JP7377775B2 - fireproof cable - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a fireproof cable with high fireproof properties.

As an example of a fire-resistant cable with high fire-resistant properties that can withstand long-term fire-resistant tests, Patent Document 1 describes a fire-resistant layer of a fire-resistant cable consisting of a conductor, a fire-resistant layer, an insulating layer, and a flame-retardant sheath. , it is described that it is constructed from a composite insulating tape of alumina cloth and other refractory materials such as laminated mica.

Japanese Patent Application Publication No. 2000-331546

As a safety measure in the event of a fire, nuclear facilities require fire-resistant cables that can withstand the high temperatures of a fire for a certain period of time and can supply power to necessary equipment without spreading the fire themselves.

Conventional fire-resistant cables are made by wrapping a mica tape lined with a backing material such as glass cloth or polyester tape around a conductor, and then forming an insulating layer and a flame-retardant sheath on the fire-resistant layer formed by this. structure is widely used.

However, most fire-resistant cables with this structure have a fire resistance that meets the 30-minute fire resistance test according to JIS-A1304, and it is difficult to pass the 3-hour fire resistance test required at nuclear power plants. There is an issue with this.

In particular, when comparing the 30-minute and 3-hour fire resistance tests, the maximum temperature of the former is about 840℃, while the maximum temperature of the latter is about 1100℃ on the cable surface, and the insulation layer of polyethylene etc. After being steamed, it becomes carbonized, resulting in a significant drop in insulation resistance.

As a conventional technique, the technique described in Patent Document 1 is known. This Patent Document 1 describes the use of a composite insulating tape of alumina cloth and other fire-resistant materials as a constituent material of a fire-resistant layer as a fire-resistant cable that can withstand a one-hour fire resistance test.

However, although the technology described in Patent Document 1 can withstand a one-hour fire resistance test, the copper conductor melts during the three-hour fire resistance test required at nuclear power plants, reducing the strength of the cable. I end up. In addition, since the insulation resistance is greatly reduced, it is necessary to further improve the fire resistance.

The present invention provides a fire-resistant cable for use in nuclear power plants that has improved fire resistance compared to conventional cables and can withstand a 3-hour fire resistance test.

The present invention includes a plurality of means for solving the above problems, and one example thereof is a fireproof cable having a wire core, the wire core comprising a conductor and a fireproof cable located on the outer periphery of the conductor. layer, and an insulator located on the outer periphery of the fireproof layer, the fireproof layer has an organic material and an inorganic material, and the content of the organic material in the fireproof layer is 0.5% by mass. It is characterized in that the amount is 10% by mass or less.

According to the present invention, the fire resistance is improved compared to the conventional one, and it is possible to withstand a 3-hour fire resistance test. Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments and examples.

FIG. 1 is a diagram schematically showing a fireproof cable of this embodiment. FIG. 3 is a diagram showing the results of insulation resistance measurement on the fireproof cable of Example 1 of the present invention. It is a figure which shows the result of insulation resistance measurement of the fireproof cable of Example 2 of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of the fireproof cable of the present invention will be described using FIGS. 1 to 3 while referring to the drawings as appropriate.

First, the configuration of the fireproof cable will be explained using FIG. 1. FIG. 1 is a diagram of a structural example schematically showing the fireproof cable of this embodiment.

The fireproof cable 10 shown in FIG. 1 is composed of two wire cores 5, an inclusion 6, a pressing tape 4, a heat insulating layer 7, and a sheath 8.

The wire core 5 includes a conductor 1 made of, for example, copper, a fireproof layer 2 located on the outer periphery of the conductor 1, an insulator 3 located on the outer periphery of the fireproof layer 2, and a pressure winding wound around the insulator 3. Consists of 4 tapes. Two of these wire cores 5 are rubbed together.

The inclusion 6 is formed by wrapping a pressure tape 4 made of polyethylene or the like around two wire cores 5 twisted together, and for example, an insulating material such as glass mica is used.

The heat insulating layer 7 covers the inclusion 6 surrounded by the pressing tape 4, and is made of a highly heat resistant material such as alumina.

The flame-retardant sheath 8 is a layer that forms the outermost layer of the fire-resistant cable 10, and is not particularly limited as long as it is made of a material that is used for the outermost layer of general fire-resistant cables.

In the present invention, the structure and materials other than the fireproof layer 2 are not particularly limited, and structures and materials suitable for fireproof cables can be used as appropriate.

