JP5663319B2 - Guide wave inspection method and apparatus - Google Patents

Description

  The present invention relates to a guide wave inspection method and apparatus for non-destructively detecting thinning and damage generated in a cylindrical structure such as a pipe or a tank using a guide wave.

  Pipes for plants such as power plants and chemical plants, pipes for pipelines that transport oil, pipes in refineries, and pipes such as water pipes and gas pipes buried in the ground for a long time after installation As time passes, deterioration due to corrosion or erosion from the inner and outer surfaces proceeds. Eventually, the corrosion or erosion reaches the thickness of the pipe. In this case, fluid flowing in the piping such as liquid and vapor leaks to the outside. In order to avoid such a situation, it is necessary to periodically perform nondestructive inspection of the pipe, evaluate the pipe thickness, and take measures such as replacement (or repair) of the pipe before leakage of internal fluid occurs. .

  A typical example of a nondestructive measuring means for inspecting the thickness of a pipe is an ultrasonic thickness gauge. An ultrasonic thickness meter is a device that measures the thickness of pipes. An ultrasonic thickness meter generally uses an ultrasonic sensor having a piezoelectric element that converts electricity and sound into each other. Install an ultrasonic sensor on the outer surface of the pipe, excite bulk waves (elastic waves such as longitudinal and transverse waves) in the pipe to be inspected, and receive the elastic wave reflected on the inner surface of the pipe with the same or another ultrasonic sensor. Measure the wall thickness of the pipe.

  This ultrasonic thickness meter is suitable for inspecting the thickness of the pipe in the center direction, but since the inspection range is narrow, it takes a long time to inspect the longitudinal direction of a long pipe. Moreover, in the inspection using the ultrasonic thickness meter, when the pipe surrounding the heat insulating material is targeted, it is necessary to remove the heat insulating material at each thickness measurement location. For this reason, the time required for removing the heat insulating material before the inspection and attaching the heat insulating material after the inspection also increases. Moreover, it is not easy to inspect concrete and piping buried in the ground.

  As one countermeasure against such problems of the ultrasonic thickness gauge, a guide wave (formed by interference of longitudinal and transverse waves traveling in an object having a boundary surface such as a pipe or a plate while reflecting or changing modes) Non-destructive inspection of piping using elastic waves) has been proposed. The non-destructive inspection using the guide wave can inspect the long distance section of the piping collectively. By using the guide wave, the place where the heat insulating material is removed is significantly reduced.

  In a non-destructive inspection apparatus using a guide wave, it is difficult to prepare a calibration test body having the same size as the measurement target. Therefore, it is important to calibrate the detection sensitivity using the actual inspection target.

  As a method for solving this problem, a method of contacting and fixing the reference reflecting member has been proposed. For example, in Patent Document 1, a reference reflecting member is contacted and fixed to a part of an inner surface or an outer surface of a cylindrical member (pipe) at a pipe position away from a guide wave sensor installation position of a pipe to be inspected. In addition, a guide wave is transmitted from the guide wave sensor, and a reflection signal from the reference reflecting member contact portion with respect to the guide wave is received. The amplitude of the received reflected signal is prepared in advance as a reference signal. In an actual flaw detection inspection, the magnitude or amount of the defect or thinning is estimated by comparing the amplitude of the reflected signal obtained by the actual inspection measurement using the guide wave with the reference signal obtained previously. .

  As another means, a calibration method using a weld line or the like has been proposed. For example, in Patent Document 2, a reflected guide wave reflected by a known weld is detected, the relationship between the intensity of the reflected guide wave and the protrusion height at which the weld protrudes from the surface of the pipe is obtained, and a reflected guide wave for inspection is obtained. The soundness is evaluated based on the strength of the.

JP 2009-293981 A JP 2010-54467 A

  In the non-destructive inspection method described in Patent Document 1 above, for example, in order to contact and fix the reference reflecting member, it takes time to remove the heat insulating material with a pipe with a heat insulating material, etc. Not applicable.

  Moreover, in the nondestructive inspection method described in Patent Document 2, there is room for improvement in calibration accuracy because the relationship between the frequency and sensitivity with respect to the weld line shape is not clear.

