JP2008058043A - Method of determining inner surface flaw of pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of determining inner surface flaws of a pipe capable of easily and accurately determining the depth of the inner surface flaws of the pipe. <P>SOLUTION: When determining the depth of the inner surface flaws of the pipe by a nondestructive inspection method, after transcribing recessed inner surface flaws onto a molding material, the height to the top of a projecting flaw transcribed part formed on the molding material is determined, and the height measured value is used as the depth of the inner surface flaws. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for measuring an inner surface defect of a tube, which can easily and accurately measure the depth of an inner surface defect of a tube by a nondestructive inspection method.

When manufacturing pipes such as steel pipes, the inspection line guarantees quality by conducting predetermined appearance and shape inspections, dimension inspections, and defect inspections according to the type of pipe (non-patented) Reference 1).
When manufacturing a pipe, for example, a concave defect (hereinafter referred to as an inner surface flaw) that is brazed with something may occur on the inner surface of the pipe. If there is such a concave inner surface flaw defect, the thickness of the portion becomes insufficient. Therefore, it is important to easily and accurately measure the depth of the concave inner surface flaw.

There are various types of non-destructive inspection methods for inspecting a tube for defects, but a simple non-destructive inspection method is adopted as a method for measuring inner surface defects of a tube. A conventional method for measuring the inner surface flaw of a pipe will be described with reference to FIGS. 6 (a) and 6 (b).
In the conventional method for measuring the inner surface flaw of a pipe, an inspector visually observes the inner surface of the manufactured pipe in detail, and if there is a concave inner flaw, a marking is made near the defective portion, and then the concave As shown in FIGS. 6A and 6B, a measuring device 5 for detecting the depth mounted with a micrometer is disposed on the inner surface of the tube to measure the depth of the tube. It was.

In the measurement process for measuring the depth of the dent, the measuring device 5 is arranged in a normal part having no defect, the measured value measured at the position, and the measuring device 5 is arranged on the inner surface ridge and measured at the position. The depth of the inner surface flaw was determined by the difference from the measured value. The depth detection measuring instrument 5 includes a micrometer in which the stylus tip 5C on the measurement target side is formed in a needle shape.
Edited by the Japan Iron and Steel Institute, "Third Edition Steel Handbook III (2)" Maruzen Co., Ltd., issued November 20, 1980, p1221

However, although the conventional method for measuring the inner surface flaw of a pipe is simple, there is a problem that the measurement value of the depth of the inner surface flaw varies greatly and it is difficult to measure accurately.
As a result of diligent examination of this cause, the conventional method for measuring the inner surface flaw of a tube measures the depth of the dent in the measurement process, and therefore measures the depth to the slope shallower than the bottom of the dent. As a result, it was found that the measured value of the depth of the inner surface flaws varied greatly.

When measuring the depth of the recess, the micrometer of the detection unit that detects a change in position when the stylus moves up and down, the base plate 5A on which the detection unit is mounted, and the base plate 5A are attached. Another difficulty is that it is difficult to accurately measure the measuring instrument provided with the leg 5B so that the stylus tip 5C formed in a needle shape is directly above the bottom of the recess.
An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for measuring the inner surface flaw of a tube, which can easily and accurately measure the depth of the inner surface flaw of the tube by a nondestructive inspection method. To do.

  In the present invention, when measuring the depth of the inner surface flaw of the tube by the nondestructive inspection method, after transferring the concave inner surface flaw to the molding material, up to the top of the convex wrinkle transfer portion formed in the molding material A method for measuring an inner surface flaw of a pipe, characterized in that the height is measured and the height measurement value is defined as the depth of the inner surface flaw. At that time, using a replica unit that has a frame and a lid fitted into the frame, and after the molding material is packed into the frame, the lid is fitted so that the molding material does not protrude from one side of the frame, It is preferable to transfer the concave inner surface flaws, and the molding material is preferably a room temperature curable material.

  It also has a detection unit that detects the change in position when the stylus moves up and down, and uses a height detection measuring instrument in which the tip of the stylus is formed in a plane when viewed from the measurement target side. Is preferably measured.

  According to the present invention, the depth of the inner surface flaw of the pipe can be easily and accurately measured by the nondestructive inspection method.

Hereinafter, a method for measuring an inner surface flaw of a pipe according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing an example of a replica unit suitable for use in the measurement method of the present invention. FIG. 2 shows an example of a concave inner surface flaw existing on the inner surface of a tube W using the example replica unit. It is a perspective view which shows the molding process which transcribe | transfers. This replica unit has a frame 2 and a lid 3 fitted in the frame 2 so that the molding material 1 does not protrude from one side of the frame 2 after the molding material 1 is packed into the frame 2. The lid 3 is fitted. As the molding material 1, it is preferable to use a room temperature curable material described in the examples. The strut 4 is a tool that presses the molding material 1 packed in the frame 2 against the inner flange portion via the lid 3.

