Inspection method, inspection apparatus, and member repair method

Abstract

To provide an inspection method and an inspection apparatus capable of accurately detecting a defective portion from a member to be inspected. 【Solution means】The inspection method according to the present invention is an inspection method for detecting a defective portion from a member to be inspected, including: a first detection step of detecting a first signal from an inspection region on the surface of the member to be inspected using an eddy current flaw detector; a second detection step of detecting a second signal from the inspection region using an ultrasonic thickness gauge; and a determination step of determining that there is a defective portion in the inspection region when at least one of the first signal and the second signal indicates an abnormal value.

Description

Technical Field

[0001] The present invention relates to an inspection method for detecting defective parts such as corrosion parts and cracks from a member to be inspected, an inspection apparatus, and a method for repairing a member.

Background Art

[0002] When an inspection target member such as a hollow member such as a pipe or a tank is corroded or damaged, problems such as leakage of the contents occur. For this reason, various inspection methods for detecting defective parts such as corrosion parts and cracks from the inspection target member have been proposed. For example, Patent Document 1 describes a method for detecting defects in a pipe using an ultrasonic thickness gauge. Further, Patent Document 2 describes a method for detecting cracks and corrosion thinning in a pipe using an eddy current flaw detector. Further, Patent Document 3 describes a method for detecting flaws such as thinning and cracks in an inspection target member using an eddy current flaw detector.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the method described in Patent Document 1 is a point measurement technique, it is impossible to detect local corrosion parts unless the entire surface of the member to be inspected is measured. Also, usually, an ultrasonic thickness gauge detects multiple reflections of ultrasonic waves generated between two parallel surfaces, and assuming that the time interval is the round-trip ultrasonic propagation time, the thickness is calculated by multiplying the ultrasonic propagation time by the known sound velocity for each material of the member to be inspected. For this reason, when there are irregularities on the surface due to corrosion or the like, or when the target surface is not parallel, multiple reflections cannot be detected and the thickness cannot be measured. Thus, according to the method described in Patent Document 1, there is a possibility of overlooking corrosion parts. As a result, in thickness inspection, although it is necessary to measure the thickness of the inspection range, even if the thickness of a sound part can be measured, the thickness may not be measurable in a corrosion and thickness-reduced part, and there is a possibility of not being able to detect the corrosion and thickness-reduced part.

[0005] On the other hand, since an eddy current flaw detector is a device that detects changes in the thickness of a member to be inspected, the methods described in Patent Document 2 and Patent Document 3 cannot measure the absolute value of the thickness of the member to be inspected. Also, since the intensity of the signal detected by the eddy current flaw detector depends on the amount of change in the thickness of the member to be inspected, it is difficult to detect a corrosion part with a small amount of change in thickness, such as a part with uniform thickness reduction, by the methods described in Patent Document 2 and Patent Document 3.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide an inspection method and an inspection apparatus capable of accurately detecting defective parts from a member to be inspected. Another object of the present invention is to provide a member repair method capable of suppressing the occurrence of troubles caused by defective parts of the member.

Means for Solving the Problems

[0007] [1] The inspection method according to the present invention is an inspection method for detecting a defective part from a member to be inspected, including: a first detection step of detecting a first signal from an inspection area on the surface of the member to be inspected using an eddy current flaw detector; a second detection step of detecting a second signal from the inspection area using an ultrasonic thickness gauge; and a determination step of determining that there is a defective part in the inspection area when at least one of the first signal and the second signal shows an abnormal value.

[0008] [2] In the inspection method according to the present invention as described in [1] above, in the determination step, when the first signal shows an abnormal value and the second signal shows a normal value, it is determined that there is a crack in the inspection area; when both the first signal and the second signal show abnormal values, it is determined that there is a pitted thinning in the inspection area; and when the first signal shows a normal value and the second signal shows an abnormal value, it is determined that there is a uniform thinning in the inspection area.

[0009] [3] The member repair method according to the present invention includes a repair step of repairing or replacing a defective part of the member detected using the inspection method described in [1] or [2] above.

[0010] [4] The inspection device according to the present invention is an inspection device for detecting a defective part from a member to be inspected, including: an eddy current flaw detector for detecting a first signal from an inspection area on the surface of the member to be inspected; an ultrasonic thickness gauge for detecting a second signal from the inspection area; and an information processing device for determining that there is a defective part in the inspection area when at least one of the first signal and the second signal shows an abnormal value.

