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.