JP5907750B2 - Inspection position detection method, inspection range confirmation method, inspection method and inspection apparatus - Google Patents

Description

  The present invention relates to an inspection position detection method, an inspection range confirmation method, an inspection method, and an inspection apparatus. In particular, when an eddy current flaw inspection is performed on an inspection target tube having a bent tube portion, the axial position of the measurement signal and the axial position of the inspection target tube are accurately associated with each other. .

Steam generators are used in pressurized water nuclear power plants. As shown in FIG. 8, a large number of inverted U-shaped heat transfer tubes 1 are arranged inside the steam generator. Although simply shown in FIG. 8, the number of the heat transfer tubes 1 is extremely large (for example, thousands), and these heat transfer tubes 1 are arranged in a state of extending in the vertical direction, and each of the heat transfer tubes 1 is arranged. The upper end is curved in an inverted U shape.
The lower ends of each heat transfer tube 1 are inserted into a large number of holes formed in the tube plate 2, and a high temperature side water chamber (not shown) and a low temperature side water chamber respectively formed below the tube plate 2. (Not shown).

  Pipe support plates 3 extending in the horizontal direction are arranged at a plurality of locations along the height direction. A large number of heat transfer tubes 1 are disposed through holes formed in the tube support plate 3.

Whether or not defects (thinning, cracks, etc.) have occurred in the heat transfer tube 1 in the production inspection performed when the steam generator is manufactured and in the periodic inspection periodically performed after the start of actual operation Inspection is performed.
Further, in the inspection performed when the heat transfer tube 1 is manufactured, as shown in FIG. 9, the single heat transfer tube 1 to which no tube support plate is attached is inspected for defects. Is called.
The heat transfer tube 1 is composed of straight tube portions 1α and 1α from the open end to the bent ends B1 and B2, and a bent tube portion 1β between the bent ends B1 and B2.

  The defect inspection of the heat transfer tube 1 is performed by eddy current testing (ECT). That is, scanning is performed in which the eddy current flaw detection probe is inserted into the heat transfer tube 1 and moved inside the heat transfer tube 1. As described above, when the eddy current flaw detection probe is scanned in the heat transfer tube 1, the defect is detected by analyzing the measurement signal obtained by the eddy current flaw detection probe.

Examples of eddy current flaw detection probes include those shown in FIGS.
The bobbin coil type eddy current flaw detection probe shown in FIG. 10 includes a sensor C having a shape surrounding the outer periphery of the probe. In the case of a bobbin coil type eddy current flaw detection probe, a measurement signal having a distribution in the circumferential direction cannot be obtained.

The multi-sensor type eddy current flaw detection probe shown in FIG. 11 includes a plurality of sensors C arranged in the circumferential direction. Some sensors are arranged in one row, and others are arranged in a plurality of rows in order to make the circumferential arrangement interval denser than the sensor diameter. FIG. 11 shows an example in which two rows are arranged.
In such a multi-sensor type eddy current flaw detection probe, for example, when twelve sensors C1 to C12 are arranged side by side in the circumferential direction, measurement signals S1 to S12 are output individually by the sensors C1 to C12. Is done.

In the rotary eddy current flaw detection probe shown in FIG. 12, the probe including one or a plurality of sensors C advances in the axial direction while rotating around the axis, so that the sensor C spirals inside the heat transfer tube 1. Move.
In such a rotating eddy current flaw detection probe, one sensor C moves spirally inside the heat transfer tube 1. Therefore, if, for example, twelve measurement positions (measurement positions in the circumferential direction) R1 to R12 are defined at regular intervals (equal intervals) along the circumferential direction of the probe, the measurement signal S output from the sensor C is linear. By performing interpolation calculation, measurement signals S1 to S12 at each position in the axial direction can be obtained and output for each measurement position R1 to R12.

Utility Model Registration No. 3096505

Using the eddy current flaw detection probe as shown in FIGS. 11 and 12 described above, the heat transfer tube 1 assembled as a steam generator as shown in FIG. 8 or a single heat transfer tube 1 as shown in FIG. Defect inspection can be done.
That is, when the measurement signal S obtained by the eddy current flaw inspection is analyzed, a signal change indicating a defect (for example, the signal value locally changes in the measurement signal S, and its waveform feature is the waveform of the defect. When there is a waveform that matches the feature, it can be determined that there is a defect.
In such an inspection, it is necessary to inspect the entire range to be inspected.

  In the eddy current flaw detection inspection, the eddy current flaw detection probe is scanned so as to move in the heat transfer tube 1 at a constant speed, and the measurement signal is a signal waveform output over time. For this reason, when the eddy current flaw detection probe moves in the heat transfer tube 1 from the axial position as a reference at a constant speed, the start point of the measurement signal corresponds to the reference position of the heat transfer tube 1 and the inspection is performed. The target range can be specified and the measurement data of the necessary range can be recorded.

However, for some reason, the moving speed of the eddy current flaw detection probe moving inside the heat transfer tube 1 may change or the movement may temporarily stop. In such a case, since the measurement signal is a signal waveform output along with the passage of time, the axial position of the measurement signal calculated assuming constant speed scanning does not coincide with the actual axial position of the sensor.
In particular, in the heat transfer tube 1 in which the curvature radius of the bending tube portion 1β is small, since the change in the scanning speed of the eddy current flaw detection probe is large in the bending tube portion 1β, the possibility of such a situation increases.

