Purpose
Zero Velocity Valves are developed to eliminate water hammer problems. In common practices Pumps and Swing Check Valves are installed on the pump discharge end. Theoretically, the swing check valve closes quickly when the pump is shut off, but actually not quick enough to prevent reversal of flow. The wedge will slam

Installation: ON MAINS where separation of water column
Operations: When pump trips, Water column separation creates partial vacuum and at that juncture air inlet poppet opens due to actionof spring. The air gets entrapped in the pipe line. With reversal of water column. entrapped air gets compressed causing