Kiln Insp E English

Plant - Country Kiln No. …, dia. x ….. m, ……… Cooler Period of Inspection: date - year

Mechanical Kiln Inspection Type E

Kiln Inspection Report Plant: Country:

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Plant - Country Inspection of Kiln No. …, dia. x …….. m, …….. Cooler

Client representatives........................Mr ……………………….. Mr ……………………….. Mr ………………………..

FLS specialists ..................................Mr ……………………….. Mr ………………………..

Participants in final meeting .............Mr ……………………….. Mr ……………………….. Mr ……………………….. Mr ………………………..

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CONTENTS Page (1) Introduction...........................................................................................................................4 (2) Conclusions ..........................................................................................................................6 (3) Recommended Actions ........................................................................................................7 (4) Terminology .......................................................................................................................10 (5) Inspection Activities Carried out -Measurements and Calculations Performed..............11 (5.1) Kiln Shell...................................................................................................................11 (5.1.1) Kiln Shell - Temperatures..............................................................................11 (5.1.2) Kiln Shell - Side Guides.................................................................................12 (5.1.3) Kiln Shell - Crank Indication.........................................................................13 (5.1.4) Kiln Shell - Wobbling ....................................................................................16 (5.2) Live Rings .................................................................................................................17 (5.2.1) Live Rings - Temperatures and Diameters....................................................17 (5.2.2) Live Rings - Migration...................................................................................18 (5.2.3) Live Rings - Reduction in Migration.............................................................22 (5.2.4) Live Rings - Lubrication................................................................................23 (5.2.5) Live Rings - Wobbling...................................................................................24 (5.2.6) Live Rings - Positions on Supporting Rollers...............................................26 (5.3) Supporting Rollers ....................................................................................................27 (5.3.1) Supporting Rollers - Temperatures and Diameters.......................................27 (5.3.2) Supporting Rollers - Centre Distances ..........................................................28 (5.3.3) Supporting Rollers - Inclination ....................................................................29 (5.4) Bearings for Supporting Rollers...............................................................................32 (5.4.1) Bearings for Supporting Rollers - Positions..................................................32 (5.4.2) Bearings for Supporting Rollers - Temperatures ..........................................33 (5.4.3) Bearings for Supporting Rollers - Lubrication..............................................35 (5.5) Baseplates..................................................................................................................36 (5.5.1) Baseplates - Levelling....................................................................................36 (5.6) Drive Station .............................................................................................................38 (5.6.1) Drive Station - Wobbling of Gear Rim .........................................................38 (5.6.2) Drive Station - Root Clearance......................................................................38 (5.6.3) Drive Station - Position of Gear Rim to Pinion ............................................38 (5.7) Kiln Axis ...................................................................................................................39 (5.7.1) Kiln Axis - Measuring Results ......................................................................40 (5.7.2) Kiln Axis - Calculations.................................................................................41

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Page (6) Visual Inspection................................................................................................................44 (6.1) Kiln Shell...................................................................................................................44 (6.1.1) Kiln Shell - Side Guides and Live Ring Supporting Blocks ........................45 (6.2) Live Rings .................................................................................................................46 (6.3) Supporting Rollers ....................................................................................................47 (6.4) Bearings for Supporting Rollers...............................................................................49 (6.5) Drive Station .............................................................................................................51 (6.6) Thrust Device............................................................................................................52 (6.7) Axial, Mechanical Balance of the Kiln....................................................................53 (6.8) Inlet Seal....................................................................................................................54 (6.9) Outlet Seal.................................................................................................................55 (7) List of Enclosures Enclosure Deflection Variations / Supporting Roller Shafts ....................................................... 1a - f Wobbling of Kiln Shell / Polar Diagrams ............................................................ 2a - e Kiln Crank Diagram............................................................................................................ 3 Live Ring Migration............................................................................................................ 4 Axial Wobbling of Live Rings..................................................................................... 5a - c Axial Wobbling of Gear Rim...................................................................................... 6 Guide Block / Arrangement Drawing ......................................................................... 7 Tool for Profile Measurement of Supporting Rollers ........................................................ 8 Work Sheets for Surface Measurement of Supporting Rollers and Live Rings.................................................................. 9a - c

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(1) Introduction The inspection was carried out in accordance with agreement ………………………, and ………………, ref. ……………., of (date).

between

The purpose of the visit was to carry out a type “E” kiln inspection. The kiln was started up in (year) as a 2-support kiln with a …… cooler. It was converted in (year) and is now a 3-support kiln with a ……. cooler. The present output is approx. …. tpd. A hydraulic thrust device is located at support III. The drive station consists of a gear rim and one pinion on the outlet side of live ring III. The kiln was last inspected by FLS in (month/year) and has operated satisfactorily since then. According to the client, the life of the lining is very satisfactory. In our report on the inspection in (month/year), ref. …/…, ………, of (date), we listed a number of actions that should be taken. However, of the recommended actions, only the supporting rollers at support I have been machined. -- o -The purpose of the activities performed in a type “E” kiln inspection is to determine the measures (i.e. adjustments, replacements, modifications, or repairs) that have to be taken to achieve and maintain a high availability level of the kiln system. The most important factors contributing to high kiln availability are to maintain: * correct axial, mechanical balance of the kiln, meaning that the axial thrust of the kiln must be absorbed by both the supporting rollers and the thrust roller. When the axial, mechanical balance of the kiln is correct, the supporting rollers absorb approx. 30% of the axial thrust, and the thrust roller absorbs the remainder; * optimum load distribution on the kiln supports, meaning that the radial load on each individual supporting roller must be kept within the limits defined when dimensioning the kiln; * good, mechanical operating condition of the kiln system, meaning that, e.g., the degree of ovality and crank formation must not exceed the limits considered acceptable.

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In order to attain the above objectives, various requirements must be met, including the following: * The kiln axis must be correctly adjusted. * The positions (skewing and inclination) of the supporting rollers must be correct. * The rolling surfaces of supporting rollers and live rings must be truly cylindrical. The inspection and measuring activities carried out during the inspection of this kiln have been supplemented with calculations made at FLS-Copenhagen taking the present loads on and stresses in kiln shell, live rings, supporting rollers, and bearings for the supporting rollers into account. These calculations are based on the measurements taken, on information from the client about the weight of the kiln lining and coating, and on the own weight of the kiln.

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(2) Conclusions The following conclusions can be drawn on the basis of the measurements and observations made at the plant during the inspection combined with the calculations made at FLSCopenhagen: Our impression of the kiln was that this production line is in a very good state of maintenance. This impression that was, in fact, confirmed by the visual inspection is indeed reflected in a very high run factor. However, the standard of cleaning should be raised considerably as a high standard of cleaning is the best possible precondition of sustaining the standard of maintenance that has been achieved. The kiln axis measured indicates a fully satisfactory load and stress distribution, and there is therefore no need for any adjustment of the supporting rollers. For the sake of the drive station, the gear rim should be aligned during a prolonged shutdown of the kiln. The heavy axial wobbling of the gear rim has a damaging effect on both gear rim and pinion, and only alignment of these components can extend their life. -- o -Should the above conclusions contain recommendations warranting the implementation of specific activities, these activities are listed in section (3), “Recommended Actions”. We suggest that the next kiln inspection should be carried out in approx. 3 years, i.e. in (year).

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(3) Recommended Actions As a result of the inspection carried out by FLS, we recommend that the client should take the actions stated below:

(A) Actions to be taken as soon as possible: * Intensify the cleaning effort at all the supports, on the baseplates, and under the supporting rollers. Please see section (6). * The system applying lubricant between the moving parts and the stationary wear parts at the inlet seal should be put in working order. Please see sections (6) and (6.8). * Check of the spray lubrication system. Please see section (6).

(B) Actions to be taken during the next kiln shutdown: * On the kiln drive, all the pinion and intermediate pinion bearings need draining of oil and thorough cleaning out which also means each bottom housing between front and rear sections (communicating channel). Use a proper flushing oil to finish. Top bearing covers should be removed one at a time to assist this function. Take the opportunity to also check the lubrication cups (one or two are loose and out of line). Replace seals as necessary and attend to leaks, particularly on the upper main pinion bearing. Furthermore, check that the shaft scrapers are in satisfactory condition and ensure that they are in the correct direction when being replaced. * The oil pipework, sight glasses, etc. associated with each bearing must be cleaned out and then re-sealed. Do not forget to clean out the small vent hole in the top cap of the sight glasses. * As the majority of dust is entering the bearings through the badly sealing top inspection cast flaps, take the opportunity to re-machine these flaps to improve the sealing ability. Otherwise it will be the same old story next year. * Fill in new oil in each bearing and check that the lubrication is satisfactory before the kiln is re-started. Do not overfill the bearings. * During the kiln stoppage, both gear sumps/casing should be cleaned out. The position of the main drive pinion should then be ascertained, and if axial movement is confirmed, a decision is to be made as to whether any practical action can be taken.

