JP2012098226A - Pipe inspection method, pipe inspection device and electromagnetic ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily confirm soundness of an electromagnetic ultrasonic sensor transmitting and receiving a guided wave and calibrate sensitivity thereof in an inspection of a pipe wall-thickness reduction or the like.SOLUTION: A pipe inspection method comprises steps of: detecting echo current in an axial direction generated at a coil by a guided wave reflected and returned by disposing an electromagnetic ultrasonic sensor such that a magnetic pole opposes to a pipe 30 and that a coil axis is oriented toward a circumferential direction of the pipe 30 and by generating the guided wave propagated in an axial direction of the pipe 30 by causing AC current to flow through the coil; detecting a circular echo current generated at the coil by the guided wave returned without being reflected by disposing the electromagnetic ultrasonic sensor such that the magnetic pole opposes to the pipe 30 and that the coil axis is oriented toward the axial direction of the pipe 30 and by generating the guided wave propagated in the circumferential direction of the pipe 30 by causing AC current to flow through the coil; calibrating sensitivity of the electromagnetic ultrasonic sensor based on the circular echo current obtained in a step of detecting the circular echo current.

Description

  The present invention relates to an electromagnetic ultrasonic sensor, and a pipe inspection method and a pipe inspection apparatus using the same.

  In pipes laid in various plants, there may be a portion where the pipe plate thickness becomes thin due to the progress of corrosion, that is, a thinned portion after a certain period of time has elapsed after laying. Therefore, the maintenance worker performs plate thickness measurement with an ultrasonic thickness gauge in order to inspect the occurrence of such a thinned portion in the maintenance work performed regularly or irregularly. This inspection is performed by removing the heat insulating material attached to the outer periphery of the pipe that is the object to be inspected, bringing the ultrasonic sensor into direct contact with the outer surface of the pipe, acquiring the ultrasonic signal, and analyzing the acquired signal. This is a method for obtaining the thickness. In the calibration method, a calibration test body made of the same material as the object to be inspected and having a known plate thickness is used, and sensitivity calibration is performed on the basis of an ultrasonic signal from the calibration test body.

  In contrast, in recent years, inspection methods and apparatuses using ultrasonic waves called guide waves or guide waves have been proposed. The guide wave method is a method of inspecting the presence or absence of a thinned portion and the plate thickness by generating an ultrasonic wave propagating in the axial direction of a pipe and analyzing a reflected echo reflected and returned at a thinned portion. Although it is necessary to remove the heat insulating material at the sensor installation location, there is a feature that it is possible to inspect the presence or absence of thinning over a wide range of several tens of meters from the sensor installation position without removing the heat insulation material other than the installation location.

  However, a calibration method for the guide wave method has not been established. In general, calibration is performed using a test specimen for calibration of the same material as the inspection object, as in the case of thickness inspection using a thickness gauge. However, in the method using the calibration test specimen, It is necessary to manufacture a test specimen for calibration, and when large-diameter pipes are to be inspected, it is necessary to transport, process, store, and manage the pipes of the same material, which requires enormous time and cost. The problem arises.

  In Patent Document 1, a reflecting member that forcibly reflects a guide wave propagating through a pipe is installed on the outer surface or inner surface of the pipe, and the sensor sensitivity and the size of the thinning are set based on the signal amplitude from the reflecting member. What to estimate is described. A metallic block, a magnet, or the like is used as the reflecting member, and the installation position is a position away from the ultrasonic sensor in the pipe axis direction, and is provided in a part or a plurality of parts with respect to the pipe circumferential direction.

  Patent Document 2 uses an ultrasonic sensor for inspection used for measurement and an ultrasonic sensor for calibration, and acquires an ultrasonic sensor for inspection based on an acquisition signal of the ultrasonic sensor for calibration. What calibrates the signal is disclosed.

JP 2009-293981 A JP 2009-236620 A

  Each of the methods described in Patent Documents 1 and 2 is a method that can be calibrated without using a calibration specimen. However, Patent Document 1 has a problem that incidental work such as installation and removal of a reflecting member occurs. In Patent Document 2, since it is necessary to prepare an ultrasonic sensor for calibration, there is a problem that the sensor cost increases.

  An object of the present invention is to make it possible to easily check the soundness and calibrate sensitivity of an electromagnetic ultrasonic sensor in inspections such as pipe thinning using a guide wave.

  In order to achieve the above object, according to one aspect of the pipe inspection method of the present invention, a first magnetic pole is formed at a first end, and a second magnetic pole is formed at the opposite side of the first end. And a coil wound around the permanent magnet around a coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole. A pipe inspection method for inspecting a pipe wall of a pipe by transmitting and receiving a guide wave that is an ultrasonic wave propagating in the pipe wall of the pipe, wherein the first magnetic pole faces a part of the pipe wall surface of the pipe, and The electromagnetic ultrasonic sensor is disposed so that the coil axis faces the circumferential direction of the pipe, and a guide wave propagating in the pipe wall direction of the pipe is generated by flowing an alternating current through the coil. Guide that has propagated in the pipe wall direction of the pipe and reflected back An axial echo detection step for detecting an axial echo current generated in the coil by the step, the first magnetic pole so as to face a part of the pipe wall surface of the pipe, and the coil axis to face the pipe axis direction of the pipe. The electromagnetic ultrasonic sensor is disposed on the coil and an alternating current is passed through the coil to generate a guide wave that propagates in the pipe wall in the circumferential direction, and propagates in the pipe wall in the circumferential direction. A circular echo detection step for detecting a circular echo current generated in the coil by the guide wave returned without being reflected, and a sensitivity of the electromagnetic ultrasonic sensor based on the circular echo current obtained in the circular echo detection step A calibration step for calibrating, an axial echo current obtained by the axial echo detection step, and the electromagnetic ultrasonic sensor obtained by the calibration step. Piping evaluation step of evaluating the state of the pipe wall of the pipe based on the sensitivity of the service, and having a.

  Another aspect of the pipe inspection method according to the present invention includes a permanent magnet in which a first magnetic pole is formed at a first end and a second magnetic pole is formed on the opposite side of the first end, A coil wound around the permanent magnet around a coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole is propagated in the pipe wall of the pipe using an electromagnetic ultrasonic sensor. A pipe inspection method for inspecting a pipe wall of a pipe by transmitting and receiving a guide wave which is an ultrasonic wave, wherein the first magnetic pole faces a part of a pipe wall surface of the pipe, and the coil shaft is a pipe of the pipe. The electromagnetic ultrasonic sensor is arranged so as to face the axial direction, and an alternating current is passed through the coil to generate a guide wave propagating in the pipe wall direction of the pipe in the pipe axial direction. Is guided to the coil by the guide wave that propagates in the direction of the pipe axis and returns after reflection. An axial echo detection step for detecting an axial echo current, and the electromagnetic superposition so that the first magnetic pole faces a part of a pipe wall surface of the pipe and the coil axis faces the circumferential direction of the pipe. An acoustic wave sensor is arranged and an alternating current is passed through the coil to generate a guide wave that propagates in the pipe wall in the circumferential direction, and propagates and reflects in the pipe wall in the circumferential direction. A round echo detection step for detecting a round echo current generated in the coil by the returned guide wave, and determining the soundness of the electromagnetic ultrasonic sensor based on the round echo current obtained in the round echo detection step Sensor health determination step, the axial echo current obtained by the axial echo detection step, and the electromagnetic supersonic wave obtained by the sensor health judgment step Piping evaluation step of evaluating the state of the pipe wall of the pipe based on the soundness of the determination result of the sensor, and having a.

