Retrofitting feedwater valves at North Anna reduces vibration and improves control

This article reports on the retrofitting of tortuous-path feedwater valves trim to permit staged pressure reduction and precise flow control and reduce excessive vibration in the system. The topics of the article include an examination of the root causes of the vibration and control problems, initial problem-solving steps, retrofitting of new valve internals into existing valve bodies, control characterization, and replacement of actuators.