[0011] [5] In the inspection device according to the present invention as described in [4] above, it includes a moving part for moving the eddy current flaw detector and the ultrasonic thickness gauge on the surface of the member to be inspected.

Advantages of the Invention

[0012] According to the inspection method and inspection device of the present invention, a defective part can be accurately detected from a member to be inspected. According to the member repair method of the present invention, it is possible to suppress the occurrence of troubles caused by defective parts of the member.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] 〔Concept of the Present Invention〕 First, the concept of the inspection method and inspection apparatus according to the present invention will be described.

[0015] There are corrosion parts, cracks, etc. in the defective parts of hollow members such as pipes and tanks, and the corrosion parts have forms such as pitting and uniform wall thickness reduction. Such defective parts need to be detected early because they may lead to troubles such as leakage of the contents. Therefore, the inventors of the present invention evaluated the relationship between the output signals of an eddy current flaw detector and an electromagnetic ultrasonic thickness gauge, respectively, and the defective parts (especially corrosion parts and cracks) for the purpose of detecting corrosion parts and cracks. Specifically, a steel plate S with artificial scratches simulating corrosion parts and cracks as shown in FIG. 1(b) was prepared, and a self-propelled carriage 1 equipped with an eddy current flaw detector and an electromagnetic ultrasonic thickness gauge was run on the steel plate S to evaluate the relationship between the output signals of the eddy current flaw detector and the electromagnetic ultrasonic thickness gauge and the corrosion parts and cracks.

[0016] Specifically, a mortar-shaped defect D1 (30φ, depth equivalent to 40% of the original thickness (12 mm) of the steel plate S) simulating pitted metal loss and a V-groove D2 (depth 5 mm, width 100 mm) simulating uniform metal loss were formed on the steel plate S. Since the V-groove D2 had about 42% metal loss relative to the original thickness of the steel plate S, it is generally at the detection target level. Also, the joint of the steel plate S was simulated as a crack by butting and arranging the end of the steel plate S with the mortar-shaped defect D1 and the end of the steel plate S with the V-groove D2. The self-propelled carriage 1 was designed to be adsorbed and travel by the drive wheels 1a with magnets, and a travel instruction and a flaw detection instruction were given to the self-propelled carriage 1 by wireless communication from an external computer. Also, an encoder was attached to one of the drive wheels 1a with magnets (see Fig. 2), and the travel distance of the self-propelled carriage 1 was measured and stored by the encoder.

[0017] As the eddy current flaw detector 2 (see Fig. 2), an E-type coil was used and arranged so that the difference in the detection signal could be taken along the travel direction of the self-propelled carriage 1. Also, the leg interval of the E-type coil was 20 mm, the number of turns was 200 turns, the excitation frequency was 10 kHz, and the lift-off was 3 mm. Also, the E-type coils were arranged in 3 channels at a pitch of 30 mm along the width direction of the self-propelled carriage 1, and the measurement was performed by switching the channels every 100 ms. Also, the power supply of the E-type coil was a battery, and it was made a separate system from the self-propelled carriage 1 as a noise countermeasure. Then, AD conversion of the detection signal was performed inside each E-type coil, and the detection signal was transmitted and recorded to the external computer by wireless communication every 100 ms.

[0018] As the electromagnetic ultrasonic thickness gauge 3 (see Fig. 2), a shear wave generation type electromagnetic ultrasonic thickness gauge was used, and measurement was performed in a so-called echo - echo mode using a center frequency of 4 MHz. Also, in order to detect the bottom echo that undergoes multiple reflections, gates were set for the so - called B1 echo and B2 echo, and the thickness of the steel plate S was calculated using the time difference between them. At the time of calculation, the shear wave velocity was assumed to be 3240 m. Also, the synchronous addition was set to 8 times, and an auto - gain up to 100 dB was set. If the B1 echo and B2 echo could not be detected in this auto - gain state, it was judged that the thickness could not be measured. The measurement results were transmitted to an external computer by wireless communication and recorded in synchronization with the measurement results of the eddy current flaw detector 2.

