EP1010185B1 - Mineralisoliertes kabel - Google Patents

Mineralisoliertes kabel Download PDF

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Publication number
EP1010185B1
EP1010185B1 EP98903200A EP98903200A EP1010185B1 EP 1010185 B1 EP1010185 B1 EP 1010185B1 EP 98903200 A EP98903200 A EP 98903200A EP 98903200 A EP98903200 A EP 98903200A EP 1010185 B1 EP1010185 B1 EP 1010185B1
Authority
EP
European Patent Office
Prior art keywords
mineral
cable
silicone oil
insulant
mineral insulant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP98903200A
Other languages
English (en)
French (fr)
Other versions
EP1010185A1 (de
Inventor
Edward Deegan
James Freestone
Carl Griffiths
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nvent Solutions UK Ltd
Original Assignee
Tyco Thermal Control UK Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tyco Thermal Control UK Ltd filed Critical Tyco Thermal Control UK Ltd
Publication of EP1010185A1 publication Critical patent/EP1010185A1/de
Application granted granted Critical
Publication of EP1010185B1 publication Critical patent/EP1010185B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/004—Apparatus or processes specially adapted for manufacturing conductors or cables for manufacturing rigid-tube cables

Definitions

  • This invention relates to the manufacture of mineral insulated electrical cables, that is to say, cables which comprise at least one elongate electrical conductor and a surrounding metal sheath, the or each elongate conductor being insulated from the sheath, and from any other conductor, by means of compacted mineral insulating powder.
  • Such cables have been manufactured for many years, and are widely employed for example where performance may be needed at high temperatures for indefinite periods, such as in systems intended to operate during fires.
  • the cables were originally manufactured by a so-called 'vertical-fill' process in which the conductors are inserted into a vertically oriented metal tube, and mineral insulant is poured into the tube while compacting it, to form a cable preform.
  • the cable preform is then subjected to a number of die drawing and annealing operations to reduce its cross-sectional area by about 99%, thereby to form the finished cable.
  • manufacturing economics have required a move to continuous processes, at least for the more commonly sold sizes of cable.
  • EP-A-0 384 778 One such process is described in EP-A-0 384 778, in which a strip of metal and one or more elongate conductors are transported along their length and the strip is continuously formed into a tube that encloses the or each conductor, opposed longitudinally extending edges of the strip are welded together, mineral insulant is inserted into the tube to form a cable preform, and the cable preform is subjected to one or more reduction operations in which its diameter is reduced to form the cable. Reduction operations have traditionally been performed in the 'vertical-fill' method by pulling the cable preform through a number of dies, the steps being separated by annealing stages.
  • the die reduction stage is replaced by banks of shaped rollers arranged in pairs about the cable preform, alternate roller pairs in each bank being arranged at 90° to one another, so that the cross-sectional area of the preform is reduced by about 40 to 70 percent as it passes through each bank of rollers.
  • An annealing stage is located between the banks of rollers and after the last bank of rollers.
  • the drawing stage will comprise three banks of rollers, each with 14 pairs of rollers, and three annealing stages. Whichever process is used, annealing temperatures lying in the range of 450 to 650°C are normally employed, depending on the speed of the cable preform through the annealing stage.
  • GB-A-2056158 discloses a mineral insulated cable, the mineral insulator being impregnated with heat-resisting silicone oil.
  • the present invention provides a method of forming a mineral insulated cable as claimed in claim 1.
  • the method according to the invention enables the manufacture of a mineral insulated cable in which the intrinsic hydrophilic nature of the mineral insulant is removed, so that moisture ingress at the ends of the cable or in the event of damage to the sheath is prevented. Furthermore, rendering the mineral insulant hydrophobic according to the process of the present invention does not affect the flowability of the mineral insulant powder (before compaction by the drawing stage) to any significant extent, so that the cable can be manufactured by a dry-filling process (i.e. by a process in which the mineral insulant is introduced into the tube as a free-flowing powder, as distinct from processes in which the mineral insulant is formed into a paste), for example by the "vertical-fill" or continuous process as described above.
  • a dry-filling process i.e. by a process in which the mineral insulant is introduced into the tube as a free-flowing powder, as distinct from processes in which the mineral insulant is formed into a paste
