The butterfly valve opening and closing piece is a disc-shaped butterfly plate, which rotates around its own axis in the body of the valve, thus achieving the opening and closing or regulating of the valve is called the butterfly valve. Butterfly valves are usually less than 90 degrees open and closed. Butterfly valves and butterfly rods do not have self-locking force. In order to locate the butterfly plate, worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make butterfly plate have self-locking ability, make butterfly plate stop at any position, but also improve the operation performance of the valve.
Industrial butterfly valves are characterized by high temperature resistance, high pressure range, large nominal diameter, carbon steel body and metal ring instead of rubber ring. Large high temperature butterfly valve is welded by steel plate, mainly used for flue gas duct and gas pipeline of high temperature medium. Concentric butterfly valve The structural characteristics of this butterfly valve are that the axis of the stem, the center of the butterfly plate and the center of the body are in the same position. The utility model has the advantages of simple structure and convenient manufacture. The common rubber lined butterfly valve belongs to this type.
The disadvantage is that the butterfly plate and valve seat are always in the state of extrusion, scratch, large resistance distance and fast wear and tear. In order to solve the problem of extrusion between butterfly plate and seat of concentric butterfly valve, a single eccentric butterfly valve is produced. Its structural feature is that the axis of the stem deviates from the center of the butterfly plate, so that the lower end of the butterfly plate is no longer the center of rotation, and the excessive extrusion between the lower end of the butterfly plate and the seat is reduced.
Double eccentric butterfly valve is the most widely used double eccentric butterfly valve, which is further improved on the basis of single eccentric butterfly valve. The structure features that the axis of the valve stem deviates from both the center of the butterfly plate and the center of the body. The effect of double eccentricity enables the butterfly plate to detach from the valve seat immediately after the valve is opened, greatly eliminating unnecessary over-extrusion and scratch between the butterfly plate and the valve seat, reducing the opening resistance, reducing wear and tear, and improving the service life of the valve seat.