Eddy-current flaw detection device and eddy-current flaw detection method

Abstract

To provide an eddy current flaw detection device and an eddy current flaw detection method capable of performing inspection in a shorter time while preventing the interference of a magnetic field.SOLUTION: An eddy-current flaw detection device includes an array coil including a pair of excitation coils disposed apart from each other in a first direction and a detection coil, and a voltage application unit that applies alternating current voltage having a phase difference of 180° between the pair of excitation coils. An eddy-current flaw detection method uses an array coil including a pair of excitation coils disposed apart from each other in a first direction and a detection coil, and includes a step of applying alternating current voltage to one of the pair of excitation coils, and a step of simultaneously applying, to the other of the pair of excitation coils, alternating current voltage having a phase difference of 180° from the alternating current voltage applied to the one of the pair of excitation coils.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an eddy current flaw detection device and an eddy current flaw detection method. [Background technology]

[0002] For example, defects such as thinning and cracks can occur inside various pipes in nuclear power plants due to the flow of high-temperature and high-pressure fluids. A device for detecting such defects is known, as described in Patent Document 1 below. The device described in Patent Document 1 below mainly includes a probe in which an array coil including an excitation coil and a detection coil is arranged in the circumferential direction. When a current is passed through the excitation coil with the probe inserted into the pipe, eddy currents are generated near the inner surface of the pipe. If a defect is present, the eddy currents are disturbed by the defect. The detection coil detects the disturbance and transmits it as an electrical signal to a downstream device.

[0003] Here, the magnetic fields generated by electromagnetic induction when current flows between the circumferentially arranged excitation coils are prone to interference with each other. Magnetic field interference can generate noise and affect detection results. For this reason, a conventional technique to prevent magnetic field interference is to slightly differ the timing at which current flows between the excitation coils. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-159984 Summary of the Invention [Problem to be solved by the invention]

[0005] Eddy current flaw detection requires the acquisition of a fixed number of data points per unit length. As described above, when the inspection is carried out while changing the excitation timing, if the time required to excite all of the circumferentially arranged excitation coils for one revolution becomes long, it becomes necessary to set the scanning speed low. This results in a long inspection time.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an eddy current flaw detection device and an eddy current flaw detection method that are capable of performing inspections in a shorter time while preventing interference with magnetic fields. [Means for solving the problem]

[0007] In order to solve the above problem, the eddy current flaw detection device of the present disclosure includes an array coil including a pair of excitation coils and a detection coil spaced apart in a first direction, and a voltage application unit that applies AC voltages with a phase difference of 180° between the pair of excitation coils.

[0008] The eddy current flaw detection method according to the present disclosure is an eddy current flaw detection method using an array coil including a pair of excitation coils spaced apart in a first direction and a detection coil, and includes the steps of applying an AC voltage to one of the pair of excitation coils, and simultaneously applying an AC voltage to the other of the pair of excitation coils that is 180° out of phase with the AC voltage applied to the one of the pair of excitation coils. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an eddy current flaw detection device and an eddy current flaw detection method that are capable of performing inspection in a shorter time while preventing interference of magnetic fields. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the configuration of an eddy current flaw detection device according to a first embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is a perspective view showing the configuration of an excitation coil and a detection coil according to the first embodiment of the present disclosure. [Figure 3] 1 is a cross-sectional view of an eddy current flaw detector according to a first embodiment of the present disclosure, viewed from the axial direction. [Figure 4] 1 is a graph showing a phase difference of an AC voltage flowing through an excitation coil in an eddy current flaw detection device and method according to a first embodiment of the present disclosure. [Figure 5] 3 is a flowchart showing each step of an eddy current flaw detection method according to the first embodiment of the present disclosure. [Figure 6] FIG. 4 is a cross-sectional view showing the configuration of an eddy current flaw detector according to a second embodiment of the present disclosure. [Figure 7] FIG. 10 is a perspective view showing a first modified example of an array coil according to each embodiment of the present disclosure. [Figure 8] FIG. 10 is a perspective view showing a second modified example of the array coil according to each embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment (Configuration of eddy current flaw detection equipment) An eddy current flaw detector 1 according to a first embodiment of the present disclosure will be described below with reference to Fig. 1 to Fig. 5. The eddy current flaw detector 1 is suitably used for detecting defects such as flaws and cracks that occur in various pipes in, for example, a nuclear power plant.

