Bearing Inner Race Failure from Vibration Analysis of a Ball Mill

During a recent vibration analysis of a ball mill (Allis Chalmers 13.5’x4H) operating at approximately 200 RPM (3.33 Hz), significant amplitude components were observed in the envelope spectrum at various harmonics, including 3.3 Hz, 6.6 Hz, 10 Hz, 13.4 Hz, 16.6 Hz, 20 Hz, and higher multiples. These peaks, aligned with the shaft's rotational frequency, indicate a potential cracked bearing inner race.

Could this be the source?

Have you encountered similar envelope patterns while diagnosing inner race cracks? What were the initial signs you noticed before the fault escalated? Share your experiences and insights in the comments.

ball mill bearing inner race vibration analysis