Bearing Failures, Causes & Remidies 25.02.08

FAG Bearings India Limited FAG Bearings India Limited Slide Slide 11

Bearing Damages - Causes and RemediesBearing Damages - Causes and Remedies



Analysing Bearing failures to identify causes Analysing Bearing failures to identify causes

SymptomsSymptoms CauseCause Application ExamplesApplication Examples

Damaged Rolling ElementsDamaged Rolling Elementsor rings.or rings.

Motor Vehicles: Increased Motor Vehicles: Increased wobbling, vibration in steering wobbling, vibration in steering systemsystem

Fans: Increased Vibration.Fans: Increased Vibration.

Saw Mills: More Knocks and Saw Mills: More Knocks and Blows in Connecting rods.Blows in Connecting rods.

ContaminationContamination

Excessive Bearing ClearanceExcessive Bearing Clearance

REDUCEDREDUCED WORKINGWORKING ACCURACYACCURACY

Wear due to contaminants Wear due to contaminants or insufficient lubricationor insufficient lubrication

Lathe: Gradual development of Lathe: Gradual development of chatter marks on work piece.chatter marks on work piece.

Damaged rings or rolling Damaged rings or rolling elementselements Grinders :Waiviness of ground Grinders :Waiviness of ground

surfacessurfaces

Cold rolling mills: Periodic surface Cold rolling mills: Periodic surface defects on rolled material such as defects on rolled material such as stretcher grains, ghost lines etc.stretcher grains, ghost lines etc.

Change in adjustmentChange in adjustment(Clearance or Preload)(Clearance or Preload)

UNEVEN UNEVEN RUNNINGRUNNING



SymptomsSymptoms CauseCause Application ExamplesApplication Examples

Analysing Bearing failures to identify causesAnalysing Bearing failures to identify causes

Insufficient operating Insufficient operating clearanceclearance

Low pitchedLow pitchedrumbling orrumbling orirregular noiseirregular noise

Excessive Clearance.Excessive Clearance.Damaged running surfaces.Damaged running surfaces.Contamination.Contamination.Unsuitable lubricant.Unsuitable lubricant.

Uncommon Uncommon Running Noise : Running Noise : Whining or high Whining or high pitched noisepitched noise

Gradual Change Gradual Change in Running noise.in Running noise.

Changes in operating Changes in operating clearance caused by clearance caused by temperature . Damaged temperature . Damaged raceway [from raceway [from Contamination / fatigue]Contamination / fatigue]

Electric Motors, Gears.Electric Motors, Gears.[The bearing noise is hard to [The bearing noise is hard to identify since it is drowned by identify since it is drowned by the noise of gears ].the noise of gears ].



B 20%B 20%

A 20%A 20%

C 15%C 15%

D 20%D 20% E 5%E 5% F 5%F 5%

G 5%G 5%

I 10% I 10%

H <1%H <1%

A Aged LubricantB Unsuitable LubricantC Lack of LubricantD Solid ContaminantsE Liquid Contaminants

Bearing Failure Query Sheet

F Problems caused by assemblyG Unknown or secondary problemsH Material or manufacturing problemsI Wrong bearing selection, e.g. too small Rating Capacity

80%80% 20%20%

Nearly 80% failure in rolling bearings can be attributed to lubrication related Nearly 80% failure in rolling bearings can be attributed to lubrication related problemsproblems



Typical reasons for rolling Typical reasons for rolling bearing damages :bearing damages :

Inexpert mountingInexpert mounting

Abnormal conditions during Abnormal conditions during operationoperation

Unfavourable environmentalUnfavourable environmentalinfluencesinfluences

Inadequate lubricationInadequate lubrication

Incorrect mounting method, Incorrect mounting method, wrong toolswrong tools

ContaminationContamination

Too tight fitToo tight fit

Too loose fitToo loose fit

MisalignmentMisalignment

Inexpert Mounting Inexpert Mounting



Abnormal conditions Abnormal conditions during operationduring operation

Over load

Absence of load

Vibrations

Excessive speeds

External heat

Dust, dirt

Passage of electric current

Humidity

Aggressive media

Unfavourable Unfavourable environmentalenvironmentalinfluencesinfluences

InadequateInadequatelubricationlubrication

Unsuitablelubricant

Lack of lubricant

Over lubrication

In many cases, a failed bearing may reveal several damage features simultaneously. In such cases it is difficult to indicate one single cause of failure. A systematic clarification of causes associated with each damage is the only answer.



Micro motion between fitted parts where fits Micro motion between fitted parts where fits are too lose in relation to the acting forces.are too lose in relation to the acting forces.

Form disturbance of fitting surfaces.Form disturbance of fitting surfaces. Shaft deflection or housing deformation.Shaft deflection or housing deformation. Floating bearing function at ring with Floating bearing function at ring with

circumferential load.circumferential load.

CAUSESCAUSES

Brownish black spots on the seats Brownish black spots on the seats occasionally with brown abraded matter near occasionally with brown abraded matter near bearing or in lubricant also.bearing or in lubricant also.

Wear at the fitting surface, fatigue fracture Wear at the fitting surface, fatigue fracture possible in case of rotating parts .possible in case of rotating parts .

Disturbance of floating bearing function Disturbance of floating bearing function possible in case of stationary parts.possible in case of stationary parts.

SYMPTOMSSYMPTOMS

Fretting corrosion reveals the size of Fretting corrosion reveals the size of the load zone at the stationary outer the load zone at the stationary outer ringring..

Fretting Fretting CorrosionCorrosionFretting Fretting CorrosionCorrosion

Fretting corrosion in bore of inner Fretting corrosion in bore of inner ring of Cylindrical roller bearing with ring of Cylindrical roller bearing with seats too looseseats too loose



Provide floating bearing function at ring with Provide floating bearing function at ring with point load.point load.

