JPH08313489A - Flaw detector - Google Patents

Abstract

PURPOSE: To enhance measuring resolving power in the peripheral and axial directions of a pipe by arranging a plurality of coils on the circumference of a circle having the center axis of a sensor probe as the center on the plane vertical to the center axis of the probe. CONSTITUTION: A multiplexer 10 is driven by a drive circuit 30. The drive circuit 30 generates a multiplexer driving signal on the basis of the signal of an oscillator 20. A bridge 40 is driven by the AC signal of the oscillator 20 and the output thereof is amplified by an amplifier 50 to be inputted to a synchronous detector 60. The synchronous detector 60 detects the bridge output from the amplifier 50 in synchronous relation to the AC signal of the oscillator 20. An operational processing part 70 receiving the detection result calculates the position or size of the flaw of a pipe to be measured. Since sensors (coils) are arranged in a circumferential direction in a multichannel manner, the distribution of flaws in the circumferential direction can be measured and measuring resolving power in the peripheral direction of a pipe can be enhanced. Since the sensor per one channel becomes small, measuring resolving power in the axial direction of the pipe can be also enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw detection inspection apparatus for inspecting flaws due to corrosion of tubes such as heat exchangers, and more particularly, to an improvement for increasing the resolution by increasing the number of channels of a sensor probe sensor.

[0002]

2. Description of the Related Art Conventionally, as a flaw detection inspection apparatus for inspecting a flaw due to corrosion of a pipe, there are a flaw detection method using an eddy current flaw detection method and a flaw detection method using a leakage flux method. In the eddy current flaw detection method, a sensor probe having two coils A and B as shown in FIG. 11 is inserted into a pipe to be measured and is swept in the pipe axial direction (also referred to as the axial direction).

In this case, as shown in FIG. 12, a coil A (inductance L _A ) and a coil B (inductance L _B ) are connected to two adjacent sides of the bridge, and a sinusoidal current I _i is passed through the bridge to bridge the bridge. Output V ₀ is drive current I
Synchronous detection is performed at _i and used as the measurement signal. When the coil is driven with an alternating current, an eddy current is generated in the pipe to be measured. If the tube is damaged, the way the eddy current is generated changes, so the inductance of the coil changes apparently. When the probe is swept, coils A and B
Since the inductance of is changed sequentially, changes in the amplitude and phase of the measurement signal appear, and it is possible to detect that the tube is damaged.

[0004]

However, in such a conventional eddy current flaw detection method, since the total sum of flaws in the pipe circumferential direction (also referred to as the circumferential direction) is measured, the distribution of flaws in the pipe circumferential direction and the individual flaws in the pipe circumferential direction are measured. The size of the scratch is unknown, and since the coil diameter is large, the distance between the coils is large and the resolution in the tube axis direction is also reduced.

On the other hand, in the leakage magnetic flux method, as shown in FIG. 13, a permanent magnet M and a coil A ₀ for detecting the strength of the leakage magnetic flux,
This is a method in which the probe P containing B ₀ is inserted into the tube T and the disturbance of the magnetic field due to the cut portion such as a flaw in the tube is detected, but there are the following problems. The diameter of the detection coil is close to the inner diameter of the tube, and only one pair of coils is used as the sensor. Therefore, similarly to the eddy current flaw detection method, the distribution of flaws in the circumferential direction of the pipe, the size of each flaw, and the like are unknown, and the distance between the coils increases and the resolution in the axial direction of the pipe decreases.

[0006] In view of the above, an object of the present invention is to provide a flaw detection inspection apparatus in which a large number of sensors are arranged in the pipe circumferential direction to improve the measurement resolution in the pipe circumferential direction and the pipe axial direction. .

[0007]

In order to achieve such an object, according to the first invention of the present application, a sensor probe is inserted into a pipe to be measured or is externally attached to a pipe to be measured so as to remove a scratch generated on the pipe to be measured. A flaw detection inspection device for exploring, wherein the sensor probe includes a first sensor group in which a plurality of coils are arranged on a circumference centered on the central axis on a plane perpendicular to the central axis of the sensor probe, A plurality of coils are arranged on a circumference centered on the center axis on a plane perpendicular to the center axis of the sensor probe, and the second sensor group is arranged close to the first sensor group, A bridge in which coil pairs on the same circumferential direction of the first and second sensor groups are selectively connected and driven by an AC signal, and a synchronous detection circuit for detecting the bridge output in synchronization with the AC signal And receiving the output of this synchronous detection circuit. Characterized by comprising a processing unit for determining the distribution and size of the circumferential and axial wound Teikan or the measured material.

