JP2000235019A - Eddy-current flaw detecting probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the number of signal lines to the number receptible within a cable and improve the spatial resolution and defect detectability by providing a switching circuit for time sharing and driving a plurality of magnetic field exciting element and magnetic field detecting element and a detection signal amplifier circuit on measuring instrument side. SOLUTION: A multiplexer is used as a switching circuit, and an excitation coil (magnetic field exciting element) group 13 and a detection coil (magnetic field detecting element) group 14 are connected to an excitation multiplexer 16 and to a detection multiplexer 18, respectively. The output of the detection multiplexer is amplified, through a detection signal line 22, by a detection signal amplifier circuit including an amplifier 20 in the course, and outputted to a measuring instrument side. The number of the signal line necessary for this line is reduced to 15, compared with at least 18 in the case using no multiplexer. Accordingly, the narrowing of signal lines is dispensed with, and the improvement in spatial resolution for a subject to be detected can be attained without changing the total diameter of signal cables.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current detection probe used for nondestructive inspection of a thin tube or the like inside a heat exchanger.

[0002]

2. Description of the Related Art An eddy current flaw detection probe equipped with a plurality of magnetic field excitation elements and magnetic field detection elements is disclosed, for example, in Japanese Patent Application Laid-Open No. 6-16 / 1994.
No. 0357 is described. As shown in FIG. 15, a set of three pancake coils is arranged on a cylindrical base 111, and one coil group is composed of two excitation coils 112 and two differentially connected pancake coils. And a detection coil 113. The feature of this probe is that one coil group detects both a defect existing in the circumferential direction of the heat transfer tube and a defect existing in the axial direction. In addition, the coil group is used to prevent a decrease in detectability between the coil groups. Are alternately arranged in two stages, and a total of eight coil groups are provided inside.

On the other hand, as an eddy current flaw detection probe having magnetic field excitation / detection pairs having different spatial arrangement patterns, for example, FIG.
6, a magnetic field detecting coil 123, a circumferential direction (for defect detection) magnetic field excitation coil 122 and an axial direction (for defect detection) as shown in FIG.
There is a rotary type eddy current flaw detection probe composed of a magnetic field excitation coil 121. This probe has a coil arrangement for detecting an axial defect of a tube and a coil arrangement for detecting a circumferential defect. Used for maximum placement.

[0004]

However, in the probe described above, the spatial resolution is restricted by the number of coil groups, so that the number of coils must be increased to improve the spatial resolution. Since the number of signal lines between the device and the probe increases, the signal lines are not contained in the sheath that includes the signal lines and connects the probe head and the flaw detection device. Of course, if the diameter of each signal line is reduced, the signal can be stored. However, in order to transmit and receive a signal over a length of 30 m or more, when the signal line is small, the signal attenuation increases.
It is not practical to reduce the diameter of the signal line due to a decrease in the S / N ratio, an increase in crosstalk between signal lines that are closer together, and an increase in the probability of disconnection due to a decrease in mechanical strength.

Although the above description has been made with respect to the interpolating type eddy current flaw detection probe, on the other hand, with respect to the penetration type probe and the upper type probe which do not have a strong restriction on the signal diameter, the weight and the diameter of the entire signal cable are increased. Increases the size of the device and strengthens the probe fixing portion, so that it is not preferable to increase the number of signal lines. Therefore, the problem that the number of coils has an upper limit still remains. In general, regarding the arrangement of the excitation element and the detection element, the detectability of the axial defect becomes the lowest when the detectability is maximized in the circumferential defect, and the detectability is the circumferential defect when the detectability is the largest in the axial defect. Sex is the worst.

The device disclosed in Japanese Patent Laid-Open No. 6-160357 is arranged so that the sensitivity of the axial defect and the sensitivity of the circumferential defect are balanced. It has also been reduced. However, in order to mount a plurality of flaw detection modes optimal for defects in each direction, coil groups having different arrangements are required, which further increases the number of signal lines.

