JPH04361155A - Ultrasonic flaw-detection device of welded pipe - Google Patents

Abstract

PURPOSE:To enable flaw detection of a side crazing at a welded portion of a welded pipe to be performed accurately and stably. CONSTITUTION:A welded steel pipe 1 where its welded portion 10 is placed downward is dipped partially into a water tank which is filled with a flaw- detection water W. An ultrasonic wave for performing aslant flaw detection is transmitted to and received from the welded portion 10 in the direction of its extension by ultrasonic probes 31 and 32 which are placed at a lower portion of the welded steel pipe 1 via the flaw-detection water W and flaw detection of the welded portion 10 is performed based on a reception result of the ultrasonic wave.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for ultrasonic flaw detection of a welded part of a welded pipe.

0002

[Prior Art] Conventionally, as a device for detecting defects in welds in welded steel pipes such as UOE steel pipes, ultrasonic flaw detection equipment performs oblique flaw detection using ultrasonic waves traveling at an angle oblique to the flaw detection surface. is used.

[0003] When performing such angle flaw detection, the welded steel pipe is made so that the welded part faces upward, and a pair of probes is placed at the top of the welded steel pipe so as to straddle the welded part. Ultrasonic waves are incident obliquely from the probe into the welded steel pipe,
The echoes were received by the other probe, and defects in the weld were detected based on the reception results. Such a flaw detection method is called the SNUP method.

Defects in welded parts of welded steel pipes include vertical cracking, which is a defect in which the welded part cracks in the longitudinal direction, and transverse cracking, which is a defect in which the welded part cracks in a direction perpendicular to the longitudinal direction. In the flaw detection method, the horizontal cracks were detected in a manner as shown in FIG. FIG. 5 is a plan view showing a method for detecting horizontal cracks in the conventional SNUP type flaw detection method. In this case, the ultrasonic probe 31 for transmission
The horizontal crack A can be detected by applying ultrasonic waves obliquely in a plan view to the horizontal crack A in the welded part 10 of the welded steel pipe 1 and receiving the reflected echo with the receiving ultrasonic probe 32. It was done.

However, when detecting transverse cracks A with this SNUP type flaw detection method, the ultrasonic wave has a long skip distance, high attenuation, low S/N ratio, and problems with welding. There was a problem in that the shoulder echo at the edge was received by the receiving ultrasound probe 32.

As a flaw detection method for solving such problems, there is a method as disclosed in Japanese Patent Laid-Open No. 58-9064 filed by the present applicant. This involves installing a probe on the welded part of a welded steel pipe with the welded part facing upward and tilted with respect to the extending direction of the welded part, and using the probe in the extending direction of the welded part. This is a method of performing oblique flaw detection. The probe is housed in a probe holder, and flaw detection water is supplied into the probe holder from above by a water jet method. In this method, angle flaw detection is performed in the extending direction of the weld, that is, in the axial direction of the welded steel pipe 1, so the skip distance of the ultrasonic waves is short, and it is believed that transverse cracks in the weld can be detected with high accuracy. Ta.

[0007]

[Problem to be solved by the invention] However, in JP-A-58
In the flaw detection method disclosed in Publication No. 9064, since the probe holder is placed above the welded steel pipe, the flaw detection inside the probe holder is detected from between the probe holder and the welded steel pipe due to the influence of gravity. Since the water easily escapes to the outside, the coupling of the flaw detection water is unstable, making stable flaw detection impossible and impractical.

The present invention has been made in view of the above circumstances, and provides an ultrasonic flaw detection device for welded pipes that enables accurate and stable detection of transverse cracks in welded portions of welded pipes. The purpose is to

[0009]

[Means for Solving the Problems] The ultrasonic flaw detection apparatus for welded pipes according to the present invention includes a liquid immersion means for immersing at least the welded part of the welded pipe, which is the target of flaw detection, in a flaw detection liquid; and a probe that transmits and receives ultrasonic waves for performing oblique flaw detection on the welded portion in its extending direction, the welded pipe that performs flaw detection of the welded portion based on the reception result of the ultrasonic waves. In the ultrasonic flaw detection apparatus, the liquid immersion means and the probe are provided below the welded pipe to detect flaws with the welded portion facing downward.

0010

[Operation] The probe installed below the welded pipe transmits and receives ultrasonic waves for performing oblique flaw detection in the extending direction of the welded part via the flaw detection liquid in the immersion means. When detecting a transverse crack defect existing in a weld, the ultrasonic skip distance is short and the transverse crack can be detected with high accuracy. Further, since the liquid immersion means is provided below the welded pipe, the flaw detection liquid does not escape from the liquid immersion means due to the influence of gravity, and flaw detection can be performed stably.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically explained below based on drawings showing embodiments thereof. FIG. 1 is a schematic diagram showing the configuration of an ultrasonic flaw detection device for welded pipes according to the present invention (hereinafter referred to as the device of the present invention).