Therefore, in order to accurately detect the position of the defect in the axial direction of the heat transfer tube, Japanese Utility Model Registration No. 3096505 in Patent Document 1 discloses a screw-type feed as a mechanism for feeding the flaw detection sensor in the axial direction. By adopting a mechanism and associating the rotation amount of the screw type feed mechanism with the feed amount of the flaw detection sensor, the position of the flaw detection sensor in the heat transfer tube 1 is grasped.
However, there is a problem that the configuration of the apparatus becomes complicated because a screw type feeding mechanism is used.

In the case of the heat transfer tube 1 to which the tube support plate 3 is attached as shown in FIG. 8, the measurement signal S includes a signal change X indicating the tube support plate 3 as shown in FIG. By recording measurement data so that the signal change indicating the tube support plate located on the outermost side of the inspection target range is recorded, it is possible to ensure the inspection range, and at the time of signal analysis, the outermost side on both sides It is possible to confirm that the signal satisfies the inspection range by checking the signal of the tube support plate located at the position.
However, since the single heat transfer tube 1 as shown in FIG. 9 does not have a structure like the tube support plate 3, the recorded measurement data is inspected based on the position of the structure (tube support plate 3). Cannot determine whether the entire range is included.

  In particular, in the heat transfer tube 1 having a small radius of curvature of the bent tube portion 1β, there is a case where only the bent tube portion 1β is inspected, but as described above, at which position in the axial direction of the heat transfer tube 1 the eddy current flaw detection probe is located. Since it may be in a state where it cannot be accurately grasped, it may not be possible to confirm whether or not the entire bent pipe portion 1β has been inspected.

  In view of the prior art, the present invention detects the position of the bent end of the heat transfer tube based on the measurement signal, and based on the detected position of the bent end, the position of the measurement signal in the axial direction of the heat transfer tube. An object of the present invention is to provide an inspection position detection method, an inspection range confirmation method, an inspection method, and an inspection apparatus for detecting whether or not an object exists.

The detection method of the inspection position of the present invention that solves the above problems is as follows .
An eddy current flaw detection probe that has a probe body and a sensor provided on the peripheral surface of the probe body, and outputs a measurement signal for each measurement position defined at a plurality of locations along the circumferential direction of the probe body,
In the inspection to be inserted into the inspection object pipe consisting of the straight pipe part and the bending pipe part, and to scan the inside of the inspection object pipe,
From the measurement signal, the absolute value signal of the difference between the measurement signals for each pair of measurement positions facing each other in the radial direction is obtained, and the average signal obtained by taking the average in the circumferential direction of the absolute value signal of the difference is a representative signal.
Specify the start position or end position of the signal change that occurs in the representative signal ,
By associating the start position or the end position of the signal change with the position of the bending end of the inspection target tube , the position of the measurement signal and the axial position of the inspection target tube are associated with each other.
In addition, the inspection position detection method of the present invention includes :
An eddy current flaw detection probe that has a probe body and a sensor provided on the peripheral surface of the probe body, and outputs a measurement signal for each measurement position defined at a plurality of locations along the circumferential direction of the probe body,
In the inspection to be inserted into the inspection object pipe consisting of the straight pipe part and the bending pipe part, and to scan the inside of the inspection object pipe,
The average value in the time axis direction is determined for each measurement signal, and the measurement signal having the maximum absolute value of the average value is used as a representative signal.
Specify the start position or end position of the signal change that occurs in the representative signal ,
By associating the start position or the end position of the signal change with the position of the bending end of the inspection target tube , the position of the measurement signal and the axial position of the inspection target tube are associated with each other.

The configuration of the inspection position detection method of the present invention is as follows.
The representative signal is
For each measurement signal, filter processing that removes high-frequency components indicating significant signal factors and noise is applied as preprocessing,
And calculating said representative signal for each measuring signal the filter.

The configuration of the inspection position detection method of the present invention is as follows.
A method for specifying a start position or an end position of a signal change that occurs in the representative signal when passing through the bent pipe portion is as follows:
Among the representative signal, the start and end positions of the section value of the representative signal exceeds a predetermined value, or, a candidate position of the maximum value of the interval axial difference absolute value signal of the representative signal exceeds a predetermined value A position change is selected, and a combination of two candidate positions that is most suitable for the positions of both ends of the bending pipe portion is selected from among the candidate positions, and a signal change that occurs in the representative signal that occurs when passing through the bending pipe portion is selected. A start position and an end position are determined.

The configuration of the inspection range confirmation method of the present invention is as follows.
If the start position or end position of the signal change that should be included in the inspection range is not obtained by the inspection position detection method, it is determined that the inspection range is insufficient.
Alternatively, it is characterized in that whether or not the designated inspection range is inspected without a lack based on the start position or the end position of the signal change detected by the inspection position detection method.

The configuration of the inspection method of the present invention is as follows.
The inspection target tube is inspected by using the inspection position detection method.

