Liquid leak detecting line

Abstract

The present invention addresses the problem of providing a liquid leak detecting line capable of suppressing erroneous detection while suppressing a significant decrease in liquid leak detection performance.　In order to resolve the abovementioned problem, the present invention provides a liquid leak detecting line comprising a plurality of detecting lines each comprising a conductor and a braided body covering the conductor, wherein the plurality of detecting lines include a first detecting line and a second detecting line, the braided body is configured from an electrically insulating yarn, and an electrically conductive liquid is detected when the liquid electrically connects the conductor of the first detecting line and the conductor of the second detecting line through the braided bodies, and wherein the braided body of one or both of the first detecting line and the second detecting line comprises a first yarn and a second yarn intersecting the first yarn, and the second yarn is thinner than the first yarn.

Description

Leak detection wire CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2023-202477, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a liquid leakage detection line.

[0003] Conventionally, a liquid leakage detection wire such as that shown in Patent Document 1 below has been used to detect leakage from a pipe or the like through which an electrically conductive liquid such as water flows. A known liquid leakage detection wire includes a plurality of detection wires, each having a conductor and a braid covering the conductor, the braid being made of electrically insulating yarn, and the braid normally ensuring electrical insulation between the conductors. When liquid leaks from a pipe or the like, the liquid electrically connects the conductors of one detection wire to another detection wire through the braid, thereby detecting a leakage. Another known liquid leakage detection wire of this type includes an outer braid that bundles the detection wires together.

[0004] When this type of leak detection wire is laid along a pipe, for example, it may be necessary to lay it over a place where pipes are connected with flanges. Furthermore, leak detection wires are often laid in narrow spaces. For this reason, leak detection wires with excellent flexibility are often used.

[0005] Japanese National Law Publication No. 6-35294

[0006] Liquid leak detection wires have a problem in which the conductors of two detection wires can unintentionally become electrically connected to each other, resulting in false detection of a leak even when no leak is occurring. A solution to this problem is needed. One possible solution is to use a detection wire in which the conductors are covered with a dense braid. However, such a solution can make it difficult to establish electrical connection between the conductors when the amount of leakage is small, which can significantly reduce leak detectability. Until now, no effective means has been provided to solve this problem. Therefore, an object of the present invention is to provide a liquid leak detection wire that can reduce false detection while preventing a significant reduction in leak detectability.

[0007] In order to solve the above problems, the present invention provides a liquid leakage detection line comprising a plurality of detection lines each having a conductor and a braid covering the conductor, the plurality of detection lines including a first detection line and a second detection line, the braid being made of electrically insulating thread, and an electrically conductive liquid being detected when the conductor of the first detection line and the conductor of the second detection line are electrically connected through the braid, and the braid of one or both of the first detection line and the second detection line comprises a first thread and a second thread intersecting the first thread, and the second thread is thinner than the first thread.

[0008] Fig. 1 is a schematic perspective view showing a leakage detection line according to one embodiment. Fig. 2 is a schematic diagram showing the shape of a cross section taken along line II-II in Fig. 1. Fig. 3 is a schematic diagram showing the shape of a cross section taken along line III-III in Fig. 1.

[0009] An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1 , a liquid leakage detection wire 100 of this embodiment includes a plurality of detection wires 10. The liquid leakage detection wire 100 of this embodiment includes a pair of a first detection wire 10a and a second detection wire 10b. Each of the first detection wire 10a and the second detection wire 10b of this embodiment includes a conductor 11 and a braid 12 covering the conductor 11. The first detection wire 10a of this embodiment includes a first conductor 11a that serves as the first conductor 11 of the liquid leakage detection wire 100 and a first braid 12a that covers the first conductor 11a. The second detection wire 10b includes a second conductor 11b that serves as the second conductor 11 of the liquid leakage detection wire 100 and a second braid 12b that covers the second conductor 11b.

[0010] Each of the first conductor 11a and the second conductor 11b is made of an electrically conductive wire. Each of the first braided body 12a and the second braided body 12b is made of an electrically insulating wire (for example, a wire having a volume resistivity of 1×10 at 25° C.). ８ The liquid leakage detection wire 100 of this embodiment is configured such that, when an electrically conductive liquid leaks from a pipe or the like, the liquid reaches the first conductor 11a through the first braided body 12a and the second conductor 11b through the second braided body 12b, electrically connecting the first conductor 11a and the second conductor 11b, resulting in a significant drop in the electrical resistance between the two detection wires 10, which should normally be electrically insulated, thereby detecting the presence of the liquid.

[0011] The liquid leakage detection wire 100 of this embodiment is not particularly limited in its use, but can be arranged, for example, along a pipe connected with a flange. It can also be arranged parallel to or wrapped around a small-diameter pipe with many bends, such as the pipe of a water-cooled large-capacity data server. The liquid leakage detection wire 100 of this embodiment, which can be arranged in a narrow space by being bent with a small radius of curvature (for example, a radius of curvature of 10 mm or less), has a small diameter and excellent flexibility and bendability.

