JPH075408Y2 - Metal flaw detection probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an eddy current flaw detector for a metal tube for detecting defects such as scratches and cracks in the metal tube, and in particular, this type has improved measurement accuracy. The present invention relates to a probe for metal flaw detection of a device.

[Prior Art] Conventionally, in an eddy current flaw detector, a test coil in which a high-frequency current is applied is inserted and moved in a metal tube to electrically change the eddy current caused by a flaw (hereinafter referred to as a defect) existing in the metal tube. I try to measure.

First, since the change in eddy current (change in impedance) is minute, it is increased by the detection unit and the amplifier and converted into voltage. This method is called the amplitude method, and the shape and depth of the defect are displayed by one signal to evaluate the defect.

Furthermore, whether the defects in the metal tube are on the inner surface or the outer surface, and the depth of the defect,
As an eddy current flaw detector for a metal tube that can be accurately and quickly measured, a device that can detect the inner surface defect and the outer surface defect and detect the defect depth from the phase of the defect signal has been proposed (Japanese Patent Application No. JP-A-57-185696 = JP-A-59-75146
Issue).

[Problems to be solved by the invention] By the way, cracks that occur in pipes such as BSTF material and brass pipes generally occur in the circumferential direction of the pipe and are small in volume, and are eddy current flaw detectors with high measurement accuracy. However, it is difficult to detect such cracks in the circumferential direction of the tube due to the induced current generated in the circumferential direction of the coil.

That is, as shown in FIG. 4, in the conventional probe 1 ′, the direction of the induced current in the coils 2 ′ a and 2 ′ b and the direction of the crack 11 in the metal tube are the same. The current does not change, so crack 11 will not be detected.

An object of the present invention is to provide a metal flaw detection probe that solves the above-mentioned conventional problems and has improved detection capability for linear defects in the circumferential direction of a metal tube.

[Means for Solving Problems] In order to achieve such an object, the metal flaw detection probe of the present invention comprises a probe main body and a test coil, and moves in the metal tube in the axial direction to cause defects in the metal tube. In a metal flaw detection probe that detects changes in the eddy current caused by the test coil, the test coil consists of a pair of coils wound in the same direction as the circumferential direction of the metal tube on the probe body, and a circle of the metal tube. It has a pair of coils that are skewed with respect to the circumferential direction and are wound 90 degrees apart from each other in the circumferential direction.

[Embodiment] Hereinafter, a metal flaw detection probe of the present invention will be described based on an embodiment shown in the drawings.

In FIG. 1A, a metal flaw detection probe 1 comprises a probe body 10 and a test coil 2 wound around the probe body 10.

The test coil 2 is composed of three pairs of coils 21, 22, and 23 on the probe body. The coil 21 is a metal tube 3
The test coils 22 and 23 are wound in the same direction as the circumferential direction of FIG. 9B, and are obliquely inclined with respect to the circumferential direction of the metal tube 3 and are wound at 90 ° offset from each other. ing.
As described above, the test coils 22 and 23 are wound obliquely with respect to the central axis of the probe main body and with winding directions different from each other.

Then, a high-frequency current from the oscillator flows through the coils 21, 22 and 23, and induced currents i ₁ , i ₂ and i ₃ are generated.

When the metal flaw detection probe 1 configured as described above is inserted and moved into the metal pipe 3 having defects such as corrosion A and cracks B ₁ and B ₂ as shown in FIG. A change in the eddy current generated in the metal tube 3 by A is detected as a change in the induced current i ₁ , i ₂ , i ₃ of each coil.

On the other hand, the crack B ₁ partially generated in the circumferential direction (0 ° direction) is parallel to the directions of the induced currents i ₁ and i ₃ of the coils 21 and 23 in this portion, and therefore the induced currents i ₁ and i _No change occurs in ₃ and is therefore not detected by coils 21 and 23.

However, since the induced current i ₂ of the coil 22 flows across the crack B _1, result in changes in the current through cracks B _1, B ₁ cracked by this change is detected. Similarly, the crack B ₁ and the crack B ₂ displaced by 90 ° in the circumferential direction are not detected by the coils 21 and 22, but are detected by the coil 23.

As described above, since the metal flaw detection probe of the present invention combines a plurality of coils having different defect detection capabilities, various flaws can be simultaneously detected by one flaw detection test.

