JP2004251839A - Pipe inner surface flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and surely inspect an inner surface of a pipe over the whole circumference and the full length, without requiring any complicated rotary mechanism. <P>SOLUTION: This pipe inner surface flaw inspecting device is provided with a detecting head 14 inserted into the pipe 10 of an inspection object, segment probes 12 attached to respective positions around a periphery of the detecting head divided into a plurality of portions, and having an eddy current test function, a driving unit 18 for moving the detecting head 14 along an axial direction integrally with the plurality of segment probes 12 attached to the periphery, and an eddy current test equipment 22 for inspecting a surface flaw existing in an inside of the pipe, based on detection signals output from the plurality of segment probes 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-pipe surface flaw inspection apparatus, and more particularly to an in-pipe surface flaw inspection apparatus that is suitably applied when non-destructively detecting a flaw existing on an inner surface of a metal pipe such as a seamless steel pipe.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a technique for non-destructively inspecting the inner surface of a seamless steel pipe over its entire circumference and length has been developed. Examples thereof include an oblique flaw detection method using an ultrasonic flaw detection technique for inspecting from the outer surface side of a pipe, and a penetration coil method using an eddy current flaw detection technique.
[0003]
All of these methods perform inspections from the outside of the tube, so that the operation of the inspection device is easy. Therefore, there is an advantage that the inspection can be reliably performed over the entire circumference and the entire length of the tube.
[0004]
However, in the case of the oblique flaw detection method, when the flaw detection probe is brought into contact with the outer surface of the tube, an inner surface flaw existing in a direction of a perpendicular line passing through the probe (refractive angle) of, for example, 40 ° is generated by ultrasonic waves. The detection accuracy is poor because the reflected echo is weak, and in the case of the penetration coil method, the inner surface can be inspected only at a depth of about 0.2 mm at most from the outer surface due to the AC skin effect. There was a problem that could not be applied.
[0005]
Therefore, a technique has been proposed in which an eddy current flaw detection probe (coil) can be inserted into a pipe and is rotated in a circumferential direction to inspect the inner surface of the pipe over the entire circumference and the entire length. 1).
[0006]
[Patent Document 1]
Japanese Patent Publication No. 7-3409
[Problems to be solved by the invention]
However, the flaw detection technology described in Patent Document 1 and the like requires that a flaw detection probe be rotated in a circumferential direction, and therefore requires a complicated rotation mechanism for rotating the probe or the tube itself. There was a problem.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and can easily and reliably inspect the inner surface of a tube over its entire circumference and length without requiring a complicated rotating mechanism. It is an object to provide a flaw inspection device.
[0009]
[Means for Solving the Problems]
The present invention provides a detection head that can be inserted into a tube to be inspected, a segment probe having an eddy current flaw detection function provided at each of a plurality of divided positions around the detection head, and the detection head provided around the detection head. Drive means for moving in an axial direction integrally with the plurality of segment probes, and an eddy current flaw detector for inspecting surface flaws present in the pipe based on detection signals output from the plurality of segment probes. Thus, the above problem has been solved.
[0010]
That is, in the present invention, a segment probe having a flaw detection function alone is attached to each position obtained by dividing the circumferential direction of the detection head into a plurality of parts, so that the entire circumference is surrounded by the plurality of segment probes. Since a tube can be inserted into the tube integrally with the head, the existence position of the internal surface flaw can be specified from the insertion position of the segment probe from which the detection signal is output and the attached position in the circumferential direction. In addition, the inner surface of the tube can be easily and reliably inspected over the entire circumference.
[0011]
According to the present invention, in the pipe inner surface flaw inspection apparatus, the segment probe may be disposed in parallel with the absolute value measuring eddy current testing coil disposed in a circumferential direction of the detection head. Detects the size (depth) and range (length) of surface flaws generated in the pipe by one operation because it has a pair of eddy current detection coils for self-comparison measurement provided can do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic side view schematically showing a main part of a tube surface flaw inspection apparatus according to an embodiment of the present invention.
[0013]
The pipe surface damage inspection apparatus according to the present embodiment includes a cylindrical detection head 14 having a plurality of segment probes (described later) 12 attached to the periphery thereof, which can be inserted into a seamless steel pipe 10 to be inspected, and the detection head. A reciprocating drive device 18 that is fixed to the center of the axis of 14, moves the holding bar 16 in the direction of the arrow, and moves the detection head 14 inserted in the tube 10 forward and backward in the same direction; When a detection signal generated as a result of moving in the tube 10 is input via the cable 20 electrically connected to each of the segment probes 12, a surface flaw in the tube is generated based on the detection signal. An eddy current flaw detection device 22 for detecting the position and the degree thereof is provided.