[0019] The evaluation results are shown in Fig. 1(a). As shown in Fig. 1(a), in the output signal (eddy current flaw detection signal) of the eddy current flaw detector 2, changes were observed at the mortar - shaped defect D1 (pit - shaped thickness reduction) and the joint (crack) of the steel plate S, and the mortar - shaped defect D1 and the joint could be detected. On the other hand, in the V - groove D2 (uniform thickness reduction), there was no significant change in the eddy current flaw detection signal, and the V - groove D2 could not be detected with a realistic signal - to - noise ratio. Specifically, the intensity of the eddy current flaw detection signal was small compared to the mortar - shaped defect D1 with approximately the same depth. This is considered to be because the width of the V - groove D2 is wider than the width of the eddy current flaw detector 2, so the amount of change in the detected plate thickness is small.

[0020] On the other hand, regarding the output of the electromagnetic ultrasonic thickness gauge 3 (thickness gauge indicated value), at the joint part, the indicated value always indicated the original thickness (12 mm) of the steel plate S. Also, in the mortar - shaped defect D1, an indicated value showing the bottom thickness (remaining thickness) was obtained only at the position corresponding to the bottom, and the reflected signal became weak on the inclined surface and no indicated value was obtained. Also, in the V - groove D2, an indicated value of a thickness (remaining thickness) thinner than the original thickness of the steel plate S was obtained throughout, and it was confirmed that there was a thickness - reduction part.

[0021] When the above evaluation results are organized, they are as shown in Table 1 below. That is, as shown in Table 1, in the sound part, there is no response to the eddy current flaw detection signal, and the plate thickness gauge indication value indicates the original thickness of the steel plate S. Also, in the case of cracks, there is a response to the eddy current flaw detection signal, and the plate thickness gauge indication value indicates the original thickness of the steel plate S. In the case of pitted thickness reduction, there is a response to the eddy current flaw detection signal, and the plate thickness gauge indication value is unmeasurable or the plate thickness indication value indicates the remaining thickness of the steel plate S. In the case of uniform thickness reduction, there is no response to the eddy current flaw detection signal, and the plate thickness gauge indication value indicates the remaining thickness of the steel plate S.

[0022]

Table 1

[0023] Therefore, as shown in Table 2 below, it was newly found that by combining the output signal of the eddy current flaw detector and the output signal of the electromagnetic ultrasonic plate thickness gauge, it is possible to determine whether the inspection area is in the sound part, cracked, pitted thickness reduction, or uniform thickness reduction. That is, as shown in Table 2, when there is no response to the eddy current flaw detection signal and the plate thickness gauge indication value indicates the original thickness of the steel plate S, it can be determined that the inspection area is the sound part. Also, when there is a response to the eddy current flaw detection signal and the plate thickness gauge indication value indicates the original thickness of the steel plate S, it can be determined that there is a crack in the inspection area. Also, when there is a response to the eddy current flaw detection signal and the plate thickness is unmeasurable or the plate thickness indication value indicates the remaining pressure of the steel plate S, it can be determined that there is pitted thickness reduction in the inspection area. Also, when there is no response to the eddy current flaw detection signal and the plate thickness gauge indication value indicates the original thickness of the steel plate S, it can be determined that there is uniform thickness reduction in the inspection area.

[0024]

Table 2

[0025] Therefore, in the inspection method and inspection device according to the present invention, based on the combination of the output signal of the eddy current flaw detector and the output signal of the electromagnetic ultrasonic plate thickness gauge, it is determined whether the inspection area is in the sound part or the defective part, and further which of the defective parts is a crack, pitted thickness reduction, or uniform thickness reduction.

[0026] Note that in the case of uniform thickness reduction, the surface of the member to be inspected is smooth and uniformly corroded, but there may also be a state where pit-shaped thickness reduction continuously exists in a drain sump or the like. Although this state is an intermediate state between the two, since the surface to be measured becomes non-uniform, ultrasonic scattering occurs, making it difficult to measure with an electromagnetic ultrasonic thickness gauge. However, the continuous existence of pit-shaped thickness reduction means that the plate thickness changes frequently and continuously. When such an area is inspected with an eddy current flaw detector, signals with large amplitudes are continuously detected. Therefore, continuous pit-shaped thickness reduction can also be detected by combining an electromagnetic ultrasonic thickness gauge and an eddy current flaw detector. In this way, even for uniform thickness reduction and healthy parts that cannot be distinguished by an eddy current flaw detector alone, the presence or absence of thickness reduction can be detected from the difference in the indicated values of the electromagnetic ultrasonic thickness gauge. Also, single pit-shaped thickness reduction and continuous pit-shaped thickness reduction can be detected by whether the eddy current flaw detection signal is continuous. Further, since the ultrasonic thickness gauge may indicate the plate thickness of the original thickness part around the pit-shaped thickness reduction, it is advisable to prioritize the eddy current flaw detection signal for thickness reduction determination.

