JP3535679B2 - Method for judging multiple reflection signals in a pipe in an ultrasonic line survey system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe multiple reflection signal judging method in a system for investigating the inside of a pipe such as a buried pipe by utilizing sound waves.

[0002]

2. Description of the Related Art Pipes such as gas pipes and water pipes buried in the ground may be corroded and deteriorated by laying for a long period of time or damaged by external force. Therefore, it is necessary to investigate the inside of the pipe and take repair measures by repair work. Conventionally, as one of the systems used for investigating the inside of this kind of pipeline, there is a system in which a device such as a camera or a fiberscope is inserted into the pipeline so that the state inside the pipeline can be directly viewed. However, the method of inserting such a device requires additional equipment such as a cable to be inserted into the pipeline and insertion work, which may result in a large amount of work and equipment for investigation. Further, if there is a breakage point or a branch point in the middle of the pipeline, it is difficult to guide the equipment at that location, which causes a problem that the entire pipeline cannot be accurately investigated. Therefore, instead of such a method, a system is proposed in which a sound wave is sent from the end of the pipeline and the state of reflection of the sound wave is observed to simply check the situation inside the pipeline from both ends or one end of the pipeline. (For example, JP-A-61-29757 and JP-A-61-202158). In the above-mentioned publication, a sounding means and a sound collecting means are arranged at the end of the conduit, and it is detected that the sound wave sent from the sounding means is reflected at the cross-sectional area change portion generated in the conduit, and the cross-sectional area is detected. A technique capable of observing the position up to the changed portion is disclosed. Such a technique can not only detect the cross-sectional area changing portion in the pipe but also investigate the position of the joint portion or the like installed in the pipe by observing the generation position of the reflected sound wave.

[0003]

However, in the case of investigating the inside of a conduit by using sound waves, multiple reflection occurs in the sound waves sent from the sounding means, and a sound wave signal due to the multiple reflection is observed. However, there is a risk that the signal may be erroneously determined to be from a reflection source inside the tube. Multiple reflection mainly occurs between the branch or end located in the pipe and the detection part of the reflected sound wave, and the timing is unrelated to the reflection signal from the regular installation position such as the joint located in the pipe. Therefore, there is a case in which it is erroneously determined that a member serving as a reflection source exists in the tube even though it does not actually exist in the tube.

FIG. 6 is a diagram for explaining a case where multiple reflections occur, (A) showing a piping path, and (B) in FIG.
Shows the reception timing of the reflected sound wave in the piping path shown in (A). In FIG. 6 (A), a speaker 1 which is a sound source and a microphone 2 which is a sound wave collecting portion are arranged at one end in the extension direction, and a branch portion D is provided in the middle of a conduit P1 extending to the other end in the extension direction. Another conduit P2 is connected separately from the conduit P1. In this case, the speaker 1
The pulsed sound wave transmitted from the
As indicated by the symbols H1 and H2, the light is reflected by the branch portion D and the end of the other conduit P2 and is received by the microphone 2. Further, as indicated by the symbol H3 in FIG. 6B,
The light is reflected by the end of the pipe P1 and received by the microphone 2. However, the sound wave reflected at the branch portion D is multiply reflected between the speaker 1 and the sound wave from the first obtained sound wave from the branch portion D, and is attenuated with a delay from the reception of the sound wave. It is received as shown in. Therefore, the multiple-reflected sound wave (H4) may be erroneously determined to have a reflecting member such as a joint member at that portion.

An object of the present invention is to easily determine whether the signal is a multiple signal or a reflection signal from a reflection source existing in the pipe, in view of the problem in the case of using the above-described conventional acoustic wave type channel survey system. It is an object of the present invention to provide a method for determining an in-pipe multiple reflection signal in an acoustic wave type channel survey system that can prevent erroneous determination when conducting an in-pipe survey.

