JP2003294711A - Eddy-current test probe and eddy-current test method using the probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy-current test probe and an eddy-current test method using the probe having high detection precision to detect defects of a heat exchanger tube with inner fins. <P>SOLUTION: The eddy-current test probe is to perform an eddycurrent test of a heat exchanger tube 74 in which inner fins 75 divides the inside of the tube into a plurality of cells 76, and uses a probe 1 provided with a bobbin 2 which has a coil 4 on which a conducting wire are wound and is inserted into the cell 76, and a conductive shield 3 which is located between the wall of the inner fin 75 and the inserted bobbin 2. The presence of defects can be detected from a Y axis component of the Lissajous waveform obtained from a standard comparison method using the probe 1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current flaw detection inspection probe used for inspecting a heat transfer tube with an inner fin used in a heat exchanger and the like, and an eddy current flaw detection inspection method using the same.

[Prior art]

An eddy current flaw detection test is generally used to nondestructively inspect a non-magnetic heat transfer tube (usually a copper tube or the like) for defects such as scratches inside the heat exchanger. . In the eddy current flaw detection, when a coil in which an alternating current is applied is placed near the test body, the AC magnetic flux generated in the coil passes through the inside of the test body, and at this time, an eddy current is induced inside the test body by electromagnetic induction. Since this eddy current causes a change in the impedance of the coil, this is an inspection method in which changes inside the test body (for example, flaws in the heat transfer tube, defects such as holes) can be indirectly known.

FIG. 7 is a block diagram showing an example of an eddy current flaw detection apparatus used for this eddy current flaw detection inspection. As shown in FIG. 7, the eddy current flaw detector 51 has a bridge circuit 53 formed of an oscillator 52, which is a circuit that produces an alternating current for giving an alternating magnetic flux to a test body, a test coil of a probe, a comparison coil, a specific resistance, and the like. An amplifier 54 for amplifying the flaw signal detected by the bridge circuit 53, and a periodic detector 5 for separating the amplified flaw signal and other noise signals.
It consists of 5, etc.

The phase shifter 5 separates the scratch signal from the noise signal.
This is performed by utilizing the fact that the flaw signal and the noise signal have different phases based on the control signal output from the control unit 6. The filter 57 is for separating noise from the waveform of the electric signal output from the synchronous detector 55 and determining the type / shape / size of the defect. The rejection 59 is for removing a small noise below a certain level and extracting only a signal having a large amplitude to improve the S / N ratio with respect to a flaw signal. As a display device, a cathode ray tube 5
8. The recorder 60 is used.

Eddy current flaw detection using such an eddy current flaw detection device 51 can be classified into two types: a standard comparison method and a self comparison method. Different probes are used for these two systems. The standard comparison method is shown in FIG.
As shown in (b), the test coil R1 and the comparison coil R2
Two probes 61 and 62 respectively provided with are used. The probe 61 equipped with the test coil R1 is inserted into the heat transfer tube (test tube 63) to be tested, and the probe 62 equipped with the comparison coil R2 is used for comparison. Heat transfer tube (standard tube 64)
To detect these differences.

On the other hand, in the self-comparison method, as shown in FIG.
A test coil R3 and a comparison coil R4 are used as a probe.
The one provided for one probe 71 is used, and this probe 71 is inserted into the inspection tube 72 to detect a difference between two adjacent portions in the inspection tube 72. For these probes 61, 62 and 71, a bobbin made of resin and a conducting wire such as a copper wire wound is usually used.

When the probes 61 and 62 are used as the probes of the eddy current flaw detector 51 (standard comparison method), FIG.
In the bridge 53, a bridge circuit including impedances R1 and R2 and specific resistances K1 and K2 as shown in FIG. 10 is formed. When the probe 71 is used as the probe of the device 51 (self-comparison method), a bridge circuit including impedances R3 and R4 and specific resistances K3 and K4 as shown in FIG. 10 is formed in the bridge 53. Where K1, K2, K3 and K
Reference numeral 4 is a specific resistance provided in advance in the eddy current flaw detector 51. If there is a defect such as a scratch in a portion of the inspection tubes 63 and 72, the impedance of the test coils R1 and R3 changes, so that the inside of the inspection tubes 63 and 72 is indirectly changed by the bridge circuit, that is, a defect. Can be known (see Non-Patent Document 1, for example).