According to a second aspect of the present invention, there is provided a flaw inspection device for inserting a sensor probe into a pipe to be measured or externally mounting the pipe on a pipe to be measured to detect a flaw generated in the pipe to be measured, wherein the sensor probe is a sensor. A permanent magnet is arranged in the center of the probe, and a plurality of coils are arranged so as to surround the permanent magnet on a circumference centered on the center axis of the sensor probe on a plane perpendicular to the center axis of the sensor probe. A first sensor group and a plurality of coils arranged on a circumference centered on the central axis of the sensor probe on a plane perpendicular to the central axis of the sensor probe, and the coils are arranged close to the first sensor group but A multiplexer including a second sensor group arranged at a position deviated from an end point, and selecting a coil pair on the same circumferential direction and a hall element on the same circumferential direction of the first and second sensor groups; This multip Inductance measuring means for measuring the inductance of the coil pair selected by the comb, and arithmetic processing for obtaining and displaying the distribution and size of flaws in the circumferential and axial directions of the pipe to be measured or the material to be measured from the output of the inductance measuring means. It is characterized by having a section.

[0009]

According to the first invention of the present application, a sensor probe having a plurality of coils arranged on a circumference centered on the center axis on a plane perpendicular to the tube axis direction of the pipe to be measured is used as a sensor probe. Two probes arranged apart from each other by L are used. Then, the coils (coil pairs) on the same circumferential direction of the two sensor groups are connected as two sides of the bridge, and the bridge is driven by an AC signal. If the pipe to be measured has a flaw, the inductance of the coil changes and an output corresponding to the size of the flaw is obtained from the bridge. Since the sensitivity range of each coil pair of the first and second sensor groups is limited, it is possible to specify the range in the pipe circumferential direction from the bridge output for a plurality of coil pairs. By sweeping the sensor probe in the axial direction of the pipe to be measured, the distribution of scratches can be measured over the entire length of the pipe to be measured.

In the second invention of the present application, as the sensor probe, a permanent magnet and a circle surrounding the permanent magnet are arranged on a plane perpendicular to the tube axis direction of the pipe to be measured and having a circumference centered on the central axis. A first sensor group in which a plurality of coils are arranged, a second sensor group in the vicinity of the first sensor group but at a position deviated from the end point of the permanent magnet, and a tube of the pipe to be measured. A probe is used which is composed of a group of Hall elements in which a plurality of Hall elements are arranged on a circumference centered on the central axis on a plane perpendicular to the axial direction. Since the sensitivity range of each coil pair of the first and second sensor groups is limited, it is possible to measure the distribution of flaws in the circumferential direction of the pipe from the inductance variation of the plurality of coil pairs and the output of the Hall element. Further, by sweeping the sensor probe in the axial direction of the pipe to be measured, the distribution of scratches can be measured over the entire length of the pipe to be measured.

[0011]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of the flaw detection inspection apparatus according to the present invention. In the figure, 1A is a first coil group, 1B is a second coil group, 10 is a multiplexer, 20 is an oscillator, 30 is a drive circuit, 40 is a bridge, 50 is an amplifier,
Reference numeral 60 is a synchronous detector, and 70 is an arithmetic processing unit.

The first coil group 1A and the second coil group 1B are each composed of a plurality of coils as described later, and each coil pair 1-1 ', 2-2', 3-.
3 ',. ． ． N-N 'is switched by the multiplexer 10 and connected to two adjacent sides of the bridge 40. The multiplexer 10 is driven by the drive circuit 30. The drive circuit 30 generates a multiplexer drive signal based on the signal of the oscillator 20.

The bridge 40 is driven by the AC signal of the oscillator 20, the output of which is appropriately amplified by the amplifier 50 and then input to the synchronous detector 60. The synchronous detector 60 is the amplifier 5
The bridge output via 0 is detected in synchronization with the AC signal of the oscillator 20. The arithmetic processing unit 70 which has received the detection result performs a predetermined arithmetic processing to obtain the position, size, etc. of the flaw on the pipe to be measured.

