JP2004028897A - Eddy-current flaw detection apparatus - Google Patents

Eddy-current flaw detection apparatus Download PDF

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Publication number
JP2004028897A
JP2004028897A JP2002188398A JP2002188398A JP2004028897A JP 2004028897 A JP2004028897 A JP 2004028897A JP 2002188398 A JP2002188398 A JP 2002188398A JP 2002188398 A JP2002188398 A JP 2002188398A JP 2004028897 A JP2004028897 A JP 2004028897A
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Japan
Prior art keywords
coil
detection
flaw
detecting
3b
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2002188398A
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Japanese (ja)
Inventor
Hiroaki Nishimura
西村 博明
Original Assignee
Osaka Gas Co Ltd
大阪瓦斯株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Osaka Gas Co Ltd, 大阪瓦斯株式会社 filed Critical Osaka Gas Co Ltd
Priority to JP2002188398A priority Critical patent/JP2004028897A/en
Publication of JP2004028897A publication Critical patent/JP2004028897A/en
Pending legal-status Critical Current

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Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy-current flaw detection apparatus which is hardly affected by the orientation of an object to be flaw-detected and detects a defect more accurately. <P>SOLUTION: In this eddy-current flaw detecting apparatus, an exciting coil 3A and a detecting coil 3B are arranged on a probe base surface which are made to face the object 1 to be flaw-detected and performs a survey such that coil axis are orthogonal each other or almost orthogonal each other, and a detecting process means 4A is arranged. The detecting process means 4A makes magnetic field generate in the exciting coil 3A, detects magnetic field 7 formed by the eddy current 6 generated in the object 1 to be flaw-detected by the magnetic field by using the detecting coil 3B, and detects the situation of the defect 2 existing in the object 1 to be flaw-detected. Three or more detecting coils 3B are arranged, and the array of the detecting coils 3B is set such that a polygon exists in the line diagram formed by connecting the coil axis of each detecting coil 3B when viewed in the coil axis direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, an eddy current flaw detection device that can be used for inspecting and diagnosing a crack generation state, a corrosion state, and the like with respect to a flaw detection target made of metal such as a pipe or a tank. An excitation coil and a detection coil are provided in such a manner that their respective coil axes are orthogonal or substantially orthogonal to the probe base surface for exploration by facing the probe, and a magnetic field is generated in the excitation coil. The present invention relates to an eddy current flaw detection device provided with detection processing means for detecting a magnetic field formed by an eddy current generated in the flaw detection target by detecting the magnetic field formed by the detection coil.
[0002]
[Prior art]
The principle of eddy current flaw detection is that a high-frequency current is applied to a probe type inspection coil placed close to a metal flaw detection target, and the eddy current generated on the flaw detection target surface is detected as the impedance of the inspection coil, If a defect exists in the flaw detection target, the eddy current changes and the impedance of the inspection coil changes, so that the defect of the flaw detection target can be detected. There was a coil configured as shown in FIG.
In other words, two inspection coils 30 formed by arranging the excitation coil 30A and the detection coil 30B having different coil diameters on the same axis so as to be overlapped inside and outside are arranged side by side in the coil diameter direction to constitute a flaw detection device. In performing the eddy current flaw detection, while moving the two inspection coils 30 along the direction in which they are arranged, the difference in impedance change between the detection coils 30B between the two inspection coils 30 is determined by the detection processing. This is detected by the means 4A.
[0003]
[Problems to be solved by the invention]
According to the conventional eddy current flaw detection device described above, as described above, if there is no change in each detection impedance of the two inspection coils, the result is that there is no defect in the flaw detection target. As shown in FIG. 7, a measurement environment in which a flaw detection target has a linear defect (a crack or the like) 2 and the direction in which the two inspection coils are arranged (corresponding to the moving direction) coincides with the longitudinal direction of the defect. In the case of (1), despite the fact that the flaw detection target has a defect, there is no difference between the impedances of the two inspection coils, so that the defect cannot be detected.
That is, according to the conventional eddy current flaw detection device, there is a problem that there is a risk of erroneous detection depending on the directionality of the defect.
[0004]
Accordingly, it is an object of the present invention to provide an eddy current flaw detection device which solves the above problems, is less affected by the directionality of a flaw detection target, and can more accurately detect defects.
[0005]
[Means for Solving the Problems]
