Method of manufacturing dynamic submarine power cable with high friction layer

Abstract

To provide a method of manufacturing a dynamic submarine power cable, where contact surfaces between an insulation system and a metallic sheath restrain movement between these components and the life expectancy of the cable is positively influenced.SOLUTION: A method of manufacturing a dynamic submarine power cable 1 includes: providing an insulation system 5 around a conductor 3, the insulation system including an inner semiconducting layer 7, an insulation layer 9 arranged around the inner semiconducting layer, and an outer semiconducting layer 11 arranged around the insulation layer; providing a semiconducting polymeric layer around the outer semiconducting layer; providing a longitudinally welded metallic radial water blocking layer 15 around the polymeric layer, the metallic radial water blocking layer being in contact with the polymeric layer; and heating the metallic radial water blocking layer to melt the polymeric layer and form an adhesive layer 13 that adheres to an inner surface of the metallic radial water blocking layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to dynamic submarine power cables. [Background technology]

[0002] A dynamic submarine power cable is a power cable designed to extend between a floating structure, such as an oil or gas platform or a floating wind turbine, and the seabed, or to be suspended between two floating structures.

[0003] Dynamic submarine power cables are specifically manufactured to better resist fatigue damage due to constant movement as a result of wave motion than static submarine power cables.

[0004] Generally, from a mechanical point of view, the service life of a dynamic submarine power cable depends on how well the cable is able to distribute the stresses during movement. Summary of the Invention

[0005] It has been found by the inventors that the service life of a dynamic submarine power cable is positively affected if the interface between the insulation system and the metallic sheath constrains movement between these components. This can be particularly problematic when the loads are dynamic and create different thermal conditions in the dynamic submarine power cable, which creates thermal expansion and contraction, which is typically the case for floating wind applications. However, high friction between the insulation system and the metallic sheath can complicate the manufacturing process, where these components may need to be able to move more freely relative to each other.

[0006] In view of the above, it is an object of the present disclosure to provide a method for manufacturing a dynamic submarine power cable that overcomes or at least alleviates the problems of the prior art.

[0007] Therefore, according to a first aspect of the present disclosure, there is provided a method of manufacturing a dynamic submarine power cable comprising: a) providing an insulation system around a conductor, the insulation system comprising an inner semiconducting layer, an insulating layer disposed around the inner semiconducting layer, and an outer semiconducting layer disposed around the insulating layer; b) providing a semiconducting polymer layer around the outer semiconducting layer; c) providing a longitudinally welded metallic radial water barrier layer around the polymer layer, the metallic radial water barrier layer being in contact with the polymer layer; and d) heating the metallic radial water barrier layer after step c) such that the polymer layer melts and forms an adhesion layer adhering to an inner surface of the metallic radial water barrier layer.

[0008] By having a bedding layer that provides high friction between the metallic water barrier layer and the outer semiconducting layer, movement between the metallic water barrier layer and the outer semiconducting layer can be limited and the service life of the dynamic submarine power cable is therefore increased. Furthermore, since the polymer layer forms an adhesion layer only when heated in step d), prior to step d) during which the polymer layer is handled, the dynamic submarine power cable has lower friction until step d). This facilitates handling of the dynamic submarine power cable during manufacture, especially since different speeds between layers during the manufacturing process can be problematic if high friction materials are used.

[0009] According to one embodiment, the layer immediately below the polymer layer is an outer semiconducting layer.

[0010] According to one embodiment, in step b), the polymer layer is formed by extrusion, and step b) further comprises cooling the polymer layer after extrusion and prior to step c).

[0011] According to one embodiment, in step b), the polymer layer is formed by a tape wrapped around the insulation system.

[0012] According to one embodiment, the tape is a laminated tape comprising a water-swellable material as an inner layer and a polymeric layer as an outer layer.

[0013] One embodiment comprises providing a bedding around the outer semiconducting layer, and in step b) a polymer layer is placed outside and in direct contact with the bedding.

[0014] According to one embodiment, the polymer layer is a polymeric adhesive compound.

[0015] According to one embodiment, the polymer layer comprises a thermoplastic polyolefin.

[0016] According to one embodiment, the metallic radial water blocking layer is smooth.

