Thermally insulated and heated double-walled pipe segment for fitting by screw fastening, and a method of implementing such a pipe segment

1. A segment designed to be fitted by screw-fastening for implementing a fluid transport pipe for transporting a fluid, which said pipe comprises an inner wall and an outer wall, said segment comprising an inner tube and an outer tube that define an annular space between them, both ends of said inner tube having a thread for assembly to adjacent segments, wherein said segment comprises at least one heating duct placed in said annular space and opening out at either end of said annular space, said annular space being designed to be closed hermetically in order to enable it to be brought to a reduced pressure, and

wherein at least one electrical heating line operating by Joule heating is placed in said heating duct and is designed to be connected to at least one electrical heating line of an adjacent segment when screw-fastened together.

2. The segment according to claim 1 , wherein said heating duct opens out through passages provided through at least two closure pieces for closing off said annular space, said pieces are placed at either end of said segment and are secured to said outer tube and to said inner tube.

3. The segment according to claim 2 , wherein said heating duct is placed against said inner tube.

4. The segment according to claim 2 , wherein a thermal insulation material is placed in said annular space against said heating duct.

5. The segment according to claim 1 , wherein said segment has a male end portion and a female end portion, said male end portion being designed to co-operate with a female end portion of said adjacent segment.

6. The segment according to claim 5 , wherein said female end portion has a first guide portion of diameter less than the diameter of said outer tube and greater than the diameter of said inner tube, said first guide portion being secured at one end to said outer tube and being placed inside said outer tube, said first guide portion being secured at the other end to said inner tube which end is set back related to the end of said outer tube, said first guide portion co-operating with said outer tube to define a thinner annular portion that extends said annular space of said segment.

7. The segment according to claim 6 , wherein said male end portion has a second guide portion that has an outside diameter designed to co-operate with the inside diameter of said first guide portion, said second guide portion being disposed around said inner tube which has its end projecting relative to said outer tube, said second guide portion being secured to said inner and outer tubes of said segment and co-operating with said inner tube to define an annular space of reduced diameter that is in communication with said annular space of said segment.

8. A fluid transport pipe for transporting a fluid, which pipe is made up of adjacent segments designed to be fitted by screw-fastening for implementing a fluid transport pipe for transporting a fluid, which said pipe comprises an inner wall and an outer wall, said segment comprising an inner tube and an outer tube that define an annular space between them, both ends of said inner tube having a thread for assembly to adjacent segments, wherein said segment comprises at least one heating duct placed in said annular space and opening out at either end of said annular space, said annular space being designed to be closed hermetically in order to enable it to be brought to a reduced pressure, and

wherein at least one electrical heating line operating by Joule heating is placed in said heating duct and is designed to be connected to at least one electrical heating line of an adjacent segment when screw-fastened together.

9. The transport pipe according to claim 8 , wherein said inner tubes of said adjacent segments are assembled together end-to-end, said outer tubes of each of said adjacent segments being joined together via a sleeve that defines a closed space inside which said electrical lines are connected together.

10. The transport pipe according to claim 9 , wherein said sleeve is made up of two half-shells that are fastened together and to said outer tubes of two adjacent segments.

11. The transport pipe according to claim 9 , wherein a filler fluid that is not electrically conductive is placed in said closed space.

12. A method of manufacturing segments designed to be assembled together end-to-end by screw-fastening for the purpose of implementing a fluid transport pipe comprising an inner wall and an outer wall, which method comprises the following steps for fitting each segment:

placing at least one heating duct around an inner tube, both ends of said inner tube having a thread for assembly to adjacent segments and configured such that at least one electrical heating line in said heating duct is connected to at least one electrical heating line of an adjacent segment when screw-fastened together;

holding said heating duct around the inner tube by fastening means;

placing an outer tube around said inner tube, said outer and inner tubes then defining an annular space between them; and

hermetically closing said annular space that is brought to a reduced pressure, said heating duct opening out at either end of said annular space.

13. A method of implementing a fluid transport pipe comprising an inner wall and an outer wall, said pipe being implemented from manufactured segments as to claim 12 , which method comprises the following steps:

placing at least one electrical heating line in said heating duct opening out at either end of said annular space of a first segment of said segments;

screwing said threaded inner tube of said first segment to said threaded inner tube of an end segment of a portion of said pipe that is already in place;

electrically connecting said electrical heating line to at least one electrical heating line in place in said end segment of said segments;

fastening a sleeve between said outer tubes of these said two segments and filling the space between said sleeve and said inner tubes with a filler fluid that is not electrically conductive; and

closing said space defined between said sleeve and said inner tubes.