JPH0562838U - Leak detection line - Google Patents

Abstract

(57) [Abstract] [Purpose] A leak detection line in which a pair of electrode wires covered with an insulator are arranged substantially parallel to each other to form a core, and a pinhole is formed in the insulator of the electrode wire in the manufacturing process. Provide a leak detection line that does not have a risk of malfunction due to rainfall even if it is scratched or damaged. [Structure] A pair of electrode wires 3 coated with a thin insulator 2 that is water resistant and dissolves in a liquid to be detected is arranged on a conductor 1 in a substantially parallel manner to form a core 6, and a core 6 is formed on the outside thereof. An internal braided body 7 in which a group of water-resistant / non-absorptive yarns that do not dissolve in the target liquid and a group of water-resistant / liquid-absorbent yarns that dissolve in the detection target liquid are alternately arranged, and A leak detection line that is formed by sequentially coating an outer braid 8 made of a water-resistant, liquid-absorbent, weather-resistant yarn that is dissolved in a liquid to be detected and that has a minute gap between the pair of electrode wires 3. A leak detection line provided with a spacer 4 that is water resistant and dissolves in the liquid to be detected.

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. (See Japanese Utility Model Application No. 61-151259).

This leak detection line is a water-resistant, wire-formed pair of electrode wires made of a conductor coated with a thin insulator that dissolves in the liquid to be detected. The inner braid consists of yarns that are not soluble in the target liquid and are water resistant and non-absorbent, and the outer braid that is composed of yarns that are soluble in the target liquid and resistant to water and absorbs. Specifically, the insulating body is made of an enamel coating formed by coating and baking an unsaturated polyester resin, and the inner braid is made of, for example, a monofilament-like polyethylene fiber thread, and the outer braid is used. For example, multifilament polyester fiber yarn was used.

In the above-mentioned liquid leak detection line, when a liquid leak such as sulfuric acid is generated, it is dissolved in the liquid to be detected and the outer braid made of water-resistant and liquid-absorbent yarn absorbs the liquid leak, and the liquid to be detected is detected. The inner braid made of water-resistant and non-absorptive yarn that does not dissolve in the liquid retains the leakage, and the leakage that permeates through the inner braid dissolves the thin insulator that is water-resistant and dissolves in the liquid to be detected. , 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 of the electrode wire will not dissolve, so that rain will not be detected.

[0005]

[Problems to be solved by the device]

 In the above-mentioned conventional leak detection wire, since a pair of electrode wires coated with an insulator are twisted together, there is a possibility that pinholes may be formed in the insulator of the electrode wire during the twisting process. Also during winding or unwinding in each process, there is a risk of damage due to friction between the electrode wire insulators. In addition, the insulator may be damaged by the pressure applied between the electrode wires due to being stepped on during laying work. In particular, the enamel coating of unsaturated polyester resin is a material that is prone to crazing and cracking due to internal stress. If the insulator of the electrode wire had pinholes or scratches, it had the problem of malfunction due to rainfall.

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 dispose a pair of electrode wires coated with an insulator substantially in parallel. We provide a leak detection line that has a core formed by using a leak detection line that does not have the risk of malfunction due to rainfall even if the insulator of the electrode line is pinholes or scratches during the manufacturing process. is there.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the liquid leakage detection line of the present invention has a core formed by arranging a pair of electrode wires coated with a thin insulator that is water resistant and dissolves in a liquid to be detected on a conductor. , The group consisting of water-resistant / non-absorbent yarns that do not dissolve in the liquid to be detected and the group consisting of yarns that are water-resistant / absorbent to the liquid to be detected are alternately arranged outside A liquid leakage detection line formed by sequentially coating the inner braid and the outer braid that is dissolved in the liquid to be detected and is water-resistant, liquid-absorbent, and weather-resistant, and between the pair of electrode wires. A spacer that holds a minute gap and is water resistant and dissolves in the liquid to be detected is provided. The above-mentioned insulator is preferably extrusion-coated with a thermoplastic polyester elastomer.

[0008]

[Action]

 Since a spacer that maintains a small gap between the electrode wires and is soluble in the liquid to be detected is provided, even if pressure is applied between the electrode wires during the manufacturing process or during installation, the insulator will be damaged by the spacer buffering action. Even if the insulator of the electrode wire is damaged or pinholes occur, the probability that the electrical resistance between the electrode wires will drop below the standard value due to rainfall will be extremely low. When the liquid to be detected leaks, the outer braid consisting of threads that dissolve in the liquid to be detected, the group of liquid-soluble threads of the inner braid and the liquid-soluble spacer dissolve, while the inner braid dissolves. The leak is retained until the insulator is dissolved by the group of threads that are insoluble in the body fluid to be detected. And when the insulator is made of polyester thermoplastic elastomer, it has excellent mechanical strength, rubber elasticity, flex fatigue resistance, and crack propagation resistance in a wide operating temperature range from low temperature to high temperature. In combination with this, pinholes and scratches are less likely to occur, and the temperature dependence of the detection time for the liquid to be detected is reduced.

