ENGINEMAN 1 & CTroubleDirty bearingSpalled or pittedrollers or racesDented (brinelled)r a c e sFailed separatorRaces abraded onexternal surfacesCracked raceExcessiveloosenessCausesImproper handling orstorageUse of dirty or improperlubricantFailure to clean housingPoor condition of sealDirt in bearingWater in bearingImproper adjustment oftapered roller bearingsBearing misaligned or offsquareImproper installation orremovalVibration while bearing isinoperativeInitial damage during in-stallation or removalDirt in the bearingLocked bearingImproper fit of racesImproper installation orremoval (cocking)Abrasives in lubricantFigure 3-23.—Antifriction bearing troubles and their causes.Brinelled or dented races are most easilyrecognized by inspection after a thorough clean-ing. Brinelling receives its name from its similarityto the Brinnell hardness test, in which a hardenedball is pressed into the material. The diameter ofthe indentation is used to indicate the hardnessof the material. Bearing races may be brinelledby excessive and undue pressures during installa-tion or removal, or by vibration from othermachinery while the bearing is inoperative. Ifheavy shafts supported by frictionless bearings areallowed to stand motionless for a long time, andif the equipment is subject to considerable vibra-tion, brinelling may occur. This is due to the peen-ing action of the rollers or balls on the races.3-36Brinelled bearings must not be placed back inservice. Steps can be taken to prevent brinelling.Proper maintenance will help a great deal, andthe best insurance against brinelling caused byvibration is to rotate the shafts supported by thefrictionless bearings at regular intervals (at leastonce a day) during periods of idleness. Theseactions will prevent the rollers from resting toolong upon the same portion of the races.Separator failure may become apparent bynoisy operation. Inspection of the bearings mayreveal loose rivets, failure of a spot weld, or crack-ing and distortion of the separator. Failure ofseparators can usually be avoided if properinstallation and removal procedure are followed,and steps are taken to exclude the entry of dirt.Abrasion (scoring, wiping, burnishing) on theexternal surface of a race indicates that relativemotion has occurred between the race and thebearing housing or shaft surface. The race adja-cent to the stationary member is usually made apush fit so that some creep will occur. Creep isa very gradual rotation of the race. This extremelyslow rotation is desirable as it prevents repeatedstressing of the same portion of the stationaryrace. Wear resulting from the proper creep isnegligible and no damaging abrasion occurs.However, abrasion caused by locked bearings orthe improper fit of the races must be prevented.Cracked races will usually be recognized bya definite thump or clicking noise in the bearingduring operation. Cleaning and inspection is thebest means of determining if cracks exist. Cracksusually form parallel to the axis of the race. Thecracking of bearing races seldom occurs ifproper installation and removal procedures arefollowed.Excessive looseness may occur on rare occa-sions even though no surface disintegration isapparent. Since many frictionless bearings appearto be loose, even when new, looseness is notalways a sign of wear. The best check for excessivelooseness is to compare the suspected bearing witha new one.Wear of bearings, which cause loosenesswithout apparent surface disintegration, isgenerally caused by the presence of fine abrasivesin the lubricant. Taking steps to exclude abrasivesand keeping lubricating oil filters and strainers ingood condition is the best way to prevent this typeof trouble.
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business