Next, details of the fireproof layer 2, which is the most characteristic feature of the fireproof cable 10 of the present invention, will be described below.

The fireproof layer 2 includes an organic material, a first inorganic material having heat resistance, and a second inorganic material having insulating properties.

Among these, the organic material is used as an adhesive to mold the powders of the first inorganic material and the second inorganic material into a sheet shape, and the organic material is used in consideration of its compatibility with the first inorganic material and the second inorganic material. It is possible to determine the material etc. For example, epoxy resin and polyester resin are preferably used, but of course the material is not limited thereto.

Further, the content of the organic material in the fireproof layer 2 is 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 5% by mass or less.

When the content of the organic material is less than 0.5% by mass, the adhesive force between the inorganic material powders becomes weak, and it is impossible to mold the powder into a sheet. Furthermore, it is desirable to contain 1% by mass or more. Thereby, the strength of the sheet can be increased.

On the other hand, if the content of the organic material exceeds 10% by mass, the fire resistance performance will be impaired, which is not preferable. More preferably, it is 5% by mass or less.

The first inorganic material maintains its mechanical strength even at 1000°C, and more preferably maintains its mechanical strength even at 1200°C or higher, since the outer surface temperature of the fireproof cable 10 reaches 1100°C after a 3-hour fire resistance test. It is desirable to have heat resistance. Mechanical strength shall be judged by tensile strength. The tensile strength may be evaluated by the same method both at room temperature and after the fire resistance test, for example, by various test methods such as JIS.

Since the strength of the fire-resistant cable 10 can be maintained by maintaining the tensile strength at 1/2 or more of that at room temperature (25°C), the temperature at which the tensile strength of the fire-resistant layer 2 decreases to 1/2 of that at room temperature is , at least 1000°C, more preferably 1200°C.

Examples of such first inorganic materials include free-cutting ceramic (SiO ₂ ), MgO, Al ₂ O ₃ composite, free-cutting ceramic: AlN, BN composite, steatite (MgO・SiO ₂ ), and stabilization. Zirconia, silicon carbide, magnesium oxide, Sialon (silicon nitride-based engineering ceramics obtained by synthesizing Si ₃ N ₄ with Al ₂ O ₃ and SiO ₂ ), Photoveil (registered trademark) (glass matrix, Shapal Hi Msoft (registered trademark) (composite of AlN and BN), quartz, Vycor (registered trademark) (by phase-separating borosilicate glass, The silica content can be increased to 96% by eluting the boric acid content. It is desirable that the above-mentioned material maintains its mechanical strength even at the above-mentioned temperature of 1000°C, and more preferably maintains its mechanical strength even at temperatures of 1200°C or higher.

The second inorganic material preferably has a volume resistivity of 1 [MΩ·m] or more at 500°C, more preferably a volume resistivity of 1 [MΩ·m] or more at 1000°C.

Even though the volume resistivity of the material constituting the fireproof layer of conventional fireproof cables is 1 [MΩ・m] or more at room temperature, the volume resistivity of the fireproof layer decreases as the temperature rises, and the volume resistivity of the fireproof layer decreases as the temperature rises, resulting in a 3-hour fireproof test. It has become difficult to maintain insulation.

Therefore, as a result of measuring the insulation resistance during a fire resistance test, the present inventors found that by using an inorganic substance with a volume resistivity of 1 [MΩ・m] or more at 500°C, it is possible to effectively suppress the deterioration of cable insulation. I figured it out. More preferably, by using an inorganic substance having a resistance of 1 [MΩ·m] or more at 1000° C., a decrease in insulation resistance can be significantly suppressed even when a composite sheet is produced using an organic material and a first inorganic material.

Examples of such second inorganic materials include alumina, sapphire, mullite (a compound of aluminum oxide and silicon dioxide), cordierite (ceramic consisting of three components of MgO, Al ₂ O ₃ and SiO ₂ ), and forsterite (MgO -Al ₂ O ₃ -SiO ₂ ceramics consisting of forsterite crystals of 2MgO.SiO ₂ (also written as Mg ₂ SiO ₄ ), silicon nitride, aluminum nitride, boron nitride, and macerite (fluorophlogopite). It is desirable that it contains one or more types. It is also desirable that the above-mentioned material has a volume resistivity of 1 [MΩ·m] or more at 500°C, more preferably a volume resistivity of 1 [MΩ·m] or more at 1000°C.

