JPH1172409A - Method for detecting leakage of piping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect with excellent precision a leakage position anytime and periodically without moving operators who inspect a leakage in a waterworks net, a gas piping, or the like and further without needing attendant operations such as a shield, etc., of an internal circulation passage. SOLUTION: This is a method for detecting a leak of water of a distributing water pipe 10 in a water circulation state. Underwater mikes 12A, 12B are installed at both ends of an inspection section, and a detection signal fetched from each of the mikes 12A, 12B is passed through a band-pass filter to classify in each frequency band. The inspection section is divided into n parts to set a tentative sound source position, and waveforms having high correlative coefficients of a signal of each band detected by both the mikes at this tentative sound source position are added to obtain synthesized waveforms 16. This process is performed ranging all sections while the tentative sound source position is renewed, and it is decided whether a leak of water is present or not from the synthesized waveforms at each tentative sound source position. An object to be applied is not only waterworks, but also a leakage of various fluids to be detected in a gas piping or a plant piping. An underwater mike is detected as a sensor, and an object to be detected is various wave motions such as a sound, a vibration or the like which are detected through a piping even in an internal fluid.

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 leaks in pipes, and is suitable for detecting leaks in water supply networks, detecting gas leaks in gas pipes, and detecting leaks in various pipes in chemical plants. The present invention relates to a method for detecting leaks in piping.

[0002]

2. Description of the Related Art It is extremely important to early determine a leak location in a water pipe, a gas pipe, an oil feed pipe, or a fluid pipe network of a chemical plant and prevent the continuation of the leak in order to effectively utilize resources. . For this reason, various leak inspections have been conventionally performed. For example, in the water leak inspection in the water supply network, the sound hearing method is used as a general method, and the worker directly hits the sound hearing stick to the valve part of the water pipe to hear the sound coming out of the pipe to detect the presence of water leak. Alternatively, a vibration sensor is placed on the ground along the water supply pipe, and the presence or absence of water leakage is detected based on vibration noise transmitted from the water supply pipe.

However, in the above-described sound hearing method, the work is performed at night because vibrations and the like caused by the traffic of the vehicle affect the measurement, and the inspection distance is extremely short because the worker measures while walking. There was a disadvantage.
In addition, since listening to sound requires skill, there is also a problem that few workers are engaged in water leak detection.

[0004]

SUMMARY OF THE INVENTION From such a viewpoint,
A method in which a microphone is inserted into a pipe and detected while moving along the pipe (Japanese Patent Application Laid-Open Nos. 50-118554 and 56-160500), and a differential pressure is detected while a pipe flow rate is reduced by an orifice. However, methods for detecting the amount of water leakage have been proposed. This method can be used to detect leak points in various fluid pipes as well as water pipe networks.

However, in any of the above-mentioned conventional methods, it is necessary to perform an operation such as withdrawing the internal fluid from the pipe or shutting off the flow path during the actual measurement. It could not be detected.

The present invention focuses on the conventional problems described above, and internal fluid is generated by sensors at both ends of a pipe inspection section.
Alternatively, it is another object of the present invention to provide a method for detecting a leak in a pipe in which a leak point can be easily detected only by an operation of detecting a sound audible through a pipe wall of the pipe.

[0007]

In order to achieve the above object, a pipe leakage detection method according to the present invention is a method for detecting leakage of a pipe in a state where a fluid is flowing therein, and includes an inspection method. Sensors are arranged at both ends of the section, the detection signal captured by each sensor is passed through a band-pass filter to discriminate into a plurality of frequency bands, the inspection section is divided into n equal parts, and a temporary sound source position is set. A waveform having a high signal correlation coefficient for each band detected by both sensors at the temporary sound source position is added to obtain a synthesized waveform, and this process is performed over the entire section while updating the temporary sound source position. In this configuration, the presence or absence of leakage is determined from the composite waveform obtained in step (1).

