JP2655367B2 - Leak detection method for sealed gas, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting leakage of a charged gas.

[0002]

2. Description of the Related Art For example, in a communication cable, a pinhole or the like is formed in a sheath or a connection point of the cable, and in order to prevent a communication failure due to infiltration of moisture or water therefrom,
Dry gas, air, etc. are sealed or pressure-fed in the cable, and the pressure drop generated when pinholes are generated is detected, and pinholes and the like are found and repaired on site.

[0003] However, even in the work at the site, even if a pinhole or the like is detected only, the worker cannot descend to the manhole, so that the environment of the manhole must first be improved. In other words, since the manhole is on the road, it is necessary to install work display boards, warning lights, etc. for traffic accidents, take measures to prevent oxygen deficiency in preparation for methane generation, etc., and infiltrate rainwater into the manhole. If there is, there is drainage work. Therefore, for the first time, the worker descended to the manhole, applied soapy water, and visually checked. Of course, since this work is performed for each manhole, the amount of work is enormous, and a large number of workers are required.

[0004] For this reason, a method has recently been used in which fluorocarbon gas is pressure-fed into a cable, a platinum electrode is used, and a detector that detects the leakage thereof using the principle of the Rice effect is used.

[0005]

Problems to be Solved by the Invention In the above-mentioned method of applying a soap solution, the operation of applying soapy water to each connection point or the like must be performed for each manhole. Requires a large number of workers, and the cost is huge.

On the other hand, when chlorofluorocarbon gas is used, since chlorofluorocarbon gas is extremely soluble in the resin used for coating the wire, it takes an enormous amount of time from sending the fluorocarbon gas to detecting it. Further, after the measurement, similar long-time cleaning work (by air, nitrogen gas, or the like) is required.
Further, since the chlorofluorocarbon gas is heavy, the residual time is long, and even if it is detected, if the worker immediately enters the manhole, there is a danger of lack of oxygen, and the work takes time and the work efficiency is low. or. Since the chlorofluorocarbon gas is heavy, it may flow out to other manholes through the pipe, making it difficult to identify the location of the leakage. Moreover,
Freon gas has many problems such as being regarded as one of the causes of environmental destruction.

In general, the amount of water vapor differs between inside and outside a manhole. When the humidity inside the manhole is high and the outside temperature is low, dew forms inside the detector, and stable measurement with high sensitivity becomes impossible. Particularly when a thermal conductivity detector is used as the detector, it is desirable that the gas within the measurement range, that is, the measurement gas and the reference gas have the same water vapor amount.

[0008]

[Means for Solving the Problems] Therefore, according to the present invention, it takes only a short time from the delivery of gas to the detection thereof, without the need for cleaning work, and because of its light weight, it scatters immediately and has no danger. It proposes a method of detecting sealed gas that can be measured very easily and at a very low cost compared to the conventional example. By enclosing hydrogen or a mixed gas in the sealed part of a communication cable or the like, tracer gas can be detected. Is introduced into the detector as an atmosphere outside the measurement target range as a control gas and detected, and when the tracer gas is introduced into the detector through the suction section, the tracer gas is passed through the water removal section to detect the control gas. The feature is to make the humidity uniform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. Reference numeral 1 denotes a detector, for example, a thermal conductivity detector using four elements of a flow type or diffusion type filament. In addition, a mass spectrometer and a luminescence (plasma luminescence) detector can be used as the detector.

Reference numeral 2 denotes a suction pipe as an air suction portion, which is connected to the control side of the bridge circuit. 3 is trace saga
In the suction pipe of the suction portion of the scan, it is provided with an ion-exchange membrane tube 4 as a moisture removing portion in the middle bridge circuit sample. In addition, a method using a desiccant such as silica gel, a cooler, or the like can be used as the water removing device. Reference numeral 5 denotes a cable, which is buried underground 6 and has a connection portion 5 in a manhole 7.
1 is exposed.

