intermittent high 1x vibration on steam turbine

[gallaz]

I have a steam turbine/generator that undergoes huge escalations in 1x radial vibration at the front turbine bearing. The odd part is that the vibration increases greatly and then reduces to normal running conditions over about a 10-20 minute period. Has anyone seen this before?

 

[GregLocock]

Interesting, I'd expect first order to stay fairly constant, although I suppose as the rotor warms up it may distort, creating unbalance.

Cheers

Greg Locock

 

[magicme]

hello again

the thermally bowed rotor i suggested would be due to the rotor stationary with the machine not operating, but still partially hot from running. if the rotor is not on a turning gear, it will heat on the top side due to radiation from the hot steam that migrates to the top side. the rotor will then bow for a time before the temperature soaks out. if you try to restart the machine, the unbalanced rotor will shake until the thermal gradients wash out and the vibration stops.
however this would not occur during continuous running, so it's not your problem.

possibly its a slight rub....the casing heats up due to rubbing and grows away from the rotor, the rub stops, the casing cools and shrinks back and rub restarts and the cycle repeats.

i could go on guessing, but would start asking a lot more questions.

that's my ten cents.

daveleo