Two steel pipes are each connected to a mounting flange for joining the two pipes, the flanges in one embodiment being fixed stationary to each other and in a second embodiment fixed movable relative to each other. A compressed knitted wire mesh seal is between the two flanges in a dynamic embodiment. Each flange has a spherical inner concave or outer convex surface and the seal has an inner concave and outer convex spherical surface. The seal outer convex spherical surface has a radius smaller than the mating flange concave inner surface. The origins of the two radii are offset. The seal inner concave spherical surface has a radius that is larger than the mating spherical outer convex surface of the corresponding flange. The seal contacts the two flanges in an annular set of pressure points to provide enhanced sealing action. In a second embodiment, the pipes are fixed stationary relative to each other and the outer flange is connected to a pipe spherical segment which segment has an inner concave spherical surface which engages the seal outer convex surface. The radii of the mating surfaces are different to provide enhanced sealing pressure points at the tangency of the mating surfaces.