Steam Turbine Bypass Valve Vibration


Thread Starter



I've been reading the messages on this forum for a while (very helpful so far!) and finally decided to post a thread. We are experiencing a vibration problem on our site and I'd like to hear your opinions on it:

We have a large steam turbine which drives a 4 pole generator (Approx 750 MW of power). The turbine has 4 steam control valves that drive steam into the machine. If, for whatever reason, the plant experiences a shutdown, those valves close and another 4 valves open (the bypass valves) which drive the steam to a different circuit through the condenser.

Our problem right now is that we are experiencing abnormal vibration levels on the bypass valves. During normal operation the valves are closed, so no steam is circulating through them.

The global vibration measured on one of these valves is 0.48 in/s (12.44mm/s) with three spectral components:

- Amp 0.09 in/s (2.5 mm/s) at 1005 cpm (cycles per minute)
- Amp 0.32 in/s (8.2 mm/s) at 1500 cpm (cycles per minute)
- Amp 0.21 in/s (5.4 mm/s) at 1755 cpm (cycles per minute)

All the other measurements in other valves give similar readings (the biggest component is always 1500 cpm) with some readings giving smaller peaks at 420 cpm. All of the readings were obtained using piezoelectric sensors.

Being that the turbine is running at 1500 cpm, the vibration crew suspects of a problem coming from the turbine, but besides that, nothing seems to be malfunctioning.

Has something like this ever happened to you? What would you recommend to check on the valves/piping? Please let me know if you need more information.

And thanks!!