Seat ring for butterfly valve

摘要

A seat ring having a hollow cylindrical body portion with a flange surface as each of its side surfaces. The cylindrical body portion has stem through-holes above and below along a stem axial direction X and a stem penetrates said through-holes. An outer circumference of the body portion is formed in an elliptic shape with the stem axial direction X as its longitudial axis. The thickness of the body portion where the stem through-holes are provided is the maximum while the thickness of the body portion along an axis perpendicular to the longitudinal axis is the minimum.