In the 1930s, the United States invented the butterfly valve, which was introduced to Japan in the 1950s, to 60 years.
The founders are widely used in Japan, and the promotion in China is after the 1970s. The main features of the butterfly valve are: small operating torque, small installation space and light weight. Taking DN1000 as an example, the butterfly valve is about 2T, and the gate valve is about 3.5T, and the butterfly valve is easy to combine with various driving devices, and has good durability and reliability. The disadvantage of the rubber sealing butterfly valve is that when it is used for throttling, cavitation will occur due to improper use, and the rubber seat will be peeled off and damaged. Therefore, how to correctly select it depends on the working conditions. The relationship between the opening of the butterfly valve and the flow rate changes substantially linearly.
If it is used to control the flow, its flow characteristics are closely related to the flow resistance of the piping. For example, the diameters and forms of the two pipe installation valves are all the same, and the pipe loss coefficient is different, and the valve flow difference is also large. If the valve is in a state of large throttle, the back of the valve plate is prone to cavitation and may damage the valve. Generally, it is used outside of 15°. When the butterfly valve is at the middle opening degree, the shape of the opening formed by the valve body and the front end of the disc is centered on the valve shaft.The two sides are formed to complete different states, the front end of one of the discs moves in the direction of the water, and the other side moves in the direction of the countercurrent water. Therefore, one side of the valve body and the valve plate form a nozzle-like opening, and the other side is similar to throttling. The hole-shaped opening, the nozzle side is much faster than the throttle side flow, and the negative pressure is generated under the throttle side valve, and the rubber seal is often peeled off. The operating torque of the butterfly valve varies depending on the opening degree and the direction of opening and closing of the valve. Horizontal butterfly valves, especially large-diameter valves, cannot be ignored due to the water depth and the head difference between the valve shaft and the head. In addition, when the valve inlet side device is bent, a bias current is formed and the torque is increased. When the valve is at the intermediate opening, the operating mechanism needs to be self-locking due to the action of the water flow torque.