JP2011128043A - Method and device for nondestructive inspection using guide wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nondestructive inspection method and device using a guide wave, capable of measuring a plate thickness without being affected by discontinuous parts such as weld zones and pipe branches in an inspection using the guide wave. <P>SOLUTION: Transmitting guide wave probes 2a, 2b, and 2c, and receiving guide wave probes 2d, 2e, and 2f are installed across an inspection object range of piping 1. An arrival time of an S0 mode component is measured based on a received waveform A by a transmission method of the guide wave on the upstream side of an internal fluid of the piping 1 and a received waveform B by the transmission method of the guide wave on the downstream side. A computation unit 16 calculates the plate thickness of a measurement unit with the arrival time and a plate thickness-speed diagram based on a waveform recording unit 13, transmitting and receiving position input unit 14, and a plate thickness-speed diagram memory 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nondestructive inspection method and a nondestructive inspection apparatus using a guide wave, and in particular, a nondestructive inspection method and a nondestructive inspection using a guide wave suitable for nondestructive inspection of a pipe having a double plate structure. Relates to the device.

  In piping constituting a power plant, chemical plant, etc., thinning due to corrosion or erosion may occur on the inner surface of the piping due to liquid or gas flowing inside the piping during long-term operation. Therefore, it is necessary to perform periodic inspections and monitoring, and to perform appropriate repairs as necessary. If the metal loss progresses, pipe breakage or through holes may be formed. In this case, fluid inside the pipe, such as liquid or steam, leaks and normal operation of the plant cannot be ensured. I do not get. For this reason, it is necessary to evaluate the soundness of the piping such as the thickness of the piping and the material state by a nondestructive inspection method, and to take measures such as replacement and repair of the piping as necessary.

  As a typical nondestructive inspection method, there is a thickness measurement method by an ultrasonic pulse reflection method defined in JIS Z 2355: 2005 (see Non-Patent Document 1). In general, a method using an ultrasonic thickness meter including an ultrasonic probe and a transmission / reception guide wave probe is used. The ultrasonic thickness meter transmits ultrasonic waves in the plate thickness direction of the pipe to be inspected, and the ultrasonic propagation time when the ultrasonic wave reflected by the pipe bottom surface is received by the ultrasonic probe and in the known material. The pipe thickness can be measured with high accuracy by the principle of obtaining the thickness using the ultrasonic velocity.

  On the other hand, in structures such as piping, when a strength higher than the conventional design strength is required due to changes in the use conditions of the structure, a double plate structure as shown in FIG. 2 is adopted and used. There is a case. FIG. 2 shows an example in which the reinforcing plate 3 is installed outside the pipe and only the end of the reinforcing plate is joined by welding 5. In such a structure, since a gap 6 is generated between the reinforcing plate 3 and the pipe 1, only the thickness of the reinforcing plate can be measured by the measurement using the ultrasonic thickness gauge, and the thinning 4 generated on the inner surface of the pipe. Detection and thickness measurement are not possible.

  On the other hand, as a thinning inspection method, there is an inspection technique using a guide wave which is a kind of ultrasonic wave. Guide wave inspection is characterized by the ability to inspect long distances and wide areas at once, but is generally used as a method for determining the presence or absence of defects such as thinning.

  The inspection using the guide wave will be briefly described with reference to FIG. A plurality of guide wave probes 2 are arranged in the pipe circumferential direction of the pipe 1. When an ultrasonic wave is transmitted from the guide wave probe 2 to the pipe 1, a guide wave is generated in the pipe 1, and this guide wave propagates in the pipe axis direction. Here, the guide wave has an infinite number of vibration modes, but only a specific vibration mode can be propagated by adjusting the transmission wave from the guide wave probe 2. If there is a discontinuous portion such as the thinning 4, the guide wave generates a reflected wave. The reflected wave is received by the guide wave probe 2 to determine whether or not the thinning has occurred. The discontinuous portion includes not only thinning but also welding and a pipe branching portion. These elements are the same as the effect of increasing the plate thickness due to the characteristics of the guide wave, and since the signal generated by these is large, the signal from the thinning 4 cannot be identified and the guide wave inspection may not be applied. .

  As a conventional inspection method using a guide wave, an inspection method using a guide wave transmission method is known (for example, see Patent Document 1). The inspection method using the guide wave transmission method measures the propagation time difference of each propagation mode on the basis of the change in the sound velocity of each propagation mode (S0 and A0) of the guide wave in the thinned portion. Next, it is a method in which the thickness of the plate is determined by checking the characteristic curve of the mode to obtain the thickness that causes the propagation time difference, and the thickness reduction is measured.

