it is my first post here, thank you in advance for all the answers.
I have been monitoring 45 kW pump, ~1480 RPM and i have seen strange harmonics approx. at ~6,31 RPM, strongest on DE pump and motor side. I have checked bearings in manufacturer catalog and it says that these should be :
Motor : 6313 DE/NDE
Pump: QJ 313 DE / 2213 NDE
None of the bearings fault frequencies match with 6,31 harmonics. The closest one are 2x BPFO motor bearing at 6,142, and pump BSF at 6,661.
Pump vane pass is in my opinion 7x RPM.
Another curious thing is that motor DE has stronger vibrations vertical, while pump DE has stronger vibrations horizontal. I have attached spectrum in PDF.
These harmonics of 6,31 RPM are clearly visible in all directions DE and NDE in velocity spectrum in pump and motor, but have much lower amplitudes.
We have two other pumps of this model, but they are in other place and they are working fine, with almost no vibration and much less noise.
What can be cause of these harmonics? Are these amplitudes dangerous?
Regards, Kamil U