing has to be considered. Even at very low pressures the volume of flash steam is many times that of the liquid if the condensate is at saturation temperature upstream of the trap (e.g. during flashing from 1.2 to 1 bar (17 to 14.4 lbf/ in 2 ) the volume increases approximately 17 times). In these cases it is possible to dimension the condensate line in accordance with the amount of flash steam formed. The flow velocity of the flash steam should not be too high otherwise water hammer (by the formation of waves), flow noises and erosion may occur. A flow velocity of 15 m/s (50ft/sec) at the end of the pipeline before the inlet into the collecting tank or flash vessel is a useful empirical value. The inside diameter of the pipeline required can be taken from Table 1. 20

10 i 8 7

~ "

8

"'

'\

3

"' "'....

~

~~

"""'

"""

""' "

~ >-

A)" I ~~ ~

"\

"'"- valve Standard g~r--

""' ""'~~g-~~~~K " ~'-r---~~~

~'1;. "'~?v'~

"~ ,...-

"' --

" ,.:> "".....,

I

_.,.. X

,...,. I--'

~

""r-..

./

~

~

"

!'\..,

" a tea. tube -r-::-?om06 '\, r--= ~~bellows)\

""'

Q)

...... 0

c Q)

·.-....u

"""

'V 0

u

"'

go• elbow

0.5

--

""' ""' "' ~ "" )r< ""' ""'"""'~ _...~~ ""....., I\I\ ""~ "'~ I\. "' ""' "'~ ""....., Tee

~~

2

""' ""' ""

""'""' "'"'"

-

Q)

u

~

""

~

--

4

;

~

"'

5

u

I~

~ """ ~ "".....,

. 0,3

""' "' "~

""'~ v v ~

.......

f.-'

0.2

0,1

10

,..,....-v 15

--

.....- _.,..

25 32

40

--

so

\0 ~a:~~

,..,.... ~

_.,..~

&&

eo

100

150

200

300

Nominal size (DN) The coefficie nts of resistance C of all pipeline components of the same size are read in the above chart. The total pressure drop 6p in bar can be dete rmined with the sum o f all individua l components (::iC) and the operating data.(see Figure 5)

Figure 2. Pressure drops in steam lines.

"'

400

~

soo

~

Table 1. Condensate line sizing (based on flash steam)

lrt

0

State of condensate before flashing

"\:j

P ressure at end of condensate line (bar a)

"'0 .;,

c.J)~

....,

s:: o

·- v :=L.....

::s .,..,

-ol:: ..., o..>

::::; ~ ~

., ..... c..

3l::l

:::l

0

~~

0

.....

"'

.0

1.0 1.2 1.5 2.0 2.5 3.0 3. 5 4.0 4.5 5 6 7 8 9 10 12

15 18 20 25 30 35 40 45 50

"':::,

'-'::::>.

::s

<':)-c: v.., c:::_

0.2

0.5

0.8

99 104 111 120 127 133 138 143 147 151 155 158 170 175 l79 187 197 206 211 223 233 241 249 256 263

3 5. 7 3 7.9 40.1 44.2 46.8 48.8 50.4 52.0 5 3.3 54.3 55.7 56.5 59.9 61.3 62 . .3 64.4 66.9 69.0 70.2 72.9 7 5.1 76.8 78.5 80.0 81.4

16.0 18.0 20.6 23.5 25.5 27.1 28.4 29.6 30.5 31.5 32.3 33.0 3 5.5 36.4 37.2 38.7 40.5 42.0 42.9 44.8 46.3 47.5 48.7 49.7 50.7

7.4 10.0 12.9 15.8 17.7 19.2 20.4 21.5 22.3 23.1 23.9 24.5 26.7 27.5 28.2 29.5 31.0 32.3 33.0 34.7 36.0 37.0 38.0 38.8 39.6

1.0

1.2

1.5

2.0

-·'

3.0

3.5

4.0

4.5

5.0

6

-

-

-

-

-

-

-

-

-

-

-

6.1 9.5 12.6 14.5 16.0 17.1 18 .2 19.0 19.8 20.5 21.1 2 3.1 23.9 24.6 25.7 2 7.2 28 .4 29.0 30.6 31.8 32.7 3 3.6 34.4 3 5.2

6.8 10.3 12.3 13.9 15.0 18.0 16.9 17.7 18.4 18 .9 20.9 21.7 22.3 23.5 24.8 26.0 26.6 28.1 29.2 30.1 31.0 31.7 32.5

-7.6 9.2 10.7 11.9 12.9 13.7 14.4 15.2 15.7 17.6 18.3 18.9 19.9 21.5 22.3 22.9 24.2 25.3 26.1 26.9 27.5 28 .2

)

r

-

-

-

5.3 7.3 8.5 9.7 10.5 11.2 11.9 12.4 14.2 14.9 15.5 16.5 17.7 18.7 19.2 20.4 21.4 22.1 22.9 23.5 24.1

-

-

-

-

4.5 6.0 3.8 7.3 5.3 8.1 6.3 8.9 7.1 9.h 7.9 10.1 8.4 11.9 10.2 12.6 10.9 13.1 11.4 14.1 12.3 15.2 1 3.4 16.2 14.3 16.7 14.8 17.9 15.9 18.8 16.8 19.5 I 7. 5 20.1 18.1 20.7 18.6 21.2 19.1

-

-

-

-

-

-

-

-

-

7 -

-

3.5 4.7 3.0 4.2 2.8 5.6 6.5 5.1 2.7 4.0 7.0 5.7 4.6 3.5 8.9 7.7 6.7 5.8 9.5 8.4 6.6 7.4 10.0 8.9 7.9 7.1 11.0 9.8 8.9 8.0 12.0 10.8 9.9 9.1 12.9 11.7 10.8 9.9 13.4 12 .2 11.2 10.4 14.5 13.2 12.2 11.4 15.3 14.0 13.0 12.1 15.9 14.6 13.6 12.7 16.5 15.2 14.1 13.2 l7.0 15.7 14.6 13.7 1 7.5 16.2 15.1 14.2

8

2.1 4.8 5.5 6.0 7.0 8.0 8.8 9.2 10.2 10.9 11.4 12.0 12.4 12.8

4.0 4 .8 5.3 6.2 7.2 8.0 8.4 9.3 10.0 10.5 11.0 11.4 11 .8

-

-

2.4 3.3 4.5 5.6 6.5 7.0 7.9 8.6 9.2 9. 7 10.] 10.5

9

10

12

15

18

20

-

-

-

-

-

-

-

-

1.7 3.1 4.0 4.5 5.0 5.4 5.7

2.5 3.4 4.0 4.5 4.9 5.2

-

-

-

-

2.1 3.6 4.8 5.7 6.2 7.1 7.8 8.4 8.6 9 .3 9.9

2.8 4.2 5.1 5.6 6.5 7.2 7.8 8.2 8.6 9.0

2.9 3.9 4.4 5.4 6.1 6.7 7.1 7.5 7.9

2.5 3.1 4.2 4.9 5.5 6.0 6.3 6.7

-

To determine the actual diameter. the above values must be multiplied with the following factors: kg, h Factor

-

100

200

300

400

500

600

700

800

900

lOUO

1500

2000

3000

5000

8000

10.000

15.000

20.000

1.0

1.4

1.7

2.0

2.2

2.-1-

2.6

2.8

3.0

3.2

3.9

4. 5

5.5

7.1

8.9

10.0

12.2

14.1

Bases fordetermt nin~ the i11side diameter. l. The flash steam <.~mount only I~ be in~ constdered. 2. Th.: flow velocity of the tlash ~team is as~umed to be 15 m/s.

~

(")

~ .,.., s::

S' .....

a·

::s

"'

Stearn FlowCalwlntions

651

For long pipelines (over 100m or 300ft) and large condensate flowrates. the pressure drop should be calculated to avoid the back pressure becoming too high. The velocity of the flash steam may be used in the calculations (see Table 1 and Figure 2). When the condensate is mainly in the liquid state (e.g. high degree of undercooling, extremely low pressure) its flow velocity should, if possible, be rated at 0 .5 m/ s (1.64 ft/ sec) or higher. The pipeline diameter can be chosen from the chart (Figure 3). If the condensate is pumped, the condensate in the pump discharge line can only be in the liquid phase. For choosing the pipeline diameter, the mean velocity can be rated at 1. 5 m/ s ( 5 ft/sec). Again, Figure 3 may be used.

100 ()

80 70

50 50 t.O 30

()

Steam

'

~

-

10 ,_

1

t r~

10 8 7

6

:-.

--

v

_i

r

I

i

'

~

a

111

Compressed air

•

,/ (')

1(1

'

I

~~

t-

5

-

3

3 '

1-

·u 0
>

Water

'

3

0

CL:

0.8 0.7

0.6 0.5

0.1. 0.3

0.2

0.1 0.1

02

O;L

0.3 05

0.7

2

3

s

7

10

20

'0 JO

70

SO

100

500

210 J00

Flowrate V in mJh

FigHre 3. Vo llllneflowra tes in pipelines.

2000

1000

DXl

6 52

Performance and Calculations

Calculation of condensate flowrates

Basic formula

If the amount or heat required in kcal / hr is known (indicated on the name plate of the heat exchanger) or easy to determine, the condensate flowrate M can be calculated:

M = 1.2 kcaljhr (1 /h ) 500 (g r The quotient 500 is the latent heat of steam (kcal/ kg) for m~dium pressures. The factor 1.2 is added to compensate for the heat losses. In SI units, the condensate flowrate is calculated as foHows:

=

2 W 1. 2000

~

1.2

M

3600 1000

X

Hence: M

w 560

(kgjhr)

W is the amount of heat required in Watts or Joule per second (J/ sec) and the quotient 2000 the latent heat of steam (kJ/ kg) for medium pressures. U the amount of heat Q per hour is not known, it can be calculated [rom the weight M of the product to be heated in 1 hour, the specific heat

(c

= ~~~ or, in SI units, c = k~K) and the difference between initial temperature

t 1 and final temperature t 2 (b.t

=

t2

-

t 1 ):

Q = M x c x b.t (kcaljhr) or in SI:

Q= M X

c 3600

X

b.t (W)

Example:

50 kg of water to be heated in 1 hour from 20 to l00°C. The amount of hea t required is: Q

= 50 x 1 x (100 - 20) = 4000

kcaljhr

or, in SI:

Q = 50

X

4187 1600

X

(100 - 20) = 4652 W

Steam Flow Calculations

The amount of condensate is:

M = 1.2 x

4000 = 9.6 kgjhr 500

or. in SI:

M = 1.2

X

4652 560

X

/

/

1---t;''-!rlr-tr':Y..- r- / -'I / 300

aoo

100

I~

/ /

v

" ~ <:-

~~

L

'/1SO ./10

9.97 kg/h

~

1.1. 5040 30

eo

20 1&

10

t6 5 4

~

1\..

1,5

1

"

0.5

Flow velocity win m/s Example : Steam temperature 300 °C, steam pressure 16 bar, Result : Flow velocity = 43 m/s. a steam flowrate 30 t/h, nominal size (ON) 200 mm . Figure 4. F low Vflocity in steam lines.

653

654

Performance and Calculations

Example Pipeline components ON 50 rnm Pipeline length 20m C = I angle valve . . . . . . . C = l standard globe valve . . C = I tee . . . . . . . . . . . . . . . C == 3 e I bows . . . . . . . . . . . . C =

LC

8.1 3.1 'i

3. 1 1.5

= 21.0

Operating data Temperature · Steam pressure Velocity

Joooc =

16 bar a 40 m/s

•

6p= 1. 1 bar

Result

Temperature in oc

0,05 ~ .0 1:::

0,1 0,2

0..

<J 0.. 0 "0

...

...::l 0

0,3


1/)

o,s 0......
1,0

Figure 5. Pressure drops in steam lines.

Steam Flow Calculations

655

Sizing of steam lines

When sizing steam lines, care must be taken that the pressure drop between the boiler and steam users is not too high. The pressure drop depends mainly on the flow velocity of the steam. The following empirical values for the now velocity have proven to be satisfactory: Saturated steam lines 20-40 m/s ( 6 5-130 ft/ sec) Superheated steam lines 3 5-65 m/s (115-215 ft/ sec) The lower figures should be used for smaller flowrates. For a given flow velocity. the required pipe diameter can be chosen from the chart (Figure 4). The pressure drop can be calculated from the charts in Figures 2 and 5. Calculation of condensate flowrates

If 50 kg of water is to be vaporised in 1 hour, the latent heat of approximately 5600 kcal/kg or 2000 kJ/ kg has to be added:

50 x 500 = 25 ,000 kcaljhr or, in SI:

50

X

1 2000 = 100 000 kH/h = lOO ,OOO X 000 = 27 778 W 3600 ' t

The total amount of heat required, and consequently the total amount of condensate formed. can be calculated as follows:

M=12 .

X

4000 + 2 5,000 = 6 9 6 k /h 500 . g

'

or, in SI:

M = l. 2 x 4652+27,778 x 3600= 7 Ok h 2000 1000 gj Each produc~has its own specific heat. Calculation of condensate flowrates

If the size of the heating surface and the temperature rise (between initial and final temperatures) of the product are known, the condensate flowrate M can be calculated with sufficient accuracy as follows: A M

=

X

k

(tsr

tl

+ tz) 2

(kg/hr)

0\

2. Heat emission from pipes Heat emission from bare horizontal pipes with ambient temperatures between 10 and 21 °C and still air conditions.

Vl

Table

Temperature difference: steam to air

0'

'\l

"'0 s,

Pipe size 15mm

20mm

25mm

32mm

40mm

oc

SOmm

....

65 rnrn

80mm

100mm

150mm

3

!:l

;:;l

"''!:l"'

W/m

::s

!:l...

56 67

78 89 100 111 125 139 153 167 180

54 68 83 99 116 134 159 184 210

241 274

65 82 100 120 140 164 191 224; 255 292 329

79 100 122 146 169 198 233 272 312 357 408

103 122 149 179 208 241 285 333 382 437 494

10 8

132

136

168 203 246 285 334 394 458 528 602 676

166 205 234 271 321 373 429 489 556

155 198 241 289 337 392 464 540 623 713 808

188 236 298 346 400 469 555 622 747 838 959

233 296 360 434 501 598 698 815 939 1093 1190

324 410 500 601 696 816 969 1133 1305 1492 1660

3in

4in

6 in

194 246 300 360 417 488 • 578 674 778 888 1010

243 308 375 451 522 622 726 849 9 78 1140 1240

337 427 521 626 725 850 1009 1180 1360 1557 1730

Heat emission from bare horizontal pipes with ambient temperatures between 50 and 70°F and still air conditions. Temperature difference: steam to air

Pipe size 1

/2

in

3

/4

in

1 in

1 1/ 4 in

OF 100 120 140 160 180 200 225 250 275 300 325

1 1h in

2in

2 1/.z in

Btu/linear ft/ hr 56 71 86 103 121 139 166 192 220 251 285

68 85 104 125 146 171 199 233 266 304 343

82 104 127 152 176 206 243 284 326 372 425

107 127 155 186 217 251 297 347 398 455 520

113 142 173 213 243 282 334 389 447 510 580

138 175 212 256 297 346 410 478 550 628 705

163 206 251 301 351 408 483 563 ' 649 742 843

(J

:::. ,._ <'> l::

::;..... >-· 0

::s

"'

Steam Flow Calclllations

6 57

or, in SI:

M= A X

t1 + t2) ( k ts 2 r

X

3 600 (k h) 1000 gf

where M = amount of condensate (kg/h) A = heating of surface (m 2 ) k = coefficient of overall heat transfer (kcal/m 2 h K)

w

or, in Sl in mlK ts = temperature of steam t 1 = initial temperature of product t 2 = final temperature of product (quite often it is sufficient t if the average temperature is known, e.g. room temperature) r = latent heat in kcal/kg or kJ/ kg (approximation for medium pressures 500 kcal/ kg or, in SI, 2000 kJ/ kg) A few empirical values for the coefficient of overall heat transfer k are given as follows: kcal m 2 hr K Insulated steam line Non-insulated steam line Unit heater with natural circulation Unit heater with forced circulation Jacketed boiling pan with agitator As above, with boiling liquid Boiling pan with agitator and heating coil As above, with boiling liquid Tubular heat exchanger Evaporator As above, with forced circulation

0.5-2 7-10 4-10 10-40 400-1300 600-1500 600-2100 1000-3000 250-1000 500-1500 800-2600

0.6-2.4 8- 12 5-12 12-46 460-1500 700-1750 700-2400 1200-3500 300-1200 580-1700 900-3000

Cavitation The phenomenon of cavitation is associated with a reduction of pressure occurring in a liquid system, reducing the liquid pressure at a localised area down to the vapour pressure of the liquid concerned. As a consequence, vapour and small gas-filled bubbles form in the liquid at this point and are entrained by the flow . As soon as they reach a region of higher pressure, they suddenly collapse at extremely high velocities, with vapour condensing into liquid again. Very high implosion pressures are generated , depending on the bubble size, and may even each 10,000 bar (140,000-150.000 lb[/in 2 ). Such high-velocity impacting pressures can show up as: noise (ii) vibration (critical oscillations) (iii) mechanical damage to construction materials.

(i)

Critical regions for the development of cavitation in a piping system are sudden cross-section enlargements or contractions, changes in flow direction and sudden changes in flow (such as at throttling gaps). The sudden contraction. illustrated in Figure 1, is a typical example. This shows the pressure distribution at the throttling point, where p 1 is the upstream fluid pressure, p 2 the downstream fluid pressure (lower because of the head loss after throttling), PA is the atmospheric pressure and p0 the vapour pressure of the fluid . At point p 3 , the pressure is reduced to the vapour pressure, generating cavitation, with subsequent pressure recovery to p 2 . Somewhere bet\.veen p 3 and p 2 the cavitation bubbles will collapse suddenly. Cavitation does not necessarily lead to damage. even if it does generate noise and vibration. It depends on the intensity of cavitation or. specifically. the lifespan of the bubbles from formation to implosion. Cavitation intensity decreases with an increase in the life of the bubbles. The pressure travel gradient (p 1 , p 3 , p0 ) is thus significant and related to the shape of the flow passage. As a general rule, the pressure drop can be influenced by streamlining the flow, although this can be optimised for one predetermined flow condition only. Thus it is rather more important to try to extend the pressure-travel gradient. Geometric shapes can be found which, despite cavitation, do not lead to damage. i.e. the bubble implosion occurs

Cavitation

6 59

r1 I I I I

/

I

PA

,__. P2

// I

I

I

Po

-

/

/

/

/

Pl

-

-

-Fl VI

~

:/1 F1 Y .1

F2 Y2

Figure I.

away from the possibility of contact with the material surfaces. From this it can be seen that only bubble implosions near the wall are destructive. If the bubbles contact material surfaces, the destruction mechanism conforms with that of liquid droplet erosion. From the point of view of metal physics, what happens is a high-velocity deformation of the metal as a result of the bubble implosion. In many cases the mechanical erosive influence is coupled with an electrochemical corrosive influence. cavitation and corrosion occurring together. It has been shown that. in the case of industrial water, damage to carbon steel and ingot iron can be reduced by cathodic protection, i.e. the corrosive influence can be removed . Among construction materials which have proved to be less prone to cavitation, austenitic steel. single-phase copper alloys (bronzes). stainless steels and stellite armouring have been most successful. These materials are largely resistant to corrosion so they are not subject to this additional attack. Typical potential points of cavitation damage are: (a) (b) (c) (d) (e)

suction pipes of pumps narrow flow spaces, leakage and bearing gaps sudden changes in flow area changes in flow direction. as in bends and pipe tees changes which lead to turbulence (f) downstream of throttle and control valves; components built into the flow stream.

6 60

Performance and Calculations

From the following list. measures can be chosen by which disadvantageous cavitation consequences can be avoided: (1) Avoidance of turbulence by proper streamlining of flow, e.g. by means of a vaned ring in a needle valve (Figure 2). (2) Prevention of wall contact after regions of pressure drop by sudden enlargement of the pipeline (Figure 3). Developing cavitation bubbles implode in the water space. Cavitation arises in a space not endangering the material. (3) Letting pressure drop occur over sharp edges. (4) Dissipation of the kinetic energy not solely through turbulent mixing but: (a) through built-in resistance, i.e. by increasing the friction-causing wall surfaces. This causes an increase in the back pressure after a point of throttling. A pressure drop below the atmospheric pressure can be avoided (Figure 4); (b) partitioning of several resisting bodies in series (multi-stage pressure drop).

Figure 2.

-

Figure 3.

Figure4.

Cavitation

661

As an approximation, the number of stages required can be calculated as follows: P2 n = -6.45 x lgPl

where p 1 = upstream pressure p 2 = downstream pressure (5) Principle or flow partition into small single cross-sections. e.g. hollow cylinders (Figures 5 and 6). The division into single jets beneficially influences the dynamic behaviour of the medium flowing off downstream of the throttling devices. In addition, the partition into small cross-sections achieves a more uniform downstream flow in the following pipe.

Figure 5. Ciloke valve with low-recovery trim.

-

Fig11re 6.

662

Performance and Calwlations

(6) Change of flow contractions by the introduction of air: (a) in free exit, similar to the effect of perlators in water taps with the well-known soft jet (Figure 7); (b) intensive ventilation in the flow passage produces the hydraulic character of an end closure. The arrangement of the valve on the air side is. from the hydraulic point of view, more favourable than that within a pipeline with ventilation. From the aforementioned it can be seen that, for throttling and control duties, special valve types are required which are designed with special seat and exit configurations. In general. valves are limited only according to the nominal pressure rating. Within the standard design requirements. the special dynamic loadings in the flow passage of the various types of valves are not considered. In the case of mere shut-off valves, such as gate and butterfly valves. the necessary adaptation cannot be achieved by means of design, (Figure 8). They are, therefore, not suitable for pronounced throttling and control duty but, because of the low permanent pressure drop, are ideal for on- off duty .

Figure 7.

lL Figure 8.

\ ...

Cavitation

663

Such valves are suitable for short-period throttling duties such as during shut-off in the case of a burst pipe. However, when dimensioning these valves. the limits which result from the energy head must be considered: Butterfly valves: PN25 7.5m/s (25ft/sec) PN16 Sm/s (16.5ft/sec) PNl 0 4 m/s (13 ft/sec) PN4 2. 5 m/s (8ft/sec) PN2AS 2 m/s ( 6. 5 ft/sec) (Flow velocities referred to valve nominal diameter.) If butterfly valves are used as safety devices in the case of a burst pipe. the responsible manufacturer considers the stresses in these circumstances and dimensions valve and operator designs in a correspondingly strong manner. Buttertly valves can be used for on-off operation. in conjunction with special parallel-gate valves with perforated fixed plates, for the continuous control of the downstream flow of water from dams. The perforated plate divides the flow into a large number of small jets to create the required throttling effect. The jets are evenly distributed over the cross-section of the pipe and the uniform small-jet configuration achieved is erfective in suppressing vibration. cavitation damage. pressure fluctuations and noise. Components of the control, shown in Figure 9, are simply two circular perforated plates and an annular body (1) mounted between pipe flanges. Plate (2) is fixed. and plate (3), on the upstream side, is free to slide up and down. In the fully open position, the orifices in the plates coincide. The fully closed position is obtained by displacing the moving plate ( 3) through a distance equal to one orifice diameter. Under normal conditions of flow control. the position is intermediate with the orifices in the fixed plate only partially blocked off by those of the moving plate. The latter may be positioned by hand or by valve actuator. In water works and water power plants, needle valves, also known as ring piston slide valves (Figure 10). have proved in more than 40 years of practice to be excellent as flow-control valves. because individual adaptation to the given operating conditions and duties is, with this type of valve. possible. With reference to cavitation, this means that. by specific configuration of the outlet shape. formation of the throttling point. design of the downstream piping. and by the selection of the point of installation, the hydraulic conditions can be influenced directly and damages due to cavitation be avoided. With these control valves, all intermediate positions. i.e. partial openings, must be possible for continuous duty to achieve variable flows or an effective change in energy. e.g. reduction of pressure. No ill effect due to cavitation or vibration

664

Performance and Calct~lations

must occur. The design of the needle valves offers all the advantages. The flow is guided through a ring-shaped passage around a ball-shaped inside body. The outside body is so designed that the free-flow cross-section continuously diminishes from the inlet to the sealing and throttling point so that flow velocity increases. Shortly before the narrowest cross-section, a vaned ring is provided, which swirls the outer flow filaments in such a way that the fluid is

Figure 9. Schematic showing comporrrnts ofcontrol for parallel-gate valve with perforatedjixPd plates.

Figure 10. Typical ring-piston slide valve.

Cavitation

665

forced against the wall of the downstream flow section so that detachments are avoided and cavitation bubble implosions are kept away from the wall. The shut-off piston in the spherical inside body moves in the opening and closing passage, i.e. in or against the direction of flow, and produces.therefore, a linear change in cross-section without causing the flow direction to change. The downstream shape of the piston is sharp-edged. In contrast to former designs with pointed piston ends. the hydraulic exit flow angle can develop,

A globPvalve fitt ed with the Smart Vnlve Interface ( SV l 0~- ) positioner/ controller.

66 6

Performance and Calculations

depending on piston position and velocity in the water area, without touching the metallic valve parts. To enable a control valve to fulfil its duty, i.e. continuous throttling of the rate of flow. the valve must be properly dimensioned. By dimensioning. not only the sizing of the valve is meant but also the adaptation to the duty prescribed, taking into account the specific operational conditions including assessment of the cavitational behaviour. The cavitational. behaviour of a valve can be observed in a model test from which the behaviour in the actual installation can be deduced . As a means of comparison, the cavitation coefficient sigma. also known as the Thomas cavitation number, has been introduced. This value indicates the start of cavitation. The cavitation number 8 is calculated from: = P2 + PA- Po 8

v2

P1- P2-2g

where PA = p2 = Po= p1 = V g =

atmospheric pressure pressure downstream of disturbance vapour pressure of water pressure in undisturbed upstream side velocity in undisturbed upstream side acceleration due to gravity

Responsible valve makers determine the behaviour of their valves in allembracing tests and therefore possess comparison values for all common operating conditions. From these data, the required design shapes can be deduced. In extreme cases for which test data are not yet available, the particular case is reconstructed in model tests and the required design determined . The main precondition is precise knowledge of the operating and instaJlation conditions at the project stage. Only with these data is it possible to determine the optimum design of the valves and piping run with the aim of avoiding damaging cavitation effects. Among the necessary details are knowledge of: (i)

static and dynamic pressure upstream and downstream of the valve referred to the desired range of rates of flow (ii) the installation situation within the pipeline (iii) the piping and built-in components downstream of the valve (iv) the maximum permissible head loss, etc. A close co-operation between designer, user and manufacturer or valves . has in the past always proved to be very beneficial, and will doubtless lead to equally satisfactory solutions in the future.

Noise Control Noise produced in pipelines may be pump-generated (changes in power and pressure. or varying amplitudes of pressure pulsations) or fluid-generated (flow instability, turbulence or simple fluid friction). Fluid-generated noise in small-bore pipes with low to moderate flow rates is generally negligible, unless pressure pulsations are present (e.g. owing to valve cavitation). Thus pipe vibration, and consequent radiation of airborne noise, is usually caused by a higher level of noise generated by fittings; pipe resonance is caused by a mechanical vibration or resonant noise generated in supporting systems. Relative noise levels are shown in Table l. Specifically, noise control (noise abatement) falls in to two distinct categories: Source treatment: i.e. design of components to ensure operation at minimum noise levels. Path treatment: to reduce source-generated noise to acceptable levels. Noise caused by the operation of valves, regulators and control elements is transient and related to the degree of turbulence or cavitation produced although. in specific designs and certain circumstances. individual elements may be subject to vibration and generate a continuous noise. So much depends on the design and finish of the flow passages involved that no general analysis can be attempted. The noise level of such devices is dependent on the design and the localised flow velocities produced, and also on the response

Table 1. Relative noise levels

130 decibels 120 decibels 110 decibels l 00 decibels 90 decibels 80 decibels 70 decibels 60 decibels 50 decibels

jet aircraft on take-off Threshold of feeling Elevated train Loud highway Loud truck Plant site Vacuum cleaner Conversation Offices

668

Performance and Calculations

Rotary eccentric plug control valve with noise control trim.

time, where applicable. The latter effect can be minimised by making sure that the response time is not shorter than that required by the system. This will result in minimum 'hammer'. 'Water hammer', in fact. depends on the switching velocity of the valve, e.g. on the spool-switching velocity in the case of spool vaJves. Valves operated by dry solenoids have uncontrolled response and so often produce 'hammer'. \Net solenoids are cushioned by the fluid so move more smoothly and open the valve passages more gradually (at the expense of some loss of solenoid power). As a general recommendation, simple undamped ball-and-spring non-return and relief valves should not be used. On the design side. every effort should be made to ensure that the flow passages of valves are swept and free from sharp edges and corners as far as possible. Directional control valves must also be carefully designed to prevent flow instability occurring. About 80% of the noise problems in process industry control valves are caused by flowing gas and 20% by flowing liquid. The noise caused by liquid is more often associated with cavitation, corrosion erosion and vibration. Noise prediction has been made a lot easier by virtue of a number of manufacturers' software programs that have become available for general use. Source treatment

Source treatment is difficult to describe in general terms because it is mainly concerned with the design of optimum flow paths through valves to reduce or eliminate noise that would otherwise be generated. In this respect, quite

Noise Control

669

different design parameters are involved in dealing with aerodynamic noise · resulting from liquid flow . Aerodynamic noise

Noise generated in gas or vapour is called aerodynamic noise. Most of it occurs during the deceleration stage in the throttling process. The area where the noise is generated can extend a long way from the orifice into downstream piping. Pressure waves inside the piping make the wall vibrate. Noise is attenuated very slowly in piping filled with gas or vapour. The sound pressure level of a gas control valve generally has a broadband frequency distribution. Maximum sound pressure levels are between 1000 and 4000Hz. There are a number of methods of diminishing aerodynamic noise. Two, in particular, are effective: (i) (ii)

reduction of pressure and velocity gradients generated during the throttling process: using, for example, multi-stage throttling and splitting the flow into several jets.

The mean flow velocity and its profile downstream of the valve have a particularly marked effect on the valve noise level. Splitting the flow into smaller parallel jets reduces noise. A typical frequency distribution of aerodynamic noise is shown in Figure 1. Two examples of aerodynamic noise treatment are shown in Figures 2 and 3, applicable to globe- and angle-valve bodies. Both are cage-style valves, one using a cage with multiple slotted orifices of special shape, size and spacing, and the other a cage with multiple hole orifices. Claimed performance is an 18 dB reduction for the former compared with a conventional valve of similar type, and a 30 dB reduction for the multi-hole orifice cage. The latter is also particularly effective for applications involving high differential pressures (pressure drop across the valve). A common feature of both these valves is an expanded outlet design to minimise regeneration of valve noise. Hydrodynamic noise

When turbulent liquid flow is stable, it does not usually cause any significant noise. Cavitation is the most common cause of noise in liquid flow . Hydrodynamic noise can be reduced by affecting the intensity of cavitation. The best way to prevent cavitation is to intensify flow losses, which reduces the intensity of pressure recovery and increases the acoustically determined differential pressure ratio of incipient cavitation. Valves can be designed so as not to direct any cavitation jets at the valve trim; this helps to lower the effect of cavitation corrosion.

6 70

Pe1jormance and Calculations Sound pressure level

dB 100~--------------------------------------~

Standard valve

90

Special valve

70

250

500

1 000

2 000

Octave band center frequency, Hz

Figure 1. Typical frequency distribution ofaerodynamic noise.

Whi~per

trim I with slo tted ori !ices.

figure 2 . Trim cage and valve-body assembly.

4 odo

Noise Control

6 71

Examples of cage-type valve trims for hydrodynamic noise treatment are · shown in Figures 4 to 7. Here, the immediate aim is to eliminate or minimise cavitation. The cage design of Figure 4 uses one stage of diametrically-opposed flow holes through the cage wall to reduce both cavitation noise and damage. Each specially-shaped hole directs a jet of cavitating liquid which impacts with the jet admitted from the opposing hole at the centre or the cage. Thus, a continuous cushion is formed which prevents cavitating liquid from contacting the metal surfaces and ensures that vapour-bubble collapse takes place in the centre of the flow stream. The cage design in Figure 5 consists of one or more concentric cylindrical sections referred to as stages. The number of stages required depends on the inlet pressure and the pressure drop. In operation, the liquid undergoes a portion of the total pressure drop in each stage of the cage. This prevents the liquid in any one stage or the cage from falling to or below its vapour pressure. Therefore, formation of vapour bubbles and their subsequent collapse is eliminated. Figure 6 shows a further trim design employing a {patented) pressure staging for elimination or cavitation with differential pressures above 200 bar (3000 lb/in 2 ). The expanding flow area design takes advantage of the ability

Whi~per

trim JII cage in Pish er EWDcontrol valve-body assembly.

Whisper trim lil cage.

Figure .3.

6 72

Performance and Calculations

of the liquid to undergo a greater pressure drop in the initial stages without cavitating. This results in a much lower inlet pressure to the final stage. This design also separates the shut-off and throttling locations to prevent clearance-flow erosion. A further design is shown in Figure 7 where the trim consists of a carefully designed bundle of tubes which minimises cavitation noise and damage by controlling the formation of cavitation-bubbles. The tubes serve three functions: they prevent the flow stream from reaching its potential minimum area, they maintain maximum pressure head to reduce cavitation bubble formation. and they limit the size and number of cavitation bubbles that do form .

Ca vitro I I cage. Cavi tr oll cage in f is her ED valve-body assembly.

Figure 4.

Ca vit.rollfl cage in Fishe r ET va lve-body assembly.

Figure S.

Noise Control

6 73

Ball valves

Rotary-control ball valves were previously noisy due to the high recovery character of the ball valve and cavitation at high differential pressures. The first low-noise anti-cavitation ball valve was introduced in 1979. It was based on a multi-stage, multi-flo'"' principle, with a trim of variable resistance depending on the valve opening.

Cavitrol IV trim. Cavitro! IV trim with fisher valve-body assembly.

Figure 6.

Cavit.rol V trim.

fnlet of Vee-Ball valve-body assembly with Cavitrol V trim.

Figure 7.

6 74

Performance and Calculations

The quiet metal-seated control-ball valve sh0\1\rn in Figure 8 combines the concept oflow noise with minimum cavitation. Parallel perforated plates in the ball flow opening smooth the pressure drop as the flow passes through. The gradual pressure reduction over the valve reduces velocities, noise generation and cavitation. When the ball is opened, the fluid passes through the upstream seating orifice encountering resistance inside the ball flow opening. The flow is forced through the holes in the perforated attenuator plates (Figure 9). The plates create a frictional path, where each plate and the seating orifices reduce the pressure step by step. This prevents excessive velocity generation. lowers the noise level and minimises cavitation. When the opening angle is increased, resistance decreases as the flow successively by-passes the plates. This gives optimal valve-flow characteristics and thus high rangeability and capacity.

Fig1.1re 8 . Quiet metal-sPatrd control ball vnlvr.

Figure 9. Principle of the IJnll with parallel perforatrd piaU'S.

Noise Control

675

This type of valve has proved successful in many applications industries including: • • • • • •

hydrocarbon processing power generation, chemical, and pulp and paper industries flow and pressure control. especially in critical flow conditions blow-down pressure equalisation high-temperature service and tight shut-off requirements

Butterfly valves

With conventiona l butterfly valves, increasing differential pressure causes a high dynamic torqu e. thus jeopardising controllability at high opening angles and causing noise with gases and cavitation with liquids. The valve shown in Figure 10 overcomes this problem. The non-symmetrical pressure-distribution pattern on both sides of the vane bas been made symmetrical with a downstream partial flow obstacle inside the valve body. This design helps to eliminate the dynamic torque and , because of the more turbulent flow pattern, lowers the recovery behaviour.

Figure 10.

·s' disc but ierfly control valve witltj low-ba/ancing and noise-control trim.

6 76

Performance and Calculations

The disc has been designed to remove fluid forces from the disc to the body and the 'flow-balancing trim' has been incorporated to optimise the inherent flow characteristics of the valve. As a result, noise and vibration are reduced . The valve is used in many process applications within the temperature range -200 to +700°C (-333 to+ 1300°F). Pressure-relief valves

The following formulae are used for calculating noise levels of gases, vapours and stream as a result of the discharge of a pressure-relief valve. The expressed formulae are derived from API Recommended Practice 5 21. Ltoo = L + 10LOG10(0.29354 W k T/M) Where 1 100 = sound level at 100ft from the point of discharge (decibels) L = noise intensity measured as the sound pressure level at 100ft from the discharge vv = maximum relieving capacity (lb/ hr) k = ratio of specific heats of the fluid (for steam, k = 1. 3 if unknown) T = absolute temperature of the fluid at the valve inlet (0 Rankine (°F + 460)) M = molecular weight of the gas or vapour obtained from standard tables When the noise level is required at a distance of other than 100 ft, the following equation should be used:

Lp

=

L10o - 20LOGIO (r/1 00)

where Lp = sound level at a distance, r, from the point of discharge (decibels) r = distance from the point of discharge (ft) Path treatment

Standard methods used for noise reduction in piping are: (i)

Damping by means of suitable isolating pipe supports. This also provides decoupling for supporting structures. (ii) Decoupling from other sources of noise or vibration in the system. (iii) Insertion of silencers. (iv) Soundproof ' lagging'. (v) Use of bearing-walled pipe. For the majority of systems, only (i), and to a lesser extent (ii), should be necessary. 'Lagging' is normally only required when there are pulsation

Noise Control

6 77

vibrations present which cannot be damped or isolated by simple means. This is most likely to occur in pumped systems employing thin-walled, large-diameter piping, particularly on the suction side. Sufficient damping for pipes is usually provided by suitable supports. or pipe clips, spaced at regular intervals, the supports having resilient linings so that vibration in the pipe is not transmitted directly to the surface to which the supports are fixed. Optimum pipe spacing can be analysed in terms of standing wave phenomena, although this is seldom necessary. The case of axial standing wave is usually academic, for practical lengths are usually substantially lower than the critical length, which is defined by:

La

=

8200 . f tor steel pipes

where La

r

resonant length of pipe (ft) = frequency of any strong vibration

Theoretically. at least, the distance between pipe supports should always be less than this resonant or critical length. It may, however, be necessary to analyse the various possible sources of noise in a fluid pipework system in more detail in order to arrive at satisfactory noise treatment. In this case, the possible sources of noise generation, in decreasing order of significance, are: (a) (b) (c) (d) (e) ([) (g) (h) (i)

pump noise (where applicable) appliance noise control element noise water hammer chatter cavitation resonance pipework noise thermal effects

Bellows

Bellows-particularly rubber bellows-can be very effective in preventing pump noise from being transmitted along pipelines. Plain elastomeric bellows provide a complete isolation joint and give the best possible sound absorption as all pipe-borne noise must pass through the bellows material. For best results. the bellows should be placed as close to the pump as possible, and the pipe to which it is connected securely anchored as near as possible to the other end of the bellows. The pump also needs to be solidly mounted to withstand both pressure forces and flexibility forces arising out of the bellows' stiffness.

Performance and Calculations

6 78

Where this is not possible (e.g. the pump is flexibly mounted), or other factors (such as high pressure) mitigate against the use of plain bellows. tied or axially-restrained be.llows must be used. Such bellows are pressurebalanced units. The flanges and tie-bars, however. now form a transmission path for vibration unless isolation treatment is incorporated. The simplest form of treatment is by the use of resilient bushes and/ or rubber washers to prevent metal-to-metal contact between the tie-bars and the backs of the restraining flanges. Even single rubber washers can be effective. if correctly selected in terms of hardness. Some noise-reduction data obtained with representative designs are shown in Figure 11. Metal bellows

Metal bellows can give inconsistent results in terms of noise and vibration isolation. Generally their performance is much below that of rubber bellows. Again some test data are shown in Figure 12. Isolating flanges

An alternative type of isolator is shown in Figure 13. Basically, this consists of a solid rubber 'washer' of appreciable thickness, into which are bonded steel flanges. These flanges are tapped to accommodate bolts for assembling the

I

STATISTICAL AVERAGE I

-;;

WATER COLUMN

50

80

80

125

~

200

-;;

u..

-I>

125

c

200

rr

315

u

"'::l

"'::l 315 a ~

STATISTICAL AVERAGE

UNTIED

50

:; c

I

NOISE REDUCTION

PIPE MATERIAL

"' u.

UNTIED

-~

~

500

500

800

800

1250 2000

1250 2000

3150

3150

5000

5000 0

-10

-20

-30

0

- 10

dB

6-----.1'1.6-~~

-20

-30

dB

== 3 bar

~---o---o

= 5 bar

c .. ..... o· · .....a

Figure 11. Typical noise reduction with simplr ntiJber bellows.

.=

8 bn r

Noise Control

6 79

isolator betvveen conventional flanges without metal-to-metal contact through the joint. Theoretically, such a form of isolator should prove better at higher frequencies than lower frequencies. although actual performance would depend on the hardness of the elastomer used. It is not generally as effective as rubber bellows, and definitely inferior for isolating lower frequencies. It does. however. ---NOISE REDUCTION---,

.-I

WATER COLUMN

PIPE MATERIAL

STATISTICAL AVERAGE

STATISTICAL AVERAGE

~

50 80

12o

.., T

,._

'" "

~

,; ~~

200 315

-~

50 80 125 200

1:

315

>-

u

500

500

c: 0>

:?.

800

800

~ lL

~250

1250

2000

2000

3150

3150

5000

5000

0

-- 10

- 20

0

-30

- 10

- 20

-30

dB

dB

Figure I 2. Typical noise reduction with corrugated-steel bellows .

.---NOISE ABSORPTION---, PIPE MATERIAL

WATER COLUMN STATI STICAL AVERAGE

STATISTICAL AVERAGE

50

50

80

80 125

125

.... I

200

> c

3 15

u

ll>

:J

cr

:I:

~ 315

c:

Q)

500

:::>

500

u:

800

2"

QJ

lL

2oo

800

1250

1250 2000

2000

3 150

3150

5000

5000 0

-10

- 20 dB

- 30

0

I

- 10

-20

- 30

dB

Figure 13. Solid metal/solid rubber isolating unit and typical noise-reduction data .

680

Performance and Calculations

have the advantage of providing a 'solid' coupling and so can be used with flexibly-mounted pumps. Acoustic filters

Acoustic filters can be fitted to systems where pressure ripple is high. These are essentially tuned silencers which are critical in design and are usually effective over only very narrow frequency bands, although the attenuation achieved can be quite high. Untuned silencers simply comprise an expansion chamber with broader coverage but reduced attenuation . An accumulator is, in effect. an untuned hydraulic acoustic silencer and is most effective at lower frequencies. Dissipative-type silencers provide for dissipation of energy through viscous flow losses and. as a consequence, consume some fluid energy. They may be combined with an untuned silencer. although the attenuation will still be appreciably lower than that of the tuned type. In general, wave-cancelling filters are to be preferred because the frequencies involved are low. If the pressure transients are narrow band, a Quinke tube and expansion chamber can be effective (Figure 14). A major disadvantage of this and other types of simple wave-cancelling filters, however, is the relatively high pressure drop produced. The more usual form of hydraulic silencer is the pressure-release type shown in Figure 15. This gives minimum c

0

Equal flows in each section

"'

'i1

....

Ill

" '0

c

-

::J

0

U)

Frequency-

Figure 14.

Rubber separator Gas space

Orifice tube

Pigtlrl' 15. Pressure-relensefiltl'r.

Noise Control

681

pressure drop and broad-band filtering, but is pressure-sensitive and needs regular routine maintenance. Shock preventers

Shock preventers are pulsation dampers (or accumulators) characterised by having very large flow-inlet apertures which are partially closed off by liquid trying to flow back out of them. They are not shock absorbers, as they prevent shock or surge occurring. For the same reason, they do attenuate shock. Shock removers

These are sensitive hydropneumatic devices which prevent a standing wave from passing farther down a system or from bouncing back through them. They are normally o[ tubular or sleeve form with a flexible membrane. Because of their length, it is possible to open a membrane so that it is exposed to the increased pressure of a wave and to close it behind the wave, thus shutting it in. See also the chapters on Cavitation and Flow of Liquids Through Pipes.