Patent No. 4094464

Japanese Industrial Standards JIS Z 2355: 2005 “Thickness measurement method by ultrasonic pulse reflection method”

  However, in the method described in Patent Document 1, if there is welding or a pipe branching portion, the sound speed changes due to these discontinuous portions also occur, and therefore there is uncertainty in the measured value.

  An object of the present invention is to provide a nondestructive inspection method using a guide wave that can measure the plate thickness without being affected by these discontinuous parts even in the case where there is a weld or a pipe branch part in an inspection using a guide wave. And providing a non-destructive inspection device.

(1) In order to achieve the above object, the present invention is a nondestructive inspection method using a guide wave of a pipe partially having a double plate structure, and guides the inspection target range of the pipe. A wave transmission / reception means is installed, a guide wave transmission condition is determined on the upstream side of the internal fluid of the pipe, a received waveform A is obtained by a transmission method of the guide wave on the upstream side of the internal fluid of the pipe, and the same conditions The received waveform B is obtained by the guide wave transmission method on the downstream side, the arrival time of the S0 mode component in the received waveform A and the received waveform B is measured, and the arrival time and the plate thickness under the two conditions are measured. -The thickness of the measurement part is calculated from the velocity diagram.
By this method, even when there is a weld or a pipe branching portion in the inspection using the guide wave, the plate thickness can be measured without being affected by these discontinuous portions.

  (2) In the above (1), preferably, a plurality of guide wave probes are arranged so as to surround the inspection target range, and the calculation processing is performed from the average plate thickness information between the probes in a plurality of pairs of probes. Thus, the spatial distribution of the plate thickness is calculated.

(3) Moreover, in order to achieve the said objective, this invention is a nondestructive inspection apparatus using the guide wave of the piping which has a double plate structure in part, Comprising: A guide wave is transmitted to a to-be-inspected object Transmitting section, receiving section for receiving a guide wave from the object to be inspected, waveform recording section for recording a reception signal at the receiving section, and transmission / reception position input for inputting the positions of the transmitting section and the receiving section , A plate thickness-velocity diagram storage unit for storing a plate thickness-speed relationship diagram representing the relationship between the plate thickness of the material and the speed change of the guide wave, and a calculation unit for calculating the plate thickness distribution of the object to be inspected And a display unit that displays the result of the calculation unit, the calculation unit is installed upstream of the internal fluid of the pipe, guide wave transmission and reception means so as to sandwich the inspection target range of the pipe, S0 mode measured from the received waveform A obtained by the guide wave transmission method The arrival time of the S0 mode component measured from the arrival time of the minute and the received waveform B obtained by the guide wave transmission method on the downstream side under the same conditions, and the plate thickness-velocity diagram storage unit The plate thickness of the measurement part is calculated from the plate thickness-velocity diagram.
With such a configuration, in the inspection using the guide wave, even when there is a weld or a pipe branch portion, the plate thickness can be measured without being affected by these discontinuous portions.

According to the present invention, in the inspection using a guide wave, even when there is a weld or a pipe branching portion, the plate thickness can be measured without being affected by these discontinuous portions.

It is a block diagram which shows the structure of the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is a cross-section figure of piping which has a reinforcement board structure. It is explanatory drawing of the general test | inspection using a guide wave. It is explanatory drawing of arrangement | positioning and the inspection method of a guide wave probe in the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is explanatory drawing of arrangement | positioning and the inspection method of a guide wave probe in the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is a flowchart which shows the content of the inspection method by the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is explanatory drawing of the plate | board thickness-speed diagram used with the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is explanatory drawing of the measurement waveform by the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention. It is explanatory drawing of the relationship between the plate | board thickness spatial distribution of the measurement result by the nondestructive inspection apparatus using the guide wave by one Embodiment of this invention, and the average plate | board thickness between probes. Description of the relationship between the average plate thickness between the transmitting guide wave probe for transmission and the receiving guide wave probe and the distance between the probes as a result of measurement by a nondestructive inspection apparatus using guide waves according to an embodiment of the present invention FIG. It is explanatory drawing of arrangement | positioning of the guide wave probe in the nondestructive inspection apparatus using the guide wave by other embodiment of this invention.