  Here, FIG. 3 shows the final stage of the molding process after the concave inner surface flaw is transferred to the molding material 1 and before the molding material 1 is taken out from the pipe. Following the modeling process, the molding material 1 is taken out of the tube, and a measurement process is performed to measure the height of the convex scissors transfer portion 1A. FIG. 3 is a perspective view showing a main part of the tube W having a concave inner surface flaw, and the measuring method of the present invention is a nondestructive inspection method, and therefore the tube W is cut at a defective portion having a concave inner surface flaw. It is not a diagram showing that.

The method for measuring the inner surface defects of a tube according to the present invention is a method of measuring the depth of the inner surface defects of the tube by a nondestructive inspection method, after transferring the concave inner surface defects to the molding material 1 and then forming the projections formed on the molding material 1. The height up to the top of the wrinkle transfer portion 1A is measured, and the measured height is taken as the depth of the inner surface wrinkles.
FIG. 4 shows a state in which the molding material 1 is taken out from the pipe in order to measure the height of the convex scissor transfer portion 1A. FIGS. 5 (a) and 5 (b) show the stylus moving up and down. A measuring step of measuring the height of the convex scissors transfer portion 1A formed on the molding material 1 by using a height detecting measuring device 5 equipped with a micrometer in the detecting portion for detecting a position change when Indicated. In this measuring step, the molding material 1 is placed on a surface plate or the like, and the height to the top of the convex wrinkle transfer portion 1A is measured with a measuring device 5 for height detection.

  At that time, the origin (reference) in the height direction of the measuring device 5 is a value measured by the normal portion where the measuring device 5 is moved in the tube axis direction from the scissors transfer portion 1A, and the measuring device 5 from the position toward the tube axis direction. If the position of the tip of the stylus 5C is approximately above the wrinkle transfer portion 1A, the tip of the stylus 5C and the top of the wrinkle transfer portion 1A can be brought into contact with each other. Can be measured easily and accurately.

  As described above, according to the present invention, the depth of the recess is not measured as in the conventional method for measuring the inner surface defect of the tube, but the convex defect transfer portion 1A formed on the molding material 1 in the measurement process is not measured. Since the height to the top is measured and the height measurement value is taken as the depth of the inner surface defect, the problem with the conventional method for measuring the inner surface defect of the tube can be solved. The method of the present invention can be measured at any position in the circumferential direction.

  At that time, in order to measure the height, a detection unit for detecting a change in position when the stylus moves up and down, a base plate 5A on which the detection unit is mounted, and a leg portion 5B attached to the base plate 5A are provided. However, it is preferable to use the height detecting measuring instrument 5 in which the stylus tip 5C is formed in a plane when viewed from the measuring object side because the height can be measured easily and accurately. The measuring device 5 for height detection is not limited to the one equipped with a micrometer as a detection unit for detecting a change in position when the stylus moves up and down, and a base plate 5A on which the detection unit is mounted, A leg portion 5B attached to the plate 5A may be provided, and a stylus tip portion 5C formed on a plane when viewed from the measurement target side may be used.

  Further, the present invention has a frame 2 and a lid 3 fitted in the frame 2, and the molding material 1 does not protrude from one side of the frame 2 after the molding material 1 is packed in the frame 2. It is preferable to use the replica unit fitted with the lid 3 so that the concave inner surface flaw can be easily and accurately transferred to the molding material 1. As the molding material 1, it is preferable to use a room temperature curable material. This is because the molding material 1 can be cured at room temperature if the molding material 1 is pressed against the inner surface ridge portion for a predetermined time, and after the concave inner surface ridge is transferred to the molding material 1, the molding material When measuring the height of the wrinkle transfer portion 1A formed in 1, the molding material 1 can be made sufficiently hard without heat treatment, and the height to the top of the wrinkle transfer portion 1A can be accurately measured. This is because it can be measured.

  A test for measuring the inner surface defects of the medium diameter steel pipe was conducted by five inspectors, and the variation in the depth of the inner surface defects when the present invention was applied was examined. The results are shown in Table 1.

  In Table 1, the height of the wrinkle transfer part (3) and the normal part (1) and (2) are as shown in FIG. 5 for detecting the height of the stylus tip 5C formed on a flat surface. This is a value measured at each position in the longitudinal direction of the pipe using the measuring instrument 5. The positions at which the altitudes (1) and (2) of the normal part were measured were the positions 5 mm away from the position at which the altitude (3) of the wrinkle transfer part was measured. As the measuring device 5 for detecting the height, a micrometer (manufactured by Mitutoyo Corporation) having an accuracy of 0.010 mm was mounted. As the molding material 1, a putty (ITW Industry Co., Ltd: FAS-STIK) made of two kinds of rod-shaped materials was used.

