JPH10122845A - Tube inspecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube inspecting apparatus for discriminating a cause of abnormality generated in a tube by an acoustic signal. SOLUTION: A transmitting element 14 of an acoustic signal and a receiving element 15 of the signal reflected in a tube T are mounted at one end T1 of the tube T. A display means 5 for displaying the signal received by the element 15 and a high pass filter 7 are provided. The signal passed through the filter 7 is compared with the signal not passed through the filter 7 and displayed by the means 5 having a personal computer 3 and a CRT unit 4. An FFT means 27 for selecting a feature part of the received signal to obtain a frequency spectrum and a memory means 25 for storing the spectrum of the signal sampled in known tube state are provided. The signal of the means 27 is sequentially compared with the signal of the means 25 and displayed on the unit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe inspection apparatus for inspecting whether a foreign substance is locked in a pipe or a pipe is blocked by the foreign substance. More specifically, a transmitter of an acoustic signal that can be attached to one end of a tube, a receiver of an acoustic signal that is also attachable to one end of the tube and that is reflected in the tube, and an acoustic signal received by the receiver. The present invention relates to a pipe inspection device provided with a display means.

[0002]

2. Description of the Related Art As is well known, for example, pipes in plants and the like allow liquids, gases, powders, granules, mixtures of liquids and powders / granules to flow as fuels and raw materials. If a foreign substance is locked on such a pipe or the pipe is blocked by the foreign substance, the flow of the pipe is obstructed. Therefore, in order to remove the foreign substance, it is necessary to specify a position where the foreign substance is locked or the like.

[0003] However, it is extremely difficult to specify a position of a foreign substance by inspecting a complicated and complicated opaque pipe in a plant or the like by percussion or the like. In addition, piping isolated from the outside, for example, housed in a reaction tower, a pressure vessel, or the like, cannot be practically inspected by percussion or the like.

On the other hand, as a method of tube inspection using an acoustic signal without percussion or the like, for example, as described in Japanese Patent Publication No. 7-1168 (Japanese Patent Application Laid-Open No. 61-29757), an acoustic pulse A method for examining the situation has been proposed. According to the publication, the phase of the irradiation wave and the phase of the reflected wave in the tube are compared to determine whether the cross sectional area in the tube is large or small at the position where the reflected wave is generated.

[0005] However, even if the same increase or decrease in the cross-sectional area of the inside of the pipe is taken, the countermeasures are completely different due to different causes such as locking of foreign matter, collapsing of the pipe, and intrusion of water or granular material. Therefore, in the prior art as described in the above publication,
Although abnormalities in the pipes could be recognized, the cause of the abnormalities could not be specified, and the information was insufficient as information for taking measures such as pipe repair.

[0006]

SUMMARY OF THE INVENTION In view of the state of the prior art, an object of the present invention is to provide a tube inspection apparatus capable of identifying the cause of an abnormality occurring in a tube by an acoustic signal. .

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, a tube inspection apparatus according to the present invention is characterized in that an acoustic signal transmitter that can be attached to one end of a pipe and a pipe that can be attached to one end of the pipe and can be attached to the inside of the pipe. In the configuration including a receiver of the acoustic signal reflected by the, and display means for displaying the acoustic signal received by the receiver, provided a filter that cuts a part of the frequency from the received acoustic signal, The display means compares and displays the signals that have passed and not passed through the filter.

According to the experiments by the inventors, as a foreign substance having a small area occupying the cross section orthogonal to the pipe, for example, a reflection signal when a plate-like body is locked in the pipe in the longitudinal direction of the pipe is expressed as:
It has been found that the signal component of the low frequency side is smaller than the reflected signal due to other causes. Therefore, a filter that cuts (removes) the low-frequency side signal as “partial frequency” or cuts a signal having a frequency higher than the low-side frequency as “partial frequency” is configured. By comparing the “passed and unpassed signals” of the filter, it is possible to determine whether or not the cause of the reflected wave is a foreign matter having a small area occupied by the cross section orthogonal to the tube.

In constructing the filter,
It is preferable that the filter cuts at least a low frequency side from the received acoustic signal as the partial frequency. According to this configuration, a signal caused by a foreign substance having a small occupied area with respect to the cross section orthogonal to the tube remains even after passing through the filter, which facilitates the determination.