Hereinafter, the configuration and operation of a nondestructive inspection apparatus using a guide wave according to an embodiment of the present invention will be described with reference to FIGS. 1 and 4 to 10.
First, the configuration of the nondestructive inspection apparatus using the guide wave according to the present embodiment will be described with reference to FIG.
FIG. 1 is a block diagram showing a configuration of a nondestructive inspection apparatus using a guide wave according to an embodiment of the present invention.

  A plurality of transmission guide wave probes 2 a, 2 b, 2 c are installed on the outer periphery of the pipe 1. In addition, a plurality of receiving guide wave probes 2d, 2e, and 2f are installed on the outer periphery of the pipe 1. Here, since the transmission guide wave probes 2a, 2b and 2c have the same function and operation, the operation will be described with the transmission guide wave probe 2a as a representative in this example. Since the reception guide wave probes 2d, 2e, and 2f perform the same functions and operations, the operation is described with the reception guide wave probe 2d as a representative in this example. In the present embodiment, a case where three transmitting probes and three receiving probes are used will be described. However, the greater the number of probes, the higher the accuracy of the plate thickness measurement result.

  The guide wave transmission / reception device 8 enters the guide wave into the tube 1 and receives the guide wave from the tube 1. The guide wave transmission / reception device 8 includes a transmission / reception control device 10, a pulsar 11, and a receiver 12. The transmission / reception control device 10 has a function of transmitting and receiving a guide wave and transmitting a guide wave reception signal to the guide wave measurement result processing device 9.

  The transmission / reception control device 10 transmits a trigger signal to the pulser 11. When the pulsar 11 receives the trigger signal, an applied voltage is generated and transmitted to the transmission guide wave probe 2 a through the electric wire 18, and a guide wave is generated in the tube 1. The guide wave propagated through the tube 1 is received by the receiving guide wave probe 2d. The reception signal obtained by the reception guide wave probe 2 d is sent to the receiver 12, and then amplified and sent to the transmission / reception control device 10. The transmission / reception control device 10 transmits a reception signal from the receiver 12 to the guide wave measurement result processing device 9 and transmits a trigger signal for the next measurement to the pulser 11. In general, when there are m transmission probes and n reception probes, m × n processes are performed, and thus this process is performed in this example.

  The guide wave measurement result processing device 9 includes a waveform recording unit 13, a transmission / reception position input unit 14, a plate thickness-velocity diagram storage unit 15, and a calculation unit 16. The received waveform transmitted from the guide wave transmitting / receiving device 8 is stored in the waveform recording unit 13. The positions of the transmission guide wave probes 2a, 2b, and 2c and the reception guide wave probes 2d, 2e, and 2f are input from the transmission / reception position input unit 14. The plate thickness-velocity diagram storage unit 15 reads a plate thickness-velocity diagram as described later with reference to FIG. 6 based on the physical properties of the inspection object and the transmission frequency information used in the transmission / reception control device 10. The calculation unit 16 receives the received waveform stored in the waveform recording unit 13, the transmission guide wave probes 2a, 2b, 2c and the reception guide wave probes 2d, 2e, Based on the position 2f and the plate thickness-velocity diagram stored in the plate thickness-velocity diagram storage unit 15, the plate thickness of the inspection target range is calculated. The thickness distribution of the inspection target range calculated by the calculation unit 16 is displayed on the display device 17.

Next, the inspection method by the nondestructive inspection apparatus using the guide wave according to the present embodiment will be described with reference to FIGS.
4 and 5 are explanatory views of the arrangement and inspection method of the guide wave probe in the nondestructive inspection apparatus using the guide wave according to the embodiment of the present invention. 4 is a plan view, and FIG. 5 is a cross-sectional view. FIG. 6 is a flowchart showing the contents of an inspection method by a nondestructive inspection apparatus using a guide wave according to an embodiment of the present invention. FIG. 7 is an explanatory diagram of a plate thickness-velocity diagram used in a nondestructive inspection apparatus using a guide wave according to an embodiment of the present invention. FIG. 8 is an explanatory diagram of a waveform measured by a nondestructive inspection apparatus using a guide wave according to an embodiment of the present invention.

  First, when an inspection is started in step 100 of FIG. 6, measurement conditions are adjusted in step 101.

