JPH05322855A - Automatic eddy current flaw detector - Google Patents

Abstract

PURPOSE:To improve defect detection accuracy of a welding part by eliminating noise components. CONSTITUTION:The title detector is provided with a eddy current sensor 2 which performs eddy current flaw detection in a welding part 1 and an optical displacement meter 3 which detects uneven displacement in the bead of the welding part 1. The signal of the eddy current sensor 2 is digitized and is input to a controller 9. The signal of the optical displacement meter 3 is digitized and is input the controller 9. The controller 9 subtracts the signal of the optical displacement meter 3 from the signal of the eddy current sensor 2, thus eliminating noise components due to bead shape and detecting defects accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic eddy current flaw detector for detecting defects in a welded portion such as a low temperature tank membrane.

[0002]

2. Description of the Related Art As a method of detecting cracks or blowholes existing in a weld, a detection coil as an eddy current sensor, in which a ferrite core is wound and an alternating current is applied to the ferrite core, is attached to the surface of the weld. An eddy current flaw detection method is widely known in which, when brought close to each other, an eddy current generated in a welded portion changes due to cracks in the welded portion and the like, and impedance and voltage of a detection coil change to detect a defect.

It would be convenient if, for example, such a eddy current flaw detection method could be used to automatically detect defects in the welded portion of a low temperature tank membrane.

[0004]

However, in the case of a low temperature tank membrane that uses corrugated plates at the side and bottom to absorb the heat shrinkage due to the cold heat of the stored liquid, the defects of this corrugated weld are automatically detected. Therefore, it is difficult to detect defects in the welded part of the membrane tank automatically by using the eddy current flaw detection method. In reality, the fact is that it is not done manually.

From the above-mentioned circumstances, the eddy current flaw detection method is used to detect defects in a base metal part having a simple shape. However, since the welding bead exists as unevenness in the welded portion, the noise component due to the unevenness causes defects. It will be detected together with the signal. Therefore, conventionally, the noise component has been removed by the combination of the first and second frequencies by using the multiple frequency method. However, since the S / N ratio of the detection signal is limited, the detection accuracy is improved. However, there is also a problem that it takes time to select an appropriate frequency.

Therefore, the present invention makes it possible to accurately remove the noise component due to the welding bead to detect the defect in the welded portion with high accuracy, and to detect the defect in the corrugated welded portion such as the membrane tank. The present invention is intended to provide an automatic eddy current flaw detector that can automatically detect the above.

[0007]

In order to solve the above problems, the present invention provides an eddy current sensor for eddy current flaw detection of a welded portion, an optical displacement meter for detecting unevenness of a bead shape of the welded portion, And a controller configured to obtain a defect in which a noise component is removed by subtracting the detection signal from the optical displacement meter from the detection signal from the eddy current sensor.

Further, a touch roller is provided on one side of the movable carriage via a pressing device for applying a downward pressing force, and the touch roller and an eddy current sensor for eddy current flaw detection of a welded portion are welded to the touch roller. An optical displacement gauge for detecting the bead shape unevenness displacement of the part is supported, and the detection signal by the optical displacement gauge is subtracted from the detection signal by the eddy current sensor to obtain only the defect signal from which the noise component is removed. A controller is provided, and the controller is further provided with a function of quantitatively calculating the area of the Lissajous waveform and discriminating the defect based on the area value.

[0009]

[Function] The flaw detection signal detected by the eddy current sensor and the displacement signal detected by the optical displacement meter are put into the controller, and the displacement signal is subtracted from the flaw detection signal to remove the unevenness of the welding bead shape. A pure defect signal containing no noise component will be detected.

Further, when the eddy current sensor and the optical displacement gauge are mounted on the moving carriage to be used for detecting a defect in a corrugated welded portion such as a membrane of a low temperature tank, the touch roller is operated by the pressing device to operate the bottom plate. When the movable carriage is moved while being pressed against the eddy current sensor, the eddy current sensor and the optical displacement meter are moved along the welded portion. Further, the signals of the eddy current sensor and the optical displacement meter are calculated by the controller. At this time, since the Lissajous waveform is quantitatively calculated, the defect can be easily discriminated.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In order to detect a defect in the welded portion 1 between the plate materials 1a and 1b, an eddy current sensor 2 for eddy current flaw detection of the welded portion 1 and the welded portion 1 are shown.
The optical displacement gauge 3 for detecting the unevenness displacement due to the bead shape as a noise component is held by the holder 4 so as to be moved integrally therewith, and the flaw detection signal detected by the eddy current sensor 2 is detected. A flaw detection signal measuring device 5 for measuring the above, an A / D converter 6 for digitizing the measurement signal by the flaw detection signal measuring device 5, a displacement signal measuring device 7 for measuring the displacement signal detected by the displacement meter 3, A / D for digitizing the measurement signal by the displacement signal measuring device 7.
A converter 8 and a controller 9 such as a personal computer configured to subtract the signal of the A / D converter 8 from the signal of the A / D converter 6 to perform a calculation for removing a noise component from the flaw detection signal. Prepare