[0027] An example of the process flow for detecting a defective part from the member to be inspected using Table 2 is shown in FIG. 3. Note that the determination operation described below is executed by an information processing device such as a computer comparing the measured eddy current flaw detection signal and plate thickness with the data shown in Table 2. More specifically, at least steps S2 to S4, S7, and S10 described later are executed by the information processing device. As shown in FIG. 3, when detecting a defective part of the member to be inspected using Table 2, first, an eddy current flaw detection signal and a plate thickness are measured in the inspection area of the member to be inspected using an eddy current flaw detector and an electromagnetic ultrasonic thickness gauge, and these measurement results are recorded in the information processing device (step S1). Note that since the measurement position may deviate depending on the arrangement positions of the eddy current flaw detector and the electromagnetic ultrasonic thickness gauge, it is desirable to correct and modify it.

[0028] Next, it is determined whether the plate thickness can be measured in the inspection area (step S2). If the plate thickness can be measured (step S2: Yes), it is determined whether the measured plate thickness indicates the original thickness of the member to be inspected (step S3). Then, if the measured plate thickness indicates the original thickness of the member to be inspected (step S3: Yes), it is determined whether there is a response to the eddy current flaw detection signal (step S4). And if there is a response to the eddy current flaw detection signal (step S4: Yes), it is determined that there is a crack in the inspection area (step S5). On the other hand, if there is no response to the eddy current flaw detection signal (step S4: No), it is determined that the inspection area is a sound part (step S6).

[0029] On the other hand, if it is determined in the process of step S3 that the measured plate thickness indicates a value different from the original thickness of the member to be inspected (step S 3: No), it is determined whether there is a response to the eddy current flaw detection signal (step S7). And if there is a response to the eddy current flaw detection signal (step S7: Yes), it is determined that there is single or continuous pitted thickness reduction in the inspection area (step S8). On the other hand, if there is no response to the eddy current flaw detection signal (step S7: No), it is determined that there is uniform thickness reduction in the inspection area (step S9). Also, in the process of step S2, if the plate thickness cannot be measured in the inspection area (step S2: No), it is determined whether there is a response to the eddy current flaw detection signal (step S10). And if there is a response to the eddy current flaw detection signal (step S10: Yes), it is determined that there is single or continuous pitted thickness reduction in the inspection area (step S11).

[0030] On the other hand, if there is no response to the eddy current flaw detection signal (step S10: No), it is determined that there may be a problem with the device, and the device is inspected (step S12). For example, when the electromagnetic ultrasonic thickness gauge has no indicated value and no eddy current flaw detection signal is detected, it indicates that the inner surface is rough enough that the reflected signal of the electromagnetic ultrasonic signal does not return, but no eddy current flaw detection signal appears, so a failure of the eddy current flaw detector is suspected. Or, it is suspected that there is a problem such as a poor lift-off of the eddy current flaw detector and no eddy current flaw detection signal or electromagnetic ultrasonic signal is detected. All of these require inspection and repair as problems with the device. In the example of FIG. 3, the determination is made based on the result of the thickness measurement, but it may also be made based on the result of the eddy current flaw detection. Also, the result of the thickness measurement and the result of the eddy current flaw detection may be compared simultaneously to search for whether it corresponds to any of those in Table 2.

[0031] Thereafter, after recording the determination result, by moving to the next inspection area and executing the same process, the entire inspection area of the inspection target member is inspected. Hereinafter, the configurations of the self-propelled cart 1, the eddy current flaw detector 2, and the electromagnetic ultrasonic thickness gauge 3 used in the inspection method and inspection apparatus according to the present invention will be specifically described.

