The role of this type of valve is to allow the media to flow in one direction, and to prevent the direction of flow. This valve is usually the work automatically, in a direction of flow of fluid under pressure, the valve flap to open; fluid flow in the opposite direction, by the fluid pressure and the valve flap from the weight of the combination of the role of the valve on the valve seat, thereby cutting off flow.
The check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valve has a hinge mechanism, as well as the same as the door of the valve flap freely on the surface of the tilt of the seat. In order to ensure that the valve flap can reach the appropriate position of the valve seat, the valve flap design in the hinge mechanism, so that the valve flap with enough swing space, and make a real, comprehensive contact with the valve seat. Valve can be all made of metal, can also be embedded in the metal on the leather, rubber, or the use of synthetic coverage, depending on the requirements of the use of performance. Swing check valve in the fully open position, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The lift check valve is located on the valve seat sealing surface of the valve body.
The valve disc is free to lift, the rest as the cut-off valve, in addition to, the fluid pressure the valve lift from the seat sealing surface, medium return to seat valve down, and cut off the flow. According to the conditions of use, the valve can be all metal structure, can also be embedded in the valve frame rubber pad or rubber ring form. As the cut-off valves, fluid through the lift check back to the valve channel is narrow, so through the lift check back valve pressure drop than the swing check valves larger and swing check valve flow by the few restrictions.
