Author: Site Editor Publish Time: 2018-12-12 Origin: Site
Butterfly valve superior performance and constant eccentricity, development and evolution closely related. In order to adapt to various operating conditions, the butterfly valve has gone through the evolution process from concentric to single eccentric, double eccentric and triple eccentric.
The evolution of the industrial butterfly valve and the development and application of the triple offset butterfly valve is briefly described as follows.
List of content for this article：
Structural characteristics of Concentric butterfly valves
Function of single offset butterfly valves
Function of double offset butterfly valves
Function of three-offset butterfly valves
The structural characteristics of the Concentric butterfly valves is that the valve stem axis, the disc center and the body center are at the same position. The structure is simple and convenient to manufacture. A common rubber-lined butterfly valve belongs to this category. In order to overcome the extrusion, scratching and sealing performance, the valve seat is basically made of elastic materials such as rubber or Teflon, but it is also limited in temperature by use, which is why it is traditionally considered that the butterfly valve is not resistant to high temperature.
The single offset butterfly valves solves the problem of the pressing of the disc and the valve seat of the concentric butterfly valve, thereby generating a single offset butterfly valve, and its structural feature is that the shaft center of the valve stem deviates from the center of the disc, so that the lower end of the disc is no longer It becomes the rotary axis, disperses and reduces the excessive extrusion of the lower end of the disc and the valve seat. However, due to the single offset structure, the scraping phenomenon of the disc and the valve seat does not disappear during the whole switching process of the valve, and the application range is similar to that of the concentric butterfly valve, so it is not used much.
The double offset butterfly valve is further improved on the basis of the single offset butterfly valve, which is the widely used double offset butterfly valve. The structural feature is that the stem axis is offset from the center of the disc and from the center of the body. The rapid disassembly of the disc from the seat after opening is due to the double bias effect, which greatly eliminates the unnecessary over-squeezing and scratching of the disc and seat, reduces opening resistance, reduces wear and improves seat life. Double eccentric butterfly valve can also be used with metal seat, improving the application of butterfly valve in high temperature field. However, because the sealing principle belongs to the position sealing structure, that is, the butterfly plate is in linear contact with the valve seat sealing surface, and the elastic deformation caused by the butterfly plate on the valve seat produces the sealing effect, which requires a lower pressure capacity, which is why the butterfly plate valve is considered to be able to resist high pressure and large leakage.
Three-offset butterfly valves need to be hard-sealed to withstand high temperature, but the leakage is large; to achieve zero leakage, soft-sealed, but not high temperature. In order to overcome the contradiction of double offset butterfly valve, the third offset of butterfly valve is carried out. The structural feature is that the axis of the conical axis on the sealing surface of the disc deflects the main cylinder to offset the position of the double counteracting rod at the same time. That is to say, after the third eccentricity, the sealing part of the disc is not a real circle, but an ellipse, the shape of the sealing surface is asymmetrical, and one side tends to parallel the center line of the body and the center line of the other side.
Tri-eccentric butterfly valve is no longer a sealing device, that is to say, it does not depend on the elastic deformation of the seat, but depends on the contact surface pressure of the seat to achieve sealing effect. Therefore, the problem of zero leakage of the metal seat has been solved, which is proportional to the medium pressure of the contact surface, and the problem of high temperature and high pressure has also been solved.
It has gone through several generations of technological changes to have our triple offset butterfly valve today, and in the future, it is believed that it will also usher in new changes. Triple offset butterfly valve's invention has epoch-making significance, if you are interested in it, please visit our website to find more related articles and products.