JP2014098630A - Eddy current flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to inspect an inner surface of a conduit by an eddy current flaw detection method according to the conduit and the shape of the inner surface thereof while keeping a distance between a sensor and the inner surface of the conduit at a small state.SOLUTION: An eddy current flaw detector 100 is inserted into the inside of a conductive conduit 10 and generate an eddy current by providing an induction current from a sensor 104 with an inner surface of the conduit to detect the defect thereof by a change in the eddy current. The eddy current flaw detector includes: a support shaft 102 that supports the sensor so as to oppose the inner surface of the conduit; and a sensor movement mechanism part 112 that reduces the diameter of the sensor toward the support shaft in a radial direction of the cross section of the conduit when the sensor comes in contact with part of the inner surface of the conduit. As the sensor movement mechanism part, an elastic member can be used that elastically reduces the diameter of the sensor toward the inner surface of the conduit in a vertical direction.

Description

  The present invention relates to an interpolated eddy current flaw detector used for detecting a defect generated on the inner surface of a conductive conduit such as a land boiler heat transfer tube.

  The heat transfer tubes provided in land boilers may cause defects such as cracks, thinning, and flaws on the inner surface, resulting in problems such as steam leakage. In order to prevent such troubles, the heat transfer tubes are nondestructive of defects generated on the inner surface of the heat transfer tubes by using an interpolated eddy current sensor using eddy current testing (ECT). The method of detecting automatically is known. In the eddy current flaw detection method, an eddy current is generated in a subject by a change in magnetic flux generated by an exciting coil supplied with an exciting current, and a detection signal representing the magnetic flux generated by the eddy current is acquired by the detecting coil, and this detection is performed. This is a technique for obtaining the position, shape, depth, and the like of a defect on the inner surface of a duct that is a subject based on a signal.

  When flaw detection is performed on the inner surface of a pipeline using an eddy current sensor, the distance (lift-off) between the eddy current sensor and the inner surface of the pipeline serving as a subject greatly affects the defect detection capability. In order to increase the detection capability of the eddy current sensor, it is important to reduce the lift-off. In Patent Document 1, eddy current flaw detection is performed by attaching a plurality of thin film-like coils to a cylindrical casing at equal intervals, and alternately wiring in order to suppress pipe end expansion and unnecessary signals from the tube sheet. An eddy current flaw detection probe is disclosed in which lift-off between the inner surface of the tube and the coil is reduced by differentially connecting to a vessel.

Utility Model Registration No. 3165804

  However, boiler heat transfer tubes have flat portions due to bending bends and locations where the inner diameter of the tubes deforms due to welding back waves. Therefore, if the lift-off between the inner surface of the subject tube and the coil is made too small, the sensor passes through the tube. The situation becomes difficult and inspection becomes difficult. That is, as the lift-off is smaller, the defect detection capability is improved, but as shown in FIG. 5, the second and subsequent heat transfer tubes that cannot pass through the bending bend portion 12 of the heat transfer tube 10 and are provided at the lower stage from the bending bend portion 12. May not be able to inspect. Further, as shown in FIG. 6, there is a possibility that the sensor 16 cannot pass due to the weld back wave 14 formed on the inner surface side of the pipe to connect the pipe. The eddy current flaw detection probe disclosed in Patent Document 1 is difficult to apply to the bend portion 12 and the welding back wave 14 having a small bending radius.

  The present invention has been made in view of the above-mentioned problems of the conventional eddy current flaw detection apparatus, and can be applied to an inspection by an eddy current flaw detection method according to the shape of a pipe line to be examined. An object is to provide an improved eddy current flaw detector.

  In one embodiment of the present invention, an inside of a conductive pipe is inserted, an induced current is applied to the inner surface of the pipe from a sensor to generate an eddy current, and a defect in the inner face of the pipe is detected by a change in the eddy current. An eddy current flaw detection device that supports the sensor so that the sensor faces the inner surface of the pipe line, and the sensor moves the support shaft when the sensor abuts a part of the inner surface of the pipe line. And a sensor moving mechanism for reducing the diameter in the radial direction of the cross section of the pipe line toward the eddy current flaw detector.

