Eccentric butterfly valves are divided into single eccentric butterfly valves, double eccentric butterfly valves, triple eccentric butterfly valves, and variable eccentric butterfly valves. Contrast with concentric butterfly valve. A 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 vertebra is called an eccentric butterfly valve.
Structure classification of eccentric butterfly valve:
Single eccentric butterfly valve
In order to solve the problem of the extrusion of the butterfly plate and the valve seat of the concentric butterfly valve, a single eccentric butterfly valve was produced. Its structural feature is that the shaft center of the valve stem deviates from the center of the butterfly plate, so that the lower end of the butterfly plate no longer becomes the rotation axis. Disperse and reduce the excessive squeezing between the lower end of the butterfly plate and the valve seat.
Double eccentric butterfly valve
On the basis of the single eccentric butterfly valve, the double eccentric butterfly valve is the most widely used double eccentric butterfly valve. Its structural feature is that the axis of the valve stem deviates from the center of the butterfly plate and the center of the body. The double eccentric effect enables the butterfly plate to be released from the valve seat immediately after the valve is opened, which greatly eliminates unnecessary excessive extrusion and scratching of the butterfly plate and the valve seat, reduces the opening resistance, reduces wear and improves The life of the valve seat is improved.
Triple eccentric butterfly valve
To withstand high temperatures, hard seals must be used, but the amount of 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.
Variable eccentric butterfly valve
The uniqueness of the variable eccentric butterfly valve is that the valve stem shaft where the butterfly plate is installed is a three-segment shaft structure. The three-segment shaft type valve stem has two shaft sections concentric, and the center line of the central shaft is offset from the two ends of the axis by a center distance , The butterfly plate is installed on the intermediate shaft section. Such an eccentric structure makes the butterfly plate a double eccentric shape when in the fully open position, and a single eccentric shape when the butterfly plate rotates to the closed position. Due to the effect of the eccentric shaft, when 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.
Features of 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 function of the butterfly plate floating up and down, left and right, without a pin link, reduces the interference area between the butterfly plate and the valve seat. Thereby greatly reducing the torque. The floating structure of the butterfly plate realizes the single eccentric manufacturing process and the use function of variable eccentricity.
There is an over-position stopper for the butterfly plate in the inner cavity of the valve body to ensure that the butterfly plate is not in place when it is closed.
Bushings are used between the upper and lower valve shaft holes of the valve body cavity and the upper and lower valve shaft holes of the butterfly plate to prevent large particles in the medium from entering the valve shaft holes.
TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D