JPH0336166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a method for detecting internal corrosion of a pipeline using an ultrasonic exploration method.

[Technical background of the invention and its problems]

Conventionally, there is a device described in Japanese Utility Model Application Publication No. 117359/1983 as a device for detecting the corrosion state of the inner surface of a pipeline. The detection method using this device is
As shown in Fig. 4, an ultrasonic probe 2 moving inside the pipeline 1 transmits ultrasonic waves to the surface of the pipe body of the pipeline 1, receives surface echoes, and determines the inner surface based on the amount of change in the position of the surface echoes. It detects the state of corrosion.

FIG. 5 is an A-scope view of a healthy part indicated by reference numeral 3 in FIG. 4, and FIG. 5 is an A-scope view of a corroded part indicated by reference numeral 4 in FIG. That is, in the conventional detection method, the position (propagation time) T1 of the surface echo S1 of the healthy part 3 and the position T2 (propagation time) of the surface echo S2 of the corroded part 4 are determined using a commercially available ultrasonic thickness meter, and T1 The internal corrosion state of the pipeline 1 is detected from the amount of change t between T2 and T2.

By the way, when sludge 5 is stored in the corroded part 4 as shown in FIG. 6, as is clear from the A scope diagram shown in FIG. S3 is received by probe 2. On the other hand, since the ultrasonic thickness gauge is designed to detect the position of the first surface echo when there are multiple surface echoes exceeding the threshold level, in FIG. If it is above the threshold level, the surface echo S of the corroded area should be measured.
The position T3 of the sludge surface echo S3, which is smaller than the position T2 of No. 2 by t', is measured, and it is determined that the depth of the corroded part is shallow by the value corresponding to t'.

FIG. 8 is a diagram showing the relationship between the angle θ between the center line of the probe 2 shown in FIG. 9 and the normal to the flat steel plate 6, and the height of the steel plate surface echo S. As shown in FIG. 8, the height of the surface echo S gradually decreases as the surface of the steel plate 6 that is exposed to the ultrasonic wave tilts. On the other hand, the bottom surface of the corroded part 4 usually has unevenness, and the ultrasonic waves are scattered by the unevenness of the bottom surface, so the height of the corroded part surface echo S2 is equal to the height of the flat part of the surface, that is, the height of the healthy part surface echo S1. It is several 10dB lower than that. This corroded part surface echo S2
The degree to which the height decreases depends on the surface properties of the corroded portion 4. Now, measure the depth of the corroded part 4 which has a surface texture that gives the same surface echo height as if the angle θ between the center line of the probe 2 and the normal line of the steel plate 6 was 10 degrees. As is clear from Fig. 8, in order to
It is necessary to set it 40dB lower.

On the other hand, FIG. 10 shows the corroded part surface echo S when the thickness d of the sludge 5 is changed in the corroded part 4 where the sludge 5 is stored and the surface is relatively flat.
2 is a diagram showing the relationship between the heights of the sludge surface echo S3 and the sludge surface echo S3. In this case, the probe 2 faces perpendicularly to the surface of the pipeline 1. As shown in FIG. 10, as the thickness d of the sludge 5 increases, the height of the corroded surface echo S2 gradually decreases, and d=
The height is approximately 16 mm, which is equal to the height of the sludge surface echo S3. Moreover, the height is about 30 dB lower than in the case where there is no sludge 5, that is, the surface is relatively flat, compared to the case where it is almost the same as the healthy part 3.

Therefore, in the conventional internal corrosion detection device, by lowering the threshold level to, for example, 40 dB, it is possible to detect the state of the corroded portion 4 where the sludge 5 has accumulated up to a thickness d of about 20 mm. However, the height of the sludge surface echo S3 is approximately 30 dB higher than the height of the surface echo S1 of the healthy part 3.
Since it is only low, there is a risk that the position T3 of the sludge surface echo S3 will be measured incorrectly. In this case, as described above, the state of the corroded portion 4 will be measured to be shallower than the actual depth.

As described above, in the conventional method for detecting corrosion inside a pipeline, the state of the corroded portion 4 where the flange 5 is stored cannot be detected with high accuracy.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for detecting corrosion inside a pipeline, which is capable of detecting with high precision the state of a corroded part where sludge is stored.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by the following configuration. That is, the present invention is characterized in that, among a plurality of surface echoes obtained by ultrasonic exploration, the amount of change in position of the surface echo with the highest level is determined, and the state of internal corrosion of the pipeline is detected from this amount of change in position.

[Embodiments of the invention]

Figures 1a, b, and c are diagrams for explaining one embodiment of the present invention, in which figure a is an A scope view of a healthy part 3, and figure b is an A scope view of a corroded part 4a without sludge.
This is a scope view, and FIG. In the figures a to c, the threshold level is set to the L line, which is 40 dB lower than the H line, which corresponds to the height of the healthy part surface echo S1. By doing this, the surface echo S2 in the corroded area 4a without sludge can be detected as shown in FIG. can.