In the figure, 1 is a welded part 1 extending in the axial direction.
0 is a welded steel pipe to be tested. Welded steel pipe 1 is
It was placed on a plurality of conveying rollers 2, 2... arranged in a water tank T storing flaw detection water W with its welded part 10 facing downward, and its lower side was immersed in the flaw detection water W. In this state, it can be transported within the water tank T in the axial direction (in the direction of the white arrow in the figure). Immediately below the welded steel pipe 1, there is an ultrasonic probe 31 for transmitting ultrasonic waves to the welded portion 10, and an ultrasonic probe 32 for receiving ultrasonic waves that receives echoes of the ultrasonic waves. A pair of ultrasonic probes 3 configured
1 and 32 extend the welded portion 10 of the welded steel pipe 1 so that they face the welded portion 10 at an inclined angle with respect to the plane of the welded portion 10 in order to conduct oblique flaw detection in the extending direction of the welded portion 10 of the welded steel pipe 1. They are arranged at a predetermined distance in the direction. Ultrasonic probe 31, 3
2 is a welded steel pipe 1 by a probe moving mechanism (not shown).
It is movable in the circumferential direction.

Further, a weld position detector 4 for optically detecting the position of the weld 10 is disposed directly below the welded steel pipe 1 and upstream of the ultrasonic probes 31 and 32 in the conveyance direction. There is. The ultrasonic probes 31, 32 and the weld position detector 4 are installed in a flaw detection device main body 5 placed outside the water tank T in order to control the ultrasonic flaw detection device and perform signal processing of the flaw detection results of the ultrasonic flaw detection device. It is connected.

In the ultrasonic flaw detector constructed as described above, the position of the weld 10 is detected by the weld position detector 4. In the flaw detection device main body 5, the ultrasonic detection is performed by the probe moving mechanism so that the flaw detection positions of the ultrasonic probes 31 and 32 follow the welding area 10 based on the detection result of the welding position detector 4. Move the tentacles 31 and 32. From the ultrasonic probe 31, the welded part 10 is detected via the flaw detection water W.
Ultrasonic waves are incident obliquely on the surface. The ultrasonic waves are used to detect defects such as horizontal cracks in the weld 10 and
0, and its echo is received by the ultrasonic probe 32. The flaw detection device main body 5 performs predetermined signal processing based on the reception results of the ultrasonic probe 32 to detect defects such as the horizontal cracks. Since the welded steel pipe 1 is transported by the transport rollers 2, 2, . . . , the entire length of the welded portion 10 is subjected to ultrasonic flaw detection.

[0015] In the above-mentioned ultrasonic flaw detection device, the welded portion 1
Since the oblique flaw detection is performed in the extending direction of the zero, the skip distance of the ultrasonic waves for flaw detection is short, and the transverse cracks can be detected with high accuracy. Further, in this ultrasonic flaw detection apparatus, since the flaw detection water W is stored in the water tank T, it goes without saying that flaw detection can be performed stably.

Next, the results of actual ultrasonic flaw detection using the apparatus of the present invention will be explained. The flaw detection conditions for this ultrasonic flaw detection are such that the welded steel pipe 1 with a wall thickness of 0.25 inches has a 3 mm long notch (artificial horizontal crack) in the welded part 10, and the ultrasonic probe 31 The transmitted ultrasonic wave had a frequency of 4 MHz and a refraction angle of 70 degrees. FIG. 2 shows the results of ultrasonic flaw detection performed using the device of the present invention and the conventional device under such flaw detection conditions.

FIG. 2 is a graph showing the relationship between notch depth and echo height when ultrasonic flaw detection is actually performed using the device of the present invention and the conventional device. %) and the echo height (dB) are plotted on the vertical axis, and the relationship between these is shown by a solid line for the device of the present invention, and a dashed-dotted line for the conventional device. As is clear from the graph in FIG. 2, the device of the present invention has improved echo height by approximately 16 dB or more compared to the conventional device.

