WO2021116374A1 - Skin-effect heating cable - Google Patents
Skin-effect heating cable Download PDFInfo
- Publication number
- WO2021116374A1 WO2021116374A1 PCT/EP2020/085703 EP2020085703W WO2021116374A1 WO 2021116374 A1 WO2021116374 A1 WO 2021116374A1 EP 2020085703 W EP2020085703 W EP 2020085703W WO 2021116374 A1 WO2021116374 A1 WO 2021116374A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- outer conductor
- skin
- effect heating
- heating cable
- conductor arrangement
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/101—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces
- H05B6/103—Induction heating apparatus, other than furnaces, for specific applications for local heating of metal pieces multiple metal pieces successively being moved close to the inductor
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/105—Induction heating apparatus, other than furnaces, for specific applications using a susceptor
- H05B6/108—Induction heating apparatus, other than furnaces, for specific applications using a susceptor for heating a fluid
Abstract
A skin-effect heating cable (1) comprising an inner conductor arrangement (5), an outer conductor arrangement (3) comprising a material configured to generate heat through hysteresis losses when exposed to an alternating magnetic field, and an inner insulation (7) arranged between the inner conductor arrangement (5) and the outer conductor arrangement (3). The mutual position of the inner conductor arrangement (5) and the outer conductor arrangement (3) is fixed along the axial direction. A pipe assembly with such a cable and a method of heating are also disclosed.
Description
SKIN-EFFECT HEATING CABLE
Technical Field
[0001] The present invention relates to a heating cable that exploits the skin-effect for generating heat.
Background Art
[0002] Skin-effect heating systems are known. A typical solution involves arranging an insulated electric cable inside a ferromagnetic heat tube. Typically, the electric cable has a conductor made of a non-ferrous metal, normally copper. The ferromagnetic heat tube is normally made of steel. It is common to arrange the electric cable loosely in the bore of the ferromagnetic heat tube.
[0003] The insulated electric cable extends between the ends of the heat tube, while being electrically insulated along the extension of the heat tube. At a remote end of the heat tube, the electric cable can connect to the heat tube or to earth. At a near end of the heat tube, the electric cable and the heat tube connect to an AC power supply. When an AC electric potential is supplied from the power supply to the circuit having the electric cable and the heat tube, the current flowing in the material of the heat tube appears only at the skin part of the inner wall portion of the heat tube. Alternating current tends to flow only in the skin of the conductor carrying it. The current in the insulated electric cable produces an opposite current in the heat tube surrounding it. The magnetic interaction between the opposite currents tends to draw the currents together. This is known as the proximity effect. Resultingly, the current in the pipe is concentrated in the inner skin part of the tube wall. The skin depth, i.e. how deep into the material the current flows, depends on the material.
[0004] Publication US20190045587 discloses a skin-effect based heating cable where a center conductor is made of twisted non-ferromagnetic conductors. The center conductor is fixed inside an outer, coaxially arranged ferromagnetic conductor by means of an inner insulation layer arranged between the inner and outer conductors.
[0005] US20180184487 A1 presents another skin-effect based heating system configured for heating of a carrier pipe. The system has a heater cable arranged inside a heat tube. The heater cable has a conductor with an inner surrounding semiconductive layer and an electrical insulation layer surrounding the semiconductive layer. The electrical insulation layer is surrounded by an outer semiconductive layer. The heater cable is arranged loosely inside the heat tube.
[0006] It is normally difficult to make long skin-effect heating cables since the electric cable is normally flushed into and sometimes pulled through the tube. This limits its length and the length between splices.
[0007] US20150237679 A1 also discloses a skin-effect heating cable. In this disclosure, an inner core conductor is fixed with inorganic ceramic insulation within a
conducting outer sheath.