  According to one aspect of the present invention, when the sensor comes into contact with a part of the inner surface of the pipe, such as a weld back wave or a bending bend of the pipe, which the inner surface of the pipe has, the sensor is radially reduced in diameter. For this reason, it is possible to inspect the inner surface of the pipe by the eddy current flaw detection method by inserting the sensor without hooking the sensor even in a portion where the inner diameter of the pipe is narrow due to welding back waves or the like or a bend having a small bending radius.

  At this time, in one aspect of the present invention, the sensor moving mechanism section may be an elastic member that elastically reduces the diameter of the sensor in the radial direction with respect to the support shaft.

  In this way, the inner surface of the pipeline can be inspected by the eddy current flaw detection method while following the shape of the pipeline and the inner surface of the pipeline while maintaining the distance between the sensor and the inner surface of the pipeline in a small state.

  In one aspect of the present invention, the support shaft is separated into a front end side support shaft and a rear end side support shaft, and the sensor moving mechanism section is provided on a rear end side of the front end side support shaft. A rear end side connection portion provided on the front end side of the rear end side support shaft, one end is connected to the sensor, the other end is connected to the front end side connection portion, and the sensor is connected to the length of the pipe line. One end is connected to the sensor, the other end is connected to the rear end side connecting portion, and the sensor is connected to the length direction and the radial direction. And a rear end-side swinging member that can swing, and the sensor may be a bent portion that can contact a part of the inner surface of the pipe line.

  In this way, the inner surface of the pipeline can be inspected by an eddy current flaw detection method while flexibly following the shape of the pipeline and the inner surface of the pipeline while keeping the distance between the sensor and the inner surface of the pipeline small.

  In one embodiment of the present invention, a plurality of sensors may be provided in the circumferential direction of the support shaft.

  In this way, the inner surface of the pipe can be inspected by the eddy current flaw detection method in all directions on the inner surface of the pipe.

  In the aspect of the invention, the sensor may be configured by arranging a plurality of array coils in a circumferential direction of the support shaft.

  If it does in this way, it will become possible to inspect by the eddy current flaw detection method over a wide range of the inner surface of the pipeline.

  As described above, according to the present invention, when the sensor contacts a part of the inner surface of the pipe, the sensor can be reduced in diameter in the radial direction of the pipe cross section toward the support shaft. For this reason, while maintaining the distance between the sensor and the inner surface of the pipe line in a small state, the inner surface of the pipe line can be inspected by an eddy current flaw detection method so as to cope with a change in the shape of the pipe line or the inner surface of the pipe line. .

It is a schematic block diagram in 1st Embodiment of the eddy current flaw detector of this invention. It is AA sectional drawing of FIG. (A), (b), (c) is operation | movement explanatory drawing of the eddy current flaw detector in the same embodiment. It is a schematic block diagram in 2nd Embodiment of the eddy current flaw detector of this invention. It is a figure which shows an example of the heat exchanger tube used as a test object with an eddy current flaw detector. It is operation | movement explanatory drawing of the problem in the conventional eddy current flaw detector.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

(First embodiment)
First, the configuration of the first embodiment of the eddy current flaw detector according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a first embodiment of an eddy current flaw detector according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  The eddy current flaw detection apparatus is an apparatus that is inserted into a conductive pipe line, generates an eddy current by applying an induced current from the sensor to the inner surface of the pipe line, and detects a defect on the inner surface of the pipe line by a change in the eddy current. It is. As shown in FIG. 1, the eddy current flaw detector 100 according to the present embodiment includes a support shaft 102, a sensor 104, a tip guide 106, and an alignment jig 108.

