JPH07333201A - Ultrasonic flaw detection of piping - Google Patents

Abstract

PURPOSE:To detect the vertical seam welded part of piping and other flaw with high accuracy by transmitting ultrasonic waves in a direction of a specific angle with respect to the advance direction of a pig by an ultrasonic probe. CONSTITUTION:The transmission direction of ultrasonic waves is set to + or -45 deg. or + or -135 deg. with respect to the advance direction of a pig. The ultrasonic waves transmitted from probes 10a, 10b, 10c,... transmit through the pipe wall or surface of piping or helically propage therethrough and the flaw detection of the whole surfaces of a matrix, a vertical seam welded part and a circumferential welded part is substantially performed accompanied by the advance of the pig and the detected flaw is measured by a measuring device and the state and position of the flaw are stored in a memory device. During a change period from a state I to a state II, the flaw 36 of the matrix is detected by the probe 10b and, in the state II, the flaw 37 in the vertical seam welded part is detected by the probe 10a. The flaw 38 of the circumferential welded part is detected by the probe 10a by the further advance of the pig.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method for continuously detecting corrosion defects, welding defects and the like of pipes using a pig.

[0002]

2. Description of the Related Art As an example of a conventional pig for detecting a defect in a welded portion of a pipe, there is a device disclosed in Japanese Utility Model Laid-Open No. 62-91254. This invention uses an ultrasonic surface wave probe for detecting the position of a welded portion in the circumferential direction of a pipe, a bevel probe for detecting defects on the inner surface of the pipe, and a pig for inspecting the inner surface of the pipe. The tentacles are arranged at a predetermined interval in the tube axis direction so that the welded portion can be continuously and accurately inspected.

Further, for example, as shown in Japanese Patent Laid-Open No. 5-11925, ultrasonic probes are symmetrically arranged on the surface of the pipe with the weld being the center, and the pipe is moved to remove defects in the weld. The two-probe method for detecting is also in practical use.

[0004]

[Problems to be Solved by the Invention]
Since the pig described in Japanese Patent Publication No. 4 transmits ultrasonic waves in a direction orthogonal to the circumferential welded portion, when detecting a defect in the circumferential welded portion or a pit-like corrosion defect in the base metal portion, defect detection is performed. The rate is proportional to the coverage of the flaw, so the pig should be equipped with as many transducers as possible.

For example, when flaw detection is performed on the circumferential welded portion of a 600 A steel pipe, if the flaw detection effective width of the probe is 20 mm,
It is necessary to equip a pig with about 95 transducers for full-line flaw detection. Therefore, depending on the size of the pig, it may be necessary to equip the probe with two, three, or staggered patterns. In reality, it was difficult to meet the requirement of 100% coverage. In principle, it was impossible to detect flaws in the vertical seam welded portion by such a pig.

Further, in the above-mentioned pig, since echoes from the extra portion of the welded portion become noise and deteriorate the detection accuracy, it is necessary to specially provide means for removing noise from the extra echo. There was a problem.

Further, according to the two-probe method disclosed in Japanese Patent Laid-Open No. 5-119025, the above problem can be solved.
It cannot be applied to a pig running in a pipe because the ultrasonic probe is placed in a complicated arrangement.

The present invention has been made to solve the above-mentioned problems, and a pig equipped with a small number of ultrasonic probes is provided.
An object of the present invention is to obtain an ultrasonic flaw detection method capable of detecting defects in a vertical seam welded portion, a circumferential welded portion of a pipe, and defects in a base material with high accuracy. Another object of the present invention is to obtain an ultrasonic flaw detection method that is not affected by echoes from the weld surplus.

[0009]

An ultrasonic flaw detection method for a pipe according to the present invention is a ± 35 ° to 55 ° or ± 125 ° to 145 ° with respect to a traveling direction of a pig from a tire type ultrasonic probe.
The ultrasonic wave is transmitted in the direction of and the echo from the defect is detected.

Further, in the above-described ultrasonic flaw detection method for piping, the ultrasonic wave transmission direction is ± 45 with respect to the traveling direction of the pig.
Or ± 135 °. Furthermore, as a tire type ultrasonic probe, a probe capable of simultaneously transmitting a transverse wave and a surface wave having a large refraction angle, a bevel probe, a surface wave probe,
Alternatively, a combination of a bevel probe and a surface wave probe is used.

