We have a steam turbine driving a nitrogen compressor. The problem is that the turbine is tripping on overspeed protection upon load rejection.

As the consumer stop suddenly their demand, the speed of the steam turbine is decreasing so the governing valve is opening to increase the speed, and at the same time the recycle valve of the compressor is opening. when the recycle valve open completely, then the governing will start to close to reduce the speed. but the problem the speed increase is very fast and the turbine is tripping.

Any advice to solve this problem?

Also what will be system response in case of actual surge of the compressor?

Also please, Is it normal to have overspeed trip on only 103%?

Who should decide the setting, the steam turbine vendor or compressor vendor?

 

hany5757,

When did this problem start?

Has it been occurring since commissioning?

Has something in the way the consumer operates their plant/process changed recently which has caused this issue to appear?

What kind of actuator does the control valve have (high- or low-pressure hydraulic; pneumatic)?

What kind of turbine control system?

Does the turbine control system also control the compressor or does it receive signals from a separate compressor control system? If there is a separate compressor control system is the signal to the turbine control system an analog signal?

What does the supplier/packager of the turbine/compressor say about the problem?

What has been done to try to troubleshoot and resolve the problem, and what were the results?

It would seem that whichever component has the lowes over speed setting would dictate the value of the overspeed setpoint. Which component (turbine or compressor) has the lower setpoint?

The compressor manufacturer would be the best entity to answer the question of what should happen in the event of a surge. Many compressors have different methods for dealing with surge/stall, including recirculation valves or safeties or bypass valves. Every application is not the same.