[0012] 1, the eddy current flaw detector 1 has a rod shape extending along an axis O. Specifically, the eddy current flaw detector 1 (probe 2) includes a probe main body 20, a plurality of array coils 30, and a voltage application unit 40.

[0013] The probe main body 20 has a pair of stabilizers 21 and a coil support part 22 arranged between the stabilizers 21. The stabilizer 21 extends along the axis O and has a cylindrical shape centered on the axis O. When the stabilizer 21 is inserted into a pipe or the like, it comes into contact with the inner surface of the pipe, thereby guiding the probe 2.

[0014] The coil support part 22 has a cylindrical shape with a diameter that is the same as or slightly smaller than that of the stabilizer 21. An array coil 30 (described later) is arranged on the surface of the coil support part 22 in the circumferential direction of the axis O. Power is supplied to the array coil 30 by a cable 23 connected to the rear end side of the probe main body 20.

[0015] (array coil configuration) The array coil 30 has a plurality of cross coils 31. As shown in Fig. 2, each cross coil 31 has an excitation coil 32 and a detection coil 33. The excitation coil 32 and the detection coil 33 are both made of copper wire wound in a circular shape. The central axis A of the excitation coil 32 and the central axis B of the detection coil 33 intersect (are perpendicular to) each other. Furthermore, these central axes are parallel to the inspection target surface 90 (i.e., the inner surface of a pipe, etc.).

[0016] When an AC voltage is applied to the excitation coil 32, an eddy current is generated in the inspection target surface 90. If a defect is present, this eddy current generates a disturbance that bypasses the defect. The detection coil 33 detects this disturbance and transmits it as an electrical signal to a subsequent analysis device, etc. As shown in FIG. 3, such cross coils 31 are arranged in the circumferential direction about the axis O.

[0017] (Configuration of voltage application unit) The voltage application unit 40 applies an AC voltage to the excitation coils 32. As shown in FIG. 3, the AC voltages supplied to a pair of excitation coils 32 arranged opposite each other in the diameter direction (sometimes referred to as the first direction X) are out of phase with each other by 180° (see FIG. 4). In FIG. 4, the AC voltage applied to one excitation coil 32 is indicated by a solid line, and the AC voltage flowing through the other excitation coil 32 is indicated by a dashed line. In other words, when viewed at the same timing, currents flow in different directions between the pair of excitation coils 32. As a result, as shown by the arrows in FIG. 3, the magnetic fields formed by the pair of excitation coils 32 are symmetrical with respect to the axis O. In other words, the magnetic field lines emanating from one excitation coil 32 travel toward one side in the circumferential direction, then extend radially through the axis O, and return to the excitation coil 32. The magnetic field lines emanating from the other excitation coil 32 head toward the other circumferential side, then pass through the axis O position, extend in the radial direction, and return to the other excitation coil 32 again. Therefore, at the center in the radial direction, the magnetic fields generated by the two excitation coils 32 face in the same direction. Furthermore, the magnetic field lines emanating from one excitation coil 32 face the magnetic field lines emanating from the other excitation coil 32 at a position 90° forward in the circumferential direction. Furthermore, at a position 270° forward, the magnetic field lines emanating from one excitation coil 32 flow in the opposite direction to the magnetic field lines emanating from the other excitation coil 32. This makes it possible to prevent interference between these magnetic fields.

[0018] Next, an eddy current flaw detection method will be described with reference to FIG. 5. This method is an example of an operation method of the eddy current flaw detection device 1. As shown in FIG. 5, first, in step S1, a sinusoidal AC voltage is applied to one of a pair of diametrically opposed excitation coils 32. Simultaneously with step S1, in step S2, an AC voltage that is 180° out of phase with the AC voltage applied to the other excitation coil 32 is applied to the other excitation coil 32. Defects are detected by repeatedly executing steps S1 and S2 with time lags for all pairs of excitation coils 32 arranged circumferentially (step S3). After acquiring a predetermined number of data points per unit length, in step S4, the probe main body 20 is moved slightly within the pipe, and steps S1 to S3 are executed at another location. Note that in practice, the probe main body 20 moves continuously. Repeating the above steps completes flaw detection inspection of a long-distance pipe.

[0019] (Action and effect)

[0020] Here, the magnetic fields generated by electromagnetic induction when current flows between the circumferentially arranged excitation coils 32 are prone to interference with each other. Magnetic field interference can cause noise and affect the detection results. For this reason, a conventional technique for preventing magnetic field interference has been to slightly differ the timing at which current flows between the excitation coils 32.

