Ssp Book.pdf

Boiler Design Calculations First Edition 2008

Preface The art of science of technology of boiler is a complicated subject. Principles of science, engineering and technology are used to evolve boiler design. Design is creative. Engineering of a boiler requires solution of mathematical equations. A boiler is defined by The Indian Boiler Regulations, 1950 (IBR) which has a close containment of capacity of above five gallons (22.75 liters) used for raising steam. Boiler is used by mankind for millenniums. The boiler pressure parts requires special treatment, since failure of pressure parts will lead to loss of the boiler.

The following chapters are given in the present book:

Part – A :

Boiler

Part – B :

Piping

Part – C :

Cold Structure

Part – D :

Hot Structure

Part – E :

Stress Analysis

Part – F :

Codes and Standards

Part – G :

A Hundred Questions on Boilers

The scope of the book is only to indicate certain computational procedures and theory. A boiler engineer should be familiar with the boiler products. Hence, a visit to a manufacturing unit and a visit to a job site are important. Boiler engineering can be classified as: design, manufacturing, construction, operation, maintenance, modernization and disposal. This book helps in design of boiler components.

Boiler design can be broadly classified into thermal engineering, mechanical engineering and electrical engineering. Thermal engineering consists of combustion, heat transfer, fluid flow, flow distribution, pressure loss, pumping power, auxiliary power consumption, plant efficiency. Mechanical engineering consists of: temperature calculation, material selection, load calculation, load combinations, thickness selection, weld design, insulation selection, support selection, guides design, drawings, Bills of Materials, material forecasts, review of boiler weight. Electrical engineering involves electrical, motor, control, instrumentation, gages, valves, Piping and Instruments Diagram (P & ID).

Introduction Boilers are of many types. The boilers may be land based or sea based. In the present book, land based boilers are considered. Strength of a component depends on the following variables: material, meterial temperature, design life, load orientations and types of loads. Computers play a major role in doing boiler design calculation for boilers. Boiler design calculations can be done by experienced and qualified persons. Design calculations are part of the design activities. The following are the design activities: design, engineering, stress analysis, detailing, drafting, documentation and document approval. In a design office the following sequence of work is carried-out: layout, arrangement of parts, design of parts and review and carry-out changes, where required.

After the advent of computers, the activities in the design office has undergone a sea change. In any project, the following three aspects are of prime importance: speed of execution, right price and acceptable quality. The designer should be diligent to strike a balance between the above said three requirements. Design is an iterative process. Designers rarely visit job sites. Designers' knowledge is bookish, most of the time. Computers are used to reduce the cycle time for design. The output of the design office is drawings and related documents.

The following design assumptions are made during design: linear material behavior, elastic material, homogeneous material, isotropic material behavior, steady-state loading, static component. The following additional requirements are to be satisfied: head room, walk way (a person with shoe, helmet and a tool box in one hand should be able to walk, erect), interference (hard clash and soft clash) and interference resolution, interfaces taken care-off, required access provided for equipment, approach to components are adequate.

The following subjects guide an engineer to understand the principles of boiler design: Thermodynamics, Heat Transfer, Fluid Mechanics, Solid Mechanics, Engineering Mechanics, Strength of Materials, Metallurgy and Stress Analysis. The designer should go beyond the codes and standards to assure “Fail Safe Design”. The designer is the mother of the product. The designer should know about the product from “Cradle to Grave”. The designer should know the product, process, problem, places, persons and prices. Knowledge of these six aspects will help in taking timely decisions.

Part – A : Boiler Contents Preface Introduction Contents A-1

Design of Boiler Pressure Parts, Piping and Supports

A-2

Calculation of Boiler Drum Thickness as per The Indian Boiler Regulations-1950, 270

A-3 Water Wall Tube Thickness Calculation as per The Indian Boiler Regulations-1950, 338(a) A-4 Thickness Calculation for Flat End Cover as per The Indian Boiler Regulations-1950, 342(b) A-5

Boiler Pipe Thickness Calculation as per The Indian Boiler Regulations-1950, 350

A-6

Pipe & Pipe Bend Thickness Calculation as per IBR-1950, 350

A-7

Calculation of Ligament Efficiency as per BS1113 – 1989

A-8

Bed Tubes Design

A-9

Design of Man-Hole Cover

A-10 The Indian Boiler Regulations, 1950 A-11 Design of Piping and Supports A-12 Loads at Ceiling from Pressure Parts A-13 Pressure Parts Hangers Design A-14 Design of a Truss A-15 Boiler Pipe and Tube Flexibility Requirements A-16 Uncompensated Holes in Boilers A-17 Pressure Parts Tubes Under Axial Tension A-18 Buckstays (sketch – A3 size) A-19 Boiler Thermal Expansion Movement Diagram A-20 Thermal Expansion Movement and Allowable Forces and Moments A-21 Design of Foundation Bolts A-22 Ceiling Girder Design (sketch – A3 size) A-23 Design of Chimneys - I A-24 Foundation Bolts for Steel Chimneys - I A-25 Foundation Bolts for Steel Chimneys – II A-26 Design of Chimney – II A-27 List of Power Plant Equipment A-28 Foundation Bolts for Steel Chimneys – III A-29 Foundation Bolts for Steel Chimneys - IV

A-30 Design Data Sheet for Duct, Flue and Casing A-31 Design of Boiler Drum Dished Ends A-32 Design of Stiffeners for Flues, Ducts and Casings A-33 Design of Flues, Ducts and Casings A-34 Design of Expansion Joints A-35 Buckstay Spacing Calculation A-36 Design of Buckstay Beams A-37 Buckstay Sizing Calculation A-38 Buckstay Beam Calculation (Example) A-39 Structural Steel Stability A-40 Design of Floor Grills A-41 List of Boiler External Piping A-42 Rationalized list of Raw Materials – Mild Steel (IS2062) A-43 Strength Calculation for Boiler Pressure Parts A-44 Boiler Drum Seismic Guides (Earth-Quake Guides) A-45 Allowable Stresses as per The American Society of Mechanical Engineers A-46 Design of Hemi-Spherical Dished Ends as per IBR-1950, 278 A-47 Strength Calculation for Pipe Bends as per IBR-1950, 350 A-48 Tube Lug Design A-49 Header Support Lug A-50 Comparison of Structural Steel Beams Design Methods A-51 Strength Calculations for Boiler Drums A-52 Design and Stress Analysis of Piping and Supports A-53 Skin Temperature of Pipe Insulation A-54 Engineering Materials and Their Properties A-55 Vibration A-56 Stress Analysis – Its Application and Use A-57 Pipes – Their Application and Use A-58 Drum Thickness Calculations A-59 Design of Structural Steel Connections as per IS 800 – 1984 A-60 Design Checks as per BS 2790 – 1989 A-61 Design of Steel Structures A-62 Structural Steel Stress Analysis A-63 Boiler Drum – IBR Requirements A-64 Strength Calculations for Shell and Tube Heat Exchangers

A-65 Design of Buckstays and Furnace Guides A-66 Strength Calculation for Inline Boiler A-67 Strength Calculation for Power Boilers A-68 Introduction to Design of Static Mechanical Equipment A-69 Ligament Efficiency for Drums and Headers

A-70 Design of 2:1 Semi-Ellipsoidal End Cover as per IBR – 278, 1950 A-71 Design of Power Tube Boilers A-72 Design Checks for Fire Tube Boilers A-73 Engineering Design A-74 Design of Flat End Covers for Shell and Tube Heat Exchanger as per IBR, 1950 A-75 Loads on Boilers A-76 Furnace Guides for Top Supported Boilers A-77 Design of Piping Supports and Restraints A-78 Design of Boiler Supporting Hangers A-79 Design of Supporting Structures for Power Boilers A-80 Design of Boiler Pressure Parts A-81 Design of Piping for Power Boilers A-82 Introduction to Thermal Power Plants A-83 Atmospheric Fluidized Combustion Boilers (AFBC) A-84 Principles of Engineering A-85 Combustion, Heat Transfer, Fluid Flow and Pumping A-86 Heat Transfer in Boilers and Heat Exchangers A-87 Convective Heat Transfer A-88 Radiant Heat Transfer A-89 Conduction of Heat A-90 Flow of Fluids inside Pipes and Tubes A-91 Design of Rigid Hangers (Free – Fixed) A-92 Design of Rigid Hangers (Guided – Fixed) A-93 Header Height above Roof A-94 Education, Training, Enabling and Empowering A-95 Design of Large Coal Fired Power Boilers A-96 Design of Boiler Framing

A-97 Arrangement of Power Boilers A-98 Safety Valves A-99 Laws of Nature A-100 Flow of Fluids A-101 Design of Vertical Tanks A-102 Design of Horizontal Pressure vessel A-103 Design of Base Plate A-104 Support of Assemblies in the Rear Pass of Boilers A-105 Design of Pin Joints A-106 Design by Analysis A-107 Load Chain Management A-108 Vibration of Heat Recovery Steam Generator (HRSG) tubes A-109 Design of Collector Channels as per IS : 800 – 1984 A-110 Torsion of ISMB200 Beam A-111 Vibration of ISMB200 Beam A-112 Design of Supporting Structures for Power Boilers A-113 Design of Piping for Power Boilers A-114 Design of Steel Structures A-115 Strength Calculations for Boilers A-116 Design of Fire Tube Boilers A-117 Design Checks for Fire Tube Boilers A-118 Stress Evaluation as per ASME Section VIII Division 2 A-119 Engineering Mechanics A-120 Stresses in a Pipe A-121 Paths to Prosperity in Business A-122 Design of Piping A-123 Vibration of Heat Recovery Steam Generator (HRSG) Tubes

A-1: Design of Boiler Pressure Parts, Piping and Supports 1. Introduction This write-up gives particulars of the design details on the above subject. Design of a product involves design, engineering, stress analysis, detailing, drafting, documentation and document approval. 2. Loads and Load Combinations Primary loads, secondary loads and occasional loads act on the components. Suitable combinations of these loads are to be considered. 3. Materials Iron and steel with various alloying elements and strength properties are used. 4. Pressure Parts Pressure parts design is based on the functional requirement. Pressure parts are used as heat exchangers. 5. Piping Piping includes pipes, valves, gages and attachments. The primary purpose of piping is conveyance of fluids. 6. Structures Structures are made of carbon steel. Use of alloy steel is also considered at present. Steel structures are usually braced. Unbraced steel structures are uneconomical. 7. Service Requirements The boiler pressure parts, piping and structures should be safe, secure, good quality and economical. 8. Design Assumptions The boilers are designed based on the following assumptions: linear material behavior, elastic material property, homogeneous materials, isotropic property of materials, steady state loading and static components. Since all these six assumptions are wrong, suitable precautions are taken in arriving at the allowable stress. The allowable stress is inversely proportional to the Factor of Safety. Factor of Safety is also known as Factor of Ignorance. 9. Human Factor Engineering As the boiler is a critical equipment covered by several safety requirements and laws, the following are to be satisfied: provide required access, introduce adequate approach, provide required head room and walk-way (a worker with a helmet, shoes and a tool box in one hand should be able to walk erect, without injury), check for clashes (soft clashes and hard clashes) and take care of interfaces.

A-2: Calculation for Boiler Drum Thickness as per The IBR – 270, 1950 1. Introduction This write-up is based on The Indian Boiler Regulations-1950, 270 for boiler drums. 2. IBR Formula WP =

2 f E (T – C) (D + T – C)

Hence, T=

WP x D (2 f E – WP)

+C

Where, T = minimum required thickness, mm WP = working pressure, kg / sq mm (g) D = drum inside diameter, mm f = drum metal allowable stress, kg / sq mm p = tube hole longitudinal pitch, mm d = tube hole diameter, mm C = 0.03 inch = 0.762 mm 3. Exercise WP = 100.0 kg / sq cm (g) D = 1500 mm f = 1400.0 kg / sq cm p = 200 mm d = 40 mm E = (p – d) = (200 – 40) = 0.8 p 200 T =

100.0 x 1500 (2 x 1400.0 x 0.8 – 100.0)

+ 0.762

= 70.9 mm Fabrication allowance = T1 = 5.0 mm Raw plate thickness required = T2 = T + T1 = 70.9 + 5.0 = 75.9 mm Raw plate thickness selected = T3 = 80 mm > T2 = 75.9 mm Hence, safe

A-3: Water Wall Tube Thickness Calculation as per The IBR – 338(a), 1950 1. Introduction The water wall tube thickness of boilers is computed using the IBR. 2. IBR Formula The following formula is from the IBR-338(a): WP = 2 f (T – C) (D – T + C) Hence, T = WP x D + C (2 f + WP) Where, T = minimum required thickness, mm WP = working pressure, kg / sq mm (g) D = tube outside diameter, mm f = tube metal allowable stress, kg / sq mm C = 0.75 mm when WP = 70 kg / sq cm (g) and lower = 0.0 mm when WP = above 70 kg / sq cm (g) 3. Exercise WP = 100.0 kg / sq cm (g) D = 51 mm f = 1200 kg / sq cm

T =

+ 0.0 mm = 2.04 mm 100 x 51 (2 x 1200 + 100)

Use T1 = 4.0 mm > T = 2.04 mm Hence, Safe

A-4: Thickness Calculation for Flat End Cover as per The IBR – 342(b), 1950 1. Introduction This write-up is based on The Indian Boiler Regulations,1950 – 342(b). 2. IBR Formula

f (t – C) 2 d2K

WP =

Hence, t =

d K x WP f

+ C

Where, t = minimum required thickness, mm d = pipe / header inside diameter, mm K = 0.28 WP = working pressure, kg / sq mm (g) f = allowable stress for end cover, kg / sq mm C = 1.0 mm 3. Exercise d = 219.1 – 2 x 20 = 179.1 mm WP = 100.0 kg / cm (g) f = 1200.0 kg / sq cm t=

179.1

0.28 x 100.0 1200.0

+ 1.0 mm = 28.4 mm

Fabrication allowance = t1 = 3.0 mm Raw plate thickness required = t2 = t + t1 = 28.4 + 3.0 = 31.4 mm Raw plate thickness selected = t3 = 32 mm

A-5: Boiler Pipe Thickness Calculation as per The IBR – 350, 1950 1. Introduction The boiler pipe thickness is computed using the IBR. 2. IBR Formula The following formula is from the IBR-350: WP = 2 f (T – C) (D – T + C) Hence, T = WP x D + C (2 f + WP)

Where, T = minimum required thickness, mm WP = working pressure, kg / sq mm (g) D = pipe outside diameter, mm f = pipe metal allowable stress, kg / sq mm C = 0.75 mm 3. Exercise WP = 100.0 kg / sq cm (g) D = 508 mm f = 1200 kg / sq cm

T =

100 x 508 (2 x 1200 + 100)

+ 0.75 mm = 21.07 mm

Negative tolerance on pipe thickness = 12.5% Nominal pipe thickness required = T1 = T x

100 = 21.07 x 100 = 24.08 mm (100 – 12.5) (100 – 12.5)

Use T2 = 25.4 mm > T1 = 24.08 mm

Hence, Safe

Sheet1

A-6: PIPE & PIPE BEND THICKNESS CALCULATION AS PER IBR, 1950 – 350

Pipe Material

Serial Number

Working Temperature

Allowable Stress

Outside Diameter

Pipe Nominal Thickness

f

D

Tn

mm

mm

[5] 219.1 114.3 101.6

[6]

Degree C Kg / sq cm [1]

[2] 1 SA106 GrB 2 SA106 GrB 3 SA106 GrB

[3]

[4] 1200 1250 1250

350 300 300

Negative Minimum Is Design Tolerance Thickness of Safe? (Is on Pipe {Tmin>T1?} Thickness Tol

25.4 12.7 12.7

Tmin mm '= Tn x % (Straight (100 – Tol) / Pipe) 100 [7] [8] 12.5 22.23 Yes 12.5 11.11 Yes 12.5 11.11 Yes

Bend Thickness of Thickness of Ligament Code Minimum Required Thickness Thinning Bend Bend Efficiency Allowance (Pipe) AllowIs Design Required Provided ance Safe? Serial T1 Thin T2 T3 WP Number C {Is mm mm mm T3>T1?} E Kg / sq cm '= Tmin x % = T1x 100 / (g) mm = (WP x D) / ( 2 f E + WP) + C (100 – Thin) / (100 – Thin) 100 [9] [10] [11] [12] [13] [14] [15] [16] [17] 1 180.0 1.0 0.75 16.04 10.0 17.82 20.0 Yes 2 120.0 1.0 0.75 5.99 12.5 6.84 9.7 Yes 3 120.0 1.0 0.75 5.4 12.5 6.18 9.7 Yes Working Pressure

Prepared PRK Date 29. Jan. 2008

Checked: SSP Date: 30. Jan. 2008

Approved: Date:

Tmin = Tn (100 – Tol) / (100) T1 = (WP D) / (2 f E + WP) + C T2 = T1 x 100 / (100 – Thin) T3 = Tmin (100 - Thin) / 100

Straight Pipe

Is Tmin > T1?

Bent Pipe

Is T3 > T1?

Page 1

SSP 30. Jan. 2008

A-7: Calculation of Ligament Efficiency as per BS113 – 1989 1. Introduction This write-up gives calculation for computing the ligament efficiency. 2. Ligament Efficiency The following ligament efficiencies are considered: a) b) c)

longitudinal ligament circumferential ligament diagonal ligament

Longitudinal ligament efficiency = E1 = (p – d) / p Circumferential ligament efficiency = E2 = 2 (pc – d) / pc Diagonal ligament efficiency = E3 =

2 A + B + (A – B) 2 + 4 C 2

A=

cos 2 α + 1 2 (1 - d cos α ) a

B = ( 1 – d cos α ) (sin 2 α + 1) / 2 a C=

sin α cos α 2 ( 1 – d cos α) a

cos α =

1 1

sin α =

+b2/a2

1 1

+ a 2/ b 2

Ligament efficiency = E = Minimum ( E1, E2, E3)

Sheet1

A-8: Bed Tubes Design Serial Number

Description & Formula Symbol 1 Tube Diameter = D Tube Thickness = 2T Tube Material = 3 MAT1 Tube Temperature 4 = t1 Tube Allowable 5 Stress = f Tube Working 6 Pressure = WP Longitudinal Pressure Stress = 7 S1 Allowable Bending Stress = S2 = 8 f - S1 9 Tube Length = L1 10 A 11 I 12 Tip Load = P 13 Z Bending Moment = 14 BM 15 Bending Stress

SSP 28. Jan. 2008

Unit mm

Case-1

mm

Case-2 63.5

6.0

6.0

SA210 GrA1 Degree C

Remarks 76.2 Input 6.0 Input

SA210 GrA1 SA210 GrA1 Input

350

350

Kg / sq mm Kg / sq mm (g)

12.00

12.00

1.00

1.00

1.00 Assumed

Kg / sq mm

1.41

1.92

2.45 Calculated

Kg / sq mm mm Sq mm Mm^4 Kg Cu mm

10.59 3000 848.23 218525.26 100 8569.62

10.08 3500 1083.85 452811.98 100 14261.79

9.55 Calculated 4000 Assumed 1323.24 Calculated 821076.31 Calculated 100 Input 21550.56 Calculated

Kg-mm Kg / sq mm

79993.95 9.33

94944.69 6.66

110387.42 Calculated 5.12 Calculated

mm mm mm

Safe 7.71 110.68 9.23

No

Checked: Date:

Case-3

51

Safe

16 Is Design Safe? 17 ∆ Tube Weight 18 ∆ Total Weight 19 ∆α 20 Is Design Safe?

Prepared: Date:

Calculation

Approved: Date:

Page 1

SSP 28. Jan. 2008

350 Assumed 12.00 Input

Safe 8.81 87.72 10.77

No

No

Output 10.12 Output 75.08 Output 12.31 Calculated Output

A-9: Design of Man-Hole Cover 1. Introduction The man-hole cover in boiler drums is used by humans to enter the boiler drum for maintenance. 2. IBR Formula t = d

K x WP f

+C

Where, d K WP f C

= 450 mm = 0.28 = 100.0 kg / sq cm (g) = 1200 kg / sq cm = 1.0 mm

t

= 450

0.28 x 100.0 1200

+ 1.0

= 69.8 mm Fabrication allowance = t1 = 5.0 mm Required thickness = t2 = t + t1 = 69.8 + 5.0 = 74.8 mm Thickness of raw plate selected = t3 = 75.0 mm > t2 = 74.8 mm

Hence, safe

A-10: The Indian Boiler Regulations, 1950 1. Introduction The Indian Boiler Regulations, 1950 was issued in the year 1950 to bring-in uniform safety of boilers. The Central Boiler Board convenes meetings to amend and interpret the IBR. 2. The Indian Boilers Act, 1923 The Indian Boilers Act, 1923 (with amendments) authorizes the government of India to implement safety requirements for boilers. 3. Material The IBR identifies materials of construction. Where particulars of materials used in foreign countries is not provided in the IBR, the foreign codes can be directly used. 4. Shapes The shapes of the boiler drums, headers, pipes and tubes are dealt in the IBR. The details of nozzles and connections preferred are also indicated. Particulars of allowable welding details are indicated. 5. Sizes Sizes indicated in the IBR includes the thickness and dimensions. Detailed indications are given for the holes, pitches, openings and area compensations. 6. Loads and Load Combinations The primary load considered is the internal pressure due to water and steam. For the fire tube boilers, the external pressure on the fire tubes are considered. Over and above the loads indicated explicitly by the IBR, additional loads such as wind load and earth-quake load shall also be considered. 7. Stress The induced stress shall be limited to the respective allowable stress. There are no clearly indicated allowable deformations as per the IBR. 8. Components Design rules for the following are clearly indicated in the IBR: drum, header, pipe, pipe bend, pipe elbow, tube, tube bend, reducer, TEE, openings, area compensation, ligament efficiency, flat end cover, dished end cover and man-hole cover. 9. Testing The pressure parts shall be tested for 1.5 times the working pressure (WP) before the operation of the boiler. Individual components of boilers can be tested separately in the work shop.

A-11: Design of Piping and Supports 1. Introduction This write-up gives particulars on the above subject. 2. Loads and Load Combinations The piping and supports are subjected to various loads and load combinations. Suitable combinations of loads are considered. 3. Materials The piping are primarily made of iron and steel. 4. Thickness The thickness of the piping is decided based on the internal pressure. 5. Supports Supports for the piping is decided considering the loads, sizes, stresses and deformation. 6. Flexibility Required flexibility is to be provided to take care of the thermal expansion of the piping. 7. Restraints Required restraints are to be provided to take care of the loads such as wind loads, earth-quake loads and safety valve blowing jet reaction. 8. Design by Stress Analysis The piping should take care of various loads. Hence, the piping is designed iteratively, improving the design at every step. 9. Design Steps a) b) c) d) e) f) g)

Finalize piping diameters Finalize piping thicknesses Calculate loads and load combinations Calculate the allowable support span Decide support locations Decide restraint locations and types Carry-out stress analysis and finalize design, iteratively

Sheet1

A-12: Loads at Ceiling from Pressure Parts

Serial Number

Location 1 Primary SH-1A 2 Primary SH-1AA 3 Primary SH-1AAA 4 Primary SH-1B 5 Primary SH-1BB 6 Secondary SH 7 Secondary SH 8 Tertiary SH 9 Tertiary SH 10 Tertiary SH 11 Front WW 12 Furnace SWW 13 Extended SWW 14 Extended SWW 15 Rear Exit Screen 16 Furnace Roof 17 Boiler Bank Side 18 Boiler Banks 19 Boiler Banks 20 Economiser Side 21 Economiser Rear 22 Economiser Panel 23 Economiser Panel 24 Drum

Load / Rod Tonne 7.416 5.562 2.781 14.830 3.707 9.750 3.656 6.500 4.875 2.437 19.170 24.000 6.400 3.200 9.625 3.000 18.500 23.300 4.236 27.750 14.500 9.100 0.941 36.250

Total

Prepared: Date:

PRK 30. Jan. 2008

Number of Rods 12 16 32 12 32 12 32 12 16 32 6 16 4 2 8 6 4 12 66 4 4 24 116 4 484.000

Checked: Date:

Total Load / Row Tonne 88.992 0 0 177.960 0 117.000 0 78.000 0 0 115.020 384.000 25.600 0 77.000 18.000 74.000 279.600 0 111.000 58.000 218.400 145.000 1967.572

SSP Approved: 31. Jan. 2008 Date:

Page 1

Remarks

SSP 31. Jan. 2008

Cal1

A13: Pressure Parts Hangers Design Serial Number

Description & Symbol

1

Hanger Location

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

27

Formula

Calculatio n

Load / Hanger = P Hanger Rod Diameter = D Thread Diameter = d Thread Pitch = p Root Diameter = DR Root Area = AR Root Section Modulus = ZR Rod Moment of Inertia = I K L KL C2 C3 Ca3 Ca4 YA W MA σt σb σ total Hanger Material Design Temperature Allowable Stress (tension) = Sm Allowable Stress (total) = 3.0 Sm

Unit

PRK

Date:

31. Jan. 2008

Case-2

Case-3

Remarks

Primary SH-1A

Primary SH1AA

Primary SH1AAA

Input

Kg

7416

5562

2781 Input

mm

60

50

32 Input

mm mm

58 4

48 4

30 Input 4 Input

mm Sq mm

54 2290.22

44 1520.53

26 Calculated 530.93 Calculated

Cu mm

15458.99

8362.92

1725.52 Calculated

mm ^ 4 1 / mm mm mm / mm

mm Kg Kg – mm Kg / sq mm Kg – sq mm Kg – sq mm

555497.2 260576.26 39760.78 Calculated 0.0008 0.0010 0.0019 Calculated 4636 8781 9874 Input 3.79 9.07 18.47 Calculated 22.07 4351.65 52269909.61 Calculated 21.09 4350.65 52269908.61 Calculated 21.09 4350.65 52269908.61 Calculated 18.28 4342.58 52269891.14 Calculated 50 50 50 Input 161.46 40.63 15.79 Calculated 188873.76 39315.52 8445.15 Calculated 3.24 3.66 5.24 Output 12.22 4.7 4.89 Output 15.46 8.36 10.13 Output IS2062 IS2062 IS2062 Input

Degree C

350

350

350 Input

Kg / sq mm

8.10

8.10

8.10 Input

Kg / sq mm

24.30

24.30

Is Design Safe?