Balancing of Hydronic Systems Excess consumption of heating energy is the result of temperature variations in a building and the generally incorrect approach taken to solve the problem. If, for example, one room is too warm and another too cold. the necessary adjustments are often made in the room that is too cold-the result being that the average temperature of the building, which to start with was probably quite sufficient had it been balanced out, now becomes too high (see Figures 1 and 2). %

18 19 20 2 1 27.

Figure I. Example of correctly 1m/anced building. Averngl' trrnparr ture 20°C. %

23 24 25 26 77 ?fl

oc

Figure 2 . Example of wrongly balanced b11ilding. A vernw tempPr atu re 2 3° C.

Balancing o{Hydronic Systems

68 3

Obviously, this higher average temperature implies a higher consumption of energy; how much higher depends on the specific heat requirement of the geographical area in degree/days. Generally speaking, however, one can say that each degree above+ 20oc (+68 °F) indoors means heating costs which are about 5 or 6% higher than normal (see Figure 3 ). In a cooling plant the conditions and the means are of course reversed, but the waste of energy is often increased. In many cases, excess temperature is even ventilated away, or the windows are opened, which can mean an average temperature which is more than 4-5°C ( 7-9°F) too high. Energy-conservation measures have always been of considerable interest and the balancing of a hydronic system is particularly interesting because only simple measures are needed and they give quick and very evident results. Savings of 20 to 30% are not unusual. Pump-energy waste

It is often forgotten that pump energy also costs money. In many cases, the

pumps are oversized. In heating systems, this is not always so very significant because the temperature differences are often high and, therefore. a relatively small amount of water is being circulated. However. particularly in refrigeration systems with their lower temperature differences, pump-energy waste can add a lot to the operating costs. Another essential difference between heating and cooling systems is that energy losses in the systems are converted to heat; this works to the benefit of a heating system but necessitates an increase in capacity for a cooling system. o/o cool

% heat

20

10

18

9

16

8

14

7

12

6

10

5

8

4

6

3

" 2

2

' .....

.........

....... __

-.

0 0

5

10

- 15

+30

+ 35

+40

1- 45

- 20

- 25

°C heat

°C cool

Fi,qure 3. Solid line: Ener(J!J cost saving in %for each degree higl1er indoor temperature at various mnximu111 outdoor l'etnperatr1res in 11 cooling system. Brokrnline: Energy cost snviny in a heating system in %for each degree lower indoor temperature at various minimum outdoor temperat11res.

684

Performance and Calculations

Over-dimensioning is generally a consequence of the following: When the pump was chosen, the designer was uncertain of the pressure drop in the system (boiler, heating batteries, valves. etc.) because the tender covering the components had not been finally accepted. (ii) Insufficient data concerning the pressure drop in the piping system. (iii) General safety factors . (i)

However. to facilitate balancing, it is wise to increase the sizes of the pump slightly, but not to exaggerate. Modifications to an over-dimensioned system (for example, by changing the pump or the impeller) , do not always lead to lower overall costs, although such measures do often prove worthwhile. For some time now, it has been taken for granted that a hydronic system in a new building must be balanced. The question being discussed is how to balance it and who is to balance it-the application engineer, the heating contractor, or a firm specialising in the balancing ofhydronic systems.

Examples of balancing valves.

Balancing ofHydronic Systems

685

Construction

To skip the piping calculations entirely and simply specify that the system shall be balanced without detailing the means or the way to do the work implies a significant amount of extra work for the person who is to perform the balancing. Furthermore, balancing is not a universal solution which will make a poorly designed system function adequately. When designing the system, care must be taken to arrange clearly demarcated sections. Calculations

For newly-built facilities in Sweden, for example the SBN 80 3 9:3 2 specifies that the method of balancing and the presetting values and water-flow values for the balancing valves must be detailed on the building permission documents. This necessitates complete piping calculations and the determination of pressure losses in the heating system. The Kv values can, in the case of radiator valves, generally be adjusted directly by means of the presetting unit which is marked off in Kv , although this only applies in a limited number of manufacturers' valves. Balancing valves must be incorporated in all branches to avoid having to balance the radiator valves in one branch against the balancing valves in other branches (Figure 4). Reverse-return mains, according to the Tischelmann system, can simplify many balancing problems. The exclusion from such a system of balancing valves will, however, lead to imbalance, because different radiators and heaters or cooling units do not have the same output or pressure drop. However, the pressure differences in the system between branches will be lower, which means that balancing will be easier. The Tischelmann reverse-return system a lso has benefits to offer when balancing the sub-circuits (Figure 5).

Balancing and sllllt-off valves.

68 6

Performance and Calculations

Balancing

Before commencing to balance a system, all valves must be opened fully. This applies particularly to thermostatic radiator valves and two-way control valves. This type of valve operates with varying flows and. unless it is ensured that the valve is fully opened, it may just have closed automatically as balancing was commenced. A thorough knowledge of the system is also important before the commencement of balancing. The information required includes the following: (a) drawings with hydronic sketches (b) data concerning flows and pressure drops across heat generator, batteries, radiator heaters, balancing and control valves (c) pumps data and pump diagram. The desk method

A well-defined system of not too great complexity generally requires only one single adjustment of all valves used. including radiator valves and balancing valves, in accordance with the values specified by the drawings. Control measurements should, however, be made on one or more extremity branches

Figure 4 . Balancing valves incorporated in all brand1es to avoid having to balance the radiator valves in one branch against the balancing valves in other branches.

I·

--l

Figure 5. The Tischelmann reverse-return system can simplify many balancing problems. Tire exclusion f rom such a system of balancing valves will. howPver. lead to imbalance, since different radiators and heaters or cooling units do not have the same output or pressure drop. but the pressure d(fferrnce in the systnn between the branches will be lowe r. This means that balancing will be easier. The Ti schelmrmn reverse-ret urn system also has benefits to off er whm balanciny the sub-circuits.

Balancing ofHydronic Systems

68 7

(farthest away from the pump) as well as on a few central branches. The flow deviations found in these control measurements should not exceed 10% of the volume or 20% of the pressure. If. after an adjustment as described earlier. there are still temperature deviations of more than 1 oc (2°F) in individual rooms. and if these cannot be related to temporary fluctuations in the heating or cooling load. the explanation will be found in one of the following: incorrect calculation of the heating/cooling facility; incorrect design/ installation of heating/ cooling facility; bad building (insufficient sealing, draughts). Temperature measurement method

This method. which is only applicable to heating systems, is based on the fact that each radiator/ heater is dimensioned according to the same temperature drop with an equal outdoor temperature. As a consequence, the system can be balanced by measuring the temperature drop at the pump and then adjusting the balancing valves so that the temperature drop is the same at the pump as it is over each branch. To achieve acceptable accuracy with this method. the outdoor temperature must be almost constant throughout the entire balancing process and. in addition, below 1 oc (34°F). It is often small temperature drops that are being measured and therefore the temperature differences become even smaller. For this reason, the system is at times less than exact (see also Figure 6 ). The temperature method can also save time if it is used as a preliminary stage prior to the proportionate balancing method described below. Proportionate balancing method

This method is one of the most frequently used and it is suitable for old facilities as well as for new ones. The procedure is to measure the pressure drop and to move proportionally from branch line to branch line. This is done as follows: {1)

Set all radiators and balancing valves according to the drawings specifications-or open them if no specifications are available (Figure 7). (2) Start by measuring branch lines 1.1, 1.2, 1.3 and 1.4 of sub-system 1 and determine the proportionate flowrate, that is to say the relationship between measured flow rate and design flow rate. If flow in 1.1 is 1500 l/h and the design flowrate is 1000 1/h, the proportionate flow rate will be 1.5. (3) Presume that 1.1 has the lowest proportionate flowrate, 1.2 the next lowest and so on. In this case. leave the valve of branch 1.1 open and balance 1.2 to give the same proportionate flowrate as 1.1 (within the tolerance applying). These two branches are now balanced and you can continue with 1.3, balancing it against 1.2 until they both have the same

6 88

Performance and Calculations

10 100

20 200

30 40 50 100 400 500

200 2000

100

1000

300 400 500 3000 5000 6. p(any unit)

Nomographic chart for the balancing of branch lines on the basis of combined pressure and temperature difference measurements. In the example, the measured pressure difference is 45 mm Hg and 1he /emperature difference is 8 oc. p If a 10 oc difference is desired the balancing valve must be 180 throttled to give a pressure 1oo difference of 29 mm Hg . )~

ir"

140

·f

120

I~

100 80

1/

60

0

I

~

1./

)A

j

40 20

v )

ll'

~

- -I --

'{_., ~" 0

20

0( 1.3)

~~

40 60 80 100 120 14 0 160

0 % 6 t %

Fig11re 6. The heat em iss ion variations in % as a function of temperature changes flt in% and flow changes ill %(an 80-60 radiator system). The diagram shows that n I %deviation in temperat11re wi/lgivea significant deviation ill heat emission. A deviation inflow will influence heat emissio11 ton muc!J lesser extent.

Balancir1g ofHydronic Systems

689

proportionate flowrate. 1.1 need not be checked. [t will change in direct proportion to 1.2 and remain in balance with 1.2. Then continue with 1.4 in the same manner. Because 1.4 is the last branch line of sub-system 1, this means subsystem lis now ready and, if any flow changes occur in the total system, the branch lines of sub-system 1 will be altered by the same proportional amount to a new common proportionate flow rate.

Figure 7.

Boiler or heat exchanger

t>.P2

For the same flow

Figure 8. Mixing valve.

cv Boiler or heat exchanger

flowcontrol BV

6P2

6Pl=t>.P2

Figure 9. Diverting valve.

690

Performance and Calculations

Boiler or hea t exchanger

BV2

Use BY! when CVI = 100°/.) to obtain TV 45 °C U se BV2 to o btain return te mperature 60 oc Use BV3 to obtain correct flo w.

Figure 10. Dou!Jie mixing valves.

(4) Proceed in a similar manner with sub-systems 2 and 3. (5) Leave the balancing valve open in the sub-system which has the lowest proportionate flowrate and balance the other sub-systems as described earlier. (6) The final stage is to determine whether or not the pump is supplying too large a quantity of water. If it is giving too much water. it can be throttled by a means of the balancing valves. by altering the pump speed, or by changing the impeller. In the case of large oversizes. it is often best to reduce the speed of the pump or change the impeller. Some other examples are given in Figures 8- 10.

SECTION 8 Duties and Services

Water Services Hygienic Services Steam Services Fire-Safe Valves Fire Hydrant Valves Marine Services Vacuum Services Cryogenic Valves Nuclear Services High Pressure Services

Water Services On a global basis, the valves produced to handle water are generally made from cast or ductile iron or cast steel. They are, in the main, larger in size than valves for other industries. The water industry can be divided into two main areas: • •

handling clean water handling dirty water or sewage.

Clean water is normally handled with butterfly and gate valves. Butterfly valves typically have steel bodies and gate valves have ductile- or cast-iron bodies. Sewage tends to be handled with gate valves as, although butterfly valves have good sealing characteristics, when the valve is opened, the disk is still flat within the channel and thus presents an obstruction to solids. Specialist applications use knife-gate valves or wafer-butterfly valves. Plastic valves are not used in hot-water supply generally. Other common valve types for water and waste-water include sewage combination air valves, cushioned swing check valves, hydraulically controlled air and vacuum valves, cone valves and air release valves. Some water companies appear to have moved to gate valves with a resilient seat with mainly rubber materials rather than metal-seat valves. These valves are also replacing rising spindle-gate valves on grounds of cost. Rubber or plastic 0-rings, including PTFE, are standard packing materials. Metal-seated AWWA-type ball valves remain a popular choice for water-works and industrial specialities. Automation with actuated valves is preferable. In the water-distribution industry, for example, the water used, whether its purpose is urban. agricultural or industrial. is distributed by an increasingly complex pattern of pipeline networks. Every new installation, development or addition to the network (building development, industrial zone, etc.) creates an imbalance. Control valves in a water-distribution system help to restore the balance by directing water distribution according to pre-determined priorities. It is important to understand that, although automation is now a major factor in the water sector, it is still limited as many valves within this industry are isolation valves that require to be operated manually.

694

Duties and Services

The main requirement is reliability in operation with little or no disruption to the service. Some common impurities in raw water are shown in Table 1. The use of the plug valve for water-supply systems dates back to Roman times and is still widely used in its modern forms, together with various other types of rotary movement and screw-down shut-off valves. The main exception has been the ball valve. Only during the last 10 years or so has this type been developed to meet the technical and economic requirements of water-supply systems. In the meantime, various manufacturers have attempted to provide an alternative for drinking-water systems by offering 'intermediate' ('mixed') construction types, such as the segmented gate and ball valves. In practice, however, these types of constructions generally turned out to be hydraulically unstable and required very high actuating moments.

