We have a horizontal overhung pump motor arrangement. Recently we have observed 2xLF on the motor in horizontal direction and the same 2xLF is also seen on the pump. (Its not 2X. We took high res data and confirmed its 2xLF)
Motor horizontal - 4.5 mm/s - Only 2xLF peak, vertical and axial values are around 1 mm/s
Pump horizontal - 7 mm/s - only 2xLF peak, vertical and axial values are around 2 mm/s
Motor solo was taken and the maximum vibration was 3.5 mm/s with 2xLF as the only peak. So the first thing we do is check for soft foot. By dial method on each foot and loosening the bolt and checking the dial reading, we haven't found any soft foot. The dial was always around 0.01 mm or 0.02 mm.
So we started to loosen each bolt in running condition to see if the vibration is changing. But no change. However when all the bolts are loosened then the vibration all of a sudden goes down to 0.3 mm/s
(Also we involved civil guys to check for the natural frequency of the foundation and after their evaluation, it is found that the natural frequency of the foundation is way below the 2xLF.)
And the solo run of the motor at our workshop is also very less at 0.5 mm/s. So we are thinking the motor foot is ok but the equipment base is not. We are planning to check the blue matching of the motor foot on the foundation.