The configuration of the inspection apparatus of the present invention is as follows:
A probe body and a sensor provided on the circumferential surface of the probe body, each outputting a measurement signal at each measurement position defined at a plurality of locations along the circumferential direction of the probe body, and bending the straight pipe portion An eddy current flaw detection probe that is inserted into an inspection target tube composed of a tube portion and scans within the inspection target tube;
A representative for calculating an absolute value signal of a difference between measurement signals for a pair of measurement positions opposed in the radial direction from the measurement signal, and calculating an average signal obtained by taking an average of the absolute values of the differences in the circumferential direction as a representative signal Signal calculation means;
And the start position and end position specifying means for specifying a start position or the end position of the signal change generated in the representative signal when passing through the bent tube portion,
The start or end point of the signal change, the location association means associating the axial position of the pipe to be inspected and position of the measurement signal by associating with the position of the bending end of the pipe to be examined,
It is characterized by having.
The configuration of the inspection apparatus of the present invention is as follows.
A probe body and a sensor provided on the circumferential surface of the probe body, each outputting a measurement signal at each measurement position defined at a plurality of locations along the circumferential direction of the probe body, and bending the straight pipe portion An eddy current flaw detection probe that is inserted into an inspection target tube composed of a tube portion and scans within the inspection target tube;
A representative signal calculating means for calculating an average value in the time axis direction for each measurement signal and calculating a measurement signal having the maximum absolute value of the average value as a representative signal;
And the start position and end position specifying means for specifying a start position or the end position of the signal change generated in the representative signal when passing through the bent tube portion,
The start or end point of the signal change, the location association means associating the axial position of the pipe to be inspected and position of the measurement signal by associating with the position of the bending end of the pipe to be examined,
It is characterized by having.

The configuration of the inspection apparatus of the present invention is as follows:
The representative signal calculation means includes:
For each measurement signal, filter processing that removes high-frequency components indicating significant signal factors and noise is applied as preprocessing,
A representative signal is calculated for each measurement signal subjected to the filtering process.

The configuration of the inspection apparatus of the present invention is as follows:
The start position / end position specifying means includes:
Among the representative signal, the start and end positions of the section value of the representative signal exceeds a predetermined value, or, a candidate position of the maximum value of the interval axial difference absolute value signal of the representative signal exceeds a predetermined value A position change is selected, and a combination of two candidate positions that is most suitable for the positions of both ends of the bending pipe portion is selected from among the candidate positions, and a signal change that occurs in the representative signal that occurs when passing through the bending pipe portion is selected. A start position and an end position are determined.

  According to the present invention, even when the heat transfer tube is subjected to eddy current flaw inspection in the absence of a structure that is marked in the direction along the axial direction of the heat transfer tube, a special probe or complicated equipment is not used. The position of the measurement signal and the axial position of the heat transfer tube can be associated with each other with high accuracy.

The side view which shows a multi sensor type eddy current test probe. The end view which omits a stabilizer and shows a multi-sensor type eddy current flaw detection probe. The block diagram which shows a multi sensor type eddy current flaw detection probe and a measurement signal analyzer. The block diagram which shows the multi sensor type eddy current flaw detection probe which scans the inside of a heat exchanger tube. The display figure which displayed the measurement signal in the multi chart. 10 is a flowchart showing an operation state of the second embodiment. FIG. 6 is a waveform diagram illustrating a signal processing calculation state according to the second embodiment. The block diagram which shows the assembled heat exchanger tube. The block diagram which shows a single heat exchanger tube. The block diagram which shows a bobbin coil type eddy current test probe. The block diagram which shows a multi sensor type eddy current test probe. The block diagram which shows a rotation type eddy current flaw detection probe. The wave form diagram which shows the measurement signal containing the signal change which shows a tube support plate.

  Hereinafter, embodiments of the present invention will be described in detail based on examples.

  A multi-sensor type eddy current flaw detection probe 10 used in Embodiment 1 of the present invention will be described first with reference to FIG. 1 which is a side view and FIG. 2 which is an end view showing a stabilizer omitted.

In this multi-sensor type eddy current flaw detection probe 10, for example, twelve sensors C <b> 1 to C <b> 12 are provided on the circumferential surface of a cylindrical probe body 11. The sensors C1 to C12 are arranged at equal intervals along the circumferential direction.
In this example, for example, twelve measurement positions (measurement positions in the circumferential direction) R1 to R12 are defined at regular intervals (equal intervals) along the circumferential direction of the probe main body 11, and each measurement position R1 to R12 is individually specified. Sensors C1 to C12 are arranged. For this reason, the measurement signals S1 to S12 when the inspection is performed at each position in the axial direction for each of the measurement positions R1 to R12 are output by the sensors C1 to C12.

Stabilizers 12 and 12 are attached to both end faces of the probe body 11. The stabilizers 12, 12 have a central axis that coincides with the central axis of the probe main body 11, and the outer diameter thereof is larger (larger diameter) than the outer diameter of the probe main body 11.
The stabilizers 12 and 12 are made of a material having flexibility and elasticity in order to ensure the passage of the eddy current flaw detection probe 10 in the bending tube portion 1β, and are deformed when a large external force exceeding a predetermined value is applied. The diameter of the portion where the external force is applied is reduced, but when the external force is lost, the diameter returns to the original shape and the diameter returns to the original size.

Therefore, as shown in FIG. 1, when the eddy current flaw detection probe 10 is inserted into the straight heat transfer tube 1 (straight tube portion 1α), the central axis of the probe body 11 is the straight heat transfer tube 1 (straight tube). The distance between the sensors C1 to C12 and the inner peripheral surface of the heat transfer tube 1 (straight tube portion 1α) becomes equal.
In FIG. 1, reference numeral 13 denotes a signal line of the eddy current flaw detection probe 10.

