Abstract: A cylindrical junction part for joining together two elements of an assembly of at least two coaxial pipes, comprising an outer pipe containing an inner pipe defining an annular space preferably containing lagging material. The forged junction part forms two annular cavities defined by branches in a fork configuration at each end of said part serving to minimize stresses and fatigue in the join zone between two junction parts at the ends of two lengths of coaxial pipe to be joined together and between each length of pipe and each junction part at the ends thereof.

Abstract: An undersea pipe of the riser type providing a connection between a floating support and the sea bottom. The riser has a rigid pipe of the catenary type extending from the floating support to a point of contact with the sea bottom. The catenary riser comprises a lower pipe portion terminating at the point of contact. The apparent weight per unit length in water of the lower pipe portion being at least 25% less than that of the remainder of the pipe constituting the catenary riser.