Q)Reduccs pres:;ure to a clistrihution systc01 when gnn,ity-fcd from
~~~~~~ ([!) Controls the h:v ..l o f tlw tan k by ~.J;:::tf~~::V' means of float re~ulation aod allows ~ distribution to tlif• vlllagt·. @Protects the pump stat JOn agulnst surges due to start-up. s hut-dow n and power failure. <[J>([!)Eliminntcs pn·ssure flllctuntinns when pump starts and shut s down . 0 Controls flow rote to the factory. @ Allows l.low hetwel'n two distribution syslt'II1S (cxnmple: feeding a water-storage tank for pcHk distribution I imd.

Typical control application examples.

Wat.erServices

695

Compared with the general class of shut-off valves, the ball valve offers the following potential advantages: In the open position. it provides free passage of water in the supply system with a diameter equal to the supply connections. (ii) It gives an unimpeded flow profile without any distortion. (iii) It offers the smallest resistance to flow, that is, a very small loss in pressure over the comparable supply-line distances. (iv) It is completely adaptable. (v) The change in the cut-off from open position to closed position requires a minimal change in place. {vi) The precise shape of the cut-off guarantees a seal of great integrity. (vii) It offers a favourable ratio of weight to stability resulting from the design of the ball or hollow sphere which withstands the pressure. (viii) It has low installation costs. (i)

Ball valves for water supplies

It was not until there were ball-valve designs which took into account the specific requirements of a drinking-water supply (such as resistance to the formation of deposits and acceptable hydraulic performance in intermediate positions), and the cost requirements (namely, amortisation of the high use of energy even at low flow rates and short periods of useful operation) , that the use or ball valves for all aspects of drinking-water supply systems became a Table 1. Some common impurities in raw water Nanll' Calcium carbona te Calcium bicarbonate

Symbol

Common name

Effect

CaCO~

Chalk. limestone

Soft sca le

Ca(HC0 3h

Soft seale + C0

2

Calcium s ulphate

caso .•

Calcium chloride

CaCI2

Corrosion

Magnesium carbona te

M~C03

Soft scale

1vlagnesium sulph<Jte

MgS04

Magnl'site

Corrosion

Mg(I-IC0 1h

Epsom salts

Scale. corrosion

NaCI

Common salt

Electrolysis

Sodium ca rbonate

Na 2 CO j

Washing soda or soda ash

Alkalinity

Sodium bicarbonate

Na HC01

Baking soda

Priming. foaming

NaOH

Caustic soda

Alka linity. embrittlement

Na 2 S0 4

Glaube r salts

Alkalinity

Si02

Silica

Hard scale

Magnesium bicarbonate Sodium chloride

Sodium bydroxide Sodium sulphate Silicon dioxide

Gypsum. plas ter of Paris

Hard scale

69 6

Duties and Services

subject of interest. In contrast to the design of a conventional ball valve with seat rings on both sides to form a seal, the principles of the rotary piston valve were borrowed as the basis for the design of a valve having flow around a ball section (Figure 1). This type of circulation stabilises the flow through the bore of the ball and prevents the damaging effects of cavitation and disintegration which occur in the intermediate positions. The ring gap is used for the through-flow of the medium as soon as a point of constriction is attained at which the pressure loss in the central bore is greater than the pressure loss in the ring gap. The basis for the stabilisation of the flow is, however. that the ring gap for circulation exhibits small transient changes in the surface, so that sudden changes in pressure or velocity can be avoided. The desired resistance of the ball valve to the formation of deposits, of the sort that might be formed from minerals and foreign particles such as sand. can be achieved in a design which makes use of a surface not requiring special finishing (Figure 2).

+--+--Figure I. Ball valve: opm positio11.

~

'it/

Figure 2. Ball valve: closed position.

WatcrServices

697

This type of design requires the fixed placement of the seal elements, so that a rubber or an elastic preformed seal. of a conventional variety would be first and foremost. To this end, there are already well-tested seals from the area of shutoff valves which have been around for decades and can be easily adapted. The counter seat in the housing can use a metallic seal made of corrosion-resistant steel with inlet and outlet edges having especially large radial sections which then provide a useful fixing in place of the rubber/ elastic preformed seal.

Figure 3. Hygienic service valve.

698

Duties and Services

In addition, the bearing for the turning point of the ball is placed on an eccentric. This reduces the frictional load of these seal elements to the smallest levels, which is, of course, a necessary requirement. Mineralogical deposits and foreign particles can in this fashion block the ball in its entire periphery. so that the operating forces of the drive unit are not sufficient to move the ball. For this reason. these types of ball valves are given a relatively large gap between the outer surfaces of the ball and the inner surfaces of the housing, to try to avoid gap corrosion-the formation of hard layers of deposits and corrosion. Additionally, the ball is provided with a scraper rim extending beyond the turning radius, which provides only a line contact and otherwise gives the ball surface free room in which to turn. As a consequence, even with a large amount of deposits, the operating forces are sufficient to actuate the valve. In intermediate positions of the ball valve, this overall ring gap results in a washing action, and the medium moving through the valve produces a kind of sel [-cleaning effect. This provides the necessary flow characteristics. One design of this type of valve is the ball valve with an alternative opening which, in a state of no pressure, permits the exchange of the elastic ring seat of the ball without removing the valve itself from the supply line (Figure 3 ). This device is particularly useful with large nominal diameters. It is a further requirement that the components for transmitting the motion and the drive unit must be solidly built and require no maintenance. For this reason, massive shaft bearings in the horizontal direction are needed. These are not exposed to the deposits of solid matter. and thus are not located at the deepest point. The resulting possible lateral arrangement of the driving mechanism

Figure 4. V-port ball control valve.

Water Services

69 9

. --._

Figun! 5. Centred-disk rlastorner-lined butterfly

valve {or large pipe sizes.

Metal-seated gate valve for potable-water a11d dirty-water applications above and below ground.

results in a relatively low construction height. These construction considerations have led to a durable and maintenance-free design of ball valves for the drinking-water supply using well-tested components at competitive prices. The ball valve shown in Figure 4 is suitable for fibrous suspension applications as well as clean water. The construction of this valve makes it ideal for pulp and paper industry duties. The packing gland is investment cast 316 stainless steel with a standard PTFE packing. In line with many developed control valves, the internal flow passages have been computer designed. Shut-off is to ANSI Class VI. PTFE-seated butterfly valves with a double-offset design offer optimum valve life, particularly if they are used primarily for isolation and flow control. The elastomer-lined centred-disc butterfly valve (Figure 5) has been specially designed for large pipe sizes-1100-3200 mm (44-128 in). This type of valve is mainly used in water supply, water treatment and electric power stations. In terms of standard performance and durability, rubber-lined butterfly valves still command a significant position in the water and waste-water industry . although PTFE is the outstanding performer. Where a rubber lining is bonded to the body of the valve. making it an integral part of the body. the valve body is not in contact with the medium so corrosion between body and

700

Duties and Services

lining is not an issue. \1\lhen installed with the shaft in a horizontal position. the valve is self-cleaning. This type of valve is suitable for both sealing and control functions. A typical example is shown in Figure 6. Other types of butterfly valves used in water service include those with an inclined-cone sealing system for metal-to-metal sealing, where the sealing system is completely integrated within the body. Gate valves (Figure 7) are still the primary valves for water and waste-water service. Manufactured in a wide range of materials. they are ideally suited for on-off duties. The valves have knife gates, wedge gates, and parallel face gates. Generally, these valves have a very low resistance to flow which, in the case of parallel-gate valves, approaches that of a straight pipe. They are also used for duties with high-pressure fluids due to the fact that upstream pressure assists the sealing between the gate and seat. Gate valves tend to be hand wheel operated for water service.

Shaft

:.ou~ 1u

Topflongc ISO 52 1 I

O..Jlf'\g ! 0 uno bush

Bnauno

Cen~ 'IC

v•tva

Vul vo body

Figure 6. Rubber-lined butterfly valvl'.

d iSC

Water Services

701

Reflux valves

Basically, this type of valve is designed for water-works duties such as normal distribution on gravity mains. Certain types include non-slam recoil reflux valves which are designed to prevent flutter at high velocities, and rocking disc reflux valves, used where pipeline dimensions are in excess of 600 mm (24 in). Some reflux valves have outside weighted levers and heavy proportioned doors to provide non-slam characteristics and assist closing. A particular type of water-works reflux valve is the multiple-door reflux valve suitable for large-diameter pump or suction mains , where flow velocity is small. Multiple doors combined with the large-area diaphragm provide a lower head loss against the valve than is possible with the valves of single door

STAINLESS STEEL KNIFE GATE VALVES

CAST IRON KNIFE GATE VALVES

e

e

Major m;lrkcts: Popa. chemical, mming. power. solids handling.

rower. OF.M

OEM

e e e e

e Sitt' range 80mm to 600mm e Raised scm face: fnr positi,·c seating e Pressurt' rating PN 16 e Actuators: Manu;rl. ckctric. pneumatic.

Sit.L' range 50mm to 2000mm i'r~'>> llr<: r.tt i n~ PN I 0

Raisc.d sea t face fo r posit ive '>eating Actuatm': Manual. clectrK.

hydraul ic

pncum;tti.:. hyuritulic

WEDGE GATE VALVES inu u,,,,

e e

Size ran<'c SOmm to 600mm Prc,~ure

Major markets: Wa~!c11 at~r. water. ~--· chemical. mining. solids handling. raper.

r.ttin:; PN 16

e Meet\ BS ~ 161 Type B Standard • ( iunmctal sc.:at

e Actu
UNIVAL PORTED GATE VALVES • M ajor markets: Paper. chemical. power.

mining. solids handli ng • StJ.e

e

rang~

80mm 1< • oOOmm

Prt·,surc rating l'i\'6 standard. PN I 0 on appl ication

e e

Bi-direct ional One piece rei nforced elastomer 5lt:eve for

~cali ng.

abrasi' and corrosive

s'-·n in:s

e

l-ull port open i ng

e

Actu;\lm': Manu:,!. clcl'tric. pneumatic. hydr~ul i c

Figure 7. Examples of gate valves.

702

Duties and Services

design. Also, the reduction of inertia reduces the risk of slamming as pump shut-down occurs. The design of the diaphragm inlet ports and body-contour shape largely avoids the action of cavitation. Valves of this type are typically suitable for velocities up to 3 m/s (10ft/sec). Non-return valves in water systems

The complexity of water-distribution network dynamics creates an unstable equilibrium of pressure and back-pressure, constantly modified by the user, leading to different appliances or collectors, some of which can be compared with veritable drains: retention vats in factories. sinks and their dishwasher. baths and their bath- or soap-water. washing machines, central-heating circuits with anti-scale additives, etc. As a result, there is the possibility that water provided through the network can be polluted by waste-water leaving the consumers returning to the mains or passing from one consumer point to another without going through the mains (from one apartment to the other).

14. Nuts and pins 1 5. Keys

1. Body inlet 2. Body outlet

3. Cover 4. Stop 5. 6. 7. 8. 9. 10. 11. 12. 13.

End caps Door Rocker arms Faces to body Faces to door Bushes to rocker arms Bushes to end caps Spindles to rocker arms Pins to rocker arms

.16. 17. 18. 19. 20. 21. 22. 23. 24. 25 .

Split pins Stud bolts to body Studs to cover Setscrews to end caps Eyebolts Body joint Cover joint End plate joinl Bu~ers

Air release plug

Multiple-door reflux valve for large-diameter pump or suction 11111ins.

11\later Services

703

This may be caused by: Depression on the mains: a considerable call for water (e.g. fire hydrants) or intervention in the main pipe (repair, new branch. breakage) can create a depression. (ii) Over-pressure at the consumer: all systems of high pressure, of course. but also all appliances for hot-water production. sanitary or otherwise. instantaneous or otherwise, can be the reason for this. (iii) Simultaneous appearance of low pressure on the mains and high pressure at the consumer. (i)

Protection systems

Theoretically, it is imperative to implement those systems which prevent water returns due to these pressure disturbances. These systems should be automatic. They can be purely hydraulic, air-hydraulic or mechanical. The hydraulic systems are theoretically the most reliable but are often expensive

Non-return stop valve.

Gotera/[mrpose valve for water, sea-water and sewage.

704

Duties and Services

or difficult to install. The mechanical systems are subject to doubts regarding function and longevity. Principal types of protection are summarised in Table 2. In the presence of all these complex phenomena, and conscious of the necessity to organise a water distribution of quality and to protect it against the risks of pollution, numerous countries have brought about legislation which defines the measures to be taken (see Table 2). The principle consists of defining the rules which a good general installation has to follow and the criteria of quality of the protection appliances to be incorporated, in order that the whole mains escapes the danger of pollution. To do this it is possible to use. individually or in combination, certain o[ the different hydraulic, air-hydraulic or mechanical systems examined later. Most industrial countries have chosen to install non-return valves (NRV). taking into account the security-cost compromise and applying very strict design and control rules which considerably reduce the possible hazards connected with the mechanical character of the design.

Handwheel nut Handwheel

Gland Gland Packing Stuff1ng Box Stuffing Box Gasket

Stem Bonnet Bonnet Bolts Bonnet Gasket

Wedge Nut

Wedge Face Ring

Body Seat Ring Wedge

Body

Cast-iror1 gate valve.

Water Services Table

705

2. Protection systems

Method Barometric loop

Overflow sa fety gap:

1. Total overUow

Geometry lO mm (33ft) loop without branch

Remarks Phys ically very safe. but costly and not always re<.~ lisable. lnopernble in case ofleakage.

- r-----....

~--~------------f.x

- ·- --..:--==---..:::::==-.----;

Essentially safe but ineiJective if tap is extended with a sample pipe.

2. A partial or overflow limit

Safe if outlet flow is well dimensioned in comparison with inlet flow. rneffectual if the tap is extended with a sample pipe.

3. Diverted overflow

Safe principle but limited in practical application.

Disconnectors:

l. Without moving parts

Safe principle but may involve head loss.

sub~tantial

2. \<\lith moving parts (a JOn-line

Safe principle. may have reliability problems.

(b)Tec

Safe principle. may have reliability problems.

Reduced press ure back flow preventer

Elaborate and costly system. generally needing regular maintenance to ensure continued proper function.

Non-return valves

Simple an d effective. Performance and reliability primarily depend on design a nd qual ity of components and manufacture.

706

Duties and Services

Table 3. State of the regulations in force in different countries

Country

Regulations with tests. agreements and/or standards

Germany Great Britain Belgium Denmark Spain France Holland Italy Sweden Switzerland

Control at the manufacturer's site

Control with the consumer or in the trade

X

X

X X X

X

X

X

X

X

X

X

X

X

X X X

X

Back-flow preventers and vacuum breakers

Back-flow arising from connections between a potable and non-potable water supply can constitute a serious public health hazard. There are numerous well documented cases where back-flow from cross connections has resulted in contamination which could be harmful to health. The problem is a dynamic one because plumbing systems are continually being installed. altered and extended. Where pollution cannot be prevented using approved check valves. the modern approach is to use vacuum breakers and back-flow preventers. Vacuum breakers are used on medium-risk lines and fawcets. In high risk areas, many Health Authorities throughout the world recommend the use of reduced-pressure back-flow preventers. These units operate on the variation of three decreasing pressures created by the head loss of two check valves. Any reversal of pressure from back-flow and/or back-siphonage is sensed by a membrane actuating a release valve which will drain polluted water to atmosphere. Non-return valve families

An NRV is an automatic appliance intended to prevent a fluid changing its flow direction. Numerous classifications exist. Here we use that of the CEN which distinguishes between four families, based on the direction of the displacement of the closing system with regard to that of the flow of water. Note that there are other NRV families but these are not for use in the sanitary field, notably the ball valve. particularly recommended for loaded liquids.

Water Services

Family 1:

Linear displacement, not parallel. Perpendicular-displacement valve with straight flap. Oblique-displacement valve with oblique flap. Famify 2:

Angular displacement. Lift valve. Butterfly valve. Family 3:

With deformable closing system. Membrane valve. Famify 4:

With linear parallel displacement. 'Guided' valves.

Back-flow preventer.

707

708

Duties and Services

Test specifications on non-return valves

These should embrace the following points: mechanical characteristics of the casing. tightness, head loss, and reliability . In the field of sanitary protection, different countries have enforced test specifications and methods for valves smaller than 50 mm (2 in). We will examine here this category only and will mention the minimum and maximum requirements for each of the characteristics listed previously.

Stainless-steel minH1ttings used to join small-bore stainless-steel tubing.

A selection of copper and gunmetalfittings.

Water Services

709

Mechanical characteristic of the casing

The resistance is defined: (i)

(ii)

To pressure: from 16 bar (230 lbf/in 2 ) in water at ambient temperature to 25 bar (360 lbf/in 2 ) at 95°C (203 °F), (duration oftest 2 to 5 min). To buckling and torsion: according to the sizes and the countries, the casings are subject to constraint in order to determine their resistance.

Certain countries require the NRVs to be of dismountable design with regard to tbe connection, with bosses for ~he following purposes: (a) To control the tightness of the NRV. (b) To drain the installation. (c) To disinfect the pipes. Also in certain countries, the alloys are specified according to the nature of the water (e.g. the problem of dezincification). It must be noted that the mechanical holding tests carried out on the casing should not modify the hydraulic characteristics of the NRV. Tightness

(i)

(ii)

Low-pressure tightness: all specifications prescribe that an NRV must be tight under a pressure of 30 mm (13 in) water column, applied during a total time of 3-10 min. High-pressure tightness: the valve must be tight under a pressure rising from 0 to 16 bar (0 to 2 30 lbf/in 2 ) applied during a total time of 3 to 10 min.

Head loss (L~ P)

We know that the head loss is a loss of pressure induced by any plumbing appliance mounted on a pipe. The design of the appliance can reduce the head loss to a minimum. In the case of an NRV, the survey of the hydraulic profile of the internal parts determines the head loss. It is usually expressed in feet or metres water column at a given flow . (It can also be expressed by a coefficient of LlP, k, square function of the average speed of flow on twice the acceleration of the weight.) The specifications usually prescribe. for a given nominal diameter. the achievement of a minimum flow at different values of LlP ranging from 0.5 to 10 m {1.6 to 32 ft) water column.

710

Duties and Services

Rei iabi Iity

Endurance tests are very important for an NRV which, insofar as being a mechanical system, is often tainted with unfavourable prejudice in comparison with purely hydraulic systems. Without modification of its principal characteristics (tightness, t..P), the appliance can undergo up to 100,000 cycles of operation at a pressure varying from 6 to 16 bar (90 to 230 lbf/in 2 ) (according to the country), one half in cold water and the other half in hot water (temperatures varying from 65 to 9 soc (l SO to 200°F) according to the country). This corresponds on average to a minimum longevity of 10 years. Opening pressure

In principle, present legislation prescribes that an NRV must be able to function in all positions, which means in this case the use of a release spring. This spring must conform to the specifications which impose a limit of opening pressure. At present, the opening pressure must always be positive and below 1m (3.28 ft) water column, according to the country. This is very important. Experience shows that, being open for 80% of its time. an NRV functions with very weak flow rates. Under these conditions, it is of prime necessity that the opening is complete, as vibrations occur which can generate strong noise nuisances. as well as their being problems of premature wear. Valve types compared

At present, only the linear parallel-displacement valve described as 'guided' seems to comply as, whatever its position, the design of this type alone gives the following results: Perfect tightness at weak pressure, mainly ensured by the quality of the guide system (difficult to obtain in the valve family with angular-displacement, lift or butterfly valves). (ii) A high-pressure tightness, mainly ensured by the compression of one face against the seat and a solid closing system, which is not ahvays the case with the family of membrane valves. (iii) Minimum head loss, the linear parallel displacement preventing a considerable deformation of the fluid flow, contrary to that given by valve families producing non-parallellinear displacement. (i)

Role and interest of the regulations

Re gulations ca n only exist if they are defined and imposed by the public authorities and if the application is controlled by the proper bodies.

Wnter Services

711

Regulations depend on two aspects: (i)

(ii)

The localisation of the protection features: it defines the list of appliances or installations in which a form of protection must be installed, in which part of the installation and what type of protection must be used. Most European countries have prescribed their own regulations by replying to two questions: 'What is to be protected?' and 'In what manner?'. The result is that, in certain cases, the choice of appliance is left to the decision of the installer. The definition of the qualitative criteria of the protection equipment: From the moment when the fitter has chosen a type of appliance. it is necessary for him to know that the appliance corresponds with a qualitative specification which allows it to be used in the considered case.

Conformity to criteria

In all the countries where regulations exist, these criteria have been the object of tests. where the operating mode is defined and where the positive result is confirmed by the issue of an Approval No. and the right to affix a distinctive sign on the body of the valve. The control of the appliance is either carried out by the body which has prescribed the regulations or by an authorised independent laboratory. whose results are confirmed by the recommended body. It is desirable that the definition of the specification is the result of co-operation between the legislators, the manufacturers and the installers but it must not be forgotten that the opinion of the legislator is predominant. Control of appliances when being designed and manufactured is insufficient if the complete installation itself is not also submitted to the control of the authorities. In the case of the whole installation having to be joined with an exterior source, it is the authorisation of the branch which is the ultimate sanction and constitutes its certificate of conformity. Finally, it is necessary to watch that the quality of the installation does not deteriorate with time. This is the purpose of the necessary periodic controls. carried out by the responsible authorities and which particularly apply to the appliances subjected to greater approval requests. This is the reason why NRVs are equipped with bosses in order that controls can be carried out easily. In some cases the regulations even state quite simply that the appliances are to be exchanged every 5 years, hence the importance of the valves being of standard dimensions and also being easily dismountable. Equally. it is ultimately necessary that regulations and specifications should extend beyond the national standards, so that the rules applicable to different countries are rendered identical for aJl. In the NRV field, the specialist commissions of the European Standards Committee are studying this problem, with the participation of the different national plumbing syndicates. It is

712

Duties and Services

desired that their studies result in rationalisation, reduction of costs and the elimination of protectionism. of which some national regulatory bodies could presently be accused. Pipes and tubes

The most common material used in domestic heating and plumbing systems is copper tube. This has proven to be a versatile and reliable tubing product, easily joined by compression fittings or more efficiently by soldering and brazing. Other methods for joining larger-diameter copper tubing include the grooved-end upper connection system that eliminates leaks more commonly associated with soldering and brazing and speeds up installation. The system is more suited to industrial applications and uses a pressure-responsive synthetic rubber gasket to seal on the outside of the tubing. Tube sizes range from 50 to 200 mm (2 to 8 in). Increasing use is being made of stainless-steel tubing . Particular advantages offered by stainless steel tubes are: (a) The appearance of finished pipework is aesthetically pleasing. Both the satin and the polished finishes are attractive, and the thin walls of capillary fittings give pipeline and fittings a neat, continuous appearance. (b) No maintenance is required after installation: the satin finish stays satin-looking and the polished finish stays polished. (c) The price is comparatively stable, not fluctuating like copper. (d) The corrosion-resistance of stainless steel is better than copper in areas of cupro-solvency and it is not prone to pitting corrosion by water. (e) The mechanical properties are good. The strength is high which means that it is less prone to damage in service. Elongation is also high which gives it good bending properties-as a. comparison, it takes the same amount of effort to bend 15 mm (0.6 in) stainless tube as a 22 mm (0.9 in) copper tube. It can be sawn easily with a hacksaw or roller cutter. (f) Copper or other non-ferrous pipe and fittings are subject to pilfering on site as they have a high scrap value. Stainless steel does not have a high second-hand value. The inherent disadvantage of stainless-steel tubing employed as pressure pipes has been the difficulty of making leak-free joints (e.g. stainless-steel tubing used on high-pressure aircraft hydraulic systems is invariably welded). However, this has now largely been overcome by the availability of suitable fittings , solders and fluxes making plumbed joints quite practicable and several jointing techniques are now well established. These fall into two major categories: (i) (ii)

techniques requiring heat joints which can be made at room temperature.

Water Services

713

Joints using heat

Techniques using heat to join are welding, soft soldering and silver soldering. Welding is not used in the majority of plumbing installations although it is an established technique for the chemical, food and cryogenic industries. Soldering implies the use of capillary fittings where the i.d. of the fitting socket is just a few thous greater than the o.d. of the tubing. Capillary attraction pulls the solder into this gap. To make successful joints in stainless steel it is essential to recognise two important properties of the metal: (a) The low thermal conductivity of stainless steel-about 1/ 30 th that of copper. (b) The property which gives the metal its stainlessness-this is because a hard oxide coating is formed within seconds of a nascent surface being presented to an oxygen-bearing atmosphere. The coating steadily increases in thickness until a stable protection is achieved. For successful soft soldering, the outside end of the tube and the inside of the fitting socket must be abraded with emery cloth to remove the oxide skin. The prepared surface should then be painted with solder paste and the joint assembled. The secret of soldering stainless steel well is not to hurry, to use a small flame and to make sure that the back of the joint (away from the plumber) gets enough heat. Using a metal reflector behind the joint can often be a help or. alternatively, the use of a cyclone burner produces a flame which will curl around the back of the fitting . vVhen the solder begins to flow a frying sound comes from the joint. The joint should be completed by end-feeding with solder wire. Many solder paints have been made and marketed over the years. One with a 5-year shelf life contains phosphoric acid base flux and also powder of the tin-lead alloy which has the lo·west melting point possible. Phosphoric acid fluxes are recommended as they only become aggressive and eat up the tenacious chromium oxide when heated ; they will not continue to attack the stainless steel when cold. For silver soldering. it is necessary to use an aggressive chloride-based flux to eat the oxide and make a good joint. It is important to remember that this flux must be removed from the joint area (inside and outside) within 24 hours of making the joint. Usually swilling with water for an hour or so will remove all trace . There are many suppliers who market silver solder and brazing rod, together with flux, especially for joining stainless steel. The majority of these are entirely satisfactory providing the suppliers' instructions are carefully followed. and there must be the same care in heating the joint as with soft soldering. Capillary fittings are at their most efficient when the gap between tube and socket is uniform. Such uniformity is achieved with a design in which the tube is held centrally by a specific deformation of the socket at three points.

714

DutiesandService.s

joints made cold

Low conductivity has undoubtedly been the cause of a number of leaking joints made by soldering and, although soldering techniques have been much improved , it is still useful to explore cold techniques. These might be used, for instance, where naked flames cannot be applied, e.g. on sites with fire risks or pipelines fitted with a plastic anti-burst liner. Three basic techniques are: cold adhesive bonding (now approved for cold-water supplies), the use of compression fittings. and the use of screw-thread fittings (the last named is only used for thick-walled pipe and. as it is not applicable to thin-walled tubing used in plumbing, will not be discussed further). Experimentation has been carried out by the adhesive makers. by stainlesssteel capillary-fitting makers and by the British Steel Corporation to determine the best adhesive to use and to devise a method of applying same. Of the many adhesives tested, the dimethacrylate esters, which are anaerobic adhesives, have proved to be the most satisfactory. These anaerobic adhesives cure in the absence of air, that is, ·when they enter the confined capillary gap they start to harden. They will cure by themselves, but in order to make a joint cure to handling strength in 2 min it is necessary to use an accelerator which can be applied from an aerosol spray. The bonding technique entails cleaning the tube ends with coarse emery cloth, spraying with accelerator and allowing the latter to dry (30 sec). A ring of the viscous adhesive is then applied to the leading edges of both the tube and the fittings. The tube is then pushed into the fitting socket and left without movement for 2 min for handling strength to be achieved. When cured, a pull-out strength of 1.1 tons is obtained for a 15 mm (0. 6 in) tube. Pipelines jointed by these adhesives will withstand internal pressures of 310 bar (4 500 lbf/in 2 ). This technique has now been approved by the UK Thames Water Authority for use with potable water and by the majority of the Regional Water Authorities in the UK. The maximum temperature for which its use with water and aqueous chemicals is recommended is 60°C (140°F). Now that mini-bore tubing is available down to 6 mm ( 1 / 4 in). together with a complete range of low-cost capillary fittings, this technique (and soft soldering for applications above 60°C (150°F) will increase the use of stainless-steel instrumentation, for medical gases and for various water applications. Stainless-steel compression fittings employ the principle of tightening a nut which causes a ferrule or olive to be compressed tightly on the tube by forcing it down a cone on to the tube end. The shape of the ferrule is the subject of many patents. Most compression fittings have two or three ferrules per fitting . Some designs dig into the tube wall-the so-called 'bite-ring' fittings-and some are just compressed tightly onto the tube. Joints are quickly and easily made with

Water Services

715

compression fittings; with most designs just two spanners, turned in opposition, are needed. A particular model employs only one screw thread to apply the forces necessary for compressing the two ferrules and the joint can be broken and remade a number of times. These fittings are intended for use with thin-walled tube to BS412 7, and this point should be checked by plumbers contemplating the purchase of stainless-steel compression fittings as some designs only work on thick-walled tube. For the handling of some liquids such as milk, milk products and beer, it is essential to have demountable joints in order to clean stainless-steel pipelines. Such joints must be free from cracks and crevices which might become breeding places for bacteria. There are a number or designs of fittings available incorporating PTFE washers and neoprene 0-rings for these applications. For other chemicals. cone-seated or flat-seated joints with gaskets are in common use. Summary

The cause of leaks in stainless-steel plumbed joints in the past can be mainly attributed to lack of knowledge of the differences between stainless steel and copper. It is worth repeating that the low thermal conductivity of the metal must be recognised. A big flame from a blow-lamp is not enough; time must be allowed for the heat to soak all round a joint. The other important difference is seen in the choice of flux . Chloride-based fluxes are a hazard as they are corrosive on stainless steel. Often hygroscopic traces of hydrochloric acid can form and cause pitting. The availability of stainless plumbing as a complete system acts as a stabilising influence on the cost of plumbing. The growth of the stainless-steel domestic plumbing market will be affected by three main factors: (a) the price of copper tubing and fittings, which may well rise again in the not too distant future; (b) the price of stainless-steel compression fittings, which is expected to fall: (c) the availability of an adhesive which will withstand boiling water for long periods without losing its strength. When this is available. the use of stainless-steel tubing in central-heating systems will be even more widely accepted. Domestic water-supply valves

The demand for shut-off and thermostatically-controlled valves has increased for domestic copper and stainless-steel pipelines with the greater use of domestic central heating, washing machines. dishwashers and showers. etc. The quarter-turn valves shown in Figure 8 are designed as emergency shut-off valves to be installed upstream of taps, ball valves and appliances, and can be

716

Duties and Services

used to isolate individual fittings for servicing without having to drain down the whole plumbing system. Alternatively, they are used for permanent plumbing-in of washing machines and other appliances. The valve has been designed to shut against a test pressure of 20 bar (300 lbf/in 2 ) and has been accepted by the UK National Water Council providing that it does not replace the mandatory screw down stop valve.

Figure 8. Quarter-t11rn slmt-off valvl's.

Handwheel

Tube cutter and seal Saddle

Backplate

Fits to all 15 mm (1/2 in) copper water supply pipes

Fig w-e 9. Selj-n1tling plumbing-in valve l
Water Services

717

A valve with a self-cutting plumbing-in kit has been developed so that it can be fitted quickly without having to turn off the water supply. The valve shown in Figure 9 is suitable for connection to 15 mm copper pipe supplying domestic cold and low-pressure hot water, and is ideal for plumbing-in washing machines, drinks dispensers and garden taps, etc. Thermostatically-controlled flow regulators and stopcocks have been developed for use with electric instantaneous showers, wall kettles, etc., to enable a selected temperature to be maintained. The regulator senses fluctuations in supply pressure causing variations in water flows and automatically adjusts to provide constant flow across the heater elements, and thus provide constant temperature.

Hygienic Services Valves have been developed for use in hygienic pipelines for dairy, brewery, food, beverage. biological and other process plants, where automatic valves manufactured to a high standard of hygienic design are demanded. These are usually stainless-steel valves free from pockets or crevices designed for the control of both product and 'cleaning-in-place' fluids . Food and beverages

The food and beverage industry is a large user of gas. steam and water on a continuous basis, indicating a requirement for general process-control valves in addition to sterile valves for handling food products. Plastic/ polymer valves are also a popular choice although use of these may be limited by the need ror aggressive or caustic cleaning. Manual shut-off valves are used in areas of planned maintenance shut-down or in problem areas which may need to be clea red. Products can then be left in the pipeline leaving only a small section to be cleared and cleaned. Double-seat valves are ideally suited for 'contained-flow systems'. eliminating the need for manual swing bends for product and cleaning lines. Filling, emptying and CIP can take place simultaneously in a totally 'closed-in' flow system with all functions automatically controlled. The butterfly valve shown in Figure 1 has a disc/ stem (A) in a 316 stainless-steel one-piece design and produces bubble-tight shut-off. The valve has acetal stem bushes (B) and a double '0' cup self-adjusting seal (C). The extended neck (D) allows ror 5 mm of piping insulation. The seat is of a tongue and groove design (E) and the primary seal (F) is achieved by an interference fit. The body (G) is a two-piece wafer or lug style. The main feature ol' this particular type of hygienic valve is its international compatibility. The rotor valve (Figure 2) is particularly suitable for rood, beverage and pharmaceutical applications. The main benefits of this type of valve are: multi-port capability, cavity-free, high- now, top-entry and quick-couple connection. Figure 3 shows an air-operated remote-control changeover valve. The movement of the valve is transmitted by a piston in the actuating cylinder.

Hygienic Services

719

The piston is operated by compressed air arranged to open or close the valve as required, the return movement being spring-assisted to provide a fail-safe feature. The diaphragm shaft seal shown is particularly suitable for aseptic duties involving the use of steam-sterilisation procedures. The seals are manufactured from PTFE and can be used at temperatures up to 150°C ( 302°F). Pharmaceuticals

The pharmaceutical industry has requirements for primary and secondary manufacturing processes. The secondary processes have standard requirements covering steam, water and quality-water supply. The material of choice tends to be 316 stainless steel with gate- or bellows-sealed valves for steam handling, bronze-gate valves for standard water handling and _diaphragm valves for quality-water handling. Primary processes require sterile valves for materials handling. The valve shown in Figure 4 is used in the pharmaceutical drug industry and in hospitals for oxygen-supply systems. The valve is fitted with a seaJed plunger mechanism to ensure there is no remnant of media in the actuating zone.

A manifold of mixproof valves installed irz a dairy.

720

Duties arrdServiccs

Sterile valves developed for use in bio-technology and food-processing applications are available, complete with valve actuator as shown in Figure 4 . Stainless-steel body extensions at both inlet and outlet permit welding into the process line with extra-thick extensions to guarantee weld integrity. Internal components can be steam-sterilised via permanent connections to a steam supply. Temperature-monitoring devices are attached to the valve to ensure total sterility and conventional bonnet backing is removed to avoid process contamination .

A colleclion of sanitary valves and pipeline components for use body-care plants.

011

process lines in food. beverages and

Hygie11ic Sl'rvices

7 21

Figure 1. Butterfly valve for hygienic services.

4-Way

5-Way

Fig11re 2. Multi-port rotor valves for food, beverage and plwrmaceuUcnl npplicntiorrs.

722

Duties and Services

Figure 3. Air-operated hygienic-service valve.

Figure 4. Plwnnaceuticnl industry stnnd11rd valve.

Hygienic Services

72 3

Stainless-steel thin-walled pipes and stainless-steel fittings are produced to various standards for use in hygienic applications. Some standards are: BS 18 64: stainless-steel milk pipes and fittings using the recessed 0-ring joint (see Figure 6). BS 3 5 81: stainless-steel cone-joint pipe fittings . American 3A: dimensionally similar to BS 3 581 with metal-to-metal cone-type joint. IDF (International Dairy Federation): lighter in construction than BS 18 64 and employing a specially shaped rubber joint to give a flush crevice-free seal (see Figure 7). This standard is now incorporated in BS 4825 Part 4 and ISO 2853.

Figure S. Sterile valve with nctuator.

724

Duties and Services

The most common material used for hygienic valves and pipes is 316 stainless steel or 18/ 10/ 3 stainless steel, also known as BS 316S16. with equivalent specifications as follows: United States: AISI type 316 France: Z.8CND Sweden: 832 SK and RRNJ44 Germany: V4A Supra Corrosion of stainless-steel pipelines can readily occur, however, if sterilising agents based on halogens are allowed to remain in contact with the metal for extended periods. See also the chapter on Corrosion of Stainless Steel. Glass pipelines

While plastic pipe and tube meets much of the demand for non-toxic pipelines, glass piping may be preferred, or even become essential. for sterile services. Glass is attacked by only a few reagents, which include hydrofluoric and hot concentrated phosphoric acids (both of which produce serious corrosion). superheated water and alkaline solutions.

BS 1864 Fittings with expanded pipe fixing

With butt weld fixing

Figure 6.

BS 3581 fittings with expanded pipe fixing , also available with butt weld fixing.

Figure 7.

Hygienic Services

72 5

Cold alkaline solutions attack glasses very slowly but, as the temperature increases. the rate of attack rises rapidly. Attack also increases with increasing alkalinity. Attack by superheated water is seldom serious enough to prevent satisfactory service life from glass tubes, although the rate of attack increases with the temperature and alkalinity of the water. Borosilicate glass pipeline systems are corrosion-resistant and neither rust nor age. They are used extensively for effluent and venting lines in accordance with DIN 1986 in scientilic institutes, hospitals, and the chemical and pharmaceutical industries (Figure 8 ). However. they have many other applications, e.g. for conveying numerous other liquids and gases in all branches of industry, laboratories, hospitals and in the [oodstuffindustry. A typical borosilicate pipeline system has a 'slip-on' coupling which allows simple assembly without specialist knowledge and this, together with traps , laboratory drip cups and supports, constitutes a range of fittings with which virtually any installation problem can be solved. Typical normal bores can be 40, 50, 80, 100 and 150 mm and pipe lengths between 100 and 2000 rom.

Figure 8 . Borosilicate glass piping system.

72 6

Duties and Services

