Abstract: For threaded connections for oil and gas applications using tubular goods of composite materials, substantially greater make up torque can be applied, with significantly improved tensile and sealing properties, by incorporating stress-relieving conical gradient sections adjacent each end of the threaded section of the composite member. Joining each of two composite tubular members to a single double ended male member having complementary surfaces, circumferential distortion is not concentrated at the end regions of the threaded sections but is distributed, relieving stresses and allowing increased makeup torque to be applied, greatly expanding the useful parameters of fiber reinforced tubular products.

Abstract: A coupling for tubings or casings having internal corrosion resistant coatings comprises a pair of tubular members having upset ends, together with outer reference shoulders and threaded regions including low profile, shallow taper threads. A collar of a length related to the reference shoulder positions is engaged against both, and in such positions the ends of the tubular members compress opposite sides of an elastomeric seal that is fitted over an integral central ring in the collar, and that is engaged by side tapers at the nose ends of the tubular members. The seal conforms to the nose ends in a fashion that insures continuity in the corrosion resistant coating while also providing a barrier against electrolytic action.