Fire safe plug valve

Claim 1

In a high pressure plug valve including a hollow body with opposed inlet and outlet ports adapted to be connected to pipeline to control high pressure fluid flow and a bonnet extending perpendicular to said body, seats at said openings, a plug rotatably mounted in said body between said seats, a stem extending upward from said plug and bearingly received in the bonnet and extending out of the body for wrench engagement to rotate the plug between open and closed positions, and a packing plate above the plug and in the bonnet to seal between the body and the stem, the improvement in the packing plate which includes an annular metal ring with O-ring grooves opposite the respective surfaces of the body and stem to be sealed and on the plug side of the stem, resilient O-rings in each of said grooves, notches in the metal ring above each of the O-ring grooves, and nonresilient high temperature graphite ring seals along each of said notches directly backing up each of the O-rings, whereby the fluid under pressure in the valve body which leaks by the mating surfaces of the plug and seats causes the O-rings and ring seals to coact and seal between the metal ring and adjacent bonnet and stem surfaces.