Eccentric butterfly valve
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Eccentric butterfly valves are divided into single eccentric butterfly valves, double eccentric butterfly valves, triple eccentric butterfly valves and variable eccentric butterfly valves. Opposite to the concentric butterfly valve. The butterfly valve whose stem axis deviates from the center of the disc and the center of the body at the same time, and the sealing pair is an oblique cone is called an eccentric butterfly valve.
The butterfly valve and the upper and lower valve shafts are connected by special-shaped holes and special-shaped shafts. During the opening and closing process of the butterfly plate, the pinless connection function of the butterfly plate floating up and down, left and right is realized, and the interference area between the butterfly plate and the valve seat is reduced. Thereby greatly reducing the torque. The floating structure of the butterfly plate realizes the manufacturing process of single eccentricity and the use function of variable eccentricity.
The inner cavity of the valve body is provided with an over-position stopper for the butterfly plate to ensure that the butterfly plate is not in place when it is closed.
The upper and lower valve shaft holes in the valve body cavity and the upper and lower valve shaft holes on the butterfly plate are protected by bushings to prevent large particles in the medium from entering the valve shaft holes.
The single eccentric butterfly valve
is to solve the extrusion problem of the butterfly plate and the valve seat of the concentric butterfly valve, thus producing a single eccentric butterfly valve. Axis, disperse, and reduce excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat.
The double eccentric butterfly valve
is further improved on the basis of the single eccentric butterfly valve and is currently the most widely used double eccentric butterfly valve. Its structural feature is that the shaft center of the valve stem deviates from the center of the butterfly plate and the center of the body. The effect of double eccentricity makes the butterfly plate break away from the valve seat immediately after the valve is opened, which greatly eliminates unnecessary excessive extrusion and scraping between the butterfly plate and the valve seat, reduces the opening resistance distance, reduces wear, and improves the life of the valve seat.
Triple eccentric butterfly valves
must use hard seals for high temperature resistance, but the leakage is large; for zero leakage, soft seals must be used, but they are not resistant to high temperatures. In order to overcome the contradiction of the double eccentric butterfly valve, the butterfly valve was eccentric for the third time. The so-called third eccentricity means that the shape of the sealing pair is not a positive cone, but an oblique cone.
The unique feature of the variable eccentric butterfly valve is that the stem shaft on which the butterfly plate is installed is a three-section shaft structure. The two shaft sections of the three-section shaft type valve stem are concentric, and the centerline of the center section shaft deviates from the axes at both ends . A center distance, the butterfly plate is installed on the intermediate shaft segment. Such an eccentric structure makes the butterfly plate a double eccentric shape when it is fully open, and a single eccentric shape when the butterfly plate turns to the closed position. Due to the effect of the eccentric shaft, when it is close to closing, the butterfly plate moves a distance into the sealing cone surface of the valve seat, and the butterfly plate matches the sealing surface of the valve seat to achieve reliable sealing performance.
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