JP2002310381A - Metal pipe with preventive execution of damage by indirect lighting stroke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any dielectric breakdown caused by the voltage rise by the indirect lightning stroke, or damages of a metal pipe. SOLUTION: An insulating tape 2 of 0.5-0.8 mm thick mainly consisting of an ethylene propylene rubber with self-bonding property is wound around the metal pipe 1 installed in a part subjected to the effect of the indirect lightning stroke. The breakdown voltage can considerably be improved thereby through a simple operation at site. Practically sufficient protective effect can be obtained against damages of the metal pipe 1 caused by the indirect lightning stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pipe installed in a portion affected by an induced lightning, and more particularly to a metal pipe which has been subjected to damage prevention by an induced lightning.

[0002]

2. Description of the Related Art Various metal pipes are used in buildings for home use and business use. These pipes penetrate the steel frame portion of the building or are attached to a wall or the like with metal. When used in such a state, the potential difference between the fixed portion of the steel frame and the metal part and the metal pipe increases due to the induced potential due to the lightning strike, which may result in dielectric breakdown. When the dielectric breakdown occurs, depending on the magnitude of the discharge current, a metal pipe may be seriously damaged such as a hole is formed. In particular, damage to gas pipes, oil supply pipes, etc. may cause serious secondary disasters. Although some of these metal pipes are provided with an anticorrosion layer, they are generally provided for the purpose of preventing the deterioration of metal, and the insulation performance is insufficient to prevent the above-mentioned dielectric breakdown due to induced lightning. Was.

[0003]

As described above, in the conventional metal pipes, no effective measures have been taken to prevent damage due to lightning, and there is a risk of causing a serious secondary disaster. . The present invention has been made in view of the above circumstances, to prevent dielectric breakdown due to potential rise due to induced lightning,
The purpose is to prevent damage to metal piping.

[0004]

In order to prevent dielectric breakdown due to an induced potential, it is necessary to apply an insulator to the metal pipe. In order to prevent dielectric breakdown by simple work on site regardless of existing or new construction, in the present invention, an insulating tape is applied to a metal pipe installed in a part affected by induced lightning as shown in FIG. It was decided to prevent dielectric breakdown. Therefore, the insulating tape material and the amount of winding of the insulating tape (tape thickness and number of winding layers) required to prevent dielectric breakdown
And the range of winding the insulating tape was examined. As a result, it has been clarified that the breakdown voltage can be significantly improved by applying a 0.5 to 0.8 mm thick insulating tape having a self-fusing property mainly composed of ethylene propylene rubber to a metal pipe. . In the present invention, as described above, a 0.5 to 0.8 mm thick insulating tape having a self-fusing property mainly composed of ethylene propylene rubber is applied to a metal pipe installed in a portion affected by the induced lightning. As a result, a practically sufficient protective effect was obtained against damage to the metal tube due to the induced lightning.

[0005]

FIG. 1 shows a metal pipe provided with an insulating tape according to the present invention. As shown in the figure, an insulating tape 2 is wrapped around the surface of a metal pipe 1 near a portion affected by induced lightning, such as a penetrating portion of a steel frame 4 of a building. Thereby, even if the electric potential of the steel frame part 4 rises, it is possible to prevent the metal pipe 1 from being damaged. With respect to the metal pipe shown in FIG. 1, the insulating tape material, the winding amount of the insulating tape (the thickness of the tape and the number of winding layers), and the range of winding the insulating tape are as follows. investigated. FIG. 2 shows a test method in the present invention for examining the breaking performance of the insulating tape. As shown in the figure, a ball electrode 3 is used as a simulation of a steel frame portion 4 and a fixing metal portion, a metal tube 1 is grounded, and a high voltage (HV) impulse voltage is applied to the ball electrode 3. A lightning impulse destruction test (hereinafter referred to as a lightning imp destruction test) of the sample wound with the insulating tape 2 was performed.

