JP4686378B2 - Pipe inspection device - Google Patents

Description

The present invention relates to a pipe inspection apparatus for inspecting pipes used in power plants, chemical plants, and the like.

  In general, piping used in power plants, chemical plants, etc., when used for a long period of time, the thickness of the piping is reduced due to deterioration due to corrosion or erosion, eventually leading to an accident due to penetration or breakage of the piping wall. For this reason, the thickness of the pipe is measured, and if deterioration is recognized, repair such as replacement is required.

  Conventionally, nondestructive inspection using an ultrasonic thickness gauge has been performed as a representative means for measuring the thickness of the pipe. The ultrasonic thickness meter generally uses an ultrasonic transducer composed of a piezoelectric element that mutually converts electro-acoustics. This is a device that converts the time interval of received waves into thickness by receiving ultrasonic waves vertically into the target pipe and receiving elastic waves reflected from the bottom of the pipe with the same or another ultrasonic transducer. .

  However, although the measurement accuracy is high, the inspection range is almost the same as the size of the sensor, and when measuring the entire surface of a long pipe, there is a drawback that pretreatment such as extensive paint removal and a huge number of measurement points are required. there were.

  In order to eliminate these problems, Lamb waves (plate waves and guide waves) propagating along the pipe surface are made obliquely incident from the pipe surface instead of vertical ultrasonic waves and measured at once in the longitudinal direction of the pipe. A method is known (see, for example, Patent Document 1). This is a method that uses the velocity dispersion characteristic of Lamb waves, and obtains the average thickness of the propagation path from the propagation time by changing the speed of sound depending on the product of the thickness and frequency. .

  In the above method, the transmitting transducer is arranged in a ring shape at one end on the circumference of the pipe, and the receiving transducer is arranged in a ring shape at another end. For a Lamb wave excited from this transmitter transducer, multiple propagation paths, such as the shortest distance or spiral, are made to a certain receiver transducer based on the arrival time of the Lamb wave propagated at a certain propagation path distance. Discriminate. In this method, the thickness of a specific propagation path is calculated for each transducer, and a tomographic process is performed to obtain a two-dimensional distribution. However, since it is necessary to arrange a transducer around the circumference of the pipe, the structure of the apparatus is complicated.

  In addition, for nuclear fuel rods, ultrasonic waves are incident on the fuel cladding tube using a wedge-shaped transducer, and the component reflected by the defect while the Lamb wave (guide wave) propagates through the cladding tube is measured to determine the defect. A method is known (see, for example, Patent Document 2). However, it is intended for a thin plate, and has not been applied to a thick wall such as a pressure pipe.

  Furthermore, a method is known in which the corrosion depth is estimated by propagating the Lamb wave in the circumferential direction and changing the amplitude of the transmitted wave that goes around the pipe (for example, see Non-Patent Document 1). This uses the fact that part of the wave is reflected by corrosion and the transmitted wave amplitude is reduced. In this method, the apparatus is simplified as compared with the method of measuring the longitudinal direction, but it is necessary to perform measurement while moving in the axial direction.

  In the above-described apparatus using Lamb waves, waves of a plurality of modes having different sound speeds propagate simultaneously due to the dispersibility of the sound speed that is a characteristic of the Lamb waves. In the Lamb wave mode, there are higher-order modes in order from the A0 mode and the S0 mode. Since the speed of sound is determined by the product of the frequency f and the plate thickness d, it becomes difficult to identify the mode of the propagated Lamb wave if there are many modes for a certain f · d value. Therefore, it is common to use the S0 mode in which the influence of such superposition of each mode is small, and it is necessary to select a low frequency corresponding to this.

  In addition, although the thickness d of the piezoelectric element which is a general transducer is determined by the following (1) formula with respect to a frequency, it is known (for example, refer nonpatent literature 2).

d = c / (2 × f0) (1)
here,
c: Frequency constant, about 4000 m · S ^{−1 in} the case of lead zirconate titanate
As an example, when the thickness to be measured is about 10 mm, a frequency of about 200 kHz is appropriate in the S0 mode. Here, when the frequency is 200 kHz, the thickness of the piezoelectric element is 10 mm from the above equation (1). In addition, when a cylindrical element is considered, since it does not vibrate well unless the diameter is twice the thickness or more, the piezoelectric element has a diameter of 20 mm.
JP 2004-85370 A JP-A-11-281630 Nakamura et al., “About thinning inspection of exchange by cylindrical guide wave”, The Japan Society of Mechanical Engineers, No02-53 Symposium Proceedings, page 52 "Ultrasonic testing technology-theory and practice-", Japan Management Association

  In the conventional pipe inspection apparatus described above, an apparatus is used that propagates Lamb waves in the circumferential direction and estimates the corrosion depth based on the amplitude change of the transmitted wave that goes around the pipe. This device requires measurement while moving in the axial direction.

