I have seen a strange behavior on a 220KWatt JEUMONT SNIJDER INDUCTION MOTOR.
We have seen only 1X vibration ( @ 49,8Hz) with amplitudes of 17,3mm/s RMS. Advanced measurement have give me information that there is only the 1X vibration in vertical direction. In the horizontal direction the vibration is 4,7mm/s.

There are no PPF, no 2Fline frequency. (220Hz, 6400Lines). Also high frequency Acceleration and vibration (0-5000Hz) gives me no specific frequencys.

shutdown
I proposed to shut down the machine to see whats going on during shutdown. I quess it's elctrical imbalance. But why are the vibration in vertical direction much higher than horizontal??

time schedule
at 12 aug 2008 the vertical vibration was 7,1mm/s RMS, suddenly at 1 sept 2008 the vibration was 17,5mm/s RMS. The circumstances were by alle measurments at steady state loading conditions, normal operations. Several measurement between 1-9-2008 and 9-9-2008 where 'stable' for ca. 18mm/s RMS (all 1X !!)

technical information:
The condition of the bearings are OK.
SKF 6318 ( x2 )
JEUMONT SNIJDER : INDUCTION MOTOR
TYPE: FNC355MR2 B3 NS 325386

I wonder whats going on with the machine...

regards,
Mario

You probably should have posted in the vibration section. Based on the directional nature of the vibration, I suspect that this machine is experiencing resonance. You may be able to confirm this diagnosis with the unit online (negative averaging or applying mass or stiffness to the machine to see if a change occurs).

If you shut down, a bump-test should be performed to check for resonance.

Sounds like good advice from Steve.

This is a horizontally mounted motor?

If so, 7.1mm/sec rms is pretty high for a motor anyway.

Check out the condition of the holding down bolts and the integrity of skid/mounting arrangement for a possible cracked/broekn bolt/support.

Hello Guys,

I did some advanced measurements with the real time function from the analyzer. In vertical direction on the motor we see a continues 1X vibration of 20 mm/s RMS (!!) One of the four foundation bolts were vibrating 8mm/s. The other where less for about 4mm/s RMS (all 1X).
Unfortunately the plant tripped ..... And so more advanced measurement with a bump test (Arie bedankt voor de tip!! ;-) ) could not be carried out. Also real time measurements from the shutdown from the motor could not been done. (For me this is frustrating. ) This was ideal because i want to see what's going on at the moment when the motor was shut down..
The reason why the plant tripped is at this moment not known.
....to be continued....
I will keep you all informed.

regards Mario