Subsea pipe-in-pipe structures

Patent metadata

Field	Value
Publication number	US-10577871-B2
Application number	US-201615547702-A
Country	US
Kind code	B2
Filing date	Jan 27, 2016
Priority date	Feb 3, 2015
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

A pipe-in-pipe assembly with thermally-insulating spacers positioned in an annulus to act radially between inner and outer pipes is disclosed. The spacers have at least one circumferentially-extending array of circumferentially-spaced ribs that define longitudinally-extending passageways in gaps between neighbouring ribs of the array. Cables including heating elements extend longitudinally along, the annulus outside the inner pipe. The cables extend longitudinally along the passageways. At least one insulation layer disposed radially outboard of the cables has insulating elements disposed in the gaps between the ribs and/or an insulating layer extending around the inner pipe, positioned radially outboard of the ribs and bridging the gaps. Bands encircle and retain components of the insulation layer. Insulation may also be disposed on the inner pipe between first and second arrays of ribs, those arrays being spaced longitudinally from each other.

First claim

The invention claimed is:

1. A pipe-in-pipe assembly comprising:
inner and outer pipes in spaced concentric relation to define a thermally-isolating annulus between them, the inner pipe being of steel;
a plurality of cables extending longitudinally along the annulus outside the inner pipe; and
thermally-insulating spacers positioned in the annulus to act radially between the pipes; wherein:
the spacers comprise first and second circumferentially-extending arrays of circumferentially-spaced ribs that define longitudinally-extending passageways in gaps between neighbouring ribs of the arrays, those arrays being spaced longitudinally from each other;
the cables extend longitudinally along the passageways;
at least one cable is a heating element positioned for direct contact with the inner pipe in a passageway;
the radial thickness of the ribs is greater than the thickness of any of the cables; and
at least one insulation layer is disposed radially outboard of the cables.

2. The assembly of claim 1 , wherein the insulating layer comprises insulating elements disposed in the gaps between the ribs.

3. The assembly of claim 1 , wherein the insulating layer comprises at least one layer of insulation extending around the inner pipe, positioned radially outboard of the ribs and bridging the gaps.

4. The assembly of claim 3 , further comprising at least one band or sleeve encircling the or each layer of insulation and retaining the or each layer of insulation on the ribs.

5. The assembly of claim 1 and comprising at least one layer of insulation extending around the inner pipe, positioned longitudinally between the arrays and radially outboard of the cables.

6. The assembly of claim 5 , further comprising at least one band or sleeve encircling the or each layer of insulation between the arrays to clamp the or each layer of insulation and the cables against the inner pipe.

7. The assembly of claim 1 , wherein the cables are free for longitudinal or angular movement with respect to the pipe in the gaps between the ribs.

8. The assembly of claim 1 , wherein the ribs of each array are joined by a circumferentially-extending band or sleeve.

9. The assembly of claim 8 , wherein the band or sleeve joining the ribs is flexible.

10. The assembly of claim 8 , wherein the band or sleeve joining the ribs is substantially rigid.

11. The assembly of claim 8 , wherein the band or sleeve joining the ribs is separate from the ribs.

12. The assembly of claim 1 , wherein the cables extend substantially parallel to each other.

13. The assembly of claim 1 , wherein the cables are substantially angularly offset from a central longitudinal axis of the inner pipe.

14. The assembly of claim 13 , wherein the passageways defined between the ribs are substantially angularly offset from the central longitudinal axis of the inner pipe.

15. A method of assembling a pipe-in-pipe structure, the method comprising:
positioning first and second circumferentially-extending arrays of thermally-insulating spacers at longitudinally spaced locations around a steel inner pipe, the arrays comprising circumferentially-spaced ribs defining longitudinally-extending passageways in gaps between neighbouring ribs of the arrays;
positioning a plurality of cables on the outside of the inner pipe such that the cables extend longitudinally along the passageways, wherein the radial thickness of the ribs is greater than the thickness of any of the cables and wherein at least one cable is a heating element positioned for direct contact with the inner pipe in a passageway; and
positioning at least one insulation layer radially outboard of the cables.

16. The method of claim 15 , wherein the arrays of spacers are positioned before positioning the plurality of cables.

17. The method of claim 15 , comprising positioning insulating elements in the gaps between the ribs.

18. The method of claim 15 , comprising positioning the arrays of spacers around the inner pipe with the spaced ribs joined by a transversely-extending band or a sleeve.

Assignees

• Acergy France SAS

Inventors

• Cherkaoui Saad
• Delaunay Nathalie
• Gerometta Gerald

Classifications

• F17D1/18

  by heating · CPC title

• E21B36/04

  using electrical heaters · CPC title

• H05B3/42

  non-flexible · CPC title

• F17D3/01

  for controlling, signalling, or supervising the conveyance of a product · CPC title

• F16L1/123

  Devices for the protection of pipes under water · CPC title