Why Is the Eccentricity of the Butterfly Valves Increasing?
Butterfly valves are divided into center line butterfly valves, single eccentric butterfly valves, double eccentric butterfly valves, and triple eccentric butterfly valves according to their structural forms. Why is the eccentricity of butterfly valves increasing? It is to improve the sealing performance of butterfly valves.
The original
butterfly valve was not tightly closed, which is also known as a baffle valve. It is only used as a flow regulating valve in the pipeline system. With the development of technology, butterfly valves are also developing towards high temperature, high pressure, large diameter, high sealing, long service life, and excellent regulating performance.
Center line butterfly valves
The sealing section of the valve plate is in a straight line with the rotation center of the valve plate, and the rotation center of the valve plate is on the center line of the valve body.
Due to the valve stem axis passing through the sealing section of the butterfly plate, it has a certain impact on the sealing of the butterfly valve. It is mainly used for butterfly valves with elastic sealing materials such as rubber seals and PTFE seals. By squeezing and sealing the valve seat with the butterfly plate, the valve seat undergoes elastic deformation to form a seal. There is significant wear on the valve seat. The commonly used center line butterfly valves are D371X, D341X, etc.
Single eccentric butterfly valves
The deviation distance X is between the sealing section of the valve plate and the rotation center of the valve plate. The center of rotation of the valve plate is on the center line of the valve body.
Due to the deviation of the valve stem axis from the sealing section of the butterfly plate, the butterfly plate forms a complete circular sealing ring, improving the sealing performance of the butterfly valve. In addition to elastic seals such as rubber and PTFE, the metal sealing seats are also used to improve the temperature and service life of butterfly valves for sealing materials.
When the valve plate rotates from 0 ° to 20 to 25 °, the valve plate seal completely disengages from the valve seat sealing surface. The wear on the sealing surface of the valve seat is reduced. The commonly used high vacuum butterfly valve adopts this structure.
Double eccentric butterfly valves
The deviation distance X is between the sealing section of the valve plate and the rotation center of the valve plate. The deviation distance Y is between the rotation center of the valve plate and the center line of the valve body. It is an eccentric distance Y added to the single eccentric sealing structure. Therefore, it's called double eccentricity.
Many high-performance butterfly valves now use this structure. The sealing material for the valve seat can be rubber, PTFE, or metal. When the valve plate rotates from 0 ° to 8 to 12 °, the valve plate seal completely detaches from the valve seat sealing surface. The wear on the valve seat is further reduced, and the sealing performance of the butterfly valve is improved.
Triple eccentric butterfly valves
The deviation distance X is between the sealing section of the plate and the rotation center of the valve plate. The deviation distance Y is between the rotation center of the valve plate and the center line of the valve body. There is an angle between the center line of the valve body and the center line of the sealing surface of the valve seat α.
It is based on a double eccentric butterfly valve to offset the sealing surface of the valve seat at a certain angle. The sealing surface of its valve seat is a conical surface. The valve plate seal will detach from the valve seat sealing surface when opened. There is almost no friction between them, greatly improving the sealing performance and service life of the butterfly valve.
The sealing pressure of the three eccentric butterfly valve is no longer provided by elastic deformation such as rubber and PTFE. Instead, a certain sealing pressure can be generated by applying torque to the butterfly valve shaft. This can be used for high-pressure pipelines and provide sufficient sealing.
The valve plate or seat is designed with a multi-level metal elastic sealing structure. It can provide bi-directional sealing capability. It is commonly used models include D343H, D373H, etc.
The gradual increase in eccentricity of butterfly valves is a process of continuous improvement and improvement of their performance. It can gradually replace the process of large-diameter gate valves and globe valves.
