JPS62240831A - Leakage detection for gas from gas transport pipe - Google Patents

Abstract

PURPOSE:To detect a leakage location correctly, by fetching a high frequency noise signal exceeding 100kHz from noise signals obtained with a microphone mounted on a pig to enable detection of a possible leakage however small the leak of gas may be. CONSTITUTION:Noise signal obtained with a microphone 6 are sent to a filter 7 while a pig 1 is running. Out of the noise signals, only high frequency noise signals exceeding 100kHz pass through a filter 7 and then, sent to a signal processor 8, from which they are sent to a memory 9 to be memorized thereinto 9 corresponding to a running distance of the pig 1 with a distance meter 5. This enables correct detection of a gas leakage location along with a judgment on whether a gas leakage occurs in a pipe 3 or not by analyzing data memorized in the memory 9 afterwards.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for detecting gas leakage from within a gas transport pipe.

[Prior art and its problems]

Conventionally, as a method for detecting whether gas is leaking to the outside from a transportation pipe for transporting gas such as city gas,
There are methods such as detecting the pressure difference between the inlet and outlet ends of the transport pipe, but this method cannot detect leaks of minute amounts of gas, and furthermore cannot detect the location of gas leaks. .

Therefore, there is a need for a method that can reliably detect the presence or absence of gas leakage even if the amount of gas leakage is minute, and can accurately detect the location of gas leakage.

Such a method has not yet been proposed.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, the present invention provides a method for detecting gas leakage from within a gas transport pipe, which can reliably detect the presence or absence of a leak even if the amount of gas leakage is minute, and can accurately detect the location of the gas leak. There is a particular thing.

[Summary of the invention]

This invention provides a method for installing a plurality of microphones radially toward the inner surface of the tube around the center axis of the tube, and passing the noise signal obtained by the microphone through a filter. extracting a high frequency noise signal of 100 KHz or more from the noise signal, detecting the presence or absence of gas leakage from inside the pipe based on the thus extracted high frequency noise signal,
The present invention is characterized in that the location of the gas leak is detected from the travel distance of the VIG when the gas leak is detected.

[Structure of the invention]

The inventors of the present application have conducted extensive research in order to achieve the above-mentioned objective. That is, the noise generated by the gas leaking from the small holes made in the pipe, and the noise generated when the VIG runs inside the pipe, such as the sliding noise between the scraper cup and the inner surface of the pipe.

The blowing sound of gas passing between the scraper cup and the inner surface of the pipe and the running sound of the VIG were measured, and the relationship between the frequency of these noises and the power density was investigated. An example of this thinning is shown in FIG.

As is clear from FIG. 1, the noise caused by gas leakage from the small holes has a higher frequency and a greater power density than noise caused by the running of the pig. Therefore, it has been found that by detecting only the noise caused by gas leakage, the presence or absence of leakage can be reliably detected even if the amount of gas leakage is minute.

This invention has been made based on the above-mentioned knowledge, and one embodiment of the invention will be described below with reference to the drawings.

FIG. 2 is a sectional view of an embodiment of the present invention, and FIG.
FIG. 3 is a sectional view taken along line A-A in FIG. 2;

In FIGS. 2 and 3, a pig 1 is conventionally known and consists of a vig body 2 and a scraper cup 4 mounted around the vig body 2 and in contact with the inner surface of a tube 3. 5 is a distance meter attached to the pig body 2 for measuring the total distance traveled by the pig body 20. A plurality of microphones 6 are attached to the rear end of the pig body 2 in the direction of travel, radially toward the inner surface of the tube 3 around the central axis of the pig body 2, and are used to listen to sounds generated from the entire circumference of the tube 3. Collect sound. Inside the Big body 2, there is a filter and a signal processor 8.
and a storage device 9 are provided.

The filter 7 passes only high-frequency noise signals of 100 KHz or more among the noise signals obtained by the microphone 6, and amplifies them to a predetermined size. Then, the storage device 9 stores the high-frequency noise signal in correspondence with the traveling distance of the pig 1 measured by the distance meter 5.

As mentioned above, 1゛00KHz by filter 7
As shown in FIG.
This is because frequencies higher than kHz do not appear.

In the method of one embodiment of the present invention configured in this way, the noise signal obtained by the microphone 6 is sent to the filter 7 while the pig 1 is running.

Among the noise signals, only high-frequency noise signals of 100 KHz or more pass through the filter 7, and then are sent to the signal processor 8, which in turn is sent to the memory 9, where the distance traveled by the pig L and the distance measured by the distance meter 5 are recorded. Correspondingly, it is stored in the storage device 9.

Therefore, by analyzing the data stored in the memory device 9 later, it will be possible to determine whether or not there is a gas leak in the pipe 3.
Gas leak locations can also be detected accurately.

〔Effect of the invention〕

As explained above, according to the present invention, even if the amount of gas leakage is minute, the presence or absence of leakage can be reliably detected, and
This has the extremely useful effect of being able to accurately detect the location of gas leaks.

[Brief Description of the Drawings] Fig. 1 is a graph showing the relationship between power density and frequency in noise caused by gas leakage and noise caused by VIG running. Fig. 2 is a sectional view of an embodiment of the present invention. 3
The figure is a sectional view taken along the line A--A in FIG. 2. In the drawings, 1...Pig, 2...Pig body, 3゛° tube, 4...Scraper cup, 5...Distance meter, 6...Microphone, 7...Filter, 8... - Signal processor, 9... memory device.

Claims (1)

[Claims] A plurality of microphones are mounted radially toward the inner surface of the pipe around the central axis of the pig to a pig that can travel inside the pipe, and the noise signals obtained by the microphones are passed through a filter to separate one from the noise signals.
A high-frequency noise signal of 00 KHz or more is extracted, and based on the high-frequency noise signal thus extracted, the presence or absence of gas leakage from the pipe is detected, and from the traveling distance of the pig when gas leakage is detected. A method for detecting gas leakage from within a gas transport pipe, the method comprising detecting a gas leakage point.