How does the check valve work?

The check valve is a valve that automatically opens and closes the valve flap, and is used to prevent the back flow of the medium depending on the flow of the medium itself. It is also called a check valve, a one-way valve, a backflow valve, and a back pressure valve. The check valve is an automatic valve whose main function is to prevent the reverse flow of the medium, prevent the reverse rotation of the pump and the drive motor, and release the medium of the container. Check valves can also be used on pipelines where the pressure may rise above the system pressure to provide supplemental systems. Check valve can be divided into swing check valve (rotation by gravity center) and lift check valve (move along axis).

The role of this type of valve is to allow only the medium to flow in one direction and prevent the direction of flow. Normally, this type of valve operates automatically. The valve flap is opened by the fluid pressure flowing in one direction. When the fluid flows in the opposite direction, the fluid pressure and the self-closing flap of the valve flap act on the valve seat to shut off the flow.

The check valve belongs to this type of valve, which includes a swing check valve and a lift check valve. The swing check valve has a hinge mechanism, and a flap like a door leans against the inclined seat surface. In order to ensure that the valve flap can reach the proper position of the valve seat face each time, the flap is designed in the hinge mechanism so that the valve flap has sufficient swirling space and the valve flap is in true and full contact with the valve seat. The flaps can be made entirely of metal. They can also be inlaid with leather, rubber, or synthetic coverings, depending on the performance requirements. Swing check valves In the fully open condition, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The poppet of the lift check valve seats on the valve seat seal surface on the valve body. In addition to the valve flap can be freely raised and lowered, the rest as the stop valve, the fluid pressure to lift the valve flap from the valve seat sealing surface, the media back to cause the valve flap fall back to the valve seat, and cut off the flow. Depending on the conditions of use, the valve flap may be of a fully metal construction, or it may be in the form of a rubber gasket or rubber ring embedded in the valve holder. Like the shutoff valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than the swing check valve, and the flow of the swing check valve is limited Very little.

The check valve can be divided according to its structure and installation method:

First, the swing check valve: swing check valve disc is disk-shaped, around the rotation of the valve seat channel for rotation, due to the valve channel into a streamlined, flow resistance than the lift check valve Small, suitable for large caliber occasions with low flow velocities and infrequent changes in flow, but not suitable for pulsating flow, its sealing performance is less than that of lift type. Swing type check valve is divided into single valve type, double valve type and more than half type. These three types are mainly divided according to the valve caliber. The purpose is to prevent the hydraulic impact from being reduced when the medium stops flowing or reverse flow.

Second, the lift check valve: valve flap sliding along the vertical centerline of the valve body, lift check valve can only be installed in the horizontal pipe, in the high pressure small diameter check valve can be used ball . The shape of the valve body of the lift check valve is the same as that of the cut-off valve (common to the cut-off valve), so its fluid resistance coefficient is large. Its structure is similar to the shut-off valve, and the valve body and the valve flap are the same as the shut-off valve. The upper part of the valve flap and the lower part of the valve cover are processed with guide sleeves, and the valve guide guides can be freely raised and lowered within the valve guide guides. When the media flows downstream, the valve flaps are opened by the medium thrust. When the medium stops flowing, the valve flaps itself. The vertical drop falls on the valve seat and acts as a counter-current to the media. The straight-through lift check valve media inlet and outlet channel direction is perpendicular to the valve seat channel direction; the vertical lift check valve has the same medium inlet and outlet channel direction as the seat channel channel, and its flow resistance is smaller than that of the straight flow channel.

Third, the disc check valve: valve flap rotation around the valve seat within the check valve. The disc check valve has a simple structure and can only be installed on a horizontal pipe, and the sealing performance is poor.

Fourth, the pipeline check valve: valve flap sliding along the valve body centerline. Pipeline check valve is a new type of valve. It has small size, light weight, and good processing technology. It is one of the development direction of check valve. However, the fluid drag coefficient is slightly larger than the swing check valve.

Fifth, the compact check valve: This valve is used as boiler feed water and steam shut-off valve, which has a lifting check valve and globe valve or angle valve integrated function.

In addition, there are some non-return valves that are not suitable for pump outlet installation, such as bottom valve, spring type, Y type and other non-return valves.