Bearing Assessment for Wartsila 20

Service, Wärtsilä Finland Oy Käyttöohje Driftsinstruktion

Engine section Engine type Ref. Date Issue Document No. Page10, 11 & 14 W20 WFI�S 12.03.2004 01 2010Q003GB 1(9)

Wärtsilä Finland Oy P.O. Box 252 (Tarhaajantie 2) Telecop. +358 10 709 7355 Tel. +358 10 709 0000 Business ID 0773744-3Service, Vaasa FIN-65101 Vaasa, Finland Telecop. +358 6 356 7339 Registered Office: Vaasa

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

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Bearing assessment for WÄRTSILÄ® 20General The purpose of these instructions is to define assessment criteria for the

sliding bearings of the WÄRTSILÄ� 20 engines (including small endbearings, big end bearings, main bearings and camshaft bearings).See the engine manual for further information:- Maintenance schedule (chapter 4)- Clearances and wear limits (chapter 6)- Bearing assembly instructions (chapters 10 and 11).

Bearing types Possible bearing types of the engine are shown in figure 1. The type of thebearing has an influence on the visual wear pattern.

Figure 1. Bearing types.

Inspection intervals Bearings are to be inspected according to the maintenance schedule. Seechapter 4 in the Engine Instruction Manual.Bearings are formed to the housing and unnecessary bearing dismantlingshould be avoided.

Service, Wärtsilä Finland Oy Operating instruction

Issue Document No. Page01 2010Q003GB 2(9)

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 oil maintenance 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

Bearing designations It is recommended that new bearings are marked with an electricalengraving pen, see also chapter 00 of the instruction manual. The big endbearing should be marked with the cylinder number (figure 2) and the mainbearing should be marked with the bearing number (figure 3).

Figure 2. Cylinder numbers. Figure 3. Bearing numbers.

Safety check After fitting a bearing, the bearing temperatures has 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 temperature

measuring device.



Main bearing and big end bearing

Bearing typeBig end bearings and main bearings are bimetal type bearings. See fig. 1.

Wear patternThe typical wear pattern of bimetal sliding bearings is a slight polishing overa broad arc on the most loaded area.

Measurement of bearing shellA ball anvil micrometer should be used to measure bearing shell thickness.Measure the thickness on a few points on both sides (A and C) and thecentre line (B) of the bearing as shown in figure 4.Free spread of the bearing is shown in figure 5. The free spread of thebearing has to be bigger than the inner diameter of the bearing housing.See Measurement record 2010V005GB for main bearing and 2011V006GBfor big end bearing.

Figures 4. Measuring points on thebearing shell.

Figure 5. Free spread of the bearingshell.

Replacement guidelines for bearing shellsIt is recommended that the bearing is replaced if one of the belowmentioned criteria is fulfilled:1. Thickness of the bearing is under the wear limit.2. Fretting on the back of the bearing.3. Fatigue marks on the sliding surface.4. Cavitation has penetrated through the bearing layer (minor cavitation is

allowed).5. Rough sliding surface: More than a few scratches or cavitation has worn

the bearing on a wide area.6. Corrosion on the bearing.7. Recommended replacement interval of the bearing has been reached.

Notes:- In case of doubt of the bearing condition, the bearing should be

replaced to avoid consequential damage.- If there are scratches on the journal, it should be polished.



Small end bearing Bearing typeSmall end bearings are trimetal bearings with flash layer or solid bronzebearing bushes. See figure 1.

Wear patternTypical wear pattern of the small end bearings is two parabolas closing toeach other in the middle of the bearing on the most loaded side. In trimetalbearings the wear pattern is more visible. See wear patterns in figures 6and 7.

Figure 6. Trimetal bearing. Figure 7. Solid bronze.

Replacement of small end bearingSmall end bearings can be used until the wear limit has been reached. Thesmall end bearing to be measured as shown in figure 8. Inner diametershould be measured in 4 directions (numbers 1-4) on both edges (A and B)by using a dial gauge. See Measurement record 2011V007GB.

