I'm monitoring the vibration of a 1.2MW vertical submerged pump(RPM: 595/ 9.917 Hz ). The motor 1x radial vibration appears to be high in one direction (pump discharge side). Radial vibration at 90 deg seems relatively low. I have checked the alignment at the coupling and any structural looseness and all seems ok.
The Motor acceleration spectrum shows harmonics of 734 Hz with a 2xline frequency side-bands. I'm assuming this is rotor bar or a winding slot pass frequency. I'm not sure of the # of rotor bars or winding slots.
I'm wondering if the high 1x vibration in possibly caused by the RBPF/WSPF??
The coupling bolts were loosened and re torqued on 22/11/18 which showed some improvement temporarily(1x reduced from 18mm/s to 8mm/s). but the vibration levels increased within hours of operation. I have attached acceleration and radial velocity spectra in the discharge direction (marked R1) and at 90 deg to R1 (marked R2). In the R1 spectra, the green plot shows vibration immediately after coupling adjustment, and blue plot, a few hours later.
Is this cause for concern?? Can anyone help with this??