Technology Tip:
Misalignment
NTN was approached to examine a failed NU324EG1C3 cylindrical roller bearing from
the drive end of an electric motor. The request originated from a BC Bearing and NTN customer.
Evident symptoms of failure included a fractured inner ring, heavy raceway wear and lubricant
deterioration. Marcus Wickert, P. Eng., Manager of Technical Resources, in the course of
thorough inspection was able to isolate the root cause of failure as misaligned operation.
Although an inner ring fracture and poor lubrication condition appeared as the most acute
symptoms of failure, distinctive wear patterns lead to the primary misalignment conclusion.
Fracture occurred only as a secondary result to elevated stress levels induced by roller
edge loading and the resultant heavy wear. An inner ring raceway Talysurf conducted at
our Canadian manufacturing facility, clearly captured the uneven wear profile caused from
rolling element edge loading.
As misalignment forces skewed roller operation, the rollers revealed severe wear on one
face from rubbing against the outer ring guide rib. The roller retainer wear mirrored
this condition with heavy tapered cage pocket wear.
Consequently, the lubrication became deteriorated from the resulting elevated
operating temperatures and advanced material wear. Thus the observed poor lubrication
condition was yet another secondary symptom to the misalignment. Photo (above): Outer complement as received.
Photo (below): Inner ring fracture site.
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