Butterfly valve refers to the closing piece (disc or butterfly plate) as a disc, revolving around the valve shaft to achieve a valve opened and closed, in the pipeline mainly cut off and throttling effect. Butterfly valve headstock is a disc-shaped butterfly plate, in the valve body around its own axis rotation, so as to achieve the purpose of headstock or adjustment. Butterfly valve fully open to the full clearance is usually less than 90 °, butterfly valve and the butterfly itself has no self-locking ability, in order to locate the butterfly plate, the valve stem to add worm gear reducer. The use of worm gear reducer, not only can make the butterfly board has self-locking ability, so that the butterfly plate stopped in any position, but also can improve the operation performance of the valve. Industrial special Butterfly valve features high temperature, applicable pressure range is also higher, valve nominal size, valve body using carbon steel manufacturing, valve plate sealing ring using metal ring instead of rubber ring. The large-scale high temperature butterfly valve uses the steel plate to weld the manufacture, mainly uses in the high temperature medium smoke duct and the gas pipeline.