In the 1930s, the United States invented the butterfly valve. It was introduced to Japan in the 1950s and was widely used in Japan in the 1960s. In China, it was promoted in 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 flow difference of the valve 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 butterfly plate is centered on the valve shaft, and the two sides are formed to complete different states. The front end of the butterfly plate moves along the water direction and the other side flows in the opposite direction. Therefore, one side of the valve body and the valve plate form a nozzle-like opening, and the other side is similar to the orifice-shaped opening, the nozzle side has a much faster flow rate than the throttle side, and the negative pressure is generated under the throttle side valve, often A rubber seal will come 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 difference between the head and the head of the valve shaft. 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.
China’s valve industry chain is numerous, but it is not a valve power. Generally speaking, China has entered the ranks of the world’s largest valve countries, but from the perspective of product quality, China still has a long gap from the valve power. The industry’s low production concentration, low-end valve research and development capabilities, and low-level manufacturing technology in the valve industry still exist, and the import and export trade deficit continues to expand. There are definitely not so many valve companies that can truly survive in the market. But this high-speed shock in the valve industry will bring huge opportunities, and the result of the shock will make the market operation more rational. The road to localization of high-end valves is unusually “frustrated.” The basic components have become a short-term constraint to the development of China’s manufacturing industry to high-end. During the 12th Five-Year Plan period, the government will continue to increase the localization of high-end equipment components. Here we select the feasibility analysis of several representative valve industries mentioned in the “Implementation Plan” for import substitution. It can be seen from the analysis that the feasibility of import substitution of valves in various sub-sectors is very different, and high-end valves are waiting for more policy guidance and scientific research support.