Prediction of Check Valve Performance and Degradation in Nuclear Power Plant Systems.

摘要

Degradation and failure of swing check valves and resulting damage to plant equipment has led to a need to develop a method to predict performance and degradation of these valves in nuclear power plant systems. The Phase I investigation developed methods which can be used to predict the stability of the check valve disk when piping disturbances such as elbows, reducers, and generalized turbulence sources are present upstream of the valve within 10 pipe diameters. Major findings include the flow velocity required to achieve a full open, stable disk position, the magnitude of disk motion developed with these upstream disturbances with flow velocities below full open conditions, as well as disk natural frequency data which can be used to predict wear and fatigue damage. Reducers were found to cause little or no performance degradation. Elbow effects must be considered when located within 5 diameters of the check valve, while severe turbulence sources have significant effect at distances to 10 diameters. Clearway swing check designs were found to be particularly sensitive to manufacturing tolerances and installation variables making them likely candidates for premature failure. Reducing the disk full opening angle on these clearway designs results in significant performance improvement.