JPH05322688A - Gas leakage detection method and device - Google Patents

Abstract

PURPOSE:To obtain an improved response also for mobile detection by detecting inclusion of flammable gas in a first detection process and then that of hydrogen gas in a second detection process. CONSTITUTION:A flammable gas sensor 17 and a hydrogen selectivity sensor 16 are mounted on a mobile gas leakage detector. Leaked gas containing hydrogen is captured at a gas capturing port 14, the outputs from sensors 17 and 16 at an operation side where a gas with a specified constituent can be detected by sensors 17 and 16 is amplified by an amplifier 210, is displayed by an indicator 220, and at the same time generates an alarm such as a lamp from a display 212 via a comparator 211. While observing the output of the sensor 17, leaked gas is detected and output is switched to the sensor 16 on reaction, thus identifying whether the leaked gas is a manufacturing gas or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects, for example, whether or not city gas containing hydrogen gas is leaking from a buried pipe by detecting gas components contained in leaking gas leaking onto the ground. The present invention relates to a gas leakage detection method and an apparatus using the method.

[0002]

2. Description of the Related Art Properly detecting on the ground surface city gas leaked from a gas pipe buried in the ground at an underground construction site or near the surface of a gas pipe burial section is an extremely important issue in terms of gas leakage countermeasures. Is. In such detection work, conventionally, hydrocarbon compounds (methane, propane, etc.) have been detected to determine the presence or absence of gas leakage. However, since these gases may be naturally generated, it has been recently proposed to accurately judge the leakage of city gas (production gas) based on the presence or absence of hydrogen on the basis of hydrogen, which hardly exists in nature.

[0003]

In this judgment method, a hydrogen-selective sensor is adopted, and a gas leakage detection device equipped with this sensor is used to continuously suck gas near the ground surface above the buried pipe. However, if it is attempted to determine the presence or absence of leaked gas, the sensor will react after passing through the leaked part because the response speed of the sensor is slow. Therefore, there are drawbacks that it is difficult to specify the leaked portion, and it takes time to specify the leaked portion. Therefore, an object of the present invention is to obtain a gas leakage detection method having a hydrogen-selective sensor, which has good responsiveness and can be adopted in so-called mobile city gas leakage detection. With
The object is to obtain a gas leakage detection device used in this method.

[0004]

[Means for Solving the Problems] A characteristic means of a gas leakage detection method for achieving the above object is to collect a leaking gas leaking on a road surface, and use a flammable gas sensor to detect the flammable gas from the leaking gas. The first detection step of detecting the presence or absence of hydrogen gas, and the second detection step of detecting the presence or absence of hydrogen from the leaked gas with a hydrogen-selective sensor, and the leaked gas contains the flammable gas in the first detection step. It is to determine that the production gas has leaked when it is detected that the hydrogen gas is contained in the second detection step.

The characteristic structure of the gas leakage detection device used in this method is that the gas leakage detection device is equipped with a gas collecting port for collecting leaked gas leaking onto the road surface, and the gas is collected in the gas collecting port. It is equipped with a hydrogen-selective sensor that can detect hydrogen from gas by separating it from other gases, and a combustible gas sensor that can detect combustible gas, and as a working sensor that detects gas, a hydrogen-selective sensor and a combustible gas sensor. And an actuation sensor determining means for actuating at least one of the above.

[0006]

In the gas leak detection of the present application, detection is performed by two kinds of sensors, a combustible gas sensor and a hydrogen selective sensor. Here, the combustible gas sensor is generally
It is a sensor that contains hydrogen as a gas to be detected and simultaneously detects methane, propane, and the like. Such a sensor has a relatively high response speed. On the other hand, the hydrogen-selective sensor uses only hydrogen as a gas to be detected, and has a relatively slow response speed. Therefore, in the present application, both of these sensors are operated simultaneously or in tandem,
When both of them detect gas, it is determined that the leaking gas leaking on the road is from the manufacturing gas. In this case, it is possible to reliably identify the leak of the produced gas from the above-mentioned existing state of the hydrogen gas in the natural world. Moreover, in the case of the present application, it is possible to quickly identify a place where leakage may occur with a combustible gas sensor with good responsiveness and to confirm hydrogen with a hydrogen selective sensor, Even when the vehicle is traveling, it is possible to stop the movement at the stage where the first detection process is completed, and it is possible to accurately identify the leak point of the manufactured gas.