[0006] The insulating tape 2 used in the test has (1) a self-fusing property based on vulcanized ethylene propylene rubber and (2) a self-fusing property using ethylene propylene rubber. Was used. The test was performed using the thickness of the insulating tape 2; t, the number of winding layers of the insulating tape 2; n and the range of winding the insulating tape; L as a parameter. First, in order to grasp the appropriate material of the insulating tape and the thickness of the insulating tape; t, the above-mentioned (1) an insulating tape having no self-fusing property, and (2) an insulating tape having a self-fusing property. A lightning imp destruction test was performed on a sample on which the insulating tape was wound so that the thickness of the insulating tape applied was constant (t × n = constant). Here, t × n = a constant value (t × n = 4 m
m) and the range L where the insulating tape is wound is L = 5000
mm. Table 1 shows the test results. In the table, the type of insulating tape (with or without self-fusing property), the thickness of insulating tape, the winding thickness of insulating tape, the lightning imp destruction of 0.3 mm thick self-fusing tape The breakdown voltage normalized by voltage is shown. From Table 1, it can be seen that the tape having the self-fusing property has a higher lightning Imp breakdown voltage than the tape having no self-fusing property.

[0007]

[Table 1]

FIG. 3 shows the relationship between the thickness of the insulating tape and the normalized breakdown voltage. In FIG. 3, the horizontal axis represents the thickness of the insulating tape, and the vertical axis represents the normalized breakdown voltage.
From FIG. 3, the breakdown voltage decreases with the thickness of the insulating tape regardless of the presence or absence of the self-fusing property. Here, the tape having the self-fusing property has a smaller degree of reduction in the breakdown voltage than the tape having no self-fusing property. In many cases, the dielectric breakdown was broken at the lap of the tape-wound surface. Therefore, the tape thickness increases,
It is considered that the breakdown voltage decreases as the winding step increases. In addition, it is considered that the tape having self-fusing property has a high degree of adhesion of the wound portion of the tape, so that the degree of decrease in breakdown voltage is reduced. From these results, it is possible to increase the breakdown voltage by using a thin tape having a self-fusing property as the insulating tape. On the other hand, when a tape is actually applied, a thin tape has a large number of windings, which leads to an increase in working time. Table 2 shows the winding time required for winding the tape. This is the average work time of five workers.

[0009]

[Table 2]

From Table 2, it can be seen that the winding time is basically shorter as the tape thickness is larger, but the tape winding time is not always inversely proportional to the tape thickness. This is because the easiness of the winding operation also affects the tape thickness, and when the tape is thin and thick, a phenomenon occurs in which the winding becomes difficult.

As described above, when a protective range is created by winding an insulating tape, the dielectric strength and the working time vary depending on the tape thickness. Then, the tape thickness for efficient protection was determined by the following method. First, the tape winding time is normalized by the 0.3 mm thick tape without self-fusing property, which was the longest working time, and a standardized winding time to determine a fraction of the required tape winding time is determined.
Next, since the purpose is to improve the dielectric strength, the normalized breakdown voltage is weighted three times and multiplied by the standardized winding time to obtain an evaluation point. Table 3 shows the results.

[0012]

[Table 3]

From Table 3, it can be seen that in order to efficiently prevent dielectric breakdown in consideration of workability, it is appropriate to apply a self-fusing insulating tape having a thickness of 0.5 to 0.8 mm. . Next, the length L for tape winding and the number n of tape winding layers
Considered optimization. The number n of layers for tape winding is two layers,
The lightning Imp destruction test was performed with four layers, six layers, and eight layers, and changing the tape winding length. The insulating tape used had a thickness of 0.5 mm and had self-fusing properties. Table 4 shows the test results.

[0014]

[Table 4]

In the table, the number n of layers for tape winding, the length L for tape winding, and the standardized breakdown voltage are shown.
The normalization of the breakdown voltage is as follows.
The measurement was performed with reference to a breakdown voltage of 0 mm. FIG. 4 shows the relationship between the tape winding length and the normalized breakdown voltage obtained from the test results in Table 4. In FIG. 4, the horizontal axis is the tape winding length L,
The vertical axis is the normalized breakdown voltage. As can be seen from FIG. 4, for any number of tape winding layers, the breakdown voltage increases as the tape winding length increases, and becomes a substantially constant value from a certain length. In the case of four, six and eight tape winding layers, the breakdown voltages are almost equal, but the breakdown voltages of the two layers are low. This relates to the location where the failure occurs. In a tape having self-fusion properties, the tape has a high adhesiveness, and thus the tape surface becomes a weak point more easily than penetrating fracture, and the surface flashes easily. In the case of four layers, six layers and eight layers of tape winding, flashing occurred on the surface. Therefore, even if the number of tape winding layers is increased, the breakdown voltage hardly increases. If the tape winding length is shorter than 1000 mm, the breakdown voltage increases as the tape winding length increases, but the tape winding length is 1 mm.
If it exceeds 000 mm, a phenomenon that the breakdown voltage hardly increases was observed.

