Extended temperature range valve seal

A seal ring for use as an extended-temperature range valve seat, the seal ring having a hard metal body formed with

• a cylindrical shoulder portion, the shoulder portion being defined by a circumferential front surface, an opposed circumferential rear surface, and two ends,
• a pair of circumferential flanges extending from the rear surface of the shoulder at each of the respective ends, each flange having a circumferential edge spaced radially from the rear surface of the shoulder portion,
• a circumferential rib extending from the front face of the shoulder portion intermediate the ends and terminating in a circumferential seating surface, the width of the rib being less than the distance between said ends of the shoulder portion,
• the seal ring being adapted to fit within an undercut circumferential groove in a seating region of a valve, such groove having substantially parallel sides spaced apart by a distance greater than the distance between the ends of the shoulder portion of the ring and an opening narrower than the distance between the sides of such groove, and the rib of the seal ring being adapted to extend through such a groove opening for movable mating engagement of the rib seating surface with a complementary sealing surface of such a valve, wherein the improvement comprises:
• a circumferential groove being formed in the seating surface of said rib, the groove having an opening narrower than the width of an interior portion thereof and
• a seat ring of material softer than the metal of the seal ring, the seat ring fitting tightly within the groove in the rib and extending through the opening of the groove in the rib and beyond the rib seating surface to terminate in a primary valve seat surface, said primary valve seat surface of said seat ring being adapted to provide the only sealing engagement with such a complementary valve sealing surface unless the temperature inside such valve exceeds the destruction temperature of the seat ring material.