[0012] The first detection wire 10a and the second detection wire 10b of the liquid leakage detection wire 100 are in contact with each other and extend in the length direction DL of the liquid leakage detection wire 100, and are arranged parallel to each other in the length direction DL of the liquid leakage detection wire 100. The liquid leakage detection wire 100 of this embodiment is provided with an outer braided body 20 that bundles and covers the first detection wire 10a and the second detection wire 10b so that they remain in contact with each other. The outer braided body 20 is configured to be tubular in shape and thick enough to enclose the first detection wire 10a and the second detection wire 10b, and to extend in the length direction DL of the liquid leakage detection wire 100.

[0013] The first detection wire 10a and the second detection wire 10b may be simply arranged side by side, or may be twisted together in the liquid leakage detection wire 100. Assuming that the liquid leakage detection wire 100 will be bent, the contact between the detection wires 10a and 10b is likely to be maintained in a good state if the first detection wire 10a and the second detection wire 10b are stacked in the bending direction. On the other hand, if the first detection wire 10a and the second detection wire 10b are arranged side by side at the bend and, for example, an edge of a pipe flange hits the midpoint between the first detection wire 10a and the second detection wire 10b, causing local stress to act on that point, the first detection wire 10a and the second detection wire 10b may become separated, resulting in reduced liquid detectability. Furthermore, even when bending stress acts evenly on two detection wires 10 arranged side by side, if the first braided body 12a and the second braided body 12b each expand laterally and their cross-sectional shapes deform into elongated elliptical cylinders, the distance between the first conductor 11a and the second conductor 11b may increase.

[0014] Twisting the first detection wire 10a and the second detection wire 10b together can prevent them from unintentionally separating from each other. Twisting the first detection wire 10a and the second detection wire 10b at a short pitch makes it easier for them to maintain contact. From this perspective, the number of twists of the first detection wire 10a and the second detection wire 10b per unit length of the liquid leakage detection wire 100 can be, for example, 15 times / m or more. The number of twists of the first detection wire 10a and the second detection wire 10b may be 20 times / m or more, or even 25 times / m or more. On the other hand, twisting the first detection wire 10a and the second detection wire 10b at a long pitch is advantageous in terms of providing the liquid leakage detection wire 100 with good flexibility. From this perspective, the number of twists of the first detection wire 10a and the second detection wire 10b per unit length of the liquid leakage detection wire 100 can be, for example, 90 times / m or less. The number of twists of the first detection wire 10a and the second detection wire 10b may be 80 times / m or less, or may be 70 times / m or less.

[0015] The liquid leakage detection line 100 may include three or more detection lines 10, including a third detection line. The liquid leakage detection line 100 may be configured to be able to detect liquid leakage not only based on the electrical connection status between the first detection line 10a and the second detection line 10b, but also based on the electrical connection status between the first detection line and the third detection line, or the electrical connection status between the second detection line and the third detection line, etc.

[0016] The liquid leakage detection wire 100 may include wires other than the detection wire 10. When measuring the electrical connection between the first detection wire 10a and the second detection wire 10b by applying a voltage between the first detection wire 10a and the second detection wire 10b at one end of the liquid leakage detection wire 100, the first detection wire 10a and the second detection wire 10b are in an open (insulated) state at the other end of the liquid leakage detection wire 100. The wires other than the detection wire 10 may be, for example, electric wires that are electrically connected to the first detection wire 10a and the second detection wire 10b at the other end of the liquid leakage detection wire 100. In this case, the conductor 11 (first conductor 11a) of one of the first detection wires 10 (e.g., the first detection wire 10a) of the first detection wire 10a and the second detection wire 10b is made of a conductor similar to that of a general electric wire (e.g., copper wire, aluminum wire, etc.), and the conductor 11 (second conductor 11b) of the other detection wire 10 (e.g., the second detection wire 10b) is made of a conductor (hereinafter referred to as a "resistive conductor") made of a material with a higher electrical resistance than the conductors of general electric wires, such as alloy wire, and by connecting the electric wires to a detection wire equipped with a resistive conductor, it becomes easier to identify the location of the leak when a leak is detected.

[0017] The wire may function as a tension member, or may be something like an interposing piece that fills the gap between the external braid 20 and the detection wire 10. When the first detection wire 10a and the second detection wire 10b are covered with the external braid 20 together with such an interposing piece, the tightening force of the external braid 20 is more likely to act as a contact force between the first detection wire 10a and the second detection wire 10b, and even if the leakage detection wire 100 is bent with a particularly small radius of curvature (for example, a radius of curvature of 8 mm or less), it is possible to prevent the detection wires 10 (conductors 11) from separating from each other.

