JPH0571741U - Leak detection line - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a liquid leakage detection line that has no risk of malfunction and has a small temperature dependence. [Structure] In a liquid leakage detection line in which a pair of electrode wires 3 and 3 are arranged substantially parallel to each other and a braided layer 5 made of at least a liquid absorbing thread is provided outside thereof, the electrode wire 3 is on a conductor 1. Insulator 2 was extruded and coated with a thermoplastic polyester elastomer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a leak detection line that detects when a pipeline or a storage tank that transports liquid such as sulfuric acid or caustic soda is damaged.

[0002]

[Prior Art]

 The Applicant previously proposed a leak detection line that can detect leaks over a wide range by using it along with a pipeline or a storage tank that transports liquids such as sulfuric acid and caustic soda. (Saikai Sho 63-57544 to Shokai Sho 63-57549). The liquid leakage detection line consists of a pair of enameled wires coated with polyester resin as an insulator on the conductor as electrode lines and arranged in parallel with each other, and a braided layer made of at least a liquid-absorbent yarn is provided outside the pair. It consists of

In this leak detection line, when a leak of sulfuric acid or the like occurs, a braided layer made of a liquid-absorbent yarn absorbs the leak, and sulfuric acid or the like that permeates through the braided layer dissolves the insulator. Then, the pair of conductors of the electrode wire is short-circuited or close to a short-circuit. Therefore, the leakage can be detected by measuring the insulation resistance between the conductors from one end of the leakage detection line. Even if normal water enters the leak detection line due to rainfall, etc., the insulator layer does not dissolve and no malfunction occurs.

[0004]

[Problems to be solved by the device]

 However, in the above-mentioned conventional liquid leakage detection wire, the insulator of the electrode wire is formed by so-called enamel coating by coating and baking polyester resin, so the pressure and pulling force applied to the electrode wire during the manufacturing process and laying work. Crazing or cracking may occur due to the stress generated in the insulator due to external force such as bending. Therefore, in order to prevent excessive external force from acting on the leak detection line during the manufacturing process and installation work, a high degree of caution was required for its management. However, its attention is limited, and there is a problem in that the leak detection line may malfunction if rainfall or other inevitable cracks penetrate. Further, the leak detection line of the enamel coating has a problem that the detection time of sulfuric acid or the like has a large temperature dependency, and particularly when the temperature is 15 ° C. or less, the detection time becomes drastically long.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a liquid leakage detection line that is free from the risk of malfunction and has small temperature dependence. To provide.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the liquid leakage detection line in the present invention comprises a pair of electrode wires arranged substantially parallel to each other, and a braided layer made of at least a liquid absorbing thread is provided on the outside thereof. In the wire, the electrode wire is formed by extrusion coating a thermoplastic polyester elastomer on a conductor as an insulator. Here, in the polyester-based thermoplastic elastomer (hereinafter referred to as a polyester elastomer), the hard segment is made of polyester, and the soft segment is a polyether-based one or a polyester-based one. As for the hard segment polyester and the soft segment polyether series, "Hytrel" (trade name of Toray-Dupont Co., Ltd.), "Perprene-P" (trade name of Toyobo Co., Ltd.), "Lomod" (Product name of Akzo company). Examples of those in which the hard segment is polyester and the soft segment is polyester include "Perprene-S" (a product name of Toyobo Co., Ltd.) and "ARINTEL-S" (a product name of Akzo).

[0007]

[Action]

 In the leak detection wire with the above configuration, the polyester elastomer that forms the insulator of the electrode wire is particularly excellent in mechanical strength, rubber elasticity, flex fatigue resistance, and crack propagation resistance in a wide operating temperature range from low temperature to high temperature. Therefore, there is no possibility that pinholes, crazing, etc. will be generated by the external force such as pressure, tensile force, bending, etc. applied to the electrode wire in the manufacturing process or the laying process or as one of the factors. Also, the temperature dependence of the detection time for the liquid to be detected such as sulfuric acid is small.

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views of the leak detection line of the present invention.

In FIGS. 1 and 2, 1 is a conductor having a circular cross section, 2 is an insulator coated on the conductor 1, and an electrode wire 3 is formed from these, and a pair of electrode wires 3 and 3 is formed. They are arranged almost horizontally (may be twisted). In FIG. 1, 4 is an inner braid layer coated on the outer circumference of the pair of electrode wires 3 and 3, and 5 is an outer braid layer. In FIG. 2, reference numeral 6 is a braid layer coated on the outer circumference of the pair of electrode wires 3 and 3.

The insulator 2 shown in FIGS. 1 and 2 is made of any one of the above polyester elastomers. The inner braid layer 4 in FIG. 1 is composed of a non-liquid-soluble, non-liquid-absorbing thread, for example, a monofilament-like thread made of fibers such as polyethylene and polypropylene. The outer braid layer 5 in FIG. 1 is composed of liquid-soluble, liquid-absorbent and weather-resistant yarns, for example, black multifilament yarns made of fibers such as tetron and polyester. The outer braid layer 5 has a mechanical protection function such as relaxing the pressure applied to the insulator 2 of the electrode wire 3 via the inner braid layer 4 at the binding portion or the like. The braid layer 6 shown in FIG. 2 has the same structure as the outer braid layer 5 shown in FIG.