  The support shaft 102 is a flexible shaft that can be bent in accordance with the shape of the pipeline, and supports the sensor 104 so as to face the inner surface of the pipeline. A distal end guide 106 is provided at the distal end of the support shaft 102 for guiding the eddy current flaw detector 100 to be inserted into the duct. Further, in order to arrange the support shaft 102 that supports the sensor 104 on the central axis of the pipe line, the front end side and the rear end side of the sensor 104 of the support shaft 102 are radially arranged around the support shaft 102, respectively. A brush-type alignment jig 108 to which a brush is attached is provided. The alignment jig 108 is not limited to the brush type, and may be another type such as a saddle type as long as the alignment jig can pass even if the tube shape changes. The eddy current flaw detector 100 is connected to a feeder (not shown) placed outside the heat transfer tube via a flexible tube 112. The feeding device is a pusher type, a hydraulic type, a pneumatic type, or the like, and operates so that the eddy current flaw detector 100 is inserted into the heat transfer tube.

  As shown in FIG. 1, the sensor 104 is configured such that a plurality of array coils 110 are arranged in the circumferential direction of the support shaft 102. By attaching a plurality of array coils 100 to the surface of the sensor 104, an eddy current flaw inspection covering almost the entire circumference of the inner surface of the pipe line can be performed.

  In addition, a plurality of sensors 104 are provided in the circumferential direction of the support shaft 102 so that the inner surface of the pipe can be inspected by an eddy current flaw detection method in all directions on the inner surface of the pipe. It is comprised so that it may become the substantially elliptical sphere shape which covers the axis | shaft 102. FIG. In the present embodiment, as shown in FIG. 2, four sensors 104 are provided so as to surround the support shaft 102. Note that the number of sensors 104 is not limited to four because the sensors 104 may be arranged in the circumferential direction of the support shaft 102 so that the entire inner surface of the pipe to be inspected can be scanned.

  In the present embodiment, as shown in FIG. 2, each sensor 104 is supported by a support shaft 102 via a spring 112. That is, the sensor 104 is supported in a direction perpendicular to the axial direction of the support shaft 102 via a spring 112 that is an elastic member that elastically moves toward the inner surface of the pipe line. In the present embodiment, when the sensor 104 abuts on a part of the inner surface of the pipe line, the spring 112 serves as a sensor moving mechanism unit that reduces the diameter of the sensor 104 toward the support shaft 102 in the radial direction of the cross section of the pipe line 10. Function. Further, in order to elastically reduce the diameter of the sensor 104 in the radial direction of the heat transfer tube 10 according to the shape of the pipe line or the inner surface of the pipe line, a predetermined distance is provided between the sensor 104 and the circumferential direction of the support shaft 102. A clearance 114 having a size of 1 mm is provided. The “part of the inner surface of the pipe line” referred to here refers to, for example, the weld back wave 14 or the bending bend portion 12 of the pipe line that is provided on the inner surface of the pipe line.

  In this way, by adopting a configuration in which the sensor 104 is supported by the support shaft 102 via the spring 112, the pipeline or pipeline can be maintained while maintaining a small lift-off, which is the distance between the sensor 104 and the pipeline inner surface. Following the shape of the inner surface, the inner surface of the pipeline can be inspected by the eddy current flaw detection method.

  Next, the operation of the inner surface defect inspection of the heat transfer tube using the eddy current flaw detector of the present embodiment will be described with reference to the drawings. FIG. 4 is an operation explanatory diagram of the eddy current flaw detector according to the present embodiment, where (a) is a state before the sensor comes into contact with the welding back wave, (b) is a state where the sensor is in contact with the welding back wave, (C) is BB sectional drawing of (b).

  The heat transfer tube 10 is formed by connecting a plurality of pipelines by welding. As shown in FIG. 3 (a), a weld back wave 14 is convex on the inner surface side of the pipeline. Formed. In the present invention, the weld back wave 14 is formed on the inner surface of the pipe in this way, and the sensor 104 is not hooked on the weld back wave 14 by reducing the diameter of the sensor 104 even at a location where the inner diameter of the pipe becomes small. It is made to be able to inspect the inner surface of the pipe line.

