Silent type check valve refers to a valve that automatically opens and closes the valve flap, which is used to prevent the back flow of the medium depending on the flow of the medium itself. It is also called a check valve, a check valve, a reverse flow valve, and a back pressure valve. The check valve is an automatic valve whose main function is to prevent the reverse flow of the medium, prevent the reverse rotation of the pump and the drive motor, and release the medium of the container. Check valves can also be used on pipelines where the pressure may rise above the system pressure to provide supplemental systems. Check valve can be divided into swing check valve (rotation by gravity center) and lift check valve (move along axis).

The role of this type of valve is to allow only the medium to flow in one direction and prevent the direction of flow. Normally, this type of valve operates automatically. The valve flap is opened by the fluid pressure flowing in one direction. When the fluid flows in the opposite direction, the fluid pressure and the self-closing flap of the valve flap act on the valve seat to shut off the flow.

The valve of the silent check valve is in the form of a disk and rotates around the rotation axis of the valve seat channel. Because the channel in the valve is streamlined, the flow resistance is smaller than that of the butterfly check valve, which is suitable for low flow rate and flow. The frequently changing large-diameter occasions are not suitable for pulsating flow and their sealing performance is not as good as a lifting type. Butterfly check valve is divided into single-valve type, double-valve type and more than half type. These three types are mainly divided according to the valve caliber. The purpose is to prevent the hydraulic shock from being reduced when the medium stops flowing or reverse flow.

Silent check valve disc check valve sliding along the vertical centerline of the valve body, the internal thread check valve can only be installed in the horizontal pipe, in the high pressure small diameter check valve can be used ball. The shape of the body of the butterfly check valve is the same as that of the cut-off valve (common to the cut-off valve), so its fluid resistance coefficient is large. Its structure is similar to the shut-off valve, and the valve body and the valve flap are the same as the shut-off valve. The upper part of the valve flap and the lower part of the valve cover are processed with guide sleeves, and the valve guide guides can be freely raised and lowered within the valve guide guides. When the media flows downstream, the valve flaps are opened by the medium thrust. When the medium stops flowing, the valve flaps itself. The vertical drop falls on the valve seat and acts as a counter-current to the media. The straight-through butterfly check valve medium inlet and outlet channel direction is perpendicular to the seat channel direction; the vertical lift check valve has the same medium inlet and outlet channel direction and the seat channel direction, and its flow resistance is smaller than the straight-through formula.