Power or Data Transmission Cable with Metallic Water Barrier and Process for Manufacturing Such a Cable

Abstract

A transmission cable includes a cable core extending along a longitudinal direction; a water barrier in form of a metallic foil folded around the cable core along the longitudinal direction with overlapped edges. The overlapped edges is bonded to one another by a bonding layer made of an inorganic mater

Claims

1. A power or data transmission cable comprising: a cable core extending along a longitudinal direction; a water barrier in form of a metallic foil folded around the cable core along the longitudinal direction with overlapped edges, the overlapped edges being bonded to one another by a bonding layer made of an inorganic material.

2. The power or data transmission cable according to claim 1, wherein the bonding layer is made of at least one metal.

3. The power or data transmission cable according to claim 1, wherein the bonding layer is made of ceramic material.

4. The power or data transmission cable according to claim 1, wherein the metallic foil is made of copper and the bonding layer is made of copper or an alloy thereof.

5. The power or data transmission cable according to claim 1, wherein the thickness of the metallic foil is between 0.1 mm and 2 mm.

6. The power or data transmission cable according to claim 1, wherein the cable is a power transmission cable.

7. The power or data transmission cable according to claim 1, wherein the cable is a data transmission cable.

8. The power or data transmission cable according to claim 1, wherein the cable is a power and data transmission cable.

9. A process for manufacturing a power or data transmission cable comprising: providing a transmission cable core extending along a longitudinal direction; providing a metallic foil made of a metal having a melting temperature, the metallic foil comprising longitudinal edges; folding the metallic foil around the transmission cable core along the longitudinal direction; applying a solder paste on at least one of the longitudinal edges, the solder paste having a sintering temperature lower than the melting temperature of the metal of the metallic foil; overlapping the two longitudinal edges of the metal foil so as to bring them in contact via the solder paste; heating at least the overlapped longitudinal edges up to the sintering temperature of the solder paste to form a bonding layer binding the longitudinal edges and yielding a water barrier.

10. The process according to claim 9, wherein the solder paste has a viscosity comprised between 10,000 and 100,000 Cps at room temperature. ii. The process according to claim 9, wherein the metallic foil has a width and the overlapping of the two longitudinal edges is of from 5% to 30% of the width of the metallic foil.

12. The process according to claim 9, wherein heating at least the overlapped longitudinal edges comprises heating all of the metallic foil.

13. The process according to claim 9, further comprising applying a pressure so that the solder paste sinters and forms the bonding layer.

14. The process according to claim 13, wherein the pressure is applied during the heating ranges between 0.1 and 10 MPa.

15. The process according to claim 9, wherein the cable is a power transmission cable.

16. The process according to claim 9, wherein the cable is a data transmission cable.

17. The process according to claim 9, wherein the cable is a power and data transmission cable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further characteristics will be apparent from the detailed description given hereinafter with reference to the accompanying drawings, in which:

[0044] FIGS. 1 is a schematic section view of a multi-core power cable according to a first embodiment of the present disclosure;

[0045] FIGS. 2 is a schematic section view of a single core power cable according to a second embodiment of the present disclosure;

[0046] FIGS. 3A-3B illustrate a portion of a cable during phases of the process for manufacturing the power or data transmission cable of the present disclosure; and

[0047] FIG. 3C is a cross-sectional view of a particular of the power or data transmission cable of FIG. 3B.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0048] With reference to the figures, a power cable according to the present disclosure is schematically represented.

[0049] The power cable 100 of FIG. 1 comprises a cable core no comprising, in turn, three electric conductors 115 each surrounded by a polymeric insulation system 200. Each polymeric insulation system 200 is sequentially formed by an inner polymeric semiconductive layer 210, an intermediate polymeric insulating layer 220, and an outer polymeric semiconductive layer 230. A metallic screen (not illustrated) may surround each outer polymeric semiconductive layer 230.

[0050] The power cable 100 also comprises a filler in surrounding the three electric conductors 115 and relevant polymeric insulation systems 200.

[0051] The power cable 100 comprises a water barrier 120 in form of a metal tube surrounding the cable core 110. In particular, the water barrier 120 is made in form of a metallic foil folded around the cable core no along the longitudinal direction with overlapped edges 121 bonded by a bonding layer 122 according to the present disclosure. Edges 121 may be overlapped of about 15% of the metallic foil width.

