The butterfly valve is a type of quarter-turn valve that uses a disc-shaped closure member, known as a butterfly plate, which rotates around its own axis within the valve body. This rotation allows the valve to open, close, or regulate the flow of media. When fully open, the butterfly valve typically requires less than 90 degrees of rotation, making it quick and efficient to operate. However, the butterfly plate and stem are not self-locking, so a worm gear reducer is often added to the valve stem to provide positioning and control. The use of this mechanism not only enables self-locking but also allows the disc to be stopped at any position, enhancing the valve's performance and reliability. Industrial special butterfly valves are designed to handle high-temperature environments and can operate under high pressure. These valves often have large nominal diameters, with the valve body constructed from carbon steel and the sealing ring made of a metal ring instead of a rubber one. Large high-temperature butterfly valves are typically fabricated by welding steel plates and are commonly used in flue ducts and gas pipelines for high-temperature media. The advantages of butterfly valves include: 1) quick and easy operation with minimal effort, 2) simple and compact design, 3) suitability for handling slurries and low-liquid media, 4) good sealing performance at low pressures, and 5) excellent flow control capabilities. However, they do have some disadvantages, such as limited operating pressure and temperature ranges and relatively poor sealing compared to other types of valves. Butterfly valves can be classified based on their structure into eccentric butterfly valves, vertical plate butterfly valves, slant plate butterfly valves, and lever-type butterfly valves. In terms of sealing, they are divided into two main types: soft-sealed butterfly valves, which use a rubber ring for sealing, and hard-sealed butterfly valves, which employ a metal ring for improved durability and performance. Depending on the connection method, they can be flanged or wafer-type. In terms of actuation, they can be manually operated, gear-driven, pneumatically operated, hydraulically operated, or electrically driven. When installing and maintaining a butterfly valve, several important points should be considered: 1) ensure the valve is closed during installation, 2) determine the opening position based on the disc’s rotation angle, 3) if the valve has a bypass, open it before starting, 4) follow the manufacturer's installation instructions, and 5) for heavy-duty butterfly valves, make sure a solid foundation is provided.