A pipe leakage detection method according to a second configuration of the present invention is a method for detecting leakage of a pipe in a state where a fluid is flowing through the inside thereof. At the same time, and discriminates each detection signal into a plurality of frequency bands, and obtains a synthesized waveform of the band signals discriminated by correlation at a temporary sound source position set at an arbitrary position during the search to determine whether or not there is leakage. It is characterized in that a determination process is performed, and this process is performed over the entire inspection section while changing the temporary sound source position.

[0009] In these cases, the pipe is a water pipe or a water pipe of a water network, and a water leak in an inspection section is detected from a submersible microphone attached to the water pipe or the water pipe of the water network. The pipe is a gas pipe, and detects a gas leak in an inspection section from a sensor attached to the gas pipe.Furthermore, the pipe is a pipe of a plant, and is attached to a pipe of the plant. The leak of the fluid in the inspection section can be detected from the sensor.

[0010]

According to the above arrangement, sound is detected by a sensor such as a submersible microphone at both ends of the inspection section of the fluid pipe, and the detected sound is discriminated into a plurality of frequency bands, and this is identified by a sound source. In the case where the sound from the same sound source has the same delay time, the sound from the sound source at the specific position is synthesized by adding the components correlated for each frequency band and combining them. Can be reproduced. By moving the temporarily determined sound source position, it is determined whether or not the synthesized waveform obtained by moving the temporary sound source position in the entire area of the inspection section is based on fluid leakage, for example, by using a pattern recognition process or the like. Can be. Therefore, it is possible to reproduce the sound generated at a specific position by detecting the sound of the fluid itself at different positions in the inspection section at the same time, discriminating this for each frequency band, and adding and synthesizing correlated ones. Since it is used, it is possible to easily determine the presence or absence of leakage simply by detecting sound at two or more locations.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description will be given below of a specific embodiment in which a pipe leakage inspection method according to the present invention is applied to a water transmission and distribution pipe leakage inspection method with reference to the drawings. FIG.
FIG. 1 is a block diagram of a device configuration for implementing a water leakage inspection method according to an embodiment. As shown in the drawing, a water leakage inspection section is set for the water transmission and distribution pipe 10 to be inspected, and underwater microphones 12 (12A, 12B) are installed at both ends. The microphone 12 detects underwater sounds, discriminates them into different frequency bands, passes them through the correlation classification filter 14, and temporarily sets sound source positions (n1, n2, n3,...) In the leak inspection section. Are synthesized by the waveform synthesizing means 16 and the presence or absence of water leakage is diagnosed by the synthesized waveform. The principle is as follows.

As shown in FIG. 1, in a water leakage inspection section, a pair of underwater microphones 12 located at both ends of the section detect underwater transmission sounds. The installation point of one underwater microphone 12A is a reference point A, and the other underwater microphone 12B is
Assuming that the installation point is a control point B and the water leak point is P, the water leak sound at the water leak point P detected at the reference point A and the water leak sound at the water leak point P detected at the control point B are the same or very similar waveforms. However, since the distance from P to A or B is different, a propagation time difference occurs. Knowing this propagation time difference, the distance la from the reference point A to the leak point P
Can be obtained by the following equation.

[0013]

(Equation 1)

Where L is the distance between points A and B, and τ
m is the water leak sound propagation time difference, and C is the water leak sound propagation speed. Therefore, if the difference in the water leak sound propagation time is known, the position of the water leak point P can be specified.

The underwater microphone 12 (12A, 12A)
B) simultaneously detects signals from a plurality of sound sources, and the detected sound is regarded as a synthesized sound over a multi-frequency range. Therefore, when a plurality of sound sources S1 and S2 are present, after detecting signals to be emitted from the plurality of microphones 12, the signals of the detected synthesized sounds are restored to signals emitted by the respective sound sources S1 and S2. Thus, the waveform of the sound emitted from the sound source at the specific position can be reproduced. For this reason, in the present embodiment, the correlation classification filter 14 is used. The specific contents will be described with reference to FIG.