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In an ideal situation, the gear rim tooth tip burrs should be removed but only if this is going to be done properly and the metal filings/grindings are thoroughly cleaned off afterwards. If this was the case, the tooth tips of the pinion could also be carefully dressed up and the side scrapers for the gear rim reinstated. As stated previously, there is little point in realigning the gear rim until it is reversed. The sliding inspection cover on the top of the intermediate gearing casing cover should be improved, not only to provide a more sealed plate to prevent ingress of dust but also for safety reasons (open rotating gears). The security of the locking plates for spring plate pins seems to continue in their variety. Some conformity should be applied to all of these. The comments made in our report of (year) still apply. Check the oil level of the main drive gearbox and adjust, if necessary. Measure when stationary and in a cold state. * At the inlet seal, check that grease is actually reaching the various termination points. Look at seal wear and take action accordingly. * At the outlet seal, lift up a number of the lamella seals at various points in order to help judge wear.

(C) Actions to be taken when convenient: * Reconditioning of the marker plate of bearing 4 at support III. Please see section (5.4.1). * Removal of remnants of weld material. Please see section (6.1). * Modification of the safety guards between supporting rollers and live rings. Please see section (6.2). * Check of the rolling surfaces of live rings and supporting rollers. They should be machined if they are not truly cylindrical. Please see sections (5.3.3) and (6.3). * Adjustment of the inclination of the left-hand supporting roller at support I. Please see section (5.3.3).

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Adjustment of the inclination should be followed up by adjustment of the skewing of the supporting rollers at support I to ensure correct axial, mechanical balance of the kiln.

(D) Preventive maintenance: * The side guides on the outlet side of live ring III should be replaced as soon as possible. Please see sections (5.1.2) and (6.1.1).

(E) Future activities (for planning purposes): * Machining of supporting rollers and live ring at support I, if necessary. Please see section (5.3.3). * Reduction in the axial wobbling of the gear rim.

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(4) Terminology The following terms are identical with those used in all other FLS documentation and will be used throughout this report. * Right-hand/left-hand side of the kiln: The right-hand/left-hand side of the kiln is determined as seen from the kiln outlet towards the inlet, i.e. against the material flow direction. * Numbering of bearings for the supporting rollers: At each support, the bearings for the supporting rollers are numbered from 1 to 4, starting with bearing 1 on the right-hand side of the support at the kiln outlet and continuing anticlockwise as shown in Fig. 1 below.

Bearing 3

Inlet

Bearing 2

Right

Left

Bearing 4

Outlet

Bearing 1

Fig. 1: Numbering of bearings for supporting rollers. * Numbering of supports: The kiln supports are numbered I - III starting from the kiln outlet. * Direction of rotation: The direction of rotation of the kiln - anticlockwise - is determined as seen from the kiln outlet towards the inlet, i.e. against the material flow direction.

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(5) Inspection Activities Carried out Measurements and Calculations Performed The following is a detailed description of the scope of the FLS inspection programme, its results, and the general and specific impact of the mechanical condition of the kiln components on the operation.

(5.1) Kiln Shell The physical condition of the kiln shell, especially the keeping of its “circular” shape while rotating, is one of the most important factors when it comes to maintaining a high availability level of the kiln system. It is common knowledge that the deformations occurring in the kiln shell while rotating are greatest under and in the vicinity of the live rings. Such deformations, which, naturally, are transmitted to the kiln lining, have an extremely great impact on the stability of the coating and the durability of the refractory lining. In addition to this, severe deformations lead to correspondingly great stresses in kiln shell and welds, and these stresses may contribute to formation of cracks. The logical consequence of this is that the below-mentioned activities are carried out with the purpose of describing and evaluating the present, physical condition of the kiln.

(5.1.1) Kiln Shell - Temperatures The highest and lowest kiln shell temperatures on both the inlet side and the outlet side of all live rings were measured by means of a radiation pyrometer (emission factor ε = 0.95). A great temperature difference at a particular measuring point is usually caused by varying thickness of lining and/or coating. This is an unfortunate phenomenon as the result may be what is called a thermal crank in the kiln shell, leading in its turn to increased loads on both the kiln shell and the supports. The measurements recorded during the inspection are shown in the table overleaf.

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Inlet side

Kiln shell temperature (ºC)

Page

Outlet side

High

Low

Difference

High

Low

Difference

I

372

327

45

344

248

96

At live ring II

296

239

57

291

222

69

At live ring III

229

137

92

181

124

57

At live ring

As will appear from the above table, the greatest temperature difference was recorded on the outlet side of live ring I. In the present case, the temperature differences measured are so small that there is no major risk of increased loads, and this evaluation is, in fact, supported by the result of the crank inspection. Please see section (5.1.3).

(5.1.2) Kiln Shell - Side Guides The purpose of the side guides is to keep the live rings in their axial position on the kiln shell. This implies that the axial thrust from the kiln shell is transmitted via the contact faces between live rings and side guides, and there is a higher or lower degree of relative, radial movement between these components depending on the degree of kiln shell ovality. Therefore, there is a risk of wear at these points. A new FLS kiln has a total clearance between live ring and side guides of approx. 4 mm (indicated by “c” and “d” in Fig. 2 below).

a

c

d

b

Fig. 2: Side guides for live ring fitted on live ring supporting blocks (type A).

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Clearance (mm)

Page

Width (mm)

c

d

a

b

At live ring I

A

12 - 15

0

165 - 170

165 - 170

At live ring II

A

0

6 - 10

190

190

At live ring III

A

20

0

45

98

As will appear from the above table, the clearances between live rings and side guides measured during the inspection range from 6 mm to 20 mm. A comparison between the above measurements and those taken during the inspection in (month/year) shows that the intervening period has seen only insignificant wear on the side guides. The wear on the side guides on the outlet side of live ring III is very marked and the side guides should be replaced as soon as possible. Regarding lubricants and lubrication methods, please see section (5.2.4).

(5.1.3) Kiln Shell - Crank Indication In a new kiln erected in the correct way, the gravity axis of the kiln shell coincides with its axis of rotation. If it should at a later date turn out that these axes are forcibly coinciding at a support, a kiln crank is said to have developed. Crank formation can get so severe that live ring and supporting rollers lose contact with each other during part of the kiln rotation. In most cases, such cranks develop as a result of irregular thickness of the coating causing uneven heating of the kiln shell in the burning zone of the kiln. This type of crank, called a thermal crank, can be reduced by changing the composition of the raw materials and/or the burning process and by choosing the right type of lining. A mechanical crank is usually caused by superheating of part of the kiln shell due to loss of lining. Other examples of causes of mechanical cranks are failure to bar the kiln during cooldown (resulting in permanent deformation of the kiln shell) and welding together of misaligned kiln sections, e.g. due to unprofessional repair work. A mechanical crank can be eliminated by cutting the kiln shell in two or more places followed by appropriate re-alignment of these kiln sections and then re-welding. This method necessitates a shutdown of the kiln during the repair.

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Alternatively, a mechanical crank can under certain circumstances be straightened by using a heat method developed by FLS allowing the kiln to continue normal operation. However, both methods require extensive preparations and a great deal of experience to be successful. During operation, the gravity axis of the kiln shell is forced to coincide with its axis of rotation under the live rings. The existence of crank formation in the kiln shell will therefore manifest itself as variations in the load on the individual supports occurring cyclically during the rotation of the kiln. The variations in the deflection of the supporting roller shafts during the rotation of the kiln directly reflect the additional loads imposed on the supports as a result of the presence of a thermal and/or a mechanical kiln crank. These additional loads can become so great that they cause fatigue fractures in the supporting roller shafts and increase the stress level in the kiln shell at the supports, causing crack formation and increased ovality, which may in their turn reduce the life of the kiln lining. The deflection variations of the supporting roller shafts are measured by means of a sensitive longitudinal transducer coupled to a measuring and recording instrument or a laptop computer via a data collector. The measuring set-up is shown in Fig. 3 below.

Fig. 3: Set-up for measurement of the deflections of supporting roller shafts. The deflection variations measured during the inspection are shown in the table overleaf, and the curve patterns recorded during the measuring process appear from Enclosures 1a - f.

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Left-hand supporting roller shaft

Right-hand supporting roller shaft

(± mm)

(± mm)

Support I

0.07

0.08

Support II

0.04

0.08

Support III

0.05

0.06

Deflection variation per kiln revolution

The measurements taken in (year) resulted in the following deflection variation values: Left-hand supporting roller shaft

Right-hand supporting roller shaft

(± mm)

(± mm)

Support I

0.01

0.03

Support II

0.04

0.07

Support III

0.04

0.01

Deflection variation per kiln revolution

In case deflection variations exceeding ± 0.15 mm are measured on one or both of the supporting roller shafts of a support (the supporting rollers and shafts are assumed to be of FLS design), a closer investigation is required in order to determine whether the kiln has a thermal crank (i.e. varying according to the operational conditions) or a mechanical crank (i.e. a permanent one). In case of a mechanical crank, we recommend that a full crank inspection be performed in order to determine the crank's size and position in the kiln shell. As will appear from the above table, the largest deflection variations were measured at support I. The values measured are markedly lower than the limit of ± 0.15 mm mentioned above.

