1. Pollution
Dirt, abrasives, chain links, dust, steel shavings from contaminated work areas, dirty hands or tools, or foreign matter in lubricants or cleaning solutions can cause damage to bearings, denting rolling elements and raceways, causing vibration, and should Filter lubricants and clean work areas, tools, fixtures and hands to reduce the risk of contamination.

2. Improper installation
In most cases, the bearing should be installed on the rotating ring with a press fit. Improper installation can lead to bearing dents, wear, ring cracking, high operating temperatures, early fatigue and premature failure, etc.

3. Misalignment
Misalignment is usually caused by a bent shaft, misaligned shoulder, misaligned gasket, misaligned clamp nut, or improper installation with a loose fit. Improper alignment can lead to overheating and separator failure. Shaft and housing shoulders and housing runout should be checked, and precision grade lock nuts should be used.

4. Corrosion
Condensation and corrosion caused by moisture, acid action, poor or damaged grease, poor packaging and excessive temperature reversals can cause wear on the finished surfaces of ball and roller bearings, red or red color on rolling elements, raceways or cages. Brown stains or deposits, increased vibration and subsequent wear, increased radial clearance or loss of preload.
Corrosive liquids should be diverted away from the bearing area, use integrally sealed bearings, and consider the use of external seals in particularly harsh environments. In addition, if corrosive environments cannot be avoided, the use of appropriate bearing materials (stainless steel) will also help.

5. Lubrication failure
Insufficient lubrication, use of improper lubricants, complete lack of lubrication or excessive temperatures can cause lubricant deterioration, discolored rolling elements (blue or brown) and rolling element tracks, overheated or excessive bearing wear. The appropriate type and correct amount of lubricant should be used to avoid grease loss and appropriate relubrication intervals should be followed.

6. Electrical damage (chatter)
Continuous passage of AC or DC current can cause electrical damage, producing brown marks on a large portion of the raceway, or covering the entire circumference of the raceway. Current flow through the bearings should be prevented by grounding or insulation, or electrically insulated bearings should be used.

7. Fatigue
Overload, excessive preload force, too tight inner ring fit, and bearing operation exceeding its calculated fatigue life. Typically causing bearing surface spalling, manifested by fractures of the running surfaces and subsequent removal of small discrete particles of material from the inner race, outer race or rolling elements, spalling is gradual and, once initiated, will spread with continued operation. Bearings should be replaced, redesign considered to use bearings with greater calculated fatigue life, internal clearances, and appropriate shaft and housing recommendations obtained.