JP2006220477A - Nondestructive inspection method of metal piping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nondestructive inspection method of metal piping constituted so as to inspect changes in morphology of the piping metal, which exists on the inside parts, surrounded by a weld line of the metal piping and cannot be inspected directly, because another structure has been welded to the outer surface of the metal piping and the piping metal exists at the inside part surrounded by weld line, in a nondestructive manner, and that has superior effects of being capable of inspecting the metal piping accurately and rapidly. <P>SOLUTION: In the method for inspecting the change in the form of the piping metal, which is provided at the inside part, surrounded by the weld line of the metal piping and cannot be inspected directly, because another structure is welded to the outer surface of the metal piping, and the piping metal is present at the inside part surrounded by the weld line, in a nondestructive manner, a probe of a ultrasonic guide wave method is placed on the outside of the part surrounded by the weld line in the vicinity of an inspection part. As the metal for the metal piping, iron can be cited. As a specific example of piping, piping for transporting a fluid in a chemical plant can be cited, and there is no restriction on the size or the shape of the piping. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nondestructive inspection method for metal piping. More specifically, the present invention provides a non-destructive change in the shape of a pipe metal in which other structures are welded to the outer surface of the metal pipe and the inner part surrounded by the weld line cannot be directly inspected. The present invention relates to a non-destructive inspection method for metal piping, which has an excellent effect of being able to be performed accurately and quickly.

  As a method for nondestructively inspecting the shape change of a metal pipe, a radiation inspection method, an ultrasonic oblique angle method, and the like are known (for example, see Patent Document 1).

  However, the radiation inspection method has a limitation in the metal pipe plate thickness, and there is a problem that inspection is difficult with a large-diameter metal pipe.

  In addition, the ultrasonic oblique angle method limits the range of ultrasonic waves that can be reached from the probe due to the thickness of the metal pipe and the incident angle of the ultrasonic waves, and detects changes in the shape at a distance from the probe. There is a problem that is difficult.

Japanese Patent Laid-Open No. 2003-14704

  In such a situation, the problem to be solved by the present invention is the form of the pipe metal in which another structure is welded to the outer surface of the metal pipe and the inner part surrounded by the weld line cannot directly inspect the part. It is a method for non-destructively inspecting a change, and is to provide a non-destructive inspection method for metal piping having an excellent effect that it can be carried out accurately and quickly.

  That is, the present invention nondestructively inspects the shape change of the pipe metal in which another structure is welded to the outer surface of the metal pipe and the inner part surrounded by the weld line cannot directly inspect the part. The method relates to a non-destructive inspection method for metal pipes in which an ultrasonic guide wave probe is placed outside a portion surrounded by a weld line in the vicinity of the inspection portion.

  According to the present invention, in the method of nondestructively inspecting the shape change of the pipe metal in which another structure is welded to the outer surface of the metal pipe and the inner part surrounded by the weld line cannot directly inspect the part. Thus, it is possible to provide a non-destructive inspection method for metal pipes having an excellent effect of being able to be performed accurately and quickly.

  The present invention is a method for non-destructively inspecting a change in shape of a pipe metal, in which another structure is welded to the outer surface of the metal pipe, and the inner part surrounded by the weld line cannot directly inspect the part. There is.

  Iron can be used as the metal of the metal pipe. As a specific example of piping, piping for transporting a fluid in a chemical plant can be given. There are no restrictions on the size or shape of the piping.

  As another structure welded to the outer surface of metal piping, the structure for supporting piping can be illustrated.

  Examples of the shape change of the pipe metal include those caused by a reduction in the thickness of the pipe due to corrosion.

  Another structure is joined to the pipe by welding, and the inner part surrounded by the weld line cannot be directly inspected. According to the present invention, such a portion can be inspected quickly and accurately in a non-destructive manner.

  In the present invention, an ultrasonic guide wave probe is placed on the outside of the portion surrounded by the weld line in the vicinity of the inspection portion to inspect.

