Butterfly valve (butterflyvalve) refers to the closing piece (disc or disc) as a disc, rotating around the valve shaft to achieve a valve on and off, mainly in the pipeline cut off and throttling purposes. Butterfly valve opening and closing pieces is a disc-shaped disc, the valve body around its own axis of rotation, so as to achieve the purpose of opening and closing or regulation. The butterfly valve fully open to the whole is usually less than 90 °, the butterfly valve and the butterfly itself does not have self-locking ability, in order to disc positioning, to install a worm reducer on the stem. The use of worm reducer, not only can make the disc self-locking ability to stop the butterfly plate in any position, but also to improve valve performance. Industrial butterfly valve features high temperature, high pressure range, the valve nominal diameter, the valve body made of carbon steel, the valve ring using a metal ring instead of rubber ring. Large high temperature butterfly valve welded steel manufacturing, mainly for high temperature medium smoke duct and gas pipelines. Butterfly valve installation and maintenance should note the following: 1. During installation, the valve should be stopped in the closed position. 2. Open position should be determined by the rotation angle of the disc. 3. Butterfly valve with bypass valve should open bypass valve before opening. 4. Should be installed according to the manufacturer's installation instructions, heavy butterfly valve, should be set up a solid foundation. The advantages of butterfly valves are as follows: 1. Opening and closing fast and easy, labor-saving, fluid resistance is small, you can often operate. 2. Simple structure, small size, light weight. 3. Can transport mud, pipe liquid accumulated in the mouth at least. 4. Low pressure, can achieve a good seal. 5. Regulate the performance. The shortcomings of the butterfly valve are as follows: 1. The working pressure and working temperature range is small. 2, poor sealing. Butterfly valve can be divided according to the structure of the bias plate, vertical plate, inclined plate and lever. According to the sealing form can be divided into more sealed and hard seal two. Rubber seals are generally used rubber ring seal, hard seal is usually used metal ring seal. According to the connection type can be divided into flange connection and the clamp connection; According to the transmission can be divided into manual, gear transmission, pneumatic, hydraulic and electric several.