JP3152676B2 - Metal remote field eddy current flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal material remote field eddy current flaw detection apparatus, and more particularly to a metal material remote device for performing maintenance management of pipes such as buried gas pipes, chemical plant pipes, heat exchanger pipes, etc. by a remote field eddy current method. The present invention relates to a field eddy current flaw detector.

[0002]

2. Description of the Related Art In order to perform flaw detection of a metal material using the remote field eddy current method, an exciting coil and one or more receiving coils are required to be about twice as large as a tube diameter. The remote field eddy current sensor arranged in the pipe axis direction is attached to the signal transmission cable, inserted into the pipe, and the excitation voltage is applied. The applied excitation signal generally uses a relatively low frequency of several tens Hz to several hundreds Hz, and the excitation voltage is several volts to several tens of volts.

[0003] Electromagnetic waves generated by the excitation signal are divided into those that pass through the thickness of the test pipe and those that propagate in the pipe. The electromagnetic waves that propagate in the pipe are separated from the waveguide by a waveguide. Since the frequency is much lower than the assumed cut-off frequency, it is rapidly attenuated and hardly propagates. On the other hand, an electromagnetic wave propagating in the pipe thickness is called an indirectly propagated wave, propagates outside the pipe along the pipe, slowly attenuates, and at the same time partially passes through the pipe thickness again, and It penetrates into and is received by the receiving coil.

The received signal detected by the receiving coil is
Very weak (several μV ~
Several tens of microvolts), and undergoes a phase change due to a skin effect caused by passage through the conduit. In the remote field eddy current method, a phase change with good linearity with the pipe wall thickness is often used as information.

In the above-mentioned remote field eddy current method, an absolute value type in which a plurality of receiving coils are arranged on the same circumference behind one excitation coil, and a reception group in a front group arranged on the same circumference. There is a differential type including a coil and a rear group of receiving coils provided behind the coil.

[0006] In the absolute value type, each coil of the receiving coil group has the same number of turns, and the plurality of receiving coils are connected to the measuring instrument by a necessary pair of lead wires for outputting sensor signals.

On the other hand, in the differential type, the receiving coils of the front group and the rear group all have the same number of turns, the front coil and the rear coil are differentially connected, and the necessary pairs of lead wires are provided. Connected to the container.

In the case of the absolute type sensor, a received signal is always obtained even in a non-defective part. However, in the case of the differential type sensor, a differential connection is required at a part other than a shape change part such as a local defect. Almost no received signal can be obtained. This phenomenon also occurs when a receiving coil (normal direction coil) having a magnetic path formed by a remote field eddy current provided in a direction perpendicular to the axis of the exciting coil is used.

When a receiving coil group composed of differential or normal direction coils is used in a remote field eddy current, a received signal sufficient for performing stable phase detection cannot be obtained in a healthy subject. In addition, noise is mixed in the flaw detection data subjected to the phase detection. For this reason, there is a problem that the flaw detection data shifts to abnormal flaw detection data.

In addition, when a remote field eddy current sensor in which a plurality of receiving coils are annularly arranged on the inner wall of a pipeline is used, there is a problem that a highly accurate pipeline diagnosis cannot be performed due to accumulated abnormal flaw detection data.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an abnormal flaw detection data is obtained by superimposing an AC signal having a predetermined phase and amplitude on a reception signal output from a reception coil. By using a remote field eddy current sensor in which generation is prevented and a plurality of receiving coils are annularly arranged on the inner wall of the pipeline, accumulation of abnormal flaw detection data due to phase detection noise included in flaw detection data can be prevented. An object is to provide a field eddy current flaw detection device.

[0012]

In order to achieve this object, a metal material remote field eddy current flaw detection apparatus according to the present invention includes a reference signal generating means for generating a reference signal when detecting a defect in a metal material; An excitation coil for generating a remote field eddy current in the test metal material by an excitation signal having the same phase as the reference signal, and an excitation coil arranged at a predetermined distance from the excitation coil to receive the remote field eddy current and transmit a plurality of reception signals A plurality of normal-type receiving coils or a plurality of differential-type receiving coils constituted by two coils arranged at a predetermined interval; and a plurality of attenuators for attenuating the excitation signal to a predetermined amplitude level, A plurality of AC signal generating means each including a plurality of phase shifters for shifting an output signal from the attenuator to a predetermined phase; a plurality of received signals and a plurality of AC signal generators; A plurality of signal adding means for adding the signals generated by the means, and a plurality of flaw detection data generating means for comparing the phases of the reference signal and the plurality of added signals generated by the plurality of signal adding means and outputting a plurality of flaw detection data Means.