  However, when considering application to piping in plants where thermal efficiency is a problem, such as in power plants, this piping is covered with a heat insulating material, and in order to measure the wall thickness, a portion of the heat insulating material is removed. There was a problem that it was necessary to attach a transducer.

  In measurement during operation, it is effective to make the hole of the heat insulating material as small as possible so that the heat insulating effect is not reduced. However, mounting the transducer under the above conditions requires that the heat insulating material be largely removed. Therefore, there was a problem that it was difficult.

  Furthermore, even in the periodic inspection with the operation stopped, there is a problem that the work efficiency deteriorates because the heat insulating material is attached and detached one by one.

  The present invention has been made in order to solve the above-described problems. In the measurement of the pipe wall thickness in the longitudinal direction by Lamb waves, the heat insulating material is not largely removed even in a pipe covered with the heat insulating material with a simple apparatus configuration. It is an object of the present invention to provide a pipe inspection apparatus and method that can be attached to a pipe.

To achieve the above object, the present invention provides a pipe inspection apparatus for measuring the wall thickness of the pipe covered with heat insulating material using a Lamb wave, and an ultrasonic generator for generating ultrasonic waves and receives ultrasonic waves Ultrasonic wave receiving means and the heat insulating material penetrate the ultrasonic wave excited by the ultrasonic wave generating means and reach the pipe to excite the Lamb wave and propagate in the circumferential direction of the pipe and spiral in the longitudinal direction A first waveguide rod having a diameter smaller than the diameter of the ultrasonic wave generating means disposed so as to be obliquely incident at an angle shifted from the circumferential direction of the pipe so as to proceed to And a first conical horn for connecting the first waveguide rod, and receiving the ultrasonic wave arranged to receive the Lamb wave propagating from the first waveguide rod and penetrate the heat insulating material A second waveguide rod having a smaller diameter than the means, and the ultrasonic receiver Wherein the second conical horn for connecting the second waveguide rod, receiving the Lamb waves propagated through the second waveguide rod and said second conical horn received by said ultrasonic receiving means and And a thickness calculating means for converting the signal appearance time into thickness data using a Lamb wave velocity dispersion curve.

According to the pipe inspection apparatus of the present invention, it is possible to measure the thickness distribution in the longitudinal direction of the pipe and specify the approximate position of the defect.
Furthermore, since the pipe covered with the heat insulating material can be attached to the pipe without largely removing the heat insulating material, the work efficiency accompanying the pipe inspection can be improved. Moreover, in the plant in operation, the thickness of the pipe can be measured without affecting the thermal efficiency.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pipe inspection apparatus and method according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram showing a pipe inspection device according to a first embodiment of the present invention.

  As shown in the figure, an ultrasonic wave generating means 21 is provided at one end of the pipe 1 to be inspected. The ultrasonic wave generating means 21 has an ultrasonic wave transmitting element 3 arranged with an angle shifted with respect to the circumferential axis of the pipe 1. An ultrasonic oscillator 2 for driving the ultrasonic transmission element 3 is disposed.

  At the other end of the pipe 1, ultrasonic receiving means 22 is provided. The ultrasonic receiving means 22 includes an ultrasonic receiving element 5 arranged on the path of the propagated Lamb wave 10. An ultrasonic receiver 4 for receiving a signal received by the ultrasonic receiving element 5 is arranged.

  Further, a thickness calculating means 23 is provided for receiving the transmission signal of the ultrasonic oscillator 2 and the reception signal of the ultrasonic receiver 4 and calculating the thickness of the pipe 1. The thickness calculating means 23 includes an AD converter 6 that performs analog / digital (A / D) conversion processing on the transmission signal of the ultrasonic oscillator 2 and the reception signal of the ultrasonic receiver 4. Moreover, it has the time measurement part 7 which measures the time interval of each signal, and has the board thickness conversion part 8 which converts into the board thickness of the piping 1 from this measured time interval. Furthermore, it is comprised from the plate | board thickness display part 9 which displays the measurement result of this plate | board thickness.