As shown in FIG. 3, the sensors C <b> 1 to C <b> 12 of the eddy current flaw detection probe 10 are excited by the measurement device 25, and the detection signals are recorded in the recording device 26 as measurement signals S <b> 1 to S <b> 12 by the measurement device 25. The measurement signal analyzer 20 reads the measurement signals S1 to S12 from the recording device 26, and performs signal processing and display on the signal display device 21.
The display method is displayed in one of a color tone map, a bird's eye view, a multi chart, a multi Lissajous, and the like. In addition, each display method can be switched and displayed.

  When displaying the measurement signals S1 to S12 output from the multi-sensor type eddy current flaw detection probe 10, the eddy current flaw detection probe 10 is positioned in the straight pipe portion 1α of the heat transfer tube 1 and the sensors C1 to C12. The signal values are adjusted so that the signal values of the measurement signals S <b> 1 to S <b> 12 are aligned and displayed in a state where the distances between the heat transfer tube 1 and the inner peripheral surface of the heat transfer tube 1 are equal.

  Although the change direction of the measurement signals S1 to S12 varies depending on the sensor method, flaw detection conditions, calibration conditions, and the like, the signal change direction when the distance between the sensor and the inner peripheral surface of the heat transfer tube 1 is short, The change direction is opposite to the signal change direction when the distance from the inner peripheral surface of the heat tube 1 is long.

  For example, in the case where the signal change is represented by a signal amplitude, the change direction of the signal amplitude when the distance between the sensor and the inner peripheral surface of the heat transfer tube 1 is short (for example, changes in the positive direction), the sensor and the heat transfer tube The change direction of the signal amplitude is opposite to the change direction of the signal amplitude when the distance from the inner peripheral surface of 1 is long (for example, the change direction is negative).

  When the signal change is represented by a signal color, the signal color change direction when the distance between the sensor and the inner peripheral surface of the heat transfer tube 1 is short (for example, the color changes in the red direction), and the sensor and the heat transfer tube. The signal color change direction is opposite to the signal color change direction (for example, the blue color direction) when the distance from the inner peripheral surface of 1 is long.

When the heat transfer tube 1 is inspected by the eddy current flaw detection probe 10 described above, the eddy current probe 10 is inserted into the heat transfer tube 1 and moved in the heat transfer tube 1 for scanning.
The measurement signals S <b> 1 to S <b> 12 obtained when the eddy current flaw detection probe 10 is scanned in the heat transfer tube 1 in this way are displayed on the display unit 21 of the measurement signal analyzer 20.

  From this display content, the presence or absence of a defect can be inspected. For example, when the measurement signals S1 to S12 are displayed in a multi-chart, a signal change indicating a defect (for example, a waveform whose signal value rises locally) is observed in the measurement signal S4, and the waveform feature matches the waveform feature of the defect. When it does, it can detect that the inspected heat exchanger tube 1 has a defect.

  In the first embodiment, among the measurement signals S obtained when the eddy current flaw detection probe 10 is moved and scanned in the heat transfer tube 1, the sensors C1 to C12 move in the bent tube portion 1β of the heat transfer tube 1. In addition, the signal region obtained when the sensor is located, and the signal position when the sensors C1 to C12 are located at the bending ends B1 and B2 of the heat transfer tube 1 in the measurement signal S are specified.

Thus, if the signal position corresponding to the bending ends B1 and B2 of the heat transfer tube 1 is specified in the measurement signal S, the specified signal position is set as the reference signal position. And the position where the defect exists in the axial direction of the heat transfer tube 1 is detected from the positional relationship between the reference signal position and the signal position where the signal change indicating the defect occurs.
In addition, in the measurement signal S, two reference signal positions corresponding to the bending ends B1 and B2 of the heat transfer tube 1 can be detected, and eddy currents are applied to the entire range of the bending tube portion 1β to be inspected. Confirm that a flaw detection was performed.

  The detection method of Example 1 will be described below in order.

FIG. 4 shows a state in which the multi-sensor type eddy current flaw detection probe 10 is moving while being positioned in the straight tube portion 1α in the heat transfer tube 1 and a position in which it is positioned in the bending tube portion 1β in the heat transfer tube 1. It shows the state of being at the same time.
Here, the distance between the sensors C1 to C12 and the inner peripheral surface of the heat transfer tube 1 is referred to as “lift-off”.

  In a state where the sensors C1 to C12 are moving while being positioned on the straight pipe portion 1α in the heat transfer tube 1, the center axis of the eddy current flaw detection probe 10 (probe body 11) is the center of the heat transfer tube 1 due to the function of the stabilizer 12. The lift-off, which is the distance between each sensor C1 to C12 and the inner peripheral surface of the heat transfer tube 1, is located at a position that coincides with the axis, and is substantially the same.

  On the other hand, in a state where the sensors C1 to C12 are moving while being positioned on the bending tube portion 1β in the heat transfer tube 1, the heat transfer tube 1 is bent, so that the sensors C1 to C12 are positioned on the ventral side (the inner peripheral side of the bending tube portion). The lift-off L1 of the sensor is different from the lift-off L2 located on the back side (the outer peripheral side of the bending pipe portion). The magnitude relationship between the lift-off L1 and the lift-off L2 varies depending on the probe operation method. For example, in the method of pulling out the probe, the lift-off L1 is smaller than the lift-off L2, and in the method of pushing in the probe, the lift-off L1 is larger than the lift-off L2. However, in the case of a certain inspection method, which of lift-off L1 and lift-off L2 is larger is fixed.

