SYSTEM TO CONVEY A FLUID

Abstract

A system to convey a fluid, in particular a fluid containing hydrocarbons, has a first pipeline, which is made of an electrically conductive material and has an internal diameter; a second pipeline, which is made of an electrically conductive material, has an external diameter smaller than the internal diameter, and is placed inside the first pipeline at a distance from the first pipeline so as to form an annular gap between the first and second pipeline; an electrically conductive layer placed in the annular gap at a distance from the first pipeline; an electrically insulating layer placed between the second pipeline and the electrically conductive layer; and a power source to apply an electrical potential difference between the second pipeline and the electrically conductive layer.

Claims

1-18. (canceled)

19. A system to convey a fluid, the system comprising: a first pipeline made of an electrically conductive material and having an internal diameter; a second pipeline made of an electrically conductive material and having an external diameter smaller than the internal diameter of the first pipeline, the second pipeline being positioned inside the first pipeline at a distance from the first pipeline to define an annular gap between the first pipeline and the second pipeline; an electrically conductive layer positioned in the annular gap at a distance from the first pipeline, the electrically conductive layer being in electrical contact with the first pipeline; an electrically insulating layer positioned between the second pipeline and the electrically conductive layer; and a power source configured to apply an electrical potential difference between the second pipeline and the electrically conductive layer.

20. The system of claim 19, further comprising a thermally insulating layer positioned in the annular gap and around the second pipeline.

21. The system of claim 20, wherein the thermally insulating layer coats the electrically conductive layer.

22. The system of claim 20, wherein the thermal insulating layer coats the electrically insulating layer.

23. The system of claim 22, wherein the electrically conductive layer coats the thermally insulating layer.

24. The system of claim 19, wherein the electrically insulating layer coats an outer surface of the second pipeline.

25. The system of claim 24, wherein the electrically conductive layer coats the electrically insulating layer.

26. The system of claim 19, wherein the power source comprises a voltage generator.

27. The system of claim 19, wherein the electrically conductive layer comprises a plurality of electrically conductive sheets longitudinally positioned side-by-side in the annular gap between the first pipeline and the second pipeline, the electrically conductive sheets being coupled together by at least one of: welding, brazing, partially overlapping, and electrically conductive connecting elements.

28. The system of claim 19, further comprising: a plurality of first pipes joined together at respective opposite ends by first welding seams to form the first pipeline; a plurality of second pipes joined together at respective opposite ends by second welding seams to form the second pipeline; and a connecting element made of an electrically conductive material and arranged at each second welding seam, the connecting element being configured to electrically connect two electrically conductive sheets arranged at opposite sides with respect to the second welding seam.

29. The system of claim 28, wherein each connecting element is in contact with two electrically conductive sheets arranged at opposite sides with respect to the second welding seam.

30. The system of claim 28, further comprising at least two connecting elements, each of the at least two connecting elements being in contact with a respective electrically conductive sheet and with the first pipeline.

31. The system of claim 28, further comprising a sleeve wrapped around the second welding seam and free ends of two adjacent pipes.

32. The system of claim 19, further comprising a plurality of annular spacers arranged between the first pipeline and the second pipeline to space the first pipeline and the second pipeline.

33. The system of claim 32, wherein each annular spacer is positioned between the electrically conductive layer and the first pipeline.

34. The system of claim 19, further comprising a plurality of annular shear stops positioned between the first pipeline and the second pipeline and configured to limit relative longitudinal displacement between the first pipeline and the second pipeline.

35. The system of claim 34, wherein each annular shear stop breaks a continuity of the electrically conductive layer and the system further comprises a plurality of connecting elements connected to the electrically conductive layer and to the first pipeline at opposite sides of each annular shear stop.

36. The system of claim 34, wherein each annular shear stop defines a plurality of openings to corresponding to a continuity of the annular gap along a longitudinal axis of the first pipeline and the second pipeline.

37. The system of claim 34, wherein each annular shear stop has a plurality of portions arranged in support on the electrically conductive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Other characteristics and advantages of the present invention will become clear from the following description of exemplary and non-limiting embodiments thereof, with reference to the enclosed figures wherein:

[0062] FIG. 1 is a longitudinal sectional view, with parts removed for clarity's sake, of a system to convey fluids realized in accordance with a first embodiment of the present invention;

[0063] FIG. 2 is a cross-sectional view, with parts removed for clarity's sake, of the system of FIG. 1;

[0064] FIGS. 3 to 6 are longitudinal section views, on an enlarged scale and with parts removed for clarity's sake, of a constructive detail of the system of FIG. 1 and relative variants;

