JP2008151588A - Flaw evaluation method of two-layered bellows and eddy current flaw detector used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw evaluation method of bellows capable of rapidly and simply evaluating the flaw such as corrosion or damage of the bellows even in the bellows having a two layered structure, and an eddy current flaw detector used therein. <P>SOLUTION: The flaw of the two-layered bellows 100 obtained by molding two metal thin plates is evaluated. A sensor 20 is scanned along the protruded surface 104a on the first layer side being the outside of the thin plate to perform eddy current flaw detection while a transmission and reception element is scanned along the protruded surface 104a on the side of the first layer to perform ultrasonic flaw detection. The flaw is evaluated on the basis of the receiving signals of eddy current flaw detection and ultrasonic flaw detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defect evaluation method for a double-layer bellows and an eddy current flaw detection apparatus used therefor. More specifically, the present invention relates to a double-layer bellows defect evaluation method for evaluating defects such as corrosion and scratches on a bellows formed by forming a two-layer metal thin plate, and an eddy current flaw detection apparatus used therefor.

  Conventionally, eddy current testing, ultrasonic testing, and the like are known as methods for nondestructive testing of defects such as corrosion and scratches on bellows. However, in eddy current testing, it has been difficult to quantitatively evaluate defects such as corrosion and scratches. In ultrasonic flaw detection, in a two-layer bellows, ultrasonic waves are reflected by the boundary surface between layers, and therefore a defect in an inner layer from the flaw detection surface cannot be detected. For this reason, the bellows are periodically opened, and visual inspection from the inner surface and a penetration flaw detection test have been applied.

  Moreover, as a defect evaluation method for bellows, for example, the one described in Patent Document 1 is known. The ultrasonic flaw detection method described in this document inserts a probe into a concave portion inside the bellows member and transmits ultrasonic waves to the concave portion. However, since the flaw detection is from the inside of the bellows member, the bellows member has to be removed, and the inspection work is complicated. In addition, since the ultrasonic flaw detection is used, the above-described problem is not solved, and only the defects existing on the surface side on the flaw detection side can be detected.

On the other hand, as a method for detecting defects by using both ultrasonic flaw detection and eddy current flaw detection, for example, a defect detection method as described in Patent Document 2 is known. However, this defect detection method is not described in detail for the case where a cast part is an inspection object and the object has a multilayer structure, and no specific solution is disclosed regarding the defect evaluation in the bellows of the two-layer structure. It has not been.
JP 2000-266735 A JP 2006-133031 A

  In view of such a conventional situation, the present invention uses a bellows defect evaluation method and a bellows defect evaluation method capable of quickly and easily evaluating defects such as corrosion and scratches on the bellows even if the bellows has a two-layer structure. An object is to provide an eddy current flaw detection apparatus.

  As a result of the inventors' research, it has been found that the stress accompanying expansion and contraction of the bellows is likely to be concentrated on the convex portion of the bellows, thereby causing defects in the convex portion of the bellows. Further, it has been found that when the bellows is horizontally disposed, a part of the fluid flowing inside tends to stay in the lower convex portion, and thereby the inner surface side of the convex portion is easily corroded.

  In view of this point, in order to achieve the above object, the feature of the defect evaluation method for a two-layer bellows according to the present invention is to evaluate the defect of a two-layer bellows for evaluating a defect of a bellows formed by forming a two-layer metal sheet. And a sensor is scanned along the surface of the convex portion on the first layer side which is the outer side of the thin plate to perform eddy current flaw detection, and a transceiver is arranged along the surface of the convex portion on the first layer side. The ultrasonic inspection is performed by scanning, and the defect is evaluated based on the eddy current inspection and the reception signals of the ultrasonic inspection.

  With this configuration, it is possible to efficiently evaluate the defects of the bellows by performing flaw detection along the convex surface where defects are likely to occur. Moreover, since the 1st layer side which contact | connects the exterior is scanned, defect evaluation can be performed simply in the state operated without removing the bellows. Furthermore, since the defect is evaluated based on the reception signals of both the eddy current flaw detection and the ultrasonic flaw detection, even if the bellows has a two-layer structure, the defect can be reliably evaluated.

  The presence or absence of a defect in the second layer may be evaluated by comparing the defect inspection result by the eddy current flaw detection and the defect inspection result by the ultrasonic flaw detection. The sensor may include at least a pair of wheels along the scanning direction, and a peripheral portion of the wheels may have a recess having a recessed central portion in the width direction. In such a case, it is desirable that the sensor can adjust the relative height with the wheel.