The characteristic configuration of the invention according to claim 1 is that the excitation coil and the detection coil are provided in such a manner that respective coil axes are orthogonal or substantially orthogonal to a probe base surface for performing an inspection while facing the inspection object, and Detection processing means is provided for generating a magnetic field in the coil, detecting a magnetic field formed by an eddy current generated in the inspection object by the magnetic field with the detection coil, and detecting a state of a defect existing in the inspection object. In the eddy current flaw detector, three or more of the detection coils are provided, and the arrangement of the detection coils in the coil axis direction is a line formed by connecting the coil axes of the detection coils in the coil axis direction. It is set so that a polygon exists in the figure.
[0006]
According to the characteristic configuration of the invention of claim 1, three or more of the detection coils are provided, and the arrangement of the detection coils in the coil axis direction is determined by the coil axis of each detection coil in the coil axis direction. Since polygons are set so as to exist in a line figure formed by connecting the cores, a polygonal arrangement by each detection coil is realized.
For example, in a case where three detection coils are provided, each detection coil has a triangular arrangement.
Therefore, even if the defect of the flaw detection target exists on a straight line and two of the three detection coils are arranged along the straight line of the defect, the other one of the detection coils has a defect. Is present at a position deviated from the position, and a difference occurs in the detection impedance between the two detection coils. This effect is similarly achieved even in a polygonal arrangement of a quadrangle or more, and regardless of the direction of the defect of the flaw detection target, one of the detection coils detects the eddy current change due to the defect, and the detection processing means In addition, it is possible to detect that the target portion of the flaw detection target has a defect.
That is, it is hard to be affected by the shape and the direction of the defect, and it is possible to perform more accurate eddy current flaw detection.
[0007]
A feature of the invention according to claim 2 is that a switching unit is provided for switching the detection of the magnetic field by the detection coil for each of a pair of adjacent detection coils.
[0008]
According to the characteristic configuration of the second aspect of the invention, in addition to the effect of the first aspect of the invention, the detection of the magnetic field by the detection coil is switched for each pair of adjacent detection coils. Since the switching means is provided to perform the eddy current flaw detection with high accuracy as a whole, a very simple detection operation using only a pair of adjacent detection coils is sequentially repeated. Therefore, the detection processing means for comparing the detection results of the respective detection coils can have a simpler configuration, and the apparatus cost can be reduced.
Furthermore, at the same moment, since detection is performed only by a pair of adjacent detection coils, noise is not generated by coils in other portions, and eddy current flaw detection with higher accuracy can be performed.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the drawings, portions denoted by the same reference numerals as those of the conventional example indicate the same or corresponding portions.
[0010]
As shown in FIG. 1, an eddy current flaw detection device K described in the present embodiment targets a test object (corresponding to a flaw detection target) 1 such as a metal pipe or a tank, for example, to detect corrosion or cracks. It is configured so that defect 2 can be detected.
[0011]
The overall configuration of the eddy current flaw detector K will be described. An inspection coil 3 including one excitation coil 3A and a plurality of (eight in this embodiment) detection coils 3B is provided. A control device 4 is connected to control the inspection coil 3 and obtain detection information for information processing.
Then, the principle of the inspection method of the defect 2 using the eddy current flaw detector K will be described. As shown in FIG. 1, the inspection of the defect 2 is performed by using the inspection coil 3. In, an alternating current of about 35 Hz flows through the exciting coil 3A, and an eddy current 6 is generated in the device under test 1. Then, the indirect magnetic field 7 generated by the eddy current 6 disturbed by the presence of the defect 2 is captured by the detection coil 3B, and the defect 2 of the inspection object 1 is grasped from the phase change of the magnetic field.
[0012]
Hereinafter, each configuration of the eddy current flaw detector K will be described.
As shown in FIGS. 2 and 3, the inspection coil 3 has a configuration in which each detection coil 3B is annularly arranged in the inner space of the excitation coil 3A at intervals along the inner circumferential direction of the excitation coil 3A. I have. Each detection coil 3B is arranged such that the direction of the coil axis is the same as the direction of the coil axis of the exciting coil 3A.
Therefore, the arrangement of the detection coils 3B in the coil axis direction is set such that the line figure formed by connecting the coil axes of the detection coils 3B in the coil axis direction becomes an octagon. .
An AC power supply is connected to the exciting coil 3A via the control device 4.
[0013]
