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Triple eccentric butterfly valve seal principle

May 18,2018 Posted by Bundor

Industry News

The triple-eccentric butterfly valve employs a sealing system similar to a shut-off valve consisting of a fixed valve seat with the same conical cross-sectional shape and a rotatable sealing surface. However, the three-eccentric butterfly valve adopts a rotary motion (instead of an axial motion), and the shut-off is achieved by the vertebral body tilted with respect to the axis of the pipe at the tip of the cone, which makes the three-eccentric butterfly valve a “stop valve for the angular stroke”.

According to the design of the shut-off valve, a single momentary contact occurs only when the sealing element is in the closed position, which is why the tri-eccentric valve can realize frictionless closing. However, unlike the shut-off valve, the triple-eccentric valve can be fully closed in both directions. Its realization is based on three "eccentricity":

1. The shaft is arranged behind the sealing surface, so that the valve obtains a complete continuous sealing surface.

2. The shaft is set on the side of the pipe/valve centerline and generates a cam effect. During the opening stroke, the seal ring and the valve seat are not in contact, effectively reducing the torque.

3. The centerline of the valve seat and the seal cone is inclined relative to the pipe/valve centerline, completely eliminating the friction between the seal ring and the seat in the 90° travel.

The design concept of a cone in the cone requires a hard metal seal to handle all possible pressure levels. High-strength Stellite Gr.21 seat overlays and a high-strength duplex stainless steel ply seal ring are used to achieve a hard metal seal.

The contact between the seat and the sealing ring is completely eliminated during the operation of the three-eccentric butterfly valve in the opening and closing, effectively extending the overall life of the sealing element and valve.This is combined with the characteristics of the valve's angular travel to make the valve's operating torque lower and more stable, and the valve moves faster and easier to operate.At the same time, the valve can be adjusted in a small Angle.This feature makes the three-eccentric butterfly valve ideal for all kinds of emergency shut-off, quick release or high frequency action applications.

Because the three-eccentric butterfly valve is the Angle stroke valve, the sealing element revolves around the axis, which can save the installation space of the site significantly and improve the performance of the operation significantly.In addition, the rotation of the angular travel also reduces the adverse effect on the packing, avoiding the extrusion of wear filler during the movement of the straight stroke valve stem, causing leakage.The three-eccentric butterfly valve can be operated by manual, electric, pneumatic and hydraulic operation, and it can be used as a control valve.

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