JPH0337541A - Method and apparatus for judging cause of leak from valve and pipe - Google Patents

Abstract

PURPOSE:To specify the cause of leak quickly by detecting ultrasonic waves caused by leak with a sound sensor, a transducing the waves into an acoustic signals, classifying the signals into the levels for frequencies, and comparing the signals with the acoustic output levels for the frequencies which are obtained by the same way beforehand. CONSTITUTION:Ultrasonic waves emitted from a valve 21 provided at a pipe 20 are transduced into electric acoustic signals through a sound sensor 22. The signals are inputted into a spectrum analyzer 24 through an amplifier 23. The signals having the frequencies of 100 - 600kHz are divided into five frequency bands separated by every 10kHz. The acoustic signals are sent into a frequency- band-output detector 25. The signal levels are discriminated into the three levels of large (h), medium (i) and small (g). The signals are sent into a frequency- band-output comparator 26. The signals are compared with reference levels for the causes of leaks which are sent from a reference-signal-level memory device 27, and the cause of the leak is specified.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention provides a method for determining the cause of leaks in valves and pipes, and a method for determining the cause of leaks in valves and pipes in various plants. Regarding a discrimination device.

(Prior art) In power plants and chemical plants, many pipes and valves are installed to transfer and control various fluids. , leakage may occur at the valve seat due to erosion.Conventionally, systems such as the one shown in Fig. .

In this system, an acoustic sensor 3 is installed in a valve 2 provided in a pipe 1, and a leak determination device 5 is connected to the acoustic sensor 3 via an amplifier 4.

A reference acoustic signal transfer device 6 is also connected to the leak determination device 5 .

If a leak occurs due to some abnormality in the valve seat when the valve 2 is in the closed state, high frequency (several tens of kHz to tens of kHz to
Ultrasonic waves of several 100 kl-1z) are generated. The acoustic sensor 3 captures this ultrasonic wave and converts it into an electrical acoustic signal. This acoustic signal from the acoustic signal 3 is amplified by an amplifier 4, and only the acoustic signal representing the valve seat leak is passed through (filtered). The leak determination device 5 converts the acoustic signal sent from the amplifier 4 into a reference acoustic signal transfer device in the form of an effective value (RMS value) or spectrum as shown in FIGS. 8 and 9, respectively. The presence or absence of leakage or its degree is detected by comparing it with the reference value sent from 6.

However, in such a system, it is not possible to identify the cause of the leak. For this reason, even if the occurrence of a leak and its extent were known, the cause of the leak could not be determined by actual G-drop, and it took time to investigate.

(Problem to be solved by the invention) In the past, although it was possible to detect the presence and extent of leaks in valves and pipes using acoustic signals, the cause of the leak could be identified using acoustic signals. Because there was no way to
The cause of the leak could not be determined until it was investigated on-site, and it took a long time to investigate.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for determining the cause of leaks in valves and pipes, and a determination device therefor, which quickly identifies the cause of the leak using an acoustic signal.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention detects ultrasonic waves caused by leaks using acoustic sensors attached to valves or pipes, converts them into acoustic signals, and outputs the acoustic signals. To provide a leak cause determination method for valves and pipes in which the leak cause is identified by dividing the levels into frequency bands and then comparing the sound output level for each frequency band for each leak cause obtained in the same way.

The present invention also provides an acoustic sensor that converts ultrasonic waves emitted from a valve or pipe into an electrical acoustic signal, and a spectrum analyzer that divides the acoustic signal output from the acoustic sensor into a plurality of frequency bands. , a frequency band output detector for detecting the output of the acoustic signal divided by frequency band by this spectrum analysis device, and a frequency band output detector for detecting the output of the acoustic signal divided by frequency band by the frequency band output detector; and a frequency band output comparator that identifies the leak cause by comparing the output with the frequency band output of the acoustic signal for each valve or pipe leak cause detected in advance using each of the above-mentioned devices. Provide a cause determination device.

