Views: 5668 Author: Site Editor Publish Time: 2020-03-10 Origin: Site
A check valve is a valve whose opening and closing member is a circular disc and acts on its own weight and medium pressure to block the backflow of the medium. 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 shut-off valve can play a role of safety isolation. Its disadvantages are high resistance and poor sealing when closed.
(1) Swing check valve
The flap of the swing check valve is disc-shaped and rotates around the rotation axis of the valve seat channel. Because the channel in the valve is streamlined, the flow resistance is smaller than that of the lifting check valve, which is suitable for large-caliber occasions with low flow rates and infrequent changes in flow. However, it is not suitable for pulsating flow, and its sealing performance is not as good as that of lifting type. Swing check valve is divided into three types: single, double and half. These three types are mainly divided according to the valve diameter, in order to prevent the hydraulic shock when the medium stops flowing or flowing backward.
(2) Lift check valve
The lift check valve is a check valve whose valve disc slides along the vertical centerline of the valve body. The lifting check valve can only be installed on horizontal pipelines. On the high-pressure small-diameter check valve, the ball can be a ball. The shape of the valve body of the lift check valve is the same as that of the shut-off valve (common with the shut-off valve), so its fluid resistance coefficient is large. Its structure is similar to a globe valve, with the same body and disc as the globe valve. The upper part of the valve disc and the lower part of the valve cover are processed with a guide sleeve, and the valve flap guide can be freely raised and lowered in the valve guide. When the medium flows downstream, the valve flap is opened by the thrust of the medium; when the medium stops flowing, the valve flap falls on the valve seat by hanging down, which prevents the medium from flowing backward. The direction of the medium inlet and outlet channels of the straight-through lift 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 that of the valve seat channel, and its flow resistance is smaller than that of the straight type.
(3) Disc check valve
It is a non-return valve whose valve disc rotates around a pin in a valve seat. The disc check valve has a simple structure and can only be installed on horizontal pipes. Its tightness is poor.
(4) Pipeline check valve
It is a valve that slides along the centerline of the valve body. Pipeline check valve is a new type of valve. Its small size, light weight, and good processing technology are one of the development directions of check valves. However, the coefficient of fluid resistance of the pipeline check valve is slightly larger than that of the swing check valve.
(5) Compression check valve
This valve is used as a boiler water and steam shutoff valve, and it has the integrated function of a lift check valve and a stop valve or an angle valve.
In addition, there are some non-return valves not suitable for pump outlet installation, such as foot valve, spring type, Y type, etc.
(1) Do not allow the check valve to bear the 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 the medium flow should be consistent with the direction of the arrow marked on the valve body.
(3) The lifting vertical flap check valve shall be installed on a vertical pipeline.
(4) The lifting horizontal flap check valve shall be installed on a horizontal pipeline.
With the acceleration of the restructuring of the valve industry, the future industry will be competition between valve product quality and safety and product brands. The products are developing towards high technology, high parameters, strong corrosion resistance and high life. Only through continuous technological innovation, development of new products, and technological transformation can we gradually improve the technical level of our products.