Center butterfly valve, single, double, three eccentric butterfly valve evolution

Butterfly valve structure is simple, easy to manufacture. Center butterfly valve structure is characterized by stem shaft, butterfly plate center, the body center in the same position. Common lacquered butterfly valves belong to this category. The disadvantage is due to the butterfly plate and the valve seat is always in the squeeze, scratch state, resistance distance, wear fast. In order to overcome the extrusion, scratch, to ensure sealing performance, the valve seat is basically rubber or PTFE and other elastic materials, but also in use by the temperature limit, so the traditional butterfly valve is not high temperature.

In order to solve the concentric butterfly valve plate and valve seat extrusion problem and produce a single eccentric butterfly valve. The structure is characterized by the valve stem axis deviated from the center of the butterfly plate, so that the upper and lower ends of the disc is no longer the axis of rotation. Disperse and reduce the upper and lower butterfly plate and the valve seat over the extrusion. because of the single eccentric structure in the valve during the entire switch process butterfly plate and the seat of the scratch phenomenon is not eliminated, in the scope of application and concentric butterfly valve much the same.

In the single eccentric butterfly valve which change to the molding is currently the most widely used double eccentric butterfly valve. Its structural feature is the valve stem axis deviation from the center of the disc, but also from the center of the body. Double eccentric effect so that the valve is opened after the butterfly plate can be quickly removed from the valve seat, a significant elimination of the butterfly plate and the valve seat of the unnecessary excessive squeeze, scraping phenomenon, reducing the opening resistance, reducing wear and tear The seat life. Scratching a substantial reduction, but also makes double eccentric butterfly valve can also use metal seat, improve the butterfly valve in the field of high temperature applications. But because of its seal principle is the location of the seal structure, that is, butterfly plate and the valve seat sealing surface for the line contact, through the butterfly plate compression caused by the elastic deformation of the valve seal effect, so the high requirements of the closed position (especially metal Seat), low pressure capacity, which is why the traditional people think that is not high pressure, leakage of large reasons.

To be high temperature, you must use a hard seal, but the leakage is large; to zero leakage, you must use a soft seal, but not high temperature. To overcome the contradiction between the double eccentric butterfly valve, resulting in a three-eccentric structure of the butterfly valve. The structural feature is characterized in conical axis of the sealing surface of the disc is deflected to the cylindrical axis of the body while the eccentric stem is eccentric. In other words, after the third eccentricity, the sealing surface of the butterfly plate is no longer circular, but elliptical, its sealing surface shape and therefore asymmetric: the other side is parallel to the body Center line. The third eccentricity of the biggest feature is to fundamentally change the seal structure, is no longer a position seal, but the torque seal, that is not dependent on the elastic deformation of the valve seat, but completely rely on the contact surface of the valve seat to achieve sealing effect, So to solve the metal valve seat zero leakage of this problem; and because the contact surface pressure and the medium pressure is proportional to the high pressure and high temperature problems are solved.