[0017] According to one embodiment, the metallic radial water blocking layer is corrugated.

[0018] According to one embodiment, the metallic radial water blocking layer comprises copper, aluminum, or stainless steel.

[0019] According to one embodiment, step c) involves winding a metallic sheath around the polymer layer and longitudinally welding the metallic sheath to obtain a metallic radial water blocking layer, the polymer layer moving at a different speed than the metallic sheath in the axial direction of the dynamic submarine power cable when forming the metallic radial water blocking layer.

[0020] According to a second aspect of the present disclosure, there is provided a dynamic submarine power cable comprising a conductor, an insulation system about the conductor, the insulation system comprising an inner semiconducting layer, an insulating layer disposed about the inner semiconducting layer, and an outer semiconducting layer disposed about the insulating layer, a polymeric semiconducting adhesion layer disposed about the outer semiconducting layer, and a longitudinally welded metallic radial water barrier layer disposed about the adhesion layer, the adhesion layer adhering to an inner surface of the metallic radial water barrier layer.

[0021] The dynamic submarine power cable of the second aspect may be obtained according to the method of the first aspect.

[0022] The dynamic submarine power cable may be a high voltage or a medium voltage power cable.

[0023] The dynamic submarine power cable may be an AC power cable or it may be a DC power cable.

[0024] In general, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless expressly defined otherwise herein. All references to a / an / the element, device, component, means, etc. are to be openly interpreted as referring to at least one instance of the element, device, component, means, etc., unless expressly stated otherwise.

[0025] Specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1A is a schematic diagram illustrating a cross-sectional view of an example dynamic submarine power cable. [Diagram 2] FIG. 2 illustrates a schematic cross-sectional view of another example of a dynamic submarine power cable. [Diagram 3] 1 is a flow chart of a method for manufacturing a dynamic submarine power cable. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The inventive concepts will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. However, the inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concepts to those skilled in the art. Like numbers refer to like elements throughout the description.

[0028] Figure 1 shows an example of a dynamic submarine power cable 1. The dynamic submarine power cable 1 in the example in Figure 1 is a single-core cable.

[0029] The illustrated dynamic submarine power cable 1 may be a DC power cable or may be a single phase AC power cable.

[0030] The dynamic submarine power cable 1 comprises a conductor 3. The conductor 3 may comprise, for example, copper or aluminium.

[0031] The dynamic submarine power cable 1 comprises an insulation system 5 arranged around the conductor 3 .

[0032] The insulation system 5 comprises an inner semiconducting layer 7 disposed about the conductor 3 , an insulating layer 9 disposed about the inner semiconducting layer 7 , and an outer semiconducting layer 11 disposed about the insulating layer 9 .

[0033] The insulation system 5 may be an extruded insulation system.

[0034] The insulating system 5 may comprise a polymeric material. The inner semiconducting layer 7, the insulating layer 9 and the outer semiconducting layer 11 may thereby have a polymer base, for example polyethylene, cross-linked polyethylene, polypropylene, EPR or EPDM.

[0035] The inner and outer semiconducting layers 7, 11 comprise conductive particles mixed with a polymer base. The conductive particles may be, for example, carbon black.

[0036] The inner and outer semiconducting layers 7 and 11 may or may not be crosslinked.

[0037] The dynamic submarine power cable 1 comprises an adhesion layer 13 disposed around an outer semiconducting layer 11 .

[0038] The adhesive layer 13 is formed from a polymer layer that is melted into the adhesive layer 13 during manufacture of the dynamic submarine power cable 1, as will be explained in more detail below.

[0039] The adhesive layer 13 is semiconductive. The adhesive layer 13 may comprise a polymer adhesive compound, such as a thermoplastic polyolefin as a base polymer. The adhesive layer 13 may comprise, for example, low density polyethylene (LDPE). The base polymer may be mixed with conductive particles, such as carbon black or other suitable conductive particles, to make the base polymer semiconductive.

[0040] The dynamic submarine power cable 1 comprises a metallic radial water blocking layer 15 disposed about the adhesive layer 13. The metallic radial water blocking layer 15 may comprise, for example, copper, such as pure copper, or a copper alloy, such as a copper-nickel alloy, stainless steel, or aluminum.

