Pipe-joining method and system for producing underwater pipelines and underwater-pipeline-laying vesel comprising such a system

A method of joining pipes to produce an underwater pipeline on a firing line comprises the steps of welding the end portions of adjacent pipes to form cutbacks, each of which is defined by two end portions, and by an annular weld bead between the two end portions;

• and forming a protective joint coating about each cutback;
• supplying the firing line with pipes having previously roughened end portions;
• and cleaning, by cryogenic blasting, the outer surface of each cutback along the firing line before applying the protective joint coating.

A system for joining pipes to produce an underwater pipeline comprising a firing line for welding the end portions of adjacent pipes to form cutbacks, each defined by two end portions and by an annular weld bead between the two end portions, and for forming a protective joint coating about each cutback;

• and a cryogenic blasting unit for cleaning, by cryogenic blasting, the outer surface of each cutback along the firing line before forming the protective joint coating;
• wherein the end portions of the pipes are roughened before being fed to the firing line.