The working principle of check valve and common fault handling methods
working principle
This type valve function just allows media to flow in one direction, and stop the flow direction. Usually the valve works automatically, under one flow direction fluid pressure effect, the disc opens; when fluid flows the opposite direction, by the fluid pressure and disc self coincidence acting on the valve seat, to cut off flow. Check valve Which belongs to this type valve, includes swing check valves and lift check valves. Swing check valves are ordinary hinge, there is a disc likes door freely against on the tilt seat surface. In order to ensure that disc can reach the appropriate position of valve seat face, the disc design in the hinge so that the disc is enough to have the swing space, and make disc a real, comprehensive connecting with the valve seat. Disc can be made of metal and can also be embedded in the leather, rubber, or synthetic cover in metal, which depends on performance requirements. Swing check valve in the fully open position, the fluid pressure is almost free of obstruction, therefore the pressure drop through the valve is relatively small. Lift check valves on the valve seat is located in the body sealing surface. In addition to this valve disc is free to lift, the other partd str the same as the globe valve, the fluid pressure makes disc lifted from the valve seat sealing surface, medium return leads to disc back to seat and cut off the flow. According to using terms, the disc can be all metal construction, it can be rack mounted rubber mat or rubber ring form in the disc. The same as the globe valves, fluid channels through the lift check valve is narrow, so the lift check valve pressure drop is a little bigger than the swing check valve, and swing check valves flow restrictions is few.
Common Failures and handle methods
Common failures are: ① disc break; ② medium backflow.
The reasons cause disc broken are: the media pressure before and after valve is close to balance and "see-saw" state, disc often breaks the seat, disc that made of some brittle materials (such as cast iron, brass, etc.) is broken.
Prevention approach is adopting the ductile material disc check valve
Medium backflow reasons: ① sealing surface damage; ② folder into the impurity. Repairing and cleaning the sealing surface impurities, that can prevent the backflow.