[0018] The first braid 12a includes a first thread (hereinafter also referred to as a "right-handed thread") wound around the first conductor 11a so as to turn clockwise around the first conductor 11a when the longitudinal direction DL of the liquid leakage detection wire 100 is defined as the direction of travel, and a second thread (hereinafter also referred to as a "left-handed thread") wound around the first conductor 11a so as to turn counterclockwise around the first conductor 11a. In the first braid 12a, the right-handed thread and the left-handed thread are interwoven while switching positions in the radial direction DD of the liquid leakage detection wire 100 toward the direction of travel. The second braid 12b is similarly braided, and is braided with a right-handed thread wound around the second conductor 11b while turning clockwise and a left-handed thread wound around the second conductor 11b while turning counterclockwise toward the direction of travel.

[0019] In each of the first detection wire 10a and the second detection wire 10b included in the leakage detection wire 100, the thickness of two threads is generated at the intersection of the right-handed and left-handed threads that make up the braided body 12. Therefore, as shown in Figure 2, the calculated outer diameter, when expressed as a radius (hereinafter also referred to as the "theoretical radius (Ri)"), is the sum of the radius of the conductor 11 and the thickness of two threads, and the diameter (hereinafter also referred to as the theoretical diameter (Di)) is the sum of the diameter Dc of the conductor 11 and the thickness of four threads.

[0020] For the reasons described above, by using thinner threads for the braid 12, the thickness of the detection wire 10 can be reduced, and the diameter of the liquid leakage detection wire 100 can also be reduced. In this regard, the inventors have focused on the structure of the liquid leakage detection wire and discovered that not all points in the braid have a thickness equivalent to two threads. For example, at the midpoint between where one right-handed thread passes over a left-handed thread and then slips under the next left-handed thread, the thickness of the braid is equivalent to one thread. That is, at this midpoint, when the direction of rotation around the conductor 10 of the detection wire 10 is defined as the circumferential direction, the right-handed thread and the left-handed thread are aligned side by side in the circumferential direction, resulting in the thickness of the braid in the radial direction of the detection wire 10 being equivalent to one thread. Therefore, if all of the threads for the braid are thin, it becomes difficult to ensure the distance between the conductors. Furthermore, when a liquid leak detection line is bent with a small radius of curvature to fit around a pipe flange, gaps between adjacent threads in the braid can become large. In such locations, the difference in bending rigidity between the braid and the conductor can cause the conductor to protrude through the gap and out of the braid. Therefore, simply thinning the threads constituting the braid not only makes the conductor more likely to protrude, but also makes it more likely that the protruding conductor will penetrate the braid of an adjacent detection line from the outside and come into contact with the conductor of that detection line. Therefore, simply thinning the threads may not provide sufficient insulation between the conductors, resulting in false detection. While it may be possible to form a dense braid using thin threads to prevent the conductor of the detection line from being exposed, this could result in a longer time for the liquid to reach the conductor through the braid, potentially reducing the responsiveness of the leak detection system.

[0021] In this embodiment, the above problem is solved by making the right-handed and left-handed twisted yarns different in thickness. That is, by making one of the right-handed and left-handed twisted yarns thinner, the theoretical diameter (Di in FIG. 2) of the detection wire 10 can be reduced. As shown in FIG. 3, where the right-handed and left-handed twisted yarns are aligned side by side in the circumferential direction, a distance is maintained between the conductors 11 equal to the thickness of the thicker yarn (first yarns 121a, 121b). Therefore, in this embodiment, false detection by the leakage detection wire 100 can be suppressed.

[0022] In the liquid leakage detection wire 100 of this embodiment, the left-handed twisted yarn may be thinner than the right-handed twisted yarn, or the right-handed twisted yarn may be thinner than the left-handed twisted yarn. In the liquid leakage detection wire 100 of this embodiment, the braid 12 may be formed by braiding only one of the first braid 12a and the second braid 12b with yarns of different diameters (thicknesses), or both braids may be formed by braiding with yarns of different diameters. In this embodiment, to more reliably achieve the above-mentioned effects, both the first braid 12a and the second braid 12b are braids formed by yarns of different diameters. Furthermore, as shown in FIG. 1 , the first braid 12a of this embodiment uses left-handed twisted yarns that are thinner than the right-handed twisted yarns. On the other hand, the second braid 12b uses right-handed twisted yarns that are thinner than the left-handed twisted yarns. In this embodiment, this configuration makes it easier for the first threads 121 of two adjacent detection lines 10 to abut against each other, and makes it easier to maintain a constant distance between the conductors 11 .

