Double Eccentric Butterfly Valve

Double eccentric butterfly valve:

      It is characterized by being offset from both the center of the disc and the center of the body at the axis of the stem. The double eccentric effect enables the butterfly plate to be quickly disengaged from the valve seat after the valve is opened, which greatly eliminates unnecessary excessive squeezing and scraping of the butterfly plate and the valve seat, reduces the opening resistance, reduces wear and improves Increased valve seat life. The greatly reduced scraping also makes the double eccentric butterfly valve also adopt metal seat, which improves the application of butterfly valve in high temperature field. But because its sealing principle belongs to the position sealing structure,

That is, the sealing surface of the butterfly plate and the valve seat is in line contact, and the elastic deformation caused by the valve plate pressing the valve seat produces a sealing effect. Therefore, the closed position is highly required (especially the metal valve seat), and the bearing capacity is low. That is why traditionally people think that butterfly valves are not resistant to high pressure and have large leakage.

Structural characteristics: The shaft of the valve stem is not only offset from the center of the sealing surface of the valve seat, but also from the centerline of the pipeline and the valve.

      Advantages: The second eccentricity generates a camming effect, that is, the valve plate and the valve seat begin to contact when the stroke is nearing the end, reducing the torque when the valve is opened and closed and the wear of the valve seat. When the valve plate opens about 15 °, the valve The plate and seat are completely disengaged (depending on valve size). When the opening degree is greater than 15 ° until fully opened, the valve plate and the valve seat are completely out of contact, which greatly reduces the wear and deformation of the valve seat. The service life of the valve seat is improved; the scraping is greatly reduced; at the same time, the double eccentric butterfly valve can adopt a metal valve seat, which improves the application of the butterfly valve in high temperature fields.

     Disadvantages: Because its sealing principle is position sealing, that is, the sealing surface of the butterfly plate and the valve seat is in line contact, and the elastic element on the butterfly plate or valve body deforms to increase the density of the sealing surface. In addition, the pressure angle of each point on the circumference of the butterfly plate varies greatly. In order to ensure the seal, the elastic components of the butterfly plate or valve body can only be deformed more greatly, which makes the friction phenomenon of the sealing surface of the butterfly plate or valve body very serious, especially in the parts of the valve body sealing surface near the ends of the shaft. It is easy to produce abrasions during use and cause seal failure.