Summary of invention
[0008] According to a first aspect of the present invention, there is provided a skin- effect heating cable comprising an inner conductor arrangement, an outer conductor arrangement comprising a material that is configured to generate heat through hysteresis losses when exposed to an alternating magnetic field, an inner insulation arranged between the inner conductor arrangement and the outer conductor arrangement. According to the invention, the mutual position of the inner conductor arrangement and the outer conductor arrangement is fixed along the axial direction.
[0009] By stating that the mutual position of the inner and outer conductor arrangements is fixed along the axial direction it is meant that the inner conductor arrangement is not free to move inside the outer conductor arrangement. This is contrary to a cable arranged loosely inside an outer tube. The inner insulation and possible additional components, such as filler elements, will fill the space between the inner and outer conductor arrangements.
[0010] Preferably, the skin-effect heating cable according to the invention can have a length of more than 100 meters, 1000 meters or even more than 10 km.
[0011] Preferably, the skin-effect heating cable according to the invention can in some embodiments be configured for medium voltages, meaning voltages in the range between 1kV and 35kV (AC). In some embodiments, the skin-effect heating cable can be configured for even higher voltages.
[0012] In some embodiments, the skin-effect heating cable according to the invention can be configured with a wet insulation system design for the inner conductor arrangement, without a metallic water-barrier. Such wet insulation system design is typical for medium voltage subsea ac-power cables.
[0013] With the term skin-effect heating cable is meant a cable as defined above, wherein the cable is useful for generating heat due to the skin-effect in the outer conductor arrangement. To obtain such heat generation, the material in the outer conductor arrangement must be of a type that exhibits hysteresis losses and/or hysteresis effects when exposed to the alternating fields from an alternating electric current in the inner conductor arrangement. A ferromagnetic material is an example of such a material.
[0014] The term ferromagnetic material, as used herein, shall thus be understood to mean materials that are not non-magnetic, and/or that exhibits said hysteresis losses. Another way of stating this meaning, is a material suitable for heating by means of the skin-effect.
[0015] The inner conductor arrangement can in some embodiments typically comprise strands of a non-ferrous, conducting material, such as copper strands. Other embodiments may however include an inner conductor arrangement with a
ferromagnetic material. Such material can for instance be the same material as in the outer conductor arrangement.
[0016] The material of the outer conductor arrangement can typically include a ferromagnetic alloy, for example stainless steel material (e.g. super duplex or Inconel).
[0017] In some embodiments, the outer conductor arrangement can comprise a plurality of outer conductor strands. This is in contrast with known skin-effect heating cables where the outer conductor arrangement is a ferromagnetic tube with an insulated heating cable arranged loosely inside the tube.
[0018] By using conductor strands as the outer conductor arrangement, the skin- effect heating cable will be more flexible. This will for instance facilitate winding and unwinding on a reel. Moreover, it will have increased tolerance to repeated dynamic movements (i.e. it can tolerate an increased number of repeated bending movements). The material of the conductor strands in the outer conductor arrangement can be a ferromagnetic material.
[0019] In embodiments where the outer conductor arrangement comprises outer conductor strands, the outer conductor arrangement can further comprise outer conductor spaces between the outer conductor strands. In such embodiments, an outer conductor space material can be arranged in the outer conductor spaces, wherein the outer conductor space material is a ferromagnetic material.
[0020] In such embodiments, where the outer conductor space material is a ferromagnetic material, the outer conductor space material can comprise a ferromagnetic plastic material or a ferromagnetic composite material.
[0021 ] The outer conductor space material can be a ferromagnetic fluid. Advantageously, the ferromagnetic fluid can be a high viscosity fluid.
[0022] In embodiments where the outer conductor space material comprises a ferromagnetic fluid, the ferromagnetic fluid can comprise bitumen.
[0023] Furthermore, the ferromagnetic fluid, the ferromagnetic plastic material, or the ferromagnetic composite material can in some embodiments comprise ferromagnetic nanoparticles or monodispersed ferromagnetic particles.
