THREADED PIPE JOINT

摘要

The invention relates to leak-tight threaded pipe joints comprising a metal-metal seal assembly. Claimed is a threaded joint for steel pipes, consisting of a tubular member (a nipple) and a coupling member, having situated thereon portions with an internal conical thread and an external conical thread, wherein the nipple terminates in a tip with an axially symmetrical shape, part of the outer surface of which constitutes a sealing surface, which interacts, upon assembly of the joint, with a mating sealing surface of the coupling. Each of the sealing surfaces consists of a conical portion and a toroidal portion, wherein the toroidal portion on the nipple is situated nearer to the threaded part, and the toroidal portion on the coupling is situated further from the threaded part. In addition, the sealing surface of the nipple and also part of the non-contacting regions of the tip that are adjacent thereto are situated higher than the line of the roots of the external thread. As a result, a metal-metal seal is formed upon assembly of the joint, which consists of three portions disposed such that a contact pressure in the central region is greater on average than triple the yield pressure of the pipe, and a change in the contact pressure in the peripheral regions is described by a Hertz function. This distribution of pressure provides for the necessary level of leak-tightness while maintaining high extreme-pressure properties in the region of the metal-metal seal of the threaded pipe joint. The invention increases the reliability of a threaded pipe joint under the effect of static and variable operational loads, including external pressure, compression, twisting and combined loads during bending and rotation of the pipe string.