JPH11244404A - Fireproof structure of cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cables from burning at the time of a fire and prevent the medium of the spreading of the fire from spreading the fire by surrounding the cables laid inside of a pit by the use of a cable fire-spreading preventing sheet. SOLUTION: Plural cables 2 laid inside of a pit 1 are surrounded by the use of the cable fire-spreading preventing sheet 5, sandbags 6 are placed on the sheet 5 and the pit 1 is covered with a pit cover 4. On the other hand, the sheet 5 is used by being installed to cover the surface part of the cables 2 positioned on the outer most side and is used by collectively surrounding the plural cables 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire prevention method for a cable, and more particularly to a cable spread prevention sheet for preventing electric wires and cables laid inside a pit or a metal duct from spreading in a fire. It relates to the fire prevention structure of the used cable.

[0002]

2. Description of the Related Art It has been pointed out that electric wires and cables laid inside pits or metal ducts may be burned in the event of a fire and serve as a medium for spreading fire, thereby spreading the spread of fire. I have.

FIG. 6 is a schematic sectional view showing an example of a conventional cable fire prevention structure. In this conventional fire protection structure, a plurality of cables 2 laid inside a pit 1 are filled with sand 3 and covered with a pit cover 4.
The sand 3 prevents burning of the cable 2 in the event of a fire and prevents the cable 2 from acting as a medium for spreading the fire. Fire prevention by this fire prevention structure is performed every 2 m to 3 m along the extension direction of the cable 2, and exhibits an excellent effect.

However, in the fire prevention structure in which the sand 3 is filled, when the cable 2 is renewed or expanded,
Once the sand 3 inside the pit 1 is removed,
Perform processing such as updating or adding cable 2,
Thereafter, the work of refilling the sand 3 is necessary, which causes a problem that the workability is poor, which has been a problem.

[0005] The work of removing and filling the sand 3 may damage the cable 2 or the pit 1 laid inside the pit 1 or the periphery thereof, and the pit 1 where the cable 2 is laid is small. In many cases, machines cannot be used due to reasons such as a small work place and a possibility of adversely affecting the surroundings, and are generally performed manually. For this reason, in addition to the heavy labor, efficiency was poor and a problem had arisen. In addition, the sand 3 removed from the pit 1 causes a problem that the periphery of the pit 1 becomes dirty, which has been a problem. In particular, when the sand 3 is removed and filled indoors, the floor and walls in the room become dirty, and the dirt must be removed. Was.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention solves such a problem, reduces the time and effort required for updating or adding a cable 2, and furthermore, the inside of a pit 1 or a metal duct. It is an object of the present invention to provide a fire prevention structure for a cable 2 that can prevent an electric wire, a cable 2, and the like laid inside or the like from burning in the event of a fire and serving as a medium of fire spread. .

[0007]

The object of the present invention is to provide a cable fire prevention structure in which a cable laid inside a pit is surrounded by a cable spread prevention sheet. Solved by the fire protection structure of the cable, which is characterized by laid sandbags.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. In FIGS. 1 and 2, reference numeral 1 denotes a pit. A plurality of cables 2 laid inside the pit 1 are surrounded by a cable spread prevention sheet 5, and a sandbag 6 is placed on the cable spread prevention sheet 5. And is covered by a pit cover 4. As shown in FIG. 2, the sandbags 6 are placed at both ends of the cable spread prevention sheet 5 surrounding the plurality of cables 2 laid in the pit 1.

The pit 1 is a pit type which is one of the methods of laying an underground power cable.
And is constructed in advance in the ground using concrete or the like so as to correspond to the cable 2 to be laid.

On the other hand, the cable spread prevention sheet 5 comprises:
As shown in FIG. 1, the cable 2 is installed and used so as to cover a surface portion of the outermost cable 2 among a plurality of cables 2 laid inside the pit 1,
It is used by surrounding a plurality of cables 2 collectively. In addition, the cable spread prevention sheet 5 is used by surrounding the cable 2 along its entire length or intermittently along the extension direction of the cable 2.

When the cable spread prevention sheet 5 is used intermittently, the length of the cable 2 which is intermittently surrounded can be 0.5 m or more, but is not particularly limited. It is preferable to set it in the range of 2.0 m to 5.0 m. In this range, a sufficient fire spread prevention effect is obtained by the cable fire spread prevention sheet, and the construction is easy, which is preferable. On the other hand, if the length of the cable 2 that is intermittently surrounded is less than 0.5 m, it is not preferable because the effect of preventing the spread of fire cannot be sufficiently obtained.

