Butterfly valve developing history In the 1930s, the United States invented butterfly valves. This valve has a small operating torque, a small installation space and a light weight. Taking DN1000 as an example, the butterfly valve is about 2T, but the gate valve is as heavy as 3.5T. The butterfly valve is easy to combine with various driving devices, and has good durability and reliability. The relationship between the opening of the butterfly valve and the flow rate changes substantially linearly. If used to control flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, if the diameters, forms, etc. of the two…