  The purpose of the present invention is to calibrate a change in reception sensitivity for each sensor installation without installing a new reference reflecting member in a pipe inspection using a guide wave, and to make it possible to evaluate a defect size with high accuracy. Is to provide.

  In order to achieve the above object, the present invention is characterized in that a guide wave is applied to a cylindrical structure including a welded portion, and the size of a defect in the structure is detected using the reflected wave. A first step of setting a cross-sectional shape of a welded portion of the cylindrical structure to obtain a first reflectance depending on the guide wave frequency, and a plurality of reflected waves appearing at the position of the welded portion of the cylindrical structure A second step of obtaining a first attenuation signal from the signal, a third step of setting a second reflectance to be measured as a defect and calibrating with the first reflectance to obtain a second attenuation signal; A fourth step of installing a sensor to transmit / receive a guide wave and a magnitude of the reflected wave obtained by the fourth step and the second attenuation signal are identified as defects, and the third reflectance at that time is determined. The fifth step and the fifth step And a third sixth step of obtaining a size of the defect from the reflectance of the.

  Further, in the first step, the cross-sectional shape of the welded portion is set by the thickness including the surplus of the weld portion and the length of the surplus portion.

  In addition, the first reflectance that depends on the guide wave frequency is defined by the amplitude and the frequency interval, the amplitude is determined by the thickness including the surplus of the welded portion, and the frequency interval is determined by the length of the surplus portion.

  Moreover, it has a plurality of defect cross-sectional area ratio characteristics on the characteristic of the reflectance with respect to the guide wave frequency, and the defect cross-sectional area ratio is obtained from the guide wave frequency and the third reflectance.

  In order to achieve the above object, the present invention is characterized in that a first ultrasonic probe array having a plurality of first ultrasonic probes arranged in the circumferential direction of a pipe, A second ultrasonic probe row having a plurality of second ultrasonic probes arranged at a predetermined distance in the longitudinal direction from the acoustic probe row and arranged in the circumferential direction of the pipe, and the longitudinal direction of the pipe The transmission time of the transmission signal applied to the first ultrasonic probe array and the second ultrasonic probe array is relatively shifted so that the guide wave propagates to one side of the In a pipe inspection apparatus including transmission / reception means for obtaining a wave as an electrical reception signal, a processing apparatus for detecting a defect in piping based on the reception signal, and an image display means, the processing apparatus has a cross-sectional shape of a welding portion of the pipe And a first means for obtaining a first reflectance depending on the guide wave frequency and a welded portion of the pipe A second means for obtaining a first attenuation signal from a plurality of reflected wave signals appearing at positions; a second reflectance to be measured as a defect; and a second attenuation obtained by calibrating with the first reflectance. Third means for obtaining a signal, and fourth means for obtaining a third reflectance at that time, while identifying a defect from the magnitude of the reflected wave obtained from the ultrasonic probe and the second attenuation signal. And fifth means for obtaining the size of the defect from the third reflectance of the fourth means.

  The image display means displays the cross-sectional shape of the welded portion of the pipe and its set value, the guide wave frequency and the first reflectance, the reflected wave and the attenuation signal.

  In the first means, the cross-sectional shape of the welded portion is set by the thickness including the surplus of the welded portion and the length of the surplus portion and displayed on the image display means.

  According to the present invention, in a pipe that cannot use a reference reflection source by contact / fixation (for example, a pipe covered with a heat insulating material other than a sensor installation place or a pipe with a rough surface), the sensor receiving sensitivity is highly accurate. The defect size can be evaluated with high accuracy.

The flowchart which shows the piping test | inspection method in the Example of this invention. The figure which shows the piping inspection apparatus used for the piping inspection method of a present Example. The figure which shows the detailed structure of the guide wave transmitter / receiver 4. FIG. The figure which shows the example of the setting screen which gives a weld line shape. The figure which shows the example of a reflectance analysis result screen. Flowchart showing the detailed operation of step S103 in FIG. The figure which shows the example of the screen which calibrates the amplitude of a welding line signal. The figure explaining the shape and dimension of thinning as an example of a defect. The figure explaining the relationship between the frequency of a guide wave, and the reflectance by thinning. The figure explaining the relationship between the frequency of a guide wave, and the reflectance by thinning.