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A comparison between the two sets of measurements shows that the deflection variations of the supporting roller shafts measured now and in 2000 are almost identical. The differences at the individual supports must be caused by thermal factors or minor mechanical crank formation in the kiln shell, the latter evaluation being based on the fact that the wobbling values of live rings I and II are higher than those measured in 2000. Please see section (5.2.5). However, we still consider the deflection variations measured to be at a satisfactory level.

(5.1.4) Kiln Shell - Wobbling The geometrical deviation between the gravity axis of the kiln shell and its axis of rotation is called the wobbling of the kiln shell. In an old kiln, the wobbling of the kiln shell normally varies in terms of both magnitude and direction throughout the whole length of the kiln. The purpose of measuring the wobbling of the kiln shell is to analyse the causes of possible wobbling of the live rings and/or the gear rim. A longitudinal transducer in contact with the kiln shell and coupled to a measuring and recording instrument or a laptop computer via a data collector is used for measurement of the wobbling of the kiln shell at a suitable number of points along the kiln. All measurements refer to the same starting point, which is normally the position of the manhole. Polar diagrams are drawn on the basis of the above measurements. From the polar diagrams, the magnitude and direction of the wobbling of the kiln shell can be determined at each of the points chosen. A total of 5 polar diagrams were drawn on the inlet sides and outlet sides of live rings I and II and on the outlet side of the gear rim. The measuring points appear from Enclosures 2a - e, which also show the wobbling of the kiln shell at the measuring points in question. The axonometric axis of the kiln, the kiln crank diagram, appears from Enclosure 3. The measurements taken of the wobbling of the kiln shell explain why the axial wobbling of live rings I and II has increased. Please see section (5.2.5). The kiln shell has become more warped between supports I and II since the last kiln inspection. The wobbling of the kiln shell on the outlet side of the gear rim has not changed. During a shutdown, the hot kiln has in all probability been at rest at the same position for too long time. No action is necessary at the present moment, but the wobbling of kiln shell and live rings should still be measured/kept under observation.

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(5.2) Live Rings (5.2.1) Live Rings - Temperatures and Diameters During the inspection, the live ring temperatures were measured by means of a radiation pyrometer (emission factor ε = 0.95) in the middle of the side faces of the live rings and on both the inlet side and the outlet side. Then the average temperature was calculated. The average temperatures appear from the table overleaf. The diameters of the live rings are calculated on the basis of measurements of their circumferences. Electromechanical measuring equipment developed by FLS for this specific purpose is used for these circumferential measurements that are taken while the kiln is in normal operation. The results of the diameter measurements taken during the inspection appear from the table below, which also shows the original diameters of the live rings (at 20°C). Measurements taken during the inspection Live rings Temperatures and Temperature Diameter (mm) Diameter (mm) at temperature measured diameters at 20ºC measured (ºC)

Original value Diameter (mm) at 20ºC

Live ring I

208

5168.6

5157

5160

Live ring II

142

5060.9

5052

5052

Live ring III

100

5017.4

5013

5020

The temperatures measured are acceptable and do not deviate significantly from those measured in (month/year). The diameter values measured deviate from the measurements taken in (year) pari passu with the live ring temperatures measured, these temperatures being momentary values. The diameters of the live rings calculated at 20ºC have remained more or less unchanged as compared with the measurements taken during the inspection in (year). The above table also shows that the diameter of live ring II calculated at 20ºC has not decreased since it was installed in (year). The reductions in the diameters of live rings I and III are caused by wear owing to the highly dust-infected atmosphere (dust coming from kiln No. ..). Each live ring will be dealt with separately in the visual inspection part of this report. Please see section (6.2).

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(5.2.2) Live Rings - Migration Live ring migration is the relative, tangential, rolling movement of contact points on kiln shell (live ring supporting blocks) and live ring in relation to one another during one revolution of the kiln. The migration is a direct measure of the circumferential difference, and accordingly of the diameter difference, between live ring and kiln shell and an indirect measure of the ovality of the kiln shell. Therefore it is an important indicator of the mechanical condition of the kiln. It should be borne in mind that kiln shell ovality is actually generated between kiln shell and live ring due to the rigidity of and the loads on the live ring and to the diameter difference between live ring and kiln shell. This means that the highest degree of ovality is found under the live ring, gradually decreasing as the distance from the live ring increases. This is the reason why FLS has chosen to investigate the ovality by measurement of the live ring migration in preference to the more traditional Shell Test method, as measurements by the latter method must necessarily be taken at some distance from the live ring showing, consequently, a lower degree of ovality. The live ring migration is measured during normal operation of the kiln by means of an instrument like the one shown in Fig. 4 below, the migration being directly measurable as the length of period of the graph drawn.

Live ring Magnet Pencil

Magnet

Supporting block

Fig. 4: Measurement of live ring migration. In a new FLS kiln, the live ring migration will under normal operational conditions be approx. 10 mm per revolution of the kiln corresponding to a relative FLS ovality of the kiln shell of approx. 0.30%, which in its turn corresponds to a calculated Shell Test ovality of approx. 0.50%.

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Generally, ovality corresponding to live ring migration of 10 - 15 mm per revolution of the kiln will have no harmful effect on the kiln lining. However, if the migration exceeds approx. 20 mm, this indicates that the ovality of the kiln shell has reached a size that will most probably contribute to a reduction in the life of the lining. Such a high degree of ovality will also add to the stress level in kiln shell and welds, and this may contribute to crack formation.

Consequently, FLS recommends that measurement of the live ring migration, the related live ring temperatures, and the temperatures on the surface of the kiln shell on both sides of the live rings should form an integral part of the normal, preventive maintenance programme carried out at the plant. This will enable monitoring of variations in the live ring migration, allowing the necessary steps to counter any problems to be taken. The migration values measured during the inspection are shown in the table below. Please also see Enclosure 4.

Live ring migration Live ring

(mm/rev.)

I

14.0

Live ring II

12.5

Live ring III

19.0

The following live ring migration values were measured during the inspection in (year):

Live ring migration Live ring

(mm/rev.)

I

12.0

Live ring II

3.0

Live ring III

14.0

The migration of all the live rings has increased since the last kiln inspection. The increase is most probably due to wear on the inside rolling surfaces of the live rings or wear on the outside surfaces of the live ring supporting blocks as a consequence of the highly dustinfected atmosphere at the kiln. However, the migration of the live rings is still at a satisfactory level, and this evaluation is, in fact, supported by the calculations shown in the table overleaf.

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FLS has used the kiln axis measured and the available data on the existing lining and coating for making a complete re-calculation of the kiln. The calculated values of the tangential bending stress in the kiln shell under the live rings are shown in the table overleaf.

Live ring migration (measured)

Live ring migration (10 mm)

Relative ovality

Tangential bending stress in the kiln shell

Relative ovality

Tangential bending stress in the kiln shell

(%)

(N/mm²)

(%)

(N/mm²)

At live ring I

0.19

23.7

0.15

18.3

At live ring II

0.26

28.2

0.23

24.1

At live ring III

0.32

34.5

0.24

23.5

FLS calculation

The kiln dimensioning process aims at ensuring a satisfactory service life of the kiln given a proper standard of maintenance. A factor that must be taken into account is that the abovementioned value of relative FLS ovality of the kiln shell of 0.30% and tangential bending stress in the kiln shell under the live rings of 30 N/mm² may occasionally be slightly exceeded even in good plant operating practices (please see the survey of kiln design values in section (5.7.2) on calculation of the kiln axis). Our calculations show that the ovality and bending stress values are satisfactory at the migration measured. An increase in the live ring migration indicates an increase in the clearance between live ring and kiln shell and, consequently, in the ovality of the kiln shell. On the other hand, a reduction in the live ring migration indicates a reduction in the clearance between kiln shell and live ring, and this may result in jamming and constriction (please see Fig. 5 overleaf). An increase in the live ring migration is normally attributable to one or a combination of the following causes: * Wear on the live ring supporting blocks or, where such blocks are not fitted, on the kiln shell itself, caused by ineffective lubrication between live ring and live ring supporting blocks. This may for instance be the case if the environment at the live ring is very dirty.

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As described in section (5.2.4), to ensure effective lubrication, it is necessary to use: - correct lubricant; - correct lubricating method; - correct lubricating frequency.

