Abstract: A flanged joint assembly for a lined pipeline having a plastic liner and in which the joint is sealed by compression of mating plastic flanges between mating steel flanges and in which plastic flange portions are differentially compressible. Each plastic flange is constructed with a flat sealing face and a thickened outer edge portion in the form of an annular disk. In the assembled joint, compression of the plastic flange is essentially restricted to this thickened flange portion by controlling the size of one of several recesses machined into the face of the steel flange face to accommodate portions of the plastic flanges. A thickened inner annular portion of the circular plastic flange is formed to create a concave frusto-conical surface having its larger circular cross section spaced axially away from the flat sealing face.