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 opening and closing or adjustment. Butterfly valve is generally less than 900 when it is fully open or fully closed. Butterfly valve and butterfly rod have no self-locking force. In order to locate butterfly plate, worm gear reducer shall be installed on the valve rod. The use of worm gear reducer can not only make the disc have self-locking ability, make the disc stop at any position, but also improve the operation performance of the valve.

The industrial butterfly valve is characterized by high temperature resistance, high applicable pressure range, large valve nominal diameter, carbon steel valve body, and metal ring instead of rubber ring for the sealing ring of valve plate. Large high temperature butterfly valve is made of steel plate by welding, which is mainly used for the flue gas duct and gas pipeline of high temperature medium.

（1） Advantages of butterfly valve:

1. The opening and closing are convenient, quick, labor-saving, with small fluid resistance, and can be operated frequently.
2. Simple structure, small volume and light weight.
3. The mud can be transported, and the minimum liquid can be accumulated at the pipe mouth.
4. Under low pressure, good sealing can be achieved.
5. Good regulation performance.

（2） Disadvantages of butterfly valve:

1. The range of working pressure and temperature is small.
2. Poor sealing.

（3） Installation and maintenance of butterfly valve:

1. During installation, the disc shall be stopped at the closed position.
2. The opening position shall be determined according to the rotation angle of butterfly plate.
3. For butterfly valve with bypass valve, the bypass valve shall be opened before opening.
4. The installation shall be carried out according to the installation instructions of the manufacturer. The heavy butterfly valve shall be provided with a firm foundation.