Another feature of the tube inspection apparatus according to the present invention is that a sound signal transmitter that can be attached to one end of the tube and a sound signal receiver that can be attached to one end of the tube and that is reflected inside the tube are also provided. A display unit for displaying an acoustic signal received by the receiver, a frequency spectrum analyzing unit for selecting a characteristic portion of the received acoustic signal to obtain a frequency spectrum, and a known pipe condition. And a known signal accumulating means for accumulating the frequency spectrum of the sampled acoustic signal, so that the signal of the frequency spectrum analyzing means can be sequentially compared with the signal of the known signal accumulating means and displayed.

According to the experiments conducted by the inventors, as described later, pipe blockage due to water and sludge, pipe end opening, pipe collapse,
It was confirmed that each of the frequency spectra of the reflected signal resulting from the locking of the foreign matter such as the plate-like body in the pipe had remarkable characteristics. Therefore, the frequency spectrum of a known cause is stored in the known signal storage means of the memory means constituted by a hard disk or the like, and the frequency spectrum of the sampling signal is compared with the frequency spectrum of the known signal, whereby the status in the pipe can be grasped.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment and the following examples, a steel pipe having a diameter of about 30 mm is used as a pipe T to be inspected. In the present embodiment, the total length of the pipe T from one end T1 to the other end T2 is 5 m. When the deformed portion is provided in the middle of the pipe, it is provided substantially at the center in the longitudinal direction of the pipe. On the other hand, when a plate-like body W having a thickness of about several mm, such as a coin, which is an example of a foreign substance having a small occupied area in the cross section orthogonal to the pipe, is locked in the pipe T in the longitudinal direction of the pipe, this one end T1 The distance from to the plate-like body W is 3.5 m. When closing the other end T2 of the pipe T with water or sludge, the pipe T is erected and the other end T2 is immersed in a container containing water or sludge.

A tube inspection apparatus 1 according to the present invention generally comprises a sensor head 2 attached to one end T1 of a tube, and a display means 5 comprising a personal computer 3 and a CRT device 4.
, A transmitter 6 and a filter 7. The personal computer 3 is configured to realize the following various functions by incorporating software into a general-purpose product.

In the sensor head 2 described above, a speaker 14 as a transmitter is supported on a partition plate 11 having an opening provided inside a case 10. In addition, a microphone that is a receiver is mounted on a support projecting from the partition plate 11 near the center of the speaker 14 toward the transmission side of the acoustic signal.
Is provided. For example, a tweeter of a general-purpose audio device can be used as the speaker 14, and a general-purpose condenser microphone can be used as the microphone 15. The case 10 has a connection tube 1 made of resin on a nozzle portion provided on the front side thereof.
2 and the connection tube is further connected to one end T of the tube T.
It is inserted and attached to 1. Of course, the connecting tube 12 can be appropriately lengthened according to the environment. The acoustic signal transmitted from the speaker 14 into the tube T is reflected by the deformed portion, the plate-like body W, the other end T2 of the tube, and the like, and the reflected signal is received by the microphone 15.

The personal computer 3 drives the oscillator 6 via the driver 22 by operating the operation unit 21. The oscillator 6 has, for example, a center frequency of 10 kHz.
A square wave of about z is generated, and this square wave is amplified by the transmission amplifier 6a to drive the speaker 14. On the other hand, the reflected acoustic signal received by the microphone 15 and amplified by the receiving amplifier 7a passes through the filter 7 or is passed through the A / D converter 24 and further passed through the A / D converter 24 to a memory means 25 such as a memory chip or a hard disk. Is accumulated in Whether the received acoustic signal is filtered by passing through the filter 7 or stored in the memory means 25 in a state where the received acoustic signal has not passed can be appropriately selected by controlling the filter via the operation unit 21.
In this embodiment and the following examples, the filter 7 is set to 10
It is composed of a low-pass filter that passes only signals of less than kHz and a high-pass filter that passes signals of more than 6 kHz. The threshold frequencies of the high-pass filter and the low-pass filter are determined by the operation unit 21.
Alternatively, it may be configured such that it can be appropriately changed by the above operation or by the direct operation of the filter. As will be apparent from the test results described later, the locking of the plate-shaped body W in the pipe is 6 times as compared with other signals.
Since there are few low-frequency components below kHz,
By low-cutting a signal of less than Hz, it is easy to distinguish from other in-tube situations. The reason why the high-frequency side of 10 kHz or more is cut is to remove high-frequency noise. If the high-frequency noise is small, the low-pass filter can be omitted. After the signal stored in the memory means 25 is processed by the processing means 28, for example,
The images are simultaneously displayed on the CRT device 4 in a manner as shown in FIGS. 2 (a1) to (a3) and FIGS. 3 (a1) and (a2). The signal filtered through the filter 7 is similarly processed by the processing means 28 and the CRT device 4 as shown in FIG.
(B1) to (b3) and in a manner as shown in FIGS. 3 (b1) and (b2). 2 (a1) to 2 (a).
3) and the graphs of FIGS. 3 (a1) and (a2) and FIG.
1) to (b3) and the graphs of FIGS. 3 (b1) and (b2) are simultaneously displayed on the CRT device 4 so that the signals that have passed through the filter 7 and the signals that have not passed therethrough are displayed in comparison.