Use bearing seats which are as tight as possible.Use bearing seats which are as tight as possible. Coat bearing seats.Coat bearing seats. Make shaft/housing more rigid to bending.Make shaft/housing more rigid to bending. Improve roundness of seats.Improve roundness of seats.

REMEDIESREMEDIES

Fretting corrosion reveals the size of Fretting corrosion reveals the size of the load zone at the stationary outer the load zone at the stationary outer ringring..

Fretting Fretting CorrosionCorrosionFretting Fretting CorrosionCorrosion

Fretting corrosion in bore of inner Fretting corrosion in bore of inner ring of Cylindrical roller bearing with ring of Cylindrical roller bearing with seats too looseseats too loose



Rotary motion between the ring and Rotary motion between the ring and shaft/housing with loose fits under shaft/housing with loose fits under circumferrential load:with static load and circumferrential load:with static load and unbalance also.unbalance also.

Axial support of rings insufficient.Axial support of rings insufficient. Sluggish movement of floating ring.Sluggish movement of floating ring.

CAUSESCAUSES

Cold welding at the fitting surfaces and axial Cold welding at the fitting surfaces and axial mating surfaces or also shiny contact areas mating surfaces or also shiny contact areas where surface roughness is good.where surface roughness is good.

SYMPTOMSSYMPTOMS Seizure Seizure Seizure Seizure

Seizing marks in the inner ring Seizing marks in the inner ring bore as a result of inner ring bore as a result of inner ring creeping on the shaft.creeping on the shaft.

Seizing marks on the OD as a Seizing marks on the OD as a result of outer ring creeping in result of outer ring creeping in the housing.the housing.

Use bearing seats which are as tight as Use bearing seats which are as tight as possible.possible.

Extend axial mating surfaces.Extend axial mating surfaces. Keep fitting surfaces dry.Keep fitting surfaces dry. Improve floating bearing function.Improve floating bearing function.

REMEDIESREMEDIES



Insufficient fixation of the bearing in the Insufficient fixation of the bearing in the housing or on the shaft.housing or on the shaft.

Large amount of external contamination with Large amount of external contamination with narrow gap between the bearing and mating narrow gap between the bearing and mating parts.parts.

Loose mating parts.Loose mating parts. Axial clearance too large.Axial clearance too large.

CAUSESCAUSES

Circumferential scratch marks /wear on the Circumferential scratch marks /wear on the faces of the bearing rings or seals.faces of the bearing rings or seals.

SYMPTOMSSYMPTOMS

Ensure proper adjustment of parts.Ensure proper adjustment of parts. Ensure proper cleanliness.Ensure proper cleanliness. Check and adjust correct axial clearance.Check and adjust correct axial clearance.

REMEDIESREMEDIES

Lateral Grazing Lateral Grazing TracksTracksLateral Grazing Lateral Grazing TracksTracks

Circumferential scoring and cold Circumferential scoring and cold welding at the faces due to welding at the faces due to grazing by a mating part.grazing by a mating part.

Seal damage due to lateral Seal damage due to lateral grazinggrazing



AA BB

Radial load of a radial bearing Radial load of a radial bearing e.g. deep groove ball bearing e.g. deep groove ball bearing Under point load and with a Under point load and with a sufficiently rigid housing, the sufficiently rigid housing, the track on the stationary ring is track on the stationary ring is shorter than half the raceway shorter than half the raceway circumference in so far as there circumference in so far as there is no radial preload. Under is no radial preload. Under circumferential load, the track circumferential load, the track spreads over the entire raceway spreads over the entire raceway circumference.circumference.

A.A.Point load for the outer ring, Point load for the outer ring, circumferential load for the circumferential load for the inner ring.inner ring.

B.B.Point load for the inner ring, Point load for the inner ring, circumferential load for the circumferential load for the outer ring.outer ring.



Axial load of a radial bearing, Axial load of a radial bearing, e.g. deep groove ball bearing. On e.g. deep groove ball bearing. On the inner and outer rings the the inner and outer rings the tracks spread off-centre over the tracks spread off-centre over the entire raceway circumference.entire raceway circumference.

Combined radial-axial load of a Combined radial-axial load of a deep groove ball bearing. In the deep groove ball bearing. In the case of the inner ring case of the inner ring (circumferential load) there is a (circumferential load) there is a constant wide track over the constant wide track over the entire raceway circumference. entire raceway circumference. The track on the outer ring (point The track on the outer ring (point load) is wider in the radial load load) is wider in the radial load zone than on the rest of the zone than on the rest of the circumference.circumference.



Indentation Caused by foreign particle contaminationIndentation Caused by foreign particle contamination

Indentation of soft foreign particles

Indentation by particles made of hardened steel

Indentation of hard mineral foreign particles

If no contamination is 1, iron chips = 0.3, sand particles = 0.05If no contamination is 1, iron chips = 0.3, sand particles = 0.05



Deep groove ball bearing Deep groove ball bearing under detrimental radial under detrimental radial preload. The tracks extend preload. The tracks extend over the entire over the entire circumference, even on the circumference, even on the point loaded ring.point loaded ring.

Oval deformation of a deep Oval deformation of a deep groove ball bearing. Two groove ball bearing. Two opposed radial load zones opposed radial load zones formed in the raceway of the formed in the raceway of the ovally deformed outer ring ovally deformed outer ring (point load).(point load).



Locating-floating bearing arrangement with two deep groove ball bearings.Locating-floating bearing arrangement with two deep groove ball bearings.

