JP2005156184A - Eddy current flaw detector for bent pipe, and eddy current flaw detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy current flaw detector, capable of simply and efficiently performing the flaw detection work of pipings having a bent part, such as an elbow or the like, having high accuracy, and being relatively simple in constitution and capable of being reduced in cost and inspection cost. <P>SOLUTION: This eddy current flaw detector 1 for the bent pipe is equipped with a plurality of segments 4 connected by a connection part 2, capable of permitting operation over a definite angle range and directionally varied along the outer surface of the elbow 3 to be subjected to flaw detection, the eddy current probe 5 provided at least to either one of the segments 4 and inspecting the crack of the elbow 3, on the basis of an eddy current and the wheels 6 provided at least to the segments 4a and 4b, arranged at both ends of the segments 4 and coming into contact with the outer surface of the elbow 3 capable of rotation and running. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an eddy current flaw detector for a bent pipe and a flaw detection method for flaw detection of a curved portion in a plant piping or the like, for example, an elbow, with an eddy current probe.

  Conventionally, an eddy current method has been frequently used as a method for inspecting a crack on a pipe surface in plant piping or the like. This eddy current method generates eddy currents on the pipe surface by scanning the pipe surface with an eddy current probe for inspection (a coil energized with an alternating current) in contact with the pipe, and generates eddy currents due to defects. This is a method of detecting flaws and detecting flaws. The eddy current probe may be applied as a single unit that serves both for energization and detection, and may be applied as a separate pair for energization and detection.

  When performing this eddy current flaw detection method, noise appears due to fluctuations in the distance between the eddy current probe and the object or the angle between the eddy current probe and the inspection surface, so the eddy current probe is scanned along the pipe. A mechanism to do this is required. Instead of scanning the eddy current probe along the pipe, it is also possible to generate an eddy current by passing the pipe through the coil that has been wound up, thereby detecting the eddy current (for example, Patent Document 1). reference).

  By the way, since there is usually no discontinuity in the existing piping, conventionally, a bobbin that can divide the coil into two in the axial (longitudinal) direction is prepared, this bobbin is attached to the piping, and the coil is attached to the bobbin. A method of winding and pressing against the pipe surface is taken. In this method, since the coil can be attached so as to surround the pipe without cutting the pipe, defect inspection of the entire circumference of the pipe can be performed.

  However, this method requires a coil winding operation, and a working space must be secured, and the accuracy of coil winding greatly affects the flaw detection result, so that a highly reliable flaw detection result can always be obtained. Have difficulty.

Therefore, in order to eliminate the coil winding work in the field, a method for flaw detection using a printed circuit board type coil element composed of a plurality of wiring patterns has been proposed (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 7-311180 JP 2000-81419 A

  The above-described eddy current flaw detection apparatus for piping is intended to be applied to a straight pipe portion of piping, and is difficult to apply to inspection of piping having a curved portion such as an elbow. That is, in order to detect an elbow or the like by a mechanism equipped with an eddy current probe, a very complicated operation mechanism is required, and it takes a lot of time to create the apparatus, and there is a problem that the inspection cost is expensive. Further, in the case of flaw detection with a coil using a bobbin that can be divided into two in the axial (longitudinal) direction of the pipe, since the bobbin can be applied only to a straight pipe part, flaw detection of a pipe bent part such as an elbow is difficult as described above. is there.

  In view of such circumstances, the present invention can perform a flaw detection operation of a pipe having a curved portion such as an elbow easily, efficiently, and with high accuracy, and has a relatively simple configuration, an apparatus cost and an inspection. An object of the present invention is to provide an eddy current flaw detector for bent tubes and a flaw detection method that can reduce the cost and the like.

  In order to achieve the above object, in the invention according to claim 1, a plurality of segments arranged along the outer surface of the curved portion of the pipe having the curved portion, and an operation within a certain angle range by connecting these segments. An eddy current probe for inspecting a crack of the pipe by eddy current, at least one of the segments disposed at both ends, There is provided an eddy current flaw detector for a bent tube comprising a wheel that can rotate in contact with the outer surface of the bent tube.

  The invention according to claim 2 provides an eddy current flaw detector for a bent pipe in which the eddy current probe can be pressed against the surface of the pipe with a constant load at all times.

  According to a third aspect of the present invention, there is provided an eddy current flaw detector for a curved pipe in which the pair of eddy current probes is arranged adjacent to one segment, one eddy current probe is an excitation coil, and the other is a detection coil. .

  In the invention according to claim 4, the pair of eddy current probes are arranged adjacently along the connecting direction of the segments, or are arranged adjacently along a direction orthogonal to the connecting direction. I will provide a.