[0013]

In this metal material remote field eddy current flaw detector, when an excitation signal is applied to the excitation coil of the remote field eddy current sensor, a reception signal is generated in the reception coil. The reception signal from which the common-mode noise has been removed by the differential amplifier of the reception signal interface and the high-frequency component has been removed by the low-pass filter is applied to the other input side of the adder. On the other hand, the excitation signal applied to the addition terminal of the addition signal processing module is attenuated by the attenuator of the addition signal generation module to the level set by the amplitude setting device. Next, in the phase shifter, if the phase angle set in advance by the phase angle setting device, for example, 15 degrees, is set, an addition signal whose phase angle is delayed by 15 degrees is sent to one input side of the reception signal processing module. Is done.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the metal material remote field eddy current flaw detector of the present invention will be described in detail with reference to FIG.

As shown in FIG. 1, the metallic material remote field eddy current flaw detector of the present invention shows a case where an exciting coil EC and a plurality of receiving coils RCn (n is 1 to 9 for explanation and a differential coil is used). ) Provided with the remote field eddy current sensor PRB, the reference signal generator 2, the excitation signal output amplifier 3, the excitation signal transmission circuit 1 provided with the reference signal generation circuit 4, the reception signal processing modules RQ1 to RQ9, and the addition signal generation modules RA1 to RA9, reception signal interface R
Receiving signal circuits RCC1 to RCC1 provided with B1 to RB9, respectively.
It is composed of RCC9.

The output side of the reference signal generator 2 of the excitation signal sending circuit 1 is connected to the input side of the excitation signal amplifier 3, and the output side of the excitation signal output amplifier 3 is connected to the terminal T0. The transmitting terminal T0 is connected to the exciting coil EC of the remote field eddy current sensor PRB by the pair of cores P0 of the cable CBL, and the receiving coils RC1 to RC9 are connected to the pair of cores P1 to P9 of the cable CBL by the pair of cores P1 to P9 of the reception signal circuit RC1 to RC9. Connected to respective receiving terminals RT2 and RT3. Pair core wire P mentioned above
0 indicates the excitation signal f0, and paired cores P1 to P9 indicate the reception signal f1.
To f9 are transmitted and received. The transmission terminal T0 is connected to the respective addition terminals RT1 of the reception signal circuits RCC1 to RCC9.

The output side of the reference signal generator 2 of the excitation signal sending circuit 1 is connected to the input side of the reference signal generation circuit 4, and the nine output sides of the reference signal generation circuit 4 have reference signal terminals T1 to T9.
Connected to The reference signal terminals T1 to T9 are connected to the respective reference terminals RT4 of the reception signal circuits RCC1 to RCC9.

Each of the addition signal generation modules RA1 to RA9 comprises an attenuator 5, an amplitude setter 5a, a phase shifter 6, and a phase angle setter 6a.
The input side of the phase shifter 6 is connected to the output side of T1. The output side of the phase shifter 6 is connected to one input side of the adder 11 of the later-described reception signal processing modules RQ1 to RQ9.

The reception signal interfaces RB1 to RB9 are connected by a differential amplifier 7, a low-pass filter 8, a reception amplifier 9, and a band-pass filter 10, respectively.
Are connected to the receiving terminals RT2 and RT3. The output side of the differential amplifier 7 is connected to the other input side of the adder 11 via a low-pass filter 8, a reception amplifier 9, and a band-pass filter 10.