  Inspection methods using the ultrasonic guided wave method are well known. For example, “Recent ultrasonic non-destructive inspection technology” (Minimum Symposium of Maintenance Inspection Special Research Committee), “Non-destructive evaluation of large structures using guide waves” ( The 10th non-destructive evaluation symposium on ultrasonics). Conventionally, the ultrasonic guide wave method has been used for inspection of the plate thickness of a steel sheet, and it is not known to be applied to inspection of a special part as in the present invention.

Next, the present invention will be described with reference to examples.
Example 1
FIG. 1 shows a structure 012 for supporting a pipe welded 101 to the outer surface of a metal pipe 011. A guide for inspecting a thickness reduction 103 caused by corrosion of an inner portion surrounded by the weld line. The state of the reflected wave in the thickness change part of the ultrasonic wave propagation 102 by the wave method and the weld 101 and the thickness reduction 103 caused by corrosion is shown in the figure.
An ultrasonic guide wave toward the direction where it is expected that there is a thickness reduction 103 due to corrosion near the weld line for the purpose of inspection of the metal pipe 011 to which the structure 012 for supporting the pipe is welded 101. Place the legal probe 001 and inspect.
On the oscilloscope screen 110 displayed on the inspection device as the inspection result, the reflected wave 111 indicating the weld 101 portion on the time axis (distance from the probe) and the reflected wave 112 indicating the thickness reduction portion 103 due to corrosion are displayed. Is displayed.
The structure 012 for supporting the pipe welded 101 to the outer surface of the metal pipe 011 is surrounded by the weld line by the spread in the time axis direction of the reflected wave 112 indicating the thickness reduction due to the corrosion and the touch width of the amplitude. Determine the location and extent and depth of the thickness reduction 103 due to corrosion of the inner part.

Example 2
FIG. 2 shows a guide for inspecting the thickness reduction 103 caused by the corrosion of the inner part surrounded by the weld line of the structure 012 for supporting the pipe welded 101 to the vertical metal pipe 011. The actual method of inspection by the wave method is shown.
The inspection is started by applying the probe 001 to the metal pipe 011 near the structure 012 for supporting the pipe to be inspected.
After the start of the inspection, the probe 001 scans in parallel with the center line of the structure 012 for supporting the pipe, records the position information moved from the scanning start point by the encoder 002, and at the same time as in the first embodiment. The oscilloscope screen 110 is continuously recorded.
FIG. 3 shows data obtained by converting the continuously recorded data by image processing.
The data recorded in the manner of FIG. 2 shows the position of the probe 001 on the horizontal axis as shown in FIG. 3, and the distance from the probe 001 of the reflected wave 104 collected by the probe 001 on the vertical axis. .
Further, the amplitude indicating the magnitude of the reflected wave 104 is displayed by a stepwise color change in which the amplitude 0 is indicated by white or an arbitrary color by image processing and the maximum amplitude is black.
Thus, in the recording shown in FIG. 3, the reflected wave 103 indicating the weld line and the reflected wave 103 indicating the thickness reduction due to corrosion are expressed by a dense image of black or dark color, Range and depth of corrosion can be read with image data.

Example 3
FIG. 4 shows a guide wave method when the structure 012 for supporting the pipe 101 welded to the bent pipe 013 is inspected for the thickness reduction 103 caused by the corrosion of the inner part surrounded by the weld line. The actual method of inspection is shown.
Similar to the second embodiment, the probe 001 is placed near the structure 012 for supporting the pipe welded 101 to the bent pipe 013, and the probe 001 is scanned parallel to the axial direction of the bent pipe 013. .
At this time, the position information of the probe 001 is recorded by the encoder 002, and at the same time, the oscilloscope screen 110 is continuously recorded as in the first embodiment.
The continuously recorded data is displayed as data converted by image processing similar to that in FIG. 3 of the second embodiment, so that the structure 012 for supporting the pipe welded 101 to the bent pipe 013 is surrounded by the weld line. The position and range of the thickness reduction 103 caused by the corrosion of the inner portion and the depth of the corrosion can be read with image data.