  As shown in FIGS. 4 and 5, a branch pipe 7 is connected to the pipe 1. A reinforcing plate 3 is attached to a place where the branch pipe 7 is connected for reinforcement. The reinforcing plate 3 is fixed to the pipe 1 by the welded portion 5. Here, when the flow from the branch pipe 7 joins the pipe 1, the thinned portion 4 may occur. Therefore, as shown in FIG. 4, in the pipe 1 having the reinforcing plate 3, the adjustment of the test condition is performed on the upstream side of the internal fluid having a low potential for occurrence of thinning.

  The transmission guide wave probes 2a, 2b, 2c and the reception guide wave probes 2d, 2e, 2f are installed so as to sandwich the object to be inspected (the place where the reinforcing plate 3 is provided). The position information is input to the measurement and transmission / reception position input unit 14. Thereafter, the transmission waveform and the transmission frequency are adjusted. Here, when there is welding, the effect of increasing the plate thickness is produced compared to when there is no welding, so frequency adjustment in consideration of the influence of the welded portion 5 is necessary.

  Next, in step 102 of FIG. 6, the upstream inspection object is measured. In this embodiment, since three guide wave probes for transmission and three guide wave probes for reception are used, as shown in step 102 of FIG. Transmission, reception by the reception guide wave probe 2d, transmission from the transmission guide wave probe 2a, reception by the reception guide wave probe 2e, and nine measurements are required. In step 103 of FIG. 6, the upstream side received waveform is stored in the waveform recording unit 13.

  Thereafter, in step 104 of FIG. 6, the downstream inspection object is measured. At this time, the installation positions of the transmission guide wave probes 2a ′, 2b ′, 2c ′ and the reception guide wave probes 2d′2e′2f ′ are symmetrical with respect to the branch pipe 7 as shown in FIG. To be. Then, as shown in step 104 of FIG. 6, it is transmitted from the transmission guide wave probe 2a ′, received by the reception guide wave probe 2d ′, and transmitted from the transmission guide wave probe 2a ′. Nine kinds of measurement are performed such as reception by the reception guide wave probe 2e ′. Then, in step 105 of FIG. 6, the downstream reception waveform is stored in the waveform recording unit 13.

  The processing after step 106 is a calculation in the guide wave measurement result processing device 9.

  Here, an example of a plate thickness-velocity diagram, which is a basis of plate thickness measurement using a guide wave, will be described with reference to FIG. This is a plate thickness-velocity diagram of the carbon steel material when the transmission frequency is 250 kHz.

  In general, a guide wave propagating through a plate has two modes (S0 mode and A0 mode) having different vibration forms. Here, it should be noted that in the range of the plate thickness of 5 to 10 mm, the sound speed change in the S0 mode is large, but in the A0 mode there is almost no sound speed change. Therefore, the A0 mode is not used for measuring the thickness change, and only the S0 mode may be used. That is, inspecting a plate material having a plate thickness of 10 mm and measuring a plate thickness change such as thinning may be performed by setting the transmission frequency to 250 kHz and paying attention to the arrival time caused by the sound speed change in the S0 mode.

  Therefore, in step 106 in FIG. 6, extraction of the S0 mode waveform component and measurement of the arrival time are performed.

  Here, the measurement waveform will be described with reference to FIG. FIG. 8 (a) is an image of the measurement waveform on the upstream side, and FIG. 8 (b) is an image of the measurement waveform on the downstream side. is there. In this case, since the sound speed of the S0 mode increases as the plate thickness decreases, if the distance between the transmitting and receiving guide wave probes is the same, the arrival time of the S0 mode component is faster due to the occurrence of thinning. Become. On the other hand, in the A0 mode, there is no difference in sound speed as described above in the setting range as shown in FIG. Therefore, the S0 mode can be extracted from the difference between FIGS. 8A and 8B, and the arrival times ta and tb of the S0 mode in FIGS. 8A and 8B can be measured.

  Next, in step 107 of FIG. 6, the thickness calculation that causes the arrival time difference is performed. Here, since the distance between the transmitting and receiving guide wave probes is known, the sound speeds va and vb in FIGS. 8A and 8B are obtained from the arrival times ta and tb in the S0 mode. When the sound velocities va and vb are collated with the plate thickness-velocity diagram shown in FIG. 7, the average plate thickness sa and sb between the probes in FIGS. 8A and 8B are obtained. Here, in the pipe having the reinforcing plate, the average plate thickness sa and sb include the influence of the welded portion 5, and thus the actual plate thickness change amount Δs = sa−sb is obtained by taking the difference between the two. . A value obtained by subtracting the plate thickness variation Δs from the plate thickness sn at the time of manufacture is obtained as an average plate thickness s = sn−Δs in the tube 1.

