ZA200509270B - An electrical cable - Google Patents
An electrical cable Download PDFInfo
- Publication number
- ZA200509270B ZA200509270B ZA200509270A ZA200509270A ZA200509270B ZA 200509270 B ZA200509270 B ZA 200509270B ZA 200509270 A ZA200509270 A ZA 200509270A ZA 200509270 A ZA200509270 A ZA 200509270A ZA 200509270 B ZA200509270 B ZA 200509270B
- Authority
- ZA
- South Africa
- Prior art keywords
- electrical cable
- fuel
- layer
- fuel barrier
- barrier layer
- Prior art date
Links
- 239000000446 fuel Substances 0.000 claims description 44
- 230000004888 barrier function Effects 0.000 claims description 24
- 239000000463 material Substances 0.000 claims description 12
- 238000009413 insulation Methods 0.000 claims description 9
- -1 polyethylene Polymers 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 6
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 6
- 229940058401 polytetrafluoroethylene Drugs 0.000 claims description 6
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 6
- 239000004698 Polyethylene Substances 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000004743 Polypropylene Substances 0.000 claims description 4
- 239000012466 permeate Substances 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- 239000004677 Nylon Substances 0.000 claims description 3
- 239000004020 conductor Substances 0.000 claims description 3
- 229920001778 nylon Polymers 0.000 claims description 3
- 229920002449 FKM Polymers 0.000 claims description 2
- 238000000034 method Methods 0.000 description 16
- 230000008569 process Effects 0.000 description 13
- 239000000203 mixture Substances 0.000 description 8
- 238000003682 fluorination reaction Methods 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 229910052731 fluorine Inorganic materials 0.000 description 6
- 239000011737 fluorine Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 238000006467 substitution reaction Methods 0.000 description 5
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 4
- 125000001153 fluoro group Chemical group F* 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 238000000071 blow moulding Methods 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 229920001684 low density polyethylene Polymers 0.000 description 2
- 239000004702 low-density polyethylene Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 229920003020 cross-linked polyethylene Polymers 0.000 description 1
- 239000004703 cross-linked polyethylene Substances 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 229920001973 fluoroelastomer Polymers 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229920001179 medium density polyethylene Polymers 0.000 description 1
- 239000004701 medium-density polyethylene Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000012454 non-polar solvent Substances 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
- H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
- H01B7/2825—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable using a water impermeable sheath
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/14—Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables
Description
AN ELECTRICAL CABLE
This invention relates to an electrical cable.
Electrical cables to be used in fuel stations and storage depots have typically not been much different from electrical cables made for other applications.
The cables have included a drawn copper core which is used to conduct ! electricity and which is covered with pigmented PVC for core identification.
These cores are then embedded in a flexible PVC sheath followed by metal strand armouring and then a PVC outer sheath making up the cable.
In certain instances, the outer sheath may be formed from different materials such as a low density polyethylene or a cross linked polyethylene.
Alternatively, the outer sheath may be formed from another material which may give the cable a fire retardant characteristic.
It has been known for manufacturers to add an extra layer between the outer sheath and the metal armouring, namely a lead liner layer which results in a lead jacketed cable. Although the lead is fuel resistant, the outer sheath is open to attack by the fuel and tends to become brittle or dissolve in fuel.
Until recently, these kind of cables have been useful, but with the introduction of new additives in fuels such as toluene, xylens, acetone and
MEK as well as new unleaded fuels, materials which have commonly been known to work in the fuel environment have been failing.
CONFIRMATION COPY
Cables have started failing due to the additives dissolving the sheath and inner liners and exposing the copper core. Once exposed, the cores which carry electricity have been known to arc and create sparks which have . caused fires.
The problems are compounded when the cables are used to supply current to submersible pumps in manholes above underground tanks where fuel fumes rich in lower flashpoint compounds accumulate. When the manhole is opened daily to dip the tanks, air is introduced into the mixtures and an explosive mixture is obtained. The spark from the cable is all that is needed to ignite the mixture and heavy manhole covers have been known to be shot up into the air several metres, for example.
It is an object of the present invention to address this.
