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GB2335304A - Electric or optic cable which evolves gas for fire protection - Google Patents

Electric or optic cable which evolves gas for fire protection Download PDF

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Publication number
GB2335304A
GB2335304A GB9805442A GB9805442A GB2335304A GB 2335304 A GB2335304 A GB 2335304A GB 9805442 A GB9805442 A GB 9805442A GB 9805442 A GB9805442 A GB 9805442A GB 2335304 A GB2335304 A GB 2335304A
Authority
GB
United Kingdom
Prior art keywords
cable
cable according
gas
blowing agent
chemical blowing
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.)
Withdrawn
Application number
GB9805442A
Other versions
GB9805442D0 (en
Inventor
Gregor Reid
Mark Froggatt
David Kemp
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.)
DELTA PLC
Original Assignee
DELTA PLC
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 DELTA PLC filed Critical DELTA PLC
Priority to GB9805442A priority Critical patent/GB2335304A/en
Publication of GB9805442D0 publication Critical patent/GB9805442D0/en
Priority to PCT/GB1999/000743 priority patent/WO1999048113A1/en
Priority to AU27404/99A priority patent/AU2740499A/en
Publication of GB2335304A publication Critical patent/GB2335304A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/44Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
    • G02B6/4401Optical cables
    • G02B6/4429Means specially adapted for strengthening or protecting the cables
    • G02B6/4436Heat resistant
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00Insulated conductors or cables characterised by their form
    • H01B7/17Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/29Protection against damage caused by extremes of temperature or by flame
    • H01B7/295Protection against damage caused by extremes of temperature or by flame using material resistant to flame

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Insulated Conductors (AREA)

Abstract

An electric or optic cable 11 comprises a copper conductor 10 surrounded by insulating layers 14 and 15 and an outer sheath 16. One of the insulating layers 14 or 15 incorporates a material, preferably a blowing agent which evolves a gas or gases at elevated temperatures. Preferably, in the event of a fire, the chemical blowing agent is activated to give off gases which cause the cable to swell to form a bulge 7. The bulge 7 provides a physical barrier to flame spread and heat propagation along the cable. The blowing agent may include sodium bicarbonate, azodicarbonamide, dinitrosopentamethylenetetramine, 4-4'-oxy-bis (benzenesulphonylhydrazide), trihydrazinotriazine, modified azodicarbonamide N,N dimethyl N, N dinitrosoterephthalamide or 5-phenyl tetrazole.