[0006]

In order to achieve this object, the invention according to claim 1 provides a sounding means for transmitting a pulsed sound wave from one end of the conduit to the inside of the conduit, and at one end of the conduit. A sound wave for investigating the inside of the pipeline from the time from the transmission of the pulsed sound wave to the collection of the sound wave using the sound collecting means for collecting the pulsed sound wave reflected in the pipeline and the sound velocity value. A first step of storing received data regarding reflected sound waves from a pipe to be surveyed by the above-mentioned pipeline survey system using sound waves,
After performing the first step, a second step of connecting a sub-pipe having a predetermined length to the pipe to be investigated, and a length of the sub-pipe in addition to the pipe length to be investigated by the second step And a fourth step of comparing the received data obtained in the first and third steps with each other, In the fourth step, if there is a received signal that does not correspond to the deviation of the reflected signal due to the connection of the sub-pipe, that signal is used as a multiple reflection signal and the received data in the pipeline without the sub-pipe is used. The feature is that it is distinguished from the matching signal.

According to a second aspect of the present invention, in the method for determining an in-pipe multiple reflection signal in the sound wave type pipe survey system according to the first aspect, the lengths of the sub-pipes are made different, and the first to fourth steps are performed. It is characterized by being implemented.

[0008]

According to the invention described in claim 1, when the reflected sound wave is received at a timing deviated from the received timing of the reflected sound wave according to the length of the sub-pipe in the third step,
It can be determined that the reception signals received with a shift are multiple reflection signals that do not correspond to the actual reflection source portion.

According to the second aspect of the present invention, by connecting the sub-pipes having different lengths, the reception timing of the reflected signal can be varied according to the length of the sub-pipes to enhance the detection accuracy of the multiple reflection signal. it can.

[0010]

The present invention will be described in detail below. FIG. 1 is a schematic diagram showing a schematic configuration of an acoustic wave type pipe survey apparatus used in a multiple reflection signal discrimination method according to the present invention.
The sound wave type pipe survey device 10 has at least the sound generating means 1.
1, sound collecting means 12, CPU 13 as a control unit, display 1
4, D / A converter 15, amplifiers 16, 17 and A / D
It is provided with a converter 18. In addition to the above-mentioned members, the sound wave type pipe survey apparatus 10 may also use a sound velocity correction means for changing the sound velocity value that changes depending on the temperature inside the pipe, the type of gas inside the pipe, and the temperature. Display 1
For CRT monitor, LED display panel, liquid crystal display, plasma display, electroluminescence, or the like, apparatus 4 is used which can visually observe the reception timing of reflected sound waves.

The determination of the multiple reflection signal using the acoustic wave type channel survey apparatus 10 is performed based on the principle described with reference to FIGS. 2 and 3. FIG. 2 is a schematic diagram of a pipe and a timing chart (FIG. 2A) showing the reception timing of a reflected sound wave from the pipe, and the multiple reflection signal determination method according to the present invention. 3A and 3B are a schematic diagram of a pipeline and a timing chart (FIG. 2B) showing the reception timing of a reflected sound wave from the pipeline. It is to be noted that the number of reflections described below corresponds to the number of times a sound wave reciprocates between the reflection source and the sounding means. In FIG. 2 (A), the reflection source existing in the pipe S (reference numeral C1 in FIG. 2 is the first reflection source, reference numeral C is
2 is shown as the second reflection source) and the sound velocity is 5 m / s for the purpose of simplifying the description, although it is different from the actual value. In this case, the time until the sound wave sent from the sound generating means 11 is collected by the sound collecting means 12 and the reflected signal is output from the sound collecting means 12 is the case of the reflected sound wave from the first reflection source C1. 2 seconds (2
s), which is 10 seconds (10 s) in the case of the reflected sound wave from the second reflection source C2. When multiple reflections occur between the first reflection source C1 and the sound generating means 11, the time until the multiple reflection signal is output from the sound collecting means 12 is that the sound wave moves by the number of reflections. It is a value obtained by multiplying the time when the sound wave reciprocates by the number of reflections. That is, the multiple reflection in this case corresponds to, for example, a plurality of reflections occurring in the path from the first reflection source C1 to the sounding means 11, and, for example, in the case of two reflections, The time until the multiple reflection signal is output from the sound collecting means 12 is the sound collecting means 12
The distance between the first reflection source C1 and the first reflection source C1 is 4 seconds (4 s), which is twice the time required for the acoustic wave to make one round trip.