The glass components are connected together by means or a coupling consisting of a single-bolt stainless-steel clamp which produces a tight connection. Within this clamp is a flexible nitrile rubber insert. which positively grips the bead flanges of the glass parts to be connected. At the actual sealing point. there is a PTFE insert which has the same chemical resistance as the glass itself, thus the medium only comes into contact with borosilicate glass and PTFE. The most complicated pipeline installation can be assembled and the low weight of glass (density only about one-third that of cast iron) is an advantage which aids installation under ceilings and other inaccessible areas. Glass piping is fragile and does require safeguarding. particularly if used in pressurised applications. Maintenance costs can be reduced by visual inspection through the pipe, which enables rapid location of potential build-up and blockages. The use of rods to remove blockages is acceptable provided that non-metallic ferrules and attachments, e.g. nylon. are used. See also the chapter on Thermoplastic Pipes. Thermoplastic pipes have their attractions because of their chemical inertness and a structure which does not harbour bacteria. Not all such materials are hygienic in the sense that they are free from tainting the product, even PTFE not being ideal for handling foodstuffs. All such materials. too , suffer from relatively low maximum-service temperatures, which can make certain types unsuitable for sterilisation via cleaning in place. Certain

Rigid clear PVCpipl'.

Hygienic Services

72 7

food products are, however, successfully handled by elastomeric pipes (hoses) or rubber-lined pipes. Plastic-lined pipe is a frequent choice in food and beverage processing and pharmaceutical facilities. Entire plastic systems that meet FDA requirements can be assembled using plastic-lined pipe and valves. Polyvinylidene chloride (PVDC) is suitable as a pipe-lining material for high purity needs to 80°C ( 17 5° F). where stream-purity protection is critical. Another successful plastic piping material for pharmaceutical and biotechnology industries is unpigmented natural polyvinylidene fluoride (PVDF). PVDF plastic piping is one of the most chemically inert engineering polymers. It is an excellent material for all types of ozonation systems, for example. particularly where both purity and strength are required. Clear Schedule 40 rigid PVC is a good choice for sight-glass and dual-contaminent applications. Made from non-toxic materials conforming to FDA standards. it has found success in wet- and dry-food processing, bakery products. medical/hospital uses and in the cosmetics industry. It is a cost-effective alternative to copper, stainless steel and glass piping. It is not recommended for compressed-gas applications or pipe threading.

Steam Services Steam is water in the vapour phase and is one of the oldest industrial tools. The first requirement in steam production is to add heat to water until it reaches its boiling point. It is then necessary to add a much greater quantity of heat to convert the water to steam. Steam allows the energy of fuel burned in the heat source or boiler to be carried to some other point where it can either provide mechanical energy through an engine or provide heating. In all types and sizes of oil and chemical plants, energy is used for process heating, power generation and driving pumps and compressors. In many refineries, primary steam is obtained by burning waste prpducts in the boilers. Although steam is the traditional means of conveying heat, there are a number of alternatives including: • • • •

high- and medium-pressure hot water. high-temperature oils. electric heating. mechanical agitation.

It is not the remit of this handbook to discuss the merits of steam or alternatives, neither is it appropriate to discuss the subject of steam in its full capacity. This subject is well documented in another more technical publication and in some specific manufacturers' literature and publications. Steam distribution

The most important link between a central steam source and the steam user is the steam-distribution system. A typical steam circuit is shown in Figure 1. The steam flow in a circuit is caused by condensation of steam which produces a pressure drop. This induces the flow of steam through the pipes to where the heat energy is required. In operation when the steam outlet (crown) valve is opened, steam passes immediately from the boiler into and along the main pipes. The pipework is cold initially so heat is transferred to it by the steam . The air surrounding the

Stemn Services

729

Space rr=n========ri="~~~==n===--rr=~===, heating system

-

Feedtank

Condensate

Boiler

Figure 1. A typical steam circuit.

pipes is cooler than the steam, so the pipework will begin to lose heat to the air. This causes the steam immediately to condense and fall to the bottom of the pipe.. It is then carried along with the steam flow and by gravity owing to the gradient in the steam main which normally falls in the direction of steam flow. The condensate is drained from the lowest points in the pipeline. By continuously feeding more fuel and water into the boiler, a continuous flow of steam is maintained to make up for the water which has already evaporated into steam. The condensate is usually returned to the boiler feed tank. The pressure at which the steam is to be distributed is to some degree determined by the point of usage on the plant needing the highest pressure. Steam at a higher pressure occupies less volume per kilogram than steam at a lower pressure. Steam boilers

Boilers are the most important part of the steam circuit. A boiler is a vessel in which the heat energy from a fuel is transferred to a liquid. In the case of saturated steam. a boiler also provides heat energy to produce a phase change from liquid to vapour. Steam boilers come in all sizes to suit both large and small applications and operate using different fuels , including commercial waste, oil, gas and coal. The choice of fuel is largely dependent on the tariff given to each type of fuel. Boilers can operate on just one or on two types of fuel (e.g. oil and gas). A typical package boiler is shown in Figure 2 .

7 30

Duties and Services

Tubes 2nd pass

Rear outlet box

Tubes 3rd pass Furnace tube

Figure 2. A typical package boiler.

Superheated steam

Steam produced from the outlet of a shell-type boiler or from the steam drum of a water-tube boiler can only be saturated steam. \1\later-tube boilers are often required to produce superheated steam by passing saturated steam from the steam drum through another set of tubes inside the main furnace area, where it is heated up beyond its saturation temperature to a gas (superheated steam). Where superheated steam is required , a boiler incorporating superheating tubes is essential. Safety valves

An important boiler fitting is the safety valve. Its function is to protect the boiler shell from over-pressure and subsequent explosion. There are many types of safety valves fitted to steam boiler pla nt but they must all meet the following criteria: • •

The minimum bore of a safety valve connected to a boiler must be 20 mm. The total discharge capacity of the safety valve(s) must be at least equal to the drum and at 100% capacity of the boiler.

Steam Services

• • •

7 31

The full rated discharge capacity of the safety valve(s) must be achieved within 110% of the boiler design pressure. The maximum set pressure of the safety valve(s) shall be the design (or maximum permissible working pressure) of the boiler. There must be an adequate margin between the normal operating pressure of the boiler and the set pressure of the safety valve.

A typical boiler safety valve is shown in Figure 3. Double safety valves are commonly found on boilers with an evaporative capacity of more than 3 700 kg/ h. Stop valves

A stop valve (crown valve) must be fitted to a boiler in order to isolate the steam boiler and its pressure from the process or plant. Typically. stop valves used are generally angle-pattern globe valves of the screw-down type. Cast-iron valves should not be used for this application. The stop valve is not designed as a throttling valve and should be fully open or closed. It should always be opened slowly to prevent any sudden rise in downstream pressure and associated water hammer. The valve should be of the 'rising hand wheel' type in order that the valve position can be easily seen. An inductor fitted to the valve also assists this procedure. Isolating valves. usually screw-down globe valves with disc-check valves sandwiched between the flanges of the two stop valves. are used on multi-boiler applications.

Fif!ure 3. A typical boiler safeLy valve.

7 32

Duties and Services

Feed-check valves

These are installed in the boiler feed-water line between the feed pump and boiler. A boiler feed stop valve is fitted at the boiler shell. Bottom blow-down valves

Steam boilers should be fitted with at least one bottom blow-down valve at a point as close as possible to where sludge or sediment is likely to accumulate. Blow-down valves should be key operated or automatically controlled by timers and electronic interlocks. Air vents and vacuum breakers

Simple cocks and pressure-balanced air vents are designed to purge air from the steam space (Dalton's Law). Vacuum breakers are fitted on the boiler shell. They are used when a boiler is taken off-line and the steam space condenses and leaves a vacuum that can result in damage to boiler flat plates and leaks from inspection doors. System valves

In addition to both safety and control valves. butterfly valves are used in steam-pipeline systems when tight shut-off is required. Check valves are used for the protection of reverse flow in pipelines. They are typically of the wafer pattern up to 40 bar. Ball valves to over 60 bar are commonly installed throughout the system . Bellows-sealed stop valves are ideal for high-pressure and high-temperature applications. Pressure reduction

Steam generators produce steam at a pressure, temperature and volume not generally acceptable to a consumer. As a consequence, it is necessary to apply steam conversion (i.e. change one. two or all three parameters) in the steam-distribution systems of power plants for public safety, heating power plants, industrial power plants and in the chemical and process industries. Conventional practice is to reduce steam pressure in a reducing valve station (see Figure 4). and reduce temperature further down the line with desuperheaters operating on a variety of principles, e.g.: direct water injection into the low-pressure steam line (ii) applying saturated steam to the hot steam (iii) steam cooling by a separate steam cooler.

(i)

Steam Services

High-prrfomwnce open-IJonnet safrty valve for saturated and superheated steam sPrvice.

Rigid moulded insulnted vnlve cover.

733

734

Duties and Services

RANGE SPRING ~,,

PILOT INLET VALVE

PISTON

PILOT EXHAUST VALVE

PILOT

PILOT - - - EXHAUST LINE

Main Valve Closed

Main Valve Partially Open

Main Valve Fully Open

Non-flowing modulating pilot-operated prcssure-rl'iief vrrlve.

Steam Services

73 5

Safety valve

Steam-

Trap set

t Condensate

Figure 4. A typical pressure-reducing valve station.

The two processes of pressure reduction and desuperheating can also be accomplished either simultaneously or sequentially in a steam converter valve. Details of steam-control valves and steam-relief valves are shown in Tables 1 and 2. Valve operation (Figure 3)

Steam-conditioning valves

Steam-conditioning valves are primarily designed for pressure and temperature control of steam. The first valve was developed in 19 2 9 and had butterfly pressure control. Steam-conditioning valves (Figure 5) combine pressure and temperature reduction in a single body and are particularly suitable for applications such as: turbine bypass valves, process steam-conditioning valves and pressure-relief valves. The use of this type of valve means less rigorous requirements for piping downstream from the steam-conditioning valves. In situations where cooling without pressure reduction is required, a desuperheater is used. Steam traps

In any steam installation, the effectiveness of the steam-distribution system and the steam-using pJant depends to a large extent on the correct selection and application of steam traps. There is a tendency to underestimate this point in order to standardise on one type of steam trap. Wrong selection and installation can cause waterlogging, damage plant performance, reduce output, upset temperature control and give rise to water hammer. Wrong sizing is often the root cause of pressurised condensate lines, short trap life and high maintenance costs.

'-1

w

Table 1. Steam control valves: applications

0'

Temperature controlling equipment Superheated steam cooler

Combined steam converting and safety valve

1::::1

s::

~

;;·

"'

Nozzle injectors

:;:, :::!

:::...

Circuit

Circuit

Cl:l

Circuit

"'....-<::

To lurbinc

.. ----------"\

~~

+1 ~

I

i

Application: For special temperature-control tasks in industrial power plants.

Application: For special temperature-control tasks in industrial power plants.

Application: For high-pressure (HP) bypass stations during start-up a nd bypass operation. primarily in public utility power plants.

Typical design: Withdrawn pipes. welded flanged (to DIN, ANSL etc.).

Typical design: Nozzle arrangement as required . Division of the spray water among several immersion pipes possible depending upon purpose.

Typical design: Forged, welded connection (to DN, ANSI. etc.). Type 500: inlet at side. Type 600: inlet from below.

Remarks: Low pressure loss. no additional atomising steam. Low noise level. No moving parts: simple ma intenance. Fitted in all positions. Sizes: DN 12 5 to DN 1600 (mm).

Remarks: High-duty nozzles for easy installation in every pipeline. No moving parts. simple maintenance. DN > 50(mm).

Remarks: In conjunction with the auxiliary control system. it functions as a safety valve. No external control media are used . only the existing live steam. With an electric pressure-control system. the valve functions as a normal control valve.

;:::;·

"'"'

Table 1. Continued

Feed-water control valves Circuit

Conventional control valves Circuit

Circuit

--~

p)

r - - - --,

p

Level control valves

~

)

$~

Application: For controlling all or part of the feed water. also available in a special version as a boiler filling valve.

Application: In plants for pressure control of oil, water, steam, etc. As auxiliary control valve. drain valve of start-up flash tank.

Application: On high- and low-pressure (HP and LP) feed-water tanks, condensers. etc.

Typical design: Cast, forged, straight-through valves, angle valves. welded connections, flanges (to DIN, ANSI. etc.).

Typical design: Cast, forged. welded pipe construction, straightthrough valves, welded connections. flanges (to DIN. ANSI, etc.).

Typical design: Cast. forged. straight-through valves, angle valves, welded connections, flanges (to DIN, ANSI, etc.) Valve parameters (ON, PN) as required.

Remarks: Versions available for all capacities encountered in practice. ON 50 to DN 500 (mm).

Remarks: Typical sizes and pressure ranges. From ON 15 to ON 1500 (mm). From PN 10 to PN640 (bar) (145 to 9300 lbf/in 2 ).

Remarks: For plant-specific problems with evaporating media (cavitation. etc.). V)

.....

"':;:,3

~ .... <::

;::;· C">

"' '-1

w

'-1

73 8

Duties and Services

Table 2. Steam relief valves: applications

Steam converting station Steam converting valve

Spray water valve

I S1cam l'Onv.:.:rllng V(llvc

2 .Sprdy water v~lvc

Application: In all thermal systems where steam pressures and temperatures are to be simultaneously reduced, e.g. in steamdistribution systems in industrial plants and. in particular, as a turbine bypass in power plants.

Application: For steam converting plants. combined steam converting and safety stations and temperaturecontrol equipment.

Typical design: Cast. forged , straight-through valves. angle valves, welded connections, flanges (to DIN. ANSI. etc.).

Typical design: Cast. forged. straight-through valves. angle valves. welded connections. flanges (to DJN. ANSI. etc.). with single- or muJti-stage perforated cage trim depending upon the pressure drop to be handled.

Remarks: Saving of space and improved control quality as a result of simultaneous pressure reduction and desuperheating in one single valve. Maximum design data for valves supplied to date: 700 t/ h. 2 76 bar (4000 lbf/ in 2 ) 56 5°C (l050° F).

Remarks: DN 15 to ON 150 (mm) and higher.

There are various types of steam trap (Figure 6 ). which include: •

•

•

Thermodynamic traps: suitable for mains drainage and for draining tracers or jacketed lines. Its simple design with one moving part. a flat disc, makes it a popular choice. This type of trap can withstand severe water hammer and freezing. Bimetallic traps operate by the movement of a bimetallic strip with temperature change. These traps work over a wide range of pressures but with a degree of waterlogging. Balanced-pressure traps have capsules manufactured in stainless steel for corrosion resistance. They also have a high resistance to water hammer and are not affected by back-pressure. The balanced-pressure principle is now widely accepted for applications where thermostatic steam traps can utilise sensible heat in the condensate and reduce flash steam losses.

Steam Services

•

•

7 39

Fixed-temperature discharge traps: one of the balanced-pressure range of steam traps for discharging condensate at just below steam temperature when installed in one altitude, or at a fixed temperature when installed in reverse. A condensate degree of sub-cooling and perhaps waterlogging is implicit in the use of a trap of this pattern. Mechanical steam traps: probably the most popular choice of steam trap is the ball-float type. First launched in the 1940s, the ball-float steam trap will pass condensate as soon as it reaches the trap but will hold back steam and

Figurr 5. Steam conditioning valves.

Ball float type

Thermodynamic type

Thermostatic type

Figure 6. Steam traps.

Inverted bucket type

7 40

•

Duties and Services

adjust itself automatically to a change in load. It is particularly suitable for draining plant which must be kept clear of condensate at all times. Automatic air vents and steam-lock release valves may also form an integral part of this type of steam trap. Ball-float steam traps generally have a high discharge capacity, whether installed in a horizontal or vertical position. Inverted-bucket steam traps normally give an intermittent discharge and are more suited to superheat conditions because they are sensitive to density. If bucket traps are used on plant which will frequently be called upon to start from cold, separate air vents should be provided in by-passes. Bi-metallic or balanced-pressure elements are more suited to this requirement. All mechanical steam traps are comparatively bulky and, since they contain water. they must be protected from freezing in exposed conditions. Swivel-connector steam traps: this type of trap is designed for ease of fitting and removal without the need to break the pipework or disrupt plant operation. The swivel quick-release connector is a permanently installed pipeline connector with a leak-free joint. Three different trap options can be incorporated into this system: thermodynamic, balanced pressure and inverted bucket. This type of steam trap is ideal in situations where altered plant or process conditions call for a different type of trap to be installed.

Steam-trap monitors

This type of unit enables steam traps to be checked while they are working. Typically, it consists of a sensor chamber capable of distinguishing bet\t\reen steam and condensate and is fitted upstream of the steam trap. It is suitable for continuous monitoring and can operate on saturated steam systems up to 32 bar. The unit can be used with any type of steam trap. Air vents

The three primary barriers to heat transfer are films of water, air and scale. By far the most resistant to heat transfer is air. In fact, air is more than 1500 times more resistant to heat transfer than iron or steel and no less than 13,000 times more resistant than copper. Thermostatic air vents automatically open to air and gases, but shut against steam. They discharge air full bore on start-up and open during running whenever air collects, irrespective of steam pressure. Air vents should be located furthest away from the steam inlet because this is where air tends to collect. Where possible they should be fitted at all high points in the system. Manually-operated air cocks are not suitable when dealing with air and uncondensable gases that are mixed in with steam.

Steam Services

741

Balanced-pressure air vents are the most widely accepted type of air vent. because they operate close to the steam-saturation temperature and can therefore differentiate between pure steam and air/ steam mixtures. They have a high resistance to superheat and water hammer. Pipeline sizing

Pipe sizes may be chosen on the basis of either • •

fluid velocity pressure drop

There is often a tendency when determining pipe sizes to be guided by the size of connections on equipment to which they will be connected. The desired volumetric flowrate may not be achieved if the pipework is sized in this way. If the pipe is too small, then high pressure drop and steam starvation at the using end will result. If the pipe is too large, the pipes will be more expensive than necessary, a greater volume of condensate will be formed due to greater heat loss and increased running costs will result. The quality of the steam will also be poorer. The most common pipe standards used when sizing pipe are those derived from API. In Europe pipe is manufactured to DIN standards. Other terms used include Blue band and Red band referred to from BS 138 7 regarding pipe thickness. Red is commonly used for steam-pipe applications and Blue for air-distribution systems. Ifpipework is sized on the basis o[velocity, then calculations are based on the volume of steam being carried in relation to the cross-sectional area of the pipe. Pipe is sized on the 'pressure drop' method by using the known pressure at the supply end of the pipe and the required pressure at the point of use. Boiler-feed calculations and steam-flow calculations are more comprehensively covered in a preceding section of this handbook. In addition, a number of specialist steam equipment manufacturers have produced some excellent publications that cover this subject in considerable detail. In any steam main, some of the steam will be condensed due to radiation losses and this water must be drained out otherwise corrosion and water hammer will result. In addition, the steam will become wet as it picks up water droplets. Steam-pipe mains should be run with a fall or not less than 40 mm in 10m h in in 10ft) in the direction of the steam flow. to ensure that both steam and condensate run in the same direction. Drain points are installed in the line to collect and remove water. Steam-distribution systems will often give more trouble than any other piped service because of the failure to recognise that the pipework contains not only steam but water and air. Saturated-steam lines should be drained at

e

742

DutiesandServices

regular intervals, at all low points where the condensate can collect. Drain points at intervals of 30-50 m (100-1 SO ft) are usual and they are most effective where pipework changes direction. Pipework should be arranged so that pockets where water can collect are avoided. Globe valves of under-and-over construction can also form a weir and prevent condensate from flowing to the next drain point. If the valve is fitted on its side, this can usually be avoided. It is important also to note that branch lines are normally much shorter in length than the steam mains. Sizing branch lines on the basis of a given pressure drop is Jess convenient on short lengths of pipe. Branch-line pipe sizes are normally selected from a table based on pipeline capacities at specific velocities. Branch connections should always be taken from the top of the main so that the driest steam is taken. Steam tracing

The temperature of process liquids being transferred through pipelines must often be maintained to meet the requirements of the process, to prevent thickening and solidification or simply as an anti-frost measure. This is achieved by the use of jacketed pipes or by attaching to the product line one or more separate tracer lines. each carrying a heating medium such as steam or hot water. External tracer lines are simple and cheap to install. The simplest form of tracer is one that is clipped or wired onto the main product line. Maximum heat flow is achieved when the tracer is in tight contact with the product line. The material for the tracer line should always be chosen to avoid electrolytic corrosion at any contact points. Tracer pipes can generally be wired on but it is better to use either galvanised or stainless-steel bands. A practical method is to use a packing-case banding machine. Where temperature difference between the tracer and the product is low, the tracer may be welded to the product line using either short-run or continuous welds for maximum heat transfer. For maximum heat transfer it can be an advantage to use a heat-conducting paste. The paste can be used to improve heat transfer with any of the clipping methods described. The surfaces should be wirebrushed clean before the paste is applied. Spacer tracing involves the use of insulating material between the tracer and the product pipe to avoid local hot spots on the pipe if the product being carried in the line is sensitive to temperature. lf pipes are to be insulated. the insulation should cover both product line and tracer but it is important that the air space remains clear. The insulation should be properly finished with a waterproof covering. Most of the sizing of external tracers is done by rule of thumb but the problem is- what rule? and whose thumb? There are widely differing opinions on lay-out as well.

Fire-Safe Valves Defining industrial fires is a difficult task. They can range from smoking. oxygen-poor, low-temperature fires with their resultant low heat flux to the extreme of a hydrogen-jet fire with flame temperatures exceeding 2800°C (5000°F). No valve is an entity by itself in a fire. The entire system has to be considered and includes effects on pipe supports. pressure-retaining bolting tanks, and concrete structures. The API (American Petroleum Institute) fire tests were designed specifically for valves in oil and gas production plants. Over many years the tests have been refined and adapted for many different industrial plants. API 607 (Rev 4). API 6FA and BS 6755, BS 5146 are the accepted standards for fire tests today and adopt the same procedures. Other test standards and procedures include OCMA FSV-1, Exxon BP3-14-l , FM 6033 and API RP6F. Many users have also established their own corporate standards for fire-safe valves. A strategy of fire fighting that appears to be universal as far as fire duration is concerned is that if the fire is not beaten in one half hour, a withdrawal and containment policy is instituted. This comes from structural component failures such as pipe-rack collapse, flange-bolt failures and concrete eruptions due to water of hydration changing to steam. Based on the limiting factors of ancillary equipment, a test duration of one half hour was established. The basis of all fire tests is that a pressurised valve must operate after being burned at a specified high temperature for a specified period and leakage after burning {which will destroy soft seals) must remain within specified limits . Valve-open or valve-closed test

Soft-seated valves which employ seats on both the upstream and downstream side of the obturator will trap fluid in the cavity formed by these seats and the pressure shell. If this fluid is an incompressible liquid, increases in temperature will cause the pressure of the trapped fluid to rise dramatically. Calculation and rather simple experiments both show that a trapped hydrocarbon liquid will increase in pressure by 12 bar for every oc of temperature rise.

7 44

Duties and Services

This is a known problem that has been so overlooked that paragraph 2.3.3 of the American National Standards B16.4, 'Valves-Flanged, Threaded and Welding end', warns about the effects of thermal expansion of fluids trapped in double-seated valves. While some ball-valve designs are capable of automatically relieving this cavity pressure when in the closed position to the upstream side. others may not. In OCMA FSV-1, the test did not evaluate the valve's resistance to cavity-pressure rise as conditions with the valve open and a vent hole in the ball stem slot did not represent those of a closed valve. API insists on a cavityfilled closed test. Specific API test requirements are: (a) The valve shall be tested in the closed position with water, with the stem and bore in the horizontal position. Check valves will be tested in their normal operating position. (b) The valve will be uniformly enveloped in flame having a temperature of 761-871 oc (1400-1600°F) average of two thermocouples, one located 25 mm (1 in) below the valve and the other 25 mm (1 in) from the upper stem packing box on the horizontal centreline. No reading shall be belo-w 704 oc (1300°F). Piping upstream of the test valve larger than 25 mm (1 in) nominal pipe size or one half of valve nominal pipe size (whichever is smaller) must be enveloped in flame for a distance of at least 152 mm (6 in). (c) The end connection piping-to-valve joint leakage (flanged, threaded or welded) is not considered a part of this test and is not included in the allowable external leakage. For the test, it may be necessary to modify this joint to eliminate leakage. Suggested systems for fire testing to API specifications are shown in Figures 1 and 2. Figure 2 is a schematic outline for systems using compressed gas as the pressure source. Test procedure is as follows: Open valve(s) (items 5 and 6) at water source, and any necessary vent valves (item 17) to flood the system and purge the air. The test valve may have to be placed in the partially-open position in order to completely flood the valve body. (ii) Close fill valve (item 5) and vent valves (item 17). and close the test valve (item 11 ). The system upstream of the test valve should be completely water-filled and the system downstream shall be drained. (iii) Pressurise the system to the appropriate pressure from Table 1. Maintain this pressure during all testing. Record the reading on the calibrated sight gauge (item 4). Empty the graduated downstream container (item 19).

(i)

Fire-Safe Valves

745

Note: 6 in"" 152 mm

Note: 6 in= 152 mm

Figure 1. System using a pump as the pressure source.

Note: 6 in= 152 mm

I. Pressure source. 2.Pressure regulator and relief. 3. Vessel for water. 4.Calibratcd sight gauge S.Water supply. o.Shutoff valve . 7. Pressure gauge. ~.Piping arranged to proviue v(:Jpour trap. 9. Enclosure for test - horizontal clearance between any part of the valve and the enclosure shall be a minimum of 152 mm (6 in). IO.Minimum height of enclosure shall he 152 mm (fi in) above the top of the valve. I!. Test valve mounted horizontally with stem in horizontal position.

12. Fuel gas supply with minimum of three burners located at 120° 13.Flarne temperature thermocouple located 25 mm (I in) from upper stem packing box on horizontal centreline . 14.Flame temperature thermocouple- to be located 25 mm ( 1 in) below the centre of the valve body. 15. Pressure gauge and relief valve (if requireu) connected to centre cavity of vctlve. 16. Shutoff valve. 17.Vent valve. JR. Condenser . 19.Calibrated container . 2!J.Check valve.

Figure 2. System using compressed gas as the pressure source.

746

Duties and Services

(iv) Open fuel supply, establish a fire, monitor the flame temperature, and when the average of the two thermocouples (items 13 and 14) reaches 761 oc (1400°F) start the test. Maintain the average temperature between 761 and 871 oc (1400 and 1600°F) for the test duration. No reading shall be less than 704°C (1300°F). (v) Record instrument readings (items 7. 13, 14 and 15) every 2 min for the test duration. (vi) At the end of the test duration ( 15 or 30 min), shut off the fuel. (vii) Immediately determine the amount of water collected in calibrated container (item 19) to establish total through-valve seat leakage. Continue recording the amount of water collected for use in establishing the external leakage rate. If the test valve is of the upstream sealing type, the volume or water that is trapped between the upstream seat seal and the downstream seat seal (when the valve is closed) shaH be determined before the test is started and identified in the test report. It is assumed that during the test this volume of water would move through the valve, past the downstream seat seal and be collected in the calibrated container. This volume has not actually leaked past the upstream seat seal, so it may be deducted from the total volume measured in the downstream calibrated container when determining the through-valve leakage. (viii) Allow the test valve to cool to 93°F (200°F) or less. Use temperaturesensitive crayons or other suitable means to indicate valve-body temperature near the thermocouples (items 13 and 14). Record the level in the sight gauge (item 4) . Use the initial and final readings to determine total leakage during the test. (ix) Close the shut-o ff valve (item 16) and operate the test valve against test-pressure differential (Table 2) to the full-open position. (x) Measure and record external leakage for a minimum of 5 min after valve is in the full-open position at test pressure. Divide the total external leakage by the duration of the test in minutes to obtain the external

Table 1. Summary from SGS Yarsley fire-test report Leakage rate (ml/min)

Through leakage rate

Maximum allowed

Burn period

Zero

5600

External leakage rate

Maximum allowed

Zero

1400

Zero

280

Zero

2800

Cool down Low hydrostatic pressure test

High hydrostatic pressure test

Zero

560

Fire-Safe Valves

747

leakage rate. The test system, excluding the test valve, may be adjusted during the test period to keep the test within the limits specified herein. Fire-safe ball valves

Fire-safe ball valves are manufactured for applications in explosive and fire-risk environments, and are specifically designed to prevent the spread of fire. The fire-safe ball valve shown in Figure 3 is of the floating ball type fire-tested to API 607, API 6FA and BS6755 Part 2. This type of valve is suitable for use in the oil. chemical. petrochemical and pharmaceutical process industries. The floating ball design relies on the downstream movement of the ball due to pressure differential to effect a seal against a resilient seat ring. The valve employs a double-stage sealing arrangement and independently loaded graphite fire-safe packing that remains unaffected by any deterioration of the main PTFE chevron packing set under fire conditions. Butterfly valves

Pyrogenic and fire-safe butterfly valves are usually certified fire-safe to BS6 7 55 Part 2 and API 6FA. They have inherently fire-safe primary metal/ metal sealing and bubble-tight shut-off in both directions. Typical fire-test results for this type of valve are shown in Table 1, which refers to the triple-offset metal-seated valve shown in Figure 4. It has zero-leakage

Table 2. Test pressure during fire test

Type of valve

Spec 6D valves

Spec 6/\ valves

Test pressure

Valve rating {PN)' Jbf/ in 1

bar

150 {20) 300 (10) 400 (64) 600 (100) 900(150) 1 500 (250) 2500(420)

210± 10% 540±10% 720± 10(}(, 1080± 10% 1620± 10% 2700± 10% 4500± 10°!.,

(14.5±10%) (3 7.2 ± 10%) (49.6±10%) (74.5 ± 10%) (111. 7±10%) (186.2 ± 10%) (310.3±10%,)

(bar) 2000 (130) 3000 (207) 5000 (345) 10,000 (690) 15,000 (1034) 20 .000(1 379)

1500±10% 2250± 10% 3750±10% 75 00± 10% 11.2 50± 10% 15.000±10%

(103.4± 10%) (15 5.1 ± 10%) (2 58 .6± 10%) (51 7.] ± 10%) (775. 7± 10%) (1034.2 ± 10t){,)

' (PN) is the pressu re class designation utilised in ISO (Internationa l Standards Organisation) documents.

74 8

Duties and Services

performance, fire-tested to API 6FA and BS6755 Part 2. The block and bleed seal configuration consists of two metal-laminate seals with an intermediate bleed channel. which connects to the bleed purge port in the valve body when the disc/ segment is in the closed position. The valve is designed as a replacement for gate, globe. ball or plug valves. Some advantages claimed of a triple-offset segment valve over ball, gate and plug valves are given in Table 3. Flame arresters

Flame arresters are employed as safety devices to extinguish flames in pipelines, ducts and vents carrying flammable gases or vapours. They prevent fire spreading to other parts of the system, helping to avoid extensive and costly damage to plant and equipment and the risk or personal injury. ------- ~ '~

ITEM COMPONENT BODY

2•

~---- --10

92--1~

9 \,. -~~ 93

~~

~

- sea

2"-1

~

?2

~

BALL H ALF

2b

BALL LOCKING

2c

BALL KEY

J

STEM

4

STEM 81\LL

'>

BALL SI'IHNG

6

GLAND

7

G LAND SCREW

9 10 11 20 21

I~ING

COVER CO VER SCR£W

SLEEVE SLEEV E SeA L SEAT RING

22

C HF.VRON RING

2.1

SPREADER RI NG

24

H EADER RING

~

25

STOP PLATE

89

LEVER OR "f·liAil/ADAPTOR

li- ~

90

LEVER SCREW

!:11

LEVER WASHER

92 9J

COVER GASKET

PlRE SEAL

Figure 3. Fire tes t certified.floatingfull-bore ANSi class 1 SO and 300 ball valve.

Firi'-Safe Valves

749

Figure 4. 1 50 mm wafer-typl' valve with stainless-steel laminated seal. Cert.ified to BS 6 7 55 Part 2.

0#1;111·1:1 A

:a:;;::

, . c;;:

M7654/C

Rot. BV.ITA.: 40.96.7654

I

.• •

In•

APPROVAL CERTIFICATE

I:III;IUII

..

L ' :=-i+f

,

' ._, .::::::z::s:t::

'*I'. . .

I

j _ lo

•

' •~-

---u:

·=

Cl1ent:OM8Sr~A~------------------------------L~~ ~~~~~~~~~·~·~·~t•~·~0~4~ . 1~1~.9~6~----------

Tho und•r&igncd ALFIO N ICOUNI, Surveyor Of BUREAU VERITAS, acting wnhin the 5COPU ol the genen•t ti''IT'H1i1i()ns which l tgullltC rhe lnterv&mione of our company, did fl ttfllnd. Dt roquc:•t of Mes.srs OMB SPA Ct.NA'I 1.: SOT rO • BERGAMO to thttlf wo;k~ f ot tho purpo"e of wi1ne~sing the F~re Sofo Tas.t according to API fi07· 198E ond 85 6756 PART 2·1987 on the following • • '•"'

I Ball Side fn1'Y BSE frunn1on Valvo 900 lbs. Fl11nged Stock Finish size 6 x 4 • Reduced Sou~ Moterlol Body·Cio•vre : ASTM A I 05N + ENP M aterilol Soot: A STM At82 F8e Clou Z ... NVIon 12 Mo!uriol S<•m: ASTM A 106N + ENP Motori•l Bali : ASTM A 182 f6o Cia$$ 2

M on..-facrvrcd and

a::;~emblccl

in

neeord~l'\ce

w ilh OMS drewiOQ no. A900A4900

uxpo~t.>d to fire lor 30- minute.!!, end dunng lht te st olt pt~ramettrs, u feQulrad by API 607 ond BS6J56 P1n 2 . w ert c hecked. rGCordcd end f·o~om~ according to STD ~qultements. For turthLtf de:rolls of tnt 1rnngcments ond test rttaults, aLtO OMS Cerrtflc1ne no 1689 herewith •nec tmd af"'d duly undonu~d.

The vn:"o wei

ON THE SASIS OF THE RESULTS,THE AllOVE !JALL VALVE SATISFACTORLY PASSED THE· FIRE SAFE TEST •

'==:r

we •-•

[~ I

L

J Typical/ire-safe certification.

'-1 U1

Table 3. Advantages of triple-offset segment valve over gate and plug valves

Gate

0

Plug

Triple-offset segment

Ball

t::l

s::

~

Sealing

Jam closures: leak becomes progressively worse with each cycle.

Pressure and/or mechanically assisted seating maintains seal.

Unique torque sealing.

Actuation

Manual: requires high torque to jam. Stem threads corrode and resist turning. often break in open or closed position.

High torque due to surface area. requires frequent takeup of sealing nut increasing torque. Impractical in gritty, caking. coking or gummy service.

Consistent torque. 1 / turn rotation. 4 Stops must be set.

Low torque. 1/ turn rotation. 4 No stops required. Seat provides mechanical stop.

;;·

"":::::::.

~

Accepts manual. pneumatic and electric motor without special requirements.

Throttling

Not used

Impractical

Yes

Yes

Relative size

Very high. bulky and heavy. Automation very large.

Bulky. Automation very large.

Large. Automated package smaller than comparable gate or plug.

Light-weight. Most compact..

\-Iaintenance costs

Very high. particularly in corrosive or erosive service due to stem freezing. wedge failure. and seat erosion. Requires [requent preventive maintaneance (greasing. etc.).

High. particularly in corrosive or gritty service.

Medium.

Very low.

Labour intensity

HIGH Installation (heavy weight). Manual actuation (high torque). Preventive maintenance. Overall maintenance.

HIGH Installation (heavy weight). Manual actuation (high torque). Preventive maintenance.

MEDIUM

VERY LOW Light-weight. i\{aintenance is simple.

High High Highest Highest Long Highest

High High High High Long High

Medium Lower Low Low Long Low

Cos t of ownership Purchase Installation Operation Maintenance Life Cost of actuation

Medium to heavyweight. Body needs to be split for maintenance.

Lowest Lowest Lowest Lowest Long Lowest

V':l

'....<::"" ;:;·

""""

Fire-Safe Valves

751

Flame arresters prevent the propagation or spread of flames by absorbing and dissipating heat from the flames on one side of the arrester. so preventing the temperature of the gas or vapour on the opposite side rising to ignition point. Ignited gas or vapour attempting to pass through a flame arrester is extinguished by the element assembly absorbing heat from the flame faster than it is developed. Thus the temperature of the flame is lowered below its ignition point. To accomplish this, the area of metal surface of the arrester element must be sufficient to absorb the heat generated. Flame arresters are used extensively in the chemical, petrochemical, petroleum. gas. marine, mining, aircraft and many other industries. They are

0.024 in cell height

Flame arrester size (nominal bore of pipe) in mm J;4 to I 19to25 llf2 38 2 50

Graph No. I

2

3 4

63

21f2

5

76 100

3 4

~

127 152

5 6

6 7

Perpendicular or triangular cell

9

200

K

!0

200

8

II

250 300 to 500

10 12 to 20

12

Graph No. 1 2

Vl

:::l

0

.s:::

~ J ~

'-

3

4

5

6

7

II

I v _j v I II/ lj I f1/; I v vv v v vv v v v / / / 1/ /; v v v v / I II v / v vv v ~. l ~ v v v v

/ v

v

/

[,/

/

_,./

/

()

5

10

15 20

40

50

60 70

Air flow cu ft/hr (OO
/

___..--- /

/

25 30

12

I

1/ v

/

I

10

9

8

v

/

L

/

/

v

~/

/ "

80 90 100 120

140 160 180 200

oc. at atmospheric pressure

For other gases the equivalent air flow is given by multiplying the gas flow by the square root of its specific grav1ty .

Figure 5. Airflow throHghjlame arrester elements in housings.

240 280

Duties and Services

7 52

also used for purging gas mains, on the air intakes of internal combustion engines, and in many processes using solvents and gases. Flame arresters are made in two basic forms : for fitting into pipelines, and onto the end of a pipe. The elements are made up of two strips of thin foil. one corrugated and the other plain. The strips are placed together and coiled into circular elements to give a spiral matrix of triangular cells and the whole assembly is fitted into an outer case. Elements are made with various cell sizes and widths depending on the applications and the gas or vapour concerned. Elements are constructed either from cupro-nickel with a brass outer case, or stainless steel for both matrix and casing. Flame arresters should be inspected frequently as part of routine plant maintenance and cleaned as necessary, and certainly if excessive pressure drop is experienced due to fouling of element cells. In the event of a flash-back, 0.018 ir;, cell height Graph No.

Flame arrester size (nominal boreofpipe) mm in 314 to I 19 to 25 I V2 38

13

14 15

16 17 18 19 20

21 24

13 14 IS

5

16

17

18

I 1/1/

/i;1/ I

I

I

v

I

I

0

I

2

4

127 152

6

2 3

s

8 8 10 12 to20

v/ /v v v v v / vv v / 20

19

v

/v v v

IV I / vv v 1

I

I

/

/

/

I

v

76 100

I Iv

I 1/

2 1/2

200 200 250 300to 500

22 23 Graph No.

50 63

/

v y l--"'v

/

~/

/

/

I

/

/

/

./

,/

/

v v/

/ __.. /

~

3 4 5 6 7 8 9 I0 I 2 14 16 18 20 Air flow cu ft/hr (OOO's) 20

23

24

v

/

/

V,/ /

/ ~/

I

/

/

22

21

/

/

v

/

25

10

35

40

50

oe, a t atmospheric pressure

For other gases the e quivalent air flow is given by multiplying the gas flow by the square root of its specific gravity .

Figure 6. Air flow throughjlamr arrester elements in housings.

60

70

80

Fire-Safe F alves

7 53

Fire-sa)(' ball valves to API 607 and BS 5 I 46.

the flame arrester should be inspected immediately and H the element is damaged or distorted. a replacement should be fitted. All flame arresters offer some resistance to flow defined as pressure drop. This value increases with the degree of hazard due to the longer cell sizes and smaller crimp required in manufacture of the arrester element to absorb heat or a specific application. To reduce the pressure drop to a minimum, elements have a straight-through cell construction and the element housing is increased to an area several times that of the nominal bore of the pipe. Graphs of pressure drop against airflow are shown for elements with a cell height of 0 .61 mm (0.024 in) in Figure 5, and a cell height of 0.46 mm (0.0 18 in) in Figure 6.

Fire Hydrant Valves Fire-hydrant valves comprise straight-way and angle ball valves as well as screw-down gate or globe valves purpose-designed to meet the requirements of International Standards, e.g. BS 750:1984 which calls for a delivery of 34 ljs (450 gal/min) at a constant running pressure or l. 7 bar (25 lbr/ in 2 ) . Ease of operation is also a most important feature of all valves and fittings used in fire-fighting . The fixed-valve fire hydrant shown in Figure 1 conforms to BS 7 50:1984 Type 2, screwed-down underground fire hydrant and exceeds the flow-delivery requirements of 1. 7 bar. The inlet mounting flange has been designed so that it is suitable for new and existing installations. The option of fixed or loose valve. either gun metal or plastic outlet and the choice of packed gland or 0-ring stem seal makes this type or fire-hydrant valve particularly versatile. A typical flow performance curve is shown in Table 1.

SLraiglrt-wn.rJ hydrant ball valve.

Fire Hydrant Valves

Angle hydrant ball valvr.

