Why should the butterfly valve be eccentric

According to the structure of the butterfly valve is divided into wafer butterfly valve, single eccentric seal butterfly valve, double eccentric seal butterfly valve, three eccentric seal butterfly valve. Why should the butterfly valve be eccentric? It is to make the butterfly valve have better sealing performance.

The original butterfly valve is loosely closed, also known as the flapper valve. It is only used as a flow control valve in the piping system. With the development of science and technology, butterfly valves are also developing in the direction of high temperature, high pressure, large diameter, high sealing, long life and excellent adjustment performance.

Center line seal butterfly valve

The sealing section of the valve plate is in a straight line with the rotating center of the valve plate, and the rotating center of the valve plate is in the center line of the valve body.

Because the stem axis passes through the sealing section of the butterfly plate, it has a certain influence on the sealing of the butterfly valve. Mainly used for rubber seal, PTFE seal and other elastic sealing material butterfly valve. The valve seat is squeezed by the butterfly plate to form a seal after elastic deformation of the valve seat. Greater wear on the valve seat.

Single eccentric seal butterfly valve

The valve plate seal section deviates from the center of rotation of the valve plate X. The rotating center of the valve plate is on the center line of the valve body.

Because the stem axis deviates from the sealing section of the butterfly plate, the butterfly plate forms a complete circular sealing ring, which improves the sealing performance of the butterfly valve. In addition to rubber, PTFE and other elastic seals, the sealing material also uses metal sealing seat, which improves the service temperature and service life of the butterfly valve.

When the valve plate is rotated from 0° to 20 ~ 25°, the valve plate seal is completely detached from the sealing surface of the valve seat. The wear on the sealing surface of the valve seat is reduced. Commonly used high vacuum butterfly valve is the use of this structure.

Double eccentric seal butterfly valve

The valve plate seal section deviates from the center of rotation of the valve plate X. The rotation center of the valve plate deviates from the center line of the valve body by a distance Y. An eccentric distance Y is added to the single eccentric sealing structure. That's why they call it double eccentric.

Now many high-performance butterfly valves are using this structure. Seat sealing material can be rubber, PTFE, metal seat. When the valve plate is rotated from 0° to 8 ~ 12°, the valve plate seal is completely detached from the sealing surface of the valve seat. The wear on the valve seat is further reduced, and the sealing performance of the butterfly valve is improved.

Three eccentric seal butterfly valve

Plate seal section and valve plate rotation center deviation distance X. The rotation center of the valve plate deviates from the center line of the valve body by a distance Y. The center line of the valve body has an Angle α with the center line of the sealing surface of the valve seat.

On the basis of double eccentric butterfly valve, the sealing surface of the valve seat is offset at a certain Angle. The sealing surface of the valve seat is conical. The valve plate seal detaches from the seat sealing surface when opened. There is almost no friction between the two, which greatly improves the sealing performance and service life of the butterfly valve.

The specific pressure of the three-eccentric butterfly valve is no longer rubber, PTFE and other elastic deformation to provide. Instead, a certain specific seal pressure can be generated by applying torque to the butterfly valve shaft. This allows it to be used in high-pressure pipes and provides adequate sealing.

The valve plate or seat is designed with a multi-layer metal elastic sealing structure. Can provide two-way sealing capability.

The eccentric of the butterfly valve gradually increases, which is the process of continuous improvement of the butterfly valve and improvement of its performance. It can gradually replace the process of large diameter gate valve and globe valve.