A trieccentric butterfly valve is a type of industrial valve where the valve stem axis is offset from both the center of the butterfly plate and the center of the valve body. The valve seat rotation axis and the valve body passage axis form an angular sealing structure. The three eccentricities are radial eccentricity (e₁), axial eccentricity (e₂), and cone angle eccentricity (β). These three parameters (e₁, e₂, β) are not merely the sum of independent values, but a combination requiring precise coordination and overall optimization. Their common goals are:

1. Trajectory Optimization: To collectively shape the three-dimensional spatial trajectory of any point on the edge of the butterfly plate (especially points on the sealing strip) during the opening and closing process. The ideal trajectory is: rapid disengagement without sliding friction during opening; and gradual, uniform wedging contact during closing.

2. Contact Control: To control the contact area, contact sequence, and pressure distribution between the butterfly plate sealing surface and the valve seat sealing surface during the final closing stage. The goal is to start from "line contact" and uniformly expand into a continuous, pressure-uniform sealing strip as torque increases.

3. Torque Balance: Minimize closing and opening torques while ensuring sufficient sealing pressure. A good combination ensures that most of the operating torque is converted into effective sealing normal force, rather than overcoming friction.

Self-Locking and Safety: Utilizing the self-locking effect generated by the cone angle β, the medium pressure increases after the valve is closed without damaging the seal, improving seal reliability.

The specific impact of eccentricity combinations on performance

1. Impact on Sealing Performance:

The β angle is the dominant factor. A larger β angle results in a stronger wedging effect, theoretically leading to a higher sealing specific pressure and better compensation for media pressure. However, an excessively large β angle can cause a sharp increase in closing torque, even leading to "over-wedging" and causing the disc to jam or the valve seat to undergo plastic deformation.

e₁ and e₂ affect contact uniformity. An unreasonable combination of e₁ and e₂ can cause the disc to contact one side before the other during closing (off-center contact), or uneven pressure on the front and rear edges of the sealing strip, resulting in localized leakage or overload.

2. Impact on Operating Torque:

e₂ is crucial. A sufficiently large e₂ ensures rapid disengagement and significantly reduces the opening torque.

The combination of e₁ and β determines the closing torque. Together, they determine the force required to "pull" the disc into the valve seat. The optimization goal is to find a "sweet spot" to achieve the maximum sealing normal force with the minimum rotational force.

3. Impact on Sensitivity to Manufacturing Errors: The eccentricity combination should be able to guarantee a reliable seal within a certain range of machining and assembly errors (such as butterfly plate thickness tolerance and valve seat roundness error). An overly "sensitive" combination, although theoretically perfect, will result in a high scrap rate in mass production.

Generally, a larger β angle places more stringent requirements on the form and position tolerances of parts (such as conical surface profile and ellipticity).