  In the present embodiment configured as described above, the ultrasonic oscillation element 3 is an element that converts a drive signal applied from the ultrasonic oscillator 2 into a mechanical displacement, and is configured by, for example, a piezoelectric element. An adapter 24 is attached to the vibration surface of the ultrasonic oscillating element 3 so as to make an oblique angle incident at an angle so as to appropriately vibrate with a Lamb wave. Furthermore, it is attached on the surface of the pipe 1 with an arbitrary angle with respect to the circumferential axis of the pipe 1, and a wave is generated in such a direction that the Lamb wave 10 travels in a spiral manner in the longitudinal direction of the pipe 1. It arrange | positions so that it may inject.

  The ultrasonic receiving element 5 is an element that converts displacement due to the Lamb wave 10 propagating through the pipe 1 into electrical energy, and is configured by, for example, a piezoelectric element. An adapter 25 for efficiently receiving a Lamb wave at an appropriate angle is attached to the vibration surface of the ultrasonic receiving element 5. The adapter 25 is disposed on a path through which the Lamb wave 10 propagates in a spiral shape.

  The ultrasonic transmitter 2 includes an arbitrary waveform generator (not shown) that can arbitrarily set the frequency of the transmission signal 2a, and a power amplifier (not shown) that amplifies the signal. The generated signal can be controlled by the control signal from the time measuring unit 7. Conversely, the trigger signal from the ultrasonic oscillator 2 may be received by the time measuring unit 7.

  The ultrasonic receiver 4 is composed of a commercially available ultrasonic receiver (not shown) or a broadband amplifier (not shown), and the signal 5 a from the ultrasonic receiving element 5 is received and output to the AD converter 6. To be connected. The AD converter 6 may be a commercially available oscilloscope (not shown) or a computer built-in board type converter (not shown). The time measuring unit 7, the plate thickness converting unit 8, and the plate thickness display unit 9 can be processed on a program using a commercially available personal computer (not shown) or the like.

  Here, the dispersibility of the sound speed of the Lamb wave in the steel plate will be described. FIG. 2 explains the dispersibility of the sound speed of the Lamb wave in the steel plate, and is a characteristic diagram showing the relationship between plate thickness × frequency and sound speed, that is, a Lamb wave velocity dispersion curve. In addition to the theoretical group velocity when propagating the circular pipe model described in Non-Patent Document 1 above, based on the sound velocity graph of the plate wave in steel described in Non-Patent Document 2, the plate thickness × frequency and The relationship of sound speed is required.

  As an example, the angle between the ultrasonic transmission element 3 and the circumferential axis of the pipe 1 is adjusted so that the helical pitch of the Lamb wave 10 propagating on the pipe 1 becomes the same size as the ultrasonic transmission element 3. Keep it. When the Lamb wave 10 is excited in the pipe 1 by the ultrasonic wave generating element 3 driven by the ultrasonic oscillator 2, the Lamb wave 10 is spirally passed through the thickness of the pipe 1 at a pitch adjusted in advance. Will propagate.

  Moreover, as shown in this figure, the way of propagation of the Lamb wave varies depending on the product of the plate thickness and the frequency. There are also a plurality of vibration modes (s0, s1... Or a0, a1...). In the higher-order mode of s1 or higher, a plurality of mode waves are superimposed and it is difficult to identify which mode wave, so attention is paid to the s0 mode. At this time, the vicinity of the plate thickness × frequency = 1 to 2 corresponding to the region where the change in the sound speed in the s0 mode is large is set as the frequency setting region.

  When the thickness of the pipe 1 is 6 mm, a thickness corresponding to the speed of sound can be obtained by exciting a Lamb wave of about 200 kHz. The average thickness on the propagation path can be obtained by propagating the Lamb wave at a known frequency and obtaining the sound velocity of the signal. In addition, if there is a portion where the wall thickness has decreased on the way in the middle, the sound speed will increase accordingly.

  Furthermore, a propagation path covering a wide area can be taken by propagating spirally.

  On this propagation path, the ultrasonic wave receiving element 5 attached at the same angle with respect to the circumferential axis as the ultrasonic wave generating element 3 can receive the propagated Lamb wave 10. In addition, the reception data digitized by the AD converter 6 via the ultrasonic receiver 4 is sent to the time measuring unit 7, where the difference between the transmission time and the reception time is obtained, thereby obtaining the spiral path length. The speed of sound is calculated. Further, the plate thickness conversion unit 8 converts the sound speed into an average thickness from the ultrasonic transmission element 3 to the ultrasonic reception element 5 with reference to the velocity dispersion curve. This average thickness is displayed on the plate thickness display section 9. Further, if there is a defect in the thickness portion in the longitudinal direction of the pipe, the approximate position of the defect can be specified by obtaining the reduced thickness portion.

