I have 10 identical flowserve water pumps.

They are driven by a 1620 HP ABB electric motor.

In 9 of these pumps I have very low amplitudes of vibration in every direction at electric motor. (0.3 -- 0.5 mm/s)

I supposed this is because of system stifness

But in one of them, specifically in axial direction I have very high levels of vibration (7.1 mm/s at exactly 18x)

This shafts turns at 1180 RPM. So frequency is aproximately 21200 CPM.

This vibration is higher (7.1 mm/s) as close to the shaft I install the accelerometter, and this frequency is not present at pump.

I have attached a picture to show the levels of vibration in two points (closer and further away the shaft).


We have checked shaft alignment tolerances and they are ok.

Please help with these.




Photos (1)
Original Post


There are two facts.

  • High vibration frequency seems to be 5th armonic of BPFO drive end bearing. As you can see in the attached spectrum (But it also matches 18x , it might be a very big coincidence )
  • There are sidebands around this freq. at 1x in 7-3-2016 measurement
  • There are small sidebands at 947 CPM in 1-4-2016 measurement.


We are recommending to monitor equipment uncoupled.

If high vibration remains so we will be pretty sure that it's an outer race bearing defect or it's maybe related with and electrical parameter, as Scout says.

I will advise you of our results.






Photos (2)

Add Reply