JPS62145131A - Acoustic leakage detector - Google Patents

Abstract

PURPOSE:To decide a leakage and an abnormality of a detecting system without bypassing the detecting system, by catching a leakage sound which is generated by following a leakage from a transport piping, and operating an amplitude of a detecting acoustic signal and a frequency distribution. CONSTITUTION:A leakage sound which is generated by following a leakage from a leakage point 101 of a cooling system piping 100 in a nuclear reactor container, and an environmental noise are detected by a microphone 1, penetrate a container 102 and inputted to an amplifier 2. An output of the amplifier 2 is inputted to an acoustic parameter computing element 3, and an effective value of an acoustic signal and an average frequency are calculated. A leakage decider 4 discriminates a normal time, a leakage generating time, a disconnection time, a short circuit time, and a sensitivity variation time, by the effective value of the acoustic signal and the average frequency, decides whether a leakage exists or not and whether the detecting system is abnormal or not, raises an alarm and also displays the contents of an abnormality.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention prevents leakage from pipes transporting water, steam, etc.

The present invention relates to an acoustic leak detector that captures and detects sound generated due to leakage, and particularly relates to an acoustic leak detector that has a self-diagnosis function in the measurement system itself.

[Background of the invention]

In order to confirm the soundness of conventional water leakage detectors that use leakage acoustics, each acoustic detection system is bypassed and its operation is checked periodically, and detailed function checks are performed during periodic inspections. Ta. However, if some channels of the leak detector are bypassed, the leak detection system
Bypass Uj K It is necessary to provide a separate operating detection channel.

Therefore, there was a drawback that the number of measurement channels increased and the leakage detection/stem became expensive.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an acoustic leak detector that can check the operation of the acoustic leak detector without bypassing the test channel during operation.

[Summary of the invention]

In order to achieve the above object, in the present invention.

It takes advantage of the fact that the amplitude and frequency distribution of the detection signal are different depending on whether the detection system is in a malfunctioning state or in a normal operating state.

In a normal state where no leakage occurs, the output signal of the detection system consists of wavenumber components having the same amplitude as the environmental noise. Also,
The amplitude and wavenumber distribution of the output signal of the detection system when a leak occurs are:
This is almost the same as the sound generated by leakage. In the case of a disconnection in the detection system, the detection system output signal contains many components of the commercial same wave number and its harmonics. Also, in the case of a short circuit in the detection system.

The interval between the detection system output signals per image becomes extremely small. When there is a sensitivity change in the detection system, the detection system output signal changes beyond the normal stroke width variation range, and the change in one frequency distribution is small. The operation check of the detection system based on these amplitude and frequency distributions can be performed without bypassing the detection system.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows an example in which the present invention is applied to an acoustic large water leak detector for cooling system piping in a reactor containment vessel. microphone 2f
'i, This is for detecting the leakage sound generated due to leakage from the leakage point 101 of the cooling system piping 100. Leakage sounds and environmental noises are converted into electrical signals by the microphone 1, and amplified by 52 VC are input through the containment vessel wall 102f. The output of the amplifier 2 is input to the acoustic parameter calculator 3.

The acoustic parameter calculator 31'j calculates the effective value and average frequency of the acoustic signal. The leakage detector 4 determines the presence or absence of leakage and the abnormality of the detection system based on two parameters: the effective value, which is a representative value of the acoustic signal amplitude, and the average river wave number, which is a representative value of the frequency distribution, and reports the leakage. At the same time, the error details are displayed. Effective value R, which is the acoustic parameter used here
MS and average frequency ν can be obtained by the following calculation.

In the above equation, f is the frequency, I)(r) is the acoustic power at the frequency f, and fH and fL are the upper and lower limit frequencies of the monitoring target. In equation (2) Vc, the denominator is equal to the effective value, and one numerator is equal to the effective value of the differential of the acoustic signal. Therefore, the calculations of equations (1) and (2) can be realized with the circuit configuration shown in FIG. The acoustic signal from which components outside the monitoring target area have been removed by the bandpass filter 31 is processed by the effective value calculator 32.
．． Input to the differentiator 33. The output of the differentiator 33 is input to the effective value calculator 34.

The effective value calculator 32 outputs the desired effective value ff&.The output of the divider 35 is output from the effective value calculator 32.3.
4, or the average frequency.

The average frequency takes a value close to the center frequency of the frequency distribution of the signal. For example, in the case of a line spectrum, if the frequency of the spectrum corresponds to the same wave number distribution having two peaks of approximately the same amplitude, the value will be close to the same wave number in the center between the peaks.

The overall configuration of the acoustic large water leak detector according to one embodiment of the present invention has been described above. Next, the abnormality determination method of the leakage determination device 4 will be explained. FIG. 3 shows how the effective value indicating the amplitude of the acoustic signal and the average frequency, which is the representative value of the 1d wave number distribution, change depending on the state of the detection system. The horizontal axis shows the effective value.

