1. Pump outlet check valve "check valve selection General pumping station project situation, for the pump outlet check valve selection, the following principles should be followed; the pump outlet pipe diameter smaller pipeline, that DN < 50mm, should be used lift check valve on the pump outlet pipe diameter DN & ge; 50mm of the pipeline, swing check valve should be used Swing check valve can be installed horizontally or vertically. Swing check valve Valve for rotation around the axis of rotation, the fluid resistance is generally less than the lift check valve, which is suitable for larger diameter occasions, the installation position is not restricted, usually installed in the horizontal pipe, which applies to larger diameter occasions. According to the number of valve can be divided into single-valve swing type, double-valve swing type and multi-valve swing type. Single-valve swing-type check valve is generally used and medium caliber occasions. Large diameter pipe selection list Valve swing check valve, in order to reduce the water hammer pressure, it is best to reduce the water hammer pressure slow closing check valve. Double-flap swing check valve for medium and large diameter pipe. Double-flap swing check valve structure is small, light weight, is a faster check ; Multi-valve swing check valve for large diameter pipe. 2. Pump outlet check valve installation â‘ Swing check valve is generally installed in the horizontal pipe: For the diameter of DN ~ 80mm check valve, but also Can be installed in the vertical or upward sloping pipeline â‘¡ straight through lift check valve should be installed on the horizontal pipe; vertical lift check valve must be installed in the vertical pipe, the medium flows from bottom to top â‘¢ due to Check valve is easy to damage, therefore, should be installed near the pump outlet check valve, check valve in the upper part of the cut-off valve (usually with a ball valve or gate valve), easy maintenance. â‘£ To facilitate the check valve before the demolition of pressure relief, Check valve itself does not take the net valve should be installed between the check valve and the shut-off valve to release the net valve 3. To prevent the hydraulic impact on the check valve sealing surface damage protection measures Check valve settings, Play a role in preventing material backflow, to avoid the pump impeller suffered liquid attack.However, the check valve itself, improperly set, will cause the water hammer produced by the valve flap on the sudden impact, damage to the check valve sealing surface Therefore, it should be taken To protect the measures 1. For the pump outlet set> 80mm swing check valve, horizontal installation should be used to weaken the valve back seat and the impact generated. 2, for the pump outlet check valve diameter> = 150mm pipeline should be set before and after the bypass valve bypass to prevent the valve before the pressure rise is too high, the check valve sealing surface damage caused by 3, the pump discharge line starting point and the end pressure is high, not The following measures can be taken to set the bypass: The safety valve is installed instead of the bypass valve, which is similar to the bypass valve, and it is installed near the outlet of the check valve. When the water hammer causes the pressure to rise, a part of the water Release to prevent damage caused by continued pressure increase Set the air or inert gas buffer tank set in the check valve near the exit, when the water hammer occurs, through the buffer tank pressurized gas is compressed to ease the pressure generated by water hammer Rise.