  Embodiments of the present invention will be described below with reference to the drawings.

  A pipe inspection apparatus 10 used in the pipe inspection method of this embodiment will be described with reference to FIG. The pipe inspection apparatus 10 includes a guide wave sensor 3 including ultrasonic probe arrays 1 and 2, a guide wave transmitter / receiver 4, an analog / digital converter (A / D converter) 5, a computer 6, and a display device 7. .

  Among these, the ultrasonic probe array 1 includes a plurality of ultrasonic probes (hereinafter simply referred to as probes), for example, four ultrasonic probes 1a, 1b, 1c, and 1d. The ultrasonic probe array 2 also includes a plurality of probes, for example, four probes 2a, 2b, 2c, and 2d. Each probe constituting the ultrasonic probe array has a transmission / reception function, and is composed of a single probe.

  Each probe can be configured by connecting a plurality of probes in parallel (or connecting a transmission probe and a reception probe in parallel). It is desirable that the probes 1a to 1d and 2a to 2d have the same number of probes. Each probe included in each of the ultrasonic probe rows 1 and 2 generates a guide wave in the pipe 9, and is constituted by, for example, a piezoelectric element. In addition, each probe constituting the ultrasonic probe array is arranged along the circumferential direction of a predetermined position of the pipe, and the two sets of ultrasonic probe arrays are guide waves used for flaw detection inspection. It is installed on the basis of being separated by a distance corresponding to ¼ of the wavelength λ. This makes it possible to efficiently perform flaw detection only in one direction with respect to the ultrasonic probe installation position of the pipe.

  The guide wave transmitter / receiver 4 is means for applying a transmission waveform (transmission signal) to each probe to transmit a guide wave, and further amplifying a reception waveform (reception signal) from each probe. The detailed configuration of the guide wave transceiver 4 will be described below with reference to FIG.

  As shown in FIG. 3, the guide wave transmitter / receiver 4 includes a controller 21, a signal generator 22 a for the ultrasonic probe array 1, a power amplifier 23 a, an element switch 24 a, and an ultrasonic probe array 2. A signal generator 22b, a power amplifier 23b, and an element switch 24b. The signal generators 22a and 22b, the power amplifiers 23a and 23b, and the element switchers 24a and 24b are mechanisms for transmitting guide waves from the corresponding probes in the ultrasonic probe arrays 1 and 2. The guide wave transmitter / receiver 4 further includes an element switch 25 and a reception amplifier 26 for inputting each received signal (guide wave reflection signal) received by each probe of the ultrasonic probe rows 1 and 2. Yes.

  The signal generators 22a and 22b are connected to the controller 21, respectively. The signal generator 22a is connected to the element switch 24a via the power amplifier 23a. The controller 21 is also connected to the element switch 24a. Each of the probes 1a, 1b, 1c, 1d is connected to an element switch 24a. The element switch 24 a switches the connection between the power amplifier 23 a and each of the probes 1 a to 1 d based on a switching command from the controller 21.

  The signal generator 22b is connected to the element switch 24b through the power amplifier 23b. The controller 21 is also connected to the element switch 24b. Each of the probes 2a, 2b, 2c, 2d is connected to an element switch 24b. The element switch 24b switches connection between the power amplifier 23b and each of the probes 2a to 2d based on a switching command from the controller 21.

  The probes 1a, 1b, 1c, 1d, 2a, 2b, 2c, and 2d are connected to the element switchers 24a and 24b through coaxial cables. The element switch 25 connected to the reception amplifier 26 is connected to the probes 1a to 1d and 2a to 2d. Connection of the probes 1a to 1d and 2a to 2d to the element switch 25 is also performed via a coaxial cable. The controller 21 is also connected to the element switch 25. The element switch 25 switches the connection between the reception amplifier 26 and each of the probes 1a, 1b, 1c, 1d, 2a, 2b, 2c, and 2d based on a switching command from the controller 21. The reception amplifier 26 is connected to the A / D converter 5 by a coaxial cable.