Description

2335304 1 CABLES The present invention relates to cables.
Cables, for example, power cables, and cables that transport electrical signals or data and optical fibres, are required to link parts of buildings. They are often laid in cavities or conduits which give free passage through walls, floors and ceilings. The materials that are used as electrical insulation in electric cables or as protective coatings for optical fibres are often of a type that supports combustion. During a fire a problem is caused if the insulation or coating of the cable is set alight. The fire can be quickly propagated along the cable through the conduits, passing under or through walls and thus spreading the fire. This will prevent containment of the fire resulting in rapid flame spread leading to increased damage to the building and greater endangerment to life. It is particularly important to reduce flame spread in areas of high airflow, for example ventilation shafts and plenums.
According to the present invention a cable comprises at least one conductor, and a layer or layers of material surrounding the conductor, the material including a material that evolves gas when the temperature is raised above normal ambient temperature to a temperature such as is experienced in the event of a fire.
f..\specspi b\3 93 68pab.98 2 The gas or gases evolved at elevated temperatures may retard flame spread by one or more of the following actions: by causing an increase in the cable volume which creates a physical barrier to flame spread, by causing the cable sheath to become discontinuous thus reducing the fuel for flame spread, or by introducing a non-flammable gas which displaces oxygen from around the cable and thus suffocates the flames.
In the case where the cable is an electric cable, the conductor is an electric conductor and the layer or layers of material will include electrical insulation. In the case where the cable is an optical cable the conductor is an optical fibre or bundle of optical fibres and the layers of material will include a coating to protect the optical fibre.
Preferably the material that evolves gas at elevated temperatures is a chemical blowing agent.
A chemical blowing agent is a material that produces a gas or gases, by its chemical decomposition, forming a cellular structure in a polymeric matrix. The decomposition process is usually exothermic, irreversible and takes place at elevated temperature, but in the case of certain chemical blowing agents, gas or gases are an endothermic reaction between two Examples of chemical blowing agents that released by components.
f:\specsp ib\3 93 68pab.98 3 evolve a gas or gases at suitable elevated temperatures include: sodium bicarbonate, azodicarbonamide, d i n i t r o s o p e n t a m e t h y 1 e n e t e t r a m i n e, 4,41-oxy-bis-(benzenesulphonylhydrazide), trihydrazinotriazine, modified azodicarbonamide, N,N dimethyl N, N dinitrosoterephthalamide or 5-phenyl tetrazole.
Preferably, the chemical blowing agent evolves a gas or gases that are non-flammable and/or non-toxic.
Preferably the chemical blowing agent decomposes at a temperature above 1800C.
Examples of the gases that are evolved by suitable chemical blowing agents are nitrogen, carbon dioxide, water (in the form of steam) and ammonia or a combination of some or all of the aforementioned gases.
Preferably, the chemical blowing agent will have a gas evolution of between 50 - 500 millilitres at normal atmospheric pressure per gram.
The material that evolves gas may be located within the insulation material, between the conductor and the layer of insulation, between further discrete layers of insulation within the insulation layer, or between the insulating layer and an external, sheath layer.
f:\specsp ib\3 93 68pab. 98 4 Where the material that evolves gas is formed as a separate layer it may be provided on a tape such as mica tape, or it may be incorporated into the cable by one or more of the following techniques: by surface dusting; by solution coating; or by spray coating.
In other embodiments the material that evolves gas may be located so that when the gas is evolved, at least a part of the insulating layer is maintained around the conductor, enabling electrical performance of the cable to be maintained at elevated temperature.
In some embodiments of the invention material that evolves gas at elevated temperatures is arranged in the cable that evolution of the gas causes at least a part of the insulation to become discontinuous.
The chemical blowing agent may be used in conjunction with an initiator or 'kicker, such as, for example, zinc stearate, calcium stearate, zinc oxide, or other metal salts. The initiator promotes decomposition of the chemical blowing agent at the decomposition temperature of the chemical blowing agent.
The present invention will now be described with reference to the accompanying drawings in which:
FIGURE 1 shows, in diagrammatic form, a section through f..\specsp ib\3 9 3 68pab. 9 8 a building showing a cable conduit; FIGURE 2 shows the cable conduit of figure 1 after exposure to a fire for a short period of time; FIGURE 3 shows, on an enlarged scale, a detailed cross section of a cable according to one embodiment of the present invention; FIGURE 4 shows, on an enlarged scale, a detailed cross section of a cable according to a second embodiment of the present invention; FIGURE 5 shows, on an enlarged scale, a detailed cross section of a cable according to a further embodiment of the present invention; FIGURE 6 shows, on an enlarged scale, a cable conduit provided with a cable according to an embodiment of the present invention; FIGURE 7 shows a section through a cable conduit provided with a cable according to a further embodiment of the present invention; and FIGURE 8 shows a section through a cable conduit provided with a cable according to a further embodiment of the present invention.
