Abstract: A seal element is provided which comprises inner and outer, concentric, radially spaced apart, tubular helical cages. Each cage is formed by a plurality of helically parallel steel coils joined at their upper and lower ends by integral sleeves. A nitrite bladder is positioned between the cages. The seal element can be expanded by supporting its base and applying compressive load.

Abstract: A swaged male element of a pipe connection of the type having a frusto-conical sealing surface adjacent to but separate from the load threads. The swaging is effected prior to final machining of the end of the pin and is followed by a cutting operation to remove surplus material from the interior surface of the pin. The swaging extends from the distal end of the pin proximally to include at least the distal end of the effective sealing surface, and preferably extends proximally to a point coinciding generally with the terminating proximal portion of the effective sealing area of the pin.

Abstract: A pipe coupling or connection comprises a female coupling component and a mating male coupling component. Each component is matingly threaded for coupling engagement, and each is provided with an adjacent frusto-conical sealing surface. The sealing surface is provided with a controlled surface roughness, viz. very shallow fine surface variations, preferably formed as microgrooves at a pitch small relative to the pitch of the threads. The slope of the frusto-conical surface of the sealing surface of the male component is slightly mismatched with that of the sealing surface of the female component to simulate the bearing force vs. axial distance characteristic of shrunk-fit circular cylindrical sealing surfaces. The mismatch enables the sealing pressure to be above a design minimum throughout the entire sealing area yet higher at each end of the sealing area. As the coupling is assembled, thread interference in the vicinity of the sealing surface lags the occurrence of interference between the sealing surfaces.

Abstract: A pipe coupling or connection comprises a female coupling component and a mating male coupling component. Each component is matingly threaded for coupling engagement, and each is provided with an adjacent frusto-conical sealing surface. The sealing surface is provided with a controlled surface roughness, viz. very shallow fine surface variations, preferably formed as microgrooves at a pitch small relative to the pitch of the threads. The slope of the frusto-conical surface of the sealing area of the male component is slightly mismatched with that of the sealing area of the female component to simulate the bearing force vs. axial distance characteristic of shrunk-fit circular cylindrical sealing surfaces. The slight mismatch enables the sealing pressure to be above a design minimum throughout the entire sealing area yet higher at each end of the sealing area.