Jenish-

The power from the Power Plant would be a reason for that. Might want to do some Online MCA of Power Quality Analysis if you have that ability.

Also as far as the bearing I was talking about he DE Fan bearing from one side of it to the other as shown by the green circles.

And I couldn't insert the data into my version of SKF. It's older. Sorry. But you do have a possible reason with the power.

Good luck!

Jenish, were you able to determine the cause of vibration on these fan bearings and motor? We also have an overhung fan that is showing almost exactly the same vibration signature as you've shown here; however, our fan runs at 1800 rpm. The fan bearings and motor show multiples of running speed--1X, 2X, 3X, 4X,... And there are sidebands around these harmonics that are roughly 0.1x running speed. The sidebands seem to vary slightly in frequency and amplitude. Waveform data on the NDE fan bearing has always shown significant 1X impacts from day 1 of install. So far these bearings have lasted from Jan 08 to present.