butterfly valve, referred to as butterfly valve (butterfly valve), refers to the closing part (valve disc or butterfly plate) is a disk, revolving around the valve shaft to achieve the opening and closing of a valve, mainly used for cutting off and throttling on the pipeline. The opening and closing part of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve the purpose of opening and closing or adjusting. The butterfly valve is usually less than 90°, the butterfly valve and the butterfly rod itself have no self-locking ability, in order to position the butterfly plate, the worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate self-locking ability, so that the butterfly plate stops in any position, but also improve the operating performance of the valve