JPH07159269A - Method for checking water leak of underground city water pipe - Google Patents

Abstract

PURPOSE:To provide a method for checking water leak of underground city water pipe which can detect a water leak point highly accurately based on the peak in the concentration distribution of rare gas while suppressing the waste of rare gas by lowering the concentration of rare gas in a tracer gas and saving labor for dissolving the tracer gas into the water. CONSTITUTION:A tracer water comprising a mixture of a rare gas and oxygen is fed into an underground city water pipe within a section to be checked through a valve coupled with the city water pipe within a section for checking a water control valve or a hydrant and controlling the section on the ground or through a terminal valve, e.g. a faucet, thus filling the city water pipe within the section to be checked with the tracer gas. The leak point is detected by detecting the rare gas ejected from a damaged part of the city water pipe within the section filled with the tracer gas and leaked up to the ground surface by means of the rare gas detector on the ground surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for investigating a leak location of an underground water pipe.

[0002]

2. Description of the Related Art Conventionally, as a method of investigating a leak location of a water pipe buried underground, the flow rate, flow velocity, and water pressure in a certain section of the underground water pipe are measured, and these values are set to prescribed values. After checking whether it has reached the water level and making a rough judgment as to the presence or absence of water leakage, a method of detecting the water leakage location based on the sound of water leakage using a sound stick or water leakage vibration hearing device (leak detector) is used. Was there.

However, this method has a drawback that it is easily affected by ambient noise, and that the work is limited to late night due to the influence of traffic noise or crowds, especially in urban areas, which greatly limits work efficiency.

In order to solve such a problem, a tracer gas such as rare gas is filled in the underground buried pipe, and a plurality of gas sampling pipes are driven from the surface along the laying path of the buried pipe to remove the buried pipe. A method of detecting the tracer gas leaking from the damaged portion through the gas sampling pipe and detecting the damaged portion of the buried pipe from the detection time of the tracer gas, the concentration distribution, etc. (Japanese Patent Laid-Open No. 63-134930). ),
Halogen gas is supplied into the water pipe with the water drained from the underground water pipe, and a plurality of small holes are drilled from the surface of the earth at regular intervals. There is a method of detecting leaking halogen gas (Japanese Patent Laid-Open No. 4-184132) and the like.

However, all of the above methods have the drawback that the work is complicated because it is necessary to drive a plurality of gas sampling pipes or to form a plurality of small holes at regular intervals. Also, when trying to investigate the leak location of the water pipe, the tap water in the water pipe of the inspection section is drained before the tracer gas is supplied. Therefore, especially when the inspection section is wide, a lot of labor is required for draining the tap water. In addition, there is also a problem that when water is passed through the water pipe after the inspection, rust or the like on the pipe wall is washed out, and so-called red water is generated at the beginning of restoration.

On the other hand, the present applicant does not need to drain tap water from the water pipe in the survey section, drive a plurality of gas sampling pipes, or bore a plurality of small holes at regular intervals from the ground surface. As a test method that does not require time and effort, tracer water in which rare gas is dissolved using a gas dissolver etc. is poured into the underground underground water pipe in the section to be inspected and released from the tracer water leaking from the leaking point. Therefore, we proposed a method of detecting the leaked point by detecting the concentration of rare gas leaking to the surface with a rare gas detector on the surface (Japanese Patent Application No. 4-174946).
issue).

[0007]

In the method of supplying tracer water in which tracer gas containing a rare gas is dissolved to a water pipe to investigate a leak location, the tracer water is supplied from a water supply port of a water purification plant, a water supply plant, or the like. The method or the method of supplying from a water control valve, a digestion plug, etc., which is connected to the water pipe in the surveyed section, is adopted. No matter which supply method is used, a device such as a gas dissolver for dissolving tracer gas in water is required, but if there is a guideline for the location of water leakage and the range of the surveyed area is narrow, etc. Considering the time and effort required to move a large-scale device such as a gas dissolver to the survey site, it cannot be said that the method of dissolving tracer gas in water is an efficient method. Also, in order to save the labor of moving the gas dissolver etc., even if the method of supplying tracer water in which tracer gas is dissolved from the water supply port of the water purification plant etc. is adopted, the surveyed area is narrow and the water supply port of the water purification plant etc. When there is a long distance from, there was a problem that it took longer than necessary to find the location of water leakage, and the tracer gas became more than necessary.

If a high concentration tracer gas leaks from the leaking point to the surface of the earth for a longer period of time, the rare gas diffuses over a wide area, making it difficult to detect the leaking point. Since it is a valuable resource with a small amount of abundance, it is important to reduce the absolute amount of rare gas used for surveys in order to save resources, reduce survey costs, and accurately detect leak points. It is preferable. Since rare gas is present in the atmosphere in a very small amount, the amount of rare gas leaked to the surface of the earth can be detected with high accuracy even if it is a very small amount. It can be reduced. However, if the concentration of tracer gas or rare gas in tracer water is reduced,
The amount of rare gas that leaks from the leaking point in the ground to the surface also decreases, and if the amount of rare gas that leaks to the surface is small, the rare gas will diffuse quickly and the peak concentration of rare gas at the leaking point will increase. There was a problem that it became difficult to be recognized.