Prepared

Case-1

Yes

Checked: SSP 1. Feb. Date: 2008

Approved:

SSP

Date:

1. Feb. 2008

Page 8

Yes

24.30 Calculated

Yes

Output

A-14: Design of a Truss 1. Introduction This write-up gives design details for a truss. 2. Forces The external forces and the internal forces on the truss are indicated in Figure-1.

5.0 t 10.0 t

10.0 t

10.0 t

15.0 t

Figure-1: Forces in a Truss 3. Design Some of the members are in tension. Some of the members are in compression. The members are designed considering the following three requirements: a) induced stress < allowable stress b) induced deformation < allowable deformation c) take care- of the vibration requirements 4. Detailing & Documentation The connections are designed to transfer the relevant forces. Required materials forecasts and Bills of Materials are issued to take action for procurement of materials.

A-15: Boiler Pipe and Tube Flexibility Requirements 1. Introduction This write-up gives an empirical check for the flexibility requirement of pipes and tubes. 2. Design Checks The following design checks are to be done: a) b) c) d)

provide thickness based on the internal pressure in kg / sq cm (g) provide supports based on the loads, including self-weight provide flexibility based on the thermal expansion requirements provide restraints based on the occasional loads, such as wind and seismic (earth-quake loads)

3. Flexibility Requirements From The Indian Boiler Regulations, 1950 – 370 ( c) (3), DY 2 (L – U)

< = 208

Where, D Y L U

= = = =

nominal pipe size in mm resultant of movements to be absorbed by pipeline in mm developed length of line axis in meter anchor distance (length of straight line joining anchors) in meter

4. Exercise D Y L U

= = = =

100 mm 50 mm 7.5 m 1.5 m

100 x 50 = 138.8 < 208 2 (7.5 – 1.5)

Hence, safe

A-16: Uncompensated Holes in Water Tube Boilers 1. Introduction This write-up gives particulars on the above subject. When holes are made in the shell or ends of drums, headers, pipes and tubes, the lost strength should be compensated. Two methods are available. They are (a) area compensation method and (b) ligament efficiency method. For the sizes of holes indicated in The Indian Boiler Regulations, 1950 – 187, the area compensation method (alone) shall be used. For all other holes, ligament efficiency method shall be used. 2. Uncompensated Holes in Water Tube Boilers The maximum diameter of any unreinforced opening shall not exceed 'd' as shown in Figures: 9B and 9C subject to a maximum of 203 mm. The notations in Figures 9B and 9C are defined as follows: K =

PD 1.82 f e

Where, P = working pressure, kg / sq cm (g) D = outer diameter of shell / end, mm d = maximum allowable diameter of opening (in case of an opening of elliptical or ob-round form, the mean value of the two axes of the opening shall be taken for d) e = actual thickness of shell, mm f = allowable stress, kg / sq cm When K has a value of unity or greater, the maximum size of an un-reinforced opening should be 51 mm (2 inch)

3. Exercise P D e f

= = = =

100.0 kg / sq cm (g) 1,500 mm 80.0 mm 1,200 kg sq cm

K =

100.0 x 1,500 1.82 x 1,200 x 80.0

= 0.86

From Figure 9C of IBR, maximum size of uncompensated opening = 8 inch = 203.2 mm

A-17: Pressure Parts Tubes Under Axial Tension 1. Introduction The boiler pressure parts tubes are under internal pressure and axial tension. The pressure parts of large boilers are top-supported. A formula to calculate the tube thickness is computed. 2. Formula f =

WP x Di 2

2

+

2

4P π ( Do

( Do – Di )

2

–

2

Di )

Hence, T =

-

Do 2

2

π f Do - 4 P 4 π ( f + WP )

Where, f = tube metal allowable stress = 12.00 kg / sq mm WP = working pressure = 1.00 kg / sq mm (g) Do = tube outside diameter = 50.0 mm Di = tube inside diameter = Do – 2 T , mm T = tube minimum required thickness, mm P = axial tensile load on each tube = 10,000 kg

Therefore, T =

50.0 2

-

π 12.00 x 50.0 4 π

( 12.00

2

__

+

4 x 10,000 1.00 )

= 6.8 mm

A-19: Boiler Thermal Expansion Movement Diagram 1. Introduction This write-up gives particulars on the above subject. 2. Expansion Movement As the boiler pressure parts are hot during operation, the thermal expansion movements are computed and shown in a diagram to check the acceptability with the field measurement. 3.

Formulas

∆x = Lx . α . ∆ xt ∆y = Ly . α . ∆ yt ∆z = Lz . α . ∆ zt

∆ Where,

=

2

2

∆ x +∆ y + ∆ z

2

∆x = thermal movement in X direction, mm ∆y = thermal movement in Y direction, mm ∆z = thermal movement in Z direction, mm ∆ = resultant thermal movement, mm Lx = length in X direction, mm Ly = length in Y direction, mm Lz = length in Z direction, mm 6 α = co-efficient of thermal expansion for steel = 12 x 10 - mm / ( mm-Degree C) - steel ∆ xt = temperature difference in X direction = (Tx - Ta), Degree C ∆ yt = temperature difference in Y direction = (Ty - Ta), Degree C ∆ zt = temperature difference in Z direction = (Tz – Ta), Degree C Tx = temperature in X direction, Degree C Ty = temperature in Y direction, Degree C Tz = temperature in Z direction, Degree C Ta = ambient temperature = 20 Degree C

A-20: Thermal Expansion Movements and Allowable Forces and Moments The thermal expansion movements and the allowable forces and moments at the boiler terminal points (floating anchors) are given below:

Table - 1 Anchor Location

Thermal Expansion Movement, mm

Allowable Force, kg

Allowable Moment, kg-m

∆x

∆y

∆z

Fx

Fy

Fz

Mx

My

Mz

500

500

500

1,000

1,000

1

Feed Water Inlet Header

40

-60

0

250

250

250

2

Main Steam Outlet Heater

10

-20

20

500

500

500 1,000

Remark

Note: (1) The thermal expansion movements indicated in Table-1 are the movements during normal operation of the boiler. (2) The Allowable Forces are the range of the allowable. (3) The Allowable Moments are the range of the allowable. (4) The piping stress analysis shall be carried-out considering cold elastic modulus of piping. (5) Credit for cold springing of piping shall not be considered. (6) X- direction is boiler front to rear. (7) Y- direction is vertically upward. (8) Z- direction is boiler left side to right side. (9) If any of the forces and moments exceed the indicated value (Table-1), boiler designer's advice is required for acceptance. (10) The (floating) anchor points shall be as indicated in the relevant drawing.

A-21: Design of Foundation Bolts 1. Introduction This write-up gives particulars about the foundation bolts design. 2. Formula

2

Allowable tensile load = F = n x S1 x π ( d – p ) / 4 Where, n d p S1

= = = =

number of bolts per foundation base plate diameter of the bolt thread, mm pitch of the bolt thread, mm allowable tensile stress, kg / sq mm

3. Exercise n S1 d p

= = = =

4 15.00 kg / sq mm 24.0 mm 3.0 mm

Hence, 2

F = 4 x 15.00 x π ( 24.0 – 3.0 ) / 4 = 20,781 kg

A-23: Design of Chimney - I 1. Types of Chimneys The following two types of chimneys are used: guyed chimney and self-supporting chimney. 2. Chimney Material The following two types of chimney materials are used: steel and cement concrete. 3. Chimney Shapes The following two types chimney shapes are used: cylindrical and conical. 4. Purpose of Chimney The following are the purposes of chimneys: dissipation of polluting gases, particles and heat, chimney draft effect. 5. Height of Chimney Chimneys of height about 300.0 meter are used in large power plants. 6. Diameter of Chimney The bottom diameter of chimney is about one tenth to one twentieth of the height. 7. Aviation Lights and Lightning Arrestors The chimneys shall be provided with aviation lights to avoid air-crash. Required lightning arrestors are to be provided. 8. Stairs, Ladders, Landing and Hand Rails Required stairs, etc. are to be provided. 9. Flue The flue pipe inside the chimney shall be corrosion resistant. 10. Wind Shield Required strength shall be provided to the wind shields of the chimney. 11. Flue Gas Entry The number of flue gas entry at the bottom can be one or two or three. 12. Chimney Foundation and Maintenance Foundation for the chimney shall be adequate to withstand the imposed loads. The chimney shall be provided with adequate provisions for painting and maintenance. 13. Vibration Suitable devices to avoid wind induced resonance and damage shall be provided. 14. Loads from Equipment Applicable loads from connected equipment shall be considered.

A-24: Foundation Bolts for Steel Chimney - I 1. Introduction This write-up gives particulars on the design of bolts for foundation of steel chimney. 2. Formula Bending moment Pitch circle diameter Bolt Circumference Bolt size Allowable load / bolt

2

2

= BM = P D H / 2 = 0.15 x 3.5 x 60.0 / 2 = 945 t - m = PCD = 4.0 m = C = π x PCD = π x 4.0 = 12.566 m = M24 x 3 mm – Property class P4.6 ( σ y = 24.0 kg / sq mm ) 2 = F = π x 0.6 x 24.0 x (24 – 3) / 4 = 4,987 kg

Number of bolts required = n =

4 x BM F x PCD

=

6

4 x 945 x 10 4,987 x 4,000

Use 200 ( n1 ) bolts, Bolt pitch = π x PCD / n1 = π x 4,000 / 200 = 63 mm Where, P D H PCD σy

= = = = =

wind pressure = 0.15 t / sq m diameter of chimney = 3.5 m height of the chimney = 60.0 m pitch circle diameter = 4.0 m yield stress of bolt material = 24.0 kg / sq mm

= 190

A-25: Foundation Bolts for Steel Chimney - II 1. Introduction This write-up gives particulars on the design of bolts for foundation of steel chimney.

2. Formula Bending moment Pitch circle diameter Bolt Circumference Bolt size Allowable load / bolt

2

2

= BM = P D H / 2 = 0.15 x 3.5 x 60.0 / 2 = 945 t - m = PCD = 4.0 m = C = π x PCD = π x 4.0 = 12.566 m = M36 x 4 mm – Property class P4.6 ( σ y = 24.0 kg / sq mm ) 2 = F = π x 0.6 x 24.0 x (36 – 4) / 4 = 11,581 kg

Number of bolts required = n =

4 x BM F x PCD

=

6

4 x 945 x 10 11,581 x 4,000

Use 88 ( n1 ) bolts, Bolt pitch = π x PCD / n1 = π x 4,000 / 88 = 143 mm Where, P D H PCD σy

= = = = =

wind pressure = 0.15 t / sq m diameter of chimney = 3.5 m height of the chimney = 60.0 m pitch circle diameter = 4.0 m yield stress of bolt material = 24.0 kg / sq mm

= 82

Sheet1

A-26: Design of Chimney – II Serial Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Description & Symbol Location Vz Pz Diameter = D UDL = D x Pz L1 (Bottom) L2 (Middle) L3 (Top) E T1 (Bottom) T2 (Midddle) T3 (Top) I1 (Bottom) I2 (Middle) I3 (Top) Z1 (Bottom) Z2 (Middle) Z3 (Top) Weight1 (Bottom) Weight2 (Middle) Weight3 (Top) Weight – Total BM1 (Bottom) BM2 (Middle) BM3 (Top) S b1 (Bottom) S b2 (Middle) S b3 (Top) ∆ 1 (Bottom) ∆ 2 (Middle) ∆ 3 (Top) ∆ 4 (Bottom) ∆ 5 (Middle) ∆ 6 (Bottom) ∆ 7 (Middle)

36

∆ 8 (Total)

37

Is Design Safe ?

Prepared: Date:

SSP 25. Feb. 2008

Formula

Calculation

= 25 – 3 = 20 – 3 = 16 – 3

=∆1+∆2 +∆3+∆4+ ∆5+∆6+∆ 7

Unit

Case-1 Tamilnad

m / sec Kg / sq m mm Kg / mm mm mm mm N / sq mm mm mm mm Mm ^ 4 Mm ^ 4 Mm ^ 4 Cu mm Cu mm Cu mm Tonne Tonne Tonne Tonne kg-m kg-m kg-m Kg / sq mm Kg / sq mm Kg / sq mm mm mm mm mm mm Mm Mm

50 152.96 3000 0.459 20000 20000 20000 200000 22 17 13 2.28E+011 1.77E+011 1.36E+011 1.52E+008 1.18E+008 9.07E+007 36.76 29.46 23.6 89.81 8.26E+005 3.67E+005 9.18E+004 5.43 3.11 1.01 7.23 5.93 3.31 42.07 16.93 78.88 25.93

mm

180.28

Yes

Checked: Date:

Approved: Date:

Page 1

Case-2

Case-3

Remarks Input Input Calculated Input Calculated Input Input Input Input Assumed Assumed Assumed Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated Calculated

Calculated

Output

A-27 List of Power Plant Equipment 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50.

Steam drum Water drum Down-comer Water wall Water wall header Risers Super-heater Re-heater Economiser Air-heater Flue duct Air duct Pent house casing Wind box casing Insulation Outer casing Refractory Inner casing Boiler integral piping Bunker Mills Motors Electro-static precipitators Mechanical precipitators Duct stiffeners Duct inside trusses Duct inside guide vanes Dampers Damper actuators Motor & impeller handling equipment Platforms Metallic expansion joint (MEJ) Non-metallic expansion joint (NMEJ) Main steam piping Feed piping Cold re-heat piping Hot re-heat piping Emergency blow-down tank Continuous blow-down tank Intermittent blow-down tank Beams Columns Bracings Foundations Foundation material Chimney Access hole Floor grill Earth-quake restraints Furnace guides

A-28: Foundation Bolts for Steel Chimney-I 1. Introduction This write-up gives particulars on the design of bolts for foundation of steel chimney. 2. Formula Bending moment Pitch circle diameter Bolt Circumference Bolt size Allowable load / bolt

2

2

= BM = P D H / 2 = 0.15 x 3.5 x 60.0 / 2 = 945 t - m = PCD = 4.0 m = C = π x PCD = π x 4.0 = 12.566 m = M24 x 3 mm – Property class P4.6 ( σ y = 24.0 kg / sq mm ) 2 = F = π x 0.6 x 24.0 x (24 – 3) / 4 = 4,987 kg

Number of bolts required = n =

4 x BM F x PCD

=

6

4 x 945 x 10 4,987 x 4,000

Use 200 ( n1 ) bolts, Bolt pitch = π x PCD / n1 = π x 4,000 / 200 = 63 mm

Where, P D H PCD σy

= = = = =

wind pressure = 0.15 t / sq m diameter of chimney = 3.5 m height of the chimney = 60.0 m pitch circle diameter = 4.0 m yield stress of bolt material = 24.0 kg / sq mm

= 190

A-29: Foundation Bolts for Steel Chimney - II 1. Introduction This write-up gives particulars on the design of bolts for foundation of steel chimney. 2. Formula Bending moment Pitch circle diameter Bolt Circumference Bolt size Allowable load / bolt

2

2

= BM = P D H / 2 = 0.15 x 3.5 x 60.0 / 2 = 945 t - m = PCD = 4.0 m = C = π x PCD = π x 4.0 = 12.566 m = M36 x 4 mm – Property class P4.6 ( σ y = 24.0 kg / sq mm ) 2 = F = π x 0.6 x 24.0 x (36 – 4) / 4 = 11,581 kg

Number of bolts required = n =

4 x BM F x PCD

=

6

4 x 945 x 10 11,581 x 4,000

Use 88 ( n1 ) bolts, Bolt pitch = π x PCD / n1 = π x 4,000 / 88 = 143 mm Where, P D H PCD σy

= = = = =

wind pressure = 0.15 t / sq m diameter of chimney = 3.5 m height of the chimney = 60.0 m pitch circle diameter = 4.0 m yield stress of bolt material = 24.0 kg / sq mm

= 82

Sheet1

A-30: Design Data Sheet for Duct, Flue and Casing Table-1 Serial Number

Flow Path Identification

Number of Flow Paths

Area per Flow Path Sq m

Flow Velocity M / sec

Operating Temperature Minimum Maximum Degree C Degree C

Design Temperature Minimum Maximum Degree C Degree C

Remarks

Table – 2 Serial Number

Flow Path Identification

Operating Pressure Minimum Maximum Mm wx (g) Mm wx (g)

Design Pressure Minimum Maximum Mm wx (g) Mm wx (g)

Page 1

Wind Load Kg / sq m

Earth-Quake Load %

Remarks

A-31: Design of Boiler Drum Dished Ends 1. Introduction This write-up deals with design of boiler drum dished ends as per The Indian Boiler Regulations, 1950. 2. Types of Dished Ends The following types of dished ends are used: a) b) c) d) e)

hemi-spherical dished end 2 : 1 semi-ellipsoidal dished end tori-spherical dished end tori-conical dished end conical-spherical dished end

3. Types of man-way openings Each drum can be provided with one or two man-way openings per drum dished end. These openings can be of any one of the following types: a) b) c) d) 4.

circular opening elliptical opening oblong opening oval opening

Man-way opening closure The man-ways are to be closed tightly using flat man-way closures. If the man-way is circular, the man-way cover is to be placed inside the drum shell, before final closure in the workshop. For all other types openings indicated under (3) above, these man-way closures can be placed after final closure. In some cases the man-way closure is provided on the outside of the drum. These man-way closures are expensive. Suitable Davit supports are used for supporting and swinging the man-way covers during maintenance. 5. Maintenance The man-way covers are to be tightly closed with gaskets before testing or operation. These gaskets are to be changed after every use.

A-32: Design of Flues, Ducts and Casings Stiffener Sizes 1. Introduction This write-up gives particulars on the above subject. 2. Formula for Stiffener Sizing Z =

p L1 L2 8 S1

I =

2

5 x 325 x p L1 x L2 384 E

3

Where, Z I p L1 L2 S1 E

= = = = = = =

required section modulus, cu mm required moment of inertia, mm ^ 4 duct design pressure, kg / sq mm (g) maximum stiffener spacing, mm length of the stiffener, mm allowable stress, kg / sq mm modulus of elasticity, kg / sq mm

3. Exercise L1 L2 S1 p E Z =

= = = = =

700 mm 1,500 mm 15.00 kg / sq mm –6 400 x 10 kg / sq mm (g) modulus of elasticity = 20,000 kg / sq mm 6

400 x 10 – x 700 x 1,500 8 x 15.00 6

2

= 5,250 cu mm

I = 5 x 325 x 400 x 10 - x 700 x 1,500

3

4

= 20 x 10 mm ^ 4

384 x 20,000 4

Use flat 6 x 80 mm, Zxx = 6,400 cu mm > Z, Ixx = 25.6 x 10 mm ^ 4 > I Hence, Safe

A-33: Design of Flues, Ducts and Casings 1. Introduction This write-up gives particulars on the above subject. 2. Formula for Stiffener Spacing L1 = 0.77 x (T – T1)

S p

Where, L1 T T1 S p

= = = = =

maximum allowable stiffener spacing, mm provided thickness, mm erosion allowance = 1.0 mm allowable stress, kg / sq mm design pressure, kg / sq mm (g)

3. Exercise T = 6.0 mm T1 = 1.0 mm S = 15.00 kg / sq mm –6 p = 400 x 10 kg / sq mm (g) L1 = 0.77 x (6.0 – 1.0)

15.00 -6 400 x 10

= 745 mm

A-34: Design of Expansion Joints 1. Introduction This write-up gives particulars on the expansion joints used for flues, ducts and casings. 2. Types Expansion Joints The following types of expansion joints are used: Metallic Expansion Joints (MEJ) and NonMetallic Expansion Joints (NMEJ). 3. Applications Non-metallic expansion joints are used where thermal expansion movements are small or moderate. 4. Selection The expansion joints are selected based on availability. 5. Material The Metallic Expansion Joints are made of metals. The Non-Metallic Expansion Joints are made of fibers. 6. Thermal Expansion Movement The thermal expansion movements of the equipment are provided by the equipment supplier. 7. Foundation Relative Settlement The relative settlement of foundation are considered, where required. 8. Setting of Expansion Joints The expansion joints are not provided with presetting. 9. Liners Suitable liners are to be provided to avoid dust accumulation and proper alignment. 10. Design Pressure The design pressure for the expansion joints is specified by the designer. The popular value of design pressure used = ± 1,000 mm wc (g) 11. Design Temperature The design temperature is specified by the designer.

A-35: Buckstay Spacing Calculation 1. Introduction This write-up gives particulars of the allowable space between any two consecutive buckstays. 2. Loads The following loads are considered: furnace operating pressure, furnace design pressure, wind loads and earth-quake loads. 3. Allowable Span

L = 10 Z {S – F / (n x Am) - Sp} Pxe Where, L = maximum allowable buckstay space, mm Z = section modulus of one furnace wall tube, cu mm S = allowable bending stress for tube metal, kg / sq mm F = total load per each furnace wall, kg n = total number of tubes per relevant furnace wall Am = metal area of each furnace wall tube, sq mm P = furnace design pressure, kg / sq mm (g) e = pitch of the furnace wall, mm Sp = tube longitudinal pressure stress, kg / sq cm 4.

Exercise

Do = 51 mm T = 5.0 mm 4 4 4 4 Z = π (Do – Di ) / (32 Do) = π (51 – 41 ) / ( 32 x 51) = 7583 cu mm S = allowable stress = 18.00 kg / sq mm F = total load on one furnace wall = 250 tonne n = 50 2 2 2 2 Am = π (Do – Di ) / 4 = π (51 – 41 ) / 4 = 722.5 sq mm P = 400 kg / sq m = 400 x 10 e = tube pitch = 76.2 mm Sp = 2.00 kg / sq mm

L =

-6

kg / sq mm

10 x 7583 {18.00 - 250,000 / (50 x 722.5) – 2.00} –6 400 x 10 x 76.2

= 4752 mm

A-36: Design of Buckstay Beams 1. Introduction This write-up gives particulars of buckstay beams design. 2. Load The buckstay beams are loaded with Uniformly Distributed Load (UDL) from the furnace. 3. Stress Buckstay beams are to be selected considering the bending stress, shear stress and deflection. 4. Deflection The deflection allowed for the buckstay beam is span / 325. 5. Formulas σ1 = p e L1 8 Zxx

∆1 =

2

< allowable stress, kg / sq mm

4

5 p e L1 384 E Ixx

< span / 325, mm

Try ISMB400, Zxx = 10,20,000 cu mm, Ixx = 20,50,00,000 mm^4, Safe Where, σ1 p A B e L1 ZR IR Zxx Ixx E ∆1 ∆a

= induced stress, kg / sq mm -6 = furnace design pressure = 400 x 10 kg / sq mm = buckstay spacing at top = 3,500 mm = buckstay spacing at bottom = 4,500 mm = (A + B) / 2 = (3,500 + 4,500) / 2 = 4,000 mm = length of buckstay beam = 6,000 mm = section modulus of buckstay beam required, cu mm = moment of inertia required, mm^4 = section modulus provided, cu mm = moment of inertia provided, mm^4 = elastic modulus of buckstay beam = 20,000 kg / sq mm = induced deflection, mm = allowable deflection = L1 / 325 = 6,000 / 325 = 18.5 mm

A-37: Buckstay Sizing Calculation 1. Introduction This write-up gives particulars of the buckstay beam sizing calculation. 2. Loads The contributory load for each buckstay elevation is considered. The load on the buckstay beam is considered to be uniformly distributed. 3. Buckstay Beam Sizing Z

= P x (A + B) L / (2 x 8 σ bc) 2

3

I = 325 x 5 x P x (A + B) L / (2 x 384 E) Where, Z P A B L

= minimum required section modulus, cu mm = buckstay design pressure, kg / sq mm (g) = buckstay spaing (top), mm = buckstay spacing (bottom), mm = length of the buckstay beam, mm σ bc = allowable bending compression stress, kg / sq mm I = required moment of inertia, mm ^ 4 E = elastic modulus, kg / sq mm 4. P A B L

Exercise = = = =

–6

400 x 10 kg / sq mm (g) 3500 mm 4500 mm 12,000 mm

σ bc = E

10.00 kg / sq mm = 20,000 kg / sq mm -6

Z

= 400 x 10

I

= 325 x 5 x 400 x 10

2

(3500 + 4500) x 12,000 / (2 x 8 x 10.00) = 1,440,000 cu mm –6

3

8

(3500 + 4500) x 12,000 / ( 2 x 384 x 20,000) = 2.92 x 10 mm^4 8

Use ISMB500, Zxx = 1,809,000 cu mm, Ixx = 4.52 x 10 mm ^ 4

Hence, Safe

Sheet1

A-38: Buckstay Beam Calculation 400 ' mm wc (g)

Buckstay Design Pressure = P = Serial Number 1 2 3 4 5 6 7 8

9

10 11 12 13 14

Description & Symbol Elevation Location Span-1 = A Span-2 = B UDL = P x (A+B) / 2 Length = L BM Allowable Bending Stress = S1 Required Section Modulus Required Moment of Inertia Beam Selected Zxx

Formula

Calculation

Case-1

mm mm mm Kg / mm mm Kg-mm

SSP

FWW 3000 4500

1.50 1.50 10000 10000 18750000 18750000

10

10

1875000

1875000

Remarks

14000 Input Input 4500 Input 4000 Input

1.70 Calculated 10000 Input 21250000 Calculated

10 Input

2125000 Calculated

Mm ^ 4

317382812 317382812 359700520.8 .5 .5 3 Calculated

Cu mm

ISMB600 ISMB600 ISMB600 Input 3060000 3060000 3060000 Input

Mm ^ 4

918130000 918130000 Yes

Checked: Date:

Case-3

9500 FWW

3500 4000

Kg /sq mm

Cu mm

Case-2

5000 FWW

Ixx Is Design Safe?