[0024] Preferably, the inner conductor arrangement can comprise strands of a non- ferrous metal, such as copper strands. In some embodiments, however, the inner conductor arrangement may be of ferrous metal, for instance the same material as in the outer conductor arrangement.
[0025] An optical fiber can be arranged with the inner conductor arrangement, with the outer conductor arrangement, or with the inner insulation arrangement. Typically, an optical fiber can be used for monitoring temperature and/or for fault monitoring.
[0026] In some embodiments including said outer conductor strands, some of or all the outer conductor strands can have a polygonal cross section.
[0027] Providing the outer conductor strands with such a shape will reduce the outer conductor spaces and consequently increase the density of ferromagnetic material in the outer conductor arrangement. In some embodiments, the outer conductor strands can have a rectangular or triangular cross section. Other shapes are also possible, for instance cross sections having a pentagon or hexagon shape.
[0028] The outer conductor strands can comprise a ferromagnetic alloy. Advantageously, the ferromagnetic alloy can be a soft ferromagnetic alloy.
[0029] In other embodiments, the outer conductor arrangement can comprise a seam-welded tube. In such embodiments, the inner insulation arrangement, possibly together with further components, will be fixed between the seam-welded tube and the inner conductor arrangement.
[0030] In some embodiments including the seam-welded tube, the seam-welded tube can be enclosed in a corrosion-protective sheath.
[0031] According to a second aspect of the invention, there is provided a pipe assembly comprising a pipeline and an assembly jacket. One or more skin-effect heating cables according to the first aspect of the invention are arranged between the pipeline and the assembly jacket.
[0032] One or more skin-effect heating cables can in some embodiments be wound about the pipeline with a helix configuration or with an alternating helix configuration.
[0033] An alternating helix configuration involves succeeding helix configurations along the pipeline, wherein the direction of helical rotation is changed repeatedly along the axial length of the pipeline.
[0034] According to a third aspect of the invention, there is provided a method of heating, comprising conducting electric current through the inner conductor arrangement of the skin-effect heating cable according to the first aspect of the invention.
Detailed description of the invention
[0035] While various features of the invention have been discussed above, a non limiting example of embodiment will be presented in the following with reference to the drawings, wherein
Fig. 1 is a perspective schematic view of a skin-effect heating assembly according to the prior art;
Fig. 2 is a cross section view through a skin-effect heating cable according to the present invention;
Fig. 3 is a cross section view through another skin-effect heating cable according to the present invention;
Fig. 4 is an enlarged portion of the view shown in Fig. 3;
Fig. 5 is a cross section view through a pipe assembly comprising a skin-effect heating assembly according to the invention;
Fig. 6 is a perspective view illustrating the assembly shown in Fig. 5;
Fig. 7 is a cross section view through an alternative embodiment of the invention; and
Fig. 8 is a cross section view through yet another embodiment of the invention.
[0036] Fig. 1 shows a principle drawing of a skin-effect heat tracing system (STS) heating arrangement 100 according to prior art. The STS heating arrangement 100 comprises an insulated cable 101 that is arranged inside an outer ferromagnetic tube 103. Typically, the ferromagnetic tube 103 will be a steel tube. The insulated cable 101 comprises an inner conductor 105, typically of a non-ferromagnetic metal, such as copper. Outside the inner conductor 105, there is an insulating material 107. As shown in Fig. 1 , the insulated cable 101 is arranged loosely inside the ferromagnetic tube 103.
[0037] When an alternating current is transmitted through the insulated cable 101 , heat will be generated in the ferromagnetic tube 103. Current can be transferred in the insulated cable 101 while a return-current or opposite current can be transferred in the ferromagnetic tube 103.
[0038] Due to the skin-effect, the current flowing though the ferromagnetic tube 103 will flow in the portion close to the inner face of the bore of the tube. The ferromagnetic tube 103 will be heated, and the generated heat can be transferred to other components, such as a steel pipeline, by heat convection.