First coil group 1A and second coil group 1B
The part consisting of is a sensor probe and has a structure as shown in FIG. The first coil group 1A has 1, 2,
3 ,. ． ． , N coils, and are arranged such that the centers of the coils are located on a plane perpendicular to the central axis of the sensor probe P on the circumference centered on the central axis of the sensor probe. The same applies to the second coil group 1B. Further, the two coil groups are arranged in parallel at the distance L, and the coils 1-1 ', 2-2', 3-3 ',. ． ．
Form a coil pair, and the line connecting the centers of the two coils forming the coil pair is arranged parallel to the central axis of the flaw detection probe.

The sensitivity range of one coil pair is a part of the circumference of the pipe to be measured, as shown in FIG. When the sensor probe P is swept in the tube axis direction, the detection output is 0 when there is no flaw within the sensitivity range, but when there is a flaw, an output is output. When this output is expressed by amplitude and phase,
As shown in FIG. When only the amplitude is expressed with respect to the sweep time, the waveform is as shown in FIG.

In such a configuration, the bridge 40
The pair of coils connected to is sequentially switched by the multiplexer 10, and the bridge output in each coil pair is detected and guided to the arithmetic processing unit 70. In this way, the size and properties of the scratch can be known as in the conventional case. According to the probe of the present invention, since the sensitivity range of one coil pair is limited, it is possible to specify in which range in the tube circumferential direction the flaw is present. Therefore, the distribution in the pipe circumferential direction can be known by summing the outputs of the respective coil pairs. Furthermore, by sweeping such a sensor probe over the entire length of the pipe to be measured, the distribution of scratches on the pipe to be measured can be measured.

It is desirable that the plurality of coil pairs as described above be manufactured by using both surfaces of the printed board as shown in FIG. The manufacturing accuracy of the coil is improved and the assembly is facilitated, so that the cost can be reduced.

The present invention is not limited to the above embodiment. For example, although one sensor probe is provided in the embodiment, two identical sensor probes may be installed at a distance X in the tube axis direction. The output in that case is output with a time shift as shown in FIG. At this time, the sweep speed of the sensor probe can be obtained from the time delay t and the distance X. Currently, the method of manually sweeping the sensor probe is the mainstream, and the position of the flaw is obtained by proportional distribution from the total length of the pipe to be measured and the sweep time for it. However, when the above two are installed, the sweep at the manual sweep is performed. Since the change in speed can be measured, the position of the scratch can be obtained more accurately.

Further, in the embodiment, the sensor probe of the present invention has a structure to be inserted into the pipe to be measured, but the structure is not limited to this. For example, the center axis of the sensor probe may be hollow, and a material to be measured such as a rod or wire may be passed through the cavity to measure the scratches on the rod or wire. Furthermore, in the case where the resolution in the pipe circumferential direction is insufficient in the configuration described in the above embodiment, a plurality of the same sensor groups are installed while being shifted in the pipe axis direction, and the installation angle of each sensor group with respect to the sensor probe central axis is set. You may make it shift.

FIG. 8 is a block diagram showing an embodiment of a flaw detection inspection apparatus using the leakage flux method. In the figure, 101 is the first
Coil group, 102 is a second coil group, 103 is a Hall element group, 110 is a multiplexer group, 121 and 122 are first and second inductance detection circuits, 123 is a magnetic field measurement circuit, 130 is an arithmetic processing unit, 140 Is a control circuit.

First and second coil groups 101, 102
The portion including the hall element group 103 is a sensor probe for magnetic flux leakage flaw detection, and has a structure as shown in FIG. First and second coil groups 101 and 102
Is similar to the coil for the eddy current flaw detection method shown in FIG.
2, 3 ,. ． ． N coils and 1 ', 2',
3 ',. ． ． Includes N'coils. Moreover, the centers of the coils are arranged so as to be located on the circumference centered on the central axis of the sensor probe on a plane perpendicular to the central axis of the sensor probe.

Further, the two coil groups are arranged in parallel at a predetermined interval, the first coil group is arranged in the permanent magnet M portion, and the second coil group 102 is arranged in a position outside the end points of the permanent magnets. . The two coil groups are the coil 1-
1 ', 2-2', 3-3 ',. ． ． Form a coil pair, and the line connecting the centers of the two coils forming the coil pair is arranged so as to be parallel to the central axis of the sensor probe.