SUMMARY OF THE INVENTION In view of the above situation, the present invention solves this problem by addressing this problem and increasing the number of coil groups and flaw detection modes while suppressing the number of signal lines to a number that can be accommodated in a cable. An object of the present invention is to provide an eddy current flaw detection probe with improved defect detection performance in both the peripheral axis and the peripheral axis.

[0008]

That is, the configuration of the eddy current detection probe of the present invention which meets the above-mentioned object comprises a plurality of magnetic field excitation elements, a plurality of magnetic field detection elements, and a time-division drive for these elements. It is characterized by comprising a switching circuit and a detection signal amplifying circuit provided on a measuring instrument side than a switching circuit for driving the plurality of detection elements in a time-division manner.

Further, the present invention comprises a plurality of magnetic field excitation and detection elements, wherein both a switching circuit for time-divisionally driving the excitation element and a switching circuit for time-divisionally driving the detection element are connected to the same element for timing. The present invention is also characterized in that the element is used as an excitation element or a detection element. In this case, it is preferable to provide a detection signal amplification circuit on the output side of the switching circuit for time-dividing the detection element, as in the above configuration. Furthermore, in each of the above configurations, it is also preferable that the plurality of magnetic field excitation elements / magnetic field detection elements have a plurality of spatial arrangements, and that the combination of the magnetic field excitation elements / magnetic field detection elements can be changed. It is an aspect.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows one embodiment of an eddy current flaw detection probe according to the present invention.
FIG. 2 is an external view showing an example, in which the eddy current flaw detection probe arranges eight coils 12 along a circumferential direction on a cylindrical base body 11 connected to a cable 15, and further arranges the coils 12 in the axial direction.
A total of 16 steps are formed. Among them, the upper coil group 13 is a coil dedicated for excitation coupled to the magnetic field excitation device so as to generate an eddy current in the tube, and the lower coil group 1
Reference numeral 4 denotes a detection coil which detects a current generated in the excitation coil coupled to the excitation device and generates a signal indicating that there is a defect in the tube. In order to consider adjacent excitation coils as pairs, a total of eight sensor pairs are provided.

FIG. 2 is a circuit block diagram of the inside of the probe of each coil. A multiplexer is used as a switching circuit. As shown in FIG. 2, an excitation coil group 13 of the coils is used for an excitation coil connected to an excitation signal line 21. To an eight-channel (ch) multiplexer 16,
The detection coil group 14 is connected to a detection 8-ch multiplexer 18. And the detection multiplexer 1
The output of 8 is connected to a detection signal line 22, amplified by a detection signal amplifier circuit including an amplification amplifier 20 provided on the way, and output to a measuring instrument, that is, a flaw detector. In the figure, reference numeral 17 denotes an excitation multiplexer control signal line, and reference numeral 19 denotes a detection multiplexer control signal line.

Here, when the multiplexer is not used, at least 18 signal lines are required in the above-described circuit, whereas four excitation multiplexer control signal lines 17 are required.
The number of detection multiplexer control signal lines 19 is four, the number of excitation signal lines 21 is two, the number of detection signal lines 22 is two, and the number of circuit driving power supplies is three. Naturally, even if the number of coils increases, the number of signal lines can be suppressed by using the multi-channel multiplexer. Therefore, it is not necessary to reduce the diameter of the signal line, or it is not necessary to reduce the diameter as compared with the conventional case. As a result, the spatial resolution related to the shape and position of the detection target can be improved without changing the diameter of the entire signal cable. . At the same time, the number of cores of the connector that connects the flaw detector and the cable is reduced, so that a smaller connector can be used and the operability when connecting the cable is improved.

Although the above-described embodiment considers a certain excitation coil and an adjacent detection coil as a pair, a combination of the excitation coil T and the detection coil R not adjacent to each other in FIG. 3 is also possible. The number of coil pairs in the arrangement state increases. The difference in the arrangement state of the coil pairs is the same as the change in the position where the detection sensitivity to the defect is maximized, so that the spatial resolution is improved without increasing the number of coils. In addition, it is also possible to change the sensitivity characteristic with respect to the defect, and it is possible to use the one kind of eddy current flaw detection probe to make the state optimal for the detection of the target defect.