The present invention has been made in view of the above points,
In particular, it is an object of the present invention to provide a method for investigating leak points of underground water pipes that can efficiently detect leak points with high accuracy when the range of the surveyed section is narrow.

[0010]

[Means for Solving the Problems] That is, the method for investigating the location of a leak in an underground water pipe according to the present invention is carried out by sending a tracer gas consisting of a mixture of rare gas and oxygen into the water pipe in the section to be investigated. The tracer gas is filled into the water pipe in the target section, and the rare gas that leaks to the surface of the ground from the damaged portion of the water pipe in the section filled with the tracer gas is detected by the rare gas detector on the surface. The feature is that it detects the water leakage location.

In the present invention, as a method of filling the tracer gas in the water pipe in the survey section, the tracer gas is supplied from a valve that can operate the survey section from the ground or a terminal valve connected to the water pipe near the survey section. It is possible to adopt a method of press-fitting into the water pipe.

In the present invention, the rare gas is helium,
Examples thereof include neon, argon, krypton, xenon, radon, etc. Among them, helium having a low density and easily diffused from the ground to the ground is most preferable. In the present invention, a mixed gas of a rare gas and oxygen is used as the tracer gas, and the mixing ratio of the rare gas and oxygen is preferably a rare gas: oxygen = 1 to 50:99 to 50, and more preferably 5 to 50:95 to 50, especially 5 to 20:95
-80 is preferable. In the method of the present invention, it is necessary that the tracer gas is a mixture of a rare gas and oxygen, but nitrogen may be mixed in a small amount. When the tap water supply pressure in the water pipe is high, the ratio of rare gas in the tracer gas can be reduced within the above range, but when the supply pressure is low, the ratio of rare gas is increased within the above range. There is a need to.

In order to supply the tracer gas into the water pipe in the survey section, a valve capable of operating the water pipe in the survey section from the ground, such as a water control valve or a digestive tap (usually provided every 200 m) ) Can be used. In this case, for example, the investigation target section is shut off by two valves sandwiching the section, and a gas cylinder filled with tracer gas is connected to one valve to press the tracer gas into the investigation target section, and the other valve is connected to the inside of the investigation section. It is possible to adopt the method of discharging the tap water and filling the water pipe in the surveyed section with tracer gas. Also, by connecting a terminal valve near the surveyed section, such as a faucet, to a gas cylinder filled with tracer gas, press the gas at a pressure higher than the water pressure in the water pipe, and tap the tap water in the water pipe by the gas pressure. It is possible to employ a method such as pushing back to fill the tracer gas in the surveyed section.

When the section to be surveyed is closed and tracer gas is pressed in from one valve side to discharge tap water from the other valve, tap water is discharged from the valve on the side discharging tap water in the water pipe. The time when the water runs out can be regarded as the time when the tracer gas fills the water pipe in the surveyed section.
In addition, when pressurizing the tracer gas from the faucet and pushing the tap water back with the tracer gas pressure to fill the gas, it is possible to know the range of the surveyed section filled with the tracer gas from the amount of tracer gas sent from the faucet. it can.

As the rare gas detector, a detector depending on the type of rare gas is used. For example, in the case of helium, a helium leak detector or a heat conduction type detector is used, and in the case of other rare gases, a heat conduction type detector is used. Detector, etc. are used.

[0016]

[Operation] Water leaking from the water pipe has penetrated into the soil near the damaged portion of the buried water pipe, and the soil around this is in a reduced state of oxygen deficiency because the air is blocked. When the tracer gas consisting of the rare gas and oxygen filled in the water pipe leaks out at the water leakage location in such a state, oxygen in the tracer gas is consumed by the oxidation of the soil in the reduced state, Tracer gas with a high concentration of rare gas leaks into. Therefore, even if the rare gas concentration in the tracer gas is low, the rare gas concentration in the tracer gas leaking to the surface is higher than in the original rare gas, so it is less susceptible to the rare gas diffusion, A peak is observed in the concentration distribution of the rare gas at the leaking point, and the leaking point can be detected more accurately.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0018]

【Example】

Example 1 and Comparative Example 1 The surveyed section of a water pipe with a known leak point was shut off by two water control valves sandwiching the leak point, and 200 liters of tracer gas was injected from one valve side for 10 minutes and the other valve. From the side
After discharging the tap water in the water pipe of the surveyed section, the injection of tracer gas was stopped and the valve was closed. During tracer gas injection, and after 3 hours and 6 hours after the tracer gas injection was stopped, the rare gas concentration around the leaked area was measured using a commercially available helium leak detector (manufactured by Nippon Vacuum Technology: DLM.
It was measured by STP-3). As the tracer gas, in Example 1, a mixed gas of 10% by volume of helium and 90% of oxygen was used, and in Comparative Example 1, 10% by volume of helium and 90% of nitrogen were used.
% Gas mixture was used. The result of Example 1 is shown in FIG.
2A to 2C show the results of Comparative Example 1 in FIGS. 2A to 2C, respectively.

