An Experience on the Elimination of Check Valve Chattering in a NPP

Tapping noise and vibration was observed at a swing check valve located on an auxiliary cooling water line during operation in a nuclear power plant. For the identification of the main cause and its elimination of continuous tapping noise in check valve, site inspection, vibration measurement and flow field analysis was done. FLUENT code was used to analyze the flow field in piping and elbow. It can be concluded as follows from inspection, measurement and analysis: A check valve should be installed so that the axis of hinge is perpendicular to the plane of the curved pipes, considering the secondary flow to be formed in the cross-section of the pipe. In this configuration the secondary flow impinged to the front side of valve disk could increase the effective incidence angle, which makes the disk kept in the fully open position.