The received signal processing modules RQ1 to RQ9 each include an adder 11, a waveform shaping circuit 12, and a phase comparator 1.
3. It is composed of a flaw detection data output unit 14. The output side of the adder 11 in which the output side of the phase shifter 6 of each of the addition signal generation modules RA1 to RA9 and the respective bandpass filters 10 of the reception signal interfaces RB1 to RB9 are connected to one input side and the other input side, respectively. It is connected to the flaw detection data terminal RT5 via the shaping circuit 12, the phase comparator 13, and the flaw detection signal output unit 14. The reference signal terminals T1 to T9 of the excitation signal transmission circuit 1 are connected to the reception signal processing modules RQ1 to RQ1.
RQ9 is connected to the comparison input side of the phase comparator 13 via the respective module-side reference terminals RT4.

When the excitation signal f0 shown in FIG. 1 is applied to the excitation coil EC of the remote field eddy current sensor PRB in the thus configured metal remote field eddy current flaw detector, the reception signals f1 to RC9 are applied to the reception coils RC1 to RC9. f9
Occurs. The reception signals f1 to f9 from which the common-mode noise has been removed by the differential amplifier 7 of the reception signal interfaces RB1 to RB9 and the high-frequency component has been removed by the low-pass filter 8 are applied to the other input side of the adder 11. On the other hand, the addition signal processing module R
The excitation signal f0 applied to the addition terminal RT1 of CC1 to RCC9 is applied to the attenuator 5 of the addition signal generation module RA1 to RA9.
, The signal is attenuated to the level set by the amplitude setting device 5a.
Next, in the phase shifter 6, if the phase angle set in advance by the phase angle setting unit 6a, for example, 15 degrees, is set to one input side of the reception signal processing modules RQ1 to RQ9, the phase angle is set to 15 degrees. An additional signal delayed by degrees is transmitted. The adder 11 adds the received signals f0 to f9 generated by the test tubes and the added signal, so that the phase noise is reliably removed by the adder 11, and the output from the adder 11 is sent to the phase comparator 13 from the output side. Received signals f0 to f9 of a constant level are transmitted. Therefore, the phase comparator 13 can perform stable phase detection. Since stable phase detection is performed, normal flaw detection data is output to each flaw detection data terminal RT5, so that abnormal flaw detection data due to noise is accumulated, and the shape, depth, and position of the defective portion are erroneously diagnosed. Such a situation does not occur.

[0022]

As is clear from the above embodiments, according to the metal remote field eddy current flaw detector of the present invention,
By superimposing an AC signal having a preset phase and amplitude on a reception signal output from the reception coil, generation of abnormal flaw detection data can be prevented, and a remote control in which a plurality of reception coils are annularly arranged on the inner wall of the pipeline. By using the field eddy current sensor, accumulation of abnormal flaw detection data due to phase detection noise included in flaw detection data can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a metal material remote field eddy current flaw detector according to the present invention.

[Explanation of symbols]

2 Reference signal generator (reference signal generation means) 5 Attenuator 6 Phase shifter 11 Adder (signal addition means) 14 flaw detection data output device (flaw detection data generation means) RA1 to RA9 ... addition signal generation module (AC signal generation means) EC ... excitation coil RC1 to RC9 ... .... Normal direction receiving coil, differential receiving coil

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Fujiwara 2-1-1-12 Nishichuo, Kure-shi, Hiroshima Inside CXR Development Division (72) Inventor Toshihide Kawabe 2-Nishichuo, Kure-shi, Hiroshima No. 1-12 Inside CXR Development Division (56) References JP-A-3-274456 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/72-27 / 90

Claims (1)

(57) [Claims] In detecting a defect in a metal material, a reference signal is detected.
Signal generating means (2) for generating a reference signal;
The excitation signal in phase with the
An excitation coil (EC) for generating a cold eddy current;
It is placed a predetermined distance away from the excitation coil, and
Multiple eddy currents and multiple received signals
Normal direction receiving coil or 2 arranged at a predetermined interval
A plurality of differential receiving coils (R
C1 to RC9) and a predetermined amplitude level of the excitation signal
Attenuators (5) for attenuating to
Phase shifters that shift the output signal of the phase shifter to a predetermined phase
(6) A plurality of AC signal generating means (RA1-R
A9) and a plurality of reception signals and a plurality of AC signal generation means
A plurality of signal adding means for adding the generated signals (11)
And the reference signal and the complex generated by the plurality of signal adding means.
Multiple flaw detection data by comparing the phase of
A plurality of flaw detection data generating means (14)
Metal field remote eddy current flaw detector
Place .