Subsynchronous vibration phenomena in Steam Turbine

[Arunvenkatesh1978]

We are operating a 30MW condensing Steam turbine supplied by Siemens. Machine installed in 2006. We have noticed that the presence of sub synchronous vibration phenomena in 2010. After that once machine stopped/tripped and restarted, SS vibration got vanished and the overall vibration level also came down. With continuous running the machine vibration will increase slowly, upon vibration analysis, we could notice the SS vibration contribution (88Hz). Twice we opened the turbine and inspected (Aug 2015 & Dec 2016).
Now Again the SS vibration phenomena started and Shaft vibrations are fluctuating from 30 to 60 microns in turbine front and rear bearing.

Process parameters are almost stable

Any body throw some light on the alien frequency 88Hz source.

Turbine speed - 7059 rpm, Generator - 1500 rpm

Venkatesh

 

[GregLocock]

It seems odd that you are getting almost exactly 0.75 order of the turbine.

Cheers

Greg Locock


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