Figure 8: Measuring points of the small end bearing.



Camshaft bearing Bearing typeCamshaft bearings are bimetal or solid bronze bearing bushes and thrustbearing solid bronze bearing bushes. See figure 1.

Wear patternTypical wear pattern of the camshaft bearing is slight polishing on theloaded side of the bearing bush.

Replacement of camshaft bearingCamshaft bearings are recommended to be replaced according to themaintenance schedule.A bearing bush is to be measured in the housing. As shown in figure 9, theinner diameter of the bearing bush should be measured in 4 directions(numbers 1-4) on both edges (D and E) by using a dial gauge. SeeMeasurement record 2014V008GB.

Figure 9. Measuring points of bearing bush.

Damage types Some typical sliding bearing damage is described below:

Smearing, wipingSmearing 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, because this kind ofdamage might lead to fatigue.

Figure 10. Wiping damage.



CavitationCavitation 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 instance

water/air in the oil, high oil temperature or dirty oil).

Bearings as shown in figure 11 are to be replaced.

Figure 11. Cavitation damages.

FatigueFatigue 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 figure 12.

Figure 12. Fatigue damage.



Solid particlesIf solid particles are bigger than the oil film thickness, they will scratch thesliding surfaces or get embedded in the overlay material. See figure 13.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 13. Embedded particle (magnification 10x).

CorrosionCorrosion is the result whenever chemical reaction with the environmentpredominates. For example, an aluminium sliding surface is sensitive towater and cooling water additives.

A bearing exposed to corrosion is to be replaced.

Figure 14. Corrosion damage.



FrettingFretting might occur on the back of the bearing if there is micro movementbetween the housing and the bearing.Possible reasons for fretting:- Low tightening torque of the 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 beforemounting a new bearing.

Figure 15. Fretting damage on the back of the bearing.

Misalignment and shape errorsMisalignment 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 16. Polished side edges.



Bearing assembly related problemsIf the bearing is not properly assembled in the housing, the bearing mightbe 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 theback of the bearing.

Figure 17. Fatigue damage around the locating lug.

Warranty Unless otherwise expressly set forth, no recommendation contained in thisdocument is to be construed as provided due to a defect in the engine, butmerely as an improvement of the engine and/or the maintenanceprocedures relating thereto. Any actions by the owner/operator as a resultof the recommendations are not covered under any warranty provided byWärtsilä and such actions will thus be at the owners/operators own cost andexpense.

Letter distribution Wärtsilä Service Network and owners/operators of WÄRTSILÄ� 20engines.

Letter validity Until further notice.

Enclosures Measurement records 2010V005, 2011V006, 2011V007 and 2014V008.

2004 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 copyrightholder. Wärtsilä Finland Oy makes no representation, warranty (express or implied) in this publication and assumes noresponsibility for the correctness, errors or omissions for information contained herein. Information in this publication issubject to change without notice.

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.

Service, Wärtsilä Finland Oy

Engine section Engine type Ref. Date Issue Document No. Page10 Engine block 20 WFI�S 12.03.2004 01 2010V005GB 1(1)



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Installation name: Engine type: Engine No: Fuel viscosity (cSt): Ambient temperature: Engine running hours:

Main bearing shell (lower) Measuring points

Bearing shell ID:

Big end bearing nominal thickness = 7,405-7,420 mmBig end bearing wear limit = 7,36 mm

Measure with a ball anvil micrometer.Note: Pay attention not to press the measuring head in the running layer.

Bearing number1 2 3 4 5 6 7 8 9 10

A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3

Bearingthickness(deviation in1/100 mm)

C4 Component running hours: Remarks/ Manufact. No:

Crankshaft (journal) Measuring points

Shaft designations:

Bearing journal nominal diameter = 209,971-210,000 mmBearing journal diameter, wear limit = 209,900 mmBearing journal out of circularity, nominal = 0,015 mmBearing journal out of circularity, wear limit = 0,05 mmBearing journal taper, nominal = 0,02/100

The diameter to be measured in 4 directions, fill in the min and max measure in the table.

