Abstract: A sealing gasket for insertion into a circumferentially continuous groove of a flange joint for joining axially aligned tube ends, the flange joint being of the type having axially opposed flanges at the tube ends to form a groove there between when the joint is assembled, the groove being formed by axially opposed seal faces and radial end faces of the flanges, the groove comprising a groove first portion that is open to an interior flow passage of the tubes and a groove second portion that extends radially outward from the groove first portion, the gasket having a gasket first portion that seals the groove first portion and a gasket second portion that extends from the gasket first portion and into the groove second portion; the gasket second portion being axially compressed when the joint is assembled and engaging with the radial end faces to produce a radial compression of the gasket; the gasket second portion having a volume that is less than volume of the groove second portion to form an expansion space