[0041] The metallic radial water blocking layer 15 may be welded longitudinally.

[0042] The metallic radial water blocking layer 15 may be corrugated or smooth.

[0043] The adhesive layer 13 is in direct contact with the inner surface of the metallic radial water blocking layer 15. The adhesive layer 13 adheres to the inner surface of the metallic radial water blocking layer 15.

[0044] The adhesive layer 13 may be in direct contact with the outer semiconductive layer 11. Alternatively, if the dynamic submarine power cable 1 comprises a bedding, for example comprising a water-swellable material and / or a binder tape, disposed around the outer semiconductive layer 11 and below the adhesive layer 13, the adhesive layer 13 may be in direct contact with the bedding.

[0045] The bedding may be extruded onto the outer semiconductive layer 11. Alternatively, the bedding may be in the form of a tape wrapped around the outer semiconductive layer 11. This allows the adhesive layer 13 to be in direct contact with the inner surface of the metallic radial water blocking layer 15 and with either the outer semiconductive layer 11 or the bedding simultaneously.

[0046] The dynamic submarine power cable 1 may comprise a further polymeric layer or sheath 17 disposed around the metallic water blocking layer 15 .

[0047] Additionally, the dynamic submarine power cable 1 may comprise one or more armor layers 19, each comprising a plurality of helically laid armor wires 21. The armor wires may comprise a metal, such as, for example, galvanized steel, stainless steel, or copper, or a synthetic material, such as a polymeric material, for example, coated aramid fiber, or the armor layers 19 may comprise both metallic and synthetic material armor wires 21.

[0048] The dynamic submarine power cable 1 may comprise an outer sheath or jute wrap 23, if present, disposed around the sheath 17 and around the armor layer 19. The outer sheath or jute wrap 23 may comprise a polymeric material.

[0049] Figure 2 shows another example of a dynamic submarine power cable. The dynamic submarine power cable 1' in Figure 2 is a multi-core dynamic submarine power cable comprising a plurality of power cores 25a-25c. Each of the power cores 25a-25b is very similar in structure to the dynamic submarine power cable 1 described above. Thus, each of the power cores 25a-25c comprises a respective insulation system 5, adhesive layer 13, and metallic water barrier layer 15.

[0050] In the installed state, the dynamic subsea power cable 1, 1' is connected to a floating structure, for example through a bending stiffener or bellmouth, and extends from the floating structure down to the seabed or to another floating structure.

[0051] FIG. 3 is a flow chart of a method for manufacturing a dynamic submarine power cable, such as the dynamic submarine power cable 1, 1'.

[0052] In step a), an insulating system 5 is provided around the conductor 3 .

[0053] In step b), a semiconducting polymer layer is provided around the outer semiconducting layer 11 of the insulating system 5 .

[0054] The polymer layer may be extruded onto the outer semiconductive layer 11 or the polymer layer may be in the form of a tape wrapped around the outer semiconductive layer 11 .

[0055] If the dynamic submarine power cable 1, 1' comprises a water-swellable material, the polymer layer may be provided around the water-swellable material if it is extruded onto the outer semiconducting layer 11 or if it is formed by a separate tape. Alternatively, the water-swellable material and the polymer layer may form a laminated tape, the water-swellable material forming the inner layer of the tape and the polymer layer forming the outer layer.

[0056] In step c), a metallic radial water-blocking layer 15 is provided around the polymer layer. Step c) involves wrapping a metallic sheath around the polymer layer and longitudinally welding the metallic sheath, thereby forming the radial water-blocking layer 15.

[0057] In step c), the metallic sheath and the metallic radial water-blocking layer 15, which is gradually created by wrapping the metallic sheath around the polymer layer and welding its opposing edges together, may move at a different speed during processing in the manufacturing line than the cable core structure formed by the conductor, insulation system and polymer layer.

[0058] In step c), the metallic radial water-blocking layer 15 is placed in contact with the polymer layer, i.e. in direct contact with the polymer layer, which can be done by crimping the metallic radial water-blocking layer 15 after it has been longitudinally welded, for example using a roller or a die.