Fig. 5: Constriction of kiln shell under live ring. * Constriction caused by superheating of the kiln shell under the live ring. This situation may arise if, e.g., the kiln lining gets worn or falls out or if the coating does not have the thickness required. As to the latter point, starting up a kiln with a new lining is a particularly critical matter. If start-up (heating) is effected too quickly, the kiln shell may expand so much that it gets jammed under the live ring. This may lead to a permanent deformation of the kiln shell, resulting in an increased clearance between live ring and live ring supporting blocks (kiln shell) when temperatures return to normal and the kiln contracts. If the kiln suffers from constriction, it may be impossible to do a proper piece of lining installation work, and the result of this may be an unacceptably short life of the lining. In such a situation, the kiln section in question should be replaced.

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(5.2.3) Live Rings - Reduction in Migration If the live ring migration increases to a point where the ovality and bending stress values cause mechanical problems and/or problems with the lining, corrective action should be taken to reduce the migration (and thus the ovality) in order to avoid a real breakdown. The method to be applied depends on the type of kiln shell: with or without live ring supporting blocks. Kiln shell with live ring supporting blocks: For this type of kiln shell, the clearance between live ring supporting blocks and live ring can be reduced by installation of shims between the blocks and the kiln shell. The average thickness “t” of such shims is calculated according to the following formula where “v” is the live ring migration:

t=

v − 10 (“t” in mm and “v” in mm/rev.) 2π

By installing shims with an average thickness of “t” mm, the live ring migration will be reduced to 10 mm per revolution of the kiln. We know from experience that the live ring migration can vary within pretty wide limits. To take this natural variation into account, the following measuring programme must always be carried out before deciding on the thickness of the shims to be installed under the live ring supporting blocks: * Measurement of live ring migration. * Measurement of temperature on the side faces of the live ring (average). * Measurement of the kiln shell temperature on both the inlet side and the outlet side of the live ring. These measurements must be taken at least twice every 24 hours for a period of 3 - 4 weeks. It is a condition that the kiln is in normal operation throughout this period. Please note that, as a rule, the lowest value of the live ring migration measured is to be used for calculation of the shims. Moreover, the condition of the lining and the stability of the coating in the kiln area in question must also be evaluated.

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(5.2.4) Live Rings - Lubrication Where maintenance of live rings is concerned, use of the correct lubricating method is of paramount importance in the following two areas: * The contact faces between live ring and live ring supporting blocks/kiln shell/side guides. Lubrication should be carried out by means of a pump to ensure that the lubricant is distributed over the entire contact face. Lubricate as required, however, at least once or twice a month. The following lubricants are suitable for this purpose: Lubricant Producer Chesterton Klüber Lubrication Never-Seez Comp. Corp. Fuchs Lubritech

Product 785 Parting Lubricant Wolframcoat C Never-Seez 1 Ceplattyn HT

We normally recommend lubrication between live rings and live ring supporting blocks and between side guides and live rings in order to reduce the wear between these components and in order to avoid scuffing between live ring supporting blocks and live rings. However, considering the highly dust-infected atmosphere in the kiln building, it is not always advisable to apply lubricant between live rings and side guides and between live rings and live ring supporting blocks at the intervals mentioned above as the combination of dust and lubricant will no doubt accelerate the wear on the components. If lubrication is necessary, a mixture of water and powdered graphite can be used. * The contact faces between live ring and supporting rollers. These areas should be lubricated with dry graphite only. (A liquid lubricant would penetrate into micro-cracks on the surface and come under extremely high pressure during the contact phase, thus further increasing the crack formation. Pitting or scaling would invariably result.)

1

Never-Seez, which is supplied as a paste, can be mixed with oil to improve its flow between live ring and live ring supporting blocks/side guides/kiln shell. In that case, the mixture ratio must be approx. 40% Never-Seez to approx. 60% oil, and the oil used must have a high flash point.

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(5.2.5) Live Rings - Wobbling The axial wobbling of the live rings is measured by means of a longitudinal transducer coupled to a measuring and recording instrument or a laptop computer via a data collector (please see Fig. 6 overleaf).

Wobbling of live ring

Recorder

Transducer

Fig. 6: Measurement of axial wobbling of live ring. Measurement of the axial wobbling of live rings forms part of the evaluation of contact conditions between live ring and supporting rollers. Severe wobbling of a live ring indicates poor contact conditions, resulting in increased Hertz pressure, which in its turn causes wear, convex/concave rolling surfaces, rolling-out of the rolling surfaces, as well as a risk of pitting. The permissible, axial wobbling of the live rings of a new FLS kiln is ± 1 mm. The measurements taken during the inspection are shown in the table below. Please also see Enclosures 5a - c. Axial wobbling of live rings

(± mm)

Live ring I

2.0

Live ring II

1.3

Live ring III

1.7

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The following wobbling values were measured during the inspection in (month/year):

Axial wobbling of live rings

(± mm)

Live ring I

0.64

Live ring II

0.37

Live ring III

1.72

Comparing the two sets of measurements shows that the wobbling of live rings I and II has increased. The cause is no doubt, as mentioned in section (5.1.4), that, during a shutdown, the hot kiln has been at rest at the same position for too long time. The polar diagrams drawn on the inlet sides and outlet sides of live rings I and II show relatively heavy wobbling of the kiln shell, confirming the axial wobbling of the live rings measured. No action in respect of the wobbling of the live rings is necessary at the present moment, but it should be kept under observation, and in case the values measured continue to rise, action should be taken possibly by cutting the kiln shell in two or more places. If the wobbling of the kiln shell continues to increase, the result will be unacceptable, heavy axial wobbling of the live rings which will damage the rolling surfaces of live rings and supporting rollers as they will be worn into convex and concave configurations, respectively.

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(5.2.6) Live Rings - Positions on Supporting Rollers

Left SR

4

3

S4

S1

1

S3

LR

S2

SR

2

Right

Fig. 7:

Position of live ring on supporting rollers.

The table below shows the positions of the live rings on the various supporting rollers using the designations shown in Fig. 7 above.

Positions of live rings on supporting rollers

Positions of live rings (mm)

Width of supporting roller (SR)

Width of live ring (LR)

S1

S2

S3

S4

(mm)

(mm)

Support I

135

45

10

170

1200

1020

Support II

55

65

65

55

800

680

Support III

60

60

75

45

800

680

The positions of the live rings on the supporting rollers are satisfactory.

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(5.3) Supporting Rollers (5.3.1) Supporting Rollers - Temperatures and Diameters The supporting roller temperatures were measured by means of a radiation pyrometer (emission factor ε = 0.95) in the middle of the side faces of the rolling surfaces of the supporting rollers and on both the inlet side and the outlet side. Then the average temperature was calculated. The average temperatures appear from the table overleaf. The diameters of the supporting rollers are calculated on the basis of measurements of their circumferences. Electromechanical measuring equipment developed by FLS for this specific purpose (the same equipment as that used for measuring the live ring circum-ferences) is used for these circumferential measurements that are taken while the kiln is in normal operation. The results of the diameter measurements taken during the inspection appear from the table overleaf, which also shows the original diameters of the supporting rollers (at 20°C).

Supporting rollers

Support II

Support III

Original value

Temperature measured (ºC)

Diameter (mm) at temperature measured

Diameter (mm) at 20ºC

Diameter (mm) at 20ºC

Left

75

2480.4

2478.4

2500

Right

75

2476.4

2474.3

2500

Left

72

1500.3

1497.4

1500

Right

70

1498.6

1499.1

1500

Left

59

1492.7

1491.8

1500

Right

65

1489.0

1488.0

1500

Temperatures and diameters Support I

Measurements taken during the inspection

The temperatures measured are normal and therefore do not give rise to any further comments. It appears from the above table that the diameters of all the supporting rollers calculated at 20ºC have been reduced.

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The reduction in the supporting roller diameters at support I is mainly due to the rollers having been machined but is also to some extent caused by the dust accumulating under the supporting rollers. The latter problem is also in evidence at supports II and III. The dust accumulating under the supporting rollers at all the supports should be removed now and then in order to avoid unnecessary wear on the rollers. The condition of each individual supporting roller will be discussed in section (6.3) on the visual inspection of the rollers. Machining of the rolling surfaces of some of the supporting rollers may be necessary as they are perhaps not truly cylindrical.

(5.3.2) Supporting Rollers - Centre Distances The centre distance between the two supporting rollers at a kiln support is measured as the distance between the centres of the two shaft ends on both the inlet side and the outlet side. These measurements are taken to check the degree of parallelism between the supporting rollers at each individual support.

Bearing 3

C inlet

Left side

Bearing 4

Fig. 8:

Bearing 2

Right side

C outlet

Bearing 1

Measurement of centre distances between supporting rollers.

