care and maintenance of bearings contents 1 introduction 2 inspection of bearings 3 inspection when machine is running 3 1 bearing temperature 3 2 operating sounds of bearing 3 3 vibration of bearing 3 4 lubricant selection 3 5 relubrication 4 check of bearings after operation 5 bearing failures and solutions 5 1 flaking 5 2 peeling 5 3 spalling 5 4 smearing 5 5 wear 5 .6 speckles and discoloration 5 7 indentations 5 8 chipping 5 9 cracking 5.10 rust and corrosion 5.11 seizing 5.12 fretting and fretting corrosion 5.13 electrical pitting 5.14 rolling path skewing 5.15 damage to retainers 5.16 creeping 3 3 3 3 3 5 5 5 7 7 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2
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3.3 vibration of bearing damage to the bearing can be detected early by measuring the vibration of the machine the degree of damage is inferred from quantitative analysis of the amplitude and frequency of the vibration however values measured differ depending on the measuring point and the operating condition of the bearing it is desirable to accumulate measurement data and establish evaluation criteria for each machine 3.4 lubricant selection the purpose of lubricating the bearing is to cover the rolling contact surfaces and sliding contact surfaces with a thin oil film to avoid direct metal-to-metal contact effective lubrication of the rolling-element bearing has the following effects 1 reduces friction and abrasion 2 transports heat generated by friction 3 prolongation of service life 4 prevents rust corrosion 5 keeps foreign objects or contamination away from rolling elements and raceways for these purposes a lubricant should be selected by referring to the following criteria 1 gre
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table 3.7 frequency of lubricating oil analysis inspection interval lubrication system disk lubrication method oil bath or splash lubrication circulating lubrication normal operating conditions one year 6 months 9 months severe operating conditions 6 months 3 months 1 to 3 months 5 bearing failures and solutions the bearing is generally usable up to the end of the rolling fatigue life if handled properly if it fails earlier it may be due to some fault in the selection handling lubrication and/or mounting of the bearing it is sometimes difficult to determine the real cause of bearing failure because many interrelated factors are possible it is however possible to prevent the recurrence of similar problems by considering possible causes according to the situation and condition of the machine on which the bearings failed also installation location operating conditions and surrounding structure of the bearings should be taken into consideration bearing failures are classified and illustrat
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photo a-5 ˇinner ring of deep groove ball bearing ˇflaking on one side of the raceway surface ˇthe cause is an excessive axial load photo a-6 ˇinner ring of spherical roller bearing ˇflaking only on one side of the raceway surface ˇthe cause is an excessive axial load photo a-7 ˇtapered roller bearing ˇflaking on 1/4 circumference of inner ring raceway with outer ring and rollers discolored light brown ˇthe cause is excessive pre-load photo a-8 ˇouter ring of double row angular contact ball bearing ˇflaking on 1/4 circumference of outer ring raceway ˇthe cause is poor installation photo a-9 ˇthrust ball bearing ˇflaking on inner ring raceway bearing ring fastened to shaft and balls ˇthe cause is poor lubrication photo a-10 ˇouter ring raceway of double row tapered roller bearing rct bearing ˇflaking originated from electric pitting on the raceway surface refer to section 5.13 electrical pitting 9
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5.3 spalling condition score accompanying seizing mounting score in axial direction scores on roller end face and guide rib-cycloidal scores scratches in spinning direction on raceway surface and rolling contact surfaces cause poor mounting and removing practice oil film discontinuation on the contact surface due to excessive radial load foreign object trapping or excessive pre-load slippage or poor lubrication of rolling elements solution 1 improvement in mounting and removing procedures 2 improvement in operation conditions 3 correction of pre-load 4 selection of adequate lubricant and lubrication system 5 improvement of sealing efficiency photo c-1 ˇinner ring of cylindrical roller bearing ˇspalling on rib ˇthe cause is excessive load photo c-2 ˇinner ring of cylindrical roller bearing ˇspalling on raceway surface and cone back face rib ˇthe cause is poor lubrication photo c-3 ˇrollers of tapered roller bearing ˇcycloidal spalling on the end faces scuffing ˇthe cause is poor lubrica