The combination of the coil pairs can be easily changed by a command from the flaw detector and the control circuit, so that the probes can be used with different sensitivity characteristics without changing the probes. An amplification circuit is usually required to amplify the detection signal by the multiplexer. However, the amplification amplifier can be omitted particularly when deterioration of the detection signal is not a problem.

FIG. 4 is an external view showing a second embodiment of the eddy current flaw detection probe according to the present invention, in which eight coils 42 are arranged at equal intervals on the circumference of the probe base 41 along the circumferential direction. It is. Here, each coil is connected to both the excitation multiplexer 43 and the detection multiplexer 44 as shown in FIG.
, The coil other than the coil operates as the detection coil R. FIG. 6 shows the state of each coil at the time of the time-division driving.

As shown, in time slots 1 to 8, a coil is an excitation coil T in time slot 1,
The b coil adjacent thereto is the detection coil R, and the b coil detected earlier in the next time slot 2 is the excitation coil T, and the adjacent c coil is used as the detection coil R. In this way, in the above embodiment, the excitation / detection coils are switched one after another, so that although the total number of coils is eight, it can be used as a total of eight excitation / detection coil pairs.

In the second embodiment, as another usage, instead of forming an excitation / detection coil pair between adjacent coils as described above, excitation is performed by skipping one coil as shown in FIG. -It can be a detection coil pair.
For example, in FIG. 7, when the a coil is in the excited state, the c coil can be used as the detection coil R, and in the time slot 2, the b coil can be used as the excitation coil and the d coil can be used as the detection coil.

Further, a case where an excitation / detection coil pair is formed by adjacent coils shown in FIG. 6 is referred to as flaw detection mode A, and a case where alternate excitation / detection coil pairs are formed as shown in FIG. 7 is referred to as flaw detection mode B. A total of 16 pairs of both modes can be created with eight coils, and only the A mode or the B mode can be used, or both modes can be used simultaneously by increasing the number of time divisions. In this case, the configured coil group is the same in the A mode and the B mode,
Looking at the individual element pairs, the constituent elements have different spatial arrangement patterns in both modes, so that the spatial resolution and the sensitivity characteristics to defects are naturally different.

Next, FIG. 8 shows a third embodiment of the present invention, in which eight coils are provided in three stages on the circumference of a cylinder 81, for a total of 24 coils.
And 8 coils for the excitation coil and 8 coils for the detection coil as shown in FIG.
Channel multiplexers 86, 88, 91, 92 and signal amplifiers 87, 89, 93, 94 are provided.

The connection of the circuit shown in FIG. 9 will be described in detail. The upper eight coil groups 82 and the lower eight coil group 84 of the three-stage coil group are detection-only coil groups. They are connected to 8-ch multiplexers 86 and 88, respectively, and amplification amplifiers 87 and 89 are provided on the output side.

The middle eight coil group 83 is an excitation / detection coil group, and is connected to the detection 8ch multiplexer 92 like the excitation 8ch multiplexer 90 and the detection 8ch multiplexer 91, and is connected to the output side of each detection multiplexer. Are connected to amplification amplifiers 93 and 94, respectively. Of course, the multiplexers 91 and 92 always have the separate coils active.

FIG. 10 shows the operating state of each coil group. Four coils adjacent to a certain excitation coil T operate as detection coils R, and eventually, five coils operate as a group. It indicates that The switching of the coil group is the same as in the second embodiment, and the excitation / detection coil group is switched for each time slot.