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The measurements recorded during the inspection appear from the table below. Supporting rollers Centre distances

C inlet (mm)

C outlet (mm)

C original (mm)

Support I

3787

3782

3830

Support II

3327

3328

3318

Support III

3254

3255

3262

The measurements recorded show that the centre distances at support I have changed since the last inspection. The parallelism between the supporting roller pairs measured during the last kiln inspection was satisfactory. After machining of the supporting rollers at support I, the centre distances were adjusted, and so was perhaps the inclination (?). In consequence, the skewing of the rollers at support I has increased. It appears from section (5.3.3) that the inclination of the left-hand roller at support I is incorrect, and the question is whether the machining has made the supporting rollers truly cylindrical. We recommend that the rolling surfaces of the rollers be measured. For further details, please see section (6.3). Correct skewing and inclination of the rollers and truly cylindrical rolling surfaces of live rings and supporting rollers will reduce the risk of hot bearings and ensure correct thrust on the thrust roller and good contact conditions between supporting rollers and live rings. For further comments, please see section (6.7).

(5.3.3) Supporting Rollers - Inclination The inclination of the supporting rollers was checked. This check is made primarily with a view to analysing the axial, mechanical balance of the kiln, as axial thrust is generated if the inclination of the supporting rollers deviates from that of the kiln (live rings) at the corresponding positions, and secondarily in order to evaluate the causes of possibly poor contact conditions between supporting rollers and live rings and between live rings and live ring supporting blocks/kiln shell. The targeted, ideal inclination for a set of supporting rollers corresponds to the inclination of the kiln at the point in question, i.e. the nominal inclination of the kiln adjusted according to the kiln deflection and to the desire for axial, mechanical balance and correct contact conditions. The current, available data on the existing lining and coating conditions are included in the calculation of these ideal values.

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The inclination was measured by means of an inclinometer designed by FLS for this specific purpose. The inclinometer is fixed to the end faces of the supporting roller shafts by means of magnets, usually permitting the measurement to be taken during normal kiln operation. The table below shows the inclination values of the supporting rollers measured during the inspection and the corresponding calculated, ideal values. The calculation of the ideal values is based on the kiln inclination measured of 3.474%.

Inclination of

Left-hand supporting roller

Right-hand supporting roller

supporting rollers

Ideal value (%)

Measured value (%)

Ideal value (%)

Measured value (%)

Support I

3.463 - 3.483

3.541

3.463 - 3.443

3.468

Support II

3.481 - 3.501

3.451

3.481 - 3.461

3.463

Support III

3.465 - 3.485

3.501

3.465 - 3.445

3.512

The thicknesses of the shims to be installed or removed in order to attain correct inclination of the supporting rollers appear from the table overleaf. Thickness of shims (mm)

Bearing 1

Bearing 2

Bearing 3

Bearing 4

Support I

0.3

-

-

1.6

Support II

-

0.5

0.6

-

Support III

-

-

-

0.4

If the difference between the calculated, ideal value and the one measured is too large (> 0.5 mm), the inclination of the supporting roller in question should be adjusted. This adjustment is carried out by installation (+) or removal (-) of a shim of suitable shape and thickness under one of the bearings for the supporting rollers. Bearing 4 at support I is to be adjusted.

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We recommend the following procedure when adjusting the inclination of supporting rollers: * Check the rolling surfaces (profiles) of live ring and supporting rollers. If the surfaces are not level, i.e. if they have been worn into conical, convex, or concave configurations, they should be machined. As to measurement of the surfaces, please see the last part of section (6.3). * Carry out machining, if necessary. Machining of supporting rollers and live rings changes the axial and radial load from the kiln on the rollers. It is therefore important that necessary adjustments of the supporting rollers should be made as the machining operation proceeds in order to avoid overheating of bearings and to maintain the axial, mechanical balance of the kiln. * During the first shutdown of the kiln after completion of machining, make the recommended adjustments of the inclination at the support where machining has taken place. * After adjustment of the inclination, check the inclination of the supporting rollers. Supplementary adjustments of the inclination may be necessary in a few cases. The shims are made of mild steel plate in the dimensions indicated in Fig. 9 and the table overleaf.

Fig. 9:

Two-piece shim for adjustment of the inclination of supporting rollers.

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Size of bearing

A

B

C

D

E

630

1550

500

130

85

1310

450

1250

400

100

80

1060

Adjustment of the inclination and skewing of supporting rollers must always be succeeded by a check of the axial thrust from the kiln on the supporting rollers in question and of the overall axial, mechanical balance of the kiln. This check is made by measuring the bearing temperatures (please see section (5.4.2)) or by using the equipment for measurement of the axial thrust (please see section (6.7)). The latter method can only be used, however, if the rolling surfaces of supporting rollers as well as live rings are truly cylindrical and if the journals of the bearings are in optimum condition.

(5.4) Bearings for Supporting Rollers (5.4.1) Bearings for Supporting Rollers - Positions Marker plates like the one shown in Fig. 10 overleaf indicating the positions of the bearings on the baseplates are installed during the erection of, among others, FLS kilns.

Fig. 10: Position of bearing on baseplate. The present positions of the bearings were checked during the inspection and compared with their original positions. The results appear from the table below. A negative “a”-value indicates that the bearing in question has been moved inward towards the centreline of the kiln.

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Bearing 1

Bearing 2

Bearing 3

Bearing 4

a (mm)

a (mm)

a (mm)

a (mm)

Support I

*)

- 18.0

- 36.0

**)

Support II

+ 2.5

+ 2.5

+ 4.0

+ 1.5

Support III

- 5.0

- 7.0

- 5.0

***)

*)

The marker plate is located between two lines scribed on the baseplate. These lines are scribed at - 13/- 2.

**)

The marker plate is located between two lines scribed on the baseplate. These lines are scribed at - 15/- 4.

***) Defective marker plate. The thickness “t” of any existing shims between baseplates and bearings installed to raise the bearings with a view to adjusting the inclination of the supporting rollers is shown in the table overleaf.

Bearing 1

Bearing 2

Bearing 3

Bearing 4

t (mm)

t (mm)

t (mm)

t (mm)

Support I

8.5

7.0

11.0

11.5

Support II

0.0

0.0

0.5

0.0

Support III

1.0

0.5

1.0

0.5

Thickness of shims

(5.4.2) Bearings for Supporting Rollers - Temperatures The bearing temperatures were measured by means of a contact thermometer. The following temperature measurements were taken on each bearing: two measurements on the journal, one as close to the supporting roller as possible but inside the bearing housing and the other at a point approx. 30 mm from the thrust collar (Txm and Txe, respectively), and one measurement on the thrust collar (Txk). (Please note that in the bearings where thrust collar and liner were not in contact, measurements were only taken at Txm and Txe.)

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Left

e= Journal at thrust collar k= Trust collar m= Journal

Right

Fig. 11: Temperatures of bearings for supporting rollers. Measuring points. The normal temperature profile in a bearing will show the highest temperature at the supporting roller, the temperature will decrease across the length of the journal, and the lowest temperature will be registered on/at the thrust collar. It is extremely important to be attentive to any changes in the temperature on the thrust collar as such changes may indicate changes in the operational conditions. If the temperature on a thrust collar (Txk) is more than approx. 2°C higher than that on the adjacent journal (Txe), this may be an indication that excessive axial thrust is being transmitted through the bearing, entailing a risk of its running hot. In such cases, corrective action to restore normal temperatures should be taken as soon as possible. In a new FLS kiln, where all rolling surfaces are truly cylindrical and general conditions are ideal, the supporting rollers are adjusted so that all rollers exert a slight uphill thrust on the kiln. These adjustments are made on the basis of measurements taken with equipment for measurement of the axial thrust. The bearing temperatures measured during the inspection are shown in the tables below. An “x” indicates contact between the thrust collar and the bearing liner of the bearing concerned.

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Bearing

Page

Left-hand supporting roller

temperatures

Bearing 4

Bearing 3

(°C)

a4

T4k

T4e

T4m

T3m

T3e

T3k

a3

Support I

-

-

35.9

40.9

43.3

37.4

37.7

x

Support II

x

37.3

35.9

40.0

35.7

32.2

-

-

Support III

-

-

31.1

*)

33.4

29.6

30.2

x

Bearing

Right-hand supporting roller

temperatures

*)

Customer Services

Bearing 1

Bearing 2

(°C)

a1

T1k

T1e

T1m

T2m

T2e

T2k

a2

Support I

x

36.4

36.3

40.1

42.6

36.5

-

-

Support II

-

-

38.9

39.5

34.5

32.1

32.5

x

Support III

-

-

32.0

37.8

36.8

32.9

33.3

x

It was not possible to measure the journal temperature as the cover fitted on the bearing housing could not be opened.

The bearing temperatures measured are satisfactory.

(5.4.3) Bearings for Supporting Rollers - Lubrication The bearings of the rotary kiln are hydrodynamically lubricated journal bearings. Due to the low speed of rotation, it is very important that the difference in diameters between the journal and the bearing liner be exactly so great as to produce the wedge effect necessary for the generation of an adequate oil film thickness. Satisfactory operation of the bearings is therefore highly dependent on the use of an oil type with the proper viscosity and on keeping the oil free of abrasive dust and other contaminants.