  It should be noted that the processing of step 106 and step 107 is performed by the number of conditions measured in the processing of step 102 and step 104 (9 patterns in this example).

  Then, reconstruction calculation processing is performed from the average plate thickness s in the tube 1 obtained in step 107 and the distance between the transmission / reception guide wave probes to obtain the spatial distribution of the plate thickness in the inspection target range. First, in step 108 of FIG. 6, the assumption of the spatial distribution of the plate thickness of the site to be inspected is performed. Next, in step 109 of FIG. 6, the average plate thickness si for each transmission-reception group with the assumed spatial distribution is calculated. Subsequently, in step 110 of FIG. 6, the assumed average plate thickness si obtained in step 109 is compared with the average plate thickness s obtained in step 107. If the error is within the allowable value, the assumed thickness distribution is determined in step 111 of FIG. However, if the error exceeds the allowable value, the assumption of the spatial distribution of the plate thickness is reset in step 108 of FIG.

  Here, the relationship between the spatial distribution of the plate thickness and the average plate thickness between the probes will be described with reference to FIG. FIG. 9 is an example of the spatial distribution of the pipe plate thickness assumed on the downstream side. The plate thickness is displayed in black and white shades, and the display lattice spacing is 0.1 m. Reference numerals 2a 'to 2c' denote transmission guide wave probes, and 2d 'to 2f' denote reception guide wave probes.

  FIG. 10 is a table summarizing the average plate thickness and the inter-probe distance between the transmitting guide wave probe and the receiving guide wave probe. The average plate thickness between the probes was calculated as the average value of the plate thickness of the lattice through which the straight line connecting the probes passes. From this result, it can be seen that the average plate thickness is different for each straight line connecting the probes. Here, regarding the average plate thickness between the probes, the result of the average plate thickness actually obtained by inspection (step 107) matches the result calculated from the assumed spatial distribution (step 109), or the error is an allowable value. If it is within the range, the assumed spatial distribution of the plate thickness is determined 111. The method shown here is a basic method of reconstruction operation, and a similar calculation method may be used for reconstruction.

  The obtained plate thickness and thinning depth are the average values between the transmitter and receiver, and when applied to locations where deep thinning or multiple thinnings are locally distributed, there is uncertainty in the measured value. However, as described above, this uncertainty can be eliminated by obtaining the spatial distribution.

  Thereafter, in step 112 of FIG. 6, an image of the plate thickness spatial distribution is displayed on the display device 17. The video is an image as shown in FIGS. With this display, the inspection is completed.

  In order to increase the accuracy of the plate thickness measurement result, it is possible to increase the number of probes and reduce the lattice spacing of the spatial distribution.

  With the non-destructive inspection device and non-destructive inspection method described above, even when there is welding or pipe branching in the inspection using guide waves, the plate thickness is measured without being affected by these discontinuities. it can.

Next, the configuration and operation of a nondestructive inspection apparatus using a guide wave according to another embodiment of the present invention will be described with reference to FIG. The configuration of the nondestructive inspection apparatus using the guide wave according to the present embodiment is the same as that shown in FIG.
FIG. 11 is an explanatory diagram of the arrangement of guide wave probes in a nondestructive inspection apparatus using a guide wave according to another embodiment of the present invention. The same reference numerals as those in FIGS. 1 and 4 indicate the same parts.

  The transmitting guide wave probes 2a, 2b, 2c and the receiving guide wave probes 2d, 2e, 2f sandwich the object to be inspected (location where the reinforcing plate 3 is provided) and in the flow direction. Install it diagonally. Then, the installation position is measured and the position information is input to the transmission / reception position input unit 14, and then the transmission waveform and the transmission frequency are adjusted.

  Then, the upstream inspection object is measured. In this embodiment, since three guide wave probes for transmission and three guide wave probes for reception are used, as shown in step 102 of FIG. Transmission, reception by the reception guide wave probe 2d, transmission from the transmission guide wave probe 2a, reception by the reception guide wave probe 2e, and nine measurements are required. In step 103 of FIG. 6, the upstream side received waveform is stored in the waveform recording unit 13.