[0011] Now, 0.6K hydrogen gas will describe its use as a tracer gas into the cable 5
It is fed at a pressure of about g / cm ² . The desired pressure can be selected. The desired pressure can be selected. Alternatively, the pressure can be simply filled and filled in the cable 5 and sealed as it is. Alternatively, a long cable or leakage can be continued in anticipation of leakage. Of course, it is good. Thus, the term encapsulation includes not only literal encapsulation, but also continuous delivery or press-fit. The hydrogen gas may be 100% hydrogen gas. However, if hydrogen is present at 4% or more in the atmosphere at 21 ° C. and 1 atm, there is a danger of explosion. Therefore, hydrogen is mixed and diluted with nitrogen or other inert gas. Good to use. If there is a damage 52 such as a pinhole in the cable 5 to the connection portion 51, hydrogen gas leaks out therefrom.

Reference numeral 8 denotes a suction pump. In use, suction is performed through the suction pipe 2 and the suction pipe 3 by the operation of the suction pump 8. From the suction pipe 2 and the suction air, tray suction pipe 3 in the manhole 7 by inserting or hanging in the manhole 7
Inhale sirgas . At this time, it is not always necessary to bring the end of the suction pipe 3 close to the cable 5 or the connection portion 51 thereof, because the hydrogen gas is lightweight and diffuses, so that the rate of uneven distribution in the manhole 7 is small.

The gas sucked from the suction pipe 3 is supplied to the detector 1
On the way through the ion-exchange membrane tube 4 which is a water removing portion. At this time, the gas passing therethrough is a gas having a humidity substantially equal to that of the atmosphere by utilizing a process of selectively removing water vapor from the mixed gas and drying the mixed gas due to the permeability of the ion exchange membrane. Accordingly, the tracer gas sucked from the suction pipe 3 has the same humidity as the air as the control gas, enters the sample side of the detector 1 , and the difference from the air entering the control side, that is, the presence of hydrogen is determined by the bridge circuit. Detected and displayed on meter.

Needless to say, if there is no difference between the humidity in the manhole 7 and the humidity in the atmosphere, and if the humidity in the manhole 7 and the humidity in the atmosphere are almost the same, the necessity and operation of the water removing unit 4 may be reduced. No need.

[0015]

According to the present invention as described above, hydrogen or a mixed gas thereof is sealed in a sealing portion of a communication cable or the like.
Tracer gas is introduced into the detector using the atmosphere outside the measurement target range as a control gas, and the tracer gas is detected.
Upon introduction into the detector by inhalation portion of the gas, let align more control gas and humidity to pass through the moisture removal unit,
Leaving flaws such as pinholes, which are obstacles to communication cables and the like, can be easily detected by a very simple method by a simple operation in a very short time.

As a result, the work of the worker is reduced, the work can be performed extremely efficiently, the number of workers can be reduced, the cost can be reduced, and the environmental destruction can be prevented. .

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a use state of an embodiment of the present invention.

FIG. 2 is a schematic explanatory view of the thermal conductivity detector.

[Description of Signs] 1 Detector 2 Suction pipe 3 Suction pipe 4 Ion exchange membrane tube 5 Cable 6 Underground 7 Manhole 8 Suction pump

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tadashi Mimura 237-2 Sayamagahara, Iruma City, Saitama Prefecture Inside the Musashi Plant of G-Science Inc. (56) References JP-A-52-104283 (JP, A) 60-83954 (JP, U) JP 49-39946 (JP, B1)

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein hydrogen or a mixed gas thereof is sealed as a tracer gas in a sealed portion of a communication cable or the like.
In the method of detecting gas leakage, a torch connected to the detector
Inject the racer gas inlet into the measurement area such as a manhole
To absorb the air at the measurement point mainly containing tracer gas.
Into the detector and into the detector as a control gas.
A method for detecting leakage of a sealed gas or the like, wherein the detection is performed in comparison with the atmosphere outside the measurement target range . 2. The leak detection of a sealed gas or the like according to claim 1, wherein when the tracer gas is introduced into the detector by the suction unit, the humidity is made equal to that of the control gas by passing through the water removal unit. Method.