BUTTERFLY VALVE

摘要

A butterfly valve opened and closed by the rotation of a disk-like valve element (3) in an elastic seat ring (2) installed on the inside of a tubular valve box (1), wherein pressing valve parts (10, 11) coming into contact pressingly with the elastic seat ring (2) in the small opening area or very small opening area of the valve element (3) are formed at least on the orifice side (8) of the valve element (3), a space part (12) is formed in the valve element (3) at the outer peripheral edge or on the downstream side of the outer peripheral edge, and a communication part (13) communicating from the space part (12) toward the downstream side is formed in the valve element (3) or the pressing valve parts (10, 11), whereby an erosion can be prevented from occurring to allow a very small flow to be regulated in the small opening area or very small opening area of the valve so that a high rangeability can be assured.