Working principle of check valve:
The check valve is used in the pipeline system, and its main function is to prevent the medium from flowing backward, preventing the pump and its driving motor from reversing, and releasing the medium in the container. Check valves can also be used to supply pipelines for auxiliary systems whose pressure may rise above the pressure of the main system. According to different materials, check valves can be applied to pipelines of various media. The check valve is installed on the pipeline and becomes one of the fluid parts of the complete pipeline. The opening and closing process of the valve disc is affected by the transient flow state of the system where it is located; in turn, the closing characteristic of the valve disc have an effect on fluid flow again
Check valve classification
Swing check valve
The disc of the swing check valve is disc-shaped, and it rotates around the shaft of the valve seat channel. Because the inner channel of the valve is streamlined, the flow resistance is smaller than that of the lift check valve, which is suitable for low flow rates and infrequent changes in flow. It is not suitable for pulsating flow, and its sealing performance is not as good as the lifting type. The swing check valve is divided into three types: single, double and multiple disc valves. These three types are mainly classified according to the valve diameter. The purpose is to prevent the medium from stopping or flowing backwards and weaken the hydraulic shock.
Lift check valve
A check valve whose disc slides along the vertical centerline of the valve body. A lift check valve can only be installed on a horizontal pipeline. A round ball can be used for the disc of a high-pressure small-diameter check valve. The valve body shape of the lift check valve is the same as that of the globe valve (which can be used in common with the globe valve), so its fluid resistance coefficient is relatively large. Its structure is similar to the globe valve, and the valve body and disc are similar to the globe valve.
Silent check valve
The upper part of the valve disc and the lower part of the valve cover are processed with guides. The valve guides can rise and fall freely in the valve guides. When the medium flows downstream, the valve disc are opened by the thrust of the medium. When the medium stops, the valve disc hang down. Land on the valve seat to prevent the medium from flowing backward. The direction of the medium inlet and outlet channel of the straight-through lift check valve is perpendicular to the direction of the valve seat channel; the vertical lift check valve has the same direction of the medium inlet and outlet channels as the valve seat channel, and its flow resistance is smaller than that of the straight-through type.
Butterfly check valve
A check valve in which the disc rotates around a pin shaft in the valve seat. The disc check valve has a simple structure and can only be installed on a horizontal pipeline, with poor sealing performance.
Pipeline check valve
A valve in which the disc slides along the centerline of the valve body. In-line check valve is a new type of valve. It is small in size, light in weight, and good in processing technology. It is one of the development directions of check valves. But the fluid resistance coefficient is slightly larger than that of the swing check valve.
Compression check valve
This kind of valve is used as a boiler feed water and steam shut-off valve. It has a comprehensive function of a lift check valve and a stop valve or an angle valve.
In addition, there are some check valves that are not suitable for pump outlet installation, such as bottom valve, spring type, Y type, etc.
Precautions for check valve installation method:
1. Do not allow the check valve to bear weight in the piping system. Large check valves should be independently supported so that they are not affected by the pressure generated by the piping system.
2. When installing, pay attention to the direction of medium flow should be consistent with the direction of the arrow marked on the valve body.
3. The lift-type vertical disc check valve should be installed on the vertical pipeline.
4. The lift-type horizontal disc check valve should be installed on the horizontal pipeline.
