JPH02269960A - Probe for flaw detection - Google Patents

Abstract

PURPOSE:To detect a defect over a wide range without any irregularity in sensitivity by making 1st and 2nd coils which are wound annularly cross each other at a specific angle, and matching the 1/2 angle line of this angle with the lengthwise direction of a conductor-made tube. CONSTITUTION:The probe P for flaw detection is constituted by making the 1st coil 2 wound in an elliptic shape and the 2nd coil 3 formed in the same shape cross each other at right angles while having their diameter axes in common. The the probe P is fixed to a nonmetallic holder and run as shown by an arrow K while a 45 deg. line which is a half as large as the angle of intersection of the coils 2 and 3 is matched with the lengthwise direction of the tube 1, and the probe P is excited to generate a vortex flow in the tube 1 with magnetic force lines B. Consequently, if there is a defect J having an angle to the lengthwise direction of the tube 1, the coil 2 parallel to the defect J hardly detects the defect, but the winding of the coil 3 crosses the defect J almost at right angles and detects it with sufficient sensitivity. Then the coils compensate their characteristics mutually to detect any kind of defect in the tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flaw detection probe, and particularly to a probe of the type that detects the presence or absence of flaws in a tube by changing coil impedance.

[Conventional technology]

As a flaw detection probe for detecting flaws in metal tubes (hereinafter referred to as defects), a test coil with a high-frequency current flowing through it is inserted and moved inside the metal tube, and the eddy current that changes due to the defect existing in the metal tube is electrically detected. There are known devices designed to detect the

Changes in this eddy current can be detected as changes in the impedance of the coil, but since the changes are extremely small, they are amplified and then F■ (frequency/potential) converted and displayed. From this single data, it is now possible to judge the shape and depth of the flaw and evaluate the defect.

Separately, from the phase of the obtained high-frequency signal, it is possible to detect whether a defect in a metal tube is on the inner surface or the outer surface, and how deep the defect is. There is one described in Japanese Patent Application No. 57-185696.

By the way, cracks that occur in brass tubes made of BSTF materials generally occur in the circumferential direction of the tube, and are often small in volume. This type of defect is difficult to detect. That is, as shown in FIG. 6, in the conventional probe, the coils 91 and 92 are wound so as to match the direction of the crack 93 in the metal tube, so the lines of magnetic force B are in the direction of the arrow and are generated in the circumferential direction of the tube. The change in the eddy current G due to the crack 93 is slight, and the crack 93 cannot be detected.

To solve this problem, the applicant proposed a probe in which the winding direction of the coil is oblique to the circumferential direction of the pipe, thereby increasing the sensitivity to cracks that occur in the circumferential direction of the pipe. This made possible a significant improvement.

[Problem to be solved by the invention]

By the way, the method proposed by the applicant is to insert two coils wound in an elliptical shape sequentially into a tube in parallel, and to display the phase difference between the two as a Lissajous while each coil is excited. .

In this type of probe, it is unavoidable that sensitivity directionality occurs depending on the winding direction. Therefore, it is extremely difficult to obtain the same sensitivity to defects of all types (directions).

When considered from this point of view, simply arranging two coils in parallel cannot complement the characteristics of these coils, resulting in a low-sensitivity portion.

The present invention has been made in view of the above-mentioned problems, and its technical object is to provide a flaw detection probe that can detect defects over a wide range with high sensitivity.

[Means to solve the problem]

In order to solve the above technical problem, the present invention provides a flaw detection probe for detecting the presence or absence of flaws in a conductor tube by inserting a coil into the conductor tube 1 and detecting a change in coil impedance. The structure was as follows.

That is, a first coil 2 wound in an annular shape and a second coil 3 formed in the same shape as the first coil 2 are fixed so that their diameter axes are common and intersect with each other at a predetermined angle.

Then, the 1/2 angle line of this angle was made to coincide with the longitudinal direction line of the conductor tube 1.