[0023] The right-handed or left-handed twisted yarn may be a monofilament yarn, a multifilament yarn, or a spun yarn. The right-handed or left-handed twisted yarn is preferably a monofilament yarn or a multifilament yarn. The right-handed or left-handed twisted yarn is preferably not deformed by a force applied in the radial direction (thickness direction), and is preferably a monofilament yarn, or in the case of a multifilament yarn, a twisted yarn may be preferably employed. Examples of the monofilament yarn include polyolefin resin monofilaments such as polyethylene resin monofilaments and polypropylene resin monofilaments; polyester resin monofilaments such as polyethylene terephthalate resin monofilaments, polybutylene terephthalate resin monofilaments, polylactic acid resin monofilaments, and polyethylene terenaphthalate resin monofilaments; polyamide resin monofilaments such as polyamide 6 resin monofilaments, polyamide 66 resin monofilaments, polyamide 610 resin monofilaments, semi-aromatic polyamide resin monofilaments, and wholly aromatic polyamide resin monofilaments; polytetrafluoroethylene resin monofilaments, ethylene-tetrafluoroethylene copolymer resin monofilaments, and polytetrafluoroethylene copolymer resin monofilaments. The monofilament may be an ethylene-perfluoroalkyl ether copolymer resin monofilament, a tetrafluoroethylene-hexafluoropropylene copolymer resin monofilament, a fluororesin monofilament such as a polyvinylidene fluoride resin monofilament, a super engineering plastic monofilament such as a polyethersulfone resin monofilament, a polysulfone resin monofilament, a polyphenylsulfone resin monofilament, a polyphenylene sulfide resin monofilament, a polyetherimide resin monofilament, or a polyphenylene ether resin monofilament, an ethylene-vinyl acetate copolymer resin monofilament, a polyvinyl chloride resin monofilament, a polyurethane resin monofilament, or a thermoplastic elastomer monofilament. The monofilament yarn may be made of a highly hydrophilic resin such as a polyester resin monofilament or a polyamide resin monofilament, as these have excellent detectability when the detection target is water, etc.Furthermore, the monofilament thread may be a super engineering plastic monofilament in order to improve the flame retardancy of the leakage detection wire 100 .

[0024] Examples of materials for the multifilament yarn include those similar to those for the monofilament yarns exemplified above. When the multifilament yarn is a twisted yarn, the multifilament yarn may be a soft twist yarn having a twist count of less than 500 times (500 T / m) per 1 m length, a medium twist yarn having a twist count of 500 times (500 T / m) or more but less than 1000 times (1000 T / m), a hard twist yarn having a twist count of 1000 times (1000 T / m) or more but less than 2500 times (2500 T / m), or an ultra-hard twist yarn having a twist count of 2500 times (2500 T / m) or more. One of the right-handed and left-handed twisted yarns may be a monofilament yarn and the other a multifilament yarn. When one or both of the right-handed and left-handed twisted yarns are twisted yarns, the twisted yarns may be S-twisted yarns or Z-twisted yarns. The right-handed and left-handed yarns may be S-twisted yarns and Z-twisted yarns, or both may be S-twisted yarns, or both may be Z-twisted yarns.

[0025] The thickness of the first thread (the right-handed thread in the first detection wire 10a and the left-handed thread in the second detection wire 10b), which is the thicker of the right-handed and left-handed threads, and the second thread (the left-handed thread in the first detection wire 10a and the right-handed thread in the second detection wire 10b), which is the thinner thread, can be changed as appropriate depending on the location of use of the leakage detection wire 100 and the thickness of the first conductors 11a and second conductors 11b. In this embodiment, the thickness (diameter: D1) of the first thread 121 can be, for example, anywhere in the range of 0.2 mm to 0.3 mm. In this embodiment, the thickness (diameter: D1) of the first thread 121 can be 0.21 mm or more or 0.22 mm or more. The thickness (diameter: D1) of the first thread 121 can be 0.29 mm or less or 0.28 mm or less. In this embodiment, the thickness (diameter: D2) of the second thread 122 can be, for example, any value within a range of 0.05 mm or more and less than 0.2 mm. In this embodiment, the thickness (diameter: D2) of the second thread 122 may be 0.08 mm or more, or 0.10 mm or more. The thickness (diameter: D2) of the second thread 122 may be 0.18 mm or less, or 0.17 mm or less.

[0026] The thickness (D1, D2) of the first thread 121 and the second thread 122 can be measured using a digital micrometer, and can be calculated by arithmetically averaging the thickness values ​​measured with the digital micrometer at multiple randomly selected locations (e.g., 10 locations) of a single thread.

[0027] The difference in thickness between the first thread 121 and the second thread 122 (ΔD = D1 - D2) can be, for example, 0.05 mm or more and 0.15 mm or less. The difference in thickness between the first thread 121 and the second thread 122 (ΔD) may be 0.06 mm or more, or 0.07 mm or more. The difference in thickness between the first thread 121 and the second thread 122 (ΔD) may be 0.14 mm or less, or 0.13 mm or less.

[0028] The ratio (D2 / D1) of the thickness of the second thread 122 to the thickness of the first thread 121 can be, for example, 0.30 or more and 0.80 or less. The ratio (D2 / D1) may be 0.35 or more, or 0.40 or more. The ratio (D2 / D1) may be 0.75 or less, or 0.70 or less.

[0029] The first braid 12a and the second braid 12b may each be composed of a plurality of right-handed twisted yarns and a plurality of left-handed twisted yarns. The material and thickness of the right-handed twisted yarns in the first braid 12a may be the same as or different from the material and thickness of the right-handed twisted yarns in the second braid 12b. The material and thickness of the left-handed twisted yarns in the first braid 12a may also be the same as or different from the material and thickness of the left-handed twisted yarns in the second braid 12b. The first braid 12a and the second braid 12b may have the same or different weave structures.