  Another aspect of the pipe inspection method according to the present invention includes a permanent magnet in which the first magnetic pole and the second magnetic pole are directed in opposite directions, and a straight line connecting the first magnetic pole and the second magnetic pole. A first coil wound around the permanent magnet around a vertical first coil axis, and perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole, and perpendicular to the first coil axis And a second coil wound around the permanent magnet around the second coil axis, and using an electromagnetic ultrasonic sensor, a guide wave which is an ultrasonic wave propagating in the pipe wall of the pipe A pipe inspection method for transmitting and receiving and inspecting a pipe wall of a pipe, wherein the first magnetic pole faces a part of a pipe wall surface of the pipe, and the first coil axis faces a circumferential direction of the pipe. The electromagnetic ultrasonic sensor is arranged so that the second coil axis faces the pipe axis direction of the pipe. A sensor placement step, and after the sensor placement step, an alternating current is passed through the first coil to generate a guide wave propagating in the pipe wall direction of the pipe in the pipe axis direction. An axial echo detection step for detecting an axial echo current generated in the first coil by a guide wave that propagates in the pipe axis direction and is reflected and returned, and after the sensor placement step, the second coil By causing an alternating current to flow, a guide wave propagating in the circumferential direction in the pipe wall of the pipe is generated, and the guide wave propagated in the circumferential direction in the pipe wall of the pipe and returned without reflection. A circular echo detection step for detecting a circular echo current generated in the second coil; and the electromagnetic ultrasonic sensor based on the circular echo current obtained in the circular echo detection step. A state in the pipe wall of the pipe based on the calibration step for calibrating the degree, the axial echo current obtained by the axial echo detection step, and the sensitivity of the electromagnetic ultrasonic sensor obtained by the calibration step. And a pipe evaluation step to be evaluated.

  One aspect of the pipe inspection apparatus according to the present invention is a pipe inspection apparatus having an electromagnetic ultrasonic sensor that transmits and receives a guide wave that is an ultrasonic wave traveling inside a pipe wall of the pipe, and the electromagnetic ultrasonic sensor includes: A permanent magnet disposed such that the first magnetic pole faces a part of the pipe wall surface of the pipe and the second magnetic pole faces away from a part of the pipe wall surface; the first magnetic pole and the second magnetic pole; A first coil wound around the permanent magnet around a first coil axis perpendicular to a straight line connecting the magnetic poles of the first magnetic pole, a perpendicular to the straight line connecting the first magnetic pole and the second magnetic pole, and the first coil A second coil wound around the permanent magnet around a second coil axis perpendicular to the first coil axis so that an alternating current can be supplied to the first coil and the second coil It is comprised by these.

  One aspect of the electromagnetic ultrasonic sensor according to the present invention is an electromagnetic ultrasonic sensor that transmits and receives a guide wave, which is an ultrasonic wave traveling inside a pipe wall of a pipe, wherein the first magnetic pole is a pipe wall surface of the pipe. A permanent magnet disposed so as to face a part and the second magnetic pole faces away from a part of the wall surface of the tube, and a first perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole A first coil wound around the permanent magnet around a coil axis, and a second coil perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole and perpendicular to the first coil axis And a second coil wound around the permanent magnet around an axis.

  According to the present invention, soundness confirmation and sensitivity calibration of an electromagnetic ultrasonic sensor can be easily performed in inspections such as pipe thinning using a guide wave.

It is a schematic diagram which shows the state at the time of transmission of the electromagnetic ultrasonic sensor of the piping inspection apparatus which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the state at the time of reception of the electromagnetic ultrasonic sensor of FIG. It is a perspective view which shows the condition which transmits / receives an ultrasonic wave to the axial direction of piping used as a test object using the electromagnetic ultrasonic sensor of FIG. It is a time chart which shows the example of a received signal when transmitting / receiving an ultrasonic wave to the axial direction of piping shown in FIG. It is a perspective view which shows the condition which transmits / receives an ultrasonic wave in the circumferential direction of piping used as a test object using the electromagnetic ultrasonic sensor of FIG. It is a time chart which shows the example of a received signal when transmitting and receiving an ultrasonic wave in the circumferential direction of piping shown in FIG. It is a graph which shows the relationship between the amplitude level in the piping inspection method using the piping inspection apparatus which concerns on the 1st Embodiment of this invention, and the thickness reduction size. It is a graph which shows the relationship between the propagation time of an ultrasonic echo, and an amplitude level in the pipe inspection method using the pipe inspection apparatus which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure and effect | action of an electromagnetic ultrasonic sensor of the piping inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the condition which transmits / receives an ultrasonic wave to the axial direction of piping used as a test object using the electromagnetic ultrasonic sensor of FIG. It is the schematic diagram which looked at the electromagnetic ultrasonic sensor of FIG. 9 from the X-axis direction. It is a perspective view which shows the condition which transmits / receives an ultrasonic wave in the circumferential direction of piping used as a test object using the electromagnetic ultrasonic sensor shown in FIG. 9 and FIG. It is a perspective view which shows the condition which transmits / receives an ultrasonic wave to the axial direction and circumferential direction of piping used as a test object using the piping inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a top view which shows the condition which transmits the ultrasonic wave to piping used as inspection object using the piping inspection apparatus which concerns on the 2nd Embodiment of this invention, Comprising: The figure which shows the case where an ultrasonic wave is transmitted to the circumferential direction of piping. It is. It is a top view which shows the condition which transmits the ultrasonic wave to piping used as inspection object using the piping inspection device concerning a 2nd embodiment of the present invention, Comprising: It is a figure which shows the case where it transmits. It is a graph which shows the relationship between the frequency | count of a circumference echo in the situation of FIG. 14 and FIG. 15, and a circumference echo level. It is the schematic diagram which looked at the condition which attached the piping inspection apparatus which concerns on the 3rd Embodiment of this invention to piping from the pipe-axis direction. It is the schematic diagram which looked at the condition which attached the piping inspection apparatus which concerns on the 4th Embodiment of this invention to piping from the pipe-axis direction. It is the schematic diagram which looked at the condition which attached the piping inspection apparatus which concerns on the 5th Embodiment of this invention to piping from the piping-axis direction. It is a graph which shows the example of the output waveform of each electromagnetic ultrasonic sensor of the piping inspection apparatus which concerns on the 5th Embodiment of this invention.

  Hereinafter, embodiments of 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.

[First Embodiment]
A pipe inspection apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram illustrating a state at the time of transmission of an electromagnetic ultrasonic sensor of a pipe inspection apparatus according to the first embodiment of the present invention. The electromagnetic ultrasonic sensor 1 includes a permanent magnet 2 and a coil 3. The permanent magnet 2 is magnetized in the direction from the outer peripheral surface to the inner peripheral surface of the pipe 30, and in FIG. 1, the side closer to the wall surface of the pipe 30 is the N pole and the far side is the S pole. A plurality of coils 3 are wound around the permanent magnet 2 around a coil axis 50 perpendicular to a line connecting the N pole and the S pole of the permanent magnet 2. An alternating voltage 4 can be applied to the coil 3 by applying an alternating voltage.

