Fire-tested butterfly valve - includes fusible washer or protrusion in valve seat which melt to give fire-resistant seal

摘要

The fire-tested butterfly valve has an annular resilient seat member and an annular, flexible metal seat member, both held in place in a valve housing by being clamped between cooperating surfaces of the valve housing and a valve seat retaining ring insert, a fusible washer with a lower destruction temperature than that of the annular resilient seat is positioned between the resilient seat and the metal seat. Alternatively, an integrally formed protrusion on the annular resilient seat contact the metal seat. In both embodiments, the metal seat is held out of contact with the butterfly disc until exposure to a fire melts the fusible washer or the seat protrusion, at which time the metal seat comes into contact with the disc to establish a secondary, metal-to-metal fire resistant seal.