Sealing apparatus

Claim 1

Flange sealing apparatus for sealing the gap between the confronting coupling surfaces of a pair of coupled flanges surrounding a fluid-containing pipe, comprising: means defining a circular groove in the coupling surface of one of said flanges; a resilient O-ring engaged in said groove and under compression between the bottom of said groove and the confronting coupling surface of the other of said flanges; two backup rings engaged in said groove and engaging said O-ring on the atmosphere side thereof; axially-extending grooves formed in the radially-inward side wall of said circular groove and extending from said confronting surface of said one flange to a position radially inward of said O-ring; said sidewall containing a circumferential groove located radially inward of said O-ring connecting said axial grooves to each other; said backup rings being positioned one above the other between the bottom of said groove and said confronting surface, and having inclined-plane surfaces such that the upper of said backup rings is urged upward against the confronting surface of the other of said flanges in responce to radially-outward pressure exerted by said O-ring; whereby increased fluid pressure, supplied to the radially-inward side of said O-ring by way of said axially-extending grooves upon opening of the gap between said flange surfaces, causes said upper backup ring to move axially outward against said confronting surface of said other flange thereby to maintain backup of said O-ring.