All bearings have some defects, and they are graded accordingly. It is only a matter of degree of defects that separates’ out the highest –quality bearings from the lowest quality ones. The primary causes of bearing failures are:
1. Contamination, including moisture (Some sources claim that 40 percent of bearing failures are caused by contamination).
3. Lack of lubrication
4. Defects created after manufacturing
Bearings typically achieve only about 10 percent of their rated life. Tests of bearing life under laboratory conditions yield lives of 100 to 1000 years. Clearly, the design and manufacturing do not present deficiencies that limit their life. In the laboratory, there is no contamination of dirt or water, there is little imbalance or misalignment to cause overstress, the lubrication is the best, and the bearing is handled as if it were a delicate instrument, which it is. Under service conditions, these factors are not all optimum as they wear during the laboratory tests. The prediction of bearing failure is useful information to the production manager, but the root cause of the failure is the key information that can prevent a recurrence. The point of this discussion is that very few root cause failure modes originate at the factory, the majority of failures are worked into bearings once they get into our hands.
This experiment shows the four important bearing faults and their characteristic vibrational frequency. The equipment can be done by changing various factors such as no. of balls, rpm, etc.