  A magnetic flux 6 indicated by a hollow arrow is applied to the pipe 30 by the permanent magnet 2, but when an alternating current 4 is passed through the coil 3, an eddy current 7 is induced on the surface of the pipe 30. If the direction of the eddy current 7 is the depth direction as shown in FIG. 1, the magnetic flux 6 and the eddy current 7 are orthogonal to each other. Therefore, the Lorentz force 8 is applied to the pipe 30 in the direction indicated by the black arrow according to Fleming's left-hand rule. appear. Since this Lorentz force 8 is generated by the eddy current 7 induced by the alternating current 4, it changes over time, and is reversed 180 degrees from the illustrated arrow direction, and then again becomes the same direction as the illustrated arrow direction. repeat. Since the vibration of the Lorentz force 8 is caused by the alternating current 4, vibration (ultrasonic waves) having the same frequency as that of the alternating current 4 is generated in the pipe 30.

  The above description is an operation of generating ultrasonic waves, but the operation of receiving ultrasonic waves is the reverse process. FIG. 2 is a schematic diagram showing a state during reception of the electromagnetic ultrasonic sensor of FIG. In the electromagnetic ultrasonic sensor 1 of FIG. 2, if vibration reaches the pipe 30 with the magnetic flux 6 applied, an electric field is generated on the pipe surface according to Fleming's right-hand rule. Due to this electric field, an eddy current 7 is generated on the surface of the pipe 30, and an interlinkage magnetic flux 9 is generated by the eddy current 7. Since this interlinkage magnetic flux 9 interlinks with the coil 3, an electromotive force 10 based on Faraday's law by the interlinkage magnetic flux 9 is generated at both ends of the coil 3. Using this electromotive force 10 as an electric signal, ultrasonic waves can be detected.

  Therefore, the electromagnetic ultrasonic sensor 1 shown in FIG. 1 can transmit and receive ultrasonic waves.

  For example, if the thickness of the pipe 30 is 10 mm and the sound speed is 3000 m / s, when the ultrasonic frequency is set to a high frequency of 5 MHz, for example, the wavelength of the guide wave is 0.6 mm, which is shorter than the plate thickness. For this reason, the ultrasonic wave propagates in the thickness direction. On the other hand, if the frequency of the ultrasonic wave is set to 50 kHz, for example, the wavelength is 60 mm, which is longer than the plate thickness, and therefore propagates in the axial direction of the pipe 30 as a guide wave 20 as shown in FIG. From this, it can be considered that the frequency of electromagnetic ultrasonic waves is generally in the range of several tens of kHz to several hundreds of kHz.

  FIG. 3 is a perspective view showing a situation in which ultrasonic waves are transmitted and received in the axial direction of a pipe to be inspected using the electromagnetic ultrasonic sensor of FIG. As shown in FIG. 3, the guide wave 20 has a vibration direction in the circumferential direction of the pipe 30 and a propagation direction in the axial direction of the pipe 30. The vibration direction is the vibration direction of the Lorentz force 8 described above, and the guide wave 20 propagates in the same direction as the winding direction of the coil 3.

  Thus, if the guide wave 20 propagates in the axial direction of the pipe 30, it is reflected by the thinning portion 31 as shown in FIG. 3 and detected by the electromagnetic ultrasonic sensor 1 as the reflected guide wave 22. FIG. 4 is a time chart showing an example of a received signal when ultrasonic waves are transmitted and received in the axial direction of the pipe shown in FIG.

  Without the thinned portion 31 serving as a reflection source, the guide wave 20 is attenuated while continuing to propagate in the axial direction of the pipe 30 without being reflected, so that no reflected echo is detected in the received signal.

  Next, as shown in FIG. 5, the electromagnetic ultrasonic sensor 1 is rotated 90 degrees and arranged. FIG. 5 is a perspective view showing a situation in which ultrasonic waves are transmitted and received in the circumferential direction of a pipe to be inspected using the electromagnetic ultrasonic sensor of FIG. In this case, the guide wave 20 propagates in the circumferential direction while vibrating in the axial direction of the pipe 30. Propagating in this way makes it possible for the electromagnetic ultrasonic sensor 1 to detect the guided wave that has circulated. FIG. 6 is a time chart showing an example of a received signal when ultrasonic waves are transmitted and received in the circumferential direction of the pipe shown in FIG.

  In general, the guide wave has a characteristic of propagating to a long distance, and propagates for about 10 m. Therefore, the circulating guide wave propagating in the circumferential direction can be detected several times. In this embodiment, this circular guide wave signal is used as a reference signal for calibration.

  In a sensor that transmits and receives a guide wave using a piezoelectric element that is generally used for ultrasonic flaw detection, the sensor cannot be rotated as in this embodiment because the sensor needs to be in close contact with the pipe. This is because the curvature of the piping varies depending on the mounting direction of the sensor. On the other hand, in the electromagnetic ultrasonic sensor 1, since the piping itself is a vibration generating source as shown in FIGS. 1 and 2, the piping vibrates even if there is a gap of several mm between the sensor and the piping. It is possible to give Further, since the electromagnetic ultrasonic sensor 1 is attracted to the pipe 30 with a constant pressing pressure by the magnetic force of the built-in permanent magnet 2, the mounting accuracy is high, and a stable received signal can be obtained even if the sensor installation direction is changed by 90 degrees. Obtainable.

  By using the electromagnetic ultrasonic sensor in this way, it is possible to propagate guide waves in both the axial direction and the circumferential direction of the pipe without using a reflection source.

  5 and 6, the amplitude of the circulating guide wave detected after circulating in the circumferential direction of the pipe 30 is obtained in advance using a cylindrical body of the same shape, and this is used as a reference. As the intensity, the amplitude of the circulating guide wave detected after rotating in the same manner with the actual inspection object is set as the calibration intensity, and the degree of deterioration of the sensor can be quantitatively obtained from the difference between the reference intensity and the calibration intensity. This ensures the reliability of the inspection. Further, if the sensor fails and the guide wave cannot be transmitted or received, the circular guide wave shown in FIG. 6 is not detected, so that the presence or absence of the failure can be easily confirmed.

  The guide wave has a correlation that increases the amplitude of the reflected guide wave if the thinned portion of the pipe 30 is large. By using this correlation, the magnitude of the thinning can be estimated. Here, if the fluctuation of the sensor sensitivity is corrected, the correlation becomes stronger and the estimation accuracy can be improved.

  If the difference between the reference intensity and the calibration intensity is used as the sensor sensitivity correction, the sensitivity fluctuation can be obtained quantitatively. If this sensitivity variation is used for calibration of the received signal detected during the thinning measurement in which the propagation direction of the guide wave is the pipe axis direction, the size of the thinning can be estimated.

  Furthermore, the propagation time of the guide wave can be obtained in one round in the pipe circumferential direction from the echo interval of the circulating guide wave in FIG. In FIG. 6, the time difference (t1) between the guide wave transmission echo in the received signal and the circulating wave detected in the first round, and the time difference (t2, t3) of the received signal detected in each round pass through the same path. Since it circulates, it is constant, and it becomes the propagation time regardless of which time interval is used. Moreover, you may use the average time difference of t1-t3.

  From the propagation time T obtained from this and the outer size (propagation distance L) of the cylindrical body as the inspection object, the sound velocity V of the guide wave propagating through the pipe can be easily obtained by the equation V = L / T. it can.

  If the received signal when propagating in the axial direction of the pipe 30 is converted into a propagation distance using the sound velocity obtained from the above-mentioned circulation guide wave, the position of the thinned portion is converted from the actually measured sound velocity. (Distance from sensor) can be accurately identified.

  FIG. 7 is a graph showing the relationship between the amplitude level and the thickness reduction in the pipe inspection method using the pipe inspection apparatus according to the first embodiment. FIG. 8 is a graph showing the relationship between the propagation time of the ultrasonic echo and the amplitude level in the pipe inspection method using the pipe inspection apparatus according to the first embodiment.

