H44 American standard swing check valve refers to the valve that relies on the flow of the medium itself and automatically opens and closes the valve disc to prevent the medium from flowing back, also known as check valve, check valve, reverse flow valve, and back pressure valve. The purpose of this type of valve is to allow the medium to flow in only one direction and prevent the flow in one direction. Usually this valve works automatically, and under the action of fluid pressure flowing in one direction, the valve disc opens; When fluid flows in the opposite direction, the fluid pressure and the self-closing disc of the disc act on the valve seat, thereby cutting off the flow.