Further, the ratio of the first inorganic material and the second inorganic material in the fireproof layer 2 is in the range of 10 to 40% by mass: 60 to 90% by mass, for a total of 100% by mass, and more preferably 20 to 30% by mass: It is desirable that the total amount is 100% by mass within the range of 70 to 80% by mass.

The ratio of the first inorganic material is in the range of 10% by mass or more, more preferably 20% by mass or more (that is, the ratio of the second inorganic material is 90% by mass or less, more preferably 80% by mass or less). , sufficient mechanical strength can be maintained. Further, the ratio of the second inorganic material is 60% or more, more preferably 70% by mass or less (that is, the ratio of the first inorganic material is 40% by mass or less, more preferably 30% by mass or less). Therefore, a decrease in insulation resistance after a 3-hour fire resistance test can be effectively suppressed.

From these relationships, the optimal ratio of the organic material, first inorganic material, and second inorganic material is 0.5 to 10% by mass: 9 to 40% by mass of the organic material, first inorganic material, and second inorganic material. Mass %: 54 to 90 mass %, totaling 100 mass %, more preferably 1.0 to 5.0 mass %: 1.0 to 29.7 mass %: 66.5 to 79. It is desirable that the total amount is 100% by mass within the range of 2% by mass.

With such a combination, the fireproof layer 2 can maintain sufficient insulation resistance and mechanical strength even during a 3-hour fireproof test.

Next, examples and comparative examples of the present invention will be described with reference to FIGS. 2 and 3, but the technical scope of the present invention is not limited thereto.

<Fire resistance test>
The fire resistance test was conducted in accordance with the domestic fire resistance test standard JCS 7503:2009 "Cable Fire Resistance Test Method" for fire resistance cables for general industry stipulated by the Fire Service Act, and the United States Fire Resistance Testing Standards (IEEE 1844, UL 2196). The heating furnace used was a large heating furnace specified in JCS 7503:2009.

<Judgment test>
(1) Current test
The current test was conducted in accordance with the current test method specified in JIS C3005. A direct current of 18 A was applied to the conductor, and a buzzer was used to check for disconnection. The criterion was that after heating in a heating furnace for 3 hours, a buzzer sounded and electricity was confirmed to be OK.

(2) Dielectric strength test
The dielectric strength test was based on the test method specified in JCS 7503. A specified AC voltage with a waveform close to a sine wave with a frequency of 50 [Hz] or 60 [Hz] was applied between the conductor and the ground, and it was examined whether it could withstand the specified time. The criterion was that it was OK if it could withstand AC600 [V] during heating in a heating furnace for 3 hours.

(3) Insulation resistance measurement
Conformed to the insulation resistance value stipulated in Article 13 of the Interpretation of Technical Standards for Electrical Equipment Related to Nuclear Power Plants. The insulation resistance between the cable conductor and the ground was measured using an insulation resistance meter. The criterion was that the insulation resistance value was 0.4 [MΩ] or more after being heated in a heating furnace for 3 hours.

<Example 1>
The structure of the fireproof cable 10 was as follows. The conductor 1 was a copper wire whose surface was plated with nickel. The fireproof layer 2 is made by blending Vycor as a first inorganic material and mullite as a second inorganic material in a powder state at a ratio of 1:9 to 4:6, and adding 5% by mass of epoxy resin as an organic material. It was molded into a sheet. This was wound around the circumference of the conductor 1.

An insulator 3 made of silicone rubber to which 40% by mass of magnesium hydroxide was added was formed on the circumference of the fireproof layer 2. A polyethylene pressing tape 4 was wrapped around it. After rubbing the wire cores 5 against each other, a glass mica inclusion 6 is placed on top of the wire cores 5, and a heat insulating layer 7 made of polyethylene and a heat insulating layer 7 made of alumina covering the pressure winding tape 4 and the outermost periphery. A flame retardant sheath 8 was formed.

Figure 2 shows the results of insulation resistance measurements. As shown in FIG. 2, the ratio of the first inorganic material to the second inorganic material is 10 to 40% by mass: 60 to 90% by mass, for a total of 100% by mass, and more preferably 20 to 30% by mass. : It was found that by setting the total amount to 100% by mass in the range of 70 to 80% by mass, the decrease in insulation resistance was further suppressed.