When the sound emitted from the sound source S1 is output by frequency through a band-pass filter, the frequencies f1, f2,
When there is a signal of f3 and the sound source S2 emits signals of frequencies f4 and f5, the sounds detected by the microphone 12A close to the sound source S1 and the microphone 12B close to the sound source S2 are the sounds of both sound sources S1 and S2. Detected in a mixed state. Microphone 1
When the positions of the sound sources 2A and 12B and the sound sources S1 and S2 are fixed, sounds from the same sound source detected by the microphone 12A have no propagation time difference regardless of frequency, and sounds from different sound sources have the same propagation time difference. Therefore, the correlation of the waveform of the sound detected for each frequency is calculated, and when the correlation value is large, it can be determined that the sound is emitted from the same sound source. By extracting this, the sound sources S1, The sound from each of S2 can be reproduced.

Therefore, as shown in FIG.
The signal detected from the correlation classification filter 14B
To input. In this filter 14, frequency analysis circuits 18A corresponding to the microphones 12A and 12B,
18B, the frequency-discriminated signal is applied to the correlation calculation circuit 2
0 and output to the arithmetic circuit 22, and the correlation between the outputs of the frequency analysis circuits 18A and 18B is calculated for each frequency band. Then, based on the lower limit value and the upper limit value of the delay time set by the delay time setting circuit 24, the arithmetic circuit 22
Outputs a time-varying waveform of the level of the frequency band based on the change in the set delay time.

FIG. 4 is a graph of the cross-correlation coefficient of the waveform passing through the band-pass filter.
It is divided into 0 bands. When a certain threshold value is set for the correlation coefficient with respect to the output data as shown in FIG. Such a composite waveform is obtained. This is output to the water leakage diagnosis device 26, where the presence or absence of water leakage is determined and output.

In such processing, the inspection section of the water distribution pipe is divided into n equal parts, and the sound source positions n1, n2,
n3,... The determination of water leakage from the synthesized waveform is based on the fact that the synthesized signal is continuously performed, the strength obtained from the amplitude of the synthesized waveform (FIG. 5A), and the number of additions of the frequencies up to the synthesized waveform (FIG. 2)) may be derived to make the determination. This makes it possible to easily determine the presence or absence of water leakage, its position, and to estimate the amount of water leakage from the amplitude. The computer may perform the arithmetic processing and display it on the display means. A pair of underwater microphones 12A, 12B
When the water leakage inspection in the inspection section is completed, the inspection section is updated and the same processing is performed over the entire water network.

In the above-described embodiment, a method for detecting water leakage in a water transmission / distribution pipe in a water-passing state, in which underwater microphones are installed at both ends of an inspection section, and a detection signal captured by each microphone is used as a band After passing through a pass filter, discrimination is performed for each frequency band, the test section is divided into n equal parts, and a temporary sound source position is set. In addition to obtaining the combined waveform by adding the waveforms, this process is performed over the entire section while updating the temporary sound source position, and the presence or absence of water leakage is determined from the combined waveform at each temporary sound source position. The effect is obtained that the leaked portion can be easily detected only by the operation of detecting the sound with the underwater microphone at both ends of the inspection section.

In the above embodiment, the method of detecting the water supply network by using the underwater microphone has been described. However, an acceleration pickup is used as a sensor instead of the underwater microphone, and this is used to expose the pipe wall or the exposed wall to the outside. It is also possible to use the fact that the sound inside the pipe is vibrated and transmitted to the pipe wall. In other words, the sound caused by water leakage, the vibration caused by this sound, or the change in pressure caused by water leakage causes the propagation of a negative pressure wave, and the sensor capable of detecting these as a wave signal is the same as the embodiment. The leak location can be detected by the method described in (1).

The present invention can be applied not only to water leak inspection in a water supply network, but also to gas leak detection in a gas piping network and leak detection in general fluid piping in a chemical plant or the like. For example, when the present invention is applied to gas leak detection, a microphone for detecting gas flow noise may be inserted into the pipe at intervals to detect gas flow noise. Since the sound of gas leakage includes high-frequency sound in the ultrasonic range, an AE sensor can be used in addition to the acceleration pickup. This may be set at the mounting position on the pipe wall of the exposed portion of the pipe or between the exposed branches.

