lmbo^qfkd fkpqor`qflk Services, Wärtsilä Finland Oy Engine section 10, 11 & 14
Engine type
W32, W34SG
Ref. WFI–S/Joku
Date 20.11.2006
Issue 01
Document No. 3210Q046
Page 1(8)
Bearing assessment for WÄRTSILÄ ® 32 based engines General
The purpose of these instructions is to define assessment criteria for the main bearings, big end bearings, small end bearings, and camshaft bearings of the WÄRTSILÄ ® 32, 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 an influence on the visual wear pattern.
Figure 1. Bearing types.
Inspection intervals
Bearings are to be inspected according to the maintenance schedule. See chapter 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 during operation - Proper lubricating oil care including regular and optimized separation routines - Proper maintenance of lube oil filters - Clean working conditions while working inside the engine - Regular draining and cleaning of lube oil tanks
Wärtsilä Finland Oy Services, Vaasa
P.O. Box 252 (Tarhaajantie 2) FIN-65101 Vaasa, Finland
Telecop. +358 10 709 1847 Telecop. +358 10 709 1380
Tel. +358 10 709 0000
Wärtsilä Finland Oy Services, Turku
P.O. Box 50 (Stålarminkatu 45) FIN-20811 Turku, Finland
Telecop. +358 10 709 3279 Telecop. +358 10 709 3410
Tel. +358 10 709 0000
Business ID 0773744-3 Registered Office: Vaasa
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Bearing designations
Figure 3. Cylinder numbers.
Figure 4. Bearing numbers.
After fitting a bearing, the bearing temperatures have to be checked and confirmed to be even between corresponding bearings: -
Wear pattern
Page 2(8)
It is recommended that new big end bearings and main bearings are marked with an electrical engraving pen on the side edge of the bearing (figure 2). See also chapter 00 of the instruction manual. The big end bearing should be marked with the cylinder number (figure 3) and the main bearing should be marked with the bearing number (figure 4).
Figure 2. Bearing shell
Safety check
Document No. 3210Q046
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 temperature measuring device.
The typical wear pattern of sliding bearings is slight polishing over broad arc on the most loaded area. In bearings with a flash layer the normal wear pattern is that the flash layer is worn off from the most loaded area. See the wear pattern of a bearing shell in figure 5. Wear pattern on the small end bearing of the connecting rod differs from the other sliding bearings. On the small end bearing the typical wear pattern is two parabolas closing to each other in the middle of the bearing on the most loaded side. See wear pattern in figure 6.
Figure 5. Bearing shells
Figure 6. Small end bearing.
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Wear indication
Document No. 3210Q046
Page 3(8)
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 shell thickness. Measure the thickness on a few points on both sides (A and C) as shown in figure 7. See measurement record 3210V035. See also engine manual section 10.3.2 for more limits.
Figure 7. Measuring points on Figure 8. Free spread of the bearing the bearing shell. shell. Trimetal main bearing Visual inspection is the proper wear indicator for trimetal bearings. If nickel-dam is exposed on trimetal bearings, the bearing has to be changed (A nickel dam can be identified by scratching the sliding surface with 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 the bearing has to be at least 0.5 mm bigger than the inner diameter of the bearing housing, see measurement record 3210V035.
Small end bearing Wear of small end bearings can be indicated by a visual inspection as shown in figure 9. See the Measurement Records for small end bearing and big end bearing bore: - 3211V017 (WÄRTSILÄ ® 32) - 3411V033 (WÄRTSILÄ ® 16V34SG and 20V34SG)
Figure 9: Measuring point of the small end bearing.
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Document No. 3210Q046
Page 4(8)
Replacement guidelines It is recommended that the bearing is replaced if one of the below mentioned criteria is fulfilled: 1. 2. 3. 4. 5.
The thickness of the bearing is under the wear limit. The nickel layer is visible (trimetal bearings) Fretting on the back of the bearing. Fatigue marks on the sliding surface. Cavitation has penetrated through the bearing layer (minor cavitation is allowed). 6. Rough sliding surface: More than a few scratches or cavitation has worn the bearing on a wide area. 7. Corrosion on the bearing. 8. The recommended replacement interval of the bearing has been reached.
Notes: -
Damage types
In case of doubt of a bearing condition, the bearing should be replaced to avoid consequential damage. If there are minor scratches on the journal, it can be polished e.g. with a 500 grid emery paper. Bearings are formed to the housing. Thus unnecessary dismantling of the bearing should be avoided.
Some typical sliding bearing damage is described below:
Smearing, wiping Smearing and wiping is bearing damage related to adhesion. This occurs if there 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.
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Document No. 3210Q046
Page 5(8)
Cavitation Cavitation is a phenomenon related to vaporisation pressure of the lube oil. Cavitation bubbles are formed when lube oil pressure decreases below the vaporisation pressure. When the local pressure rises above the vaporisation pressure, 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 instance water/air in the oil, high oil temperature or dirty oil).
Cavitation damages are shown in figures 11 and 12.
Figures 11. Cavitation damages on bimetal
bearing.
Figure 12. Cavitation damages
on trimetal bearing.
Fatigue Fatigue in the bearing surface layer begins with micro cracks, which are hardly visible without a microscope. These cracks will grow until the bearing layer 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 bearing failure. The bearings are to be replaced whenever fatigue marks are visible. Fatigue damage is shown in figures 13 and 14.
10 mm
Figure 13. Fatigue damage on bimetal bearing.
10 mm
Figure 14. Fatigue damage on trimetal bearing
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Document No. 3210Q046
Page 6(8)
Solid particles If solid particles are bigger than the oil film thickness, they will scratch the sliding surfaces or get embedded in the overlay material. See figures 15 and 16. 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
10 mm
Figure 15. Embedded particle on
10 mm
Figure 16. Scratch on trimetal bearing.
bimetal bearing.
Corrosion Corrosion is the result whenever chemical reaction with the environment predominates. 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 on bimetal bearing.
Figure 18. Corrosion damage on trimetal bearing.
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Document No. 3210Q046
Page 7(8)
Fretting Fretting might occur on the backside of a bearing if there is micro movement between 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 might occur due to following reasons: -
Journal shape error Shaft misalignment Housing shape error
If this kind of wear pattern occurs, the reason should be investigated and corrected if necessary.
Figure 20. Polished side edges.
Services, Wärtsilä Finland Oy
Operating instruction Issue 01
Document No. 3210Q046
Page 8(8)
Bearing assembly related problems If the bearing is not properly assembled in the housing, the bearing might be damaged (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 housing and 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 the back of the bearing.
Figure 21. Polished area on the bearing, because of dirt between the bearing and the bearing housing.
Letter distribution
Wärtsilä Service Network and owners/operators of concerned engines.
Letter validity
Until further notice.
2006
Wärtsilä 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. Wärtsilä Finland Oy makes no representation, warranty (express or implied) in this publication and assumes no responsibility for the correctness, errors or omissions 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 a defect in the engine, but merely as an improvement of the engine and/or the maintenance procedures relating thereto. Any actions by the owner/operator as a result of the recommendations are not covered under any warranty provided by Wärtsilä and such actions will thus be at the owners/operators own cost and expense. NO LIABILITY WHETHER DIRECT, INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL, IS ASSUMED WITH RESPECT TO THE INFORMATION CONTAINED HEREIN. THIS PUBLICATION IS CONFIDENTIAL AND INTENDED FOR INFORMATION PURPOSES ONLY.
