SEAT RING FOR BUTTERFLY VALVE

摘要

A seat ring for a butterfly valve, in which, without increasing operational torque of a stem, valve seat sealing characteristics about stem through-holes is improved and sealing effect against seeping of a fluid from a gap at the inner periphery of the seat ring, between the stem through-holes and the stem, is improved. A seat ring (1) made of EPDM is integrally formed with a hollow cylindrical main body portion (5) and with flange faces (6) at both sides of the main body portion. Stem through-holes (9, 10) through which a stem (3) penetrates are formed in the upper and lower portions in a stem shaft direction (X) of the main body portion (5). An outer periphery (7) of the main body portion (5) is formed in an elliptic shape with the stem shaft direction (X) as the major axis. That is, the seat ring is formed such that a thickness (a) is maximum at portions where the stem through-holes (9, 10) are provided, and a thickness (b) is minimum at portions on the horizontal line that is 90 degrees from the line passing the stem through-holes, and that an inner periphery (8) is formed in a flat face and a circular shape.