As shown in FIG. 1, the control device 4 sends AC electricity to generate a magnetic field in the excitation coil 3A, and is formed by an eddy current 6 generated in the inspection object 1 by the magnetic field generated by the excitation coil 3A. A detection processing unit 4A for detecting the state of the defect 2 present in the inspection object 1 by detecting the indirect magnetic field 7 with the detection coil 3B, and detecting the magnetic field by the detection coil 3B with a pair of adjacent detection coils A switching means 4B for switching and implementing each coil 3B is provided. The detection information detected by the detection processing means 4A is output by the output device 4C.
Specifically, the detection processing unit 4A compares the detection data from the pair of adjacent detection coils 3B switched by the switching unit 4B, and if there is a difference, the detection data is sent to the corresponding part of the test object 1 It is configured to output the result to the output device 4C assuming that the defect 2 exists. Then, the indirect magnetic field 7 is detected for all of the annularly arranged detection coils 3B while sequentially switching the detection coils 3B by the switching means 4B. Therefore, as shown in FIG. 4, even when a defect 2 such as a linear crack exists in the inspection object 1, a difference in the detection value occurs in any one of the eight detection coils 3 </ b> B. , The defect 2 can be detected more accurately.
[0014]
According to the eddy current flaw detector K of the present embodiment, since the inspection coils 3 are arranged in an octagonal shape as described above, even if the defect of the inspected object 1 is in any direction, any of the detection coils 3B is caused by the defect. By detecting the change in the eddy current 6, the detection processing unit 4A can detect that the defect 2 exists in the target portion of the inspection object 1, and it becomes possible to perform more accurate eddy current flaw detection.
In addition, the detection of the indirect magnetic field 7 by each detection coil 3B can be performed only by repeatedly switching a very simple detection operation using only a pair of adjacent detection coils 3B sequentially, and can be detected in a state where noise is less likely to enter. Therefore, the overall detection accuracy can be kept high.
Therefore, since the detection processing means 4A can have a simpler configuration, it is possible to achieve a reduction in apparatus cost and to perform eddy current flaw detection with higher accuracy.
[0015]
[Another embodiment]
Hereinafter, other embodiments will be described.
[0016]
<1> As described in the above embodiment, the inspection coil 3 is provided with eight detection coils 3B in the inner space of one excitation coil 3A at intervals along the inner circumferential direction of the excitation coil 3A. The configuration is not limited to the one that is arranged in a ring shape. For example, as shown in FIG. 5, eight detection coils are provided outside of one excitation coil 3A at intervals along the outer circumferential direction of the excitation coil 3A. The coil 3B may be configured by arranging it in a ring shape.
The number of the detection coils 3B is not limited to eight, and three or more detection coils may be provided. In short, three or more detection coils 3B are provided, and the arrangement of the detection coils 3B in the coil axis direction is determined by connecting the coil axes of the respective detection coils 3B in the coil axis direction. Should be set so that a polygon exists. However, the polygon referred to here refers to a polygon that is more than a triangle, and is not necessarily a regular polygon, but is preferably a regular polygon.
<2> On the other hand, the excitation coil 3A is not limited to one provided for the plurality of detection coils 3B as described in the previous embodiment. For example, as shown in FIG. A configuration in which different excitation coils 3A and detection coils 3B are arranged one by one on the same axis so as to overlap inside and outside to form a test coil 3, and three or more test coils 3 are provided, that is, the excitation coil 3A It is also possible to adopt a configuration in which a plurality of detection coils are provided similarly to the detection coil 3B.
<3> The switching mechanism 4B is configured to switch the detection coil 3B to be activated by turning on / off the cable contact from each of the detection coils 3B, or to activate all the detection coils 3B. In such a state, a configuration may be adopted in which the detection value corresponding to the adjacent detection coil 3B is selected and received from among the respective pieces of detection data, and is switched so as to be received.
However, it is also possible to adopt a configuration in which the switching mechanism 4B is omitted.
[0017]
Note that, as described above, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the entry.
[Brief description of the drawings]
FIG. 1 is a conceptual view showing an eddy current flaw detector. FIG. 2 is a conceptual plan view showing an inspection coil. FIG. 3 is a conceptual perspective view showing an inspection coil. FIG. 4 is a conceptual plan view of an inspection coil showing an inspection situation. FIG. 6 is a conceptual plan view showing a test coil according to another embodiment. FIG. 6 is a conceptual plan view showing a test coil according to another embodiment. FIG. 7 is a conceptual plan view showing a conventional test coil.
REFERENCE SIGNS LIST 1 flaw detection target 2 defect 3A excitation coil 3B detection coil 4A detection processing means 4B switching means 6 eddy current 7 indirect magnetic field

