JPH0243130B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Industrial Application Field This invention relates to a liquid leakage detection electric wire and a liquid leakage detection sensor using the electric wire. The present invention relates to a leakage detection wire and sensor that can specifically detect the accident point.

(2) Prior art 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 due to the infiltration of liquid, but in order to repair the leakage point or eliminate the cause of the leakage, it is necessary to identify the leakage point. In many cases, it has been difficult to perform such identification using only the leakage detection line. For example, in order to detect liquid leaks using detection wires installed under the floor of the free access floor of a computer room and search for the leak location, the floor must be turned over each time, but the leak location cannot be found at a glance. In many cases, leakage alarms were caused by malfunctions, making it very troublesome to detect the point of failure at the time of leakage.

Conventionally, methods for detecting fault points such as wire breaks and short circuits include the Murray loop method and Burley loop method, which measure the distance to the fault point by applying the Wheatstone-Bridge principle. Capacitance method, AC method that inputs AC to the line under test and uses the distortion of the reflected wave to find the fault point, moves a search coil along the line to be measured to which a low frequency signal is input, and calculates the induced electromotive force in the coil. The search coil method, which determines the fault point using the method, and the pulse reflection method or pulse radar method, which sends a pulse voltage to the fault cable, measures the delay time of the reflected pulse from the fault point, and calculates the distance to the fault point, etc. has been
With some exceptions, these methods can also be used to detect leak points, but each requires special equipment, such as a pulse generator or synchroscope in the pulse reflection method, and the measurement work must be carried out by an experienced person. There was a problem in that the process required a considerable amount of time and effort.

(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 accuracy for practical use. It is an object of the present invention to provide a leakage detection electric wire and a sensor that can easily determine the leakage point.

(4) Means for Solving the Problems In order to solve the above problems, the electric wire for liquid leakage detection of the present invention has three or more electrode wires arranged substantially parallel to each other and insulated to allow liquid to flow through them. Therefore, at least two of the electrode wires have different resistance values per unit length.

In addition, the sensor for detecting liquid leakage uses the above electric wire, connects this electric wire to a power source via a switch,
The switch selectively connects two of each electrode wire of the electric wire to the electric power source to form a closed circuit of one of the connected electrode wires, the power source, the other electrode wire, and one electrode wire. A resistance value measuring means of the closed circuit is interposed between the switch of the closed circuit and the power source.

(5) 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. 2a and 2b.

Three electrode wires X, Y and Z having electrical resistances per unit length of x ₁ , x ₂ and x ₃ ohm/meter (x ₁ ≠ x ₃ ) are arranged substantially parallel to each other over the entire length, And at the leakage point P, the resistance values between the electrode wires X and Y, Y and Z, and Z and X are respectively
Assume that R ₁ , R ₂ and R ₃ (indicated by dashed lines in FIG. 1).

The measurement ends N _x of these electrode wires X, Y and Z,
If the distance from N _Y and _{N Z} to the leak point P is l, then _the circuit from the measurement end _N The circuits up to the measuring terminal N _Z are respectively represented by the equivalent circuits shown in Figure 2 a and b, and the resistances R _XY and R _YZ between the measuring terminals N _X and N _Y and between N _Y and N _Z are as follows. It is given by Eq.

_{R _ _ _ _ _ _ _ _}
1) R _YZ = (x ₂ + x ₃ ) l + R ₂ (R ₁ + R ₃ ) / R ₁ + R ₂ + R ₃ ………(
2) From the above equations (1) and (2), the following equation (3) is obtained.

_{R YZ −R _ _ _ _ _ _ _ _ _ _} Although it varies somewhat depending on the amount of leaked liquid permeating between each wire and the variation in the distance between the wires, when the three electrode wires are evenly matched, R ₁ ≒ R ₂ ≒ R ₃ ,
Furthermore, when the electrode lines X, Y, and Z are arranged in parallel on the same plane at equal intervals as shown in Figure 1, R ₁ ≒
R ₂ , and the second term on the right side of equation (3) is generally considered to be negligibly small.

_{Therefore , R YZ −R _ _ _} For _example , as _shown in _{Fig . 1} , _R
The current of each closed circuit formed by this is measured by an ammeter 2.
The distance l from the measurement end to the leakage point P can be found from equation (4).
In this case, the ammeter 2 serves as the resistance value measuring means, and R _YE and R _XY are determined from the measured current value and the voltage value of the localization power source 1.

However, since the distance l obtained in this manner ignores the second term on the right side of equation (3), it becomes larger than the actual value by Δl shown in the following equation.

Δl=(R ₂ −R ₁ )R ₃ /(R ₁ +R ₂ +R ₃ )(x ₃ −x ₁ )……(
5) As is clear from equation (5), this error Δl is equal to R ₂
The smaller the difference in R ₁ is, and the larger the difference between x ₃ and x ₁ is, the smaller the difference is, 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 x ₂ per unit length of the electrode wire Y.

