Patent ID: 7523766

Claim:
An undersea coaxial assembly of two pipes suitable for being laid empty and to rest on the seabed at depths in excess of 1000 m, comprising an outer pipe containing an inner pipe suitable for transporting fluids, the two pipes being interconnected by centralizing mechanical connections with a space between said inner pipe and said outer pipe, wherein said outer pipe comprises: a tubular wall having at least one external peripheral reinforcing element creating a plurality of localized zones on the outside surface of said tubular wall, the radial distance between the outside surface of the outer pipe and the longitudinal axis of said tubular wall in said localized zones being greater than the outside radius of tubular wall portions lying between said localized zones in a longitudinal direction, two successive ones of said localized zones being spaced apart in said longitudinal direction of said tubular wall by a distance equal to ½ to 4 times the outside diameter of said tubular wall portions, said successive localized zones being spaced apart regularly.