JP2933778B2 - Ultrasonic flaw detection method for insulator tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for ultrasonically inspecting an insulator tube having a rotationally symmetrical cap on its outer peripheral surface for defects from the inner surface of the insulator tube.

[0002]

2. Description of the Related Art An ultrasonic flaw detection method has conventionally been used for inspecting the presence or absence of a defect inside an insulator tube. However, since the porcelain tube has a large number of shades on the outer peripheral surface, the ultrasonic waves transmitted from the probe are reflected by these shades to form shade echoes, and as shown in FIG. Mixing is inevitable. For this reason, a skilled worker conventionally distinguishes a shade echo from a defect echo based on experience. However, this method causes variation in quality judgment by the worker.

[0003] Further, with the improvement of reliability required for the insulator tube, it is required to perform ultrasonic flaw detection from the inner surface of the insulator tube. However, for this purpose, it is necessary for an operator to enter the inside of the insulator tube or to operate the probe with his / her arm in accordance with the diameter of the insulator tube, and the workability and inspection accuracy are low.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and it is an object of the present invention to accurately and efficiently detect the presence or absence of a defect of an insulator having a cap on the outer peripheral surface from the inner surface of the insulator. It has been completed in order to provide an ultrasonic flaw detection method for an insulator tube that can be used.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to set a rotary shaft having an arm provided with a probe to be crimped on the inner surface of an insulator tube on the center axis of the insulator tube. Ultrasonic inspection is performed while giving relative rotation and axial displacement between the rotating shaft and the insulator tube, and the inspection waveform thus obtained is equally divided into a number of sections along the time axis. The waveform is converted into a waveform peak-held at the maximum value for each section, and the presence or absence of a defect is determined based on the difference between the flaw detection waveforms at two adjacent positions on substantially the same circumference.

[0006]

According to the present invention, the probe at the tip of the arm of the rotary shaft is provided while the relative rotation and the axial displacement are applied between the rotary shaft and the rotary shaft set on the central axis of the hollow tube. Ultrasonic flaw detection is performed by pressure bonding to the inner surface of the. In this case, since the cap of the insulator tube is formed to be rotationally symmetric, if the above-described displacement speed in the axial direction is set to be smaller than the rotation speed, the probe will move on substantially the same circumference of the insulator tube. It is possible to move and obtain a flaw detection waveform on substantially the same circumference. Therefore, if the flaw detection waveform is equally divided into a number of sections along the time axis and converted into a waveform peak-held at the maximum value for each section, and the difference between the flaw detection waveforms at two adjacent positions is obtained, Should appear similarly in the flaw detection waveforms at two adjacent positions, so that the influence of the shade is canceled and only the change in the flaw detection waveform due to the defect can be extracted.
Therefore, according to the method of the present invention, ultrasonic flaw detection from the inner surface of the insulator tube becomes possible without being affected by the shade.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the illustrated embodiments. FIGS. 1 and 2 show a first embodiment of the present invention. An insulator tube 1 provided with a number of rotationally symmetrical caps 2 on the outer peripheral surface is hung horizontally by two ropes 3. . One of these ropes 3 is driven by a powered pulley 4 and the other rope 3 is supported by a free pulley 5 so that the porcelain tube 1 can be rotated around its central axis.

Reference numeral 6 denotes a rotating shaft set on the central axis of the above-mentioned insulator tube 1, and N rotating shafts (N = 1, 2,.
3) are provided. In the embodiment, N =
3 and three arms 7 are provided. A probe 8 that is crimped to the inner surface of the insulator tube 1 is attached to the tip of each arm 7. For the sake of explanation, three probes 8 have A,
The symbols of B and C shall be attached. Since the rotating shaft 6 of the embodiment is threaded and screwed with the base of each arm 7, the probe 8 is moved together with each arm 7 in the axial direction of the insulator tube 1 by rotating the rotating shaft 6. Can be moved.

The probe 8 is a commercially available oblique probe, and is driven by a trigger clock of, for example, 63 Hz, and is operated by a channel selector 9 for each of the trigger clocks A, B, C as shown in FIG. The flaw detection waveform from the probe 8 is sequentially taken into the arithmetic unit. Next, the ultrasonic flaw detection step of the present invention will be described with reference to FIGS.

First, the rotating shaft 6 is rotated while rotating the porcelain tube 1 as described above, and each probe 8 is moved in a gentle spiral shape along the inner surface of the porcelain tube 1. But insulator 1
Since the moving speed of the probe 8 in the axial direction is smaller than the rotation speed, each probe 8 can be regarded as moving on substantially the same circumference of the insulator tube 1.

As shown in the flowchart of FIG. 4, first, t _i , which means the number of the trigger clock, is set to one.
Then, the acquisition of the flaw detection waveform from the probe 8 of A corresponding to t _i = 1 is started. In this case, equally divided into N intervals along the flaw waveform between the trigger clock in the time axis, to the peak hold the maximum value of the waveform in the interval for each interval N _i which is divided, the lower part of FIG. 3 Convert to the waveform shown. When the conversion is completed for the N sections, the data corresponding to the conversion is transferred to the memory. The memory has a capacity capable of storing waveforms corresponding to a multiple of 3, and here, for simplification of description, a memory (T = 6) capable of storing six waveforms of t _i = 1 to 6 is used. Shall be.