As the gas leakage detection device, if a combustible gas sensor and a hydrogen selective sensor are provided and a means for controlling the operation of these sensors is provided, the gas leakage detection can be performed by the above detection procedure.

[0008]

According to the method of the present invention, therefore, the production gas can be specified by separately detecting the gas such as methane generated from the natural environment and the hydrogen gas. Further, in improving its response performance, in a gas leakage detection method equipped with a hydrogen selective sensor, a combustible gas sensor is adopted, and the response is good, and it is also used in so-called mobile city gas leakage detection. It was possible to obtain a gas leakage detection method and device capable of performing the above.

[0009]

[Embodiment] Regarding the city gas which is a leak detection target of the invention,
First, a description will be given. City gas is made with natural gas (LNG)
It can be roughly divided into gas production. The production gas is coal gas (coke
Gas), petroleum gas (naphtha gas) and LPG metamorphic gas
Can be classified. The composition of gas differs depending on each gas company.
However, if you are using natural gas, CH_Four
Is about 88%, and hydrocarbons with 2 to 4 carbon atoms are about 1
Many contain about 0%. With the production gas, the calorific value is also
The composition of the composition differs depending on the coal gas, petroleum gas, etc.
The growth varies, but 5000 Kcal / m³The city of
About the composition of the gas, H₂32-46, CH_Four18-2
2, CO5-10, C _mH_n(Medium hydrocarbon) 4-10% remaining
Ri N₂, C₂, CO₂Is. Therefore, in the production gas, H₂gas
It can be seen that is included in large quantities.

Here, hydrogen gas is the lightest in weight as compared with other gases, and since its molecule is small, it easily diffuses, so that it easily appears on the surface of the earth, and it hardly exists in nature. Therefore,
By detecting this hydrogen gas, gas leakage of city gas (specifically, manufacturing gas) can be detected efficiently.

Next, a gas leakage detection device used when carrying out the method of the present invention will be described. FIG. 1 is a partially cutaway side view of the apparatus, 10 shows the entire mobile gas leakage detection apparatus as a gas leakage detection apparatus, 11 is a base, 1
Reference numerals 2 and 13 are wheels provided on the base 11, reference numeral 14 is a gas collecting port, the cross section of which is trapezoidal as shown in the drawing, and the lower surface of which is a rectangular opening 15. Now, from this opening 15, the gas collected at this portion 15 is introduced into the pipe 1
A pump P that leads to the detection device main body 19 via 8 is provided, and a hot wire semiconductor type hydrogen selective sensor 16 and a combustible gas sensor 17 for detection are further provided in this gas path. A cable 20 and a display device 21 for displaying the detected amount of hydrogen gas are provided for the sensors 16 and 17. Further, the detection device body 19 is
It is operated by the grip 23 provided on the handle 22.

When this gas leakage detection device 10 is used, the gas collection port 14 is slid on the road surface GL, and the leak gas leaked onto the road surface GL is collected by the gas collection port 14 and each sensor is detected. A predetermined gas is detected at 16 and 17, and the amount of gas is displayed on the display device 21.

The above is the schematic configuration of the gas leakage detection apparatus 10. The configuration, detection characteristics, responsiveness, etc. of each sensor 16, 17 will be described below. (1) Hydrogen Selective Sensor 16 The hydrogen selective sensor 16 detects hydrogen by separating it from other gases, and has high sensitivity to hydrogen and almost no sensitivity to other gases. Furthermore, the response to hydrogen gas is relatively slow. This sensor 16 is shown in FIG.
The configuration of is shown. Here, 201 is a heater, 20
2 is a substrate made of Al ₂ O ₃ (alumina), 20
Reference numeral 3 denotes a pair of planar comb-shaped Pt (platinum) vapor deposition films printed on the substrate 202, and 204 denotes the substrate 202.
And SnO ₂ which is a metal oxide coded on the Pt deposition film 203. Reference numeral 205 denotes an SiO ₂ film which is formed as a dense and uniform thin film by filling the vicinity of the surface of the SnO ₂ sintered body 204 (see Japanese Patent Publication No. 61-31422). The SiO ₂ film 205 thus formed is
A molecule having a radius as small as a hydrogen molecule easily passes, but a molecule having a radius larger than that has a property of being hard to pass, and thus exhibits a highly sensitive detection property.