[0039] Reference is now made to Fig. 2, which depicts a cross section through a skin-effect heating cable 1 according to the present invention. The skin-effect heating cable 1 has an inner conductor arrangement 5, which is arranged within an inner insulation 7. The inner insulation 7 is made of an electrically insulating material. The inner conductor arrangement 5 comprises a plurality of inner conductor strands 51. The conductor strands 51 are advantageously made of a non-ferrous metal, such as copper. As can be appreciated from Fig. 2, formed between the inner conductor strands 51 are inner conductor spaces 53. Advantageously, the inner conductor spaces 53 can be filled with an inner conductor space material. The inner conductor space material can for instance be one or more of the following materials: waxes, epoxies, RTV silicones, specialty asphalts, rubber modified asphalts, butyl rubber sealants, solvent based coatings, water-based coatings and hydrocarbon resins.
[0040] The skin effect heating cable 1 has an outer jacket 4, a sleeve or similar. Between the outer jacket 4 and the inner insulation 7 there is an outer conductor arrangement 3. The outer conductor arrangement 3 comprises a plurality of outer
conductor strands 31. The outer conductor strands 31 are of a ferrous material, such as steel.
[0041] The outer conductor strands 31 can be in the form of solid rods or solid elongated members having for instance a circular or polygonal cross section. Alternatively, the outer conductor strands 31 can also be in the form of wire bundles 32, wherein each wire bundle comprises a plurality of wires. Such wire bundles 32 can also have a circular or polygonal cross section.
[0042] Referring still to Fig. 2, formed between the conductor strands 31 are outer conductor spaces 33. Advantageously, the outer conductor spaces 33 are filled with an outer conductor space material. The outer conductor space material can advantageously be a ferrous material. Preferably, the outer conductor space material can be a material with ferrofluid or ferromagnetic-fluid properties. It may be a ferrofluid. Advantageously, it may be a high viscosity ferrofluid.
[0043] By filling the outer conductor spaces 33 with a ferrous material, the ferrous material will together with the outer conductor strands 31 magnetically enclose the inner conductor arrangement 5. This will enhance the heat generation in the inner portion of the outer conductor arrangement 3. In other words, the combination of outer conductor strands 31 and the intermediately arranged outer conductor space material will act as one single magnetic body that encircles the inner conductor arrangement 5.
[0044] The outer jacket 4 can preferably be made of a material suitable for heat convection, to transport heat generated in the outer conductor arrangement 5 to adjacent components.
[0045] Fig. 3 and Fig. 4 depict an embodiment where the conductor strands 31 of the outer conductor arrangement 3 have a polygonal cross section. In this embodiment, the outer conductor strands 31 have a rectangular cross section. By providing the outer conductor strands 31 with a polygonal cross section, the volume of the outer conductor spaces 33 can be reduced. Large parts of adjacent outer conductor strands 31 can abut against each other, thereby reducing the need for the outer conductor space material to magnetically “seal” or connect the outer conductor strands 31 to each other.
[0046] Fig. 4 depicts an embodiment where the outer conductor strands 31 are in form of wire bundles 32, as briefly discussed above. Several wires are indicated in one of the outer conductor strands 31.
[0047] Fig. 5 and Fig. 6 depict an embodiment where skin-effect heating cables 1 according to the invention are used as a part of a pipe assembly 10. The pipe assembly 10 has a pipe 11 configured to carry a hydrocarbon-containing fluid. Typically, such fluid can be a fluid produced from a subsea or onshore hydrocarbon well. As is known to the skilled person, such hydrocarbon-containing fluids may tend to solidify at low temperatures. Thus, one may need to provide heating of the pipe 11 to avoid solidification.
[0048] Fig. 7 and Fig. 8 show an alternative embodiment of the skin-effect heating cable 1 according to the invention. In this embodiment, the outer conductor arrangement is in the form of a tube 3. The inner insulation 7 completely fills the space (annulus) between the inner conductor arrangement 5 and the outer conductor arrangement 3. In other embodiments, there may be additional filler elements in addition to the inner insulation 7, which together with the inner insulation 7 completely fills the pace between the inner and outer conductor arrangements 3, 5.
