Double eccentric butterfly valve suitable for controlling low temperature fluid under high pressure and safe against fire, wherein the structures of a seat ring and a retainer required for the valve are simplified in structure to facilitate production of the valve. An annular body has uniform thickness and width is employed as the parent body of the seat ring.
A thin fixation portion is formed by cutting an outer peripheral part of the parent body from the surface side. A groove having a uniform cross-section is formed by cutting an intermediate portion of the parent body to a depth greater than the thickness of the fixation portion from the side opposite the surface. The seat ring produced in this way is integrated with a synthetic resin. In inserting the seat ring into the groove, a backup ring is abutted against the opening side of the groove, a retainer is abutted against the backup ring, and the fixation portion is fixed to the main body of the valve.
