Device for thermal insulation of at least a submarine pipeline comprising a phase-change material confined in jackets

"Device to thermally isolate at least one submarine conduit containing a material that changes phase confined in bags." The present invention relates to a device for thermally insulating at least one undersea conduit (1) having: - a heat insulating sheath (1 ~ 3 ~ ~ 3 ~ -3) to engage said conduit or said - a external housing sealingly protection (2) which is cover said coating, and that the housing (2) consisting of a flexible material or semi-rigid able to stay in contact with the outer surface of said insulating sheath (3) when it is warp, characterized by the fact that: - said insulating coating is made of a phase change material, preferably an insulating material phase shifter (3 ~ 1 ~) confined in at least one pocket (3-2-) made of a flexible deformable material or semi-rigid (3 ~ ~ 2), and - said pouch or said bags (3 ~ ~ 2) are disposed around said conduit (1).