Butterfly valve, also known as flap valve, is a simple control valve, which can be used for the on-off control of low-pressure pipeline medium. It refers to a valve whose closing piece (disc or butterfly plate) is a disc and rotates around the valve shaft to open and close. The valve can be used to control the flow of air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It is mainly used to cut off and throttle the pipeline. The opening and closing part of butterfly valve is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so as to achieve the purpose of opening and closing or adjustment.

Various types of butterfly valves ,For example, pneumatic butterfly valve, cast Iron butterfly valve,Center seal butterfly valve ,wafer center line butterfly valve,Forced seal butterfly valve,flanged double eccentric butterfly valve etc.

The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. The butterfly valve is simple in structure, small in volume and light in weight. It is only composed of a few parts, and can be opened and closed quickly only by rotating 90 °. The operation is simple. At the same time, the valve has good fluid control characteristics. When the butterfly valve is in the fully open position, the butterfly plate thickness is the resistance when the medium flows through the valve body, so the pressure drop generated through the valve is very small, so it has better flow control characteristics. If butterfly valve is required to be used as flow control, the main thing is to correctly select the size and type of valve. The structure and principle of butterfly valve is especially suitable for making large-diameter valve. There are two kinds of butterfly valves commonly used: wafer butterfly valve and flange butterfly valve. Double clip butterfly valve is to connect the valve between two pipe flanges with stud bolts. Flange butterfly valve is to connect the flange on both ends of the valve to the pipe flange with bolts. Butterfly valve, as a component used to realize on-off and flow control of pipeline system, has been widely used in many fields, such as petroleum, chemical industry, metallurgy, hydropower, etc. In the well-known butterfly valve technology, the sealing structure is mostly adopted, and the sealing materials are rubber, polytetrafluoroethylene, etc. Due to the limitation of structural features, it is not suitable for industries such as high temperature, high pressure, corrosion resistance and wear resistance. A more advanced butterfly valve is a three eccentric metal hard seal butterfly valve. The valve body and valve seat are connected components. The sealing surface of valve seat is overlaid with heat-resistant and corrosion-resistant alloy materials. The multi-layer soft laminated seal ring is fixed on the valve plate. Compared with the traditional butterfly valve, this butterfly valve has the advantages of high temperature resistance, light operation, no friction between opening and closing. When closing, it compensates the seal with the increase of the torque of the transmission mechanism, improving the sealing performance of the butterfly valve and prolonging its service life.