JPH0545341A - Ultrasonic probe for flaw inspection of boiler tube - Google Patents

Abstract

PURPOSE:To inspect a crack in the circumferential direction of a boiler tube to which an inspector is inaccessible, in the non-destructive optimum condition from inside the tube. CONSTITUTION:This probe is to inspect a crack of a boiler tube in the circumferential direction from inside of the tube according to the underwater ultrasonic inspection method. This probe is provided with a main body 6 inserted rotatably in the periphery of the axis of the boiler tube, a vertical probe 7 mounted to the main body 6 so as to confirm the shape and position of the welding bead and to measure the thickness of the tube, and two inclined probes 8a, 8b mounted to the main body 6 so as to detect a crack in the circumferential direction of the tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler tube ultrasonic probe suitable for detecting circumferential cracks generated in a welded weld of a boiler tube.

[0002]

2. Description of the Related Art A circumferential fatigue crack is generated in a welded portion of an adhered metal such as a superheater or a reheater of a thermal power boiler due to thermal stress associated with start and stop. However, the superheater, the reheater, and the like cannot be accessed by the inspector because the tube interval is as narrow as 50 to 100 mm. For this reason, conventionally, the confirmation of fatigue cracks has been performed by collecting a sample tube. Therefore, the investigation place is limited, and it takes a lot of cost to restore the sample collecting position.

[0003]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above circumstances, and non-destructively develops a circumferential crack generated in a portion of a boiler tube inaccessible by an inspector from the inside of the tube. It is an object of the present invention to provide an ultrasonic probe for flaw detection in a boiler tube, which is inspected in an optimal state.

[0004]

To this end, the present invention provides a probe for inspecting cracks in the circumferential direction of a pipe from the inside of a boiler tube by means of water-immersion type ultrasonic flaw detection. A probe body that is rotatably inserted around, a vertical probe for checking the weld bead shape and position and measuring the pipe wall thickness that is mounted on the probe body, and is mounted on the probe body And two bevel probes for detecting a circumferential crack in the pipe.

[0005]

According to the ultrasonic probe for boiler tube flaw detection of the present invention, a crack generated in a welded metal weld of a boiler tube can be inspected from the inside of the tube non-destructively by water immersion type ultrasonic flaw detection. It is possible to inspect welded metal welds such as superheaters and reheaters of thermal power boilers that inspectors cannot access, and it is not necessary to polish the outer surface of the pipe for inspection. In addition to the confirmation of the shape and position of the weld bead, a vertical probe that can also measure the wall thickness of the pipe is mounted, so it is easy to confirm the flaw detection position and identify defects. Furthermore, since two bevel probes are inclined in the pipe axis direction by an arbitrary amount with respect to the diametrical pipe center line of the pipe, the pipe circumferential direction generated in the toe part and root part of the welded metal weld It is possible to detect cracks.

[0006]

1 is a side view of the present ultrasonic probe, FIG. 2 is a longitudinal sectional view of a rotating mechanism of the same, and FIG. Is an explanatory view of a flaw detection procedure with the present probe, FIG. 4 is an explanatory view of a procedure for detecting a welding bead with a vertical probe, and FIG. 5 is a side view showing a mode in which the present probe passes through a curved pipe section, FIG. 6 is a side view showing a mode in which the present probe detects flaws on a welded metal weld, and FIG. 7 is an explanatory view of an alignment jig in the same as above.

In FIG. 1, a vertical probe 7 for welding bead detection and pipe wall thickness measurement is mounted in the center of a probe body 6, and two probes for circumferential crack detection are provided on both sides of the vertical probe 7. The oblique-angle probes 8a and 8b are arranged symmetrically. Further, spring shafts 9 are attached to both ends of the probe body 6 in order to mount a jig for aligning the probe body 6.

As shown in FIG. 2, the spring shaft 9 is directly connected to bearings 11 attached to both ends of the probe main body 6, and has a vertical probe 7 and two oblique angle probes 8a. , 8b are mounted on the probe body 6 and are rotated by a spring shaft 9 and a rotor shaft 10 having a double structure. That is, since the bearing 11 is built in between the probe main body 6 and the spring shaft 9 and the probe main body 6 and the rotor shaft 10 are directly connected by the set piece 12, the probe is accompanied by the rotation of the rotor shaft 10. The main body 6 also rotates.

To detect a circumferential crack in a boiler tube by using such an ultrasonic probe, as shown in FIG.
As shown in (A) and (B), the circumferential crack 4 generated in the welded portion 3 of the metal deposit 2 of the boiler tube 1 is ultrasonically detected from the inside of the boiler tube 1 through water 5. In order to do so, the bevel probes 8a, 8b are held inclined with respect to the diametrical tube center line in the tube axis direction by an angle θ _i that maximizes the detection of defects. However, since the two bevel probes 8a and 8b are symmetrically arranged, the corners formed by the cracks 4 and the pipe surface are always formed regardless of the welding root portion and the welding toe portion of the welding portion 3. Since either one of the ultrasonic waves can be incident on the part, flaw detection can be performed regardless of the axial feed direction.

To confirm the weld bead with the vertical probe 7, the procedure shown in FIGS. 4 (A) and 4 (B) is used. That is, in FIGS. 4A and 4B, the vertical probe 7 is held on the diametrical direction tube center line, and when the vertical probe 7 is in the position in the tube axis direction P ₁ , it is incident on the tube material. Ultrasonic waves are reflected on the outer surface of the tube, and multiple reflection echoes due to the wall thickness of the tube are obtained. On the other hand, at the position P ₂ of the vertical probe 7 in the pipe axis direction, the ultrasonic wave incident on the pipe material propagates into the welded portion 3 and is diffusely reflected on the surface of the welded portion 3, so that a reflection echo cannot be obtained. As described above, when confirming the weld bead with the vertical probe 7, the fact that the multiple reflection echo of the wall thickness of the weld 3 disappears is used. When measuring the wall thickness of the tube, the case where the above multiple echo is obtained is used.