As shown in FIG. 2, the sandbag 6 placed on the cable spread prevention sheet 5 covers the cable spread prevention sheet 5 so as to cover a distance of about 0.5 m from the end of the cable spread prevention sheet 5. It is placed and holds the cable spread prevention sheet 5. The sandbag 6 is one in which sand 3 and the like are packed in a bag or the like, and has an advantage that the sand 3 and the like can be handled as one lump when the sand 3 or the like is moved.

FIG. 3 shows an example of a cable spread prevention sheet used in the present invention.
Is a rubber sheet. The rubber sheet 7 is laminated and integrated with the metal sheet 8 to form the cable spread prevention sheet 5.
It has become. The rubber mixture forming the rubber sheet 7 includes:
Oxygen index (OI) is 28 or more, preferably 30 or more, high flame retardancy, and 0 to 350 mg / g, preferably 0 to 80 mg of hydrogen halide gas such as hydrogen chloride during combustion.
/ G.

[0014] The oxygen index here is based on JIS K7201.
And the amount of hydrogen halide gas generated during combustion is based on the measurement method specified in IEC-754-1. If the oxygen index is less than 28, the cable spread prevention sheet 5 itself tends to burn, and the fire spread prevention effect becomes insufficient. Further, even if the amount of hydrogen halide gas generation exceeds 350 mg / g, the effect of preventing fire spread will no longer increase, and moreover, a large amount of hydrogen halide gas will be generated, which is inconvenient. The thickness of the rubber sheet 7 is 0.1 to 3 mm, preferably 0.5
If it is less than 0.1 mm, the effect of preventing fire spread cannot be obtained, and if it exceeds 3 mm, the sheet itself becomes heavy and the handleability is poor.

The rubber mixture constituting the rubber sheet 7 includes:
There are two types that generate hydrogen halide gas during combustion and those that do not generate hydrogen halide gas. Examples of generating hydrogen halide gas include polychloroprene, chlorinated polyethylene, and chlorosulfonated polyethylene. Examples include halogenated rubber-based admixtures, and admixtures in which a halogen-based flame retardant is blended with a non-halogen-based rubber such as a nitrile rubber, a butyl rubber, an ethylene propylene rubber, or a natural rubber. This type of admixture generates hydrogen halide gas upon combustion. On the other hand, rubber mixtures that do not generate hydrogen halide gas include non-halogen rubbers such as butyl rubber, ethylene propylene rubber and natural rubber, as well as water-containing inorganic compounds such as aluminum hydroxide and magnesium hydroxide, and large amounts of non-halogen flame retardants. What was blended in.

Among these mixtures, the rubber admixture which generates hydrogen halide gas during combustion is preferably a polychloroprene admixture. For example, 100 parts by weight of chloropyrene rubber and 10 to 20 parts of magnesium hydroxide are used.
0 parts by weight, antimony oxide 5 to 50 parts by weight, phosphate frit 5 to 50 parts by weight, antioxidant 0.1 to 5 parts by weight,
10 to 100 parts by weight of inorganic filler, 5 to carbon black
The mixture containing 50 parts by weight or the like is most preferable because it can be carbonized and solidified after the rubber sheet 7 is burned, and can surround the wires and cables and block the air even after the burning.
As the rubber compound that does not generate hydrogen halide gas during combustion, a polyolefin compound is preferable. For example, 100 parts by weight of ethylene propylene rubber (EPM) or ethylene propylene diene rubber (EPDM) is used.
Magnesium hydroxide 50 to 300 parts by weight, phosphate frit 5 to 50 parts by weight, antioxidant 0.1 to 5 parts by weight, inorganic filler 10 to 100 parts by weight, carbon black 5 to 5
An admixture containing 0 parts by weight or the like is preferable, and this admixture also has the property of being carbonized and solidified after combustion.

Further, as the rubber sheet 7, a thermally foamable rubber admixture having an oxygen index of 28 or more, generating no hydrogen halide gas, and having a foaming degree of 4 times or more, having a thickness of 0.1 to 0.1% is used.
Thickness 0.2 obtained by applying to both sides of 0.5 mm woven fabric
A laminated rubber sheet having a thickness of up to 3.0 mm may be used.
The thermally foamable rubber compound has a high flame retardancy of 28 or more, preferably 50 or more, does not generate hydrogen halide gas such as hydrogen chloride during combustion, and foams when heated. And an admixture having a property that the degree of foaming becomes four times or more and solidifies.

Specific examples of such a heat-foamable rubber admixture include rubbers containing no halogen element such as butyl rubber, ethylene propylene rubber, natural rubber, ethylene-vinyl acetate copolymer, aluminum hydroxide and water. A mixture of a large amount of a water-containing inorganic compound such as magnesium oxide and a chemical blowing agent such as azodicarbonamide, dinitronepentamethylenetetramine, and 4,4-oxybisbenzenesulfonylhydrazide. However, it is preferable to use an ethylene-vinyl acetate copolymer having a vinyl acetate content of 6 to 90% by weight as a main component and blended with the above-mentioned hydrated inorganic compound, foaming agent, antioxidant, carbon black and the like.