The sound signal stored in the memory means 25 in a state where the sound signal has not passed through the filter 7 can be selected by operating the operation unit 21, and the selected one of the sound signals performs fast Fourier transform. The frequency spectrum is obtained by the FFT means 27. The selection of the feature is performed by converting the distance of the feature from one end T1 into time by a timer 26 that is linked to the operation of the driver 22. The graph of the frequency spectrum processed by the FFT unit 27 and the processing unit 28 is displayed on the CRT device 4 in a manner as shown in FIGS. 4 and 5, for example. Further, a hard disk or the like which constitutes a part of the memory means 25 is shown in FIG.
Among the signals of the characteristic portion of the acoustic signal shown in (1), the frequency spectrum of each of the acoustic signals sampled under the known in-tube condition is accumulated. Then, the CRT device 4 is configured to sequentially compare the frequency spectrum of the acoustic signal to be inspected with the known signal stored in the hard disk or the like of the memory unit 25, so that the in-tube state can be estimated. .

[0017]

2 (a1) to 2 (a3) show reception waveforms of an acoustic signal which has not passed through the filter 7 and which is displayed on the CRT device of the tube test apparatus constructed as described above. FIG. 2 (a1)
Is a case of a healthy pipe with the other end T2 opened, and a signal Sa at a reference time ta indicates a sound emitted from the speaker 14, and this time ta is a reference for the distance. The difference between the time t1 of the open end signal S1 and the reference time ta is a representative value representing the distance to the other end T2. The signal S2 in FIG. 2 (a2) corresponds to a case where the other end T2 of the tube T is immersed in water to close the tube T with water, and the signal S3 in FIG.
This corresponds to the case where No. 2 is blocked with sludge. On the other hand, FIG.
The signals S1 'to S3' of (b1) to (b3) are obtained by passing the signals S1 to S3 of the sound pipe and the water occlusion and the sludge occlusion through the above-described filter 7 to a signal of less than 6 kHz and 10
The signals obtained by cutting signals higher than kHz are shown. When the signals before and after passing through the filter 7 are displayed in comparison with the CRT device, it is clear that the difference between the two is large.

The signal S4 in FIGS. 3 (a1) and 3 (a2)
S6 is a signal similarly displayed on the CRT device, and is a signal when the plate-like body W is locked to the tube in a posture in which the plane faces the longitudinal direction of the tube as shown in FIG. This corresponds to the signal that has not passed through the filter 7 in each case where the plate-shaped body W is locked to the tube and the tube T is crushed to half its diameter before the tube.

On the other hand, the signals S4 'to S6' in FIGS. 3 (b1) and 3 (b2) are signals displayed on the CRT device and are signals after passing the signals S4 to S6 through the filter 7. Are respectively shown. The signals S4 'and S5' after passing through the filter due to the plate-like body W are not significantly attenuated as compared with the signals S4 and S5 before passing through the filter. On the other hand, the signals S1 'to S3' and S6 'after passing through the filter due to causes other than the plate-like body W are greatly attenuated as compared with the signals S1 to S3 and S6 before passing through the filter.
Such a difference is caused by the fact that the reflected signal from the plate-shaped member W is unlikely to reflect a low-frequency signal of less than 6 kHz from the plate-shaped member W having a small pipe area. Therefore, by comparing the signal intensity before and after passing through the filter 7 with respect to the acoustic signal based on the same reflection source, it is possible to determine whether or not the abnormality in the tube is caused by the plate-shaped body W.

The graphs of the frequency spectra shown in FIGS. 4A to 4D correspond to the signals S1 to S in FIGS.
3, S6 is frequency-analyzed by the FFT means,
It is displayed on the device. On the other hand, the graph of the frequency spectrum shown in FIG. 4E shows the reception reflection signal S of the plate W in a state where the plate W is locked over the diameter of the tube.
4, S5 are frequency-analyzed by the FFT means.