  Each elevation has a reference height of the measuring instrument 5 set to zero, from which one side surface of the molding material 1 in which the stylus tip 5C is in contact with the lid 3 of the replica unit (under the molding material 1 in FIG. 5). The moving distance in a direction perpendicular to the side surface). The height (4) of the wrinkle transfer portion 1A was obtained by subtracting the average values of the altitudes (1) and (2) of the normal portion from the altitude (3) of the wrinkle transfer portion. After transferring the concave inner surface flaw to the molding material 1 in this way, the height to the top of the convex wrinkle transfer portion 1A formed on the molding material 1 is measured, and the measured value is taken as the depth of the inner surface flaw. did.

As a result, as shown in Table 1, the height 1σ (standard deviation) to the top of the wrinkle transfer portion 1A is 0.015 mm, the variation in the depth of the inner surface wrinkles is small, and the true wrinkle depth It can be seen that the difference from (= 0.14 mm) is also small and can be measured easily and accurately.
However, the procedure of the molding process for transferring the shape of the inner surface flaw of the tube to the molding material 1 was as follows.

  Step 1: Apply grease as a release agent to the inner surface of the tube. Step 2: Two types of rod-shaped materials are cut to appropriate lengths (30 to 40 mm). Step 3: Two kinds of cut rod-shaped materials are kneaded well. Step 4: A predetermined amount of molding material 1 (putty) is packed into the frame 2. Step 5: Grease the lid 3 of the replica unit, and attach the lid 3 to one side of the frame 2 in which the molding material 1 is packed. In this way, a replica unit is created (FIG. 1).

  Step 6: Next, a replica unit is arranged on the inner surface of the greased tube so that the other side not covered is directed to the other side, and the stick 4 is pushed on one side covered with the lid 3 so that the molding material 1 does not protrude. Then, the molding material 1 packed in the frame body 2 is pressed against the inner surface ridge portion through the lid 3 in contact with the tension rod 4 (FIG. 2). Step 7: Wait until the molding material 1 solidifies in this state (at least 5 minutes for this putty). Step 8: After removing the tension bar 4, the lid 3, and the frame 2, observe one side surface of the molding material 1 in contact with the lid 3 (FIG. 3). If one side surface of the molding material 1 is flat, the molding material 1 is sufficiently filled in the inner surface ridge portion, and the convex inner surface ridge is accurately transferred to the other side surface of the molding material 1. (FIG. 4). Step 9: Remove the molding material 1 from the tube. Step 10: Remove the grease adhering to the molding material 1.

It is a perspective view which shows a replica unit of an example suitable for using for the measuring method of this invention. It is a perspective view which shows the molding process which transfers the shape of an inner surface flaw to a molding material using the replica unit of an example. It is a perspective view which shows the state just before taking out a molding material from a pipe | tube after transferring the shape of an inner surface flaw to a molding material using the replica unit of an example. It is a perspective view which shows the state which took out the molding material in which the convex wrinkle transcription | transfer part was formed from the inside of a pipe | tube. It is the perspective view (a) which shows the measuring process for measuring the height of the measuring device for height detection, and the convex wrinkle transcription | transfer part using the same, and sectional drawing (b) which shows the principal part. It is the front view (a) explaining the problem of the conventional measuring method, and sectional drawing (b) which shows the principal part.

Explanation of symbols

W tube (measuring object)
DESCRIPTION OF SYMBOLS 1 Molding material 1A Acupuncture transfer part 2 Frame body 3 Lid 4 Strut stick 5 Measuring instrument 5A Base plate 5B Leg part 5C Tip of stylus

Claims (4)

  When measuring the depth of the inner surface flaw of the pipe by the nondestructive inspection method, after transferring the concave inner surface flaw to the molding material, measure the height to the top of the convex wrinkle transfer part formed in the molding material And the inner surface wrinkle measuring method of the pipe | tube characterized by making the height measured value into the depth of the said inner surface wrinkle.   Using a replica unit that has a frame and a lid that is fitted in the frame, and that is filled with molding material into the frame so that the molding material does not protrude from one side of the frame, 2. The method for measuring an inner surface flaw of a pipe according to claim 1, wherein transfer is performed.   The method for measuring an inner surface flaw of a pipe according to claim 1 or 2, wherein the molding material is a room temperature curable material.   It has a detector that detects the change in position when the stylus moves up and down, and the height of the stylus is measured using a measuring instrument for detecting the height of the stylus tip that is formed in a plane when viewed from the measurement target side. The method for measuring an inner surface flaw of a pipe according to any one of claims 1 to 3, wherein measurement is performed.

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