High pressure electrical isolation flange gasket

Claim 1

An electrical isolation flange gasket for high pressure use between two bored, bolt-type flange halves whose inner surfaces are grooved for use with a metallic seal ring, said gasket comprising first and second outer metal layers having substantial thickness; each of said metal layers having a perimeter surface, an aperature extending therethrough, an outer face surface and an inner face surface; said aperature adapted to allow fluid flow between the bored portions of each of said flange halves when the flange halves are properly aligned and installed; said outer face surface of each of said metal layers being adapted to face an inner surface of one of said flange halves and being grooved and adapted for use with a metallic seal ring; said inner face surface of each of said metal layers facing each other and having at least one ridge located between said aperature and said perimeter, said ridges located around said aperature; said metal layers being sufficiently thick throughout to withstand without significant yielding the stresses created when said gasket is installed between said flange halves and the flange halves are bolted together and torqued to specification; an inner layer of an electrical insulating material between said two outer metal layers and the crests of each of said ridges and the other metal layer, said electrical insulating material separating said metal layers from electrical contact with each other, and said metal ridges and said electrical insulating material being sufficiently strong to withstand a pressure of 2500 p.s.i. inside said aperature with atmospheric pressure exerted on said perimeter surface of each of said metal layers when said gasket is mounted between said bolt-type flange halves and said bolt-type flange halves are torqued to specification.