  As shown in FIG. 7, the amplitude level of the reflected echo generated in the thinned portion is proportional to the thickness of the thinned portion. In this case, it is necessary to consider the attenuation rate of the ultrasonic waves in the tube wall. Therefore, if the correlation coefficient between the thinning size and the amplitude level is acquired in advance, the size of the thinning can be estimated from the amplitude level. However, as shown in FIG. 8, the amplitude level varies depending on the attenuation rate. That is, the amplitude level has an error in the estimated value because the propagation attenuation rate changes due to differences in pipes. Therefore, the amplitude level is corrected by calculating the propagation attenuation factor of the guide wave from the amplitude level of the circulating echo detected when the propagation direction of the guide wave is the pipe circumferential direction.

  Since the propagation attenuation rate is a decrease rate of the amplitude level per unit propagation time (= propagation distance), a quantitative propagation attenuation rate can be obtained from the amplitude level for each circulation of the circular echo in FIG. By correcting the propagation attenuation rate in this way, the error is reduced and the estimation accuracy of the thinning size can be improved.

  According to the first embodiment described above, it is possible to easily check the soundness and calibrate the sensitivity of the electromagnetic ultrasonic sensor in an inspection such as pipe thinning using a guide wave. Further, since the sound velocity propagating in the pipe wall of the pipe can be measured, the position of pipe thinning or the like can be accurately specified.

[Second Embodiment]
With reference to FIG. 9 thru | or FIG. 15, the piping inspection apparatus which concerns on the 2nd Embodiment of this invention is demonstrated.

  FIG. 9 is a schematic diagram showing the configuration and operation of the electromagnetic ultrasonic sensor of the pipe inspection apparatus according to the second embodiment of the present invention. FIG. 10 is a perspective view showing a situation in which ultrasonic waves are transmitted and received in the axial direction of a pipe to be inspected using the electromagnetic ultrasonic sensor of FIG. FIG. 11 is a schematic view of the electromagnetic ultrasonic sensor of FIG. 9 viewed from the X-axis direction. FIG. 12 is a perspective view showing a situation in which ultrasonic waves are transmitted and received in the circumferential direction of a pipe to be inspected using the electromagnetic ultrasonic sensor shown in FIGS. 9 and 11.

  The electromagnetic ultrasonic sensor 51 includes a permanent magnet 2, a first coil 53, and a second coil 54. The permanent magnet 2 is magnetized in the direction from the outer peripheral surface to the inner peripheral surface (Y direction) of the pipe 30, and in FIG. 9, the side closer to the pipe 30 is the N pole and the far side is the S pole. The first coil 53 is wound around the permanent magnet 2 around the first coil axis 60 in the X direction perpendicular to the line (Y direction) connecting the N pole and the S pole of the permanent magnet 2. Yes. There are a plurality of second coils 54 around the permanent magnet 2 around the second coil axis 61 (see FIG. 11) in the Z direction perpendicular to the line (Y direction) connecting the N pole and S pole of the permanent magnet 2. It is wound. The first coil shaft 60 and the second coil shaft 61 are orthogonal to each other, and the second coil 54 is wound around the first coil 53.

  With this configuration, a first transmission / reception unit that transmits and receives a guide wave by the permanent magnet 2 and the first coil 53 and a second transmission / reception unit that transmits and receives a guide wave by the permanent magnet 2 and the second coil 54 are formed. Since the electromagnetic ultrasonic sensor 51 includes the permanent magnet 2, if the pipe 30 is a magnetic body, the electromagnetic ultrasonic sensor 51 is attracted to the pipe 30 with a constant pressing pressure by a magnetic force. The electromagnetic ultrasonic sensor 51 is connected to a guide wave transmitter / receiver (not shown) for sending an electric signal for driving the sensor.

  With this configuration, the transmission / reception operation of the guide wave propagating in the axial direction of the pipe 30 is as follows.

  First, the operation of the first transmitter / receiver will be described with reference to FIG. Although the magnetic flux 6 in the Y direction is applied to the pipe 30 by the permanent magnet 2, when an alternating current 55 is passed through the first coil 53, an eddy current 57 is induced on the surface of the pipe 30. Since the direction of the eddy current 57 is the depth direction (Z direction) in FIG. 9, the magnetic flux 6 and the eddy current 57 are orthogonal to each other, and a Lorentz force 58 is generated in the X direction in the pipe 30 according to Fleming's left-hand rule. . Since this Lorentz force 58 is generated by the eddy current 57 induced by the alternating current 55, it changes over time. After the direction of the Lorentz force 58 is reversed by 180 degrees, the Lorentz force 58 repeats the original direction again. This is a guide wave that propagates through the pipe 30.

  Thus, the vibration generated in the pipe 30 is caused by the alternating current 55, and the frequency of the guide wave can be set by the frequency of the alternating current 55.

  Although the above description is a guide wave generating operation, the receiving operation is the reverse process. That is, if vibration reaches the pipe 30 with the magnetic flux 6 applied, an electric field is generated on the surface of the pipe 30 according to Fleming's right-hand rule. Due to this electric field, an eddy current 57 is generated on the pipe surface, and an interlinkage magnetic flux is generated by the eddy current 57. Since the interlinkage magnetic flux interlinks with the first coil 53, an electromotive force based on Faraday's law is generated at both ends of the first coil 53, and an ultrasonic wave can be detected as an electric signal. .

  Here, for example, if the pipe thickness is 10 mm, the sound velocity is 3000 m / s, and the guide wave frequency is 5 MHz, for example, the guide wave wavelength is 0.6 mm, which is shorter than the plate thickness. For this reason, the ultrasonic wave propagates in the plate thickness direction (Y direction). On the other hand, if the frequency of the ultrasonic wave is set to 50 kHz, for example, the wavelength is 60 mm and is longer than the plate thickness, so that it propagates in the axial direction (Z direction) of the pipe 30 as a guide wave 20 as shown in FIG. . For this reason, the frequency used in electromagnetic ultrasonic waves is generally in the range of several tens of kHz to several hundreds of kHz.

  Further, as shown in FIG. 10, the guide wave 20 has a vibration direction in the pipe circumferential direction (X direction) and a propagation direction in the pipe axis direction (Z direction).

  As shown in FIG. 10, a part of the guide wave 20 is reflected by the thinning portion 31 and detected by the electromagnetic ultrasonic sensor 51 as the reflected guide wave 22, as shown in FIG. 4 described in the first embodiment. A received signal is detected. If there is no thinned portion 31 that becomes a reflection source, the reflection echo is not detected because it attenuates while continuing to propagate without being reflected. By these actions, guide waves can be transmitted and received in the pipe axis direction (Z direction) shown in FIG.

  Next, the operation of the second transmitter / receiver will be described with reference to FIG. Although the magnetic flux 6 in the Y direction is applied to the pipe 30 by the permanent magnet 2, if an alternating current 65 is passed through the second coil 54, an eddy current 67 is induced on the surface of the pipe 30. Since the coil winding direction of the second coil 54 is orthogonal to that of the first coil 53, the eddy current 67 is generated in a direction orthogonal to the previous eddy current 57 (X direction). Here, since the magnetic flux 6 and the eddy current 67 are orthogonal to each other, a Lorentz force 68 is generated in the pipe 30 in the direction shown in FIG. The Lorentz force 68 is such that the coil winding direction of the second coil 54 is orthogonal to the winding direction of the first coil 53, so that the vibration direction is orthogonal to the vibration direction by the first transmitting / receiving unit. Then, a circulating guide wave 21 propagating in the pipe circumferential direction (X direction) is generated.