Tracks on bearings in working order. The locating Tracks on bearings in working order. The locating bearing shows the characteristics of a bearing bearing shows the characteristics of a bearing under combined load, the floating bearing those of under combined load, the floating bearing those of a bearing under mainly/purely radial load.a bearing under mainly/purely radial load.

The deep groove ball bearing on the work end The deep groove ball bearing on the work end is designed as the locating bearing, the bearing is designed as the locating bearing, the bearing on the drive end as the floating bearing.on the drive end as the floating bearing.

Tracks on bearings under detrimental axial Tracks on bearings under detrimental axial preload (outer ring of floating bearing does not preload (outer ring of floating bearing does not move). Each bearing shows the characteristics move). Each bearing shows the characteristics of a combined load. The detrimental axial of a combined load. The detrimental axial preload is clear from the symmetric tracks of preload is clear from the symmetric tracks of both bearings.both bearings.



Development of tracks in the case of a self-aligning ball Development of tracks in the case of a self-aligning ball bearing with rotating inner ring under detrimental axial bearing with rotating inner ring under detrimental axial preload and radial loadpreload and radial load



Tilting of the inner rings relative to the Tilting of the inner rings relative to the outer rings in the case of misaligned outer rings in the case of misaligned housing seatshousing seats

MISALIGNMENTMISALIGNMENT



Tilting of the inner rings relative to the Tilting of the inner rings relative to the outer rings in the case of misaligned outer rings in the case of misaligned housing seatshousing seats




Tracks of a misaligned deep Tracks of a misaligned deep groove ball bearing with rotating groove ball bearing with rotating inner ringinner ring

Tracks of a misaligned deep Tracks of a misaligned deep groove ball bearing with rotating groove ball bearing with rotating outer ringouter ring




False BrinellingFalse BrinellingFalse BrinellingFalse Brinelling

Eliminate or absorb external vibration.Eliminate or absorb external vibration. Use lubricants containing antiwear additives.Use lubricants containing antiwear additives.

REMEDIESREMEDIES

Vibrations in stationary machines leading to Vibrations in stationary machines leading to micro motion between rolling elements and micro motion between rolling elements and raceways.raceways.

When the bearing isn’t turning, an oil film When the bearing isn’t turning, an oil film cannot be formed to prevent raceway wear .cannot be formed to prevent raceway wear .

CAUSESCAUSES

Elliptical wear marks in an axial direction at Elliptical wear marks in an axial direction at each ball position with a bright finish and each ball position with a bright finish and sharp demarcation.sharp demarcation.

Often surrounded by a ring of brown debrisOften surrounded by a ring of brown debris

SYMPTOMSSYMPTOMS



Over HeatingOver HeatingOver HeatingOver Heating

Thermal or overload controls.Thermal or overload controls. Adequate heat pathsAdequate heat paths Supplemental coolingSupplemental cooling

REMEDIESREMEDIES

Heavy electrical heat loadsHeavy electrical heat loads Inadequate heat pathsInadequate heat paths Insufficient cooling or lubrication when loads Insufficient cooling or lubrication when loads

and speed are excessiveand speed are excessive

CAUSESCAUSES

Discoloration of the rings, rolling elements and Discoloration of the rings, rolling elements and cages from gold to blue.cages from gold to blue.

Temperatures in excess of 400°F can anneal Temperatures in excess of 400°F can anneal ring and rolling element materials, reducing ring and rolling element materials, reducing the bearing capacity and causing early failurethe bearing capacity and causing early failure

SYMPTOMSSYMPTOMS



Outer Ring Outer Ring FractureFracture

Outer Ring Outer Ring FractureFracture

CAUSESCAUSES

Poor support of the rings in the bearing housing Poor support of the rings in the bearing housing

Improvement in bearing mounting.Improvement in bearing mounting. Follow FAG mounting instructions for appropriate Follow FAG mounting instructions for appropriate

recommendationsrecommendations

REMEDIESREMEDIES

Typically a crack spreads evenly in the Typically a crack spreads evenly in the circumferential direction, with several fractured circumferential direction, with several fractured pieces often originating with axial load.pieces often originating with axial load.

Fractures usually occur a little beyond the Fractures usually occur a little beyond the middle of the raceway.middle of the raceway.

Outside outer ring shows irregular load pattern.Outside outer ring shows irregular load pattern.

SYMPTOMSSYMPTOMS



SlippageSlippage

Rolling elements slide on the raceways when the Rolling elements slide on the raceways when the load is low and lubrication is poor.load is low and lubrication is poor.

Occasionally occurs if load zones are too short, Occasionally occurs if load zones are too short, causing rolling elements to brake in the unloaded causing rolling elements to brake in the unloaded zone and accelerate again when entering the load zone and accelerate again when entering the load zone.zone.

Fast changes in speedFast changes in speed

CAUSESCAUSES

REMEDIESREMEDIES

Select Bearing with lower load carrying capacity.Select Bearing with lower load carrying capacity. Preload Bearings, Reduce Bearing Clearance, Preload Bearings, Reduce Bearing Clearance,

Improve Lubrication.Improve Lubrication.

Spotted smear marks.Spotted smear marks. Roughening of rolling elements or racewaysRoughening of rolling elements or raceways

SYMPTOMSSYMPTOMS



MisalignmentMisalignment

CAUSESCAUSES

Bent shafts.Bent shafts. Burrs or dirt on shaft or housing shoulders.Burrs or dirt on shaft or housing shoulders. Shaft threads that are not square with shaft Shaft threads that are not square with shaft

seats.seats. Locking nuts with faces that are not square to Locking nuts with faces that are not square to

the thread axisthe thread axis REMEDIESREMEDIES Inspect shafts and housings for runout of Inspect shafts and housings for runout of

shoulders and bearing seats.shoulders and bearing seats. Use single point- turned or ground threads on Use single point- turned or ground threads on

non-hardened shafts and ground threads only on non-hardened shafts and ground threads only on hardened shafts.hardened shafts.

