wartsila 32 bearing assessment

7/22/2019 Wartsila 32 bearing assessment

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Services,Wrtsil Finland Oy

Engine section Engine type Ref. Date Issue Document No. Page

10, 11 & 14 W32, W34SG WFIS/Joku 20.11.2006 01 3210Q046 1(8)

Wrtsil Finland Oy P.O. Box 252 (Tarhaajantie 2) Telecop. +358 10 709 1847 Tel. +358 10 709 0000 Business ID 0773744-3Services, Vaasa FIN-65101 Vaasa, Finland Telecop. +358 10 709 1380 Registered Office: Vaasa

Wrtsil Finland Oy P.O. Box 50 (Stlarminkatu 45) Telecop. +358 10 709 3279 Tel. +358 10 709 0000Services, Turku FIN-20811 Turku, Finland Telecop. +358 10 709 3410

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Bearing assessment for WRTSIL32 basedengines

General The purpose of these instructions is to define assessment criteria for themain bearings, big end bearings, small end bearings, and camshaftbearings of the WRTSIL32, 16V34SG and 20V34SG engines.

See the engine instruction manual for further information:

- Maintenance schedule (chapter 04)

- Clearances and wear limits (chapter 06)

- Bearing assembly instructions (chapters 10 and 11).

Bearing types Bearing types concerned are shown in figure 1. The type of bearing has aninfluence on the visual wear pattern.

Figure 1. Bearing types.

Inspection intervals Bearings are to be inspected according to the maintenance schedule. Seechapter 04 in the engine instruction manual.

Bearing lifetime Bearing lifetime will be influenced by:

- Engine load profile and operating conditions

- Fuel and lube oil properties

- Adequate prelubrication before starting and sufficient lubrication duringoperation

- Proper lubricating oil care including regular and optimized separationroutines

- Proper maintenance of lube oil filters

- Clean working conditions while working inside the engine- Regular draining and cleaning of lube oil tanks


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Services,Wrtsil Finland Oy Operating instruction

Issue Document No. Page01 3210Q046 2(8)

Bearing designations It is recommended that new big end bearings and main bearings aremarked with an electrical engraving pen on the side edge of the bearing(figure 2). See also chapter 00 of the instruction manual. The big endbearing should be marked with the cylinder number (figure 3) and the mainbearing should be marked with the bearing number (figure 4).

Figure 2. Bearing shell Figure 3. Cylinder numbers. Figure 4. Bearing numbers.

Safety check After fitting a bearing, the bearing temperatures have to be checked andconfirmed to be even between corresponding bearings:

- Run the engine for about 5 minutes up to nominal speed with no load.

- Follow the engine behaviour.

- Stop and check the bearing temperatures by hand or with a temperaturemeasuring device.

Wear pattern The typical wear pattern of sliding bearings is slight polishing over broad arcon the most loaded area. In bearings with a flash layer the normal wearpattern is that the flash layer is worn off from the most loaded area. See thewear pattern of a bearing shell in figure 5.

Wear pattern on the small end bearing of the connecting rod differs from theother sliding bearings. On the small end bearing the typical wear pattern istwo parabolas closing to each other in the middle of the bearing on the mostloaded side. See wear pattern in figure 6.

Figure 5. Bearing shells Figure 6. Small end bearing.


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Wear indication Big end bearing

Big end bearings should be replaced whenever the bearing housing is split.Main bearing

Bimetal main bearing

Measuring is a proper wear indicator for bimetal bearings only.A ball anvil micrometer should be used to measure the bearing shellthickness. Measure the thickness on a few points on both sides (A and C)as shown in figure 7. See measurement record 3210V035. See also enginemanual section 10.3.2 for more limits.

Figure 7. Measuring points onthe bearing shell.

Figure 8. Free spread of the bearingshell.

Trimetal main bearingVisual inspection is the proper wear indicator for trimetal bearings.If nickel-dam is exposed on trimetal bearings, the bearing has to bechanged (A nickel dam can be identified by scratching the sliding surfacewith a sharp tool. The bearing overlay is much softer than the nickel dam).

Free spread of the bearing shell

Free spread of the bearing shell is shown in figure 8. The free spread of thebearing has to be at least 0.5 mmbiggerthan the inner diameter of thebearing housing, see measurement record 3210V035.

Small end bearingWear of small end bearings can be indicated by a visual inspection asshown in figure 9. See the Measurement Records for small end bearing andbig end bearing bore:

- 3211V017 (WRTSIL32)

- 3411V033 (WRTSIL16V34SG and 20V34SG)

Figure 9: Measuring point of the small end bearing.


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Replacement guidelines

It is recommended that the bearing is replaced if one of the belowmentioned criteria is fulfilled:

1. The thickness of the bearing is under the wear limit.

2. The nickel layer is visible (trimetal bearings)

3. Fretting on the back of the bearing.

4. Fatigue marks on the sliding surface.

5. Cavitation has penetrated through the bearing layer (minor cavitation isallowed).

6. Rough sliding surface: More than a few scratches or cavitation has wornthe bearing on a wide area.

7. Corrosion on the bearing.8. The recommended replacement interval of the bearing has been

reached.

Notes:

- In case of doubt of a bearing condition, the bearing should be replacedto avoid consequential damage.