  The invention according to claim 5 provides an eddy current flaw detector for a bent tube in which the eddy current probe is provided alone in the segment.

  According to a sixth aspect of the present invention, there is provided an eddy current flaw detector for a bent pipe in which the eddy current probe is arranged at a position different from each other in a direction orthogonal to a connecting direction for each adjacent segment.

  In the invention according to claim 7, the bent tube eddy current flaw detector according to any one of claims 1 to 6 is defined as one unit, and two or more units selected from these are arranged on the detection surface side of the eddy current probe. Provided is an eddy current flaw detector for a bent pipe which is integrated by facing and capable of flaw detection at different positions in the circumferential direction on the outer surface side of the pipe at the same time.

  According to an eighth aspect of the present invention, there is provided an eddy current flaw detector for a bent pipe in which each unit is integrated by a segment fixing arm having a telescopic function, and the segment can be pressed against the pipe with a constant load.

  In the invention which concerns on Claim 9, the said segment fixed arm provides the eddy current flaw detector for curved pipes which can be expanded-contracted according to the diameter of the pipe to test.

  According to a tenth aspect of the present invention, the apparatus according to any one of the first to ninth aspects is disposed along an outer surface of a bent portion of a pipe to be flaw-detected, and the segment is allowed to travel in contact with the outer surface of the pipe. However, by supplying an alternating current to the eddy current probe to excite the eddy current in the pipe, the eddy current probe captures the disturbance of the eddy current excited in the pipe at the defect position as an impedance change, Provided is an eddy current flaw detection method for bent pipes, characterized by performing flaw detection on the pipe.

  According to the present invention, a plurality of segments that can be arranged in a curved line along the outer surface of the bent portion of the pipe to be flaw-detected are connected by the connecting portion in a state that allows operation within a certain angle range, and at least the segments An eddy current probe that inspects cracks in pipes by eddy currents is placed in one of them, and the pipes are inspected while the segments are running in contact with the outer surface of the pipes. The flaw detection work of the pipes possessed can be performed easily, efficiently and with high accuracy, and the configuration of the apparatus to be used becomes relatively simple, so that the apparatus cost and the inspection cost can be reduced. .

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an eddy current flaw detector for a bent tube and an eddy current flaw detection method according to the present invention will be described with reference to the drawings. In the following embodiment, a case where an elbow is applied as a curved pipe will be described.

[First Embodiment (FIGS. 1 to 3)]
FIG. 1 is an explanatory view showing a usage state of the eddy current flaw detector for a bent tube according to the first embodiment of the present invention, and shows a case where flaw detection is performed on the outer surface on the large diameter side of the elbow. FIG. 2 is a basic configuration diagram showing a mounting state when not in use, and FIG. 3 is an enlarged cross-sectional view showing a segment portion of the bent tube eddy current flaw detector. In each of the above drawings, the upper, lower, left, and right directions are shown in common, so in the following description, regarding the description of the arrangement, orientation, operation direction, and the like of the structural members, Use expressions such as “bottom, left, right, vertical, horizontal”. Note that these expressions do not limit the present invention.

  As shown in FIG. 1 to FIG. 3, the eddy current flaw detector 1 for a bent tube according to the present embodiment is connected by a connecting portion 2 that can allow operation in a certain angle range, and is oriented along the outer surface of an elbow 3 to be flawed. Eddy current probe 5 for inspecting the crack of elbow 3 by eddy current, and segment 4 at least arranged at both ends , 4b, and a wheel 6 capable of rotating while contacting the outer surface of the elbow 3.

  Each segment 4 is configured as a cylindrical or box-shaped housing, and a total of five, for example, of the same outer shape are arranged in a row in the horizontal direction. On the side of the same height position on the upper end side of each segment 4 is formed an arm portion 2a constituting the connecting portion 2 along the direction facing each other, and these arm portions 2a are adjacent to each other. The segments 4 are connected to each other in such a manner that they can be sequentially rotated by parallel connecting shafts 2b that are perpendicular to the connecting direction a of the segments 4 (that is, the direction perpendicular to the paper surface). Thereby, each segment 4 is integrally comprised as 1 unit which can respectively rotate in a fixed angle range toward the up-down direction.

  Among the segments 4, horizontal axles 7 are respectively provided above the segments 4 a and 4 b arranged at both ends, and wheels 6 are supported on these axles 7. Each wheel 6 has a unicycle structure with a predetermined width that can roll along the curved outer surface of the elbow 3 along the axial direction, and these wheels 6 are driven by a free wheel or a motor that can be arbitrarily rotated by hand, for example. Configured as a ring or the like.

