A study on the rate-of-loading applied in design basis performance evaluation for motor operated valves

Rate-of-loading(ROL) is defined as the characteristics of change in stem thrust of Motor Operated Valves (MOVs). ROL can cause leakage through disk because the valve is not closed fully under differential pressure conditions (design basis conditions) if the Torque Switch Trip (TST) setpoint is conducted under static conditions. Dynamic and static test should be implemented to quantify ROL, value. Design basis performance evaluation for MOVs is implemented in other to address the regulatory recommendation issued by the ministry of science and technology. In the evaluation the uncertainty value of ROL, 10% is applied for the valves that their design basis differential pressure is less than 50 psid or can not be tested dynamically. The value had been used in the design basis performance evaluation of U.S. In order to confirm the applicability of 10% value statistic analysis was conducted based on the ROL values evaluated from the valves that both static and dynamic tests were conducted. The applicability of the values for current design basis performance evaluation was confirmed because confidence distribution of values was ranged from 90% to 95%