[0030] The first braid 12a and the second braid 12b can be, for example, braided with right-handed and left-handed threads in a plain weave, twill weave (twill weave), satin weave, or other weave. In a satin weave, one of the right-handed and left-handed threads crosses the other thread with a skip of four or more threads. This allows the threads to be in close contact where the detection line is straight, but the gaps between the threads tend to widen where the detection line is bent with a small radius of curvature, potentially exposing the conductor. In a plain weave with right-handed and left-handed threads, each of the right-handed and left-handed threads crosses the other thread every single thread, making it difficult for adjacent right-handed and left-handed threads to be closely aligned. In addition, a plain weave of right-handed and left-handed yarns tends to reduce the flexibility of the sensing wire when bending compared to a satin weave, but the yarns are less likely to widen even in areas where the sensing wire is bent with a small radius of curvature. Among the braids braided in the above weave, a braid braided in which right-handed and left-handed yarns are braided to form a twill weave can achieve a good balance between flexibility and the effect of suppressing conductor exposure. In particular, a braid braided in which right-handed and left-handed yarns are braided to form a 2 / 2 diagonal pattern is suitable for the first braid 12a and the second braid 12b of this embodiment.

[0031] In the first braided body 12a and the second braided body 12b, it is preferable that the number of right-handed twisted threads (number of held threads) and the number of left-handed twisted threads (number of held threads) that make up one stitch are small in order to prevent gaps from forming between the threads and prevent exposure of the conductor 11, and it is preferable that the number of held threads is 2 or less for each, and it is more preferable that the number of held threads is 1 for each.

[0032] The number of stitches (thread count) formed in the first braid 12a within a section making one turn around the first conductor 11a and the number of stitches (thread count) formed in the second braid 12b while making one turn around the second conductor 11b vary depending on the sizes of the first conductor 11a and the second conductor 11b, but are, for example, between 4 and 20. The number of stitches in the first braid 12a and the second braid 12b may be 16 or less, or may be 12 or less.

[0033] The winding pitch of the right-handed or left-handed twisted yarn in the first detection wire 10a (the distance traveled per revolution around the first conductor 11a) can be, for example, 4 mm or more and 20 mm or less. Similarly, the winding pitch of the right-handed or left-handed twisted yarn in the second detection wire 10b (the distance traveled per revolution around the second conductor) can be, for example, 4 mm or more and 20 mm or less. The winding pitch may be 5 mm or more, 6 mm or more, or 7 mm or more. The winding pitch may be 18 mm or less, 16 mm or less, or 14 mm or less.

[0034] The conductor diameter (Dc) of the first conductor 11a and the second conductor 11b may be the same or different, and may be, for example, 0.20 mm or more and 1.00 mm or less. The conductor diameter (Dc) of the first conductor 11a and the second conductor 11b may be 0.25 mm or more, or 0.30 mm or more. The conductor diameter (Dc) of the first conductor 11a and the second conductor 11b may be 0.80 mm or less, or 0.60 mm or less.

[0035] The first conductor 11a and the second conductor 11b may be a single wire, but are preferably twisted wires. The first conductor 11a and the second conductor 11b have a nominal cross-sectional area of, for example, 0.024 mm ２ More than 0.5 mm ２The nominal cross-sectional area of ​​the first conductor 11a and the second conductor 11b may be 0.035 mm ２ It may be 0.05 mm or more. ２ The nominal cross-sectional area of ​​the first conductor 11a and the second conductor 11b may be 0.3 mm or more. ２ It may be 0.2 mm or less, ２ It may be less than 0.15 mm ２ It may be the following:

[0036] When the first conductor 11a or the second conductor 11b is a twisted wire, it may be a bunched twisted conductor or a concentric twisted conductor. When the first conductor 11a or the second conductor 11b is a twisted wire, the twist pitch of the radially outermost wire is, for example, 3 mm or more and 50 mm or less. The twist pitch may be 4 mm or more, or 5 mm or more. The twist pitch may be 30 mm or less, 20 mm or less, or 15 mm or less.

[0037] The first conductor 11a and the second conductor 11b are preferably made of annealed copper wires, which may be tin-plated or unplated.

[0038] In the braid 12, the thicker first thread 121 (right-handed in the first detection wire 10a) has higher rigidity than the thinner second thread 122 (left-handed in the first detection wire 10a), and has higher resistance to twisting in the direction in which the thicker thread tightens (clockwise in the first detection wire 10a). When the first conductor 11a and the second conductor 11b are twisted wires, by twisting the outermost layer of wires in the opposite direction to the twisting direction of the first thread 121 (counterclockwise: S twist in the first detection wire 10a), it is possible to expect an effect of suppressing the twist from unraveling and the wires from coming out of the braid 12. Meanwhile, in the braid 12, the thinner second thread 122 (left-handed in the first detection wire 10a) has better conformability to the surface of the conductor 11 than the thicker first thread 121 (right-handed in the first detection wire 10a). When the first conductor 11a and the second conductor 11b are twisted wires, the twist direction of the outermost wire is opposite to the direction of rotation of the second thread 122 (clockwise: Z twist for the first detection wire 10a), which is expected to have the effect of preventing the tip of the broken wire from protruding from the braided body 12 in the event of a break in the wire.