[0011]

According to the present invention, the ultrasonic waves transmitted from the tire type ultrasonic probe basically propagate in the pipe wall or the surface of the pipe, or propagate in the pipe wall or the surface in a helical shape. ,
With the progress of the pig, it is possible to substantially perform full-face flaw detection on the base metal, full-line flaw detection on the vertical seam welded portion, and full-line flaw detection on the circumferential welded portion. In an extreme case, that is, when the output of the probe is high, the receiving sensitivity is high, the flaw detection distance is long enough, and the diameter of the pipe is relatively small, the entire surface can be measured with one probe. And it is possible to perform flaw detection on all lines.

In general, when an ultrasonic wave is obliquely incident on a plane with respect to a welding line, the echo does not return in the incident direction even if there is reflection from the extra scale. Therefore, it is not necessary to consider noise removal for extra echoes usually associated with ultrasonic flaw detection, and the complexity of hardware and software can be eliminated.

The intersection where the vertical seam welded portion and the circumferential welded portion intersect in a T-shape may serve as a reflection source of ultrasonic waves in the flaw detection method according to the present invention. Since the inner and outer surface bulges near the pipe end of the vertical seam weld are deleted, consideration for this point is unnecessary.

[0014]

FIG. 2 is a side view of an example of a pig used in the present invention, and FIG. 3 is an AA enlarged sectional view thereof. In both figures, 1 is a pig, and a storage device 7 and an ultrasonic measuring device 8 are mounted on the measuring instruments pigs 2 and 3 of the first and second vehicles, respectively.
A plurality of tire type ultrasonic probes 1 are provided on the sensor pig 4 of the vehicle eye.
0a to 10h are mounted. And these are connected by the couplers 5a and 5b. 6a and 6b are measuring rollers provided at the rear end of the sensor pig 4.

A plurality of tire-type ultrasonic probes (hereinafter referred to as probes) 10a to 10h (hereinafter referred to as probes) 10a to 10h (hereinafter referred to as "probe") are arranged on the sensor pig 4 via leaf springs 9 at equal intervals. (Sometimes simply indicated by reference numeral 10). This probe 10, as shown in one example in FIGS. 4 and 5,
A water chamber 12 containing water as an ultrasonic signal propagating body on the inner side of the shaft 11 and a rubber tire 13 on the outer side.
And an ultrasonic sensor 14 attached to the shaft 11 in the water chamber 12. In addition, 15 is a holder and P is piping.

By the way, the inventors have found that the echo heights of the tube axis direction defect and the circumferential direction defect, the echo heights of the longitudinal seam welded portion extraneous and the circumferential welded extraneous portion, and the ultrasonic transmission / reception direction (angle). As a result of repeated long-term research and many experiments on the relationship with, the conclusions shown in FIG. 6 were obtained.

As is apparent from FIG. 6, the ultrasonic wave transmission / reception direction by the probe, that is, the transmission / reception angle α is 35 ° to 55 ° centering 45 ° with respect to the traveling direction of the pig.
In the range (or 125 ° to 145 °), the echo height of both the tube axis direction defect and the circumferential direction defect exceeds the defect detection level, so that one type of probe causes defects in all directions. Can be detected. Therefore, the number of probes can be reduced. Further, in the above range, the echo heights from the vertical seam welded portion extraneous and the circumferential welded portion extraneous are both lower than the noise level, so that there is no influence of noise upon detection of defects.

On the other hand, in the range A of α <35 °, the echo of the tube axis direction defect is lower than the defect detection level, and α> 55.
In the range B of °, the echo of the circumferential defect is lower than the defect detection level. Therefore, in these ranges, it is impossible to detect defects in all directions with one type of probe, and defects in all directions are detected. Therefore, the number of probes cannot be reduced because two or more types of probes are required. Also, the above α <35
In the range of 0 ° and α> 55 °, the height of the echo from the circumferential welded portion surplus and the vertical seam welded portion surplus is high, so that it is easily affected by noise and accurate flaw detection may not be possible.

