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.