Use precision grade lock nut’s.Use precision grade lock nut’s.

A wear path not parallel to raceway edges on A wear path not parallel to raceway edges on the raceway of the non-rotating ring.the raceway of the non-rotating ring.

SYMPTOMSSYMPTOMS



Excessive loading of the rolling elements when Excessive loading of the rolling elements when interference fits exceed the radial clearance at interference fits exceed the radial clearance at operating temperatures.operating temperatures.

Continued operation under such conditions Continued operation under such conditions leads to rapid wear and fatigue.leads to rapid wear and fatigue.

CAUSESCAUSES

Decrease total interference with better Decrease total interference with better matching of bearings to shafts and housings.matching of bearings to shafts and housings.

Consider operating temperaturesConsider operating temperatures

Increased radial clearance in bearing selectionIncreased radial clearance in bearing selection

REMEDIESREMEDIES

A heavy rolling element wear path in the bottom A heavy rolling element wear path in the bottom of the racewayof the raceway

SYMPTOMSSYMPTOMS

Tight FitsTight Fits



CAUSESCAUSES

Bearing slippage, Rotation of inner ring on the Bearing slippage, Rotation of inner ring on the shaft.shaft.

Too tight of fit to shaft.Too tight of fit to shaft.

Grooved shaft, Out-of-roundness.Grooved shaft, Out-of-roundness.

Grazing against Surrounding parts.Grazing against Surrounding parts.

AXIAL CRACKSAXIAL CRACKS Inner ring partly or completely cracked in the Inner ring partly or completely cracked in the axial direction.axial direction.

Slightly rounded fractured edges indicate that Slightly rounded fractured edges indicate that the fracture originated during operation and was the fracture originated during operation and was cycled (cracked edges may break off after cycled (cracked edges may break off after prolonged operation).prolonged operation).

Sharp edged cracks indicate fracture during Sharp edged cracks indicate fracture during dismounting.dismounting.

SYMPTOMSSYMPTOMS



Improve lubrication with additives or Improve lubrication with additives or increased oil quantities.increased oil quantities.

Select suitable fitSelect suitable fit

Avoid grazingAvoid grazing

Provide for better seating conditions.Provide for better seating conditions.

Consider special heat treatment for ringsConsider special heat treatment for rings

REMEDIESREMEDIES

AXIAL CRACKSAXIAL CRACKS



Normal FatigueNormal Fatigue

Bearing has remained in operation beyond its Bearing has remained in operation beyond its calculated fatigue lifecalculated fatigue life

CAUSESCAUSES

Replace the bearing and/or consider Replace the bearing and/or consider redesigning to use a bearing with a greater redesigning to use a bearing with a greater calculated fatigue lifecalculated fatigue life

REMEDIESREMEDIES

Often referred to as spalling; indicated by the Often referred to as spalling; indicated by the fracture of the running surfaces and subsequent fracture of the running surfaces and subsequent removal of small discrete particles of material removal of small discrete particles of material from the inner ring, outer ring or rolling from the inner ring, outer ring or rolling elements.elements.

Spalling is progressive, and once initiated will Spalling is progressive, and once initiated will spread with continued operation.spread with continued operation.

Always accompanied by a notice able increase in Always accompanied by a notice able increase in vibrationvibration

SYMPTOMSSYMPTOMS



TRUE TRUE BRINELLINGBRINELLING

TRUE TRUE BRINELLINGBRINELLING

Static overload of the bearing, Severe impact to Static overload of the bearing, Severe impact to the bearingthe bearing

Using a hammer to install the bearing.Using a hammer to install the bearing. Dropping or striking assembled equipment.Dropping or striking assembled equipment. Pressing a bearing to the shaft by applying Pressing a bearing to the shaft by applying

force to the outer ring.force to the outer ring.

CAUSESCAUSES

Observe static load ratings in making bearing Observe static load ratings in making bearing selection.selection.

Install bearings using appropriate equipment Install bearings using appropriate equipment and by applying force only to the ring being and by applying force only to the ring being press-fittedpress-fitted

REMEDIESREMEDIES

Brinell marks appear as indentations in the Brinell marks appear as indentations in the raceways, increasing bearing vibration (noise).raceways, increasing bearing vibration (noise).

Severe Brinell marks can cause premature Severe Brinell marks can cause premature fatigue failure.fatigue failure.

SYMPTOMSSYMPTOMS



Lubricant Lubricant FailureFailure

Lubricant Lubricant FailureFailure

CAUSESCAUSES

Restricted lubricant flow.Restricted lubricant flow.

Excessive temperatures that degrade the Excessive temperatures that degrade the lubricant.lubricant.

REMEDIESREMEDIES

Use of the appropriate and correct amount of Use of the appropriate and correct amount of lubricant.lubricant.

Ensure proper bearing fit.Ensure proper bearing fit.

Control Preload to reduce bearing temperatures.Control Preload to reduce bearing temperatures.

Discolored rolling elements (blue/brown) and Discolored rolling elements (blue/brown) and rolling element tracks.rolling element tracks.

Excessive wear of rolling elements, rings, and Excessive wear of rolling elements, rings, and cages follow, resulting in overheating and cages follow, resulting in overheating and catastrophic failure.catastrophic failure.

SYMPTOMSSYMPTOMS



CorrosionCorrosion

Exposing bearings to corrosive fluids or Exposing bearings to corrosive fluids or atmospheresatmospheres

CAUSESCAUSES

Divert corrosive fluids away from bearing areasDivert corrosive fluids away from bearing areas

Use integrally sealed bearingsUse integrally sealed bearings

Consider external seals for particularly hostile Consider external seals for particularly hostile environmentsenvironments

REMEDIESREMEDIES

Red/brown stains or deposits on rolling Red/brown stains or deposits on rolling elements, raceways or cages.elements, raceways or cages.