In this embodiment, since the coil arrangement has the maximum sensitivity for each of the axial defect and the circumferential defect of the heat transfer tube, each of the defects has a flaw detection mode. It is possible to do. In addition, by providing a single-wire ground input channel and a differential input channel on the flaw detector side, the probe can be used as an absolute type or a differential type. When using the axial defect sensor pair as a differential type,
The detection signal of the upper coil group 82 may be connected to the non-inverting input of the differential amplifier of the flaw detector, and the detection signal of the lower coil group 84 may be connected to the inverting input. Similarly, if the output of the multiplexer 91 is connected to the non-inverting input and the output of the multiplexer 92 is connected to the inverting input, the circumferential defect sensor pair can also be used as a differential type. Of course, since this is a connection inside the flaw detector, it can also be used as an absolute channel at the same time.

If it is assumed that the absolute type channel is not used, the amplifiers 87 and 89 may be collectively used as a differential input amplifier, in which case the circuit mounting space and the number of signal lines can be reduced. It becomes possible. This is the same for the amplifiers 93 and 94.

FIG. 11 shows a fourth embodiment of the present invention.
Coil 101-108 and Coil 2 for circumferential defect detection
01 to 208, the coil 101 for detecting an axial defect.
To 108 and coils 301 to 308.
In this case, in the illustrated example, in the axial direction detection mode, the coil 301 is used in order to eliminate the sensitivity reduction region in the axial direction.
308 are arranged at different angles from the coils 101 to 108 and 201 to 208. For example, the coil 301 is arranged on a straight line connecting the midpoint between the coils 101 and 102 and the midpoint between the coils 201 and 202. Regarding the driving, when the coil 102 is in the excited state, the coil 3
01 and the coil 302 enter the detection state, and further, the control device makes a difference between the signal of 301 and the signal of 302. Also,
Similarly, in the circumferential defect detection mode, when the coil 101 is in the excited state, the coil 103 enters the detection state. Thereafter, the coil 201 enters the excitation state, and the coil 203 enters the detection state. In the control device, the output of the coil 103 and the coil 2
The difference signal of the circumferential defect can be obtained by subtracting the output of No. 03.

FIG. 12 shows the operating state of each coil group shown in FIG. 11, which is shown as an example of time division driving as shown in Table 1 below. In the table, s1 indicates a first slot, s2 indicates a second slot, and the like. For example, in the first slot s1, the coil 101 is used as an excitation coil.
This shows that the coils 103, 308, and 301 operate as detection coils.

[0028]

[Table 1]

In addition to the above embodiments, the arrangement shown in FIG. 13 and the arrangement and operation shown in FIG. 14 are also possible. The embodiments of the present invention have been described above. In this description, coils are used as the magnetic field excitation element and the magnetic field detection element. However, the present invention is not limited to this, and other elements are also effective. Similarly, the number of coils and the number of channels of the multiplexer, which is a switching circuit, need not be 8 channels at all, and may be increased or decreased as needed. The location where the circuit is built is most preferably inside the probe matrix, but when physically impossible, it can be provided inside or around the tube containing the signal line generally called a sheath.

[0030]

As described above, the eddy current flaw detection probe of the present invention comprises a plurality of magnetic field excitation elements, a plurality of magnetic field detection elements, a switching circuit for time-divisionally driving these elements, and a plurality of The detection signal amplification circuit is provided on the measuring device side rather than the switching circuit that drives the detection element in a time-division manner.By using a multi-channel multiplexer, the increase in the number of signal lines is suppressed. There is no need to reduce the diameter, the number of detection elements can be increased without changing the diameter of the entire signal cable, and the spatial resolution of the insertion type eddy current flaw detection probe can be improved. The number of cores of the connector for connecting the cables is also reduced, so that a small connector can be used, and a remarkable effect of improving the operability of the cable can be obtained.

Further, in the eddy current flaw detection probe of the present invention, the voltage drop in the signal line can be ignored by providing the amplifier circuit on the output side of the detection-side switching circuit, and at the same time, the same element is used by using the switching circuit. By using as a detection element and an excitation element, an effect that a plurality of flaw detection modes having different sensitivity characteristics can be used without changing the physical element arrangement is also achieved.

[Brief description of the drawings]

FIG. 1 is a schematic external view showing an example of an eddy current flaw detection probe of the present invention.