  According to the present embodiment, the ultrasonic wave generating means arranged to be obliquely incident so that the Lamb wave propagates in the circumferential direction of the pipe and spirals in the longitudinal direction is provided, and propagates in this spiral shape. By providing the ultrasonic wave receiving means for receiving the Lamb wave propagating on the path, the thickness distribution measurement in the longitudinal direction of the pipe and the approximate position of the defect can be specified. That is, it is possible to measure the thickness in the longitudinal direction of the pipe with a pair of transmission / reception units without arranging a large number of transducers in a cylindrical shape. Furthermore, since the pipe covered with the heat insulating material can be attached to the pipe without largely removing the heat insulating material, the work efficiency accompanying the pipe inspection can be improved.

  FIG. 3 is a configuration diagram showing a pipe inspection apparatus according to the second embodiment of the present invention. In the present embodiment, conical horns 11 and 12 are provided instead of the adapters 24 and 25 for oblique incidence of the first embodiment, and the same or similar parts as the first embodiment. A common reference numeral is assigned to each to omit redundant description.

  As shown in the figure, the basic configuration is the same as that of the first embodiment. A transmission horn 11 formed from a conical horn as transmission transmission means is provided at the tip of the ultrasonic transmission element 3. Further, a reception horn 12 formed from a conical horn conical horn as reception transmission means is also provided at the tip of the ultrasonic receiving element 5.

  The kind of said conical horns 11 and 12 is not specifically limited. FIG. 4 is a front view showing the structure of the conical horn of FIG. 3, and FIG. 5 is a front view showing a modification of the structure of the conical horn of FIG.

  As shown in the figure, as an example, a conical conical horn 26 is provided at the tip of the ultrasonic transmission element 3 or the ultrasonic reception element 5. Alternatively, the wedge-shaped adapter 15 is attached to the tip of the conical horn 26 via the waveguide rod 14.

  The pipe 1 is covered with a heat insulating material 13. A transmission horn 11 is disposed at one end of the pipe 1 at an angle with respect to the circumferential axis of the pipe 1 through the heat insulating material 13. A receiving horn 12 is provided at the other end of the pipe 1 so as to be on the path of the propagated Lamb wave.

  In the present embodiment, first, the vibration generated by the ultrasonic generator 3 by being driven by the ultrasonic oscillator 2 is transmitted to the transmitting horn 11 disposed on the vibration surface of the ultrasonic generator 3.

  In general, a horn is used as a mechanical transformer that transforms vibration speed, vibration force, and mechanical impedance, and a large vibration speed can be obtained at the narrow end of the horn without fatigue of the vibrator. It is also used as an impedance matching unit that enables the vibrator to be used in an efficient state. As typical types of horns, there are an exponential shape, a conical shape, a catenoidal shape, a uniform step shape and the like, and there are also shapes in which these shapes are combined.

  The size of the horn is determined by the size of the ultrasonic wave generating element, the shape of the horn, and the vibration characteristics. When the frequency f0 of 200 kHz is used from the s0 mode curve of FIG. 2, the thickness d of the ultrasonic wave generating element is determined by the following equation (2).

d = c / (2 × f0) (2)
here,
c: speed of sound in piezoelectric element crystal, speed of sound 4000 in the case of lead zirconate titanate
m · S ^-1
As an example, when a pipe wall thickness of 6 mm is measured, the thickness d of the ultrasonic wave generating element is 10 mm. When the ultrasonic generating element is cylindrical, the diameter of the ultrasonic generating element is 20 mm because the diameter is empirically required to be twice or more the thickness in order to vibrate.

  The diameter of the hole that can be opened in the heat insulating material 13 is 5 mm, and the thickness of the heat insulating material 13 is 50 mm. When the conical horn 26 is formed in the conical shape shown in FIG. 4, the diameter of the end face on the pipe side is 1 mm. The total length l of the conical horn 26 is determined by solving the following frequency equation (3).

tankl = ((K−1) ² kl) / ((kl) ² · K + (K−1) ² ) (3)
here,
K = √ (S2 / S1), k = ω / c
S1: Area on the pipe side end surface S2: Area on the ultrasonic generator side ω: Angular velocity c: Sound velocity Under the above conditions, the total length is about 241 mm as an example of a solution when aluminum is used as the material of the conical horn 26. In the combination of the conical horn 26 and the waveguide rod 14 of FIG. 5, when the waveguide rod has a diameter of 5 mm and penetrates the heat insulating material, the length of the waveguide rod 14 is about 57 mm. The length of the conical horn 26 is about 15 mm. Vibration is propagated to the surface of the pipe 1 by the wedge-shaped adapter 15 provided at the tip of the waveguide rod 14, and a Lamb wave is excited on the surface of the pipe. Since the transmission horn 11 is arranged at a different angle with respect to the circumferential axis of the pipe 1, the Lamb wave 10 shown in FIG.

