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Difference between offset butterfly valves

Author: Site Editor     Publish Time: 2018-12-13      Origin: Site


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The offset butterfly valve is divided into single offset butterfly valve, double offset butterfly valve, and triple offset butterfly valve. A butterfly valves whose valve stem axis is at the same time deviated from the center of the disc and the center of the body, and whose sealing pair is a slanting vertebra is called an offset butterfly valve.

List of content for this article:

  • Double offset butterfly valve

  • Triple offset butterfly valve

  • Variable offset butterfly valve

Double offset butterfly valve


Double eccentric butterfly valve 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. The scratch is greatly reduced. At the same time, the double eccentric butterfly valve can also use metal seat, which improves the application of butterfly valve in high temperature field.


Further improved molding on the basis of the single offset butterfly valve is currently the most 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 double offset effect allows the disc to be quickly disengaged from the valve seat after the valve is opened, which greatly eliminates unnecessary over-squeezing and scraping of the disc and the valve seat, reduces the opening resistance, reduces wear and improves seat life.


Triple offset butterfly valve


To withstand high temperature, a hard seal must be used, but the amount of leakage is large; for zero leakage, a soft seal must be used, but it is not resistant to high temperature. In order to overcome the contradiction of the double offset butterfly valve, the butterfly valve was subjected to the third eccentricity. The so-called third eccentricity means that the shape of the sealing pair is not a positive cone but a tapered cone.


Variable offset butterfly valve


The unique feature of the variable offset butterfly valve is that the valve stem shaft of the installation disc is a three-stage shaft structure. The two shaft sections of the three-section shaft stem are concentric, and the center line of the central section shaft is offset from the axis of the two ends by a center distance. The disc is mounted on the intermediate shaft section. Such an offset structure causes the disc to become double offset in the fully open position and to be single offset when the disc is rotated to the closed position. Due to the action of the offset shaft, the disc is moved into a distance from the sealing cone of the valve seat when it is close, and the butterfly plate and the sealing surface of the valve seat are matched to achieve a reliable sealing performance.The butterfly valve and the upper and lower valve shafts are connected by a special-shaped hole and a special-shaped shaft. During the opening and closing process of the butterfly plate, the function of the pin-free connection of the upper and lower sides of the butterfly plate is realized, and the interference zone between the butterfly plate and the valve seat is reduced. This greatly reduces the torque. The floating structure of the disc realizes the single offset manufacturing process and the function of eccentricity.An anti-butter plate overflow valve is installed in the body cavity to ensure that the disc is not in place when it is closed.

The bushing between the upper and lower axle holes of the body cavity and the lower axle of the butterfly plate is protected by the bushing to prevent large particles from entering the axle hole of the valve.



This is an introduction to different offset butterfly valves, hoping to give you a better understanding of these offset butterfly valves. If you want to know more about them, you are welcome to visit our website. As a professional valve manufacturer, we will wholeheartedly provide you with the best quality service.


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