[0014]
In the present embodiment, segment probes 12 each having an eddy current flaw detection function are arranged around the detection head 14 at respective positions equally divided into eight (plural) areas. That is, the detection head 14 has a configuration in which eight (plural) segment probes 12 are provided in the circumferential direction with the segment probe 12 as a unit schematically illustrated in FIG. I have.
[0015]
One segment probe 12 includes an absolute value measuring eddy current flaw detection coil 26 disposed on a base 24 made of a rectangular insulating material along the circumferential direction of the detection head 14, and is disposed in parallel with the coil 26. And a pair of eddy current inspection coils 28 for self-comparison measurement provided.
[0016]
As shown in FIG. 3, a part of the segment probe 12 is arranged around the detection head 14 so that the arrangement directions of the flaw detection coils 26 and 28 are aligned with each other in the circumferential direction. The portions of only the non-existent base are overlapped, and the coils 26 and 28 provided on each segment probe 12 are disposed so that both ends thereof substantially coincide with each other in the circumferential direction. Thereby, as schematically shown in FIG. 4 in the state viewed from the axial direction with the overlapped portions being hatched, the eight segment probes indicated by reference numerals 12 (1) to 12 (8) The detection head 14 is covered over the entire circumference, and each of the flaw detection coils 26 and 28 formed on each of the segment probes 12 is configured to be continuous in the length direction.
[0017]
The segment probe 12 formed around the periphery by the detection head 14 as described above has a distance (G shown in FIG. 1) to the inner surface of the tube when the segment probe 12 is inserted into the tube 10 according to an object to be measured. Is adjusted, for example, to about 1 mm.
[0018]
Next, the operation of the present embodiment will be described.
[0019]
As shown in FIG. 5, the inner surface is inspected by moving the detection head 14 provided with the plurality of segment probes 12 in the circumferential direction in the direction of the arrow and inserting it into the tube 10. As shown in FIG. 6 (A), a longitudinal section taken in a longitudinal direction is viewed from an oblique direction, and FIG. 6 (B) shows a transverse section of the tube. It is assumed that a scratch X having a size (depth) D in a range (length) L in the direction is generated on the inner surface.
[0020]
In this case, when the segment probe 12 reaches the flaw X, the depth of the flaw as shown in FIG. 7A, that is, the flaw, as shown in FIG. A detection signal having a waveform corresponding to the size D is output, and a pair of self-comparative measurement eddy current flaw detection coils 28 output two peaks corresponding to the length L of the flaw as shown in FIG. Is output.
[0021]
That is, in one segment probe 12 shown in FIG. 2, the eddy current inspection coil 26 for absolute value measurement and the eddy current inspection coil 28 for self-comparison measurement have the functions of an excitation coil and a detection coil, respectively. When it is, the other is excited. Then, as shown schematically in FIG. 8, the absolute value measurement eddy current flaw detection coil 26 together with an output waveform corresponding to a part of the tube cross section, the coil 26 moves in the direction of the arrow, and moves to the position of the flaw (recess). Upon arrival, a detection signal having an amplitude waveform corresponding to the distance to the surface of the flaw is output, so that the depth of the flaw can be detected from the magnitude of the amplitude.
[0022]
On the other hand, the eddy current flaw detection coil 28 for self-comparison measurement is similar to the two coils A and B shown in FIG. As shown in (B), a circuit in which the impedance Z4 is variable is configured, and correction is made with Z4 so as to balance Z1 × Z3 = Z2 × Z4. With such a configuration, the pair of coils A and B move in the direction of the arrow, and output a peak signal when the start and end of the wound coincide. That is, when the coil B passes through the start end, an output waveform appears. When the coil A passes through the start end, the output waveform becomes flat because the balance is maintained, and the output waveform has the same change at the end. The length of the flaw can be detected from the interval between the peak waveforms.
[0023]
In addition, since the segment probe 12 has the eddy current inspection coil 26 for absolute value measurement and the eddy current inspection coil 28 for self-comparison measurement, the relationship between each output and the cross-sectional shape of the flaw is shown in FIGS. As schematically shown in FIG. 2B, even if two outputs have the same apparent output from the eddy current inspection coil 28 for self-comparison measurement, the difference is clearly clarified by using the eddy current inspection coil 26 for absolute value measurement in combination. Can be distinguished. Conversely, in the case of only the absolute value measurement eddy current flaw detection coil 26, noise is often picked up, so that the range of the flaw becomes unclear, but it can be clarified by using the coil together.
