JP2017187337A - Water leakage investigation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water leakage investigation method capable of easily specifying a water leakage position according to an object of the present invention.SOLUTION: An water leakage investigation method for a duct using a plurality of vibration sensors 200 includes: a first measuring process of measuring vibrations of a pipe network 110 by the plurality of vibration sensors 200 respectively; a waveform storing process of storing vibration waveforms measured in the first measuring process; a water leakage occurrence determination process of reading the vibration waveforms stored in the waveform storing process, and determining whether water leakage is occurring from a cross correlation function of vibration waveforms of adjacent vibration sensors 200; a time synchronizing process of achieving time synchronization among vibration sensors where water leakage is determined in the water leakage determination process; a second measuring process of measuring vibration waveforms in a certain period after the time synchronization in the time synchronizing process; and a generation source specifying process of specifying a water leakage place from the cross correlation function of the vibration waveforms measured in the second measuring process.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for investigating leaks in pipelines.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2013-210347) discloses a leak detection method for a pipe in which fluid is flowing inside, in which installation of a sensor is simple, detection accuracy is high, and reliability is high. , A leak detection method, a leak detection device, and a leak detection device are disclosed.

  The leak detection method for a pipe in which a fluid flows inside Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-210347) has two acoustic sensors placed at a certain distance from each other and at a certain distance from the pipe location. The acoustic data acquisition process in which the acoustic sensors acquire acoustic data, and the acoustic sensors constituting the pair of acoustic sensors are time-synchronized. A time difference calculating step for obtaining a difference in arrival time of sound, a distance difference calculating step for calculating a difference in distance between the sound source of sound and each acoustic sensor from the difference in arrival time, and a point in which the difference in distance from each acoustic sensor is constant. It includes a hyperbola acquisition step for obtaining a hyperbola with the position of each acoustic sensor as a focus, which is a set, and a position specification step for specifying a leakage position from the intersection of the pipe and the hyperbola.

JP 2013-210347A

As in Cited Document 1, there is a method of specifying a water leak location from the cross-correlation function of vibration waveforms at a plurality of locations. However, since it is necessary to synchronize the time for all vibration sensors, the amount of wireless communication at the same time becomes enormous when measuring vibrations, and a large-scale wireless network is required when conducting a wide area water leakage investigation. There's a problem.
In addition, there is a method for acquiring sound pressure data by a vibration sensor and determining the presence or absence of water leakage from the sound pressure threshold, but since there is a uniform evaluation of vibrations with various sources, there is a problem that the determination accuracy is not sufficient. is there.

  A main object of the present invention is to provide a water leakage investigation method that can easily specify a water leakage position.

(1)
The water leakage investigation method according to one aspect is a water leakage investigation method for a pipeline using a plurality of vibration sensors, in a first measurement process for measuring vibrations of the pipeline in each of the plurality of vibration sensors, and in the first measurement process A waveform storage step for storing the measured vibration waveform, a vibration waveform stored in the waveform storage step, a leakage presence / absence determination step for determining the presence / absence of leakage from the cross-correlation function of the vibration waveforms in adjacent vibration sensors, In the time synchronization step of synchronizing the time with the vibration sensor determined to have water leakage in the determination step, the second measurement step of measuring the vibration waveform for a certain period after time synchronization in the time synchronization step, and the second measurement step A generation source specifying step of specifying a water leak location from the cross-correlation function of the measured vibration waveform.

In this case, only the presence or absence of water leakage is determined using the first measurement step, the waveform storage step, and the water leakage presence / absence determination step. Thereafter, only when it is determined that there is a water leak, the location of the water leak can be specified using the time synchronization process, the second measurement process, and the generation source specifying process. As a result, since the presence or absence of water leakage is determined in the previous stage, it is not necessary to perform the time synchronization process at all locations. As a result, it is possible to easily specify the water leakage position.
Further, by performing time synchronization only on the vibration sensor determined to have water leakage, it is possible to reliably identify the water leakage location. Furthermore, it is not necessary to synchronize the time for all the vibration sensors, and the processing process of the water leakage investigation can be simplified. Further, unnecessary time synchronization processes can be reduced for a plurality of vibration sensors.

