Electrical Pitting Causes and Countermeasures

How:

Grease isolate the O/R、I/R and ball after uniform distribution in the bearing, but under some circumstance electric potential difference would cumulative, the current force to pass O/R and I/R instantaneous when it reach critical value, cause the spark inside the bearing, make the surface of raceway and rolling elements into molten state, it is electrical pitting.

Possible source of voltage and current:

External: With encoder, frequency converter, etc.

Unbalance: Gap unequal between rotor and stator, cause shaft voltage (shaft current) during operation.

Static electricity: Running belt, belt etc. cause triboelectric.

Performance after the electrical pitting:

Grease discoloration (turn to dark), discharge cause overheating.

Pit (slight), wave (severe) trace on the raceway.

Pit(Slight)

ZOOM

Wave(Severe)

ZOOM

Countermeasures:

Conduct:(1) Conductive grease (contain with Carbon or Molybdenum disulfide).(2) Earth bolt or carbon brush etc. at the circuit.

Insulate:(1) Replace the rolling element to ceramic ball.(2) Ceramic layering on the bearing.