The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. Within the cylindrical channel of the valve body of the butterfly valve, the disc-shaped butterfly plate rotates around the axis, with the rotation angle ranging from 0° to 90°. When it rotates to 90°, the valve is in the fully open state. 

The butterfly valve has a simple structure, small size and light weight, consisting of only a few components. It can be quickly opened and closed by rotating 90°, with simple operation. Moreover, this valve has excellent fluid control characteristics. When the butterfly valve is fully open, the thickness of the butterfly plate is the resistance of the medium flowing through the valve body. Therefore, the pressure drop generated by this valve is very small, and it has good flow control characteristics. The butterfly valve has two sealing types: elastic sealing and metal sealing. For the elastic sealing valve, the sealing ring can be embedded in the valve body or attached around the butterfly plate. 

Valves with metal seals generally have a longer service life than those with elastic seals, but it is difficult to achieve complete sealing. Metal seals can withstand higher working temperatures, while elastic seals have the drawback of being limited by temperature. 

If the butterfly valve is to be used for flow control, the key is to correctly select the size and type of the valve. The structural principle of the butterfly valve is particularly suitable for manufacturing large-diameter valves. The butterfly valve is widely used in general industries such as petroleum, gas, chemical engineering, water treatment, etc., and is also applied in the cooling water system of thermal power stations. 

The commonly used butterfly valves include the flanged butterfly valve and the threaded butterfly valve. The flanged butterfly valve is connected between two pipe flanges by using double-headed bolts. The flanged butterfly valve has a flange on the valve itself and uses bolts to connect the two end flanges of the valve to the pipe flanges.