  The transceiver may be scanned in the vicinity of the defect position specified by the eddy current flaw detection. The thin plate may be made of stainless steel.

  In order to achieve the above object, the eddy current flaw detection apparatus according to the present invention is characterized in that in the eddy current flaw detection apparatus used for the defect evaluation method for a two-layer bellows described above, the probe is in the scanning direction with the main body. Along with this, at least a pair of wheels and a coil are provided, and an outer peripheral portion of the wheel has a concave portion in which a central portion in the width direction is recessed, and the relative height of the coil with respect to the wheel is adjustable.

  According to the two-layer bellows defect evaluation method according to the present invention and the features of the eddy current flaw detection apparatus used therefor, even with a two-layer bellows, defects such as corrosion and scratches on the bellows can be reliably and quickly confirmed. It became possible to evaluate.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

Next, the present invention will be described in more detail with reference to the accompanying drawings as appropriate.
The present invention is for detecting defects such as cracks and corrosion occurring in the bellows 100 used for piping and the like. In the present embodiment, the inspection apparatus 1 including both the eddy current flaw detection apparatus 2 shown in FIG. 1 and the ultrasonic flaw detection apparatus 3 shown in FIG. 5 is used, and the eddy current flaw detection test and the ultrasonic flaw detection test are used in combination. I do.

  As shown in FIGS. 2, 5, and 6, the bellows 100 to be inspected is a two-layer thin plate formed of a stainless steel material and is formed into a cylindrical or spiral shape. It is formed as a bellows. The first layer 101 refers to an outer layer in contact with the outside O of the bellows 100, and the second layer 102 refers to an inner layer in contact with a fluid flowing inside the bellows 100. In these flaw detection tests, scanning is performed along the crest surface 104a on the first layer 101 side exposed to the outside O.

  An eddy current flaw detection test performed using the eddy current flaw detector 2 will be described. In the eddy current flaw detection test, first, the sensor 20 incorporating the coil 21 is brought close to the bellows 100 to be inspected, and the coil 21 is excited to generate an eddy current inside the bellows 100. And the impedance change of the coil 21 accompanying the change of the magnetic flux produced | generated by an eddy current is measured, and damages, such as a crack and corrosion, are detected.

  As shown in FIG. 7, the eddy current flaw detector 2 generally includes a probe 10 that supports the sensor 20, an oscillator 22, a bridge 23, a phase shifter 24, an automatic balancer 25, an amplifier 26, a synchronous detector 27, and a display 29. Is provided. The coil 21 includes first and second coils 21a and 21b that are similarly configured, and the bridge 23 is a bridge circuit that includes the pair of coils 21a and 21b and a variable resistor (not shown).

  The AC output from the oscillator 22 is applied to the coil 21 to excite the bellows 100 and detect the magnetic flux accompanying the eddy current. The automatic balancer 25 makes the output of the bridge 23 at the healthy part zero. The unbalanced output between the first and second coils 21a and 21b is amplified by the amplifier 26, sent to the synchronous detector 27, and detected together with the output of the phase shifter 24. Then, the waveform of the received signal is taken into the personal computer 28, and the waveform as shown in FIG.

  In the eddy current flaw detection, as shown in FIG. 5, a defect D1 that exists across the first layer 101 and the second layer 102 is possible, and is present only in the second layer 102 in the sensor indicated by reference numeral 20 ′. It is also possible to detect the defect D2. Therefore, the entire defect in the peak portion 104 of the bellows is detected by eddy current flaw detection.

  Next, the ultrasonic flaw detector 3 will be described. This apparatus mainly tests a portion where a defect signal is detected by the above-described eddy current flaw detection test.

  As shown in FIG. 7, the ultrasonic flaw detector 3 includes a transmitter / receiver 30 including a pair of transmitters 30a and 30b that scan the surface 101a of the first layer 101, and a pulsar 31 for exciting the transmitter 30a. And a receiver 32 for processing the waveform received by the receiver 30b. Further, a wire encoder 33 is attached to the transceiver 30, and the movement position of the transceiver 30 is recorded. The output of the receiver 32 is processed by the personal computer 34 together with the positional information recorded by the encoder 33, and the result is displayed on the display 35 as a B scope image as shown in FIG.