On the other hand, in FIG. 2B, the auxiliary pipe L1
When (for convenience of explanation, the length is set to 5 m) is continuously connected to the conduit S, the sound wave reflected from the first reflection source C1 is collected by the sound collecting means 12 and reflected from the sound collecting means 12. The time until the signal is output is 4 seconds (4 s) including the round trip time of the sound wave corresponding to the length of the sub-pipe L1, and the reflection signal from the second reflection source C2 is output from the sound collecting means 12. It takes 12 seconds (12 seconds) including the round-trip time of the sound wave for the length of the sub-pipe L1. With respect to the reception timing of the reflected sound waves from the first and second reflection sources C1 and C2, the multiple reflection signal due to the multiple reflection is similar to the first reflection source C1 as in the case shown in FIG. When two reflections (corresponding to two round trips of a sound wave) occur with the sound collecting means 12, the time required for the sound waves to travel the distance to the first reflection source C1 including the auxiliary pipe L1 is multiplied by the number of reflections. 8 seconds (8
s).

From the reception timing obtained in the state where the sub-pipe L1 shown in FIG. 2B is connected, the round-trip time of the sound wave for only the length of the sub-pipe L1 is subtracted from the reception timing.
A signal in which the result obtained under the same conditions as in the case of measuring the reflection time of the sound wave in the pipe S shown in (A) matches the reception timing shown in FIG. 2A is connected to the sub-pipe L1. It can be said that the reflection source exists at the same position as when it does not, and this is the basis for determining the existence of the reflection source. On the other hand, the multiple reflection signal is output from the reception timing shown in FIG.
Even if the round-trip time of the sound wave for the length is subtracted, it does not match the reception timing shown in FIG.
In other words, while it is 4 seconds (4s) in FIG. 2 (A),
In FIG. 2B, it is 6 seconds (6s). Therefore, even when the conditions for measuring the reflection time of sound waves are the same, it is possible to determine a signal generated at timings that do not match as a multiple reflection signal. Thus, the multiple reflection signal is
The reception timings of the reflected sound waves from the first and second reflection sources C1 and C2 are deviated by a time obtained by multiplying the time of reciprocating in the auxiliary pipe L1 by the number of reflections.

A configuration applied to the method for determining a multiple reflection signal according to the present invention based on the above principle is as shown in FIG. That is, the sub-pipe 22 is connected to the end of the pipe 20 to be investigated. The sub-pipe 22 connected to the pipeline 20 has a connection structure in which reflection and sound wave attenuation do not occur on the inner surface of the connection position, and specifically, a step portion, a seam, or the like that changes the cross-sectional area. The end faces are made to have the same inner diameter so as not to exist.

The method for determining multiple reflection signals according to the present invention is
The procedure is as follows. (1) First Step In this step, the sound wave type duct survey device 10 stores the received data relating to the reflected sound waves from the duct to be surveyed. In the present embodiment, the receiving state of the reflected sound wave in the pipe is described for the pipe configuration including the branch pipe 21 connected in the middle of the pipe 20.
Of course, only those equipped with are not subject to the survey. From the CPU 13 of the sound wave type channel survey device 10, a pulsed sound wave having a predetermined frequency and amplitude is set.
It is sent from 1. When the sound wave sent to the piping system including the pipeline 20 and the branch pipe 21 is reflected, the reflected sound wave is collected by the sound collecting means 12, and a reception signal corresponding to the reflected sound wave is generated via the A / D converter 18. It is stored in a storage unit (not shown) in the CPU 13. The memory content in this case is
It is also possible to display on the display unit 14.