Prepared: PRK Date: 2. Feb. 2008

Unit

Approved: SSP Date:

Page 1

Yes

918130000 Input Yes

Output

A-39: Structural Steel Stability 1.0 Structural steel is used to resist various forces and moments. The forces and moments can be due to primary loads or secondary loads or occasional loads. Suitable combinations of these loads are considered by the designer. To ensure structural steel stability, the following formula shall be satisfied: fn–r–c=m Where, f = 1 for one dimensional structures = 2 for two dimensional structures = 3 for three dimensional structure n = number of nodes r = number of restraints at supports c = number of constraints (connection continuity) m = number of members (elements) 2.0 One dimensional Structure f=1 n=2 r=1 c=0 m=1 Therefore, 1x2–1–0=1=m

Hence, safe

3. Two dimensional structure f=2 n=6 r=4 c=1 m=7 Therefore, 2x6–4–1=7=m

Hence, safe

To ensure structural steel stability, the following shall also be satisfied: “The determinant of the stiffness matrix shall be non-zero”

A-40: Design of Floor Grills 1. Introduction This write-up gives the allowable loading on the floor grills. 2. Floor Grill The load bearing bar size is 5 x 25 mm. The unsupported length is 100 mm. The pitch of the load bearing bards is 40 mm. 3. Floor Grill Sketch

4. Formulas

A-41: List of Boiler Piping 1. Main Steam Line 2. Feed Line 3. Cold Re-heat Line 4. Hot Re-heat Line 5. Soot Blower Line 6. Soot Blower Drains 7. Safety Valves Exhaust Lines 8. Boiler Drain Lines 9. Boiler Vent Lines 10. Start-up Vent Line 11. Boiler Water Filling Line 12. Boiler Washing Line 13. Chemical Dosing Line 14. Hydro-static Testing Line 15. Drain from Boiler Drain Trays 16. Oil Filling Line 17. Pulverized Coal Piping 18. Ash Conveying Line 19. Cooling Water Line 20. Fire Fighting Line 21. Drinking Water Line 22. Sewerage Line 23. Furnace Bottom Ash Pit Filler Line 24. Continuous Blow-down line 25. Intermittent Blow-down line 26. Black Liquor Line 27. Green Liquor Line 28. White Liquor Line 29. Storm Water Discharge Line 30. Emergency Blow-Down Line

A-42: RATIONALIZED LIST OF RAW MATERIALS MILD STEEL (IS2062)

Beams

Channels

Angles

ISMB125 ISMB150 ISMB200 ISMB250 ISMB300 ISMB350 ISMB400 ISMB450 ISMB500 ISMB600

ISMC75 ISMC100 ISMC125 ISMC150 ISMC200 ISMC225 ISMC250 ISMC300 ISMC350 ISMC400

ISA25x25x3 ISA40x40x4 ISA50x50x6 ISA65x65x6 ISA75x75x6 ISA90x90x6 ISA100x100x10 ISA100x100x12

Plate (Thickness) Rod (Diameter)

Fasteners (P4.6)

2.5 mm 3.15 mm 4.0 mm 5.0 mm 6.0 mm 8.0 mm 10.0 mm 12.0 mm 16.0 mm 20.0 mm 25.0 mm 32.0 mm 36.0 mm 40.0 mm

M6 x 1 mm M8 x 1.25 mm M10 x 1.5 mm M12 x 1.75 mm M16 x 2 mm M20 x 2.5 mm M24 x 3 mm M30 x 3.5 mm M33 x 3.5 mm M36 x 4 mm

2.5 3.15 4.0 5.0 6.0 8.0 10.0 12.0 16.0 20.0 25.0 32.0 36.0 40.0

mm mm mm mm mm mm mm mm mm mm mm mm mm mm

A-43: Stress Analysis of Boiler Pressure Parts 1. Introduction This write-up gives particulars on the stress analysis of boiler pressure parts. 2. Stress According to Hooke's law, “Stress is proportional to strain, within elastic limits”. Stress is a Tensor. Change on geometry of parts introduces secondary stresses and stress concentration. 3. Strain Strain is equal to Stress / Elastic modulus. During fatigue loading, strain accumulates. Loading for long duration leads to strain accumulation, in the creep range of temperatures. 4. Elastic Modulus Elastic modulus, also known as Young's Modulus, is equal to Stress / Strain. 5. Assumptions During stress analysis, the following are assumed: a) linear behavior of material b) elastic material c) homogeneous material d) isotropic material e) steady-state loading f) static component 6. Stress Analysis Tools Stress analysis can be done by manual calculations or using a calculator or using a computer. 7. Stress Limits The stresses due to various loads are limited to various limits. The stresses of various kinds are limited to various levels. 8. Strain Limits There no universally acceptable strain limits. 9. Deformations Deformations can be linear or angular. They are limited to empirical values. 10. Factor of Safety Factor of safety takes care of the imponderables. Factor of Safety is also known as Factor of Ignorance. The approximate value of Factor of Safety is 1.5 (based on Yield Stress).

A-44: Boiler Drum Seismic Guides (Earth-Quake Guides) 1. Introduction This write-up gives particulars on the boiler drum supports, drum seismic guides and settings. 2. Loads The following loads are considered: a) b) c) d) e) f)

self weight imposed loads thermal expansion loads wind loads seismic loads (earth-quake loads) equipment loads

3. Load Combinations Applicable load combinations are considered. 4. Supports Two U-rods are provided to take care of the vertical loads. 5. Seismic Guides Limit stops are provided to take care of the seismic loads. 6. Boiler Neutral Axis The boiler neutral axis is given below: a) front to rear - near the boiler rear wall b) vertically downwards - pent house top c) left side to right side - boiler center line The zero point for boiler thermal expansion is a virtual zero point. 7. Boiler Drum Neutral Axis The boiler drum neutral axis is given below: a) front to rear - drum horizontal axis b) vertically downwards - pent house top c) left side to right side - drum center line The zero point for boiler drum thermal expansion is a virtual zero point.

A-45: Allowable Stress as per The American Society of Mechanical Engineers 1. Introduction This write-up gives particulars of the allowable stress as per The ASME. 2. Allowable Stress as per ASME-I (Power Boilers) The basic allowable stress (Sm) is the minimum of the following seven values: a) ultimate tensile strength at room temperature / 3.5 b) 1.1 x ultimate tensile strength at metal design temperature / 3.5 c) yield stress at room temperature / 1.5 d) yield stress at metal design temperature / 1.5 e) minimum stress to produce a creep strain of 0.01% in 1,000 hours f) average stress to produce rupture in 100,000 hours / 1.5 g) minimum stress to produce rupture in 100,000 hours / 1.25 3. Allowable Stress for Welds as per The ASME-I (Power Boilers) a) groove-weld in tension = 74 % Sm b) groove-weld in shear = 60 % Sm c) fillet-weld in shear = 49 % Sm Where, Sm = basic allowable stress 4. Allowable Stress as per The ASME-B31.1 (based on fatigue and creep) - Power Piping SA = f (1.25 Sc + 0.25 Sh) Where, SA Sc Sh f

= = = = = = = = = =

allowable stress range for expansion stresses allowable stress at room temperature allowable stress at metal design temperature fatigue stress range reduction factor 1.0 for 1 to 7,000 fatigue cycles of metal 0.9 for 7,001 to 14,000 fatigue cycles of metal 0.8 for 14,001 to 22,000 fatigue cycles of metal 0.7 for 22,001 to 45,000 fatigue cycles of metal 0.6 for 45,001 to 100,000 fatigue cycles of metal 0.5 for 100,001 and over

SA + SL = f (1.25 Sc + 1.25 Sh) Where,

SL = longitudinal stress due to pipe / tube internal pressure

Sheet1

A-46: Design of Hemi-Spherical Dished End as per IBR-1950, 278 Serial Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Description & Symbol Drum Inside Diameter = Di Drum Material = MAT1 Working Metal Temperature = t1 Working Pressure = WP Allowable Stress = f Is Man-Hole Fully Compensated? Thickness Assumed = e Outside Diameter = D = Di + 2 e H = Di / 2 + e H/D d From Fig. 18, “K” Factor C T = (WP D K / 2 f) +C Fabrication Allowance = T1

16

Raw Material Thickness Required = T2 = T + T1

17

Is Design Safe?

Prepared: Date:

SSP

Formula

Calculation

Unit

Case-1

mm

Case-2

1524

Case-3

1524

SA515 Gr70 SA515 Gr70

Input Input

Degree C

350

350

Input

Kg / cm (g)

125

125

Input

Kg / sq cm

1200

1200

Input

Yes

No

Input

mm

60.0

85.0

Assumed

mm mm

mm

1644 822 0.5 410 0.55 0.75

1694 847 0.5 410 0.842 0.75

Calculated Calculated Calculated Input Input Input

mm

47.8

75.0

Calculated

mm

3.0

3.0

Input

mm

50.84

78.04

Input

mm

Yes

Checked: Date:

Remarks

Approved: Date:

Page 1

Yes

Output

Sheet1

ENMAS ANDRITZ PRIVATE LIMITED, Chennai, India Strength Calculation for Pipe Bends as per IBR-1950, 350

A47_West Coast Paper Mills- 1,100 TPD Serial Number

1 2 3 4 5 6

Description & Symbol

11

Case-2

Case-3

Remarks Input

Kg / sq cm (g)

125.0

Input

Degree C

350

Input

Allowable Stress = f

Kg / sq cm

1200

Input

Joint Factor = E

Is Design Safe?

10

Case-1 219.1

13

9

Unit mm

12

8

Calculation

Outside Diameter = D Working Pressure = WP Working Temperature = t1

Code Factor = C Minimum Thickness Required = T Negative Tolerance on Thickness = Tol Nominal Thickness Required = T1 Thinning Allowance = Thin Nominal Thickness of Pipe Bend Required = T2 Nominal Thickness Selected = T3

7

Formula

Prepared: SSP Date: 16. Feb. 2008

1.0

Input

mm

0.75

Input

mm

11.6

Calculated

%

12.5

Input

mm %

mm mm

Checked: Date:

Approved: Date:

Page 1

13.25 12.5

15.15

Calculated Input

Calculated

16.0

Input

Yes

Output

A-51: Strength Calculations for Boiler Drums 1. Introduction This write-up gives the requirements of strength checks for boiler drums. 2. Strength Checks a) b) c) d) e) f) g) h) i) j) k) l) m) n) p) q) r)

Un-drilled shell plate thickness calculations Maximum allowable size of uncompensated holes Ligament efficiency calculations Area compensation calculations Bending stress check for the drum shell Dished end cover thickness calculations Flat end (man-hole cover) cover thickness calculations Allowable taper for drum shell and dished ends Fillet radius requirements Safety valve stub strength calculation Local stresses in the drum nozzles Seismic guides for the drum Design of davit for man-hole cover Discontinuity stress checks Lifting lugs design Drum supports design Drum welds load paths calculations

3. Material Requirements The following material requirements are prepared: a) b) c) d) e)

Drum shell cutting plan Dished ends requirements Drum nozzles requirements Drum welded attachments Miscellaneous requirements

A-52: Design and Stress Analysis of Piping and Supports 1. Introduction This write-up gives particulars of the above subject. 2. Materials Industrial piping is made of iron and steel. Fasteners are made of high strength materials. 3. Loads and Load Combinations The following loads are experienced: primary load, secondary load and occasional load. Suitable combinations of these loads are to be considered. 4. Stress The induced stress is computed and limited the allowable stress. 5. Deformation The deformations can be linear or angular. The deformation can be in the vertical plane or horizontal plane. These are to be limited to the allowable. 6. Vibration Critical piping are to be checked for vibration. In the power plant practice, equivalent loads are considered to take care of the vibration. 7. Standard Components Standard components are available across the counter to speed-up the project. Some of the standard components are: elbow, reducer, TEE, flange, blind cover and fasteners. 8. Testing After fabrication, many piping components are tested in the factory. These tests are non-destructive and destructive testing. 9. Commissioning Commissioning of any plant requires multiple level of checking, including the functioning of individual items. The complete system is checked for water-tight joints and ability to withstand the hydraulic test pressure. 10. Maintenance Any plant used for production of components and services are to be maintained. The Operations & Maintenance (O & M) crew is responsible for safe and secure running of the plant at optimum costs. 11. Disposal The designer should be aware of the methods by which equipment are to be disposed-off. The designer is the mother of the product. The designer should be aware of “cradle to grave” of the

equipment.

A-53: Skin Temperature of Pipe Insulation 1. Introduction This write-up provides guidelines for insulation thickness selection for pipes. 2. Calculation The governing equations are given in the following: Rti =

Rt1 =

1 hi 2 π r1 L log e (r2 / r1) 2 π L k1

Rt2 = Log e (r3 / r2) 2 π L k2 Rto =

1 ho 2 π r3 L

R = Rti + Rt1 + Rt2 + Rto Q = ∆t R 3. Example: hi ho L ti to k1 k2

= = = = = = =

Rti = Rt1 = Rt2 = Rto =

= (ti – to) = (ts - to) R Rto

50 k cal / (hr-sq m- Degree C) 8.0 k cal / (hr-sq m-Degree C) 1.0 m 400 Degree C 45 Degree C 40.0 k cal / (hr-m-Degree C) 0.1 k cal / (hr-m-Degree C) 0.033 hr-m-Degree C / k cal 0.0005 hr-m-Degree C / k cal 1.18 hr-m-Degree C / k cal 0.087 hr-m-Degree C / k cal

R = Rti + Rt1 + Rt2 + Rto = 0.033 + 0.0005 + 1.18 + 0.87 = 1.3 hr-m-Degree C / k cal Q = ∆t / R = (400 – 45) / 1.3 = 273 k cal / hr Q = ∆t1 / Rto = 273 k cal / hr = (ts – to) / Rto ts

o

= to + 273 / (2 π L ho r3) = 45 + 273 x 0.087 = 45 + 24 = 69 Degree C < 70 C Safe

A-54: Engineering Materials and Their Properties Engineering materials are many. Materials can be solid or liquid or gas. Solid materials are used for construction. Solids are classified as metals and non-metals. Metals are conductors of heat and electricity. Materials can be crystalline or amorphous. Material properties can be classified as chemical property, physical property, thermal property, electrical property and magnetic property.

All the material properties are found-out by experiments. Attempts are made to compute the material property from their chemical composition. Use of materials for engineering applications is known from time immemorial. Ancient people used metal swords for hunting. Heat is used to improve material properties. In the olden days, the materials were classified into the following five elements: water, fire, earth, sky and wind. Later, the elements were classified in the Periodic tables by Dimitry Mendeleev. The present day periodic table contains more than one hundred elements. Many compounds are formed using these elements. Mixtures and compounds are different.

Engineers try to use the local materials and local labor. This gives economic solutions to real-life problems. Application of science is engineering. Application of mind is science. Used materials are thrown-out and are serious threat to ecology. The power plants use large amounts of fuels and spew-out tons of polluting gases and particles into the atmosphere. This leads to green-house effect. Green-house effect increases the global warming. To reduce global warming, scientists are working to improve the present power plants and motor vehicles. Engineering design is a compromise between speedy delivery, economic product and quality workmanship. This is achieved by using the expedient technology. No design is ideal. No design is optimum. Designs should be expedient and serve the functions. Pollution can be classified as solid pollution, water pollution, air pollution and noise pollution. Pollution can be reduced by using environmentally acceptable products and services. Engineering materials plays a major role in pollution. Engineers use standardized and rationalized products to reduce inventory. These are arrivedat based on the past experience. Engineering is a multi-disciplinary activity. Engineered products perform well and avoid pollution and unexpected failure. The used computer parts are disposed-off without caring for the after effects in polluting the environment. If polluting products are to be disposed-off, adequate precaution should be taken. Pollution can be reduced by changing our life style.

A-55 Vibration Vibration is movement of objects with respect to time. Vibration of components requires analysis to check for their longevity. Vibration of boiler components is a specialized subject and is of utmost importance in analyzing boiler components. Vibration can be attenuated by suitable damping. Solutions for vibrations is attempted from time immemorial. The governing equation for a single degree of freedom system is given in the following: 2

m d x + c d x + k x = A Sin ( wt + φ ) dt

2

dt

Where, m x t c k A w f

= mass, kg (m) = X – direction, m = time, sec = damping co-efficient, N - sec / m = stiffness, N / m = amplitude of vibration, N = frequency of vibration, radian / sec = phase angle, radian

The general solution for the above differential equation is difficult to obtain. Vibration problems are solved from case to case basis. It is difficult to foresee the vibration problems on the drawing board. A solution to the vibration problem involves the following: First find-out the undamped natural frequency. Then, find-out the damped natural frequency. Check for resonance with the forcing function. If resonance occurs, improve the design. If resonance doesn't occur, check for fatigue and life of the component. Failure of a component can lead to unplanned shut-down. This will lead to disruption to normal work. Several methods are available to check for the safe operation of the component. They are as follows: a) b) c) d)

check for resonance mode shape analysis fatigue analysis time-history analysis

The natural frequency of undamped single degree of freedom system is given below. 'f

= 1 2π

f k m g ∆

= = = = =

k m

= 1 2π

g ∆

frequency of vibration, cycles / sec stiffness of the system, N / m mass of the system, kg (m) acceleration due to gravity = 9.80665 m / sq sec deflection due to load, m

A-56 Stress Analysis – It's Application and Use Stress is a concept developed to explain many real life problems. “Stress is proportional to strain”, within elastic limit”, said Robert Hooke. If we take Poisson's effect into consideration, this basic law can be proved wrong. Poisson's ratio is the ratio of the lateral strain to longitudinal strain. Poisson's ratio is usually less than 0.5. Materials have many properties. Yield stress is the point on stress strain diagram that divide elastic region and plastic region. The Ultimate Tensile Stress (UTS) is the maximum stress the component can withstand. Rupture point is lower (in stress-strain diagram) than the UTS. Stress is a tensor. Following equation is to satisfied for uni-axial tensile test specimen. Stress =

Load (kg) Area (sq mm)

For a beam under bending, the following equation is to be satisfied: M I Where,

=

f y

=

M I f y E R

= = = = = =

E R

bending moment, kg-mm moment of inertia, mm ^ 4 stress, kg / sq mm distance of fiber from the center of gravity axis, mm elastic modulus (Young's modulus), kg / sq mm radius to which the beam is bent, mm

For a shaft under torsion, the following equation is used: T J Where,

τ R

=

T J τ R G E ν θ L

=

Gθ L

= torsional bending moment, kg-mm = polar moment of inertia, mm ^ 4 = shear stress, kg / sq mm = radius from member axis, mm = modulus of rigidity, kg / sq mm = E 2 ( 1 + ν) = elastic modulus (Young's modulus), kg / sq mm = Poisson's ratio = angle of rotation, radian = length of shaft, mm

A – 57 : Pipes – Their Uses and Applications Pipes are used from time immemorial for conveying of fluids. Pipes are usually hollow cylindrical in shape. Pipes can carry a single phase fluid or a two phase fluid or a three phase fluid. Pipes are specified by their outside diameter and nominal thickness. Alternately, pipes are also specified by the nominal bore and the Schedule of pipe. Pipes can convey water or steam or steam-water mixture. Pipes can also carry pulverized coal with hot air. Pipe can carry the ash mixed with water. Pipe can carry sewer – which contains solid, liquid and gas. Piping material can be iron or steel or copper or aluminum or Reinforced Cement Concrete (RCC). Steel is used for pipes based on techno-economic considerations. The pressure inside the pipe drops when the fluid flows. To ensure flow in pipe, the fluid has to be pumped. If the pipe diameter is large, the initial cost will be high. If the pipe diameter is small, the running cost will be high. Hence, we have to strike a balance between the two and arrive-at an optimum diameter. This diameter is known as economic diameter. Piping are joint by many methods. They are: flanged, butt welded, riveted and bonded. Butt welded piping are popularly used in the industry. The American Society of Mechanical Engineers (ASME) have formulated a standard (ASME: B16.34) to indicate the pressure temperature rating of pipe fittings. When the temperature increases, the allowable pressure decreases. The following are the fitting popularly used in the piping industry: TEE, branch, elbow, bend, reducer, Y – piece and nozzle. Pipe bends are made from straight pipes. The Ovality of a pipe bend is defined as follows: % Ovality

= 2 x (maximum diameter – minimum diameter) (maximum diameter + minimum diameter)

Allowable Ovality is 10 %. Allowable thinning at the pipe outer (extrados) is 10 %. Minimum required flow area is 80 %. The requirement of Ovality, thinning and flow area are empirical and change with industry. Pipes are subjected to the following loads: primary load, secondary load and occasional load. Pipes are subjected to the following load combinations: primary load + secondary load and primary load + occasional load. The following load combination is not considered: primary load + secondary load + occasional load. The allowable stress for the piping change with type of load and nature of load. The piping is subjected to elasticity, plasticity, creep, fatigue and corrosion. The life expected for piping is twenty five years. If longer service life is required, necessary design changes are to be done. Reference:

Piping Handbook, Mohinder L Nayyar – Ed. - 7 th Edition, Mc Graw Hill, 2000

A – 81 : Design of Ping for Power Boilers Power boilers have integral piping and external piping. Integral piping are used to connect various heat transfer surfaces. Examples of integral piping are: (a) economizer links to drum, (b) down-comers, ( c) supplies, (d) risers, (e) saturated steam lines and (f) links between super-heaters. Examples of external piping are: (i) feed line, (ii) main steam lines, (iii) cold re-heat line and (iv) hot re-heat line. These lines carry water or steam or steam-water mixture. Purpose of piping is conveyance of fluids.

The following drawings and documents are prepared for piping design: (1) scheme, (2) Process Flow Diagram (PFD), (3) Piping and Instruments Diagram (P & ID), (4) piping layout, (5) isometric diagram, (6) stress analysis, (7) detailed design, (8) joints design, (9) drafting, (10) documentation and (11) document approval. While laying-out piping, the piping interference and interfacing shall be taken care-of. The piping is subjected to the following loads: self weight, contents weight, imposed load, thermal load, thermal movements of floating anchors, wind load, seismic loads (earth-quake loads), flood, fire, tsunami, snow, ice, relative settlement of foundations and supports. The stresses induced due to various loads are limited to the respective allowable. The piping is allowed to shake-down due to thermal loads. There are many unknowns in the piping design. Factors of safety (also known as Factors of ignorance) are used to assure safety of piping. The Factor of safety used is 1.5 (on yield stress).

The following are some of the components used in the piping: bend, long radius elbow, short radius elbow, concentric reducer, eccentric reducer, equal TEE, unequal TEE, branch, Y – piece, flanges, flanged fittings, blind flange, weld-neck flange and thermo-wells. These components are designed based on analytical and empirical formulas. Empirical formulas are arrived-at based on experiments and experience. Theory and practice are two hands to swim through the process of evolution of products and services. At present the following two computers software are used for stress analysis of piping: CAESAR II and CAEPIPE. The design of piping is based on design by stress analysis.