Increased vibration followed by wearIncreased vibration followed by wear

Increase in radial clearance or Loss of PreloadIncrease in radial clearance or Loss of Preload

SYMPTOMSSYMPTOMS



FlutingFluting

Constant passage of alternating or direct Constant passage of alternating or direct currentcurrent

Even low currentsEven low currents

CAUSESCAUSES

Prevent currents from flowing through the Prevent currents from flowing through the bearing by means of grounding or insulating.bearing by means of grounding or insulating.

Use current insulated bearingsUse current insulated bearings

REMEDIESREMEDIES

Brownish marks parallel to the axis on a large Brownish marks parallel to the axis on a large part of the raceway, or covering the entire part of the raceway, or covering the entire raceway circumferenceraceway circumference

SYMPTOMSSYMPTOMS

Current Density : > 0.1 amp / mm2 ; Potential : > Current Density : > 0.1 amp / mm2 ; Potential : > 0.8 V0.8 V



Excessive Excessive LoadsLoads

Excessive Excessive LoadsLoads

Excessive loading of the bearingExcessive loading of the bearing

CAUSESCAUSES

Reduce the loadReduce the load

Redesign using a bearing with greater capacity.Redesign using a bearing with greater capacity.

REMEDIESREMEDIES

Heavy rolling element wear pathsHeavy rolling element wear paths

Evidence of overheatingEvidence of overheating

Widespread fatigue areas (spalling)Widespread fatigue areas (spalling)

SYMPTOMSSYMPTOMS



Lip FracturesLip Fractures

Axial load unacceptably high.Axial load unacceptably high.

Lip insufficiently supported.Lip insufficiently supported.

Axial shock load.Axial shock load.

Mounting damage.Mounting damage.

CAUSESCAUSES

Ensure good lip support design.Ensure good lip support design.

Keep load within specified limits.Keep load within specified limits.

Observe appropriate mounting instructions & Observe appropriate mounting instructions & procedures.procedures.

REMEDIESREMEDIES

Supporting lips are partly or completely broken Supporting lips are partly or completely broken off or cracked.off or cracked.

SYMPTOMSSYMPTOMS



SeizureSeizure

Inadequate lubrication with high loads and high Inadequate lubrication with high loads and high speeds (quantity or operating viscosity of speeds (quantity or operating viscosity of lubricant too low)lubricant too low)

Inadequate lubrication with high loads and low Inadequate lubrication with high loads and low speeds.(When there is no hydrodynamic speeds.(When there is no hydrodynamic lubricating film between the roller face and lip).lubricating film between the roller face and lip).

Detrimental Preload due to heat expansion. Detrimental Preload due to heat expansion.

Skewing of rollers due to raceway wear or ring Skewing of rollers due to raceway wear or ring tilting.tilting.

Axial load too high on cylindrical roller bearings. Axial load too high on cylindrical roller bearings. Axial Preload too high for out-of-square mating Axial Preload too high for out-of-square mating surfaces.surfaces.

CAUSESCAUSES

Partial or large-area welding and deep scratches Partial or large-area welding and deep scratches in the lip and roller face areas, also lubricant in the lip and roller face areas, also lubricant coking in this areacoking in this area

SYMPTOMSSYMPTOMS



Improve lubrication (increase viscosity, EP Improve lubrication (increase viscosity, EP additives, increase quantity).additives, increase quantity).

Ensure correct adjustment of bearings.Ensure correct adjustment of bearings.

REMEDIESREMEDIES

SeizureSeizure



Reverse Reverse LoadingLoading

Ensure proper installation of angular contact Ensure proper installation of angular contact bearings.bearings.

REMEDIESREMEDIES

Angular contact ball bearings are designed to Angular contact ball bearings are designed to accept an axial load in one direction only.accept an axial load in one direction only.

When loaded in the opposite direction, the When loaded in the opposite direction, the elliptical contact area on the outer ring is elliptical contact area on the outer ring is truncated by the low shoulder on that side of the truncated by the low shoulder on that side of the outer ring.Result is excessive stress and an outer ring.Result is excessive stress and an increase in temperature followed by increased increase in temperature followed by increased vibration and early failure.vibration and early failure.

CAUSESCAUSES

Balls will show a grooved wear band caused by Balls will show a grooved wear band caused by the ball riding over the outer edge of the the ball riding over the outer edge of the racewayraceway

SYMPTOMSSYMPTOMS



CratersCraters

Sparking over current for example during welding Sparking over current for example during welding or due to earth failure.or due to earth failure.

CAUSESCAUSES

Do not direct the current through the bearing Do not direct the current through the bearing during Electro weldingduring Electro welding

REMEDIESREMEDIES

Craters in the raceway due to local melting at the Craters in the raceway due to local melting at the contact area of the parts in rolling, sometimes contact area of the parts in rolling, sometimes several craters in a row or whole chains around several craters in a row or whole chains around the circumference.the circumference.

SYMPTOMSSYMPTOMS

Current Density : 2 amp / mm2Current Density : 2 amp / mm2



Rolling ElementRolling Element Edge RunningEdge Running

Fig2

Fig1 CAUSESCAUSES

Excessive (Axial Load).Excessive (Axial Load). Moment Load too High.Moment Load too High. Operating Clearance too high.Operating Clearance too high. Tilting.Tilting.