  That is, when the sensor 104 comes into contact with the welding back wave 14 when the eddy current flaw detector 100 scans the inside of the heat transfer tube 10, the sensor 104 is supported as shown in FIGS. The spring 112 contracts elastically, and the sensor 104 contracts while moving toward the support shaft 102. When the spring 112 supporting the sensor 104 contracts and the outer diameter of the cross section in the axial direction of the sensor 104 becomes smaller, the sensor 104 can pass without being caught by the welding back wave 14.

  Thus, in the present embodiment, the sensor 104 is configured to move in the radial direction of the cross section and reduce the diameter when contacting the part of the inner surface of the pipe of the heat transfer tube 10. For this reason, the sensor 104 is reduced in diameter by reducing the diameter of the sensor 10 even at a portion where the inner diameter of the heat transfer tube 10 is narrowed by the welding back wave 14 or the like or at the bend portion 12 (see FIG. 5) having a small bending radius. The pipe inner surface can be inspected by being inserted without being caught on a part of the inner surface. That is, a flexible sensor structure that can follow a deformed portion such as the weld back wave 14 and the bending bend portion 12 while maintaining a small lift-off between the sensor 104 and the inner surface of the pipe line can be obtained.

(Second Embodiment)
Next, the configuration of the second embodiment of the eddy current flaw detector according to the present invention will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram of a second embodiment of the eddy current flaw detector according to the present invention.

  As shown in FIG. 4, the eddy current flaw detector 200 of the present embodiment includes a front end side support shaft 202a, a rear end side support shaft 202b, a sensor 204, a front end guide 206, an alignment jig 208, and a front end. A side swing member 212, a rear end side swing member 214, a front end side connecting portion 216, and a rear end side connecting portion 218 are provided. The configurations and functions of the tip guide 206 and the alignment jig 208 are the same as those in the first embodiment, and a description thereof will be omitted.

  As shown in FIG. 4, the sensor 204 is configured such that a plurality of array coils 210 are arranged in the circumferential direction of the support shaft 202. By attaching a plurality of array coils 210 to the surface of the sensor 204, an eddy current flaw inspection covering almost the entire circumference of the inner surface of the pipe line can be performed.

  Further, the sensor 204 includes a front end side support shaft 202a and a rear end side support shaft 202b so that the inner surface of the pipe line can be inspected by eddy current flaw detection in all directions of the inner surface of the pipe line. A plurality are provided in the circumferential direction of the support shaft. In the present embodiment, as shown in FIG. 4, two sensors 204 are provided so as to sandwich the center line of the front end side support shaft 202a and the rear end side support shaft 202b. Note that the number of the sensors 204 is not limited to two, as long as the sensors 204 are arranged in the circumferential direction of the support shafts 202a and 202b so that the entire inner surface of the pipe to be inspected can be scanned.

  In the present embodiment, the configuration of the sensor moving mechanism that reduces the diameter of the sensor 204 in the radial direction when the sensor 204 abuts on a part of the inner surface of the pipe is different from that of the first embodiment. That is, in this embodiment, the support shaft is separated into the front end side support shaft 202a and the rear end side support shaft 202b, and the sensor moving mechanism section includes the front end side swing member 212, the rear end side swing member 214, and the front end The side connection portion 216 and the rear end side connection portion 218 are provided. Further, as shown in FIG. 4, the sensor moving mechanism portion is a bent portion in which the sensor 204 can come into contact with a part of the inner surface of the pipe line, and is bent by the front end side swing member 212 and the rear end side swing member 214. It is configured to form a shape.

  The distal end side connecting portion 216 is provided on the rear end side of the distal end side support shaft 202 a and is connected to the distal end side swinging member 212. The rear end side connecting portion 218 is provided on the front end side of the rear end side support shaft 202 b and is connected to the rear end side swinging member 214.

  The distal-side oscillating member 212 is formed of an elastic member such as a spring, and has one end coupled to the sensor 204 and the other end coupled to the distal-side support shaft 202a via the distal-side coupling part 216. The sensor 204 is connected to the heat transfer tube. 10 has a function of elastically rocking in the length direction and the radial direction. The rear end side swinging member 214 is formed of an elastic member such as a spring, one end is connected to the sensor 204, and the other end is connected to the rear end side support shaft 202 b via the rear end side connecting portion 218. Has a function of elastically rocking the heat transfer tube 10 in the length direction and the radial direction.