[0032] 〔Self-Propelled Cart〕 The self-propelled carriage 1 corresponds to the moving part in the inspection apparatus according to the present invention. The self-propelled carriage 1 is a carriage that adsorbs to the member to be inspected and self-propels. In order to perform flaw detection while self-propelling on the member to be inspected, the self-propelled carriage 1 is provided with an adsorption mechanism and a self-propelling mechanism. As an example, since the self-propelled carriage 1 can adsorb while traveling on the member to be inspected, it is provided with magnet wheels. In this case, the magnet wheels may also serve as both the adsorption mechanism and the traveling mechanism. As an example, it is preferable that it is a traveling mechanism and adsorption mechanism combined as a drive wheel with a magnet. Also, as an example, it may be provided with an endless track of a permanent magnet. It may be in a form having an adsorption mechanism by a magnet and a drive device such as wheels or an endless track for traveling. Also, it is preferable that it has a specification that can overcome the presence of a welding bead or the like and can travel. Also, the position (travel distance, etc.) of the self-propelled carriage 1 may be measured by an encoder or the like and recorded as the flaw detection position. Attitude measurement by an inertial measurement unit (IMU), surveying and position measurement means such as a total station, or self-position detection by GPS or the like may be used. The flaw detection position of the self-propelled carriage 1 is recorded by some method. The self-propelled carriage 1 is preferably a device that operates wirelessly. If it is wireless, it is not restricted by the constraints of the drive and signal transmission cables, and inspection in an arbitrary range becomes possible. Of course, the moving part in the present invention is not limited to the above self-propelled carriage 1. Instead of the self-propelled carriage 1, an ordinary carriage may be used and moved manually. Also, instead of the self-propelled carriage 1, it may be installed as a part of the manufacturing equipment in combination with an arm that can be operated by a drive device.

[0033] 〔Eddy current flaw detector〕 The eddy current flaw detector 2 is equipped with an exciting coil, a detecting coil, and a signal processing unit including phase detection. Also, when inspecting steel pipes or the like, the eddy current flaw detector 2 is equipped with an external magnetization exciter. The eddy current flaw detector 2 applies an exciting signal of an arbitrary (appropriate) frequency to the exciting coil to generate eddy currents in the member to be inspected. The eddy currents generated near the surface of the member to be inspected are detected by the detecting coil. If there are defects or thickness changes in the member to be inspected, the distribution of the eddy currents changes, and the signal detected by the detecting coil changes. For the detected signal, processing including phase detection is performed in the signal processing unit, and the detection voltage and phase information are extracted. When using a differential type detecting coil, if there are thickness differences or defects near the detecting coil, they are output as voltage signals. Thereby, thickness changes, cracks, defects, etc. between the detecting coils can be detected.

[0034] Considering the size of the defective part to be detected, lift-off, etc., the size of the detecting coil is appropriately designed. When using a differential type detecting coil, the impedance of the detecting coil and the difference in the change of the alternating magnetic field near the detecting coil are detected as the flaw detection signal. Therefore, if the size of the pit-shaped thinning or the like of the detection target is too large for the detecting coil, there will be no difference between the two detecting coils and it will not appear as a detection signal. Generally, the pit-shaped thinning is a mortar-shaped thinning part of about 10 to 30 mm, so it is preferable that the dimensions of the eddy current flaw detector are of the same order as these. When the member to be inspected is a ferromagnetic material, since the eddy currents are distributed only very close to the surface, in order to detect the thickness change of the ferromagnetic material, a magnetic field close to magnetic saturation is applied from the outside to reduce the magnetic permeability and distribute the eddy currents to the inside. Therefore, in this case, the eddy current flaw detector 2 has a magnetizer for applying external magnetization. Considering mounting the magnetizer on the self-propelled carriage 1, it is preferably a permanent magnet, and further, a rare earth magnet such as a neodymium magnet is preferable from the viewpoints of cost and magnetic field strength. If the magnet is powerful, it contributes to miniaturization and weight reduction.

[0035] The eddy current flaw detector 2 detects changes in eddy currents between differential detection coils, and an output is generated if there is a difference in thickness at each position of the differential coils. In a defective part, the thickness of the metal part decreases due to loss of material or oxidation, etc. Therefore, the eddy current distribution changes, and thinning can be detected by eddy current flaw detection. There is a correlation between the amplitude of the eddy current flaw detection signal and the thinning ratio, which can be quantified in advance using test pieces, etc. By creating artificial defects in the detection target (depth / thickness), the corrosion depth can be quantified from the detected amplitude.