  In addition, it is not necessary to communicate with a large number of vibration sensors at a time, and it is not necessary to make a minute error in time synchronization depending on the communication path, or to take measures not to wrap the frequency band in order to prevent crosstalk.

  In addition, when calculating the time difference from the cross-correlation function of the vibration waveform and specifying the location of the water leak, pipe information such as the pipe length or pipe type between the sensors and the diameter is required. Therefore, it is not necessary to link the pipeline information and the cross-correlation function, and processing can be performed with a minimum amount of calculation.

  In addition, when installing a vibration sensor on a gate valve or a fire hydrant attached to a water pipe, it is necessary to close the iron cover of the handhole to prevent traffic obstruction, and because the distance for wireless communication is short, many Although there is a problem that a repeater is required, since it is only necessary to deal with the specified vibration sensor, cost reduction can be realized. In addition, even when time synchronization means such as GPS or a radio timepiece is adopted, it is necessary to install it outside the iron lid, so that the equipment cost can be minimized.

(2)
The water leakage investigation method according to the second invention is the water leakage investigation method according to one aspect, wherein in the water leakage presence / absence determination step, the presence / absence of water leakage is determined from the peak height of the vibration waveform measured in the first measurement step. In the specific process, the time difference may be calculated from the peak position of the vibration waveform measured in the second measurement process.

In this case, by using the peak height in the water leakage presence / absence determination step and the peak position in the generation source identification step, it is possible to conduct a survey to identify the water leakage location by a simple and reliable method.
That is, since the presence or absence of water leakage is determined based on the peak height, the presence or absence of water leakage can be easily determined. Then, since it is only necessary to specify the water leakage position by the generation source specifying step only when it is determined that there is water leakage by the water leakage presence / absence determination, simplification of the process can be realized.

(3)
The water leakage investigation method according to the third invention is the water leakage investigation method according to one aspect or the second invention, wherein the cross-correlation function used in the water leakage presence / absence determination step is a waveform of a plurality of sections of the vibration measured in the first step. The plurality of waveforms may overlap with a part of an adjacent section.

In this case, the accuracy of the cross-correlation function is improved by overlapping with a part of the adjacent section.
For example, a power supply is required for vibration measurement. When the power source is covered by a battery, the longer the waveform recording time, the more battery consumption. By overlapping a part of adjacent sections, it is possible to minimize the waveform length necessary for the calculation and to calculate many cross-correlation functions. By calculating a large number of cross-correlation functions, the accuracy of determining whether there is a water leak is improved, and it is possible to conduct a survey to identify a water leak location by a simple and reliable method.

(4)
According to a fourth aspect of the present invention, in the water leakage investigation method according to the second or third aspect, the plurality of vibration sensors include a recording unit, and the recording unit includes the measured vibration and Time may be recorded.

  In this case, since the vibration and time are recorded in the recording unit, the cross-correlation function can be obtained from the vibration data in accordance with the time recorded in the recording unit later. Therefore, the time synchronization process can be performed separately.

It is a schematic diagram for demonstrating the condition of the water leak location specifying method. It is a schematic diagram which shows an example of the water leak position detection apparatus containing a vibration sensor. It is a flowchart which shows an example of the identification method of the abnormal sound generation position concerning this Embodiment. It is a flowchart which shows an example of the identification method of the abnormal sound generation position concerning this Embodiment. It is a schematic diagram explaining the setting of waveform length. It is a schematic diagram which shows an example of the extraction method of waveform length. It is the schematic diagram which showed the overlap of waveform length. It is a schematic diagram which shows an example of a histogram with water leakage. It is a schematic diagram which shows an example of the histogram without water leakage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<Situation explanation of water leak location method>
FIG. 1 is a schematic diagram for explaining the situation of the water leakage position specifying method.

  As shown in FIG. 1, a pipe network 110 is provided in the ground. The pipe network 110 is provided with vertical holes (manholes) 120 at regular intervals. In the present embodiment, vertical holes 120 are provided at intervals between point A and point B. In this case, vibration sensors 200 are provided in the vertical holes 120 at point A and point B in FIG.

<Description of vibration sensor>
FIG. 2 is a schematic diagram illustrating an example of a water leakage position detection device including a vibration sensor.