[0008]

[Non-patent document 1] Non-destructive inspection technology series "Overflow flaw detection test II", pp. 68-71, 1989, published by Japan Non-destructive Inspection Association

However, in the case of inspecting the heat transfer tube 74 with the inner fin 75 as shown in FIG. 11, if a normal probe in which a copper wire is simply wound around a resin bobbin is used, scratches existing on the inner fin 75, In some cases, the heat transfer tube 74 itself cannot be inspected because local material changes and impurities are also detected. The inner fin 75 is a partition provided inside the heat transfer tube 74 for the purpose of improving heat exchange efficiency. Further, the heat transfer tube 74 is manufactured by inserting the inner fin 75 into the element tube in the axial direction and drawing the element tube to extend it to a predetermined size.

[0010]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an eddy current flaw detection inspection probe and an eddy current flaw detection inspection method using the same, which can improve the detection accuracy of defects occurring in the heat conduction tube itself in a heat transmission tube with an inner fin. Is to provide.

[0011]

The probe for eddy current flaw detection of the present invention is a probe for performing eddy current flaw detection inspection of a heat transfer tube having a plurality of cells partitioned by inner fins, in which a conductor wire is wound. A bobbin having a coil and inserted into the cell, and a conductive shielding plate which is integrated with the bobbin and is interposed between a wall surface of the inner fin and the bobbin. Accordingly, when the probe is inserted into the cell, since the conductive shield plate is interposed between the inner fin and the bobbin, the eddy current hardly flows to the inner fin and flows through the shield plate.
Therefore, it is possible to detect only the defects of the heat transfer tube itself, since the scratches existing on the inner fins are not detected.

In the present invention, it is preferable that the shielding plate has a shape and a size such that there is substantially no gap between the shielding plate and the wall surface of the inner fin when the shielding plate is inserted into the cell. With this, when the shield plate is inserted into the heat transfer tube, the shield plate fits the inner fins and the stability is improved, so that rattling of the probe inside the heat transfer tube can be suppressed. Therefore, the noise (wobble signal) generated by the rattling of the probe is less likely to occur, and the accuracy of detecting a defect in the heat transfer tube is improved.

In the probe for eddy current flaw detection of the present invention, the shield plate is preferably made of copper, aluminum or stainless steel. Copper and aluminum as used herein include copper alloys and aluminum alloys.

The eddy current flaw detection method of the present invention is characterized by determining the presence or absence of a defect from the Y-axis component of the Lissajous waveform obtained by the standard comparison method using the probe.
Here, the Y-axis of the Lissajous waveform refers to the vertical axis (vertical axis) of the Lissajous waveform, and the X-axis is the horizontal axis (horizontal axis).
I mean.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1A is a sectional view showing an eddy current flaw detection inspection probe 1 according to an embodiment of the present invention, and FIG.
FIG. 3 is a side view showing an eddy current flaw detection probe 1. This probe 1 is used for the standard comparison method.

As shown in FIGS. 1A and 1B, the probe 1 includes a plurality of cells 7 partitioned by inner fins 75.
A probe for conducting an eddy current flaw detection on a heat transfer tube 74 having a bobbin 2 having a coil 4 around which a wire is wound and inserted into the cell 76, and the inner bobbin 2 being integrated with the bobbin 2. The conductive shield plate 3 is provided between the wall surface of the fin 75 and the bobbin 2. Two probes 1 and two heat transfer tubes 74 are prepared, and one probe 1 is a cell 76 of the heat transfer tube 74 (inspection tube) to be inspected.
The other probe 1 is inserted into the heat transfer tube 74 for comparison.
Insert into cell (standard tube) 76. It is also possible to test multiple cells simultaneously using multiple probes. In the case of the heat transfer tube having five cells shown in FIG. 1, up to five probes are inserted into each cell and moved simultaneously for inspection. This can shorten the inspection time. A wiring diagram when five probes are used is shown in FIG.

The bobbin 2 is for winding the coil 4, and its shape and material are not particularly limited. For example, as shown in FIG. 1A, when the cross section of the shield plate 3 is V-shaped, it is preferable that the cross section of the bobbin 2 has a trapezoidal shape that matches the inclination of the shield plate 3. As the material of the bobbin 2, for example, a high magnetic permeability material such as high density ferrite can be used. The bobbin 2 can be fixed, for example, by filling a gap between the shield plate 3 and the bobbin 2 with a filling resin 5 such as an epoxy resin (“Epomount” manufactured by Refinetech Co., Ltd.). The position for fixing the bobbin 2 is such that when the probe 1 is inserted into the cell 76, the bobbin 2
Is preferably close to the heat transfer tube 74.