The average frequency is plotted on the vertical axis. This is a case where no leakage occurs in the range 401 and the microphone 1 captures only the environmental noise. The frequency distribution of environmental noise ranges from low frequency to 2 to 3K.
It is flat up to Hz, and the amplitude decreases at higher frequencies. Range 402 is a case where a leak occurs;
Both the effective value and the average frequency are higher than in the normal range 401.

Leakage sound has a flat frequency distribution, and IKH
z to 40 KHz or more.

[Box 406 is a case where a short circuit occurs between microphone 1 and amplifier 3, and the effective value becomes extremely small. Since the signal becomes small and exceeds the dynamic range of the acoustic parameter calculator 3, the value of the average frequency can take various values depending on how the acoustic parameter calculator 3 is adjusted. range 40
Number 5 is a case where a disconnection occurs between the microphone 1 and the amplifier 2. When a disconnection occurs, noise from the commercial power supply often appears in the output of the amplifier 2, and the commercial frequency and its harmonic components appear, and the average frequency ranges from several tens of Hz to
It becomes several hundred Hz. The range 403° to 404 shows cases where the sensitivity decreases and cases where the sensitivity increases. There are many large changes in the frequency distribution, and the effective value changes. As shown in FIG. 3, the effective value and average frequency of the acoustic parameters are good indicators of the state of the detection system. R+ to R5+ in Figure 3
ν1 ~ whiteba, effective value and average of each possible state of the detection system +! ! It shows the boundary value of the a number. The state of the detection system,
The relationship between these boundary values is as follows, where the effective value and the measured value of the average frequency are denoted by tl, R, MS, and ν, respectively.

(1) Short, final state: RMS < R2 (2) Sensitivity deterioration failure'a+ < RMS < R2, ν3×ν×ν4(
3) Normal state: R3<RMS (R,s, ν3×ν×ν4(4) C-cut state: R,MS>as
, ν3kuν<ν4(5) Disconnected state: RMS>R2, ν1
〈νkuν2(6) When leakage occurs: RMS >R4, νs
ν〈In the white leakage determiner 4, the above six states are discriminated by a general logic circuit including a conoparator, and the judgment results such as normal, detection system abnormality, leakage, etc. are displayed, and the detection system abnormality is detected. or generates an alarm when a leak occurs.

In the embodiments described above, it is also possible to use frequency analysis means using techniques such as fast Fourier transform in order to obtain information regarding the amplitude and frequency of the acoustic signal. The acoustic parameter calculator z3 is.

There is no problem in replacing the analog circuit shown in the embodiment with a digital circuit. If we can reduce the range of fluctuations in environmental noise during normal times when leaks occur or not, abnormalities such as changes in sensitivity can be detected more sensitively. For this purpose, the position and size of the area of the normal range 401 on the graph may be dynamically determined for K based on the effective value of the plurality of microphone outputs and the average of the average frequencies. As this average and nine directions,
Considering the main sources of environmental noise and the microphone position, *,
It is also possible to use standard weighting factors.

A feature of the present invention is that the operating state of the detection system is checked using amplitude information and frequency information of the acoustic signal.

The first embodiment described above has the following effects.

(1) Since the function of the detection system is continuously checked, the reliability of the detection system is improved.

(2) Since the cause of the abnormality can be known, the repair period can be shortened, and the risk of loss of part or all of the plant's functions due to the late IRK is shortened.

It has the effect of improving the operating rate.

(3) Since the repair period is short, it has the effect of reducing radiation exposure during repair work.

(4) Since the leakage determination is performed using two parameters, the amplitude and frequency distribution of the detection signal, the leakage detection sensitivity is improved, which has the effect of improving the performance of the acoustic hole leakage detector.

〔Effect of the invention〕

As explained above, according to the present invention, the detection thread? Since the health of the leak detection system can be confirmed without bypassing, the bypass detection system used in the past for checking the health is no longer necessary, which has the effect of reducing the cost of the leak detection system.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a leak detector according to an embodiment of the present invention;
FIG. 2 is a block diagram of the acoustic parameter calculator, and FIG. 3 is an explanatory diagram of the relationship between acoustic parameters, the state of the detection system, and the leakage state. DESCRIPTION OF SYMBOLS 1...Microphone, 2...Amplifier, 3...Acoustic parameter calculator 24...Leakage determiner, 31...Band pass filter, 32.34...Effective value calculator:
U3...differentiator, :(5...divider.
(,.

Claims (1)

[Claims] 1. In an acoustic detector that detects leakage by capturing the leakage sound that occurs with leakage, the amplitude and frequency distribution of the detected acoustic signal are calculated, and the amplitude and frequency distribution of the detected acoustic signal are determined when the amplitude and frequency distribution are normal and when a leak occurs. , an acoustic leak detector characterized in that it determines leakage and detection system abnormality by utilizing differences depending on when a wire is disconnected, when a short circuit occurs, and when sensitivity changes.