[0024]
As described above, according to the present embodiment, the position in the length direction of the flaw generated on the inner surface of the tube 10 is determined based on the moving distance of the segment probe 12 by the reciprocating drive device 18 in the circumferential direction. The position in the circumferential direction can be detected from the arrangement position of the segment probe 12 attached to the detection head 14, that is, from any of the segment probes 12 (1) to 12 (8).
[0025]
Therefore, the position of the flaw occurring on the inner surface of the tube can be accurately detected without using a complicated rotating mechanism, and at the same time, the size (depth) and length of the flaw can be determined. It can be detected accurately.
[0026]
Next, a result of an inspection performed by actually using the inspection apparatus of the present embodiment will be described.
[0027]
It was applied to the torsion line of 13CR oil country tubular goods with dimensions of 60.3 to 244.5 mmφ and length of 12 m, and was inspected at a flaw detection speed of 1 to 2 m / sec. 100% of surface scratches could be detected. At that time, the distance (air gap) between the inner diameter of the steel pipe and the segment probe 12 was 1.6 mm at the maximum.
[0028]
Also, while the conventional through-coil method could detect only a flaw of 25% or more of the wall thickness of the steel pipe, according to the present embodiment, the same steel pipe had a depth of 5% or more of the wall thickness. Scars could be detected.
[0029]
As described above, the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.
[0030]
For example, the specific configuration of the in-tube surface flaw inspection apparatus according to the present invention is not limited to the one shown in the above-described embodiment, and the segment probe is not limited to the one in which the entire circumference is divided into eight.
[0031]
Further, the segment probe is not necessarily limited to a combination of the eddy current inspection coil for absolute value measurement and the eddy current inspection coil for self-comparison measurement as long as it has an eddy current inspection function.
[0032]
【The invention's effect】
As described above, according to the present invention, the inner surface of a pipe can be easily and reliably inspected over the entire circumference and the entire length without requiring a complicated rotation mechanism.
[Brief description of the drawings]
FIG. 1 is a schematic side view schematically showing a main part of an in-pipe surface flaw inspection apparatus according to an embodiment of the present invention. FIG. 2 is a schematic view of a segment probe applied to the in-pipe surface flaw inspection apparatus of this embodiment. FIG. 3 is a schematic perspective view showing a method of disposing a segment probe. FIG. 4 is a schematic front view schematically showing a state in which the entire segment probe is viewed from an axial direction. FIG. FIG. 6 is a schematic cross-sectional view showing the length and size of a flaw present on the inner surface of the pipe. FIG. 7 is a diagram showing an example of the measurement results obtained by the pipe inner surface flaw inspection apparatus of the present embodiment. FIG. 8 is an explanatory view showing the principle of measurement by the in-pipe surface flaw inspection device of the present embodiment. FIG. 9 is another explanatory view showing the measurement principle by the in-pipe surface flaw inspection apparatus of the present embodiment. Explanatory drawing showing another measurement result by the surface scratch inspection device Description of the code]
DESCRIPTION OF SYMBOLS 10 ... Steel pipe 12 ... Segment probe 14 ... Detection head 16 ... Holding bar 18 ... Reciprocating drive device 20 ... Cable 22 ... Eddy current flaw detector 24 ... Base 26 ... Eddy current flaw detection coil 28 for absolute value measurement ... Eddy current flaw detection coil for self-comparison measurement

Claims (2)

A detection head that can be inserted into a tube to be inspected,
A segment probe having an eddy current flaw detection function attached to each position obtained by dividing the periphery of the detection head into a plurality,
Driving means for moving the detection head in the axial direction integrally with a plurality of segment probes attached to the periphery,
An in-tube surface flaw inspection device, comprising: an eddy current flaw detection device for inspecting surface flaws present in the tube based on detection signals output from the plurality of segment probes. The segment probe includes an absolute value measurement eddy current inspection coil disposed in the circumferential direction of the detection head, and a pair of self-comparison measurement eddy current inspection coils disposed in parallel to the absolute value measurement eddy current coil. The intra-tube surface flaw inspection apparatus according to claim 1, wherein the inspection apparatus has an internal surface.

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