(2) Second Step In this step, the auxiliary pipe 22 is connected to the end of the pipe 20. In the present embodiment, as shown in FIG. 1, the inner surface of the conduit 20 is provided at the end portion on the side where the sound producing means 11 and the sound collecting means 12 provided in the acoustic wave type pipe survey apparatus 10 are arranged. The sub-pipe 22 is arranged in a state where the same inner diameter is maintained and sound wave reflection and attenuation are not generated.

(3) Third step In this step, the auxiliary pipe 22 connected in the second step is used.
Pulsed sound waves are transmitted to the pipes 20 and 21 including the lines, and the reception data relating to the reflected sound waves generated in the pipes 20 and 21 are stored.

(4) Fourth Step In this step, the received data relating to the reflected sound wave obtained in the first step and the received data relating to the reflected sound wave obtained in the third step are compared. This comparison is performed based on the principle described in FIG. FIG. 3 is a timing chart showing received data for each of the first and third steps regarding a schematic diagram of a pipeline to be investigated including the branch pipe 21 and a reflected sound wave generated in the pipeline. In the figure,
In the reception data of the reflected sound wave when the sub-pipe 22 is not connected (the upper timing chart in the timing chart of FIG. 3), the branch portion (the position indicated by the symbol A in FIG. 3) of the pipeline 20 and the branch pipe 21 A reception signal corresponding to the reflected sound waves from the end portion (the same position indicated by the reference numeral B) of the pipe 20 and the end portion (the same position indicated by the reference numeral C) of the conduit 20 is obtained, and a signal corresponding to the multiple reflection signal Is obtained. On the other hand, the reception data of the reflected sound wave when the auxiliary pipe 22 is connected (see FIG. 3).
In the timing chart in the lower part of FIG. 3), each reflection is caused in a state in which a time lag (time lag indicated by T1 in FIG. 3) including the time required to reciprocate the distance of the auxiliary pipe 22 is generated. A reception signal corresponding to the reflected sound waves from the portion corresponding to the source, that is, the branch portion A, the branch pipe end portion B, and the conduit end portion C is obtained. As described with reference to FIG. 2, the multiple reflection signal is obtained by multiplying the moving time of the sound wave traveling back and forth through the distance of the sub-pipe 22 by the number of reflections (2) with respect to the reception timing of the reflected sound wave from each reflection source (T2 = 2 x T
1) Only shift. Therefore, even if the time required to make one round trip of the distance of the sub-pipe 22 is subtracted, the reception timing of the multiple reflection signal is such that the branch portion A and the branch pipe end portion B, which are the respective reflection sources when the sub-pipe 22 is not connected. And the reception timing from the conduit end portion C is significantly different. Therefore,
It is possible to easily determine that the signal that does not coincide with the time when the sub-pipe 22 is not connected is a multiple signal.

According to this embodiment, it is possible to discriminate between the reflection signal from the reflection source and the multiple reflection signal due to the multiple reflection by a simple operation of connecting the auxiliary pipe to the end of the pipeline. It can be easily determined by the difference in size.