Comparative Example 1
Regarding the structure 012 for supporting the pipe welded 101 to the outer surface of the metal pipe 011 similar to that of the first embodiment, the inspection of the thickness reduction 103 caused by the corrosion of the inner part surrounded by the weld line FIG. 5 shows a case where the inspection is performed by the high-power ultrasonic oblique flaw detection method as the inspection means described in No. -14704.
High-power ultrasonic oblique angle flaw detection method Ultrasonic waves emitted from the probe are reflected on the inner surface of the metal pipe 011 and are reflected when they reach the thickness reduction 103 due to corrosion existing on the surface when they reach the surface again. It becomes a wave and the reflected wave is received by the probe.
However, the ultrasonic wave does not reach the thickness reduction 104 caused by the corrosion existing further than the thickness reduction 103 caused by this corrosion, and all the ultrasonic waves are reflected by the thickness reduction 103 caused by the corrosion. Therefore, it is impossible to detect the thickness reduction 104 caused by the corrosion existing in the back.
FIG. 6 shows a case where the thickness reduction 103 due to corrosion does not exist in the range that can be inspected by the high-power ultrasonic oblique flaw detection method as the inspection means described in Japanese Patent Laid-Open No. 2003-14704.
In the high-power ultrasonic oblique angle flaw detection method as an inspection means described in Japanese Patent Laid-Open No. 2003-14704, although it depends on the set angle of the ultrasonic wave, a range of about 2 to 5 times the thickness of the metal pipe 011 is generally used. This is the limit that can be inspected.
The thickness reduction 103 caused by corrosion does not exist in the range in which this inspection is possible, and if it exists far away, it is difficult to determine the position and the degree of corrosion.
In the guide wave method of the first embodiment as a solution, since the ultrasonic wave propagates through the entire cross section of the metal pipe 011, there is a thickness reduction 103 due to corrosion, and a part of the ultrasonic wave becomes a reflected wave thereby. However, since most ultrasonic waves continue to propagate further, even if there are multiple thickness reductions 104 due to multiple corrosions, they generate their own reflected waves, so they can receive each reflected wave and indicate its position. Is possible.
In this method, although the distance that the ultrasonic wave reaches varies depending on the number, width, and depth of the thickness reduction 103 due to the surface condition and corrosion of the metal pipe 011, it is 200 mm to 500 mm regardless of the thickness of the metal pipe 011. Can be inspected.

It is explanatory drawing of the test result displayed with the ultrasonic wave propagation of the guide wave method and an oscilloscope. It is explanatory drawing of the vertical direction metal piping inspection method. It is a figure of the inspection result which carried out image processing conversion about the inspection result displayed on the oscilloscope. It is explanatory drawing of the bending metal piping inspection method. It is explanatory drawing of the thickness reduction inspection method resulting from the continuous corrosion by an ultrasonic bevel method. It is explanatory drawing of the test | inspection method when there exists thickness reduction resulting from corrosion out of the range which can be test | inspected by the ultrasonic bevel method.

Explanation of symbols

001: Ultrasonic probe
002: Encoder
011: Metal piping
012: Structure for supporting piping
013: Metal piping including bending
101: Welding
102: Ultrasonic guide wave
103: Wall thickness reduction due to corrosion
104: Thickness reduction due to corrosion existing far from the probe
110: Test results displayed on the oscilloscope
111: Amplitude indicating the weld
112: Amplitude indicating thickness reduction due to corrosion

Claims (5)

A method of non-destructively inspecting a change in the shape of a pipe metal in which another structure is welded to the outer surface of the metal pipe and the inner part surrounded by the weld line cannot directly inspect the part, A nondestructive inspection method for metal pipes in which an ultrasonic guide wave probe is placed outside the portion surrounded by the weld line near the inspection portion. The method according to claim 1, wherein the pipe metal is iron. The method according to claim 1, wherein the change in shape of the pipe metal is due to a reduction in the thickness of the pipe due to corrosion. The method according to claim 1, wherein the structure is a structure for supporting a pipe. The method of claim 1 wherein the piping is for transporting fluid within a chemical plant.

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