Reasons Why Bearings Fail
1. Lubrication Failure According to a recent study, up to 80 percent of bearings failures are caused by improper lubrication. This includes insufficient lubrication, use of improper lubricants or excessive temperatures that degrade the lubricant.
What to Look for Look for discolored rolling elements (such as blue or brown) and rolling-element tracks as well as overheating or excessive wear in the bearing. How to Fix it Use the appropriate type and correct amount of lubricant, avoid grease loss, and follow appropriate relubrication intervals.
2. Contamination Contamination is caused by foreign substances getting into bearing lubricants or cleaning solutions. These include dirt, abrasive grit, dust, steel chips from contaminated work areas and dirty hands or tools. What to Look for Watch for denting of rolling elements and raceways that cause vibration. How to Fix it Filter the lubricant and clean work areas, tools, fixtures and hands to reduce the risk of contamination.
3. Improper Mounting In most instances, bearings should be mounted with a press fit on the rotating ring. What to Look for A number of conditions can cause denting, wear, cracked rings, high operating temperatures, early fatigue and premature failure of bearings. These include mounting bearings on shafts by applying pressure or blows to the outer race, mounting bearings into a housing by pressing on the inner ring, loose shaft fits, loose housing fits, excessively tight fits, out-of-round housings and a poor finish on the bearing seat.
4. Misalignment Bent shafts, out-of-square shaft shoulders, out-of-square spacers, out-of-square clamping nuts and improper installation due to loose fits can cause misalignment, which may result in overheating and separator failure. What to Look for A wear path that is not parallel to the raceway edges of the non-rotating ring should be noted. How to Prevent it Inspect shafts and housings for runout of shoulders and bearing seats, and use precision-grade locknuts.
5. False Brinelling Rapid movement of the balls in a raceway while equipment is idle wears away at the lubrication. In addition, a lack of rotation in the bearing does not allow fresh lubricant to return to the spot. Both of these conditions result in false brinelling. What to Look for You may see linear wear marks in the axial direction at the rolling-element pitch or no raised edges as opposed to marks due to incorrect mounting. How to Fix it Eliminate or absorb external vibration that could cause the balls to move. Also, be sure to use lubricants containing anti-wear additives.