As shown in FIG. 2, the abnormal sound generation specifying device 100 according to the present embodiment includes an arithmetic device 300 and at least a pair of vibration sensors 200. The pair of vibration sensors 200 is a resonance type vibration sensor 200.
The vibration sensor 200 of FIG. 2 includes a pedestal 210, support columns 220, thin film electrodes 230 and 240, lead wires 231 and 241, a piezoelectric element 250, a weight 260, a recording device 261, and an internal clock 262.
The arithmetic device 300 includes a generation unit 310 that generates a filter, and an arithmetic unit 320.

  As shown in FIG. 2, in the vibration sensor 200, a support 220 is fixed on an iron base 210. A piezoelectric element 250 is provided at the upper end of the support 220. One end of the piezoelectric element 250 is cantilevered by the upper end of the column 220.

A pair of upper and lower thin film electrodes 230 and 240 formed by applying silver paste on both surfaces of the piezoelectric element 250 are provided. The column 220 and the pair of thin film electrodes 230 and 240 are insulated.
A weight 260 is placed on the other end of the piezoelectric element 250 and on the thin film electrode 230.

A lead wire 231 is connected to the thin film electrode 230, a lead wire 241 is connected to the thin film electrode 240, and the lead wires 231 and 241 are connected to the arithmetic unit 300.
The potential difference output from the lead wires 231 and 241 is output as a vibration waveform by a processing device such as an arithmetic device.
In this embodiment, the lead wires 231 and 241 are used. However, the present invention is not limited to this, and a functional unit capable of transmitting and receiving with the arithmetic device 300 may be provided.

  The piezoelectric element 250 is formed of a stretched film (PVDF film) of polyvinylidene fluoride which is a polymer piezoelectric material.

  When the specific parameters are the elasticity E of the piezoelectric material, the secondary moment J of the cross section, the length L, the width b, and the height h, the spring constant k is expressed as follows.

^{k = 3EJ / L 3 (J} = bh 3/12) ··· (1)
Can be shown.

  The resonance frequency fo of the system composed of the piezoelectric element 250 and the weight 260 is expressed as follows.

  fo = √ (k / M) / 2π (2)

The resonance type vibration sensor 200 is formed so that at least one resonance frequency fo exists within a range of 60 Hz or more and less than 1000 Hz.
The resonance type vibration sensor 200 according to the present embodiment is formed so that there are four resonance frequencies fo between 100 Hz and 500 Hz. The reason for this is that abnormal sounds transmitted through the pipe network 110, particularly water leakage sounds, are often audible sounds, especially those below 1000 Hz.

  In this embodiment, the resonance type vibration sensor 200 is used. However, the present invention is not limited to this, and a conventional vibration sensor may be used.

  Further, the vibration sensor 200 according to the present embodiment records the vibration waveform in the recording device 261 while counting the time with the internal clock 262.

<Leakage location identification method>
Hereinafter, a specific example of the method for specifying the abnormal sound occurrence position according to the present embodiment will be described. 3 and 4 are flowcharts showing an example of a method for specifying an abnormal sound occurrence position according to the present embodiment, FIG. 5 is a schematic diagram for explaining setting of the waveform length, and FIG. 6 is a waveform length. FIG. 7 is a schematic diagram for explaining an overlap of waveform lengths, FIG. 8 shows an example of a histogram with water leakage, and FIG. 9 shows no water leakage. It is a schematic diagram which shows an example of this histogram.

  First, as shown in FIG. 3, setting is made so that recording can be performed for 100 seconds in the recording device 261 of the vibration sensor 200 (step S11). Next, the plurality of vibration sensors 200 are installed in a gate valve or a fire hydrant in a vertical hole (manhole) 120 (step S12). Next, the vibration sensor 200 is collected, the lead wires 231 and 241 are attached, and vibration data is taken into the arithmetic device 300 (step S13).

  In the present embodiment, the vibration waveform is recorded in the recording device 261 of the vibration sensor 200 for 100 seconds. However, the present invention is not limited to this, and another predetermined time may be used. That is, when the transmission speed of the vibration of the synthetic resin pipe is 300 m / second and the distance between the vibration sensors 200 (the distance between the points A and B in FIG. 1) is 300 m at maximum, the cross-correlation function is calculated from the waveform for one second. Thus, it becomes possible to search for a common vibration source.