The woven fabric is made of natural fibers such as cotton, hemp and jute, synthetic fibers such as nylon, polyester and acrylic, regenerated fibers such as human silk, and inorganic fibers such as glass fiber and carbon fiber. Thickness 1.0 ~
A fabric having a thickness of 0.5 mm and a basis weight of 10 to 300 g / m ² is used. To apply the heat-foamable rubber mixture to the fabric, this mixture is dissolved in an organic solvent such as xylene or toluene MEK to obtain a paint having a solid content of 10 to 80% by weight, and this paint is applied to both sides of the fabric at least once. The drying is performed, and the thickness of the obtained laminated rubber sheet is 0.2 to 3.0 m.
m, preferably 0.3 to 0.5 mm.

The metal sheet 8 has a melting point of 600 such as iron, steel, copper, copper alloy, aluminum, aluminum alloy, or the like.
A metal foil having a thickness of 15 to 200 μC or higher.
m. A metal having a melting point of less than 600 ° C. is unsuitable because it melts in a fire and cannot maintain its shape. If the thickness is less than 15 μm, the effect of the metal sheet 8 cannot be obtained.
Is reduced, which causes inconvenience in handling.

The lamination and integration of the rubber sheet 7 and the metal sheet 8 can be easily performed by using an adhesive such as a rubber adhesive. The dimensions of the cable spread prevention sheet 5 are not particularly limited, but are usually 40 to 1 in width.
A roll having a size of 00 cm and a length of 10 to 20 m is preferable from the viewpoint of productivity and workability.

Such a cable spread prevention sheet 5 is
It has the following fire spread prevention effect. That is, an electric wire or cable having flammability enough to burn down in the cable vertical combustion test specified in IEEE 383 is used as a sample, and the sampled electric wire or cable is placed in a Steiner tunnel horizontal combustion furnace shown in FIG. Attach. The cable spread prevention sheet 5 is intermittently or continuously wound over a length of about 4.5 m at a substantially central portion of the 7.32 m-long electric wire or cable 2 attached to the tray 9 of the Steiner tunnel horizontal combustion furnace, A combustion test was performed under the following conditions, and burner 1
After the combustion stoppage of 0, the electric wire or the cable 2 naturally extinguishes fire, and it is necessary to have an effect of preventing the spread of fire beyond a level that does not cause the fire. Calorific value of burner 10: 150,000 BTU / hour Burning time of burner 10: 40 minutes Ventilation rate in furnace: 0.6 m / sec Dimensions of tray 11: width 285 mm, length 7.32 m

The cable spread prevention sheet 5 is
In the following vertical combustion test, the wire or cable 2
Also has the effect of preventing the spread of fire. That is, IEC performed using a combustion test apparatus as shown in FIG.
In the cable vertical combustion test of 332-3, an electric wire or cable 2 having flammability that burns completely under the conditions of category C with a burner burning time of 20 minutes and a burner calorific value of 70000 BTU / hour was used as a sample. 2 is a ladder 11 of the combustion test apparatus.
The cable spread prevention sheet 5 is wound intermittently around the electric wire or cable 2 30 cm above the burner 10 as shown in FIG. Category A conditions, burner burning time 40 minutes, burner calorific value 7
A combustion test is performed at 0000 BTU / hour, and the sample has an effect of preventing fire spread beyond a level at which the wire or cable 2 of the sample is not completely burned.

The cable spread prevention sheet 5 is arranged and laminated so that the rubber sheet 7 and the metal sheet 8 are exposed on the front and back surfaces of the cable spread prevention sheet 5, respectively. Each of the surfaces exposed to the outside of the sheet 7 may have a radiation coefficient (ratio of a heat dissipation coefficient by radiation to a black body) of 0.5 or more to facilitate heat radiation. In order to set the radiation coefficient of the surface of the metal sheet 8 to 1.5 or more, black, gray,
A method of applying a dark-colored paint such as black brown, a method of applying a similar dark-colored plastic film, a method of coating a similar dark-colored rubber, and roughening the surface of the metal sheet 8 by sandblasting or the like. And the like. In order to make the radiation coefficient of the surface of the rubber sheet 7 0.5 or more, it is most practical to use, as the rubber admixture constituting the rubber sheet 7, a compound containing a black coloring agent such as carbon black. However, besides this, a dark colorant may be used.