In order to detect defects in the welded portion 1, the holder 4
When the eddy current sensor 2 and the displacement gauge 3 held by the eddy current sensor 1 are moved integrally along the welded portion 1, the flaw detection signal detected by the eddy current sensor 2 is measured by the flaw detection signal measuring device 5, and then A
The signal is digitized by the / D converter 6 and input to the controller 9. On the other hand, at the same time, the bead-shaped displacement signal detected by the displacement meter 3 is measured by the displacement signal measuring device 7, then digitized by the A / D converter 8 and input to the controller 9 as well. .. In the controller 9, the signal of the A / D converter 8 is subtracted from the signal of the A / D converter 6.
That is, the signal digitized by the A / D converter 6 is a defect signal including a noise component of the welded portion 1 detected and processed by the eddy current sensor 2, while A / D
Since the signal digitized by the D converter 8 is the signal of the unevenness of the bead as the noise component detected and processed by the displacement meter 3, the controller 9 controls the noise from the defect signal including the noise component. By subtracting the components, only pure defect signals that are unaffected by the bead ruggedness displacement are detected. Therefore, the defect of the welded portion 1 can be detected with high accuracy.

Next, FIGS. 2 to 4 show another embodiment of the present invention. In a membrane tank using a corrugated plate for the bottom plate 10, defects in the corrugated welded portion 1 of the bottom plate 10 are automatically detected. An example in the case of being configured to be able to detect is shown.

An electric horizontal slider 13 which can be displaced in the left-right direction with respect to the traveling direction is installed on a movable carriage 12 which can travel along the guide rails 11, and one end of the horizontal slider 13 is provided. An electric vertical slider 14 that can be displaced in the vertical direction is continuously provided, and a substrate 15 is fixedly mounted on the vertical slider 14 and the substrate 1
A touch roller 16 for abuttingly disposing on the bottom plate 10 is attached to a lower end portion of the shaft 5 by a shaft 18 via a support frame 17 so as to be swingable in the traveling direction of the carriage, and the vertical slider 14 is pressed downward. Functioning as the touch roller 16 when the moving carriage 12 is traveling.
The corrugated shape of 0 is adapted to be rolled, and the support frame 17 of the touch roller 16 is
A holding frame 4 holding an eddy current sensor 2 and an optical displacement meter 3 is integrally supported, and the eddy current sensor 2 and the optical displacement meter 3 are attached to the welded portion 1 as the touch roller 16 moves. It should be possible to imitate the robot while maintaining a certain interval.

As shown in FIG. 1, the moving carriage 12 is provided with measuring devices 5, 7, A / D converters 6, 8 and a controller 9, and further the above controller. 9 is provided with a function for quantitatively calculating the area of the Lissajous waveform based on the digitally processed signal of the eddy current sensor 2 so that the defect can be discriminated.

When detecting a defect in the corrugated welded portion 1 of the bottom plate 10 in the membrane tank, first, the guide rail 11 is laid parallel to the lateral position of the welded portion 1 and the guide rail 11 is laid. Trolley 1 moving on 11
Place 2. Next, activate the horizontal slider 13,
The eddy current sensor 2 and the optical displacement meter 3 are located right above the welded portion 1, and the vertical slider 14 is operated to bring the touch roller 16 into contact with the bottom plate 10. In this case, the vertical slider 14 is set so as to function as a downward pressing device for the touch roller 16. At this time, at the position where the touch roller 16 is in contact with the bottom plate 10, a predetermined gap is formed between the eddy current sensor 2 and the optical displacement meter 3 and the welded portion 1.

In this state, when the movable carriage 12 is run along the guide rail 11, the movement of the movable carriage 12 causes the touch roller 16 to roll on the bottom plate 10, and further the vortex sensor 2 and the optical displacement. The total 3 is also moved integrally with the touch roller 16. At this time, the moving carriage 12 moves horizontally on the guide rails 11, whereas the touch roller 16 moves on the corrugated bottom plate 10. However, the support frame 17 of the touch roller 16 moves to the vertical slider 14. The fixed substrate 15
Since the shaft 18 is swingably supported at the lower end of the touch roller 16 and a downward pressing force is always applied by the vertical slider 14, the touch roller 16 is changed from the two-dot chain line state to the solid line state in FIG. It is possible to move stably by freely following the corrugated shape of the bottom plate 10. Therefore, the eddy current sensor 2 and the optical displacement meter 3
4 is also integrally displaced from the state of the chain double-dashed line to the state of the solid line in FIG. ..