It should be noted that in the above-mentioned embodiment, the test coil was parallel to the circumferential direction, and two kinds were obliquely used, but three kinds in total were used, but more various combinations are possible. It is applied to a phase analysis type metal flaw detector as shown in FIG.

The metal flaw detector shown in FIG. 2 mainly includes an oscillator 4, detection portions 51, 52 and 53 of the metal flaw detection probe 1, phase detectors 61a to 63b provided corresponding to the detection portions, and cathode ray tubes 71, 72 and 7.
3. The oscillator 4 sends a high frequency current to the detectors 51, 52 and 53 of the probe 1 and the phase detector.

Detectors 51, 52 and 53 are test coils 21, 22 and 23, respectively.
The probe 1 is configured as a whole with a bridge circuit configured to include. 1 on the output side of each detector 51, 52 and 53
A pair of phase detection circuits 61a, 61b, 62a, 62b and 63 respectively
Connected with a and 63b.

One set of phase detection circuits phase-detects the output signal of the corresponding detection section by two control signals having different phases, and the outputs from the one set of phase detection circuits are cathode ray tubes 71, 72 and 73.
It is displayed as a combined Lissajous waveform on the screen. This Lissajous waveform changes in response to the phase of the output signal of the detector changing due to a defect in the metal tube.

That is, the Lissajous waveform corresponding to the defect detected by the detection unit 51 is displayed on the cathode ray tube 71, and the detection unit 52 is detected on the cathode ray tube 72.
The Lissajous waveform corresponding to the defect detected in step (b) and the Lissajous waveform corresponding to the defect detected in the detector 53 are displayed on the cathode ray tube 73. For example, in the case of the metal flaw detection probe shown in FIG. 1 (a), it corresponds to the corrosion, crack (0 ° direction) B ₁ , and crack (90 ° direction) B ₂ of the metal tube 3 as shown in FIG. 1 (b). Then, a Lissajous waveform as shown in FIG. 3 can be obtained. Therefore, when the amplitude of the Lissajous waveform is [detection unit 51] = [detection unit 52] = [detection unit 53], there is a corrosion defect and [detection unit 52] or [detection unit 53]> [detection unit 51] Sometimes it can be determined that it is a cracking defect.

The arithmetic processing unit 8 obtains the phase angle by electrically reading the amplitude of the signal from each phase detector similar to that input to each cathode ray tube 71, 72 and 73 to obtain the circumferential angle cracks and other scratches. Discrimination and scratch depth are calculated using a CPU (central processing unit), and these are recorded by the recorder 7.

[Effects of the Invention] As is apparent from the above embodiments, the metal flaw detection probe of the present invention comprises a probe body and a test coil,
In a metal flaw detection probe that moves in the metal tube in the axial direction and detects changes in the eddy current caused by defects in the metal tube, the test coil is placed on the probe body in the same direction as the circumferential direction of the metal tube. By arranging a pair of wound coils, and a pair of coils wound obliquely with respect to the circumferential direction of the metal tube and being displaced from each other by 90 ° in the circumferential direction,
Simultaneous detection of linear defects such as minute cracks in the circumferential direction of metal pipes and other defects such as internal corrosion by a single flaw detection test,
Can be evaluated.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) and 1 (b) are diagrams showing a metal flaw detection probe and a metal tube of the present invention, and FIG. 2 is a block diagram of an eddy current flaw detection device,
FIG. 3 is a Lissajous waveform diagram, and FIG. 4 is a diagram showing a conventional metal flaw detection probe. 3 …… Metal tube A, B ₁ , B ₂ … Metal tube defect 1 …… Metal flaw detection probe 2 …… Test coil 10 …… Probe body 21 …… Wound in the same direction as the circumferential direction of the metal tube A pair of coils 22 and 23 ... A pair of coils that are skewed with respect to the circumferential direction of the metal tube and are wound 90 ° apart from each other in the circumferential direction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 61-264252 (JP, A) JP-A 59-200956 (JP, A) JP-A 63-275951 (JP, A) JP-A 62- 240852 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A probe body (10) and a test coil (2)
And a probe for metal flaw detection (A) which moves in the metal tube (3) in the axial direction and detects a change in eddy current caused by defects (A, B ₁ , B ₂ ) of the metal tube by the test coil ( 1)
In the above, the test coil is a pair of coils (21) wound on the probe body in the same direction as the circumferential direction of the metal tube, and obliquely with respect to the circumferential direction of the metal tube. A pair of coils (22,
23) A probe for metal flaw detection, characterized in that