  Next, the arithmetic unit 300 sets the waveform length (step S14). Specifically, as illustrated in FIG. 5, the arithmetic device 300 sets the waveform length in consideration of the deviation of the internal clock 262. In the present embodiment, it is assumed that the time lag between adjacent vibration sensors 200 is a maximum of ± 1 second.

Here, the time lag in the present embodiment depends on the accuracy of the internal clock 262. For example, a crystal oscillator is used as the internal clock. Since the crystal oscillator may cause a time lag due to temperature change, it is preferable to perform correction by a temperature compensation circuit. The maximum time lag can be assumed from the timing of matching the clock time and the time until the actual waveform is measured.
In this embodiment, measurement is performed 24 hours after the timing of setting the time of the internal clock, and in consideration of the accuracy of the internal clock, the time deviation after 24 hours is a maximum of ± 1 second. Assuming a gap width. If the measurement timing is 48 hours later, it is preferable to assume ± 2 seconds as a time lag.

Next, the arithmetic unit 300 extracts the waveform length considering the shift of the internal clock without taking time synchronization (step S15). Specifically, as shown in FIG. 6, assuming that the time lag between adjacent vibration sensors 200 is ± 1 second at the maximum, the waveform length is 3 seconds. When the vibration transmission speed of the resin pipe is 300 m / second and the sensor installation interval is 300 m at maximum, the time for vibration to be transmitted between the sensors is 1 second at maximum. A time lag of ± 1 second is added to this 1 second to make 3 seconds. Further, if the measurement timing is 48 hours later, ± 2 seconds may be added to obtain 5 seconds.
As shown in FIG. 6, the waveform length of 3 seconds is extracted so that 2 seconds overlap. In this case, 98 waveform lengths can be extracted from the vibration waveform of 100 seconds.

  Next, the cross-correlation function is created to the maximum from the extracted waveform length (step S16). Here, FIG. 7 is a schematic diagram showing an overlap of waveform lengths.

As shown in FIG. 7, the relationship between the vibration sensor A and the vibration sensor B at a specific time is shown for each extracted waveform.
In FIG. 7, with respect to the extracted waveform 1, the vibration sensor A is advanced by 1 second and the vibration sensor B is delayed by 1 second. Here, the extracted waveforms of the vibration sensor A and the vibration sensor B do not completely coincide with each other because they are not synchronized with each other. However, since they have a width of 1 second before and after, the extraction of the vibration sensor A is performed. The waveform and the extracted waveform of the vibration sensor B have a time coincidence point.
Therefore, when the cross correlation function is calculated, a value is taken at a specific time difference. In addition, this situation is the same when the transition to the extracted waveform 2 is performed, and the cross-correlation function is calculated in a specific width. In this way, up to 98th cross-correlation function can be created for the extracted waveform.

Subsequently, the arithmetic unit 300 integrates the peak values of the created cross correlation function (step S17), and determines whether or not the integration result is greater than or equal to a predetermined value (step S18).
Here, in the present embodiment, the peak value may be only the maximum peak value or may be integrated from the largest peak value to the third largest peak value.

Here, FIG. 8 is a schematic diagram illustrating an example of a histogram with water leakage, and FIG. 9 is a schematic diagram illustrating an example of a histogram without water leakage.
8 and 9, the horizontal axis indicates the time difference, and the vertical axis indicates the frequency.

As shown in FIG. 8, when there is a water leak, a peak value with a high frequency appears when the largest peak value to the third largest peak value are integrated.
As mentioned above, this is because accurate time synchronization is not achieved in the relationship between the vibration sensor A and the vibration sensor B, but the cross-correlation function is calculated with a width that takes into account the time deviation. In this work, it is impossible to accurately measure the location of the water leakage location as an absolute value, but since the calculation is performed with a specific width, the peak height is increased by repeating the calculation of the cross-correlation function with a specific time difference. The reliability is high. Therefore, the presence or absence of water leakage itself can be detected by accumulating this and confirming the frequency (peak height).
On the other hand, as shown in FIG. 9, when there is no water leakage, a peak value with high frequency does not appear.
Thus, when the integration result is equal to or greater than the predetermined value (Yes in step S18), it is determined that there is water leakage (step S19). Moreover, when an integration result is less than predetermined (No of step S18), it determines with no water leak (step S20).
In addition, you may determine suitably the threshold value regarding determination of the presence or absence of water leakage according to the frequency | count of integration. In the present embodiment, it is determined that there is water leakage if the peak value of the frequency is 7 times or more. By calculating in this way, it is possible to appropriately determine the presence or absence of water leakage by counting the peak frequency without obtaining accurate time synchronization.

