- The check valve is an automatic valve whose main function is to prevent the backflow of the medium, the reverse rotation of the pump and drive motor, and the release of the container medium. Check valves may also be used on lines supplying 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).
- Structure and installation:
1. The valve disc of the low-temperature check valve is disc-shaped and rotates around the rotating axis of the valve seat channel. Because the inner channel of the valve is streamlined, the flow resistance is smaller than that of the rising butterfly check valve. It is suitable for low flow rates and infrequent flows. It is suitable for changing large diameter situations, but it is not suitable for pulsating flow, and its sealing performance is not as good as that of the lifting type. Butterfly check valves are divided into three types: single-disc type, double-disc type and multi-half type. These three forms are mainly divided according to the valve diameter. The purpose is to prevent the medium from stopping the flow or backflow and weakening the hydraulic impact.
2. The low-temperature check valve is a check valve whose disc slides along the vertical centerline of the valve body. The internal thread check valve can only be installed on horizontal pipelines. The valve disc of high-pressure small-diameter check valve can be made of round balls. The valve body shape of the butterfly check valve is the same as that of the globe valve (can be used universally with the globe valve), so its fluid resistance coefficient is larger. Its structure is similar to that of a globe valve, and its valve body and disc are the same as those of a globe valve. The upper part of the valve disc and the lower part of the valve cover are processed with guide sleeves. The valve disc guide sleeve can be freely raised and lowered in the valve guide sleeve. When the medium flows forward, the valve disc opens by the thrust of the medium. When the medium stops flowing, the valve disc opens by itself. It falls vertically on the valve seat to prevent the backflow of the medium. The direction of the medium inlet and outlet channels of the straight-through butterfly check valve is perpendicular to the direction of the valve seat channel; the direction of the medium inlet and outlet channels of the vertical lift check valve is the same as the direction of the valve seat channel, and its flow resistance is smaller than that of the straight-through type.
3. Low temperature check valve: a check valve in which the valve disc rotates around the pin in the valve seat. The disc check valve has a simple structure and can only be installed on horizontal pipelines, with good sealing performance.
4. Low temperature check valve: a valve whose disc slides along the center line of the valve body. The pipeline check valve is a new type of valve. It is small in size, light in weight and has good processing technology. It is one of the development directions of check valves. However, the fluid resistance coefficient is slightly larger than that of the swing check valve.
5. Pressure check valve: This valve is used as a boiler water and steam cut-off valve. It has the comprehensive functions of a lift check valve and a stop valve or angle valve.
In addition, there are some check valves that are not suitable for installation at the pump outlet, such as foot valves, spring-type, Y-type and other check valves.