(6) Embodiment In FIGS. 3a and 3b, a leakage detection electric wire 3 according to an embodiment of the present invention consists of three electrode wires X and Y each covered with an internal braided layer 4 of polyethylene monofilament yarn. and Z, and as shown in FIG. After being
Furthermore, it is covered with an outer braided layer 6 of Tetoron multifilament yarn.

In the above example, the electrode wires X and Y have a resistivity of 23.1 ohms/meter and
The electrode wire Y is a 150.7 ohm/meter nichrome wire and a Suzmetsuki 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 placed, leakage resistance occurs between the electrode wires only when liquid leaks, preventing malfunctions due to high temperature and humidity, etc.
Leakage can be detected reliably. 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. Also, the cotton thread 5 is used to make the distance between the electrode wires X, Y, and Z uniform.
It is not limited to cotton thread, but may be other threads or tapes.

Next, in order to demonstrate the effectiveness of the electric wire for leakage detection of the present invention, a series of experiments were conducted using the above-mentioned examples. The results will be explained below.

First, assuming that the leakage resistances R ₁ and R ₂ at the leakage points between electrode wires X and Y and between Y and Z in Fig. 3a are equal, R ₁ , R ₂ and electrode wire Z X
The leakage resistance R ₃ between is replaced with a fixed resistor,
R ₁ = R ₂ = 3 (KΩ), R ₁ = R ₂ = 5 (KΩ) and R ₁
= R ₂ = 7 (KΩ), and R ₃ is twice the resistance value of R ₁ and R ₂ to form a measurement circuit as shown in Figure 1, and the resistance R is changed by changing the connection position of the fixed resistor. _XY
By measuring and R _YZ , the distance (l) to the leakage point P (connection position of the fixed resistor) determined by the above equation (4) was compared with the actual distance (lo).
The results are shown in FIG. As is clear from FIG. 4, if the leak resistance (R ₁ , R ₂ ) between the electrode wires is equal over the entire length, the distance to the leak point can be measured with almost no error.

Next, for the case where the leakage resistances R ₁ and R ₂ between the electrode wires were different, an experiment similar to the above was conducted by also substituting a fixed resistance. The results are shown in FIG. As is clear from Fig. 5, it is desirable to reduce the difference between R ₁ and R ₂ in order to reduce the error, but if R ₃ is about twice R ₁ , for example, the data point △・(R ₁ = 5KΩ, R ₂ = 4.7KΩ, R ₃ =
As in the case of 10KΩ), if R ₂ - R ₁ is within about ±0.3KΩ, 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 leakage point can be easily found visually from the point corresponding to the measured value.
It is clear from equation (5) that the smaller R ₃ becomes, the smaller the error becomes.

Next, in a leakage test conducted by actually soaking a small amount of water, the leakage detection wire of the above example showed stable leakage resistance after about 10 seconds at the leakage point, indicating sufficient detection sensitivity. Ta. That is, R ₁ ,
It was confirmed that the levels of R ₂ and R ₃ were approximately 0.7 to 1.9 kilohms, the difference between R ₂ and R ₁ was approximately 0.4 kilohms, and the error in the distance l to the leak point 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 possible when there are four or more electrode wires. Those that are integrated with electrode wires, etc., or those that are integrated with electrode wires X', Y',
Naturally, the present invention also includes a liquid leakage detection electric wire 30 in which Z' is embedded in parallel to the vinyl sheet 40, and a liquid leakage detection electric wire in which a liquid-absorbing protective layer is attached thereon. Furthermore, it is clear that an application example in which the calculation according to the above-mentioned equation (3) or (4) is automatically performed and is combined with means for digital display can be easily implemented.

(7) Effects As explained above, according to the present invention, the structure is simple, and the leak point can be identified with sufficient accuracy for practical use without requiring any special equipment or skill.

[Brief explanation of drawings]

The figures show one embodiment of the present invention. Figure 1 is a circuit diagram showing the principle of a sensor for detecting liquid leakage, Figure 2 a and b are its equivalent circuit diagrams, and Figure 3 a is a sensor for detecting liquid leakage. Perspective view showing a part of the electric wire as an internal exploded view, Part 3
FIG. b is a schematic sectional view thereof, FIGS. 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...Leakage detection electric wire, 4...Inner braided body layer, 5...Cotton thread, 6...Outer braided body layer, P...
...Leak point, X, Y, Z; X', Y', Z'... Electrode wire,
N _X , N _Y , N _Z ...Measurement end.

Claims (1)

[Claims] 1. Three or more electrode wires arranged substantially in parallel are insulated from each other so that liquid can pass therethrough, and at least two of the electrode wires have different resistance values per unit length. An electrical wire for liquid leakage detection, which is characterized by: 2 Three or more electrode wires arranged approximately in parallel are insulated to allow liquid to pass through each other, and at least two of the electrode wires have different resistance values per unit length to detect liquid leakage. The electric wire is connected to a power source via a switch, and the switch selectively connects two of each electrode wire of the electric wire to the power source, and connects one of the connected electrode wires to the power source. , the other electrode wire and one electrode wire can form a closed circuit, and a resistance value measuring means of the closed circuit is interposed between the switch of the closed circuit and the power source. A sensor for detecting liquid leakage.