  Next, in step 104 of FIG. 6, the downstream inspection object is measured. At this time, the installation positions of the transmission guide wave probes 2a ′, 2b ′, 2c ′ and the reception guide wave probes 2d′2e′2f ′ are set so as to sandwich the branch pipe 7 as shown in FIG. And installed in an oblique direction with respect to the flow direction. Then, as shown in step 104 of FIG. 6, it is transmitted from the transmission guide wave probe 2a ′, received by the reception guide wave probe 2d ′, and transmitted from the transmission guide wave probe 2a ′. Nine kinds of measurement are performed such as reception by the reception guide wave probe 2e ′. Then, in step 105 of FIG. 6, the downstream reception waveform is stored in the waveform recording unit 13.

  Subsequent processing is the same as step 106 to step 112.

  When the transmission / reception guide wave probe is arranged in an oblique direction with respect to the pipe axis direction of the pipe 1 as in the present embodiment, the thinned portion existing between the transmission / reception guide wave probes becomes one place. The distance between the transmitting and receiving probes is shortened. As a result, errors during measurement can be reduced. In the state shown in FIG. 11, the right side thinning portion 4 shown in the figure can be measured, but the left side thinning portion 4 shown in the figure cannot be measured. For example, the transmitting guide wave probe 2a It is necessary to measure from the direction rotated with respect to the installation direction of ', 2b', 2c 'and the receiving guide wave probe 2d'2e'2f'.

Even with the non-destructive inspection apparatus and the non-destructive inspection method of the present embodiment as described above, in the inspection using the guide wave, even if there is a weld or a pipe branching portion, it is not affected by these discontinuous portions. The plate thickness can be measured.

DESCRIPTION OF SYMBOLS 1 ... Tube 2 ... Ultrasonic probe, guide wave probe 2a, 2b, 2c, 2d, 2e, 2f ... Guide wave probe for transmission 2a ', 2b', 2c ', 2d', 2e ' 2f '... Receiving guide wave probe 3 ... Reinforcing plate 4 ... Thinning part 5 ... Welding part 6 ... Gap 7 ... Branch tube 8 ... Guide wave transmission / reception device 9 ... Guide wave measurement result processing device 10 ... Transmission / reception control device DESCRIPTION OF SYMBOLS 11 ... Pulser 12 ... Receiver 13 ... Waveform recording part 14 ... Transmission / reception position input part 15 ... Plate thickness-velocity diagram storage part 16 ... Calculation part 17 ... Display apparatus 18 ... Electric wire

Claims (3)

A nondestructive inspection method using a guide wave of a pipe having a double plate structure in part,
Install a guide wave transmitting / receiving means so as to sandwich the inspection target range of the pipe,
The guide wave transmission condition is determined on the upstream side of the internal fluid of the pipe, and the received waveform A is obtained by the transmission method of the guide wave on the upstream side of the internal fluid of the pipe.
Under the same conditions, obtain the received waveform B by the guide wave transmission method on the downstream side,
Measure the arrival time of the S0 mode component in the received waveform A and the received waveform B,
A nondestructive inspection method using a guide wave, characterized in that a plate thickness of a measurement part is calculated from an arrival time and a plate thickness-velocity diagram under the two conditions. In the nondestructive inspection method using the guide wave according to claim 1,
A plurality of guide wave probes are arranged so as to surround the inspection target range,
A nondestructive inspection method using a guide wave, characterized in that, in a plurality of pairs of probes, a spatial distribution of plate thicknesses is calculated by calculation processing from average plate thickness information between probes. A nondestructive inspection device using a guide wave of a pipe having a double plate structure in part,
A transmitter for transmitting a guide wave to the object to be inspected;
A receiver for receiving a guide wave from the object to be inspected;
A waveform recording unit for recording a reception signal at the reception unit;
A transmission / reception position input unit for inputting positions of the transmission unit and the reception unit;
A plate thickness-velocity diagram storage unit for storing a plate thickness-velocity relationship diagram representing the relationship between the plate thickness of the material and the velocity change of the guide wave;
A calculation unit for calculating the thickness distribution of the object to be inspected;
A display unit for displaying a result of the calculation unit;
The computing unit is
The arrival of the S0 mode component measured from the received waveform A obtained by the guide wave transmission method when the guide wave transmitting / receiving means is installed on the upstream side of the internal fluid of the pipe so as to sandwich the inspection target range of the pipe. Time,
The arrival time of the S0 mode component measured from the received waveform B obtained by the guide wave transmission method on the downstream side under the same conditions,
A nondestructive inspection apparatus using a guide wave, characterized in that a plate thickness of a measurement unit is calculated from a plate thickness-velocity diagram stored in the plate thickness-velocity diagram storage unit.

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