The coil 4 is formed by winding a copper wire having excellent conductivity around the bobbin 2. The number of coil turns and the coil width of the coil 4 are not particularly limited, and may be appropriately determined according to the size of the probe 1. Generally, for example, the number of coil turns is 100 to 50.
A coil winding width of about 0 to 10 mm is used. An alternating current is applied to the coil 4 through a cable 6.

The shield plate 3 serves as a bypass through which the eddy current flows, and is provided so that the eddy current hardly flows to the inner fin 75. The shape and size of the shielding plate 3 are not particularly limited, but the inner fin 75 is inserted into the cell 76.
It is preferable that the shape and the size are such that there is substantially no gap between the heat transfer tube 74 and the inner fin 75 when the probe 1 moves in the heat transfer tube 74. The size is preferably such that it is not difficult to move.

The shielding plate 3 may be made of any material such as copper, aluminum, stainless steel, etc. as long as it is electrically conductive. The thickness of the shielding plate 3 is usually 0.5 mm.
The thing of about 3 mm is used.

FIG. 2 (a) is a sectional view showing another eddy current flaw detection probe 11 of the present invention, and FIG. 2 (b) is a side view thereof, which is used for the self-comparison method. Figure 2
As shown in (a) and (b), the probe 11 is a probe for performing an eddy current flaw detection inspection of a heat transfer tube 74 having a plurality of cells 76 partitioned by inner fins 75.
A bobbin 12 having a test coil 14a and a comparison coil 14b wound with a conductive wire and inserted into the cell 76, and is interposed between the bobbin 12 and the wall surface of the inner fin 75 and the bobbin 12. And a conductive shield plate 13.

The bobbin 12, the shield plate 13, the coils 14a and 14b, and the filling resin 15 in the probe 11 may have the same shape and material as those of the probe 1. The distance between the coils 14a and 14b is usually adjusted to about 1 to 10 mm. Also in this case, it is possible to simultaneously inspect using a plurality of probes.

An eddy current flaw detection method for a heat transfer tube having five cells, which is an embodiment of the present invention, will be described below. The eddy current flaw detection method of the present invention is the probe 1 described above.
Of the Lissajous waveform obtained by the standard comparison method using
Determining the presence or absence of a defect from the axial component, and discriminating whether the defect exists on the inner surface or the outer surface of the heat transfer tube from the phase angle of the Lissajous waveform obtained by the self-comparison method using the probe 11 if necessary. Is.

<Judgment by Standard Comparison Method> For example, the probe 1 of the present invention is used as the probe of the eddy current flaw detection inspection device 51 having the configuration shown in FIG.

First, one to five probes 1 are inserted into a heat transfer tube with an inner fin to be inspected (inspection tube), and another probe 1 is inserted into a heat transfer tube with an inner fin to be compared (a standard tube). Insert one. In order to insert these probes 1 and 1, other than the method of simply pushing in manually,
For example, a method of pulling with a wire or a method of applying a pressure of a pressurized fluid (such as air) can be used. The inspection tube and the standard tube usually have the same shape and material.

Then, the alternating current is started to be applied to the 1 to 5 probes 1, 1 inserted to the predetermined position, and the 1 to 5 probes 1 inserted to the test tube are set to the predetermined position. To the inspection end position at a predetermined speed (or further pushed). While one to five probes 1 move inside the test tube,
Impedance changes are measured.

Data of the series of inspection results is collected and analyzed by the eddy current flaw detection inspection device 51, and the inspection result is obtained as a Lissajous waveform. An example of a graph obtained by separating the obtained Lissajous waveform into a Y-axis component and an X-axis component is shown in FIGS. 3A and 3B, respectively. Figure 3 (a)
Is a graph of the Y-axis component of the Lissajous waveform, in which the vertical axis represents the voltage value and the horizontal axis represents the movement distance of the probe 1. FIG. 3B is a graph of the X-axis component of the Lissajous waveform, in which the vertical axis represents the voltage value and the horizontal axis represents the movement distance of the probe 1.

Here, paying attention to the graph (FIG. 3A) showing the Y-axis component of the Lissajous waveform, in the case where a peak is seen in the negative direction of the vertical axis in this graph (FIG. 3A). ))) Indicates that the heat transfer tube to be inspected has no defects such as scratches. On the other hand, in the graph, when a peak is seen in the positive direction of the vertical axis (Fig.
In this case, it means that the heat transfer tube to be inspected has a defect such as a scratch.