- If there are minor scratches on the journal, it can be polished e.g. with a500 grid emery paper.

- Bearings are formed to the housing. Thus unnecessary dismantling ofthe bearing should be avoided.

Damage types Some typical sliding bearing damage is described below:

Smearing, wiping

Smearing and wiping is bearing damage related to adhesion. This occurs ifthere is metal-to-metal contact due to failed oil film. Possible reasons are:

- Inadequate lubrication (e.g. starting without pre-lubrication)

- Low viscosity of lube oil

- High bearing load

- Small clearances (e.g. inadequate fitting of bearing housing)

Bearings as shown in figure 10 are to be replaced.

Figure 10. Smearing / wiping damage.


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Cavitation

Cavitation is a phenomenon related to vaporisation pressure of the lube oil.Cavitation bubbles are formed when lube oil pressure decreases below thevaporisation pressure. When the local pressure rises above the vaporisationpressure, the bubbles will collapse and cause erosion wear of the material.

Cavitation phenomenon is influenced by:

- Big clearance

- Incorrect lube oil pressure

- Vaporisation pressure of the lube oil has decreased (for instancewater/air in the oil, high oil temperature or dirty oil).

Cavitation damages are shown in figures 11 and 12.

Figures 11. Cavitation damages on bimetalbearing.

Figure 12. Cavitation damageson trimetal bearing.

Fatigue

Fatigue in the bearing surface layer begins with micro cracks, which arehardly visible without a microscope. These cracks will grow until the bearinglayer starts to peel off in small flakes.

Fatigue is influenced by:

- Low viscosity of lube oil

- Bearing overload

- Improper bearing clearance

- High lube oil temperature

Fatigue on the bearing develops rather fast and will likely lead to bearingfailure. The bearings are to be replaced whenever fatigue marks are visible.Fatigue damage is shown in figures 13 and 14.

Figure 13. Fatigue damage onbimetal bearing.

Figure 14. Fatigue damage on trimetalbearing

10 mm10 mm


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Solid particles

If solid particles are bigger than the oil film thickness, they will scratch thesliding surfaces or get embedded in the overlay material. See figures 15 and16.

The origin of solid particles could be:

- Dirt from overhauling

- Particles passing the filtrations

- Particles from the combustion process

- Wear particles from engine

Note: Proper filtration is essential for lube oil cleanliness

Figure 15. Embedded particle onbimetal bearing.

Figure 16. Scratch on trimetal bearing.

Corrosion

Corrosion is the result whenever chemical reaction with the environmentpredominates. Possible reasons for corrosion:- Lubrication oil (e.g. low BN or water in oil)- Storage

A bearing exposed to corrosion is to be replaced.

Figure 17. Corrosion damage onbimetal bearing.

Figure 18. Corrosion damage ontrimetal bearing.

10 mm10 mm


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Fretting

Fretting might occur on the backside of a bearing if there is micro movementbetween the housing and the bearing.

Possible reasons for fretting are:

- Low tightening torque of the hydraulic screws

- Low surface roughness

- Improper assembly of the bearing

- Reassembling of bearing with too low free spread

- Dirt between the bearing and the housing

Note: If fretting occurs, the bearing housing has to be dressed up before

mounting a new bearing.

Figure 19. Fretting damage on the back of the bearing.

Misalignment and shape errors

Misalignment and shape error wear pattern (polishing) on the bearing mightoccur due to following reasons:

- Journal shape error

- Shaft misalignment

- Housing shape error

If this kind of wear pattern occurs, the reason should be investigated andcorrected if necessary.

Figure 20. Polished side edges.


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Bearing assembly related problems

If the bearing is not properly assembled in the housing, the bearing might bedamaged (polishing, fatigue, wiping, etc.).

Most of the assembly errors are caused by:- Incorrect mounting (for instance big end bearing shells grip each other

during assembly)

- Remaining dirt and/or black staining (oil carbon deposit) on the housingand the bearing back surfaces

- Locating lug is not properly in its place

Usually this kind of error can also be identified by the contact pattern on theback of the bearing.

Figure 21. Polished area on the bearing, because of dirt between thebearing and the bearing housing.

Letter distribution Wrtsil Service Network and owners/operators of concerned engines.

Letter validity Until further notice.

2006 Wrtsil Finland Oy All rights reserved

No part of this publication may be reproduced or copied in any form or by any means (electronic, mechanical, graphic, photocopying,recording, taping or other information retrieval systems) without the prior written permission of the copyright holder. Wrtsil Finland Oymakes no representation, warranty (express or implied) in this publication and assumes no responsibility for the correctness, errors oromissions for information contained herein. Information in this publication is subject to change without notice.

Unless otherwise expressly set forth, no recommendation contained in this document is to be construed as provided due to adefect in the engine, but merely as an improvement of the engine and/or the maintenance procedures relating thereto. Any actionsby the owner/operator as a result of the recommendations are not covered under any warranty provided by Wrtsil and suchactions will thus be at the owners/operators own cost and expense.

NO LIABILITY WHETHER DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL, IS ASSUMED WITHRESPECT TO THE INFORMATION CONTAINED HEREIN. THIS PUBLICATION IS CONFIDENTIAL AND INTENDEDFOR INFORMATION PURPOSES ONLY.

wartsila 32 bearing assessment

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