Claims (2)

  1. An excitation coil and a detection coil are provided in such a manner that the respective coil axes are orthogonal or almost orthogonal to the probe base surface for performing the exploration by facing the flaw detection target, and a magnetic field is generated in the excitation coil. An eddy current flaw detection device provided with detection processing means for detecting a magnetic field formed by an eddy current generated in the flaw detection target by the detection coil and detecting a state of a defect present in the flaw detection target,
    The three or more detection coils are provided, and the arrangement of the detection coils in the coil axis direction is a polygon in a line figure formed by connecting the coil axes of the detection coils in the coil axis direction. Eddy current flaw detector set to exist.
  2. The eddy current flaw detection device according to claim 1, further comprising a switching unit that switches the detection of the magnetic field by the detection coil for each of a pair of adjacent detection coils.
JP2002188398A 2002-06-27 2002-06-27 Eddy-current flaw detection apparatus Pending JP2004028897A (en)

Priority Applications (1)

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Application Number Priority Date Filing Date Title
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010505093A (en) * 2006-09-28 2010-02-18 プリューフテヒニーク ディーター ブッシュ アクチェンゲゼルシャフト Leakage magnetic flux inspection device for tube-shaped object
JP2012026806A (en) * 2010-07-21 2012-02-09 Toshiba Corp Remote field eddy current flow detector, and method
CN103323522A (en) * 2012-03-22 2013-09-25 奥林巴斯Ndt公司 Eddy current system and object detecting method by using the same
JP2015194419A (en) * 2014-03-31 2015-11-05 日立Geニュークリア・エナジー株式会社 Eddy current flaw detection method and eddy current flaw detection device

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010505093A (en) * 2006-09-28 2010-02-18 プリューフテヒニーク ディーター ブッシュ アクチェンゲゼルシャフト Leakage magnetic flux inspection device for tube-shaped object
JP2012026806A (en) * 2010-07-21 2012-02-09 Toshiba Corp Remote field eddy current flow detector, and method
CN103323522A (en) * 2012-03-22 2013-09-25 奥林巴斯Ndt公司 Eddy current system and object detecting method by using the same
JP2015194419A (en) * 2014-03-31 2015-11-05 日立Geニュークリア・エナジー株式会社 Eddy current flaw detection method and eddy current flaw detection device

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