Next, as illustrated in FIG. 4, the arithmetic device 300 performs time synchronization processing on the vibration sensors 200 determined to have water leakage, and measures a waveform for a total of 50 seconds after the processing (step S <b> 21).
The arithmetic device 300 divides the waveform for 50 seconds every second (step S22). Subsequently, the arithmetic device 300 calculates a cross-correlation function from the divided waveforms (step S23), and integrates the calculated cross-correlation function (step S24).
Next, a peak position is specified from the cross-correlation function, and a time difference is calculated from the peak position (step S25).
Finally, the water leakage position is calculated from the relationship between the propagation speed of vibration based on the tube type and the time difference (step S26).

  As described above, by performing time synchronization only on the vibration sensor 200 that is determined to have water leakage, it is possible to reliably identify the water leakage location. That is, it is not necessary to perform time synchronization for all the vibration sensors 200, and the processing process of the water leakage investigation can be simplified. Further, unnecessary time synchronization processes can be reduced for the plurality of vibration sensors 200.

  Since the presence or absence of water leakage is determined based on the peak height, the presence or absence of water leakage can be easily determined. Then, since it is only necessary to specify the water leakage position by the generation source specifying step only when it is determined that there is water leakage by the water leakage presence / absence determination, simplification of the process can be realized.

  In the present invention, the pipe network 110 corresponds to a “pipe line”, the vibration sensor 200 corresponds to a “vibration sensor”, and the process from step S11 to step S26 corresponds to a “pipe leakage inspection method”. The process of step S13 corresponds to a “first measurement process, waveform storage process”, the process of step S18 corresponds to a “water leakage presence / absence determination process”, and the process of step S21 is “a time synchronization process for synchronizing time, This corresponds to the “second measurement process”, the process in step S26 corresponds to the “generation source specifying process”, and the recording device 261 corresponds to the “recording unit”.

  A preferred embodiment of the present invention is as described above, but the present invention is not limited thereto. It will be understood that various other embodiments may be made without departing from the spirit and scope of the invention. Furthermore, in this embodiment, although the effect | action and effect by the structure of this invention are described, these effect | actions and effects are examples and do not limit this invention.

110 Pipe network 200 Vibration sensor 261 Recording device 262 Internal clock

Claims (4)

In the method of investigating leaks in pipelines using multiple vibration sensors,
A first measurement step of measuring vibration of a pipeline in each of the plurality of vibration sensors;
A waveform storage step for storing the vibration waveform measured in the first measurement step;
The vibration waveform stored in the waveform storage step is read out, and the water leakage presence / absence determination step of determining the presence / absence of water leakage from the cross-correlation function of the vibration waveform in the adjacent vibration sensor;
A time synchronization step of synchronizing time with a vibration sensor determined to have water leakage in the water leakage presence determination step;
A second measurement step of measuring a vibration waveform for a predetermined period after time synchronization is taken in the time synchronization step;
A water leakage investigation method, comprising: a generation source identification step of identifying a water leakage location from the cross-correlation function of the vibration waveform measured in the second measurement step. In the water leakage presence / absence determination step, the presence / absence of water leakage is determined from the peak height of the vibration waveform measured in the first measurement step,
The water leakage investigation method according to claim 1, wherein, in the generation source specifying step, a time difference is calculated from a peak position of the vibration waveform measured in the second measurement step.   The cross-correlation function used in the water leakage presence / absence determination step is calculated based on the waveforms of a plurality of sections of the vibration measured in the first step, and the plurality of waveforms overlaps with a part of an adjacent section. The water leakage investigation method according to claim 1 or 2. The plurality of vibration sensors have a recording unit,
The water leakage investigation method according to claim 1, wherein the recording unit records the measured vibration and time.

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