Design principle
Concentric Butterfly Valve
The inflection point is in the center of the seat and in the center of the pipe.
· Only possible with resilient seat valves
1st Eccentricity
The inflection point of the disc moves along the direction of the pipe
· This is 100% friction between seat and disc seal
· Increase torque and wear
2nd Eccentricity
The inflection point of the disc is also offset by the center of the pipe towards the outer edge.
· Friction between seat and disc seal is reduced by approximately 30%
3rd eccentricity
The seat is conical in shape. The cone tip moves from the center of the pipe to the outer edge. A circular cone results in an elliptical seat with the valve body.
· Friction is reduced from 2 to 5% the friction between seat and disc seal
4th eccentricity
The outlet cone used is elliptical, but the section under a particular angle results in a larger and circular shaped area for sealing.
· No friction
· Higher Kv
· Maximum tightness, even in extreme conditions