  Returning to FIG. 2, the A / D converter 5 has a function of converting a reception waveform of a guide wave, which is an analog signal, into a digital waveform, which is a digital signal. As the A / D converter 5, for example, a commercially available external A / D converter or a board-type A / D converter built in a computer is used.

  The computer 6 functions as a central control device 6a and a signal processing device 6b. The A / D converter 5 converts each reception signal (reception waveform) output from the reception amplifier 26 into a digital signal and inputs the digital signal to a signal processing device 6 b included in the computer 6. The central control device 6a outputs a control command such as a guide wave transmission command to the controller 21.

  The display device 7 further displays the display information such as the image information generated by the signal processing device 6b, as necessary, as a digital signal (from the reception amplifier 26) that the signal processing device 6b inputs from the A / D converter 5. (Corresponding to the output signal) is displayed as it is.

  A pipe inspection method using the pipe inspection apparatus 10 will be described below with reference to the flowchart of FIG. Prior to the implementation of the flowchart of FIG. 1, first, preparation for a flaw detection inspection is made. In the preparation stage, the probes of the ultrasonic probe rows 1 and 2 in FIG. That is, the ultrasonic probe row 1 is arranged at an inspection position where the pipe 9 to be inspected is present. The ultrasonic probe row 2 is basically arranged at a position separated from the ultrasonic probe row 1 by a predetermined interval λ / 4 in the axial direction of the pipe 9. When the probes of the ultrasonic probe rows 1 and 2 are arranged in the circumferential direction of the pipe 9, a part of the heat insulating material surrounding the pipe 9 is removed in advance.

  The pipe to be inspected in the present invention is a general pipe as shown by 9 in FIG. 2, and can be widely applied to cylindrical structures such as a tank. The pipe 9 includes a pipe end 9a and a welded portion 9c, as is the case with a general pipe. Further, it is assumed that the pipe 9 has a thinned portion or a crack 9b.

  In the flowchart of FIG. 1, after the placement of the probes 9 in the circumferential direction of the pipes 9 is completed, the operator uses the input device (not shown) to measure the central controller 6a on the measurement target in step S101. The thickness of the pipe 9 in FIG. 2 and the weld line cross-sectional shape of the weld 9c are input.

  FIG. 4 shows a screen displayed on the display device 7 of FIG. 1, and FIG. 4a shows a condition setting screen 100 for inputting the thickness of the measurement object 9 and the weld line cross-sectional shape of the weld 9c. It is an example. The condition setting screen 100 includes a weld line shape display screen 101 and a shape input screen 102. Among them, the screen 101 shows the thickness of the pipe 9 and the shape of the welded portion of the welded portion 9c, and the screen 102 shows the input values of the numerical values of the respective parts regarding the thickness of the pipe 9 and the shape of the welded portion of the welded portion 9c. Is displayed.

  Since the cross-sectional shape of the weld line of the welded portion 9c is usually axially symmetric with respect to the piping, the cross-sectional shape including the central axis is given. The input value of the shape is given by numerical values such as thickness d1, extra height d2, extra shaft length l1, back wave height d3, back wave axis length l2, etc., and the shape is approximated by an arc. decide. The curve can be approximated by other than a circular arc, and is preferably close to the actual weld line shape. It is also possible to provide point cloud data that simulates the shape relatively well. It should be noted that when each part value is input on the shape input screen 102, the input result is preferably reflected on the shape of the display screen 101.

  Next, in step S102, the operator gives an instruction for reflectance calculation from an input device (not shown) to the central controller 6a, and the central controller 6a calculates the reflectance in consideration of the frequency information.

  FIG. 4B is a display screen (reflectance analysis result display screen 103) showing an example in which the reflectance calculation result is output to the display device 7. The screen 103 shows the guide wave frequency on the horizontal axis and the reflectivity at this frequency on the vertical axis. The reflectivity of the guide wave at the weld line of the welded part 9c having the shape given in step S101 tends to periodically change depending on the frequency. Here, for example, in the case of using a guide wave with a frequency of 40 kHz, the reflected wave from the weld line of the welded portion 9c when the reflected wave from the total reflection portion such as the tube end 9a is 100%. Is calculated to be 15% in the amplitude ratio.