The sub-pipe 22 is not limited to being connected to the end of the pipe 20, but can be connected corresponding to the pipe to be investigated. That is, in the example shown in FIG. 1, the auxiliary pipe 22 is connected to the end of the conduit 20 corresponding to the main pipe, but the branch pipe is investigated by connecting to the end of the branch pipe branched from this main pipe. It is also possible to determine the multiple reflections of interest. FIG. 4 shows this case, in which the sub-pipe 22 is connected to the end of the branch pipe 21. Although not shown in FIG. 4, the sound producing means 11 and the sound collecting means 12 that compose the acoustic wave type channel survey device 10 are located at the same positions (in FIG. 4, as in the example shown in FIG. 1).
It is arranged at the left end portion of the conduit 20. With such an arrangement configuration of the sub-pipe 22, when the sub-pipe 22 is not arranged, the reception timing as shown in the timing chart in the upper part of FIG. 4 can be obtained. On the other hand, when the sub-pipe 22 is connected, as is apparent from the timing chart shown in the lower part of FIG. 4, the reflected sound waves from the branch portion A and the conduit end portion C at the position where the sub-pipe 22 does not pass through. Is the same as the reception timing when the sub-pipe 22 is not connected, but the reflection signal of the reflected sound wave from the end of the branch pipe including the sub-pipe 22 (indicated by reference numeral B ′ for convenience) indicates the distance of the sub-pipe 22. It appears as it is deviated by the time it takes to make a round trip. On the other hand, the multiple reflection signal generated between the branch pipe 21 and the sounding means is the number of reflections during the time of reciprocating the distance including the sub pipe 22 when the number of reflections in that section is two. The time is multiplied by (times), and in this case, it is twice (corresponding to the number of times of reflection) deviation (T2 = 2 × T) with respect to the reception timing of the reflected signal from the end portion B ′ of the branch pipe.
1) is generated and revealed. By connecting the sub-pipes 22 in this way, it is possible to easily determine the multiple reflection signal generated when the inside of the pipe including the sub-pipes 22 is investigated, regardless of which of the pipes is the target. You can

By the way, according to the above-mentioned principle, the reception timing of the multiple reflection signal obtained by the distance of the auxiliary pipe may overlap with the reception timing of the reflected sound wave from the reflection source. In this case, it may not be possible to determine the multiple reflection signal even though the auxiliary pipe is connected. In the present invention, in order to reliably determine the multiple reflection signal even in such a case, the sub-pipes 22 having different lengths are connected to each other and the reception timing of the reflected sound waves is observed to detect the reception signal by the multiple reflection. I am sure that I can represent it. Less than,
This will be described. FIG. 5 shows the reference numeral L1 in FIG.
1 and corresponds to the case of the length (5 m) of the auxiliary pipe indicated by reference numeral 22 in FIG. 1 and the auxiliary pipe 22 ′ having a length of 2.5 m which is different from this length are connected. 3A is a timing chart showing the received data regarding the reflected sound wave in the case of FIG. 3A, and FIG. 3A shows the received data when the sub-pipe L1 shown in FIG. 2 (corresponding to the member indicated by reference numeral 22 in FIG. 1) is not connected. , (B) are the auxiliary pipes 2 shown in FIG.
2 shows reception data relating to reflected sound waves when 2 is connected, and (C) shows reception data when connecting a 2.5 m sub-pipe 22 'having a different length from the sub-pipe 22 shown in FIG. 1, respectively. ing. In FIG. 5, as shown in FIG. 5B, when the length of the sub-pipe 22 is set to 5 m, the reception timing of the multiple reflection signal with the sub-pipe 22 connected is equal to the number of reflection times of the distance of the sub-pipe 22. Although the timing is shifted by (twice), the timing coincides with the timing of the signal by the reflected sound wave from the second reflection source C2. Therefore, when the auxiliary pipe 22 is not connected (see FIG.
It may not be possible to determine whether the multiple reflection signal obtained in (A) is an actual multiple reflection signal. Therefore, in this embodiment, a sub-pipe 22 'having a length (2.5 m) different from that of the sub-pipe 22 is connected, and the reception data regarding the reflected sound wave in the pipeline including the sub-pipe 22' is stored. . In FIG. 5 (C), in the reception data of the reflected sound wave in the pipeline including the auxiliary pipe 22 ′ (length 2.5 m),
If the signal due to multiple reflections travels back and forth through the distance of the sub-pipe 22 ′, and is shifted by the time obtained by multiplying the number of reflections (twice),
It is obtained at the timing of seconds (6 s), and it is 5 seconds (5 s) even after subtracting the time for one round trip of only the sub-pipe 22 ′, which is obtained in a state where it does not coincide with the reception timing of the reflected sound wave from the second reflection source C2. To be As a result, the occurrence of the multiple reflection signal and the determination of the multiple reflection signal can be surely performed, so that the accuracy for determining the multiple reflection signal can be improved.

