How to choose to prevent the backflow valve media This type of valve is the role of the media to only allow flow in one direction, but also to prevent the direction of flow. Normally this valve works automatically, in a direction of fluid flow under pressure, the valve opens; the opposite direction of fluid flow, fluid pressure and valve from the self-overlap effect on the valve seat, thereby cutting off flow. Which belongs to this type of check valve valve, which includes the swing check valve and lift check valves. Swing check valve with ordinary hinge, there is a door the same as freedom against the valve seat surface tilt. To ensure that every time the valve seat surface to reach the appropriate position, the valve flap hinge design, the valve has to have enough swing space, and a real disc, full with the valve seat. Valve can all be made of metal, can also be embedded in the metal on leather, rubber, or synthetic cover, depending on performance requirements. Swing check valve in the fully open position, the fluid pressure is almost free of obstruction, so the pressure drop through the valve is relatively small. Valve lift check valve located in the valve body seat sealing surface. In addition to this valve is free to lift the valve, the valve the same as the rest, the fluid pressure to the valve lift from the valve seat sealing surface, return media led down to the valve seat, and cut off the flow. Depending on conditions, the valve can be all metal construction, it can be rack mounted in the valve rubber or rubber ring form. The same as the cut-off valve, lift check valve fluid through the channel is narrow, so by the lift check valve pressure drop than the swing check valve bigger, and swing check valve flow restrictions very little.