(2) Combustible gas sensor 17 The combustible gas sensor 17 is a sensor having a certain sensitivity to hydrogen and gases other than hydrogen (methane, propane, etc.) and has a fast response to the gas. The structure of this sensor is shown in FIG. Here, 302 is an alumina substrate, 303 is a Pt film resistor, and the alumina substrate 302 is
It is meandered by vapor deposition on the top. 304 is SnO ₂
A sintered body is provided on the alumina substrate 302 so as to cover the Pt film resistor 303.
20681). Here, the sensor 17 shown in FIG.
In, the Pt film resistor is also used for heating resistance detection. The combustible gas sensor 17 formed in this manner exhibits high sensitivity and good responsiveness to combustible gas. Sensitivity characteristics of each sensor 16 and 17 with respect to various gases Table 1 shows outputs of each sensor with respect to various combustible gases.

[Table 1]

From the table, it can be seen that the combustible gas sensor 17 has sensitivity to gases other than hydrogen. Response Performance of Each Sensor FIG. 3 shows the response performance of the combustible gas sensor 17 and the hydrogen selective sensor 16. 90% response time (90% of gas concentration
The time required to react up to%) is about 3 seconds for the combustible gas sensor 17 and about 15 seconds for the hydrogen-selective sensor 16. Therefore, the response of the combustible gas sensor 17 is about 5 times faster.

Measuring Circuit FIG. 4 shows an example of the measuring circuit provided for each of the sensors 16 and 17. As shown, each sensor 1
The resistors R ₀ , R ₁ and R ₂ , the power source E, the variable resistor VR, and the voltmeter V are provided for 6 and 17 to form a bridge circuit, and a change in the resistance value of the sensor is detected as a voltage output. ..

Detection Circuit Configuration of Gas Leak Detection Device 10 As described above, the device 10 includes the combustible gas sensor 1
7 and a hydrogen-selective sensor 16 are mounted, and these sensors are configured so that the respective outputs can be displayed by the changeover switch 24 in the display device 21, and selectively. A configuration in which the sensor output can be read is adopted.

FIG. 5 shows a block diagram of the mobile gas leakage detection device 10. As shown in the figure, the operation sensor determination unit 100 is provided for the combustible gas sensor 17 and the hydrogen selective sensor 16, and the sensor to be output is freely selected depending on the detection status. For gas detection,
Leakage gas containing hydrogen is collected at the gas collection port 14, and the gas of a predetermined component is detected by each sensor. The output from the sensor on the operating side is amplified by the amplifier 210, displayed on the indicator 220, and the comparator 211.
An alarm, such as a flashing lamp or buzzer or an intermittent buzzer, can be emitted from the display 212 through the display. 213 is a power source and 214 is a constant voltage circuit.

As a detection method, usually, while watching the output of the combustible gas sensor 17, while detecting the air near the ground surface above the buried pipe, walking is performed to detect leak gas. Since the combustible gas sensor 17 is sensitive to other gases such as methane, the production gas cannot be specified, but when the sensor reacts, the response to the gas is fast, and the detection result can be immediately known. After that, by switching the output to the hydrogen selective detection sensor 16, it is possible to identify whether or not the leak gas is the production gas. That is, when both sensors detect gas, it can be determined that gas leakage has occurred. That is, in the first detection step, the combustible gas sensor 17 quickly detects a gas considered to be a production gas, and in the second detection step, the hydrogen selectivity sensor 16 determines that the gas is a production gas.