FIG. 5 is output by the sensors C1 to C12 when the section including the bent tube portion 1β between the bent ends B1 and B2 of the heat transfer tube 1 is inspected using the multi-sensor type eddy current flaw detection probe 10. The measurement signals S <b> 1 to S <b> 12 are displayed on the display unit 21 of the measurement signal analyzer 20 in a multi-chart display.
Prior to such multi-chart display, the sensors C1 to C12 are positioned in the straight tube portion 1α of the heat transfer tube 1, and the distances between the sensors C1 to C12 and the inner peripheral surface of the heat transfer tube 1 are equal. In this state, the signal values are adjusted in advance so that the signal values of the measurement signals S1 to S12 are displayed together.
If the positions of all sensors in the probe axis direction are not the same, such as when the sensor arrangement of multi-sensor eddy current flaw detection probes is two or more, correct the time axis in advance so that each sensor has the same position. It is adjusted so that the signals when passing through are displayed at the same time axis position.

  The position in the axial direction (time axis direction) of the measurement signals S1 to S12 in FIG. 5 corresponds to the position along the axial direction of the heat transfer tube 1, and the position in the circumferential direction in FIG. It corresponds to. The horizontal axis for each frame indicates the measurement signal value. The eddy current flaw detection signal (measurement signal) is a complex value, but FIG. 5 shows only the real part or the imaginary part as a representative.

  In the example of FIG. 5, the measurement signal S8 output from the sensor C8 located at the measurement position R8 changes its signal amplitude to the right and has a large amplitude value. The change of the signal when passing through the bending pipe in this inspection method is confirmed in advance. For example, when it is confirmed that the measured value of the sensor passing through the ventral side changes to the right side, the inspector sees this. Thus, it can be detected that the sensor C8 is located on the ventral side (the inner peripheral side of the bending pipe portion).

Further, in the axial direction (time axis direction) of the measurement signals S1 to S12, the position (abdominal side or back) where the signal amplitude rises between the measurement signal S8 output from the sensor C8 and the measurement signal S2 output from the sensor C2. The signal position at which the signal change that has passed through the bent tube portion on the side starts) is defined as a reference signal position b1 corresponding to one bending end B1.
Further, in the axial direction (time axis direction) of the measurement signals S1 to S12, a position where the signal amplitude falls between the measurement signal S8 output from the sensor C8 and the measurement signal S2 output from the sensor C2 (on the ventral side or The signal position at which the signal change that has passed through the bending tube on the back side is completed is set as a reference signal position b2 corresponding to the other bending end B2.

  In this way, when the reference signal position b1 corresponding to one bending end B1 and the reference signal position b2 corresponding to the other bending end B2 are detected in the axial direction (time axis direction) of the measurement signals S1 to S12. When a waveform indicating a defect is found in the measurement signal S4 output from the sensor C4, the heat transfer tube is determined from the positional relationship between the reference signal positions b1 and b2 and the signal position where the waveform indicating the defect (signal change) occurs. It is possible to detect a position where a defect exists with respect to one axial direction.

  Moreover, in the measurement signals S1 to S12, it was possible to detect the two reference signal positions b1 and b2 corresponding to the bent ends B1 and B2 of the heat transfer tube 1, that is, among the measurement signals S1 to S12, Since the signal region (signal between the reference signal position b1 and the reference signal position b2) obtained when the bending tube portion 1β of the heat transfer tube 1 is scanned can be specified, the entire range of the bending tube portion 1β to be inspected It can be confirmed that the eddy current flaw inspection was conducted.

  As described above, in Example 1, as shown in FIG. 9, even when an eddy current flaw inspection is performed in a state where there is no structure that becomes a mark along the axial direction of the heat transfer tube 1, the eddy current flaw detection probe is used. When flaw detection is performed on the bent tube portion 1β, which is likely to change in speed, it is possible to specify the position of the defect in the axial direction of the heat transfer tube 1 without using a special probe or complicated equipment. it can.

In the first embodiment, an example using the multi-sensor type eddy current flaw detection probe 10 is shown, but a rotary type eddy current flaw detection probe can also be adopted. In other words, any type of eddy current flaw detection probe that can obtain measurement signals at a plurality of measurement positions along the circumferential direction of the eddy current flaw detection probe can be used even if the detection method is different.
In the case of a multi-sensor type eddy current testing probe, the number of sensors arranged in the circumferential direction may be arbitrarily increased or decreased.
Further, the heat transfer tube to be inspected may be not only a U-shaped heat transfer tube but also a square heat transfer tube.

  Moreover, in the said Example 1, although the case where the inspection range included the whole bending pipe part was shown, when only a straight pipe part is made into an inspection object, the signal which shows the bending end of the one side of a bending pipe part by the same method is shown. , And confirm that the entire straight pipe part to be inspected is inspected by checking that the pipe end signal and the signal indicating the bending end on one side of the bent pipe part are measured. You can also

In the first embodiment, the inspector looks at the measurement signal displayed on the display unit 21 of the measurement signal analyzer 20, and the reference signal positions b1 and b2 corresponding to the positions of the bent ends B1 and B2 of the heat transfer tube 1 are obtained. It was detected (specific).
On the other hand, in the second embodiment, the measurement signal analyzer 20 performs signal processing calculation to detect (specify) the reference signal positions b1 and b2 corresponding to the positions of the bent ends B1 and B2 of the heat transfer tube 1, Based on the relationship between the reference signal positions b1 and b2 and the signal position where the waveform (signal change) indicating the defect is generated, the position where the defect is in the axial direction of the heat transfer tube 1 is detected by automatic processing. .

