Development of Remote Diagnostic Monitoring System for Motor-Operated Valves

摘要

It is requested to monitor periodically the performance and the condition of motor-operated valves (MOVs) for the purpose of the safety, especially in the nuclear plants. However, it is very difficult, sometimes impossible, to acquire the signals at the valve while operating even though it also costs much time and money. In this paper, a new method is introduced to remotely estimate the motor torque and the stem thrust, which are recommended as two most effective parameters in diagnosing MOVs by NRC (Nuclear Regulatory Commission). The technique to be utilized includes electrical measurements and signal processing. The motor torque is calculated using electrical signals such as voltages and currents, which can be measured in the motor control center (MCC). The stem thrust is calculated considering the characteristics of the MOV and the estimated motor torque. The procedures to evaluate the accuracy of each method were established and the accuracies were obtained though the experiments under various conditions. In addition, the applicability of the methods was tested in the plants.