Valve opening and closing member is a disc-shaped disc, the valve body about its axis of rotation, so as to open and close a valve or regulating valve is called. Butterfly valve fully open to fully closed is usually less than 90 degrees, butterfly and butterfly lever itself is not a strong self-locking, in order to locate the disc to be installed on the valve stem worm reducer. By worm reducer, not only can make the disc with self-locking capability, so that the disc is stopped in any position, but also to improve the operational performance of the valve. Industry-specific characteristics of butterfly valves to high temperature, pressure range is higher, the valve nominal diameter large carbon steel valve body, valve plate seal with metal ring instead of the rubber ring. Large temperature valve welded steel plate manufacturing, mainly for high-temperature medium smoke duct and gas pipelines.