  • the method according to the invention is preferably conducted so that the cable preform does not reach a temperature exceeding 400°C and especially not exceeding 380°C during the annealing steps, since to high annealing temperatures will degrade the polymerised silicone coating on the mineral insulant.
  • Annealing temperatures quoted herein are the temperatures reached by the mineral insulant in the cable preforms rather than the annealing furnace temperatures, since the temperature reached by the cable preforms will depend inter alia on the dwell time in the furnace.
  • the annealing temperature is preferably at least 350°C.
  • the annealing temperatures employed in the process according to the present invention are significantly lower than those employed conventionally, for example in the region of 575°C, in order to prevent any degradation of the polymerised silicone in the mineral insulant.
  • the silicone oil is preferably purely aliphatic, and is preferably a medium molecular weight aliphatic silicone.
  • the silicone oil is added to the mineral insulant during the coating step to an amount of not more than 5%, by weight (based on the total weight of the mineral insulant and the silicone oil).
  • a relatively low quantity such as this is used in order to reduce or prevent any gas evolution from the end of the cable or from any damaged portion of the cable sheath during prolonged exposure to fire.
  • the silicone oil is employed in an amount of not more than 2% by weight and especially not more than 1% by weight.
  • the silicone oil is normally employed in an amount of at least 0.2% by weight since quantities significantly below this may not provide sufficient hydrophobic nature to the mineral insulant, and more preferably at least 0.5% by weight (all percentages being based on the total weight of the mineral insulant and the silicone oil). Normally the quantity of silicone oil used will be 0.75% by weight.
  • the process according to the present invention is applicable to the production of mineral insulated cables employing any mineral insulant, for example magnesium oxide, alumina or boron nitride.
  • any mineral insulant for example magnesium oxide, alumina or boron nitride.
  • materials such a magnesium oxide have the disadvantage, at least in some applications where the cable is intended to carry signals instead of, or in addition to electrical power, that the relative permitivity ( ⁇ r ) of the mineral insulant is relatively high (in the region of 4.6 for magnesium oxide) with the result that the capacitance of the cable is relatively high and its characteristic impedance relatively low.
  • the mineral insulant it is preferred, at least in some cases, for the mineral insulant to have a relatively low relative permitivity, for example of not more than 3.
  • the mineral insulant comprises amorphous silica (which has a relative permitivity in the region of about 2.3).
  • the mineral insulant more preferably comprises at least 80% by weight amorphous silica, most preferably at least 90% by weight silica, and especially substantially entirely silica (based on the total inorganic content).
  • conventional mineral insulants such as magnesium oxide, alumina and boron nitride may be employed, preferably magnesium oxide.
  • particulate amorphous (fused) silica mineral insulant is mixed for about 15 to 20 minutes with 0.75% by weight medium weight silicone oil (DC 1107 sold by Dow Corning), and the coated silica is heat treated for one hour at 150°C in order to polymerise the silicone oil and drive off any hydrogen gas generated during the polymerisation.
  • a length of a mineral insulated cable preform is then formed by a "vertical-fill" method in which a copper tube of 50 to 60 mm diameter is held vertically and a solid copper conductor is held inside the tube by means of a die at the bottom of the conductors so that it is spaced from the tube.
  • the coated mineral insulant which is freely-flowable after polymerisation of the silicone oil, is introduced into the tube an packed down at the bottom by vertical oscillation of the die. As more mineral insulant is introduced into the tube, the die rises, and introduction of the insulant is terminated when the die reaches the top of the tube.
  • the cable preform so formed is then subjected to a number of drawing steps in which the preform is pulled through dies of decreasing diameter so that the diameter of the preform is reduced from the original 50 to 60 mm down to about 5 mm (about 30 die drawing steps). After each two to three draws, the preform is annealed at 375°C for about one hour.
  • the invention provides a mineral insulated cable as claimed in claim 10.
  • Preferred materials, designs and compositions for the cable are as described above.
  • the cables have been described only with reference to one sheath, it is quite possible for the cable to include more than one sheath, for example to be in the form of a triax cable.