A – 82 : Introduction to Thermal Power Plants Thermal power plants are used for the past two hundred years for producing economic power. Thermal power plants evolved with industrial revolution. Thermal power plants use solid fuels or liquid fuels or gaseous fuels or combinations of these. Solid fuels are powdered into small size and pumped into the furnace. Required thermal energy is available in the furnace for combustion. This type of firing is known as pulverized coal firing. Liquid fuels and gaseous fuels are easy to handle and fire. As the coal reserves in India are high, coal fired power plants are popular in India.

Coal can be fired using Atmospheric Fluidized Bed Combustion Boiler (AFBC) or Circulating Fluidized Bed Combustion Boiler (CFBC) or Entrained Bed Fluidized Boiler (EBFB) or pulverized coal boiler. The walls of the furnace are cooled with water or steam. The heat transfer areas are arranged in the first pass and second pass. The metal working temperature for heat transfer surfaces is given in the following (based on The Indian Boiler Regulations, 1950):

Economizer Water walls Steam cooled walls Convection super-heater & re-heaters Radiant super-heater & re-heaters

= = = = =

fluid temperature + 11 Degree C fluid temperature + 28 Degree C fluid temperature + 28 Degree C fluid temperature + 39 Degree D fluid temperature + 50 Degree C

The circulation in the furnace can be natural circulation or forced circulation or combined circulation. The basic equation for computing the thickness of tubes as per IBR – 338 (a), 1950 is given below.

T

= WP x D

+

C

2 f + WP Where,

T WP D f C C

= = = = = =

required thickness, mm working pressure, kg / sq cm (g) tube outside diameter, mm allowable stress at tube metal working temperature, kg / sq cm 0.75 mm up-to WP = 70 kg / sq cm (g) 0.0 above WP = 70 kg / sq cm (g)

The pressure parts thickness can be calculated as per The IBR, 1950. They are IBR-270 (drums and headers), IBR-338 (tubes and tube bends) and IBR-350 (pipe and pipe bends).

A – 83 : Atmospheric Fluidized Bed Combustion Boilers (AFBC) Atmospheric Fluidized Bed Combustion boilers (AFBC) are used in industries for burning solid fuels. Solid fuels can be coal or bio-mass. Perforated plates are used as the bed. Air at high velocity comes from the bed and fluidize the solid fuel. The flame in the bed behaves like a fluid and assists in high heat transfer rates and mixing. The fluidized bed combustion is efficient and economical. Fluidized bed can be provided with convective heat transfer surfaces. The convective tubes in the heat transfer surfaces are provided with fins to improve heat transfer. The convective tubes are water-cooled. Steam cooled tubes are rarely used in the bed.

The tubes in the bed are made of carbon steel or low-alloy steel. The air-fuel mixture flows in the bed and transfers heat to the tubes. The local velocity of the fluidized bed is many fold the average velocity. The efficiency of combustion of the fluidized boiler is lower than that of pulverized fuel boilers. The pulverized coal fired boilers require mills. These mills are not required for AFBC boilers. The initial investment for AFBC boilers is lower compared pulverized boilers.

The behavior of AFBC boilers is estimated from the past experiments. These experimental results are interpolated and extrapolated to predict the behavior of AFBC boilers. Design of AFBC is difficult. Hence, inputs from existing boilers are used for new boilers. The following equipments are used for AFBC boilers:

1. Bunkers 2. Feeders 3. Coal distributors 4. Drums 5. Water walls 6. Super-heaters 7. Economizers 8. Air-heaters 9. Electro-static precipitaters 10. Chimney

A – 84 : Principles of Engineering The word “engineering” is derived from “ingenious”. Engineers use ingenious ways to solve real-life problems. For doing a job, the following are required: skill, knowledge and attitude. Skill can be attained by practice. Knowledge can be attained by education and training. Attitude can be developed by monetary and non-monetary aspects. Art is evolved into skills. Assimilation of skills is technique. Techniques enlarges into technology. Technology is synonymous with engineering. Engineering is explained by science.

Engineers build houses, dams, bridges, machines, power plants, chimney, electric motor, transformer, switch gear. Engineering activities can be classified as design, engineering, procurement, manufacturing, storage, erection, commissioning, operation, maintenance, up-gradation, modernization and disposal. For effective engineering, humans, machine, material and time should be managed judiciously. For construction of a project, the following should be known: product, process, problem, persons and place. When a product is manufactured, several laws are invoked. Hence, an engineer should be familiar with the laws of the lands.

Engineers automate several processes. Hence, the productivity increases. Productivity in design offices, work shops, agricultural fields and industry has increased multi-fold in the past century. This leads to unemployment. The price of a commodity changes with supply and demand. If the supply is more, the price is less. If the demand is more the price is high. In the power industry the equipment become outdated within a decade. Hence, engineers have to continually up-date their knowledge. Unemployment can be of three categories. They are under-employment, outstation employment and real unemployment.

The cost price of a commodity is decided by direct material plus indirect material plus direct labor plus indirect labor plus taxes and duties, depreciation, over-heads and profit. The selling price is decided by the market forces. India has become a market economy from planned economy. The effect of various parameters on the selling price of a product is difficult to predict. By improving the image of the company, the profitability can be increased. In the industry, to carry-out a function, one per cent intelligence, nine per cent knowledge and ninety per cent labor is required. Success or failure of an

industry depends on the alertness of the management. A stitch in time saves nine.

A – 85 : Combustion, Heat Transfer, Fluid Flow and Pumping Combustion is a exo-thermic chemical reaction. When two elements react with each other and release heat, it is known as combustion. The following combustion equation is popularly used: C + O 2 = C O 2 + heat energy The heat released is used for raising steam in the boiler. The heat from hot flue gases reaches the heated fluid through the following four methods of heat transfer: conduction, free convection, forced convection and radiation. Conduction takes place in solids. Free convection is due to free movement of fluids. Forced convection is due to forcing the fluid using pumps. Radiation is through electro-magnetic radiation. Electro-magnetic radiation can be in the visible spectrum or the non-visible spectrum.

Flow of fluids inside hollow cylindrical pipes have been researched extensively. Flow can be broadly classified as laminar flow or turbulent flow. Turbulent flow is more effective in mixing and heat transfer. When fluid flow around a cylinder, the cylinder is dragged and lifted due to friction forces. The force due to dragging is given in the following:

F = Cd ρ A V

2

g Where,

F

= force, kgf

Cd

= drag co-efficient

ρ

= density, kg / cu mm

A

= projected area, sq mm

V

= velocity, mm / sec

g

= gravitational constant = 9,806.65 m / sec

2

Pumps are positive displacement pumps and centrifugal pumps. Positive displacement pumps are used where the flow has to be assured. Pumps can be operated by electric motor or steam. Electric motor pump converts electrical energy into pressure energy. In a steam pump, pressure energy is converted into pressure energy of the pumped fluid. In power plants, the feed pump is considered as the heart of

the power plant.

A – 86 : Heat Transfer in Boilers and Heat Exchangers In boilers and heat exchangers, the thermal energy from the hot fluid is transferred to the cold fluid. The heat exchangers can be of mixing type or non-mixing type. In mixing type, fluids of different constituents and different temperatures mix and exchange heat. In non-mixing type of heat exchangers, the flow can be parallel flow or counter flow or cross flow. The following heat transfer equations are used in the design of boilers and heat exchangers:

Where,

LMTD

k A ∆T L

Q

=

Q

=

Q

= σ (T1 – T2 ) A

Conduction

h A LMTD

Free convection or forced convection

4

4

Radiation

Q k A ∆T L h LMTD σ

= = = = = = = =

T1, T2

= temperatures at two locations, Degree K

=

heat transfer, kcal / hr thermal conductivity, kcal / hr-m-Degree C heat transfer area, sq m T1 – T2 = temperature difference between two locations, Degree K distance between two points of interest, m convective heat transfer co-efficient, kcal / hr-sq m-Degree C Log Mean Temperature Difference, Degree C -8 4 Stefan-Boltzmann constant = 4.876 x 10 kcal / hr-sq m-K

(T1 – t1) – (T2 - t2)

Parallel flow

Log e {(T1 – t1)/ (T2 - t2)} LMTD

=

{(T1 – t2) – (T2 – t1) ) Log e {(T1 – t2) / (T2 – t1)}

T1

= entry temperature of hot fluid, Degree C

T2

= exit temperature of hot fluid, Degree C

t1

= entry temperature of cold fluid, Degree C

t2

= exit temperature of cold fluid, Degree C

Counter flow

A – 87 : Convective Heat Transfer Convective heat transfer can be forced convective heat transfer or natural convective heat transfer. The governing equation for convective heat transfer (for constant wall temperature) is given below. Nu x = 0.332 Re x

0.5

Pr

0.333

6

Nu x = 0.332 (2.747 x 10 ) Where,

0.5

for 0.6 < Pr < 50 2.22

Nu x

= Nusselt number

Re x

=

Pr

= Prandtl number

Nu

= hL k = hd k = ud

Nu Re

0.333

= 717.6

Reynolds number

= 10.0 x 0.1

= 2.747 x 10

6

-6

Pr

v = Cp µ k

0.364 x 10 = 2.22 (water at 80 Degree C)

h

= convective heat transfer co-efficient, kcal / hr-sq m-Degree C

L

= characteristic length, m

k

= thermal conductivity of fluid, k cal / hr-m-Degree C = 0.575

d

= inside diameter of hollow cylinder, m = 100.0 mm = 0.1 m

u

= stream velocity, m / sec = 10.0 m / sec

v

= kinematic viscosity, sq m / sec = 0.364 x 10

Cp

= specific heat at constant pressure, k cal / kg-Degree C = 1.00

µ

= dynamic viscosity, kg / m-sec

x

= distance from reference point, m

-6

sq m / sec

Flow of fluids inside pipes has been extensively researched. The results of the research are given in published literature. An engineer is guided by the past research and intuition. Solution to these equation gets us designs. Usually a configuration is assumed and the process is analyzed using the governing formulas. Design of heat exchangers and boilers is iterative.

'h

= Nu k / d = 717.6 x 0.575 / 0.1 = 4126 k cal / hr-sq m-Degree C

A – 88 : Radiant Heat Transfer Heat is transferred from the flame in furnace to the water walls through radiant heat transfer. The furnace flame temperature is 1,000 Degree C. The water wall temperature is 350 Degree C. The heat transferred from the flame to the water wall can be calculated using the Stefan-Boltzmann equation.

Where,

4

4

Q

= σ (T1 – T2 ) A

Q

= heat transferred, k cal / hr-sq m

σ

= Stefan-Boltzmann constant = 4.876 x 10

T1

= 1,000 Degree C + 273 = 1273 K

T2

= 350 Degree C + 273 = 623 K

A

= heat transfer area, sq m

Q

= 4.876 x 10

-8

4

4

-8

k cal / hr-sq m-K

4

4

(1,273 – 623 ) = 12 x 10 k cal / hr-sq m

The furnaces of boilers are designed considering heat transfer, mass transfer and construction. The following furnace parameters are popularly used: φ 51 x 4.0 mm @ 63.5 mm pitch – SA210 GrA1 φ 51 x 4.5 mm @ 76.2 mm pitch – SA210 GrA1 φ 63.5 x 4.5 mm @ 76.2 mm pitch – SA210 GrA1 φ 63.5 x 5.0 mm @ 76.2 mm pitch – SA210 GrA1 φ 63.5 x 5.2 mm @ 76.2 mm pitch – SA210 GrA1 φ 63.5 x 5.2 mm @ 88.9 mm pitch – SA210 GrA1

A – 89 : Conduction of Heat Heat is conducted in solids due to vibration of atoms and molecules. Metals are good conductors of heat. Non-metals are bad conductors of heat. The following equation governs the heat transfer through conduction:

Where,

k A ∆T L

Q

=

Q

= heat transferred, k cal / hr

k

= thermal conductivity, k cal / hr-m-Degree C

A

= cross sectional area, sq m

∆T

= temperature difference, Degree C

L

= distance between points of measurement, m

k

= 40.0 k cal / hr-m-Degree C

A

= 2.0 sq m

T1

= 120 Degree C

T2

= 80 Degree C

∆T

= T1 – T2 = 120 – 80 = 40.0 Degree C

L

= 0.2 m

Q

=

Exercise:

k A ∆T = L

40.0 x 2.0 x 40.0 = 16,000 k cal / hr 0.2

A – 90 : Flow of Fluids Inside Pipes and Tubes Fluids can be liquid or gas or liquid-gas combination. Flow of fluids can be inside the pipes and tubes or outside the pipes and tubes. Flow of fluids has been extensively researched. The pressure of the fluid drops when it flows inside pipes and tubes. The pressure drop, pumping power and flow distribution in the pipe can be calculated. The flow can be due to gravity or pumping or natural heat convection. Fluids have many properties. Some of the properties are: (a) density, (b) specific heat, ( c) Prandtl number, (d) dynamic viscosity, (e) kinematic viscosity and (f) thermal conductivity.

The flow can be laminar flow or turbulent flow. If the viscosity is high, the pressure drop and pumping power are more. The pressure drop across valves are found-out experimentally. For measurement of flow, venturies, orifices and flow nozzles are used. When there is a change in the direction of flow, an unbalance force is created. This is due to centrifugal force. The forces due to pressure inside the pipe is self limiting. When the pressure is not self limiting, pressure blocks, made of Reinforced Cement Concrete (RCC), are used. The longitudinal force due to internal pressure is computed in the following exercise:

F

= pressure x area 2

= (80.0 kg / sq cm (g)) x ( π (11.43 – 2 x 0.866) ) 4 = 5,909 kg

Exercise:

Find the unbalance force in a short radius elbow with following inputs:

Pipe size

= φ 219.1 x 8.2 mm

Bend angle

= 90 Degree

Bend radius

= 203.4 mm

Pressure

= 85 kg / sq cm (g)

Unbalance force

= 85

2

2

π (21.91 – 2 x 0.82) / 4 = 38,791 kg

A – 94 : Education, Training, Enabling and Empowering Education is provided in schools and colleges. Training is given in institutes and industries. Persons are enabled to perform duties. Empowered people are required for decision making. Education can be classified as theory and practice. Practice is in the laboratory. In engineering education, mathematics is a compulsory subject. Practice can be a visit to nearby industries, power plants and foundries. The education starts at primary level. Then secondary education is imparted. After this college education is given. Education is mostly theory and bookish. Schools and colleges don't have required funds to give proper practical training. Theory and practice are two hands to swim through the process evolution of products and services.

Presently the education starts at Kinder Garden level. School education is for fourteen years, including the Kinder Garden. College education is for three years. Engineering education is for four years. Students can pass tenth and complete the Poly-technique education and obtain a diploma in three years. After diploma, the students can join the engineering colleges as lateral entry in the second year. So, the Bachelor of Engineering degree is eighteen years. After this post graduate education can be followed. Education makes a person a complete person. Working in office or factory is for earning a lively-hood.

Professional education can be engineering, medicine, agriculture, horticulture or accounting. Professionals follow professional ethics. Education is inculcating the incomprehensible to the incompetent. Engineering education requires a strong foundation in mathematics. Good English knowledge is also required. A pleasing personality with accommodation with others will improve the relationships in the work place. Good communication skills and public speaking abilities are required for managers. A businessman believes in luck. Whereas, a professional believes in his abilities.

After formal education in the colleges, informal education in the the industry is needed. The technology and machinery becomes out-dated within a decade. Hence, visit to places where technology upgradation is taking place is required. Computers of different varieties are available. Computer peripherals of different varieties are available. To take care of the information revolution, knowledge explosion and automation, required funds should be set-on every year to upgrade the systems. What is known is hand-full. What is unknown is universe-wide. Educated persons should be employed properly. Unemployment, under employment and outstation employment are to be tackled with a right

spirit. A – 95 : Design of Large Coal Fired Power Boilers Large coal fired boilers are used in India since other sources of power are not appealing. Oil and gas fired power plants are expensive to run and maintain. Nuclear power is risky. Hydro-electric power is seasonal. Wind mill power is inadequate. Solar power is expensive. Pumped storage of power is used to even-out the load requirement. Coal is dirty fuel. Coal is of the following types: (a) bituminous coal, (b) sub-bituminous coal, ( c) anthracite and (d) lignite. In power plants, sub-bituminous coal is generally used. The coal is ground in mills and pumped into the furnace for combustion. Combustion is an exothermic reaction. Heat is released due to combustion of coal with Oxygen. The products of combustion, namely the flue gas and fly ash are flowing into the heat transfer surface. The following equipment are used in power plants: mills, coal pipes, burners, scanners, thermo-couples, furnace, furnace hopper, heat transfer surfaces, headers, piping, drums, pressure part panels, ash handling equipment, coal handling equipment, chimney, Flue Gas De-Sulfurization plant (FGD), electro-static precipitater, de-aerator, feed water tank, down-comers, saturated steam lines, boiler integral pipes, boiler external pipes. Design is creative. Engineering is logical. In the following some of the equations widely used for boiler engineering are given. Stress =

Load Area

Where,

M I

=

T J

= τ R M I f y E R T J τ R G

f = y

E R

= Gθ L = = = = = = = = = = =

ν

bending moment, kg-mm moment of inertia, mm ^ 4 bending stress, kg / sq mm distance of fiber from center of gravity, mm elastic modulus, kg / sq mm radius to which the beam is bent, mm torsion moment, kg-mm polar moment of inertia, mm ^ 4 shear stress, kg / sq mm radius at which the shear stress is measured, mm E 2 (1 + ν) = Poisson's ratio

θ

= angle through which the bar is bent, radian

L

= length of the bar, mm

A - 96 : Design of Boiler Framing Boiler framing is known as buckstays. Buckstays stay the buckling of the walls. The buckstay beams are cold, while the connected walls are hot. Hence, buckstays are known as hot structure. Buckstays and furnace guides guide the boiler zero point of expansion. Zero point of boiler is a virtual point. Buckstays can be wrap around or grid type. Wrap around buckstays are popularly used. Grid type buckstays are used for large boilers. The buckstays for once-through boilers are of special construction. The buckstays are designed for up-set conditions. The design pressure for buckstays is given in the National Fire Protection Association (NFPA, U. S. A.). The design pressure for large boilers is + / - 21 “ (+ / - 533.4 mm wc (g)) = + / - 533.4 kg / sq m (g).

Buckstays contain the following components: (a) buckstay beam, (b) buckstay vertical beam, ( c) stirrup, (d) channel, (e) corner connections, (f) levelers, (g) furnace bottom support, (h) rear arch support, (i) rear pass hopper support, (j) vertical buckstays, (k) furnace guide and (l) fasteners. Buckstay design is done using the following two steps: (i) spacing, (ii) sizing. Number of buckstays in a wall is decided based on the wall height and the allowable buckstay spacing. The design calculations for furnace bottom, rear arch, rear pass hopper are complicated. The levelers level the buckstay beams. It also provides lateral support for the buckstay beams.

The furnace guides are provided in all the four walls. The particulars of furnace guides is shown in Figure – 96.1 : Furnace Guides.

A – 98 : Safety Valves Safety valves are used to safe-guard the boiler and pressure vessels against excess pressure. Safety valves can be dead weight type or lever type or spring loaded type. Large safety valves are spring loaded type. Safety valves ensure safety of the boilers. When the pressure in boiler increases, the safety valve opens and releases steam. This decreases the pressure of the steam within the boiler and provides safety.

In dead weight safety valves, like that used in pressure cookers , the dead weight is lifted due to steam pressure and saves the cooker. In lever type safety valves, levers are provided to gain mechanical advantage and reduce the dead load. This improves the economy of the safety valves. In large boilers spring loaded safety valves are used. Spring loaded safety valves are safe, compact and economical. Safety valves are provided on the drum, main steam line and hot reheat line.

Some of the construction of safety valves are shown in Figure – 98.1.

A – 99 : Laws of Nature (i) First Law of Newton Every body continues to be in a state of rest or of uniform motion along a straight line, unless compelled by an external force.

(ii) Second Law of Newton Rate of change of momentum with respect to time is force. (iii) Third Law of Newton For every action, there is an equal and opposite reaction. (iv) Newton's General Law of Gravitation Every body attracts every other body due to gravitational force. This force is directly proportional to the mass of each body. This force is directly proportional to the inverse square of the distance between the center of gravity of the two masses.

(v) Einstein's Conjectures (a) Length shrinks with velocity, when velocity is near that of velocity of light. (b) Mass increases with velocity, when velocity is near that of velocity of light. ( c) Time dilates with velocity, when velocity is near that of velocity of light. (vi) Zeroth Law of Gravitational If two systems are both in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.

(vii) First Law of Thermodynamics In an isolated system, the total energy of the system remains constant. (viii) Kelvin-Planck Statement of the Second Law of Thermodynamics It is not possible to construct an engine, which while operating in a cycle produces no other effect

except to extract heat from a single reservoir and do equivalent amount of work. A – 100 : Flow of Fluids From Bernoulli's theorem, we know that, 2

p1 + u1 + z1 ρg 2g

-

hf

=

p2 ρg

+

2

u2 2g

+

z2

Where, p1

= pressure at point “1”

= 85 kg / sq cm (g)

ρ

= density of fluid (water)

= 0.001 kg / cu cm

g

= acceleration due to gravity

= 980 cm / sq sec

z1

= elevation of point “1”

= 1,000 cm

hf

= pressure drop due to flow

= 120 mm wc = 0.012 kg / sq cm

u1

= velocity of fluid at point “1”

= 1,200 cm / sec

p2

= pressure at point “2”

= 82 kg / sq cm (g)

z2

= elevation at point “2”

= 900 cm

u2

= 2g

p1 + u1 ρg

= 2 x 980

= 7,595 cm / sec

2

+

z1 - hf - p2 - z2

2g

ρg

85 0.001 x 980

+

2

1,200 2 x 980

+

1,000 - 0.012 82 - 900 0.001 x 980

A – 101 : Design of Vertical Tanks Vertical tanks are used to store liquid or gas. Vertical tanks are cylindrical with a conical top. The tank shell is designed to withstand pressure from the liquid or gas. Required protections are provided in the tank to avoid accidents. The thickness of the shell is computed considering hoop stress. The tank top is designed considering a imposed load (live load) of 500 kg / sq m. Tank bottom is lined to take care of the liquid or gas contained. The formula for tank shell thickness is given below.

T

=

HρD 2 E Sm

Where,

H

= height of the tank

= 20 m

ρ

= density of liquid stored

= 800 kg / cu m

D

= diameter of tank

= 30 m

E

= weld efficiency

= 1.0 for full radiography of welded joints = 0.85 for spot radiography of welded joints & = 0.7 for no radiography of the welded joints

Sm

= allowable stress

= 14.00 kg / sq mm

T

=

= 0.017 m

20 x 800 x 30 2 x 1.0 x 14.00 x 10

= 17 mm

6

Use 18 mm thick plate

Thickness of the conical roof

=

IL x D

=

2 E Sm Cos θ = 0.0005 m = 0.5 mm

500 x 30 6

2 x 1.0 x 14.00 x 10 x Cos 12

o

Use 6 mm thick plate

A-102: Design of Horizontal Pressure Vessels Pressure vessels can be horizontal or vertical. Pressure vessels are subjected to pressure from inside the vessel. Pressure vessels are used as containers with pressure. The pressure vessels are designed as per the American Society of Mechanical Engineers – Section VIII, Division 1. Pressure Vessels are subjected to hydraulic test after completion of fabrication. Pressure vessels are filled with water and checked for leakage. After that, the pressure vessels are subjected to hydraulic test of 1.3 times the Maximum Allowable Working Pressure (MAWP). An example of the pressure vessel design is given in the following:

Thickness

= t

=

PR SE – 0.6 P

Where,

t

P

= Maximum Allowable Working Pressure = MAWP = 80.0 kg / sq cm (g)

R

= inside radius of shell = 762 mm

S

= allowable stress = 1400.0 kg / sq cm

E

= joint efficiency = 1.0

=

80.0 x 762

= 45.1 mm

1400.0 x 1.0 – 0.6 x 80.0 Fabrication allowance

= 4.0 mm

Raw plate thickness required = 45.1 + 4.0 = 49.1 mm, Raw plate to be used = T = 50.0 mm Vessel length provided

= L = 10.0 m

Steel weight

=

Water weight

= π x 762 x 10,000 x 10

Total weight

= W1 = 19,409 = 18,241 = 37,650 kg

Bending moment

= BM = W1 x L = 37,650 x 10,000

2

2

π (( 762 + 50 ) – 762 ) x 10,000 x 7.85 x 10 2

8 Section modulus

–6

–6

= 19,409 kg

= 18,241 kg

= 47.06 x 10

6

kg - mm

8 4

4

= Z = π (( 762 + 50) – 762 )

6

= 100.6 x 10 cu mm

4 x 762 Bending stress

= BM = 47.06 x 10 6 = 0.47 kg Z

100.6 x 10

6

sq mm

< allowable stress = 10.0 kg SAFE

sq mm

A-103 : Design of Base Plate The base plates of columns are subjected to axial compression, shear forces and moments. Steel structures are usually arranged such that the induced bending moments are negligible. The following gives a procedure for design of a base plate: Fx

= 1,000 kg

Fy

= - 25,000 kg

Fz

= - 1,500 kg

Mx

= 0.0 kg-mm

My

= 0.0 kg-mm

Mz

= 0.0 kg-mm

Allowable stress for compression on concrete (M20)

= 0.4 kg / sq mm

Base plate (square) width required

=

25,000 / 0.4

= 250 mm Use 300 x 300 base plate Unit pressure

=

25,000 300 x 300

Out-stand of base plate

= 75 mm

Plate thickness required

=

= 0.28 kg / sq mm

2

0.28 x 75 x 6 10 x 2

= 21.7 mm Use 25 mm Thick plate

A-104 Vibration of Heat Recovery Steam Generator (HRSG) Tubes When flue gas flows across the tubes in Heat Recovery Steam Generator tubes, vibration is experienced. This is due to the eddies shed by the flue gas behind the tubes. The tubes are subjected to vibration, drag and lift. In the present study, a set of HRSG tubes is analyzed.