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Systematic maintenance of the bearings in accordance with directions given in the instruction manuals for maintenance is of paramount importance to trouble-free operation of the bearings. FLS normally recommends the use of a mineral oil with FLS symbol EP-680 for lubrication of bearings for supporting rollers. In case of abnormal overheating of a bearing, we recommend the use of an oil type with FLS symbol EP-1000. For further information, please see the relevant instruction manuals for maintenance.

(5.5) Baseplates (5.5.1) Baseplates - Levelling

Fig. 12: Levelling of baseplate heights. Any movement of the foundations may have a direct effect on the geometry of the kiln axis. Such movements can be regarded as being composed of purely vertical movements, called settlement, and rotations both in the vertical plane including the kiln axis and in a likewise vertical plane being perpendicular to the kiln axis. The latter rotations, called tilting, interfere with the horizontal component of the kiln axis whereas the vertical movements affect the vertical component of the kiln axis. To determine whether the foundations have moved, the differences in height between the baseplates were measured at all supports during the inspection by means of a levelling instrument (please see Fig. 12 above).

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The results of the levelling of the baseplates appear from the table below, which also shows the original height differences between the baseplates.

Difference in height between the foundations Support

Settlement of foundations

Accumulated difference in height

Original height

Height measured

Difference in height

Change

(mm)

(mm)

(mm)

(mm)

R-I

0

0

0

0

I - II

1325

1325

0

0

II - III

815

825

+ 10

+ 10

The tilting values shown in the table below are pure rotations around the baseplate centres. Therefore, they are the same size numerically but given with opposite signs on the right-hand and the left-hand sides of the baseplates, a “+” indicating the highest point. Please also note that the tilting is stated as seen from the burner’s platform.

Difference in height from side to side on baseplate front edge Tilting of foundation

Left-hand side

Right-hand side

(mm)

(mm)

Support I

- 6.00

+ 6.00

Support II

+ 0.75

- 0.75

Support III

- 2.00

+ 2.00

The measurements show that both settling and major tilting of especially foundations I and III have occurred after the erection. It is not possible at the present moment to draw any conclusions as to whether the settlement/tilting have stopped. The baseplates should therefore still be checked at regular intervals. The differences in height measured may vary slightly from inspection to inspection. The reason why is that the measurements are taken along a hot kiln. To achieve accurate measurements, the kiln must be completely cold, and the above values are therefore only to be taken as a guide.

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(5.6) Drive Station (5.6.1) Drive Station - Wobbling of Gear Rim The wobbling of the gear rim was measured in order to evaluate the quality of mesh between gear rim and pinion. The axial wobbling was measured by means of a longitudinal transducer coupled to a site computer (please see the figure in section (5.2.5) on wobbling of live rings). The results are shown in Enclosure 6 from which it appears that the axial wobbling is ± 4.5 mm which is very slightly up from (year). In a new installation, the permissible axial wobbling is ± 0.75 mm. For safety reasons, the radial wobbling of the gear rim was not measured or observed. However, measuring the movement of the adjacent downhill kiln shell gave a variation of ± 4.4 mm compared with ± 3 mm in (year). On this assumption, we may take it that the estimated radial wobbling of the gear rim is in the order of ± 3.5 mm. In a new installation, the permissible radial wobbling is ± 1.5mm.

(5.6.2) Drive Station - Root Clearance Visual indication at one temporary stationary position gave a clearance between pinion tooth and root of gear rim of 12 - 13 mm. This compares to a theoretical clearance of 10 mm.

(5.6.3) Drive Station - Position of Gear Rim to Pinion Observations indicate that the pinion is in a similar position to that of the (year) inspection, i.e. downhill. During a shutdown of the kiln, the exact situation should be ascertained and a decision made on any action that may be required.

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(5.7) Kiln Axis The loads in the kiln shell and on the supports are determined in the design phase assuming a given geometry of the axis of rotation. To ensure that reactions are distributed evenly on the two supporting rollers of a support, the horizontal component of this axis of rotation is always straight. The vertical component of the axis of rotation, on the other hand, can sometimes be recommended not to be straight as this may provide, e.g., better distribution of the reactions on the various supports. Consequently, any changes that may occur in the geometry of the axis of rotation in the course of time entail changes in the distribution of loads in the kiln shell and on the supports. Such changes in load, the magnitude of which is closely related to the rigidity of the kiln (i.e. the relationship between kiln diameter, plate thickness of kiln shell, and distance between the supports), may involve the risk of a breakdown or reduced service life of the kiln components. Frequent checks of the kiln axis should therefore form an integral part of the maintenance work done at the plant. To be able to correctly evaluate the consequences of any deviation from the optimum kiln axis, it is necessary to have detailed knowledge of both the rigidity of the kiln and the strength of the individual components at the supports, i.e. the mechanical condition of the kiln. Moreover, the measurements themselves must naturally be taken under the most realistic conditions, i.e. while the kiln is in operation. The conclusions contained in this inspection report are based on these basic assumptions.

Teodolite Teodolite with laser

Fig. 13: Set-up for measurement of kiln axis (laser measurement). The present kiln axis was determined by using two electronic precision theodolites, one of which is equipped with a laser instrument (please see Fig. 13 above). Readings and

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calculations were made by means of a laptop computer integrated in the set-up but not shown in the figure. The coordinates of six points on the rolling surface of each live ring were determined in a three-dimensional system of coordinates. Knowing these coordinates and the geometry of the live rings, the coordinates of the centres of the live rings were calculated and the common axis of rotation was determined. The centres of the kiln shell were calculated on the basis of the centres of the live rings, taking both ovality and temperatures into account.

(5.7.1) Kiln Axis - Measuring Results At the time of measurement, the kiln axis deviated from a straight line under the live rings as follows: Vertical deviation 2

Horizontal deviation 3

(mm)

(mm)

Support I

0

0

Support II

-4

-2

Support III

0

0

Kiln axis Deviation from a straight line

Using supports I and III as fixed points (0), the current inclination of the kiln was calculated to be: 3.474%

2

Positive deviations mean that the kiln axis measured is at a higher position than the straight line. Negative deviations mean that it is at a lower position.

3

Positive deviations mean that the kiln axis measured is farther away from the basis line of the measurement (the X-axis, please see the figure in section (5.7)) than the straight line. Negative deviations mean that it is closer to the basis line.

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Fig. 14 below shows a schematic illustration of the kiln axis measured.

Fig. 14: Kiln axis measured (schematic).

(5.7.2) Kiln Axis - Calculations The deviation of the kiln axis from its optimum shape affects the supports as well as the kiln shell and the live rings. To illustrate the consequences, FLS has calculated the load on the bearings for the supporting rollers and the stresses and ovality in kiln shell and live rings. The calculations have been performed for both the measured and the recommended kiln axis, and the results should be evaluated in relation to the following values which apply to the design of a new FLS kiln: * * * * * * *

Longitudinal bending stress in the clear span of the kiln shell ................. Tangential bending stress in kiln shell under live rings ............................ Tangential bending stress in live rings....................................................... Hertz pressure ............................................................................................. Relative FLS ovality in kiln shell............................................................... Nies ovality in live rings............................................................................. Load on bearings.........................................................................................

30 N/mm² 30 N/mm² 60 N/mm² 440 N/mm² 0.30 % 0.20 % 4.4 N/mm²

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Please note that the above value of 4.4 N/mm² corresponds to a bearing load of 100%. As far as the loads on the bearings of this kiln are concerned, please see the table below. -- o -The results of a calculation are shown in the tables below. In this calculation, the horizontal component of the kiln axis is taken as straight, and the vertical component is taken as the kiln axis measured.

Kiln axis measured

Recommended kiln axis

Load on bearings

Load on bearings

(%)

(%)

Support I

38

23

Support II

62

71

Support III

59

55

FLS calculation

Kiln axis measured

Recommended kiln axis

Bending stress in live ring

Hertz pressure

Bending stress in live ring

Hertz pressure

(N/mm²)

(N/mm²)

(N/mm²)

(N/mm²)

Support I

18

269.9

16

258.1

Support II

40

393.3

47

423.4

Support III

40

384.0

36

369.2

FLS calculation

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Kiln axis measured

Recommended kiln axis

Ovality

Ovality

Live ring

Kiln shell 4

Live ring

Kiln shell 4

(%)

(%)

(%)

(%)

Support I

0.07

0.19

0.05

0.16

Support II

0.13

0.26

0.14

0.29

Support III

0.12

0.32

0.11

0.31

Comments on the kiln axis measured: The greatest longitudinal bending stress calculated for the kiln shell is 18.2 N/mm² located 9820 mm from the middle of live ring I in the direction of the kiln inlet at the transition between the 25 mm and 30 mm thick kiln sections. This bending stress level is acceptable (please see the above design values). Comments on a straight kiln axis: The greatest longitudinal bending stress calculated for the kiln shell is 12.9 N/mm² located 900 mm from the middle of live ring III in the direction of the kiln outlet at the transition between the 28 mm and 57 mm thick kiln sections. This bending stress level is acceptable (please see the above design values). The values resulting from our calculations of the kiln axis measured and of a straight vertical kiln axis are almost identical. Consequently, we do not recommend any adjustment of the vertical kiln axis measured. The horizontal kiln axis deviates 2 mm from a straight line at support II which is within the permissible range of variation of the method of measurement used. Therefore no adjustment is to be made at this support.

