There are many reasons for bearing failure, but the common ones are incorrect use, pollution, improper use of lubricants, damage during loading and unloading or handling, and installation errors. Diagnosing the cause of the failure is not difficult, as the cause of the bearing failure can be determined from the marks left on the bearing. However, when post-mortem analysis provides valuable information, it is best to avoid failure altogether by correctly selecting the bearing in the first place. 

1. Reasons for bearing failure

About 40% of ball bearing failures are caused by dust, dirt, debris contamination and corrosion. Contamination is usually caused by incorrect use and poor use environment, it can also cause torque and noise problems. Bearing failures caused by the environment and contamination are preventable and the cause of such failures can be determined by simple visual inspection. 
Through the post-failure analysis, we can know which aspects should be checked for the bearing that has failed or is about to fail. Understanding failure mechanisms such as erosion and fatigue failure can help eliminate the source of the problem. 
As long as the use and installation are reasonable, bearing erosion is easy to avoid. Denudation is characterized by indentations in the raceway of the bearing ring that result from shock loading or incorrect installation. Exfoliation usually occurs when the load exceeds the yield limit of the material. Erosion can also occur if installed incorrectly so that a load traverses the bearing rings. Indentations in the bearing rings also generate noise, vibration and additional torque. 
A similar defect is the oval indentation caused by the vibration of the balls between the rings when the bearing is not rotating. This kind of damage is called low-load vibration erosion. Such damage occurs in equipment in transit and in equipment that vibrates when not in operation. In addition, debris from low-load vibration acts like abrasive particles and can further damage the bearing. Unlike denudation, low-load vibratory corrosion is usually characterized by a reddish color in lubricants due to fretting corrosion. 
Eliminating vibration sources and maintaining good bearing lubrication can prevent low-load vibration. Isolating the equipment or isolating the base can reduce vibrations in the environment. In addition, adding a small preload to the bearing not only helps the ball and bearing ring to maintain close contact, but also helps to prevent low-load vibration and corrosion during equipment transportation.
The causes of bearing jamming are lack of internal clearance, improper lubrication and excessive load. Excessive friction and heat soften the bearing steel before it seizes. Overheated bearings usually change color, usually bluish-black or yellowish. Friction can also stress the cage, which can damage the support frame and accelerate bearing failure. 
Premature fatigue failure of materials is caused by excessive preload after heavy loading. If these conditions are unavoidable, bearing life should be carefully calculated to develop a maintenance plan. 
Another solution is to replace the material. If standard bearing materials do not guarantee adequate bearing life, special materials should be used. In addition, if the problem is caused by excessive load, a bearing with higher load resistance or other structure should be used. 
Creeping is not as common as premature fatigue. Bearing creep is caused by excessive clearance between the shaft and the inner ring. Creep is very harmful, it not only damages the bearing, but also damages other parts. 
Creeping is marked by scratches, scuffs, or color changes on the shaft and inner ring. In order to prevent creep, the bearing housing parts and shaft accessories should be visually inspected first. 
Creeping is related to improper installation. If the bearing ring is misaligned or warped, the balls will follow a non-circular orbit. This problem is caused by incorrect installation or tolerances or insufficient verticality at the bearing installation site. If the deflection exceeds 0.25°, the bearing will fail prematurely. 
Checking for lubricant contamination is much more difficult than checking for misfit or creep. Contamination is characterized by premature bearing wear. Solid impurities in lubricants are like abrasive particles. Poor lubrication between the balls and cage can also wear and weaken the cage. In this case, lubrication is essential for the cage in fully machined form. In contrast, belt or crown cages allow the lubricant to reach all surfaces more easily. 
Rust is a form of moisture contamination and its presence often indicates poor material selection. If a material has been tested to be suitable for the job, the easiest way to prevent rust is to pack the bearing and not unpack it until it is installed and used.