Where,

Strouhal Number

= Df V

= 0.2

Drag co-efficient

= CD

= 0.5 (assumed)

D

= outside diameter of tube = 50.8 mm

T

= tube thickness = 3.25 mm

V

= 20 m / sec

f

= 0.2 V = 0.2 x 20 = 78 cycles / sec D

Drag force = w I Z

0.0508 2

2

= CD ρ A V = 0.5 x 1.0 x 5.08 x 2000 = 10.35 kg / cm g 1,000 x 981 4 4 = ( 50.8 - (50.8 – 2 x 3.25) ) = 43,880 mm ^ 4 64 = 43,880 x 2 = 1727 cu mm = 1.73 cu cm 50.8

Tube length

= L

= 400 cm

Bending moment

= BM

Bending stress

= σb

= wL 8 = BM Z

2

2

4

= 10.35 x 400 = 20.7 x 10 kg-cm 8 4 4 = 20.7 x 10 = 12 x 10 kg / sq cm 1.73

A-105 Design of Pin Joints Pin joints are used to transfer loads between structural parts. Pin joints can be single pin joint or multiple pin joint. In the present study, a single pin with two adjacent plates is studied. The design code is IS : 800 – 1984. Plate in Axial Tension σt = P

=

T(W–D)

12,000

( P = axial tensile load, kg )

20 ( 150 – 52 )

( fy = yield stress, kg / sq mm )

= 6.1 kg / sq mm < 0.6 fy = 0.6 x 24 = 14.4 kg / sq mm Pin under Bearing σ br

=

P

=

Td

12,000 20 x 50

= 12.0 kg / sq mm < 0.75 fy = 0.75 x 24 = 18.00 kg / sq mm Plate Double Shear τ

=

1.5 x P

=

2xT(E - D) Pin Bending σ bn

=

1.5 x 12,000 2 x 20 ( 75 - 52 )

2 2 PT

= 9.2 < 0.45 fy = 0.45 x 24 = 10.8 mm

2 = 2 x 12,000 x 20 = 9.8 < 0.66 fy = 0.66x24 = 15.8 kg / sq mm

3

3

4 x π d / 32

4 x π x 50 / 32

Pin Double Shear τ

=

P

= 2

2xπd /4

12,000 2

2 x π 50 / 4

= 3.06 < 0.4 fy < 0.4 x 24 = 9.6 kg / sq mm

All dimensions are in mm A-106 Design by Analysis Design is a creative activity. Design includes engineering, process analysis, stress analysis, detailing, drafting, documentation and document approval. Engineering is analytical and requires logic. Process analysis is done by the thermal process designer. Stress analysts check the stress and find-out the strength of the product to withstand the design load. Detailing requires design of connections and parts detailing. Drafting is drawing lines as per agreed practices. Documentation is writing Bills of Materials (BOM) and other documents. Document approval is by clients and statutory authorities.

The material properties of parts is find-out from the laboratory testing. The following tests are done: (a) uni-axial tensile test at room temperature, (b) creep testing, ( c) fatigue testing, (d) Charpy V notch testing, (e) Izod V notch testing, (f) hardness testing, (g) fracture mechanics testing. Testing is done in a laboratory with controlled conditions. The field information gives us experience. In the field, many parameters are not controlled properly. Hence, there is always ambiguity about the loads and material behavior in the field. To take care of these imponderables, Factors of Safety is used. Factor of Safety used is about 1.5 (on yield stress). Factor of Safety is also known as Factor of Ignorance. We can never predict our level of ignorance.

The whole of science, engineering and technology are based on structured common sense. Many empirical relationships have been developed to study the material and forecast their behavior. These empirical relationships are based on laboratory studies and field studies. The behavior of an uni-axial tensile test specimen is studied and the product behavior in four dimensions is forecast. The four dimensions are X, Y, Z and Time. The latest studies of Fracture Mechanics are still in development stage. The objective of design is performance without failure. Failure can be process failure or mechanical failure. “Fail Safe Design” is the watch-word. Fail Safe Design is possible by limiting the induced stress to the allowable stress. The allowable stress changes with type of loading and kind of supports. In the boiler industry only the equivalent static analysis is done. Vibration studies and creepfatigue interactions are rarely encountered. In the mechanical static equipment design, the Stress Concentration Factor (SCF) is not considered. This is due to the fact that only ductile materials are used. These materials are not subjected to high cycle fatigue. These materials deform at stress concentration points and the stress is redistributed favorably. In the analysis of piping, Stress Intensification Factors (SIF) are considered. These are obtained by testing the piping components in the

laboratory. A-107 Load Chain Management The boilers are subjected to loads and load combinations. The loads can be used to find-out the stress and deformation, induced. The induced stress is to be limited to the allowable stress, for “Fail Safe Design”. Cracks initiate before rupture in ductile material. Hence, ductile materials are preferred for boiler pressure parts. Ductility can be measured from uni-axial tensile test. The percent elongation and percent reduction in area are measures of ductility. The energy absorbed in Charpy V – notch test and Izod V – notch tests are also used as a measure of ductility. Stress Concentration Factors (SCF) are used for assessing components subjected to high cycle fatigue.

The pressure parts of large boilers are supported from the top to avoid buckling of water walls and steam cooled walls. The pressure parts expands cubically with the “Virtual Zero Point” as the datum. The Virtual Zero Point is at the top, near the pent house. The strength of the chain is in the weakest link. When any one link fails, the component fails. The following are the loads to be considered: (a) self-weight, (b) imposed load (live load), ( c) thermal expansion load, (d) thermal contraction load, (e) loads due to relative settlement of foundations, (f) ash load, (g) water load, (h) steam load, (i) hydraulic test water load, (j) hydraulic test pressure load, (k) Maximum Allowable Working Pressure (MAWP), (l) furnace pressure excursions, (m) pressure surges, (n) slag load, (o) seismic load (earth-quake load), (p) wind load (q) snow load, ( r) ice load, (s) flood load, (t) fire load, (u) tsunami load and (v) wave load.

Suitable load combinations are considered. The loads are classified as (i) primary load, (ii) secondary load and (iii) occasional load. The following load combinations are considered: primary load + secondary load

and

primary load + occasional load

Out of several occasional loads, one occasional load at a time is considered. The following load combination is not considered:

primary load + secondary load + occasional load

The following gives the stress limits as per The American Society of Mechanical Engineers – VIII, 1: primary membrane stress

< code allowable stress

local primary membrane stress

< 1.5 x code allowable stress

primary stress + bending stress

< 1.5 x code allowable stress

secondary stress

< 1.5 (cold allowable stress + hot allowable stress)

peak stress

< allowable stress for parts subjected to fatigue

A-108 Vibration of Heat Recovery Steam Generator (HRSG) Tubes When flue gas flows across the tubes in Heat Recovery Steam Generator tubes, vibration is experienced. This is due to the eddies shed by the flue gas behind the tubes. The tubes are subjected to vibration, drag and lift. In the present study, a set of HRSG tubes is analyzed.

Where,

Strouhal Number

= Df V

= 0.2

Drag co-efficient

= CD

= 0.6 (assumed)

D

= outside diameter of tube = 50.8 mm

T

= tube thickness = 3.25 mm

V

= flue gas velocity = 10 m / sec (assumed)

f

= 0.2 V = 0.2 x 10 = 39 cycles / sec D

0.0508

Drag force = w

= 0.6 V

I

= ( 50.8

Z

2

= 0.6 x 10

2

= 60 N / sq m = 6 kg / sq m

4

4

- (50.8 – 2 x 3.25) ) = 43,880 mm ^ 4 64 = 43,880 x 2 = 1727 cu mm = 1.73 cu cm 50.8

Tube length

= L

= 400 cm

Bending moment

= BM

Bending stress

= σb

= 6 x 5.08 x 400 = 60.96 kg-cm = w Do L 8 100 x 100 x 8 = BM = 60.96 = 35.2 kg / sq cm Z 1.73 = 0.35 kg / sq mm < 14.00 kg / sq mm OKAY

Natural Frequency

= C

2

gEI w L

= 1.57 4

= 3.9 cycles / sec

2

4

9810 x 2 x 10 x 43,880 x 1000 5.35 x 4000

4

A-112 – Design of Supporting Structures for Power Boilers Supporting structures are required for power boilers to resist the forces of nature. The forces of nature are computed from the past and the structures are designed to give a working life of fifty years. Structures are made of steel. In India, Mild Steel (IS 2062) is popularly used. Presently, low-alloy steel is used considering the economy of boiler structure. Boilers of different shapes require different types of supports. Small boilers are bottom supported. Large boilers are top supported. The difference between small and large boilers are not defined clearly. The following are the reasons for topsupporting the large boilers (a) reduce thermal stress, (b) avoid buckling due to boiler pressurization and ( c) improve stability of boiler envelop walls.

Structural steel is used for boiler supporting structure. Supporting structure is in the “Critical Path” in boiler erection. Hence, the foundation loads of the boiler is finalized before the completion of design of boiler. Design is a creative activity and requires experience. Design is like a puzzle. If the answer to the puzzle is known, the design is easy to understand. Un-braced steel structures is uneconomical. Bracings are rarely used for Reinforced Cement Concrete (RCC) structure. Shear walls are provided for RCC structure to carry the horizontal structure due to wind load and seismic loads (earth-quake loads). The necessary condition to check for the stability of steel structure is given below.

FxN–R–C<=M Where,

F

= 1.0 for one dimensional structures

F

= 2.0 for two dimensional structure

F

= 3.0 for three dimensional structures

N

= number of nodes

R

= number of restraints at supports

C

= number of connection continuity (constraints)

M

= number of members (elements)

The necessary and sufficient condition for stability of stel structure is given below. “The determinant of the stiffness matrix shall be non-zero” Structural connections are any one of the following types: bolted, riveted, welded, brazed, soldered and bonded. Welding is popularly used for work-shop joints. Bolting is popularly used for field (job site) joints. Bearing type of joints are more popular than friction type of joints.

A-113 Design of Piping for Power Boilers Power boilers have integral piping and external piping. Integral piping are used to connect various heat transfer surfaces of the boiler. Examples of integral piping are: (a) economizer links to drum, (b) downcomer, ( c) supplies, (d) risers, (e) saturated steam lines and (f) links between super-heaters. Examples of external piping are: (i) feed line, (ii) main steam line, (iii) cold re-heat line and (iv) hot re-heat lines. These lines carry steam or water or steam-water mixture. Purpose of piping is conveyance of fluid.

The following drawings nd documents are prepared for piping: (1) scheme, (2) Process Flow Diagram (PFD), (3) Piping and Instruments Diagram (P & ID), (4) piping layout, (5) isometric drawing, (6) stress analysis, (7) detailed design, (8) joints design, (9) drafting, (10) documentation, (11) document control, (12) document approval. While laying-out the piping, interfacing, interference and the related checks are to be done. The piping is subjected to the following loads self-weight, imposed loads, thermal load, thermal movements of connected equipments, relative settlement of supports and foundations, wind load, seismic loads (earth-quake loads), flood, fire, tsunami, snow, ice, vehicle loads for under-ground piping.

The stress induced due to various loads is limited to respective allowable. The thermal loads are selflimiting. Hence, this load is strain controlled stress. The piping is allowed to be shake-down due to thermal load. There are many unknowns in the piping design. Factors of Safety (Factors of Ignorance) are used to assure safety of piping. The Factor of Safety used is 1.5 (on yield stress). The following are some of the components used in the piping: bends, long radius elbow, short radius elbow, concentric reducer, eccentric reducer, equal TEE, unequal TEE, Y – piece, flanges, flanged fittings, blind flange, weld-neck flanges, end cover and thermo-wells. These components are designed based on analytical and empirical formulas. Empirical formulas are arrived-at based on experiments and experience.

Theory and practice are two hands to swim through the process of evolution of products and services. At present, the following two computer softwares are popularly used for piping stress analysis: CAEPIPE and CAESAR – II. The computer carries-out numerical experiments to assess the acceptability of the piping. Before the advent of computers the design of piping was based on design by rules. The design of piping is based on design by stress analysis.

A-119 : Engineering Mechanics Father of Mechanics is Sir Isaac Newton. Father of Engineering Mechanics is Stephen P Timoshenko. In the ancient times, several machines were used to simplify the work. Then machine tools were invented to produce components fast. As the industry grew, several persons worked on improving the Mechanical Advantage and efficiency of machines. Machines were initially controled by humans. Then, electrical and electronic controls were introduced. Now, many machines are computer-controlled.

Engineering Mechanics deals with the following: resolution of forces, vector analysis, Lame's theorem, Newton's laws, solution of beams, solution of trusses, solution of frames. Engineering Mechanics is taught in Engineering colleges, world-over. After the advent of computers, engineering calculations, drafting and documentation are automated. Engineering Mechanics can solve the following problems:

1. beams under bending 2. trusses under loads 3. frames under loads 4. three dimensional structures 5. joints deign 6. stability checks 7. strength checks 8. natural frequency of shafts 9. vibration 10. thermal stresses 11. tubes under internal pressure 12. shell analysis 13. columns design 14. bracings design 15. base plates design 16. gusset plates design 17. pins design 18. fasteners design 19. splices design

20. girders design

A121 : Paths to Prosperity in Business Business is done for prosperity. Business is becoming a gambling. Businessmen believe in luck and God. Professionals believe in their talent and skills. Business involves production, transportation, distribution and consumption. In the industry, to produce anything, humans, machines, materials and time are required. The businessman should know the products, process, problem, persons, places and politics.

Prosperity in business is possible by suppling right quality material at reasonable price within the assigned time. A satisfied customer is an asset for the business. Business Process Outsourcing (BPO) is done in large scale in India. Engineering Process Outsourcing (EPO) is also done. In EPO a parent company in the West sets-up a small outlet in India. Then, Engineering drawings and documents are produced by the Indian engineers sitting in India. This process is supported by computer professionals, software and networking of computers.

In EPO the basic thermal calculations and the layout drawings and the arrangement drawings are prepared by the parent company in the West. The detailed drawings and documentation are prepared in India. The project manager in the West manages the project by visiting the Indian outsourcing group and the West. These drawings are issued to the fabricator as soft copy. The fabricator manufacture the components and supply them to the job site directly. In the job site required computer facilities and plotting facilities are provided to carry-out the job.

An inspector is deputed by the main contractor to the job site to assure quality and expediting. Weekly and monthly reports are prepared. These are reviewed in the weekly and monthly meetings. The EPO is feasible only because of well-equipped offices with required facilities are available in India for reasonable costs. The EPO companies personnel are well trained by the parent company in the West.

West and East join hands to assure good speed of delivery with reasonable quality and affordable price. The costs in India are low because the living standard in India is low. Indian engineers are brilliant and they produce good quality output within the assigned time.

A-123 : Vibration of Heat Recovery Steam Generator (HRSG) Tubes Natural frequency

= C

Time period for vibration

= 1 C

Where,

C w w1 w2 w L1 L2 E I

Tn1

4

wL gEI

= constant for mode – 1 = 1.57 = tube weight / m = steel weight + water weight = π (50.8 - 3.25) x 3.25 x 7.85 1,000 2 = π (50.8 – 2 x 3.25) 4 x 1,000 = w1 + w2 = 3.81 + 1.54 = tube length = 4.0 m = tube length = 8.0 m 10 = elastic modulus = 2 x 10 kg / sq m = moment of inertia 4 4 12 = π ((50.8 - (50.8 – 2 x 3.25) ) / (64 x 10 )

=

1 1.57

Tn2

gEI 4 wL

=

9.81 x 2 x 10

1 1.57

4

5.35 x 4.0 10

5.35 x 8.0 9.81 x 2 x 10

10

x 13.78 x 10

Tn3

= 0.14

9.81

= 0.44 sec / cycle

Tn4

= 0.57 9.81

= 1.79 sec / cycle

= 1.54 kg / m = 5.35 kg / m

= 13.78 x 10

–8

= 0.14 sec / cycle –8

4

x 13.78 x 10

= w1 + w2, kg / m = 3.81 kg /m

= 0.57 sec / cycle –8

Note: 1. Tn1 and Tn2 are Time period of vibration in the vertical direction 2. Tn3 and Tn4 are Time period of vibration in the horizontal direction

m^4

A-124 : Properties of Area Find the following properties of a rectangle of size 100 x 200 mm x mm.

Cross sectional area

= A

=

Circumference

= C

=

Paint area / m length

= Ap =

Moment of inertia about X – X axis = Ixx

=

Moment of inertia about Y – Y axis = Iyy

=

Product of inertia

= Ixy =

Section modulus about X – X axis

= Zxx =

Section modulus about Y – Y axis

= Zyy =

Radius of gyration about X – X axis = rxx = Radius of gyration about Y – Y axis = ryy =

A-125 : Earth-Quake Resistant Design of Steel Structures as per IS : 1893 (Part 1) - 2002 From Clause 12.1 of IS : 800 – 2007, Steel frames shall be so designed and detailed as to give them adequate strength, stability and ductility to resist severe earthquakes in all zones classified in IS 1893 (Part 1) – “Criteria for earthquake resistant design of structures: Part 1 General provisions and buildings” - without collapse. Frames, which form a part of the gravity load resisting system but are not intended to resist the lateral earthquake loads, need intended to resist the lateral earthquake loads, need not satisfy the requirements of this section, provided they can accommodate the resulting deformation without premature failure.

From Clause 6.4.2 of IS : 1893 (Part 1) - 2002 The design horizontal seismic co-efficient Ah

for a structure shall be determined by the following

expression: Ah

= ZISa 2Rg

Where,

Z

= Zone factor (from Table 2 of IS 1893 (Part 1) : 2002)

I

= Importance factor (from Table 6 of IS 1893 (Part 1) : 2002)

R

= Response reduction factor (from Table 7 of IS 1893 (Part 1) : 2002)

S a / g = From Clause 6.4.5 of IS 1893 (Part 1) : 2002 Following formula is used to calculate the equivalent horizontal force induced on the structure due to earthquake: F

= (applicable mass) x Ah, kg

This load is applied at appropriate locations in the structure and the resultant forces and moments are to be resisted by the structure and the foundation. The stress analysis is carried-out with F applied in the following four horizontal directions (any one direction at a time):

F

- in positive X – direction, kg

F

- in negative X – direction, kg

F

- in positive Z – direction, kg

F

- in negative Z – direction, kg

A-126 : Design of Flat End Covers for Shell and Tube Heat Exchanger as per IBR, 1950 Shell and tube heat exchangers are closed at both the ends by flat ends. As the flat ends are subjected to internal pressure, the same is retained in place by stay tubes or stiffeners or stay rods. In the present write-up we consider a single pass heat exchanger. Flue gas at about 600 Degree C enters the fire tubes inner at one end. The surrounding water at pressure, boils and steam is taken out through the steam outlet pipes.

All the tubes provided are considered to be stay tubes and are strength welded. The steam space of the boiler has the flat plate exposed to the internal pressure due to steam. This steam side flat end cover can be strengthened by stiffeners or stay tubes. In the present design, the length of the stay rods is to be 7.0 meter. Number of stay rods depends on the total load and load carrying capacity of each rod. Figure – 1 gives the method of finding the pressure circle diameter (PCD). The thickness of the flat end cover as per IBR – 574, 1950 e = cd

P

+ e1

f1 Where,

e

= required thickness, mm

c

= Code Factor = 0.40

d

= Pressure Circle Diameter (PCD) = 267.9 mm

P

= 23 kg / sq cm (g)

Material

= SA516 Gr70

Steam temperature

= 221 Degree C

Temperature margin = 28 Degree C Working temperature = 221 + 28 = 249 Degree C Allowable stress

= f = 1407.21 kg / sq cm

f1

= 0.85 f = 0.85 x 1407.21 = 1196.12 kg / sq cm

e1

= 0.75 mm

e = cd

P f1

+ e1

= 0.40 x 267.9

23

+ 0.75 = 15.6 mm

1196.12 < thickness provided = 25 – 2.5 = 20.45 mm 1.1

A-127 : Structural Steel Design as per IS : 800 – 2007 Design of structural steel as per IS : 800 – 2007 (General Construction in Steel – Code of Practice) requires knowledge of design, analysis and materials. Among the structural steel, the popularly used material is IS : 2062. Design, engineering, stress analysis, functional requirements, detailing, drafting, documentation, document control and document approval require knowledge of many subjects.

IS : 800 was first published by the Bureau of Indian Standards (BIS) in 1956. The first revision was issued in 1962. The second revision was issued in 1984. The present revision (IS : 800 – 2007) was issued in December 2007. At present all structural steel designed in India should meet the requirements of IS : 800 – 2007, subject to contract conditions. Structural steel can be plain carbon steel or low-alloy steel. Analysis of structures is done considering elasticity. The present standard permits the following methods of design:

1. Working stress method 2. Limit state method 3. Fatigue design 4. Design assisted by testing 5. Fire resistant design

Presently the working stress method is used popularly. Design requires the following checks:

a)

Access to various locations

b)

Approach to all the locations

c)

Walk-way requirements

d)

Head-room requirements

e)

Interferences (hard clashes and soft clashes)

f)

Interfaces

In the industrial structures, a worker with shoes and helmet and a toolbox in one hand should be able to walk erect without injury. In homes, safety of children and elders should be taken care-of. Structures should be designed to be “Fail Safe” under various loading.

A128_Comparison of Indian Structural Design Codes IS 800 – 1984 & IS 800 – 2007 The Indian structural design code IS 800 was introduced in 1956. The fist revision was issued in 1962. The second revision was issued in 1984. The present revision (IS 800 – 2007) was issued in November 2007. Now, any structural steel design made in India shall be as per IS 800 – 2007. There are several changes between IS 800 – 1984 and IS 800 – 2007. The following gives a gist of the changes:

Table - 1 Sl No.

Parameter

IS 800 - 1984

IS 800 - 2007

Remarks

(1)

(2)

(3)

(4)

(5)

1

d / tw (maximum)

90

42

2

Out-stand (compression)

16

15.7

3

Out-stand (tension)

20

15.7

4

Out-stand (bending)

16

15.7

5

Deflection limit (L / ∆)

325

300

6

Drift (column)

325

300

7

Slenderness ratio (K L / ry)

Table 3.1 of IS 800 - 1984

Table 3 of IS 800 - 2007

Legend: 1. 2. 3. 4. 5. 6.

d tw K L ry ∆

= = = = = =

depth of un-stiffened web of beam, mm thickness of web, mm column parameter (see Table 11 of IS 800 - 2007) applicable length of column, mm radius of gyration about the applicable axis, mm deflection in vertical direction, mm

Note: All the values indicated under column (2) of Table – 1, above are maximum values permitted.

A-129 : Load and Resistance Factor Design (LRFD) as per AISC Load factor and Resistance Factor Design (LRFD - 3rd Edition, 2001) of the American Institute of Structural Construction (AISC) is the twelfth major update of the AISC Manual of Steel Construction, which was published in 1927. With this revision, members and connections design information has been condensed back into a single volume. It has been reorganized and reformatted to provide practical and efficient access to the information it contains, with a road-map format guide the user quickly to the applicable specifications, codes and standards, as well as the applicable provisions in those standards. From page 5-7 of AISC LRFD - 3rd Edition,

Where,

φbMp

= 0.9 F y Z x

φb

= Resistance factor for flexure

Mp

= Moment defined in LRFD Specification (AISC), kg - mm

Fy

= Specified minimum yield stress, kg / sq mm

Zx

= Plastic section modulus about X – axis, cu mm

The AISC Load and Resistance Factor (LRFD) specification for Structural Steel Buildings is based on reliability theory. This specification has been based upon past successful usage, advances in the state of knowledge, and changes in design practice. The Specification has been prepared as a consensus document to provide a uniform practice in the design of steel-framed buildings. The intension is to provide design criteria for routine use and not to provide specific criteria for infrequently encountered problems, which occur in the full range of structural design.