[0009]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a leak detection line of the present invention.

In FIG. 1, reference numeral 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, forming a pair of electrode wires 3. Reference numeral 4 is a small-diameter spacer provided between the pair of electrode wires 3, and 5 is a large-diameter interposer arranged so as to be in contact with the electrode wire 3 and the spacer 4. The electrode wire 3, the spacer 4, and the interposer 5 described above are arranged substantially in parallel, or are twisted together to form the core 6. Further, the inner braid 7 and the outer braid 8 are sequentially coated on the outside of the core 6.

The insulator 2 of the electrode wire 3 is water-resistant and thin so as to be dissolved in the liquid to be detected. For example, there is a polymer insulator with an ester bond, and it is a resin formed by polycondensation of polyvalent organic acids and polyvalent alcohols. Is obtained and is dissolved in a leaked liquid such as sulfuric acid. Among them, unsaturated polyester resins have water resistance and are quickly dissolved in sulfuric acid or caustic soda.

The insulator 2 is preferably formed by extrusion coating a thermoplastic polyester elastomer. Here, in the thermoplastic polyester elastomer (hereinafter referred to as polyester elastomer), the hard segment is made of polyester and the soft segment is polyether or polyester. Polyester-based hard segment and polyether-based soft segment include "Hytrel" (trade name of Toray-Dupont Co., Ltd.), "Perprene-P" (trade name of Toyobo Co., Ltd.), and "Lomod". (Akzo's product name) and so on. Examples of those in which the hard segment is polyester and the soft segment is polyester include "Perprene-S" (trade name of Toyobo Co., Ltd.) and "ARIN TEL-S" (trade name of Akzo). Polyester elastomer has excellent mechanical strength, rubber elasticity, bending fatigue resistance, and crack propagation resistance over a wide temperature range from low temperature to high temperature.Therefore, the pressure, tensile force, There is no risk of pinholes or scratches due to external forces such as bending or as a single factor. Further, it is particularly preferable because it has little temperature dependence on the detection target liquid such as sulfuric acid during detection.

The spacer 4 has a small diameter that is water resistant and dissolves in the liquid to be detected, and is made of, for example, a polyester string. The spacer 4 forms a minute gap between the pair of electrode wires 3.

The interposer 5 is used to make the core 6 substantially circular, and for example, a polyester string is used. In the illustrated example, the interposer 5 has substantially the same diameter as the electrode wire 3, and the electrode wire 3 and the interposer 5 are twisted in a star shape around the spacer 4.

The inner braid 7 has a group of yarns that are not dissolved in the liquid to be detected and are water-resistant / non-absorbent, and a group of yarns that are dissolved in the liquid to be detected and are water-resistant / absorbent. It is arranged in the. As shown in FIG. 3, a group 7a consisting of water-resistant / non-absorptive yarns that do not dissolve in the detection target liquid and a group 7b consisting of water-resistant / absorptive yarns that dissolve in the detection target liquid Some are braided. The filaments of group 7a are preferably monofilament yarns made of fibers such as polyethylene and polypropylene, and the yarns of group 7b are preferably multifilament yarns made of polyester fibers such as Tetron. It should be noted that the group of yarns means one yarn that is fed from one supply reel or a plurality of yarns that are gathered into one yarn when braiding. Upon contact with a leaked liquid such as sulfuric acid, the leaked liquid is absorbed into the multifilament yarn, and the multifilament yarn melts. However, since the monofilament-like thread is not dissolved and remains in the lattice shape, the leaked liquid in which the multifilament-like thread is dissolved dissolves the insulator 2 while being held by the lattice.

The outer braid 8 is made of a water-soluble, liquid-absorbent, weather-resistant yarn that is dissolved in the liquid to be detected, and is bonded to the insulator 2 of the electrode wire 3 via the inner braid 7 at the binding portion or the like. It has a mechanical protection function such as relieving the pressure applied to. As the water-soluble, liquid-absorbent and weather-resistant yarn which is dissolved in the liquid to be detected which constitutes the outer braid 8, for example, black multifilament yarn made of polyester fiber is preferable. When a leaked liquid such as sulfuric acid is generated, the outer braid 8 first absorbs it, and the inner braid 7 holds it. In particular, since the outer braid 8 has weather resistance due to black color, the outer braid 8 absorbs sunlight rays such as ultraviolet rays and prevents the inner braid 7 from changing with time.

