Anti-friction Bearings & Electrical Discharging Here is an acceleration spectrum recorded on the drive motor of the Penthouse 7 Supply Fan.

Sideband peaks occurring at the BPFO defect frequency Anti-friction Bearings & Electrical Discharging Sideband peaks occurring at the BPFO defect frequency High frequency, non-synchronous peaks appear in the upper region of the spectrum. These peaks contain “sideband” peaks that coincide with the fault frequency of the outer race (BPFO) for the outboard bearing.

Actual fault frequency is occurring at 3.628xRPM Anti-friction Bearings & Electrical Discharging LOOKUP In Bearing File: MVWBRG.DAT ************************************************** ID# BEARING TYPE #B/R FTF BSF BPFO BPFI ------- ----------------------- ------ ------ ------- --------- -------- 8303 NSK 6208z 9 .401 2.421 3.607 5.393 8608 NSK 6208 (MVW) 9 .401 2.421 3.607 5.393 Actual fault frequency is occurring at 3.628xRPM The outer race defect (BPFO) lists a defect frequency at 3.607 orders. The actual faults are occurring at sidebands 3.628 orders. The frequency is higher because of geometrical changes that have occurred as a result of degradation.

Anti-friction Bearings & Electrical Discharging Over 28 G’s pk to pk acceleration Impacting with high peak to peak energy Waveform data indicates signs of severe impacting. Peak to peak energy exceeds 28.0 G’s of acceleration. The waveform data helps determine a sense of severity of the bearing defect.

Before bearing replacement After bearing replacement Anti-friction Bearings & Electrical Discharging Before bearing replacement After bearing replacement A comparison spectrum shows the drive motor condition both before and after bearing replacement. Note the amplitude reduction in the non-synchronous harmonic peaks.

A shaft grounding brush was installed on this drive motor! Anti-friction Bearings & Electrical Discharging Outer bearing race has indications of “fluting” as a result of electrical discharging. A shaft grounding brush was installed on this drive motor!