The check valve is a kind of valve that depends on the medium flow itself to open and close automatically to prevent the reverse flow, also known as the reverse valve, one-way valve, non-return valve(NRV) and backpressure valve. The purpose of the check valve is to prevent reverse flow of the medium, to prevent the pump and drive motor from reversing, and to prevent the release of the container medium. When the fluid flows in the specified direction, the pressure of the fluid causes the disc to open, but when the fluid flows in the opposite direction, the pressure of the fluid and the self-aligning disc work together on the seat to prevent backflow, and can also be used to supply the auxiliary system where the pressure may rise above the system pressure. According to the structure, the check valve can be divided into swing check valve, wafer check valve, lift check valve, vertical check valve, double check valve, butterfly check valve, ball type check valve, Y type check valve.
Swing check valve
Swing check valves are divided into single-disc, double-disc and multi-disc check valves. The round disc around the seat axis moves for rotary, flow resistance is small because of the streamlined valve inside the channel, suitable for low flow rate and flow is not often changed in large-caliber pipeline. To ensure that the disc reaches the seat face in the proper position each time, the disc is designed in a hinged mechanism so that the disc has sufficient swing space and is in full contact with the seat. The disc may be made entirely of metal, may be covered with leather and rubber, or made by cladding cover, that depending on performance requirements.
Lift Check Valves
Lifting check valve can be divided into vertical and straight through according to the structure. The lift check valve disc is located on the seat sealing face, similar to the globe valve, the fluid pressure causes the disc to rise from the seat sealing face, the medium backflow causes the disc to fall back to the seat and cut off the flow. A vertical lift check valve is generally used in a nominal 50mm horizontal pipe. Straight-through lift check valves can be installed in both horizontal and vertical pipelines. The bottom valve is generally only installed on the vertical pipe at the sump pump, and the medium flows from bottom to top. The sealing performance of lift check valve is better than that of swing check valve.
Butterfly check valve
Also known as the wafer check valve, generally, straight through, the butterfly check valve is suitable for low pressure, large diameter and installation are limited occasions. Because the butterfly check valve’s working pressure is not high, generally below 6.4mpa, but the nominal diameter can reach more than 2000mm.The installation position of the wafer type check valve is not restricted. It can be on the horizontal pipeline, or on the vertical or on the inclined pipeline.
Diaphragm check valve
The diaphragm check valve is suitable for pipeline that easy to produce water hammer, the diaphragm can be very good to eliminate the water hammer effect when the medium countercurrent. Limited by the material of diaphragm, the diaphragm check valve is generally used in low-pressure normal temperature pipelines, especially in the water pipeline. The working temperature of the medium is -20 ~ 120℃ and the working pressure is less than 1.6mpa, and the diameter can reach up to 2000mm. Due to its excellent waterproof performance, simple structure and low manufacturing cost, it has been widely used in recent years.