  In the signal processing calculation in the measurement signal analysis device 20 in the second embodiment, software (program) incorporated in the measurement signal analysis device 20 is processed by hardware incorporated in the measurement signal analysis device 20. The detection result is obtained.

  The second embodiment is characterized by the method of signal processing operation in the measurement signal analyzing apparatus 20, and the equipment used is basically the same as that of the first embodiment, so that the same function as the first embodiment is exhibited. Parts are denoted by the same reference numerals, and redundant description is omitted.

In the second embodiment, the multi-sensor type eddy current flaw detection probe 10 shown in FIGS. 1 and 2 is used. The eddy current flaw detection probe 10 is inserted into the heat transfer tube 1 and moved in the heat transfer tube for scanning.
Measurement signals S1 to S12 obtained at the time of scanning are input to the measurement signal analyzer 20 (step 1 in FIG. 6).

  The measurement signal analyzer 20 detects whether or not a signal waveform indicating a defect exists in the measurement signals S1 to S12.

The measurement signals S1 to S12 are signals obtained while the eddy current flaw detection probe 10 scans the inside of the heat transfer tube 1, but depending on the measurement signal recording range, a signal passing through the tube end may be recorded. The tube end signal is usually a large signal and can be easily distinguished. In the following processing, signals in the axial range excluding the tube end signal are targeted.
When the speed change range assumed when passing through the bending tube portion 1β of the heat transfer tube 1 is known, even if the speed change occurs, the range is limited to the axial range of the signal that sufficiently includes the entire range of the bending tube portion. And may be processed.

Note that the multi-sensor type eddy current flaw detection probe 10 is positioned in the straight tube portion 1α of the heat transfer tube 1, and the distances between the sensors C1 to C12 and the inner peripheral surface of the heat transfer tube 1 are equal. The signal values are adjusted in advance so that the signal values of the measured signals S1 to S12 are aligned.
If the positions of all sensors in the probe axis direction are not the same, such as when the sensor arrangement of multi-sensor eddy current flaw detection probes is two or more, correct the time axis in advance so that each sensor has the same position. It is adjusted so that the signals when passing through are displayed at the same time axis position.
When a rotary eddy current flaw detection probe (see FIG. 12) is used instead of the multi-sensor eddy current flaw detection probe 10, adjustment of the signal value as described above is not necessary. Instead, the sensor signals obtained from one sensor are interpolated to obtain the measurement signals S1 to S12 at each position in the axial direction of the heat transfer tube 1 for each of the measurement positions R1 to R12. A general interpolation method such as linear interpolation can be applied to the interpolation.

  Hereinafter, measurement signals S1 to S12 obtained while the eddy current flaw detection probe 10 moves in the section including the bent tube portion 1β between the bent ends B1 and B2 of the heat transfer tube 1 are processed by the measurement signal analysis device 20. The calculation procedure will be described.

<Preprocessing: Step 2 in FIG. 6>
Measurement signals S <b> 1 to S <b> 12 (measurement signals shown in FIG. 7A) obtained while the eddy current flaw detection probe 10 passes through the heat transfer tube are set as subsequent signal processing targets.
If necessary, a filter that reduces high-frequency components is applied to the measurement signals S1 to S12 that are signal processing targets. Examples of this filter include a low-pass filter, an average value filter, and a median filter. By performing a filtering process that reduces high-frequency components, components that show scratches (defects) and noise that have a higher frequency than the signal caused by the passage through the bending tube are removed.
FIG. 7B shows measurement signals S <b> 1 to S <b> 12 whose high frequency components have been reduced by the filtering process.

<Calculation of representative signal: Step 3 in FIG. 6>
A representative signal S0 representatively indicating the signal change state of the preprocessed measurement signals S1 to S12 is obtained.

A first example for obtaining the representative signal S0 will be described.
In the first example, a signal indicating an absolute value of a difference between measurement signals is obtained for each pair of measurement positions facing each other in the radial direction among a plurality of measurement positions set in the circumferential direction.
Specifically, as shown in FIG.
In a pair of measurement positions R1 and R7 facing each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S1 and the measurement signal S7 is a signal S17,
In the pair of measurement positions R2 and R8 facing each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S2 and the measurement signal S8 is a signal S28,
In a pair of measurement positions R3 and R9 that face each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S3 and the measurement signal S9 is a signal S39,
In the pair of measurement positions R4 and R10 that are opposed to each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S4 and the measurement signal S10 is a signal S410,
In a pair of measurement positions R5 and R11 opposed to each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S5 and the measurement signal S11 is a signal S511,
In the pair of measurement positions R6 and R12 facing each other in the radial direction, a signal indicating the absolute value of the difference between the measurement signal S6 and the measurement signal S12 is referred to as a signal S612.

  Further, an average signal of the signals S17, S28, S39, S410, S511, and S612 is set as a representative signal S0 (see FIG. 7D).