[0021] However, when the inspection is performed while changing the excitation timing as described above, if the time required to excite all of the circumferentially arranged excitation coils 32 for one revolution becomes long, it becomes necessary to set the scanning speed low. As a result, the inspection takes a long time. To solve this problem, the present embodiment employs the above-described configurations and methods.

[0022] According to the above configuration, AC currents with phase differences of 180° flow simultaneously between a pair of excitation coils 32 arranged at a distance from each other. As a result, the magnetic fields formed by the pair of excitation coils 32 are symmetrical to each other. Therefore, near the center in the first direction X where the two magnetic fields intersect, the magnetic field lines are oriented in the same direction. Furthermore, the magnetic field lines emanating from one excitation coil 32 face the magnetic field lines emanating from the other excitation coil 32 at a position 90° circumferentially forward. Furthermore, at a position 270° forward, the magnetic field lines emanating from one excitation coil 32 flow in the opposite direction to the magnetic field lines emanating from the other excitation coil 32. This prevents magnetic field interference between the pair of excitation coils 32. This reduces the possibility of noise in the detection results. Furthermore, because current can be simultaneously passed through a pair of excitation coils 32, even when multiple excitation coils 32 are installed, the inspection can be completed in a short time and the device can be moved to another location. This makes it possible to significantly reduce the time required for flaw detection testing, and ultimately improve the operating rate of plants and the like.

[0023] According to the above configuration, multiple array coils 30 are mounted on the probe body 20. Among the excitation coils 32 included in these array coils 30, by passing AC currents with a phase difference of 180° between a pair of diametrically opposed excitation coils 32, it is possible to form magnetic fields that are less likely to interfere with each other. This reduces the possibility of noise occurring in the detection results. Furthermore, because current can be passed through a pair of excitation coils 32 simultaneously, even when multiple excitation coils 32 are provided, it is possible to complete the inspection in a short time and move the device to another location. This makes it possible to significantly reduce the time required for flaw detection inspection.

[0024] According to the above configuration, it is possible to perform eddy current flaw detection of the mutual induction type using the cross coil 31. This improves the detection resolution, making it possible to precisely detect even minute defects.

[0025] The first embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0026] For example, the number and shape / configuration of the cross coils 31 shown in the drawings in the first embodiment are merely examples and can be changed as appropriate depending on the design and specifications. The shape of the probe main body 20 can also be changed as appropriate. Even in this case, the same effects as those described above can be obtained.

[0027] In addition, the above configuration can also be applied to a self-induction type cross coil in which excitation / detection is performed on each of the coils that make up the cross coil, and the presence or absence of defects is evaluated by taking the difference between the results.

[0028] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 6. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0029] 6, the eddy current flaw detector 101 according to this embodiment is a gap probe 102 for performing inspection while being inserted into a narrow gap. The gap probe 102 is inserted into a gap 203 formed between a first member 201 and a second member 202, and is thereby capable of detecting defects in the first member 201 or the second member 202.

[0030] The eddy current flaw detector 101 includes a plate-shaped member 111 and a plurality of array coils 30. The plate-shaped member 111 has a thickness that allows it to be inserted into the gap 203. A plurality of cross coils 31 are arranged on each of the surfaces of the plate-shaped member 111 facing both sides in the thickness direction (first direction X). Although not shown in detail, as an example, the plurality of cross coils 31 are arranged in a lattice pattern when viewed from the thickness direction.

[0031] The voltage application unit 40 applies an AC voltage to the excitation coil 32 on one side in the thickness direction. At the same time, it applies an AC voltage to the other excitation coil 32 that is 180° out of phase with the AC voltage applied to the excitation coil 32 on one side. As a result, the magnetic fields generated by the pair of excitation coils 32 are symmetrical with respect to the center in the thickness direction. Therefore, at the center in the thickness direction, the magnetic fields generated by the two excitation coils 32 are oriented in the same direction. This makes it possible to prevent interference between these magnetic fields.

[0032] (Action and effect) According to the above configuration, by applying AC voltages with a phase difference of 180° between the excitation coils 32 arranged on both sides of the plate-like member 111 in the thickness direction, it is possible to form magnetic fields that are less likely to interfere with each other. Therefore, it is possible to reduce the possibility of noise occurring in the detection results. Furthermore, because voltage can be applied to a pair of excitation coils 32 simultaneously, even if multiple excitation coils 32 are provided, it is possible to complete the inspection in a short time and move the device to another location. This makes it possible to significantly reduce the time required for flaw detection inspection.