In FIGS. 4A to 4D, a comparison between (a) to (d) and (e) shows that the reflected signal due to the plate-like body W is less than 5 kHz in the entire frequency spectrum as compared with the reflected signal due to other causes. Was found to be relatively small. In other words, among the envelopes E1 and E2 of the frequency spectrum at around 5 kHz, the envelope E1 shown in FIGS. 4 (e) shows that the envelope E2 of the plate-like body locking or the like is relatively flat. Therefore, a signal of less than 5 kHz, preferably 6 kHz
By comparing the state where the signal of less than Hz is low-cut by the above-described filter 7 with the state as it is, the abnormality in the pipe due to the plate-like body W can be determined as described above.

A comparison between the group of sludge closing at the other end T2 of FIG. 4 (a) and the other end T2 of FIG. 4 (c) and the group of water blocking and tube deformation at (b) in FIG. 4 (b) is shown. It can be seen that the latter has more high frequency components greater than 10 kHz than the former. It is presumed that the former is caused by the fact that high frequency components are easily scattered or absorbed. (A)
Comparing (c) with (c), it was found that the high-frequency component was more likely to be absorbed by the sludge, but more easily reflected than the open end. Further, comparing (b) and (d), it was found that the high frequency component can be more flatly reflected in the case of water occlusion than in the case of tube deformation. That is, it was confirmed that the frequency spectrum of the reflected signal due to various causes has a feature for each cause, and each cause can be specified by pattern recognition.

FIG. 5 is a graph showing the correlation between the thickness of the plate-like body W retained inside the pipe over the length of the pipe diameter and the attenuation difference in the signal before and after passing through the filter 7. That is, assuming that the voltages of the signals S4 and S4 'in FIG. 3 are V4 and V4', respectively, the attenuation difference can be expressed by the equation 20 log (V4 / V4 ') [dB]. According to the graph, as the plate-shaped body W becomes thicker,
In other words, it was confirmed that as the area of the plate-shaped body W occupying the cross section orthogonal to the tube increases, the attenuation difference in the signal before and after passing through the filter increases. Therefore, it can be said that it is possible to estimate the approximate size of the foreign matter in the pipe in the cross section of the pipe based on the attenuation difference of the signal before and after passing through the filter.

Finally, the possibility of another embodiment of the present invention will be described. In the above embodiments and examples, the steel pipe having a diameter of about 30 mm in the plant was inspected. However, the main pipe inspection apparatus can be applied to pipes of various diameters other than the plant and the like. Needless to say, in the present invention, in addition to cast iron, stainless steel, and lead pipe, rubber pipes and resin pipes can be inspected. In addition, the in-pipe state that can be identified is not limited to the above-described sludge / water blockage, plate-like body locking, and the like. As an example of a foreign substance having a small occupied area in the pipe cross-sectional direction, a plate-like body is exemplified.
For example, an icicle growing inside the tube, a wire locked inside the tube, and the like are also applicable.

In the above embodiment, 6 which is an example of the threshold value is used.
A signal that has passed through a filter that low-cuts a signal of less than kHz is compared with a signal that has not passed through the filter. Was determined. However, a signal that has passed a filter that cuts a signal higher than the threshold value through a high-cut filter is compared with a signal that has not passed. If the signal attenuation rate is large, it is determined that the foreign matter has a small area occupied in the cross-sectional direction of the tube. It may be configured as follows. However, the configuration using the high-pass filter that performs the above-described low cut is excellent because both signals before and after passing through the filter 7 can be easily confirmed. Low cut in the present invention is synonymous with bypass, and high cut is synonymous with low pass. In the above embodiment, the threshold value is 6 kHz.
However, the optimum threshold value is not limited to this.

In the above embodiment, it has been found that the distribution of the high-frequency side signal component of, for example, 10 kHz or more has a characteristic due to the substance causing the blockage or the like. Therefore, for example, a substance that causes blockage or the like may be estimated based on a difference in attenuation of a signal before and after passing through a low-pass filter having a threshold value of about 10 kHz.

In order to compare and display the signals that have passed through the filter and the signals that have not passed, the two signals can be displayed simultaneously as described above, or only the difference between these two signals can be displayed. is there. Further, the display device according to the present invention may include not only the display device but also a light emitting diode or the like that is turned on when the signal intensity exceeds or does not exceed a certain value. If the difference between the signals is smaller than a certain value, the light emitting diode or the like may be turned on to indicate that the plate-like body or the like is locked. When only the difference is displayed, the timer 26 may be used to select only the signal based on the same reflection source without using the FFT unit 27.