4

This degree of ovality corresponds to the live ring migration measured.

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(6) Visual Inspection The visual inspection constitutes an important part of the mechanical kiln inspection. Its main objective is to give a description of the present, mechanical condition of the kiln, including where and how it deviates from the original specifications as given in drawings, instruction manuals, etc. In addition to design modifications, such indication of deviations can also cover position and propagation of cracks and wear. This kind of knowledge of the kiln components is essential for a reliable evaluation of how the present, mechanical, operational conditions affect the availability of the kiln and how the operational conditions can be improved. Actions to be taken as soon as possible: A very dusty environment is detrimental to the operation of any plant, and this kiln is no exception. A real effort should be made to cure this problem and allow the plant to function in a cleaner situation. The auto greaser at the inlet seal should be seen to be working and supplying the seal with grease (Mobile Temp 1) as discussed with Mr N. Appleyard at the plant. The spray nozzles lubricating the gear rim should be cleaned and a test carried out to determine whether the spray pattern is in accordance with the specifications. Spray against a white sheet at set distance etc. Normal checks in respect of air requirements, spray periods/frequency, and dosage of lubricant should be carried out as discussed with Mr N. Appleyard at the plant. Please note: From the hand-written notes on the control panel, the current spray period has increased from the earlier setting.

(6.1) Kiln Shell Our visual impression of the kiln was that the kiln shell surface was without bulges or deformations. There were only few signs of thermal overload in the burning zone. Thermal deformations in areas with welds may cause cracks. Therefore, during shutdowns, welds and areas close to welds should always be checked for crack formation. No cracks were observed in the welds on the parts of the kiln shell that could be inspected from gangways, platforms, or from the ground.

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There are remnants of weld material in a few places on the kiln shell. These welds stem from the erection of the kiln and from hooks for lifting of jacks etc. All such remnants must be ground off, and the surface must be checked for cracks, as such remnants (even if they have been present for many years) are potential starting points of cracks in the kiln shell.

(6.1.1) Kiln Shell - Side Guides and Live Ring Supporting Blocks Side guides and live ring supporting blocks at supports I and II: The original side guides and live ring supporting blocks at supports I and II have been replaced by the design now used by FLS for new kilns. The problem is, however, that the shims installed under the live ring supporting blocks tend to slide out. FLS is aware of the problem, and minor design modifications have therefore been introduced. Please see Enclosure 7, point (7). Support I: *

Welds between side guides and live ring supporting blocks: No cracks were observed in the welds between the live ring supporting blocks and the side guides.

*

Bolts for live ring supporting blocks: All bolts and lock washers were intact.

*

Live ring supporting blocks: No cracks were observed in the live ring supporting blocks.

Support II: *

Welds between side guides and live ring supporting blocks: No cracks were observed in the welds between the live ring supporting blocks and the side guides.

*

Bolts for live ring supporting blocks: All bolts and lock washers were intact.

*

Live ring supporting blocks: No cracks were observed in the live ring supporting blocks.

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Support III: *

Welds between side guides and live ring supporting blocks: No cracks were observed in the welds between the live ring supporting blocks and the side guides. The side guides on the outlet side are worn and should be replaced.

*

Bolts for live ring supporting blocks: All bolts and lock washers were intact.

*

Live ring supporting blocks: No cracks were observed in the live ring supporting blocks.

(6.2) Live Rings Safety guards: Due to the safety guards installed, it was not possible to evaluate contact conditions between the live rings and the supporting rollers at any of the supports. The guards located between live ring and supporting rollers on the side where live ring and supporting rollers move downwards should be removed as they do not, in our opinion, serve any safety-related purpose. The guards located on the other side should be modified in such a way that checks of the contact conditions can be carried out. Live ring I: The condition of the rolling surface of this live ring is satisfactory. Insignificant pitting formation was noted. The surface of the life ring is almost plane. Rolling-out was noted on the inlet side of the live ring (3 mm). No rolling-out on the outlet side. Live ring II: The condition of the rolling surface of this live ring is satisfactory. Much, slight pitting formation was noted, but this is of no consequence.

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The surface of the life ring is almost plane. Rolling-out was noted on the inlet side of the live ring (1 mm). No rolling-out on the outlet side. Live ring III: The condition of the rolling surface of this live ring is satisfactory. Slight pitting formation was noted. At the present moment, however, we do not expect it to cause any problems. The surface of the life ring is almost plane. No rolling-out was noted on the inlet side of the live ring. The surface of the taper section of the live ring is in satisfactory condition. It has been worn into slightly concave configuration.

(6.3) Supporting Rollers Graphite lubrication between live rings and supporting rollers: The graphite lubrication equipment should be cleaned and tested. Too much set clinker dust and oil remnants (support III) prevent the free movement of the graphite blocks. We definitely recommend that graphite be the only lubricant applied on the rolling surfaces. Support I: Both supporting rollers are of the anvil type. The condition of the rolling surfaces of both supporting rollers is satisfactory. The surface of the left-hand roller is almost plane. The right-hand one has been worn into concave configuration (1 mm). Rolling-out was observed on the inlet side of the right-hand roller (5 mm). No rolling-out on the outlet side. Rolling-out was observed on the inlet side of the left-hand roller (8 mm). No rolling-out on the outlet side.

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Support II: The right-hand supporting roller is of the box type whereas the left-hand one is of the anvil type. The condition of the rolling surfaces of both supporting rollers is satisfactory. The surface of the left-hand roller is almost plane. The right-hand one has been worn into slightly concave configuration. No rolling-out was observed on the sides of any of the supporting rollers. Support III: Both supporting rollers are of the box type. The condition of the rolling surface of the left-hand supporting roller is satisfactory. So is the condition of the rolling surface of the right-hand one, but incipient pitting formation was noted on its surface. The surface of the left-hand roller has been worn into concavo-convex configuration (0.5 - 1 mm). The surface of the right-hand one has been worn into concave configuration (2 mm). No rolling-out was observed on the sides of any of the supporting rollers. -- o -The above measurements of the rolling surfaces were taken with a straightedge and therefore do not tell whether the supporting rollers and live rings are also conical. We recommend that profile measurement of the rolling surfaces of supporting rollers and live rings be taken in order to determine the degree of concavity/convexity/tapered wear. Measuring of the surfaces can be carried out with the equipment shown in the sketch attached (please see Enclosure 8) and by using the work sheets attached as Enclosures 9a - c, but this measuring equipment can only be used for checking the surfaces of the supporting rollers. It is possible, however, to check the surfaces of the live rings with some accuracy by means of a straightedge. The straightedge is placed at the top of the live ring. Then the distance from the straightedge to the kiln shell is measured (both on the inlet side and on the outlet side of the live ring) and also from the straightedge to the surface of the live ring. These measurements will give a pretty good picture of the surface of the live ring. We normally recommend machining when the conical and/or concave/convex configuration of supporting rollers and live rings exceed 0.5 mm. Supporting rollers and live rings should also be machined when their mutual area of contact is reduced by 20 per cent.

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If, for instance, the measurements show that one or more supporting rollers should be machined, also the live rings should in all probability be machined. If only the supporting rollers are machined, because this is a relatively easy job not requiring any special lathe, problems will arise on the long view. Combined with the poor surface of a live ring, the good surface of a supporting roller will soon be damaged.

(6.4) Bearings for Supporting Rollers General remarks: In order to prevent all fixing and adjusting screws of the bearing housings from being covered by set clinker dust, we recommend that they be coated with grease and wrapped up in sackcloth or the like. Regular cleaning on the foundations should be introduced owing to the extremely dustinfected atmosphere (dust especially coming from kiln No. ..). The standard of cleaning should in particular be enhanced around the bearing housings, in the troughs under the supporting rollers, and on the caps of the bearings. The dust has a directly damaging effect on live rings, supporting rollers, and bearings. The rubber sleeves around the inlets of the cooling water pipes into the bearing housings cover openings which are notoriously very sensitive areas where dust can penetrate into the lubricating oil. The sleeves should be replaced if they are cracked or defective in any other way. As an extra precautionary measure against ingress of dust into the bearings at the rubber sleeves, a layer of silicone can be applied between rubber sleeve and bearing housing. -- o -The following comments and recommendations apply to the bearings for the supporting rollers at the respective supports. As to numbering of the bearings, please see Fig. 15 overleaf. Support I: Bearing No. 1: No comments except that there is some dust in the bearing. Bearing No. 2: No comments except that there is a little dust in the bearing. Bearing No. 3: No comments except that there is a little dust in the bearing. Bearing No. 4: No comments except that there is some dust in the bearing.