  In the present embodiment, a single eddy current probe 4 is provided in the centrally arranged segment 4c. The eddy current probe 4 is held so as to be vertically movable in a vertically long upper opening accommodating portion 8 provided in the segment 4c, and its upper end can protrude upward from the accommodating portion 8 of the segment 4c via the upper opening. It has become. The lower end side of the eddy current probe 4 protrudes upward from the bottom side of the storage portion 8, that is, toward the lower surface of the elbow 3 shown in FIG. 1 by elastic means, for example, an eddy current probe pressing spring 9 such as a compression coil spring. Is biased in the direction. As a result, the eddy current probe 4 can always be pressed against the surface of the elbow 3 with a constant load.

  By adjusting the strength of the eddy current probe pressing spring 9, it is possible to set the eddy current probe 5 so as to protrude to an appropriate position above the wheel 6. In this way, by adjusting the strength of the eddy current probe pressing spring 9, when the wheel 6 moves in the axial direction along the surface of the elbow 3, for example, the eddy current probe 5 always hits the pipe surface with a constant load. It becomes like this. As a result, the distance (lift-off amount) between the eddy current probe 5 and the surface of the elbow 3 and the perpendicularity between the eddy current probe 5 and the elbow 3 are also constant, being hardly affected by noise due to fluctuations, and improving detection accuracy. Can be planned.

  The eddy current probe 5 is configured to have a core 10 made of ferrite and a detection coil 11 disposed so as to surround the core 10. The detection coil 11 is also configured to function as an exciting coil. That is, an alternating current can be supplied to the detection coil 11 via a wiring (not shown) with the eddy current probe 5 in contact with the elbow 3. Thereby, when an alternating current is passed through the detection coil 11, an eddy current is excited in the elbow 3. When a defect has occurred in the elbow 3, eddy current excited at the position of the defect is disturbed. By detecting this eddy current disturbance as a change in impedance of the detection coil 11, defect inspection can be performed. .

  At the time of use, as shown in FIG. 1, flaw detection of the pipe is performed while the segment is in contact with the outer surface of the pipe and traveling in the axial direction (arrow a). The segment 4 is bent along the curvature of the elbow 3. If the curvature of the elbow 3 is significantly smaller than the size of the segment 4, it can be dealt with by making the segment 4 smaller.

  In this way, a plurality of segments 4 that can be arranged in a curved shape along the outer surface of the elbow 3 to be flaw-detected are connected by the connecting portion 2 in a state that allows operation within a certain angular range, and at least one of the segments 4 is connected. One of them is an eddy current probe 5 for inspecting the crack of the elbow 3 by eddy current, and the elbow 3 is flawed while the segment 4 is running in contact with the outer surface of the elbow 3. That is, defect flaw detection is performed by grasping the disturbance of eddy current excited by the elbow 3 at the defect position as an impedance change.

  According to the present embodiment, defect inspection of the elbow 3 by the eddy current method can be performed in a stable state with little noise.

  FIG. 4 shows a modification of the first embodiment. In this modification, a pair of eddy current probes 5 are arranged adjacent to one segment 4, one of the eddy current probes 5 arranged adjacent to the segment 4 is an excitation probe, and the other is a detection probe. Yes.

  In FIG. 4, the pair of eddy current probes 5 are adjacent to each other along the connecting direction of the segments 4. However, the pair of eddy current probes 5 may be adjacent to each other along the direction orthogonal to the connecting direction (that is, the direction perpendicular to the paper surface). Good.

  Thus, according to the configuration in which two eddy current probes 5 are arranged adjacent to each other, the eddy current excitation probe and the detection probe are separated from each other, so that the current difference between the excitation probe and the detection probe is measured. Thus, noise such as material change can be reduced.

  Further, the two eddy current probes 5 can be arranged in a direction other than the connecting direction of the segments 4 and the direction perpendicular thereto, for example, the vertical direction or the concentric direction by changing the size of the coil.

  In addition, although not shown in figure as another modification of this embodiment, the eddy current probe which makes a single unit or a pair with respect to each segment can also be provided. In this case, the eddy current probes may be arranged so that the positions of the eddy current probes are different from each other in the connecting direction or the direction perpendicular thereto.

  When each eddy current probe is arranged in the connecting direction of the segments 4, by providing a plurality of segments 4, more detailed flaw detection results can be obtained. Further, when the segment eddy current probe 5 is arranged in the direction orthogonal to the connecting direction of the segments 4, the flaw detection range can be expanded in the direction orthogonal to the moving direction, and a wider range of flaw detection is possible. .

