Tapered Roller Bearing Diagnosis

GENERAL INFORMATION
Consider the following factors when diagnosing bearing condition:
1. General condition of all parts during disassembly and inspection
2. Classify the failure with the aid of the illustrations.
3. Determine the cause.
4. Make all repairs following recommended procedures.

ABRASIVE ROLLER WEAR





Pattern on races and rollers caused by fine abrasives. Clean all parts and housings, check seals and bearings and replace if leaking, rough or noisy.

ABRASIVE STEP WEAR





Pattern on roller ends caused by fine abrasives. Clean all parts and housings, check seals and bearings and replace if leaking, rough or noisy.

GALLING





Metal smears on roller ends due to overheat, lubricant failure or overload. replace bearing check seals and check for proper lubrication.

ETCHING





Bearing surfaces appear gray or grayish black in color with related etching away of material usually at roller spacing. Replace bearings, check seals, and check for proper lubrication.

BENT CAGE








Cage damaged due to improper handling or tool usage. Replace bearing.

CAGE WEAR





Wear around outside diameter of cage and roller pockets caused by abrasive material and inefficient lubrication. Clean related parts and housings. Check seals and replace bearings.

INDENTATIONS





Surface depressions on race and rollers caused by hard particles of foreign material. Clean all parts and housings. Check seals and replace bearings if rough or noisy.

FRETTAGE





Corrosion set up by small relative movement of parts with no lubrication. replace bearing. Clean related parts. Check seals and check for proper lubrication.

SMEARS





Smearing of metal due to slippage. Slippage can be caused by poor fits, lubrication, overheating, overloads or handling damage. Replace bearings, clean related parts and check for proper fit and lubrication.

STAIN DISCOLORATION





Discoloration can range from light brown to black caused by incorrect lubricant or moisture. Re-use bearing if stains can be removed by light polishing or if no evidence of overheating is observed. Check seals and related parts for damage.

HEAT DISCOLORATION





Heat discoloration can range from faint yellow or dark blue resulting from overload or incorrect lubricant. Excessive heat can cause softening of races or rollers. To check for loss of temper on races or rollers a simple file test may be made. A file drawn over a tempered part will grab and cut metal, whereas, a file drawn over a hard part will glide readily with no metal cutting. Replace bearings if overheating damage is indicated. Check seals and other parts.

MISALIGNMENT





Outer race misalignment due to foreign object. Clean related parts and replace bearing. Make sure races are properly sealed.

CRACKED INNER RACE





Race cracked due to improper fit, cocking, or poor bearing seats. Replace bearing and correct bearing seats.

FATIGUE SPALLING





Flaking of surface metal resulting from fatigue. Replace bearing, clean all related parts.

BRINELLING





Surface indentations in raceway caused by rollers either under impact loading or vibration while the bearing is not rotating. Replace bearing if rough or noisy.