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5.5 wear condition surface is worn and dimensions are reduced compared with other portions surface mostly roughened and scored cause ingress of solid foreign objects dirt and other foreign objects in lubricant poor lubrication skewing of rollers solution 1 selection of optimum lubricant and lubrication system 2 improvement in sealing efficiency 3 filtration of lubricating oil 4 elimination of misalignment photo e-1 ˇouter ring of cylindrical roller bearing ˇstepped wear on raceway surface ˇthe cause is poor lubrication photo e-2 ˇinner ring of cylindrical roller bearing inner ring of which is shown in photo e-1 ˇstepped wear on full circumference of raceway ˇthe cause is poor lubrication photo e-3 ˇouter ring of double row angular contact ball bearing hub unit bearing ˇwear on one side of the raceway ˇthe cause is poor lubrication photo e-4 ˇretainer of cylindrical roller bearing ˇwear of pockets of machined high tensile brass casting retainer g1 13
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5.8 chipping condition partial chipping of inner ring outer ring or rolling elements cause trapping of large solid foreign objects impacts or excessive load poor handling solution 1 trouble shooting and improvements of impacts and excessive load 2 improvement in handling 3 improvement in sealing characteristics photo h-1 ˇcylindrical roller bearing ˇchipping of guide ribs of inner and outer rings ˇthe cause is excessive impact load photo h-2 ˇinner ring of spherical roller bearing ˇrib chipped ˇthe cause is excessive impact load photo h-3 ˇinner ring of tapered roller bearing ˇchipping of cone back face rib ˇthe cause is impact due to poor mounting photo h-4 ˇinner ring of double row tapered roller bearing ˇchipping of side face ˇthe cause is impact due to improper handling 16
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5.10 rust and corrosion condition rusting or corrosion of bearing ring and rolling element surfaces sometimes rusted at spacing equal to the distances between the rolling elements cause ingress of water or corrosive material such as acid condensation of moisture contained in the air poor packaging and storing conditions and handling with bare hands solution 1 improvement in sealing effect 2 periodic inspection of lubricating oil 3 careful handling of bearing 4 measures for preventing rusting when not operating for a long period of time photo j-1 ˇinner ring of tapered roller bearing ˇrusting on raceway surface spacing equivalent to the distance between rollers the cause is water in lubricant photo j-2 ˇouter ring of tapered roller bearing ˇrusting on raceway surface spacing equivalent to the distances between rollers the cause is water in lubricant some points are corroded photo j-3 ˇroller of spherical roller bearing ˇrust as well as corrosion on rolling contact surface ˇingress of wa
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5.12 fretting and fretting corrosion condition fretting surfaces wear producing red rust colored particles that form hollows on the raceway surface dents called false brinelling are formed at spacing equal to distances corresponding to the rolling elements cause if a vibrating load works on contacting elements resulting in small amplitude oscillation lubricant is driven out from contact and parts are worn remarkably oscillation angle of the bearing is small poor lubrication no lubrication fluctuating load vibration during transportation vibration shaft deflection installation error loose fit solution 1 inner ring and outer ring should be packaged separately for transportation if not separable bearings should be preloaded 2 use oil or high consistency grease when bearings are used for oscillation motion 3 change lubricant 4 fix shaft and housing 5 improve fit photo l-1 ˇinner ring of cylindrical roller bearing ˇcorrugated fretting along full circumference of raceway ˇthe cause is vibrat
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5.14 rolling path skewing condition rolling element contact path on raceway surface strays or skews cause deformation or tilt of bearing ring due to poor accuracy of shaft or housing poor rigidity of shaft or housing deflection of shaft due to excessive clearance solution 1 improvement in machining accuracy of shaft and housing 2 improvement in rigidity of shaft and housing 3 employment of adequate clearance photo n-1 ˇspherical roller bearing ˇcontacts on inner ring outer ring and rollers are not even ˇthe cause is poor mounting photo n-2 ˇouter ring of tapered roller bearings ˇcontact path on raceway surface strays ˇthe cause is poor mounting photo n-3 ˇrollers of tapered roller bearing of which outer ring is shown in photo n-2 ˇcontact marks on rolling contact surfaces are not even 22
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5.16 creeping condition fitting surfaces are glazed or matted and sometimes spalled as well cause fitting of inner ring is loose on inner ring drive bearing and that of the outer ring is loose on outer ring drive bearing if the housing is made of a light alloy such as aluminum fit may become loose due to the difference of thermal expansion solution 1 improvement in fit 2 improvement in machining accuracy of shaft and housing photo p-1 ˇinner ring of deep groove ball bearing ˇbore wall glazed by creep photo p-2 ˇinner ring of tapered roller bearing ˇspalling due to creep at the middle of bore wall photo p-3 ˇinner ring of thrust ball bearing ˇspalling and friction cracking due to creep on bore wall photo p-4 ˇinner ring of tapered roller bearing ˇspalling and friction cracking on width surface due to creep crack developed into a split reaching bore wall 24
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