Hello,

I’m hoping someone could clear up something for me. My plant (PWR) is experiencing excessive turbine control valve vibrations as a result of historically low valve lifts. The turbine is double reheat with four control valves operating in full arc admission. The control system is a GE MK vie.

Valve position has slowly decreased over the past 20 years from about 68% to 45% open. The unit operates with elevated moisture carryover from the steam generators at approximately 2% and has a history of inaccurate, feed water flow, and cycle Isolation issues.

How can I determine how the control valves will respond to changes in secondary plant parameters such as main steam pressure and feed water, flow or moisture carryover? I was able to find the control valve characteristic curve as a function of normalized steam flow in the MK vie software. Any information would be much appreciated. Please let me know if I can provide any clarification.

 

When was the most recent performance testing of your unit system

 

When was the most recent performance testing of your unit system

An ASME PTC 6 test was conducted in 2003/2004.

 

Assuming the generator demand is stable over the years, valve vibration issues, together with reduced lift, are indicative of needing valve rebuild or replacement.

 

Generator output has decreased gradually by 15 MWe over 20 years or so largely due to moisture carryover in main steam. We will be replacing the steam generator moisture separators in the next several years. We will also be inspecting some of the turbine valves (stop and control) in the upcoming outage.