Working principle of check valve

A check valve refers to a valve that automatically opens and closes the valve disc based on the flow of the medium itself, used to prevent the backflow of the medium. It is also known as a check valve, one-way valve, backflow valve, and back pressure valve. A check valve is an automatic valve whose main function is to prevent medium backflow, damage caused by the reverse rotation of mechanical equipment such as pumps and drive motors in front of the valve, and backflow discharge of container medium. Check valves can also be used on pipelines to supply auxiliary systems where the pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).

The function of check valves is to allow the medium to flow only in one direction and prevent the flow in the opposite direction. Usually, this type of valve works automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the pressure of the fluid and the self weight of the valve disc act on the valve seat, thereby cutting off the reverse flow.

Check valves belong to this type of valve, which includes swing check valves and lift check valves. The swing check valve has a hinge mechanism and a valve disc like a door that freely rests on the inclined valve seat surface. In order to ensure that the valve disc can reach the appropriate position on the valve seat surface every time, the valve disc is designed in a hinge mechanism so that the valve disc has sufficient swing space and truly and fully contacts the valve seat. The valve disc can be made entirely of metal, or it can be embedded with leather, rubber, or a synthetic cover on top of the metal, depending on the performance requirements. When the swing check valve is fully open, the fluid pressure is almost unobstructed, so the pressure drop through the valve is relatively small. The valve disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. This valve is similar to a globe valve, except that the valve disc can be freely raised and lowered. Fluid pressure lifts the valve disc from the sealing surface of the valve seat, causing the medium to reflux and causing the valve disc to fall back onto the valve seat, cutting off the flow. According to the usage conditions, the valve disc can be made of all metal structure or embedded with rubber pads or rubber rings on the valve disc frame. The passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is greater than that through the swing check valve, and the flow rate of the swing check valve is less restricted.