JP2014219342A - Leakage detection method and device of buried duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage detection method and device of a buried duct capable of appropriately identifying a leakage sound by separating the leakage sound and a noise even when a continuous sound acting as a noise to the leakage sound occurs.SOLUTION: A leakage detection device 1 of a buried duct includes: a first vibration sensor 5 for detecting a vibration sound generated by fluid leakage from a water service duct (buried duct) 2; and a second vibration sensor 6 for detecting waveform information for subtracting a noise component from waveform information of the first vibration sensor 5. The first vibration sensor 5 is disposed in an exposed section on a piping member 4 of the water service duct 2. The second vibration sensor 6 is disposed in a place (e.g. ground surface G) that is near the first vibration sensor 5 and does not come into contact with the piping member of the water service duct 2.

Description

  The present invention relates to a buried pipe leakage detection method and apparatus, and more particularly to a buried pipe leakage detection method and apparatus for accurately detecting fluid leakage from a pipe in a water pipe buried underground.

  Conventionally, there is a technique for detecting a vibration sound (leakage sound) generated by fluid leakage by installing a vibration sensor in an exposed portion of an embedded pipeline. For example, in Patent Document 1, a sound pressure detector with a built-in acceleration sensor is installed in a buried pipeline, sound pressure data is collected over a predetermined measurement time, and is counted for each dB, thereby providing a place with high noise. However, it is said that it can detect leaked sound.

Japanese Patent No. 2887443

  However, in the method of summing up sound pressure data as in the above-mentioned Patent Document 1, there is a case where erroneous determination is made when noise with the same sound pressure is always generated. For example, it may be a transformer sound generated from a vending machine, or when there is continuous traffic on a main trunk road.

  In particular, leaking sound generated in synthetic resin pipes and large-diameter metal pipes where vibration attenuation is large and leakage detection is difficult is a low frequency band of 300 Hz or less, and such a low frequency band is generated as the above noise. Since it is close to the frequency of the sound, there was a problem that it was difficult to separate the leaked sound from the noise.

  The object of the present invention is to leak a buried pipeline that can properly identify the leaked sound by separating the leaked sound from the noise even when a continuous sound that becomes noise is generated with respect to the leaked sound. It is to provide a detection method and apparatus.

  According to the present invention, there is provided a leak detection method for a buried pipe, a first vibration sensor for detecting vibration sound generated by fluid leakage from the buried pipe, and waveform information for subtracting noise from the waveform information of the first vibration sensor. The first vibration sensor is installed on the exposed portion of the piping member of the buried pipeline, and the second vibration sensor is in the vicinity of the first vibration sensor and in contact with the piping member of the buried pipeline. It is characterized by being installed in a place that does not.

  According to the present invention, there is provided a leak detection device for a buried pipe, which detects a vibration sound generated by fluid leakage from the buried pipe and detects waveform information for subtracting noise from the waveform information of the first vibration sensor. The first vibration sensor is installed at an exposed portion of the piping member of the buried pipeline, and the second vibration sensor is in the vicinity of the first vibration sensor and the piping member of the buried pipeline. It is installed in a place not touching

  The piping member includes a pipe, a joint, a gate valve and the like. The first vibration sensor is installed at an appropriate exposed portion (a wall surface of a pipe, a joint, a gate valve, or the like) of the piping member so as to be able to detect a leakage sound that is transmitted through the buried pipeline along with the leakage.

  The vibration detected by the first vibration sensor installed on piping members such as pipe walls and gate valves includes leakage and noise, and the vibration generated outside the buried pipeline that is noise is The vibration is captured by the second vibration sensor and canceled as noise from the vibration detected by the first vibration sensor.

  It is preferable to install the second vibration sensor on the ground surface (especially on asphalt ground), and this makes it easy to capture noise.

  Frequency analysis is performed on the waveforms obtained from the first vibration sensor and the second vibration sensor, and the presence or absence of leakage is detected based on information obtained by subtracting the frequency spectrum information of the second vibration sensor from the frequency spectrum information of the first vibration sensor. Is preferred.

  In order to detect the presence or absence of leakage by subtracting the waveform information of the first vibration sensor and the second vibration sensor, it is preferable to analyze the frequency of the waveform for a certain period of time and subtract the spectral intensity of each frequency. By this calculation, when there is leakage, a peak exists at a predetermined frequency, and it is possible to easily determine whether there is leakage.