It should be noted that it is sufficient to carry out the inspection by the above-mentioned standard comparison method if it is only necessary to detect whether or not there is a defect in the heat transfer tube, but it is sufficient if the inspection determined by the standard comparison method is present. If the heat tube is further inspected by the following self-comparison method, it is possible to discriminate whether the defect exists on the inner surface or the outer surface of the heat transfer tube, so that more accurate inspection can be performed.

<Judgment by Self-Comparison Method> An eddy current flaw detection test is conducted by the self-comparison method for the heat transfer tube judged to have a defect by the standard comparison method, and it is judged whether the defect exists on the inner surface or the outer surface of the heat transfer tube. . The probe 11 is used as a probe of the eddy current flaw detection inspection device 51.

First, one to five probes 11 are inserted to a predetermined position inside the heat transfer tube determined to have a defect, and an alternating current is supplied. Then, similarly to the above, the probe 11 is pulled back (or further pushed) from the predetermined position to the inspection end position at a predetermined speed. During this time, a Lissajous waveform is obtained by measuring the impedance change between the coil 14a and the coil 14b. An example of the obtained Lissajous waveform is shown in FIG. From the angle formed by the central axis A and the X axis (horizontal axis) of the Lissajous waveform shown in FIG. 5, that is, the phase angle (θ), the characteristics of the defect can be read as follows. In the eddy current probe used for maintenance inspection of heat transfer tubes without inner fins, when the wobble signal generated when moving inside the heat transfer tubes is set in the X axis direction (horizontal axis direction), there is a through hole in the heat transfer tube. The phase angle (θ) is about 135 °, and the phase angle (θ) when there is a defect on the outer surface of the heat transfer tube is in the range of about 0 ° to 135 °, and there is a defect on the inner surface of the heat transfer tube. Phase angle (θ) is about 13
Many eddy current flaw detectors have a range of 5 ° to 180 °.
However, when the probe 11 shown in FIG. 2 is used,
When the wobble signal is set in the X-axis direction, the through-hole signal is 1
It was shifted from 35 ° to 180 ° by about 10 ° to 20 °. Phase angle (θ) -thinning rate evaluation curves obtained using one probe and five probes are shown in FIGS. 13 and 14, respectively.

[0032]

The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

Example 1 In order to confirm whether or not the heat transfer tube for the heat exchanger has a defect such as a flaw, an eddy current flaw detection test by a standard comparison method was carried out.

<Test body> The test body has an inner fin 75 inside as shown in FIG. 11 and a tube diameter of 15.8.
The following four types of copper heat transfer tubes having a length of 8 mm, a length of 3000 mm and a wall thickness of 0.8 mm were used. Specimen 1: Unused heat transfer tube Specimen 2: Unused heat transfer tube Specimen 3: Heat transfer tube used for heat exchanger for 9 years Specimen 4: Heat transfer tube used for heat exchanger for 3 years

<Apparatus> In Example 1, as a eddy current flaw detector, "Mini Fezek" manufactured by Hocking Co. was used. As the probe, the bobbin material is high-density ferrite, the number of coil turns is 200, and the coil material is the wire diameter φ.
A probe 1 shown in FIG. 1 having a 0.05 mm copper wire, a coil winding width of 2 mm, and a shielding plate made of copper was used.

<Test conditions for standard comparison method> Eddy current flaw detector setting conditions Test frequency: 5KHz Phase angle: 253 ° Sensitivity: 27dB

The results of Example 1 are shown in FIG. FIG. 6 is a graph showing the Y-axis component of the Lissajous waveform obtained by the eddy current flaw detection test by the standard comparison method for the test bodies 1 to 4. As a result of the inspection, there is no defect in the test bodies 1 to 3,
It was found that the test body 4 had defects. As a result of actual visual observation, the above test results and the visual observation results were in agreement.

Example 2 Eddy current flaw detection was conducted by the standard comparison method under the same apparatus and test conditions as in Example 1 except that the following test pieces were used.

