Pelletizing Disc Drive Dual Fault - Gear Backlash and Bearing Damage
Condition monitoring of a pelletizing disc drive identified a combined mechanical fault on the pinion shaft. The fault, diagnosed using SPM and HD envelope analysis, was caused by excessive backlash and an inner race bearing defect.
Dual Fault Detection in Pelletizing Disc Drive with 32Rpm– Gear Backlash & Bearing Inner Race Damage
During routine condition monitoring on a pelletizing disc drive, we identified a combined mechanical fault on the pinion shaft (Point #10), diagnosed using SPM shock pulse and HD envelope analysis.
📌 The pinion (24 teeth, 32.5 RPM) showed a dominant peak at ~13 Hz in the spectrum, consistent with gear mesh frequency. This was linked to excessive backlash, confirmed audibly as metallic clattering during operation — a typical symptom of tooth surface wear and pitting.
📈 The SPM time signal showed strong periodic impacts, while the HD envelope revealed modulated impulses at shaft speed (~0.53 Hz), a clear indicator of an inner race bearing defect.
🔍 Post-shutdown inspection validated the diagnosis:
Severe wear on pinion gear teeth
Spalling on the inner ring of the bearing
🛠️ After component replacement, vibration levels dropped significantly. Shock pulse values and envelope signals normalized, confirming successful corrective action.
🎯 This case illustrates how combining SPM + envelope techniques, along with proper sensing hardware, can isolate multiple concurrent faults — even in slow-speed, high-load applications.
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