  Further, since the basic configuration of the second transmission / reception unit is the same as that of the first transmission / reception unit, reception can be performed in the same manner as the first transmission / reception unit. With these actions, the second transmitting / receiving unit can transmit and receive a guide wave whose vibration direction is the pipe axis direction (Z direction) and whose propagation direction is the pipe circumferential direction (X direction) as shown in FIG. Since the guide wave has a characteristic of propagating to a long distance and propagates about 10 m, the circulating guide wave 21 propagating in the pipe circumferential direction (X direction) is detected up to a plurality of circulating echoes as shown in FIG. can do.

  The electromagnetic ultrasonic sensor 51 having the above configuration generates two guide waves, a guide wave 20 propagating in the pipe axis direction (Z direction) and a circular guide wave 21 propagating in the pipe circumferential direction (X direction). Can do.

  If the direction in which the electromagnetic ultrasonic sensor 51 is attached to the pipe 30 is rotated 90 degrees, the guide wave generated in the first transmission / reception unit becomes the circular guide wave 21 propagating in the pipe circumferential direction, and the second transmission / reception unit The guide wave generated in the step becomes the guide wave 20 propagating in the pipe axis direction.

  It is possible to propagate the guide wave in two directions, the pipe axis direction and the pipe circumferential direction, by a method using a piezoelectric sensor other than the electromagnetic ultrasonic method. However, in the piezoelectric sensor, at least the propagation direction of the guide wave may be different. Two piezoelectric elements are required. On the other hand, the electromagnetic ultrasonic sensor of this embodiment can share the permanent magnet as a constituent member, so that it is possible to propagate the guide wave in two directions by providing two coils with different winding directions. .

  FIG. 13 is a perspective view illustrating a situation in which ultrasonic waves are transmitted and received in the axial direction and the circumferential direction of a pipe to be inspected using the pipe inspection apparatus according to the second embodiment.

  The connection between the first transmission / reception unit and the second transmission / reception unit in the electromagnetic ultrasonic sensor 51 and the guide wave transmitter / receiver 40 is connected via a connection switch 41 that can be arbitrarily selected to only one. The guide wave transceiver 40 is connected to the data processing unit 70.

  The data processing unit 70 includes a calibration unit 71, a sensor soundness determination unit 72, and a pipe evaluation unit 73.

  The calibration unit 71 increases the sensitivity of the electromagnetic ultrasonic sensor 51 based on the circular echo current generated in the second coil 54 by the guide wave that propagates in the circumferential direction in the pipe wall of the pipe 30 and returns without being reflected. Calibrate. The sensor soundness determination unit 72 is based on the circular echo current generated in the second coil 54 by the guide wave that propagates in the pipe wall of the pipe 30 in the circumferential direction and returns without being reflected. Determine the soundness of the.

  The pipe evaluation unit 73 includes an axial echo current generated in the first coil 53 by a guide wave that propagates in the pipe wall direction of the pipe 30 in the pipe axis direction and reflects back, and the electromagnetic wave calibrated by the calibration unit 71. Based on the sensitivity of the ultrasonic sensor 51, the state in the pipe wall of the pipe 30 is evaluated. The pipe evaluation unit 73 includes a sound speed evaluation unit 74 and a distance specifying unit 75.

  The sound velocity evaluation unit 74 obtains the sound velocity of the guide wave propagating in the pipe wall of the pipe 30 based on the circulating echo current. The distance identifying unit 75 uses the sound velocity obtained by the sound velocity evaluating unit 74 to determine the position between the electromagnetic ultrasonic sensor 51 and the position where the guide wave that has propagated in the pipe wall direction of the pipe 30 and returned is reflected. Find the distance.

  In this embodiment, since the first transmitter / receiver and the second transmitter / receiver are connected to the guide wave transmitter / receiver 40 via the connection switch 41, the guide wave 20 in the pipe axis direction and the pipe circumferential direction are switched by switching. The two received signals of the circular guide wave 21 can be detected individually without overlapping.

  In general, operation of the electromagnetic ultrasonic sensor and the transmission / reception apparatus is first performed in the operation of the guide wave method. The operation confirmation can be confirmed by the presence or absence of a reflection echo. However, since the reflection echo cannot be detected if there is no reflection source on the propagation path in order to confirm by the guide wave propagating in the pipe axis direction, there is a possibility that the operation confirmation cannot be performed. On the other hand, if a guide wave propagating in the circumferential direction of the pipe is also used for operation confirmation, a circular echo is detected. Therefore, the operational confirmation can be easily performed from this circular echo. For example, if a transmission wave shown in FIG. 6 is not detected, a failure on the transmission side of the guide wave transmitter / receiver, and if a circular echo is not detected, a failure on the reception side of the guide wave transmitter / receiver, both the transmission wave and the circular echo must be detected. In this case, the electromagnetic ultrasonic sensor 51 can be identified from the echo so as to cause a problem.

  FIG. 14 is a plan view showing a situation in which ultrasonic waves are transmitted to a pipe to be inspected using the pipe inspection apparatus according to the second embodiment, and a case where ultrasonic waves are transmitted in the circumferential direction of the pipe. FIG. FIG. 15 is a plan view showing a situation in which ultrasonic waves are transmitted to a pipe to be inspected using the pipe inspection apparatus according to the second embodiment, and is superordinate in a direction inclined with respect to the circumferential direction of the pipe. It is a figure which shows the case where a sound wave is transmitted. FIG. 16 is a graph showing the relationship between the number of circulations of circular echoes and the level of circular echoes in the situation of FIGS. 14 and 15.

  The propagation direction of the guide wave can be optimized by arbitrarily switching to only one of the guide wave 20 propagating in the pipe axis direction and the circulating guide wave 21 propagating in the pipe circumferential direction. For this optimization, a circular guide wave 21 propagating in the pipe axis direction is used. Since the circular guide wave 21 circulates in the pipe circumferential direction and reaches the electromagnetic ultrasonic sensor 51, the circular echo is detected in the received signal a plurality of times (see FIG. 6).

  If the angle θ formed between the propagation axis of the guide wave and the axis in the pipe circumferential direction is not zero, the circulating guide wave 21 propagates spirally in the pipe axis direction as shown in FIG. For this reason, the amplitude level of the circular echo detected by the electromagnetic ultrasonic sensor 51 decreases. Further, if the angle θ shown in FIG. 15 is large, the echo arrival position deviates from the position of the electromagnetic ultrasonic sensor 51 in the pipe axis direction every time the circulation is repeated. The relationship between this angle θ and the amplitude level for each revolution of the circular echo is as shown in FIG.

  Therefore, if the installation angle of the electromagnetic ultrasonic sensor 51 is adjusted so that the amplitude level in a specific turn of the circular echo is maximized or the attenuation rate of the amplitude level for each circulation is minimized, the propagation axis of the guide wave is set. It can be matched with the pipe circumferential axis. Further, the propagation axis of the guide wave propagating in the pipe axis direction by this axis adjustment also coincides with the axis in the pipe axis direction.

  As shown in FIG. 6, the received signal obtained by propagation in the circumferential direction of the pipe detects a transmission wave and a circular echo. However, since it circulates on the same path, the propagation distance for each circulation is the same. The time difference t1 between the wave and the 1st week's orbital echo and the time difference t2 between the 1st and 2nd week's orbital echoes are equally spaced, and the time difference between the circulating echoes at the other number of laps is also equal. Therefore, the time difference is the same even if an average using a part or all of the time differences t1 to tN is used.

