Check valve refers to a valve whose opening and closing parts are circular discs and rely on its own weight and medium pressure to generate actions to block the back flow of the medium. It is an automatic valve, also known as check valve, one-way valve, return valve or isolation valve. The movement of the disc is divided into lift type and swing type. The lift check valve is similar in structureto the shut-off valve , but lacks the valve stem that drives the disc. The medium flows in from the inlet end (lower side) and flows out from the outlet end (upper side). When the inlet pressure is greater than the sum of the weight of the disc and its flow resistance, the valve is opened. On the contrary, the valve is closed when the medium flows back. The swing check valve has a disc that is inclined and can rotate around the axis, and the working principle is similar to that of the lift check valve. The check valve is often used as the bottom valve of the pumping device to prevent the backflow of water. The combination of check valve and stop valve can play a role in isolation. The disadvantage is that the resistance is large and the sealing performance is poor when closed.
The valve that opens or closes on its own by the force of the flow of the medium to prevent the medium from flowing back is called a check valve. Check valves belong to the category of automatic valves, which are mainly used in pipelines where the medium flows in one direction, and only allow the medium to flow in one direction to prevent accidents.
According to the structure, it can be divided into three types: lift check valve, swing check valve and butterfly check valve:
1. Lift check valves are divided into two types: vertical and horizontal.
2. Swing check valves are divided into three types: single valve, double valve and multi valve.
3. The butterfly check valve is a straight-through type.
Check valve can be divided into four types in connection form: threaded connection, flange connection, welding connection and wafer connection.
Check valves can also be used to supply pipelines for auxiliary systems where the pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).
The function of this type of check valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat , thereby cutting off the flow.