  In ultrasonic flaw detection, as shown in FIG. 6, the defect D1 existing across the first layer 101 and the second layer 102 is detected by a reflection signal from the defect D1, and the depth of the defect D1 is measured. Is possible. However, the defect D2 existing only in the second layer 102 is detected by the ultrasonic wave reflected by the boundary surface 103 between the first layer 101 and the second layer 102 in the transmitter / receiver indicated by reference numeral 30 ′. I can't.

  Therefore, by inspecting in combination with eddy current flaw detection and ultrasonic flaw detection, a defect in the peak portion 104 is detected by eddy current flaw detection, and the depth of the defect D1 existing across the first layer 101 and the second layer 102 is exceeded. It can be measured by acoustic flaw detection. Moreover, although the defect was detected by the eddy current flaw detection, it can be understood that the portion where the defect cannot be detected by the ultrasonic flaw detection is a portion where the defect D2 exists, and at least the soundness of the first layer 101 can be evaluated. .

Next, the probe 10 of the eddy current flaw detector 2 will be described with reference to FIGS.
The probe 10 generally includes a main body 11 formed of resin or the like, and a pair of wheels 12 and an adjustment mechanism 15 that adjusts the lift-off distance of the sensor 20. The coil 21 of the sensor 20 includes a pair of first and second coils 21 a and 21 b in the probe traveling direction Y, and generates an eddy current in the bellows 100. As shown in FIG. 4, the coil 21 is entirely formed in a rod shape, and the first and second coils 21 a and 21 b are wound around a core material 21 c supported on the housing 20 a of the sensor 20.

  The pair of wheels 12 is provided with the sensor 20 interposed therebetween in the traveling direction Y of the probe 10. V-grooves 12 a serving as recesses are formed in the circumferential direction of the wheel 12, and both end portions thereof become contact portions 12 b that come into contact with the peak surface 104 a of the bellows 100. Therefore, since the probe 10 is supported by the contact portions 12b of the pair of front and rear wheels 12, 12, the lateral displacement of the probe is prevented, and scanning can be performed stably. In addition, as shown in FIG. 3, even if the curvature of the ridge surface changes as shown by reference numeral 104 ', a pair of contact portions are formed by the recess, so that even if the curvature changes, the lateral displacement of the probe is prevented. it can.

  The adjustment mechanism 15 is generally composed of a fixing plate 16 to which the sensor 20 is attached, a screw 17 and a nut 18 that are screwed into the main body portion 11a. The screw 17 is connected to the fixing plate 16, and the screw 17 can adjust the relative height between the sensor 20 and the wheel 12, that is, the lift-off distance H between the sensor 20 and the mountain surface 104a. As shown in FIG. 3, the adjustment mechanism 15 can inspect with a constant lift-off distance H even if the curvature of the ridge surface changes as indicated by reference numeral 104 ′ due to the difference in the scanning position of the ridge 104. . Further, the probe 10 can be applied to bellows having different curvatures.

Next, the flaw detection test procedure for the bellows 100 will be described.
First, an eddy current flaw detection test is performed using the eddy current flaw detector 2. The sensor 20 is attached to the probe 10, and the adjustment mechanism 15 adjusts the lift-off distance between the sensor 20 and the first layer surface 101a of the peak portion 104. Then, scanning is performed by moving the probe 10 in the longitudinal direction Y of the peak 104 (the pipe circumferential direction of the bellows 100) along the peak surface 104a of the bellows 100.

  Then, while checking the waveform of the reception signal displayed on the display device 29, the inspector marks the defect signal portion on the bellows 100. Next, scanning is performed along the crest surface 104a in parallel with the scanning direction at intervals in the direction X orthogonal to the previous scanning direction Y, and the defect signal portion is marked. This procedure is repeated to perform surface flaw detection on the crest 104.

  Next, an ultrasonic flaw detection test is performed on the mountain portion 104 using the ultrasonic flaw detector 3. First, the transmitter 30 a and the receiver 30 b are arranged on the mountain portion 104. Next, an ultrasonic wave is transmitted from the transmitter 30a toward the mountain surface 104a, and a reflected wave to be reflected is received by the receiver 30b. The same path as the previous scan is scanned while performing this transmission / reception. Then, the B scope image is displayed based on the received signal received and the position information acquired by the encoder 33.