Figure 1. M11lti-purpose fixed-valve fire llydra11t.

7 55

Duties and Services

7 56

Table 1. Typical performance curve

FLOW PERFORMANCE CURVE 4.0 3.11

KEY

3.5

f -1- ~ --

3.21

Extract from

3.0

I

S.S. 750:1984 dcJUSe 6.2

1 IS

'The Hydrant shall deliver not less than

2.SO

2000

t:Jt:.

2.25

1] BAR at the inlet to ·the Hydrant .

VI

7.0

t:Jt:.

< co

.... => VI

1.7 BAR -r-

w

t:Jt:.

a...

L/min at a con-stant pressure of

l.IS

l

.

u

Full open Cv = 9-. 511/1 !111hdl· •l

Z·l

1.25

Cv~

!I

l0

~I

0.71

~

6Pi...n.!J Q .. flow role in Litres/Sec V

!5 ~ J 6P =Pressure drop across valve in metres

0.50

~·

0.21 0 800

910

1100

1210

1400

lSSO

1100

1850

2000

2150

1300

' 1450

1600

1710

2900

JOSO

3200

3310

JSOO

FLOW RATE · LITRES/MIN.

If the valve seat and 0-seal to the body cover need to be replaced. it is important to ensure that the main has been depressurised before the valve is dismantled. Depending on local conditions. fire-hydrant valves should be inspected at least every 3 months for: 1. physical damage to the surface box 2. rubble or silt in the chamber preventing access to the hydrant 3. loss of parts.

Every 12 months, the valve should be tested unless the visual inspection reveals any damage. The valve should be checked to see that it is free from leaks and operates correctly when fully open. Fire landing valves

These valves are designed to meet the technical requirements of wet-rise systems in high-rise buildings or other structural installations where similar fire-protection systems are employed. They are typically manufactured with flanged inlet and instantaneous female outlet connections with metal-to-metal seating.

Fire Hydrant Valves

75 7

Figure 2. Standard Class F hose pressure regulator.

Pressure-regulating valves

Combined hydrant-stop and pressure-regulating valves are used for a wide range of fire-protection equipment suitable for refinery, chemical, petrochemical pian ts and offshore applications. The Class 'F' valve shown in Figure 2 is a high-pressure regulator. It is suitable for: • • • • •

fire mains systems in high-rise buildings high-pressure systems on oil-rig platforms and in oil refineries and chemical plants fixed monitors and hand lines where individual pressure requirements vary applications with high pressure drops caused by the length of water mains applications with low-pressure conditions produced by pump characteristics

This type of valve maintains a uniform fire-fighting pressure at every hydrant in a fire-protection system, irrespective of location. The unit incorporates a spring-loaded 'balanced' pressure-reducing valve combined with a hydrant-stop valve. The stop-valve element is operated in exactly the same way as a conventional hydrant-stop valve.

7 58

Duties and Services

The reducing-valve element is opened by the load applied to the pressureadjusting spring and closed by the reduced pressure acting upon the underside of the low-pressure seal. Under working conditions, the balance of these two forces determines the degree of valve opening required to maintain a a steady outlet pressure. Pressure control is achieved by a venturi section in the outlet flow area. Valves of this type may also be fitted with a set-pressure override device which , when actuated, allows full opening of the valve without regulating the downstream pressure, thereby bringing it close to the available inlet pressure.

Marine Services The main requirement in marine valves is full material compatibility with the fluid being handled. e.g. gunmetal or nickel- aluminium bronze being a normal choice for sea-water systems. Corrosion problems are often aggravated by the fact that many such valves, e.g. sea cocks. can remain open or closed for long periods. The type of valve used is largely immaterial provided it performs the required function, but ball valves are genera lly preferred. Table 1 lists some applications typical of naval vessels where the highest standards are normally specified. Environmental pollution caused by a series of oil tanker accidents has resulted in a number of attempts to improve standards and legislation in the marine sector. Until legislation is formally established, there will be uncertainty about requirements for valves and users should always look to the highest standards ror guidance.

Lloyd:~ and defence approved two-piece fire-safe !Jail valve.

7 60

Duties and Services

Table 1. Applications for naval vessels

Application and working pressure

Material

Valve type

Systems

LP fluid services Generall5.86 bar (230lbf/in.!)

Gunmetal

flanged

Sea-water Chilled water Fresh water Air Furnace fuel oil Diesel fuel oil Lubricating oil

LP fluid services General!5.86 bar (230 lbf/in 1 ) MP fluid services 34.4 7 bar (500 lbf/in 2 )

Ni. Al, bronze

Screwed Sea-water Female 13SP Chi lieu water Air Furnace fuel oil Diesel fuel oil Lubricating oil

LP fluid ~ervices General 15.86 bar (230 lbf/in 2 )

Aluminium

Screwed Some cooling systems Fem<~le BSP Air systems Fuel systems Lubricating oil Where weight is at a premium

LP fuel systems 15.86bar (230 lbf/in 2 ) Fire-sa fp

Carbon steel

Flanged

Furnace fuel oil Diesel fuel oil Lubricating oil

LP fuel systems 15.86 bar (230 lbf/in 2 ) Fire-safe

Stainless steel

Flanged

Helicopter fuelling systems and some gas turbine fuel systems where scrupulous cleanliness is regu ired. Sea-wat·er displaced fuel systems where any possible corrosion risk is secondary to a fire-safe requirement

May also be produced in non-magnetic materials.

HP fuel systems 62.05 bar (900 Jbf/io 2 ) Fire-safe

Carbon steel

Flanged

Furnace fuel oil or diesel fuel oil supply to certain types of steam boilers

Fire-safe valves.

MP fuel systems 27.58 bar (400 lbf/in 1 ) Fire-safe

Carbon steel

Flanged ANSI 300

F'uel supply for certain steam <~tomisation type of boilers. Refrigeration gas for refrigerant systems

l-IP hydreaulic fluids 62.05 bar (900 lbf/in 1 )

Carbon steel

Screwed Female BSPor unified

Missile handling hydraulics HP air Gun turret. general service hydraulics Propellor pitch control

Actuators 5.25 bar (RO lbf/ in 1 ) 8.27 bar (120 lbf/in 2 J

Steel and aluminium

LP. low pressure; MP. medium pressure: l-IP. high pressure.

Remarks

May also be produced in non-magnetic materials.

These valves are non-magnetic.

Fire-safe valves.

MarineService~

Marine tanker wedge-gate valve.

Globl' valvPs with 11011-turning stems for certain marine service applications.

761

762

Duties andServices

Marine t.n.nk cleaning valve.

When loading and discharging liquids and gases through port installations, environmental requirements insist that valves must be leak-tight to avoid leakage into harbours and docks. There is also a requirement for ancillary services such as water, fire-fighting. boiler, bilge and tank cleaning , with the latter having leak-tight requirements. Gas movements in offshore areas a re by pipeline and tanker and both safety and environmental requirements call for leak-tight operations.

Vacuum Services The main types of valves used for vacuum services are butterfly, diaphragm, globe, gate and ball valves. Typical forms of diaphragm vacuum valves are shown in Figure 1. The factor which limits the pressure at which a diaphragm valve can be used is that a large area of elastomer (usually nitrile rubber) is exposed to the process. At low pressures, the molecules trapped on the surface of the elastomer are given off, limiting the ultimate pressure which can be obtained. Although materials such as Viton and PTFE, which have lower outgassing rates, can be used, it is more usual to employ different types of valve for low-pressure applications. In medium to high applications where automatic or remote control is required, magnetically-operated valves can be used. These valves have nitrile rubber \"lasher seals which are kept open under spring load. Air admittance valves, which automatically open when switched off, are also available. As a general rule, reinforced diaphragms are used in valves for vacuum services. The ba II valve shown in Figure 2 is a soft-seated bi-directional sealing valve suitable for vacuum down to 2 x 10 - l torr. The standard seat-ring material is virgin PTFE or UHMW Polyethylene. High-performance butterfly valves using the wafer-type sealing principle are capable of vacuum tight sealing up to 2.264 x 10- 5 bar (2 x 10- 2 torr) (Figure 3 ).

Figure I.

764

Duties and Services

Figurp 2. Reduced-bore ball valve for vacuum down to 2 X

High-performance butterfly valve.

zo-2 torr.

Vawum Services

765

A simple single-piece, flexible polymeric seat that is pressure-energised provides positive shut-off. The seat is designed to seal effectively regardless of direction of flow. Butterfly valves are a useful type for vacuum services. Vacuum seal-off valves

The vacuum seal-off valve generally offers a highly reliable means of evacuating a vacuum space and a high degree of resistance to accidental opening or tampering. These valves are typically used in conjunction with a 'valve operator' which opens and closes the seal-off valve (Figure 4). The valve operator is installed onto the seal-off valve and vacuum applied to the side port. The valve-operator stem is inserted, and the inner valve unthreaded and withdrawn into the valve operator. This provides maximum conductance for evacuation. One p1ece s1ngle dtametcr shaft gives great rtgidity with mintmal deflection.

Packing take-up w1thout loading of scat.

PoSI{ive stop cast in to valve body.

-----

PTFE chevron packing , .- nngs. (Graphite also ) available).

Body insert protects seat from abrasion and erosion

/ /

/ Double eccentnc disc prevents p1vormg on seat. reduces torque and seat wear . actio~

/ ,.-/ /

Dtsc des1gn reduces torque peaks experienced with conventional valves fhrust washers keep diSc centered Pins welded in place to avotd flow obnruction and turbulence. No chance of loosenmg from vibration. Pinning of shaft and dtsc to mtntmize shear stress and prevent through leakage

Stainless steeliPTFE shaft bearings provide htgh corroston reststance and are self-lubncating

Spherteal profile of disc edge.

Flextble ltp seat assures posttive shut-off. self-compensates for wear. Seat removal without disassembly of shaft and disc.

Figure 3. Butterfly valve o{'wafer-spiTere' design for vacuum service.

766

Duties and Services

Figure 4. Vawtcm seal-off valve (left) and valve operator ( rigil t). Table 1. Valves for vacuum services

Vacuum

Valve type

Rough to medium

Diaphragm

Outgassing l'rom elastomeric diaphragm limits the ultimate pressure which can be obtained in the system.

Globe

With metallic bellows bonnet seal.

Ball

Generally more suitable than other types.

Ball

More precisely machined than for medium to rough service.

Plate

May be preferred to ball or diaphragm valve for services down to 10-7 torr.

Quarter-turn swing valve

As pipeline valve, or incorporated in a pumping stack.

Gate

Higher conductivity than quarter-turn swing valve.

Baffle valves

Baffies associated with an isolating valve for isolating a working vapour diffusion pump when the system is let up to atmospheric pressure.

Very high

Right-angle plate valve Quarter-swing valve Ball valve Gate valve Baffle valve

With non-elastomeric seals.

Ultra-high

High conductivity type

Special designs and constructions.

Medium to high

Remarks

Vacuum Services

767

Following the evacuation process, the handle is re-inserted, the inner seal tightened into place to establish the seat seal and the valve operator removed. The valves described in Table 1 are just a typical basic selection for use in vacuum conditions.

Cryogenic Valves Cryogenics is the branch of physics dealing with processes and materials at very low temperatures, normally below -lOPC (-239°F). The need to handle very low-temperature liquids and gases is a commonplace requirement with fluids such as oxygen , liquid hydrogen and nitrogen. Valves that can provide tight shut-offfor isolation or modulation for control requirements at temperatures down to -196°C ( -410°F) are an essential part of process plant. Valves that are lightweight in construction are better suited to cryogenic use since the valve mass which must be cooled down from ambient to cryogenic temperatures on start-up is much reduced . Also, the lower conductivity of lighter weight valves can assist in reducing heat influx which can occur in heavier design styles of valve. The use of valves in low-temperature and cryogenic conditions presents an array of problems.

Cryogenic triple-offset. butterfly valve.

Cryogenic Valves

769

The definition as to what temperature is to be deemed cryogenic as opposed to low temperature is to some degree arbitrary, but it is generally accepted that low temperature refers to temperatures below minimum ambient (about -30°C) down to -100°C. In considering the types of valves to be used in such services, it should be borne in mind that leakage rates which may be acceptable in conventional applications may not be acceptable at cryogenic temperatures. Any leakage of fluids, whether to the downstream side of a valve or to the atmosphere through gland seals or gaskets, will result in instant freezing with probable adverse effects on the performance of valves and associated equipment. Such leakage at the valve stem would lead to increased localised icing, which could culminate in seizure of the valve-operating mechanism. Valve types used for handling liquid oxygen, nitrogen. methane. natural gas. ammonia, etc .. at cryogenic temperatures may be of ball, gate, globe, butterfly or check type, with an increasing preference for high performance and true-zero leakage as defined by API598. All are special designs, normally identified by having extended bonnets to position the valve-stem seals away from the cold source. This extension can also serve the purpose of providing an insulation space between the pipeline and the lever or handwheel operating the valve. Valves for cryogenic services may range in size from 3 to 2240 mm I 8 to 88 in), with pressure ratings from ultra-high vacuum up to 700 bar (10,000 lbf/ in 2 ), capable of working down to -254°C ( - 425°F).

e

PIPE (BODY) CIL

CONE GIL

~

~ t:c

0

:z:

Ill

SEAL OFFSET

Triple-offset geometry.

7 70

Duties and Services

Construction may be in aluminium, brass, bronze, monel. incoloy, stainless steel and zirconium, rendered antistatic either by a graphite gland assembly or external bonding. On ball valves, specially designed seats are required to minimise the effect of differential expansion by reducing seal volume to a minimum. Seals are normally made in PTFE. Valve-stem seals must be of a type not requiring lubrication (lubricants would freeze; also they could not be tolerated in oxygen systems). Seals used are normally graphite, TFE or PTFE. Pressure is normally equalised bet\.v een the valve body and cavity within the extended bonnet. All valves for cryogenic services need to be cleaned, degreased and finally assembled in a clean room. Low-temperature valves

Valves designed for low-temperature but not cryogenic services may follow a similar form, but not necessarily, the same extended bonnet. Valve bodies may also be in carbon steel instead of stainless steel. Suitable carbon steels are available for services down to -73°C ( -100°F). Triple offset

A typical high-pressure performance valve for cryogenic applications is the triple-offset butterfly valve. This type of valve has become increasingly popular over the single- and double-offset design (Figure 1 ).

Figure l. Triple-offset cryogenic butterfly valve.

Cryogenic Valves

7 71

The shall offsets are created by designing the valve with the shaft located behind the centre-line of the sealing surface and slightly to one side of the pipe centre-line. The function of these offsets is to reduce the rubbing and thus the wear between the seat and seal to approximately 20° of travel as well as to eliminate all seat to seal rubbing throughout the valve's entire 90° of rotation (Figure 2). Typically, triple-offset valves (TOSV) of this type used for cryogenic duties have a resilient stainless-steel ring installed in the disk assembly and it is this that provides a true 'zero-leakage' seal. The seal and seat-contact surface is 'cone-in-cone' where both cones are inclined and the angle of contact between the seal and seat generates a slight '".redging effect that flexes and radially compresses the disc-seal ring. The valve is able to shut-off completely, regardless of the direction of flow or line pressure. Ball valves

Double-seal, reduced- and full-bore ball valves are used for LPG , LNG , thermal fluids and other cold applica tions including oxygen and nitrogen (Figure 3 ).

Figure 2.

Trip/1'-o}]:~et

inclined-cone conf iguration.

772

DutiesandServices

Valves of this type incorporate a vapour space of sufficient height to allow gasification in the area below the gland. This ensures that the gland packing remains at near ambient temperature. When standard valves are fitted with actuators, they should be installed with extensions in the vertical position. The LNG market has imposed its own demands on valves as the profile of valve usage changes. Modern LPG operations have meant that pipe and valve sizes have increased dramatically, with a much larger percentage being fitted with actuators for remote operation. These factors have lead to increasing demand for the quarter-turn ball and soft-seated double-eccentric butterfly valve types which offer easier actuation and lower size/weight ratio combined with high performance in terms of shut-off capability and lifetime durability. Gate and globe valves are more difficult and costly to actuate and become less economical as pipeline size increases. Such valve types tend to be restricted to use on smaller pipe sizes and applications where remote operation is not required. High purity

Ultra-clean process technologies require preservation of product cleanliness throughout the gas-distribution system from cryogen storage to point of use delivery.

Fig uri' 3. Double-sealed reduced- and full-bore ball vn]vC' for cold applications.

Cryogenic Valves

Safety valve for cryogenic duty . ACME threads

Stainl~s

steel

Opt'n stem & yoke

Stem seals- Viton(lo) Redundant static ~~a is

Optional VCR® bonne t purge port

E

t - -- - Ophonal vacuum jaC'ket

CLOSED

Non-contacting guide to reduce conwdive •nput KEL-P~

seat seal

3161. barstock body EP 1nterior finish I 0 Ra all wett~.od ~urfacc~

-

D ---

Figurr 4. Ultra-high purity cryogenic clean valve.

773

774

DuUesandServices

Ultra-high purity gas valves (Figure 4) are used in a variety of applications including dewars, vacuum-insulated piping systems, trailers, tanks and cold boxes. Typically, the interior surfaces and the bellows which seal the valve stem are electropolished. This type of valve has no contacting metal surfaces and may be manually or pneumatically operated with a safety return actuator which returns the valve to fail-safe position in the event of supply failure.

Nuclear Services Nuclear valve glands

Most types of valves can be found in a variety of applications in nuclear services. These include: nuclear power plant, primary. secondary and auxiliary systems, fuel cycle dangerous fluid (radioactivity), fundamental research. experimental reactors, test loops, steam-supply systems for the propulsion of nuclear submarines and aircraft carriers, and a variety of other applications from saturated or superheated steam to dangerous or corrosive fluids via special liquids or gasses. Valve types include: wedge-gate valves. gland or bellows globe valves, plug and ball valves, check valves and instrumentation valves. Many of these products can be fitted with actuators. Other valves for special service include highperformance butterfly valves with PTFE. metallic or elastomer seats and pressure-relief valves for both primary and secondary systems. Pressure-balanced safety valves are used extensively for pressurised water reactor primary service and dual-function valves for automatic or emergency override operation for boiling water reactors. Pressure-relief valves for secondary steam systems include power-operated pressure-relief valves for two-phase flow, large-orifice. pilot-operated and

Adjustable stem sea ling. Double Belleville washers:_-----::~~ compensate for wear and temperature fluctuations. Resilient seats to give bubbletight st·aling.

Burst proof body design.

\

Quarter-turn. Handle indicates direction of flow.

Compact. safe. blow-out proof stem. Cannot be removed when valve is under pressure. Smooth two-way O.ow path for maximumC". Fully enclosed bolting to prevent exterior corrosion.

Typical ba/1-valvP design for nuclear service.

77 6

Duties and Services

spring-loaded pressure-relief valves for protection of moisture-separator reheaters and pressure-relief valves for auxiliary fluid service. Valve position indicator systems provide direct. continuous, remote indication of valve-stem position and permits positive monitoring of pressure-relief valves in nuclear environments. Typical safety and pressure-relief valves are shown in Figure l. Electrically powered, rotary-actuated clamp valves are used successfully in nuclear power plants to provide full-flow on-off or throttling service (Figure 2). The system includes an air motor that automatically operates the valve to the fully closed (or open) position on loss of electric pml\rer.

Isolating and regulating rzllclear valves.

NuclearServices

777

The very highest integrity is an obvious requirement of valve glands in nuclear plant, demanding satisfactory performance in the following areas: mechanical: deformation, resistance and recovery (ii) dynamic: behaviour under spindle movement, under pressure and at elevated temperatures (iii) corrosion: elimination of valve steam corrosion. (i)

Figure 1. Press11re-reliej and safety valves for nuclear service.

Figure 2. Electric-powered rotary-actuated clamp valve.

778

Duties nndServices

The main fluids to be handled are demineralised water, saturated steam (BWR plants) and borated water (PWR plants); but with possibly 1500 pieces of equipment in each division of a nuclear power plant, the multiplicity of problems involved can be immense. Desirable features of a nuclear valve gland are shown in Figure 3. Sn ndlc • ,1 SJO~·b&O supponod ou1: de fill) Ql~nd oli~J

• ~rcfully mttctl~. hJrd SUrllK:n (JfOJhiO).

2 or 3 bolt~ Ttorcad

not too lone

surfltoo hrW!ill tomooJn na o .19 •~ • rousld - no flats - SJCkt
• end Ctlamlof 10 a d flltrng of pacl<mg wrthoot d.Jf1\J<j0

SpMg washc•s (8 0 iiOVIII9 typo) lor mo3Sunng arod conttOihng

• no t;erlt!Chilii or nthBc ,..,,r1,1C'C

d=Jge

the load on the pactunq (300-400 bar)

Provrde adequate play

W a tch lor p~tailel closrng progrossi\IO and bdlancud. Rcrarn space lor t'9htening. tnrrodocrron or adQrronat tlll9

Chamlttr lo 83S,Sf 1ntroduct10n of P<JCK•ng nn115 wrthout danl<.ll /(!

Play· ·

should not o•cced

Follower gurde-d on oulStdH Ommotor

0 5 n>m radodl

Cateful m.Jchirtrng of oox to a l11uoh

or Ra t 6 ,, or bolf(lf.

Box tlblghl between 1 5 and 2 hmos tl'lo spondlc dJamutur.

Oonom ot box nat to coinctdo Wtfh form and prOOOmpt9SSIOO of pacl
Olhtlf'WlSO tit fl!tl

metal nng W atct'l conosion.

Or specii•Citlly

mouldeo Mel

Pf ec:o!'T"'Pf OSSCd nfl9

I

Fluid to be sealed. Bush 10 reducv htlrghl

Water 300-320 •c 170- 180 bar

of overlong gland

Figure 3. Desi rnblefenlures of a nuclear valw alaw/.

NuclearServices

779

The gland material now generally considered the most suitable in application is nuclear-purity expanded graphite (plus corrosion inhibition, if specifically called for). This is readily formed in mechanically sound rings from tape to provide the necessary resilience and deformability to behave as an efficient seal. To accommodate extrusion of the packing, expanded-graphite rings are normally combined with plaited rings at the top and bottom of the gland-a logical choice here for high-temperature working being pure graphite/ asbestos braided packing which can also incorporate a corrosion inhibitor and a suitable proportion of anodes material to act as a sacrificial anode. An alternating arrangement of graphite fibre and expanded-graphite rings does not produce as satisfactory a seal. The braided packing rings serve to eliminate the risk of extrusion of the expanded graphite where radial play at the bottom of the box exceeds 0. 5 and 0 . 3 3 mm ( 0 .02 and 0.01 in) around the gland follower. This packing arrangement, after extensive laboratory testing by EDF. has been used successfully in French nuclear power plants for many years and is rapidly being extended through all primary circuits. Should it be necessary to avoid asbestos products, rendering even wet-spun, dust-free product unacceptable, a graphite fibre packing can be employed for antiextrusion purposes. This would, however, introduce problems of fragility and of potential corrosion risks (the stem alloys having to be chosen with extreme care). Gland dimensions

The dimensional relationship between stem, box and packing rings is of prime importance. Interference between ring and stem with play between ring and box is to be avoided as leading to high stem torque and poor sealing. lt is preferable to begin with a tight fit to the box and a small clearance to the stem, O.lmm (0.0004 in). Surface finish is important, particularly on the valve stem, to realise minimum packing wear and low operating torque. Recommended values are Ra = 0.4 m for the stem and Ra = 1 . 6 m for the gland surface. Spring discs

The maintenance of a leak-free seal is directly dependent on the maintenance of an adequate loading on the gland packing. Spring discs (Belleville-type washers) can compensate for loss of loading due to: • • • •

relaxation of the packing, very slight for expanded graphite, of the order of 4% at 3 50 bar ( 5000 lbf/in 2 ) vvear differentia I expansions temperature variations

780 Duties and Services

The introduction of spring discs also assist the precision with which gland loadings can be determined (i.e. by height reduction of disc). The cost of suitable spring discs is small in relation to the advantages they bring. Gland geometry

The depth of a valve gland should be 1. 5 to 2 times the stem diameter. A greater depth serves no purpose. Many glands are too deep. Should the number of packing rings exceed six to seven, transmission of gland loading becomes very uneven and stem torque increases disproportionately. Tests made by the EDF showed that an increased number of rings/depth of gland could result in increased leakage. Recommendations for stem diameter/ ring sizes are given in Table 1. Causes of leakage

The initial cause of leakage developing is not always apparent. particularly as one fault can lead to another. Experience has indicated that, in order of seriousness, likely causes are: (i)

The use of braided packings that lose volume too readily and harden in use. (ii) Damage to packing rings during fitting. (iii) Bad meeting of ring ends where cut rings are used . (iv) Incorrect disposition of ring joints, forming leak path. (v) Insufficient gland loading. (vi) Poor support to stem. (vii) Poor ability of packing to withstand thermal shock. (viii) Reduction in gland loading owing to packing relaxation, packing wear/ volume loss. (ix) Incorrect dimensional tolerances bet\·Veen stem / packing box. (x) Gland too deep. (xi) Stem-surface finish of low order.

Table 1. Recommendations for stem dameter/ring size

Stem diameter (mm)

10 20 30 40 50 60

Ring square section (mm) 4 6

8

8-10 10 12

Nuclear Savices

781

(xii) Play at bottom and top of box too great. (xiii) Corrosion of stem and abrasion of packing during stem operation. (xiv) Too many rings above lantern. Corrective actions

The following are points to observe, not necessarily in order of significance. Each one is important in achieving satisfactory gland performance. l. 2. 3. 4. 5. 6. 7. 8.

Correct gland design. Entry to facilitate fitting of packing rings. Optimum gland depth. Correct surface finishes. Adequate capacity for gland loading/adjustment. Spring discs to compensate for wear. Good stem support. Use of expanded-graphite sealing rings particularly recommended (expanded graphite is permanent, resilient, has better relaxation, maintains its volume and withstands thermal shock). 9. Correct dimensional tolerances between packings and gland. 10. Correct fitting and loading of gland before service operation. Nuclear power piping

Special safety standards are required for the design of piping in nuclear plants. For a proposed British PWR plant, the design is based on the American Standardised Unit Nuclear Power Plant System (SNUPPS). The safety-related piping are those pipelines associated with the safe operation and shut-down of the reactor. These can vary from the main coolant loop pipelines to the coolant high-pressure injection systems, and the coolant pipelines necessary for heat removal from the reactor. In a typical SNUPPS design. the length of safety-related piping can be approximately 17,100 m (56.090 ft) out of a total length of piping of about 90,000 m (2 9 5.200 ft) . The design code used is the ASME Boiler and Pressure Vessel Code Section III and the safety-related piping are class 1, 2 and 3 pipelines. The ANSI B31 .1 Power Piping Code is also used for other piping within the safety-related buildings, which consist of the reactor. auxiliary. control, fuel and diesel buildings. Piping systems are designed to withstand the dead-weight of the pipe and contents and, where applicable, to ·withstand temperature changes and pressures up to 197 bar (2856lbf/in 2 ). Design for earthquake and pipe-break conditions has also to be taken into consideration. A PWR plant is to be designed to withstand an earthquake at a level of0.2 5 g free field. The Safe Shutdown Earthquake (SSE) is the level of earthquake at

782

DutiesnndService.s

Seamless pipe bend of the material x 10 CrNiNb 18 9 ( 1.4 5 50) within a piping system in n 1wclenr power station. Pipe dimensions: 348 mm inside diameter. 40 111m wall thickness: bendillfJ radius R=I.5 X OD.

which the station is designed to be shut dm·vn safely, with continued capacity for heat removal from the reactor core, but not necessarily to have the ability to be started up again. The Operational Shutdown Earthquake (OSE) is a level set which, if exceeded, will result in the initiation of a controlled shut-down of the station. This level of earthquake has been set as one fifth of the SSE. As at the set level of OSE, the piping design is still covered by the analysis carried out under SSE loading, the only additional piping analysis required is in the detailed fatigue analysis required for class 1 piping. Sample analyses on selected class 1 pipes will be carried out to determine the effect of the additional cycles of OSE events on fatigue usage factor. Pipe-break conditions are considered in high-energy pipelines containing fluid at a temperature above 95°C (203°F), and/ or at a pressure exceeding 19 bar (2 7 5 lbf/ in 2 ). Although piping is designed not to break, in order to ensure the safety of a PWR station under all foreseen circumstances, there is a requirement that breaks in high-energy pipelines arising from unanticipated events are considered. Piping \Vhich falls into this category includes the main reactor coolant piping as \Veil as subsidiary piping systems.

Nuclear Services

78 3

Three main effects should be considered when designing for pipe-break conditions: Main-loop piping break: pipes connected to the main-loop piping are required to continue to function following a loop break. These have to be designed to withstand movements imparted to them and any pressure transients involved caused by the sudden efflux of fluid from the broken loop. (ii) Pipe whip: caused by the sudden release of fluid when high-energy pipes break. It is a safety requirement that the whipping pipe does not cause the failure of other safety-related equipment in the vicinity. This is carried out either by segregating the system from other safetyrelated systems by walls or distance, or by enclosing the pipes in energy-absorbing devices to catch the pipe and absorb the energy in a controlled manner. (iii) Jet impingement: after a high-energy pipe break the high-velocity jet efflux released can cause damage to surrounding structures. Adjacent pipelines will therefore be analysed for the effect ofjet impingement.

{i)

Other inputs will include water or steam hammer where these are likely to occur, detailed system transients for class 1 analysis, and general vibration caused by pumps where this can be identified as a likely occurrence.

High Pressure Services High pressure can be so classified if it is in excess of 140 bar (2000 lb/ in 2 g). Some typical high-pressure applications are shown in Table 1. The units, symbols and conversion methods used in pressure measurement are as follows: Unit/ Symbol

Unit

lbf/ in 2 N/in 2 Pa kgf/ cm 2

pound force per square inch newton per square metre pascal kilogram force per square centimetre (technical atmosphere) bar= 10 5 N/m 3 standard atmosphere 1 technical atmosphere 1 pascal

bar Atm. G. 1 kgf/cm 2 = 14.2 2 3 lbf/ in 2 (AT) 1 N/ in 2 = 1.45038 x 10-4 lbf/in 2

High-pressure metal-seated ball vnlvefor severe service.

High Pressure Services

785

In common with most other pipe systems, high-pressure systems require valves to isolate and control flow as well as to vent, drain, check and relieve the pressured medium. In all cases. the basic function of the valve is the same as any other standard pattern valve. the main differences being: (a) (b) (c) (d) (e)

wall thickness selection of materials greater care in heat treatment and condition of materials an extremely high standard of non-destructive testing and quality control finer limits and fits. and surface finishes (f) closing members are more precisely formed (g) high manufacturing precision (h) each valve should have stress checks against application. High-pressure valves

High-pressure valves fall into specific categories. All valves used on hydraulic circuits, for example, are high-pressure types, typically designed and constructed to accommodate working pressures of 140 bar (2000 lbf/in 2 ), or higher in other specialised systems (e.g. aircraft hydraulics). Table 1. Typical high-pressure applications Pressure

Medium

Application

J 40 bar (2000 lb/in 2 g)

Oil Hydrogen Steam Light gases Natural gas

Hydraulic systems Propulsion systems Boiler plant Liquefaction Wellhead

3 50 bar ( 5000 lb/ in 2 g)

Drilling fluid (med) Urea/carbonate Hydrogen Synthesis gas Water Methane

Drilling Urea production Hydrogenation Ammonia Oil field: reinjection Oil field: reinjection

700 bar ( 10,000 lb/in 2 g)

Cement Water Methane Natural gas Oil/water/gas (mixed)

Oil well 'kill' Water-jet cutting Oil field: reinjection Wellhead Wellhead

1400 bar(20.000 lb/in 2 g)

Oil/gas

Wellhead completion Wellhead choke and kill

2100 bar (30,000 lb/in 2 g)

Ethylene

Low-density polyethylene production

MetaJ

Hydrostatic extrusion

Minerals

Synthetic diamond production

10.000 bar (140,000 lb/ in 2 g) 2

50.000 bar (700.000 lb/in g)

78 6

Duties and Services

In fluid handling, certain processes require the use of high-pressure valves, the most widely known being ammonia synthesis. the oxy process, and processes for the production of urea and methanol as well as polymerisation processes for the production of low-density polyethylene. Apart from these, high-pressure valves are also required in hydrogenation processes , e.g. coal liquefication or gasification. The demands on the different items of process equipment vary depending on the process, operating pressure, operating temperature, and corrosivity of the media. Handling aggressive coal slurry, for example, which contains up to 30% pulverised coal at 10-30 microns particulate size can lead to enormous erosion problems in valves. Erosion can also be a problem in other types of high-pressure valves handling clean fluids. resulting from high localised fluid velocities. Flow-passage design, as well as material selection. is thus important in high-pressure valves. Such valves are, therefore. normally individual designs. not modifications of standard valve types with stronger components and greater wall thicknesses. Special materials such as silicon nitride for seats and plugs may also be required to cope with severe conditions of abrasion and temperature. Special demand may also be placed on valve-stem seals, particularly as operating temperature may restrict material choice. The ultimate test of a high-pressure valve is, however, the same as any other type of valve. It should be capable of performing its function reliably.

Hydraulic valve sy stem for on/ offslwrc applications.

High Pressure Services

78 7

without leakage, and have an acceptable life. It is only the parameters that are more arduous. Valve and pipe connections

in order to ensure sound leak-proof closures, all high-pressure joints should be precise in terms of concentricity, dimensional correctness, known material condition and predetermined bolt loading. Figures 1 to 5 show some examples. In order to generate the high closing forces required for larger valves at high pressure and to minimise operating time, a variety of actuators are used. Hydraulic actuators (Figure 6) are ideal for larger valve sizes, although the hydraulic circuit and power pack can be expensive. Electrical actuators are

Lens ring 2000 to JOOO bar I inch and above Figurl' 1.

Huh and clamp seal Up to 700 bar A II sizes

fiyurc3.

Cone ring 2000 to 3000 bar Smaller sizes, ie instrument lines

Figure 2.

Ring joint Up to 400 bar All sizes Figurf 4.

78 8

Duties a11d Services

suitable for larger sizes provided torque is then transmitted through a suitable gearbox. Pneumatic actuators are suitable for smaller valves provided the mechanical advantage is increased via a suitable gearbox. No matter what the application , it will be found that, in addition to high pressures, other conditions invariably prevail, whether it be temperature,

Union joint 2000 to 3000 bar S ma ll sizes

Figure 5 .

High-pressure check valve rated to 6000 lb/ in2 withflexible seal sent.

Figure 6 . Hydraulic spring-return actuator.

High Pressure Services

789

Hydraulical/y-control/ed. combined-function valve for hydro-electric power plant.

erosion, corrosion or a combination of either, resulting in the choice of materials being vital. Consultation with manufacturers would be advisable in all cases. See also the chapters on Valve Actuators and Pipe Joints and Couplings. For a more comprehensive coverage of high-pressure valves and applications, refer to the Hydraulic Handbook, also published by Elsevier Science Limited.

SECTION 9 Engineering Data

Glossary Standards and Designations

Glossary ABOVE GROUND: specifically referring to installations associated with a buried pipeline that are physically above the ground level (e.g. valves, etc.). ABSOLUTE PRESSURE: pressure above absolute vacuum; or, in practice, gauge pressure plus atmospheric pressure. ACME THREAD: square-cut thread form. ACTUATOR: a device supplying force and motion to the closure member (ball, disc. plug, etc.) of a valve. ADAPTOR: coupling or fitting used to connect pipes of different diameter sizes, join pipes of similar diameter but in different metals, join pipes with ends fabricated for different types of joints. AERIAL MARKER: pipeline marker post visible from the air. AMBIENT TEMPERATURE: temperature of the surrounding atmosphere. ANCHOR BLOCK: concrete (or similar) block to which a pipe is attached, or in which it is embedded. to prevent movement. ANGLE VALVE: type or globe valve with inlet and outlet passages at right angles. or some other angle {oblique valve). ANNULAR FILL: material filling the annular space between a pipe and a sleeve surrounding it. ANNULUS: annular space between a pipe and surrounding sleeve, or between two concentric pipes, etc. ANODE: positive electrode in an electrolytic system (e.g. as in cathodic protection). AQUEDUCT: man-made channel or pipe for carrying water. BACKFILL: soil or other material used to fill in a trench. BACK-PRESSURE: pressure acting against the outlet side of the valve. BAG HOLE: hole cut in a pipe for insertion of a gas bag. BAG PIPE: a hook or device for insertion or removal of an inflated gas bag from a gas main. BALL COCK: valvewhosemovementisoperated by afloat attached to the end. BALL VALVE: type of valve where the valve element is a spherical plug. BAR: international standard unit of pressure. BAR HOLE: small-diameter hole made by drilling or driving in a bar to search for source of leakage from an underground pipeline.

794

Engineering Data

BARREL: measure of volume equal to 42 US gallons: also name given to wrought-iron or wrought-steel gas-service pipes. BATTER: sloping sides of a trench. BED: ground or material on which a buried pipe is first laid. BELL AND SPIGOT: corresponds to spigot and socket. BELLOWS SEAL: corrugated seal form providing isolation of a valve stem. BITUMEN/BITUMINOUS PRODUCTS: petroleum-based products used for coatings, linings, etc. BLANK: solid plug, disc or end fitting for sealing an open-pipe end. BLOW-DOWN: reducing pipeline (usually gas) pressure by venting to atmosphere. BONDING: connecting of all metal parts in a system with a conductor. BODY: the framework that holds together the parts of a valve. BONNET: the case enclosing the stem on a screw-down valve. BORE: internal diameter of a pipe or tube. BRANCH: specifically refers to a connection to or from a main pipe to secondary pipes. Described under various types and construction. e.g. tee, Y, etc.; welded, forged. cast, etc. BRANCH LINE: secondary pipeline(s) related to the main pipeline. BULL PLUG: temporary closure or plug fitted to a pipeline under construction to prevent ingestion of dust, etc. BURSTING DISC: pressure-relief device arranged to rupture and vent excess pressure to atmosphere. BTJTTERFLY VALVE: type of valve where the moving element is a disc mounted at right angles to the flow and pivoted in a place at right angles to the flow . BUTTERFLY CHECK VALVE: similar geometry to a butterfly valve except that the disc is hinged about a diameter at right angles to the flow. BYPASS: alternative flow passage to the main stream. CAP: fitting which goes over the end of a pipe to seal it. CAPPING VALVE: in pulp mills. a remotely operated shut-off valve used for chip feeding on batch digesters. CARRIER PIPE: describes the pipe carrying the fluid in any installation where the pipe itself is surrounded by a sleeve or second pipe. CATALYST: as distinct from a hardener, a catalyst is generally an organic peroxide which initiates polymerisation of polyester, vinyl ester resins. CATHODIC PROTECTION: method of inhibiting corrosion by making system components in the system cathodic and confining corrosion to an attached sacrificial anode. CHANGE FITTING: fitting for connecting Imperial (inch) size pipes to nearequivalent metric size pipes (i.e. nominally equivalent bore sizes). CHECK VALVE: valves designed to shut off flow in one direction but permit free flow in the opposite direction. Also known as a non-return valve . CLOSURE MEMBER: The moving component of a valve that throttles or shuts off flow through the valve body, such as a disc, a ball, etc.

Glossary

79 5

COCK: general description of a small on-off valve, of which there are several basic types. CODES OF PRACTICE: recommendations rather than obligatory requirements issued by national and international authorities. COMPACTION: measure of the density of the soil at any given location. CONDENSATE: liquid formed by wet air or gases, or vapours, when subject to cooling and/or pressure reduction. CONTOUR LAYING: laying of underground pipelines at substantially constant buried depth, i.e. following the contours of the bend. CONTROL VALVE: general description for a type of valve used for controlling flow or pressure and usually referred to by function, e.g. throttling valve, flow-control valve, pressure-control valve, etc. COUPLING: fitting used to connect pipes. COVER: the buried depth (i.e. depth below ground level) of a buried pipe or pipelines. CRITICAL APPLICATIONS: applications or systems where failure of a pipe or valve could have serious consequences. CRUDE LINE: pipeline for conveying crude oil. CRYOGENIC SYSTEMS: systems whose components are designed to operate at and withstand extremely low temperatures. Generally descriptive of systems handling liquefied gases. DEAD BAND: the range through which an input signal to a valve can be varied without initiating a response. DEAD MAIN: a main pipeline not in use, e.g. not yet connected or temporarily or previously disconnected. DIAPHRAGM VALVE: valve type in which the moving element is a flexible diaphragm. DISC: refers to any disc-shaped element in a valve, as distinct from a plug shape, ball, poppet, etc. DOG LEG: abrupt change in the direction of a pipeline. DOWNSTREAM: any position in the direction of flow distant from the reference point involved. EQUIVALENT LENGTH: friction or head loss generated by pipes, fittings, etc. expressed in termsoflengthofsamediameterpipe having the same frictional losses. ELBOW: a sharp-bend fitting with less radius than a normal pipe bend for the same degree of bend. EXTENSION STEM: extended stem fitted to valves to facilitate operation under particular circumstances (e.g. on cryogenic valves to remove operating point from a low temperature region). FALL: the gradient at which a pipeline is laid. FEEDER: a main pipeline carrying fluid at a higher pressure than in the secondary distribution pipes. FITTING: general description for couplings, etc., used on pipes and tubes. In some industries this may also include bends, valves, etc.

796

Engineering Data