  In the screen 103, the maximum value W1 of the analysis value W is mainly the thickness d1, the extra height d2, and the back wave height among the numerical values indicating the cross-sectional shape of the weld line of the weld 9c input on the screen 102. The interval W2 is determined as a function of the extra-shaft axis length l1 and the back wave axis length l2.

  As is apparent from the above description, the welded portion 9c is present in general piping as much as possible, and its position can be grasped in advance. In addition, the amplitude of the reflected wave from the weld 9c can be calculated as the ratio of the reflected wave from the total reflection portion. Accordingly, by evaluating the amplitude of the reflected wave from the thinned portion or the crack 9b on the basis of the amplitude of the reflected wave from the welded portion 9c, information on the magnitude as well as the position can be obtained. In the following steps, these pieces of information are obtained from the reflected wave.

  Next, in step S103, the operator inputs an inspection start signal to the central controller 6a. The operation here will be described in detail with reference to FIG.

  The central control device 6a in FIG. 2 to which the inspection start signal is input executes each processing of steps S1031, S1032, and S1034 shown in FIG. Note that the signal processing device 6b executes the processes of steps S1033 and S1035 shown in FIG.

  In step S1031, first, the central controller 6a outputs each guide wave transmission command (transmission control signal) to the ultrasonic probe array 2.

  The controller 21 in FIG. 3 that has input a guide wave transmission command to the ultrasound probe array 2 outputs a switching command (switching control signal) to the element switch 24b. The element switch 24b connects the probes 2a, 2b, 2c, and 2d to the power amplifier 23b substantially simultaneously based on the input switching command. The controller 21 receiving the guide wave transmission command outputs a second excitation command (second excitation control signal) for the probes 2a to 2d to the signal generator 22b. The signal generator 22b outputs second excitation signals for the probes 2a to 2d based on the second excitation command. The power amplifier 23b amplifies these second excitation signals. The amplified second excitation signals are applied substantially simultaneously to the corresponding probes 2a to 2d via the element switch 24b that is switched as described above. The probes 2a to 2d each receive the second excitation signal.

  Next, the central controller 6a outputs each guide wave transmission command (transmission control signal) to the ultrasound probe array 1 in step S1032.

  The element switch 24a connects the probes 1a, 1b, 1c, and 1d to the power amplifier 23a substantially simultaneously based on the switching command. The controller 21 receiving the guide wave transmission command outputs a first excitation command (first excitation control signal) for the probes 1a to 1d to the signal generator 22a. The signal generator 22a outputs the first excitation signals for the probes 1a to 1d based on the first excitation commands. The power amplifier 23a amplifies those first excitation signals. The amplified first excitation signals are applied substantially simultaneously to the corresponding probes 1a to 1d via the element switch 24a that is switched as described above. Each of the probes 1a to 1d receives a first excitation signal.

  In this case, the first excitation signal input to the probes 1a to 1d is guided more in the ultrasonic probe array 2 in the pipe 9 than the second excitation signal input to the probes 2a to 2d. And the ultrasonic probe row 1 are delayed by a time required to propagate the distance (hereinafter referred to as a delay time), the absolute value is the same, and the sign is reversed. This delay is achieved by delaying the time point when the first excitation command is output from the controller 21 to the signal generator 22a by the delay time described above from the time point when the second excitation command is output from the controller 11 to the signal generator 22b. it can.

  Since the first excitation signals input to the probes 1a to 1d are delayed by the above delay time with respect to the second excitation signals input to the probes 2a to 2d, in FIG. It is possible to increase the amplitude of the guide wave traveling to the right side of the probe rows 1 and 2 in the same phase, and reverse the amplitude of the guide wave traveling to the left side of the ultrasonic probe rows 1 and 2. It becomes possible to decrease by phase.