On the other hand, as shown in Figure c, the height of the sludge surface echo S3 in the corroded part 4b where the sludge is
Corresponds to the M line, which is 30bB lower than the H line. in this case,
As shown in FIG. 10, if the thickness d of the sludge is 16 mm or less, the corroded part surface echo S2 is higher than the sludge surface echo S3. Therefore, by detecting the position of the surface echo with the maximum level among the plurality of surface echoes having a threshold level or higher, it is possible to measure the depth of the corroded portion 4b in which the sludge 5 having a predetermined thickness or less is stored.

FIG. 2 is a block diagram showing an example of the configuration of an electronic circuit for realizing the above embodiment, and FIG. 3 is a signal waveform diagram of each part in FIG. 2. In FIG. 2, a video waveform corresponding to the A scope view in the ultrasonic survey shown in FIG. 3A is applied to the terminal 11. This video waveform is supplied to gate circuits 12 and 13. A signal input terminal of the gate circuit 12 is supplied with a constant frequency pulse shown in FIG. 3B generated by a clock pulse generator 14. As shown in FIG.
It is designed to turn on at the rising edge of the transmission pulse p in Figure A). Therefore, the gate circuit 12 outputs a pulse signal as shown in FIG. 3D to the pulse counter 15. In the counter 15, the pulse signal (FIG. 3D) is counted, and the pulse count output is supplied to the gate circuit 16.

On the other hand, in the gate circuit 13, a waveform as shown in FIG. 3E is extracted from the video waveform (FIG. 3A) during a predetermined period starting from a point in time when a predetermined time has elapsed from the transmission pulse p. The signal is output to the comparator 17 of No. 1. In the first comparator 17, a voltage below a predetermined threshold level (shown by the dashed line in FIG. 3E) is cut off, and a signal as shown in FIG. 3F is output. The output of the first comparator 17 (FIG. 3F) passes through the peak picker 18 to extract the peak voltage shown in FIG. It has become a matter of supply. The output of the first comparator 17 (FIG. 3F) is directly supplied to the other input terminal of the second comparator 19, and the second comparator 19 generates the waveform shown in FIG. 3G. The voltage is compared with the voltage of the waveform shown in FIG. 3F, and if the two voltages are equal or the voltage of the waveform shown in FIG. 3F is larger, the gate circuit 16 is turned on. If the voltage of the waveform shown in Fig. 3G is larger,
The gate circuit 16 is turned off. In this way, the gate circuit 16 is turned ON/OFF as shown in FIG. 3H, and as a result, the memory 2
0 stores the pulse count output as shown in FIG.

Using the electronic circuit configured in this manner, the time from the transmission pulse p to the surface echo S2 with the maximum height among the plurality of surface echoes exceeding the threshold level can be determined. Therefore, it is possible to accurately measure not only the condition of the corroded area 4a without flutters as shown in FIG. 4, but also the condition of the corroded area 4b where sludge 5 is accumulated as shown in FIG. can.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, the amount of change in position of the highest level surface echo among a plurality of surface echoes obtained by ultrasonic exploration is determined, and the state of internal corrosion of the pipeline is detected from this amount of change in position. As a result, it is possible to provide a method for detecting corrosion inside a pipeline, which is capable of measuring with high precision the state of a corroded part where sludge is stored.

[Brief explanation of drawings]

FIGS. 1a, b, and c are diagrams for explaining one embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of an electronic circuit for realizing the same embodiment, and FIG. The signal waveform diagrams of each part in the figure, Figures 4 to 10 are diagrams for explaining the conventional example, and Figures 4 and 5 are diagrams for explaining the surface echo of a healthy part and the surface echo of a corroded part without sludge. Figures 6 and 7 are diagrams for explaining the surface echo in a corroded area with sludge, Figures 8 and 9 are diagrams for explaining the relationship of the surface echo to the inclination of the steel plate, and Figure 10 is a diagram for explaining the relationship between the surface echo and the inclination of the steel plate. The figure is a diagram for explaining the relationship between the corroded part surface echo and the sludge surface echo with respect to the sludge thickness. 1...Pipeline, 2...Ultrasonic probe, 3
...Healthy part, 4... Corroded part (4a... Corroded part without sludge, 4b... Corroded part with sludge), 5...
… Suratji.

Claims (1)

[Claims] 1. In a method of detecting the internal corrosion state of a pipeline by using an ultrasonic exploration method, the amount of change in the position of the surface echo with the highest level among multiple surface echoes obtained by ultrasonic exploration is determined, and from this amount of change in position, the amount of change in the position of the pipe is determined. A method for detecting internal corrosion of a pipeline, characterized in that the state of internal corrosion of the line is detected.