<Test body> The test body has an inner fin 75 inside as shown in FIG. 11 and a tube diameter of 15.8.
The following five types of copper heat transfer tubes having a length of 8 mm, a length of 75 mm and a wall thickness of 0.8 mm were used. Specimen 5: Heat transfer tube with a through hole of φ2 mm Test specimen 6: Diameter of φ2 mm and depth of 50% of wall thickness (0.4
mm) dented heat transfer tube test body 7 having a diameter of 2 mm and a depth of 30% of the wall thickness (0.2
Heat transfer tube test body 8 having a 4 mm) recess on the outer surface: transfer with a 0.2 mm width, 10 mm length axial slit having a 50% (0.4 mm) depth recess on the outer surface. Heat pipe test body 9: Heat transfer pipe having an axial slit having a width of 0.2 mm and a length of 10 mm and having a recess having a depth of 30% (0.24 mm) of the wall thickness.

As a result of performing an eddy current flaw detection test by the standard comparison method, it was determined that all test bodies had defects. As a result of actual visual observation, the above test results and the visual observation results were in agreement.

Reference Example 1 In order to confirm whether the heat transfer tube for a heat exchanger has a defect such as a flaw, a phase angle-thinning rate evaluation curve for carrying out an eddy current flaw detection test by a self-comparing method was prepared. <Test Body for Creating Phase Angle-Thinning Ratio Evaluation Curve with One Probe> As a test body, the inner fin 75 is provided inside as shown in FIG. 11, and the pipe diameter is 15.88 mm.
The following four types of copper heat transfer tubes having a length of 75 mm and a wall thickness of 0.8 mm were used. Specimen 5: Heat transfer tube with a through hole of φ2 mm Test specimen 6: Diameter of φ2 mm and depth of 50% of wall thickness (0.4
mm) dented heat transfer tube test body 7 having a diameter of 2 mm and a depth of 30% of the wall thickness (0.2
Heat transfer tube test body 10 having a dent of 4 mm) provided on the outer surface: diameter is φ2 mm and depth is 50% of the wall thickness (0.
4 mm) heat transfer tube with a recess on the inner surface

<Apparatus> As an eddy current flaw detector for making a phase angle-thinning rate evaluation curve, "AV100SE" manufactured by Hocking Co. was used. As the probe, the bobbin material is high-density ferrite and the number of coil turns is 20.
One time, the probe 11 shown in FIG. 2 in which the coil material is a copper wire having a wire diameter of 0.05 mm, the coil winding width is 2 mm, and the shielding plate material is copper is used 0 times.

[0043] <Test conditions for self-comparison method with one probe>   Eddy current flaw detector setting conditions     Test frequency: 10KHz     Phase angle: 2nd quadrant (oscillation signal is set to X axis)     Sensitivity: 1 coil sets Y amplitude value of 2φ through hole to 20mm

With the one probe shown in FIG.
The test body 6, the test body 7, and the test body 10 were flaw-tested, the phase angle from each artificial defect was read, and the phase angle-thinning rate evaluation curve was created. The result is shown in FIG. When flaw detection was performed on the heat transfer tube incorporated in the heat exchanger, the wall thickness reduction rate could be read from the phase angle.

<Creation of Phase Angle-Thinning Rate Evaluation Curve with Five Probes> The same test body, apparatus and test conditions as those used for producing the phase angle-thinning rate evaluation curve with one probe are used. Then, 5 probes were simultaneously inserted into the test body to prepare a phase angle-thinning rate evaluation curve.

In order to detect flaws simultaneously with five probes,
Five probes connected by the connection circuit shown in FIG. 12 were inserted into the tube, and one of the probes was used to determine the phase angle from the artificial defect of the test body. The result is shown in FIG.
It was shown to.

Example 3 Five probes were connected using the connection circuit shown in FIG. 12 used in Reference Example 1 in order to inspect the heat transfer tube in the state of being incorporated in the heat exchanger. Since the outer surface of the heat transfer tube under the baffle is also the inspection target in this connected state, the baffle signal was erased by the mixing function of the eddy current flaw detector. The setting conditions of the eddy current flaw detector are shown below. Eddy current flaw detector; ASSORT PC2 (Aswan Electron) Test frequency; Mixing process phase adjustment at 10 KHz and 5 KHz; 2φ through-hole signal set to 35 degrees Sensitivity adjustment; 2φ through-hole Y amplitude value set to 20 mm

As a result of the eddy current flaw detection test, a defect signal was detected from the heat transfer tube immediately below the baffle portion. The thinning rate was calculated from the phase angle-thinning rate evaluation curve obtained in Reference Example 1. Next, the heat transfer tube in which the defect signal was detected was removed, and the inspection performance was confirmed. As a result, local corrosion occurred on the outer surface of the heat transfer tube immediately below the baffle plate. Local corrosion depth measured by extubation (reduction rate)
15 shows the relationship between the defect depth (thickness reduction rate) estimated by eddy current flaw detection. The thinning rate matches with an inspection accuracy of ± 15%.