The hall element group 103 includes a plurality of hall elements H.
1, H2 ,. ． ． Is attached to the outer peripheral surface of the cylinder 104, and each Hall element is arranged so as to be located on the circumference centered on the central axis of the sensor probe on a plane perpendicular to the central axis of the sensor probe. The Hall element may be manufactured on the flexible printed board.
With such a structure, the arrangement and assembly of the Hall element can be facilitated.

The control circuit 140 includes a multiplexer group 110.
To sequentially switch the multiplexers 111, 112, and 113 for the first and second inductance detection circuits 12
1, 122 to coils 1 and 1 ', coils 2 and 2' ,. ． ．
And the Hall elements H1 and H in the magnetic field measuring circuit 123.
2 ,. ． ． Are connected in sequence. Inductance detection circuit 1
Reference numerals 21 and 122 measure the inductance of the connected coil and output it as a voltage output. The magnetic field measuring circuit 123 outputs a voltage according to the magnetic field measured by the Hall element. The arithmetic processing unit 130 uses the inductance detection circuit 12
1, 122 and the output of the magnetic field measuring circuit 123, it is possible to obtain the site of the wound of the tube T and the variation of the inductance and the magnetic field with respect to the sweep time.

In such a structure, when the sensor probe is swept in the tube axis direction (generally, manual sweeping), if there is no flaw within the sensitivity range, the inductance of the coil does not change, but if there is a flaw, scratches occur. The inductance fluctuates due to the leakage magnetic flux of the part. Further, when the wall thickness of the tube gradually changes, the output of the Hall element changes. When these changes are expressed with respect to the sweep time, it becomes as shown in FIG. From these outputs, the size and nature of the scratch can be known as in the conventional case.

In such a flaw detection inspection apparatus using the leakage magnetic flux method, since the sensitivity range of one coil pair or Hall element is limited, it is possible to specify in which range in the circumferential direction the flaw is present. Therefore, the distribution of flaws in the circumferential direction of the tube can be known by summing the outputs of the respective coils and Hall elements. By sweeping the sensor probe over the entire length of the pipe to be measured, the distribution of scratches on the pipe to be measured can be measured.

When two sets of the same sensor probe are installed at a distance X in the tube axis direction, their outputs are as shown in FIG.
As in the case of the eddy current flaw detection method shown in (1), the output is delayed in time. The sweep speed of the sensor probe can be obtained from the time delay t and the distance X at this time. The effect of using two sets of sensor probes is similar to that of the probe using the eddy current flaw detection method, and the position of the flaw can be more accurately obtained as compared with the manual sweep. In addition, as described in the embodiment of the eddy current flaw detection method, the center axis of the sensor probe may be hollow, and the rod or wire may be passed through it to measure the flaw on the rod or wire.

When the resolution in the tube circumferential direction is insufficient, a plurality of the same sensor coil groups are displaced in the tube axis direction and a plurality of them are installed, and the installation angles of the respective coil groups with respect to the center axis of the sensor probe are different from each other. You may shift and arrange. This improves the resolution in the tube circumferential direction. Also,

As described above, according to the present invention (the first and second inventions), since the sensor (coil) is configured to have multiple channels in the circumferential direction, the distribution of scratches in the circumferential direction. Can be measured, and the measurement resolution in the pipe circumferential direction can be increased. Further, since the sensor for each channel is small, the resolution in the tube axis direction is also improved. Furthermore, when two identical sensor probes are arranged in the tube axis direction, the position of the measured flaw in the tube axis direction can be obtained more accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a flaw inspection device by an eddy current flaw detection method according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a sensor probe for an eddy current flaw detection method.

FIG. 3 is a diagram for explaining a sensitivity range of a sensor probe.

FIG. 4 is a diagram showing an example of detection output.

FIG. 5 is a diagram showing another example of detection output.

FIG. 6 is a diagram showing a configuration example in which a coil of a sensor probe is arranged on a printed board.

FIG. 7 is a diagram showing an example of detection output when two identical sensor probes are installed in the tube axis direction.

FIG. 8 is a configuration diagram showing an embodiment of a flaw detection inspection apparatus using a leakage magnetic flux method.

FIG. 9 is a configuration diagram showing an embodiment of a sensor probe of the leakage magnetic flux method.

FIG. 10 is a diagram showing an example of the detected inductance fluctuation and magnetic field fluctuation.

FIG. 11 is a diagram showing an example of a conventional sensor probe.

FIG. 12 is a diagram showing an example of a bridge circuit for connecting a conventional sensor probe.

