Check valve installed in the pipeline, which becomes one of the components of the complete fluid pipeline, the valve will open and close the process by which it is affected by the system transient flow state; in turn, the valve closure characteristics have made effect on the fluid flow state. Check valve work is characterized by a large load change, the opening and closing frequency is small, a closed or open state, the applicable cycle is very long, and does not require the movement of parts. But once again the "switch" requirement, it must be flexible, this requirement is more stringent than the common mechanical movement.
The role of this type of valve is to allow the media to flow in one direction, and to prevent the direction of flow. Usually the valve is automatically work, fluid pressure flow in one direction, the valve open; the opposite direction of fluid flow by gravity, fluid pressure and valve closing effect on the valve seat, thereby cutting off flow.
Swing check valve in the fully open position, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. Lift check valve of the valve seat is located on the valve seat sealing surface. In addition to this valve disc is free to lift, like the rest of the cut-off valve, the fluid pressure valve from the valve seat sealing surface lift, medium return led down to the valve seat, 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. The same as the cut-off valve, lift check valve fluid through the channel is narrow, so the check valve by lifting the pressure drop than the swing check valve a little bigger, and swing check valve flow restrictions very little.
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 a door like the same as 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.
The physical reason is the result of the combined action of the fluid, the inertia of the fluid motion and the elasticity of the pipe. In order to prevent water hammer in pipes hidden for many years, people in the valve design, with a number of new structures, new materials, in order to ensure the check valves for performance at the same time, the impact of water hammer to minimize the have made gratifying progress. Check valve is in accordance with the flow of the media itself and automatically open, close the valve flap, used to prevent the media back valve, also known as check valve, check valve, counter flow valve, and back pressure valve. Check valve is an automatic valve, its main role is to prevent the media back, to prevent the pump and drive motor reversal, as well as the release of the container medium. Check valve can also be used to give the pressure may rise to more than the system pressure of the auxiliary system to provide supply pipeline. Check valve can be divided into swing check valve (according to the center of gravity rotation) and lift check valve (along the axis of movement).