  The sound velocity of the guide wave varies depending on the difference in solids due to impurities, etc., even if the same material is used. However, it is necessary to calibrate for each measurement object. From the propagation distance (L), the sound velocity V of the guide wave propagating through the pipe can be obtained by V = L / tx.

  If the received signal when propagating in the axial direction of the pipe 30 is converted into a propagation distance using the sound velocity obtained from the above-mentioned circulation guide wave, the position of the thinned portion is converted from the actually measured sound velocity. (Distance from sensor) can be accurately identified.

  According to the second embodiment described above, as in the first embodiment, the soundness confirmation and sensitivity calibration of the electromagnetic ultrasonic sensor can be easily performed in the inspection of pipe thinning using a guide wave. be able to. Further, since the sound velocity propagating in the pipe wall of the pipe can be measured, the position of pipe thinning or the like can be accurately specified.

  Furthermore, according to the second embodiment, both transmission / reception of the guide wave propagating in the pipe axis direction and transmission / reception of the guide wave propagating in the pipe circumferential direction can be performed without changing the direction of the electromagnetic ultrasonic sensor. Work efficiency is good. Furthermore, the direction of the coil of the electromagnetic ultrasonic sensor can be accurately directed in the pipe axis direction and the pipe circumferential direction.

[Third Embodiment]
FIG. 17: is the schematic diagram which looked at the condition which attached the piping inspection apparatus which concerns on the 3rd Embodiment of this invention to piping from the piping axis direction. In this embodiment, a plurality of (four in the illustrated example) electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are installed at equal intervals in the circumferential direction of the pipe (every 90 degrees in the illustrated example). It has become. Also, all of the plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are connected in series. Although FIG. 17 shows a case where four electromagnetic ultrasonic sensors are arranged, the number of sensors may be other than that.

  According to the third embodiment, since the plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are connected in series, it is possible to simultaneously transmit / receive guide waves from the plurality of sensors.

  Since the number of sensors used increases, the transmission power of the propagating guide wave can be increased in the pipe axis direction. Further, since the reception side is also performed by a plurality of sensors, the reflection echo level of the reception signal can be increased. Since the sensor intervals are the same in the pipe circumferential direction and all the electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are driven at the same timing, any electromagnetic ultrasonic sensor 51a, 51b, 51c, 51d circulates with the same propagation time. An echo is detected. Since all the circular echoes are added and received, the circular echo level can be increased.

[Fourth Embodiment]
FIG. 18 is a schematic view of the pipe inspection apparatus according to the fourth embodiment of the present invention attached to the pipe as viewed from the pipe axis direction. This embodiment is a modification of the third embodiment, in which a plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are installed in the circumferential direction of the pipe, and the plurality of these are arranged in the circumferential direction of the pipe. Installed at intervals. In this embodiment, all of the plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are connected in parallel.

  In this embodiment, since the plurality of electromagnetic ultrasonic sensors 51 are connected in parallel, it is possible to transmit and receive a guide wave even if one of the connection cables is disconnected.

  Moreover, the amplitude level of the reception signal of the reflected guide wave 22 propagating in the pipe axis direction and the circulating guide wave 21 propagating in the pipe circumferential direction can be increased by adding the detection signal for each sensor. Moreover, even if the connection cable is broken, the remaining connection cable can be used for transmission / reception, so that the reliability in the case of continuous guide wave transmission / reception is improved.

[Fifth Embodiment]
FIG. 19 is a schematic view of the pipe inspection apparatus according to the fifth embodiment of the present invention attached to the pipe as viewed from the pipe axis direction. FIG. 20 is a graph showing an example of an output waveform of each electromagnetic ultrasonic sensor according to the fifth embodiment.

  This embodiment is a modification of the fourth embodiment, and a plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are installed at equal intervals in the pipe circumferential direction. Further, all of the plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d are connected in parallel. In the plurality of electromagnetic ultrasonic sensors 51a, 51b, 51c, 51d, a guide wave transmitter / receiver 40 connected to the first transmitter / receiver and the second transmitter / receiver includes the first transmitter / receiver and the second transmitter / receiver. Guide wave transmitter / receiver via a connection switch 41 having a function of arbitrarily switching the connection to the unit to only one and a drive sensor selector 42 capable of arbitrarily selecting one or a specific number of electromagnetic ultrasonic sensors to be driven It is connected to the.

  According to this embodiment, it is possible to arbitrarily switch between the measurement drive for propagating the guide wave in the pipe axis direction and the calibration drive for propagating the guide wave in the pipe circumferential direction. Moreover, since the electromagnetic ultrasonic sensors 51a, 51b, 51c, and 51d to be driven can be arbitrarily selected, sensor calibration can be performed individually.

  Thereby, the measurement direction of the plurality of electromagnetic ultrasonic sensors 51 and the driving of the specific sensor can be performed by one guide wave transmitter / receiver, so that the cost can be reduced.

  Furthermore, according to this embodiment, the connection switch 41 and the drive sensor selector 42 propagate the guide wave in the circumferential direction of the pipe from only one of the electromagnetic ultrasonic sensors, and circulate by all the electromagnetic ultrasonic sensors. A guide wave can be acquired for each sensor. For example, if the sensor used for transmission is the first electromagnetic ultrasonic sensor 51a shown in FIG. 19, the circular guide wave 21 received by each sensor is as shown in FIG.

  Since the first electromagnetic ultrasonic sensor 51a is used as a transmission sensor, a transmission wave and a circulating wave are detected. In the second electromagnetic ultrasonic sensor 51b, the propagation direction of the guide wave transmitted from the first electromagnetic ultrasonic sensor 51a is the two directions indicated by arrows R and L shown in FIG. A first received wave detected at / 4 rounds and a third received wave propagating through the L side and propagated at 3/4 rounds are detected. In the third electromagnetic ultrasonic sensor 51c, since the propagation distance is the same for the two guide waves indicated by the arrows R and L, the third received wave is received in 2/4 rounds. Since the fourth electromagnetic ultrasonic sensor 51d has a positional relationship opposite to that of the second electromagnetic ultrasonic sensor 51b, the first received wave and the third received wave are almost the same as the second electromagnetic ultrasonic sensor 51b. A wave is detected.

  Here, the amplitude level in the propagation time corresponding to the first to third received waves (1/4 turn to 3/4 turn) is calculated from the change in the amplitude level of the turning wave of the first electromagnetic ultrasonic sensor 51a. Compare the calculated value with the measured amplitude level. If the sensitivity of the sensor is deteriorated, the amplitude level of the first to third received waves to be detected also decreases, so that sensor sensitivity deterioration can be detected.

  In FIG. 20, the circular guide wave 21 to be used is up to the first round. However, since a plurality of rounds are detected in the round wave, a round signal after the second round may be used.

  In this way, the sensitivity deterioration of a plurality of sensors can be evaluated by a single measurement. Further, the degree of decrease in sensitivity can be quantitatively grasped from the ratio between the calculated value and the measured amplitude level.

  Here, the propagation time at the position corresponding to the first to third received waves (1/4 turn to 3/4 turn) is calculated from the difference in propagation time between the transmission wave and the turn wave of the first electromagnetic ultrasonic sensor 51a. If the installation intervals are equal, t1 / 4 is the time difference between echoes received every quarter turn. This calculated value is compared with the detected propagation time. Here, if the installation intervals of adjacent sensors are all the same, the propagation time obtained at t1 / 4 matches the propagation time difference t1-1 to t1-4 of the detected received wave, but the sensor installation intervals are different. If so, the propagation time difference is different.

