Design Life vs. Service Life For Bearings

There are a number of reasons that the actual life of a bearing in operation may fall short of the design life.

•Normal Fatigue (statistically very few)

•Over-Loading

•Excessive Speed

•Poor Lubrication

•Improper Fits

•Extreme Temperatures

•Contamination

•Poor Handling

•Electrical Damage

Recognizing the symptoms and taking appropriate countermeasures can reduce bearing failures and increase machine reliability.

Failure Modes and Causes



Fatigue (Subsurface Initiated)

Over a period of extended use, under favorable  operating conditions, it is normal for small fatigue cracks to form beneath the surface and grow until the surface is reached.

Eventually, a chunk of material breaks off forming a spall.

This is a normal fatigue failure and generally happens after the bearing reaches its design life.



Subsurface Initiated Fatigue

Symptom: Spall(s) in loaded portion of raceway or roller. Pattern of spalling may indicate normal or abnormal load distribution.

Cause: Normal material fatigue, high load (short life), abnormal loading (if indicated by spall pattern).

Countermeasures (if abnormal): Select larger or improved load rating bearing, reduce load, correct cause of abnormal loading.

Wear/Spall Pattern Analysis

Spalling or wear typically occurs in a pattern that shows how the load was distributed in the bearing. This can be a clue to identifying unusual load conditions.