The check valves (also known as reverse stop valve) is a valve that is automatically open and closed by the flow of the medium itself, and is used to prevent the flow of the medium from the valve, also called check valve, one-way valve, backflow valve, and back pressure valve.Check valves belong to an automatic valve, whose main function is to prevent the backflow of the medium, to prevent the pump and drive motor reversal, as well as the release of the container medium.Check valves can also be used to supply the pressure to the auxiliary systems that exceed the system pressure.Check valves are mainly divided into swing check valves (rotation of the center of gravity) and lift check valves (along the axis).

Non-return valve disc in disc, seat around tunnel axis rotation, due to the channel into a streamline in the Silicone Valves, flow resistance is smaller than l butterfly check valve, suitable for low flow velocity and flow not often change the large diameter of occasions, but should not be used for oscillating flow, its sealing performance than lift.Butterfly check valves are divided into three types: single, double, and multi-valve. The three forms are mainly divided into valve aperture, which is designed to prevent the flow of the medium from stopping flow or reverse flow.

The effect of the Check Valves is to only allow the medium to flow in one direction, and to prevent the reverse flow.Normally this valve is operated automatically, and under a fluid pressure that flows in one direction, the disc opens;When the fluid is in the opposite direction, the self - overlapping disc of the fluid pressure and the disc ACTS on the seat, thus cutting off the flow.The internal thread check valve, the butterfly check valve is in this type of valve, which includes swing check and lift check valves.The swing check valve has a hinge mechanism, and a gate like valve is free to rest on the inclined seat surface.In order to ensure that each disc to seat the appropriate location, in valve design hinge agencies, so that the disc with enough space of a swing, and real, comprehensive, and the valve seat contact.The disc can be made entirely of metal and can be embedded in the metal with leather, rubber or synthetic coverage depending on the performance requirements.When the swing check valve is fully open, the fluid pressure is almost impervious, so the pressure drop through the valve is relatively small.The valve flap of the lift check valve is located on the seat seal on the valve body.In addition to this check valve can be freely valve movements, like the rest of the cut-off valve, fluid pressure from the valve seat sealing surface lift, medium return led to the disc back to seat, and cut off the flow.Depending on the conditions of use, the disc may be an all-metal structure or in the form of a rubber pad or rubber ring on the disc rack.Like a Cutting valve, fluid through the lift check valve channel is narrow, so the lift check valve through the pressure drop than the swing check valves are bigger, and swing check valves are very few restrictions.