Timken Bearing Damage Analysis With Lubrication Reference .

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Timken Bearing Damage Analysiswith Lubrication Reference Guide

2TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE 2015 The Timken Company

NOTEWARNINGFailure to observe the following warnings couldcreate a risk of death or serious injury.Proper maintenance and handling procedures are critical. Always followinstallation instructions and maintain proper lubrication.Never spin a bearing with compressed air. The rollers may be forcefully expelled.Overheated bearings can ignite explosive atmospheres. Special care mustbe taken to properly select, install, maintain, and lubricate bearings that areused in or near atmospheres that may contain explosive levels of combustiblegases or accumulations of dust such as from grain, coal, or other combustiblematerials. Consult your equipment designer or supplier for installation andmaintenance instructions.If hammer and bar are used for installation or removal of a part, use a mild steelbar (e.g., 1010 or 1020 grade). Mild steel bars are less likely to cause release ofhigh-speed fragments from the hammer, bar or the part being removed.WARNINGFailure to observe the following warnings couldcreate a risk of serious injury.Tensile stresses can be very high in tightly fitted bearing components.Attempting to remove such components by cutting the cone (inner race) mayresult in a sudden shattering of the component causing fragments of metal tobe forcefully expelled. Always use properly guarded presses of bearing pullersto remove bearings from shafts, and always use suitable personal protectiveequipment, including safety glasses.CAUTIONFailure to follow these cautions may result in property damage.Do not use excessive force when mounting ordismounting the unit.Follow all tolerance, fit, and torque recommendations.Always follow the Original Equipment Manufacturer’sinstallation and maintenance guidelines.Ensure proper alignment.Never weld housed units.Do not heat components with an open flame.Do not operate at bearing temperaturesabove 121 C (250 F).DISCLAIMERThis catalog is provided solely to give you analysistools and data to assist you in your product selection.Product performance is affected by many factorsbeyond the control of Timken. Therefore, you mustvalidate the suitability and feasibility of all productselections for your applications.Timken products are sold subject to Timken termsand conditions of sale, which include our limitedwarranty and remedy. You can find these atwww.timken.com/termsandconditionsofsale.Please consult with your Timken engineer formore information and assistance.Every reasonable effort has been made to ensurethe accuracy of the information in this writing, butno liability is accepted for errors, omissions or forany other reason.Do not use damaged bearings.Do not use damaged housed units.Warnings for this product line are in this catalog and posted onwww.timken.com/warnings. 2015 The Timken Company TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE3

Let’s face it – bearingswork in a tough world.Excessive contamination. Poor lubrication. Highheats. Heavy vibrations. These merely scratch thesurface of all the wear and tear your bearings gothrough on a given day.That’s where the knowledge and precision of Timkencome into play.Our sales and service engineering teams solveproblems and offer solutions for customers invirtually every industry. Couple this experiencewith a long-standing history in material science andtribology, and you gain a team of experts uniquelyqualified to help you analyze bearing damage.And we want to share this knowledge with you. Wedeveloped this reference guide to help you identifysome of the most common types of bearing damage,explaining the possible causes and discussing thenecessary actions needed to avoid them. We alsoinclude useful bearing references and lubricationguidelines you can follow.If your bearing damage goes beyond what we cover,or if you just need help getting started, call us. Ourservice engineers can work with you – often on-site –to get to the root cause of your problems. We evenoffer in-depth training that’s customized to yourspecific industry or application.It’s a tough world out there. Let us help you make yourbusiness roll forward more smoothly.4TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE 2015 The Timken Company

Table of ContentsPreparation and Approach to Bearing Damage Analysis . . . . . . . . . . . . . . . . . . . . 6Types of Bearing DamageWear – Abrasive Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Wear – Pitting and Bruising . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Wear – Grooving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Etching – Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Inadequate Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Fatigue Spalling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Excessive Preload or Overload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Excessive Endplay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Misalignment and Inaccurate Seat and Shoulder Machining . . . . . . . . . . . . . . . . 14Handling and Installation Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Damaged Bearing Cages or Retainers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16High Spots and Fitting Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Improper Fit in Housings or Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Brinell and Impact Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19False Brinelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Burns from Electric Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Cam Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Understanding Bearing LifeBearing Service Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Lubrication Reference GuideFactors that Impact Lubrication Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Lubrication Guidelines – Required Grease Quantity . . . . . . . . . . . . . . . . . . . . . . . . 26Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Types of Bearings and Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Tapered Roller Bearing Speed Capability Guidelines . . . . . . . . . . . . . . . . . . . . . . 30Temperature Guidelines for Roller Bearing Installation . . . . . . . . . . . . . . . . . . . . 31Cone Bore Growth Expansion Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Reference the Timken Industrial Bearing MaintenanceManual (Order No. 10213) for additional information.Conversion Equivalents for U.S. and Metric Measurements . . . . . . . . . . . . . . . . 33Conversion Chart Showing Millimeter, Fractional andDecimal Inch Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Temperature Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Timken Bearing Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Timken Product and Service Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2015 The Timken Company TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE5