In order to detect leakage of a transport fluid in a chemical plant or the like, a method of monitoring pressure is used to detect the propagation of a negative pressure wave due to internal fluid leakage using a pressure gauge as a sensor, and this is shown in the embodiment of water leak detection. Processing can be performed to identify the leak location. Also, it is naturally possible to use a method based on acoustic monitoring, and when detecting the wave of the internal fluid as leak sound, it is sufficient to insert a microphone inside the pipeline, since the pipeline is installed on the ground surface, In some cases, it may be arranged around the pipe to detect sound leaking out through the pipe wall. Further, similarly to the case of the gas leak detection, vibration on the wall surface of the pipeline can be detected using an AE sensor in addition to the acceleration pickup. In any of the above cases, the algorithm for detection is the same as in the case of the water leakage inspection.

[0024]

As described above, according to the present invention,
This is a method of detecting leaks of pipes in a state where fluid is flowing inside, by arranging sensors at both ends of the inspection section, and passing a detection signal taken by each sensor through a bandpass filter to a plurality of frequencies. Bands are discriminated, the test section is divided into n equal parts to set a temporary sound source position, and a waveform having a high signal correlation coefficient for each band detected by both sensors at the temporary sound source position is added to obtain a composite waveform. At the same time, this process is performed over the entire section while updating the temporary sound source position, and the presence or absence of leakage is determined from the composite waveform at each temporary sound source position, or the fluid is flowing inside. A method for detecting leaks in a pipe, wherein sounds in a leak inspection section are simultaneously detected at different positions, each detection signal is discriminated into a plurality of frequency bands, and a temporary set at an arbitrary point between the searches. A process was performed to determine the presence or absence of leakage by obtaining a composite waveform of the band signal discriminated by correlation at the source position, and to perform this process over the entire inspection interval while changing the temporary sound source position. The effect of being able to detect leaks regularly and accurately at any time without the need for workers to move to detect the location and without the need for ancillary operations such as shutting off the pipe flow path. can get.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a water leakage detection method according to the present invention.

FIG. 2 is an explanatory diagram of a correlation classification filter.

FIG. 3 is a specific configuration diagram of the filter.

FIG. 4 is an output graph of a correlation coefficient with respect to a delay time for each frequency band.

FIG. 5 is an output diagram of a water leakage inspection result of the water leakage inspection system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Water distribution pipe 12 (12A, 12B) Underwater microphone 14 Correlation classification type filter 16 Waveform synthesis means 18 (18A, 18B) Frequency analysis circuit 20 Correlation calculation circuit 22 Operation circuit 24 Delay time setting circuit

Claims (5)

[Claims] 1. A method for detecting leakage of a pipe in which a fluid is flowing inside, wherein sensors are arranged at both ends of an inspection section, and a detection signal taken by each sensor passes through a band-pass filter. Then, the test section is divided into n equal parts to set a temporary sound source position, and a waveform having a high signal correlation coefficient for each band detected by both sensors at the temporary sound source position is added. A method for detecting a leak in a pipe, wherein the process is performed over the entire section while updating the temporary sound source position, and the presence or absence of leakage is determined from the synthetic waveform at each temporary sound source position. 2. A method for detecting leakage of a pipe in a state in which a fluid is flowing inside, wherein sounds in a leakage inspection section are simultaneously detected at different positions, and each detection signal is discriminated into a plurality of frequency bands. At the same time, a process of obtaining a composite waveform of the band signal discriminated by the correlation at the temporary sound source position set at an arbitrary position during the search to determine whether or not there is leakage is performed, and performing this process to change the temporary sound source position. A pipe leakage inspection method characterized in that the inspection is performed over the entire inspection section. 3. The water supply pipe or water distribution pipe of a water supply network, wherein the underwater microphone attached to the water supply pipe or water distribution pipe of the water supply network detects water leakage in an inspection section. 3. The method for detecting leakage of piping according to 1 or 2. 4. The pipe leakage inspection method according to claim 1, wherein the pipe is a gas pipe, and a gas leak in an inspection section is detected by a sensor attached to the gas pipe. 5. The pipe according to claim 1, wherein the pipe is a pipe of a plant, and a leak of the fluid in the inspection section is detected from a sensor attached to the pipe of the plant. Inspection methods.