Next, the operation of the liquid leakage detection line having the above-described configuration will be described below. In FIG. 1, when there is rainfall, the rainfall passes through the outer braid 8 and the inner braid 7 to reach the insulator 2 of the electrode wire 3. In this case, since the spacer is provided between the pair of electrode wires 3 and the minute gap is held between the electrode wires 3, even if the insulator 2 of the electrode wire 3 is damaged or pinholes are generated, The probability that the electric resistance value between the electrode wires 3 falls below the reference value is extremely low, and there is no risk of malfunction. Further, when the insulator 2 is made of a polyester thermoplastic elastomer, scratches and pinholes are less likely to occur, and in combination with the spacer 4, malfunctions can be further reduced. When there is a leak of the liquid to be detected, the leak is absorbed by the outer braid 8, passes through the inner braid 7, and is guided to the electrode wire 3. Since the outer braid 8 is made of water-resistant, liquid-absorbent, and weather-resistant yarn that dissolves in the liquid to be detected, it not only absorbs and guides the internal liquid when there is liquid leakage, but it also dissolves quickly to prevent leakage of liquid. make it easier. The inner braided body 7 has a group of yarns which are not dissolved in the liquid to be detected and are water resistant and non-absorbent, and a group of yarns which are soluble in the liquid to be detected and are water resistant and liquid absorbent. As a result, the group of liquid-soluble yarns is quickly dissolved by the liquid leakage, and a passage of the liquid leakage to the internal electrode 3 is secured, and the group of non-liquid-soluble yarns is not dissolved or absorbed. Instead, the leakage of the liquid-soluble thread is prevented from diffusing to the periphery and held until the insulator 2 of the internal electrode 3 is dissolved. Therefore, there is less variation in the time required to detect the leak, and it is possible to reliably detect the leak. Further, since the core 6 is kept circular by the intervening body 5, the entire liquid leakage detection line covering the outer braided body 8 and the inner braided body 7 becomes circular, which improves the handleability.

FIG. 2 is a sectional view of a liquid leakage detection line according to another embodiment. The difference from FIG. 1 is that instead of the small-diameter spacer 4 between the pair of electrode wires 3, a spacer 4'made of a tape wound around the electrode wires 3 and soluble in the detection target liquid due to water resistance is used. Since it is a liquid-soluble tape, it does not prevent the leakage of liquid from reaching the electrode wire 3. As such a tape, for example, a polyester tape is used. Since it is a tape, the minute gap between the pair of electrode wires 3 can be easily adjusted by changing the thickness and winding density of the tape itself. Further, since it is only necessary to secure a minute gap between the pair of electrode wires 3, it is possible to wind the tape only on one of the electrode wires 3.

Next, the difference in the case of using various materials for the insulator will be described with reference to Examples 1 to 4 of the present invention in Table 1. Inventive Example 1 uses an extruded coating of Hytrel of 40 μm as an insulator, Inventive Example 2 uses an extruded coating of halprene of 40 μm as an insulator, and in Inventive Example 3, a coating of terephthalic acid alcohol varnish is applied as an insulator (so-called enamel). 20 μm), and in Invention Example 4, terephthalic acid alcohol varnish coating baking of 40 μm was used as an insulator. The specific structure other than the insulator is shown in Table 1. In the invention example 4, an outer diameter of 0.74 mm is obtained by coating a 45 μm enamel insulator thicker than the thickness of 20 μm of the invention example 3. In this case, since the outer diameter of the electrode wire is thicker than the outer diameter of 0.69 mm in the third example of the present invention, the dimensions of the other components are changed as follows. First, the outer diameter of the central spacer is 0.3 mmφ and the outer diameter of the intervening body 5 in the outer layer is 0.74 mmφ. Second, the inner braid consists of a left-handed thread and a right-handed thread, each of which has 100 denier twin yarns of black TETRON yarn 7b, 3 strokes 4 strokes, and 200 denier single yarn of white polyethylene thread 7a, 3 strokes 4 strokes. The total number of strokes is 16 and the outer diameter is about 2.6 mm. Thirdly, the outer braid is made of 100 denier twin yarns of black Tetron yarn 4 having 24 strokes and braided at a pitch of about 14 mm to have an outer diameter of about 3.4 mm.

[0020]

[Table 1]

By increasing the thickness of the insulator of the electrode wire as in the case of the present invention example 4, as compared with the case of the present invention example 3, even if the insulator is damaged during the manufacturing process or during installation, the pinhole The risk of occurrence is almost zero, and the malfunction due to the isolation effect of the spacer can be reduced. However, the thicker the insulator, the longer the leak detection time. Therefore, as in Examples 1 and 2 of the present invention, those obtained by extrusion-coating a thermoplastic polyester elastomer such as Hytrel or Perprene as an insulator are preferable. This polyester-based thermoplastic elastomer has a unique effect that not only scratches and pinholes are unlikely to occur, but also temperature dependence at low temperatures is small. Therefore, Table 2 shows the results of the temperature dependence tests of Examples 1 to 4 of the present invention.