Each probe 1 mounted on the pig 1 according to the present invention
Based on the results of the above research and experiment, 0 is a direction of ± 35 ° to 55 ° or ± 125 ° to 145 ° with respect to the traveling direction a of the pig 1 from the ultrasonic sensor 14 as shown in FIG. 7. ,
Preferably, it is configured to transmit ultrasonic waves in the directions of ± 45 ° or ± 135 °.

FIG. 8 is a block diagram of an example of the measuring device. The pulser 22 sequentially transmits the transmission pulses to the probes 10a to 10h by the signal from the delay circuit 21. Received signals from the probes 10a to 10h are amplified by the preamplifier 23 and the defect detecting main amplifier 24a. The defect detecting main amplifier 24a is an automatic sensitivity adjusting amplifier 24b.
The sensitivity is automatically adjusted by the reference echo detection circuit 25b.

The echo from the defect is a defect echo detection circuit 2
5a, the echo height is detected by the echo height measuring circuit 27.
Is measured at. The time from the transmission of ultrasonic waves to the reception of echoes due to defects is measured by the time measuring circuit 26.
Then, the height and time measurement data of the defect echo are aggregated by the data aggregating circuit 28 at a constant distance according to the signals from the measuring roller 6 and the odometer 30, and the aggregated data is stored in the storage device 29. . Measuring device 8
Are controlled by the control signal circuit 20.

Next, referring to FIG. 1, an example of an ultrasonic flaw detection method for detecting a defect in a pipe by using the above-described pig 1 will be described. FIG. 1 is a schematic view showing an embodiment in which a defect of a pipe is detected in a pipeline by the ultrasonic flaw detection method according to the present invention, and P indicates a state in which the pipe to be inspected is developed in a plane shape. In the figure, 10a, 10b, 10c, ...
With the probe mounted at the interval L on the pig 1 shown in FIG. 3, the pig 1 advances in the pipe P in the direction of arrow a. As described with reference to FIG. 7, each of the probes 10a, 10b, 10c, ... Simultaneously transmits a transverse wave and a surface wave having a large refraction angle in the + 35 ° to 55 ° direction with respect to the traveling direction a of the pig 1. In this embodiment, it is transmitted in + 45 ° direction and propagated.

Reference numeral 34 is a surplus of the vertical seam welded portion, 35 is a surplus of the circumferential welded portion, 36 is a base material defect of the pipe P, 37 is a defect of the vertical seam welded portion, 38 is a defect of the circumferential welded portion. Is.

In the above structure, the relative position between the pig 1 and the inner surface of the pipe P, that is, the probes 10a, 10b,
When the positional relationship between 10c and the inner surface of the pipe P is in the state I, the ultrasonic waves 31a, 31b, 31c transmitted from the respective probes 10a, 10b, 10c have defects 36, 37, 38.
I have not encountered. In addition, the extra seam of the vertical seam weld 34
In some cases, the ultrasonic wave is reflected, but the extra echo 32a does not return to the probe 10a. Therefore,
It does not become a noise source.

As the pig 1 advances, the probes 10a, 10
b and 10c change from state II to III, the base material defect 36 is detected by the probe 10b during the change from state I to II, and in state II, the defect 37 in the vertical seam weld is detected.
Is detected by the probe 10a. In the state III, the ultrasonic wave 31a from the probe 10a passes through the intersection 39 between the extra seam welded portion 34 and the circumferential welded portion 35 to detect flaws in the circumferential welded portion. There is. This intersection 39 may be a reflection source of ultrasonic waves,
Since the bulge 34 of the vertical seam welded portion at the end of the pipe is removed so that both the inner and outer surfaces are flush with the base material, it does not become a reflection source, and thus a noise source in this case.

The reflection and transmission of ultrasonic waves in the extra weld 35 of the circumferential welded portion are the same as those described for the vertical seam welded portion. In short, the extra echo from a healthy weld can be ignored. In addition, defect 3 of the circumferential weld
8 is the probe 10 as the pig 1 further advances.
detected by a.

