JPH02302662A - Automatic ultrasonic flaw detecting method for solid-core insulator - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of an inner defect by suppressing the height of forest-shaped echoes which are inevitably generated in solid-core insulators to a lower value. CONSTITUTION:Probes 3 are brought into contact with deflected positions which are deviated to the outside from the central axis of the insulator at both end surfaces of upper and lower parts of a solid-core insulator. The probes 3 are turned around the central axis of the insulator by one time. Thus the inside of the solid-core insulator 1 undergoes ultrasonic wave flaw detection. The contact positions of the probes 3 to both end surfaces of the upper and lower parts of the solid-core insulator 1 are made to be the deflected position which are deviated from the central axis of the insulator. In this way, the height of a forest-shaped echo can be made to be 1/2 or lower than the height when the contact positions of the probes 3 are made to be the position on the central axis of the insulator. For example, the probes 3 at both end surfaces 2 are alternately selected with a multiplexer 4 which is an electronic switching device, and the waveform of a flaw is outputted through an ultrasonic-wave flaw detector 5. The analog waveform outputted from the flaw detector 5 is digitized with an A/D converter 6. The signal is inputted into a computer 7 and processed with software. Only the waveform of the defect is detected.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an object having a large number of shades around a solid porcelain body such as a solid insulator or a long-stem insulator (hereinafter referred to as a solid insulator). This invention relates to an automatic ultrasonic flaw detection method for solid insulators, which is used to detect flaws in the interior of solid insulators.

(Prior Art) In general, both ends of the porcelain body of a solid insulator are cut off and polished to have smooth end faces after firing.

Therefore, in order to inspect the presence or absence of defects inside the porcelain of solid insulators, an ultrasonic flaw detection test is carried out by bringing the probes of an ultrasonic flaw detector into contact with both polished end faces of the solid insulators.

The directivity angle of such a probe can generally be determined by the following equation.

θ. ! -170×λ/2a (degrees) where θ. is the directivity angle of the probe, a is the radius of the probe, and λ is the wavelength of the ultrasonic wave.According to actual measurement data, the sound speed inside the solid insulator is 5900 m/sec, and the probe used The radius of the child is 10IIIM, the vibration frequency is 2゜0MH
2 is normal, so by substituting these values into the above equation, the directivity angle θ0 of the probe becomes approximately 10 degrees, which is illustrated in FIG. 4. The maximum diameter of solid insulators is 225-1
The total length is 1218 m, but the sound spread in this largest product is a circle with a diameter of 225 square meters, which is equal to the diameter of the body, at a distance of 638 cm from the end face, as shown in Figure 4. Therefore, if flaws are detected from the upper and lower end faces, the entire body of the porcelain can be covered as a defect detection range, so it is understood that the probe should be placed at the center of the end face of the insulator. Conventionally, solid insulators have been inspected for internal defects using such a method.

However, solid insulators have many caps on their bodies, so even if there are no internal defects, the flaw detection waveform obtained by the above flaw detection method will be a special waveform with forest echoes as shown in Figure 1. This is thought to be due to the echoes from each shade interfering with each other. In addition, if there is a defect inside, defect echoes F+, Pg,
F, occurs, so these defective echoes are automatically detected and determined to be defective, but only defective echoes whose height exceeds the forest echo can be detected; As the height of the echo increases, the defect echo is hidden, resulting in a problem of low internal defect detection accuracy.

(Intelligence B to be Solved by the Invention) An object of the present invention is to solve the above-mentioned conventional problems and reduce the height of forest echoes that inevitably occur in solid insulators, thereby reducing internal defects. An object of the present invention is to provide an automatic ultrasonic flaw detection method for solid insulators that greatly improves detection accuracy.

(Means for Solving the Problems) In order to solve the above problems, the present inventor conducted repeated tests on the occurrence of forest echoes in solid insulators, and as a result, the contact position of the probe was changed from the conventional one. Contrary to common sense, we have found that the height of the forest echo can be reduced by locating the insulator at an eccentric position away from the central axis.

The present invention was completed based on this knowledge, and consists of bringing a probe into contact with an eccentric position away from the center axis of the insulator on both the upper and lower end surfaces of a solid insulator, and moving the probe around the center axis of the insulator. This method is characterized by performing ultrasonic flaw detection on the inside of a solid insulator while rotating it once.

