The disc of the butterfly valve is installed in the diameter direction of the pipe. In the cylindrical passage of the butterfly valve body, the disc-shaped disc rotates around the axis at a rotation Angle of 0-90. When the valve is rotated to 90, the valve plate is fully open.Butterfly valve simple structure, small size, light weight, only a few parts. The valve is easy to operate and has good fluid control characteristics. When the butterfly valve is in the fully open position, the butterfly plate thickness is the only 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. Butterfly valve has spring seal and metal seal two types. Resilient seal valve, detachable ring can be mounted on valve body or attached to disc periphery.Valves with metal seals generally have a longer life than valves with elastic seals, but it is difficult to achieve a complete seal. Metal seal can adapt to higher operating temperature, elastic seal has the limitation of temperatureIf butterfly valves are required for flow control, it is important to select the correct size and type of valve. The structure principle of butterfly valve is especially suitable for making large caliber valves. Butterfly valve is not only widely used in petroleum, gas, chemical industry, water treatment and other general industries, but also in thermal power plant cooling water system.