REMEDIESREMEDIES

Avoid Overloading.Avoid Overloading. Use bearing with higher load carrying capacity.Use bearing with higher load carrying capacity. Reduce operating clearance.Reduce operating clearance. Avoid tilting.Avoid tilting.

In case of balls ,arch shaped notches on the In case of balls ,arch shaped notches on the surface or described as ‘woolen balls’ of notches, surface or described as ‘woolen balls’ of notches, edges rounded since they are plastically edges rounded since they are plastically deformed . See fig 1 & 2. These are not to be deformed . See fig 1 & 2. These are not to be confused with scratches by foreign particles. confused with scratches by foreign particles. Circumferential notches near the face in case of Circumferential notches near the face in case of rollers. rollers.

SYMPTOMSSYMPTOMS



Unusual Unusual TracksTracks

Fig 1

Fig 2

CAUSESCAUSES Insufficient lubricant quantity available in the Insufficient lubricant quantity available in the

bearing.bearing. Viscosity of the lubricant is insufficient for the Viscosity of the lubricant is insufficient for the

operating temperature and speed.operating temperature and speed.

REMEDIESREMEDIES Improve lubricant supply.Improve lubricant supply. Use lubricant with a suitable viscosity & appropriate Use lubricant with a suitable viscosity & appropriate

additives.additives. Use bearing parts with surface coating.Use bearing parts with surface coating.

The visual pattern of the tracks and the surface as The visual pattern of the tracks and the surface as observed by microscope,that is roughness makes it observed by microscope,that is roughness makes it possible to conclude about the quality of the lubrication.possible to conclude about the quality of the lubrication.

The thinner the lubricant film the greater the influence The thinner the lubricant film the greater the influence on the surface.See fig 1 for poor surface seperation.on the surface.See fig 1 for poor surface seperation.

When the specific load is high in the contact areas,the When the specific load is high in the contact areas,the tracks are bright,pressure polished and frequently shiny tracks are bright,pressure polished and frequently shiny and a clear contrast to the uncycled part of the raceway. and a clear contrast to the uncycled part of the raceway.

SYMPTOMSSYMPTOMS



OverheatingOverheating

CAUSESCAUSES Bearing clearance too low during operation, Bearing clearance too low during operation,

particularly with high speed bearings.particularly with high speed bearings. Inadequate lubrication.Inadequate lubrication. Radial Preload due to external over heating.Radial Preload due to external over heating. Over lubrication.Over lubrication. Impeded running due to cage fracture. Impeded running due to cage fracture.

REMEDIESREMEDIES

Increase bearing clearance, Avoid lubrication Increase bearing clearance, Avoid lubrication pile up- Improve lubrication.pile up- Improve lubrication.

In the case of external heating ensure, In the case of external heating ensure, sufficiently slow heating up and cooling down, sufficiently slow heating up and cooling down, that is to ensure uniform heating of the that is to ensure uniform heating of the complete bearing.complete bearing.

Raceway/rolling elements plastically deformed to Raceway/rolling elements plastically deformed to a large extent.a large extent.

Discolourisation of the bearing.Discolourisation of the bearing.

SYMPTOMSSYMPTOMS



Score Score MarksMarks

CAUSESCAUSES

During mounting,if the single ring and the ring with During mounting,if the single ring and the ring with the rolling elements are not concentric and are the rolling elements are not concentric and are forcefully shoved damages as shown in the photo forcefully shoved damages as shown in the photo are done to the inner ring. This can be particularly are done to the inner ring. This can be particularly dangerous with large moving pass(large shaft is dangerous with large moving pass(large shaft is shoved with the bearing inner ring and rolling shoved with the bearing inner ring and rolling element into the outer ring which has already been element into the outer ring which has already been pressed into the housing.pressed into the housing.

Material displacement at rolling element pitch Material displacement at rolling element pitch parallel to the axis in raceways and rolling parallel to the axis in raceways and rolling elements of seperable cylindrical rollers or elements of seperable cylindrical rollers or tapered roller bearings.Several marks are found tapered roller bearings.Several marks are found displaced to one another by a few degrees on displaced to one another by a few degrees on the circumference. Frequently found on the 1/3 the circumference. Frequently found on the 1/3 of the circumference and no on the whole.of the circumference and no on the whole.

SYMPTOMSSYMPTOMS



Use suitable mounting aids.Use suitable mounting aids. Avoid Misalignment.Avoid Misalignment. If possible assemble parts with slow rotating If possible assemble parts with slow rotating

movement.movement.

REMEDIESREMEDIES

Score Score MarksMarks



Wear of cage guiding surfaces.

CAUSESCAUSES

Insufficient lubricant supply to the contact Insufficient lubricant supply to the contact areas,often inadequate drainage of the areas,often inadequate drainage of the lubricant.lubricant.

Contaminated lubricant.Contaminated lubricant. Speed too high for the bearing.Speed too high for the bearing. Excess tilting during assembly.Excess tilting during assembly. Unexpectedly high temperatures in the case of Unexpectedly high temperatures in the case of

outer ring guided brass cages(different outer ring guided brass cages(different coefficient of expansion between steel and coefficient of expansion between steel and brass).brass).

Wear may result when cages -particularly brass Wear may result when cages -particularly brass are guided at the lip of bearing cages.The surface are guided at the lip of bearing cages.The surface is badly roughened and Seizure also results. A is badly roughened and Seizure also results. A shoulder develops at the lip when there is lot of shoulder develops at the lip when there is lot of wear since the cage is not as a rule in contact wear since the cage is not as a rule in contact with its entire width.with its entire width.

SYMPTOMSSYMPTOMS



Increase lubrication. Greater flow , more Increase lubrication. Greater flow , more cleanliness.cleanliness.

Use bearings designed for operating conditions Use bearings designed for operating conditions in question.in question.