In FIG. 1, when a liquid leak such as sulfuric acid occurs, the liquid-absorbent liquid-soluble outer braid layer 5 first absorbs it, and the inner braid layer 4 holds it. Also in FIG. 2, when a leak of sulfuric acid or caustic soda occurs, the liquid-absorbing and liquid-soluble braided layer 6 absorbs and holds it. Then, the leaked liquid such as sulfuric acid dissolves the insulator 2, and the pair of conductors 1 and 1 of the electrode wire 3 is short-circuited or in a state close to a short-circuit, and the leak is detected.

Next, the results of measuring the leak detection performance with respect to sulfuric acid will be described for the present invention example ,,, and comparative example described below. The present invention example and the comparative example have an inner braid layer and an outer braid layer as shown in FIG. 1, and their specific structures are shown in Table 1. The present invention example and the comparative example have a simple braided layer as shown in FIG. 2, and their specific structures are shown in Table 2.

[0013]

[Table 1]

[0014]

[Table 2]

Particularly, the difference between the present invention example ,, and the comparative example is that in the present invention example, a product in which Hytrel is extrusion-coated to a thickness of 40 μm is used as an insulator. In contrast, the insulator used is extruded and coated with Perprene-S to a thickness of 40 μm, whereas in Comparative Example, the insulator is terephthalic acid polyhydric alcohol varnish coated and baked to a thickness of 20 μm (so-called enamel coating). ) Is used, and in the comparative example, an enamel coating having a thickness of 45 μm is used.

With respect to the above-mentioned present invention example ,, and comparative example, as shown in FIG. 3, the detection sample 11 having a length of about 1 m is placed on the pad 12, and the conductors in the electrode wires at both ends are placed. It was exposed, and a 5 kilo-ohm resistor 13 was connected to one end with a clip 14, and a leak detector 15 with a recorder 16 was connected to the other end with a clip 14. The liquid leakage detector 15 converts, for example, an AC power supply that applies an AC voltage between the electrode wires, and a current flowing by the voltage application into a DC voltage by a circuit resistance or a rectifier circuit inserted in the voltage application circuit, and then converts the reference voltage into a DC voltage. The recorder 16 detects the occurrence of abnormal current by comparing with the value, and the recorder 16 records the change in the DC voltage. Then, the detection sample 11 is placed in a thermostatic chamber where the temperature can be set to a predetermined temperature, a buret 17 is installed in the upper middle of the room, and sulfuric acid with a concentration of 98% is dropped at a rate of 0.02 ml / sec. The time (minutes) to reach to was measured.

The results of the present invention example corresponding to FIG. 1 and the comparative example are shown in Table 3 and FIG. In particular, in the low temperature range of 15 ° C or lower, the detection time of the comparative example tends to increase sharply, but the detection time of the invention example does not increase so much even in the low temperature range.

[0018]

[Table 3]

The results of the present invention example corresponding to FIG. 2 and the comparative example are shown in Table 4 and FIG. As in the case of Table 3 and FIG. 4, in the present invention example, the detection time does not increase so much even in the low temperature range.

[0020]

[Table 4]

[0021]

[Effects of the Invention] The liquid leakage detection wire of the present invention comprises an electrode wire formed by extrusion-coating a polyester elastomer as an insulator on a conductor, and this polyester elastomer is used in a wide operating temperature range from a low temperature to a high temperature. Since it has excellent mechanical strength, rubber elasticity, bending fatigue resistance, and crack propagation resistance, pinholes, crazing, etc. occur due to external force such as pressure applied to the electrode wire, tensile force, and bending during the manufacturing process and laying process. Therefore, there is no risk of malfunction due to rainfall. In addition, since the detection time is less dependent on the temperature of the liquid to be detected, such as sulfuric acid, and it is an insulator, it is possible to detect liquid leakage in a short time even at low temperatures.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid leakage detection line of the present invention.

FIG. 2 is a cross-sectional view of another liquid leakage detection line of the present invention.

FIG. 3 is a diagram showing a device for inspecting a leak detection line.

FIG. 4 is a graph showing the temperature dependence of the detection time in the leak detection line of FIG.

5 is a graph showing the temperature dependence of the detection time in the leak detection line of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 conductor 2 insulator (polyester elastomer) 3 electrode wire 4 inner braid layer 5 outer braid layer 6 braid layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadaaki Masui 2-3-1, Iwata-cho, Higashiosaka-shi, Osaka Prefecture Tatsuta Electric Cable Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A leak detection line comprising a pair of electrode wires arranged substantially in parallel with each other and a braided layer made of at least a liquid-absorbent thread provided outside the electrode wires, wherein the electrode wires serve as an insulator on a conductor. A liquid leakage detection line characterized by extrusion coating a polyester-based thermoplastic elastomer.