<Example 2>
In Example 2, an inorganic material containing silicon carbide (dense) as the first inorganic material and alumina (A482R) as the second inorganic material in a ratio of 1:9 by mass was used for the fireproof layer 2. . As the organic material, polyester resin was added in an amount of 0.5% by mass or more and 10% by mass or less. Figure 3 shows the results of insulation resistance measurements. As shown in FIG. 3, the decrease in insulation resistance is suppressed when the content of the organic material is in the range of 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 5% by mass or less. Do you get it.

<Example 3>
Sialon is used as the first inorganic material of the fireproof layer 2, and the first inorganic material and the second inorganic material are blended in powder form at a ratio of 2:8, and 5% by mass of polyester resin is used as the organic material. It was added and molded into a sheet.

As shown in Table 1 below, the second inorganic material includes alumina (A482R, A459, A471, A473, A484, A476, A479, A479S) having a volume resistivity of 1 [MΩ・m] or more at 500°C. , A479M/A479G, A480S, A601D/A601L), sapphire (SA100), mullite (ML652), cordierite (CO220, CO720), forsterite (F1120, F1023, FC112M), silicon nitride (SN201B, SN260, SN240, SN24) 1 ), aluminum nitride (AN216A, AN2000), boron nitride (binderless), and macerite (fluorine phlogopite) were used.

The results of the performance evaluation are shown in Table 1. As shown in Table 1, the above evaluation test results were OK in all items, and it was found that the required performance was satisfied even in the 3-hour fire resistance test.

<Example 4>
Table 1 shows the exception that alumina (A445), which has a volume resistivity of less than 1 [MΩ・m] at 500°C, was used instead of the second inorganic material of the fireproof layer 2 shown in Example 3. Evaluation test results for a cable produced in the same manner as in Example 3 are also shown.

As shown in Table 1, although the cable of Example 4 can satisfy the performance required in the 3-hour fire resistance test, it is clear that the cable of Example 4 has lower performance than the material of Example 3.

<Example 5>
Macerite (fluorine phlogopite) is used as the second inorganic material of the fireproof layer 2, the first inorganic material and the second inorganic material are blended in powder form at a ratio of 2:8, and polyester resin is used as the organic material. was added in an amount of 5% by mass and molded into a sheet.

As the first inorganic material, as shown in Table 2 below, free-cutting ceramic: SiO ₂ = 46%/MgO = 17%/Al ₂ O ₃ = 16%, free-cutting ceramic: AlN, BN composite , steatite: MgO/SiO ₂ , stabilized zirconia (dense), silicon carbide (dense), magnesium oxide (dense), Sialon, Photoveil II, Photoveil II-S, M-soft, quartz, Vycor 20 The first inorganic material blended in mass% was used.

The results of the performance evaluation are shown in Table 2. As shown in Table 2, the above evaluation test results were OK in all items, and it was found that the required performance was satisfied even in the 3-hour fire resistance test.

<Example 6>
Table 2 also shows Example 5 except that glass mica, whose tensile strength at 1000°C is reduced to 1/2 of that at room temperature, was used in place of the first inorganic material of fireproof layer 2 shown in Example 5. The evaluation test results of a cable fabricated in the same manner as above are also shown.

As shown in Table 2, although the cable of Example 6 can satisfy the performance required in the 3-hour fire resistance test, it is clear that the cable of Example 6 has lower performance than the material of Example 5.

Next, the effects of this embodiment will be explained.

The fireproof cable 10 having the wire core 5 of the present embodiment described above includes a conductor 1, a fireproof layer 2 located on the outer periphery of the conductor 1, an insulator 3 located on the outer periphery of the fireproof layer 2, The fireproof layer 2 includes an organic material and an inorganic material, and the content of the organic material in the fireproof layer 2 is 0.5% by mass or more and 10% by mass or less.

With such a configuration, a cable with high fire resistance that can withstand a 3-hour fire resistance test can be obtained, which is extremely useful in increasing safety in the event of a fire at a nuclear power plant.

Further, in the fireproof layer 2, the content of the organic material is 1% by mass or more and 5% by mass or less, so that the first inorganic material and the second inorganic material can be molded more effectively.

Furthermore, the first inorganic material has heat resistance such that the tensile strength at 1000°C, more preferably 1200°C or higher, is maintained at 1/2 or more of that at room temperature, so that it can be used as a cable even after a 3-hour fire resistance test. The strength of the material can be sufficiently ensured.

In addition, the second inorganic material has a volume resistivity of 1 [MΩ・m] or more at 500°C, more preferably at 1000°C, so that insulation properties are sufficiently ensured even after a 3-hour fire resistance test. The cable can be made into a cable whose performance is sufficiently guaranteed even if it is exposed to a fire accident environment.