As described above, the cable spread prevention sheet 5 surrounds the electric wire or the cable 2 to prevent the electric wire or the cable 2 from burning and exhibits an excellent fire spread prevention effect. In addition, the surrounding operation of the electric wire or the cable 2 is extremely easy, and it is easy to remove and re-use.
It has the advantage that the allowable power of the electric wires and cables surrounded by the cable spread prevention sheet 5 does not decrease.

Examples of such a cable spread prevention sheet 5 include “F Sheet” (trade name, manufactured by Fujikura Co., Ltd.).

In such a fire prevention structure for a cable, a plurality of cables 2 laid inside the pit 1
Since it is surrounded using the cable spread prevention sheet 5, the cable spread prevention sheet 5 can prevent the cable 2 from burning at the time of fire. In addition, since the surface portion of the cable 2 is covered with the cable spread prevention sheet 5, a structure capable of protecting the cable 2 from damage can be provided.

Furthermore, a plurality of cables 2 laid inside the pit 1 are surrounded at a time, but since both ends are open, heat due to energization causes heat inside the cable spread prevention sheet 5 to enter the space inside the cable spread prevention sheet 5. It is possible to provide a structure in which the cable 2 is hardly stuck, is efficiently radiated to the outside, suppresses a rise in the conductor temperature, and does not easily reduce the allowable current of the cable 2. Further, the radiation coefficient of each surface of the rubber sheet 7 and the metal sheet 8 as the cable spread prevention sheet 5 is set to 0.5.
In the case of using the above, the heat generated by the power supply to the cable 2 in normal times is unlikely to stay inside the space surrounded by the cable spread prevention sheet 5,
A structure in which the temperature rise of the electric wire or the cable 2 itself is suppressed, and the allowable current of the cable 2 is hardly reduced.

Since the cable spread prevention sheet 5 prevents the cable 2 from burning at the time of fire, it is not necessary to fill the sand 3 for fire prevention.
For example, when performing a new fire prevention process, or when performing a process such as updating or adding a cable 2, the labor for removing and filling the sand 3 can be reduced. Further, the sandbag 6 is used as a material for holding the cable spread prevention sheet 5.
For example, when installing or removing the cable spread prevention sheet 5, sand 3 and the like can be handled as one lump, and the inconvenience that the surroundings of the pit 1 are stained by the sand 3 is less likely to occur, and workability is improved. It will be good.

[0030]

As described above, the cable fire prevention structure of the present invention is a fire prevention structure in which the cable laid inside the pit is surrounded by the cable spread prevention sheet. It is possible to prevent the cable from burning in the event of a fire, and to prevent the spread of the spread of the fire by using an electric wire, a cable, or the like laid inside the pit or inside the metal duct as a medium for spreading the fire.

In addition, the structure is such that the heat generated by the current is hardly trapped in the space inside the cable spread prevention sheet, is efficiently radiated to the outside, and the rise in the conductor temperature is suppressed, so that the allowable current of the cable is hardly reduced. Can be. Further, since the surface portion of the cable is covered with the cable spread prevention sheet, a structure capable of protecting the cable from damage can be provided. Furthermore, since it is not necessary to use sand as in the case of performing fire protection by a method of filling sand, for example, when performing a new fire protection treatment, or when performing a process such as updating or adding a cable, the work is performed. A structure with good efficiency and excellent workability can be obtained.

The fire prevention structure of the cable of the present invention is a fire prevention structure in which an earthen sand is placed on a cable spread prevention sheet. Is less likely to be inconvenient and workability can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a fire prevention structure of a cable according to the present invention as viewed from a direction perpendicular to an extension direction.

FIG. 2 is a schematic sectional view showing an example of a fire prevention structure for a cable according to the present invention, as viewed from an extension direction.

FIG. 3 is a schematic sectional view showing an example of a cable spread prevention sheet used in the present invention.

FIG. 4 is a schematic configuration diagram showing a combustion test of a cable spread prevention sheet used in the present invention by a Steiner tunnel horizontal combustion furnace.

FIG. 5 is a schematic configuration diagram showing a cable vertical combustion test of a cable spread prevention sheet used in the present invention.

FIG. 6 is a schematic cross-sectional view showing an example of a conventional cable fire prevention method.

[Explanation of symbols]

1 ... pit, 2 ... cable, 5 ... cable spread prevention sheet

 ──────────────────────────────────────────────────の Continued on the front page (72) Eiji Katayama Inventor Fujikura Co., Ltd. 1-5-1, Kiba, Koto-ku, Tokyo

Claims (2)

[Claims] 1. A fire prevention structure for a cable, wherein a cable laid inside a pit or a metal duct is surrounded by a cable spread prevention sheet. 2. The fire prevention structure for a cable according to claim 1, wherein a sandbag is placed on the cable spread prevention sheet.