  A similar conical horn 26 is also provided on the reception side, and the reception signal is transmitted to the ultrasonic reception element through the heat insulating material 13, and the plate thickness is converted from the arrival time of the reception wave.

According to the present embodiment, by providing the conical horn 26, it is possible to measure the thickness distribution in the longitudinal direction of the pipe and specify the approximate position of the defect. That is, it is possible to measure the thickness in the longitudinal direction of the pipe with a pair of transmission / reception units without arranging a large number of transducers in a cylindrical shape. Furthermore, since the pipe covered with the heat insulating material can be attached to the pipe without largely removing the heat insulating material, the work efficiency accompanying the pipe inspection can be improved. In the plant in operation, it is possible to measure the thickness of a Ku pipe affecting the thermal efficiency.

  FIG. 6 is a block diagram showing a pipe inspection apparatus according to the third embodiment of the present invention. In the present embodiment, an amplitude measuring unit 16 is added to the second embodiment, and the same or similar parts as those in the second embodiment are denoted by common reference numerals, thereby overlapping. Description is omitted.

  As shown in the figure, the basic configuration is the same as that of the first embodiment and the second embodiment. An amplitude measuring unit 16 that measures the waveform amplitude of the received waveform is provided. Furthermore, a plate thickness conversion unit 8 is provided for calculating the defect depth on the propagation path with reference to the relationship between the measured amplitude change and the defect depth.

  In this embodiment, first, in the process in which the Lamb wave 10 excited in the pipe 1 propagates, if there is a defect due to corrosion or the like on the inner surface of the pipe on the propagation path, a part of the wave is reflected and the transmitted wave amplitude is increased. Get smaller. According to Non-Patent Document 1 described above, it has been confirmed that a defect on the inner surface of a tube can be measured with a Lamb wave by measuring the transmission amplitude.

  FIG. 7 is a characteristic diagram showing changes in the ratio of the defect depth to the pipe thickness and the amplitude. As shown in this figure, the change in amplitude is shown when the ratio of the defect depth to the thickness of the pipe 1 is 0, 0.33, 0.5, and 0.66, respectively. The amplitude of the transmitted wave decreases in proportion to

  The amplitude measurement unit 16 measures the amplitude of the received wave that has propagated. In the plate thickness conversion unit 8 which measures and stores the relationship between the amplitude change and the defect depth, the pipe thickness is calculated by the difference from the amplitude when there is no defect.

  According to the present embodiment, by providing the amplitude measuring unit 16, it is possible to measure the wall thickness of the pipe with higher accuracy by using the defect measurement based on the transmitted wave amplitude together with the average wall thickness measurement based on the sound velocity. It becomes.

  FIG. 8 is a block diagram showing a pipe inspection apparatus according to the fourth embodiment of the present invention. In this embodiment, a plurality of receiving horns 12 according to the second embodiment are provided, and the same or similar parts as those in the second embodiment are denoted by common reference numerals, and a duplicate description is given. Omitted.

  As shown in the figure, the basic configuration is the same as that of the first embodiment and the second embodiment. In the present embodiment, the ultrasonic receiving element 5, the reception horn 12 that is a reception transmission means, and the reception receiver 4 are configured by providing a plurality of channels from 1 ch to nch. The receiving horns 12 and the ultrasonic receiving elements 5 of the respective channels are arranged on the propagation path of the Lamb wave 10 with a certain distance from the longitudinal direction of the pipe. Each channel in the reception receiver 4 is connected to AD converters 6 for n channels.