[0033] According to the above configuration, it is possible to perform eddy current flaw detection of the mutual induction type using the cross coil 31. This improves the detection resolution, making it possible to precisely detect even minute defects.

[0034] The second embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit and scope of the present disclosure.

[0035] For example, the number, shape, and configuration of the cross coils 31 shown in FIG. 6 are merely examples, and can be changed as appropriate according to the design and specifications.

[0036] (Other embodiments) Each embodiment of the present disclosure has been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0037] As a modified example common to all the embodiments, the following configuration can be adopted. For example, in each of the above embodiments, an example has been described in which the voltage application unit 40 itself generates AC voltages of different phases and supplies them to each excitation coil 32. However, it is also possible to configure the voltage application unit 40 to generate only AC voltages of the same phase, and to reverse the wiring directions of a pair of opposing excitation coils 32 so that AC voltages of a 180° phase difference are applied as described above. Even in this case, the same effects as those described above can be obtained.

[0038] Furthermore, the phase difference between the AC voltages flowing through the pair of excitation coils 32 does not necessarily have to be exactly 180°, and an error of about ±10° is permitted.

[0039] Furthermore, in each of the above embodiments, an example using the cross coil 31 has been described. However, as other examples, it is also possible to use a pancake coil 131 shown in Fig. 7 or a tangential coil 231 shown in Fig. 8.

[0040] 7, pancake coil 131 is a single coil that is annular and serves as both excitation coil 32 and detection coil 33. Central axis C of pancake coil 131 is perpendicular to surface 90 under inspection.

[0041] According to the above configuration, by arranging the pancake coil 131 so that its central axis is perpendicular to the inspection target surface 90, it is possible to distribute eddy currents over a wider range on the inspection target surface 90. This makes it possible to easily detect defects over a wide range in a short time.

[0042] 8, the tangential coil 231 is a single coil that is annular and serves as both the excitation coil 32 and the detection coil 33. The central axis D of the tangential coil 231 is parallel to the surface 90 to be inspected.

[0043] According to the above configuration, by arranging the tangential coil 231 so that its central axis is parallel to the inspection target surface 90, it is possible to concentrate eddy currents in a narrower range on the inspection target surface 90. This makes it possible to detect defects in a specific range in a concentrated manner with high accuracy.

[0044] In addition, the above configuration can also be applied to a self-induction type cross coil in which excitation / detection is performed on each of the coils that make up the cross coil, and the presence or absence of defects is evaluated by taking the difference between the results.

[0045] <Additional Notes> The eddy current flaw detection device 1 and the eddy current flaw detection method described in each embodiment can be understood, for example, as follows.

[0046] (1) The eddy current flaw detector 1 according to the first aspect includes an array coil 30 including a pair of excitation coils 32 and a detection coil 33 spaced apart in a first direction X, and a voltage application unit 40 that applies AC voltages having a phase difference of 180° between the pair of excitation coils 32.

[0047] The above configuration can prevent magnetic field interference between the pair of excitation coils 32. This reduces the possibility of noise occurring in the detection results.

[0048] (2) The eddy current flaw detector 1 according to the second aspect is the eddy current flaw detector 1 of (1), and includes a plurality of the array coils 30 arranged circumferentially around an axis O direction perpendicular to the first direction X, and a probe body 20 supporting the plurality of array coils 30.

[0049] According to the above configuration, magnetic fields that are less likely to interfere with each other can be formed between a pair of diametrically opposed excitation coils 32. This reduces the possibility of noise occurring in the detection results.

[0050] (3) The eddy current flaw detector 1 according to the third aspect is the eddy current flaw detector 1 of (1), and includes a plate-shaped member 111 having the first direction X as its thickness direction, and the array coil 30 provided on both sides of the plate-shaped member 111 in the thickness direction.

[0051] According to the above configuration, it is possible to form a magnetic field that is less likely to interfere with each other between the excitation coils 32 arranged on both sides of the plate-shaped member 111 in the thickness direction, thereby reducing the possibility of noise occurring in the detection results.

[0052] (4) The eddy current flaw detection device 1 according to the fourth aspect is an eddy current flaw detection device 1 according to any one of the aspects (1) to (3), wherein the array coil 30 is a cross coil 31 having the annular excitation coil 32 and the detection coil 33, which is annular with its central axis intersecting the central axis of the excitation coil 32 and is arranged perpendicular to the excitation coil 32, and the central axes of the excitation coil 32 and the detection coil 33 are parallel to the surface 90 to be inspected.