[0039] It is preferable that the first braid 12a and the second braid 12b cover the first conductors 11a and the second conductors 11b so as to satisfy the following inequality (1).

[0040] Length occupancy rate≦45% (1) Length occupancy rate={(Wn1×Cn1×D1) / P1+(Wn2×Cn2×D2) / P2}×100% Wn1=number of holds of first yarn, Wn2=number of holds of second yarn, Cn1=number of skeins of first yarn, Cn2=number of skeins of second yarn, D1=diameter of first yarn (mm), D2=diameter of second yarn (mm), P1=circumference pitch of first yarn (thick yarn) in the length direction of the detection line (mm), P2=circumference pitch of second yarn (thin yarn) in the length direction of the detection line (mm) The winding pitch (P1) of the first thread 121 and the winding pitch (P2) of the second thread 122 can be determined by measuring the length (length of the detection line) traveled by the right-handed or left-handed thread until it has wound around the conductor 11 a predetermined number of times (for example, 10 times) with the length direction of the first detection line 10a or the second detection line 10b as the direction of travel, and then dividing this length by the number of times of winding.

[0041] The length occupancy ratio calculated by the above formula may be 43% or less, 41% or less, 39% or less, 37% or less, or 35% or less. The length occupancy ratio may be, for example, 10% or more. The length occupancy ratio may be 12% or more, 15% or more, or 18% or more.

[0042] The first braided body 12a and the second braided body 12b have an area (π·(Di ２ -Dc ２ ) / 4), the cross-sectional area occupation ratio calculated as the area ratio of the yarn in the total area of ​​the yarn is preferably 30% or more and 50% or less. The cross-sectional area occupation ratio may be 32% or more, 33% or more, or 34% or more. The cross-sectional area occupation ratio may be 35% or more. The cross-sectional area occupation ratio may be 48% or less, 46% or less, or 44% or less. The cross-sectional area occupation ratio may be 40% or less.

[0043] The cross-sectional area occupancy rate can be calculated using the following formula (2).

[0044] Cross-sectional area occupancy rate (%) = {(ΣS1 + ΣS2) / (Si - Sc)} × 100 ΣS1: Cross-sectional area of ​​the first yarn (thick yarn) (π D1 ２ / 4) × number of first threads (thick threads) in the detection line cross section ΣS2: cross-sectional area of ​​second threads (thin threads) (π D2 ２ / 4) × number of second threads (thin threads) in the cross section of the detection line Si: theoretical cross-sectional area of ​​the detection line (= {(π × Di ２ ) / 4}) Di: Theoretical diameter of the detection wire (= conductor diameter + diameter (D1) of the first thread (thick thread) × 2 + diameter (D2) of the second thread (thin thread) × 2) Sc: Conductor cross-sectional area (= {(π × Dc ２ ) / 4}) Dc: conductor diameter The outer braid 20 covering the first detection wire 10a and the second detection wire 10b can be made of, for example, glass fiber yarn, basalt fiber yarn, aramid fiber yarn, polyester fiber yarn, or the like.

[0045] The liquid leakage detection wire 100 of this embodiment can be used to detect not only water but also aqueous solutions and organic solvents with high conductivity. －３ The conductivity of the liquid to be detected at room temperature (e.g., 25°C) is preferably 1 x 10 －２ (μS / cm) or more, and may be 1×10 －１ The resistivity may be 1 (μS / cm) or more, or 1 (μS / cm) or more. Specific examples of liquids suitable for detection include water; acidic solutions such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and acetic acid; alkaline aqueous solutions such as ammonia and sodium hydroxide; and hydrophilic organic solvents such as methyl alcohol, ethyl alcohol, acetone, propylene glycol, and ethylene glycol.

[0046] The liquid leakage detection wire 100 of this embodiment is useful for detecting liquid leakage in devices with significant installation space constraints, such as water-cooled data servers, but its use is not particularly limited, and it can also be used to detect liquid leakage in pipes, joints, valves, etc. in general equipment, and can also be used to detect liquid leakage in heat exchangers, tanks, etc. In other words, the disclosure of the liquid leakage detection wire 100 in this embodiment is limited, and the liquid leakage detection wire 100 of the present invention is in no way limited to the above examples.

