the problem of the turboexpender

[KRISCHUANG]

I need some help
on my company ,have a turboexpender of mafi trech ,and when i open the inlet valve(hand valve)the turboexpende"s vibration is crease from 2um up to 75um (and the high value is 25um ,the SD value is 35um ,but when the turbine run to normal speed ,the vibration is decrease to 22um ,i donnot know the reason ,please explain why .
-

 

[unclesyd]

For start i would look into the critical speed of the rotor. The manufacturer should have the speed data.

 

[KRISCHUANG]

the normal speed is 35000RPM,and the critical speed is 126%RATED SPEED ,SO I FEEL it donnot have the resonate .