Need vibration limits on large AC vertical motors

[bopsyseng]

I have a large AC motor (1750HP, 1800 rpm) installed vertically. every time it trips the vibs goes up by 0.1ips
Started with 0.3ips after two trips 0.5ips. how long can I continue before s/d the motor and get it balanced.

 

[tophat]

bopsyseng, How or why is this motor tripping out? If motor 1x goes up every time this motor trips, then there must be an electical problem in the motor. Something must be moving or loose to allow an increase in vibration. Is the phase on the vibration stable or is it shifting with each trip?

Tophat

 

[bopsyseng]

Motor was balanced before installation. One time motor tripped due to ground fault, second time it tripped due to blackout (08/14/2003). Motor also has a Mechanical Seal.

 

[tophat]

Tripping out should not cause an imbalance problem. If no phase history then try to start one. If level increases to .7 ips then I would recommend inspecting motor, coupling, and driven unit. What is unit driving and what are levels on the driven unit. Had a call out on a vertical motor one time due to high vibrations. It was driving a pump they had not taken readings on. The bearings in the pump were trashed. Problem solved with repairs.

 

[bopsyseng]

The vibration analysis shows only one variable sine curve. We assume it may be due to imbalance. The bearings appear to be in good shape (based on sine curve). We did recommend 0.7ips as cut off vibs to remove pump from service. The vibs at present are stable at 0.5ips. We will try to balance in a week or so.