[0065] FIG. 7 is a longitudinal sectional view, with parts removed for clarity's sake, of a detail of the system of FIG. 1;

[0066] FIG. 8 is a perspective view, with parts removed for clarity's sake, of a variant of the detail of FIG. 7;

[0067] FIG. 9 is a cross-sectional view, with parts removed for clarity's sake, in accordance with the variant of FIG. 8;

[0068] FIG. 10 is a cross-sectional view, with parts removed for clarity's sake, of a further variant of the detail of FIG. 7;

[0069] FIG. 11 is a longitudinal section view, with parts removed for clarity's sake, of the further variant of FIG. 10;

[0070] FIGS. 12, 13 and 14 are longitudinal section views, with parts removed for clarity's sake, of respective variants of a further constructive detail of the system of FIG. 1;

[0071] FIGS. 15 and 16 are longitudinal section views, with parts removed for clarity and on a reduced scale, of a further variant of the detail of FIG. 13

[0072] FIG. 17 is a longitudinal section view, with parts removed for clarity's sake, of a detail of the system of FIG. 1;

[0073] FIG. 18 is a longitudinal sectional view, with parts removed for clarity's sake, of a system to convey fluids realized in accordance with a second embodiment of the present invention; and

[0074] FIG. 19 is a cross-sectional view, with parts removed for clarity's sake, of the system of FIG. 18.

PREFERRED EMBODIMENT OF THE INVENTION

[0075] With reference to FIGS. 1 and 2, 1 denotes as a whole a system to convey a fluid, in particular a fluid containing hydrocarbons. The system 1 is adapted to operate in a body of water at a considerable depth and at low temperature.

[0076] The system 1 comprises a pipeline 2, which extends along an axis A1, is made of an electrically conductive material, and has an internal diameter D1; a pipeline 3, which is substantially coaxial to the pipeline 2, is made of an electrical conductive material, has an external diameter D2 smaller than the internal diameter D1, and is placed inside the pipeline 2 at a distance from the pipeline 2 to form an annular gap 4 between the pipelines 2 and 3; an electrically conductive layer 5 placed in the annular gap 4 at a distance from the pipeline 2; an electrically insulating layer 6 placed between the pipeline 3 and the electrically conductive layer 5; and a potential power source 7 connected to the pipeline 3, to the electrically conductive layer 5 and to the pipeline 2. In fact, the electrically conductive layer 5 and the pipeline 2 are earthed and are at the same potential.

[0077] In practice, the electrically insulating layer 6 coats the external face of the pipeline 3 while the electrically conductive layer 5 coats the external face of the electrically insulating layer 6.

[0078] The system 1 comprises a thermally insulating layer 8 placed in the annular gap 4 around the second pipeline 3. In particular, the thermally insulating layer 8 coats the electrically conductive layer 5.

[0079] As shown in FIGS. 1 and 2, part of the annular gap 4 remains free and the pipeline 2 is provided with an external protective layer 9.

[0080] With reference to FIG. 3, the electrically conductive layer 5 is made by means of electrically conductive sheets 10 and generally of aluminium with a thickness ranging from a few tenths of a mm to a few mm. The sheets 10 of discrete length are wrapped around the pipeline 3 and are arranged adjacent to each other but need to be joined in the longitudinal direction to ensure electrical continuity.

[0081] In the case shown in FIG. 3, the sheets 10 are joined by welding or brazing.

[0082] In the variant of FIG. 4, the electrical continuity between the adjacent sheets 10 is achieved by means of connecting elements 11, the opposite ends of which are in contact with two adjacent sheets 10.

[0083] In the variant of FIG. 5, the electrical continuity of the electrically conductive layer 5 is ensured by the partial overlapping of the ends of the adjacent sheets 10.

[0084] In the variant of FIG. 6, the electrical continuity is ensured by connecting elements 12 which in this case are additional sheets of reduced length and overlapped on the ends of the adjacent sheets 10.

[0085] With reference to FIGS. 1 and 2, annular spacers 13 are arranged between the pipelines 2 and 3 and the function of which is to keep the pipelines 2 and 3 substantially coaxial; and annular shear stops 14, the function of which is to limit the relative longitudinal displacements between the pipelines 2 and 3, that is, the relative displacements substantially parallel to the axis A1.

[0086] In the case shown, each annular spacer 13 is arranged in support on the electrically conductive layer 5 and is arranged to be in contact with the internal face of the pipeline 2.

[0087] Each annular shear stop 14 adheres to the pipeline 2 and to the pipeline 3 and breaks the continuity of the electrically conductive layer 5.