  The second excitation signals input to the probes 2a to 2d have the same signs as the first excitation signals input to the probes 1a to 1d, and the second excitation signals input to the probes 1a to 1d. It may be delayed by the above delay time rather than one excitation signal. Accordingly, the probes 1a to 1d to which the first excitation signal is applied substantially simultaneously and the probes 2a to 2d to which the second excitation signal is applied substantially simultaneously are guided to the pipe 9 by vibrating. Generate each wave. These guide waves 8 propagate in the axial direction of the pipe 9.

  In FIG. 2, the guide wave 8 propagated in the axial direction is reflected and reflected by the guide wave 8 when a pipe end portion 9 a, a thinned portion or crack 9 b, and a welded portion 9 c exist in the pipe 9. (Reflected signal) and travels in the opposite direction. This reflected wave is received by the probes of the ultrasonic probe rows 1 and 2.

  In step S1033, a reception signal from the ultrasonic probe array on one side is received. The element switch 25 connects the probes 1a, 1b, 1c, and 1d to the reception amplifier 26 substantially simultaneously by a switching operation based on a switching command from the controller 21. Received signals (received waveforms) received by the probes 1a, 1b, 1c, and 1d are input to the receiving amplifier 26 through the element switch 25 and amplified by the receiving amplifier 26. The amplified received signal is transmitted to the A / D converter 5. The A / D converter 5 converts each received signal received into a digital signal. The controller 21 outputs a trigger signal to the A / D converter 5 based on the input guide wave transmission command. After inputting this trigger signal, the A / D converter 5 starts converting the received signal, which is an analog signal, into a digital signal. The signal processing device 6B of the computer 6 inputs the digital signal (digitized reception signal) output from the A / D converter 5. These digital signals are stored in a storage device (not shown) of the computer 6.

  Next, in step S1034, it is determined whether or not a reception signal is input to both ultrasonic probe trains. The central controller 6a inputs the input information of each digital signal input by the signal processor 6b from the signal processor 6b. These digital signals correspond to individual ultrasonic probe trains. Based on the input information of each digital signal, the central control device 6a determines whether or not the reception signal is input to both ultrasonic probe arrays. If the determination result is “YES”, the process of step S1035 is executed, and if the determination result is “NO”, the process of step S1031 is executed.

  By repeating the processing in steps S1031 to S1034, the signal processing device 6b performs the processing on each reception signal output from both the ultrasonic probe rows, the ultrasonic probe row 1 and the ultrasonic probe row 2. Input each digital signal. These received signals are reflected signals from the same reflection source (for example, the pipe end portion 9a, the thinned portion 9b, and the welded portion 9c).

  In step S1035, the signal processing device 6b synthesizes the received signals when the determination information “YES” described above is input from the central control device 6a. The reception signal combining process in step S1035 is a process of extracting a guide wave propagating from the right side of the ultrasonic probe rows 1 and 2 toward the ultrasonic probe rows 1 and 2 in FIG. It is.

  Through the series of processes shown in FIG. 5, the guide wave transmission / reception step (step S103) in FIG. 1 is completed. When this is completed, the process returns to FIG. After step S104, the position and size of the thinned portion 9b are obtained by analysis of the reflected wave.

  Next, the operator selects a weld line signal of the welded portion 9c from the composite signal obtained in step S103 of FIG. 5 (the appearance position of the signal can be confirmed in advance by drawing or visual observation). Then, input to the central controller 6a (step S104).

An example of the screen display of the display device 9 at that time (reflected wave display screen 104) is shown in FIG. In FIG. 6, the lower part of the reflected wave display screen 104 shows a pipe 9 to be inspected, which has a pipe end portion 9a, one thinned portion 9b, and three welded portions 9c (9c1, 9c2, 9c3). . The reflected wave display screen 104 shows the pipe distance from the sensor on the horizontal axis and the amplitude on the vertical axis. Here, the weld line signal means the reflected waves from the three welds 9c (9c1, 9c2, 9c3). 31, 32, and 33 are displayed. The reflected wave display screen 104 also displays a signal 36 that means a reflected wave from the thinned portion 9b.

