Device for heating and thermally insulating at least one undersea pipeline

Apparatus for heating and lagging at least one undersea main bottom-to-surface connection pipe for carrying a flow of hot effluent, the apparatus comprising:

• a covering of at least one thermally insulating material surrounding said main pipe(s);
• said insulating covering being covered by a leaktight outer protective casing that is preferably cylindrical in shape;
• the apparatus being characterized in that it comprises:
• a) an internal chamber preferably of cylindrical shape and coaxial inside said outer casing, such that:
• said insulating covering surrounds said internal chamber and preferably fills the annular space between said outer casing and said internal chamber;
• and
• said main pipe is contained inside said internal chamber, that is preferably cylindrical in shape;
• and
• b) means suitable for maintaining the temperature of a heat-transfer fluid and for causing it to circulate inside said internal chamber, said heat-transfer fluid surrounding the main pipe contained inside a said internal chamber.