Butterfly valve assemblies

A butterfly valve assembly, comprising:

• a housing comprising an inner wall defining a bore that extends along a longitudinal axis;
• a disc mounted in the bore for pivotal movement about a pivot axis that extends transverse to the longitudinal axis, the disc having a lateral chord that extends along the disc in a direction orthogonal to the pivot axis;
• and
• an actuator operable to pivot the disc about the pivot axis between an open position and a closed position;
• wherein, with the disc in the closed position, the disc defines a first oblique angle relative to the longitudinal axis;
• wherein the disc has a flat outer edge that defines a second oblique angle relative to the lateral chord;
• and
• wherein the first oblique angle and the second oblique angle correspond to one another such that the flat outer edge extends along the inner wall when the disc is in the closed position.

A butterfly valve assembly, comprising:

• a housing comprising an inner wall defining a bore that extends along a longitudinal axis;
• a disc mounted in the bore for pivotal movement about a pivot axis that extends transverse to the longitudinal axis, the disc has a minor axis that extends along the pivot axis, the disc has a major axis that extends in a lateral direction perpendicular to the minor axis, the disc is symmetric about both the minor axis and the major axis such that the disc has an elliptical shape, the disc having an outer edge that has a semicircular shape;
• and
• an actuator operable to pivot the disc about the pivot axis between an open position and a closed position;
• wherein, with the disc in the closed position, the semicircular outer edge of the disc engages the inner wall.