Next, the manner in which the ultrasonic probe passes through the curved pipe portion will be described with reference to FIG. 5. Since both ends of the probe main body 6 are supported by the spring shafts 9, the curved pipe of the boiler tube 1 will be described. It is easy to pass through the department.

Further, referring to FIG. 6, the manner in which the attached metal welded portion (circumferential direction welded portion) of the boiler tube is flaw-detected by using this ultrasonic probe will be explained with reference to FIG. It is held on the tube axis center line of the boiler tube 1 by the aligning jig 13. As a result, the vertical probe 7 and the beveled probes 8a and 8b are always fed in the axial direction by running water or the like while rotating in the boiler tube 1 under constant conditions, and the welding beads are detected, the wall thickness of the pipe is measured, Furthermore, flaw detection of circumferential cracks is performed. In the figure, 14 is a centering jig pressing spring, 15 is a pressing spring adjusting nut, and 16 is a guide.

Here, the aligning mechanism of the aligning jig 13 and the structure of the guide 16 will be described. The aligning jig 13 uses nylon 17 as a material, and the number of materials per stock and the material are used at the time of manufacture. 8 is controlled, and as shown in FIG. 8, when the diameter of the centering jig 13 is larger than the inner diameter of the tube, the nylon 17 is uniformly crushed and the centering of the probe main body 6 becomes possible. .. In this case, if the center of the probe main body 6 is poor, the holding condition of the vertical probe 7 and the oblique angle probes 8a, 8b with respect to the tube axis and the like during rotation and axial feeding will not be constant, and the flaw detection performance will deteriorate or It becomes impossible to detect flaws. The guide 16 has a Teflon ball attached to the tip of the spring shaft 9, and prevents the tip of the spring shaft 9 from sticking to a protrusion such as the inner surface of the welded portion.

Thus, according to such an ultrasonic probe, the cracks 4 in the circumferential direction of the adhered metal welded portion 3 can be detected from the inside of the boiler tube 1 by the water immersion method.
No polishing is needed for sample collection. Further, since the vertical probe 7 for detecting the weld bead is mounted in the center of the probe body 6, the welding shape and position can be confirmed, defects can be easily identified, and the wall thickness of the pipe can be measured. it can. Moreover, since two bevel probes 8a and 8b facing each other are mounted,
Regardless of the welding root and welding toe, either one of the ultrasonic waves can always be incident on the corner formed by the pipe surface and cracks, so flaw detection can be performed regardless of the axial feed direction, and detection sensitivity is good, It is possible to detect flaws in minute cracks.

[0015]

In summary, according to the present invention, a probe for inspecting a crack in the circumferential direction of the pipe from the inside of the boiler tube by means of water immersion ultrasonic flaw detection, which is rotated around the axis in the boiler tube. A probe body inserted as much as possible, a vertical probe for confirming the weld bead shape and position and measuring the pipe wall thickness mounted on the probe body, and a pipe mounted on the probe body. With two bevel probes for detecting circumferential cracks, it is possible to optimize non-destructively the circumferential cracks that occur in locations where boiler tube inspectors cannot access. INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because an ultrasonic probe for boiler tube flaw detection is obtained under the condition.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of an ultrasonic probe for boiler tube flaw detection according to the present invention.

FIG. 2 is a vertical cross-sectional view of the above rotating mechanism.

FIG. 3 is an explanatory diagram of a flaw detection procedure by the present probe.

FIG. 4 is an explanatory diagram of a procedure for detecting a welding bead with a vertical probe.

FIG. 5 is a side view showing a mode in which the present probe passes through a curved tube portion.

FIG. 6 is a side view showing a mode in which the present probe detects flaws on an attached metal weld.

FIG. 7 is an explanatory diagram of an alignment jig in the above.

[Explanation of symbols]

 1 Boiler tube 2 Adhesive metal 3 Welding part 4 Crack 5 Water 6 Probe body 7 Vertical probe 8a, 8b Angle probe 9 Spring shaft 10 Rotor shaft 11 Bearing 12 Set piece 13 Aligning jig 14 Adjusting Core jig Holding spring 15 Holding spring adjusting nut 16 Guide 17 Nylon

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Keiichi Iwamoto 1-1, Atsunoura-machi, Nagasaki City Nagasaki Research Institute, Mitsubishi Heavy Industries, Ltd. (72) Inventor Yukio Kato 4-10-13 Ibori, Kokurakita-ku, Kitakyushu City New Japan Non-destructive inspection Co., Ltd. (72) Inventor Akihiro Ueno 4-10-13 Ibori, Kokurakita-ku, Kitakyushu City New Japan Non-destructive inspection Co., Ltd.

Claims (1)

[Claims] 1. A probe for inspecting a crack in a circumferential direction of a pipe from the inside of a boiler tube by water immersion ultrasonic flaw detection, the probe being rotatably inserted around the axis in the boiler tube. Sub-body, vertical probe mounted on the above-mentioned probe main body for confirming weld bead shape and position and measuring pipe wall thickness, and pipe circumferential crack detection mounted on the above-mentioned probe main body An ultrasonic probe for flaw detection in a boiler tube, characterized in that it has two bevel probes.