How Check Valves Work
The purpose of this type of valve is to allow the medium to flow in only one direction and prevent flow in the opposite direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincident valve flap of the valve flap act on the valve seat, thereby cutting off the flow.
Among them, the check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valves have a hinge mechanism and a door-like disc that rests freely on the sloping seat surface. In order to ensure that the valve disc can reach the proper position of the valve seat surface every time, the valve disc is designed in the hinge mechanism, so that the valve disc has enough swing space and makes the valve disc truly and comprehensively contact the valve seat. The disc can be made entirely of metal, or inlaid with leather, rubber, or synthetic overlays, depending on the performance requirements. In the fully open condition of the swing check valve, the fluid pressure is almost unimpeded, so the pressure drop across the valve is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the valve disc can rise and fall freely, the rest of the valve is like a globe valve. The fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the backflow of the medium causes the valve disc to fall back to the valve seat and cut off the flow.