In this way, the probes 10a, 10b,
The ultrasonic waves transmitted from 10c, ... Propagate in the pipe wall or the surface of the pipe, or in the pipe wall or the surface in a helical manner, and substantially progress with the progress of the pig 1 as the base material and the vertical seam. Defects detected by performing flaw detection on the entire surface of the welded portion and the circumferential welded portion are measured by the measuring device 8 described with reference to FIG. 8, and the defect state and position thereof are stored in the storage device 7.

Further, even if there is reflection from the extra seams 37 and 38 of the vertical seam welded portion and the circumferential welded portion, the extraneous echoes are not returned to the incident direction of the ultrasonic wave, that is, the probe. Therefore, it is not affected by extra echo, and thus noise.

As described above, according to the present invention, the ultrasonic waves are oblique to the traveling direction of the pig 1, that is, in the present embodiment, 4
By propagating in the direction of 5 °, it becomes possible to carry out full-face flaw detection of the pipe base material and full-line flaw detection of the vertical seam welded portion and the circumferential welded portion with a small number and one kind of probe, and these defects 36 , 37, 38 can be detected easily and with high accuracy.

In the above description, the case where the ultrasonic wave is transmitted in the direction of 45 ° with respect to the traveling direction of the pig by the probe capable of simultaneously transmitting the transverse wave and the surface wave having a large refraction angle has been described. Is not limited to this, and a bevel probe, a surface wave probe, or both may be used. Also, the transmission direction of ultrasonic waves is ± 35 ° to 55 ° or ± 125 ° to 145 ° with respect to the traveling direction of the pig.
It may be a direction.

Further, the pig used in the present invention is not limited to the configuration shown in FIGS. 2 to 5 and the measuring device shown in FIG. 8, and may be used in pigs having other configurations and measuring devices. it can.

[0032]

As is apparent from the above description, according to the present invention, the ultrasonic ultrasonic probe is used in the direction of ± 35 ° to 55 ° or ± 125 ° to 145 ° with respect to the traveling direction of the pig. To detect defects in the piping,
The following remarkable effects can be obtained.

(1) Since coverage of flaw detection can be increased with a small number of probes, the detection rate and detection accuracy can be improved. (2) Since it is not affected by the extra echo from the extra portion of the welded portion, consideration for removing noise from the extra echo is unnecessary, and both hardware and software can be simplified.

(3) Since the number of the probes can be greatly reduced and the pigs can be formed by a small number of vehicles, the equipment cost and running cost can be reduced. (4) Running stability is improved because the number of pigs is small.
The risk of stacking is reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a flaw detection method according to the present invention.

FIG. 2 is a side view showing an example of a pig used in the present invention.

3 is a cross-sectional view taken along the line AA of FIG.

4 is a cross-sectional view of the probe shown in FIG.

5 is a sectional view taken along line BB of FIG.

FIG. 6 is a diagram showing a relationship between ultrasonic wave transmission / reception directions and echo heights.

FIG. 7 is a schematic diagram showing a propagation direction of ultrasonic waves of the probe of FIG.

FIG. 8 is a block diagram showing an example of a defect measuring device using a pig.

[Explanation of symbols]

 1 Pig 7 Storage Device 8 Measuring Device 10a to 10h Probe P Piping

Claims (3)

[Claims] 1. An ultrasonic flaw detection method for detecting a defect in a base material or a welded portion of a pipe by a pig equipped with a tire type ultrasonic probe and traveling in the pipe, wherein the tire type ultrasonic probe is used. An ultrasonic flaw detection method for a pipe, characterized in that ultrasonic waves are transmitted in a direction of ± 35 ° to 55 ° or ± 125 ° to 145 ° with respect to the traveling direction of the pig, and an echo from the defect is detected. . 2. The ultrasonic flaw detection method for a pipe according to claim 1, wherein the ultrasonic wave transmission direction is ± 45 ° or ± 135 ° with respect to the traveling direction of the pig. 3. A tire type ultrasonic probe capable of simultaneously transmitting a transverse wave and a surface wave having a large refraction angle, a probe, a bevel probe, a surface wave probe or a bevel probe and a surface wave. The ultrasonic flaw detection method for a pipe according to claim 1, wherein the ultrasonic flaw detection is used in combination with a probe.