  If a defect is detected by ultrasonic flaw detection at the above-mentioned marking, it is when both the first and second layers 101 and 102 are eroded, and the defect depth can be measured. is there. On the other hand, if no defect is detected by ultrasonic flaw detection at the marking location, it is determined that the defect D2 exists in the second layer 102, and there is no defect in the first layer 101. At least the first layer 101 is healthy. It is evaluated that it is.

Finally, reference is made to the possibilities of other embodiments of the invention.
In the embodiment, the sensor 20 is a self-inductive self-comparison coil. However, the coil mode is not limited to the self-induction self-comparison method, and various types of coils may be applied.

  In the embodiment described above, the lift-off distance of the sensor 20 is adjusted by the screw 17, but not only the screw but also various adjustment means can be applied. Moreover, although the recessed part formed in the wheel was V-shaped, if it is a shape in which a pair of contact part is formed, circular arc shape may be sufficient and it can change according to a use.

  In the above embodiment, the inspector marks the result of the eddy current flaw detection. However, defect position information may be recorded in eddy current flaw detection, and ultrasonic flaw detection may be performed based on the defect position information. In the above embodiment, the ultrasonic flaw detection result is displayed as a B scope image. However, it is also possible to display a C scope image using a biaxial scanner.

  The present invention can be used as a defect evaluation method for a two-layer bellows and a defect evaluation apparatus used therefor. Note that the present invention is not limited to the two-layer structure, and can be applied to a single-layer bellows.

It is a side view which shows the relationship between a bellows and an eddy current flaw detector. It is the figure which represented the structure of the bellows typically. It is a front view of a probe. It is sectional drawing of a coil. It is a schematic diagram explaining the defect detection in an eddy current test. It is a schematic diagram explaining the defect detection in an ultrasonic flaw detection test. It is a block diagram of an inspection device. It is a graph which shows the example of a waveform of the scanning result example of eddy current flaw detection. It is a B scope image of the scanning result example of ultrasonic flaw detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Defect detection apparatus, 2: Eddy current flaw detection apparatus, 3: Ultrasonic flaw detection apparatus, 10: Probe, 11: Main part, 12: Wheel, 12a: V groove (recessed part), 12b: Contact part, 13: Shaft, 15 : Adjustment mechanism, 16: fixing plate, 17: screw, 18: nut, 20: sensor, 21a: first coil, 21b: second coil, 21c: core material, 22: oscillator, 23: bridge, 24: phase shift 25: Automatic balancer, 26: Amplifier, 27: Synchronous detector, 28: Personal computer, 29: Display, 30: Transceiver, 30a: Transmitter, 30b: Receiver, 31: Pulser, 32: Receiver 33: wire encoder, 34: PC, 35: display, 100: bellows, 100a: fold, 101: first layer, 102: second layer, 103: boundary surface, 104: mountain, D1, 2: defect , I: Inside O: External

Claims (7)

A double-layer bellows defect evaluation method for evaluating defects such as corrosion and scratches on a bellows formed by forming a two-layer metal sheet,
An ultrasonic flaw detection is performed by scanning the sensor along the convex surface on the first layer, which is the outer side of the thin plate, and scanning the transceiver along the convex surface on the first layer side. A defect evaluation method for a two-layer bellows, characterized in that the defect is evaluated based on reception signals of the eddy current flaw detection and the ultrasonic flaw detection. The defect evaluation method for a two-layer bellows according to claim 1, wherein the presence or absence of a defect in the second layer is evaluated by comparing a defect inspection result by the eddy current flaw detection and a defect inspection result by the ultrasonic flaw detection. 3. The double-layer bellows according to claim 1, wherein the sensor has at least a pair of wheels along a scanning direction, and an outer peripheral portion of the wheels has a concave portion in which a central portion in the width direction is recessed. Defect evaluation method. The defect evaluation method for a double-layer bellows according to claim 3, wherein the sensor is capable of adjusting a height relative to the wheel. The defect evaluation method for a double-layer bellows according to claim 1, wherein the transceiver is scanned in the vicinity of a defect position specified by the eddy current flaw detection. The said thin plate consists of stainless steel, The defect evaluation method of the double layer bellows in any one of Claims 1-5 characterized by the above-mentioned. An eddy current flaw detector used in the defect evaluation method for a double-layer bellows according to any one of claims 1 to 6,
The probe includes at least a pair of wheels and a coil along the scanning direction with the main body, and the outer peripheral portion of the wheel has a concave portion whose central portion in the width direction is recessed, and the coil has a relative height adjusted with the wheel. Eddy current flaw detector characterized in that it is possible.