FIG. 2 is a circuit block diagram showing an electrical connection of the eddy current flaw detection probe of FIG. 1;

FIG. 3 is an explanatory view in which a coil arrangement according to the embodiment of FIG. 1 is planarized;

FIG. 4 is a schematic external view of a eddy current detection probe according to a second embodiment of the present invention.

FIG. 5 is a circuit block diagram showing an electrical connection of the eddy current detection probe of FIG. 4;

FIG. 6 is an explanatory diagram showing one state of each coil during time-division driving in the embodiment.

FIG. 7 is an explanatory diagram showing another state of each coil during the time-division driving of the embodiment of FIG. 5;

FIG. 8 is a schematic external view showing a third embodiment of the eddy current flaw detection probe of the present invention.

FIG. 9 is a circuit block diagram showing electrical connections in the embodiment of FIG.

FIG. 10 is an explanatory diagram showing an operation state at the time of time-division driving of each coil group in the embodiment of FIG. 8;

FIG. 11 is a schematic external view showing a fourth embodiment of the eddy current flaw detection probe of the present invention.

FIG. 12 is an explanatory diagram showing an operation state of each coil at the time of time-division driving in the fourth embodiment of FIG. 11;

FIG. 13 is an explanatory view showing still another coil arrangement mode and an operation state of the eddy current detection probe of the present invention.

FIG. 14 is an explanatory view showing still another coil arrangement state of the eddy current flaw detection probe of the present invention and an operation state at the time of time division driving.

FIG. 15 is a schematic external view showing an example of a conventional eddy current flaw detection probe.

FIG. 16 is a schematic external view showing another example of a conventional eddy current flaw detection probe.

[Explanation of symbols]

13 Excitation coil (magnetic field excitation element) 14 Detection coil (magnetic field detection element) 16, 43, 90 Multiplexer for excitation (switching circuit) 18, 44, 86, 88, 91, 92 Multiplexer for detection (switching circuit) 20, 47, 87, 89, 93, 94 Amplification amplifier (detection signal amplification circuit)

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 599019948 4495 Wilfrid-Hamel Quebec, Qbec, Canada (72) Inventor Yutaka Harada 1-3-7 Tosabori, Nishi-ku, Osaka-shi Nuclear Engineering Co., Ltd. (72) Invention Person: Junri Shimone 1-3-7 Tosabori, Nishi-ku, Osaka-shi Nuclear Engineering Co., Ltd. (72) Inventor Florian Hardy Canada. St-Augustine, Quebec 121 Rue de Labandiere 121 (72) Inventor Rock Samson St. Nicholas de la Chaudier, Quebec 177 F-term (reference) 2F063 AA03 BC02 BD07 CA08 CA09 CA34 DA01 DD07 DD09 EB24 GA08 LA09 LA11 2G053 AA11 AB21 BA12 BA23 CB19 DB02 DB04 DB27

Claims (5)

[Claims] 1. A plurality of magnetic field excitation elements, a plurality of magnetic field detection elements, a switching circuit for driving these elements in a time-division manner, and a switching circuit for time-divisionally driving the plurality of detection elements on the measuring instrument side. An eddy current flaw detection probe comprising a detection signal amplification circuit provided. 2. The method according to claim 1, wherein the plurality of magnetic field excitation elements / magnetic field detection elements are:
2. The eddy current detection probe according to claim 1, wherein the probe has a plurality of spatial arrangement patterns. And a switching circuit for driving the excitation element in a time-division manner and a switching circuit for driving the detection element in a time-division manner in the same element. An eddy current flaw detection probe using the same element as an excitation element or a detection element. 4. The eddy current flaw detection probe according to claim 3, wherein a detection signal amplification circuit is provided on an output side of a switching circuit for time-dividing the detection element. 5. The magnetic field excitation element / magnetic field detection element according to claim 1,
5. The eddy current flaw detection probe according to claim 3, wherein the probe has a plurality of spatial arrangements, and a combination of a magnetic field excitation element and a magnetic field detection element can be changed.