Check valves can also be used to supply a line in which the pressure may rise above the system pressure in an auxiliary system. Check valve can be divided into swing type check valve (according to the center of gravity rotation) and lift type check valve (moving along the axis).
Check valve The purpose of this type of valve is to allow the medium to flow only in one direction and to prevent the opposite direction of flow. Usually this valve is automatic work, in one direction of the flow of fluid pressure under the action of the disc open; When the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve disc act on the valve seat, thus cutting off the flow.
The check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valves have a hinged mechanism and a door-like disc that rests freely against the sloped seat surface. In order to ensure that the valve disc can reach the proper position of the valve seat surface every time, the valve disc is designed in the hinge mechanism, so that the valve disc has enough space to swing, and the valve disc is truly and fully in contact with the valve seat. The disc can be made entirely of metal, or the metal can be inlaid with leather, rubber, or a synthetic cover, depending on the performance requirements. Swing check valves, when fully open, allow almost unimpeded fluid pressure, resulting in a relatively small pressure drop through the valve. The disc of a lift check valve is located on the seat sealing surface of the valve body. In addition to the valve disc can be freely lifted up and down, the rest of the valve as the globe valve, fluid pressure makes the valve disc from the valve seat sealing surface, the medium backflow causes the valve disc back to the valve seat, and cut off the flow. According to the conditions of use, the disc can be all-metal structure, or it can be in the form of rubber pad or rubber ring inlaid on the disc rack. Like the globe valve, the fluid through the lifting check valve channel is narrow, so the pressure drop through the lifting check valve than the swing check valve is larger, and the flow of the swing check valve is limited very little.