  By configuring the sensor moving mechanism of this embodiment as described above, when the sensor 204 is swung in the front end direction, the front end side swing member 212 is contracted and the rear end side swing member 214 is extended. Let Further, when the sensor 204 is swung in the rear end direction, the front end swing member 212 is extended and the rear end swing member 214 is contracted. Further, when the sensor 204 is swung in a direction approaching the support shafts 202a and 202b, the front end-side swing member 212 and the rear end-side swing member 214 are contracted, and the sensor 204 is moved away from the support shafts 202a and 202b. When swinging the front end side swinging member 212, the front end side swinging member 212 and the rear end side swinging member 214 are extended.

  Thus, in this embodiment, when the sensor 204 abuts a part of the inner surface of the pipe, the diameter of the sensor 204 can be reduced while swinging in the pipe length direction and the pipe radial direction. . For this reason, the sensor 204 can follow changes in the inner diameter of the heat transfer tube 10 due to the bending bend portion 12 and the welding back wave 14. That is, the inner surface of the pipeline can be inspected by an eddy current flaw detection method while flexibly following the shape of the pipeline and the inner surface of the pipeline while maintaining the lift-off between the sensor 204 and the inner surface of the pipeline in a small state.

  Although the first and second embodiments of the present invention have been described in detail as described above, it will be apparent to those skilled in the art that many modifications that do not substantially depart from the novel matters and effects of the present invention are possible. Will be easily understood. Therefore, all such modifications are included in the scope of the present invention.

  For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term anywhere in the specification or the drawings. Further, the configuration and operation of the eddy current flaw detector are not limited to those described in the first and second embodiments of the present invention, and various modifications can be made.

10 Heat transfer tube (pipe)
12 Bend Bend 14 Weld Back Wave 100, 200 Eddy Current Flaw Detection Device 102, 202a, 202b Support Shaft 104, 204 Sensor 106, 206 Tip Guide 108, 208 Alignment Jig 110, 210 Array Coil 112 Elastic Member (Sensor Moving Mechanism) Part)
114 Clearance 212 Front end side swinging member 214 Rear end side swinging member 216 Front end side connecting portion 218 Rear end side connecting portion

Claims (5)

It is an eddy current flaw detector that is inserted into a conductive pipe line, generates an eddy current by applying an induced current from a sensor to the inner surface of the pipe line, and detects a defect on the inner surface of the pipe line by a change in the eddy current. And
A support shaft that supports the sensor so as to face the inner surface of the pipe line;
A sensor moving mechanism for reducing the diameter of the sensor in the radial direction of the cross section of the pipe line toward the support shaft when the sensor comes into contact with a part of the inner surface of the pipe line. Eddy current flaw detector.   The eddy current flaw detector according to claim 1, wherein the sensor moving mechanism unit is an elastic member that elastically reduces the diameter of the sensor in the radial direction with respect to the support shaft. The support shaft is separated into a front end side support shaft and a rear end side support shaft,
The sensor moving mechanism unit is
A distal end side connecting portion provided on a rear end side of the distal end side support shaft;
A rear end side connecting portion provided on a front end side of the rear end side support shaft;
One end is connected to the sensor, the other end is connected to the tip-side connecting portion, and a tip-side swinging member that enables the sensor to swing in the length direction and the radial direction of the conduit;
One end connected to the sensor, the other end connected to the rear end side connecting portion, and a rear end side swinging member that enables the sensor to swing in the length direction and the radial direction,
The eddy current flaw detector according to claim 1, wherein the sensor is a bent portion capable of contacting a part of the inner surface of the pipe line.   The eddy current flaw detector according to claim 2 or 3, wherein a plurality of the sensors are provided in a circumferential direction of the support shaft. The eddy current short device according to claim 1, wherein the sensor is configured by arranging a plurality of array coils in a circumferential direction of the support shaft.

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