We are finding a large amplitude of 0.4 inches/second @ 4300 cpm on a 3500 rpm pump.
We tried a bump test on the pump while it was not running (the operator couldn't switch it on at the time). Found a very low peak @ the same frequency as well as a much higher amplitude from the neighboring operating pump, will go back when they can switch over pumps.
Could this be resonation? If not what could it be?
(Sorry for the limited fft graph)
Approximately 4300cpm (3580 cpm = RPM)