The Indian Standard – IS 800 : 2007 (General Construction in Steel – Code of Practice) provides rules for design and construction to satisfy the design requirements with regard to stability, serviceability, brittle fracture, fatigue, fire and durability such that they meet the strength and functional requirements. Generally structures and elements can be designed by limit state method. Where limit state method can't be conveniently adopted, working stress design (see section 11 of IS 800 – 2007) may be used. The reliability of design is ensured by satisfying the requirement:

Design action

< = Design strength

A-130 : Structural Steel Connections Structural steel connections are of the following types: riveted, bolted, welded, bonded and brazed. Soldering is used only for electronic components. Riveting can be done in workshop or at job site (field). Bolting is done in workshop and job site. Welded connections are done with controlled environment and controlled parameters. Welding requires preheating, post-welding heat treatment (PWHT) and inter-pass temperature control. Bonded connections are rarely used. Brazing is used only for non-critical applications.

Welded joints are designed as per IS : 816 – 1969 (Code of practice for use of metal arc welding for general construction in mild steel). The symbols for welding indicated in the drawing are as per IS : 813 – 1986 (Scheme of symbols for welding). Bolted connections are designed considering the load distribution in the bolts. The following stresses are checked: tension, compression, bending, bearing, shear, tearing, buckling and instability. Gusset plates are used for connections. Connection design considers the following: location, orientation, type of connection, connection standards, materials, allowable loads, type of members joined, member orientation and member strength.

The bolted connections can be of bearing type or friction type. In the bearing type of connections, bearing stresses are considered. In the friction type of connections friction is developed between surfaces to transfer loads. Connections can be rigid, semi-rigid and flexible as indicated in IS : 800 – 2007 (General Construction in Steel – Code of Practice). Connection drafting can be done using the software X – STEEL.

The popularly used bolts are as per ASTM A325 and A490. Suitable nuts, lock nuts, washers and spacers shall be used. The pitch, edge distance, thickness of gusset plate, layout and orientation are decided considering the strengths required for the connections. Standard connection details and standard parts are used. The connections are designed to withstand the following forces: Fx, Fy, Fz, Mx, My and Mz. In the case of trusses the moments (Mx, My and Mz) are not induced. Connections can be designed as pinned or fixed. Design of fixed connections is complicated, since they carry moments. Connection design can be done using the Micro Soft EXCEL spread sheet. All the loads and load combinations shall be considered.

A-131 : Stress Analysis – It's Application and Use Stress is a concept developed to explain many real life phenomena. “Stress is proportional to strain, within elastic limit”, said Robert Hooke. If we take Poisson's effect into consideration, this basic law can be proved wrong. Poisson's ratio is the ratio of the lateral strain to the longitudinal strain. This value is usually less than 0.5. Materials have many properties. Yield stress is the point on the stressstrain diagram that divides elastic region and plastic region. The Ultimate Tensile Stress (UTS) is the maximum stress the component can withstand. Rupture point is lower (in the stress-strain diagram) than the UTS. Stress is a tensor. Following equation is to be satisfied for uni-axial tensile test specimen. Stress =

Load (kg) Area (sq mm)

For a beam under bending, the following equation is used:

M = f = E I Where,

M I 'f y E R

y = = = = = =

R

bending moment, kg-mm moment of inertia, mm^4 stress, kg / sq mm distance of fiber from the center of gravity axis, mm elastic modulus (Young's modulus), kg / sq mm radius to which the beam is bent, mm

For a shaft under torsion, the following equation is used: T = τ = Gθ J Where,

R T J τ R G E ν θ L

= = = = =

L

torsional bending moment, kg-mm polar moment of inertia, mm^4 shear stress, kg / sq mm radius from member axis, mm E modulus of rigidity, kg / sq mm 2(1+ν) = elastic modulus (Young's modulus), kg / sq mm = Poisson's ratio = angle of rotation of shaft, radian = length of shaft, mm

A-132 : Design of Structural Steel as per IS 875 (Part 3) : 1987 – Wind Loads Design of structural steel is done in India as per IS 800 – 2007 (General Construction in Steel – Code of Practice). The loads are specified in various parts of IS 875. The earthquake load is given in IS 1893 (Part 1) – 2002. From Clause 5.3 of IS 875 (Part 3) – 1987,

Where,

Vz

= V b k 1 k 2 k 3, m / sec

Vz Vb

= design wind speed at any height z in m / sec = basic wind speed in m / sec, see Figure 1 of IS 875 (Part 3) - 1987

k1

= probability factor (risk coefficient) see 5.3.1 of IS 875 (Part 3) – 1987

k2

= terrain, height and structure size factor, see 5.3.2 of IS 875 (Part 3) - 1987

k3

= topography factor, see 5.3.3 of IS 875 (Part 3) – 1987

From Clause 5.4 of IS 875 (Part 3) – 1987, the design wind pressure (p z) is given in the following: pz

2

= 0.6 V z , N / sq m

Load (F) on the structure from any direction is calculated using the following formula:

Where,

F

= p z A, N

A

= projected area, sq m

Stress analysis shall be carried-out with F applied in the following four horizontal directions (any one direction at a time): F

- in positive X – direction, kg

F

- in negative X – direction, kg

F

- in positive Z – direction, kg

F

- in negative Z – direction, kg

If the structure has large openings, applicable area in the calculation shall be reduced as recommended by the Indian Standards. While carrying-out the stress analysis, the earthquake load and the wind load shall not be applied simultaneously. The wind load and the earthquake loads are considered mutually exclusive.

Part – B : Piping Contents B1. Introduction B2. Materials B3. Loads B4. Load Combinations B5. Allowable Stress B6. Working Pressure B7. Support Span B8. Deformations B9. Valves B10. Gages B11. Types of Supports B12. Flow Analysis B13. Codes and Standards B14. Flexibility Analysis B15. Supports Design B16. Lateral Restraints B17. Fail-Safe Design B18. Insulation and Refractory B19. Standard Components B20. Creep and Fatigue B21. Design and Stress Analysis of Piping and Supports B22. Pressure and Temperature Drop in Pipelines B23. References

P1: Introduction Piping are used from time immemorial for conveying fluids. Piping can convey single phase or two phase or three phase fluids. A pipe is a large tube. A tube is a small pipe. Pipe is usually hollow cylindrical in shape. Hollow rectangular tubes are used for buildings. In the present treatment of the subject, piping used in the industry is considered. In the industry most of the piping are iron and steel. Reinforced Cement Concrete (RCC) pipes are used for water applications. The piping is designed considering techno-economics. The pipe diameter is selected considering the fluid flow requirements. In the present write-up flow inside the piping alone is considered. Piping under water, such as under river and under sea, are not considered in the present write-up.

P2: Materials The piping can be made of any one of the following materials: iron, steel, aluminum, copper, brass, Reinforced Cement Concrete (RCC). The material selected depends on the medium conveyed and the design temperature. At high temperature, creep is governing. At low temperature, brittleness is governing. Materials with good impact strength and malleability are used. Cross-country piping experience different environments. The valves, gages, instruments and appurtenances should be compatible with the piping. The cost of the piping is directly related to the material of construction.

Commonly Used Seamless Tube and Pipe Specifications in Boiler Pressure Parts and Applicable Service Temperatures Nominal Product Composition

ASME

CSN

DIN

BS

Temperature Limit

CS

T

SA192 SA210Gr A1 SA210 C

St35.8 St45.8

BS 3059 P2 S2 45

800 o F (427 o C)

CS

P

SA106 B SA106 C

St35.8 St45.8

BS 3602 HFS 27

800 o F (427 o C)

1 / 2 Mo

T

SA209T1

--

15 Mo3

--

900 o F (482 o C)

1 Cr ½ Mo

T

--

--

13Cr Mo44

BS3059 P2 S2 620

995 o F (535 o C)

1 Cr ½ Mo

P

SA335 P12

15111.1 13Cr Mo44

BS3604 HF620

995 o F (535 o C)

1 ¼ Cr ½ Mo T

SA213 T11

--

--

--

1025 o F (552 o C)

2 ¼ Cr 1 Mo T

SA213 T22

--

10 Cr Mo 910

BS3059 P2 S2 622/50

1070 o F (577 o C)

2 ¼ Cr 1 Mo P

SA335 P22

----

----

BS3604 HF 622/31

1070 o F (577 o C)

½ Cr ½ Mo V T

---

15123.1 14MoV63

+BS3604 CD660

1070 o F (577 o C)

½ Cr ½ Mo V P

----

15123.1 14MoV63

+BS3604 CD660

1070 o F (577 o C)

18Cr 8Ni

T

SA213TP304H

----

----

---

1300 o F (704 o C)

18Cr 10Ni 4C Ti0.6

T

SA213TP321H

-----

X10Cr Ni Ti 89

----

1300 o F (704 o C)

18CR10Ni 8C Co+Ta

T

SA213TP347H

----

----

---

1300 o F (704 o C)

18 Cr10Ni 5C Ti0.7

T

----

-----

-----

BS3605 822Ti

1300 o F (704 o C)

Legend: T – Tube, P – Pipe, All materials are in per cent. Remaining material is Iron.

P3: Loads The loads on the piping can be classified into the following three categories: a) Primary Loads: internal pressure, external pressure, self weight, insulation weight, refractory weight, weight of inner lining, weight outer lining, equipment loads, valves, fittings, gages, instruments and supports.

b) Secondary Loads: thermal load, thermal transients, anchor displacements, foundation relative settlement and constrains for movement.

c) Occasional Loads: wind load, seismic load (earth-quake load), snow load, ice load, flood load, fire load, vehicle passing load (under ground piping), tsunami loads and cyclone load.

P4: Load Combinations The following load combinations are considered: a) primary load + secondary load b) primary load + occasional load Occasional loads consists of the following: 1. wind in positive X – direction 2. wind in negative X – direction 3. wind in positive Z – direction 4. wind in negative Z – direction 5. earth-quake load in positive X – direction 6. earth-quake load in negative X – direction 7. earth-quake in positive Z – direction 8. earth-quake in negative Z – direction 9. hydraulic test pressure load + water load All the nine loads indicated above are considered to be mutually exclusive. The following load combination is not considered: primary load + secondary load + occasional load

P-5: Allowable Stress 1. Introduction This write-up gives particulars of the allowable stress as per the ASME. 2. Allowable Stress as per ASME-I (Power Boilers) The basic allowable stress (Sm) is the minimum of the following seven values: a) ultimate tensile strength at room temperature / 3.5 b) 1.1 x ultimate tensile strength at metal design temperature / 3.5 c) yield stress at room temperature / 1.5 d) yield stress at metal design temperature / 1.5 e) minimum stress to produce a creep strain of 0.01% in 1,000 hours f) average stress to produce rupture in 100,000 hours / 1.5 g) minimum stress to produce rupture in 100,000 hours / 1.25 3. Allowable Stress for Welds as per The ASME-I (Power Boilers) a) groove-weld in tension = 74 % Sm b) groove-weld in shear = 60 % Sm c) fillet-weld in shear = 49 % Sm Where, Sm = basic allowable stress 4. Allowable Stress as per The ASME-B31.1 (based on fatigue and creep) - Power Piping SA = f (1.25 Sc + 0.25 Sh) Where, SA Sc Sh f

= = = = = = = = = =

allowable stress range for expansion stresses allowable stress at room temperature allowable stress at metal design temperature fatigue stress range reduction factor 1.0 for 1 to 7,000 fatigue cycles of metal 0.9 for 7,001 to 14,000 fatigue cycles of metal 0.8 for 14,001 to 22,000 fatigue cycles of metal 0.7 for 22,001 to 45,000 fatigue cycles of metal 0.6 for 45,001 to 100,000 fatigue cycles of metal 0.5 for 100,001 and over

SA + SL = f (1.25 Sc + 1.25 Sh) Where,

SL = longitudinal stress due to pipe / tube internal pressure

P6: Working Pressure The working pressure of a component is the Maximum Allowable Working Pressure (MAWP) for the metal working temperature (design temperature). The MAWP permitted for different components as per The Indian Boiler Regulations, 1950 – with amendments – are given below:

IBR Formula for Headers and Drums WP =

2 f E (T – C) (D + T – C)

Hence, T=

WP x D (2 f E – WP)

+C

Where, T = minimum required thickness, mm WP = working pressure, kg / sq mm (g) D = drum inside diameter, mm f = drum metal allowable stress, kg / sq mm p = tube hole longitudinal pitch, mm d = tube hole diameter, mm C = 0.03 inch = 0.762 mm E = (p – d) / p = ligament efficiency IBR Formula for Tubes WP = 2 f (T – C) (D – T + C) Hence, T = WP x D + C (2 f + WP) Where, T = minimum required thickness, mm WP = working pressure, kg / sq mm (g) D = tube outside diameter, mm f = tube metal allowable stress, kg / sq mm C = 0.75 mm when WP = 70 kg / sq cm (g) and lower = 0.0 mm when WP = above 70 kg / sq cm (g)

P7: Support Span The distance between two consecutive supports is to be limited to the allowable. The allowable support span for horizontal pipe lines is given in Table-P7

Table-P7: Suggested Horizontal Pipe Support Spacing Nominal Pipe Size

Suggested Maximum Span

NPS

NPS

Water Service

Steam, Gas, or Air Service

Inch

' mm

'm

'm

1

1

25

2.1

2.7

2

2

50

3.0

4.0

3

3

75

3.7

4.6

4

4

100

4.3

5.2

5

6

150

5.2

6.4

6

8

200

5.8

7.3

7

12

300

7.0

9.1

8

16

400

8.2

10.7

9

20

500

9.1

11.9

10

24

600

9.8

12.8

Serial Number

If the pipeline is inclined, the support span indicated in Table-P7 can be increased. Table-P7 is based on the following assumptions: a) Suggested maximum spacing between pipe supports for horizontal straight runs of standard and heavier pipe at maximum operating temperature of 750 o F (400 o C). b) This table does not apply where span calculations are made or where there are concentrated loads between supports, such as flanges, valves, specialties, etc. c) The spacing is based on a fixed beam support with a bending stress not exceeding 2,300 psi (15.86 MPa) and insulated pipe filled with water or equivalent weight of steel pipe for steam, gas, or air services, and the pitch of the line is such that a sag of 0.1 Inch (2.5 mm) between supports is permissible.

P8: Deformations Deformation can be linear deformation or angular deformation. Linear deformation is known as deflection. The deformation can be in the horizontal plane or in the vertical plane. There limits on the deformation suggested by different codes and standard. These are not mandatory. These are only empirical in nature. The allowable deviation to vertical plane is 3.0 mm per meter. The allowable deviation to horizontal plane is 3.0 mm per meter. The allowable angular deformation is 0.5 Degree. The induced deformation are computed using computer software. These are reviewed for deformation. These deformations are not applicable to thermal expansion induced movements.

The following loads induce deformations: primary loads, secondary loads and occasional loads. Suitable load combinations are considered. The following types of restraints are used: limit stops, hydraulic snubbers, slings and two way restraints. The rigid supports for the piping also work as deformation limits.

P9: Valves The following types of valves are used: 1. stop valve 2. check valve 3. non-return valve 4. butter-fly valve 5. globe valve 6. gate valve 7. safety valve 8. dead weight safety valve 9. relief valve 10. safety-relief valve 11. motor operated valve 12. pneumatically operated valve 13. hydraulically operated valve 14. valve with integral by-pass 15. swing type non-return valve 16. fire resistant valve

P10: Gages The following types of gages and instruments are used: 1. liquid level gage 2. pressure gage 3. temperature measurement 4. flow measurement 5. pressure differential measurement 6. quality of medium measurement

The following types of indication and recording are used: 1. local indicator 2. remote indicator 3. local recording 4. remote recording 5. Data Acquisition System (DAS)

The following types of controls are used: 1. pneumatic controls 2. hydraulic controls 3. electronic controls 4. mechanical controls 5. feed-forward control system 6. feed-back control system

P11: Types of Supports The following types of supports and are used: 1. rigid support 2. Variable Load Hanger (VLH) 3. semi constant load hanger 4. Constant Load Hanger (CLH) 5. restraints 6. limit stops 7. vibration snubber 8. anchors 9. floating anchors 10. directional restraints 11. bottom support 12. sliding bottom support 13. composite support 14. collector support 15. hanger bifurcation

P12: Flow Analysis The pressure drop and the pumping power required for a pipe carrying water at ambient temperature in a horizontal pipe is considered in this write-up. From Darcy's formula, Pressure drop = hf =

4fl W

2

2gd Exercise f = friction factor = 0.02 l = length of pipe = 1,000 m V = mass flow rate = 10 tonne / hr = 10 x 1,000 / 3,600 = 2.78 kg / sec ρ = density of fluid (water) = 1,000 kg / cu m W1 = flow rate = V / ρ = 2.78 / 1,000 = 0.00278 cu m / sec Use NPS 4 Schedule 80 Pipe – φ 114.3 x 8.6 mm d = pipe inside diameter = 114.3 – 2 x 8.6 = 97.1 mm = 0.0971 m AF = pipe flow area = π (114.3 – 2 x 8.6)

2

g = gravitational constant = 9.80665 m / sec

/ (4 x 10

6

) 7405 x 10

HP =

4flW 2gd

2

= 4 x 0.02 x 1,000 x 0.375 2 x 9.80665 x 0.0971

hf ρ W AF 75

=

sq m

2

W = velocity of flow = W1 / AF = 0.00278 / (7405 x 10 hf =

-6

2

-6

) = 0.375 m /sec

= 5.9 m

5.9 x 1,000 x 0.375 x 7405 x 10 75

-6

= 0.218 HP

Assuming a pump efficiency of 80 %, HP required = 0.218 / 0.8 = 0.273 Use 0.5 HP Pump

P13: Codes and Standards 1. Codes, standards, regulations and rules are provided by many groups to simplify and unify the work. 2. The following codes and standards are used in the piping industry: a) The Indian Boiler Regulations, 1950 b) American Society of Mechanical Engineers, Section – I, Power Boilers c) American Society of Mechanical Engineers, Section – VIII, Pressure Vessels d) American Society of Mechanical Engineers, B31.1 (Power Piping) e) ASME B16.9 - “Factory-Made Wrought Butt Welding Fittings” f) ASME B16.11 - “Forged Fittings, Socket-Welding and Threaded” g) ASME B16.25 - “Butt Welding Ends” h) ASME B16.34 - “Valves – Flanged, Threaded and Welding End” i) ASME B36.10 - “Welded and Seamless Wrought Steel Pipe” j) BS 1113, 1989

P14: Flexibility Analysis 1. Introduction This write-up gives particulars of the flexibility analysis of piping. 2. Strength The piping is subjected to internal pressure. Required thickness is provided to resist the internal pressure. 3. Stiffness Suitable supports are provided to withstand the self weight and imposed loads. 4. Flexibility The piping is subjected to thermal and occasional loads. Required flexible loops are provided to take care of the thermal loads. 5. Restraints The piping is provided with required restraints to take care of the occasional loads, such as wind load and seismic load (earth-quake load). 6. Flexibility Check as per The Indian Boiler Regulations, 1950 The following equation shall be satisfied for a two anchor problem:

DY < 208 2 (L – U) Where, D Y L U

= = = =

nominal diameter of pipe, mm total thermal movement to be absorbed, mm developed length of piping, m shortest distance between the two anchors, m

7. Exercise a) b) c) d)

D = Y = L = U =

100 mm 24 mm 6.8 m 3.3 m

100 x 24 = 196 < 208 2 (6.8 – 3.3)

Safe

P15: Supports Design 1. Introduction This write-up gives particulars of the supports for piping.

2. Types of Supports The following three types of supports are used: primary support, secondary support and tertiary support.

3. Primary Support The following are primary supports: lug, bolt, washer, nut, hanger rod, Variable Load Hanger (VLH), Constant Load Hanger (CLH), semi-constant load hanger, clamps, rockers, pins and cotter pins.

4. Secondary Support The following are secondary supports: knee brackets, moment brackets, channels, angles, beams and spacers.

5. Tertiary supports The following are tertiary supports: beams, columns, bracings, base plates, foundations, foundation material and attachments.

6. Strength Requirements The following shall be taken care-of: a) induced stress < allowable stress b) induced deformation < allowable deformations c) vibration of piping - to be taken care of

P16: Lateral Restraints 1. Introduction This write-up gives particulars of the lateral restraints and the loads resisted.

2. Loads The following loads are considered: thermal movement induced loads, wind load, seismic load (earth-quake load), vibration of equipment.

3. Load Combinations The following load combinations are considered:

a) primary load + secondary load b) primary load + occasional load

The following load combination is not considered:

a) primary load + secondary load + occasional load

4. Lateral Restraints Lateral restraints retain the piping layout against the forces of nature, such as wind load and seismic load (earth-quake load). Hydraulic snubbers or mechanical snubbers can be used for this purpose. However, limit stops are used commonly. The loads, locations and direction of loads are obtained from a stress analysis of piping. Lateral restraints are provided to serve the following purposes:

a) guide for piping b) resist horizontal loads c) resist horizontal movement d) reduce vibration

P17: Fail Safe Design “Fail Safe Design” is the objective of design. The designer has to compromise between the following three requirements: quality product, timely delivery and economic product. The designers are of the following types: process designer, product designer and project manager. Designs can be ready-made or tailor-made. Boiler parts are tailor-made. But some of the modules are standardized. Only few of the standard design are used. These designs are known as rationalized designs.

Suitable loads and load combinations are considered. Design is an iterative process. Design by analysis is the order of the day. The analysis can be process analysis or stress analysis. As designers are held responsible for negligence in duty and dereliction of duty, the designer should be careful. The guarantee and warrantee of the design is only 18 months. Hence, if there is a failure after 18 months, the required products and support are provided at the cost of the buyer.

The following checks are done by the designer:

a) procurable b) fabricate-able c) ship-able d) store-able e) erect-able f) commission-able g) operate-able h) service-able i) upgrade-able j) disposable The designer is responsible for “Cradle to Grave” of the product. Pre-planing and pre-engineering are required for timely delivery of products.

P18: Insulation and Refractory Insulation is provided primarily to reduce the heat loss from equipment. Insulation is provided for personal protection, also. Insulation is generally provided on the out side of the piping. Outer casing of light thickness (1.6 mm) is provided to protect the insulation. The insulation is made of fibrous materials, such as slag wool, mineral wool and glass wool. Outer casing is made of aluminum or galvanized iron (GI) sheets. Thickness of the insulation is calculated considering heat loss and personal protection considerations.

Refractory is made of refractory clay. Refractory is applied on the inner of the piping. Refractory is applied to reduce pipe metal temperature and improve economics. Inner casing (liner) is provided to retain the refractory in place. Where the pipe inside temperature is high (above 700 Degree C), insulation retainers are provided. Insulation retainers can be welded with the pipe inner or bolted.

The following gives the calculation for loss of heat through the piping insulation (hollow cylindrical shape):

Q =

∆t R

2 π L (ti – to)

= 1

hi r1

+

1 Log r2 +

1

k1

ho r2

r1

Where, Q ∆t R L ti to hi ho k1 r1 r2 Log

= heat transferred, kcal / hr = temperature difference, Degree C = resistance for flow of heat, hr – Degree C / k cal = length of pipe, m = pipe inside temperature, Degree C = pipe outside temperature, Degree C = convective heat transfer co-efficient inside pipe, k cal / hr – Degree C – sq m = convective heat transfer co-efficient outside pipe, k cal / hr – Degree C – sq m = thermal conductivity, k cal / hr – Degree C - m = pipe inside radius, m = pipe outside radius, m = logarithm to the base “e”

P19: Standard Components Piping industry uses many standard components. They are: elbow, TEE, reducer, Y-Piece, flange, etc. Standard pipes are also used. Pipes are classified into Schedule pipes. The dimensions of Schedule pipes is given in the attachment. The fittings of the piping are rated based on Classes. A typical pressure temperature rating is given in the attachment. The standard components are to be arranged and supported. Piping and Instrument Diagram (P & ID) is prepared considering the operation of the plant. After a trial layout, a trial stress analysis is done using a computer. Based on the results of the trial stress analysis, the design is updated and finalized.

Standard components are available across the shelf. This improves the project execution time. As the materials, shape, size and details are similar, the design activity is done fast. This helps in completing the contract execution, early.

P20: Creep and Fatigue Pipe experiences vibration when a fluid flow inside the piping. Vibration of piping under flow of fluid outside the piping is more critical. When the fluid flow is outside the piping and across, the vibration is considerable. Vibration of banks of tubes under cross flow vibration has been extensively researched. The piping at high temperature undergoes creep. The American Society of Mechanical Engineers (Power Boilers) consider 100,000 hours of creep life. This is equivalent to eleven years of continuous operation. The behavior of the piping subjected to fatigue and creep, simultaneously is not known.