[0036] In the example of this embodiment, three eddy current flaw detectors are arranged in the width direction of the moving part (here, the self-propelled carriage 1). Here, the width direction of the moving part is in the same plane and perpendicular to the traveling direction of the self-propelled carriage 1. In this way, by arranging a plurality of eddy current flaw detectors in the width direction, a wider range can be measured than in the case of one, which is preferable. The dimensions of one eddy current flaw detector can be determined as appropriate. On the other hand, when the eddy current flaw detector becomes larger compared to the pit-shaped thinning, the sensitivity tends to decrease. Therefore, instead of increasing the dimensions of one eddy current flaw detector, it is preferable to use a plurality of them, which can achieve both maintaining the sensitivity, expanding the measurement range, and shortening the measurement time. However, if the number of eddy current flaw detectors is increased too much, problems such as the moving part becoming larger, making it difficult to handle the entire inspection device including the moving part, or the mimicking structure of the inspection target and the eddy current flaw detector becoming complicated may occur, so attention should be paid.

[0037] 〔Electromagnetic ultrasonic thickness gauge〕 The electromagnetic ultrasonic thickness gauge 3 consists of a coil and a magnet, and induces ultrasonic waves in the inspection target member by the Lorentz force or magnetostrictive force generated by the interaction between the magnetic field applied by the magnet close to the inspection target member, which is a conductor, and the eddy current generated in the inspection target member by applying a current pulse to the similarly close coil. A permanent magnet or an electromagnet can be used to apply a magnetic field to the inspection target member. When loading it on the self-propelled carriage 1, it is preferable to use a rare earth magnet (permanent magnet) such as a neodymium magnet from the perspective of weight.

[0038] When using a permanent magnet, the permanent magnet is brought close to the inspection target member within a range of several millimeters (about 1 to 5 mm or less), and a magnetic field is applied. Next, a coil is placed in the range where the magnetic field is applied, and a single-shot or several-shot burst current of about 100 kHz to 5 MHz is applied. As a result, eddy currents are induced on the surface of the inspection target member facing the coil, and an interaction occurs between the eddy currents and the static magnetic field applied by the magnet, generating a Lorentz force on the test object. Consequently, ultrasonic waves of the same frequency as the applied current are generated and propagate through the inspection target member. The ultrasonic vibrations generated on the surface propagate through the inspection target member, return to the surface, and vibrate the surface.

[0039] Since the detection of the signal can be performed by the coil as the reverse process of generation, the transmission probe and the reception probe can be the same. The detected signal is amplified by a preamplifier as appropriate, and then captured by a computer, a microcomputer, etc. through AD conversion, and averaged (noise removal) by synchronous addition or the like as appropriate to calculate the propagation time of the ultrasonic waves. When used as a thickness gauge, when multiple reflections occur on the surface and the bottom surface of the measurement target, the time difference of the reflection times is calculated, and the known sound speed is multiplied by it to obtain the plate thickness. For example, the sound speed of steel is a known sound speed, about 3240 m / s (in the case of shear waves), and it can be calculated accordingly. The sound speed is calibrated as appropriate according to the steel type and alloy components.

[0040] Electromagnetic ultrasonic waves are generated by the eddy currents induced by the coil and the static magnetic field applied by a magnet or the like, so they can be used without being in close contact with the measurement target. Also, the thickness gauge using electromagnetic ultrasonic waves is stable against changes in probe angles and the like and disturbances. Due to these advantages, when automating the inspection method and / or inspection device according to the present invention, the use of an electromagnetic ultrasonic thickness gauge is very suitable.

[0041] The captured ultrasonic waveform and the plate thickness calculation result are preferably transmitted to an external computer or the like by wireless transmission. Or, they are transmitted to the control unit of the self-propelled cart 1, the eddy current flaw detector 2, etc., and recorded and stored together. They are used as the plate thickness measurement result in combination with the flaw detection result of eddy current flaw detection and the traveling result (position, attitude, etc.) of the cart.

[0042] In the description of the present invention, an electromagnetic ultrasonic thickness gauge was described as an example of an ultrasonic thickness gauge. As described above, this is because the electromagnetic ultrasonic thickness gauge is relatively easy to handle. However, the effects of the present invention can also be obtained with ultrasonic thickness gauges other than the electromagnetic ultrasonic thickness gauge. In this case, a suitable medium may be flowed between the inspection target member and the ultrasonic thickness gauge. For example, while applying or interposing water, ultrasonic gel, etc. to the inspection target member, the thickness of the inspection target member is measured with an ultrasonic thickness gauge.

