Patent ID: 7506900

Claim:
Threaded joint, defining a longitudinal axis, comprising a first and a second pipe segment, the first pipe segment defining a male member ( 1 ) of the joint, the second pipe segment defining a female member ( 2 ) of the joint, wherein the first pipe segment ( 1 ) is provided with at least one male thread at one end, and the second pipe segment ( 2 ) is provided with at least one female thread ( 7 ) adapted to be screwed to the male thread to constitute the joint, wherein there are provided a first seal surface on the first segment ( 1 ) and a second seal surface ( 4 ) on the second segment ( 2 ) arranged between one end of the female thread and the nearest end of the second pipe segment, the first and the second ( 4 ) seal surfaces having dimensions such as to generate a reciprocal interference by deformation of the material of the first and second segments of pipe, at least in the end of make up position, thus constituting a metal-metal type joint seal, wherein there is provided a reinforcement section ( 5 ), positioned at the end of the second pipe segment which protrudes beyond the female thread ( 7 ) and having at all points an internal diameter larger than the external nominal diameter of the first pipe segment, the joint being characterised in that said reinforcement section ( 5 ) has a minimum axial length L minimum given by the following formula L minimum =5(ln(wt) /OD 0.125 ), in which OD is the nominal external diameter of first and second pipe segments and wt is the nominal thickness of the wall of first and second segments of pipe, such as not to generate any contact between the first and second pipe segments throughout the length of the reinforcement section ( 5 ).