Preparation and Approach toBearing Damage AnalysisBearing Damage: Overview of the FactsTimken analyzes bearings from operations across the world. Our bearingservice and repair specialists find that fully 50 percent of the bearingssubmitted to us haven’t reached their calculated lives.In some cases, the cause is contact fatigue (inclusion origin, pointsurface origin, geometric stress concentration and micro-spalling). In 90percent of the cases, though, the cause is non-fatigue factors, including: Foreign materials. Corrosion. Inadequate lubrication. Improper handling. Bad running conditions.If you’re concerned that your bearing isdeteriorating, look for the following signs: Vibrations – whether felt by hand or measuredwith a frequency analyzer. Abnormal noises. Displacement of rotational centerline. Running temperature increase. Odd smells. Lubricant deterioration. Lubricant leakage. Visual discovery during routinemaintenance check.Suggested Procedure for Bearing AnalysisFollow the steps below for an accurate and complete analysis wheninvestigating any bearing damage or system breakdowns. If you need help,contact one of our sales or service engineers.1. Gather operating data from bearing monitoring devices; analyze serviceand maintenance records and charts; and secure application diagrams,graphics or engineering drawings.2. Prepare an inspection sheet to capture all your observations. Takephotographs throughout the procedure to help document or describe thedamaged components.3. Extract any used lubricant samples from bearings, housing and sealareas to determine lubricant conditions. Package it separately and label itproperly.4. Secure a sample of new, unused lubricant. Record any specification orbatch information from the container. Obtain the technical specificationsand any related material safety data (handling, disposal, toxicological)documentation to accompany lubricant shipments.5. Check the bearing environment for external influences, like otherequipment problems, that preceded or occurred at the same time bearingdamage was reported.6. Disassemble the equipment (either partially or completely). Record anassessment of the mounted bearing condition.7. Inspect other machine elements, especially the position and condition ofcomponents adjacent to the bearing, including locknuts, adapters, sealsand seal wear rings.6TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE 8. Mark and record the mounted position of thebearings and components prior to removal.9. Measure and verify shaft and housing size,roundness and taper using certified gauges.10. Following removal, but before cleaning, recordobservations of lubricant distribution andcondition.11. Clean parts and record the manufacturers’information from markings on the bearing rings(part number, serial number,date code).12. Analyze the condition of the internal rollingcontact surfaces, load zones and thecorresponding external surfaces.13. Apply preservative oil and repackage thebearings to avoid corrosion.14. Compile a summary report of all data fordiscussion with Timken sales or serviceengineers. 2015 The Timken Company

Types of Bearing DamageMany different operating conditions can cause bearing damage. Those listedin this section make up the most commonly identified causes of damage foranti-friction bearings, including cylindrical, spherical, tapered and ball designs.Remember that you must follow proper bearing maintenance and handlingpractices to ensure your bearings achieve optimal performance levels.Wear – Abrasive ContaminationForeign particles cause wear and damage. Foreign particle contamination cancause abrasive wear, bruising or circumferential lining (grooving).Abrasive WearFine foreign material in the bearing can causeexcessive abrasive wear. Sand, fine metal fromgrinding or machining, and fine metal or carbidesfrom gears wear or lap the rolling elements andraces. In tapered bearings, the roller ends andcone rib wear to a greater degree than the races.This wear causes increased endplay or internalclearance, which can reduce fatigue life andcreate misalignment in the bearing. Abrasivewear also can affect other parts of the machinein which the bearings are used. The foreign particles may get in through badly worn or defectiveseals. Improper initial cleaning of housings andparts, ineffective filtration or improper filtermaintenance can allowabrasive par ticles toaccumulate.Fig. 1. Fine particle contamination entered this sphericalroller bearing and generated wear between the cagesurfaces, rollers and races.Fig. 2. The roller end wear on this spherical bearing alsowas caused by fine particle contamination.Fig. 3. Fine particle contamination caused abrasive wearon this tapered roller bearing.Fig. 4. Exposure to abrasives and water in a severeenvironment caused extreme wear on this pillow blockbearing. 2015 The Timken Company TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE7

Wear – Pitting and BruisingHard particles rolling through the bearing may cause pitting and bruising of the rolling elements and races. Metal chips or large particlesof dirt remaining in improperly cleaned housings can initiate early fatigue damage.Common external debris contaminants include dirt, sand and environmental particles. Typical causes of internal debris contaminationinclude wear from gears, splines, seals, clutches, brakes, joints, improperly cleaned housings, and damaged or spalled components.These hard particles travel within the lubrication, through the bearing and eventually bruise (dent) the surfaces. Raised metal aroundthe dents acts as surface-stress risers to cause premature spalling and reduce bearing life.Fig. 5. A tapered roller bearing innerrace (cone) with spalling from debriscontamination bruises.Fig. 6. Hard particles causedcontamination bruising on this sphericalroller bearing.Fig. 8. This photo, taken with a microscope, showsa debris contamination bruise on a bearing race. Acorresponding surface map of the dent is shown in Fig. 9.Fig. 7. Debris from other fatigued parts, inadequatesealing or poor maintenance caused bruising on thistapered roller bearing race.Fig. 9Wear – GroovingExtremely heavy wear from chips or metal particlescan cause grooving. These contaminants becomewedged in the soft cage material and cut grooves inthe rolling elements. This condition generatesimproper rolling contact geometry and can reduceservice life.Fig. 10. Large particle contaminationimbedded into the soft cage material canresult in grooving and circumferentiallining of the rollers and raceways.8TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE Fig. 11. Horizontal grooves causeimproper rolling contact, reducingbearing life. 20152014 The Timken Company