(Function) In the present invention, the ultrasonic wave generated due to a leak in a valve or pipe is determined by the main frequency component obtained by dividing the sound velocity of the fluid flowing through the valve pipe by the length of the point causing the leak. Note that

That is, an acoustic sensor is installed in the valve or pipe to detect ultrasonic waves caused by a leak in the valve or pipe and convert it into an electrical acoustic signal. The output of this acoustic signal is then normalized for each frequency band and represented at one of several preset levels. On the other hand, with respect to ultrasonic waves generated due to various leak causes, the acoustic output level for each frequency band is determined in advance in the same way. Finally, the cause of the leak is identified by comparing the acoustic output levels of both.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 6.

The frequency of ultrasonic waves generated when there is a leak in a valve or pipe has various components within a certain frequency range, even in the case of a leak due to the same erosion. Further, for example, the frequency of an acoustic signal based on turbulence and shock waves due to -4:t vibration has components different from this.

However, such ultrasonic waves can be used to measure the speed of sound in fluids flowing through valves and pipes.
Then, it is considered that the frequency expressed by v/1 is the main component. For example, as shown in Fig. 2 (A), when a groove with a width of 1 is formed in the valve seat 20 due to erosion,
/1, ma1 ・As shown in Fig. 2 (B), when a gap with a diameter of 12 mm is created between the valve seat 20 and the valve body 21 due to a foreign object being caught, the V/1 and V/j! The frequency represented by 3(j!3-πD) is the main component.

FIG. 3 is a diagram showing spectra when various ultrasonic waves generated due to leakage are converted into electrical acoustic signals. The spectrum a generated due to erosion has a (principal component) peak in a high frequency band. The spectrum due to the bite between the valve seat and the valve body shows gentle peaks over a wide range of frequencies. The spectrum due to valve stem leakage shows low beat in the low frequency band. spec 1 ~ le d
is the background.

By the way, when the signal level is normalized by frequency band and represented by the three levels of high, medium, and low for such a multiple-shaped subekle, Figure 4 (A), (B),
It becomes a simple shape as shown in (C) and (D).

Therefore, although it is not possible to determine the cause of the acoustic signal spectrum of ultrasonic waves generated by leakage from the overall shape, it is difficult to determine the cause of the acoustic signal spectrum of ultrasonic waves generated by leakage. ′? Determine in advance the typical output level for each frequency band, including the frequency band that is used. Then, for the actually measured signal, determine the output level for each frequency band in the same way, and compare the output levels of both. , it becomes possible to identify the cause of the leak.

FIG. 1 is a diagram showing a schematic configuration of a valve leak cause determining device for determining the cause of leak in a valve seat according to a first embodiment of the present invention.

Ultrasonic waves emitted from a valve 21 provided in the pipe 20 are converted into electrical acoustic signals by an acoustic sensor 22. Amplifier 23 amplifies the acoustic signal from acoustic sensor 22 and filters a signal representing, for example, a valve seat leak. The valve seat leak signal is then sent to spectrum analyzer 2.
For example, a signal with a frequency of 100 to 600 kHz is divided into five frequency bands of 100 kHz each.

Next, this acoustic signal divided into frequency bands is sent to a frequency band output detector 25, which divides the signal output into large, medium, and
It is classified into three levels: small and small.

The acoustic signal that has been extracted by the level for each frequency band is then sent to the output comparator 26 for each frequency band.
Reference signal levels are also sent, which are classified in advance into large, medium, and small based on the acoustic signals for each leak cause and are expressed in Table 28 format. Then, in the frequency band output comparator 26, the acoustic signal level-divided by frequency band sent from the frequency band output detector 25 and the reference signal level for each leak cause sent from the reference signal level storage 27. By comparing the values, you can easily identify the cause of the valve seat leak.

Next, a second embodiment of the present invention will be described.

As shown in FIG. 5(A), also in the pipe 30, there are cracks 32 in the welded portion 31, and as shown in FIG. 5(B),
Leakage occurs in the erosion part 33 due to drain attack.

