What is the sealing principle of the double eccentric sealing butterfly valve?

This kind of butterfly valve is usually called high performance butterfly valve.

1. Structural features: The center of rotation of the valve plate (the center of the valve shaft) forms a dimension “a” offset with the valve plate sealing section, and forms a dimension “b” offset with the centerline of the valve body.

2. Sealing principle: On the basis of the single eccentric sealing butterfly valve, the center of rotation of the valve plate (the center of the valve shaft) is offset by a dimension “b” with the center line of the valve body. The result of the offset can be seen from the cross-sectional view of Figure A-A(below). When the double eccentric sealing butterfly valve is fully open, its valve plate sealing surface will be completely separated from the valve seat sealing surface, and a gap larger than the “x” gap in the single eccentric sealing butterfly valve is formed between the valve plate sealing surface and the valve seat sealing surface “y”. Due to the appearance of the dimension “b” offset, the turning radius of the valve plate is divided into long-radius rotation and short-radius rotation. On the large semicircle of the valve plate with long-radius rotation, the tangent of the rotational trajectory of the disc sealing surface will form a “θ” angle with the seat sealing surface. When the valve plate is opened and closed, the sealing surface of the valve plate has the function of gradually exiting and gradually entering the sealing surface relative to the sealing surface of the valve seat, it further reduces the mechanical wear and abrasion of the sealing surface of the butterfly valve when the valve plate is opened and closed.

When the valve plate of this type of butterfly valve is opened from 0^O ~ 90^O, the sealing surface of the valve plate will be separated from the valve seat seal faster than that of the single eccentric sealing butterfly valve. In the usual design, when the valve plate rotates from 0^O to 8^O ~ 12^O, the sealing surface of the valve plate can be completely separated from the sealing surface of the valve seat, so that the valve plate and the sealing surface of the valve seat are relatively mechanically worn during the opening and closing process of the butterfly valve, the extrusion angle stroke is shorter, so that the mechanical wear and extrusion deformation are reduced, and the sealing performance of the butterfly valve is further improved.

When the butterfly valve is closed, through the rotation of the valve plate, the outer sealing surface of the valve plate gradually approaches and squeezes the composite valve seat of polytetrafluoroethylene and spring steel wire, causing it to elastically deform and form an elastic force, which is used as the sealing pressure to ensure the butterfly valve. seal. The function of the spring steel wire wound with PTFE is to make the valve seat have greater and better elasticity.

More details of butterfly valves, please go to https://www.mingpinmetals.com/Butterfly-Valve-pl3507724.html