A pipe joint formed by screwing a pin portion having a tapered male thread formed on the outer peripheral surface of the end of a pipe into a box portion having a tapered female thread formed on the inner peripheral surface of the end of a pipe or a short pipe so as to threadingly engage with the tapered male thread, the pipe joint having the following shape: In addition, the taper of the incomplete thread portion of the pin portion is preferably 0.96-0.90 times the nominal taper of the complete thread portion.

An elongated drive string assembly includes a plurality of hollow sucker rods and connecting elements with an axis, connected together and between a drive head located at the surface of an oil well and a rotary pump located deep down in an oil well. Each hollow sucker rod has at least a first end including an internal female threaded surface engaging an external male threaded surface on a connecting element, such as a nipple. The first end also includes a torque shoulder, which engages a torque shoulder formed on the connecting element. The threads are frusto-conical, non-symmetrical threads with a differential diametral taper. The torque shoulders have a maximized mean diameter and cross-sectional area to resist storing reactive torque in the drive string. The nipple has a wall cross-section that increases towards the torque shoulders from each free end, to increase fatigue resistance.

The invention relates to a seal for medium-conducting components, whereby the components (12, 13) comprise sealing surfaces (20, 25), which are exactly complementary to each other and which are directly pressed together to form a gap-free seal. The contact surfaces (44) between the sealing surfaces is limited to a narrow region directly adjacent to the medium cavity (19). Said gap-free and dead-volume-free seal can be used, for example in germfree, or sterile processes.

A threaded joint to be expanded, including a lip at the end of the male element end a housing for the lip on the female element to make the threaded joint capable of being sealed and of having a maximum internal passage cross-section after being subjected to diametral expansion by more than 10%. The free male end surface is socketed before expansion into a partially transverse shoulder surface of the female housing through the matching rebating shapes of the surfaces. And, the male lip outer peripheral surface is arranged with little play of the internal peripheral surface of the female housing. Such a threaded joint is particularly useful for casings and tubings used in oil wells.

A riser connector uses a box and upset pin connector threadform design having S-shaped load flanks that provide a variable load angles depending on the radial position along the engaged teeth. This design promotes a load path that changes with position along the axial length of the engaged thread, as well as increasing or decreasing external loads on the connector. The connector also varies radial distention of the pin from the box in a manner that is different from one thread to the next. The threadform uses a combination of thread cuts that vary in shape, pitch, and/or thread cone angle to provide load and stab flanks, as well as a load path, that vary from one axial end of the engaged thread to the other.