Coat cage.Coat cage.

REMEDIESREMEDIES

Wear of cage guiding surfaces.



Worn sealing Worn sealing lip trackslip tracks

CAUSESCAUSES Extreme amount of external dirt particularly in Extreme amount of external dirt particularly in

moist environment.moist environment. Lip runs dry.Lip runs dry. Fig.- Corrosion in the area of the sealing track at Fig.- Corrosion in the area of the sealing track at

the lip of an angular contact ball bearing.the lip of an angular contact ball bearing.

Use preseals e.g. flinger rings.Use preseals e.g. flinger rings. Lubricate sealing lips. Lubricate sealing lips.

REMEDIESREMEDIES

At the area of the sealing lip contact a At the area of the sealing lip contact a circumferrential groove , usually shiny develops. circumferrential groove , usually shiny develops. Also in conjunction frequently with worn sealing Also in conjunction frequently with worn sealing lips and damage to the bearing as a result of lips and damage to the bearing as a result of penetrating contaminants.penetrating contaminants.

Corrosion in the seal area found in many cases. Corrosion in the seal area found in many cases. Increase lubrication. Greater flow , more Increase lubrication. Greater flow , more cleanliness.cleanliness.

SYMPTOMSSYMPTOMS



Fig Shows cage wear due to Fig Shows cage wear due to starved lubrication and starved lubrication and contaminants’’’’’contaminants’’’’’

Cage Wear

CAUSESCAUSES

Lubricant contaminated with hard foreign Lubricant contaminated with hard foreign particles.particles.

Too little or unsuitable lubricants.Too little or unsuitable lubricants.

REMEDIESREMEDIES Ensure clean assembly conditions.Ensure clean assembly conditions. Filter the lubricant that is recycled.Filter the lubricant that is recycled. Increase lubricant through and/or apply a Increase lubricant through and/or apply a

different viscosity.different viscosity.

In the case of cages with lip guidance wear in In the case of cages with lip guidance wear in the side edges is observed.the side edges is observed.

In the case of cages guided by rolling elements In the case of cages guided by rolling elements wear in the pockets will be observed.wear in the pockets will be observed.

SYMPTOMSSYMPTOMS



Fig Shows cage wear due to grazing Fig Shows cage wear due to grazing at the bearing outside diameter.*at the bearing outside diameter.*

Cage WearCage Wear

CAUSESCAUSES

Excessive speed.Excessive speed. Unsuitable cage construction selected.Unsuitable cage construction selected.

REMEDIESREMEDIES Select suitable cage material as per the speed Select suitable cage material as per the speed

application.application.

Wear of cage outside diameter due to grazing at Wear of cage outside diameter due to grazing at the bearing outer ring.the bearing outer ring.

SYMPTOMSSYMPTOMS



Fig Shows cage wear due to roller skewingFig Shows cage wear due to roller skewing

Cage WearCage Wear

CAUSESCAUSES

Unpermissible tilting of the bearings.Unpermissible tilting of the bearings. Faulty adjustment of clearance in the bearings.Faulty adjustment of clearance in the bearings.

REMEDIESREMEDIES

Adjust bearing correctly.Adjust bearing correctly. Use self aligning bearing , avoid misalignment.Use self aligning bearing , avoid misalignment.

Wear is observed on the cage pockets Wear is observed on the cage pockets accompanied by fractures between crosspiece accompanied by fractures between crosspiece and and side edge. and and side edge.

SYMPTOMSSYMPTOMS



Fig Shows cage wear Fig Shows cage wear due to rings tilting due to rings tilting towards one another.towards one another.

Cage WearCage Wear

CAUSESCAUSES

Excess tilting of the bearing rings to one Excess tilting of the bearing rings to one another. Eg. Ball bearings with combined another. Eg. Ball bearings with combined load.Varying circumferential velocity of balls as load.Varying circumferential velocity of balls as a result.a result.

Stress in cage area high, particularly with poor Stress in cage area high, particularly with poor lubrication.lubrication.

REMEDIESREMEDIES

Avoid tilting.Avoid tilting. Apply eventually self aligning bearing or Apply eventually self aligning bearing or

bearing with polyamide cages.bearing with polyamide cages. Special design long hole pockets can be Special design long hole pockets can be

used.used.

Intense wear at the webs between the cage Intense wear at the webs between the cage pockets, deformation or fracture may occur.pockets, deformation or fracture may occur.

SYMPTOMSSYMPTOMS



Cage WearCage Wear

Fig Shows fractured Fig Shows fractured cage rivet connections cage rivet connections resulting From resulting From vibratory stresses.vibratory stresses.

CAUSESCAUSES

Vibration or shocks which superimpose the Vibration or shocks which superimpose the normal cage stress.normal cage stress.

Tilting in the case of deep groove ball bearings.Tilting in the case of deep groove ball bearings.

REMEDIESREMEDIES

Use of solid cage instead of a pressed cage.Use of solid cage instead of a pressed cage. Use of window type cage particularly when Use of window type cage particularly when

stress is great.stress is great.

Loosening of riveted joints, rivet fracture.Loosening of riveted joints, rivet fracture. Breaking of cage prongs.Breaking of cage prongs.

SYMPTOMSSYMPTOMS



Cage WearCage Wear

Fig Shows disruptive Fig Shows disruptive fracture at the side edge fracture at the side edge of a spherical roller of a spherical roller bearing.bearing.

CAUSESCAUSES

Mounting damage.Mounting damage. Kinematically permissible speed exceeded.Kinematically permissible speed exceeded. Moment load too high.Moment load too high. As a result of wear due to poor lubrication.As a result of wear due to poor lubrication. In case of tapered roller pairs when clearance is In case of tapered roller pairs when clearance is

large and reversal of axial loading is quick.large and reversal of axial loading is quick.