[0052] In a non-illustrated embodiment, a water barrier 120 is provided around each of the three cable cores 110 of the cable 100 of FIG. 1. In this case, a further water barrier 120 as illustrated in FIG. 1 may be optionally provided.

[0053] The power cable 100 further comprise a polymeric sheath 140 around the water barrier 120. An adhesive layer 145 can be interposed between the water barrier 120 and the polymeric sheath 140 in order to ensure the adhesion of the polymeric sheath 140 and the water barrier 120.

[0054] In the embodiment of FIG. 2, the power cable 100 comprises a single cable core 110. All the numbers of this Figure refer to the same elements as from FIG. 1.

[0055] According to the present disclosure, the overlapped edges 121 are bonded to one another by the bonding layer 122 that is made of inorganic material.

[0056] The bonding layer 122 can be made of at least one metal or of a ceramic material.

[0057] If the bonding layer 122 is metallic, the water barrier 120 can act also as a metallic screen.

[0058] The water barrier 120 can be made of a metal selected from aluminum, copper or composites and alloys containing at least one of this metal.

[0059] In an embodiment, the bonding layer 122 can be made of substantially the same metal of the water barrier 120.

[0060] In an embodiment, the water barrier of the present cable is made of copper. A suitable copper for the water barrier should be a high purity one with a copper content greater than 90% and a low oxygen content, for example, from 50 ppm to 15 ppm or less. Copper alloys may also be suitable for the water barrier of the present disclosure.

[0061] A bonding layer suitable for the cable of the present disclosure is obtained through the sintering of a solder paste. The solder paste can have a sintering temperature lower than the melting temperature of the metal constituting the metallic foil.

[0062] In case the metallic foil is made of copper, the solder paste can be a copper-containing paste.

[0063] For example, in case the solder paste is a copper-containing paste, the sintering temperature is around 250-300° C. that is much lower than the melting temperature of the copper (1080° C.). In this way, the heating of at least the edges of the metallic foil is such that the underlying polymeric layer/s are not reached by potentially harmful temperatures.

[0064] An example of a copper paste that can be used is the solder paste described in EP3494184.

[0065] The bonding layer resulting from the sintering process of the solder paste is made of inorganic material, for example, it is substantially made of copper, though it can comprise residue of organic material contained in the solder paste before sintering.

[0066] The power or data transmission cable of the present disclosure can be manufactured by a process that will be described in the following.

[0067] For the sake of simplicity the process will be described with reference with reference to FIGS. 3a-3c.

[0068] The process comprises the step of providing a power or data transmitting cable core 310 extending along a longitudinal direction A. The manufacturing process of the cable core 310 is not described since it is known per-se. In an embodiment, the provision of the cable core 310 provides for advancing the cable core 310 from its manufacturing apparatus in a continuous manufacturing line.

[0069] The process of the disclosure also comprises the step of providing the metallic foil 300 having a width B, and folding such foil around the cable core 310 along the longitudinal direction A in the direction of the arrows a′, a″ so as to approach one another the two metal foil longitudinal edges 300a, 300b. The provision of the metallic foil 300 and the folding thereof may be carried out in a continuous manner in the manufacturing line.

[0070] For example, the metallic foil has a thickness comprised between 0.1 mm and 2 mm.

[0071] Then, the process of the disclosure comprises the step of applying the solder paste on at least one of the edges 300a, 300b to be overlapped, for example in a continuous manner.

[0072] The application of the solder paste may be carried out for example by an injector positioned over the cable core 310 and the folded metallic foil 300, the injector dropping the paste on at least one of the edges 300a, 300b to be overlapped.

[0073] After the application of the solder paste the process comprises the step of overlapping the longitudinal edges 300a, 300b and put them into contact via the solder paste. Edges may be overlapped of about 15% of the metallic foil width B. Then a heating step of at least the overlapped edges of the folded metallic foil is performed up to the sintering temperature of the solder paste, optionally applying a pressure, so that the solder paste sinters and forms a bonding layer 322, thus realizing the water barrier.

[0074] The bonding layer of the present cable is capable of binding the edges of the water barrier in compliance to TB446, Cigrè, 2011 (ISBN: 978-2-85873-135-0). The bonding layer has a strength suitable to bear the stresses commonly exerted on the cable during its deployment and use, without affecting its integrity and performance against the water penetration even at the pressures of a submarine application (e.g. greater than 100 bar).

[0075] The optional adhesive layer and the polymeric sheath may be sequentially extruded around the water barrier.