  According to the leakage detection method and apparatus for buried pipes of the present invention, even when a continuous sound that becomes noise is generated with respect to the leakage sound, the leakage sound and the noise can be separated, and the leakage sound can be appropriately selected. Identification is possible.

FIG. 1 is a diagram schematically showing a buried pipe leakage detection method and apparatus according to the present invention. FIG. 2 is a diagram schematically showing an example of a vibration sensor suitable for the leakage detection method and apparatus for buried pipes according to the present invention. FIG. 3 is a diagram illustrating an example of waveform information obtained by the second vibration sensor when there is leakage. FIG. 4 is a diagram illustrating an example of waveform information obtained by the second vibration sensor when there is no leakage. FIG. 5 is a diagram illustrating an example of waveform information obtained by the first vibration sensor when there is leakage. FIG. 6 is a diagram illustrating an example of waveform information obtained by subtracting the waveform information obtained by the second vibration sensor from the waveform information obtained by the first vibration sensor when there is leakage. FIG. 7 is a diagram illustrating an example of waveform information obtained by the first vibration sensor when there is no leakage. FIG. 8 is a diagram illustrating an example of waveform information obtained by subtracting the waveform information obtained by the second vibration sensor from the waveform information obtained by the first vibration sensor when there is no leakage.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 schematically shows a leak detection device for an embedded pipeline according to the present invention.

  Leakage detector (1) for buried pipelines is a water pipeline (one example of buried pipelines) constructed from piping members such as pipes (3) and gate valves (4) (2) The first vibration sensor (5) installed at a predetermined location (in this embodiment, the gate valve (4)) of the piping member of the buried pipe (2) and the ground (G ) Installed in the second vibration sensor (6), wireless communication device (7) (8) connected to each vibration sensor (5) (6), and each wireless communication device (7) (8) And processing means (9) for receiving and processing the sent information.

  As shown in FIG. 2, the first vibration sensor (5) and the second vibration sensor (6) are made of an iron base (21), a piezoelectric element (22) installed on the base (21), and a lower end portion. Is fixed to the pedestal (21) and supports the piezoelectric element (22) at its upper end, and a pair of upper and lower thin film electrodes (24) formed by applying silver paste on both sides of the piezoelectric element (22). ) (25) and a weight (26) loaded on the upper thin film electrode (24). The column (23) is insulated from the upper and lower thin film electrodes (24) (25), and lead wires (27) (28) are attached to the thin film electrodes (24) (25). .

  The pair of electrodes (24), (25) is formed in a thin film by applying silver paste on both surfaces of the piezoelectric element (22).

  The piezoelectric element (22) is formed of a stretched film (PVDF film) of polyvinylidene fluoride which is a polymer piezoelectric material. The resonance frequency fo = √ (k / M) / 2π (k is the spring constant of the piezoelectric element and M is the mass of the weight) of the system composed of the piezoelectric element (22) and the weight (26) is set to 10 Hz to 1000 Hz. Yes.

  When water leaks in the water pipe (2), the pipe member such as the pipe (3) and the gate valve (4) generates a leaking sound that is a vibration sound caused by fluid leakage. As a result, the pressure applied to the piezoelectric element (22) of the first vibration sensor (5) attached to the gate valve (4) fluctuates, and the pressure fluctuation is converted into a potential difference signal in the piezoelectric element (22). The The potential difference signal is taken out by the lead wires (27) and (28), processed by the processing means (9), and when leakage sound is detected, it is determined that there is leakage.

  Here, in the information from the first vibration sensor (5), vibration sounds other than leakage sound are included as noise. In this buried pipe leakage detection device (1), the processing means (9) uses the waveform information obtained by the first vibration sensor (5) and the second vibration sensor (6) as follows. Thus, by analyzing the frequency of the waveform for a certain time and removing the noise by the second vibration sensor (6), the accuracy of the determination of leakage is improved.

  Noise mixed in the detection signal of the first vibration sensor (5) follows the following two paths.

1. Noise such as vending machine and car traffic sound propagates through the ground and is input to the nearby pipe (3), and is transmitted to the first vibration sensor (5) through the pipe (3).

2. Noise from vending machines and car traffic propagates on the ground surface (eg asphalt) (G), and travels through the box (4a) of the gate valve (4) and the fire hydrant box to the first vibration sensor (5). It is transmitted.

  In addition, noise generated from the same source is route 1. And 2. In either case, the frequency matches.