According to the present invention there is provided an electrical cable comprising: a core comprised of an electrical conducting material; at least one insulation layer surrounding the core; and a fuel barrier layer surrounding the insulation layer, the fuel barrier . layer being formed from a fuel barrier material which does not allow liquid fuel or fuel vapours to permeate therethrough, wherein the fuel barrier layer is the outermost layer of the electrical cable.
The electrical cable may further comprise an armour layer which may be formed from a metal.
The at least one insulation layer may be formed from a pigmented PVC.
Preferably, the fuel barrier layer is formed from a polyethylene or polypropylene material which has been fluorinated.
The fuel barrier layer may be formed from PolytetraFluoro Ethylene (PTFE) or Viton.
Alternatively, the fuel barrier layer may be formed from a nylon sheath. - Preferably, the fuel barrier layer is not dissolved or otherwise broken down by liquid fuel
The accompanying drawing is a schematic drawing of an electrical cable according fo the present invention )
Referring to the accompanying drawing, an electrical cable according to the present invention includes a core 10 comprised of an electrical conducting material, typically in the form of a drawn copper core. Although the cable in the accompanying drawing includes only one core 10, the cable could equally include a plurality of cores 10.
The core 10 is surrounded with at least one insulation layer in the form of a pigmented PVC layer 12 which is used for core identification.
The prototype of the present invention included a second insulation layer in the form of a flexible PVC sheath 14.
Furthermore, the prototype of the present invention also included an armour layer 16 typically formed from metal strands surrounding the other layers to protect them. It will be appreciated that this layer may not be necessary.
It is envisaged that the second insulation layer 12 and the armour layer 16 may not always be required and may be left out of the electrical cable for certain applications.
Finally, the electrical cable is surrounded by a fuel barrier layer 18 which is formed from a fuel barrier material which does not allow liquid fuel or fuel vapours to permeate therethrough and which is not dissolved in or otherwise broken down by liquid fuel. The fuel barrier layer is the outermost layer of the electrical cable
The fuel barrier layer is preferably formed from a high density polyethylene which has been fluorinated as will be described in more detail below.
It is envisaged that the fuel barrier layer 18 may also be formed from a low or medium density polyethylene which has been fluorinated or a polypropylene material which has been fluorinated.
Polypropylene is not preferred as it is more rigid and not as good a barrier as polysthylene.
A nylon sheet may also be used as the fuel barrier layer 18, but this is not preferred as it is relatively more expensive and is not as flexible.
Alternatively, the fuel barrier layer 18 may be made from other types of materials which are resistant to fuels and chemicals such as the fluoroelastomer Viton™.
The process known as fluorination is a chemical substitution process where hydrogen atoms bonded on the carbon chains of the polymer are substituted with fluorine molecules introduced into the process as elemental fluorine in a mixture with nitrogen gas. The process being one of chemical substitution induces chemical bonding of the carbon and fluorine atoms forming a PolytetraFluoro Ethylene molecule (PTFE) or better known as . Teflon™. Due to the substitution, the fluorine atoms are integrated into the matrix of the polymer and the change is thus permanent, and can not be delaminated as other methods used to reduce fuel permeation in polyethylene matrices. The process however only occurs on the surface of the polymer.
There are two methods of fluorination, namely in-line and off-line fluorination. The in-line process is only used when a blow moulding operation is active where the blowing gas (normally air) is replaced with a fluorine/nitrogen mixture. As no blow moulding operation is undertaken in the manufacture of cable, the off-line or post fluorination process is utilized.
The process requires the cable to be coiled onto a rack, which is then placed into a heated vacuum chamber (autoclave) where the internal atmosphere is changed by removing atmospheric air by way of vacuum with the reaction gases comprising of a fluorine/nitrogen mixture. The cable is left in this atmosphere for a period of time to allow the substitution to take place to the required calculated level. The level of fluorination is calculated by working out the surface area of the product to be fluorinated.
Once this is known, the amount of fluorine can be calculated by various analytical calculating methodologies and thus the correct mass of diluted fluorine is added into the reactor. The standing time of the product in the gas mixture is determined using previous data obtained by comparing the substitution ratio of carbon/fluorine atoms to the amount of un-reacted carbon/hydrogen atoms on the surface using a Fourier Turner Infrared
Spectrophotometer (FTIR) for the purpose. The ratio obtained is thus compared to existing results of control samples. The permeation characteristics of the control samples have been subjected to various international accreditation, which determines the amount permeation over an area of the product.