On the other hand, in the case of a two-layered tape, when the tape winding length is 500 mm or less, surface flashing occurred, but when the tape winding length was 750 mm or more, a penetrating failure occurred, and the breakdown voltage was 4 layers or more. It was lower than the case. From the above results, it was confirmed that the insulation breakdown due to the induced potential can be efficiently prevented by applying about 1000 mm of four layers of the self-fusing insulating layer having a thickness of 0.5 mm to 0.8 mm.

Next, a specific application example of the metal pipe provided with the insulating tape as described above will be described. SUS (stainless steel) corrugated tube 10 of 0.2 mm thickness shown in FIG.
The insulating tape was applied to the flexible pipe 12 for gas piping provided with a PVC anticorrosive layer 11 (0.5 mm thick) to prevent dielectric breakdown due to induced potential. The flexible pipe for gas piping may be laid through the steel frame 4 of the building as shown in FIG. In this case, a potential difference is generated between the flexible pipe 12 for gas piping and the steel frame 4 due to the induced potential due to lightning, dielectric breakdown occurs at the penetration, the SUS flexible pipe 12 is damaged, and gas leakage is reported. I have. Therefore, as shown in FIG. 7, a self-fusing insulating tape 2 having a thickness of 0.5 mm and a thickness of 1000 mm
Layered. Then, a lightning impulse was applied to the steel frame portion 4 to simulate induced lightning, and a destruction test was performed. Two types of tests were performed, one with the above-described insulating tape and the other without the insulating tape for comparison. Table 5 shows the test results.

[0018]

[Table 5]

From Table 5, it can be seen that the breakdown voltage was low when no insulating tape was applied, but the breakdown voltage was significantly improved by applying the insulating tape. In general, induced lightning is more likely to produce a larger potential, so that it can be said that it has a practically sufficient protective effect. As described above, it was shown that the effect of the present invention was effective.

[0020]

As described above, in the present invention, the metal pipe is provided with a self-fusing insulating tape having a thickness of 0.5 to 0.8 mm and having a thickness of 0.5 to 0.8 mm. It is possible to obtain a practically sufficient protective effect against damage to the metal tube due to lightning. For this reason, serious secondary disasters can be prevented in gas pipes, oil supply pipes, and the like.

[Brief description of the drawings]

FIG. 1 is a view showing a metal pipe provided with an insulating tape according to the present invention.

FIG. 2 is a diagram illustrating a method for testing the insulating performance of an insulating tape in the present invention.

FIG. 3 is a diagram showing a relationship between a thickness of an insulating tape and a standardized breakdown voltage.

FIG. 4 is a diagram showing a relationship between a tape winding length and a standardized breakdown voltage.

FIG. 5 is a view showing a structure of a SUS flexible pipe for a gas pipe to which the present invention is applied.

FIG. 6 is a diagram showing an example of a piping method of a SUS flexible pipe for gas piping.

FIG. 7 is a diagram illustrating a method for testing dielectric breakdown of a SUS flexible pipe for gas piping to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal piping 2 Insulating tape 3 Ball electrode 4 Steel frame 10 SUS corrugated tube 11 PVC anticorrosion layer 12 Flexible tube for gas piping

Claims (1)

[Claims] 1. A metal pipe installed in a portion affected by an induced lightning, wherein the metal pipe has a self-fusing insulating tape having a thickness of 0.5 to 0.8 mm and made mainly of ethylene propylene rubber. A metal pipe that has been treated to prevent damage from induced lightning, which is characterized by having been treated.