Furthermore, the ratio of the first inorganic material to the second inorganic material is in the range of 10 to 40% by mass: 60 to 90% by mass, more preferably in the range of 20 to 30% by mass: 70 to 80% by mass, By having a total content of 100% by mass, the mechanical strength and insulation properties of the cable can be more reliably ensured.

In addition, the second inorganic material contains at least one of alumina, sapphire, mullite, cordierite, forsterite, silicon nitride, aluminum nitride, boron nitride, and macerite (fluorine phlogopite), resulting in 3-hour fire resistance. Decrease in mechanical strength after testing can be dramatically suppressed.

In addition, as the first inorganic material, free-cutting ceramic: SiO ₂ , MgO, Al ₂ O ₃ composite, free-cutting ceramic: AlN, BN composite, steatite: MgO/SiO ₂ , stabilized zirconia, silicon carbide. By containing at least one of , magnesium oxide, Sialon, Photoveil, M-soft, quartz, and Vycor, the decrease in mechanical strength after a 3-hour fire resistance test can be dramatically suppressed.

<Others>
Note that the present invention is not limited to the above-described embodiments, and various modifications and applications are possible. The embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described.

1... Conductor 2... Fireproof layer 3... Insulator 4... Pressure wrapping tape 5... Wire core 6... Inclusion 7... Heat insulating layer 8... Sheath 10... Fireproof cable

Claims (13)

A fireproof cable having a wire core,
The wire core is
a conductor;
a fireproof layer located on the outer periphery of the conductor;
an insulator located on the outer periphery of the fireproof layer,
The fireproof layer includes an organic material and an inorganic material,
A fire-resistant cable, wherein the content of the organic material in the fire-resistant layer is 0.5% by mass or more and 10% by mass or less. The fireproof cable according to claim 1,
The fireproof cable is characterized in that the content of the organic material in the fireproof layer is 1% by mass or more and 5% by mass or less. The fireproof cable according to claim 1,
The fireproof cable is characterized in that the inorganic material includes a first inorganic material having heat resistance and a second inorganic material having insulating properties. The fireproof cable according to claim 3,
A fire-resistant cable, wherein the first inorganic material has heat resistance such that tensile strength at 1000° C. is maintained at 1/2 or more of that at room temperature. The fireproof cable according to claim 4,
The first inorganic material has heat resistance such that its tensile strength is maintained at 1/2 or more of that at room temperature at temperatures of 1200° C. or higher. The fireproof cable according to claim 3,
A fire-resistant cable, wherein the second inorganic material has a volume resistivity of 1 [MΩ·m] or more at 500°C. The fireproof cable according to claim 6,
A fire-resistant cable, wherein the second inorganic material has a volume resistivity of 1 [MΩ·m] or more at 1000°C. The fireproof cable according to claim 3,
A fire-resistant cable characterized in that the ratio of the first inorganic material to the second inorganic material is in the range of 10 to 40% by mass: 60 to 90% by mass, for a total of 100% by mass. The fireproof cable according to claim 8,
A fireproof cable characterized in that the ratio of the first inorganic material to the second inorganic material is in the range of 20 to 30% by mass: 70 to 80% by mass, for a total of 100% by mass. The fireproof cable according to claim 3,
The ratio of the organic material, the first inorganic material, and the second inorganic material is in the range of 0.5 to 10% by mass: 9 to 40% by mass: 54 to 90% by mass, and the total is 100% by mass. A fireproof cable characterized by: The fireproof cable according to claim 10,
The ratio of the organic material, the first inorganic material, and the second inorganic material is 1.0 to 5.0% by mass: 19.0 to 29.7% by mass: 66.5 to 79.2% by mass. A fire-resistant cable having a total content of 100% by mass. The fireproof cable according to claim 3,
A fire-resistant cable characterized in that the second inorganic material contains at least one of alumina, sapphire, mullite, cordierite, forsterite, silicon nitride, aluminum nitride, boron nitride, and macerite (fluorophlogopite). The fireproof cable according to claim 3,
As the first inorganic material, free-cutting ceramic: SiO ₂ , MgO, Al ₂ O ₃ composite, free-cutting ceramic: AlN, BN composite, steatite: MgO/SiO ₂ , stabilized zirconia, silicon carbide, A fireproof cable characterized by containing at least one of magnesium oxide, Sialon, Photoveil, M-soft, quartz, and Vycor.

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