[0047] This specification includes the following disclosures regarding inventions of liquid leakage detection wires: [1] A liquid leakage detection wire comprising a plurality of detection wires each including a conductor and a braid covering the conductor, the plurality of detection wires including a first detection wire and a second detection wire, the braid being made of electrically insulating yarn, and an electrically conductive liquid being detected when the conductor of the first detection wire electrically connects with the conductor of the second detection wire through the braid, the braid of one or both of the first detection wire and the second detection wire comprising a first yarn and a second yarn intersecting the first yarn, the second yarn being thinner than the first yarn. [2] A liquid leakage detection wire according to [1], wherein the first yarn is a monofilament or multifilament yarn having a diameter of 0.2 mm or more and 0.3 mm or less, and the second yarn is a monofilament or multifilament yarn having a diameter of 0.05 mm or more and less than 0.2 mm. [3] The liquid leakage detection wire according to [2], wherein the number of the first threads held in the braid is 1, and the number of the second threads held in the braid is 1. [4] The liquid leakage detection wire according to any one of [1] to [3], wherein the conductor of one or both of the first detection wire and the second detection wire is covered with the braid so as to satisfy the following inequality (1):

[0048] Length occupancy rate≦45% (1) Length occupancy rate={(Wn1×Cn1×D1) / P1+(Wn2×Cn2×D2) / P2}×100% Wn1=number of holds of first yarn, Wn2=number of holds of second yarn, Cn1=number of skeins of first yarn, Cn2=number of skeins of second yarn, D1=diameter of first yarn (mm), D2=diameter of second yarn (mm), P1=circumference pitch of first yarn in the length direction of detection line (mm), P2=circumference pitch of second yarn in the length direction of detection line (mm)

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. (Comparative Example 1 (Conventional Example)) As shown in Table 1, a leakage detection wire of Comparative Example 1 (conventional example) was produced by braiding a first detection wire and a second detection wire together with basalt yarn and providing an outer braided body made of the basalt yarn.

[0050] The first and second detection lines had the same structure.

[0051] Each conductor was a stranded wire (strand pitch 6 mm) made by twisting together seven tin-plated annealed copper wires each having a thickness of 0.127 mm.

[0052] The conductor was braided with monofilament threads having a thickness of 0.25 mm.

[0053] The braid was produced so that the right-handed and left-handed twisted yarns had one twist and four ends, and the winding pitch of each yarn was 10 mm.

[0054] The leakage detection wire of Comparative Example 1 had a thickness (theoretical diameter) of 1.76 mm, and the length occupation rate and cross-sectional area occupation rate were calculated using the following formulas to be 20.0% (length occupation rate) and 19.8% (cross-sectional area occupation rate), respectively. Length occupation rate = {(number of right-handed thread turns 1 x number of right-handed thread turns 4 x right-handed thread diameter 0.25) / pitch 10 + (number of left-handed thread turns 1 x number of left-handed thread turns 4 x left-handed thread diameter 0.25) / pitch 10} x 100 (%) Cross-sectional area occupation rate = {cross-sectional area of ​​right-handed thread (π 0.25) ２ / 4) x number of right-handed turns 4 + left-handed turning cross-sectional area (π 0.25 ２ / 4) × number of left-handed turns 4} / [detection line theoretical cross-sectional area {π × (conductor diameter 0.76 + right-handed turn diameter 0.25 × 2 + left-handed turn diameter 0.25 × 2) ２ / 4}-conductor cross-sectional area (π × conductor diameter 0.76 ２ / 4)]×100(%) (Evaluation) The leakage detection line of Comparative Example 1 was evaluated for leakage detectability, flexibility, ease of recovery after leakage detection, and the like.

[0055] The specific evaluation method was as follows. The evaluation results are shown in Table 1. (Detectability) The liquid leakage detection wire was held approximately horizontally in the air, and water with a conductivity of 100.0 μS / cm was dropped from a position 1 cm above it at approximately constant intervals. The water was dropped at a rate of 0.6 ml per minute. The number of drops until the resistance between the detection wires fell below 100 kΩ was measured. Ten liquid leakage detection wires were tested, and the average number of drops was calculated. (Flexibility) Six liquid leakage detection wires were used as test samples. Each was bent 180° 100 times. After this bending and stretching, two detection wires were removed and observed. The number of locations where the conductor protruded from the braid was counted, and the total number for the 12 detection wires was calculated. (Recoverability (Removability)) After evaluating detectability, moisture was wiped off from the liquid leakage detection wires where the resistance between the detection wires had fallen to 100 kΩ or less, and it was confirmed whether the resistance value recovered by wiping off the moisture. If the resistance value recovered, it was evaluated as "Good", and if it did not recover, it was evaluated as "Poor". (Comparative Examples 2 to 4) Liquid leakage detection wires were produced in the same manner as in Comparative Example 1, except that the thickness of the right-handed and left-handed twisted yarns was reduced from 0.25 mm to 0.15 mm, and a braided body with a circumferential pitch as shown in Table 1 was provided, and evaluations similar to those in Comparative Example 1 were carried out. The evaluation results are shown in Table 1.