The specific 90% response time (the time required to react up to 90% of the gas concentration) in each sensor is
The hydrogen-selective sensor 16 takes about 15 seconds while the combustible gas sensor 17 takes about 3 seconds. Therefore, if it is assumed that detection is performed while walking at 4 km / h, the hydrogen-selective sensor 16 alone will move beyond the detection point of about 17 m, which is a problem. It is possible to surely carry out in a short time.

[Other Embodiments] In the above-described embodiments, an example in which a base type sensor is used as a sensor has been shown, but this may be a hot wire type sensor shown in FIG. In the figure, the materials corresponding to those in FIG. 2 are indicated by the same numbers. In these hot wire type, Pt serves for heating and resistance detection. In the above-described embodiment, the combustible gas sensor 17 increases the sensitivity to hydrogen by adjusting the heater temperature in the sensor, but it is possible to change the heater temperature by operating the detection temperature setting means (not shown). The sensitivity to the gas can be increased. That is, if it is adjusted to have a high sensitivity to methane, it can be used as a leak detection sensor for natural gas (methane content 80 to 90%). In recent years, the number of city gas companies that are switching from manufactured gas to natural gas is increasing nationwide, so it is useful to be able to detect leaks of both manufactured gas and natural gas with one unit. is there. In the above embodiment, the first detection process is performed in the traveling movement state, and the process sequence in which the second detection process is performed in the traveling stopped state following the first detection process is shown in the traveling state. In addition to performing the detection step and the second detection step, when flammable gas is detected in the first detection step, the traveling may be stopped and the second detection step may be waited for to complete the detection. .. The running and the stopping of the running may be automatically interlocked with each other based on the detection result in the first detection step.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a mobile gas leakage inspection device.

FIG. 2 is a block diagram of each sensor

[Fig. 3] Response characteristic diagram of each sensor

FIG. 4 is a diagram showing an example of a circuit used for implementing the present invention.

FIG. 5 is a block diagram of a measuring device for carrying out the present invention.

FIG. 6 is a diagram showing a configuration of a hot wire sensor.

[Explanation of symbols]

 14 Gas Collection Port 16 Hydrogen Selective Sensor 17 Combustible Gas Sensor 100 Operation Sensor Determining Means

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Hideki Kimura Inventor Hideki Kimura 1-1-17-1, Chiyo, Hakata-ku, Fukuoka City Nishibe Gas Co., Ltd. (72) Nobuo Iwai 2-5, Mitsuyachu, Yodogawa-ku, Osaka No. 4 inside New Cosmos Electric Co., Ltd. (72) Inventor Yuichi Shimakawa 2-5-4 Mitsuyachu, Yodogawa-ku, Osaka-shi, Osaka Inside New Cosmos Electric Co., Ltd.

Claims (5)

[Claims] 1. A first detection step of collecting leaking gas leaking on a road surface and detecting the presence or absence of the combustible gas by a combustible gas sensor (17) from the leaking gas, and from the leaking gas A second detection step of detecting the presence or absence of hydrogen with a hydrogen-selective sensor (16) is performed, and it is detected that the leak gas contains the combustible gas in the first detection step. (2) A gas leakage detection method for determining that a production gas has leaked when it is detected in the detection step that the hydrogen gas is contained. 2. The first detection step is performed in a traveling movement state, and subsequently to the first detection step,
The gas leakage detection method according to claim 1, wherein the second detection step is performed in a traveling stopped state. 3. The method according to claim 1, wherein the first detection step and the second detection step are performed in a traveling state, and the traveling is stopped when the combustible gas is detected in the first detection step. Gas leak detection method. 4. A gas collecting port (14) for collecting leaking gas leaking on a road surface, wherein hydrogen is separated from other gas from the leaking gas collected at the gas collecting port (14). A hydrogen-selective sensor (16) capable of detecting and a combustible gas sensor (17) capable of detecting a combustible gas are provided, and the hydrogen-selective sensor (16) and the combustible gas are used as an actual sensor for detecting gas. Operation sensor determination means (10) for operating at least one of the gas sensor (17)
0) is provided with a gas leak detection device. 5. A detection temperature setting means for changing / setting the detection temperature of the combustible gas sensor is provided.
The gas leak detection device according to.