FLASHING: in liquid service, a phenomenon where the pressure of the medium falls below vapour pressure and does not recover above vapour pressure. FLEXIBLE PIPE: any type of pipe which can flex or deform markedly without fracture. FLOW CHARACTERISTIC: in control valves, the curve relating percentage of flow to percentage of valve travel. FLOW CO-EFFICIENT: a constant, related to the geometry of a valve. for a given valve opening that is used to calculate the capacity of a control valve. Flow co-efficient Cv is defined using imperial /US measurement units, Kv using metric units. FOOT VALVE: check valve fitted to the end of the suction pipe leading to a pump. FULL FLOW: refers to a pipe flowing full of fluid, or more specifically to flow through a valve offering minimal restriction in the open position. GATE VALVE: type of valve where the sealing element is in the form of a sliding plate. disc or 'gate'. GEAR OPERATORS: type of mechanical actuator employed to assist in the opening and closing of large valves. GENERAL PURPOSE VALVE: type of valve which is suitable for use in a variety of duties, e.g. shut-off, throttling, etc. GLOBE VALVE- type of valve with a spherical or globe-shaped casing. HAMMER-BLOW HANDWHEEL: hand wheel with lugs fitted to large valves. enabling a hammer to be used to start valve opening. or effect tight closure. HEADER: pipe, tank or fitting interconnecting a number of branch pipes. HEAD: pressure exerted by a column of fluid expressed in tens of feet or metres of fluid height above a reference point. HYDRANT: fitting or connection for attaching a hose to a water main (e.g. as in fire-fighting equipment) . HYDRAULIC OPERATOR: valve actuator operated by hydraulic pressure. HYSTERESIS: the maximum difference in output value for any single input value during a calibration cycle, excluding errors due to dead band. IMPRESSED CURRENT SYSTEM: a form of cathodic protection utilising the flow of electric current through a bonded metallic system. INSIDE-SCREW VALVE: screw-down valve where the thread of the spindle is inside the bonnet. ISOLATING JOINT: insulating joint between metallic pipes. JOINT: general description for the various types of joints and couplings used to connect two pipes, or pipes to fittings, etc. LIFT-CHECK VALVE: common type of check valve where the valve element lifts off its seat to open the valve. LIMIT SWITCH: a device connected to an actuator or valve transmitting a signal when the valve reaches a pre-established position. LINE: alternative description (used in the UK) to describe a pipeline. particularly in compressed air and hydraulic systems.

Glossary

797

LNG: liquefied natural gas. LPG: liquefied petroleum gas. LUBRICATED VALVE: valve in which the moving element is lubricated by something other than the fluid being handled (e.g. lubricated plug valve). MAIN: a principal or trunk supply pipeline. MANIFOLD: a component designed to accept and provide interconnection between a number of pipes and/or valves, etc. MARKER POST: post erected to show the position of a buried pipeline, cathodic protection test point, inspection point, etc. MOLE PLOUGHING: method of making a hole to bury a small-diameter pipe using a tractor-mounted blade with a bullet-shaped foot. NETWORK: complete system of transmission or distribution pipelines. NOMINAL DIAMETER: approximate diameter size of pipes. May be reference to overall diameter or bore size. NON-RETURN VALVE: see check valve. OPERATOR: alternative name for a valve actuator. OUTSIDE-SCREW VALVE: screw-down valve where the spindle thread is outside the bonnet and fully exposed. ON STREAM: descriptive of a plant or system being operational in its normal way. ORIFICE: a hole through which fluid can flow. OVALITY: departure from a true circle in the actual cross-section of a pipe. Ovality is commonly defined as the difference between maximum and minimum diameter at a given section, divided by the mean diameter and expressed as a percentage. PACKING: general description for the sealing material used in a gland , e.g. to seal valve stems. PIG: piston-shaped device drawn through a pipeline to clean, gauge or inspect it. There are various types and shapes used for different purposes. PINCH VALVE: type of valve embodying a flexible tube which is pinched together to close the valve. PILOT VALVE: a small valve used to control supply to a larger valve to operate that valve. PILOT-OPERATEDVALVE: a larger valve operated indirectly fromapilotvalve. PIPE: general description for any reasonably long length of tubular form used to convey fluids. PIPELINE: a continuous length of pipe or pipes forming a fluid transport system. The description may also include all ancillary equipment. PLUG VALVE: type of valve where the movable sealing element is in the form of a plug, particularly descriptive of types oflocl(s. POSITIONER: a device for varying and keeping the actuator position in control-valve applications. PRESSURE RECOVERY: The difference between the minimum pressure at the valve's vena contracta and the maximum pressure at the valve's outlet.

79 8

Engineering Data

PRESSURE-REDUCING VALVE: a valve specifically designed to reduce steam, gas or liquid flow to a predetermined lower level. PRESSURE-RELIEF DEVICE: A device designed to prevent internal fluid pressure from rising above a predetermined maximum pressure in a pressure vessel exposed to emergency or abnormal conditions. PRESSURE-RELIEF VALVE: effectively a safety valve which can be used both with liquids (non-compressible fluids) and air. gas or vapours (compressible fluids). PORT: opening in a valve through which fluid flows when the valve is open. RUNNER: tool for consolidating backfill in trenches. RELIEF VALVE: generally a slow-opening valve designed to relieve excess pressure in a liquid system. REYNOLDS NUMBER: non-dimensional parameter which can be used to establish whether fluid flow is laminar or turbulent. SAFETY VALVE: quick-opening valve providing pressure relief in system involving compressible fluids. SEAT: the sealing face against which the moving or controlling element in a valve closes to provide shut-off. SLIDE VALVE: valve whose ports are opened and closed by the sliding movement of a sleeve, disc. gate, etc. SOCKET: the enlarged end of a pipe which fits over the plain end of a similar pipe. or a spigot (spigot and socket joint). SOLENOID VALVE: a valve operated directly by an electromagnet or solenoid. STACK PIPE: a vent. STATIC PRESSURE RATING (pipe): normal operating conditions of pipe systems when connected to centrifugal or turbine pumps. STANDPIPE: a vertical pipe used for withdrawing condensate (gas industry), or for providing a temporary supply of water at uniform pressure (water supply industry). STEM: the spindle of a screw-down valve. STOP COCK: description used specifically in the water industry for a shut-off valve. STOPPING OFF: fitting of a temporary plug in a pipeline. TAKE-OFF: a branch pipeline. THERMOPLASTIC: a plastic material which can be transformed under the influence of heat and which solidifies upon cooling. THERMOSET: a plastic which hardens when heated (and assisted by a chemical reaction) and which cannot be transformed or modified subsequent to this reaction . THRUST BLOCK: an anchor block located against a bend or an end tap to prevent displacement of a pipe. THROTTLING VALVE: a type of valve suitable for providing varying degrees of flow without creating excessive frictional losses.

Glossary

799

TOP ENTRY: a construction of a valve body in which the valve is assembled and disassembled through the top of the valve. TRIM: the replaceable parts of a valve. TRUNNION MOUNTING: a construction used in valves where the trim is supported with bearings. The upstream spring-loaded seat normally acts as the primary seat. TUBE: mainly descriptive of smaller diameter smooth-bore seamless pipe. UNION: threaded fitting which can be used to connect two pipes without having to rotate either pipe. UNION BONNET: type or bonnet used on smaller valves which can be assembled or disassembled by rotation of the union nut only. VALVE: virtually any device with a mechanical movement used for controlling the flow or pressure of fluids. VALVE ACTUATOR: a mechanism for operating valves which may be powered by compressed air, hydraulics or an electric motor. VALVE RANGEABILITY: the ratio of the highest controllable flow coefficient to the lowest controllable flow coefficient (max Cv/min Cv). VENA CONTRACT A: the location in a control valve where the cross-sectional area of the flowstream is at its smallest, fluid velocity at its highest and fluid pressure at its lowest level. WALL THICKNESS: the thickness of the walls of a pipe or tube. WHEEL OPERATOR: a handwheel attached to the top of a valve spindle for opening or closing the valve manually. WIRE DRAvVING: premature erosion of a valve seat caused by excessive flow velocities between the seat and the moving element of the valve. WRAPPING: an outer layer of material applied to a pipe to protect the pipe surface.

Standards and Designations Originators of American Standards

AAR (Association of American Railroads): establishes design and dimensional standards on bronze valves and 300 lb malleable pipe fittings for use by railroads. API (American Petroleum Institute): establishes purchasing standards on valves and fittings for the petrochemical industry. ASME (American Society of Mechanical Engineers): establishes codes covering pressure-temperature ratings. minimum wall thicknesses. metal specifications and performance, thread specifications. etc .. for valves made of materials meeting ASTM specifications. ASTM (American Society for Testing Materials): establishes chemical and physical requirements of all materials used in the manufacture of valves and fittings. A WW A (American Water Works Association): established standards on iron gate valves to be used in a recognised water supply system. Federal Specification (Federal Government Specification Standards): established by US agencies for design. dimensions. materials. and tests on items for use by the Armed Forces. FM (AFM) (Associated Factory Mutual): establishes standards similar to UL but is employed by Mutual Fire Insurance Companies. MIL Specifications (US Military Specifications and Standards): establishes design. dimensions. materials. and tests on items for use by the Armed Forces. MSS (Manufacturers' Standardization Society of the Valves and Fittings Industry): maintains standards on dimensions. marking, boss locations for drains and bypasses, testing. and other similar type standards. NFPA (National Fire Protection Association): establishes design and performance standards on valves and fittings used in fire protection service. USASI (USAS) (United States of America Standards Institute): establish es certain basic dimensions of valves. fittings and threads. UL (Underwriters Laboratories): establishes design and performance standards on valves and fittings used in fire protection service and handling of hazardous liquids.

Standards and Designations 801

ASTM metal and alloy designations

Bronzes and brasses High tensile steam bronze Steam bronze Cast silicon (Everdur 1000) Silicon brass Silicon brass Wrought silicon (Everdur 1012) 88-10-2 brom:e Ampco. grade C-3 Ampcoloy, grade B-2 Brass rod Naval brass Brass tubing Phosphor bronze Bronze rod

B-61 B-62 B-198 grade l2A B-198 grade 13B B-371 alloy A B-98 aUoy D B-1 ·':13 class 1A B-148 alloy 9C B-148 alloy 9B 3-16 B-21 alloy A B-135alloyG B-134 alloy B-2 B-134
Irons Cast iron Cast iron High tensile cast iron Malleable cast iron Malleable cast iron Ni-resist grey cast iron

A-126 class A A-126clnssB A-126 class C A-47 grade 35018 A-47 grade 32510 A-346typell

Cast steels Carbon steel. cast 0.1 5% Moly steel. cast Cr Moly steel. cast Cr Moly steel. cast 4. 6% Cr Moly steel 8-10% Cr Moly steel Carbon steel. cast Cnrbon Moly steel. cast 3. 5% Nickel steel. cast

A-126 grade WCB A-217 grade WCl A-217 grade WC-6 A-217 grnde WC-9 A-217 grade CS A-217 grade C-12 A-325 grade LCB A- 352 grade LC-1 A-352 gradeLC-3

Stainless steels 18.8Scast Wrought Wrought 18-8S Mo. cast Wrought 18-8S Cb. cast Wrought 11.5- 13.5 Cr steel 11.5-13.5 Cr steel Heat-resisting 25-12. cast Heat-resisting 25-20. cast Heat-resisting 25-20. wrought Heat-resisting 15-35

A-351 gradeCF8 (type 304) A-276 type 304 A-2 76 type 303 A-351 gradeCF-8M (type 316) A-276type316 A-351 grade Cf-8C (type 347) A-2 76 type 34 7 ;\-182 grade P-6 A-276type416 A-297 grade MI-l A-297 grade MK A-182 typeP310 A-297 grade Ht

Nickel alloys Nickel. cast Nickel, wrought Monel. cast Monel. wrought Hastelloy '8', cast Hastelloy 'C', wrought

A-296 CZlOO B-160 A-2% M-35W B-164 class A A-296N-l2M A-296m CW-l2M

Aluminium No 356T. cast

B-26 gradeSG70AT6

802

Engineering Data

Standards, Specifications and Codes of Practice

Pipes and pipe fittings: British Standards

BS 21:1973 (1986): Pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions). BS 6 5:1981: Vitrified clay pipes, fittings and joints. BS 78: Cast-iron spigot and socket pipes (vertically cast) and spigot and socket fittings. BS 78:Part 2:1965 (1981): Fittings. BS 416:19 73: Cast-iron spigot and socket soil. waste and ventilating pipes (sand-cast and spun) and fittings. BS43 7:1978: Specification forcastironspigotand socketdrain pipes and fittings . BS 486: 1981: Asbestos- cement pressure pipes and joints. BS 4 9 7: Part 1: 19 7 6: Cast iron and cast steel. BS 534:1981: Steel pipes and specials for water and sewage. BS 556:Part 1: 1966: Concrete cylindrical pipes and fittings,.including manholes , inspection chambers and street gullies. Part 1: Imperial units. BS 556:Part 2:1972: Concrete cylindrical pipes and fittings, including manholes, inspection chambers and street gullies. Part 2: Metric units. BS 1194:19 69: Concrete porous pipes for under-drainage. BS 1196:19 71 ( 19 77): Clayware field-drain pipes. BS 1211 :1958 (1981): Centrifugally-cast (spun) iron pressure pipes for water, gas and sewage. BS 1387:1967: Steel tubes and tubulars suitable for screwing to BS 21 pipe threads. BS 1737:1951: Jointing materials and compounds for water, town gas and low-pressure steam installations. BS 1965: Butt-welding pipe fittings for pressure purposes. BS 1965:Part 1:1963 (1983): Carbon steel. BS 19 7 2:196 7: Polythene pipe (type 3 2) for cold-water services. BS 2494:19 76: Materials for elastomeric joint rings for pipework and pipelines. BS 2 760:19 73: Pitch-impregnated fibre pipes and fittings for below and above ground drainage. BS 2 815:19 7 3: Compressed asbestos fibre jointing. BS 28 71 :Part 1:19 71: Copper tubes for water, gas and sanitation. BS 306 3:196 5: Dimensions of gaskets for pipe flanges. (Note: This BS is used only in connection with obsolescent BS 10 flanges) . BS 3284:1 967: Polythenepipe(type 50) for cold-water services. BS 3 505:1968 (19 82 ): Unplasticised PVC pipe ror cold-water services. BS 3 506:1969: Unplasticised PVC pipe for industrial purposes. BS 3656:1981: Specification for asbestos- cement pipes, joints and fittings for se\.vage and drainage.

Standards and Designations

803

BS 4508: Thermally insulated underground piping systems. BS 4 508:Part 1:1969: Steel-cased systems with air gap. BS 462 2:19 70: Grey iron pipes and fittings. BS 462 5:19 70: Pre-stressed concrete pressure pipes (including fittings). BS 4660:1973: Unplasticised PVC underground drain pipe and fittings. BS 4 7 7 2: 19 71: Ductile iron pipes and fittings . BS 49 62:19 8 2: Specification for plastic pipes for use as light sub-soil drains. BS 5178:1975: Pre-stressed concrete pipes for drainage and sewage. BS 5911: Pre-cast concrete pipes and fittings for drainage and sewage. BS 5911 :Part 1:1981: Specification for concrete cylindrical pipes, bends, junctions and manholes, unreinforced or reinforced with steel cages or hoops. BS 5911 :Part 2:1982: Specification for inspection chambers and gullies. BS 5911:Part 3:1982: Specification for ogee-jointed concrete pipes, bends and junctions, unreinforced or reinforced with steel cages or hoops. BS 59 55: Code of practice for plastic pipework (thermoplastic materials). BS 59 5 S:Part 6:19 80: Installation of unplasticised PVC pipework for gravity drains and sewers. BS 608 7:1981: Specification for flexible joints for cast-iron drainpipes and fittings (BS 43 7) and for cast-iron soil, waste and ventilating pipes and fittings (BS 416). BS 6464:1984: Specification for reinforced plastic pipes, fittings and joints for process plants. CP 2010: Pipelines. CP 2010:Part 1:1966: Installation of pipelines in land. CP 201 O:Part 2:19 70: Design and construction of steel pipelines in land. CP 2010:Part 3:19 7 2: Design and construction of iron pipelines in land. CP 201 O:Part 4:19 72: Design and construction of asbestos-cement pipelines in land. CP 2010:Part 5: 1974: Design and construction of pre-stressed concrete pressure pipelines in land. DD 76: Pre-cast concrete pipes of composite construction. DO 76:Part 1:1981: Precast concrete pipes strengthened by continuous alkali-resistant glass rovings. Valves and fittings: British Standards

BS 143 and 1256:1968: Malleable cast iron and cast copper alloy screwed pipe fittings for steam. air, water, gas and oil. BS 1010: Draw-offtaps and stop valves for water service (screwdown pattern). BS 1010:Part 2:1973: Draw-offtaps and above-ground stop valves BS 112 3:19 76: Specification for safety valves, gauges and other safety fittings for air receivers and compressed-air installations. BS 1414:1975 (1983): Steel wedge-gate valve (flanged and butt-welding ends) for the petroleum, petrochemical and allied industries.

804

Engineering Data

BS 1553:Part 1:1977: Piping systems and plant. BS 1640:19 62 and 1968: Steel butt-welding pipe fittings for the petrochemical industry. BS 165 5:19 50: Flanged automatic control valves for the process control industry (face-to-face dimensions) . BS 1868:1975 (1983): Steel check valves (flanged and butt-welding ends) for the petroleum, petrochemical and allied industries. BS 1873:1975: Steel globe and globe stop and check valves (flanged and butt-welding ends) for the petroleum, petrochemical and allied industries. BS 19 63:19 69: Pressure-operated relay valves for gas-burning appliances. BS 2080:19 7 4: Face-to-face, centre-to-centre. end-to-end and centre-to-end dimensions of flanged and butt-welding end steel valves for the petroleum, petrochemical and allied industries. BS 2580:1979 : Underground plug cocks for cold-water services. BS 3016:1983 : Pressure regulators and automatic changeover devices for liquefied petroleum gases. BS 3059: Steel boiler and superheater tubes. BS 3059:Part 1:1978 ±ISO 2604/II. ISO 2604/ III. ISO 1129: Low tensile carbon steel tubes without specified elevated temperature properties. BS 3059:Part2:1978 ±ISO 2604/II. ISO 2604/ 3, ISO 1129: Carbon. alloy and austenitic stainless steel tubes with specified elevated temperature properties. BS 3600:1976 ~ISO 3 36, ±ISO 64: Dimensions and masses per unit length of welded and seamless steel pipes and tubes for pressure purposes. BS 3604:1978 ±ISO 2604/II, ISO 2604/ IIf. ISO 2605/I: Steel pipes and tubes for pressure purposes: ferritic alloy steel with specific elevated temperature properties. BS 3 799:19 74: Steel pipe fittings, screwed and socket-welding for the petroleum industry. BS 4504: Flanges and bolting for pipes, valves and fittings. Metric series. BS 4504:Part 1:1969: Ferrous. BS 4 5 04:Part 2:19 7 4: Copper alloy and composite flanges. BS 4 7 40: Method of evaluating control-valve capacity. BS 4 7 40:Part 1:1971 : Incompressible fluids. BS 5146:19 7 4: Inspection and test of steel valves for the petroleum, petrochemical and allied industries. BS 51 SO:19 7 4: Cast-iron wedge and double-disc ga te valves for general purposes. BS 5151 :19 7 4 (19 8 3 ): Cast-iron gate (parallel-slide) valves for general purposes. BS 5152:1974 (1983): Cast-iron globe and globe stop and check valves for general purposes. BS 5153:1974 (1983) : Castiron check valves for general purposes. BS 5154:1983: Copper alloy globe. globe stop and check, check, and gate valves for general purposes.

Standards and Designations 805

BS 515 5:19 7 4: Cast-iron and carbon steel butterfly valves for general purposes. BS 515 6:19 7 4 ( 19 8 6 ): Screwdown diaphragm valves for general purposes. BS 515 7:19 74 : Steel gate (parallel slide) valves for general purposes. BS 515 8:19 7 4: Cast- iron and carbon steel plug valves for general purposes. BS 5159:1974: Cast-iron and carbon steel ball valves for general purposes. BS 5160:19 7 4: Flanged steel globe valves, globe stop and check valves. BS 5 163:1974:Double-flanged cast-iron wedge-gate valves for water-works purposes. BS 5351:1986: Steel ball valves for the petroleum. petrochemical and allied industries. BS 5352:1981 (1983): Steel wedge-gate, globe and check valves SO mm and smaller for the petroleum, petrochemical and allied industries. BS 5353:1980: Plug valves. BS 5417:19 76: Testing of general purpose industrial valves. BS 5418:1979 =ISO 5209: Marking of general purpose industrial valves. BS 5 882:1980 :;i:ISO/DIS 6215: A total quality-assurance programme for nuclear power plants. BS 668 3:19 8 6: Guide to the installation and use of valves. MA 6 5 :Parts 1-11 :19 7 5-19 7 7: General purpose and petroleum industry valves for use in marine pipeline systems.

Sl units

SI units are the seven basic units and the units derived from them coherently. i.e. with numerical factor 1. SI basic units Basic quantity Name

SI basic unit Symbol

Name

Symbol

Metre

m

Kilogram

kg

Time

Second

s

Electric curren t

Ampere

A

Length Mass

m

Thermodynamic temperature

T

Kelvin

K

Amount of substance

n

Mole

mol

Candela

cd

LuminoliS inte nsity

806

Engineering Data

Internationally defined prefixes Prefix Meaning

Name Symbol

Trillion Thousand billion Billion Thousand million Million Thousand Hundred Ten Tenth Hundredth Thousandth Millionth Thousand millionth Billionth Thousand billionth Trillionth

ex a pet a tera gig a mega kilo hecto dec a deci centi milli micro nano pico femto atto

E p T G

M k h da

d c m )l

n p f

a

Powerof10

Factor as decimal

=1 000 000 000 000 000 000 =l 000 000 000 000 000

1018 1015 10 12 10 9 10 6

= 1 000 000 000 000 = l 000 000 000

=1000 000

w>

= 1 000

10 2

= 100

10 1

= 10

w- ' w-2 w-3 w-6 w-9 10 -

= 0.1

=0.01 =0 .0()1 = 0.000 001 = 0 .000 000 001 = 0.000 000 000 001 =0.000 000 000 000 001 = 0 .000 000 000 000 000 001

12

10-15 lo - 18

Units Size

Symbol Sl units

Length Surface

Permissible units other than SI

Conversion into associated SI unit and ra tios

m (metre )

t\

I)

v

mi (cubic

metre)

I" (in = 0.254 m) I nm (nautical mile) = l R52 m

=

ml 2)

(square metre)

Volume

No longer permissible unit·s and conversioos

2)

I (litre)

11 =10

) Ill J

l b (barn 10 - 2~m 2 1 a (arc) = 10 2 m2 = ]04 m2 l ha (hectare) sq .m . } N•meollowod. sq .dm . symbol nol allowed sq.cm .. etc .

Standards and Designations

Symbol

Value

Slunils

Conversion into relevant Slunit and ratio~

Permissible units other than Sl

80 7

No longer permissible units with conversions

sr l~r = lm 2 /m 2 J o• tsquaredegreel = 3.U_46·J0· 4 sr (steradian) I O g(sqnaregrade) = 2.467·10--4 sr ------------------------------~----min (minute) 1 min = 60s h (hour) (second) l h = 3600 s rl (day) I
Solid angle Time

=

Hz (ilerlz)

Frequency Rotation spcl·d

n

Velo<:ity

v

Acceleration

(II

m

!"

I

1 Hz = l/s

-----------------------------rpm = ( /r,o)srpm 1

1

1

rpm

1 rpm == 1 (! / min )

km/h

1 km/b = (l/3 .6lm/s Normal fall acceleration 1 gal (gall = g .. =9.801i65 m /s 2

kg

1 (tonocl

lt = 10 1 kg

t/ m 1 kg/1

lt/mJ = 1000kg/m 1 lkg/1 = 1000kg/m 1

ro ··l m/s 1

l q (metric hondredweighl)

=100 kg

(kllo~-:ram) JJen ~ lty

p

kg· m1

Moment ofincrlia f

--~----------~-

1 N = l kg·m/s

N (Newton)

Torque

XI

N·m

Pressure

p

Pa (Pascali

Mechu nica l

R

lkp·m·s 2 2

=9.81 kg·m .! = LO ' N

1 dyn (dyn)

lp(pond) = 9.80665·10-JN 1 kp (kilopond ) :: 9 .iW665 N

J kpm=9.80665 Nm

=

=

1 atm 1.0132 5 bar 1 at = 0.980665 bar 1 Torr -1.333224·10- 1 b<Jr I mCE = 98.0665·10 -J bar 1 mm Hg 1.333224 ·1 o- 1 bllr

1 Pa l N/nt.! l bar = 10 5 Pa

=

I N/ m 2

=l Pa

1 kp/m ~ ::: 9.80665 N/ro 1 1i;p/cm 1 = 98.0665·1 0 ~ N/m 2 l kp/ mm1 9!1 .0665 · 10-'' N / m 1

sl re s~

=

Dynamic vi sc.:o~ity

X

Pu·s

-------------------

Kinematic viscosity

1 Pa·s = 1 N ·s/mz 2

1 P(polse) = J0- 1 Pa·s 1

I rn / s = l Pn·s·m /kg

=

eV lelectronvolt) 1 I = 1 Nm 1 H 2 0 W·h l W·h = 3.6KJ

w

4

1St (stokes) = 10

----------------------------

m 2/ s

------------------

l cal = 4.18681 l kpm = 9.80665 j l erg = JO - ~ j

Work Enc(gy

E

(Joule)

Elt·ctric ch arg<'

()

C (Coulomb)

1 C = 1 A·s

Ell'l:lrk potential

lj

V (Volt)

1V = 1W/ A

Elect(ic resistance

R

Q(Ohm)

1Q = 1V/ A

1 Qabs= l Q

Power

p

W(WHII)

l W = 1J/s = 1 Nm/s =I V·A

I PS = 7 35.49!!W lkcal/ h = l.I63W 1 kprn/ s = I 0 W

Ekctric capacitance

c

F (Farad)

1 P - 1 C/ V

-----------------------------------------------------------------------A (Ampere)

Elect ric current

Magnetic flux



------------------------------------1 Oe(oerstedi = 79.'i775 A/m --------------------------------Wh(Weberl 1 Wb = 1 V·s 1 Mx (maxwell)= 10 -s \>\'b

Mal-:nCiic llux density

13

'f (Tesla)

1ncluctancc

L

II (Henry)

G

S (Siemens)

Magnetic field strength H

A/111

----------------

Electric conductanrc

Spec. electric r~ ·j ·ra nee cr Thl'rmodynamlc temperature

'I'

Temperature ("CI

t/"6

!G(gauss) = 10

4

1'

1H = I Wb/ A l

s= l/Q

Qjm

K (Kelvin)

AJ • C' = JK

o· c = 273.15K

·c (clegree Celsius)

Tbennal capacity

IT = 1 Wb/ m1

------------

c

j /K

A 1" (' = 1 K OK ::: - 273.15 "C

1 Kcl/dcgree = 4.1868·10- \ J/K J Cl (clamius) 4. U~68 1/K

808

Engineering Data

Ball valves Typical standards of compliance

Specification Design

Test

Description

8S 5351

Specification for steel ball valves for the petroleum. petrochemical and allied industries

BS 1560

Class designated flanges

BS 4504

Valves: flanged ends

ANSI 816.5

Valves: flanged ends

ANSI 816.24

Valves: flanged ends

ISO 5211

Valve/actuator mating dimensions

API6D

Specification for pipeline valves (gate. plug. ball and check valves)

BS 6755 Part 1

Specification for production pressure-testing requirements

BS6755Part2

Specification for fire type-testing requirements

API 6PA

Specification for fire type-testing requirements

API 6D

Specification for pipeline valves

API 598

Valve inspection and test

API607

Fire test

ISO 5208

Industrial valve pressure testing

NES 729

Requirements for non-destructive examination methods. Part 1: radiographic

ASME V SE 165

Requirements for non-destructive examination methods. Dye penetrant

Standards and Designations

809

ASTM test methods

c 177-85 0149-81

Test method for steady-state heat flux measurements and thermal transmisssion properties by means of the guarded-hot-plate apparatus: 04.06.08.01.14.01. Te::;t methods for dielectric breakdown voltage and dielectric strength of solid electrical insulating materials at commercial power frequen cies: 08.01,09.02. 10.02.

0150-8 1

Test methods for A-C loss characteristics and permittivity (dielectric constant) of solid electrical insulating materials: 08.01.09.02.10.02,10.03.

D 256-84

Test methods for impact resistance of plastics and electrical insulating materials: 08.01.09.02.

D 570-81

Test method for water absorption of plastics: 08.01.

D635-81

Test method for rate of burning and/or extent and time of burning or self-supporting plastics in a horizontal position: 08.0 l.

D 638-84

Test method for tensile properties of plastics: 08 .01 .

0 648-82

Test method for deflection temperature of plastics under flexural load: 08.01.

0695-8 5

Test method for compressive properties of rigid plastics: 08.0 l .

0696-79

Test method for coefficient oClinear thermal expansion of plastics: 08.01.14.01.

0 790-84a Test methods for flexural properties ofunreinforced and reinforced plastics and electrical insulating materials: 08.01. 0791

Discontinued: replaced byE 308 .

D 792-66 (1979)

Test methods for specific gravity and density of plastics by displacement: 08.0 1.

D 1784-81 Specification for rigid poly( vinyl chloride) {PVC) compounds and chlorinated poly( vinyl chloride) (CPVC) compounds: 08 .02,08.04.

D 2240-86 Test method for rubber property: durometer hardness: 08.02.09.01.

D 2 766-83 Test method for specific heat of liquids and solids: 05.02 . D 39 J. 5-80 Specification for poly(vinyl chloride) (PVC) and related plastics pipe and fitting

compounds: 08.03.08.04. E 84-84

Test method for surface burning characteristics of building materials: 04.07.

E 162 -83

Test method for surface flammability of materials using a radiant heat energy source: 04.07.

E 308-85

Method for computing the colours of objects by using the CIE system: 14.02.

810

Engineering Data

list of relevant standards

Polyeth}'lene piping systems ISO R16l

Thermoplastic pipes for the transport of fluids.

ISO 1183

Polyethylene: measuremen I" of density.

ISO 3607

PE pipes: tolerances and o.d. and wall thicknesses.

ISO 3663

PE pressure pipes and fittings: dimensions of flanges.

ISO 443 7

Buried PE pipes for the supply of gaseous fuels.

ISO 4440

PE pipes and fittings: determination of melt flow rate.

ISO 6447

Rubber seals: joint rings used for gas supply pipes and fittings.

DIN 353 5

Seals for gas supply.

DIN 3543

PE-HD valves for pipes made from PE-HD material: dimensions.

DIN 3544

Valves in high-density polyethylene (PE-HD): specification and testing of tapping valves.

DIN 8074

Pipes in high-density polyethylene (PE-HD): dimensions.

DIN 8075

Pipes in high-density polyethylene (PE-HD). General quality requirements: testing.

DIN 16963

Pipe joints and piping components for pressure pipelines in high-density polyethylene (PE-HD).

DIN 19533

Pipes in PE-HD and PE-MD for drinking water supply: pipes. pipe joints, piping components.

DS 2131.2

Pipes. fittings and joints ofPE-type PEM and PEH for buried gas pipelines.

DVS 2207 Part 1

Welding of thermoplastic materials. (PE) pipes and pipeline components for gas and water pipelines.

DVGWG477

Manufacture, quality assurance and testing of pipes in rigid PVC and PE-HD for gas pipelines.

DVGWVP304

Gas tapping valves for PE-HD piping systems.

DVGWVP607

PE-HD fittings for gas and drinking water pipelines.

DVGWVP608

Polyethylene pipes (PESO and PE100) for gas and drinking water lines: requirements and tests.

ONorm B 5192

Pipes, pipe joints and piping components in PE for buried gas pipelines.

prEN 1555

Plastic piping systems for gas distribution: polyethylene (PE).

prEN 12201

Plastic piping systems for water distribution: polyethylene (PE).

UNI 8849

Raccordi di polietilene (PESO). saldabili per fusione mediante elementi riscaldanti. per condotte per convogliamento di gas combustibili. Tipi. dimensioni e requisiti.

UNI8850

Raccordi di polietilene (PESO). saldabili per elettrofusione per condotte interrate per convogliamento di gas combustibili: tipi. dimensioni e requisiti.

PVC piping systems ISO 2045

Minimum insertion depth for push-fit sockets.

ISO 3460

PVC adaptor for backing flange.

ISO 3603

Leak test under internal pressure.

ISO/DIN 4422

PVC pipes and fittings for water supply.

StarJdards and Designations

811

DIN 2501 Part 1

Flange: connecting dimensions.

DlN 3441 Part 1

PVC valves: requirements and testing.

DIN 3 543 Part 3

PVC tapping valves: dimensions.

DIN 42 79 Part 7

Internal pressure testing of PVC pressure pipelines for water.

DlN 8061 Part1

PVC pipes: general quality requirements.

DIN 8062 DIN 8063 Part 4

PVC pipes: dimensions.

DIN 8063 Part 5

Pipe joints and components for PVC pressure pipelines: general quality requirements and test methods.

DlN 16450

Fittings for PVC pressure pipelines: designations, symbols.

DfN 16929

Chemical resistance of PVC.

DIN 19532

PVC pipelines for drinking water supply.

KRV A 1.1.2

Push-lit joints on PVC pressure pipes and fittings: dimensions, requirements, testing.

Pipe joints and components for PVC pressure pipelines: adaptors. flanges, gaskets, dimensions.

KIWA BRL K 603 Plasticgatevalvesofnominal sizes from 25 to 150 mm.

Quality specification No.

Couplings and fittings ofunplasticised polyvinyl chloride for water pipes.

53 Criteria No. 23

Doop Spuitgieten vervaardigde PVC-hulpstukken met flensaansluitigen.

BRL2013

Rubberringen and flenspakkringen voor verbindungen in drinkwater en afva]water!eidin gen.

WJS 4-31-07

Specification for emplasticised PVC pressure fittings and assemblies for cold potable water (underground use).

812

Engineering Data

Wear- and galling-resistance chart of material combinations

304 SST 316 SST Bronze lnconel Monel HastelloyB

r

p

p

p

p

F

F p p

F

s s s s s s s s s p p p F p F F s p p p F F F F s p p p F F s F s F F F F F F F s p F F F p F F

p

p p p

Hastelloy C Titanium 7 SA Nickel Alloy 20 Type 416 hard Type 440 hard

F p p p

F p

p

s s

F F

F F

F F

17-4 PH

F F F F F

F F'

F F

p

p

F F

Alloy 6 (Co-Cr) ENC. Crplate AI bronze

p

"Eiectroless nickel coating. S, satisfactory; E fair; P. poor.

p p

F F F

F

p p

p p

s

F

F

p p

F F F F

F F F

F

F

s

s s s

p

F

F

F F F p

F

s

F

s

s

F

F F F F

F

F

F F F

F

F

p

p p

F

F

F

F

F

F

F

F

F

F

F

F

r

F F F

F

F F

F F

F F

F F

F F

S S

F F

F F

S S

F

S

S

F F F F

F F

S S

p p

F F F F

F F

S S

F F

F

F

F

F

F

S

F

s

s s s s s s s

F

F

F

S

p

p p

F F

F F

s s s s p

F

s s

s s s s s s s s s s s s s

p

F

S

S

F

F

S

F

F

S

F

F

S

S

s s s s

s s s s s p s s s s s p s s s s s p S

F

Standards and Designations Valve-trim material temperature limits Lower Material Type 304 stainless steel Type 316 stainless steel Bronze Inconel 1 K Monel' Monel

Upper

oc

op

oc

op

-268 - 268 -273 -240 - 240 -240

-450 - 450 -460 -400 - 400 -400

316 316 232 649 482 482

600 600 450 1200 900 900 700 1000 600 600 600 800

Hastelloy B2 Hastelloy C2 Titanium Nickel Alloy 20 Type 416 stainless stee l 40RC

-198 -46 -29

-325 -50 -20

371 538 316 316 316 427

CA-6NM Nitronic 50 3

-29 -198

-20 - 325

427 538

800 1000

Type 440 stainless steel 60RC 17-4 PH (CB-7CU) Alloy 6 (Co- Cr) Electroless nickel plating Chrome plating Aluminium bronze

-29 -40 -273 -268 -2 68 -2 73

-20 -40 -460 -450 -450 -460

427 427 816 427 593 316

800 800 1500 800 1100 600

Nitrile Fluoroelastomer (Viton 4 and Fluore1 5 ) TFE Nylon Polyethylene Neoprene

-40 -23 - 268 -73 -73 -40

-40 -10 -450 -100 .-100 - 40

93 204 232 93 93 82

200 400 450 200 200 180

'Trademark of International Nickel Company. Trademark of Stellite Division. Cabot Corporation. 3 Trademark of Armco Steel Corporation. 4 Trademark of E.I. DuPont de Nemours & Company, Inc. <;Trademark of 3M Company. 2

813

814

Engineering Data

US standard materials for trim parts of valves Minimum physicnl l\
Specification

Aluminium bnr

properlic~

Modulus of at 70° F (lb/in 2 x 10")

da~licity

Hardness (Brine)!)

Tensile (lb/ in 2 )

Yield (lb/in 1 I

ASTM 8211 alloy2011 -'1'3

44.000

36.000

15

Yellow brass bar

ASTM 816 1 h h ard

45.000

15.000

7

50

Nav
AS'fM 821 alloy464

60.000

27.000

22

'i'i

Leaded sttd bar

AIS112T.l4

79.000

71.000

16

52

163

Carbon steel bar

ASTM A lOR grade 1018

69.000

48.000

38

62

143

I 35.000 115.000

22

63

2') .9

25~

t\S'fl\•l A2 76 type l02

85.000

35.000

60

70

28

150

t\STJ\•l A276 type 304

85.000

35.000

60

70

Type 316 stain less steel

ASTM A276 type 316

80.000

Hl.OOO

60

70

Type H6L stninless steel

ASTi'vl A2 76 type 3161.

81.000

34.000

55

Type41 0 stainless steel

AS'J'M A276 typc41 0

75.000

40.000

35

70

29

I 55

Type 1 7-4Pl-l stainless steel

ASTM A416 grade 6 30

lJ 'i.OOO 105.000

16

'j()

2 ')

275-345

Nickel-copper alloy bar

Alloy KSOO (KMonell

100.000

70.000

~5

26

17 5-260

ASTM 13335 '13 ' )

100 .000

46.000

w

ASTM 8336

100.000

46.000

Chrome-moly steel

Type 302 stainless steel Type 304 stainless steel

---

A!SJ 4140 (suitable for AS'fM A193 grade 137 bolt mat)

Nickel-moly alloy' l3'bar

(J-la~te ll oy

Nickel-moly- chrome alloy 'C' bnr

(Hastelloy 'C')

Elongation in Reduction of;tn·;t(%) 2in (%)

10.2

1) 5

14

149

2S

149

146

US standard materials for valve bodies (pressure-containing castings) Minimum physical properties Tensile (lb/in 2 )

Yield (lb/i n 2 )

Elongation in lin(%)

Reduction ofarea(%)

Modulus of elasticity at 70°F (lb/i n 2 x 10c, I

Hardness (Brine !I)

-20 to 1000

70.000

36.000

22

35

27.9

137-187

ASTM A352 grade LCB

-50 to 650

65.000

3 5.000

24

35

27.9

1 37-18 7

Chrome moly steel

ASTM A217 grade C5

-20 to 1100

90.000

60.000

18

35

27.4

241 max

Carbon moly steel

ASTMA217 grade VVC1

-20 to 850

65.000

35,000

24

35

29.9

215 max

Chrome moly steel

ASTM 217 gradeWC6

-20 to 1000

70.000

40.000

20

35

29.9

215 max

Chrome moly steel

ASTMA217 gradeWC9

-20 to 1050

70,000

40.000

20

35

29.9

241 max

3 1 / 2 % nickel steel

ASTM A352 grade LC3

-150 to 650

65.000

40,000

24

35

27.9

137

Material

Specification

Temperature range (°F)

Carbon steel

ASTMA216 grade WCB

Carbon steel

V)

..... l::l ::::;

§.....

::::..

Chrome moly steel

ASTM A2 17 grade C12

-20 to 1100

Type 304 stainless steel

ASTM A351 grade CF-8

-425 to 1500

Type 316 stainless steel

ASTM A351 grade CF-8M

- 425 to 1500

90.000

60.000

18

35

27.4

180-240

"':::,:::

::::..

t:j

65,000

28.000

35

-

28.0

140

"'"'

~-

::::; :::,

..... c:;· ::::;

70,000

30 .000

30

-

28.3

15 6- 170

"' 00 ,..... V1

Cast iron

31,000

-

ASTMA126 class B

-150 to 450

ASTM A126 class C

-150to450

41.000

ASTMA395 type 60-45-15

-20 to 650

60.000

Ductile Ni-resist · iron

ASTM A439 type 60-45-15

-20 to 750

58 ,000

30,000

7

Standard valve bronze

ASTMB62

-325 to 450

30.000

14.000

20

17

13.5

55-65'

Tin bronze

ASTMB143 alloy 1A

-32 5 to 400

40.000

18,000

20

20

15

75-85"

Manganese bronze

ASTMB147 alloy BA

-325 to 3 50

65,000

25.000

20

20

15.4

98'

Aluminium bronze

ASTMB148 alloy 9C

-325to500

75 ,000

30.000

12 min

12

17

150

(Weldable grade)

-325 to 900

65 .000

32.500

25

-

23

120-170

Nickel-moly a lloy 'B'

ASTM A494 (Hastelloy 'B')

-32 5 to 700

72.000

46,000

6

Nickel-molychrome alloy ·c

ASTMA494 (Hastelloy ·c)

-325 to 1000

72,000

46,000

4

121,000

64.000

1 to 2

-

30.4

-

-

-

160-220

00

,.....

0"1 I:Tj

Cast iron Ductile iron

Monett alloy 411

Cobalt-base alloy No.6

--

· 500 kg load: 1for Brinell and material.

Stellite no. 6

-

45,000

-

-

15

-

-

23-26

160-220

~

143-20 7

~

s· "':::!. "" ::; tj !::)

s

-

-

-

148- 211

Conversion tables

Viscosities Kinematic viscosity centistokes density l.O 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 20 40 60 80 100 200 400 600 800 1000 5000 10.000 50.000

Absolute viscosity

Engler

Saybolt unlversal

Redwood 1

Say bolt sec fur a\

centipoise

0

sec

sec (standard)

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 20 40 60 80 100 200 400 600 800 1000 5000 10.000 50,000

1.0 1.1 1.2 1.3 1. 39 1.48 1. 57 1.65 1.74 1.84 2.9 5.3 7.9 10.5 13.2 26.4 52.8 79.2 106 132 660 1320 6600

31 34 35 37 42 45.5 48 .5 53 55 59 97 185 280 370 472 944 1888 2832 3776 7080 23.600 47.200 236.000

29 30 33 35 38 40.5 43 46 48.5 52 85 163 245 322 408 816 1632 2448 3264 4080 20.400 40,800 204.000

Ford cup no. 4 furol

-

-

-

-

-

-

-

-

-

-

-

-

15 21 30 38 47

92 184 276 368 460 2300 4600 23.000

-

18.7 25.9 32 60 111 162 217 415 1356 2713 13.560

Barbey

0

3640 2426 1820 1300 1085 930 814 723 650 320 159 106 79 65 32.5 15.9 10.6 8.1 6.6 1.23 -

Cup no. 15

sec -

-

-

-

-

5.6 6.7 7.4 11.2 18.4 26.9 35 68 240 481 2403

Absolute viscosity poise density 1.0

Kinematic viscosity

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0 .2 0.4 0.6 0.8 l.O 2.0 4.0 6.0 8.0 10 50 100 500

l.Ox1o- 6 2.0x 10- 6 3.0x w - 6 4.0x 10- 6 5.0 x 10- 6 6.0 x 10- 6 7.0 x 10- 6 8.0 x 10-6 9.0 x 10- 6 l.O x 10- 5 2.0x1o- > 4.0x lo- s 6.0xlo-s 8.0x lo-s l.O x 10- 4 2.0 x 10- 4 4.0 x 10- 4 6.0 x lo-4 8.0 x 10-4 l.O x 10- 3 5.0 x 10- 3 1.0 X 10- l s.ox 10- 2

m2 / s

Cl':l

s ::::!

Q.. ~ ""!

Q..

"'::::!s::.

Q..

c::1 <'>

"'

~·

::s ....s::.

(3' ::::!

Absolute viscosity (centipoise)= kinematic viscosity (centistokes) x density. Over 50 centistokes. conversion to SSU: SSU = centistokes x 4.62.

"' 00 ..... -......)

818

Er1gineering Data

Delivery volumes m 3/ h

l.O 0.060 0.10 0.2727 0.2273 0.0283 101.94 3600.0

L/rnin

hl/h

Imperii! I gallon/ min

US gallon/min

cu ft/ hr

cu ft/sec

m 1/ sec

lfi.667 1.0 1.6667 4.546 3.785 0.4719 Hi99

10.0 0.60 1.0 2.7270 2.27 32 0.2R32 1019.4 36.000

3.6667 0.22 0.3667

4.3999 0.2642 0.4399 1.201 1.0 0.1 247 448.83 15.838

35.315 2.1189 3.5 3 15 9.6326 8.0208 1.0 3600 127.208

9.81 x l0- 1 5.88 x 10- 4 9.81 x w - -~ 1.67 x L0 - 1 2.2J x 10- 1 2. 78x Jo-4 1.0 35 . 315

2.7S x 10 -~ 1.6 7x JO- > 2. 78x 1W 5 7.57 x i0- 5 6.31 x 1o-> 7. 86 x l0-> 0 .0282

mH20

mmHg

6 x 1o -<~.

l.O 0.832(1 0.1038 373.73 1320

l.O

hl = hectolitre =litre x 101 .

Pressure and pressure heads bar

kg/ cm 1

1.0 0.9807 0.0689 1.013 3 0.0299 0.0981 13.3 x 1o- 4 0.0339 l.Ox 10- >

1.0197 1.0 0.0 703 l.0332 0.0305 0.10 0.0014 0.0345 10.2 x 1o - ~>

lbf/in 2

ftH 1 0

atm

14.504 0.98fi9 33.445 10.19 7 14.223 32.808 10 0.9878 1.0 0.0609 2.3067 0.7031 l4.69fi 33.889 10.3 32 1..0 0.4335 0.0295 0.3048 1.0 1.422 0.0%8 3.2808 1.0 0.0193 l3.2 x 1o- 4 0.0446 0.0136 0.0334 1.1329 0.3453 0.4912 14.5x w- s 9.87x10 - 1' 3.34 x l0- 4 l0. 2x 10

1

in Hg

kPil

750.oo 29.530 100 ns.5fi 28.959 98 .0 51.715 2.036 6.89 760.0 29.921 101.3 22.420 2.99 0.882 7 73.356 2.896 9.81 L.O 0.0394 0. 13 3 ].() 25 .40 U9 75.0 x 10- 4 29.5 x w-s l.O

atm =international standard atmosphere. kg/cm 1 =metric atmosphere.

Velocity metre per second m/s

1 0.3048 18.288 0 .2778 0.4470

foot per second ft/s

foot per minute fl/ m

kilometre per hour km/ hr

mile per hour mile/hr

3.2808 1

0 .0547 0.0167

60 0.9113 1.4667

0.0152 0.0245

3.6 1.097 3 65.8368 l 1.6093

2.2369 0.6818 40.9091 0.6214

I

I

Standards and Designations

819

Volume cubic metre

m3

cubic centimetre cm 3

litre I

cubic inch inJ

cubic foot ft 3

1.000.000 1 1000.028 16.3871 28316.8 4546.09 3 785.41

999.972 0.0009997 1 0.0164 28.3161 4.546 3.7853

61.023.7 0.0610 61.0255 1 1728 277.419 231

35.3147 0.0000353 0.0353 0.00058 l 0.1605 0.133 7

.l

0.000001 0.001 0.000016 0.0283 0.0045 0.0038

UK gallon US gallon UK gal US gal

219.969 0.00022 0.22 0.0036 6.2288 1 0.8327

264.172 0.00026 0.2642 0.0043 7.4805 1.201 1

Mass kilogram kg

pound lb

hundredweight cwt

tonne

UK ton

US short ton sh ton

1 0.4536 50.802 3 1000 1016.05 907.185

2.2046 1 112 2204.62 2240 2000

0.0197 0.0089 1 19.6841 20 17.8571

0.001 0.000454 0.0508 1 1.0161 0.9072

0.00098 0.000446 0.05 0.9842 1 0.8929

0.0011 0.0005 0.056 1.1023 1.12 1

Density gram per millilitre g/ml

kilogram per cubic metre kg/cm 3

pound per cubic root lb/l't 3

pound per cubic inch lb/ in 3

1000 1 16.02 27679.9

62.428 0.062 1 1728

0.0361 0.000036 0.00058 1

1 0.001 0.016 2 7.6807

Heat flow rate watts

w 4.1868 1.163 0.2931

calorie per second cal/ s

kilocalorie per hour kca[/hr

British thermal unit per hour Btu/hr

0.2388

0.8598 3.6 1 0.252

3.4121 14.286 3.9683 1

l

0.2778 0.07

820

Engineering Data

Force kilonewton kN

kilogram force kgf

pound force lbf

pound a I pdl

1 0.00981 0.0044 0.000138

101.972 1 0.4536 0.0141

224.809 2.2046

7233.01 70.9316 32.1740 1

1

0.83]]

Torque newton metre Nm

kilogram force metre kgfm

pound force foot lbf ft

pound force inch lbf/in

0.102 1 0.1383 O.Oll5

0.7376 7.23 30 1

8.8508 86.7962 12

0.0833

l

1 9.8067 1.3558 0.113

Power watt

w 1 9.8067 735.499 1.3558 745.70

kilogram force metre per second kgfm/sec

metric horse power

foot pound force per second ft lbf/sec

horse power hp

0.102 1 75 0.1383 76.0402

0.00136 0.0133 3

0.7376 7.2330 542.476 1 550.0

0.00134 0.01315 0.98632 0.00182

1.

0.00184 0.0139

Mass volumetric rate of flow: liquids lb/hr US gal/min= 500 x SGl

m3 /h

SG 1 = water= 1 at 60°F

SG 2

=

O.O~~gjh

= water= 1 at 4°Celcius

l

Standards and Designations

821

linear conversions Fractions to decimals to millimetres Inch

I /64

1/32

3/64 1/16 5/64 3/32 7/64 1/8 9/64 5/32 I 1/64 3/16 13/64 7/32 15/64 1/4 17/64 9/32 19/64 5/16 21/64 11 /32 23/64 3/8 25/64 13/32 27/64 7/ 16 29/64

Decimal-inch

Millimetre

rnch

0.003937 0.007874 0.011811 0.015625 0.015748 0.01968 5 0.023622 0.027559 0.03125 0.031490 0.035433 0.03937 o.o4o87S 0.0625 O.On125 0.078740 0.09375 0.109375 0.118110 0.] 25 0.140625 0.15625 0.157480 0.171875 0.1875 0.196850 0.203125 0.21875 0.234375 0.236220 0.250 0.265625 0 .275591 0.28125 0.296875 0.3125 0 .314%1 0.328125 0.34375 0.354331 0.359375 0 ..375 0 ..390625 0.393701 0.40625 0.421875 0.433071 0.4375 0.45312'>

0.1 0.2 0.3 0.3%9 0.4 0.5 O.fl 0.7 0.7938 0.8 0.9 1 1.1906 1.5875 1.9844 2 2.3813 2.7781 3 3.175 3.5719 3.%88 4 4.3856 4. 7625 5 5.1594 5.5563 5.9531 6 6.350 6.7469 7 7.1438 7.5406 7.9375 8 8.3344 8.7313 9 9.1281 9.525 9.9219 10 10.3188 10.7156 11 11.1.125 11.5094

15/32 31/64 1/2 33j64 17/32 35/64 9/ 16 37/64 19/32 39/64 5/8 41 /64 21 /32 43/64 11/16 45/ 64 23/ 32 47/64 3/4 49/64 25/32 51 /64 I 3/ 16 53/64 27/32 55/64 7/8 57/64 29/32 59/64 15/16 61 /64 31 /32 63/64 I in

Decimal-inch

Nlillimetre

0.4o875 11.9063 0.472441 12 0.484375 12.3031 0.500 12 .700 0 .511811 13 0.515625 13.0969 0.53125 - - 13.4938 0.546875 13.8906 0.551181 14 o.5o25 14.2875 0.578125 14.6844 0.590551 15 0.59375 15.0813 0.609375 15.4781 0.625 15.875 0.629921 16 16.2719 0.640625 0.65625 16.6688 o.o69291 17 o.o71875 17.0656 0.6875 17.4625 0.703125 17.8594 0.708661 18 0.71875 18.2563 0 .734375 18.6531 0.748031 19 0.750 19.050 o.765o25 19.4469 19 .8438 0. 78125 0.787402 20 0.796875 20.2406 0.8125 20.6375 0.826772 21 0.828125 21.0344 0.84375 21.4313 0.859375 21.8281 0.86()142 22 - - -22.225 0 .875 0 .890625 22.6219 0.905512 23 0.90625 23.0188 0.921875 23.4156 0.9375 23.8125 0.944882 24 0.953125 24.2094 0.96875 24.6063 0.984252 - -- - 25 0 .984375 25 .0031 25.400 1

822

Engineering Data

Millimetres to inches Milli-

Inches

metres ()

0 . 039 ~7

()

10 20 30 40 50

nO

70 80 90

roo 110 120 130 140

150 160 170 180 190 200 210 220 230 240 250 260 170 281)

290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 4 70 480 490 500 5[() '>20 530 540 550 560 570 580 S90 600 610 620 630 640 650 660 670 680 690 700 710 720 730 740