f..\specspib\393 68pab.98 6 Figure 1 shows a fragmentary view of a building with a cable conduit 2 containing a cable 1. The conduit leads through a wall 4 between adjoining rooms 6 and 9. A fire 3 has occurred in room 6 and is in the process of burning part of cable 1.
Figure 2 shows the same cable conduit as in f igure 1 after the cable 1 has been exposed to the fire 3 for a short period. The cable insulation or coating has caught light and the flame 5 has spread along the cable. Flames 5 have travelled along the cable through wall 4 via the conduit 2 and into the adjacent room 9.
Figure 3 shows a cross section of an electric cable 1 1 according to one embodiment of the present invention.
The cable 1 ' has a copper conductor 10, surrounded by insulating layers 14,15. The outer insulating layer is surrounded by sheath 16. One or more of the insulating layers may be a polymeric insulating layer. Examples of materials suitable for use as insulating layers 14,15 are silicone rubber, polyethylene and glass/mica tape. The outer sheath layer 16 may be a zero halogen, low smoke type protective layer. In this embodiment a chemical blowing agent is incorporated into the formulation of one or both of insulation layers 14 or 15. Examples of suitable chemical blowing agents that evolve a gas or gases at elevated temperatures include: sodium f.. \specspib\3 93 68pab. 98 7 b i c a r b o n a t e, a z o d i c a r b o n a m i d e dinitrosopentamethylenetetramine, 4,41-oxy-bis-(benzenesulphonylhydrazide), trihydrazinotriazine, modified azodicarbonamide, N,N dimethyl N, N dinitrosoterephthalamide or 5-phenyl tetrazole.
Figure 4 shows a cross section of a cable according to a further embodiment of the present invention, in which parts similar to the previous embodiment are denoted by like numbers. The chemical blowing agent in this embodiment is incorporated as a discrete layer 16 between the insulating layer 15 and the outer sheath 11. The chemical blowing agent may be impregnated into a layer of glass tape, or as a dusting/coating layer deposited on the layer 15. In other embodiments (not shown) the chemical blowing agent may be located as a discrete layer between the conductor 10 and the insulation layer 14, or between the insulation layers 14 and 15.
If the chemical blowing agent is present in the cable as an impregnated tape 16, it may be applied to the cable by a method such as winding or wrapping, rather than by extrusion. The former methods of application have the advantage that the chemical blowing agent is not heated when being applied onto the cable, and there is thus less risk that the chemical blowing agent may be activated prematurely, for example during manufacture.
f: \specspib\3 9 3 68pab. 98 Figure 5 shows a cross section of a cable 11 according to a further embodiment of the present invention. The chemical blowing agent in this embodiment is incorporated into the formulation of the outer sheath 11.
Figures 6 to 8 illustrate how cables according to the invention might behave when exposed to the elevated temperatures associated with a fire.
Figure 6 shows a cable conduit equipped with a cable 11 according to the present invention. The cable 1 1 has been exposed to a f ire. The high temperatures have activated the chemical blowing agent, causing the chemical blowing agent to evolve gas. The gas generated causes the cable coating to swell to form a bulge 7, thereby providing a physical barrier to flame spread and heat propagation along the cable 11.
When exposed to a fire, the outer surface of cable, for example the sheath layer, will become charred at area 8.
The charred area will not burn any further after it has become charred, thus forming a further physical barrier at the surface of the cable that protects the underlying insulation layers 14,15 and prevents any further insulation being burnt; the charring therefore reduces the amount of fuel that can come into contact with the flames.
f:\specspib\3 93 68pab. 98 9 Figure 7 shows a cable conduit equipped with a cable ill according to the present invention. A chemical blowing agent is included in the cable. The cable has been exposed to a fire and the elevated temperatures have caused the chemical blowing agent to evolve gas. The gas generated may make the cable coating shatter into fragments 12a, thus removing fuel from the proximity of the flames, or may crack the sheath thus making it discontinuous as illustrated in area 12b.
Figure 8 shows a cable conduit equipped with a cable 11 according to a further embodiment of the present invention. The cable includes a chemical blowing agent. During a fire, the chemical blowing agent evolves a gas because of the elevated temperatures. The gas may remove oxygen from the immediate proximity of the cable sheath and replace the oxygen with a nonflammable gas such as, for example, nitrogen, carbon dioxide, water (in the form of steam), ammonia, or a combination of some or all of the aforementioned gases. This in effect 'chokes" or,suffocates, the flames 5. The gas or gases evolved may also be flame retardant, thus having an additional fire quenching effect.
When exposed to a fire, the cable might behave in one or more of the ways illustrated in f igures 6 to 8 and described in the accompanying text.
f..\speesp ib\3 93 6 8pab. 98 The behaviour may depend on one or more combinations of the following factors:
i) The position or location of the chemical blowing agent within the cable; ii) The materials that are used to form the components of the cable; iii) The amount or proportion of chemical blowing agent, compared with the other constituents of the cable; iv) The temperature profile experienced by the cable within the fire (for example behaviour may depend on the rate of temperature change and whether the heating is localised or over a large area of the cable).
f:\specspib\3 93 68pab.98 W

