JPS59150320A - Water leak detecting apparatus - Google Patents

Abstract

PURPOSE:To perform the detection of leaked water without using pipeline data such as pipe material quality or a pipe length, in the water leak detecting apparatus of a water pipe, by fixedly attaching a sensor to the water supply pipe of a demand end so as to immerse the same in water while providing two criterions (the frequency component intrinsic to water leak and the level difference of noise and a signal). CONSTITUTION:A water leak detecting apparatus is constituted of a pressure- electricity converter 1 for detecting the variation of water pressure and a water leak sound discriminating part 2 for discriminating a water leak sound by receiving the output from the pressure-electricity converter 1 while the water leak sound discriminating part 2 is constituted of an amplifier 10, a high band pass filter 1, a low band pass filter 12 and a comparator 13. A water leak sound is propagated through a pipeline as a minute water pressure variation wave and converted to an electric signal by the pressure-electricity converter 1 while the signal amplified through the amplifier 10 passes through the high band pass filter 11 and the low band pass filter 12 to obtain a signal with a frequency band intrinsic to the water leak sound and only a signal with judge reference voltage egamma is outputted through the comparator 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a water leak detection device for detecting water leaks in water pipes.

[Technical background of the invention and its problems]

The amount of water leaking from water distribution pipes and water supply pipes on the way from water treatment plants or distribution reservoirs to customers is 10% of the total water distribution amount.
The development of countless new water sources requires a huge amount of money, and currently, there is an urgent need to control the amount of water leakage. Therefore, it is necessary to promptly know when a water leak has occurred. However, since most of the leakage occurs underground, it is extremely difficult to detect it from above ground.

As is well known, a typical method for detecting underground water leakage that has been put to practical use is a method using audio and listening techniques. In this method, a listening stick is applied to the area where the pipe is buried. Alternatively, it can be brought into direct contact with the buried conduit through the polled hole. Alternatively, the vibration sound transmitted from the listening rod can be mechanically or electrically amplified by touching it to a part of a fire hydrant, water meter, etc. that is exposed above the ground. The presence or absence of water leakage can be determined by listening to the sound.

However, this method requires skill in distinguishing between water leakage sounds and other noises.

In addition, it takes a huge amount of labor and time for inspectors with this technology to patrol the entire city area, resulting in problems such as slow progress in discovering water leaks.

On the other hand, recently, automation of water leak detection has been promoted.
There is a correlative water leak detection device that has started trial use. This is 2
The system attempts to determine the location of water leaks by cross-correlating signals from vibration sensors attached to fire hydrants. However, this has the following drawbacks. That is, firstly, the branching of the pipeline in the survey section;
Accurate knowledge of pipe material and pipe length data.

Second, if there are any branch pipes along the way, the branch pipes must be investigated separately. Thirdly, although no expert skills are required, early detection of water leaks is limited because it requires patrolling the city.

etc.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and does not require a patrol inspection because it is fixedly installed at each demand end, and does not require pipe line specifications such as pipe material and length. The purpose of the present invention is to provide a water leakage detection device that is free from water leakage.

[Summary of the invention]

In general, about 90 cases of water leakage occur in water supply pipes leading to customers, including points where water pipes branch off. The present invention does not accurately determine the location of water leaks. However, early repair is the key to leak prevention work, so by early detection of water leaks at each demand end, it is possible to concentrate the concentration of inspectors, and there is no need for wasteful patrol surveys in areas where there are no P1 water leaks. Become. In the present invention, a method is adopted in which the sensor is installed underwater in a pipe where it is hardly affected by external noise. This is only possible by permanently installing the water leakage detection device.

Conventionally, automatic detection of water leak sounds has been considered difficult because the characteristics of water leak sounds vary depending on the state of pipe damage, soil conditions, pipe material, pipe length, and other factors. However, according to the research conducted by the present inventors, by limiting the installation of the water leakage detection device to the water supply pipe at the demand end as described above and installing the sensor underwater, it was found that It turned out that automatic detection is possible. Therefore, in the present invention, the water leakage sound is determined based on the following two conditions.

(a) Water leakage sound must have a unique frequency component.

((b) If the signal size is larger than a predetermined value in order to distinguish it from background noise in a situation where there is no water leakage, the signal is set to 0. [Embodiment of the Invention] Fig. 1 shows an embodiment of the present invention. , the present invention provides a pressure-electric converter 1 for detecting water pressure fluctuations in water pipes, and a pressure-electric converter 1 for detecting water pressure fluctuations in water pipes.
The water leakage sound discrimination section 2 includes an amplification 510. It is composed of a high-pass filter 11, a low-pass filter 12, and a comparator 13. In such a configuration, water leakage sound propagates in the pipe as a minute water pressure fluctuation wave, is converted into an AC electrical signal by the pressure-to-electrical converter 1tC, and the signal amplified via the amplifier 1O is a high-pass signal. The filter 11 and the low-pass filter 12 pass signals in a frequency band specific to water leakage sound, and only the signals having the determination reference voltage 04 or higher are outputted via the comparator 13.