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Bearing 3

Inlet

Right

Left

Bearing 4

Bearing 2

Outlet

Bearing 1

Fig. 15: Numbering of bearings for supporting rollers. Support II: Bearing No. 1: The oil scraper and the felt seal between bearing housing and journal could not be inspected as the inspection cover close to the supporting roller cannot be opened. The cover knocks against the shield fitted alongside live ring and supporting roller. The shield should be modified to enable inspection of the bearing. In spite of the above, we saw some dust in the bearing. Bearing No. 2: No comments except that there is some dust in the bearing. Bearing No. 3: No comments except that there is a little dust in the bearing. Bearing No. 4: No comments except that there is some dust in the bearing. Support III: Bearing No. 1: No comments except that there is a little dust in the bearing. Bearing No. 2: No comments except that there is a little dust in the bearing. Bearing No. 3: The oil scraper is missing. Bearing No. 1: The oil scraper and the felt seal between bearing housing and journal could not be inspected as the inspection cover close to the supporting roller cannot be opened. The cover knocks against the shield fitted alongside live ring and supporting roller. The shield should be modified to enable inspection of the bearing.

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(6.5) Drive Station The drive station is relatively smooth in operation, but like the rest of the inlet end of the kiln, it is suffering from high levels of dust settlement, mainly from the inlet end of the adjacent kiln. Something should be done about this continued problem. The basic gearing is similar to the gearing inspected in (year), but some changes have occurred. In (month/year), a new drive pinion (non-FLS), intermediate gear/pinion, shafts, and associated bearing liners were installed. The existing gear rim and spring plates were purchased by the client direct from …….., in (year) and were erected by others sometime later. The profile of the gear rim teeth is still satisfactory, and wear on the contact surfaces is uniform across the tooth width and consistent with the prevailing situation. Burrs are evident on the tooth tips and on the ends of the teeth, showing that the profile is gradually changing and hence producing these burrs (metal flow). Some old pitting and surface disturbance have occurred at the pitchline of the teeth, but this is not altogether surprising where there is a rolling but little or no sliding action, and initial pitting quite often occurs. Furthermore, when pitting occurs, the metal particles that fall out can with the help of the lubricant get caught up in the mesh and cause some disturbance to the tooth surfaces. The pinion which as stated above is relatively new has a full profile with very mild tooth tip burrs. Some incipient pitting is evident along the pitchline on the inlet side of the teeth. This pitting is most likely the result of some mild misalignment with the gear rim, particularly in the early stages, resulting in higher than normal surface pressure. The rest of the pinion contact surfaces are smooth and polished. It does appear, however, that the pinion has moved to a position downhill similar to that observed during the (year) inspection, but the situation needs confirming when the kiln is stopped and it is safe to do so. The excessive axial wobbling of the gear rim has no doubt some influence on this situation. The intermediate pinion and spur wheel appear to be operating satisfactorily. However, the lubricant in the relevant sump for these components looks rather semi-solid rather than semi-fluid, no doubt because of some dust contamination and a certain degreee of solidifying through the heat of the kiln. The lubricant used here is Mobilgear OGL 007, a specialist semi-fluid, open-gear lubricant with extreme pressure additives and finely dispersed graphite for load carrying. Lubrication of the gear rim is via four spray nozzles using Krafft KGP-2/P grease which is a special, adhesive grease with high concentration of solid lubricant for highly loaded open gears regularly lubricated by automatic spraying system.

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All the shaft bearings are still to a greater or lesser degree contaminated with dust. Access is via the poorly sealed inspection covers. The upper bearing of the main drive pinion shaft is suffering from a bad oil leak. All air bleed holes in the oil level sight glass top caps are blocked. The intermediate pinion and spur wheel are similarly suffering from some dust contamination as the sliding inspection cover in the top casing is an ideal candidate for entry of dust, and also a safety hazard. The gear rim guard is open to dust contamination, and the gear rim side scrapers are virtually non-existent. The kiln main drive gearbox appears to be a little low on oil. The barring gear oil level is satisfactory. The gear oil type used in both components is Mobilgear 634 and appears to be clear and full-bodied. The drive torsion shaft/membrane coupling have non-FLS membranes with the result that the shaft is running eccentrically.

(6.6) Thrust Device A hydraulic thrust roller is located at support III.

Fig. 16: Hydraulic thrust device.

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The hydraulic thrust device is dimensioned to be capable of absorbing all of the axial thrust from the kiln during operation or barring, allowing all supporting rollers to be placed parallel to the kiln axis. However, in order to secure axial, mechanical balance of the kiln, the supporting rollers are usually skewed so that approx. 30% of the axial thrust from the kiln is apportioned evenly between them while the thrust device absorbs the remaining 70%. The pressure in the pump station of the hydraulic thrust device should normally range between 40 and 60 bar. The surface of the taper section of the live ring is in good condition. It has been worn into slightly concave configuration. The taper rolling surface of the thrust roller is also in satisfactory condition. It has been worn into convex configuration (approx. 0.5 mm). Contact conditions between live ring and thrust roller are good. We recommend thorough cleaning of the thrust device, and seals and piping system should be checked and reconditioned in order to avoid oil spillage. Moreover, both the top side and the bottom side of the thrust roller should be inspected for cracks at least once a year as cracks are more easily detected if the thrust roller is clean.

(6.7) Axial, Mechanical Balance of the Kiln The concept of “axial, mechanical balance” covers the way in which a balance between the various elements of axial thrust on the kiln is achieved. The axial thrust stems from four different sources: * The gravitational pull has an axial component arising from the inclination of the kiln. This axial component exerts a constant, downhill thrust on the kiln. * The reaction from the thrust roller in the opposite direction of the above-mentioned gravitational pull. The primary task of this reaction is to counterbalance the gravitational pull, but it also has to absorb any other downhill, axial thrust. This means that the function of the thrust roller is to secure the position of the kiln/live rings on the supporting rollers.

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* Axial thrust resulting from the contact between supporting rollers and live rings. Such thrust that may become rather substantial is generated if the axes of rotation of live rings/kiln and supporting rollers are not parallel, i.e. if a supporting roller is in a skew position and/or if its inclination deviates from that of the kiln in this particular place. * Wear also affects the axial, mechanical balance of the kiln. If rolling surfaces have been worn into concave, convex, or conical configurations, meaning that they are no longer truly cylindrical, it may be difficult or even quite impossible to attain axial, mechanical balance in a way that ensures a level of internal forces being as low as possible. In such cases, supporting rollers and live rings should be machined. Machining can be carried out during normal kiln operation by means of equipment that can be purchased or hired from FLS. When the above irregularities caused by wear have been eliminated, the supporting rollers can be adjusted to a position almost parallel to the kiln axis. In case of FLS kilns, this adjustment can be made on the basis of measurements taken with the equipment for measurement of the axial thrust developed by FLS for this specific purpose. With this equipment it is possible to attain optimum axial, mechanical balance of the kiln so that supporting rollers and thrust device absorb their respective share of the axial thrust exerted by the kiln. Under these conditions, the contact faces between live rings and supporting rollers should be lubricated with dry graphite only. If leaving the limited and slow, axial movements made by the rotary kiln in relation to the thrust device out of account, the kiln is always in axial, mechanical balance. This means that the resulting, axial thrust from the kiln is insignificant. However, this insignificant, axial thrust may on the one hand be composed of a number of unacceptably large, internal forces acting in mutually opposite directions (e.g. caused by incorrect skewing and/or inclination of the supporting rollers) subjecting the bearings to heavy thrust loads and increased risk of overheating. On the other hand, the resulting, axial thrust from the kiln may also be composed of acceptable, foreseeable, internal forces. For the sake of the availability of the kiln, it is obvious that the latter situation is to be preferred.

(6.8) Inlet Seal The inlet seal is spring loaded and supported on a vertical hanger support on either side. The seal joint is relatively close but operating dry. There is very little evidence of grease lubrication. The seal has an auto greaser but the fault light is on continuously. As found during the previous inspection, runout at the seal gives a variation of some 30 - 40 mm compared with approx. 20 mm during the inspection in (year).

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(6.9) Outlet Seal The outlet lamella seal looks fine. All the lamella are in place, have the correct shape, and are in close contact with the wear ring. The total runout variation at this wear ring is in the order of 25 mm as compared with 12 mm previously. A check on the adjacent kiln shell indicated a similar reading of 25 mm. The wear ring on the casing for air has been coated with low-thermal coating through an arc spray patented by Eutectic Castolin Group. The deposit has a surface hardness of 600 HV and will work-harden to 1100 HV.

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