FIG. 3 is a schematic diagram of an ultrasonic flaw detection apparatus showing another embodiment of the present invention. Components in FIG. 3 that correspond to those in FIG. In the ultrasonic flaw detection apparatus shown in FIG. 2, the entire length of the welded steel pipe 1 is not immersed in water, but a portion of the entire length is immersed in the flaw detection water W. The flaw detection water W is stored in a partial water immersion box 6 that immerses the lower side of a part of the welded steel pipe 1 in the axial direction. The water is supplied from a water supply port 60. This partial immersion box 6 is a box-shaped tank with an opening formed in its upper part so that a part of the circumferential surface of the welded steel pipe 1 can enter therein, and ultrasonic probes 31, 32 and A weld position detector 4 is provided. This partial water immersion box 6 is arranged between the transport rollers 2, 2... (only one shown) which are not immersed in water, and the welded steel pipe 1 transported by the transport rollers 2, 2... is immersed in this partial water. Soaking box 6
By passing through the welded steel pipe 1, the welded portion 10 of the welded steel pipe 1 is subjected to ultrasonic flaw detection.

This ultrasonic flaw detection apparatus differs from the ultrasonic flaw detection apparatus shown in FIG. 1 in that flaw detection water W is supplied into the partial water immersion box 6. However, since the partial water immersion box 6 is provided below the welded steel pipe 1, it has excellent coupling of the flaw detection water W, and the conventional device disclosed in Japanese Patent Laid-Open No. 58-9064 as mentioned above The flaw detection water W will not escape due to the influence of gravitational force. Therefore, flaw detection is performed stably as shown in FIG. 4 below.

Next, the results of actual ultrasonic flaw detection using the ultrasonic flaw detection apparatus shown in other embodiments of the present invention will be described. The flaw detection conditions for this ultrasonic flaw detection are a wall thickness of 1.00 inches, a diameter of 36 inches,
The welded steel pipe 1 having a total length of 12 m and being transported at 15 m/min was the object of flaw detection, and the ultrasonic waves transmitted by the ultrasonic probe 31 had a frequency of 5 MHz and an incident angle of 19 degrees. FIG. 4 shows the results of ultrasonic flaw detection performed using the device of the present invention and the conventional device under such flaw detection conditions.

FIG. 4 shows the elapsed time for flaw detection when flaw detection was actually performed using the ultrasonic flaw detection device shown in another embodiment of the present invention and the conventional device disclosed in Japanese Patent Laid-Open No. 58-9064. This is a graph showing the relationship between and echo height (dB), where the horizontal axis is the elapsed testing time and the vertical axis is the echo height (dB).
The relationship between these is shown by the solid line in the device of the present invention,
The conventional device is shown in dashed lines. As is clear from the graph of FIG. 4, the echo height of the conventional device fluctuates widely and is unstable, but the echo height of the device of the present invention is stable at a constant value. In this way, the device of the present invention performs stable flaw detection.

[0022]

Effects of the Invention As detailed above, in the device of the present invention, the probe transmits and receives ultrasonic waves for performing oblique flaw detection in the extending direction of the weld. When detecting transverse crack defects, the ultrasonic skip distance is short, and the transverse cracks can be detected with high accuracy.Also, since the immersion means is provided below the welded pipe, the immersion means can be separated from the welded pipe by the influence of gravity. The device of the present invention has excellent effects, such as being able to perform stable flaw detection without allowing the flaw detection liquid to escape.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an ultrasonic flaw detection device for welded pipes according to the present invention.

FIG. 2 is a graph showing the relationship between notch depth and echo height when ultrasonic flaw detection is actually performed using the device of the present invention and the conventional device.

FIG. 3 is a schematic diagram of an ultrasonic flaw detection device showing another embodiment of the present invention.

FIG. 4: Elapsed flaw detection time and echoes when flaw detection was actually performed using the ultrasonic flaw detection device shown in another embodiment of the present invention and the conventional device disclosed in Japanese Patent Laid-Open No. 58-9064. It is a graph showing the relationship with height.

FIG. 5 is a plan view showing a method for detecting horizontal cracks in the conventional SNUP type flaw detection method.

[Explanation of symbols]

1 Welded steel pipe 5　Flaw detection device body 6 Partial immersion box 10 Welded part 31, 32 Ultrasonic probe T　Aquarium W　Flaw detection water

Claims (1)

[Claims] 1. A liquid immersion means for immersing at least a welded part of a horizontally oriented welded pipe as a flaw detection target in a flaw detection liquid, and an oblique flaw detection performed on the welded part in the extending direction of the welded part through the flaw detection liquid. In the welded pipe ultrasonic flaw detection apparatus, the welded pipe ultrasonic flaw detection apparatus includes a probe that transmits and receives ultrasonic waves for flaw detection of the welded portion based on the reception results of the ultrasonic waves. An ultrasonic flaw detection device for a welded pipe, characterized in that a liquid immersion means and the probe are provided below the welded pipe.