The function of this type of valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve disc opens; when the fluid flows in the opposite direction, the valve seat is acted on by the fluid pressure and the self-weight of the valve disc to cut off the flow.

Among them, the stainless steel wafer check valve belongs to this type of valve, which includes swing check valve and lift check valve. The swing check valve has a hinge mechanism, and a door-like disc freely leans on the inclined seat surface. In order to ensure that the valve clack can reach the proper position of the seat surface every time, the valve clack is designed in the hinge mechanism, so that the valve clack has enough swing space, and makes the valve clack truly and comprehensively contact with the valve seat. The disc can be made entirely of metal, or it can be inlaid with leather, rubber, or a synthetic cover on the metal, depending on the performance requirements. When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. According to the conditions of use, the disc can be of all-metal structure, or in the form of a rubber pad or rubber ring inlaid on the disc frame.