[Effect]

A first coil 2 wound in an annular shape and a second coil 3 formed in the same shape as the first coil 2 are fixed with their diameter axes common and intersecting at a predetermined angle. This is detected by coils that have mutually different directivities for one defect. Then, by making the 1/2 angle line of this angle coincide with the longitudinal direction line of the conductor tube 1, the sensitivity becomes linearly symmetrical and the sensitivity is balanced. As a result, defects can be detected over a wide range with uniform sensitivity.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 1 to 5.

This flaw detection probe P is inserted into the inside of the conductor tube 1 to detect the presence or absence of flaws in the conductor tube 1 by detecting a change in coil impedance. This flaw detection probe P is composed of a first coil 2 wound in an elliptical shape and a second coil 3 formed in the same shape as the first coil 2, which are crossed at right angles with each other having a common diameter axis. There is.

The flaw detection probe P having the above structure is fixed to a non-metallic holder (not shown), and can be moved in the direction indicated by the arrow in the conductor pipe I by external operation. .

Furthermore, as shown in FIG.
A 45° line, which is 1/2 of the intersecting angle (right angle) with the coil 3, is aligned with the longitudinal direction line of the body tube 1.

FIG. 5 shows a block diagram of a circuit for processing signals from the flaw detection probe P, in which each coil 2.3 is excited by an oscillator 20. The phases of the output signals from these coils 2.3 are detected by phase detectors 21.21, and the XY
The phase difference is displayed on the display unit 22 as a Lissajous pattern. This phase difference signal is also input to the arithmetic processing section 723 to calculate the comprehensive defect state, and then the contents are recorded on the recorder 24.

The operation will be explained below.

First, when the flaw detection probe P is excited by the oscillator 20, magnetic lines of force B are generated as shown in the figure. As a result, a vortex is generated in the conductor tube 1. This eddy current does not change as long as the conductor pipe is uniform, but due to variations in the wall thickness of the pipe or defects
It changes depending on.

This variation is detected as a change in impedance of the coil, and the abnormality can be detected by detecting the phase difference between both coils.

As shown in Fig. 4, if there is a defect J with a certain angle to the longitudinal direction of the conductor tube I, this defect J
This is difficult to detect due to the eddy current of the first coil 2, which has a winding parallel to Since the winding and the defect J are substantially orthogonal to each other, this can be detected with sufficient sensitivity. In this way, each coil has its unique characteristics that complement each other, so that all types of defects can be detected over the entire circumference of the conductor tube 1.

Note that the angle between the first coil 2 and the second coil 3 may be appropriately set depending on the object to be inspected.

Of course, it is not limited.

〔Effect of the invention〕

According to the present invention, the first coil 2 wound in an annular shape and the second coil 3 formed in the same shape as the first coil 2 are fixed with their diameter axes common and intersecting at a predetermined angle. Therefore, defects in the conductor tube 1 can be detected using coils with mutually different directivities.

By making the 1/2 angle line of this angle coincide with the longitudinal line of the conductor tube l, the sensitivity becomes linearly symmetrical and the sensitivity can be balanced.

Therefore, defects can be detected over a wide range with uniform sensitivity.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention, in which FIG. 1 is a partially cutaway perspective view of a state where the conductor is attached to a pipe, FIG. 2 is a plan view, FIG. 3 is a side view, and FIG. Figure 4 is a diagram for explaining the principle of operation, Figure 5 is a block diagram of a circuit that processes signals from the flaw detection probe, and Figure 6 shows how a conventional flaw detection probe is used. , 2・
... 1st coil, 3... 2nd coil, P.
...Probe for flaw detection. Patent applicant: Mitsui Petrochemical Industries, Ltd. China X-ray Co., Ltd. Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) In a flaw detection probe for detecting the presence or absence of flaws in the conductor tube 1 by inserting a coil into the conductor tube 1 and detecting changes in coil impedance, the first A coil 2 and a second coil 3 formed in the same shape as the first coil 2 are fixed so that they intersect with each other at a predetermined angle, with their diameter axes common to each other, and a 1/2 angle line of this angle is connected to the conductor pipe 1. A flaw detection probe characterized by being aligned with the longitudinal direction of the probe.