1、 Mid line butterfly valve (single eccentric butterfly valve)

Valve stem position: located at the geometric center of the valve body and valve plate, with the valve plate rotating around the central axis.

-Sealing form: The valve plate directly squeezes the rubber sealing ring (mainly soft sealing), relying on elastic deformation to achieve sealing.

-Typical structure: The valve plate is disc-shaped, and the sealing ring is embedded at the edge of the valve body or valve plate, with a simple and compact structure.

2、 Double eccentric butterfly valve (eccentric rotary butterfly valve)

-Double eccentric design:

1. Axial eccentricity: The valve stem deviates from the centerline of the valve body (usually offset by 0.5~2 times the thickness of the sealing ring);

2. Radial eccentricity: The centerline of the valve plate sealing surface deviates from the axis of the valve stem (forming an eccentricity).

-Sealing form: Soft seal (rubber) or hard seal (metal+wear-resistant coating), the valve plate and sealing ring only come into contact when closed.

3、 Triple eccentric butterfly valve (triple eccentric metal hard seal butterfly valve)

-Triple eccentric design:

1. Axial eccentricity: The valve stem deviates from the centerline of the valve body;

2. Radial eccentricity: the sealing surface of the valve plate is eccentric;

3. Angular eccentricity (conical eccentricity): The sealing surface of the valve plate is at a certain angle (usually 3-5 °) with the sealing ring of the valve body, forming a conical sealing surface.

-Sealing form: Metal hard seal (such as stainless steel+Stellite alloy, nickel based alloy), with a sealing surface grinding accuracy of micrometer level.