[0022]

According to the first aspect of the present invention, the sub-pipe is installed, the reception timing of the reception signal corresponding to the reflected sound wave including the distance of the sub-pipe, and the reception timing in the pipeline not using the sub-pipe. It is possible to easily discriminate the reflected signal from the originally reflected portion and the multiple reflected signal by only subtracting the shift of the reception timing corresponding to the distance of the sub-pipe by a simple operation of comparing and. As a result, even if multiple reflections occur during the morphological survey in the pipeline, the multiple reflection signals can be easily and reliably determined. It is possible to eliminate the erroneous determination as a source.

According to the second aspect of the present invention, by connecting the sub-pipes having different lengths, the reception timing of the reflection signal is changed according to the length of the sub-pipes to enhance the detection accuracy of the multiple reflection signal. I can do things.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an apparatus and a pipe used in a multiple reflection signal determination method according to the present invention.

2A and 2B are a schematic diagram and a reception timing chart of a reflected signal when a sub-pipe is not connected in order to explain one mode of the principle for the multiple reflected signal determination using the apparatus shown in FIG.

3 is a timing chart showing received data obtained in a first step and a third step for discriminating multiple reflection signals using the apparatus shown in FIG.

4A and 4B are a schematic diagram showing a modified example of a pipe line configuration for multiple reflection signal determination using the apparatus shown in FIG. 1 and a timing chart showing received data in the pipe line.

5A and 5B are a schematic diagram of a pipeline and a timing chart showing reception data of reflected sound waves obtained in the pipeline for explaining an embodiment of the invention described in claim 3;

FIG. 6 is a schematic diagram of a pipe and a reception timing chart of the multiple reflection signal for explaining a case where a multiple reflection signal is generated in the pipe.

[Explanation of symbols]

10 Sonic pipe survey equipment 11 Pronunciation means 12 Sound collecting means 20 pipelines 21 Branch pipe 22, 22 'auxiliary piping

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-29757 (JP, A) JP 8-21717 (JP, A) JP 61-202158 (JP, A) JP 6- 230120 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 29/00-29/28 G01B 17/00-17/08

Claims (2)

(57) [Claims] 1. A sounding means for sending a pulsed sound wave into the conduit from one end of the conduit, and a sound collecting means for collecting the pulsed sound wave reflected in the conduit at one end of the conduit. In a sound wave type duct survey system that investigates the inside of a duct from the time from when the pulsed sound wave is transmitted to when it is collected and the sound velocity value, a survey target is made by the duct survey system using the above sound wave. A first step of storing reception data relating to a reflected sound wave from a pipe to be a second step, and a second step of connecting a sub-pipe having a predetermined length to the pipe to be investigated after the first step is carried out; A third step of storing the reception data regarding the reflected sound wave for the pipeline including the length of the sub-pipe in addition to the pipeline length to be investigated by the second step, and the first and third steps Received data obtained in In the fourth step, if there is a received signal that does not correspond to the deviation of the reflected signal due to the connection of the auxiliary pipe, the signal is determined as a multiple reflected signal. Method for determining multiple reflection signals in a pipe in a sound wave type pipe survey system. 2. The method of determining a multiple reflection signal in a pipe in a sound wave type pipe survey system according to claim 1, wherein the lengths of the sub-pipes are different from each other, and the first to fourth steps are carried out. Method for judging multiple reflection signal in pipe in sound wave type pipe survey system.