A second example for obtaining the representative signal S0 will be described.
In the second example, among the preprocessed measurement signals S1 to S12, the signal having the largest absolute value of the average value in the time axis direction of each signal, for example, the measurement signal S9 is set as the representative signal S0.
In the case of the second example, generally, a measurement signal output from a sensor located on the ventral side (the inner peripheral side of the bent tube portion 1β) of the bent tube portion 1β of the heat transfer tube 1, or One of the measurement signals output from the sensor located on the back side (the outer peripheral side of the bent tube portion 1β) of the bent tube portion 1β of the heat transfer tube 1 is the representative signal S0.

<Determination of bending end: Step 4 in FIG. 6>
Using the representative signal S0, reference signal positions b1 and b2 corresponding to the bent ends B1 and B2 of the heat transfer tube 1 are determined among the signal positions of the representative signal S0.
There are several methods for determining the reference signal positions b1 and b2 as follows.

  In the first example in which the reference signal positions b1 and b2 are determined, the end of the range where the representative signal S0 exceeds a predetermined threshold is set as the reference signal positions b1 and b2 corresponding to the bending ends B1 and B2.

In the second example for determining the reference signal positions b1 and b2, a section in which the absolute value SD (FIG. 7 (e)) of the constant width difference in the axial direction of the representative signal S0 exceeds a predetermined threshold is extracted. A position where the SD is the maximum value in each section is set as a candidate position, and “optimal combination” among the combinations of the candidate positions is set as reference signal positions b1 and b2 corresponding to the bending ends B and B.
Examples of optimal combination selection methods include
-Select the combination whose distance between candidate positions is closest to the design value.
-Select the combination with the longest distance between candidate positions.
There is an example.

Instead of the method of obtaining SD described in the second example for determining the reference signal positions b1 and b2, the representative signal S0 is subjected to low frequency component removal processing (high pass filter, median filter signal subtraction, moving average signal subtraction, etc.) The absolute value signal of the signal obtained by) may be SD.
SD calculated by these methods is a signal for detecting a position where the change rate of the representative signal S0 is large (the change is steep).

In the case where a problem occurs in the middle of processing such as a case where a plurality of candidate positions cannot be picked up by the above-described method, it can be determined that the measurement signal does not include the entire bending portion.
In addition, the time difference between the detected reference signal position b1 and the reference signal position b2 is a time difference estimated from the bending tube length by the design value and the set probe scanning speed and the change in scanning speed allowed when passing through the bending pipe. When it is out of the range, it can be determined that the measurement signal does not include the entire bent pipe section or is a defective signal in which a speed change deviating from a speed change allowed when passing through the bent pipe section has occurred.

<Detection of Axial Position: Step 5 in FIG. 6>
When the reference signal position b1 corresponding to one bending end B1 and the reference signal position b2 corresponding to the other bending end B2 are determined in the axial direction (time axis direction) of the measurement signals S1 to S12 as described above. For example, when a waveform indicating a defect is found in the measurement signal S5 output from the sensor C5, the reference signal positions b1 and b2 and a signal position where a waveform (signal change) indicating a defect in the measurement signal S5 is generated. From the positional relationship, a position where a defect exists in the axial direction of the heat transfer tube 1 is detected.

  Moreover, in the measurement signals S1 to S12, it was possible to detect the two reference signal positions b1 and b2 corresponding to the bent ends B1 and B2 of the heat transfer tube 1, that is, among the measurement signals S1 to S12, Since the signal region (signal between the reference signal position b1 and the reference signal position b2) obtained when the bending tube portion 1β of the heat transfer tube 1 is scanned can be specified, the entire range of the bending tube portion 1β to be inspected It can be confirmed that the eddy current flaw inspection was conducted.

  In addition, when a range of a certain distance or more from the bending end is specified as the inspection range, the specified range is inspected without a shortage by confirming the measurement signal range from the reference signal positions b1 and b2. Can be confirmed.

  As described above, in the second embodiment, the measurement signal analyzing apparatus 20 performs signal processing calculation on the measurement signals S1 to S12, so that there is no structure that becomes a mark in the direction along the axial direction of the heat transfer tube 1 as shown in FIG. Even when an eddy current flaw inspection is performed in a state, when a flaw detection is performed on the bent pipe portion 1β, where the speed change of the eddy current flaw probe is likely to occur, a defect can be detected without using a special probe or complicated equipment. However, it is possible to accurately identify the position in the axial direction of the heat transfer tube 1.

In the second embodiment, an example in which the multi-sensor type eddy current flaw detection probe 10 is used has been shown. In other words, any type of eddy current flaw detection probe that can obtain measurement signals at a plurality of measurement positions along the circumferential direction of the eddy current flaw detection probe can be used even if the detection method is different.
In the case of a multi-sensor type eddy current testing probe, the number of sensors arranged in the circumferential direction may be arbitrarily increased or decreased.
Further, the heat transfer tube to be inspected may be not only a U-shaped heat transfer tube but also a square heat transfer tube.

