A check valve is a valve that can automatically prevent the backflow of fluid. The valve disc of the check valve opens under the action of fluid pressure, and the fluid flows from the inlet side to the outlet side.
When the pressure on the inlet side is lower than that on the outlet side, the valve disc automatically closes under the action of factors such as fluid pressure difference and its own gravity to prevent the backflow of fluid.
According to the structural form, it is divided into lift check valve and swing check valve. The lift check valve has better sealing than the swing check valve and has greater fluid resistance. For the suction port of the pump suction pipe, a bottom valve should be selected. Its function is to fill the pump inlet pipe with water before starting the pump; keep the inlet pipe and pump body full of water after stopping the pump in preparation for restarting. The bottom valve is generally only installed on the vertical pipe at the pump inlet, and the medium flows from bottom to top.
Check valves are generally suitable for clean media, and should not be used for media containing solid particles and high viscosity. When DN≤40mm, it is advisable to use a lifting check valve (only allowed to be installed on horizontal pipes); when DN＝50～400mm, it is advisable to use a swing lifting check valve (it can be installed on both horizontal and vertical pipes. If installed on a vertical pipe, the medium should flow from bottom to top); when DN≥450mm, it is advisable to use a buffer check valve; when DN＝100～400mm, a wafer check valve can also be used; the swing check valve can be made into a very high working pressure, PN can reach 42MPa, and it can be applied to any working medium and any working temperature range according to the different materials of the shell and seals. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The medium working temperature range is between -196～800℃.