FIG. 6 shows a pipe leak cause determining device for determining the cause of leak in the pipe 32. Components similar to those in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted.

The reference signal level memory 27 in this system includes:
Regarding leak causes such as weld attack and drain attack, the acoustic output is expressed in three levels of high, medium, and low for each frequency band of 100 l as shown in Table 34.

Then, in the same manner as in the first embodiment, the cause of the leak in the tube 30 is identified in the frequency band output comparator 26.

In the above embodiment, the level of the output signal is divided into three levels, high, medium, and low, but it may be divided into more levels. Further, cause items such as large erosion and small erosion may be set depending on the degree of damage.

Furthermore, the output level may be determined not by the absolute level but by the difference from the background.

In addition, the device used in the system of the above embodiment may be of a digital type or an analog type.

(Effects of the Invention) As explained above, in the present invention, in order to investigate the cause of a leak in a valve or pipe, a sound *1 is applied to the valve or pipe (J t), and a sound is applied to the valve or pipe. Detects the ultrasonic waves caused by and converts them into electrical acoustic signals. We focused on the fact that the main frequency component of ultrasonic waves generated due to leaks in valves or pipes is the sound velocity of the fluid flowing through the valve or pipe divided by the length of the point where the leak occurs. The output of the acoustic signal is normalized by frequency band and represented by one of several preset levels. On the other hand, for ultrasonic waves generated due to various leak causes, the acoustic output level for each frequency band is determined in advance in a similar manner, and the leak cause is finally identified by comparing the two acoustic output levels. Therefore, 1. According to the method of the present invention, the cause of a leak in a valve or pipe can be quickly identified using an acoustic signal.

[Brief explanation of drawings]

Figure 1 is a block diagram of a system implementing the first embodiment of the present invention, Figures 2 (A), J5 and (B) are cross-sectional views showing valve leak locations, and Figure 3 is an acoustic spectrum based on the leak. Figures 1 to 1 are not shown; Figures 4 (A) to D) are diagrams in which the spectrum in Figure 3 is divided into levels; Figures 5 (A) and (B) are cross-sectional views showing valve leak points; Fig. 6 is a block diagram of a system implementing the second embodiment of the present invention, Fig. 7 is a block diagram of a conventional system for determining the presence or absence of leakage or the degree of leakage, and Figs. 8 and 9 are respectively FIG. 3 is a diagram showing output as an RMS value and a spectrum. 22...Acoustic sensor, 24...Spectrum analyzer, 25...Frequency band output detector, 26...Par frequency band output comparator, 27...Reference signal level storage device 2 (A) CB) Diagram (Erosion) (A) (Valve shaft leak) (Cn (*Fukomi, 7+) (B) (A"z77 Parauno 0 (D) Same wave number diagram 2 j (A) (B) Figure S question 8 (J4 oil soldier

Claims (1)

[Claims] 1. Ultrasonic waves caused by leaks are detected by an acoustic sensor attached to a valve or pipe and converted into an acoustic signal, and the output of this acoustic signal is divided into levels according to frequency bands, and then the same process is performed in advance. A method for determining the cause of leaks in valves and pipes, which identifies the cause of the leak by comparing it with the sound output level for each frequency band determined by the leak cause. 2. An acoustic sensor that converts ultrasonic waves emitted from a valve or pipe into electrical acoustic signals, a spectrum analyzer that divides the acoustic signals output from this acoustic sensor into multiple frequency bands, and this spectrum analyzer. A frequency specific output detector detects the output of the acoustic signal divided by frequency band according to the frequency band, and the frequency specific output of the acoustic signal detected by the frequency specific output detector is detected in advance using each of the above-mentioned devices. A leak cause determination device for valves and pipes, comprising a frequency specific output comparator that identifies the leak cause by comparing the frequency specific output of an acoustic signal for each leak cause of the valve or pipe.