[Second Embodiment (FIGS. 5 and 6)]
FIG. 5 is a block diagram showing a second embodiment of the present invention, and FIG. 6 is an enlarged sectional view taken along line AA of FIG.

  In this embodiment, the eddy current flaw detector 1 for a bent tube is set as one unit, and two or more units selected from these, for example, two units are integrated with the detection surface side of the eddy current probe 5 facing each other. Different positions in the circumferential direction on the outer surface side, for example, two upper and lower positions can be simultaneously detected.

  Specifically, each unit is integrated by a segment fixing arm 12 having a telescopic function, and the segment 4 can be pressed against the elbow 3 with a constant load. The segment fixing arm 12 has a function of expanding and contracting in accordance with the pipe diameter, for example, a tension coil spring 13. Since the other configuration is the same as that of the eddy current flaw detector 1 for curved pipes shown in the first embodiment, the same reference numerals as those in the first embodiment are attached to the drawing, and the description thereof is omitted.

  According to the present embodiment, the eddy current for the bent pipe is provided at a plurality of positions on the elbow 3 by connecting two or more units constituting the eddy current flaw detector 1 for the bent pipe with elastic force in the pulling direction. The flaw detection apparatus 1 is pressed.

  Therefore, according to the present embodiment, the vertical direction, which is the main defect generation site of the elbow, can be detected at a time, and the inspection time can be shortened.

The schematic diagram which shows 1st Embodiment of this invention and shows an eddy current flaw detection state. The 1st Embodiment of this invention is shown, and the block diagram of the eddy current flaw detector for curved tubes. The 1st Embodiment of this invention is shown, and the enlarged view of a segment. The schematic diagram which shows 1st Embodiment of this invention and shows the eddy current flaw detector for curved tubes at the time of arrange | positioning two eddy current probes adjacently. The 2nd Embodiment of this invention is shown, and the block diagram of the eddy current flaw detector for curved tubes. The 2nd Embodiment of this invention is shown, and the sectional view on the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Eddy current flaw detector 2 for curved pipes Connecting part 3 Elbow 4 Segment 5 Eddy current probe 6 Wheel 7 Axle 8 Storage part 9 Eddy current probe pressing spring 10 Core 11 Detection coil 12 Segment fixed arm 13 Tension coil spring

Claims (10)

A plurality of segments arranged along an outer surface of a curved portion of a pipe having a curved portion, a connecting portion that connects these segments to allow operation in a certain angle range, and at least one of the segments An eddy current probe provided for inspecting a crack of the pipe by an eddy current; and a wheel provided on at least both ends of the segment and capable of rotating in contact with an outer surface of the pipe. Eddy current flaw detector for curved pipes. 2. The eddy current flaw detector for a bent pipe according to claim 1, wherein the eddy current probe is capable of being pressed against the surface of the pipe with a constant load at all times. 2. The eddy current flaw detector for a bent pipe according to claim 1, wherein one pair of the eddy current probes is arranged adjacent to one segment, one eddy current probe is an excitation coil, and the other is a detection coil. 4. The eddy current flaw detector for a bent pipe according to claim 3, wherein the pair of eddy current probes are arranged adjacent to each other along a connecting direction of the segments or adjacent to each other along a direction orthogonal to the connecting direction. 2. The eddy current flaw detector for a bent pipe according to claim 1, wherein the eddy current probe is provided alone in the segment. 6. The eddy current flaw detector for a bent pipe according to claim 3, wherein the eddy current probe is arranged at a position different in a direction orthogonal to a connecting direction for each adjacent segment. The eddy current flaw detector for a bent pipe according to any one of claims 1 to 6, wherein one unit is formed, and two or more units selected from these are integrated with the detection surface side of the eddy current probe facing each other, and the pipe An eddy current flaw detector for a bent tube, which enables flaw detection at different positions in the circumferential direction on the outer surface side of the tube. 8. The eddy current flaw detector for a bent pipe according to claim 7, wherein each unit is integrated by a segment fixing arm having a telescopic function, and the segment can be pressed against the pipe with a constant load. 9. The eddy current flaw detector for a bent pipe according to claim 8, wherein the segment fixing arm can be expanded and contracted in accordance with a diameter of a pipe to be flawed. An apparatus according to any one of claims 1 to 9, wherein the device is arranged along an outer surface of a bent portion of a pipe to be flaw-detected, and the segment is caused to contact the outer surface of the pipe while the eddy current probe is subjected to an alternating current. A defect is detected in the pipe by supplying current to excite the eddy current in the pipe and capturing the disturbance of the eddy current excited in the pipe at the defect position as an impedance change by the eddy current probe. An eddy current flaw detection method for bent pipes.

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