Claims (19)

1. A cable comprising at least one conductor, and a layer or layers of material surrounding the conductor, the material including a material that evolves gas when the temperature is raised above normal ambient temperature to a temperature such as is experienced in the event of a fire.
2. A cable according to claim 1 in which the material that evolves gas at elevated temperatures is a chemical blowing agent.
3. A cable according to claim 2 in which the chemical blowing agent evolves a gas or gases that are non-flammable and/or non-toxic.
4. A cable according to claim 2 of 3 in which the chemical blowing agent decomposes at a temperature above HO'C.
5. A cable according to claim 2, 3 or 4 in which the chemical blowing agent has a gas evolution of between 50 - 500 millilitres at normal atmospheric pressure per gram.
6. A cable according to any of claims 1 to 5 in which the material also includes an initiator which promotes decomposition of the chemical blowing agent at the decomposition temperature of the chemical blowing agent.
W
7. A cable according to any of the preceding claims in which the cable is an electric cable, the conductor is an electric conductor and the layer or layers of material includes electrical insulation.
8. A cable according to claim 7 in which the material that evolves gas is located within the insulation material, between the conductor and the layer of insulation, between further discrete layers of insulation within the insulation layer, or between the insulating layer and an external, sheath layer.
9. A cable according to claim 7 or 8 in which the material that evolves gas at elevated temperatures is so arranged in the cable that evolution of the gas causes at least a part of the insulation to become discontinuous.
10. A cable according to any of claims 1 to 6 in which the cable is an optical cable, the conductor is an optical fibre or bundle of optical fibres and the layers of material includes a coating to protect the optical fibre.
-
1 1.
A cable according to any of the preceding claims in which the material that evolves gas when the temperature is raised is arranged to cause an increase in the cable volume so as to create a physical barrier to flame spread.
12. A cable according to any of the preceding claims in which the material that evolves gas when the temperature is raised is arranged to cause the cable sheath to become discontinuous, thus reducing the fuel for flame spread.
13. A cable according to any of the preceding claims in which the material, that evolves gas when the temperature 13, is raised introduces a non-flammable gas which displaces oxygen from around the cable and thus suffocates the flames.
14. A cable according to any of claims 2 to 10 in which the chemical blowing agent includes sodium barcarbonate, azodi-carbonamide, dinitrosopentamethylenetetramine, 4, 4 '-ox y-bis(benzenesulphonylhydrazide), trihydrazinotriazine, modified azodicarbonamide, N,N dimethyl N, N dinitrosoterephthalamide or 5-phenyl tetrazole.
15. A cable according to any of claims 1 to 10 in which the gas evolved by the material at elevated temperatures is nitrogen, carbon dioxide, water in the form of steam, ammonia or a combination of some or all of the aforementioned gases.
16. A cable according to any of the preceding claims in which the material that evolves gases is formed as a separate layer.
17. A cable according to claim 16 in which the separate layer comprises a tape.
18. A cable according to claim 16 in which the separate layer is formed by surface dusting, solution coating or by spray coating.
19. A cable substantially as herein before described with reference to the accompanying drawings.
GB9805442A 1998-03-13 1998-03-13 Electric or optic cable which evolves gas for fire protection Withdrawn GB2335304A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB9805442A GB2335304A (en) 1998-03-13 1998-03-13 Electric or optic cable which evolves gas for fire protection
PCT/GB1999/000743 WO1999048113A1 (en) 1998-03-13 1999-03-12 Cables
AU27404/99A AU2740499A (en) 1998-03-13 1999-03-12 Cables

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9805442A GB2335304A (en) 1998-03-13 1998-03-13 Electric or optic cable which evolves gas for fire protection

Publications (2)

Publication Number Publication Date
GB9805442D0 GB9805442D0 (en) 1998-05-13
GB2335304A true GB2335304A (en) 1999-09-15

Family

ID=10828543

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9805442A Withdrawn GB2335304A (en) 1998-03-13 1998-03-13 Electric or optic cable which evolves gas for fire protection

Country Status (3)

Country Link
AU (1) AU2740499A (en)
GB (1) GB2335304A (en)
WO (1) WO1999048113A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2436395A (en) * 2006-03-24 2007-09-26 Tyco Electronics A heat resistant cable

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2238578C1 (en) * 2003-10-08 2004-10-20 Общество с ограниченной ответственностью "ПетроЛайт" Fiber-optic cable for measuring temperature distribution in steam-forcing wells
CN112670020B (en) * 2020-12-15 2022-05-13 江苏赛德电气有限公司 From protection type fireproof cable

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1254580A (en) * 1968-12-05 1971-11-24 Stauffer Wacker Silicone Corp Electrical cables
GB2043326A (en) * 1979-02-26 1980-10-01 Kabel Metallwerke Ghh Fire resistant cable

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2105096C3 (en) * 1971-02-04 1975-02-20 Felten & Guilleaume Kabelwerke Ag, 5000 Koeln Use of a flame retardant compound
DE2915188C2 (en) * 1979-04-10 1983-02-17 Siemens AG, 1000 Berlin und 8000 München Plastic-insulated electrical cable with a flame-retardant inner sheath
DE3409369C2 (en) * 1984-03-12 1986-03-13 Siemens AG, 1000 Berlin und 8000 München Cable jacket for a communications cable
AU716298B2 (en) * 1996-07-08 2000-02-24 Nu-Chem, Inc. Platinum-containing thermal protective compositions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1254580A (en) * 1968-12-05 1971-11-24 Stauffer Wacker Silicone Corp Electrical cables
GB2043326A (en) * 1979-02-26 1980-10-01 Kabel Metallwerke Ghh Fire resistant cable

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DE3419352 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2436395A (en) * 2006-03-24 2007-09-26 Tyco Electronics A heat resistant cable

Also Published As

Publication number Publication date
WO1999048113A1 (en) 1999-09-23
AU2740499A (en) 1999-10-11
GB9805442D0 (en) 1998-05-13

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732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)