  For example, if the installation position of the third electromagnetic ultrasonic sensor 51c is not at a position corresponding to 2/4 turn, the propagation distance from the R side is different from the propagation distance from the L side, and therefore the second received wave is the third wave As shown by the dotted line in FIG. 20, two echoes are detected by the electromagnetic ultrasonic sensor 51c. If the installation position of the second electromagnetic ultrasonic sensor 51b is different, the first received wave and the received wave are received at different times as shown by the broken line in FIG. This broken line shows a reception echo when the second electromagnetic ultrasonic sensor 51b is close to the first electromagnetic ultrasonic sensor 51a.

  The uniformity of the sensor installation interval can be detected from the propagation time calculated in this way and the detected propagation times of the first to third received waves.

[Other Embodiments]
Each embodiment described above is merely an example, and the present invention is not limited thereto.

  For example, in each of the above embodiments, the electromagnetic ultrasonic sensor is arranged outside the pipe, but the electromagnetic ultrasonic sensor can be arranged inside the pipe. When a piezoelectric element is used for guide wave transmission / reception, the piezoelectric element becomes a vibration source, so the sensor needs to be in close contact with the object to be measured. It is necessary to change the curvature. On the other hand, in an electromagnetic ultrasonic sensor, the piping itself, not the sensor, is the source of vibration. Therefore, even if there is a gap of several millimeters between the electromagnetic ultrasonic sensor and the pipe wall surface, vibration is applied to the pipe. Even if there is a curvature, the guide can be transmitted and received.

  In the description of the above embodiment, the thinning is detected by using the reflection of the ultrasonic wave at the thinning portion of the pipe. However, if the ultrasonic wave is reflected even by a defect other than the thinning, etc. This can be detected.

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic ultrasonic sensor 2 ... Permanent magnet 3 ... Coil 4 ... AC current 6 ... Magnetic flux 7 ... Eddy current 8 ... Lorentz force 9 ... Linkage magnetic flux 20 ... Guide wave 21 ... Circumferential guide wave 22 ... Reflection guide wave 30 ... Piping 31 ... Thinning part 40 ... Guide wave transceiver 41 ... Connection changer 42 ... Drive sensor selector 50 ... Coil shaft 51, 51a, 51b, 51c, 51d ... Electromagnetic ultrasonic sensor 53 ... First coil 54 ... Second Coil 55 ... alternating current 57 ... eddy current 58 ... Lorentz force 60 ... first coil shaft 60
61 ... Second coil shaft 61
65 ... AC current 67 ... Eddy current 68 ... Lorentz force 70 ... Data processing section 71 ... Calibration section 72 ... Sensor soundness judgment section 73 ... Pipe evaluation section 74 ... Sonic evaluation section 75 ... Distance identification section

Claims (20)

