Full scale valve qualification and flow interruption testing provides insights on industry motor operator sizing shortcomings and diagnostic testing limitations

Valve test programs sponsored by the United States Nuclear Regulatory Commission (USNRC) and conducted by researchers from the Idaho National Engineering Laboratory (INEL) have yielded important insights concerning motor-operated valve operator sizing and in situ testing. The most significant of these test programs was a full-scale, high-energy qualification and flow-interruption gate valve test program conducted in the spring of 1988. For this program, we modified two representative 6 in., 900 lb valve assemblies to include a high-temperature load cell in each of the valve stems to directly measure stem thrust. Instrumentation in the flow loop and on the motor operators measured the important responses and parameters. At various times during the test program, each of the currently popular diagnostic test systems was installed to monitor the performance of the valve motor operators. The valves were subjected to the hydraulic and leakage testing requirements specified in ANSI B16.41 (QV-4) and to flow interruption (valve closure) testing at boiling water reactor (BWR) temperatures and pressures at line break conditions. Results show that for the tested valves, the variables used in current industry motor operator sizing equations underpredict actual valve thrust requirements at high temperature loadings; for one valve design, the equation may need an additional term to account for nonlinear performance. Results also show that the thrusts needed to close the valves were sensitive to the fluid temperature, and that the results of testing at lower pressures, temperatures, and flows cannot be extrapolated to design basis conditions.