In the above, the defect of the welded portion is detected in a state where the noise component, which is the uneven displacement of the weld bead, is removed in the same manner as in the embodiment shown in FIG. Since the controller 9 is provided with a function of quantitatively calculating the area of the Lissajous waveform and discriminating the defect, it is possible to accurately detect the depth of the crack or the like.
That is, in the past, when a defect was discriminated, the amplitude wave and the Lissajous waveform by the eddy current sensor were relied on based on the experience and intuition of the operator's visual observation, but there were variations in visual observation and individual differences in determination. In that respect, in the present invention, the Lissajous waveform is quantitatively calculated by the controller 9 such as a personal computer.
As shown in the Lissajous waveform inside of FIG. 5, or in the case of a large defect, it can be calculated as an area like the Lissajous waveform outside of FIG. 5, and the defect can be discriminated without causing individual differences or visual variations. There is an advantage that can be done.

In the above-described embodiments shown in FIGS. 2 to 4, a case in which the moving carriage 12 is made to travel along the guide rails 11 has been shown, but it is also possible to make it run by the drive wheels. , The touch roller 16 to the bottom plate 10
A pressing spring mechanism or the like may be adopted instead of the vertical slider 14 as the pressing device to be pressed upward.
Needless to say, various changes can be made without departing from the scope of the present invention.

[0021]

As described above, according to the automatic eddy current flaw detector of the present invention, the eddy current sensor equipped with the eddy current sensor for eddy current flaw detection of the welded portion and the optical displacement gauge for detecting the unevenness of the bead of the welded portion are provided. Since it is equipped with a controller that finds a defect in which noise components are removed by subtracting the detection signal from the optical displacement meter from the detection signal from the sensor, it is possible to accurately detect a pure defect that is not affected by the uneven displacement of the welding bead. Can be detected.

Further, since the movable carriage is provided with a touch roller so that a downward pressing force is applied by the pressing device, and the eddy current sensor and the optical displacement meter are supported on the touch roller, the bottom plate is attached to the bottom plate. When detecting defects in corrugated welds such as membrane tanks that use corrugated plates, the eddy current sensor and optical displacement gauge can be made to follow the weld through the movement of the touch roller, and defect detection work can be performed. Can be automatically performed, and further, since the controller is provided with the function of quantitatively calculating the area of the Lissajous waveform, the defect can be easily identified.
It exhibits excellent effects such as.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an automatic eddy current flaw detector according to the present invention.

FIG. 2 is a schematic view showing another embodiment of the present invention.

FIG. 3 is an enlarged view in the direction of arrow III in FIG.

FIG. 4 is an enlarged arrow view in the IV direction of FIG.

FIG. 5 is a diagram showing an example of a Lissajous waveform.

[Explanation of symbols]

 1 Welded part 2 Eddy current sensor 3 Optical displacement gauge 12 Moving carriage 14 Vertical slider (pressing device) 16 Touch roller

Front page continuation (72) Inventor Atsushi Kubota 5-13-4 Taishi-do, Setagaya-ku, Tokyo (72) Inventor Eiichi Ikeura 1-272 4978-2 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture (72) Shinichi Kawahara 1-4-38 Wakaba-cho, Chofu-shi, Tokyo

Claims (2)

[Claims] 1. An eddy current sensor for eddy current flaw detection of a welded portion, an optical displacement meter for detecting unevenness of a bead shape of a welded portion, and a detection signal by an optical displacement gauge is subtracted from a detection signal for the eddy current sensor. An automatic eddy current flaw detector having a configuration including a controller configured to obtain a defect from which a noise component has been removed. 2. A touch roller is provided on one side of a movable carriage via a pressing device that applies a downward pressing force, and the touch roller is welded with an eddy current sensor for eddy current flaw detection of a welded portion. An optical displacement gauge for detecting the bead shape unevenness displacement of the part is supported, and the detection signal by the optical displacement gauge is subtracted from the detection signal by the eddy current sensor to obtain only the defect signal from which the noise component is removed. An automatic eddy current flaw detector having a controller provided with a function of quantitatively calculating an area of a Lissajous waveform and discriminating a defect based on the area value.