Patent ID: 7793992

Claim:
An assembly of at least two coaxial pipes constituted in an intermediate portion of the assembly by an outer pipe and an inner pipe of said two coaxial pipes, an annular space defined between the outer pipe and the inner pipe, the assembly including at least two coaxial pipe assembly elements, each of said two coaxial pipe assembly elements having at least one end a junction part joined to the junction part of the other of said two coaxial pipe assembly elements, each of the two said junction parts being a body of revolution defined as follows: in a radial direction relative to a longitudinal axis XX′ of symmetry of each said junction part, each said junction part is defined by a cylindrical inner wall of substantially the same diameter as the intermediate portion of said inner pipe, and by a cylindrical outer wall of diameter substantially equal to the outside diameter of the intermediate portion of said outer pipe; and in the direction of the longitudinal axis XX′: on the end of each said junction part that is connected by welding to the ends of said outer and inner pipes of said coaxial pipe assembly element having said junction part, said outer and inner walls of each said junction part forming in longitudinal section respective outer and inner first branches of substantially the same thickness as said outer and inner pipes to which said outer and inner first branches are connected, said outer and inner first branches defining a first annular cavity; and at the opposite end of each said junction part that is joined to the junction part of the other of said two coaxial pipe assembly elements, each said junction part is connected by welding to the end of the other of said two coaxial pipe assembly elements, said outer and inner walls forming in longitudinal section respective outer and inner second branches defining a second annular cavity; the two said junction parts being welded to each other solely via the ends of said outer second branches, the ends of said two inner branches that are not welded together being in abutting contact one against the other such that said second annular cavities are not sealed off from the inside of said inner wall and said inner pipe; and the bottoms of said first and second cavities being spaced apart in said longitudinal direction XX′ so as to define a massive solid zone of each said junction part in which said outer and inner walls form the outer and inner faces of a single cylindrical wall.