Check valve refers to a valve that actively opens and closes the valve flap by relying on the activity of the medium itself to avoid backflow of the medium. It is also called a check valve, a check valve, a reverse flow valve, and a back pressure valve. The non-return valve belongs to an active valve, and its primary effect is to avoid backflow of the medium, avoid reversal of the pump and drive motor, and discharge of the container medium.
The check valve can also be used on the supply line where the pressure in the auxiliary system may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis). The effect of this type of check valve is to only allow the medium to move in one direction and block the movement in the opposite direction. Usually this kind of valve works actively. Under the effect of the fluid pressure moving in one direction, the valve flap opens; when the fluid moves in the opposite direction, the fluid pressure and the self-coincidence of the valve flap overlap the valve seat, and then cut off the activity. The check valve belongs to this type of valve, which includes a swing check valve and a lift check valve. The swing check valve has a hinge mechanism, and a flap like the door freely rests on the skewed seat surface. In order to ensure that the valve flap can reach the proper orientation of the valve seat surface every time, the valve flap is designed in a hinge mechanism, so that the valve flap has enough space for unscrewing, and the valve flap can be truly and fully touched with the valve seat. The clapper can be made of metal in its entirety, or it can be inlaid with leather, rubber, or may be used to form a cover, depending on the performance requirements. When the swing check valve is fully opened, the fluid pressure is not blocked, so the pressure drop across the valve is relatively small. The valve flap of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the valve flap can be freely raised and lowered, the rest of the valve is the same as a shut-off valve. The fluid pressure lifts the valve flap from the sealing surface of the valve seat. The medium backflow causes the valve flap to fall back to the valve seat and cut off the activity. Depending on the operating conditions, the valve flap can be an all-metal structure, or it can be inlaid with a rubber pad or rubber ring on the valve flap holder. Like the shut-off valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is restricted Very little.
The experimental status of the check valve: the valve axis of the lifting check valve is in a straight position with the horizontal; the channel axis and the valve axis of the swing check valve are in a position parallel to the horizontal line.
During the strength test, the experimental medium is introduced from the inlet end to the specified value, and the other end is closed. It is qualified to see that the valve body and the valve cover have no leakage.
In the leak tightness experiment, the experimental medium is introduced from the outlet end. At the inlet end, the sealing surface is checked, and there is no leakage at the packing and gasket.