A permanent magnet having a first magnetic pole formed at the first end and a second magnetic pole formed on the opposite side of the first end, and a line perpendicular to the straight line connecting the first magnetic pole and the second magnetic pole A pipe wall of a pipe that transmits and receives a guide wave, which is an ultrasonic wave propagating in the pipe wall of the pipe, using an electromagnetic ultrasonic sensor including a coil wound around the permanent magnet around a coil axis A pipe inspection method for inspecting
The electromagnetic ultrasonic sensor is arranged so that the first magnetic pole faces a part of the pipe wall surface of the pipe, and the coil axis faces the circumferential direction of the pipe, and an alternating current is passed through the coil to An axial echo current generated in the coil by a guide wave that propagates in the pipe wall direction of the pipe and propagates in the pipe axis direction after being reflected and returned inside the pipe wall. An axial echo detection step for detecting
By arranging the electromagnetic ultrasonic sensor so that the first magnetic pole faces a part of the pipe wall surface of the pipe, and the coil axis faces the pipe axis direction of the pipe, and by passing an alternating current through the coil A guide wave propagating in the circumferential direction in the pipe wall of the pipe is generated, and a circular echo current generated in the coil by the guide wave propagating in the circumferential direction in the pipe wall and returning without reflection is generated. A circular echo detection step to detect;
A calibration step of calibrating the sensitivity of the electromagnetic ultrasonic sensor based on the circular echo current obtained in the circular echo detection step;
A pipe evaluation step for evaluating the state in the pipe wall of the pipe based on the axial echo current obtained by the axial echo detection step and the sensitivity of the electromagnetic ultrasonic sensor obtained by the calibration step;
A pipe inspection method characterized by comprising: A permanent magnet having a first magnetic pole formed at the first end and a second magnetic pole formed on the opposite side of the first end, and a line perpendicular to the straight line connecting the first magnetic pole and the second magnetic pole A coil wound around the permanent magnet around a coil axis, and using an electromagnetic ultrasonic sensor comprising a guide wave, which is an ultrasonic wave propagating in the pipe wall of the pipe, transmits and receives the pipe wall of the pipe A pipe inspection method to inspect,
By arranging the electromagnetic ultrasonic sensor so that the first magnetic pole faces a part of the pipe wall surface of the pipe, and the coil axis faces the pipe axis direction of the pipe, and by passing an alternating current through the coil An axial echo generated in the coil by a guide wave that propagates in the pipe wall of the pipe in the pipe axis direction and propagates in the pipe axis direction and is reflected and returned. An axial echo detection step for detecting current;
By arranging the electromagnetic ultrasonic sensor so that the first magnetic pole faces a part of the pipe wall surface of the pipe, and the coil axis faces the circumferential direction of the pipe, and by passing an alternating current through the coil, A guide wave propagating in the circumferential direction in the pipe wall of the pipe is generated, and a circular echo current generated in the coil by the guide wave propagating in the circumferential direction in the pipe wall and returning without reflection is generated. A circular echo detection step to detect;
Sensor soundness determination step for determining soundness of the electromagnetic ultrasonic sensor based on the circular echo current obtained in the circular echo detection step;
Based on the axial echo current obtained by the axial echo detection step and the soundness judgment result of the electromagnetic ultrasonic sensor obtained by the sensor soundness judgment step, the state in the pipe wall of the pipe is evaluated. Piping evaluation step to perform,
A pipe inspection method characterized by comprising: The pipe evaluation step includes
A sound velocity evaluation step for determining the sound velocity of the guide wave propagating in the pipe wall of the pipe based on the circular echo current;
Using the sound velocity obtained in the sound velocity evaluation step, a distance specifying step for obtaining a distance between the electromagnetic ultrasonic sensor and a position where the guide wave that has propagated in the pipe wall direction of the pipe and propagated back in the pipe axial direction is reflected. When,
The piping inspection method according to claim 1, wherein the pipe inspection method is provided. The orbital echo detection step detects a guide wave that has propagated in the circumferential direction in the pipe wall of the pipe and returned around a plurality of times,
The sound velocity evaluation step is characterized in that the sound velocity is obtained by using a circular echo current generated in the coil by a guide wave propagating in a circumferential direction in the pipe wall of the pipe and returning around a plurality of times. Item 4. The piping inspection method according to Item 3.   The pipe inspection method according to any one of claims 1 to 4, wherein a state of the pipe in the pipe wall is a thinning of the pipe. A permanent magnet having a first magnetic pole and a second magnetic pole facing in opposite directions, and a circumference of the permanent magnet around a first coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole. Around the permanent magnet around a second coil axis perpendicular to the straight line connecting the first and second magnetic poles and perpendicular to the first coil axis. A pipe inspection method for inspecting a pipe wall of a pipe by transmitting and receiving a guide wave, which is an ultrasonic wave propagating in the pipe wall of the pipe, using an electromagnetic ultrasonic sensor provided with a wound second coil. And
The first magnetic pole faces a part of the pipe wall surface of the pipe, and the first coil axis faces the circumferential direction of the pipe, and the second coil axis faces the pipe axis direction of the pipe. A sensor placement step of placing the electromagnetic ultrasonic sensor;
After the sensor placement step, an alternating current is passed through the first coil to generate a guide wave that propagates in the pipe wall in the pipe axial direction, and propagates in the pipe wall in the pipe axial direction. An axial echo detection step for detecting an axial echo current generated in the first coil by the guide wave reflected and returned;
By passing an alternating current through the second coil after the sensor placement step, a guide wave propagating in the circumferential direction in the pipe wall of the pipe is generated and propagated in the circumferential direction in the pipe wall of the pipe. A circular echo detection step of detecting a circular echo current generated in the second coil by the guide wave returned without being reflected;
A calibration step of calibrating the sensitivity of the electromagnetic ultrasonic sensor based on the circular echo current obtained in the circular echo detection step;
A pipe evaluation step for evaluating the state in the pipe wall of the pipe based on the axial echo current obtained by the axial echo detection step and the sensitivity of the electromagnetic ultrasonic sensor obtained by the calibration step;
A pipe inspection method characterized by comprising: The sensor placement step is to place a plurality of the electromagnetic ultrasonic sensors at intervals in the circumferential direction of the pipe,
The circular echo detection step propagates in the pipe wall of the pipe in the circumferential direction by passing an alternating current through the second coil of the first electromagnetic ultrasonic sensor among the plurality of electromagnetic ultrasonic sensors. Other sensor circular echo that detects a circular echo current generated in the second coil of the electromagnetic ultrasonic sensor other than the first electromagnetic ultrasonic sensor among the plurality of electromagnetic ultrasonic sensors Including a detection step,
The calibration step calibrates each electromagnetic ultrasonic sensor in consideration of the result obtained by the other-sensor circular echo detection step,
The pipe inspection method according to claim 6.   The pipe inspection method according to claim 7, further comprising an interval confirmation step of confirming an interval between the plurality of electromagnetic ultrasonic sensors based on a result obtained by the other sensor circular echo detection step. . A pipe inspection apparatus having an electromagnetic ultrasonic sensor for transmitting and receiving a guide wave that is an ultrasonic wave traveling inside a pipe wall of a pipe,
The electromagnetic ultrasonic sensor is
A permanent magnet disposed so that the first magnetic pole faces a part of the pipe wall surface of the pipe and the second magnetic pole faces away from a part of the pipe wall surface;
A first coil wound around the permanent magnet about a first coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole;
A second coil wound around the permanent magnet about a second coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole and perpendicular to the first coil axis;
And a piping inspection device configured to supply an alternating current to the first coil and the second coil. The electromagnetic ultrasonic sensor is arranged so that the first coil axis faces the circumferential direction of the pipe and the second coil axis faces the pipe axis direction of the pipe, and an alternating current is applied to the second coil. The second coil is generated by the guide wave that is supplied and propagates in the pipe wall of the pipe in the circumferential direction and propagates in the pipe wall of the pipe in the circumferential direction and returns without being reflected. A calibration unit that calibrates the sensitivity of the electromagnetic ultrasonic sensor based on the circular echo current generated in
The electromagnetic ultrasonic sensor is arranged such that the first coil axis faces the circumferential direction of the pipe and the second coil axis faces the pipe axis direction of the pipe, and an alternating current is applied to the first coil. A guide wave that is supplied and propagates in the pipe axis direction of the pipe in the pipe axis direction is generated, and the first guide wave is propagated in the pipe axis direction of the pipe and reflected and returned. A pipe evaluation unit that evaluates the state in the pipe wall of the pipe based on the axial echo current generated in the coil and the sensitivity of the electromagnetic ultrasonic sensor calibrated by the calibration unit;
The piping inspection device according to claim 9, further comprising: The electromagnetic ultrasonic sensor is arranged so that the first coil shaft faces the axial direction of the pipe and the second coil shaft faces the circumferential direction of the pipe to supply an alternating current to the second coil. Then, a guide wave propagating in the circumferential direction in the pipe wall of the pipe is generated, and the second coil is caused by the guide wave propagating in the circumferential direction in the pipe wall of the pipe and returning without reflection. A sensor soundness determination unit for determining soundness of the electromagnetic ultrasonic sensor based on the generated circular echo current;
The electromagnetic ultrasonic sensor is arranged so that the first coil shaft faces the axial direction of the pipe and the second coil shaft faces the circumferential direction of the pipe to supply an alternating current to the first coil. Then, a guide wave propagating in the pipe axis direction in the pipe wall of the pipe is generated, and the first coil is generated by the guide wave propagating in the pipe axis direction in the pipe axis and reflected and returned. A pipe evaluation unit that evaluates the state in the pipe wall of the pipe based on the axial echo current generated in the sensor and the soundness determination result of the electromagnetic ultrasonic sensor obtained by the sensor soundness determination unit;
The piping inspection device according to claim 9, further comprising: The pipe evaluation unit
A sound velocity evaluation unit for obtaining a sound velocity of a guide wave propagating in a pipe wall of the pipe based on the circular echo current;
A distance identifying unit that obtains a distance between the electromagnetic ultrasonic sensor and a position where a guide wave that has propagated in the pipe wall direction of the pipe and returned is reflected using the speed of sound obtained by the sound speed evaluation unit. When,
The piping inspection device according to claim 10 or 11, characterized by comprising:   The sound velocity evaluation unit obtains a sound velocity using a circular echo current generated in the second coil by a guide wave propagating in the circumferential direction in the pipe wall of the pipe and returning after a plurality of circular turns. The piping inspection device according to claim 12.   The pipe inspection apparatus according to any one of claims 9 to 13, wherein a state in the pipe wall of the pipe is a thinning of the pipe.   15. The switch according to claim 9, further comprising a switch that switches an electrical connection so that an alternating current flows through only one of the arbitrarily selected first coil and second coil. The piping inspection device according to one item.   The pipe inspection according to claim 15, wherein there are a plurality of the electromagnetic ultrasonic sensors, and the plurality of electromagnetic ultrasonic sensors are arranged at intervals in the circumferential direction of the pipe. apparatus.   The pipe inspection apparatus according to claim 16, wherein the first coils and the second coils of the plurality of electromagnetic ultrasonic sensors are electrically connected in series.   The pipe inspection apparatus according to claim 16, wherein the first coils and the second coils of the plurality of electromagnetic ultrasonic sensors are electrically connected in parallel.   The pipe inspection apparatus according to claim 18, further comprising a drive sensor selector that selectively operates only an arbitrary part of the plurality of electromagnetic ultrasonic sensors. An electromagnetic ultrasonic sensor that transmits and receives a guide wave that is an ultrasonic wave traveling inside a pipe wall of a pipe,
A permanent magnet disposed so that the first magnetic pole faces a part of the pipe wall surface of the pipe and the second magnetic pole faces away from a part of the pipe wall surface;
A first coil wound around the permanent magnet about a first coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole;
A second coil wound around the permanent magnet about a second coil axis perpendicular to a straight line connecting the first magnetic pole and the second magnetic pole and perpendicular to the first coil axis;
An electromagnetic ultrasonic sensor comprising:

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