[0088] In the detail shown in FIG. 7, annular shear stops 14 are shown which are arranged directly in contact with both pipelines 2 and 3, in particular adhering to the pipelines 2 and 3. In this case, the continuity of the electrically conductive layer 5 is broken, which is connected to the pipeline 2 by means of connecting elements 15 made of electrically conductive material.

[0089] An alternative solution to ensure the electrical continuity of the electrically conductive layer 5 consists in making windows 16 in the electrically conductive layer 5 and in the electrically insulating layer 6, as shown in FIG. 8, and in making an annular shear stop 17 by casting which grips the external surface of the pipeline 3 at the windows 16 as shown in FIG. 9.

[0090] A further alternative solution shown in FIGS. 10 and 11 provides for making an annular shear stop 18 with a grooved internal face which grips the pipeline 3 at windows 19 formed along the electrically conductive layer 5 while the grooved parts ensure the continuity of the electrically conductive layer 5.

[0091] With reference to FIG. 12, the pipelines 2 and 3 are formed by respective pipes 20 and 21 of unitary length, generally 12 m, which are joined to each other at their opposite ends through respective welding seams 22 and 23. Along the pipeline 3, the electrically insulating layer 6, the electrically conductive layer 5 and the thermally insulating layer 8 are interrupted at the opposite ends of each pipe 21. After joining the pipes 21, the continuity of the electrically insulating layer 6 is restored by means of a sleeve 24 made of polymeric material around the free ends of the pipes 21. Subsequently, the electrical continuity is achieved between the electrically conductive layers 5 of two adjacent tubes 21 by means of connecting elements 25 fixed to the adjacent electrically conductive layers 5. Finally, the two adjacent pipes 20 are welded the one to the other.

[0092] In the variant of FIG. 13, the connecting elements 25 connect an electrically conductive layer 5 to the corresponding pipe 20. In this way, the pipeline 2 ensures the electrical continuity along the system 1.

[0093] In the variant of FIG. 14, the system 1 comprises a connecting element 26, which is a strip of sheet of conductive material applied above the welding seam 23 which electrically connects the layers of conductive material 5 arranged astride the welding seam 23.

[0094] The variant of FIGS. 15 and 16, shows a solution similar to that of the variant of FIG. 13 and in which the connecting elements 25 are sufficiently long and flexible to allow the axial sliding of at least one of the two pipes 20 so as to allow the restoration of the continuity of the electrically conductive layer 5 obtained by means of the welding seam 22 in a simple and fast manner.

[0095] With reference to FIG. 17, the system 1 comprises a bulkhead 27 of electrically conductive material, which is arranged at the ends of the pipelines 2 and 3 and is configured to ensure the closure of the electrical circuit by putting the pipelines 2 and 3 in contact.

[0096] In use, with reference to FIG. 1, the pipeline 2 and the electrically conductive layer 5 are earthed, while a potential difference is applied to the pipeline 3, on the one hand, and to the electrically conductive layer 5 and to the pipeline 2, on the other hand, at the central part of the system 1.

[0097] The thermal energy generated by Joule effect along pipeline 3 is transferred to the fluid. Some of the heat generated by Joule effect along the electrically conductive layer 5 is also confined towards the fluid thanks to the thermally insulating layer 8 arranged around the electrically conductive layer 5. Although the electrically conductive layer 5 and the pipeline 2 are connected in parallel, the lower resistance of the electrically conductive layer 5 results in most of the current to cross the electrically conductive layer 5, significantly limiting the thermal energy losses in the environment outside the system 1.

[0098] This increases the efficiency of system 1 because the generation of heat by Joule effect is concentrated at the pipeline 3 through which the fluid flows.

[0099] In some variants of the embodiment described, when the continuity of the electrically conductive layer 5 is broken, a by-pass is made through the pipeline 2 which, as already mentioned, is subject to the same potential as the electrically conductive layer 5.

[0100] In the embodiment of FIGS. 18 and 19, the thermally insulating layer 8 is applied on the electrically insulating layer 6 and the electrically conductive layer 5 is applied on the thermally insulating layer 8. The system 1 comprises annular spacers 28 arranged in contact with the electrically conductive layer 5, and annular shear stops 29, which adhere to the pipeline 2 and to the pipeline 3 and break the continuity of the electrically conductive layer 5.

[0101] This embodiment of the invention has a lower efficiency because the thermally insulating layer 8 does not coat the electrically conductive layer 5.

[0102] Finally, it is evident that variations with respect to the embodiments described can be made to the present invention without however departing from the scope of protection of the attached claims.