in our cement plant we have eight cooler fan one of them has high vibration in only horizontal plane:
Motor NDE H-10MM/S
MOTOR DE H-11MM/S
FAN DE H-10MM/S
FAN NDE -11MM/S
motor kw-132 kw overhung fan
In all other direction vibration i.e in (vertically and axial) is below 2mm/s . in FFt spectrum only 1x with an amplitude of 9.2mm/s is dominated in all the direction i.e horizontal. i did cross phase analysis on motor and fan also for checking unbalance but cross phase in all direction is 180 degree.
wait but the story is not ended here sometime in whole day its vibration is recorded below 2mm/s in all the direction. this phenomenon of reduction in vibration confused me more.because we measured the fan in same parameters like same damper position same flow everything but still some time vibration is above 10mm/s and sometime below 3mm/s.
please suggest me whats going wrong here