A study on the efficiency behavior of Limitorque Actuators for Motor Operated Valves

A motor operated valve (MOV) consists of a motor, an actuator, and a valve, and is an essential element to control the piping flow in a nuclear power plant. In fact, the operational failure of a safety-related MOV can have catastrophic results. Therefore, by the regulatory requirement, the operability of the safety-related MOVs should be ensured. The requirement recommends utilities to consider the fact that aging can decrease the thrust/torque output of actuators. Up until now, it has been assumed that the actuator efficiency, one of the most important factors in evaluating the actuator output, does not degrade over time. The purpose of this paper is to confirm the validation of the design efficiency by analyzing the efficiency behavior over time for Limitorque actuators. The diagnostic field test data are used in the calculation of actuator efficiency and its behavior analysis over time