In both FIG. 1 and FIG. 2, the drawing with the symbol (a) shows the measurement results during tracer gas injection, and the drawing with the symbol (b) shows the measurement results after 3 hours have elapsed since the tracer gas injection was stopped. The results are shown in the figure with the symbol (c), which is the result 6 hours after the injection of the tracer gas was stopped. In addition, in the figure, the areas designated by reference numerals 1 to 5 have the range of the above-mentioned measuring machine set to "10".
Is the concentration range shown on the meter of the measuring instrument when measuring the rare gas concentration (the display on the meter is 0% to 100
%), The code 1 ranges from over 80% to 100% on the meter, and the code 2 ranges from over 60% to 80%,
Reference numeral 3 is a range from more than 40% to 60%, and reference numeral 4 is 2
The range from 0% to 40%, the code 5 exceeds 0% to 2
Reference numeral 6 indicates a range up to 0%, and reference numeral 6 indicates a range where the meter indicates 0%.

As is apparent from the results shown in FIGS. 1 and 2, in the method of the present invention in which a mixture of helium and oxygen is used as the tracer gas, the rare gas concentration on the surface of the earth is maintained both during the injection of the tracer gas and after the injection of the tracer gas is stopped. It was confirmed that there was a peak in the measurement result and that the leak location could be detected efficiently even with a small amount of rare gas used. On the other hand, when a mixture of helium and nitrogen is used as the tracer gas, a peak is observed in the rare gas concentration distribution detected on the ground surface while the tracer gas is being injected, but after the rare gas injection is stopped, the leakage location The peak of rare gas concentration distribution was observed at a position different from the above, or the peak was not observed, and it was difficult to accurately detect the leak location. Using a mixture of helium and nitrogen as the tracer gas,
It is necessary to continue to press-in the tracer gas until the leak point is detected, but it becomes impossible to reduce the amount of rare gas used, and when the accumulated amount of rare gas leaked from the leak point increases, it leaked. It was recognized that this method has a problem that rare gas diffuses in a wide range, which makes it difficult to detect a leaked point accurately.

[0021]

According to the method of the present invention, the underground water pipe is filled with the tracer gas, and the rare gas in the tracer gas leaking from the leaking point is detected by the rare gas detector on the ground surface to detect the leaking point. In this method, by using a mixture of a rare gas and oxygen as the tracer gas, the total amount of the rare gas used can be reduced, and even though the concentration of the rare gas in the tracer gas is reduced, the rare gas at the leakage site is rare. As a result of the peak of gas concentration being clearly generated, there is an effect that the location of the water leakage can be detected with high accuracy. Further, in the method of the present invention, the peak of the rare gas concentration distribution at the water leakage location can be recognized for a long time even after the injection of the tracer gas is stopped, so that the water leakage location can be detected very efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing a rare gas concentration distribution in the vicinity of a water leakage point in the method of Example 1.

FIG. 2 is a diagram showing a rare gas concentration distribution in the vicinity of a water leakage point in the method of Comparative Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhisa Masuda 1-8-12-1, Higashihimemiya, Miyashiro-cho, Minami-Saitama-gun, Saitama Prefecture (72) Inventor Kazuro Senoo 3-16-4 Uchikanda, Chiyoda-ku, Tokyo Nissho Kogyo Incorporated (72) Inventor Kiyokatsu Takato 3-16-4 Uchikanda, Chiyoda-ku, Tokyo Nissho Kogyo Co., Ltd. (72) Inventor Saho 1-9-13 Koyama, Shinagawa-ku, Tokyo Toyo Oxygen Co., Ltd. (72) Inventor Norio Tadashi Seki Noochu 1-9-13 Koyama, Shinagawa-ku, Tokyo Toyo Oxygen Stock Company

Claims (3)

[Claims] 1. A tracer gas composed of a mixture of rare gas and oxygen is fed into the water pipe in the surveyed section to fill the water pipe in the surveyed section with the tracer gas,
The underground that is characterized by detecting rare gas that spouted from the damaged part of the water pipe in the section filled with tracer gas and leaked to the surface with the rare gas detector on the surface Method for investigating leak points in buried water pipes. 2. The tracer gas is press-fitted into a water pipe in the survey target section from a valve capable of operating the survey target section from the ground to fill the water pipe in the survey target section with the tracer gas. Method for investigating leakage points of underground underground water pipes described. 3. The tracer gas is filled into the water pipe of the survey target section by press-fitting the tracer gas into the water pipe from a terminal valve connected to the water pipe near the survey target section. Method for investigating leakage points of underground water pipes in Japan.