In the above embodiment, the transmitter and the receiver of the acoustic signal are each constituted by a separate speaker and a microphone. However, the transmitter and the receiver may be constituted by the same device. For example, a single speaker may be provided as a transmitter / receiver, a pulse voltage may be applied to the voice coil, and a voltage generated at both ends of the boil coil due to the received acoustic signal pulse may be analyzed.

[0029]

As described above, according to the feature of the present invention, by comparing signals that have passed or not passed through the filter, it is possible to determine whether or not the cause of the reflected signal is a foreign matter occupying a small area in the cross section orthogonal to the tube. Can be determined and identified easily and quickly. As a result, the approximate shape and the like of the foreign matter and the like can be estimated from the spread of the foreign matter and the like locked on the pipe with respect to the cross section orthogonal to the pipe.

According to another feature of the present invention, a frequency spectrum stored in correspondence with each in-pipe abnormality is stored;
By comparison with the sampled frequency spectrum,
It became possible to identify various types of in-tube abnormalities.
As a result, the cause of an abnormality in the pipe can be accurately grasped without exposing the pipe, and thorough measures can be taken when removing foreign matter in the pipe or repairing the pipe.

It should be noted that the reference numerals described in the claims are merely for convenience of comparison with the drawings, and the present invention is not limited to the configuration shown in the attached drawings. .

[Brief description of the drawings]

FIG. 1 is a logical block diagram schematically showing a tube inspection apparatus according to the present invention.

FIG. 2 is a graph showing a change in intensity of a received signal with respect to time after transmission of an acoustic pulse signal to a tube (a1).
(A3) to (a3) are graphs showing a signal not passed through the filter, and (b1) to (b3) are graphs showing a signal after passing through the filter.

FIG. 3 is a graph having the same meaning as in FIG. 2, wherein (a1),
(B1) shows the results when (a2), (b)
2) corresponds to the case where the pipe is further deformed.

FIG. 4 is a graph showing a frequency spectrum of a part of a reflected signal, in which (a) is an open end, (b) is water occlusion, (c) is sludge occlusion, (d) is pipe deformation, and (e) is a graph. This is attributable to the locking of the plate.

FIG. 5 is a graph showing a correlation between the thickness of a plate-like body W and an attenuation difference of a signal before and after passing through a filter 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection apparatus 2 Sensor head 3 Personal computer 4 CRT apparatus 5 Display means 6 Oscillator 7 Filter 6a Transmission amplifier 7a Receiving amplifier 10 Case 11 Partition plate 11a Support body 12 Connection tube 14 Speaker (transmitter) 15 Microphone (receiver) 21 Operation Part 22 driver 24 A / D converter 25 memory means 26 timer 27 FFT means 28 processing means T tube T1 one end T2 other end W Plate. ..

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Keiichi Tsuji 1-18-14 Kitahorie, Nishi-ku, Osaka Non-destructive Inspection Co., Ltd.

Claims (3)

[Claims] 1. An acoustic signal transmitter (14) attachable to one end (T1) of a tube (T), and an end (T1) of the tube (T).
The receiver (1) of the acoustic signal that can be attached to 1) and reflected in the pipe
5) and a display device (5) for displaying an acoustic signal received by the receiver (15), wherein a part of the frequency is cut from the received acoustic signal. A pipe inspection device provided with a filter (7), wherein the display means (5) compares and displays signals passed and not passed by the filter (7). 2. The tube inspection apparatus according to claim 1, wherein the filter (7) cuts at least a low-frequency side from the received acoustic signal as the partial frequency. 3. An acoustic signal transmitter (14) that can be attached to one end (T1) of the tube (T), and an end (T) of the tube (T).
The receiver (1) of the acoustic signal that can be attached to 1) and reflected in the pipe
5) and a display means (5) for displaying an acoustic signal received by the receiver (15), wherein a characteristic part of the received acoustic signal is selected and a frequency is selected. Frequency spectrum analysis means (2) for obtaining a spectrum
7) and a known signal storage means (25) for storing a frequency spectrum of an acoustic signal sampled in a known pipe condition, wherein the signal of the frequency spectrum analysis means is sequentially compared with the signal of the known signal storage means. Tube inspection device configured to be able to display.