  1. As described above, the vibration detected through the tube (3) and detected by the first vibration sensor (5) includes leakage sound that should be detected. On the other hand, since the leakage sound generated in the buried state attenuates in the ground, 2. In such a manner, it does not propagate through the ground surface (G) or the box (4a) and is input again to the first vibration sensor (5).

  Therefore, if the vibration of the ground surface (G) or box (4a) is captured by the second vibration sensor (6) and subtracted as noise from the signal of the first vibration sensor (5), only the leaked sound can be separated. it can.

  Hereinafter, an example in which the ground surface (G) is asphalt in the detection of water leakage from the vinyl chloride pipe (3) in the water pipe (2) will be described.

  First, using the second vibration sensor (6), there is a leak through the water pipe (2), and on the asphalt surface (G) away from the leak location in the state where there is no water flow. The waveform was measured and the waveform was fast Fourier transformed. The frequency spectrum at that time is shown in FIG. 3 and FIG. FIG. 3 shows a case with leakage, and FIG. 4 shows a case without leakage.

  3 and 4, both have relatively low-frequency waveforms, and this low-frequency peak appears even when there is no leakage, so that it can be seen that it originates from noise other than the leakage sound.

  Next, when there is a leak using the first vibration sensor (5), the first vibration sensor (5) is placed on the gate valve (4) which is about the same distance as the second vibration sensor (6) from the leak point. The vibration waveform was recorded. The frequency spectrum at that time is shown in FIG. This is often the same frequency band as the waveform derived from the previous noise, and leakage cannot be determined only by FIG.

  Here, when the frequency spectrum (FIG. 3) in the case of leakage of the second vibration sensor (6) is subtracted from FIG. 5, the result is as shown in FIG. Even if the frequency spectrum derived from noise is subtracted, a low-frequency peak still occurs, so that it can be determined that leaking sound is generated.

  FIG. 7 shows a frequency spectrum obtained by the first vibration sensor (5) when there is no leakage. When the frequency spectrum (FIG. 2) of the second vibration sensor (6) when there is no leakage is subtracted from the frequency spectrum of FIG. 7, the peak disappears as shown in FIG. From this, it can be determined that the peak in FIG. 7 is noise and is not actually leaking.

  In this way, by subtracting the spectrum intensity of each frequency of the second vibration sensor (6) from the spectrum intensity of each frequency of the first vibration sensor (5), it is possible to separate the leaked sound from the noise. Identification is possible.

  When subtracting the spectrum intensity of each frequency, all frequencies may be subtracted uniformly, or may be subtracted after applying a predetermined coefficient.

(1): Leakage detection device for buried pipelines
(2): Water pipe (buried pipe)
(5): First vibration sensor
(6): First vibration sensor
(9): Processing means

Claims (6)

  Using a first vibration sensor that detects vibration sound generated by fluid leakage from the buried pipe and a second vibration sensor that detects waveform information for subtracting noise from the waveform information of the first vibration sensor, the first vibration is used. A buried pipe characterized in that the sensor is installed at an exposed portion of the piping member of the buried pipeline, and the second vibration sensor is installed in the vicinity of the first vibration sensor and not in contact with the piping member of the buried pipeline. Road leak detection method.   The leak detection method for an embedded pipeline according to claim 1, wherein the second vibration sensor is installed on the ground surface.   Frequency analysis is performed on the waveforms obtained from the first vibration sensor and the second vibration sensor, and the presence or absence of leakage is detected based on information obtained by subtracting the frequency spectrum information of the second vibration sensor from the frequency spectrum information of the first vibration sensor. The leakage detection method for an embedded conduit according to claim 1 or 2.   A first vibration sensor that detects vibration sound generated by fluid leakage from the buried pipeline, and a second vibration sensor that detects waveform information for subtracting noise from the waveform information of the first vibration sensor; 1 vibration sensor is installed in the exposed part of the piping member of the buried pipeline, and the second vibration sensor is installed in the vicinity of the first vibration sensor and not in contact with the piping member of the buried pipeline. Leakage detection device for buried pipes.   The leak detection device for an embedded pipeline according to claim 4, wherein the second vibration sensor is installed on the ground surface.   Processing for analyzing the frequency of waveforms obtained from the first vibration sensor and the second vibration sensor and detecting the presence or absence of leakage based on information obtained by subtracting the frequency spectrum information of the second vibration sensor from the frequency spectrum information of the first vibration sensor 6. The buried pipe leakage detection apparatus according to claim 4, further comprising means.

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