Check valve is to rely on medium oneself activity and open actively, close valve disc, used to avoid medium backflow valve, also known as backflow valve, one-way valve, countercurrent valve, and back pressure valve.Check valve belongs to an active valve whose primary effect is to avoid reverse flow of medium, reverse pump and drive motor, and discharge of container medium.

The check valve may also be used in the supply line of the auxiliary system where the pressure may rise above the system pressure.Check valve can be divided into swing check valve (rotating according to the center of gravity) and lift check valve (moving along the axis).The effect of this type of valve is to allow the medium to move only in one direction and to obstruct the opposite direction.Usually this valve is active, in a direction of the fluid pressure effect, valve flap;When the fluid moves in the opposite direction, the valve seat is affected by the pressure of the fluid and the self-aligning disc of the disc, and then the movement is cut off.Among them, the check valve belongs to this type of valve, which includes swing check valve and lift check valve.Swing check valves have an intermediate hinged mechanism and a gate - like disc that rests freely on an askew seating surface.To ensure that the disc reaches the proper position of the seat surface each time, the disc is designed in a hinged mechanism so that the disc has sufficient swing space and the disc is truly and fully touching the seat.The disc may be made entirely of metal, or may be inlaid with leather, rubber, or composition covering, depending on performance requirements.Swing check valves are fully opened, the fluid pressure is virtually unimpeded, and the pressure drop through the valve is relatively small.The lifting check valve disc is located on the upper valve seat sealing surface of the valve body.This valve in addition to the disc can be freely raised and lowered, the rest of the same as the globe valve, the fluid pressure makes the disc from the valve seat sealing surface to lift, media backflow causes the disc back to the valve seat, and cut off the activity.Depending on the operating conditions, the disc may be of all-metal construction, or may be mounted on the disc rack with a rubber pad or rubber ring.Like the globe valve, fluid flow through the lift check valve is narrow, so through the lift check valve pressure drop than swing check valve, and swing check valve flow is limited.

Check valve test status: lifting check valve disc axis is in a straight horizontal direction;Swing check channel axis and disc axis are approximately parallel to the horizontal line.

During the strength test, the test medium shall be introduced from the inlet end to the specified value, and the other end shall be closed. The valve body and cover shall be qualified if there is no leakage.

The sealing test introduces the test medium from the outlet end, and checks the sealing surface at the inlet end. It is qualified if there is no leakage at the packing and gasket.