[0049]

According to the present invention, since the conductive shield plate is interposed between the inner fin and the bobbin when the probe is inserted into the heat transfer tube, eddy current hardly flows to the inner fin. Since there is no detection of flaws existing on the inner fins flowing through the shield plate, it is possible to detect only the defects of the heat transfer tube itself, and there is an effect that the accuracy of detecting the defects of the heat transfer tube is improved.

According to the present invention, when the shielding plate has a shape and a size in which there is substantially no gap between the shielding plate and the wall surface of the inner fin when inserted in the cell, noise generated by rattling of the probe is generated. Since (wobble signal) is less likely to occur, there is an effect that the accuracy of detecting a defect such as a scratch on the heat transfer tube can be further improved.

According to the present invention, when determining the presence or absence of a defect from the Y-axis component of the Lissajous waveform obtained by the standard comparison method using the probe, the presence or absence of the defect can be accurately determined. effective.

[Brief description of drawings]

1A and 1B are a cross-sectional view and a side view, respectively, showing an embodiment of an eddy current flaw detection inspection probe according to the present invention.

2A and 2B are a cross-sectional view and a side view, respectively, showing another embodiment of the eddy current flaw detection probe according to the present invention.

FIG. 3A shows an example of a graph of a Y-axis component of a Lissajous waveform obtained by the eddy current flaw detection method of the present invention, and FIG. 3B shows an example of a graph of an X-axis component. It is shown.

FIG. 4 shows an example of a graph of the Y-axis component of the Lissajous waveform obtained by the eddy current flaw detection method of the present invention.

FIG. 5 is a graph showing a Lissajous waveform obtained by the eddy current flaw detection method according to the present invention.

FIG. 6 is a graph showing the Y-axis component of the Lissajous waveform of test bodies 1 to 4 obtained by the eddy current flaw detection method of the present invention in Example 1.

FIG. 7 is a block diagram showing an example of an eddy current flaw detector.

FIG. 8 (a) is a schematic view showing a state where a probe equipped with a test coil used in the standard comparison method is inserted into a heat transfer tube (inspection tube), and FIG. 8 (b) is used in the standard comparison method. It is the schematic which shows the state which inserted the probe provided with the compared coil into the heat transfer tube (standard tube).

FIG. 9 is a schematic view showing a state where a probe used in the self-comparison method is inserted into a heat transfer tube.

FIG. 10 is a schematic diagram showing a bridge circuit composed of impedance and specific resistance of a coil.

FIG. 11 is a front view showing an example of a heat transfer tube with inner fins.

FIG. 12 is a connection diagram when five probes are used.

FIG. 13 is a phase angle-thinning rate evaluation curve obtained by using one probe.

FIG. 14 is a phase angle-thinning rate evaluation curve obtained using five probes.

FIG. 15 is a diagram showing a relationship between a wall-thickness reduction rate measured by extubation and a wall-thickness reduction rate estimated by eddy current flaw detection.

[Explanation of symbols]

1 Eddy current inspection probe 2 bobbins 3 Shield 4 coils 5 Filling resin 6 cables 11 Eddy current inspection probe 12 bobbins 13 Shield 14a test coil 14b Comparison coil 15 Filling resin

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Claims (4)

[Claims] 1. A probe for performing an eddy current flaw detection test of a heat transfer tube having a plurality of cells partitioned by inner fins, the probe having a coil around which a conductive wire is wound, and a bobbin inserted into the cell. A probe for eddy current flaw detection, characterized by comprising a conductive shielding plate which is integrated with the bobbin and is interposed between the wall surface of the inner fin and the bobbin. 2. The eddy current flaw detection inspection probe according to claim 1, wherein the shielding plate has a shape and a size such that there is substantially no gap between the shielding plate and a wall surface of the inner fin when the shielding plate is inserted into the cell. 3. The eddy current flaw detection inspection probe according to claim 1, wherein the shielding plate is made of copper, aluminum or stainless steel. 4. Y of a Lissajous waveform obtained by a standard comparison method using the probe according to claim 1.
An eddy current flaw detection method characterized by determining the presence or absence of a defect from an axial component.