JPS612034A - Sensor for detecting leaked solution - Google Patents

Abstract

PURPOSE:To simplify the struction of the titled device and to detect a leaked solution point easily with practically sufficient accuracy without requiring specific devices or skill by using three or more electrode lines arranged in parallel each other and insulating these lines each other so that a solution can flow through these lines. CONSTITUTION:A sensor consists of three electrode lines X, Y, Z each of which is coated with an internal knitted body layer 4 made of polyethylene monofilament thread e.g. and these electrode lines X, Y, Z are twisted so that their intervals are kept constantly over the whole length, fastened tightly with a cotton thread 5 and then coated with an external knitted body layer 6 made of ''Tetoron'' multifilament thread. When it is defined that electric resistance in each unit length is x1, x2, x3OMEGA/m(x1 x3), resistance values between respective electrode lines at a leaked solution point P are R1, R2, R3 and resistance values between measuring terminals NX and NY and between NY and NZ are RXY and RYZ, RYZ-RXY (x3-x1)l is formed, so that the distance l up to the leaked solution point P can be found out independently of the resistance x2 per unit length of the electrode line Y.

Description

[Detailed Description of the Invention] (1) Field of Industrial Application This invention relates to a sensor for detecting liquid leakage. The present invention relates to a sensor for detecting liquid leakage.

(2) Conventional technology When storing and transporting various liquids such as water, chemicals such as sulfuric acid and hydrochloric acid, oils such as crude oil and petroleum, and solvents, leakage can cause losses and accidents, and can also cause damage to computers. If a leak occurs in a room or a storage room for various materials, there is a risk that various equipment may malfunction or the materials may deteriorate. When this occurs, it is necessary to detect it early and prevent losses and accidents from occurring. Liquid leakage can generally be detected using a liquid leakage detection wire whose electrical characteristics change dramatically due to the infiltration of liquid. In many cases, it has been difficult to perform such identification using only the leakage detection line. For example, in order to detect a liquid leak using a detection wire installed under the floor of a free access floor in a computer room and locate the leak location, the floor must be turned over and inspected, or the leak location may not be visible at a glance. In many cases, it was caused by a liquid leakage alarm or a malfunction, and detecting the point of failure at the time of liquid leakage was extremely troublesome.

In addition, as a conventional method for detecting fault points such as disconnections and short circuits,
The Murray loop method and Burley loop method apply the Wheatstone bridge principle to measure the distance to the fault point, the capacitance method is especially used to identify the break point, and the method involves inputting alternating current to the line under test and measuring the distortion of the reflected wave. The alternating current method uses the method to find the fault point, the search coil method moves a search coil along the line to be measured into which a low frequency signal is input, and uses the induced electromotive force of the coil to find the fault point, and the search coil method applies pulse voltage to the fault cable, etc. The pulse reflection method or pulse radar method, which determines the distance to the fault point by measuring the delay time of the reflected pulse from the fault point, is known. For example, are pulse generators and synchroscopes used in pulse reflection methods each requiring special equipment?1 Measurement work must be carried out by experienced personnel with considerable time and effort. There was a problem.

(3) Problems to be Solved by the Invention This invention was made in view of the above-mentioned circumstances, and its purpose is to have a simple structure, no special equipment or skill required, and sufficient precision for practical use. An object of the present invention is to provide a sensor for detecting liquid leakage that can easily determine the point of liquid leakage.

(4) Means for Solving the Problems In order to solve the above problems, the liquid leak detection sensor of the present invention connects three or more electrode wires arranged substantially parallel to each other. It is characterized in that it is fluidly insulated and that at least two of the electrode wires have different resistance values per unit length.

(51 Operation) The principle of operation of the liquid leak detection sensor of the present invention having the above configuration will be explained with reference to FIG. 1 and FIGS. 2(a) and (b).