0.39370 078740 1.18110 1.5 7480 l. 968 so 2.36220 2.7559 1 3.1496 1 3.54331 3.93701 4.33071 4 72441 5. 11811 5.5 1181 5.905 51 6.29921 6.69291 7.08661 7.480 31 7 87402 s 26772 8 ri6142 9.05512 9.44S82 9.84252 lll.2362 10.6299 11.0236 J 1.417 3 11.8110 12.2047 12.5984 12 .9921 13 .38 58 13.7795 14.1732 14. 56fiY 14 .9606 15.3543 15 .7480 16. 1417 16.53'54 16.929 1 17.322X 17.7 165 18. 1102 18.5039 18.89 76 19.2913 19.6850 20.0787 20.4 724 208661 21.2 598 21.6535 22.0472 22.4409 22.8346 23.2283 23.6220 24.0157 24.4094 24.8031 25.1969 25 .5906 25.9843 26.3780 26.77 17 27. 1fi54 27.5591 27.9528 28.3465 28.740 2 29.1 339

0.4 3307 0.82677 1.22047 1.614 1 7 2.00787 2.40157 2.79528 3.18898 3.58268 3.97638 4.37008 4. 76378 5.15 741! 5.55llS 'i.':/4488 6.33858 6.73228 7. 12598 7.51969 7.9 133':1 8. 30709 8 .70079 9.09449 9.488 I 9 9 S8189 10. 2 756 10.6693 I 1.0630 1l.45fi7 11.8 504 12.2441 12.6378 J 3.031 5 13.4251 13.8189 14.2 126 14.6063 15.0000 15. 3937 15 .7874 16.1 8 11 16. 5748 16.9685 17.3622 17.7559 .18.1496 18.5433 18.9370 19.3307 19 7244 20.1 181 20.5118 20.9055 2 1.2 992 21.6929 22.0866 2 2.4803 22.8740 23.2677 23 .6614 24.05 51 24.4488 24.842 5 25.2362 2 5.6299 26.0236 2 f>.41 37 26.!! 11 0 27.2047 2 7. 5984 27.9921 28.3858 28 7795 29. 1732

2

3

4

0.07M74 0.47244 0.86614 1.2 5984 1.65354 2.04724 2. 440')4 2.8 3465 3. 22835 3.62205 4.01575 4.4094 5 4.80315 'i. 19685 5.59055 5.98425 6.37795 6.77165 7.16535 7 55906 7.95276 8.34646 8.74016 9.1 338(, 9. 52 756 9.921 26 10.3150 10.7087 1 1.1024 11.4961

0.11811 0.51181 0.90551 1.29921 1.69291 2.086() I 2.4803 1 2.87402 3.26772 3.66142 4.0551 2 4.448 S2 4.84 252 5.23()22 5.62992 6.02 362 6.41732 6.81102 7.20472 7.59843 7.99213 8.38583 8.77953 9.17323 9.56693 9.96063 10.3543 l0.74XO 11.1417 1 I .53 54 11.9291 12.3228 1.2 .7165 I 3 ll02 13.5039 13 .8976 14.29 13 14.6850 I 'i.0787 15.4724 15 .86 61 16.259S 16.6535 17.0472 17.4409 I 7.8346 18.2283 18 .6220 19.0157 19.4094 191W3J 20.1969 20.5906 20.9843 21.3 780 21.7717 22.1654 22.5591 22.9528 23.3465 23.7402 24 . 1339 24. 5276 24.9213 25.3150 2 5. 7087 26.1024 26.4961 26 8898 27.2835 27.6772 28.0709 2fL4646 28.8583 29. 2 520

0.15748 0.55118 0.94488 1.33858 ).73 228 2.12598 2.5 1969 2.91339 3.30709 3.70079 4.09449 4.488 19 4.88 l R9 5.27559 S.!i6929 6.0h299 6.4 5669 6.85039 7.24409 7.6 3 780 8.03 1 50 8.425 20 8.81890 9.21260 9.60630 I 0.0000 10.39 37 10.7874

1 1.~89 8

12.2835 12 .6772 13.0709 J 3.4 64fi 13.858 3 14.2 .520 14.64 57 15.0394 15.433 1 15.8268 I 6.2205 16.6142 17.00 7') 17.401 6 17.7953 18.1 891J 18.5827 18.9764 1':1.3701 19.7638 20.1575 20.55 12 20.9449 2 1.3386 21.7323 22.1260 22.5197 22.9134 23.3071 2 3. 7008 24.0945 24.4882 24.8819 2 5.2756 2 5.6693 26.06 30 26.4567 26.8504 27.2441 27.6378 28.0315 28.4252 28.8189 29.2 126

ll.liJlJ

11.5 748 I 1.9685 1.2.3622 12. 7559 1 3.14% 13.5433 13.9370 14.3307 14.7244 15.1181 15.51 18 15.9051 I 6.2992 lfi.6929 ]70866 174803 I 7 8740 18.2677 18.fih14 J 9.055 1 19.4488 19.8425 20.2362 20.6299 21.0236 21. 41 7 ~

21.8110 22.204 7 22.5984 22.9':121 23.3858 23 7795 24.1732 24.5669 24.9606 25.3543 2 5. 7480 26.1417 26.5354 26.9291 27.3228 27.7165 28.1102 28.5039 28.8976 29.2913

6 0 . 1968 5 0 .59055 0 .98425 1.3779 5 1.77165 2.16535 2.55906 1 95276 3.34646 3.7401 6 4 .13386 4.5275h 4 .92l26 5. 314% 5.70866 6.10236 6.4%0 6 (i 88976 7.28346 7.677 17 8 0708 7 1l46457 8.8 5827 9.25197 9.64567 10.03 94 10.43 31 IO.X268 11.220 5 11.6142 12.(10 79 12.4016 12.7953 J 3.1890 13 582 7 13.97(>4 14.3701 14.7638 1 5. 157'5 1 s 5512 15.9449 16.HH6 I 6.7 323 17 1260 17.5197 17.91 34 11U071 1 S. 700X I 9 0945 I 9.481l2 19 8819 20.275h 20.669 3 21.06W 2 1.4567 2 1.85 04 22.24 41 22.6378 23.03 1 5 23.42 52 23.8189 24.2126 24.6063 25.0000 25.3937 25.7874 26.18 11 26.574 8 26.9685 27 ..3622 27.7559 28.1496 28 54 33 28.'!370 29.3307

0.23622 0.6299 2 1.02 362 1.417 32 1.8 ll 02 2.204 72 2.59H43 2.99213 3.3!!583 3.779'i3 4.17323 4. 5nn9 3 4. 9606 3 5.354.\3 5. 74803 6.14173 6.53543 6.9291 3 7.322X3 7.716~4

8.1 I ll 24 IU0\94 IL89764 'J.29 134 9.68504 10.0787 I 0.4 724 10.8661 11.2598 I I .f15 3S 12.04 72 I 2.4409 12.8346 13.2283 13.6220 14.0157 14.4094 14.803t 15 I %9 15. 5906 I 3.9R43 16.3 780 16.77 17 17.1654 I. 7. 559 I 17.9528 18.3465 18.7402 19. I 339 19.5 276 19.921 3 20.~150

20. 7087 21.1024 21.4%1 2l.llll98 22 2835 22.6772 23.0 709 23.4646 .U8583 24.2520 24.64'>7 2 5.0394 25.433 I 2 '>.ll268 2h.220~

26.6142 27.0079 2 7.4016 27.7953 28. I 890 28.5827 28.97()4 29.3701

7

8

<)

0.27~S':I

0.314.90 o. 7086n 1. 10 236 1.49606 1.88976 2.21) 346 2.(>7717 3.07087 3.4645 7 3.85827 4.25 19 7 4 .645n 7 5.03937 5.4 3 307 5.82677 6.2204 7 6.6141 7 7.0078 7

0.3 5433 0.74803 1.14173 1.53543 1.92913 2. 3228 3 2.71654 3.11024 3.503')4 3.89764 4.2'1 I ~4 4.68'i1H 5.07R7-I '5.47 2-11 ~.X66 14 6.2 ~984 6.h5 ~'i4 7.0'17 24 7.44094 7.83465 8.228 j 'i IL6221l5 9.01575 9.4094 5 9.8031 5 JO.I969 10.5906 111.984 3 I 1.3 780 11. 7717 I 2.16'>4 12.:; '>9 1 12 9521> I 3.l465 13.7402 14.1 )19 14.'>276 14 .':1213 I 5. 3 1 '50 15.7087 I h. 1024 I 6.4%1 I 6.8.~')8 17.28 ~5 I 7.6772 18 0709 18.4646 I ll.858 3 19 2 5 20 19.6457 20.0394 20.4 33 I .W.fi26X 21.220'> 21.61 42 22.0079 22.4016 2 2 79 53 2 3. I 890 2 ~.'>827 23.97h4 24.3701 24.7638 25. 1575 25.5512 2 5.9449 26.3386 26. 7 323 27. 12r>0 27.5 197 27.9 134 28.3071 28.7008 29 .0 94 5 294882

0.66929 I .06299 I .41669 1.8 SO JY 2.24409 2.63780 3.031 50 3.42 520 3.81890 4.21260 4.60630 'i.OOOIJO ~.39370

'i.78740 h.! X110 6.57480 h.%850 7.36220 7.75591 8.14961 tl. 54l31 8.93 70 I 9.33071 9.72441 I l l.l 18 I 10.51 I 8 I 0.9055 I 1.29':12 11 .6929 12.086h l2.4S03 12.8740 I 3.2677 13.6614 14.0 5'5 I 14.44 8!1 14.!!425 15.2362 I 5.6299 1<>.0236 16.4 I 7 3 16 .8 110 17.2047 l7.'i984 17 9921 I 1). 385!! 18. 7795 19 .17 32 1 ':!.5669 19.9606 20.3543 20 .7480 21.1417 21.5 3 54 21.929 1 22. 3 228 22.7 165 23.1102 23.5039 23.8976 24.291.3 24.6850 25.0787 25.4724 25.8h61 26.2 598 26.6535 27.0472 27.4409 27.83 46 21U283 28.6220 290157 29.4094

7.4 01~ 7

7.7952H 1<. I 88'J8 IL 51<268 8.97h31.i 9. 37008 9.76378 I 0.1 'i 7'i 10.5 5 I 2 Ill. 944 y 1 I. 3 }IJ() I 1.7323 12.1260 12 . 'i I 97 12.9134 I 3.3071 I 3. 7008 14.09 45 14.48 82 14.8X19 ! S.275f> I 'i.6693 16.0610 1h.·l5b7 16.8 '5 1'14 17.2441 17.6 378 18.0 .1 15 18.42'i2 I 8./l 189 I 'J.2 12 6 19.6063 20.0000 20.3937 20.7874 2 1. I X 1 I 21.S74S 21.961l5 22.3622 22.75 59 23.14% 23.5433 23.9370 24.3307 24.7244 2 5.1 18 I 2 'i.51 18 2'i.'J055 26.6992 26.6929 27.0866 27.41HH 27.8 740 28.2677 28.6614 29.0551 29.4488

Standards and Designations

823

Temperature conversion chart Celsi us to Fahrenheil Note: The numbers in boldface refer to temperature in degrees. either Celsius or Fahrenheit. which it is desired to convert to the ot·her scale. If converting from l'ahrenh.eit to Celsiu~ degrees. the equivalent temperature will be found in the left column: while if converting from Celsius to Fahrenheit, the answer will be found in the column on the right. Fahrenheit Celsius

Celsius

-7 3. 3 -67.S -62.2 -59.4 -56.7 -53.9 -'il.J

-48.3 -45.6 -42.8 -40.0 -3 7.2 -.34.4 -3 .1.7 -28.9 - 26.1 -23.3 -20.6 -17.8 -17.2 -16.7 -16.1

-100 -90 -80 -75 -70 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 I 2 3

-I 'i.6 -15.0

4 5

-14.4 - 13.9 -13.3 -12.8 -) 2.2 -11.7 -1 J. 1 -10.6 -10.0 -9.4 -8.9 -8.3 - 7.8 - 7.2 -6.7 -6.1 -5.6 -5.0 -4.4 -3.9 -1.3 -2.8 -2.2 -.1.7 -l.l -0.6 0.0 0.6

6 7 8 9 10

1.1

1.7 2.2

I I

12 13 14 )5 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

34 35 36

-.14H.O -130.0 -112 .0 -103.0 -94.0 -85.0 -76.0 -67.0 -58.0 -49.0 -40.0 - 31.0 -22.0 - 1 3.0 -4.0 5.0 14.0 2 3.0 32.0

33.8 35.6 37.4 39.2 4 .I .0 42.8 44.6 46.4 4R.2 50.0 51.8 5 3.h 55.4 57.2 59.0 oo.8 62.6 64.4 n6.2 fi8.0 h9.8 71.6 7 3.4 75.2 77.0 78.8 80.6 82.4 84.2 86.0 R7.S 89.6 91.4 93.2 95.0 96.8

2.8 3.3 3.9 4.4 5.0 5.6

6.1 6.7 7.2 7.8 8.3 8.9 9.4 10.0 10.6 1 I. J ll.7 12.2 12.8 13.3

13.9 14.4

l 5.0 1 5.6 16.1 16.7 17.2 17.8 18.3 18.9 19.4 20.0 20.h 21.1 21.7 22.2 22.8 23.3 23.9 24.4 25.0 25.6 26.1 26.7 27.2 27.8 28.3 28.9 29.4 30.0 30.6 31.1 31.7 32.2 32.8

The formulae on the right: may also be used for converting Celsius or Pahrenheit degrees into the other scale.

Fahrenheit Celsius

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91

98.6 100.4 102.2 104.0 105 .8 107.6 109 .4 111.2 113.0 114.8 116.6 Il8.4 120.2 122.0 J 23.8 125.6 127.4 J 29.2 l3 1.0 132.8 134.h 13hA 138.2 140.0 141.8 143.6 145.4 147.2 149 .0 150.8 152.6 154.4 156.2 158.0 159.8 161.6 163.4 165.2 1n7.o 168.8 170.() 172.4 174.2 176.0 177.8 179.6 181.4 183.2 1S5.0 186.8 188.6 190.4 192.2 194.0 195.8

33.3

33.9 34.4 35.0 3 5.6 36.1 36.7 37.2 37.8 43.0 49 .0 54.0 60.0 66.0 71.0 77.0 82.0 88.0 93.0 99 .0 100.0 104.0 110.0 116.0 l 2 ].() 12 7.0 132.0 138.0 143.0 149.0 154.0 1f>O.O 16n.o 171.0 177.0 182.0 188.0 193.0 199.0 204.0 210.0 216.0 221.0 227.0 232.0 238.0 243.0 249.0 254.0 2 f>O.O 266.0 271.0 277.0 282.0 288.0

Degrees Cets. oc

=~

Fahrenheit Celsius

92 93 94 95 96 97 98 99 100 J I0 120 130 140 150 160 170 180 190 200 210 212 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550

Fahrenheit

197.6 199.4 201.2 203.0 204.8 206.6 208.4 210.2

293 299 304 310 316 321 327 332

560 570 580 590 600 610 620 630

212 .0 230.0 248.0 266.0 284.0 302.0 320.0 338.0 3 56.0 374.0 392.0 410.0 414.0 428.0 446.0 4n4.o

338 343 349 354 3()() 366 3 71 377 382 388 393 399 404 410 416 421 427 432 438 443 449 454 460 466

640 650 660 670 680 690 700 710 720 730 740 750 760 770 780 790 800 810 820 830 840 850 860 870

471 477 482 488 493

880 890 900 910 920 930 940 950 960 970 980 990 1000 1050 1100 IISO 1200 1250 1300 1350 1400 1450 1500

482.0 500.0 518.0 536.0 5 54.0 572.0 590.0 ()08.0 626.0 644.0 662.0 680.0 h98.0 716.0 734.0 752.0 770.0 788.0 80n.o 824.0 842.0 860.0 878.0 896.0 914.0 932.0 950.0 968.0 986.0 1004.0 1022.0

(°F + 40) - 40

499 504 510 'il6

521 527 532 538 566 593 n21 649 677 704 732 760 788 816

1040.0 1058.0 1076.0 ] 094.0 1112.0 ] 1 30.0 1148.0 1166.0 1 184.0 1202.0 1220.0 1238.0 1256.0 1274.0 1292.0 1.310.0 1328.0 1346.0 1364.0 1382.0 1400.0 1418.0 1436.0 1454.0 1472.0 1490.0 1508.0 1526.0 1544.0 1562.0 I 580.0 1598.0 1616.0 1634.0 1652 .0 1670.0 168H.O 1706.0 1724.0 1742.0 1760.0 1778.0 1 796.0 1814.0 1832.0 1922.0 2012.0 2102.0 2192.0 2282.0 2372.0 2462.0 2552.0 2642.0 2732.0

Degrees rilhr. °F = ~ ( C + 40) - 40 ~

824

Engineering Data

OF = 9/5

Temperature

0 (

c·

(•

r•

-213

-419 -410

r·

c·

+32

300

r·

=

oc + 32 0

5/9 ( f - 32)

c·

f"

c·

f"

900

16SO

1100 +100 610

-710

310

610

1100

910

!ISO 100 1110 1800 +700 400

-200

1000

100 1300

1810 -300

800 1310 1900 -1SO -ISO

•ISO

·300

ISO

410

1010

810

1400 1910 -200 •3SO 900 1410 2000 -100

-ISO

+200

1100

SOD

•400 9SO 1100 2010 ·410 1000 1110 810

.ISO

•2SO

liSO

2100

·100 lOSO 1600 7110

•SIO 1100 +11

+300

600

900

1610

1100

1190

Standards and Designations

82 5

Pressure conversions Pounds per square inch (lbf/in 2 ) to bar 1- 40

41- 80

81-200

205-500

510-900

910-1500

bar

lbf/in 2

bar

lbf/ in 2

bar

lbf/in 2

bar

lbf/in 2

bar

lbf/ in 2

bar

0.07 0.14 0.21 0.28 0.34

4I 42 43 44 45

2.83 2.90 2. 96 3.03 1.10

81 82 83 84 85

5. 58 5.65 5.72 5.79 5.86

205 210 215 220 225

14.13 14.48 14.82 15.17 15. 51

510 520 530 540 550

35.16 35.85 36.54 37.23 37.92

910 930 940 950

62.74 63.43 64.12 64.81 65.50

10

0.41 0.4H 0.55 0.62 0.69

46 47 48 49 50

3.17 3.24 3.31 3.38 3.45

86 87 88 89 90

5.93 6.00 6.07 6.14 6.21

230 235 240 245 250

15.86 16.20 16.5 5 16.89 17.24

SfiO 570 580 590 600

38.61 39.30 39.99 40.68 41.37

960 970 980 990 1000

66.19 66.88 67.57 68.26 68.95

ll 12 13 14 15

0. 76 0 .8 3 0.90 0.97 l.03

51 52 53 54 55

3.52 3.59 3.65 3.72 3.79

91 93 94 95

6.27 6.34 6.41 6.48 6.55

255 260 265 270 275

17.58 17.93 18.27 18.62 18.96

610 620 630 640 650

42.06 42.75 43.44 44.13 44.82

1010 1020 1030

69.64 70.33 71.02 71.7 J 72.39

16 17 18 19 20

1.10 1.1 7 ].24 1.31 1.38

56 57 58 59 60

3.86 3.93 4.00 4.07 4.14

96 97 98 99 100

6.62 6.69 6.76 6.83 6.89

280 285 290 295 300

19.31 19.65 19.99 20.34 20.68

660 670 680 690

45 . 51 46.19 46.88 47.57 48.26

21

1.4 5 1.52 1.59 1.65 1.72

61 62 63 64 65

4 .2 1 4.27 4.34 4.41 4.48

lOS 110 liS 120 125

7.24 7.58 7.93 8.27 8.62

310 320 .330 340 350

21.3 7 22.06 22.75 23.44 24.13

710

66

28 29 30

1. 79 1.86 1.93 2.00 2.07

68 (,9 70

4.55 4.62 4.69 4.76 4.83

130 135 140 14 5 1 50

8.96 9.31 9.65 10.00 10.34

360 370 380 390 400

31 32 33

2.21 2.28 2.34

35

2.41

4.90 4.90 5.03 5.10 5.17

155 160 165 170 175

10.69 11.03 11.38 11.72 12.07

410 420

34

71 72 73 74 75

36 37 38 39 40

2.48 2.55 2.62 2.69 2.7n

76 77 78 79 80

5.24 5.31 5.38 5.45 5.52

180 185 190 195 200

12.41

lbf/in 2

1 2 3 4

5 ()

7 8 9

22 23 24 25 26 27

2.14

fi7

92

12.76 13.10 13.44 13.79

920

1040 1050

1080 1090 llOO

73.08 73.77 74.46 75.15 75.84

730 740 750

48.95 49.64 50.33 51.02 51.71

1120 1140 1160 1180 1200

77.22 78.60 79.98 81.36 82.74

24.82 25 .51 26.20 26.89 27.58

760 770 780 790 800

52.40 53.09 53.78 54.47 55.16

1220 1240 1260

84.12

440 450

28.27 28.96 29.65 30.34 31.03

810 820 830 840 850

460 470 480 490 500

31.72 32.41 33.09 33.78 34.47

RoO 870 880 890 900

4.30

700 720

1060

10 70

1300

85.49 86.87 88.25 89.63

55.85 56.54 57.23 57.92 58.61

1320 1340 13 60 1380 1400

91.01 92.39 93.77 95.15 96.53

59.29 59.98 60.67 61.36

1420 1440 1460 1480 1500

97.91 99 .28 100.66 102.04 103.42

62.05

1280

Standards and Designations

827

Steam tables Metric SI units Pressure

Specillc enthalpy W
Evaporation (hrg)

Steam (bg)

Specific volume steam (v8 )

kJ/kg

k) / kg

k)/kg

m 3 /kg

Temperature bar

0 .30 0 . 50 0 .75

kPa

absolute

0.95 0

0.10 0 .20

30.0 50.0 75.0 95.0 ()

gauge

10.0 20.0

0.30 0.40 0.50 0.()()

30.0 40.0 50.0 60.0

0.70 0.80 0.90

70.0 80.0 90.0 100.0 110.0 120.0

1.00 1.10 1.20

1.30 1.40 l. so 1.60 1.70 1.80

130.0 140.0 150.0 160.0 170.0 180.0

1.90 2.00 2.20 2.40 2.60 2 .80 3.00 3.20 3.40 3.60

190.0 200.0 220.0 240.0 260.0 280.0 300.0 320.0 340.0 360.0

3.80 4 .00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50

380.0 400.0 450.0 500.0 550.0 600.0 650.0 700.0 750.0 800.0 850.0

oc 69.10 81.33 91.78 98.20

289.23 340.49 384.39 411.43

2336.1 2305.4 2278.6 2261.8

2625 .3 2645.9 2663.0 2673.2

5.229 3.240 2.217

100.00 102.66 l05.10 107.39 109.55 111.61 113.56 115.40 117.14 118.80 120.42

419.04 430.2 440.8 450.4 459.7 468.3 476.4 484 .1 491.6 498.9

225 7.0 2250.2 2243.4 22 3 7.2 2231.3 2225.6 2220.4 2215.4 2210.5 2205.6

2676.0 2680.4 2684.2 2687.6 2691.0 2693.9 2696.8 2699.5 2702.1 2704.5

505.6 512.2 518.7 524.6 530.5 536.1 541.6 547.1 552.3

2201.1 2197.0 2192.8 2188.7 2184.8

2706.7 2709.2 2711.5 2713.3 2715.3

2181.0 2177.3 2173.7 2170.1 2l(i6.7

2066.0 2056.8 2047.7

2717.1 2718.9 2720.8 2722.4 2724.0 2725.5 2728.6 2731.4 2733.9 2736.4 2738.7 2741.0 2742.9 2744.9 2746.9 2748.8 2753.0 2756.9 2760.3 2763.5 2766.5 2769.1

1.673 1.533 1.414 1.312 1.225 1.149 1.083 1.024 0.971 0.923 0.881 0.841 0.806 0.773 0.743 0.714 0 .689 0 .6()5

2039.2 2030.9 2022.9

2771.7 2774.0 2776.2

121.96 123.46 124.90 126.28 127.62 128.89 130.13 131.37 132.54 133.69 135.88 138.01 140.00 141.92 143.75 145.46 147.20 148.84 150.44 151.96 155.55 158.92 162.08 165.04 167.83 170.50 173 .02 175.43 177.75

557.3 562.2 571.7 580.7 589.2 597.4 605.3 612 .9 620.0 627.1 634.0 640.7 655.3 670.9 684.6 697.5 709.7 721.4 732.5 743.1 753.3

2Hi3.3 2156.9 2 150.7 2144.7 2139.0 2133.4 2128.1 2122.9 2117.8 2112.9 2108.1 2096.7 2086.0 2075.7

1.777

0.643 0.622 O.f>03

0.%8 0.531) 0.509 0.483 0.461 0.440 0.422 0.405 0.389 0.374 0.342 0.315 0.292 0.272 0.255 0.240 0 .227 0.215 0.204

828

Engineering Data

Steam tables Metric SI units Pressure

Specific enthalpy

Specific volume

Temperature bar

9.00 9.50 10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 14.00 14.50 15.00 1h.OO 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 32.00 33.00 34.00 35.00 36.00 37.00 38.00 39.00 40.00 42.00 44.00 46.00 48.00 50.00

kPa

oc

Water (hr) k)/kg

900.0 950.0 1000.0 1050.0 1100.0 1150.0 1200.0 1250.0 1300.0 1350.0 1400.0 1450.0 1500.0 1600.0 1 700.0 1800.0 1900.0 2000.0 2100.0 2200.0 2300.0 2400.0 2500.0 2f>OO.O 2700.0 2800.0 2900.0 3000.0 3100.0 3200.0 3 300.0 3400.0 3 500.0 3600.0 3700.0 3800.0 3900.0 4000.0 4200.0 4400.0 4600.0 4800.0 5000.0

179.97 182.10 184.13 186.05 188.02 189.82 191.68 193.43 195.10 196.62 198.35 199.92 201.45 204.38 207.17 209.90 212.47 214.96 217.35 219.65 221.85 224.02 226.12 228.15 230.14 2 32.05 2 33.93 235.78 237.55 239.28 240.97 242.63 244.26 245.86 247.42 248.95 250.42 251.94 2'>4.74 257.50 260.13 262.73 265.2()

763.0 772.5 781.6 790.1 798.8 807.1 815.1 822.9 830.4 837.9 845. 1 852.1 859.0 872.3 885.0 897.2 909.0 920.3 931.3 941.9 952.2 962.2 972.1 981.6 990.7 999.7 1008.6 1017.0 102 5.6 1033.9 1041.9 1049.7 1057.7 10115.7 1072.9 1080.3 1087.4 1094.6 1108.6 LJ22.1 1 13 5.3 1148.1 1160.8

Evaporation

(hr~tl

Steam (hg)

kJ/kg

kJ!kg

2015.1 2007.5 2000.1 1993.0 1986.0 J 979.1 1972.5 1%5.4 1959.6 1953.2 1947.1 1941.0 1935.0 1923.4 1912.1 1901.3 1890.5 1880.2 1870.1 1860.1 1850.4 1804 .9 1 831.4 1822.2 1813.3 1804.4 J 795.6 1787.0 1778.5 1770.0 J 761.8 1753.8 1745.5 1737.2 1729.5 1721.6 1714.1 1706.3 1691.2 1676.2 1661.6 1647.1 1()32. 8

277R.l 27HO.O 2781.7 2783.3 2784.8 2786.3 2787.6 2788.8 2790.0 2791.1 2792.2 2793.1 2794.0 2 79 5. 7 2797.1 2798.5 2799.5 2800.5 2801.4 2802.0 2802.6 2803.1 2803.5 2803.8 2804.0 2R04.1 2804.2 2804.1 2R04. I 2803.9 2803 .7 2803.5 2803.2 2802.9 2802.4 2801.9 2 80 l. ') 2 800.9 2799.8 2798.2 27%.9 2 795.2 2793.6

steam (v~) m.\/kg

0.194 0.185 0.177 0.171 0.163 0.157 0.151 0.148 0.141 0.136 0.132 0.128 0.124 0.117 0.110 0.105 0.100 0.0949 0 .0906 0.0868 0.0832 0.0797 0.0?68 0.0740 0.0714 0.0689 0.0()66 0.0645 0.0625 0.0605 0.058 7 0.0571 0.0554 0.0539 0.0524 0.0510

o.o4n 0.0485 0.0461 0.0441 0.0421 0.0403 0 0386

Standards and Designations Imperial units

OF

Sensible heat Btu/Lb

Latent heat Btu/lb

Total heat Btu/lb

Volume dry saturation cu ft/lb

15 10 5

179.0 192.0 203.0

147.0 160.0 171.0

991.0 983.0 976.0

1138.0 1143.0 1147.0

51.41 39.40 31.80

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58

212.0 218.5 224.5 230.0 234.8 239.4 243.7 247.9 251.7 255.4 258.8 262.3 265.3 268.3 271.4 274.0 276.7 279.4 281.9 284.4 286.7 289.0 291.3 293.5 295.6 297.7 299.7 301.7 303.6 305.5 307.4 309.2 310.9 312.7 314.3 316.0 317.7 319.3 320.9 322.4 323.9 325.5 326.9

180.2 186.8 192.7 198.1 203.1 207.9 212.3 216.4 220.3 224.0 227.5 230.9 234.2 273.3 240.2 243.0 245.9 248.5 251.1 253.7 256.1 258.5 260.8 263.0 265.2 267.4 269.4 271.5 273.5 275.3 277.1 279.0 280.9 282.8 284.5 286.2 288.0 289.4 291.2 292.9 294.5 296.1 297.6

970.6 966.4 962.6 959.2 956.0 952.9 950.1 947.3 944.8 942.4 940.1 937.8 935.8 933.5 931.6 929.7 927.6 925.8 924.0 922.1 920.4 918.6 917.0 915.4 913.8 912.2 910.7 909.2 907.8 906.5 905.3 904.0 902.6 901.2 900.0 898.8 897.5 896.5 895.1 893.9 892.7 891.5 890.3

1150.8 1153.2 1155.3 1157.3 1159.1 1160.8 1162.3 1163.7 1165.1 1166.4 1167.6 1168.7 1170.0 1170.8 1171.8 1172.7 1173.5 1174.3 1175.1 1175.8 1176.5 1177.1 1177.8 1178.4 1179.0 1179.6 1180.1 1180.7 1UH.3 1181.8 1182.4 1183.0 1183.5 1184.0 1184.5 1185.0 1185.5 1185.9 1186.3 1186.8 1187.2 1187.6 1187.9

26.80 23.80 21.40 19.40 17.90 16.50 15.30 14.30 13.40 12.70 12.00 11.40 10.80 10.30 9.87 9.46 9.08 8.73 8.40 8.11 7.83 7.57 7.33 7.10 6.89 6.68 6.50 6.32 6.16 6.00 5.84 5.70 5.56 5.43 5.31 5.19 5.08 4.97 4.87 4.77 4.67 4.58 4.49

Temperature Pressure Inches of vacuum psig

()()

62 64 66 fi8 70 72 74 76 78 80 82 84

829

830

Engineering Data

Imperial units

Pressure

86 88 90 92 94 96 98 100

lOS 110 115 120 125 130 135 140 145 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400

Temperature

op

Sensible heat Btu/lb

Latent heat Btu/lb

Total heat Btu/lb

328.4 329.9 331.2 332.6 333.9 335.3 336.6 337.9 341.1 344.2 347.1 350.1 3 52.8 355.6 358.3 360.9 363.5 365.9 370.7 375.2 379.6 383.7 387.7 391.7 395.5 399.1 402.7 406.1 409.3 412.5 415.8 418.8 421.7 424.7 427.5 430.3 433.0 435.7 438.3 440.8 443.3 445.7 448.1

299.1 300.6 302.1 303.5 304.9 306.3 307.7 309.0 312.3 315.5 318.7 321.8 324.7 327.6 330.6 333.2 335.9 338.6 343.6 348.5 353.2 357.6 362.0 366.2 370.3 374.2 378.0 381.7 385.3 388.8 392.3 395.7 398.9 402 .1 405.2 408.3 411.3 414.3 417.2 420.0 422.8 425.6 428.2

889.2 888.1 887.0 885.8 884.8 883.7 882.6 881.6 879.0 876.5 874.0 871.5 869.3 866.9 864.5 862.5 860.3 858.0 853.9 849.8 845.9 842.2 838.4 834.8 831.2 827.8 824.5 821.2 817.9 814.8 811.6 808.5 805.5 802.6 799.7 796.7 793.8 791.0 788.2 785.4 782.7 779.9 777.4

1188.3 1188.7 1189.1 1189.3 1189.7 1190.0 1190.3 1190.6 1191.4 1192.0 1192.7 1193.3 1194.0 1194.5 1195.1 1195.7 1196.2 1196.6 1197.5 1198.3 1199.1 1199.8 1200.4 1201.0 1201.5 1202.0 1202.5 1202.9 1203.2 1203.6 1203 .9 1204.2 1204.4 1204.7 1204.9 1205.0 1205.1 1205.3 1205.4 1205.4 1205.5 1205.5 1205.6

Volume dry saturation cu l't/lb

4.41 4.33 4.25 4.17 4.10 4.03 3.96 3.90 3.74 3.60 3.46 3.34 3.23 3.12 3.02 2.93 2.84 2.76 2.61 2.48 2.35 2.24 2.14 2.04 1.96 1.88 1.81 1.74 1.68 1.62 1.5 7 1. 52 1.47 1.43 1.39 1.35 1.31 1.2 7 1.24 1.21 1.18 1.15 1.12

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Engineering Data

Nomogram for pipe losses 1000 900 800 700 600 500

Q 1/s

400

Q

= flow rate

d. '

"" internal diameter mm

I/ s

L1pP1 = pressure drop mm/m

300

v

= velocity m/ s

200

100 90 80 70 60

40

10 9 8 7

v

mm

mm/m

m/s

300

'

''

- 2

''

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4 6 8 10

100 '90

4

50

60'

40 30

2 20 1

0,4 0,6 0,8 1

200

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0,04 0,06 0,08 0.1 0,2

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500

30

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1000 900 800 700 600

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0,2

0,3 0,4 0,5 0,6 0,7 0 ,8 0,9 1

20

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40 60 80 100 ,200

40~

600 800' 1000

2 3 4 5 6 - 7 8

9 10

Standards and Designations

8 33

Nomograph solution of Manning's formula for discharge of circular pipes running full (n = 0.011) L.486

O=A where,

n

0 is the discharge in millions of gallons per day A is the area of wetted cross-section of the pipe in square feet n is the empirically derived coefficient used to represent the interior surface characteristics of the pipe R is the hydraulic radius of wetted cross-section of the pipe in feet Sis the slope of hydraulic gradient Slope of hydraulic gradient, in/ft ~

N

0

c

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Slope of hydraulic gradient n = 0.011

-

.o 6

Notes: l. Unless otherwise known, a value of 0.013 is recommended for n for pipes of all materials. 2.The velocity of flow (averaged over the wetted cross-section) should be kept between 2ft/sec and J 0 ft/sec.

834

Engineering Data

Nomograph solution of Manning's formula for discharge of circular pipes running full (n = 0.013) 1.486

Q=A n where,

Q is the discharge in millions of gallons per day A is the area of wetted cross-section of the pipe in square feet n is the empirically derived coefficient used to represent the interior surface characteristics of the pipe R is the hydraulic radius of wetted cross-section of the pipe in feet S is the slope of hydraulic gradient

Slope of hydraulic gradient, inlft

g

0 N

0

0

0

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100.0 r- - t-

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0 Slope of hydraulic gradient n = 0.013

Notes: 1. Unless otherwise known, a value of 0.013 is recommended for n for pipes of all materials . 2. The velocity of flow (averaged overthe wetted cross-section) should be kept between 2ft/sec and I 0 ft/sec.

Head-loss characteristics of water flow through rigid plastic pipe This nomograph pro I• ides approximate values for a wide range of plastic pipe sizes . .\lore precise values should be calculated from the Williams and Hazen formula. Experimenral test value of C ta constant for inside pipe roughness) ran ges from I 55 to 165 for various types of p lastic p1pe. Use of a value of 150 wi U ensure conservative friction-loss values. Values for bead loss on PVC and CPVC fittmgs and valves arc not available at the present time. Since directional changes and restrictions contribute the most head loss. use of head-loss data for comparable metal valves and fitt10gs w1li provide conservative values.

;.,_

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0

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0'1

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.,

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0

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ln11de diameter of

P•pe •n 1nches

0

Head lou •n PSI

oer >00 fl. of pipe

Head loss 1n feet per 100ft. of pipe

V:l

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tv

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<71

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N

rv

N------

0\D
THE VA LUES OF THIS GRAPH ARE BASED ON THE WILLIAMS & HAZEN FORMULA

100 1.852 91.852 I = .2083 I C ) X d4 .8655 WHERE:

f • Friction head in lee! of water per 100 feet. d

= Inside diameter of P•pe in

Q

= flow•ng oallons per m•nute

•nches.

Nomograph courtesy of Plastics Pipe Institute. a division of The Society of the Plast ics lndustry.

-

0

"'0 "'0

0

"'0

0

..;,., ..

"' "' omc-c.Nom"'•~ o

~

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~

V. ia ;_, N

;....

0

0

;.,

The nomograph is used by lining up values on the scale by means of a ruler or straight edge. Two independent variables must be set to obtain the other va lues. For example. line ( 1) indicates that 500 gallons per minute may be obtained with a 6-io inside diameter pipe at a head loss of about 0.65 pounds pa squ
!:1.

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83 6

Engineering Data

Weight (mass) density and specific volume of gases

The mass density (p) of a gas or vapour in lb/ ft 3 can be calculated from the following equations: -

l44P p = -RT where

P=

absolute pressure in lb/ in 2 (=gauge pressure+ 14. 7) R = individual gas constant T = absolute temperature in °Rankine -

MP P = 10.72T

where M = molecular weight

270P X Sg p = -- - T

where Sg is the pecific gravity of the gas or vapour. Table 1 gives the weight (mass) density for air at various temperatures and gauge pressures. It can also be used directly for steam. For other gases. multiply the corresponding mass density figure for air by the specific gravity of the gas. For example, for the m a ss density of butane at similar temperatures and pressures, factor table values by 2.06 7.

Table 1. Weight (mass) density of air lb/ft 3 for gauge pressures in lb/in 2

lb/ in 2

Air temperature

op 30 40

so 60 70 80 90 100 110 120 130 140 150 175 200 225 250 275 300 350 400 450 500 550

600

0

5

10

20

30

40

50

60

70

80

90

100

110

120

130

0.0811 0.0795 0.0782 0.0764 0.07 so 0.0736 0.0722 0 .0709 0.0697 0.068 5 0.0673 0.0662 0.0651 0.0626 0.0602 0.0580 0.05 59 0.0540 0.0523 0.0490 0.0462 0.0436 0.0414 0.0393 0.03 75

0.1087 0.1065 0.1048 0.1024 0.1005 0.0986 0.0968 0.0951 0.0934 0.0918 0.0902 0 .0887 0.0873 0.0834 0.0807 0 .0777 0.07 50 0.0724 0.0700 0.0657 0.0619 0.0585 0.0555 0.0527 0.0502

0.1363 0.1335 0.1314 0.1284 0.1260 0.1236 0.1214 0.1192 0.1171 0.1151 0.1131 0.1113 0.1094 0.1051 0.1011 0.0974 0.0940 0.0908 0.0878 0.0824 0.0776 0.0733 0.0695 0.0661 0.0630

0.1915 0.1876 0.1846 0.1804 0.1770 0.1737 0.1705 0.1675 0.1645 0.1617 0.1590 0.1563 0.1537 0.1477 0.1421 0.1369 0.1321 0.1276 0.1234 0.1158 0.1090 0.1030 0.0977 0.0928 0.0885

0.247 0.242 0.238 0.232 0.228 0.224 0.220 0.216 0.212 0.208 0.205 0.201 0.1981 0.1903 0.1831 0.1764 0.1702 0.1644 0.1590 0.1491 0.1405 0.1327 0.1258 0.1196 0.1140

0.302 0.295 0.291 0.284 0.279 0.274 0.269 0.264 0.259 0.255 0.251 0.246 0.242 0.233 0.224 0.216 0.208 0.201 0.1945 0.1825 0.1719 0.1624 0.1540 0.1464 0.1395

0.357 0.350 0.344 0.336 0.330 0.324 0.318 0.312 0.307 0.302 0.296 0.291 0.287 0.275 0.265 0.255 0.246 0.238 0.230 0.216 0.203 0.1921 0.1821 0.1731 0.1649

0.412 0.404 0.397 0.388 0.381 0.374 0.367 0.361 0.354 0.348 0.342 0 .337 0.331 0.318 0.306 0.295 0.284 0.275 0.266 0.249 0.235 0.222 0.210 0.1999 0.1904

0.467 0.458 0.451 0.440 0.432 0.424 0.416 0.409 0.402 0.395 ().388 0 .382 0.375 0 .361 0.347 0.334 0 .322 0.311 0.301 0.283 0.266 0 .252 0.238 0.227 0.216

0.522 0.512 0.504 0.492 0.483 0.474 0.465 0.457 0.449 0.441 0.434 0.427 0.420 0.403 0.388 0.374 0.361 0.348 0.337 0.316 0.298 0.281 0.267 0.253 0.241

0.578 0 .56 6 0.557 0.544 0.534 0.524 0.515 0.505 0.497 0.488 0.480 0.472 0.464 0.446 0.429 0.413 0.399 0.385 0.3 72 0.349 0.329 0.311 0.295 0.280 0.267

0.633 0.620 0.610 0.596 0.585 0.574 0.564 0.554 0.544 0 .535 0.525 0.51 7 0. 508 0.488 0 .470 0 .453 0.437 0.422 0.408 0.383 0.360 0.341 0.323 0.307 0.292

0. 688 0.674 0.663 0 .648 0.636 0.624 0.613 0.602 0.591 0.581 0.571 0.562 0.553 0.531 0.511 0.492 0.4 7 5 0.459 0.443 0.416 0.392 0.370 0.351 0 .334 0.318

0.743 0.728 0.71 7 0 .700 0.687 0.6 74 0.662 0 .650 0.639 0 .628 0.61 7 0.607 0.597 0.573 0.552 0.531 0.513 0.495 0.479 0.449 0.423 0.400 0.379 0.360 0.343

0. 798 0.7 82 0.770 0.752 0 .738 0 .724 0.7 11 0 .698 0.686 0.674 0 .663 0.652 0.641 0.6 16 0.593 0.5 7 1 0.551 0.532 0.515 0.483 0.455 0.430 0.40 7 0.38 7 0.369

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... )::)

~

:;::, ;::J

:;:,... Cj <'>

..."'

r.i:;'

i:5

~

c;· ;::J

"' continued

oo w

"'-..]

00

Table 1.

w

-continued

00

OF

tr:l

lb/in 2

Air temperature

== '2.

140

150

175

200

225

250

300

400

500

600

700

800

900

1000

0.853 0.836 0.823 0.804 0.789 0.774 0. 760 0.747 0.734 0.721 0. 709 0.697 0.686 0.659 0.634 0.610 0.589 0.569 0.550 0.516 0.486 0.459 0.43 6 0.414 0. 394

0.909 0.890 0.876 0.856 0.840 0.824 0.809 0.795 0.781 0.768 0.755 0.742 0.730 0.701 0.675 0.650 0.627 0.606 0.586 0.550 0.518 0.489 0.464 0.441 0.420

1.047 1.026 1.009 0.986 0.968 0.950 0.932 0.916 0.900 0.884 0.869 0.855 0.841 0.807 0.777 0.749 0.722 0.698 0.675 0.633 0.596 0.563 0.534 0.508 0.484

1.185 1.161 1.142 1.116 1.095 1.075 1.055 1.036 1.018 1.001 0.984 0.967 0.951 0.914 0.879 0.847 0.817 0.790 0.764 0.716 0.675 0.638 0.604 0.575 0.547

1.323 1.296 1.275 1.246 1.223 1.200 1.178 1.157 1.137 1.117 1.098 1.080 1.062 1.020 0.982 0.946 0.913 0.881 0.852 0.800 0.753 0.712 0.675 0.641 0.611

1.460 1.431 1.408 1.376 1.3 so 1.325 1.301 1.278 1.2 55 1.234 1.213 1.193 1.173 1.127 1.084 1.044 1.008 0.973 0.941 0.883 0.832 0.786 0.745 0.708 0.675

1. 736 1. 702 1.674 1.636 1.605 1.575 1. 54 7 1.519 1.492 1.467 1.442 1.418 1.395 1.340 1.289 1.242 1.198 1.157 1.119 1.050 0.989 0.934 0.886 0.842 0.802

2.29 2.24 2.21 2.16 2.12 2.08 2.04 2.00 1.967 1.933 1.900 1.868 1.838 1.765 1.698 1.636 1.579 1.525 1.475 1.384 1.303 1.232 1.167 1.110 1.05 7

2.84 2.78 2.74 2.68 2.63 2.58 2.53 2.48 2.44 2.40 2.36 2.32 2.28 2.19 2.11 2.03 1.959 1.893 1.830 1. 717 1.618 1. 529 1.449 1.377 1. 312

3.39 3.32 3.27 3.20 3.14 3.08 3.02 2.97 2.92 2.86 2.82 2.77 2.72 2.62 2.52 2.43 2.34 2.26 2.19 2.05 1.932 1.826 1. 731 1.645 1.567

3.94 3.86 3.80 3.72 3.65 3.58 3.51 3.45 3.39 3. 33 3.27 3.22 3.17 3.04 2.93 2.82 2.72 2.63 2.54 2.38 2.25 2.12 2.01 1.912 1.822

4.49 4.40 4.33 4.24 4.16 4.08 4.00 3.93 3.86 3.80 3.73 3.67 3. 61 3.47 3.34 3.21 3.10 3.00 2.90 2.72 2. 56 2.42 2.29 2.18 2.08

5.05 4.95 4.87 4.76 4.67 4.58 4.50 4.42 4.34 4.26 4.19 4.12 4.05 3.89 3.75 3.61 3.48 3.36 3.2 5 3.05 2.87 2.72 2.58 2.45 2.33

5.60 5.49 5.40 5.28 5.18 5.08 4.99 4.90 4.81 4.73 4.65 4.57 4.50 4 .32 4.16 4.00 3.86 3. 73 3.61 3.39 3.19 3.01 2.86 2.72 2.59

""""==~. ==

30 40 50 60 70 80 90 100 110 120 130 140 150 175 200 225 250 275 300 350 400 450 500 550 600

~

~

£'

Standards and Designations

839

Typical properties of gases Molecular

Coefficient

i\11

Ratio or specific heats k(l4.7psia)

psi<~

Critical temperature ( R) (°F+460)

Acetylene Air Ammonia Argon Benzene

26.04 28.97 17.()3 39.94 78.11

1.25 1.40 1.30 1.66 1.12

342 356 347 377 329

0.899 1.000 0.588 1.379 2.6%

890 547 1638 706 700

555 240 730 272 1011

N-butane !so-butane Carbon dioxide Carbon disulplude Carbon monoxide

58.12 58.12 44.0 l 76.13 28.01

1.18 1.19 1.29 1.21 1.40

335 336 346 338 456

2.006 2.006 1.519 2.628 0.967

551 529 1072 1147 507

766 735 548 994 240

Chlorine Cyclohexane Ethane Ethyl alcohol Ethyl chloride

70.90 84.16 30.07 46.07 64.52

1.35 1.08 1.19 1.13 1.19

352 325 336 330 336

2.447 2.905 1.038 1.590 2.227

1118 591 708 926 766

751 997 550 925 829

Ethylene Freon 11 Preon J 2 Preon 22 Freon 114

28.03 137.37 120.92 86.48 170.93

1.24 1.14 1.14 1.18 1.09

341 331 331 335 326

0.968 4.742 4.174 2.985 5.900

731 654 612 737 495

509 848 694 665 754

Helium N-heptetne Hexane Hydrochloric acid Hydrogen

4.02 100.20 86.17 36.47 2.02

1.66 1.05 1.06 1.41 1.41

377 321 322 357 357

0.139 3.459 2.974 1.259 0.070

33 397 437 1198 188

10 973 914 584 60

Hydrogen chloride sulphide Methaoe 1\,fethyl alcohol Methyl butane

36.47 34.08 16.04 32.04 72.15

1.41 1.32 1.3] 1.20 1.08

357 349 348 337 325

1.259 1.176 0.554 1.106 2.491

1205 1306 673 1154 490

585 672 344 924 829

Methyl chlori.de Natural gas (typical) Nitric oxide Nitrogen Nitrous oxide

50.49 19.00 30.00 28.02 44.02

1.20 1.27 1.40 1.40 1.31

337 344 356 356 348

1.743 0.65fi 1.036 0.967 1.520

968 671 956 493 1054

749 375 323 227 557

N-octane Oxygen N-pentaoe !so-pentane Propane

114.22 32.00 72.15 72.15 44.09

1.05 1.40 1.08 1.08 1.13

321 356 325 325 330

3.943 1.105 2.4n 2.491 1.522

362 737 490 490 617

1025 279 84fi 829

Sulfur dioxide Toluene

64.04 92.13

1.27 1.09

344 326

2.211 3.180

1141 611

775 1069

Gas or Vi:! pour

Hydro~en

wei ~ht

·rr ·c· is not known. then use C = 315.

c·

Specific Critical gravity pressure

0

666

00

H'o

Pipe dimensions BS 3505 for PVC-U pipe: inch

0

CT'j

:::s

~

Diameter Class C 9.0 bar Nominal size

s· ,_. "'..., :::s

Wall thickness Mean outside diameter

Individual outside diameter

~

Class D 12.0 bar

Class E 15.0 bar

~

c:J

Average value

Individual value

Average value

Individual value

Average value

Individual value

min.

max.

min.

max.

max.

min.

max.

max.

min.

max.

max.

min.

max.

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

17.0 21.2 26.6 33.4 42.1

17.3 21.5 26.9 33.7 42.4

17.0 21.2 26.6 3 3.3 42.0

17.3 21.5 26.9 3 3.8 42.5

1.5 1.7 1.9 2.2 2.7

1.9 2.1 2.5 2.7 3.2

4 5

4 8.1 60.2 88.7 114. 1 140.0

48.4 60.5 89.1 114.5 140.4

48.0 60.0 88.4 113.7 139.4

48.5 60.7 89.4 114.9 141.0

6 8 10 12 14

168.0 218.8 272.6 323.4 3 55.0

168.5 219.4 273.4 324.3 356.0

167.4 218.0 271.6 322 .2 3 53.7

16 18 20 24

405.9 456.7 507.5 609.1

406.9 457.7 508.5 610.1

404.3 454.9 505 .4 606.5

3/ s 1

11

3/4

1

11 /* 1l I 2 2 3

-

-

-

-

-

-

-

-

-

-

-

-

2 .7

-

-

2.2

-

2.7

1.9 2.1 2.5 2.7 3.2

2.5 3.1 4.6 6.0 7.3

3.0 3.7 5.3 6.9 8.4

3.7 4.5 6.5 8.3 10.1

3.1 3.9 5.7 7.3 9.0

3.7 4.5 6.6 8.4 10.4

8.8

-

-

-

-

-

-

-

-

-

-

-

-

3.0 4.1 5.2 6.3

2.5 3.5 4.5 5.5

3.0 4.1 5.2 6.4

3.0 3.7 5.3 6.8 8.3

169 .1 220.2 2 74.4 32 5. 5 3 57.3

7.5 8.8 10.9 12.9 14.1

6.6 7.8 9.7 11.5 12.6

7.6 9.0 11 .2 13.3 14.5

9.9 11.6 14.3 17.0 18.6

10.3 12 .8 15.2 16.7

10.2 11.9 14.8 17.5 19.2

12.1 14.1 17.5 20.8 22.8

10.8 12.6 15.7 18.7 20.5

12.5 14.5 18.1 21.6 23.6

408.5 459.5 510.6 612.7

16.2 18.2 20.2 24.1

14.5 16.3 18.1 21.7

16.7 18.8 20.9 25.0

21.1 23.8

19.0 21.4

21.9 24.6

26.0

23.4

27.0

::::,

;::;-

BS 5391 for ABS pipe: inch \Nail thickness

Diameter Nominal size

Mean outside diameter

Individual outside diameter

Class B 6.0 bar

Class D 15.0 bar

Class C 9.0 bar

Class E 15.0bar

ClassTt 12.0bar

max.

min.

max.

min.

max.

min.

max.

min.

max.

min.

max.

min.

max.

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

17.0 21.2 26.6 33.4

17.3 21.5 26.9 33.7

17.0 21.2 26.6 33.4

17.3 21.5 26.9 33.7

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

1.9

2.1

2.5

2.7

1.6 1.9 2 .4 3.0

1.8 2.1 2.6 3.3

3.4 3.5 3.5 4.2

3.6 3.7 3.7 4.5

42.1 48.1 60.2 88.7

42.4 48.4 60.5 89 .1

42.0 48.0 60.0 88.4

42.4 48.5 60.7 89 .4

-

-

11 .' 2 2 3

-

-

2.4 2.7 3.4 5.0

2.6 3.0 3.7 5.3

3.1 3.6 4.5 6.5

3.4 3.9 4.9 6.9

3.8 4.4 5.4 8.0

4.1 4.7 5.8 8.5

5.1 5.8 7.0

5.5 6.2 7.4

4 6 8

114.1 168.0 218.8

114.5 168.5 219.4

113.7 167.4 218.1

114.9 169.1 220.2

6.4 9.4 12.2

6.9 10.4

8.4 12.3

8.9 13.3

10.3

10.9

min. mm 3/ '6

lh 3

/4

1

11:4

-

-

-

-

-

-

-

6.1 8.4

6.4 8.8

13.2

··Mean outside diameter' of a pipe is taken to be the arithmetic mean of any two perpendicularly opposed individual outside diameters. Alternatively, the mean outside diameter mat be determined by means of a circumference tape. tctass T pipe is intended only for threading. Its maximum sustained working pressure (12 bar) applies when threading is carried out in accordance with BS 21.

V'J ....

~

:::

l::l.. ~

~

"' ~

:::

l::l..

~

"' ::: l:l .... c;·

~-

:::

"'

00

H:>~

842

Engineering Data

PVC-U, PVC-C and ABS metric pipe sizes and tolerances

Size

6 bar

10 bar

16 bar

25 bar

o.d.

wall emm

wall emm

wall

emm

wall emm

1.5 1.8 1.9 2.4 3.0 3.6 4.3 5.3 6.0 6.7 7.7 8.6 9.6 10.8 11.9 13.4 1 5.0 16.9 19.1

1.0 1.0 1.0 1.0 1.2 1.5 1.9 2.4 3.0 3.7 4.7 5.6 6.7 8.2 9.3 10.4 11.9 13.4 14.9 16.7 18.6 20.8 23.4 26.3 29.7

6 8 10 12 16 20 25 32 40 50 63 75 90 110 125 140 160 180 200 225 250 280 315 355 400

1.8 1.8 1.9 2.2 2.7 3.2 3.7 4.1 4.7 5.3 5.9 6.6 7.3 8.2 9.2 10.4 11.7

1.0 1.0 1.0 1.0 1.8 2.3 2.8

Outside dia meter tolerances o.d. 5- 63 75- 125 140- 200 225- 250 280- 315 355-400

± 0.2 0.3 0.4 0.5 0.6 0.7

Tolerances on wall thickness o.d. 1.0 1.2-2 .0 2.2-3 .0 3.2-4.0 4.1-5 .0 5. 3-6 .0 6.2-7.0 7.2-8 .0 8.2- 9.0 9.2-10.0 10.4-11.0 11.7-11.9 12 .3-12.4 13.2-14.0 14.6-15.0 15.6-15. 7 16.4-16.9 17.7-17.8 18.4-18.6 19.1-20.0 20.7-20.8 2 1.5 22.3 23.3- 23.9 25 26.3 and 26.7 2 7. 8 29.5- 30.0

± 0.3 0.4 0.5 0.6

0.7 0.8 0.9 1.0 l.l 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.9 3.0 3.2

Standards and Designations

843

PP-H and PE metric pipe sizes and tolerances

-- Size

2.5 bar

6 bar

lObar

o.d.

wall emm

wall emm

wall e rrun

1.8 1.8 2.0 2.3 2.9 3.6 4.3 5.1 6.3 7.1 8.0 9.1 10.2 11.4 12.8 14.2 15.9 17.9 20.1 22.7

2.0 2.5 2.7 3.0 3.7 4.6 5.8 6.9 8 .2 10.0 11 .4 12.8 14.6 16.4 18.2 20.5 22.8 25.5 28.7 32.3 36.4

16 20 25

32 40 50 63 75 90 110 125 140 160 180 200 225 250 280 315 355 400

1.8 1.8 1.9 2.2 2.7 3.1 3.5 3.9 4.4 4.9 5.5 6.1 6 .9 7.7 8.7 9.8

Outside diameter tolerances o.d. 10- 32 40 50 63 75 90 110 125 140 160 180 200 225 250 280 315 355 400

± 0.3 0.4 0.5 0.6 0.7 0.9 1.0 1.2 1.3 1.5 1.7 1.8 2.1 2.3 2.6 2.9 3.2 3.6

Tolerances on wall thickness o.d.

1.8- 2.0 2.2-3.0 3.1-3.9 4.3-4.9 5.1-5.8 6.1 ·7.0 7.1-8.0 8.2-8. 7 9.1- 10.0 10.2-11.0 11 .4 12.2 and 12.8 13.7 14.2 and 14.6 15.4and15.9 16.4 17.4 and 17.9 18.2 19.3 and 19.6 20.1 and 20.5 21.6 22.0 and 22.8 24.3 and 24.4 25.5 27.4 28.3 and 28.7 30.8 31.7 32.3 34.7 35 .7 36.4

± 0.4 0.5 0.6 0.7 0.8 0.9 l.O 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.7 2.8 3.0 3.1 3.3 3.4 3.5 3.7 3.8 3.9

844

Engineering Data

Support spacing (ft) for PVC pipe*

Horizontal pipe-systems support spacings are greatly influenced by operating temperature. The charts show the recommended support spacing according to size. schedule and operating temperatures. Do not clamp supports tightly- this restricts axia l movement or the pipe. If short spacing is necessary. continuous supports may be more economical. Charts are based on liquids up to l.OO specific gravity. but do not include concentrated loads, nor do they include allowance for aggressive reagents. Pipe

$CHEDIJLE40

si7.e

temperature (0 P)

in

60

80

100

120

140

60

80

100

j

4

3'12

3111 3 1/z

2

2

4

4

3 112

2 1/z

2

2

1

1

4

1

1

4

4

4 4

1

1 14

5 1/z

5

1

1

5 h

5h

7

h

5 5 6 1h

1

/z

4

h

5

3 112

6

6

5

1

1

/z

llO

140

5

5

4 1h

3

2 112

5

1

4 lz

3

3

S

! 1h

3 lz

5 1h

3

6

3

1

6 12

6

6 1 /z

6 112

6

4

3 1 lz

7 1lz

7

f. 1 h

4

3 1 lz

4 1 /2

h

'> 112

3 1 lz

3

7

6 1/z

6

4

3 1 /.!

7 112

7 1h

6 ' 12

4 1/z

4

8

7 ' /2

7

8

1

7

1

4

1

8 h

8

1

7 h

4 1 12

7 1h

4 112

7

/z

3 112 3 1 i l

4

12

7

S 1lz

s

? 1 l2

9

8 1 lz

7

9

8 111

7 112

9 1h

9

9

8

9 11z

9

9

8

5

4l1z

11

10

1

1

5

12

5 lz

12

13

12

14

13 112

u

11

14

13 1 /l

ll 1l1

16

12 112

11 1 h

18

13

12

l0 1h

7 1h 6 ' h

SOR4l 11

13

1

12

8

7

9

8

4

8 1lz 5 1l2

SDR 26

9

14

7

8

lY/z 12 /z ll' h 8 h 1

3

3 1h

6 1 12

()

8 l2

5 12 3 1h 1

3

10

14

lOU

3 1 /z

6

22

SO

/z 2 h

S 1h

6

9 11,

20

()()

2 12 2 h

5

10

2

140

1

6

7

4

20

2 112 2 1h

5

6 7

2

1

4 1/1

6

8

SCHEDULE 120

SCHEDULE 80

7

1

/ 1

8

15

15 111

14 1/

15

12 2

12 1 /z

13

9 1 h 8 11? 10

9

'Alt hough support spacing Is shown at 140°1'. consideration should be given to the use o f CPVC or continuous suppo(t abow 120° f. The possibil ity of temperat\l(e overrides beyond regu lar working temperatures and cost may make either o r the altl'matiws more desirable. This chnrt is based on continuou s spans and for iniusulated line carrying nuirls of specific gravily up to 1.00.

Standards and Designations 845 Support spacing (ft) for CPVC pipe• Pipe size in

73

100

112

5 5

4 1lz 5 1 5 12 5 1/z 6 6 7 7 1 7 12 7 1lz 8 9 10 10 1 12

314 l 1 114 1 1 I2 2 2 1 12

3 1

3 Iz 4 6 8 10 12

SCHEDULE 80 temperature °F

SCHEDULE40 temperature °F

5 112 5 112 6 6 7 7 1 7 lz 7 1h 8 1/z 9 1h 10 112 1

11 h

120 140 160 180 4 4 112 4 4 112 1 5 4 12 5J./z 5 1 5 5 h 1 5 5 I2 61 /z 6 7 6 7 61/z 6 1/z 7 1 7 l2 7 8 112 71/z 8 9 1h 10 81/z

2 112 2 1h 21h. 21/z 3 21/z 3 3 3 112 3 31 /z 3 31 /z 4 4 Vh 4 4 1 4 12 4 5 4 112 1 5 12 5 6 5 1/z 1 6 12 6

73

100

120

140

S1l2

5 5 lz 6 6

4 1lz 5 1 5 I2

1

6 61 h. 71l z 71/z 8 81 /z 9 10 10 112 11 1l 2

41h 41/z 5 51 /z 51/z 6 1 6 I2 7 71/z 7 1h 8 9 1 9 12 10 1/z

5 112

6 61 /z 7 7 8 8

81I 2

8 1I 2 10

11 11 112 12 1/z

1

6 12 7 7 12 8 1 8 lz 9 9 1/z 10 1h 1

11

12

6

160 180

3 3

3 1 12

2 112 21 /-2 3

3 1h

3 3 112 3 112 4 3 1I z 41/z 4 41 /z 4 1 5 4 l2 5 4 1 12 51 /z 5 6 5 1 12 6 112 6 7 1 l z 6 1 12

This chart is based on continuous spans and for in insulated line carrying fluids of specific gravity up tol.OO. ·The data furnished herein is based on information furnished by manufacturers of the raw material. This information may be considered as a basis for recommendation, but not as a guarantee. Materials should be tested under actual service to determine duitability for a particular purpose.

846

Engineering Data

Pipe-bracket spacing for liquids with a density of

<

1 gtcm 3 and for gases

PVC-U Pipe bracket intervals Lin em at

d

mm

in

20°C

30°C

40°C

50"C

16 20 25 32 40

3/s

80 90 95 105 120 140 150 165 180 200 210 225 240 255 270

70 80 85 90 llO 130 140 155 170 190 200 215 230 240 260

50 60 65 70 90 110 120 135 150 170 185 195 210 220 240

Continuous su pport 55 40 60 45 70 55 85 65 95 70 110 80 95 125 145 115 125 160 170 140 185 155 200 170 215 185

Jh

J/4

1 1 1/4 11I z 2

so

63 75 90 110 125 140 160 200 225

21/z

3 4

5 6 7 8

60°C

PVC-C Pipe bracket intervals Lin em at

d

mm

in

20°C

30°C

40°C

50°C

60°C

70°C

80°C

16 20 25 32 40 50 63 75 90 110 160 225

3/ s

100 115 120 135 150 16.5 18.5 205 225 250 300 355

95 110 115 125 140 160 175 195 210 235 285 335

90 100 110 120

85 95 100 110 125 140 160 175 190 210 255 300

75 87 90 100 115

67

60 70 70 80 90 110 125 135 150 165

liz

3/4

1 1 1/ 4 1

1 /2

2 21/z

3

4 6 8

130

1.50 165 185 200 220 270 320

130

150 165 180 195 240 280

77

80 90 105 120 135 150 165 180 220 260

200

235

ABS

d mm

Pipe bracket intervals Lin em at in

20°C

30°C

40°C

sooc

60°C

3/ 8

70 80 85 100 110 115 130 160 180 230

65 70 80 90 100 110 120 145 165 210

60

55 60

45 50 60 65 75 80 85 105 120 155

16 20 25 32 40

Jl /4

63 90 110 160

1 1 /2 2 3 4 6

so

liz 3/4

1

65

75 85 95 100 110 135 155 200

65

75 85 90 100 120 135 175

The bracket spacings shown in the table are for Class C and PN 10 pipe and are given in em. For other pipe classes the figures must be multiplied by the following factors: Class B 0.90 Class C 1.05 Class E 1.09

Standards and Designations

847

pp

d

Pipe bracket intervals Lin em at

mm

200C

30"C

40°C

50°C

600C

80°C

100°C

16 20 25 32 40 50 63 75 90 110 125 140 160 180 200 225 250 315

75 80

70 7') 85 95 110 120 135 150 165 180 190 205 225 240 250 260 275 305

70 70 85 95 105 115 130 145 155 175 185 195 210 225 235 250 265 295

65 70 80 90 100 110 125 135 150 165 180 190 200 215 225 240 255 285

65 65 75 85 95 105 120

55 60 70 75 85 90

40 45 50 55 60 70 80 85 95 105

85

100 110 125 140 155 16'> 185 200 210 225 240 250 265 280 315

130

145 160 170 180 190 200 215 230 240 270

lOS 115 125 140 150 155 165 170 185 200 210 235

ll5 125 130 135 145 200 225

llO

PB d

Pipe bracket intervals Lin em at

mm

20°C

30°C

40°C

50°C

60°C

80°C

100°C

16 20 25 32 40 50 63 75 90

70 78 81 93 103 115 130 141 154 188

69

68 76 79 90 100 112 126 137 150 184

66 74

64 72 75 85 95 106

60 68 71 80 90 100 112 122 134 164

55 61 64 73 81 90 102

llO

77

80 91 102 114 128 139 15 2 186

77

88 98 109 123 133

146 179

119

130 142 173

llO 121 148

848

Engineering Data

PE

d

Pipe bracket intervals Lin em at

mm

20°C

30°C

40°C

sooc

60°C

20 25 32 40

75 80 90 100 115 130 140 1S5 170 185 195 210 235 2SO

70 80 90 100 110 125 135 lSO 165 175 185 200 220 235

65 75 85 95 lOS 120 130 145 160 170 180 190 210 220

6S 70 80 90 100 115 125

60 65 75 85 95 lOS llS 130 140 150 155 170 186 200

so

63 75 90 110 125 140 160 200 225

135

150 160 170 180 200 210

-

-- -

PVDF d

Pipe bracket intervals Lin em at

mm

20°C

40°C

60°C

80°C

100°C

120°C

140°C

16 20 25 32 40

75 80 85 100 110 12 5 140 155 165 185 200 210 22S 2 50 265

70 75 85 95 110 120 135 150 16S 180 190 20S 22 5 250 260

70 70 85 95 lOS 115 130 145 155 175 185 195 210 235 250

65 70 80 90 100 llO 125 135 150 165 180 190 200 225 240

65 65 75 85 95 105 120 130 145 160 170 180 190 21 5 230

55 60 70 75 85 90 105 115 125 140 150 155 165 185 200

40 45 50 55 60 70 80 85 95 105 110 115 125 13 5 145