[0059] If the polymer layer is made by extrusion, the polymer layer may be cooled prior to step c).

[0060] In step d), the metallic radial water blocking layer 15 is heated after step c). The metallic radial water blocking layer 15 is heated to a temperature that causes the polymer layer to melt and form an adhesive layer 13. The adhesive layer 13 thereby adheres to the inner surface of the metallic radial water blocking layer 15. The adhesive layer 13 also adheres to the layer directly below it, e.g. the outer semiconducting layer 11 or bedding. The adhesive layer 13 thereby provides high friction and / or even grip between the metallic radial water blocking layer 15 and the layer directly below the adhesive layer 13. However, before the polymer layer is melted, the friction between the metallic radial water blocking layer 15 and the layer directly below the polymer layer is lower than when the adhesive layer 13 is formed.

[0061] The material from which the polymer layer is constructed is selected to have a lower melting point than the outer semiconducting layer 11 but a higher melting point than the maximum allowable operating temperature of the dynamic submarine power cable 1, 1'.

[0062] The inventive concept has been described above primarily with reference to a few examples. However, as will be readily appreciated by those skilled in the art, other embodiments than those disclosed above are equally possible within the scope of the inventive concept as defined by the appended claims.

Claims

1. A method for manufacturing a dynamic submarine power cable (1;1'), comprising the steps of: a) providing an insulation system (5) around a conductor (3), said insulation system comprising an inner semiconducting layer (7), an insulating layer (9) arranged around said inner semiconducting layer (7), and an outer semiconducting layer (11) arranged around said insulating layer (9); b) providing a semiconducting polymer layer around said outer semiconducting layer (11); c) providing a longitudinally welded metallic radial water barrier layer (15) around and in contact with said polymer layer; d) heating the metallic radial water-blocking layer (15) after step c) so that the polymer layer melts and forms an adhesive layer (13) that adheres to the inner surface of the metallic radial water-blocking layer (15); A method comprising:

2. The method of claim 1 , wherein the layer immediately beneath the polymer layer is the outer semiconducting layer (11 ).

3. 3. The method of claim 1 or 2, wherein in step b) the polymer layer is formed by extrusion, and step b) further comprises cooling the polymer layer after the extrusion and prior to step c).

4. 3. The method according to claim 1 or 2, wherein in step b) the polymer layer is formed by a tape wound around the insulation system (5).

5. The method of claim 4, wherein the tape is a laminated tape comprising a water-swellable material as an inner layer and the polymeric layer as an outer layer.

6. 5. The method according to claim 1, comprising providing a bedding around the outer semiconducting layer (11), and in step b) the polymer layer is arranged outside the bedding and in direct contact with the bedding.

7. The method of claim 1 , wherein the polymer layer is a polymeric adhesive compound.

8. The method of claim 1 , wherein the polymer layer comprises a thermoplastic polyolefin.

9. 9. The method according to any one of claims 1 to 8, wherein the metallic radial water blocking layer (15) is smooth.

10. 9. The method according to any one of claims 1 to 8, wherein the metallic radial water blocking layer (15) is corrugated.

11. 11. The method of any one of claims 1 to 10, wherein the metallic radial water blocking layer (15) comprises copper, aluminum, or stainless steel.

12. 12. The method according to any one of claims 1 to 11, wherein step c) involves winding a metal sheath around the polymer layer and longitudinally welding the metal sheath to obtain the metallic radial water-blocking layer (15), the polymer layer moving at a different speed than the metal sheath in the axial direction of the dynamic submarine power cable (1; 1') when forming the metallic radial water-blocking layer (15).

13. A conductor (3); an insulation system (5) around the conductor (3), the insulation system (5) comprising an inner semiconducting layer (7), an insulation layer (9) arranged around the inner semiconducting layer (7), and an outer semiconducting layer (11) arranged around the insulation layer (9); a polymeric semiconducting adhesion layer (13) disposed around said outer semiconducting layer (11); a longitudinally welded metallic radial water barrier layer (15) disposed around said adhesive layer (13), said adhesive layer (13) adhering to an inner surface of said metallic radial water barrier layer (15); A dynamic submarine power cable (1;1').

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