DESCRIPTION OF SYMBOLS 1 Heat transfer tube 1 (alpha) Straight pipe part 1 (beta) Bending pipe part 2 Tube plate 3 Tube support plate 10 Eddy current flaw detection probe 11 Probe main body 12 Stabilizer 13 Signal line 20 Measurement signal analyzer 21 Display part 25 Measurement apparatus 26 Recording apparatus B1, B2 Bending end C1 to C12 sensors S1 to S12 measurement signal S0 representative signal SD differential signal absolute value signal R1 to R12 measurement position

Claims (11)

An eddy current flaw detection probe that has a probe body and a sensor provided on the peripheral surface of the probe body, and outputs a measurement signal for each measurement position defined at a plurality of locations along the circumferential direction of the probe body,
In the inspection to be inserted into the inspection object pipe consisting of the straight pipe part and the bending pipe part, and to scan the inside of the inspection object pipe,
From the measurement signal, the absolute value signal of the difference between the measurement signals for each pair of measurement positions facing each other in the radial direction is obtained, and the average signal obtained by taking the average in the circumferential direction of the absolute value signal of the difference is a representative signal.
Specify the start position or end position of the signal change that occurs in the representative signal ,
Detection inspection position, characterized by associating the axial position of the signal the start or end point of the change, the position inspected tube measurement signals by associating with the position of the bending end of the pipe to be examined Method. An eddy current flaw detection probe that has a probe body and a sensor provided on the peripheral surface of the probe body, and outputs a measurement signal for each measurement position defined at a plurality of locations along the circumferential direction of the probe body,
In the inspection to be inserted into the inspection object pipe consisting of the straight pipe part and the bending pipe part, and to scan the inside of the inspection object pipe,
The average value in the time axis direction is determined for each measurement signal, and the measurement signal having the maximum absolute value of the average value is used as a representative signal.
Specify the start position or end position of the signal change that occurs in the representative signal ,
Detection inspection position, characterized by associating the axial position of the signal the start or end point of the change, the position inspected tube measurement signals by associating with the position of the bending end of the pipe to be examined Method. The representative signal is
For each measurement signal, filter processing that removes high-frequency components indicating significant signal factors and noise is applied as preprocessing,
Detection method of inspecting positions according to claim 1 or claim 2, characterized in that calculating the representative signal for each measuring signal the filter. A method for specifying a start position or an end position of a signal change that occurs in the representative signal when passing through the bent pipe portion is as follows:
Among the representative signal, the start and end positions of the section value of the representative signal exceeds a predetermined value, or, a candidate position of the maximum value of the interval axial difference absolute value signal of the representative signal exceeds a predetermined value A position change is selected, and a combination of two candidate positions that is most suitable for the positions of both ends of the bending pipe portion is selected from among the candidate positions, and a signal change that occurs in the representative signal that occurs when passing through the bending pipe portion is selected. detection method for inspection position according to any one of claims 1 to 3, characterized in that to determine the start and end positions. When the start position or end position of the signal change that should be included in the inspection range by the inspection position detection method according to any one of claims 1 to 4 is not obtained, it is determined that the inspection range is insufficient. Inspection range confirmation method characterized by performing. 6. Specified based on the start position or end position of the signal change detected by the inspection position detection method according to any one of claims 1 to 4 and the inspection range confirmation method according to claim 5 . An inspection range confirmation method characterized by confirming whether or not the inspection range is inspected without a shortage. An inspection method for inspecting the inspection target tube using the inspection position detection method or the inspection range confirmation method according to any one of claims 1 to 6 . A probe body and a sensor provided on the circumferential surface of the probe body, each outputting a measurement signal at each measurement position defined at a plurality of locations along the circumferential direction of the probe body, and bending the straight pipe portion An eddy current flaw detection probe that is inserted into an inspection target tube composed of a tube portion and scans within the inspection target tube;
A representative for calculating an absolute value signal of a difference between measurement signals for a pair of measurement positions opposed in the radial direction from the measurement signal, and calculating an average signal obtained by taking an average of the absolute values of the differences in the circumferential direction as a representative signal Signal calculation means;
And the start position and end position specifying means for specifying a start position or the end position of the signal change generated in the representative signal when passing through the bent tube portion,
The start or end point of the signal change, the location association means associating the axial position of the pipe to be inspected and position of the measurement signal by associating with the position of the bending end of the pipe to be examined,
An inspection apparatus comprising: A probe body and a sensor provided on the circumferential surface of the probe body, each outputting a measurement signal at each measurement position defined at a plurality of locations along the circumferential direction of the probe body, and bending the straight pipe portion An eddy current flaw detection probe that is inserted into an inspection target tube composed of a tube portion and scans within the inspection target tube;
A representative signal calculating means for calculating an average value in the time axis direction for each measurement signal and calculating a measurement signal having the maximum absolute value of the average value as a representative signal;
And the start position and end position specifying means for specifying a start position or the end position of the signal change generated in the representative signal when passing through the bent tube portion,
The start or end point of the signal change, the location association means associating the axial position of the pipe to be inspected and position of the measurement signal by associating with the position of the bending end of the pipe to be examined,
An inspection apparatus comprising: The representative signal calculation means includes:
For each measurement signal, filter processing that removes high-frequency components indicating significant signal factors and noise is applied as preprocessing,
The inspection apparatus according to claim 8, wherein a representative signal is calculated for each measurement signal subjected to the filtering process. The start position / end position specifying means includes:
Among the representative signal, the start and end positions of the section value of the representative signal exceeds a predetermined value, or, a candidate position of the maximum value of the interval axial difference absolute value signal of the representative signal exceeds a predetermined value A position change is selected, and a combination of two candidate positions that is most suitable for the positions of both ends of the bending pipe portion is selected from among the candidate positions, and a signal change that occurs in the representative signal that occurs when passing through the bending pipe portion is selected. 10. The inspection apparatus according to claim 8 , wherein a start position and an end position are determined.

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