so 63 75 90 110 125 140 160 200 225

SECTION 10 Author's Acknowledgements

Author's Acknowledgments Abacus Valves Mfg Ltd ASCO I Joucomatic N HBennett Biwater Industries British Standards Institute Buracco SA BVAMA Crosby Valve Inc CUES Dan foss Dow Chemical Company Dresser Industries Durabla Fluid Technology Inc. Fisher-Rosemount FMC Corporation George Fischer Griffin Pipe Products Harvel Plastics Inc.

Hindle Cock burns Ltd Hitachi Valves Ltd IMI Bailey Birkett Ltd KSB Microfinish Valves Limited Neles-Jamesbury OMBSpA Pipes & Pipelines International Realm Products Ltd Rotork Controls Ltd A Searle Shafer Products Spirax-Sarco P. Stockford Vanessa Srl Victualic International T D Williamson Inc

SECTION 11 Buyer's Guide to Valves and Pipes

Classified Index by Product Category Alphabetical List of Manufacturers Trade Names Index Editorial Index Advertisers Index

Classified Index by Product Category Valve & Pipe Equipment

Air Valves Posi-Flate

Valves & Actuators Angle Seat Valves Actuated Valves-Electric

Asco/Joucomatic (ASCO Controls BV)

PCC Flow Technologies Hindle Cock burns Ltd NAFAB Spirax-Sarco Limited Victaulic Company Georg Fischer AG

Spirax-Sarco Limited Hattersley Newman Hender Ltd

Actuated Valves-Hydraulic Hindle Cockburns Ltd NAFAB

Actuated Valves-Manual PCC FIO\·v Technologies Hindle Cockburns Ltd NAFAB Pos i-Flate Victaulic Company Georg Fischer AG

Actuated Valves-Pneumatic PCC Flow Technologies Hindle Cock burns Ltd NAFAB Posi-Flate Spirax-Sarco Limited Victaulic Company Hattersley Newman Hend er Ltd

Actuated Valves-Portable Hindle Cockburns Ltd

Automatic Temperature Control Valves

BaJI Valves PCC Flow Technologies Changdel Industrial Co. Ltd Hindle Cockburns Ltd NAFAB Haitima Corporation Spirax-Sarco Limited Victaulic Company Hattersley Newman Hender Ltd Georg Fischer AG

Ball Float Valves Hindle Cock burn s Ltd NAFAB Hattersley Newman Hender Ltd

Block and Bleed Valves Hindle Cock burns Ltd

Blow Down Valves Hindle Cockburns Ltd NAFAB Victaulic Company Spirax-Sarco Limited

Actuators PCC Flow Technologies Auma Werner Riester GmbH & Co KG Hindle Cock burns Ltd NAF AB Posi-Flate Hattersley Newm an Hender Ltd Georg Pischer t\G

Butterfly Valves PCC Flow Technologies NAFAB Posi-Plate Spirax-Sarco Limited Hatte rs ley Newman Hender Ltd Georg fischer AG

85 6

Buyer's Guide to Valves and Pipes

Cast Steel Valves PCC Flow Technologies NAFAB Posi-Flate Hattersley Newman Render Ltd Check Valves PCC Flow Technologies Changdel Industrial Co. Ltd ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd NAFAB Spirax-Sarco Limited Victaulic Company Hattersley Newman Hender Ltd Georg Fischer AG Control Valves PCC Flow Technologies NAFAB Posi-Flate Spirax-Sarco Limited Victaulic Company Hattersley Newman Hender Ltd Georg Fischer AG Diaphragm Valves ASCO/Joucomatic (ASCO Controls BV) Hatters ley Newman Hender Ltd Georg Fischer AG Diverter Valves Hindle Cockburns Ltd Electronically Operated Valves NAFAB Fire Safe Valves NAFAB

Float Control Valves Victaulic Company Hattersley Newman Hender Ltd Flow Valves Posi-Fiate Victaulic Company Hattersley Newman Hender Ltd Foot Valves Hattersley Newman Hender Ltd Gas Valves ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Hattersley Newman Hender Ltd Georg Fischer AG

Gate Valves Hindle Cockburns Ltd NAFAB Hattersley Newman Hender Ltd

Gear Operated Valves PCC Flow Technologies NAFAB Posi-Flate Victaulic Company Hattersley Newman Render Ltd Globe Valves Hindle Cockburns Ltd NAFAB Hattersley Newman Hender Ltd High Pressure Vah•es PCC Flow Technologies Hindle Cockburns Ltd ASCO/Joucomatic (ASCO Controls BV) Hatters ley Newman Hender Ltd

High Temperature Valves PCC Flow Technologies Hindle Cockburns Ltd ASCO/ Joucomatic (ASCO Controls BV) NAFAB Posi-Fiate Hydraulically Operated Valves Hindle Cockburns Ltd Intrinsically Safe Valves ASCO/Joucomatic (ASCO Controls BV) Isolating Valves ASCO/ Joucomatic (ASCO Controls BV) NAFAB Spirax-Sarco Limited Hatters ley Newman Hender Ltd Level Control Valves Rattersley Newman Render Ltd

Manifold Valves ASCO/Joucomatic (ASCO Controls BV) Metal Valves Hindle Cock burns Ltd NAFAB Metering Valves Hindle Cock burns Ltd Hattersley Newman Hender Ltd Mixing Valves Spirax-Sarco Limited Georg Fischer AG

Classified Index by Product Category Motor Operated Valves

Regulating Valves

NAFAB

NAFAB Hattersley Newman Render Ltd

Needle Valves NAFAB Hattersley Newman Bender Ltd

Relief Valves NAFAB Hattersley Newman Hender Ltd

Non-return Valves PCC Flow Technologies Hindle Cockburns Ltd NAFAB Hattersley Newman Hender Ltd

Rotary Valves NAFAB

Rotary Control Valves NAFAB

Pinch Valves ASCO/Joucomatic (ASCO Controls BV)

Pipeline Valves Hindle Cockburns Ltd Posi-Flate

Safety Valves ASCO/Joucomatic (ASCO Controls BV) NAFAB Spirax-Sarco Limited Hattersley Newman Hender Ltd

Plastics Valves

Screwdown Valves

Georg Pischer AG

Hattersley Newman Render Ltd

Plug Valves (Cocks)

Segment Control Valves

Victaulic Company Hattersley Newman Hender Ltd

NAFAB

Slide Valves Pneumatic Valves

ASCO/Joucomatic (ASCO Controls BV) Hattersley Newman Hender Ltd

ASCO/Joucomatic (ASCO Controls BV) NAFAB Posi-Flate Hattersley Newman Hender Ltd Georg Fischer AG

Solenoid Valves

Poppet Valves

Spool Valves

ASCO/joucomatic (ASCO Controls BV)

ASCO/Joucomatic (ASCO Controls BV)

Pressure Control Valves

Stainless Steel Valves

NAFAB Spirax-Sarco Limited Hattersley Newman Hender Ltd

PCC Flow Technologies Hindle Cockburns Ltd ASCO/Joucomatic (ASCO Controls BV) NAFAB Victaulic Company Hattersley Newman Render Ltd

Pressure Relief Valves NAFAB Hatters ley Newman Bender Ltd

ASCO/Joucomatic (ASCO Controls BV) Georg Fischer AG

Steam Valves Pressure Operated Valves ASCO/joucomatic (ASCO Controls BV) Spirax-Sarco Limited

ASCO!Joucomatic (ASCO Controls BV) NAFAB Spirax-Sarco Limited Hattersley Newman Hender Ltd

Process Valves PCC Flow Technologies Hindle Cock burns Ltd NAFAB Posi-Plate

Quiet Valves ASCO/joucomatic (ASCO Controls BV) NAFAB

Stem Guided Valves ASCO/Joucomatic (ASCO Controls BV)

Stop Valves Hindle Cockburns Ltd NAFAB Spirax-Sarco Limited Hattersley Newman Hender Ltd

8 57

8 58

Buyer's Guide to Valves and Pipes

Swingcheck Valves

Pipe Fitt.ings-Piastics

PCC Flow Technologies NAFAB Hatters ley Newman Hender Ltd

Victaulic Company Georg Fischer AG

Tank Valves

Georg Fischer AG

Pipe Fusion Equipment ASCO/}oucomatic (ASCO Controls BV)

Pipe Joints Temperature Control Valves

Georg Fischer AG

NAFAB Spirax-Sarco Limited Hatters ley Newman Hender Ltd

Plastic Pipe Victaulic Company Georg Fischer AG

Throttling Valves NAFAB Hatters ley Newman Hender Ltd

Pressfit Pipe

Triple Offset Valves

PVC-C Pipe

PCC Flow Technologies NArAB

Georg Fischer 1\G

Vacuum Valves

Georg Fischer AG

Victaulic Company

PVC-UPipe ASCO/Joucomatic (ASCO Controls BV)

Thermoplastic Pipe Knife Gate Valves

Georg Fischer AG

PCC Flow Technologies

Pipes & Piping

Ancillary Equipment & Services

ABS Pipe

Insulated Valves Covers

Georg Fischer AG

Hattersley Newman Hender Ltd

CPVC Pipe

Leak Detection Equipment

Georg Fischer AG

Spirax-Sarco Limited

Dual/Double Containment Pipe

Noise Control

Georg Fischer AG

NAFAB

Flexible Pipe

Pad:ings

Georg Fischer AG

Latty International SA

PE Pipe

Positioners

Georg Fischer AG

NAFAB Spirax-Sarco Limited

Pipe Clamps Georg Fischer AG

Process Controllers NAFAB

Pipelines Couplings Victaulic Company Georg Fischer AG

Regulators NAFAB Hattersley Newman Render Ltd

Pipe Cutting Equipment Georg Fischer AG

Seals Latty International SA

Pipe Fittings- Iron and Steel Victaulic Company Georg Fischer AG

Sealing Materials Latty International SA

Classified Index by Product Category Silencers

Food & Beverage

NAFAB

Beverage Steam Traps Spirax-Sarco Limited Ratters ley Newman Render Ltd

Traps/Drainers

PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Posi-Flate Rattersley Newman Hender Ltd

Rattersley Newman Hender Ltd

Brewery Valve Position Indicators NAFAB Hattersley Newman Hender Ltd

Valve Testing Hindle Cock burns Ltd Hattersley Newman Hender Ltd

PCC Flow Technologies Posi-Flate

Dairy PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV)

Distiller:s

Industries & Applications Water Boiler Feed PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) NAFAB Spirax-Sarco Limited Hattersley Newman Hender Ltd

Brackish Water PCC Flow Technologies

Cooling Water PCC Flow Technologies Hattersley Newman Hender Ltd ASCO/Joucomatic (ASCO Controls BV) NAFAB

Drinking Water PCC Flow Technologies Hattersley Newman Hender Ltd ASCO/ Joucomatic (ASCO Controls BV)

PCC Flow Technologies HattersJey Newman Render Ltd

General Food PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV) NAFAB Posi-Flate

Sugar PCC Plow Technologies NAFAB Hattersley Newman Hender Ltd

Wine PCC Flow Technologies Hattersley Newman Hender Ltd

Chemical & Process Catalysts PCC Flow Technologies Hindle Cock burns Ltd Posi-Flate

Sea Water PCC Flow Technologies Hattersley Newman Hender Ltd

Sewage PCC Flow Technologies Hatters ley Newman Hender Ltd ASCO/Joucomatic (ASCO Controls BV)

Chlor Alkali PCC Flow Technologies Hindle Cockburns Ltd NAFAB

Clarifying PCC Flow Technologies Hindle Cock burns Ltd

Waste Water PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hatters ley Newmao Hender Ltd

Emulsions PCC Flow Technologies Hindle Cock burns Ltd

8 59

860

Buyer's Guide to Valves and Pipes

Fuel Oil (Heavy) PCC Plow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd

Solvents & Bleaching PCC Flow Technologies Hindle Cock burns Ltd Posi-Flate

Fuel Oil (Light) PCC Plow Technologies ASCO/ Joucomatic (ASCO Controls BV) Hindle Cockbums Ltd

Pulp & Paper NAFAB

Grease/Lubricating Oil PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV) Hindle Cock burns Ltd Hattersley Newman Render Ltd Industrial Chemicals PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd NAFAB Posi-Flate

lnl<s & Dyes PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cock burns Ltd Posi-Flate Oils PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Paints PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Posi -Flate Polymers PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Posi-Flate

Gas & Pollution Cryogenic Gas PCC Flow Technologies ASCO/)oucomatic (ASCO Controls BV) Hindle Cock burns Ltd Dioxins PCC Flow Technologies Hindle Cock burns Ltd Effluent PCC Flow Technologies Hindle Cock burns Ltd

Flue Gas Desulph. PCC Flow Technologies Hindle Cock burns Ltd Gas PCC Flow Technologies NAFAB Hindle Cockburns Ltd Hattersley Newman Render Ltd Hot Gas PCC Plow Technologies Hindle Cockburns Ltd Industrial Waste Water PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV) Hindle Cock burns Ltd Hattersley Newman Hender Ltd

Public Utility Process PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd Posi-Flate Resins PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cock burns Ltd Posi-Fiate

Electricity PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV) Posi-Fiate Hattersley Newman Hender Ltd Gas PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cockburns Ltd

Classified Index by Product Category Nuclear ASCO/joucomatic (ASCO Controls BV) NAFAB Power Station PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) Hindle Cock burns Ltd NAFAB Hattersley Newman Hender Ltd Water PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) NAFAB

Sewage & Sludge Raw Sewage PCC Flow Technologies Sewage (Sludge) PCC Flow Technologies Rattersley Newman Bender Ltd Sewage (Treated) PCC Flow Technologies Hattersley Newman Render Ltd Slurry PCC Flow Technologies NAFAB Posi-Fiate Rattersley Newman Render Ltd

Pharmaceutical PCC Flow Technologies Hindle Cock burns Ltd Posi-Flate

Other Applications Automotive PCC Flow Technologies Posi-Flate Hattersley Newman Bender Ltd Aviation & Aerospace Posi-Flate Cement Slurry PCC Flow Technologies NAFAB Posi-Fiate Rattersley Newman Render Ltd Coal Mining PCC Flow Technologies NAPAB Posi-Plate Hatters ley Newman Render Ltd Coal Washing PCC Flow Technologies Concrete Handling PCC Flow Technologies Posi-Flate Ratters ley Newman Bender Ltd

Thick Sludge PCC Flow Technologies NAFAB

Condensate Extraction PCC Flow Technologies

Pharmaceutical, Medical

Oescaling PCC Flow Technologies

Biotechnology PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV)

Fire Stationary PCC Flow Technologies Rattersley Newman Render Ltd

Cosmetics PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV)

Glass PCC Flow Tecbnologies Posi-Plate

Laboratory PCC Flow Technologies ASCO/ Joncomatic (ASCO Controls BV)

Heating PCC Plow Technologies ASCO/Joucomatic (ASCO Controls BV) Hattersley Newman Hender Ltd

Medical PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV)

High Pressure Hindle Cockburns Ltd

8 61

862

Buyer's Guide to Valves and Pipes

Hydro-Pneumatic Posi-Flate Irrigation (Intake) PCC Flow Technologies Hattersley Newman Render Ltd Irrigation (Spray) PCC Flow Technologies Hattersley Newman Bender Ltd Land Drainage PCC Flow Technologies Machine Tool Coolants PCC Flow Technologies Hattersley Newman Bender Ltd Marine PCC Flow Technologies NAFAB Hattersley Newman Hender Ltd Military /Defence Hindle Cock burns Ltd Mineral Processing PCC Flow Technologies Mining PCC Flow Technologies Mine Drainage & Dewatering PCC Flow Technologies Nuclear ASCO/ Joucomatic (ASCO Controls BV) Oil & Gas PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV)

Petrochemical PCC Flow Technologies ASCO/Joucomatic (t\SCO Controls BV) Hindle Cock burns Ltd NAFAB Posi-Flate Printing PCC Flow Technologies Posi-Flate Pulp & Paper PCC Flow Technologies ASCO/Joucomatic (ASCO Controls BV) NAFAB Posi-Flate Hattersley Newman Render Ltd Refining PCC Flow Technologies ASCO/ Joucomatic (ASCO Controls BV) NAFAB Shipping PCC Flow Technologies Hindle Cockburns Ltd NAFAB Tar & Liquor PCC Flow Technologies NAFAB Hattersley Newman Hender Ltd Textiles PCC Flow Technologies ASCO/Joucomatic (ASCO Cootr:-ols BV) Tyres & Rubber PCC Flow Technologies NAPAB Posi-Piate Viscous Products PCC Flow Technologies

Alphabetical List of Manufacturers ASCO/Joucomatic (ASCO Controls BV) Industrielaan 21, 392 5 BD. Scherpenzeel. The Netherlands Tel: +31 33 2 77 7911 Fax: +31 33 2774561 E-mail: asco(qJasco.joucoma.nl Website: www.ascovalve.com Auma Werner Riester GmbH & Co Kg Renkenrunsstrasse 20, D-79 3 79 Mi.illheim. Germany Tel: +49 7631 8090 Fax: +49 763113218 E-mail: riester(a!auma .com Website: www.auma.com Changdel Industrial Co., Ltd 3 FL 92-l, Sec.2. Ho-Ping West Road. Taipe i. Taiwan 100 Tel: +886 2 2305 32 501 Fax: +886 6 2 2307 9818 E-mail: changdel@ ms19.binet.net

Hat.tersley Newman Hender Ltd Burscough Road. Ormskirk , Lancashire L49 2XG. UK Tel: +44 (0) 1695 5 77199 Fax: +44 (0) 169 55 78 775 E-mail: uksales(i1:,hattersley-valves.co.uk export (~ hattersley-valves.co. uk Website: www.hattersley-valves.co.uk Hindle Cockburns Ltd Victoria Road, Leed, LS11 SUG, UK Tel: +44 (0) 1132 443 741 E-mail: salesbindle@ tyco-valves.com John-Valve MFG Factory Company Ltd No 1149-11. Bee San Road. Tsao-Tun Town. Nan-Tou Hsien. Taiwan 542. ROC Tel: +886 49 3 780078 Fax: +886 49 3754978 E-mail: johnvalv@ ms13.hinet.net Website: www.johnvalve.com.tw Lattylii>International SA

EMG Eleldro-Mechanik GmbH Industriestrasse l. D-57482 Wenden . Germany Tel: +49 7634 5 51320 Fax: +49 7634 55J 325 E-mail: Ka uaemg (t(aol.com Website: www.emg-wenden.de

Head Office: Latty 0·l· International SA. 57 bis Rue de Versailles. F- 91400 Orsay, France Tel: + 33 169 861112 fax:+33169869625 E-mail: sales-market:ing@ latty.com Website: www.latty.com

Georg Fischer AG Rohrleitunsyrk, Ebnat Strasse ll. Cl-1-8201 Schaffhausen. Switzerland Tel: +4152 6311111 Fax: +41 52 6312875

Plant Qffice: Latty " International SA. l. Rue Xavier-Latty, BP 13. F-28160 Brou. France Tel: +33 2 37 44 77 77 Fax: +33 2 37 44 77 99 E-mail: [email protected] Website: www.latty.com

Haitima Corporation SF. No 201 Titing Boulevard Sec2. Neihu Area. Taipei, Taiwan 114. ROC Tel: +886 2 26585800 Fax: +886 2 26582266 E-mail: haitima (£ilms8.binet.net

Latty"<' International Ltd, Westfield Road . Retford, Nottinghamshire. DN22 7BT. UK Tel: +44 (0) 1777 708 8368 Fax: +44 (0) 1777 707 474 Website: www.latty.co.uk

864

Buyer's Guide to Valves and Pipes

NAFAB Gelbgjntaregatan 2. S-5818 7 Linkoping, Sweden Tel: +4613 3 316000 Fax: +4613 136054 E-mail: [email protected] Website: www.naf.se PCC Fl.o w Technologies Unit C. Ryknild Street. Barton Turn.

Barton Under Need wood, Staffordshire. DE13 8EB, UK Tel: +441283 713034 Fax: +441283 716930 Website: [email protected] Posi-Fiate

Corporation Headquarters: Posi-flate, 1125 Willow Lake Boulevard. StPaul. MN 55110. USA Tel: +1 651484 5800 Fax: +1651484 7015 U11ited Kingdom: Posi-flate, 14 Carters Lane. Kiln Farm, Milton Keynes, MK11 3ER. UK Tel: +44 (0) 1908 564455 Fax: +44 (0) 1908 564615 Website: www. posiflate.com

Rotork Brass Mill Lane, Bath. BA1 3JQ. UK Tel: 01225 733261 Fax: 01225 733539 Spirax-Sarco Limited Charlton House. Cheltenham. Gloucestershire GL53 8ER. UK Tel: +441242 521361 Pax: +441242 573342 E-mail: [email protected] Website: www.spirax-sarco.com Victnalic Company of America Po Box 31. Easton PA. 18044-0031, USA Tel: + 1 610 5 59 3 3 00 Fax: +1610 250 8817 E-mail: [email protected] Website: www.victualic.com Wyeco Auto Valves Co Ltd 4F No 98 Section 3, Chien Kuo N. Road. Taipei. Taiwan 104, ROC Tel: +886 2 2502 5166 Fax: +886 2 2501 2863 Yih Kuang Metal Corporation l2F-l, No 51. Fu Hsing N. Road, Taipei 105. ROC Tel: +886 2 277 66455 Fax: +886 2 277 66795

Trade Names Index 4-WAY-Four waydivertal valve-Hindle Cockburn Ltd AS3-AS50-Electric part-turn actuatorsAuma Werner Riester GmbH & Co KG ASCO-Solenoid and pressure operated valves-ASCO/Joucomatic (ASCO Controls BV) AUMA MA TIC-Actuator Controls-Auma Werner Riester GmbH & Co KG 81-Quick release butterfly valve-PCC Plow Technologies 810-Split body hygienic butterfly valvePCC Flow Technologies 811-Wafer type butt:ertly valve-PCC Flow Technologies 812- Lugged type butterfly valve-PCC Flow Technologies 814-PTFE-BPDM Backed seat butterfly valve-PCC Flow Technologies 8 16A- Aluminium vertically split bodied butterfly valve-PCC Flow Technologies 816C-Carbon steel vertically split bodied butterfly valve-PCC Flow Technologies 8 160-Ductile iron vertically split bodied butterfly valve-PCC Flow Technologies 816S-Stainless steel vertically split bodied butterfly valve-PCC Flow Technologies 82-Tablet butterfly valve-PCC Flow Technologies 820-High performance butterfly valvePCC Flow Technologies 825-Wafer check Valve-PCC Flow Technologies 855F- Two piece full bore ball valve- PCC Flow Technologies B55R-One piece full bore ball valve-PCC Flow Technologies 8641 -Three piece full bore ball valve-----PCC Flow Technologies CHANGDELL-Butterfly valves and check va lves-Changdel Industrial Co., Ltd DREHME-Electric actuators for remote valve operation- EMG Elektro-Mechanik GmbH

EMG-Eiectric actuators for remote valve operation-EMG Elektro-Mechanik GmbH GENrE- Butterfly va lves and check valvesChangdel Industrial Co., Ltd GILFLo-Fiowmeters- Spirax-Sarco Limited GK10.2-GK 40.2-Bevel gearboxesAuma Werner Riester GmbH & Co KG GS40-GS500-Worm gearboxes-Auma Werner Riester GmbH & Co KG GST10.1-GST40.1-Spur gearboxesAuma Werner Riester GmbH & Co KG HATTERSLEY- Valves for all applications-Hattersley Newman Hendler Ltd HAITIMA CORPORATION-Ball Valves& Pipe Fittings-Haitima Corporation HEPHAISTOS"'-- Insulating productsLatty International SA HYPROMA TIK-Humidifiers- SpiraxSarco Limited JOHN-VALVE-Ball/ gate/ globe/check valves-John Valve MFG Factory Co Ltd JOUCOMATIC-Pneumatic valves and components-ASCO / Joucomatic (AS CO Controls BV) LATTYCH.'CAR8-Carbon gasket materialsLatty International SA LATTYct•' FLESE-Spiral wounded gasketsLatty International SA LATTY 0-°FLON-PTFE packings and/or gasket materials-Latty International SA LA TTY 01)GOLD-Asamid/synthetic filter gasket materials-Latty International SA LATTYSEAL--Mechan ica l Seals-Latty International SA LATTYTESC-Packings mad e of difficult fibres-Latty International SA

866

Buyer's Guide to Valves and Pipes

METASEAL GENERAL VALVE-Metal seated ball valve-Hindle Cockburn Ltd MONNIER-Compressed air productsSpirax-Sarco Limited NAF-CHECK-Metal seated swing check valve--NAF AB NAF-DUBALL-Metal Seated ball valvesNAFAB NAF-LINK IT-Intelligent valve positioner- NAF AB NAF-SETBALL-Metal seated ball segment valves-NAF AB NAF-TOREX-Metal seated buttertly valves-NAP AB NAF-TRIMBALL-Low-noise ball control valve-NAF AB NAP-TURNEX-Pneumatic controls actuator- NAF AB POSIFLATE "'-Inflatable seated butterfly valve--Posi-Flate SA07.1-SA48.1-Eiectric multi-turn actuators-Auma Werner Riester GmbH & Co KG SARV07.1-SARVI 05-Electric multi-turn actuators-Au rna Werner Riester GmbH & Co KG SG05.1-SG12.1-Electric part-turn actuators Auma Werner Riester GmbH & Co KG SPIRAFLO-Flowmeters-Spirax-Sarco Limited SPIRATEC-Steam trap monitorsSpirax-Sarco Limited SUPASEAL-Morntro ball valves-Hindle Cockburn Ltd

TORK-MATE 11 '- Pneumatic ActuatorPosi-flate TRAK-LOK0 ' -Limit switch/position monitor-Posi-Fl ate TRI-SEAL-3 piece lloating ball valveHindle Cockburn Ltd TWIN SEAL GENERAL VALVE-Double block & bleed plug-Hindle Cockburn Ltd ULTRASEAL-Floating ball valve-Hindle Cockburn Ltd VARIOMATIC-Actuator Controls- Auma Werner Riester GmbH & Co KG VIC-BALV'h - Grooved and ball valveVictaulic Company VIC-300-Grooved end butterfly valveVictaulic Company VIC-PLUG-Grooved end plug valveVictaulic Company YIH-TAl BRAND-Stainless steel ball valves, screwed end- Yih Kuang Metal Corporation YIH-T AI BRAND-Stain less steel gate/ globe/swing check valves- Yib Kuang Metal Corporation YIH-TAl BRAND-Stainless steel sanitary fittings/valves- Yih Kuang Metal Corporation YIH-TAI BRAND-Stainless steel screwed fittings- Yih Kuang Metal Cot:poration YIH-TAl BRAND-Stainless steel/ cast steel ball valves. flanged endYih Kuang Metal Corporation ZERO-FLEX 1!'- Rigid coupling for grooved pipe VIC-CHECK1H-Grooved end check valve

Editorial Index 2-way valves 3-way valves 4-way valves

148 149 150

A

Acoustic filters 680 Acrylonitrile butadiene styrene (ABS) 3 73 Actuation 15. 76.106.132.173.256. 259.266, 750. 772 Ad~baticflow 576.579 Aerodynamic noise 669 Aggressivecbemicals 337,465.470 Air relief valves 236 Air vents 732. 740 Angular movement of joints 432 Askania-type valves 142 ASTM test methods 809 Back-flow preventers and vacuum breakers 706 B Backfilling of pipes 625.627 Bacterial corrosion 3 31. 443, 44 7 Balancing 46,139,286.676,682 Ball check valves 187.189 Ballfloatvalves 63.301 Ball foot valve 245 Ball valves 3.19. 41. 47.181.252.254. 255.257.259.261.279.492.673.693696.698,699.732.747.754.759.763. 771. 775. 793. 808 Basic valve nomenclature 11 Bellows 54. 94. 105. 13 7. 178. 209 . 225. 428.430.677 Bellows seal-gate valves 104 Boiler-feed calcu Iations 63 7 Boiler-feed pump head 6 39 Bonded joints 420 Bottom blow-down valves 732 Brazing and soldering 424 Buckling strength 622 Bmied flexible pipes 618 Buried Pipes 352. 610.628 Bursting strength 62 2

Butt fusion 366. 3 70. 3 71. 384,421 Butterfly check valves 82 Buttedlyvalves 67.185 , 252.254.255, 257,266.663.675.693,699.732. 747. 763, 775

c Calculation of condensate flowrates 6 52. 655 Capacitance probes 304 Carbon steel pipe 3 3 2, 401 Cathodic protection 444.451.453,454. 456.462.472.473,659 Cavitation 190, 236.286.443.462. 566. 600,637,658.669,671,673.675.677. 696. 702 Cement mortar lining 328.465 Cement-buried pipelines 610 Centrifugal casting 345 Chatter 139, 165,554.677 Check valves 20. 82, 164.185.243.469, 492,693,706.731 . 732,744.775 Chemical resistance 355,359.364.368, 430.469 . 470 Choice of energy system 2 59 Clamp valves 116. 776 Class B bedding 62 5 Class C bedding 624 Cold-solvent cement welding 3 74 Colebrook-White equation 549 Colour codes for pipeline identification 3 5 Combined loading 629 Communication and supervisory control 271 Complex mixture flow 55 7 Compound joints 434 Compressible flow in pipes 5 72 Compression jointing 3 90 Compression moulding 344 Contact or hand lay up mouldings 344 Contractions and enlargements 596 Control valves 158. 192,199,229.250. 256,261 , 266.275.280. 587.659,663. 668.686. 693,699.732

868

Buyer's Guide to Valves and Pipes

Conversion tables 817 Corrective actions 781 Corrosion and cathodic protection 44 3 Corrosion by acids 448 Corrosion by alkalis 448 Corrosion control 462 Corrosion control by insulating joints 453 Corrosionofstainlesssteel 457,724 Corrosion probes 449 CPVC 31,210.364,3 72.420.506.626, 845 Crevice corrosion 443, 445, 460, 462 Critical deposition velocity 561 Critical velocity 56 7 Crushing strength 622.630 Cryogenic valves 768 Cylinder actuators 2 51, 2 55

D Deflection 352,402.610.618.620 Depth of trench 624 Desirable features of an insulating joint 455 Diaphragm actuators 251.256 Diaphragm valves 118,719 Direct-acting valves 151,160,225.229, 230 Discharge through penstocks 1 70 Discharge through pipes and fittings 595 Domestic water-supply valves 715 Double-containment piping 371.527 Double-disc valves 100 Double-seat valves 288. 718 Double-spool vaJves 143 Dual-containment piping 371.527

E Eccentric valves 176 Effect of inclined flow 5 51 Electric control 266 Electric solenoid 139,251.256 Electric systems 266 Electric-motor actuators 2 56 Electrical continuity 452 Electromagnetic control valves 2 9 7 Electromechanical methods of pipeline cleaning 4 79 Enhanced cleaning pigs 490 Epoxy resin-based pipe systems 342. 345 Erosion-corrosion 461 Expansion and contraction joints 42 7 External loading 628. 630 p Feed-check valves 732 fibre-reinforced plastic (FRP) pipe 3 3 9 Fieldbus control 77,272 Filament winding ofFRP pipe 344

Fire landing valves 756 Fire sprinkler systems 3 73 Fire-hydrant valves 754 Fire-safeballvalves 747 Fire-safe valves 743 Fitting of balance pipes 2 3 5 Flame arresters 748 Flanged couplings 408 Flexibility 432 Float control valves 301 Flow characteristics of valves 19 Flow coefficient Cv 58 7 E'low from stagnation conditions 5 79 E'low of liquids through pipes 533 Flow ofmixtures through pipes 556 Flow pattern 112. 559. 600 Flow regulators 321. 717 Flow through orifices 599 E'low values 21 Flow velocity 533. 545, 580 Fluid performance ll5 Fluoroplastics 4 70 Folding plugging head 508 Food and beverages 718 Foot valves 185. 187. 189. 243 Frictional factor 56 7 Frictional losses 3 74. 541. 563. 567. 596 Fusion jointing 380,422 G Galvanic corrosion 444.451.453 Gasket joints 405 Gate valves 98. 133. 181.257.492.693. 700, 701.719, 775 Gearoperators 278 Gland dimensions 779 Gland geometry 780 Glass pipelines 724 Globe valves 91. 107. 133. 181.231.300. 731.742.754.772.775 Grooved-end pipe and couplings 401 Guided or lift-type disc valves 18 7

H Handwheel drives for powered actuators 2 54 Head loss through valves and fittings 59 3 Heterogeneous flow 53 8. 55 8 High-integrity flange 415 Homogeneous flow 538,558.560 Hot tapping and plugging 506 Hybrid jacketing 523 Hydraulic and pneumatic check valves 187,195 Hydraulic systems 2 7. 265. 78 5 Hydrodynamic noise 669 Hygienic services 718

Editoriallndex

Impressed current systems 4 52 In-line spring assisted valves 190 Infra-red fusion 423 Infra-redsetting 250,269 Inherent and installed flow characteristics 78. 283 Installed exposure to sun 3 79 Iron and steel pipes 325.497 Isolating flanges 678 Isothermal flow 57 3

J Jacketed system design 524 Jacketed valves 525 Jacketing and dual containment jointsmadecold 714 Joints using heat 713

0 Oblique valves 97 Optimum pipeline cleaning methods 492,495 Overshoot 283

702

481,

p

522

L Laminar and turbulent flow 5 38 Launchers and receivers 484 Laying conditions 332 Leakde~ction 518 Leak-off 643 Level probes 303 Limit switches 2 78 Limiting length 5 77 Limiting pressure 5 77 Limiting temperature 5 77 Limiting values 575 Limiting velocity 576 Line protection 51 9 Location of sub-marine pipelines 520 Long pipelines and tunnels 517 Longitudinal strength 622 Losses in bends and fittings 584 Low-temperature valves 770

M Manual operators 2 51 Manual reset valves 150 Marine services 7 59 Mechanical characteristic of the casing 709 Mechanical joints 3 52. 397 Metal-seated ball valves 53 Metallic bellows 94. 430 Mitred bends 608 Modulating control valves 292. 300 Multi-turn actuators- modulating duty 250 Multi-turn actuators-on- off duty 2 50 N Natural gas regulators 316 Needle valves 92.107.133.663 Noisecontrol 667

Non-return valves in water systems Nozzle flow 580 Nozzle-flapper spool valves 14 3 Nuclear power piping 781 Nuclear services 775 Nuclear valve glands 775

869

Paperstock(pulp) 571 Parallel-slide valves 100 Path treatment for noise control 66 7, 6 76 Penstocks 168 Pharmaceuticals 719 Pigging 482 Pilot-operated valve 151. 158, 229 Pinch valves llO Pipe bends 500, 608 Pipe cutting and bending 49 7 Pipe joint sleeves 431 Pipe sizing 535 Pipe-wall thickness according to British Standards 603 Pipeline cleaning 4 79 Pipeline inspection and evaluation 511 Pipeline protection 328,451.471 Pipeline sizing 741 Pipewraps 473 Piston check valves 188 Piston-operated control valves 2 92 Pitting corrosion 460, 712 Plastic bellows 430 Plastic coatings 465 Plastic pipes 339.356.436 Plastic-lined pipe 335,345 . 354.474, 727 Plug valves (cocks) 41 Pneumatic control valves 296 Pneumatic piston controlled on-off valve 173 Pneumatic actuation systems 259 Polybutylene (PB) 368,423 Polyester. vinyl ester and bisphenol resin-based pipe systems 345 Polyethylene 354.357,361.371.374, 402.421 . 467, 471, 763 Polyethylene encasement 328.471 Polymervalves 178.718 Polypropylene (PP) 123, 178, 336,354. 368.371.390,421.442,468 Polyvinylchloride(PVC) 178.210,354, 357,362.374.377. 379.392,402,405, 420,467, 470,474.506.626,727

8 70

Buyer's Guide to Valves and Pipes

Pulyvinylidene fluoride (PVDF) 123. 210, 336,354.360.366.371.390,421.442. 469.471.474.527,529.727 Poppet lift foot valve 243 Position surveys 518 Post-chlorinated polyvinyl chloride (PVC-C or CPVC) 364 Preparation of trench bedding 624 Pressure-temperature ratings ofvalves 58 Pressure-balanced taper-plug valves 45 Production ofFRP pipe systems 344 Proportionate balancing method 68 7 Protection systems 703 Protective coatings and linings 465 Protective treatments 471 Puddle flanges 413 Pump delivery 640 Pump-energy waste 683 Pyrotechnic jointing 42 5 R

Radii of bends 505 Reducing valves in parallel 231 Reflux valves 185.701 Regulators 314 Reliefvalves 172.200.2 36.554.6 68 . 676.735.775 Resistance coefficients 5 84 Return-spring effect 15 5 Rotary-plate valves 141 Rotor valves 86, 718

Socket fusion 362 . 368.382.421 Socket fusion by hand .381 Solenoid enclosures l 56 Solenoid valves 146 Specialist pipe coati ngs 4 69 Split-spool valves 141 Spool valves 138.297. 668 Spring-loaded check valves 190. 199 Stagnation state 57 7 Stainless steel and speciality alloys for pipes 334 Standard pipe jacketing 522. 523 Steam boilers 729. 7 32 Steam-conditioning valves 7 3 5 Steam distribution 225. 728 Steam flow calculations 645 Steam flow through pipes 646 Steam services 226.435. 728 Steam tracing 742 Steam tra ps 234. 735 Steam-trap monitors 740 Stop valves 133.231.731 Stray-current corrosion 446 Stress-corrosion cracking 430.458.462 Superheated steam 220. 234. 646. 655. 7 30. 775 Support of plastic piping 3 7 3 Surge relievers 321 Surge-prone pipe systems 5 54 Survey methods for pipeline inspection 515 Swaged pipe jacketing 523 Swing check (flap) valves 164

s Safety and relief valves 200 Safety factors 357 Screw threads 418 Screw-down valves 133 Screwed connections 416 Screwedunions 419 Sealed joints 413 Segment control valve 286 Self-acting reducing valves 2 2 5 Self-operated regulator 3 14 Servo-valves 140 Shock preventers 681 Shock removers 681 Signalling 254 Simple corrosion 443 Simplified orifice formulae 582 Sizing of condensate-return lines 648 Sizing of steam lines 65 5 Slidevalves 127. 138 Sliding-platevalves 141 Sludge 117.128 . 327.538.556,567 Sluice valves 102 Slurries 73 . 100,111 . 128,137.326.538, 556.560, 562 Smart pigs 490

T Tee junctions and intersections 609 Temperature control valves 306 Temperature measurement method 68 7 Test specifications on non-return valves 708 Thermal insulation of pipes 380 Thermoplastic inner liners 3 54, 4 74 Thermopl astic pipe 356.506.626.726 Thickness of bends 504 Thrustactuators-on-oiTduty 250 Tilting disc check v alves 18 7 Tracking systems for pigs 48 5 Trench beddings 636 Trenching 623 Triple offset butterfl y valve 770 Tube bending 502 Tunneldiverter va lve 1 73 Turbulent flow 538.542.574 TV surveyin g of pipelines 513 Two-stagevalves 142 Two-wire communication systems 2 72 ()

Ultra-violet light

3 60

Editorial Index

v Vacuum breakers 706 Vacuum seal-off valves 765 Vacuum services llS. 119. 763 Valve actuators 249 Valve coefficients and tlow values 16 Valve corrosion 462 Valve linings 468 Valve positioning 275 Valve sizing 21. 79, 161.282 Valve trim 11.671 Valve-open or valve-closed test 743 Valve-spindle corrosion 463

8 71

Vane actuators 251. 255 Vanesystems 262

w Wafercheckvalves 187.194 Water hammer 173.176,185.191.197.

295,406.551.649. 668,677.731,738, 741 Water services 120. 368.463 . 467. 693 Wedge-gate valves 100. 775 Welded pipeline fittings 510 Welded joints 423.510 Width of trench 623

Advertisers Index ASCO/Joucomatic (ASCO Controls BV) Auma Werner Riester GmbH & Co KG Changdel Industrial Co, Ltd EMG Elektro-Mechanik GmbH Georg Fischer AG Haitima Corporation Hatters ley Newman Render Ltd Hindle Cock burns Ltd John- Valve MFG Company Ltd Latty
xvi Facing page 2 51 Facing page 7 5 Facing page 250 vi Facing page 59 viii Double page spread between 40 and 41 90 Facing page 283 Facing page 58 40 Facing page 7 4 Facing page 2 51 Facing page 2 8 2 Facing page 410 Facing page 2 8 3 Facing page 59

www.naf.se

Intelligent valves When you require an intelligent valve solution in your process there are three main points to consider: Better control, Predictive maintenance and Communication. NAF control valves with the NAF-LinkiT™ intelligent valve positioner provides you with the practical solution that makes the vision of the intelligent valve systems come true.

NAFAB SE-581 87 LINKOPING SWEDEN Telephone Facsimile e-mail webpage

+46 13 31 61 00 +46 13 13 60 54 [email protected] www.naf.se

NAF intelligent valve systems combine the unique experience and vast resources of the worlds largest intelligent automation company INVENSYS pic. Within INVENSYS we combine our knowledge in control systems, instruments and valves to provide our customers with a closed loop solution.

~ensys

Intelligent Automation

· STAINLESS STEEL BALL VALVES, SCREWED END ·STAINLESS STEEUCAST STEEL BALL VALVES, FLANGED END ·STAINLESS STEEL SANITARY FITTINGS. VALVES · STAINLESS STEEL SCREWED FITTINGS · STAINLESS STEEL GATE/GLOBE/SWIN( CHECK VALVES & Y-STRAINERS

YIH KUANG METAL CORP. 12F-1 , Sun Plaza, 57 Fu Hsing N. Road, P.O.Box 34-303 TAIPEI,TAIWAN Tel: 886-2-2776-6455- 9 Fax: 886-2-2776-57 E-mail: yihkuang @ms23.hinet.net

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HAITIMA VALVES

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How It Works:

Closed, unsealed, depressurized.

Closed, sealed, pressurized.

Open, unsealed, depressurized.

www.posiflate.com Corporate Headquarters 1125 Willow Lake Blvd. St. Paul, MN 55110 U.S.A. Phone (651) 484-5800 • Fax (651) 484-7015

pos··flat butterfly valves United Kingdom 14 Carters lane, Kiln Farm, Milton Keynes MK11 3ER, England Phone +44 (O) 1908 564455 • Fax +44 (0) 1908 564615

CHECK VALVES WAFER TYPE: DUAL, SINGLE PLATE BUTTERFLY VALVES: WAFER TYPE, LUG TYPE Manufacturing: e Standard: ANSI, ISO, DIN, API, BS, JIS • Material: Stainless Steel, Carbon Steel, Cast Iron e Size: 40 MM(l-1/2") - 1200MM(48")

CHANGDEL INDUSTRIAL CO., L TO. P.O.BOX 37-121 TAIPEI, TAIWAN JFL 92-1 SEC. 2, HOPING WEST RD., TAIPEI, TAIWAN FAX: 886-2-23079818 PHONE: 886-2-23053256-1 ISO 9002 EMA.a: [email protected] MORE THAN 18 YEARS

Remote settings

Contactless measurements

Applications - Waterworks and waste water treatment plants - Power stations - Waste Incinerator -Chemical and Petrochemical Industry

AUMA CONTROLS THE FLOW! Valve automation is one of the most important considerations in modern industries. The design of entire plants is based on constant electronic monitoring and control. Whether for open loop or closed loop control, modern electric actuators determine the precise and reliable fulfillment of important flow control parameters. Electric actuators with integral or remote motor cont rols are used in weatherproof or explosionproof environment.

AUMA manufactures electric valve actuators. Do not take a chance select AUMA.

Werner Riester GmbH & Co KG • Postfach 1362 • D-79373 M OIIhe1m l ei. 07631/809-0 • Fax 0763 1113218 • e-mail· riester@aurna com Internet: www auma com ·

... PLUS worldwide support from a company whose pro-active engineering advice, education, training and 'lifelong support package' provides full product guarantees. In addition you will benefit from optimum standards of service and technical support for as long as you need it.

spirax /sarco

Pipeline Controls & Instrumentation

Spirax-Sarco Limited, Charlton House, Cheltenham, Gloucestershire, GL53 8ER. Tel: 01242 521361 Fax: 01 242 573342 lntemct: llttv//www.spirax-sarco.co.uk c-11/flil: [email protected]

No other product reduces friction and performs under pressure like LATTY One compliments the other when solving your comprehensive valve sealing applications. LAITYgraf6940 resolves high pressure and high Easy to Fit temperature problems while maintening low friction For High-Pressure characteristics. High-Temperature LATTY flon 3260 LM has been specially designed Manual actuated Valves for modulating control valves eliminating hysterists prob!ems due to stem frict:on operating at high pressures. Both materials are capable to withstar.d chemtcal attack. Secure Stem Sealing In many cases, tn many industries, just the two gland For Modulating packing materials suHico to cover total plant Inventory Control Valves helping to reduce stock and eliminate choices.

LATTYgraf 6940

LATTYflon 3260 LM

LATTY 505 (Save On Sto(k)

LATTY®international s.a.

F01 the bCStln !TlOdern SABIIfi!J :ncluua~;e PLANT & OFFICES 1. rue Xavier-Laity - F-28160 Brou - nBIICO Tel +33 (0)2 31 44 77 7 1 - Fax· •J3 (0)2 37 44 77 99

e-mail. customerservicoOiany.com w."Y Iaiiy com

e LATTY. reg<StCfO
WYECO AUTO VALVES CO., LTO. WYECO

Office: 4F No.1 Sec.3 Chien Kuo N. Road Taipei, Taiwan Tel: 886-2-2502-5166.2509-7107 Fax: 886-2-2501-2863 Factory: No.6 Lane 2 Sec.3 Shan lin Rd. Luchu Hsiang Taoyuan Hsien Taiwan Tel: 886-3-324-5116--7. 324-4056--8 Fax: 886-3-324-5196 E-mail: wyeco@ms 1.hinet.net Home Page: http:// www.wyeco.com.tw

Diaphragm type Control Valve

Cylinder Operated Control Valve Y- Type

Cylir~der

Control Valve

Cryogenics Service Valve Short - Stem

llyper-Cryoqen
With Over 24 years of experience, Wyeco Auto Valves is one of Taiwan's leading valve manufacturers. We supply: • Cast Iron, Carbon Steel, Stainless Steel

• ANSI, JIS, DIN Standard

• Valve modification

• OEM manufacturing

w to cut time and money

out of piping installation. Victaulic grooved- and plain-end mechanical piping systems reduce total installed costs 10 to 40%, slash project calendar days, and minimize subsequent maintenance. You get shorter outage downtime and faster production changeover Pioneered 75 years ago and perfected by Victaulic ever since, these remarkable systems require no flame and need no alignment. Installation is easy to make up, fast, and reliable.

For Almost Any Type of Pipe Victaulic offers a system for most services from -30° to +230°F, pressures to 1,000 PSI (higher with special products), in sizes as large as 144". Carbon steel - Complete couplings and fittings systems up to 48"; valves and accessories to 24"; (BS, JIS and other standards). Stainles~ steel - Rigid or flexible for Type 316/3161 (standard) and 304 (optional) piping 3/4" through 18"; fittings and valves for process piping; fluoro -elastomer gaskets for process chemicals; white nitrile to FDA 21CFR. Part 177.2600.

Copper Complete system of couplings, fittings, and - - ·-- valves to CTS sizes (BS, DIN and AS) 2" through 8". No lead. No flame. No hassle. Fast. easy installation with hand tools. HDP plastic- Unique helical teeth bite into high density poly pipe -no fusing. special solvents. or adapters. Direct HOP-to-grooved transitions allow use of standard fittings, valves, and accessories. Sizes 2" through 20". Aluminum - A coupling and fitting system for aluminum pipe from 1" through 8", compatible with standard valves and accessories. PVC plastic - Standard couplings join Schedule 40 or 80 roll grooved or cut grooved PVC plastic pipe for varied services. to the working pressure of the pipe. Ductile iron - Sewage, waste, water treatment, and underground water supply lines from 3" through 36" (AWWA. BS, others) are easily, quickly joined with Victaulic products designed to ANSI/AWWA C-606 and related standards.

Tools - Victaulic has tools for in-place, job site, or shop roll grooving of pipe from 3/4" through 48"; cut grooving; and hole cutting. Available through worldwide stocking distribution. supported by 200 factory -trained piping specialists globally.

See us on the web- www.victaulic.com Or, for full facts: contact your Victaulic distributor or piping specialist, requesting catalog G-103. Phone: 610/559-3300 Fax: 610/250-8817 Write: PO Box 31, Easton,PA 18044-0031 USA e-mail: victauliOO.">victaulic.com

ictaulic·~ An .jjO 9001 certified company

Vl~l,;hc IS a leglS!erOO lr.ldcma.tk ol V~etaullc l.;ornt~•llY o! AUlt'J 101

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Company ol Ammrn Allt>',lh\G rose~wxl

36th year of publication: all previous editions sold out Section One: Introduction SI Units Pump Evolution Pump Classification Pump Trends

PUMPING MANUAL 9th Edition

Section Two: Pump Performance and Characteristics Fluid Characteristics Pump Performance Calculations, Type Number and Efficiency Area Ratio Pipework Calculations Computer Aided Pump Selection

By Christopher Dickenson \\'idL·h recognised a s the tir-.r source of refence o n .1ll .hpL·ds of pump tvL·hn()lt>g\· and .lplliL·;nions the Pumping \ Lmu.1i w ill en~1blc \'Oll to .. .

Section Three: Types of Pumps Centrifugal Pumps Axial and Mixed Flow Pumps Submersible Pumps Seal-less Pumps Disk Pumps Positive Displacement Pumps (General} Rotary Pumps (General} Rotary Lobe Pumps Gear Pumps Screw Pumps Eccentric Screw Pumps Peristaltic Pumps Metering and Proportioning Pumps Vane Pumps Flexible Impeller Pumps Liquid Ring Pumps Reciprocating Pumps (General} Diaphragm Pumps Piston, Plunger Pumps Self Priming Pumps Vacuum Pumps

Section Four: Pump Materials and Construction Marallic Pumps Non Metallic Pumps Coatings and Linings

• Sf,L'Ctty th e right pump tur tlw usk • I k-.ign cost-ctfcctin· pumf, systems • l ~tHkr -.und thL· tcrtnin ology •

effective in:-.ull.n ion, oper.nion ;111d tll;lintl'nance of <111 your r'umpmg FthltrL'

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Section riVe: Pump Ancillaries Engines Electric Morors and Controls Magnetic Drives Seals and Packaging Bearings Gears and Couplings Control and Measurement

Section Six: Pump Operation Pump Installation Pump Start-up Cavitation and Recirculation Pump Noise Vibration and Critical Speed Condition Monitoring and Maintenance Pipcwork Installation

Section Seven: Pump Applications Water Pumps Building Services Sewage and Sludge Solids Handling Irrigation and Drainage Mine drainage Pulp and Paper Oil and Gas Refinery and Petrochemical Pumps Chemical and Process Dosing Pumps Power Generation Food and Beverage Viscous products Fire Pumps High Pressun: Pumps

Section Eight User Information Standards and Data Buyers Guide Editorial Index Advertisers Index

1000+ pages 1500 figures and tables ISBN: 185617 215 5

State-of-the-art piping systems

Modern piping systems ore on effective port of water trea tm ent a nd distribution systems. They ore equa lly indispensable fo r th e

A complete system of fitti ngs, pipes, valves, measurement and co ntro l technology and plastic pumps.

anviro nmentol technologies to protect air, .voter and soil. Toke advantage of our kn ow-how and experience in ABS, PVC-U, PVC-C, PB, PP,

Excellence

PE, SYGEF'''-PVDF

in piping systems

3eorg Fischer Piping Systems Ltd., C H-820 I Schaffhausen/Switzerland f el. +41 10152-631 I I I I, Fox +4 I 10152-631 28 46 e-mail : [email protected], Internet: http:! /www.piping. georgfischer.com

GEORG FISCHER +GF+

...,.,41 ., ~(., Flow Technologies

111

THE PCC ADVANTAGE BRINGING AEROSPACE QUALITY TO THE VALVE INDUSTRY PCC Flow Technologies offer a complete range of Butterfly, Ball and Check Valves, including: 81 - Quick Release Butterfly Valve. 82 - Tablet Butterfly Valve. 810 - Split Body Hygienic Butterfly Valve. 811 - Wafer Type Butterfly Valve. 812 - Lugged Type Butterfly Valve. 814 - PTFE/EPDM Backed Seat Butterfly Valve. B16A - Aluminium Vertically Split Bodied Butterfly Valve. 8160 - Ductile Iron Vertically Split Bodied Butterfly Valve. B16C - Carbon Steel Vertically Split Bodied Butterfly Valve. 816S - Stainless Steel Vertically Split Bodied Butterfly Valve. 820 - High Performance Butterfly Valve. 825 - Wafer Check Valve. 855R - One Piece Reduced Bore Ball Valve. 855F - Two Piece Full Bore Ball Valve. 8641 - Three Piece Full Bore Ball Valve. TechTorq range of Double Acting and Single Acting Quarter Turn Pneumatic Actuators.

Butterflv ... Valve Materials available are: Body Disc Shaft Seats

-

Aluminium, Cast Iron, Ductile Iron, Carbon Steel and Stainless Steel. Ali-Bronze, Cast Iron, Stainless Steel. Stainless Steel. EPDM (Black and White), Buna, Silicon, Viton, Nitrile, PTFE

HEAD OFFICE: Spiersbridge Terrace Unit 5/6- Block 6 Thornliebank Industrial Estate Glasgow G46 8HZ Telephone 0141 638 8138 Fax 0141 638 8588

SALES OFFICE: Unit C, Ryknild Street Barton Turn, Barton Under Needwood Nr Burton On Trent Staffordshire DE13 8EB Telephone 01283 713034 Fax 01283 716930

(PCC Flow Technologies Ltd. is a wholly owned subsidiary of Precision Castparts Corp., a worldwide manufacturer of complex metal components and products serving a wide variety of aerospace and general industrial applications)