METHOD OF ASSEMBLING TWO HERMETIC THREADED TUBULAR JOINTS COMPRISING A LOCAL AND INITIAL ADDED THICKNESS, BY MEANS OF PLASTIC EXPANSION

摘要

A second tubular element is made with two opposite ends of a female-female connecting sleeve separated by a central zone. Each pair of second and third butting surfaces press together and/or each pair of first and fourth butting surfaces press together. The assembly is designed so after a radial plastic deformation, gripping and sealed contacts make the assembly watertight. A first tubular element (EM) has a first part with a male thread and a second part (P2) extending the first part and including a first annular lip (L1) with a first axially butting surface (SB1), a first internal surface and a first external surface, and a second butting surface (SB2). A second tubular element (EF) has a female thread matching the male thread and screwing onto it, a second annular lip (L2) with a third butting surface (SB3) pressing against the second butting surface, a second external surface placed opposite the first internal surface and a second internal surface, a fourth butting surface (SB4) and a third internal surface facing the female thread and defining with the second external surface and the fourth butting surface an annular seating (LO) for the first lip. An annular zone between the two ends of the sleeve has a thinning chosen so that the sleeve thickness at this zone is greater than or equal to the product of the section of the tube running length by the effectiveness of the joint. The thinning section is bath-shaped, with a maximum thinness in the middle and side walls inclined at an angle of less than 30[deg], preferably equal to 15[deg]. This shape extends into the zone between the last two threads of the two female threads. An annular groove is placed on the third internal surface of the second tubular element near the first external surface. The groove has two curvilinear portions with identical radii of curvature of between 2 and 20 mm, separated by a cylindrical central part. The male and female threads have threads with a bearing flank with a negative angle of between -3[deg] and -15[deg] and an engaging flank with a positive angle of between +10[deg] and +30[deg]. The threads are designed after screwing and before deformation to leave an axial play between their engaging flanks of between 0.1 and 0.3 mm. The threads are conical or cylindrical. An independent claim is included for the production of the above joint by screwing the parts together and then expanding them radially using an axially displaced expansion tool.