  In the present embodiment, first, the Lamb wave 10 excited in the pipe 1 by the ultrasonic wave generating element 3 and the transmission horn 11 propagates in a spiral shape in the pipe longitudinal direction at a preset angle. The signals are received in the order in which they are arranged by a plurality of receiving horns 12 and ultrasonic receiving elements 5 arranged on this propagation path. At this time, a reception signal first appears in ch 1 arranged at the shortest distance, and thereafter, a reception signal appears in each channel for each arrival time expressed in order of propagation distance / sound speed. In the time measuring unit 7, the sound speed between the channels is converted by measuring the appearance time of the reception signal of each channel. Further, the average wall thickness between each channel is obtained by converting the sound speed between the channels with reference to the velocity dispersion curve. It is also possible to provide at least one ultrasonic receiving element 5 and switch the ultrasonic receiving element 5 to use.

  According to this embodiment, by providing the ultrasonic receiving elements 5 and the receiving horns 12 for a plurality of channels, Lamb waves can be grasped at a plurality of receiving locations, and the thickness distribution measurement in the longitudinal direction of the pipe can be performed. It is possible to improve the accuracy of specifying the approximate position of the defect.

  Furthermore, the present invention is not limited to the embodiments described above, and may be changed to a combination of an adapter and a conical horn, and various modifications may be made without departing from the spirit of the present invention. Can be implemented.

The lineblock diagram showing the piping inspection device of a 1st embodiment of the present invention. The characteristic view which demonstrates the dispersibility of the sound velocity of the Lamb wave in a steel plate, and shows the relationship between board thickness x frequency and sound velocity. The block diagram which shows the piping inspection apparatus of the 2nd Embodiment of this invention. The front view which shows the structure of the conical horn of FIG. The front view which shows the structure of the modification of the conical horn of FIG. The block diagram which shows the piping inspection apparatus of the 3rd Embodiment of this invention. The characteristic view which shows the change of ratio of the defect depth with respect to pipe thickness, and an amplitude. The block diagram which shows the piping inspection apparatus of the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Piping, 2 ... Ultrasonic oscillator, 3 ... Ultrasonic transmission element, 4 ... Ultrasonic receiver, 5 ... Ultrasonic reception element, 6 ... AD converter, 7 ... Time measuring part, 8 ... Thickness conversion part, 9 DESCRIPTION OF SYMBOLS ... Thickness display part, 10 ... Lamb wave, 11 ... Transmission horn, 12 ... Reception horn, 13 ... Insulation material, 14 ... Waveguide rod, 15 ... Wedge-shaped adapter, 16 ... Amplitude measurement part, 21 ... Ultrasonic wave generation means, 22 ... Ultrasonic wave receiving means, 23 ... Thickness calculating means, 24, 25 ... Adapter, 26 ... Conical horn.

Claims (3)

In a pipe inspection device that measures the wall thickness of a pipe covered with a heat insulating material using Lamb waves,
An ultrasonic wave generating means for generating an ultrasonic wave;
Ultrasonic receiving means for receiving ultrasonic waves;
The ultrasonic wave penetrating through the heat insulating material, the ultrasonic wave excited by the ultrasonic wave generation means reaches the pipe, excites Lamb waves, propagates in the circumferential direction of the pipe, and spirals in the longitudinal direction. A first waveguide rod having a diameter smaller than the diameter of the ultrasonic wave generating means arranged to be obliquely incident at an angle shifted from the circumferential direction of the pipe;
A first conical horn for connecting the ultrasonic wave generating means and the first waveguide rod;
A second waveguide rod that is arranged to receive the Lamb wave propagating from the first waveguide rod and penetrate the heat insulating material, and having a diameter smaller than that of the ultrasonic wave receiving means;
A second conical horn for connecting the ultrasonic wave receiving means and the second waveguide rod;
Meat for converting Lamb waves propagating through the second waveguide rod and the second conical horn from the appearance time of the received signal received by the ultrasonic wave receiving means into wall thickness data using a Lamb wave velocity dispersion curve. A thickness calculating means;
A pipe inspection apparatus characterized by comprising: Transmitted wave amplitude measuring means for measuring the waveform amplitude of the received Lamb wave, and thickness calculating means for converting into thickness data using the relationship between the amplitude change measured by the transmitted wave amplitude measuring means and the defect depth; The piping inspection device according to claim 1 , comprising: A plurality of reception transmission means provided on the propagation path of the Lamb wave and including the second waveguide rod and the second conical horn, and a Lamb wave propagating through the reception transmission means is received as a reception signal. A plurality of ultrasonic receiving means, and a wall thickness calculating means that is converted from the appearance time of the reception signal of the ultrasonic receiving means to the wall thickness data of the section divided by the position where each ultrasonic receiving means is provided, The piping inspection device according to claim 1, comprising:

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