After the flaw detection waveform from the A probe 8 corresponding to t _i = 1 is converted and transferred to the memory as described above, then the B probe 8 corresponding to t _i = 2 is transferred from the A probe 8 to the memory. Is converted in the same manner and transferred to the memory. Furthermore, t _i = 3
Is transferred to the memory, and similarly, the second, A, B, and C flaw detection waveforms corresponding to t _i = 4, 5, and 6 are transferred to the memory. I do. In FIG. 3, A
Only the flaw detection waveform from the probe 8 is shown, but actually different flaw detection waveforms may also be generated from the B and C probes 8. In this way, when t _i = 6, the difference between the flaw detection waveforms at two adjacent positions on substantially the same circumference (that is, obtained from the same probe 8) is calculated.

First, it is assumed that t _i = 1, and in the embodiment, the waveform of A at t _i = 1 and the waveform of A at t _i = 4 are compared. Comparison was carried out by a method for determining the difference between the peak hold value of each section N _i, determines absolute value of the presence or absence of a defect on whether exceeds the threshold alpha. As described above, since the influence of the shade 2 is rotationally symmetrical shape should appear similar to the flaw waveform 2 position adjacent on the same circumference, t _i = 1 of A
By calculating the difference between the waveform of A and the waveform of A at t _i = 4, the influence of the shade 2 is canceled, and only the change in the waveform due to the defect can be extracted. If a defect is detected, a failure signal is generated. If no defect is detected, t _i =
2, and a comparison is made between the waveform of B at t _i = 2 and the waveform of B at t _i = 5. Thus, the waveform of C at t _i = 3 and t _i
One cycle is completed by comparing with the waveform of C = 6, and the same calculation is repeated thereafter.

As described above, in the first embodiment, flaw detection waveforms obtained from the probes 8 of the three arms 7 provided on the rotary shaft 6 are sequentially taken in, and the flaw detection waveforms at two adjacent positions are obtained. By sequentially calculating the difference between the flaw detection waveforms, ultrasonic flaw detection at three cross-sectional positions can be performed in parallel. In the above embodiment, the waveform at t _i = 1 and the waveform at t _i = 4 immediately adjacent thereto were compared. However, in actuality, the capacity of the memory was increased, and the flaw detection waveforms at two positions a little further apart were measured. It is preferable to calculate the difference.

Next, FIGS. 5 and 6 show a second embodiment of the present invention. In the second embodiment, the probe 8 is rotated along the inner surface of the insulator tube 1 by fixing the insulator tube 1 and rotating the rotary shaft 6 set on the center axis thereof. In this case, in order to prevent a cable for extracting a signal from the probe 8 from being twisted, it is necessary to perform ultrasonic flaw detection while alternately reversing the rotation direction in a clockwise direction and a counterclockwise direction. If the same probe is used to detect flaws on the same circumference as in the embodiment,
The rotation angle may be set to 120 °, and the twist of the cable is reduced. Also in the second embodiment, three probes 8 are A, B,
In the case of C, it is possible to perform the calculation in the same manner as described in the first embodiment and extract only the waveform change due to the defect.

[0016]

As described above, according to the ultrasonic flaw detection method for an insulator tube of the present invention, the presence or absence of a defect of the insulator tube having a shade on the outer peripheral surface can be accurately determined from the inner surface of the insulator tube without being affected by the shade. Ultrasonic flaw detection can be performed efficiently and efficiently, and it is particularly suitable for inspecting the presence or absence of internal defects in a large insulator tube for transmitting ultra-high voltage. Therefore, the present invention, as an ultrasonic flaw detection method for insulator tubes, which solves the conventional problems, greatly contributes to industrial development.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first embodiment of the present invention.

FIG. 2 is a side view illustrating the first embodiment of the present invention.

FIG. 3 is a graph showing a flaw detection waveform of each flaw detector.

FIG. 4 is a flowchart illustrating a procedure of waveform processing according to the present invention.

FIG. 5 is a sectional view illustrating a second embodiment of the present invention.

FIG. 6 is a side view illustrating a second embodiment of the present invention.

FIG. 7 is a waveform diagram when an insulator tube is inspected by a conventional ultrasonic inspection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulator pipe 2 Cap 6 Rotary shaft 7 Arm 8 Probe

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 29/00-29/28

Claims (1)

(57) [Claims] 1. A rotary shaft having an arm provided with a probe crimped on the inner surface of a porcelain tube is set on a central axis of the porcelain tube, and a relative rotation and an axial direction between the rotary shaft and the porcelain tube are set. Ultrasonic flaw detection is performed while applying a displacement, and the flaw detection waveform obtained in this manner is equally divided into a number of sections along the time axis, and converted into a waveform peak-held at a maximum value for each section, and is then substantially converted. Close two on the same circumference
An ultrasonic flaw detection method for a porcelain pipe, wherein the presence or absence of a defect is determined based on a difference in flaw detection waveform at a position.