Next, each component of the water leakage sound determination section 2 will be explained in detail.

Nozomi and Minoru Nisumi set the sound pressure signal level at the pressure receiving part of the pressure-to-electricity converter 1 to 5 dB (for example, 1 μPa pressure is OdB), and the pressure sensitivity of the pressure-to-electric converter 1 to KdB (for example, 1 μPaa!). Sensitive O that can obtain IMV voltage output
dB), and the gain of the amplifier 10 is AdB.

Moreover, a high-pass filter 11 and a low-pass filter 12
Assuming that the attenuation of the signal component at is negligible, the input signal level yEdB of the voltage comparator 5 is expressed by the following equation (1). The gain of the amplifier 10 is determined based on the design standard, which corresponds to (corresponding to ■) in terms of effective value.

If we adopt -22dB as a general value of K, then A22
20-8 ...... (2). Second
The figure shows the results of measuring the sound pressure signal level at the pressure receiving part twice for each leakage sound from two different systems of 20-diameter lead pipes buried 1 meter underground. 2137
5=1
If it is 20 dB, then F A = 100 dB can be obtained from equation (2).

","Filter 11゛Filter b Fig. 3(a) shows the sound of running water when the faucet is opened as a pressure-
Figures (b) and (c) show the power spectrum obtained by converting the signal into an electric signal using an electric converter and using a fast Fourier transform analyzer. It shows the power spectrum of water leakage sounds from two different systems of lead pipes (when the water leakage flow rate is 51/outside). From these data, it can be seen that the power spectrum of water leakage sound has a lower limit frequency of about 1 kHz, and an upper limit frequency of about IQkHz. Still, the power spectrum of the sound of running water from a faucet, which must be distinguished from the sound of water leakage, is mainly distributed below 1 cIkHz.

Therefore, in the present invention, a high-pass filter and a low-pass filter are connected in series in order to eliminate water, which is the largest among background noises. Of course, a bandpass filter having the same function can also be used. The lower limit cutoff frequency of the filter is approximately 1.5kHz, and the upper limit cutoff frequency is 10
Approximately kHz is good. The curve fH in FIG. 4 shows the characteristics of the high-pass filter 11, and the curve fL shows the characteristics of the low-pass filter 12, both of which have attenuation slope characteristics of 30 dB/.

A commercially available active filter can be used as a filter having such characteristics.

Next, a method for determining the determination reference voltage e of the comparator 13 will be explained. In the above equation (1), K=-220dBA
= 100 dB, B = S -120 (3) Furthermore, the relationship between the voltage waveform value eV and its level EdB is given by equation (4).

E = 20 Aog e/9 (4
) Therefore, (3), (According to equation 41, the relationship between pe and S is -120 e-like・1020 ...... (5). Figure 5 shows that according to equation (5), 100dB≦S≦120
It shows the voltage calculated for the dB range.

According to this, when a signal having a sound pressure level as high as 115 dB is determined to be a water leak sound, the determination reference voltage er of the comparator becomes 0,795 V.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to provide an effective water leakage detection device that does not require a patrol survey and does not require pipe specifications such as material and length.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a measurement diagram of water leakage sound from a lead pipe buried underground, and Fig. M3 (
a), (b), (c)? i: Buried underground i
Figure 4 is a measurement result diagram showing the power spectrum of water leakage sound from t'L fc ie f. Figure 4 is a characteristic diagram of the high frequency pass filter and low frequency pass filter used in the present invention.
The figure is an explanatory diagram of the criteria for determining water leakage sound using a voltage comparator. l...Pressure-electricity converter, 2...Water leakage sound discrimination unit, 1
0...Amplification visit 13...Comparator. Figure 2: Small amount of water leakage C17 min. LHr) - Figure 4; Takahisa □ ・Figure 5 1. Sound pressure V-vein S (dB) of Aido (dB-1 Procedural amendment (voluntary) Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, of the case Indication Patent Application No. 58-16110 2, name of the invention Water leak detection device 3, relationship with the amended case Patent applicant (307') Tokyo Shibaura Electric Co., Ltd. 4, agent Address: 100 Uchisaiwai-cho, Chiyoda-ku, Tokyo 1-1-6 Tokyo Shibaura Electric Co., Ltd. Tokyo Office Interior Drawing 6. Figure 5 of the revised drawings is corrected as shown in the attached sheet. Figure 5 Sound pressure level S (dn) of the pressure receiving part

Claims (1)

[Claims] A pressure-to-electrical converter is installed underwater in the water pipe to detect water pressure fluctuations in the water pipe, an amplifier amplifies the detection output of this pressure-to-electrical converter, and the output of this amplifier is input to remove unnecessary signal components. a high-pass filter and a low-pass filter that attenuate the water leakage sound and pass only frequency components specific to water leakage sound;
A water leakage detection device, comprising: a comparator that inputs the output of the filter, compares it with a reference value, and outputs a determination signal; and a comparator that determines wet water sound by distinguishing it from noise and background noise.