[0049] When manufacturing the skin-effect heating cable 1 shown in Fig. 7 and in Fig. 8, the tube 3 can be folded onto the inner insulation 7 and welded into the tube shape with the welding seam 90. In this manner, the length of the produced skin- effect heating cable 1 can be made long. In some embodiments, the welding seam 90 can be provided by laser welding.
[0050] The material of the outer conductor arrangement, i.e. the tube 3, should thus be possible to form into the tubular shape and welded. Both the material of the tube 3 and the material of the welding seam 90 must be of an appropriate material, enabling use of the skin-effect.
[0051] Examples of material in the tube 3 shown in Fig. 7 and Fig. 8 include corrosion-resistant steel alloys, such as alloys sold under the name Inconel or alloys known as super duplex.
[0052] As shown in Fig. 7 and Fig. 8, embedded in the inner insulation there is an optical fiber 61 configured for temperature monitoring.
[0053] Further presented herein is a method of manufacturing a pipe assembly 10 having a pipeline 11 , an assembly jacket 41 and one or more skin-effect heating cables 1 positioned between the pipeline and the assembly jacket. The method includes providing the one or more skin-effect heating cable 1 by enclosing an inner conductor arrangement 3 within an inner insulation 7, and further enclosing the inner insulation 7 inside a seam-welded tube 5, during assembly of the further components of the pipe assembly 10. Such further components of the pipe assembly comprise said pipeline 11 and assembly jacket 41 , and possible additional components such as for instance optic fiber, filler material, electric power cable.
Claims
1. A skin-effect heating cable (1) comprising
- an inner conductor arrangement (5);
- an outer conductor arrangement (3) comprising a material configured to generate heat through hysteresis losses when exposed to an alternating magnetic field;
- an inner insulation (7) arranged between the inner conductor arrangement (5) and the outer conductor arrangement (3); characterized in that the mutual position of the inner conductor arrangement (5) and the outer conductor arrangement (3) is fixed along the axial direction.
2. A skin-effect heating cable (1) according to claim 1 , characterized in that the outer conductor arrangement (3) comprises a plurality of outer conductor strands (31).
3. A skin-effect heating cable (1) according to claim 2, characterized in that it further comprises outer conductor spaces (33) between the outer conductor strands (31), and that an outer conductor space material is arranged in the outer conductor spaces (33), wherein the outer conductor space material is a ferromagnetic material.
4. A skin-effect heating cable (1) according to claim 3, characterized in that the outer conductor space material is a ferromagnetic plastic or a ferromagnetic composite material.
5. A skin-effect heating cable (1 ) according to claim 3, characterized in that the outer conductor space material is a ferromagnetic fluid.
6. A skin-effect heating cable (1) according to claim 5, characterized in that the ferromagnetic fluid comprises bitumen.
7. A skin-effect heating cable (1) according to claim 4, claim 5 or claim 6, characterized in that the ferromagnetic fluid, the plastic material, or the composite material comprises - ferromagnetic nanoparticles; or
- monodispersed ferromagnetic particles.
8. A skin-effect heating cable (1) according to one of the preceding claims, characterized in that an optical fiber (61) is arranged with the inner conductor arrangement (5) or with the outer conductor arrangement (3).
9. A skin-effect heating cable (1) according to any one of claims 2 to 8, characterized in that some of or all of the outer conductor strands (31) have a polygonal cross section.
10. A skin-effect heating cable according to claim 1 , characterized in that the outer conductor arrangement (3) comprises a seam-welded tube.
11. A skin-effect heating cable according to claim 10, characterized in that the seam-welded tube (3) is enclosed in a corrosion-protective sheath (4).
12. A pipe assembly (10) comprising a pipeline (11 ) and an assembly jacket (41), wherein one or more skin-effect heating cables (1) according to one of the preceding claims are arranged between the pipeline and the assembly jacket.