The life of piping is expected to be twenty five years. Hence, the number of fatigue cycles expected: 25 years x 300 cycles / year = 7,500 fatigue cycles An approximate treatment of the interaction (based on numerical experiments) of fatigue and creep is given in the following: 1. Design temperature

= 400 Degree C

2. Design pressure

= 100 bar (g)

3. Number of cold starts

= 100

per cent life lost (fatigue) = 12 %

4. Number of warm starts

= 1,000

per cent life lost (fatigue) = 6 %

5. Number of hot starts

= 10,000

per cent life lost (fatigue) = 10 %

6. Number of load variations

= 100,000

per cent life lost (fatigue) = 25 %

7. Duration at 430 Degree C

= 100 hour

per cent life lost (creep) = 2 %

8. Duration at 420 Degree C

= 1,000 hour

per cent life lost (creep) = 8 %

9. Duration at 410 Degree C

= 10,000 hour

per cent life lost (creep) = 13 %

10. Duration at 400 Degree C

= 100,000 hour

per cent life lost (creep) = 10 %

Total life lost (fatigue + creep) = 86 % Expected life of piping = 25 years / 0.86 = 29 years

P21: Design and Stress Analysis of Piping and Supports Step-01: Prepare Process Flow Diagram (PFD) Step-02: Prepare Piping and Instrument Diagram (P & ID) Step-03: Prepare piping layout drawing Step-04: Prepare piping isometric drawing Step-05: Select valves, gages, instruments and appurtenants Step-06: Locate valves, gages, instruments and appurtenants Step-07: Obtain allowable forces and moments for equipment Step-08: Obtain thermal expansion movements for equipment (floating anchors) Step-09: Select pipe diameter based on flow considerations Step-10: Select pipe thickness based on hoop stress Step-11: Select pipe insulation based on heat loss and personal protection Step-12: Select pipe outer casing Step-13: Locate pipe supports Step-14: Calculate wind load Step-15: Calculate seismic load (earth-quake load) Step-16: Calculate hydraulic test pressure Step-17: Obtain hydraulic test water weight Step-18: Finalize load combinations Step-19: Make trail run of the piping stress analysis Step-20: Obtain allowable stresses Step-21: Carry-out stress analysis iteratively Step-22: Check acceptability of forces and moment on anchors and floating anchors Step-23: Select hangers, restraints, limit stops and Constant Load Hangers (CLH), Variable Load Hangers (VLH) Step-24: Set hangers, restraints, limit stops, Constant Load Hangers (CLH) and variable load hangers (VLH) Step-25: Prepare Close-Out Report

P22: Pressure and Temperature Drop in Pipe Line 1. Introduction This write-up gives design calculation for pressure drop and temperature drop in steam pipe line. 2. Example Given: Pipe size Steam temperature Steam pressure Enthalpy Specific weight density

= = = = = =

φ Do x T = φ 323.9 x 25.4 mm T1 = 460 Degree C P1 = 65 kg / sq cm (a) i = 792.4 k cal / kg v = 0.04895 cu m / kg ρ = 1 / 0.04895 = 20.4 kg / cu m

Calculation 2

hf = (4 f L W )

=

2

(4 x 0.02 x 100 x 30 ) = 1343 m steam column

2gd

2 x 9.81 x 0.2731

P2 = P1 – 1343 x 20.4 = 65 – 2.74 = 62.26 kg / sq cm (a) 10,000 P1 V1 V2 V1

=

1.4

= P2 V2

(P1 ) ( P2 )

(1 / 1.4)

1.4

= ( 65 )

(1 / 1.4)

(1 / 1.4)

(62.26 )

(1

= 1.031

/ 1.4)

V2 = 1.031 x 0.04895 = 0.0505 cu m / kg P1 V1 = m1 R1 T1 P2 V2 m1 R1 T2 T2 = (460 + 273) x 62.26 x 0.0505 65 x 0.04895 Temperature drop = 460 – 451 = 9 Degree C

=

724 K = 724 – 273 = 451 Degree C

P23: References 1. The Indian Boiler Regulations, 1950 (with amendments) 2. American Society of Mechanical Engineers – Section - I (Power Boilers) 3. American Society of Mechanical Engineers – Section – VIII, Division 1 (Pressure Vessels) 4. American Society of Mechanical Engineers – Section – VIII, Division 2 (Pressure Vessels – Alternate Rules) 5. ASME B16.9 - “Factory-Made Wrought Butt Welding Fittings” 6. ASME B16.11 - “Forged Fittings, Socket-Welding and Threaded” 7. ASME B16.25 - “Butt Welding Ends” 8. ASME B16.34 - “Valves – Flanged, Threaded, and Welding End” 9. BS 1113 : 1989 - “Design and Manufacture of Water-Tube Steam Generating Plant (Including Super-Heaters, Re-Heaters and Steel Tube Economizers)” 10. ISO Recommendation – R 831 – “Rules for Construction of Stationary Boilers”

Part – C : Cold Structure Contents C-1

Introduction

C-2

Loads

C-3

Materials

C-4

Shapes and Sizes

C-5

Design

C-6

Structural Engineering

C-7

Stress Analysis

C-8

Detailing

C-9

Drafting

C-10 Documentation

Appendix C-11

Beam Formulas

C-12

Frame Formulas

C-13

Material Properties

C-14

Standard Shapes and Properties

C-15

Combined Properties

C-16

Matrix Method of Structural Analysis

C-17

Stress Limits

C-18

Deformation Limits

C-19

Foundations

C-20

Soil Studies

C-21 Author Index C-22

Subject Index

C-1. Introduction The structures are designed to withstand the forces of nature and to retain the shape of components. Steel structures are of the following two types: braced structure and framed structure. Steel structures can be statically determinate or hyper-static. The steel structure forms a skeleton to withstand forces. The steel structure can undergo gross buckling or local buckling. Reinforced Cement Concrete (RCC) structures are labor intensive. The construction time for RCC structures is longer than a comparable steel structure. In India, steel structures are used widely for factory buildings. The connections of the steel structures can be riveted or bolted or welded. Welded connections are done in the factory or under covered sheds. Bolted connections are done in the field (open to atmosphere). The bolted connections can be bearing type or friction type. Bearing type of bolted connections are widely used in structural steel industries in India. Friction type of connections require high quality parts and discipline among the working groups. The structure has a life of fifty years and shall be painted once in three years. The steel structure has the following three main parts: beam, column and bracing. The following parts are also used: base plate, foundation bolt, joints, foundation materials, purlin, rafter, eve's girder, roof girder, etc.

C-2. Loads The loads on the structure are classified as: primary load, secondary load and occasional load. The primary loads are: self weight, equipment loads, weight of contents, weight of insulation, weight of refractory and imposed loads (live loads). The secondary loads are: thermal loads, loads due to relative settlement of columns and equipment thermal movement loads. The occasional loads are: wind load, seismic load (earth-quake load), fire load, flood load, tsunami load, snow load and ice load.

C-3 Materials The popularly used material for steel structure is Mild Steel (IS2062). The fasteners are made of IS1367. Low alloy steel are not popularly used. The following material properties are checked: chemical composition, yield strength, ultimate tensile strength, ductility, malleability and impact strength.

C-4 Shapes and sizes Many shapes and sizes are used. The steel structure can have the following basic shapes: square, rectangle, ELL, channel and “I” section. Combinations of these sections are used. The cross section of

any structural member has the following properties: area of cross section, circumference, moment of inertia about X – axis, moment of inertia about Z – axis, product of inertia, section modulus about X axis, section modulus about Z – axis, warping constant, center of gravity, distance to extreme fibers and paint area.

C-5 Design Design is a creative activity. The designs are arrived-at based on the previously used types. Design of components aims at technically correct economic design. Design is based on many assumptions. The following are assumed in design of structures: linear material property, elastic material, homogeneous material, isotropic material, steady-state load and static component. The design involves checking for the following: head room provision, walk-way requirements (a person with shoe, helmet and tool box in one hand should be able to walk erect), interference (hard clashes and soft clashes), interfacing of equipment and components, approach to equipment and access to components. Design is an iterative activity. Designer is the mother of the product. Designer should be aware of the following: procureability, manufacture-ability, transportability, store-ability, erect-ability, commission-ability, operateability, service-ability and dispose-ability. Designer should be aware of “Cradle to Grave” of the equipment.

C-6 Structural Engineering Structural engineering is an art of science of molding materials in to shapes and sizes that withstand the forces of nature within the prescribed time and economics. Structural engineer should be aware of the following subjects: Mechanics, Applied Mechanics, Strength of Materials, Stress Analysis. The structural engineer uses the following subjects in every day use: arithmetic, algebra, trigonometry, analytical geometry and computer graphics. The structural engineering uses the following steps: design, engineering, stress analysis, detailing, drafting, documentation and document approval. Design is creative. Engineering is analytical. Stress analysis requires computation. Stress analysis requires deformation analysis, also. Deformation can be linear deformation or angular deformation. Linear deformation is known as deflection. Detailing requires design of joints. Drafting is done using computers. Drafting practices are many. In the Mechanical Engineering industry, AUTOCAD computer program is used widely. Documentation requires preparation of Bills of Materials (BOM), material forecasts, fabrication specifications and erection requirements. Document approval involves approval from the clients and the government.

The structures should be stable and strong. The stability of the structure is checked using the following equation (necessary condition):

FxN–R–C < M Where,

F

= 1.0 for one dimensional structures

F

= 2.0 for two dimensional structure

F

= 3.0 for three dimensional structure

N

= number of nodes

R

= number of restraints at supports

C

= number of connection connectivity (constraints)

M

= number of members (elements)

The necessary and sufficient condition for structural steel stability is given below.

“The determinant of stiffness matrix shall be non-zero”

C-7. Stress Analysis Stress analysis of structures is a complicated subject. The following stress analysis methods are used: a) manual calculation using standard formulas b) computer methods with equivalent static loads c) modal analysis depending on mode shapes d) time-history analysis

The basic requirement in stress analysis is given below: induced stress < allowable stress Both the values “induced stress” and “allowable stress” are calculated and compared. Stress analysis helps the designer to do a “Fail Safe” design. Design by rules was used in many situations. Design by analysis is based on stress analysis. The following types of stresses are considered: tensile stress, compressive stress, bending stress, bearing stress, shear stress, buckling stress and local stress. Stress analysis uses infinitesimal elements. The Finite Element Method (FEM) uses elements of finite size. The following computer programs are used for stress analysis: a) CAESAR – II b) CAEPIPE c) STAAD.Pro d) ANSYS e) COSMOS f) NASTRAN g) ABACUS h) SAP2000 i) CATIA

C-8. Detailing The following are part of detailing of structure: a) connection design b) stiffener layout c) stiffener design d) weld design e) welding design f) field weld location g) field weld details h) paint area calculation Standard practices are followed. Standard weld design, pre-heating requirements, post-weld heating requirements and stress relieving requirements are provided.

C-9. Drafting Drafting is done by draftsmen using computer software. Commonly used software is AUTOCAD. Drafting involves the following works: a) arrangement drawings b) part drawings c) tolerances d) plan e) elevation f) end view g) cut-sections h) type of projection i) drawing title j) dimensions

C-10. Documentation Documentation consists of Bills of Materials (BOM), material forecasts, welding schedules, heat treatment schedules, transport requirements and shipping documents.

C-16: Matrix Method of Structural Analysis Matrices are used in solving structural mechanics problems. The structural mechanics problems can be expressed in the form of linear simultaneous equations.

2 1 Figure 1: Spar Subjected to Axial Tension 1 P1 E = σ ε ∴

=

P L Α ∆

P1 = A E L

∆1

P2 = A E ∆2 L P1 = - A E ∆2 L P2 = - A E ∆1 L

P1 = P2

AE L

1

-1

∆1

-1

1

∆2

This can be written as: Force Vector = Stiffness Matrix x Displacement Vector Solution for this problem can be obtained from this equation.

C16 – Matrix Method of Structural Analysis (Continued) Matrices are used in solving structural mechanics problems. The structural mechanics problems can be expressed as linear simultaneous equation. By solving these equations using computer, these problems can be solved. Consider a rectangular prism. The governing equations are given in the following:

Fx

=

0

∆x

6EI

∆y

0

AE L

Fy

=

0

12 E I L

Mz

=

0

6EI L

F

=

K

E L I A Fx Fy Mz ∆x ∆y θz

= = = = = = = = = =

2

L

2

4EI L

∆

Force Vector = Stiffness Matrix

Where,

3

x Displacement Vector

elastic modulus = Young's modulus, kg / sq mm length, mm moment of inertia, mm ^ 4 area, sq mm force in X – direction, kg force in Y – direction, kg moment about Z – axis, kg – mm deflection in X – direction, mm deflection in Y – direction, mm rotation about Z – axis, radian

θz

C16 – Matrix Method of Structural Analysis (Continued) Matrices are used in solving structural mechanics problems. The structural mechanics problems can be expressed as linear simultaneous equation. By solving these equations using computer, these problems can be solved. Consider a rectangular prism. The governing equations are given in the following in the form of matrices:

Fx1

AE L

Fy1

0

0

0

0

12 E I z 3 L

0

0

0

0

6EIy 2 L

0

∆ z1

0

0

θ x1

0

θ y1

Fz1

0

0

12 E I y 3 L

Mx1

0

0

0

My1

0

0

Mz1

0

6EIy 2 L

6EIz 2 L

F

=

0

K

GJ L 0

4EIy L

0

∆

Force Vector = Stiffness Matrix

x Displacement Vector

0

0

∆ x1

0

6EIz 2 L

4EIz L

∆ y1

θ z1

C16 – Matrix Method of Structural Analysis (Continued) Where,

E

= elastic modulus = modulus of elasticity = Young's modulus, kg / sq mm

G

= shear modulus =

E

, kg / sq mm

2 (1 + ν) L

= member length, mm

ν

= Poisson's ratio

Iy

= moment of inertia about Y – Y axis, mm ^ 4

Iz

= moment of inertia about Z – Z axis, mm ^ 4

J

= polar moment of inertia, mm ^ 4

A

= area, sq mm

Fx

= force in X – direction, kg

Fy

= force in Y – direction, kg

Fz

= force in Z – direction, kg

Mx

= moment about X – X axis, kg – mm

My

= moment about Y – Y axis, kg - mm

Mz

= moment about Z – Z axis, kg – mm

∆x

= deflection in X – direction, mm

∆y

= deflection in Y – direction, mm

∆z

= deflection in Z – direction, mm

θ x

= rotation about X – axis, radian

θ y

= rotation about Y – axis, radian

θ z

= rotation about Z – axis, radian

C-17: Stress Limits The stress limits for structural steel as per the Indian Standard: IS 800 – 2007 (General Construction in Steel – Code of Practice) are given in the following:

tensile stress

<

60 % of yield stress

compressive stress

<

allowable buckling stress

bending tensile stress

<

60 % of yield stress

bending compressive stress

<

allowable torsional-lateral buckling stress

average shear stress

<

40 % of yield stress

bearing stress

<

75 % of yield stress

increase in allowable stress (wind)

<

33 % of respective allowable (members)

increase in allowable stress (seismic)

<

33 % of respective allowable (members)

increase in allowable stress (wind)

<

25 % of respective allowable (fastener)

increase in allowable stress (seismic)

<

25 % of respective allowable (fastener)

allowable combined stress – see IS 800 - 2007

C-18: Deformation Limits Deformation can be linear deformation or angular deformation. Linear deformation is deflection. Allowable deflection is “span / 325”. The columns sway in horizontal direction. The allowable sway is “height / 325”. The deflection can be in horizontal plane or vertical plane. The allowable angular deformation is 0.5 Degree. The limits on deformations are empirical. All the limits indicated for deformation are suggestive. Suitable precautions should be taken to limit the deformation of critical and lethal equipment against performance related issues. The deformation of single member can be calculated using standard formulas. The deformation of assemblage of members into truss and frame shall be computed using computer software, and limited to the respective allowable.

C-19: Foundations Foundations are made of cement concrete. Foundation can be any of the following two categories: Reinforced Cement Concrete (RCC) or cement mortar. Foundations can be used to carry simple axial compressive stress. Most of the foundations in industries are single footing type. Raft foundations are used where required. Following are the components in a foundation: foundation bolts, nuts, lock nuts, washers, base plates, shear keys, foundation anchors and foundation concrete. In a general case, a foundation footing has to carry the following loads: Fx, Fy, Fz, Mx, My and Mz. The stress distribution in the foundation concrete is complicated. The foundation design requires soil studies. Foundations are designed to carry the design load, without sinking. The following types of foundations are used: single footing, raft foundation and pile foundation.

Foundations subjected to uplift due to wind load or earth-quake load are to be anchored properly. The concrete mix used for foundation is usually Mix M20. The following types of foundation materials are available in the market:

Cold Twisted Deformed rods (CTD) Thermo-Mechanically Treated rods (TMT) Both of these type of rods have serrations on their surface. This enable the reinforcing rods to carry 30 % more shear load from the concrete. This aspect gives an economical foundation design.

Part – D : Hot Structure D – 1 Introduction: Hot structures in a boiler consists of pressure part hangers, buckstays and casings. In small boilers the pressure parts are supported from the bottom. In large boilers, pressure parts are hung from the top to avoid buckling of walls. Pressure part hangers are solid round rods. Part of the pressure parts is suspended from variable load hangers (VLH). Buckstays are stiffeners to withstand the loads from furnace walls and retain the shape of the furnace walls. Casings are used to cover boiler parts to protect from loss of heat. The following are identified as hot structures:

a) buckstays b) hangers c) pent house casing d) furnace bottom casing e) economizer casing f) rear arch casing

The design pressure for buckstays is about + / - 400 mm wc (g) (+ / - 400 kg / sq m (g)). Hangers are designed to carry axial tension, at the same time accommodate lateral thermal expansion movements. Pent house casing is formed to reduce heat loss through leakage of flue gas into the atmosphere. Furnace bottom casing is provided to have a seal-tight connection between the pressure parts and nonpressure parts. Economizer casing is provided as an ash collecting device and to support the economizer inlet header. Rear arch casing is provided to support the rear arch against forces from the furnace.

The hot structures are designed such a way that the load transfer takes place at the same time thermal expansion is accommodated. The rise in temperature reduce the allowable stress of the products. This aspect should also be considered. When one side of a product is hotter than the other side, thermal stresses are introduced. This is to be taken care off.

The cost of the hot structure is only a small per cent of the cost of the boiler. However, at most importance is given to this subject, since failure of hot structure leads to power plant shut down.

D – 2 Buckstays: Boiler framing is known as buckstays. Buckstays stay the buckling of the walls. The buckstay beams are cold, while the connected walls are hot. Hence, buckstays are known as hot structure. Buckstays and furnace guides guide the boiler zero point of expansion. Zero point of boiler is a virtual point. Buckstays can be wrap around type or grid type. Wrap around buckstays are popularly used. Grid type buckstays are used for large boilers. The buckstays for once-through boilers are of special construction. The buckstays are designed for up-set conditions. The design pressure for buckstays is given in the National Fire Protection Association (NFPA, U. S. A.). The design pressure for large boilers is + / - 21 inch wc (g) (+ / - 533.4 mm wc (g)) = + / - 533.4 kg / sq m (g).

Buckstays contain the following components: (a) buckstay beam, (b) buckstay vertical beam, ( c) stirrup, (d) channel, (e) corner connections, (f) levelers, (g) furnace bottom support, (h) rear arch support, (i) rear pass hopper support, (j) vertical buckstays, (k) furnace guide and (l) fasteners. Buckstay design is done using the following two steps: (i) spacing, (ii) sizing. Number of buckstays in a wall is decided based on the wall height and the allowable buckstay spacing. The design calculations for furnace bottom, rear arch, rear pass hopper are complicated. The levelers level the buckstay beams. It also provides lateral support for the buckstay beams.

The furnace guides are provided in all the four walls and at two levels. The particulars of furnace guides is shown in Figure – D.1 : Furnace Guides.

Part – E : Stress Analysis Contents S-1 Stress analysis of boiler parts S-2 Thin-walled vessels subjected to internal pressure S-3 Stresses in a beam S-4 Stresses in thick pipe S-5 Stresses in members S-6 Structural steel stability S-7 Stresses in Pipe S-8 Stresses in a hollow cone S-9 Stresses in a hollow sphere S-10 Discontinuities and stress concentrations S-11 Probability of correct design S-12 Engineering Design S-13 Vibration S-14 Governing Equations for Stress Analysis

S-1: Stress Analysis of Boiler Parts 1. Introduction This write-up gives particulars on the stress analysis of boiler parts. 2. Boiler Parts The following boiler parts are considered: boiler drums, headers, tubes, tube bends, pipes, pipe bends, beams, columns, bracings, tanks, vessels, de-aerators, base plates and foundations. 3. Stress Analysis The objective of stress analysis is “Fail-Safe Design”. Hence, the stress analyst should go beyond the codes and standards. An appreciation of the codes and standards is a pre-requisite. 4. Stress Limits The stresses computed are limited to the respective allowable. The following types of stresses are considered: tensile stress, compressive stress, bending stress, bearing stress, shear stress, buckling stress and local stress. The loads are classified as primary loads, secondary loads and occasional loads. The stresses due to different kinds of loads are limited to different levels of stresses. 5. Deformation The deformation due to various loads and load combinations are computed. The deformation can be linear deformation or angular deformation. The linear deformation is also known as deflection. The deformation can be in the horizontal plane or in the vertical plane. Theses are limited to empirical (allowable) values. 6. Vibration Vibration is not considered for the Mechanical Static Equipment. At present, vibration requirements are taken care-of by equivalent static loads. 7. Fatigue and Creep The boiler parts are subjected to thermal transients, dynamic loads and shocks. The number thermal transient fatigue cycles considered is 10,000. The number of hours of creep of the boiler parts considered is 100,000 (equivalent to 11 years). 8. Materials Boiler parts are made of iron and steel. Non-metallic materials such as asbestos is also used. 9. Equilibrium Considerations The following six equilibrium considerations shall be taken care-of: Σ Fx = 0.0 Σ Fy = 0.0 Σ Fz = 0.0

Σ Mx = 0.0 Σ My = 0.0 Σ Mz = 0.0

S2: Thin-Walled Vessels Subjected to Internal Pressure 1. Introduction This write-up gives the requirements of stress analysis of thin walled vessels 2. Shape The shape of the pressure vessel can be any one of the following: a) b) c) d) e) f) g)

spherical hemi-spherical tori-spherical tori-conical conical ellipsoidal cylindrical

3. Size The size and thicknesses of the vessels are finalized based on the volume required, materials, loads and design temperatures. 4. Material The pressure vessels are usually made of iron or steel. Alloy steel is also used. 5. Loads and Load Combinations The primary load considered is the internal pressure. The gage pressure is considered in design calculations. Applicable load combinations are considered. 6. Deformations The deformations can be linear deformation or angular deformation. The deformation can be in the horizontal plane or in the vertical plane. There are no universally accepted limits on deformations. 7. Vibration Requisite vibration considerations are taken care of in lethal and critical pressure vessels. 8. Codes and Standards The following codes and standards are used: a) American Society of Mechanical Engineers: Section – VIII, Division1 b) American Society of Mechanical Engineers: Section – VIII, Division2 c) IS-2825 9. Design Assumptions The following design assumptions are made: linear material, elastic material behavior, homogeneous material, isotropic material behavior, steady state loading and static component.

S3: Stress Analysis of Beams as per IS: 800-1984 1. Introduction This write-up gives particulars of the design of beams as per IS800-1984. 2. Indian Material The material as per IS: 2062 (Mild Steel) is popularly used. 3. Design Checks The following design checks are made: a) induced stress shall be less than the allowable. b) induced deformation shall be less than the allowable. c) take care of vibration of beam 4. Shapes The shape of the beam is as shown in IS808. 5. Size The size of the beam is selected considering the strength requirements.