  On the reflected wave display screen 104, the initial welding line signals 31, 32 and 33 and the signal 36 of the thinning portion are displayed in a pulse shape. Although these magnitudes (amplitudes) are various, since the position of the welded portion on the pipe 9 is known, it is easy to distinguish which is the weld line signal.

  Of these, for example, the operator selects the welding line signal 31 and the signal 32. As a result, a distance attenuation curve 34 through which the signal 33 also passes is drawn. The distance attenuation curve 34 is drawn as an attenuation curve that passes through the amplitude values of the signal 31 and the signal 32. This distance attenuation curve 34 is an attenuation curve when the reflectance from the weld line obtained in step S102 is 15%.

  Further, a distance attenuation curve serving as a threshold for extracting defects is determined based on the distance attenuation curve 34. For example, assume that the threshold for extracting defects is 3% reflectance. The distance attenuation curve 35 is a curve drawn proportionally because the distance attenuation curve 34 has a reflectance of 15%. The reflected wave 36 from the thinned portion 9b is compared with the distance attenuation curve 35 having a reflectance of 3%.

  Next, the central controller 6a extracts a signal exceeding the distance attenuation curve 35 (step S105). In FIG. 6, the signal 36 is extracted. The signal level of the signal 36 is measured as a reflectance by the ratio of the distance attenuation curve 35. In the illustrated example, for example, it is assumed that the signal level of the signal 36 is 4%.

  Finally, in step S106, the operator evaluates the sectional area ratio of the defect based on the reflectance of the signal 36. Also at this time, the reflectance varies depending on the shape of the defect, particularly the length in the guide wave propagation direction, and therefore, a method equivalent to that in steps S101 to S102 is used. However, the shape of the thinning is local unlike the weld line and is often not axially symmetric with respect to the piping.

The shape can be given as a part of a sphere with parameters as shown in FIG. 7, for example. In the example of FIG. 7, the defect is defined by a length b in the guide wave propagation direction, a length a in a direction orthogonal thereto, a depth c, and a radius r. Among these, the magnitude of the reflected waves 36 from the defect of FIG. 6 (4%), the cross-sectional area ratio of the length b and the defect of the guide wave propagation direction (except the cross-sectional area S of the defect at the cross-sectional area S ₀ of the pipe Value).

  FIG. 8a is a diagram showing the reflectivity with the guide wave transmission frequency (40 kHz in the previous example) and the reflectivity axis as a parameter with the length b in the guide wave propagation direction as 10 mm and the defect cross-sectional area ratio as a parameter. Yes, ask in advance. In this case, since the frequency of the guide wave is 40 kHz and the magnitude of the reflected wave 36 from the defect is 4%, it can be estimated from FIG. 8a that the defect has a cross-sectional area ratio of about 10%. As a more effective method, as shown in FIG. 8b, when the frequency of the guide wave is 40 kHz and the magnitude of the reflected wave 36 from the defect is 4%, the length of the guide wave propagation direction obtained in advance is obtained. Reference is made to a plurality of reflectances with b as a parameter. By referring to such data and measuring by changing the frequency in the vicinity of 40 kHz, it is possible to estimate the length b in the guide wave propagation direction and the sectional area ratio of the defect.

  As described above, in the present embodiment, calibration is performed in consideration of the frequency characteristics using a discontinuous portion such as a weld line existing in the pipe, so that the receiving sensitivity of the sensor is highly accurate. Calibration can be performed, and the defect size can be evaluated with high accuracy. Especially in cases where the reference reflecting member cannot be used, such as piping covered with a heat insulating material, other than where the sensor is installed, or in cases where it is difficult to install the reference reflecting member, such as piping with a rough surface. Defect size can be evaluated.