[0022]

[Table 2]

Here, the leak detection time was measured by the test apparatus shown in FIG. A detection sample 11 having a length of about 1 m is placed on the pad 12, the conductors of the electrode wires at both ends are exposed, a 5 kΩ resistor 13 is connected to one end by a clip 14, and a recorder 16 is connected to the other end. The attached leak detector 15 was connected with a clip 14. The liquid leakage detector 15 converts the current flowing by voltage application into a DC voltage by a circuit resistance or a rectifier circuit inserted in a voltage application circuit, for example, an AC power supply that applies an AC voltage between the electrode wires, and compares it with a reference voltage value. Then, the occurrence of abnormal current is detected, and the recorder 16 records the change in the DC voltage. Then, the detection sample 11 is placed in a temperature-controlled room 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 dripped at a rate of 0.02 ml / sec. The time (minutes) required to reach less than a kilohm was measured.

The data in Table 2 is shown graphically in FIG. 5 and the results are clarified. In particular, in the low temperature range of 15 ° C or lower, the invention examples 1 and 2 in which the polyester thermoplastic elastomer such as hightrel or perprene is used as an insulator do not significantly increase the detection time even in the low temperature range, but the enamel is used. Inventive examples 3 and 4 made of an insulator show a tendency that the detection time rapidly increases in a low temperature range. As is clear from this result, the invention examples 3 and 4 are sufficient when the low temperature characteristics are not required, but the invention examples 1 and 2 are preferable when the low temperature characteristics are required.

[0025]

[Effect of the device]

 The leak detection line of the present invention is provided with a spacer that is water-resistant and holds a minute gap between a pair of electrode lines and that dissolves in the detection target liquid. Pressure is applied between the electrode lines during the manufacturing process or during installation. Even if an electric shock is applied, there is no risk that the insulator will be damaged due to the buffering effect of the spacer, and even if there is a pinhole in the insulator of the electrode wire, the electrical resistance between the electrode wires will drop below the standard value due to rainfall or other factors. The probability is extremely low. When the liquid to be detected leaks, the outer braid consisting of the liquid-soluble yarn, the group consisting of the liquid-soluble yarns of the inner braid and the liquid-soluble spacer are dissolved, while the inner braid is dissolved. Leakage is held until the insulator is dissolved by the group consisting of non-liquid-soluble yarns, and variations in leak detection time are reduced. If the insulating material is a thermoplastic polyester elastomer, pinholes and scratches are less likely to occur due to the buffering function of the spacer, and the temperature dependence of the detection time for the liquid to be detected is further reduced. Almost no liquid can be detected, and leaks can be detected 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 structural diagram of an inner braid.

FIG. 4 is a diagram showing a device for inspecting a leak detection line.

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

[Explanation of symbols]

 1 conductor 2 insulator 3 electrode wire 4, 4'spacer 5 interposer 6 core 7 inner braid 8 outer braid

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sainori Kawakami 2-3-1 Iwata-cho, Higashi-Osaka City, Osaka Prefecture Tatsuta Electric Wire Co., Ltd. (72) Mitsuo Ishizaka Iwata-cho, Higashi-Osaka City, Osaka Prefecture 2-3-1, Tatsuta Electric Cable Co., Ltd.

Claims (4)

[Scope of utility model registration request] 1. A pair of electrode wires coated with a thin insulator that is water resistant and dissolves in a liquid to be detected is arranged substantially in parallel on a conductor to form a core. For the inner braid and the liquid to be detected, in which a group of non-dissolving water-resistant and non-liquid-absorbing yarns and a group of water-soluble and liquid-absorbing yarns that dissolve in the liquid to be detected are arranged alternately A leak detection line formed by sequentially coating an outer braid composed of melted, water-resistant / liquid-absorbing, weather-resistant yarn, which is water-resistant and has a minute gap between the pair of electrode wires. A leak detection line characterized by having a spacer that dissolves in the liquid. 2. The leak detection line according to claim 1, wherein the insulator is extrusion-coated with a polyester thermoplastic elastomer. 3. The leak detection wire according to claim 1, wherein a pair of large-diameter interposers having an outer diameter substantially equal to that of the pair of electrode wires are arranged around the spacer and are twisted in a star shape. A leak detection line characterized by having a substantially circular core. 4. The leak detection line according to claim 1, wherein at least one electrode wire is wrapped with a tape which is water resistant and dissolves in a liquid to be detected to form a spacer. ..