Abstract: Systems and methods for coupling pipes made of dissimilar materials in applications that are subject to large variations in temperature. In one embodiment, a connection comprises a first flange made of a first material and a second flange made of a second material. Each flange is designed to be welded to a pipe of the same material. One of the flanges has a male mating surface, while the other flanges as a female mating surface. The male flange is made of the material that experiences greater expansion or less contraction when the temperature of the connection is changed from a connection temperature to an operating temperature. The female flange is made of the other material. A sealing ring having elastic properties is preferably used between the mating surfaces of the flanges.

Abstract: Systems and methods for coupling conduits such as pipe sections, where the resulting conduit (e.g., pipeline) will be externally pressurized. One embodiment comprises first and second flanges and a seal ring. The flanges have male and female mating surfaces, respectively. The mating surfaces form a tapered space in which the seal ring is positioned. The space between the mating surfaces is tapered so that it is wider at an end which is exposed to pressure external to the connection and narrower at an end which is exposed to pressure internal to the connection. The mating surfaces of the flanges and inner and outer surfaces of the seal ring may be conic sections, where the male mating surface and inner seal ring surface form a smaller angle with the axis of the connection and the female mating surface and outer seal ring surface form a larger angle with the axis.