1, 2: Ultrasonic probe rows 1a, 1b, 1c, 1d: Ultrasonic probes 2a, 2b, 2c, 2d: Ultrasonic probe 3: Guide wave sensor 4: Guide wave transmitter / receiver 5: A / D converter 6: computer 6a: central control device 6b: signal processing device 7: display device 8: guide wave 9: piping 10: piping inspection device

Claims (9)

In a method of applying a guide wave to a cylindrical structure including a welded portion and detecting the size of a defect in the structure using the reflected wave,
A first step of setting a cross-sectional shape of a welded portion of a cylindrical structure to be measured to obtain a first reflectance depending on a guide wave frequency, and a second step of installing a sensor and transmitting / receiving a guide wave And a third step of obtaining a first distance attenuation curve from a plurality of reflected wave signals appearing at the position of the welded portion of the cylindrical structure, and setting a second reflectance to be measured as a defect , A fourth step of obtaining a second distance attenuation curve at the second reflectance from the first reflectance, the second reflectance and the first distance attenuation curve is obtained by the second step. A fifth step of determining a third reflectance at that time from the magnitude of the reflected wave and the second distance attenuation curve obtained, and a defect from the third reflectance of the fifth step Consisting of a sixth step to obtain the size of Guided wave inspection method characterized. The guided wave inspection method according to claim 1,
In the first step, the guide wave inspection method is characterized in that the cross-sectional shape of the welded part is set by a thickness including the extraneous portion of the welded part and the length of the extraneous part. In the guide wave inspection method according to claim 2,
The first reflectivity depending on the guide wave frequency is defined by an amplitude and a frequency interval, the amplitude is determined by a thickness including an extra portion of a welded portion, and the frequency interval is determined by the length of the extra portion. Guide wave inspection method. In the guide wave inspection method according to any one of claims 1 to 3,
A guide wave inspection method having a plurality of defect cross-sectional area ratio characteristics on a characteristic of reflectivity with respect to a guide wave frequency, and obtaining a defect cross-sectional area ratio from the guide wave frequency and the third reflectivity . A first ultrasonic probe array having a plurality of first ultrasonic probes arranged in a circumferential direction of the pipe, and a predetermined distance in the longitudinal direction from the first ultrasonic probe array; A second ultrasonic probe array having a plurality of second ultrasonic probes arranged in the circumferential direction of the pipe, and a guide wave to propagate to one side in the longitudinal direction of the pipe The transmission time of the transmission signal applied to the first ultrasonic probe array and the second ultrasonic probe array is relatively shifted, and the reflected wave of the guide wave is obtained as an electrical reception signal. In a pipe inspection apparatus including a transmission / reception means, a processing device for detecting a pipe defect based on the received signal, and an image display means,
The processing apparatus sets a cross-sectional shape of a welded portion of the pipe to obtain a first reflectance that depends on a guide wave frequency, and a plurality of reflected wave signals appearing at the position of the welded portion of the pipe. The second means for obtaining the first distance attenuation curve from the second reflectance, the second reflectance to be measured as a defect is set, and from the first reflectance, the second reflectance, and the first distance attenuation curve. And a third means for obtaining a second distance attenuation curve at the second reflectance, and a defect is identified from the magnitude of the reflected wave obtained from the ultrasonic probe and the second distance attenuation curve. And a fourth means for obtaining the third reflectance at that time and a fifth means for obtaining the size of the defect from the third reflectance of the fourth means. apparatus. In the guided wave inspection apparatus according to claim 5,
A guide wave inspection apparatus, wherein the image display means displays a cross-sectional shape of a welded portion of a pipe and its set value, a guide wave frequency and a first reflectance, a reflected wave and an attenuation signal. In the guided wave inspection apparatus according to claim 5,
In the first means, the guide wave inspection apparatus is characterized in that the cross-sectional shape of the welded portion is set by the thickness including the welded portion and the length of the welded portion, and displayed on the image display means. In the guided wave inspection apparatus according to claim 5,
The first reflectivity depending on the guide wave frequency is defined by an amplitude and a frequency interval, the amplitude is determined by a thickness including an extra portion of a welded portion, and the frequency interval is determined by the length of the extra portion. Guide wave inspection device. In the guide wave inspection apparatus according to any one of claims 5 to 8,
A guide wave inspection apparatus having a plurality of defect cross-sectional area ratio characteristics on a characteristic of reflectance with respect to a guide wave frequency, and obtaining a defect cross-sectional area ratio from the guide wave frequency and the third reflectance. .

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