[0053] According to the above configuration, even minute defects can be precisely detected.

[0054] (5) The eddy current flaw detector 1 according to the fifth aspect is an eddy current flaw detector 1 according to any one of aspects (1) to (3), in which the array coil 30 is a pancake coil 131 that is annular and serves as both the excitation coil 32 and the detection coil 33, and the central axis of the pancake coil 131 is perpendicular to the surface 90 to be inspected.

[0055] According to the above configuration, defects over a wide range can be detected easily and in a short time.

[0056] (6) The eddy current flaw detector 1 according to the sixth aspect is an eddy current flaw detector 1 according to any one of aspects (1) to (3), wherein the array coil 30 is a tangential coil 231 that is annular and serves as both the excitation coil 32 and the detection coil 33, and the central axis of the tangential coil 231 is parallel to the surface 90 to be inspected.

[0057] According to the above configuration, defects in a specific range can be detected intensively with high accuracy.

[0058] (7) The eddy current flaw detection device 1 according to the seventh aspect is an eddy current flaw detection device 1 according to any one of aspects (1) to (3), in which the array coil 30 is a self-induction type cross coil in which two coils serve as the excitation coil 32 and the detection coil 33.

[0059] According to the above configuration, even minute defects can be precisely detected.

[0060] (8) An eddy current flaw detection method according to an eighth aspect is an eddy current flaw detection method using an array coil 30 including a pair of excitation coils 32 and a detection coil 33 spaced apart in a first direction X, and includes the steps of applying an AC voltage to one of the pair of excitation coils 32 and simultaneously applying an AC voltage to the other of the pair of excitation coils 32 that is 180° out of phase with the AC voltage applied to the one of the pair of excitation coils 32.

[0061] The above method can prevent magnetic field interference between the pair of excitation coils 32. This reduces the possibility of noise occurring in the detection results. [Explanation of symbols]

[0062] REFERENCE SIGNS LIST 1...Eddy current flaw detector 2...Probe 20...Probe body 21...Stabilizer 22...Coil support section 23...Cable 30...Array coil 31...Cross coil 32...Excitation coil 33...Detection coil 40...Voltage application section 100...Inspection target surface 101...Eddy current flaw detector 102...Gap probe 111...Plate-shaped member 131...Pancake coil 201...First member 202...Second member 203...Gap 231...Tangential coil A...Central axis B...Central axis C...Central axis D...Central axis O...Axis X...First direction

Claims

1. an array coil including a pair of excitation coils and a pair of detection coils spaced apart in a first direction; a voltage application unit that applies AC voltages having a phase difference of 180° between the pair of excitation coils; An eddy current flaw detection device comprising:

2. a plurality of the array coils arranged in a circumferential direction around an axial direction orthogonal to the first direction; a probe body supporting the plurality of array coils; The eddy current flaw detector according to claim 1 .

3. a plate-like member having a thickness direction in the first direction; the array coils provided on both sides of the plate-like member in the thickness direction; The eddy current flaw detector according to claim 1 .

4. The array coil is a cross coil having an annular excitation coil and a detection coil that is annular with its central axis intersecting the central axis of the excitation coil and is arranged perpendicular to the excitation coil, and the central axes of the excitation coil and the detection coil are parallel to the surface to be inspected.

5. 4. An eddy current flaw detection device according to claim 1, wherein the array coil is a pancake coil that is annular and serves as both the excitation coil and the detection coil, and the central axis of the pancake coil is perpendicular to the surface to be inspected.

6. 4. An eddy current flaw detection device according to claim 1, wherein the array coil is a tangential coil that is annular and serves as both the excitation coil and the detection coil, and the central axis of the tangential coil is parallel to the surface to be inspected.

7. 4. The eddy current flaw detector according to claim 1, wherein the array coil is a self-induction type cross coil in which two coils function as both the excitation coil and the detection coil.

8. An eddy current flaw detection method using an array coil including a pair of excitation coils and a detection coil spaced apart in a first direction, applying an AC voltage to one of the pair of excitation coils; simultaneously applying to the other of the pair of excitation coils an AC voltage that is 180° out of phase with the AC voltage applied to the one of the pair of excitation coils; 2. An eddy current testing method comprising:

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