For long periods of time, we are experiencing higher vibrations on our ABB motor, journal bearing with 2 proximity probes (no keyphasor).
- 6000 V , 1050 kW, 3000rpm [thrust bearing at drive end side]
- compressor aprox speed 10k rpm (no probes mounted and no visual casing vibr or data)
Finally we have acquired voltage channel splitter to take orbit data from the probes at the motor. Here I can see a clear sign of high preload (in my opinion).
When we were measuring the casing vibration via accelerometer on the compressor bearing housing (low speed shaft), the motor tripped again on vibration: high-high level (+80 microns pk-pk).
Bearing clearance at the drive side bearing 0.18mm (in tol, limit 0.13-0.19mm).
The only plots and analysis I have:
1) high preload orbit shape at drive end, when measuring the direct values were aprox 35-40 micron pk-pk (few min later trip to aprox 80..)
2) casing vibrations on the compressor; 0.43xRPM - 2,2 mm/s !
instable bearing behavior / oil whirl. But is this cause or effect? Few seconds later the motor tripped.
* during a stable run measurement in July 2022 we had no such oil whirl freq vibration peak.
What could possibly cause this high preload conditions?
- we have checked the 'magnetic center' of the motor, we corrected this by moving the rotor 2mm in axial position. Recoupled and alligned motor.
- removed the bearing shells at the drive side, visual inspection and clearance (OK).
* Can this relative small compressor cause this high preload on the motor, causing it to trip? Or should the problem most likely to be found at the motor itself.
Thanks in advance