Permeation of any substance depends on four processes, namely wetting, compatibility, mobility (migration) and evaporation. If any of these steps can be stopped then permeation through the substance will not occur.
Wetting is the process whereby the solvent will wet the surface of the solid. in the present case, petrol wets the surface of polyethylene. This would mean that the solvent will penetrate the surface of the solid.
Compatibility means that if the solvent has the same polarity as the solid it will be able to be absorbed or the two will mix (polar solvent/polar solid or non-polar solvent/non-polar solid are compatible).
Mobility means that the molecules which are compatible must be able to move through the material, i.e. they should be small enough for them to pass in between the molecules of the solid.
Evaporation means that the solvent when it gets to the other side of the wall must be removed by a process e.g. evaporation, otherwise the polymer will become saturated and the process will stop
By stopping or limiting any one of the above processes, permeation will be halted. In the case of fluorination of the surface, the first step is halted, namely wetting and thus the permeation is halted at the surface.
The present invention has a number of advantages. Firstly, no fuel is allowed to permeate into the substrate of the polymeric sheath.
The fluorination layer is chemically bonded into the PE substrate, and therefore cannot wear off, or be delaminated.
The sheath is a cost effective sheath.
The material is easy to handle during the manufacturing process and avoids any excess layers being added to the cable.
The cable meets the South African Bureau of Standards 1507 requirements.
The cable is fuel and chemical resistant.
Claims (8)
1. An electrical cable comprising: a core comprised of an electrical conducting material; at least one insulation layer surrounding the core; and a fuel barrier layer surrounding the insulation layer, the fuel barrier layer being formed from a fuel barrier material which does not allow liquid fuel or fuel vapours to permeate therethrough, wherein the fuel barrier layer is the outermost layer of the electrical cable.
2. An electrical cable according to claim 1 further comprising an armour layer formed from a metal.
3. An electrical cable according to claim 1 or claim 2 wherein the at least one-insulation layer is formed from pigmented PVC.
4. An electrical cable according to any preceding claim wherein the fuel barrier layer is formed from a polyethylene or polypropylene material which has been fluorinated.
5. An electrical cable according to claim 4 wherein the fuel barrier layer is formed from PolytetraFluoro Ethylene (PTFE) or Viton.
6. An electrical cable according to claim 4 wherein the fuel barrier "layer is formed from a nylon sheath.
7. An electrical cable according to any preceding claim wherein the fuel barrier [ayer is not dissolved or otherwise broken down by liquid fuel.
8. An electrical cable substantially as herein described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA200509270A ZA200509270B (en) | 2003-05-16 | 2004-05-11 | An electrical cable |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA200303815 | 2003-05-16 | ||
| ZA200509270A ZA200509270B (en) | 2003-05-16 | 2004-05-11 | An electrical cable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| ZA200509270B true ZA200509270B (en) | 2007-01-31 |
Family
ID=33453100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| ZA200509270A ZA200509270B (en) | 2003-05-16 | 2004-05-11 | An electrical cable |
Country Status (2)
| Country | Link |
|---|---|
| WO (1) | WO2004102590A1 (en) |
| ZA (1) | ZA200509270B (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL9002602A (en) * | 1990-11-28 | 1992-06-16 | Nkf Kabel Bv | Electrical cable having good chemicals, oils and solvents resistance - contg core of electrical or fibre=optic conductors, thin polyester foil and wound metallic layer having synthetic resin layer on each side |
| FR2709592B1 (en) * | 1993-09-02 | 1996-02-02 | Pirelli Cables | Cable resistant to chemical attack. |
| DE19828501C2 (en) * | 1998-06-26 | 2001-10-04 | Eilentropp Kg | Electrical high-voltage line |
| WO2000074075A1 (en) * | 1999-06-02 | 2000-12-07 | Tyco Electronics Corporation | Insulated electrical conductor |
-
2004
- 2004-05-11 ZA ZA200509270A patent/ZA200509270B/en unknown
- 2004-05-11 WO PCT/IB2004/001490 patent/WO2004102590A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004102590A1 (en) | 2004-11-25 |
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