[0056] The results in Table 1 show that simply thinning the threads that make up the braid makes the conductor more likely to pop out, which could result in false detection. (Comparative Examples 5 to 8) Leak detection wires were produced in the same manner as in Comparative Example 1, except that the thickness of the right-handed and left-handed threads was reduced from 0.25 mm to 0.15 mm, the number of turns of the right-handed and left-handed threads was increased from 4 to 8, and a braid was provided with a winding pitch as shown in Table 1, and evaluations were carried out in the same manner as in Comparative Example 1. The evaluation results are shown in Table 1.

[0057] The results in Table 1 show that while it is possible to suppress conductor protrusion to some extent by thinning the threads that make up the braid and increasing the number of strands, it is difficult to sufficiently suppress conductor protrusion by simply doubling the number of strands. (Comparative Examples 9 to 11) Leak detection wires were produced in the same manner as in Comparative Example 1, except that the thickness of the right-handed and left-handed twisted threads was reduced from 0.25 mm to 0.15 mm, the number of strands of the right-handed and left-handed twisted threads was increased from 4 to 12, and a braid was provided with a winding pitch as shown in Table 1, and evaluations were carried out in the same manner as in Comparative Example 1. The evaluation results are shown in Table 1.

[0058] The results in Table 1 show that, by increasing the number of strands to three times that of Comparative Examples 1 to 4, as in Comparative Examples 9 to 11, conductor protrusion can be further suppressed compared to Comparative Examples 5 to 8, in which the number of strands was doubled. Furthermore, the results in Table 1 show that tripling the number of strands also significantly reduces detectability. (Examples 1 to 3) Of the right-handed and left-handed twisted yarns, the thickness of only the left-handed twisted yarn was reduced from 0.25 mm to 0.15 mm, the number of strands of the right-handed and left-handed twisted yarns was increased from 4 to 12, and a braid with a winding pitch as shown in Table 2 was provided. A liquid leakage detection wire was fabricated in the same manner as in Comparative Example 1, and evaluations were performed in the same manner as in Comparative Example 1. The evaluation results are shown in Table 2.

[0059] The results in Table 2 show that by thinning one of the threads, although the detectability was slightly inferior to that of Comparative Example 1, the protrusion of the conductor was greatly improved, making it possible to achieve both detectability and prevention of false detection. (Examples 4 to 6, Comparative Examples 12 to 14) Leakage detection wires were fabricated so that the first and second detection wires were simply placed side by side and housed in the outer braid without being twisted together, and evaluations were carried out in the same manner as before. The results are shown in Table 3.

[0060] From Table 3, it can be seen that by varying the yarn thickness, the same effect as the results shown in Table 2 can be achieved even when the first detection wire and the second detection wire are not twisted together.

[0061] Furthermore, the results in Tables 1 to 3 show that adjusting the length occupancy rate and cross-sectional area occupancy rate to predetermined values ​​is advantageous in terms of achieving a significant effect.

[0062]

[0063]

[0064]

[0065] From the above, it can be seen that the present invention can provide a liquid leakage detection line that can prevent a significant decrease in liquid leakage detectability while also suppressing false detections.

[0066] 10: Detection wire (10a: first detection wire, 10b: second detection wire), 11: Conductor (11a: first conductor, 11b: second conductor), 12: Braid (12a: first braid, 12b: second braid), 121: first thread, 122: second thread, 20: outer braid, 100: Leak detection wire, DD: radial direction (of leakage detection wire), DL: longitudinal direction (of leakage detection wire)

Claims

1. A liquid leakage detection line comprising a plurality of detection wires each comprising a conductor and a braid covering the conductor, the plurality of detection wires including a first detection wire and a second detection wire, the braid being made of electrically insulating thread, and an electrically conductive liquid being detected when the liquid electrically connects the conductor of the first detection wire and the conductor of the second detection wire through the braid, the braid of one or both of the first detection wire and the second detection wire comprising a first thread and a second thread intersecting the first thread, the second thread being thinner than the first thread.

2. A leakage detection wire as described in claim 1, wherein the first thread is a monofilament or multifilament thread having a diameter of 0.2 mm or more and 0.3 mm or less, and the second thread is a monofilament or multifilament thread having a diameter of 0.05 mm or more and less than 0.2 mm.

3. A liquid leakage detection wire as set forth in claim 2, wherein the number of said first threads held in said braid is one, and the number of said second threads held in said braid is one.

4. The leakage detection wire according to any one of claims 1 to 3, wherein the conductor of one or both of the first detection wire and the second detection wire is covered with the braid so as to satisfy the following inequality (1): Length occupancy rate ≦ 45% ... (1) Length occupancy rate = {(Wn1 x Cn1 x D1) / P1 + (Wn2 x Cn2 x D2) / P2} x 100% Wn1 = number of first thread holds, Wn2 = number of second thread holds, Cn1 = number of first thread skeins, Cn2 = number of second thread skeins, D1 = diameter of first thread (mm), D2 = diameter of second thread (mm), P1 = winding pitch of the first thread in the length direction of the detection wire (mm), P2 = winding pitch of the second thread in the length direction of the detection wire (mm)

Images