S4: Stresses in Thick Pipe 1. Introduction This write-up gives particulars of the stresses induced in thick pipes due to internal pressure and external pressure. 2. Stresses From “Design Data” by PSG College of Technology, 2001 Radial Stress = σ r = Pi Di

2

Do

2

Hoop Stress = σ θ = Pi Di

2

Do

2

-

Po Do

- Di

-

2

+

Di

2

2

D

Po Do

- Di

2

Longitudinal Stress = σ L = Pi Di

2

Do

2

Where, Pi = internal pressure, kg / sq cm (a) Po = external pressure, kg / sq cm (a) Di = pipe inside diameter, mm Do = pipe external diameter, mm D = pipe diameter, mm

Do

2

+

Di

2

-

Po Do - Di

2

2

2

2

(Po – Pi) (

Do

2

Do D

2

2–

2

Di )

(Pi – Po) (Do

2–

2

Di )

S5: Stresses in Members 1. Introduction This write-up gives particulars of the equations required for stress analysis. 2. Hangers The basic formula used for hangers is given below: σ1 = P A

ε1 = ∆ L

Ε = σ1 ε1

Where, σ1 P A ε1 ∆1 L E

= induced stress, kg / sq mm = imposed load, Kg = cross sectional area, sq mm = induced strain, mm / mm = induced deflection, mm = length of the member, mm = elastic modulus (Young's modulus), kg / sq mm

3. Beam The basic formula for beam is given below: M = f = E I y R Where, M I f y E R

= = = = = =

bending moment, kg – mm moment of inertia, mm ^ 4 bending stress, kg / sq mm distance from the neutral axis, mm elastic modulus (Young's modulus), kg / sq mm radius through which the beam bends, mm

4. Torsion The basic formula used in torsion is given below: T = τ = Gθ J y L Where, T = torsion moment, kg – mm J = moment of inertia (torsion), mm ^ 4 τ = shear stress, kg / sq mm y = distance from the neutral axis, mm G = shear modulus = E / (2 (1 + ν)), kg / sq mm ν = Poisson's ratio L = length of member, mm θ = angular deformation, radian

S-6: Structural Steel Stability 1. Structural steel is used to resist various forces and moments. The forces and moments can be due to primary loads or secondary loads or occasional loads. Suitable combinations of these loads are considered by the designer. To ensure structural steel stability, the following formula shall be satisfied: fn–r–c=m Where, f = 1 for one dimensional structures = 2 for two dimensional structures = 3 for three dimensional structure n = number of nodes r = number of restraints at supports c = number of constraints (connection continuity) m = number of members (elements) 2. One Dimensional Structure f=1 n=2 r=1 c=0 m=1 Therefore, 1x2–1–0=1=m

Hence, safe

3. Two Dimensional Structure f=2 n=6 r=4 c=1 m=7 Therefore, 2x6–4–1=7=m

Hence, safe

To ensure structural steel stability, the following shall also be satisfied: “The determinant of the stiffness matrix shall be non-zero”

S-7: Stresses in Pipe 1. Introduction This write-up gives particulars of the stresses induced in pipes due to forces and moments. 2. Internal Pressure The stresses due to internal pressure are given below: a) σ hoop = WP x (D – T + C) / (2 (T – C)) b) σ longitudinal = WP x (D – T + C) / (4 (T – C)) c) σ radial = - WP 3. Forces and Moments The stresses induced due to the forces and moments are given in the following:

S-8: Stresses in a Hollow Cone 1. Introduction This write-up gives particulars of the stresses induced in a hollow cone subjected to internal pressure. 2. Hollow Cone Hollow cone has two primary radii. One radius can be measure based on the Figure-8. Another radius is infinity.

S-9: Stresses in a Hollow Sphere 1. Introduction This write-up gives particulars of the stresses induced in a hollow sphere subjected to internal pressure. 2. Hollow Sphere Hollow sphere has two primary radii. Each radius is equal to “R”. We know that, σ1 + σ2 = σ1 R1 R2 R

σ1 R

= p h

Hence, 2 σ1 = p R h

σ1 =

p R 2h

3. Exercise internal pressure radius thickness σ1 =

= p = 100.0 kg / sq cm (g) = R = 1000 mm = h = 75.0 mm 100.0 x 1000 2 x 75

= 667 kg / sq cm < σ a = 1,000 kg / sq cm Safe

S-10: Discontinuities and Stress Concentrations 1. Introduction This write-up deals with discontinuities and stress concentrations in the pressure vessels. 2. Discontinuities The following are considered as discontinuities in pressure vessels: a) b) c) d) e) f)

hollow cylinder to hollow hemi-sphere hollow cylinder to hollow semi-ellipsoidal shape hollow cylinder to hollow tori-spherical shape hollow cylinder to hollow cylinder hollow sphere to hollow cylinder hollow sphere to hollow cone

3. Stress Concentrations The following are considered as stress concentrations (stress raisers) in pressure vessels: a) b) c) d) e) f)

holes intersections fillet radius under cuts attachments corner radius

4. Stress Limits a) b) c) d) e) f)

the membrane stresses due to primary loads are limited to Sm the bending + membrane stress due to primary loads is limited to 1.5 Sm the local membrane stress due to primary loads is limited to 1.5 Sm the local membrane stress due to secondary loads is limited to 1.5 Sm the membrane + bending stress due to discontinuity is limited to 3.0 Sm the total stress is limited to the allowable fatigue stress (2 Sa)

S11: Probability of Correct Design Design is a creative activity. Engineering is logical. Stress analysis is calculations. Detailing involves connections design. Drafting is drawing lines as per specifications to satisfy design requirements. Documentation is writing Bills of Materials (BOM) and related documents. Documents are to be approved by the clients and government officials.

The following are assumed in engineering: (i) linear material behavior, (ii) elastic material, (iii) homogeneous material, (iv) isotropic material, (v) steady-state loading and (vi) static component. Detailing takes care of the following aspects: (a) head room, (b) walk way, ( c) access to places, (d) approach to access equipment, (e) interfaces between components and (f) interferences (hard clashes and soft clashes). Stress analysis takes care of loading. Some of the loading are: (1) internal pressure, (2) external pressure, (3) self weight, (4) weight of equipment, (5) weight of contents, (6) weight of insulation, (7) weight of outer casing, (8) weight of refractory, (9) weight of inner casing, (10) weight of valves, gages and instruments, (11) thermal load, (12) relative settlement of foundations, (13) movement of floating anchors, (14) wind load, (15) seismic load (earth-quake load), (16) flood load, (17) fire, (18) rain, (19) tsunami load and (20) snow.

Total number of parameters to be considered (from the above paragraph) = 32. Assuming that we take care of each of the assumptions and loads indicated in the above paragraph equal to 99 % each, the probability of correct design for the project = 0.99

32

= 0.725 = 72.5 %

S-12: Engineering Design A designer is a person held responsible for all the mistakes of an organization. Design is a multifunctional work. A designer is expected to know the product, its application and use. Industrial design can be sub-divided into thermal design, mechanical design and electrical design. Thermal design involves combustion, heat transfer, thermodynamics, fluid flow, flow distribution, pumping power, piping, valves, gages, plant efficiency, auxiliary power consumption and layout. Mechanical design involves temperature calculation, material selection, thickness selection, construction feasibility, power loss, arrangement of parts, stress analysis, detailing, connection design, drafting, documentation (preparation of bills of materials) and document approval. Electrical design involves assistance in Process Flow Diagram (PFD), Piping and Instrument Diagram (P & ID), logic diagram, electrical, motor, control, instruments, Data Acquisition System (DAS) and control room.

Engineering design involves the following steps: design, engineering, stress analysis, process analysis, detailing, drafting, documentation, document approval. The following assumptions are made in stress analysis: linear material behavior, elastic material, homogeneous material, isotropic material behavior, steady-state loading, static component. The following are to be checked during engineering design: head room, walk way (a worker with a helmet, shoe and a tools box in one hand should be able to walk, erect), access to equipment, approach to places, interference (hard clash and soft clash) and interfaces. The following loads shall be considered: primary load, secondary load and occasional load. The following three checks are done:

a) induced stress < allowable stress b) induced deformation < allowable deformation c) take care of vibration requirements The following constitute primary loads: self weight, weight of contents, insulation, refractory, platforms, imposed loads (live loads) and moving loads. The following constitute secondary loads: thermal loads, relative settlement of foundations, sudden heating, sudden cooling and pipeline expansion loads. The following constitute occasional loads: wind load, seismic load (earth-quake load), rain, flood, tsunami, wave, fire and snow. Applicable load combinations are considered. The following load combinations are considered: Primary load + Secondary load, Primary load + Occasional Load. The following load combination is not considered: Primary load + Secondary load + Occasional load.

S-13: Vibration S-13.1 Vibration is movement of objects with respect to time. Vibration of components requires analysis to check for their longevity. Vibration of boiler components is a specialized subject and is of utmost importance. Vibration can be attenuated by suitable damping. The damping co-efficient for steel structure is about 2 % of the critical damping. The solutions for vibration is attempted from time immemorial. The governing equation for vibration in single degree of freedom is given below: ' m d 2 x + c d x + k x = A Sin (w t + φ)

dt2

dt

A general solution for this equation is impossible. Vibration problems are solved on case-to-case basis. First the natural frequencies of vibration are calculated. Then, possible resonance is checked. If resonance doesn't occur, check for fatigue and find-out the number of years the components will function safely. Failure of a component can lead to un-planned shut-down. This is a nuisance and will lead to disruption of normal work. Several methods are available to check for vibration. Some of them are given in the following: a) check for resonance b) mode shape analysis c) fatigue analysis d) time-history analysis In the boiler the following components can be checked for vibration: a) cold structures b) hot structure c) pressure parts d) flue duct e) air duct f) furnace walls g) down-comers h) piping i) water & steam piping

S-13.2 Natural Vibration

When components are disturbed from their equilibrium position, they vibrate at their natural frequency. The natural frequency of a single mass system is given in the following: f = 1

k

2π

m

Where, f = frequency of vibration, cycles per second k = stiffness of the system, N / mm m = mass of the system, kg (m)

Example k = 20 N / mm m = 200 kg (m) f = 1 2π

20

= 0.05 cycles / sec

200

S-13.3 Forced Vibration

Forced vibration induces fatigue cycles to the components in a system. This will lead to pre-mature failure. In the forced vibration of a system, it is difficult to find-out the forcing function. The forcing function can be from fluid flow or rotating equipment or wind. The amplitude of vibration is computed using several parameters. Equipment such as pump, compressor and motor induce vibration to connected structure. The foundations of the rotating equipment are to be separated from the structural steel columns. Vibration can be reduced by increasing the damping. The damping co-efficient of structural steel is 2 % of the critical damping co-efficient. To avoid failure of structure, resonance should be avoided. Resonance occurs when the natural frequency of the structural steel is same as the imposed (forced) frequency of vibration.

S – 14 : Governing Equations for Stress Analysis δσ xx + δτ xy + δτ xz + Fx = 0 δx δy δz δτ xy + δσ yy + δτ yz + Fy = 0 δx δy δz δτ xz + δτ yz + δσ zz + Fz = 0 δx δy δz 2 2 δ γ xy = δ ε xx + δ 2 ε yy δxδy δy2 δx2 2 2 δ γ yz = δ ε yy + δ 2 ε zz δyδz δz2 δy2 δ 2 γ xy = δ 2 ε zz + δ 2 ε xx δzδx δx2 δz2 2 δ 2 ε xx = δ ( - δ γ yz + δ γ z x + δ γ x y ) δy δz δ x ( δ x δy δz) 2 2 δ ε yy = δ ( δ γ yz - δ γ z x + δ γ x y ) δz δx δ y ( δ x δy δz) 2 2 δ ε zz = δ ( δ γ yz + δ γ z x - δ γ x y ) δx δy δ z ( δ x δy δz) ε xx = 1 ( σ xx - ν(σ yy + σ zz) ) E ε yy = 1 ( σ yy - ν (σ xx + σ zz) ) E ε zz = 1 ( σ zz - ν (σ yy + σ xx) ) E γ xy = 2 (1 + ν) τ xy E γ yz = 2 (1 + ν) τ yz E γ zx = 2 (1 + ν) τ zx E δ u = 1 ( σ xx – ν ( σ yy + σ zz)) δx E δ v = 1 ( σ yy – ν ( σ xx + σ zz)) δy E δ w = 1 ( σ zz – ν ( σ xx + σ yy)) δz E δ u + δ v = 1 τ xy δ y. δ x µ δ v + δ w = 1 τ yz δ z. δy µ δ w + δ u = 1 τ zx δ x. δz µ

(1)

(2)

(3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

(13) (14) (15) (16) (17) (18) (19) (20) (21)

S – 14 : Governing Equations for Stress Analysis (Continued) σ xx

= normal stress in X – direction, kg / sq mm

σ yy

= normal stress in Y – direction, kg / sq mm

σ zz

= normal stress in Z – direction, kg / sq mm

Fx

= force in X – direction, kg

Fy

= force in Y – direction, kg

Fz

= force in Z – direction, kg

τ xy

= shear stress in XY – plane, kg / sq mm

τ yz

= shear stress in YZ – plane, kg / sq mm

τ zx

= shear stress in ZX – plane, kg / sq mm

ε xx

= normal strain in X – direction, mm / mm

ε yy

= normal stain in Y – direction, mm / mm

ε zz

= normal strain in Z – direction, mm / mm

γ xy

= shear strain in XY – plane, mm / mm

γ yz

= shear strain in YZ – plane, mm / mm

γ zx

= shear strain in ZX – plane, mm / mm

ν

= Poisson's ratio

u

= deformation in X – direction, mm

v

= deformation in Y – direction, mm

w

= deformation in Z – direction, mm

µ

= shear modulus =

E

, kg / sq mm

2 (1 + ν) E

= modulus of elasticity = Young's modulus, kg / sq mm

S – 15 : Questions on Stress Analysis Q1. What is Stress? A1. Q2. What is Strain? A2. Q3. What is lateral strain? A3. Q4. What is the hoop stress for a hollow cylinder under internal pressure “P”? A4. Q5. What is the longitudinal stress for a hollow cylinder under internal pressure “P”? A5. Q6. What is the radial stress for a hollow cylinder under internal pressure “P”? A6. Q7. What is a thin shell? A7. Q8. What is a thick shell? A8. Q9. What is allowable stress? A9. Q10. What is Stress Concentration Factor (SCF)? A10. Q11. What is creep? A11. Q12. What is fatigue? A12. Q13. What is corrosion? A13. Q14. What is erosion? A14. Q15. What is abrasion? A15.

S – 16 : Introduction to Stress Analysis Stress at a point is given below. Stress

=

Strain

=

Limit { F(x + ∆x) – F(x) } ∆x .> 0 ∆x Stress Elastic modulus

Lateral strain =

Lateral displacement Longitudinal displacement

Beam formula M = I

2

f =

E = E d y

y

R

dx

Shaft formula T = τ = Gθ J R L Thin Shell Formula σ1 R1

= σ2 R2

=

p t

2

= Poisson's ratio = ν

Part – F : Codes and Standards Strength Calculations as per ASME Section I (Power Boilers) Contents F-1 Introduction F-2 Allowable Stress F-3 Tubes and Tube Bends F-4 Pipes and Pipe Bends F-5 Headers F-6 Drums F-7 Ligament Efficiency F-8 Area Compensation for Shell F-9 Area Compensation for Dished End Heads F-10 Area Compensation for Flat End Covers F-11 Header and Drum Bending Stress F-12 Tube Lug Calculations F-13 Hemi-Spherical Dished End Covers F-14 2 : 1 Semi-Ellipsoidal Dished End Cover F-15 Tori-Spherical Dished End Cover F-16 Tori-Conical End Cover F-17 Flat End Cover F-18 Conical Vessel F-19 Load Path Calculations F-20 Hollow Cylinder Under External Pressure F-21 Man-Hole Way Cover Thickness F-22 References

Part - G A Hundred Questions on Boilers Q1. What are the fuels used in boilers? A1. Coal, oil and fuel gas. Q2. What are the types of boilers used? A2. Power boilers, industrial boilers. Q3. What are the Balance of Plant (BOP) in a power station? A3. Coal handling, ash handling, auxiliary piping, cooling water plant, chemical treatment plant, etc. Q4. What is a buckstay? A4. Buckstay is a product used to avoid buckling of the slim water walls and steam cooled walls. Q5. What is a de-super heater? A5. De-super heater reduces the temperature of the super-heated steam. Q6. What is a de-aerator? A6. De-aerator is a product used to remove oxygen and other gases from the water. Q7. What is a burner? A7. Burner is used to burn solid or liquid or gaseous fuels. Q8. What is a water wall? A8. Water wall is made of series of tubes connected with each other. Water flows inside the tubes.. Q9. What is a steam cooled wall? A9. Steam cooled wall is made of tubes connected with each other. Steam flows inside these tubes. Q10. What are the types of air-heaters? A10. Air-heaters can be rotary type or stationery type. Q11. Why ash collection devices are used? A11. Ash collection devices are used to reduce pollution. Q12. What are the types of ash collection devices? A12. Mechanical precipitation and Electro-static precipitation are the two types used. Q13. What are soot blowers? A13. Soot blowers are used to clean the heat transfer surfaces of boiler. Q14. What are the mediums used for soot blowing? A14. Air blowing or steam blowing are the two methods used. Q15. What are the types of soot blowers? A15. Wall blowers and long retractable blowers are used.

Q16. What are the types of heat transfer surfaces used? A16. Plain surfaces and finned surfaces are used for heat transfer. Q17. What is the function of the economizer? A17. Economizer economizes the power plant operation. Q18. What are the functions of steam drum? A18. (a) steam separation, (b) steam-water circulation and ( c) purifying steam. Q19. What is the function of super-heater? A19. Super-heater is used to super heat the steam and get higher thermal efficiency of the plant. Q20. Why large boilers are top supported? A20. (a) avoid buckling of furnace walls, (b) allow thermal expansion and ( c) reduce thermal loads. Q21. Why steel structures (avoiding concrete) are used for boiler structures? A21. Steel structures are used for speeding-up the construction schedule and facilitate changes. Q22. What is aviation light? A22. Aviation lights are used in tall buildings to warn aero-planes against collision and accident. Q23. What is lightning arrestor? A23. Lightning arrestors receive the electrical current during lightning and save the structure. Q24. What is wind load? A24. Movement of air is wind. The wind load for India is given in IS875 Part 3. Q25. What is seismic load? A25. Seismic load, also known as earth-quake load, is due to movement of earth. (see IS1893). Q26. What is the allowable deflection? A26. The allowable deflection was set as one inch per ten yards. As per IS800-1984, ∆ = span / 325. Q27. What is resonance? A27. When the natural frequency and the induced frequency matches resonance takes place. Q28. Why resonance should be avoided? A28. During resonance, high vibration and stress will occur. Hence, resonance should be avoided. Q29. What is the life of a power plant? A29. Life of the power plant is about 50 years. But, many components need replacement and repair. Q30. What is safety requirement for boiler, in India? A30. The Indian Boiler Regulations, 1950 (with amendments). Q31. What are the materials used for boiler pressure parts? A31. Carbon steel, low alloy steel, medium alloy steel and stainless steel.

Q32. What are the materials used for boiler structures? A32. Mild steel as per IS2062 is used. For fasteners, IS1367 is used. Q33. What is the material used for boiler insulation? A33. Slag wool, mineral wool and glass wool are used. Q34. What is the material used for boiler foundation? A34. Reinforced Cement Concrete (RCC) with a specification “M20” is used. Q35. What are the types of bolted connections used for boiler structures? A35. Bearing type connection and Friction type connections are used. Bearing type is popularly used. Q36. What is a shear key? A36. Shear key are flat plates welded at the bottom of the structure base plates to transfer shear forces. Q37. What are the types of chimneys? A37. RCC chimney and steel chimney are used. Q38. What are the types of steel chimneys? A38. Self supporting type and guyed chimney are used. Q39. Why conical chimneys are preferred? A39. Conical chimneys are economical. Q40. What is the corrosion allowance used for steel chimney? A40. Corrosion allowance = 3.0 mm (typical). Q41. Which boiler code is governing in India? A41. The Indian Boiler Regulations, 1950 (with amendments) is governing in India. Q42. Who is the authorized inspector in India? A42. The Chief Inspector of Boiler (CIB) is the authorized inspector for the respective states. Q43. Which body is empowered to amend The Indian Boiler Regulation? A43. The Central Boiler Board (CBB) is authorized to amend the IBR. Q44. Why steel is used for boiler pressure parts? A44. The cost to weight ratio is favorable for steel. Hence, steel is used. Q45. What is the purpose of refractory? A45. Refractory is provided where the flue gas temperature is high (above 800 Degree C). Q46. What is the purpose of refractory retainers? A46. Retainers are embed within the refractory and they retain the refractory to the surfaces. Q47. What are the steps in design? A47. Design, engineering, process analysis, stress analysis, detailing, drafting, documentation and document approval.

Q48. What are the aspects to be taken care-off in design? A48. Head-room, walk-way, access, approach, clash detection, clash resolution and interfacing. Q49. What are the softwares used in design office? A49. MS Windows, MS Office, STAAD.Pro, CAEPIPIE, CAESAR -II. Q50. What are the hardware required in design office? A50. Computer with accessories, Un-interrupted power supply (UPS), Xerox machine, FAX Q51. What software are used for piping stress analysis? A51. CAEPIPE and CAESAR – II. Q52. What are the plant design computer programs used? A52. CATIA, Plant Design System (PDS), Plant Design Management System (PDMS). Q53. What are the Finite Element Analysis (FEA) software available? A53. ANSYS, COSMOS, ABACUS and NASTRAN. Q54. What is the head room required? A54. Head room required = 1,800 mm. Q55. What is the walk-way width required? A55. Walk-way width required = 900 mm. Q56. What is the load per unit area on the boiler floors? A56. Load per square meter = 500 kg. Q57. What is the allowable deflection due to loads? A57. Allowable deflection = “Span / 325”. Q58. What is the allowable drift? A58. Allowable drift = “Height / 325”. Q59. Why stress concentration factor (SCF) is not considered in boiler design? A59. The boiler materials are ductile steel. The stress, after yielding, re-distributes favorably. Q60. What is virtual zero point? A60. Large top supported boilers expand cubically with respect to a virtual zero point near the top. Q61. What is floating anchor? A61. Floating anchors are anchors with thermal expansion movements. Q62. What is buckstay channel? A62. Buckstay channel is used to support the furnace walls and helps in transfer of loads. Q63. What is furnace guide? A63. Furnace guides fix the virtual zero point. This is used to transfer load from hot structure to cold structure.

Q64. List the drum internals. A64. Turbo-separator or cyclone separator, wire screen, pipes for vents, drains and chemical dosing. Q65. What is the purpose of a header? A65. Header collects or distributes steam or water or steam-water mixture. Q66. State ideal gas law. A66. P V = m R T Q67. State zoreth law of thermodynamics. A67. If systems A and B are in equilibrium with system C, then systems A and B are in equilibrium. Q68. State the First law of thermodynamics. A68. In an isolated system, the energy is always conserved. Q69. State the Second law of thermodynamics. A69. A system has to deliver heat with a sink while pumping heat from a lower source to a higher source. Q70. State First law of Newton A70. A body will be in its state of rest or steady motion along a straight line unless acted upon by external force. Q71. State Second law of Newton. A71. The rate of change of momentum is equal to force. Q72. State Third law of Newton. A72. For every action, there is an equal and opposite reaction. Q73. State Newtons universal law of gravitation. A73. All bodies attract each other. The force of attraction is inversely proportional to the square of distance of separation. Q74. What are the types of pollution? A74. Solid pollution, liquid pollution, air pollution and noise pollution. Q75. What is the causes of air pollution? A75. The main causes of air pollution are power plants and automobiles. Q76. Why Reinforced Cement Concrete (RCC) is used? A76. RCC is labor intensive and economical in India. Q77. What is pre-stressed concrete? A77. Pre-stressing with steel rods in the RCC is pre-stressed concrete. Q78. What is the function of foundation bolts? A78. Foundation bolts holds-down the structure to earth.

Q79. What is Flue Gas De-sulfurisation (FGD)? A79. FGD is used to remove sulfur and sulfur compounds from the flue gas. Q80. Name a few structural elements (members). A80. Column, beam and bracing. Q81. What is the design criteria for column? A81. Axial compressive load. Q82. What is the design criteria for beam? A82. Beams are designed to withstand bending. Q83. What is the design criteria for bracing? A83. Axial tension or axial compression. Q84. What is the function of base plate? A84. Base plate distributes forces from the columns and bracings to the foundation. Q85. What are the types structural steel connections? A85. Bolted or welded or riveted or bonded connections. Q86. What is the minimum thickness of structures to be used? A86. Six millimeter. Q87. Where hand hole plates are used? A87. Hand hole plates are used in the boiler pressure parts to view and clean the inside surfaces. Q88. Where man-hole ways are used? A88. Man-hole ways are used to access the boiler inner parts. Q89. What is the function of boiler drum level gages? A89. Level gages are used for finding the water level inside the boiler drums. Q90. What are thermo-couples? A90. Thermo-couples are used to measure the temperature of components. Q91. What is flow nozzle? A91. Flow nozzle is used to find-out the quantity of flow inside a pipe. Q92. What is an orifice? A92. Orifice is a sharp opening in a plate to facilitate flow measurement. Q93. What is a venturi? A93. Venturi is used measure the flow in a pipe. Q94. What is a valve? A94. Valves are used control flow in pipes.

Q95. What is DAS? A95. Data acquisition System (DAS) is used record readings. Q96. What is VLH? A96. Variable Load Hangers (VLH) are used for support, permitting limited support load variation. Q97. What is CLH? A97. Constant Load Hanger (CLH) are used for support, permitting small load variation. Q98. Why water quality is control in boilers? A98. Water quality is controlled to avoid corrosion of boiler parts. Q99. Why paints are required? A99. Paints are required to protect the surface of boiler. Q100. Why rockers are used for boiler hanger supports? A100. Rockers reduce the induced bending load. This leads to economic design.