JPS6212829A - Method and device for detecting leak place of buried pipe of gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and apparatus for detecting leakage points in buried pipes for supplying city gas and the like.

(Prior art) As a method for detecting leakage points in buried pipes for city gas supply, etc., polling is carried out at multiple points along the buried pipe, measuring the leakage gas concentration in each polling hole, and detecting leakage points from the leakage point. A method has been used to estimate the location of this leakage based on the concentration gradient with respect to the distance.

(Problems to be Solved by the Invention) However, with the conventional method of simply measuring the leakage gas concentration in the poling hole after polling, in the case of a leak in which a large amount of gas is ejected from a buried pipe, the concentration of leaked gas in the vicinity of the leakage point is Inside the poling holes, the gas concentration was 100%, making it impossible to pinpoint the leakage point within a narrow range. For this reason, conventional methods have problems in that it may take a long time to discover leakage points, and that the number of polling points increases, increasing costs such as road restoration costs.

The purpose of the present invention is to solve such conventional problems, and even when the amount of leakage is large, it is possible to identify the leakage point within a narrow range. This reduces the number of polling locations and reduces costs such as road restoration costs.

(Structure and operation of the invention) In order to solve the above-mentioned problems, the present invention polls multiple locations along the buried pipe, replaces the internal atmosphere in each borehole with outside air, and The gist of the method is to measure the gas concentration after an equal amount of time has elapsed after the replacement, and to search for a leakage point by comparing the measured gas concentrations for the plurality of poling holes. A detailed explanation will be given below based on the drawings.

In FIG. 1, reference numeral 1 indicates a buried pipe, and 2 indicates a leakage location. Code 3 (3a, 3b.

3c, 3d, 3e, 3f, 3g, """)
This is done by poling holes at a plurality of locations along the buried pipe 1, and any suitable method such as a conventional method can be used for this poling.

By the way, the gas leaking from leak point 2 permeates underground at a speed determined by various conditions such as the underground condition and the amount of gas emitted, and after a certain amount of time has passed, it spreads, for example, to the area shown by the imaginary line in the figure. Therefore, if the gas concentration in the polling hole 3 is directly measured, it will be 1 in the vicinity of the leakage point 2.
It shows the gas concentration at or near 009G,
The leakage location 2 cannot be specified in a narrow range.

Therefore, in the present invention, prior to measuring the gas concentration in each poling hole 3, the atmosphere inside the hole is first replaced with outside air, and then the gas concentration is measured after an equal amount of time has elapsed.

However, as shown in FIG. 2, Q(i
/h) of leakage gas flows in, as well as qOn h) of air flows in, and Q'+ q (w//h).
When the amount of the hole atmosphere flows out, the change in the hole gas concentration C after replacing the hole atmosphere with outside air is expressed by the following equation.

Here, the amount of leakage gas flowing into the poling hole 3 Q'
is smaller as the distance from the leakage point 2 increases, and increases as the distance from the leakage point 2 increases.
In 3a to 3g), the change in gas concentration over time after replacement with outside air is as shown schematically in Figure 3 for the amount of leakage. After measuring the gas concentration in each poling hole 3,
By comparison), it is possible to detect a difference in the inflow amount Q' of the leaked gas, that is, a difference in gas concentration due to a difference in distance from the leak point 2. As described above, each polling hole 3 (3a to 3
For g), when we measure the gas concentration after an equal amount of time has passed after replacing it with outside air, we see a concentration gradient as shown in Figure 4.
The leak location 2 can be estimated as being near the polling hole 3e where the gas concentration is highest. As shown in FIG. 4, the concentration gradient becomes gradual over time, and if the amount of leakage is large, the concentration gradient becomes difficult to detect if more than a certain amount of time passes. However, even in this case, the concentration gradient can be detected by shortening the elapsed time until the concentration is measured, thereby identifying the polling hole 3e closest to the leakage point 2. I can do it.

As described above, the method of the present invention is different from the conventional method of simply measuring the leakage gas concentration in the poling hole after poling).
Prior to the measurement, first replace the atmosphere inside the hole with outside air.
After that, the concentration of each gas is measured after an equal amount of time has elapsed, and the values are compared.
It is possible to detect the concentration gradient near the leak point in a leak where a large amount of gas is ejected, and thus the leak point can be specified in a narrow range.

A method for replacing the atmosphere inside the polling hole 3 with outside air may be a method in which the atmosphere in the hole is sucked in and discharged by a suction pump, or a method in which air is ejected into the hole by a pump to expel the atmosphere in the hole. In addition, the method for measuring the gas concentration in the holes is as described above, after replacing each hole with outside air,
Any suitable method may be used as long as it can measure the gas concentration after an equal amount of time has elapsed.

