What is the Butterfly valve

Butterfly valve refers to a valve whose closing part (disc or butterfly plate) is a disc and rotates around the valve shaft to open and close. It is mainly used for cutting and throttling on the pipeline. The opening and closing part of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjustment. The butterfly valve is usually less than 90° from fully open to fully closed. The butterfly valve and butterfly rod have no self-locking ability. In order to position the butterfly plate, a worm gear reducer should be installed on the valve rod. The use of the worm gear reducer not only enables the butterfly plate to have self-locking ability, makes the butterfly plate stop at any position, but also improves the operating performance of the valve. The characteristics of the industrial special butterfly valve are high temperature resistance, high applicable pressure range, large nominal diameter of the valve, the valve body is made of carbon steel, and the sealing ring of the valve plate is made of a metal ring instead of a rubber ring. Large-scale high-temperature butterfly valves are manufactured by welding steel plates and are mainly used for flue gas ducts and gas pipelines for high-temperature media. Discussion of knowledge in the process of using the butterfly valve In the 1930s, the United States invented the butterfly valve, and it was introduced to Japan in the 1950s.

At present, butterfly valves above DN300 mm have gradually replaced gate valves in the world. Compared with gate valves, butterfly valves have shorter opening and closing time, smaller operating torque, smaller installation space and light weight. Taking DN1000 as an example, the butterfly valve is about 2T, while 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 rubber-sealed butterfly valves is that when they are used for throttling, cavitation will occur due to improper use, which will cause peeling and damage of the rubber seat. For this reason, metal-sealed butterfly valves have been developed internationally, and the cavitation zone has been reduced. In recent years, metal-sealed butterfly valves have also been developed in my country, and comb-shaped butterfly valves with cavitation resistance, low vibration, and low noise have also been developed in Japan in recent years. ? Generally, the service life of the sealing seat is 15-20 years for rubber and 80-90 years for metal under normal circumstances. But how to choose correctly depends on the requirements of the working conditions. The relationship between the opening of the butterfly valve and the flow rate basically changes linearly. If it is used to control the flow, its flow characteristics are also closely related to the flow resistance of the piping. For example, if two pipes are installed with the same valve diameter and form, but the loss coefficients of the pipes are different, the flow of the valves will also vary greatly.

If the valve is in a state of large throttling, cavitation is prone to occur on the back of the valve plate, which may damage the valve. Generally, it is used outside 15°. ? When the butterfly valve is in the middle opening, the opening shape formed by the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides form different states. The front end of the butterfly plate on one side moves along the direction of the flowing water, and the other side moves against the direction of the flowing water. Therefore, one side of the valve body and the valve plate form a nozzle-shaped opening, and the other side is similar to a throttle-shaped opening. The nozzle side has a much faster flow rate than the throttle side, and negative pressure will be generated under the throttle side valve. Often rubber seals come off. The operating torque of the butterfly valve varies with the opening and the opening and closing direction of the valve. For horizontal butterfly valves, especially large-diameter valves, the torque generated by the difference between the upper and lower heads of the valve shaft due to the water depth cannot be ignored. In addition, when an elbow is installed on the inlet side of the valve, a bias flow is formed and the torque will increase. When the valve is in the middle opening, the operating mechanism needs to be self-locking due to the action of the water flow torque. Material, valve body material and other elements. The standardization of valve models provides convenience for the design, selection and distribution of valves.