As described above, in the present invention, the contact position of the probe on both the upper and lower end surfaces of the solid insulator is set at an eccentric position away from the central axis of the insulator. Thereby, the height of the forest echo can be reduced to 1/2 or less of the height when the contact position of the probe is on the center axis of the insulator. However, when we investigated the appropriate amount of eccentricity using a sample that was known to have an internal defect in the center, we were able to detect 100% defect echoes at a position 10 cm from the insulator center axis; At this position, defective echoes could not be detected approximately once in five times.

Therefore, the eccentricity is 15 for solid insulators of normal size.
-Should be:

Furthermore, as shown in Figure 4, if the flaws are detected from both the upper and lower end surfaces of the solid insulator, the entire body will be within the detectable range, so it was thought that it would be possible to fix the position of the flaw detector, but the When observing defect echoes while rotating the tentacle around the insulator's central axis, the defect echoes sometimes disappeared at certain angles. This is thought to be because the echoes from each shade interfered with each other due to the bending of the solid/insulator in the axial direction, variations in the spacing between the shades, etc., and the defective echoes happened to disappear. Therefore, in the present invention, by performing ultrasonic flaw detection while rotating the probe once around the central axis of the insulator,
It is now possible to detect 100% of internal defects.

As described above, according to the present invention, the height of the forest echoes generated by the shade of solid insulators can be reduced to 1/2 or less of the conventional height, so that it is possible to detect defective echoes hidden in the forest echoes. This makes it possible to greatly improve the accuracy of detecting internal defects.

Next, preferred embodiments of the present invention will be shown.

(Example) As shown in Fig. 3, both upper and lower end surfaces (2) of a solid insulator (1) whose porcelain body has a diameter of 200 m and a total length of 1000 m,
The probes (3) and (3) are automatically brought into contact with each other at a position 5 degrees eccentric from the center axis of the insulator (2), and the vibration frequency is 2.0 while rotating 360 degrees around the center axis of the insulator. ?
An ultrasonic flaw detection test using IHz ultrasonic waves was conducted.

During the test, the multiplexer (4), which is an electronic switching device, switches the probe (3) on both end faces (2), (2),
(3) are selected alternately, and the flaw detection waveform is changed to the ultrasonic flaw detector (5
) was output through. Output ultrasonic flaw detector (5)
The analog waveform was digitized by the ^/D converter (6), taken into the computer (7), and subjected to software processing, and only defective waveforms were detected.

By the method of the present invention, 100
When we performed ultrasonic flaw detection on a solid book insulator, we were able to detect internal defects with 100% accuracy. On the other hand, when similar ultrasonic flaw detection was performed with the probe (3) fixed on the center axis of the insulator as in the conventional manner, the internal defect detection accuracy decreased to 87%.

(Effects of the Invention) As explained above, the present invention, in an automatic ultrasonic flaw detection test of solid insulators, places the probe at a position eccentric from the center axis of the insulator, and By rotating, the height of forest echoes was reduced, and the accuracy of detecting internal defects was successfully improved significantly. Therefore, the present invention contributes to the development of industry as an automatic ultrasonic flaw detection method for solid insulators suitable for detecting internal defects in solid insulators that produce forest-like echoes, such as solid SP insulators and long-stem insulators. However, it is extremely large.

[Brief explanation of drawings]

Figure 1 is an ultrasonic flaw detection waveform diagram of a solid insulator with no internal defects. Figure 2 is a defective echo F7, Fts during forest echo.
An ultrasonic flaw detection waveform diagram of a defective product containing PS, Figure 3 is a block diagram explaining the embodiment, and Figure 4 shows the relationship between the spread of sound waves inside solid insulators and the defect detectable range. FIG. (1): Solid insulator, (2): Both end faces, (3): Probe.

Claims (1)

[Claims] The probe (3) is brought into contact with the upper and lower end surfaces (2) of the solid insulator (1), at eccentric positions away from the insulator center axis (2), and the probe (3) is moved around the insulator center axis. An automatic ultrasonic flaw detection method for solid insulators characterized by ultrasonic flaw detection inside the solid insulator while rotating the solid insulator once.