Landscapes

  • Insulated Conductors (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Organic Insulating Materials (AREA)

Claims (14)

  1. Verfahren zum Bilden eines mineralisolierten Kabels, umfassend:
    (i) Beschichten eines besonderen mineralischen Isolierstoffs mit nicht mehr als 5 Gewichtsprozent eines unvernetzten Silikonöls, basierend auf dem Gesamtgewicht des mineralischen Isolierstoffs und des Silikonöls,
    (ii) Unterziehen des beschichteten mineralischen Isolierstoffs einem Wärmebehandlungsschritt, damit das Silikonöl mindestens teilweise polymerisiert wird und ein beliebiger Wasserstoff, der während der Polymerisation entsteht, entfernt werden kann;
    (iii) Einführen des sich ergebenden mineralischen Isolierstoffs in ein Metallrohr, das einen oder mehrere verlängerte Leiter umfasst, die sich entlang seiner Länge erstrecken, um eine Kabelvorform zu bilden, wobei der oder jeder Leiter mittels des mineralischen Isolierstoffs gegen das Rohr und gegen jeden Leiter isoliert ist / sind, der vorhanden sein kann; und
    (iv) Unterziehen der Kabelvorform mehreren Zieh- und Temperschritten, wobei die Vorform im Durchmesser verringert wird, wobei die Temperschritte so sind, dass die Kabelvorform keine Temperatur erreicht, die die 450 °C übersteigt;
  2. Verfahren nach Anspruch 1, wobei die Kabelvorform während der Temperschritte keine Temperatur erreicht, die über 400 °C liegt.
  3. Verfahren nach Anspruch 1 oder 2, wobei mindestens ein größerer Teil des mineralischen Isolierstoffs ein Mineral umfasst, das eine relative Permittivität von nicht mehr als 3 besitzt.
  4. Verfahren nach Anspruch 3, wobei mindestens ein größerer Teil des mineralischen Isolierstoffs amorphes Siliziumoxid umfasst.
  5. Verfahren nach einem der Ansprüche 1 bis 4, wobei der mineralische Isolierstoff nicht mehr als 2 Gewichtsprozent Silikonöl umfasst.
  6. Verfahren nach Anspruch 5, wobei der mineralische Isolierstoff nicht mehr als 1 Gewichtsprozent Silikonöl umfasst.
  7. Verfahren nach einem der Ansprüche 1 bis 6, wobei der mineralische Isolierstoff mindestens 0,2 Gewichtsprozent Silikonöl umfasst.
  8. Verfahren nach Anspruch 7, wobei der mineralische Isolierstoff mindestens 0, 5 Gewichtsprozent Silikonöl umfasst.
  9. Verfahren nach einem der Ansprüche 1 bis 8, wobei das Silikonöl ein aliphatisches Silikonöl ist.
  10. Mineralisoliertes Kabel, das ein Metallrohr, einen oder mehrere verlängerte Leiter, die sich innerhalb des Rohrs befinden und die sich entlang der Länge des Rohrs erstrecken und einen mineralischen Isolierstoff umfasst, der das Rohr füllt und der den oder die Leiter gegen das Rohr und (wenn mehr als ein Leiter vorhanden ist) gegen einander isoliert, wobei der mineralische Isolierstoff Teilchen umfasst, die mit nicht mehr als 5 Gewichtsprozent eines polymerisierten Silikonöls, basierend auf dem Gesamtgewicht des mineralischen Isolierstoffs und des Silikonöls, beschichtet ist.
  11. Kabel nach Anspruch 10, wobei der mineralische Isolierstoff eine relative Permittivität von nicht mehr als 3 besitzt.
  12. Kabel nach Anspruch 10 oder 11, wobei mindestens ein größerer Teil des mineralischen Isolierstoffs amorphes Siliziumoxid umfasst.
  13. Kabel nach einem der Ansprüche 10 bis 12, wobei der mineralische Isolierstoff nicht mehr als 2 Gewichtsprozent des polymerisierten Silikonöls umfasst.
  14. Kabel nach einem der Ansprüche 10 bis 13, wobei der mineralische Isolierstoff mindestens 0,5 Gewichtsprozent des polymerisierten Öls umfasst.
EP98903200A 1997-02-12 1998-02-12 Mineralisoliertes kabel Expired - Lifetime EP1010185B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9702827 1997-02-12
GBGB9702827.8A GB9702827D0 (en) 1997-02-12 1997-02-12 Mineral insulated cable
PCT/GB1998/000438 WO1998036425A1 (en) 1997-02-12 1998-02-12 Mineral insulated cable

Publications (2)

Publication Number Publication Date
EP1010185A1 EP1010185A1 (de) 2000-06-21
EP1010185B1 true EP1010185B1 (de) 2005-11-02

Family

ID=10807465

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98903200A Expired - Lifetime EP1010185B1 (de) 1997-02-12 1998-02-12 Mineralisoliertes kabel

Country Status (4)

Country Link
EP (1) EP1010185B1 (de)
AU (1) AU6001498A (de)
GB (1) GB9702827D0 (de)
WO (1) WO1998036425A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104779017A (zh) * 2015-04-01 2015-07-15 江苏港宏电线电缆有限公司 一种线缆过粉干燥设备
CN105609213A (zh) * 2015-12-21 2016-05-25 无锡裕德电缆科技有限公司 一种矿物绝缘电缆的制备方法
CN115331868B (zh) * 2022-07-15 2023-06-20 广东南缆电缆有限公司 一种挤出型二氧化硅绝缘耐火电缆

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8003259A (nl) * 1979-07-27 1981-01-29 Okazaki Mfg Co Ltd Kabelsamenstel, werkwijze voor het vervaardigen daarvan.
GB9010582D0 (en) * 1990-05-11 1990-07-04 Ass Elect Ind Manufacture of mineral insulated electric cables

Also Published As

Publication number Publication date
WO1998036425A1 (en) 1998-08-20
GB9702827D0 (en) 1997-04-02
AU6001498A (en) 1998-09-08
EP1010185A1 (de) 2000-06-21

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