Bearing number1 2 3 4 5 6 7 8 9 10

D min D max E min E max F max

Journaldiameter(deviation in1/100 mm)

F max Component running hours: Remarks/ Manufact. No:

Date of measurement: Place: Name:


Engine section Engine type Ref. Date Issue Document No. Page11 Crank Mechanism 20 WFI�S 12.03.2004 01 2011V006GB 1(1)



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Big end bearing shell Measuring points

Bearing shell ID:

Big end bearing nominal thickness = 4,930-4,950 mmBig end bearing wear limit = 4,900 mm

Measure with a ball anvil micrometer.Note: Pay attention not to press the measuring head in the running layer.

Cylinder number1 2 3 4 5 6 7 8 9

A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3

Bearing shellthickness(deviation in1/100 mm)

C4 Component running hours: Remarks/ Manufact. No:

Crankshaft pin Measuring points

Shaft designation:

Crank pin nominal diameter = 179,975-180,000 mmCrank pin diameter, wear limit = 179,900 mmCrank pin out of circularity, nominal = 0,015 mmCrank pin out of circularity, wear limit = 0,05 mmCrank pin taper, nominal = 0,03/100

The diameter to be measured in 4 directions, fill in the min and max measure in the table.


D min D max E min E max F max

Pin diameter(deviation in1/100 mm)

F max Component running hours: Remarks/ Manufact. No:



Engine section Engine type Ref. Date Issue Document No. Page11 Crank Mechanism 20 WFI�S 12.03.2004 01 2011V007GB 1(1)



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Small end bearing Measuring points

Bearing bush ID:

Bearing nominal diameter, assembled = 90,050-90,102 mmBearing wear limit, assembled = 90,140 mm

Diameter of the bearing to be measured with a dial gauge.

Note: Pay attention not to damage the running layer.


A1 A2 A3 A4 B1 B2 B3

Bearingdiameter(deviation in1/100 mm)

B4 Component running hours: Remarks/ Manufact. No:

Gudgeon pin Measuring points

Pin designations:

Pin nominal diameter: = 89,990-90,000 mm

The diameter to be measured in 4 directions, fill in the min andmax measure in the table.


C min C max D min D max E min

Gudgeon pindiameter(deviation in1/100 mm)

E max Component running hours: Remarks/ Manufact. No:



Engine section Engine type Ref. Date Issue Document No. Page14 Valve Mechansim, Camshaft 20 WFI�S 12.03.2004 01 2014V008GB 1(1)



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Camshaft bearing Measuring points

Bearing designations:

Bearing nominal diameter, assembled = 140,125-140,190 mmBearing wear limit, assembled = 140,210 mm

Diameter of the bearing to be measured with a dial gauge.

Note: Pay attention not to damage the running layer.

Bearing number1 2 3 4 5 6 7 8 9 10

A1 A2 A3 A4 B1 B2 B3

Bearingdiameter(deviation in1/100 mm)

B4 Component running hours: Remarks/ Manufact. No:

Camshaft bearing piece Measuring points

Shaft designations:

Camshaft journal nominal diameter = 139,975-140,000 mm

The diameter to be measured in 4 directions, fill in the min andmax measure in the table.

Camshaft bearing piece to be measured with micrometer.

Bearing number1 2 3 4 5 6 7 8 9 10

C min C max D min

Camshaftdiameter(deviation in1/100 mm) D max Component running hours: Remarks/ Manufact. No:


Bearing Assessment for Wartsila 20

Documents

bearing assessment

bearing lifetime

bearing housing

bearing temperatures

bearing condition

bearing number figure

measurement of bearing

bearing shell thickness