REMEDIESREMEDIES

Mount carefully.Mount carefully. Filter lubricant.Filter lubricant. Operate bearing pair preloaded if possible.Operate bearing pair preloaded if possible. Avoid tilting as much as possible.Avoid tilting as much as possible.

Fracture of cage edges, crosspiece fracture Fracture of cage edges, crosspiece fracture more seldom.more seldom.

SYMPTOMSSYMPTOMS



Cage WearCage Wear

Fig Shows melted face of a Fig Shows melted face of a plastic cage resulting from plastic cage resulting from incorrect heating on incorrect heating on heating plate.heating plate.

CAUSESCAUSES

Incorrect heating of the bearing for mounting.Incorrect heating of the bearing for mounting. Unsuitable mounting aids.Unsuitable mounting aids.

REMEDIESREMEDIES Mount the bearing as the manufacturer’s Mount the bearing as the manufacturer’s

recommendation. Refer FAG publication WL 80 recommendation. Refer FAG publication WL 80 100 “Mounting and Dismounting of rolling 100 “Mounting and Dismounting of rolling bearings”bearings”

Initial fusing in the case of plastic cages, grooves Initial fusing in the case of plastic cages, grooves or warping in the case of metallic cages.or warping in the case of metallic cages.

SYMPTOMSSYMPTOMS



Sealing Damage

Fig a

Fig b

CAUSESCAUSES Operating temperature too high for sealing Operating temperature too high for sealing

material.material. Extreme amount of dirt at the sealing lip.Extreme amount of dirt at the sealing lip. Sealing interference too high.Sealing interference too high. Sealing lip is not lubricated.Sealing lip is not lubricated.

REMEDIESREMEDIES

Use suitable sealing material.Use suitable sealing material. Use non rubbing preseal.Use non rubbing preseal. Grease sealing lips.Grease sealing lips.

Sealing lips no longer like edges but widened.Sealing lips no longer like edges but widened. Cracks in sealing material,sealing lip partly broken Cracks in sealing material,sealing lip partly broken

off. off.

Fig a -Cross section of a worn sealing lip.Fig a -Cross section of a worn sealing lip. Fig b -Hardened sealing with wear and fractures.Fig b -Hardened sealing with wear and fractures.

SYMPTOMSSYMPTOMS



Sealing Damage

Fig a

Fig a

Fig b

CAUSESCAUSES

Incorrect mounting aids.Incorrect mounting aids. Bearing over heated.Bearing over heated. Sealing occasionally removed.Sealing occasionally removed. Bearing blown off with compressed air.Bearing blown off with compressed air.

REMEDIESREMEDIES

Ensure careful mounting with suitable mounting Ensure careful mounting with suitable mounting devices.devices.

Never open sealed bearings if they are to be Never open sealed bearings if they are to be subsequently used.subsequently used.

Seal is too far inside, dented, discoloured, Seal is too far inside, dented, discoloured, scratched. Sealing lips are turned up.scratched. Sealing lips are turned up.

Fig a -Dented seal with scorings.Fig a -Dented seal with scorings. Fig b -Turned-up sealing lips.Fig b -Turned-up sealing lips.

SYMPTOMSSYMPTOMS



INTRODUCTION ON HOW TO RECOGNISE TAPERED INTRODUCTION ON HOW TO RECOGNISE TAPERED ROLLING BEARING DAMAGESROLLING BEARING DAMAGES

ABRASIVE WEARABRASIVE WEAR



GROOVING GROOVING ETCHINGETCHING



DEEP INDENTATION CAUSEDDEEP INDENTATION CAUSEDBY FOREIGN MATTERBY FOREIGN MATTER

EXCESSIVE EXCESSIVE PRELOAD/OVERLOAPRELOAD/OVERLOADD



ADVANCED DAMAGE ADVANCED DAMAGE CAUSED BY INADEQUATE CAUSED BY INADEQUATE LUBRICATIONLUBRICATION

RESULT OF OFF TAPER RESULT OF OFF TAPER CONDITON IN THE HOUSINGCONDITON IN THE HOUSING



CAGE DAMAGE BY CAGE DAMAGE BY IMPROPER HANDLINGIMPROPER HANDLING



HIGH SPOTS OR BURRS IN THEHIGH SPOTS OR BURRS IN THECUP CAUSED DUE TO INCORRECTCUP CAUSED DUE TO INCORRECTMOUNTING PRACTICESMOUNTING PRACTICES

DAMAGE CAUSED DUE TO DAMAGE CAUSED DUE TO IMPROPER FITS OF CUPS OR IMPROPER FITS OF CUPS OR CONESCONES



FALSE BRINELLING CAUSED FALSE BRINELLING CAUSED OWING TO TRANSPORTATIONOWING TO TRANSPORTATION

FALSE BRINELLINGFALSE BRINELLING



DAMAGE CAUSED BY SEVEREDAMAGE CAUSED BY SEVEREIMPACT LOAD - ALSO CALLED IMPACT LOAD - ALSO CALLED TRUE BRINELLINGTRUE BRINELLING

ADVANCE STATE OF ADVANCE STATE OF DAMAGEDAMAGECAUSED BY INADEQUATECAUSED BY INADEQUATELUBRICATION.LUBRICATION.



FLUTING OR GROOVES CAUSED BY PASSAGE OF ELECTRIC FLUTING OR GROOVES CAUSED BY PASSAGE OF ELECTRIC CURRENT.CURRENT.



EXCESSIVE PRELOAD OR OVERLOADEXCESSIVE PRELOAD OR OVERLOAD

Documents

Bearing Failures, Causes & Remidies 25.02.08