Electrical resistance per unit length or xl and x, respectively.

and x3 ohm/meter (Xl/x3) three electrode wires X, Y, and Z are arranged approximately parallel to each other over the entire length, and at the leakage point P, the electrode wires X, YSY, and Z
Assume that the resistance values R, , R8 and Ra (indicated by dashed lines in FIG. 1) are between Z and X, respectively.

If the distance from the measurement ends NX+NY and NZ of these electrode lines X, Y, and Z to the leakage point P is l, then the measurement end N
The circuit from X to measurement end NY through leakage point P, and the circuit from measurement end NY to measurement end Nz through leakage point P are equivalent circuits in Figure 2 (a) and (b), respectively. The resistances RXY and RYZ between the measurement terminals NX and NY and between NY and >hNz are given by the following equations, respectively.

R1(R2+R3) Rxy −(X1+X2)l+ −
-... (1) k engineering + R2 + R3 kY □ - (x2 + Xa) J + Mirowaki 1. --------
8[21R1+R2+R3 From the above equation (1) and +21, the following equation (3) can be obtained.

Ryz−Rxy−(・・−・・)l＋ノと−−・k・・
......(3) R1 + R2 + R3 Here, R1 + "2 + R3 may vary slightly depending on the amount of leakage permeating between each line at the leak point P, variations in the distance between the lines, etc., or the difference between the three electrode wires. If they are evenly matched, R8 out of 2 will be approximately R1*, and the electrode wires x, y,
When z are arranged in parallel on the same plane at equal intervals as shown in Figure 1, it is thought that R1 = 2, and the formula (
The second term on the right-hand side of 3) is generally considered to be negligibly small.

Therefore, in RYZ-RXY (x a - x l) l -----
(4) However, since x3'1 is a known constant (X□/x3), the resistances RX Y, RY Z between the above measurement terminals can be changed by connecting the constant voltage power supply 1 to the switch S as shown in Figure 1.
Switch and connect between NX-N7 and NY-N2 by
If the current in each closed circuit thus formed is measured by the current meter 2, the distance from the measurement end to the leakage point P can be determined from equation (4).

However, the distance l obtained in this way is larger than the actual value by Δl shown in the following equation because the second term on the right side of equation (3) is ignored.

As is clear from equation (5), this error Δl is k.

The smaller the difference of 1 between and the larger the difference between X8 and Xo, the smaller the difference, which is preferable.

Note that, as is clear from the above equations (3) and (4), the distance l to the leakage point P can be determined regardless of the electrical resistance X2 per unit length of the electrode wire Y.

(6) Embodiment In FIGS. 3A and 3B, a liquid leakage detection sensor 3 according to an embodiment of the present invention has three electrode wires X each covered with an internal braided layer 4 of polyethylene monofilament yarn , Y, and Z, and these three electrode wires are tightly twisted together at an appropriate pitch so that the distance between them is kept constant over the entire length as shown in FIG. In addition to being bound, it is further covered with an outer braided layer 6 of Tetoron multifilament yarn.

In the above embodiment, the electrode wires X and Y have resistivities of 23.1 ohm/meter and 1'50.m, respectively.
The electrode wire Y is a 7 ohm/meter nichrome wire and a tin-plated wire. The inner braided layer 4 is non-hygroscopic, and the outer braided layer 6 is hygroscopic, but both are water permeable or liquid permeable. When the body layer is provided, leakage resistance occurs between the electrode wires only when liquid leaks, so malfunctions due to high temperature and humidity can be prevented, and liquid leakage can be reliably detected. Therefore, these braided body layers are not limited to the above-mentioned materials as long as they satisfy the above-mentioned hygroscopic and non-hygroscopic conditions. Further, the cotton thread 5 is used to make the distance between the electrode wires x, y, and z uniform, and is not limited to cotton thread, but may be other thread or tape.

Next, in order to demonstrate the effectiveness of the liquid leak detection sensor of the present invention, a series of experiments were conducted using the above embodiment. The results will be explained below.

