Abstract: A valve disk of a double eccentric butterfly valve having boss sections (3, 4) for accommodating a stem (8) and rib sections (6, 7) each extending toward outer edge portions of the valve disk in a direction intersecting a stem (8) from the boss sections are provided on a surface on one side of a disc (2), and each of the ribs respectively excluding the boss sections is provided such that a height from a surface (2a) of the disc on the side on which a distance to an end on the edge portion side of the valve disk is longer than that on the side on which a distance to an end on the edge portion side of the valve disk is short when the heights are respectively compared at positions spaced an equal distance apart from a stem center axis (20), and the butterfly valve.

Abstract: A lined butterfly valve and manufacturing method, the lined butterfly valve including a valve disk (2) with a core metal (20) covered with a lining layer (22) provided rotatably inside a body (3) by a stem (5). The lining layer includes a front/back-side lining part (32) provided on each of front and back sides of the core metal and an outer circumferential lining part (33) provided on an outer circumferential side of the core metal. The front/back-side lining part is provided on each of the front and back sides of the core metal in which no occurrence of warpage is assumed so as to have a thickness T1, and the outer circumferential lining part has a thickness T2 from an outer circumferential end of the core metal to a tip seal surface of an outer circumferential end of the valve disk.

Abstract: A valve disk of a double eccentric butterfly valve having boss sections (3, 4) for accommodating a stem (8) and rib sections (6, 7) each extending toward outer edge portions of the valve disk in a direction intersecting a stem (8) from the boss sections are provided on a surface on one side of a disc (2), and each of the ribs respectively excluding the boss sections is provided such that a height from a surface (2a) of the disc on the side on which a distance to an end on the edge portion side of the valve disk is longer than that on the side on which a distance to an end on the edge portion side of the valve disk is short when the heights are respectively compared at positions spaced an equal distance apart from a stem center axis (20), and the butterfly valve.