Butterfly valve development and use

First, the development of butterfly valves

In the 30's, the United States invented the butterfly valve. It was introduced to Japan in the 1950s. It was generally adopted in Japan in the 1960s, and promotion in China was after the 1970s. At present, in the world, butterfly valves with DN300 mm or more have gradually replaced gate valves. Compared with the gate valve, the butterfly valve has a short opening and closing time, a small operation, a small installation space and a light weight. Taking DN1000 as an example, the butterfly valve is about 2T and the gate valve is about 3.5T. The butterfly valve is easy to be combined with various driving devices and has good durability and reliability. The disadvantage of the rubber seal butterfly valve is that if it is used for throttling, cavitation may occur due to improper use, and the rubber seat may peel off or be damaged. For this reason, the metal seal butterfly valve is now being developed internationally, and the cavitation area is reduced. In recent years, China has also developed a metal seal butterfly valve. In recent years, Japan has also developed a comb-shaped butterfly valve that is resistant to cavitation erosion, low vibration, and low noise. Generally the life of the seal seat is under normal conditions, rubber 15 years - 20 years, metal 80 years - 90 years. However, how to use it correctly must be based on working conditions.

Second, the use of butterfly valve

The relationship between the opening and the flow of the butterfly valve is basically a linear proportional change. If it is used to control the flow, its flow characteristics are also closely related to the flow resistance of the piping. If the diameters and forms of the two pipeline installation valves are the same, and the pipeline loss coefficient is different, the flow difference of the valves will also be very large. If the valve is in a large throttling state, the back of the valve plate is prone to cavitation and may damage the valve. Generally, it is used outside 15°.

When the butterfly valve is in the middle opening degree, the shape of the opening formed by the front end of the valve body and the butterfly plate is centered on the valve shaft, and the two sides form different states. The front end of the butterfly plate moves in the direction of the flowing water and the other side flows in the direction of the flowing water. Moving, therefore, one side of the valve body and the valve plate form a nozzle-like opening, the other side similar to the orifice-shaped opening, the nozzle side faster than the throttle side of the flow rate, and the throttle valve will produce negative pressure, often Rubber seals will come off. ?

Butterfly valve operating torque, due to opening and valve opening and closing direction of different values, horizontal butterfly valve, especially large-diameter valve, due to water depth, the shaft shaft, the head of the water generated by the torque can not be ignored. In addition, when the elbow on the inlet side of the valve is deflected, the bias flow will increase. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the effect of the water flow torque.