FIG. 13 is a diagram showing an example of a leakage magnetic flux method sensor probe.

[Explanation of symbols]

 1A, 101 1st sensor group 1B, 102 2nd sensor group 1, 2, 3 ,. ． ． , N coils 1 ', 2', 3 ',. ． ． , N'coil 10,110 multiplexer 20 oscillator 30 multiplexer drive circuit 40 bridge 50 amplifier 60 synchronous detection circuit 70,130 arithmetic processing unit 103 Hall element group 121,122 inductance detection circuit 123 magnetic field measurement circuit 140 control circuit P sensor probe M permanent magnet

Claims (7)

[Claims] 1. A flaw detection inspection apparatus for detecting a flaw generated in a pipe to be measured by inserting the sensor probe into a pipe to be measured or externally attached to a pipe to be measured, wherein the sensor probe is perpendicular to a central axis of the sensor probe. A first sensor group in which a plurality of coils are arranged on a circumference centered on the central axis on a flat plane, and on a circumference centered on the central axis on a plane perpendicular to the center axis of the sensor probe A second sensor group having a plurality of coils arranged in proximity to the first sensor group, wherein a coil pair in the same circumferential direction of the first and second sensor groups is selectively A bridge that is connected and driven by an AC signal, a synchronous detection circuit that detects the output of the bridge in synchronization with the AC signal, and an output of the synchronous detection circuit that receives the output of the synchronous detection circuit and the circumferential direction of the pipe to be measured or the material to be measured. Find distribution and size of axial scratches A flaw detection inspection apparatus comprising an arithmetic processing unit for activating. 2. The flaw detection inspection apparatus according to claim 1, wherein the first and second sensor groups are formed on both surfaces of a printed board. 3. The sensor probe comprises the first and second sensors.
2 sets of sensor probes composed of the sensor group are arranged in the tube axis direction, and the arithmetic processing unit calculates the sweep speed of the sensor probe from the time difference between the interval of the two sets of sensor probes and the output signal, and scratches in the sweep direction. The flaw detection inspection apparatus according to claim 1, further comprising a function of determining the position of 4. A flaw detection inspecting apparatus for detecting a flaw generated in a pipe to be measured by inserting the sensor probe into the pipe to be measured or externally mounting the pipe to the material to be measured, wherein the sensor probe is arranged at a central portion of the sensor probe. And a first sensor group in which a plurality of coils are arranged so as to surround the permanent magnet on a circumference centered on the central axis of the sensor probe on a plane perpendicular to the central axis of the sensor probe. And a plurality of coils arranged on a circumference centered on the central axis on a plane perpendicular to the central axis of the sensor probe, close to the first sensor group, but at a position deviated from the end point of the permanent magnet. A multiplexer provided with a second sensor group arranged, and selecting a coil pair on the same circumferential direction of the first and second sensor groups and a Hall element on the same circumferential direction; and a multiplexer selected by this multiplexer. Ko An inductance measuring means for measuring the inductance of a pair of cables, and an arithmetic processing part for obtaining and displaying the distribution and size of flaws in the circumferential direction and the axial direction of the pipe to be measured or the material to be measured from the output of the inductance measuring means. A flaw detection inspection device. 5. The flaw detection inspection apparatus according to claim 4, wherein the first and second sensor groups are formed on both surfaces of a printed board. 6. The sensor probe includes a Hall element group in which a plurality of Hall elements are arranged on a circumference centered on the central axis of a plane perpendicular to the central axis of the sensor probe, and the multiplexer is The first and second sensor groups are also configured to select Hall elements on the same circumferential direction, and a magnetic field measuring circuit that obtains a magnetic field from the output of the Hall elements selected by the multiplexer is provided, and the arithmetic processing unit is The flaw detection inspection apparatus according to claim 4, further comprising a function of obtaining a distribution of flaws on the pipe to be measured or the material to be measured from the output of the magnetic field measuring circuit. 7. The sensor probe has a configuration in which two sets of sensor probes each including the permanent magnet and first and second sensor groups are arranged in a pipe axis direction, and the arithmetic processing is performed by a gap between the two sets of sensor probes. 5. The flaw detection inspection apparatus according to claim 4, further comprising a function of calculating a sweep speed of the sensor probe from a time difference between the output signal and the output signal and obtaining a flaw position in the sweep direction.