First, assuming that the leakage resistance at the leakage point between electrode wires X and Y and between Y and Z in FIG. 3(a) is equal to 0, R1, R2 and electrode wire Z The leakage resistance between X is replaced with a fixed resistor, and R1-R2-3
(Ω), R, = R2 = 5 (KΩ) and R1 = R2-7
(KΩ), R3 is twice the resistance value of R1 and R2, form a measurement circuit as shown in Figure 1, and measure the resistances RXY and r(yz) by changing the connection position of the fixed resistor. The distance to the leakage point P (connection position of the fixed resistor) calculated using the above equation (4) (l and the actual distance (I)
! A comparison was made with o). The results are shown in FIG.

As is clear from FIG. 4, if the leakage resistances (R, R2) between the electrode wires are equal over the entire length, the distance to the leakage point can be measured with almost no error.

Next, an experiment similar to the above was conducted in the case where R2 was different depending on the leakage resistance between the electrode wires, but by using a fixed resistance instead. The results are shown in FIG. Fifth
As is clear from the figure, to reduce the error □ and 2
Is it desirable to reduce the difference between R8 and R2?
-4,7 Ω.

As in the case of R8-IQKΩ), R2-R is approximately ±0.
If it is within 3 kilohms, the error can be sufficiently suppressed to within ±2 meters. In practice, if the error is about ±3 meters, there is no problem because the leak point can be easily found visually from the point corresponding to the measured value. It is clear from equation (5) that the smaller R8 is, the smaller the error will be.

Next, in a water leakage test conducted by actually soaking a small amount of water, the leakage detection sensor of the above example showed stable leakage resistance after about 10 seconds at the water leakage point, demonstrating sufficient detection sensitivity. Ta. That is, the level of "l +" 2 and R3 is about 0.7 to 1.9 kilohms, the difference from R2 is approximately 0.4 kilohms, and the error in the distance l to the leak point is It was confirmed that the distance was within ±1.5 meters.

- Although the above embodiment has been described for the case where there are three electrode wires, the same embodiment is also possible when there are four or more electrode wires. The electrode wires x/, YJ, z/ may be integrated with the signal line etc. or the electrode wires x/, YJ, z/ may be attached to the vinyl sheet 4 as shown in Fig. 6.
Naturally, the present invention also includes a liquid leakage detection sensor 30 embedded in parallel to 0, a liquid leakage detection sensor on which a liquid-absorbing protective layer is attached. Furthermore, it is clear that an application example in which calculations based on the above-mentioned equations (3) or (4) are automatically performed and is combined with means for digital display can be easily implemented.

(7) Effects As explained above, the present invention has a simple structure, does not require any special equipment or skill, and can identify the leak point with sufficient accuracy for practical use.

[Brief explanation of the drawing]

The figures show an embodiment of the liquid leakage detection sensor of the present invention. Fig. 1 is a circuit diagram showing its principle, Fig. 2 ta+ and (b) are its equivalent circuit diagrams, and Fig. 3 (a) is a partially exploded perspective view of the interior; FIG. 3(b) is a schematic cross-sectional view;
4 and 5 are graphs showing the results of a series of experiments conducted on the above embodiment, and FIG. 6 is a perspective view of another embodiment of the present invention. 3.30... Sensor for liquid leakage detection, 4... Internal braided body layer, 5... Cotton thread, 6... External braided body layer, P...
Leak point, x, y, Z; X', Y', z
i... Electrode wire, NX + NY h "Z"' measurement end. Patent Applicant Tuck Electric Cable Co., Ltd. Agent Kama 1) Text 2 Figure 4 Figure 5 Actual position of fixed resistor l○ (m) R3 = 6 Ω R3 = 10 Ω R3 = 14 Ω

Claims (1)

[Claims] A leakage liquid comprising three or more electrode wires arranged substantially in parallel and insulated to allow liquid to pass through each other, and at least two of the electrode wires have different resistance values per unit length. Detection sensor.