Etching – CorrosionEtching (or corrosion) remains one of the most serious problems anti-frictionbearings encounter. Without adequate protection, the high degree of surfacefinish on races and rolling elements makes them susceptible to corrosion damagefrom moisture and water.Etching is most often caused by condensate collecting in the bearing housingfrom temperature changes. Moisture or water can get in through damaged,worn or inadequate seals. Improperly washing and drying bearings when youremove them for inspection also can cause considerable damage. After cleaningand drying or preparing bearings for storage, you should coat them with oil oranother preservative and wrap them in protective paper. You should alwaysstore bearings, new or used, in a dry area and keep them in original packagingto reduce the risk of static corrosion appearing before mounting.Fig. 12. This cup has heavy corrosion on the race. This type of corrosion may only bea surface stain without pitting. If the staining can be cleaned with a fine emery cloth orcrocus cloth, the bearing may be reused. If there are pits that cannot be cleaned withlight polishing, the bearing should either be discarded or, if practical, refurbished.Fig. 13. This cylindrical bearing inner ring has etchingand corrosion.Fig. 14. Advanced spalling initiated at wateretch marks on the cup race makes this bearingunsuitable for further service.Fig. 15. Heavy water damage is shown on thisball bearing inner ring and cage. 2015 The Timken Company Fig. 16. This ball bearing outer race alsodepicts etching and corrosion.TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE9

Inadequate LubricationInadequate lubrication can create a wide range of damage conditions. Damagehappens when there isn’t a sufficient amount of bearing lubricant to separatethe rolling and sliding contact surfaces during service.It’s important that the right lubricant amount, type, grade, supply system,viscosity and additives be properly engineered for each bearing system. Baseyour selection on history, loading, speeds, sealing systems, service conditionsand expected life. Without proper consideration of these factors, you mayexperience less-than-expected-bearing and application performance.The damage caused by inadequate lubrication varies greatly in both appearanceand performance. Depending on the level of damage, it may range from very lightheat discoloration to total bearing lockup with extreme metal flow.The following section outlines the progressive levels of bearingdamage caused by inadequate lubrication:Level 1 – Discoloration Metal-to-metal contact results in excessive bearing temperature. High temperatures result in discoloration of the races and the roller. In mild cases, the discoloration is from the lubricant staining thebearing surfaces. In severe cases, the metal is discolored fromhigh heat.Fig. 17. Level 1 – Discoloration due to elevated operatingtemperatures.Level 2 – Scoring and Peeling Insufficient or complete lack of lubricant. Selecting the wrong lubricant or lubrication type. Temperature changes. Sudden changes in running conditions.Fig. 18. Level 2 – Micro-spalling or peelingresults from thin lubricant film due to high loads/lowrevolutions per minute (RPM) or elevated temperatures.10Fig. 19. Level 2 – Advanced rib scoring is due toinadequate lubricant film.TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE 2015 The Timken Company

Level 3 – Excessive Roller End Heat Inadequate lubricant film results in localized hightemperatures and scoring at the large ends of therollers.Fig. 20. Level 3 – Heat damage on these tapered rollerswas caused by metal-to-metal contact.Level 4 – Total Bearing Lockup High localized heat produces metal flow in bearings, altering the original bearing geometry and the bearing’s material.This results in skewing of the rollers, destruction of the cage, metal transferand complete seizure of the bearing.Careful inspection of all bearings, gears, seals, lubricants and surrounding partsmay help determine the primary cause of damage. See the Lubrication ReferenceGuide on page 23 to learn more about how lubrication conditions impact bearingperformance.Fig. 21. Level 4 – Excessive heat generation causedadvanced metal flow of the rollers,as well as cone rib deformation andcage expansion.Fig. 22. Level 4 – This is an example of total bearinglockup. 2015 The Timken Company TIMKEN BEARING DAMAGE ANALYSIS WITH LUBRICATION REFERENCE GUIDE11

Fatigue SpallingSpalling is the pitting or flaking away of bearing material. Spalling primarilyoccurs on the races and the rolling elements. We show many types of “primary”bearing damage throughout this reference guide that eventually deteriorateinto a secondary spalling damage mode. We classify three distinct spallingdamage modes:Geometric Stress Concentration (GSC) SpallingCauses for this type of damage mode include misalignment, deflection or edgeloading

2015 The Timken Company TIMKEN BEARING DAMAGE ANALSIS WITH LUBRICATION REFERENCE GUIDE 7 Types of Bearing Damage Many different operating conditions can cause bearing damage. Those listed in this section make up the most commonly identified causes of damage for anti-friction bearings, including cylindrical, spherical, tapered and ball designs.

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