13. A pipe assembly (10) according to claim 12, wherein the one or more skin- effect heating cables (1) is/are wound about the pipeline (11) with a helix configuration or with an alternating helix configuration.
14. A method of heating, comprising conducting electric current through the inner conductor arrangement (5) of the skin-effect heating cable (1 ) according to one of the preceding claims 1 to 11.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB2208920.5A GB2605722A (en) | 2019-12-11 | 2020-12-11 | Skin-effect heating cable |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO20191471 | 2019-12-11 | ||
| NO20191471 | 2019-12-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2021116374A1 true WO2021116374A1 (en) | 2021-06-17 |
Family
ID=76329367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/EP2020/085703 WO2021116374A1 (en) | 2019-12-11 | 2020-12-11 | Skin-effect heating cable |
Country Status (2)
| Country | Link |
|---|---|
| GB (1) | GB2605722A (en) |
| WO (1) | WO2021116374A1 (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006115943A1 (en) * | 2005-04-22 | 2006-11-02 | Shell Internationale Research Maatschappij B.V. | Grouped exposed metal heaters |
| WO2008131168A1 (en) * | 2007-04-20 | 2008-10-30 | Shell Oil Company | Electrically isolating insulated conductor heater |
| CN1717529B (en) * | 2002-10-24 | 2010-05-26 | 国际壳牌研究有限公司 | Method and system for heating underground or wellbores |
| US20110247817A1 (en) * | 2010-04-09 | 2011-10-13 | Ronald Marshall Bass | Helical winding of insulated conductor heaters for installation |
| US20150237679A1 (en) | 2009-04-02 | 2015-08-20 | Pentair Thermal Management Llc | Mineral Insulated Skin Effect Heating Cable |
| EP3068191A1 (en) * | 2015-03-12 | 2016-09-14 | Mikhail Leonidovich Strupinskiy | Skin-effect based heating cable, heating unit and method |
| US20180184487A1 (en) | 2016-05-10 | 2018-06-28 | Pentair Flow Services Ag | Shielded Fluoropolymer Wire for High Temperature Skin Effect Trace Heating |
-
2020
- 2020-12-11 WO PCT/EP2020/085703 patent/WO2021116374A1/en active Application Filing
- 2020-12-11 GB GB2208920.5A patent/GB2605722A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1717529B (en) * | 2002-10-24 | 2010-05-26 | 国际壳牌研究有限公司 | Method and system for heating underground or wellbores |
| WO2006115943A1 (en) * | 2005-04-22 | 2006-11-02 | Shell Internationale Research Maatschappij B.V. | Grouped exposed metal heaters |
| WO2008131168A1 (en) * | 2007-04-20 | 2008-10-30 | Shell Oil Company | Electrically isolating insulated conductor heater |
| US20150237679A1 (en) | 2009-04-02 | 2015-08-20 | Pentair Thermal Management Llc | Mineral Insulated Skin Effect Heating Cable |
| US20110247817A1 (en) * | 2010-04-09 | 2011-10-13 | Ronald Marshall Bass | Helical winding of insulated conductor heaters for installation |
| EP3068191A1 (en) * | 2015-03-12 | 2016-09-14 | Mikhail Leonidovich Strupinskiy | Skin-effect based heating cable, heating unit and method |
| US20190045587A1 (en) | 2015-03-12 | 2019-02-07 | Mikhail Leonidovich Strupinskiy | Skin-effect based heating cable, heating unit and method |
| US20180184487A1 (en) | 2016-05-10 | 2018-06-28 | Pentair Flow Services Ag | Shielded Fluoropolymer Wire for High Temperature Skin Effect Trace Heating |
Also Published As
| Publication number | Publication date |
|---|---|
| GB202208920D0 (en) | 2022-08-10 |
| GB2605722A (en) | 2022-10-12 |
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