Example

[0043] In this example, a pipe with actual corrosion and wall thickness reduction was inspected using the present invention. As shown in Fig. 4(a), 1 / 4 of the outer circumference of the pipe P was inspected from the bottom to the side by a self-propelled trolley. The original wall thickness of the pipe was 10 mm, and aluminum tape (conductive tape) was attached to two sound areas to create simulated scratches simulating cracks. Also, it was known in advance that there was a pitted wall thickness reduction area and a uniform wall thickness reduction area due to corrosion adjacent to each other at the lower part of the pipe. As the eddy current flaw detector 2, an E-type coil was used and arranged so that the difference in the detection signal could be obtained in the traveling direction of the self-propelled trolley 1. The leg spacing of the E-type coil was 20 mm, the number of turns was 200 turns, the excitation frequency was 10 kHz, and the lift-off was 3 mm. Also, the E-type coils were arranged in 3 channels at a pitch of 30 mm along the width direction of the self-propelled trolley 1, and the channels were switched every 100 ms for measurement. Also, the power supply for the E-type coils was a battery, AD conversion of the detection signal was performed inside each E-type coil, and the detection signal was transmitted, recorded, and judged by wireless communication to an external computer which is an "information processing device" every 100 ms. On the other hand, the measured values of the electromagnetic ultrasonic thickness gauge were aggregated at a pitch of 100 mm, and the variation (±1σ) in the range of ±50 mm was calculated as an error bar.

[0044] The measurement results are shown in Fig. 4(b). As shown in Fig. 4(b), the amplitude of the eddy current flaw detection signal is small in the sound part. On the other hand, near the simulated flaw part and the bottom of the pipe, the amplitude of the eddy current flaw detection signal is large, clearly indicating that the wall thickness of the pipe has changed. On the other hand, the measured value of the electromagnetic ultrasonic thickness gauge indicates near the original wall thickness of 10 mm in the sound part, and the variation is small. In contrast, near the bottom of the pipe, the measured value of the electromagnetic ultrasonic thickness gauge indicates a wall thickness thinner than the original wall thickness, and the variation has become large. From these facts, it was determined that there is a simulated flaw of crack on the side surface of the pipe, there is pitting wall thickness reduction and a uniform wall thickness reduction part adjacent to it near the bottom of the pipe, and the rest other than these two places is sound. Thus, according to the present invention, it was confirmed that the defective part of the pipe can be accurately detected.

[0045] As described above, the embodiments to which the invention made by the present inventors is applied have been described. However, the present invention is not limited by the description and drawings that form a part of the disclosure of the present invention according to this embodiment. That is, all other embodiments, examples, and operation techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

Explanation of Signs

[0046] 1 Self-propelled carriage 1a Driving wheel 2 Eddy current flaw detector 3 Electromagnetic ultrasonic thickness gauge D1 Mortar-shaped defect D2 V-groove P Pipe S Steel plate

Claims

1. An inspection method for detecting a defective part from an inspection target member, comprising: a first detection step of detecting a first signal from an inspection area on a surface of the inspection target component using an eddy current flaw detector; a second detection step of detecting a second signal from the inspection area using an ultrasonic thickness gauge; a determining step of determining that a defective portion is present in the inspection area when at least one of the first signal and the second signal indicates an abnormal value; Including, The determination step includes the steps of determining that a crack exists in the inspection area when the first signal indicates an abnormal value and the second signal indicates a normal value, determining that pit-like thinning exists in the inspection area when both the first signal and the second signal indicate abnormal values, and determining that uniform thinning exists in the inspection area when the first signal indicates a normal value and the second signal indicates an abnormal value.

2. A method for repairing a component, comprising a repairing step of repairing or replacing a defective portion of the component detected by using the inspection method according to claim 1.

3. An inspection device for detecting a defective part from an inspection target member, an eddy current flaw detector for detecting a first signal from an inspection area on a surface of the inspection target component; an ultrasonic thickness gauge for detecting a second signal from the inspection area; an information processing device that determines that a defective portion exists in the inspection area when at least one of the first signal and the second signal indicates an abnormal value; Equipped with The information processing device determines that a crack exists in the inspection area when the first signal indicates an abnormal value and the second signal indicates a normal value, determines that pit-like thinning exists in the inspection area when both the first signal and the second signal indicate abnormal values, and determines that uniform thinning exists in the inspection area when the first signal indicates a normal value and the second signal indicates an abnormal value.

4. The inspection device according to claim 3 , further comprising a moving unit that moves the eddy current flaw detector and the ultrasonic thickness gauge on the surface of the inspection target member.

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