Next, a specific example of the gas concentration measuring device 4 used in carrying out the method of the present invention will be explained based on FIG. 5. This device 4 includes a concentration sensor section 61C connected to the intake pipe 5.

A forced exhaust pipe 8 provided with a suction pump 7 and a natural exhaust pipe 9 are provided, and the gas concentration measurement and display system 10 by the concentration sensor section 6 displays the concentration after a set time has elapsed from the start of measurement. This configuration includes a timer 11 whose setting time is variable. However, this device has a timer 11
The gas concentration can be measured by setting a desired time for this and inserting the intake pipe 5 into the polling hole 3 in which the atmosphere inside the hole has been replaced with outside air. At this time, the atmosphere inside the polling hole 3 can be maintained by activating the built-in suction pump γ, forcibly suctioning it from the intake pipe 5 to reach the concentration sensor section 6, and exhausting it from the forced exhaust pipe 8. If the self-injection pressure of the leaked gas is high, the suction pump 7 should not be activated, but the self-injection pressure itself should be used to reach the concentration sensor unit 6 from the intake pipe 5, and be exhausted from the natural exhaust pipe 9. An appropriate selection can be made depending on the leakage state. In the former case, the end of the natural exhaust pipe 9 is closed with the lid 12, and in the latter case, the end of the forced exhaust pipe 8 is closed. However, timer 11
After the set time has elapsed, read the gas concentration displayed on the measurement display system 10 and apply it to each polling hole 3 (3 &~3g
), and by creating a graph or the like, it is possible to detect the concentration gradient after an equal period of time has elapsed after replacing the air with outside air, and in this way, the location of the leak can be estimated. If the amount of gas ejected is large and a clear concentration gradient cannot be obtained with the above-mentioned set time, set a shorter time and re-measure. In this manner, the apparatus of the present invention can obtain an appropriate concentration gradient without having to change the set time of the timer 11 according to various conditions such as the amount of gas ejected and the underground condition. Incidentally, a pump for replacing the inside atmosphere of the hole may be built into the device 4, so that the replacement of the outside air inside the hole and the subsequent concentration measurement can be performed automatically. In addition, the device 4
If a recording section for recording the gas concentration at each lapse of time is provided inside the device so that the gas concentration at different time points can be measured in one measurement, there is no need to remeasure the gas concentration in the above-mentioned case. It disappears.

(Effects of the Invention) The method of the present invention differs from the conventional method in which the leakage gas concentration in the poling hole is simply measured after poling.
Prior to the measurement, first replace the atmosphere inside the hole with outside air.
After that, the concentration of each gas is measured after an equal amount of time has elapsed, and the values are compared.
In a leak where a large amount of gas is ejected, the entire concentration gradient near the leak point can be detected, and the leak point can be pinpointed within a narrow range, reducing the time required to discover the leak point. This has the special effect of reducing polling locations and reducing costs such as road restoration costs. In particular, the gas concentration measuring device used in carrying out the method of the present invention has a configuration in which the atmosphere inside the polling hole is forcibly brought to the gas concentration sensor section by a suction pump or selectively by the self-injection pressure of the leaked gas. In addition, by installing a timer with a variable set time to display the concentration after the set time has elapsed from the start of measurement, it is possible to This has the advantage that an appropriate concentration gradient can be obtained at all times.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the ground plane for explaining the method of the present invention;
Fig. 2 is a partially enlarged sectional explanatory diagram, Fig. 3 is a schematic diagram showing changes in gas concentration after replacement with outside air, Fig. 4 is an explanatory diagram showing an example of the gradient of gas concentration, and Fig. 5 is a method of the present invention. FIG. Code 1: Buried pipe, 2: Leakage location, 3 (3a,
3b. 3 c, 3 d = 3 e -3f -3g,
......) - polling hole, 4... measuring device, 5
... Intake pipe, 6... Concentration sensor section, 7... Suction pump, 8... Forced exhaust pipe, 9... Natural exhaust pipe, 1.
0...Measurement display system, 11...Timer, 12...
·lid. Figure 1 Figure 4 Figure 2 Figure 3 Between n → Figure 5

Claims (2)

[Claims] (1) Poll multiple locations along the buried pipe, replace the atmosphere inside the hole with outside air at each polling hole, measure the gas concentration after an equal amount of time has elapsed after the replacement, and poll the multiple locations. A method for detecting a leakage point in a buried gas pipe, characterized in that the leakage point is detected by comparing the measured gas concentration with respect to a hole. (2) A forced exhaust pipe equipped with a suction pump and a natural exhaust pipe are installed in the concentration sensor section connected to the intake pipe, and the gas concentration measurement and display system by the concentration sensor is displayed after a set time elapses from the start of measurement. A gas concentration measuring device for detecting a leakage point in a buried gas pipe, characterized in that it is equipped with a timer with a variable setting time for displaying the concentration of gas.