JPH0829576A - Flaw detector at welded part of nozzle - Google Patents

Abstract

PURPOSE:To obtain a flaw detector at the welded part of a nozzle by which the flaw can be detected with high accuracy regardless of the spreading of a beam irradiated from a probe. CONSTITUTION:A truck is run along the outer circumference of a nozzle. When a plurality of probes are moved along a flaw detection arm fixed to the truck, a control means controls the rotary mechanism 31 mounted on one 18a of the plurality of probes 18, 18a, 18b, which is shifted from the central axis of the flaw detection arm, such that the incident direction of ultrasonic wave from the probe 18a is matched constantly with the center of nozzle depending on the moving position in the radiating direction of nozzle. Consequently, the flaw can be detected while directing all probes toward the center of nozzle regardless of the moving position. This structure enhances accuracy in the location of flaw thus realizing high accuracy flaw detection without causing deterioration of accuracy due to spreading of ultrasonic beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw detection device for a nozzle welded portion for detecting the soundness of a welded portion of a nozzle welded to a device body such as a reactor pressure vessel or a pressure vessel of a chemical plant. The tentacle is always directed toward the center of the nozzle so that scanning can be performed.

[0002]

2. Description of the Related Art Equipment such as reactor pressure vessels and pressure vessels of chemical plants are required to undergo regular inspections to ensure their safety. For example, non-destructive inspections are mainly applied to reactor pressure vessels. The inspection is conducted during the in-service period.

For example, as one of the inspection objects of the reactor pressure vessel, the nozzle (cylindrical) 1 and the body (cylindrical) of the reactor pressure vessel 2 as shown in FIGS. 3 (a) and 3 (b) are welded. There is a welded part 3.

Since the welded portion 3 has a complicated three-dimensional saddle shape, it has been difficult to perform automatic flaw detection by a machine, but a flaw detection device for automatically flaw detection has already been developed.
The structure is as shown in FIG.

The flaw detection device 10 includes a running wheel 11 of a permanent magnet having a drive mechanism that runs along the outer peripheral surface of the shoulder portion of the nozzle 1 and a permanent magnet rolling along the inclined surface of the shoulder portion of the nozzle 1. The two guide wheels 12 are attached to the front and rear sides in the traveling direction, respectively, and the two supporting wheels 13 roll along the side surface of the nozzle 1 at the center in the traveling direction.
It is equipped with a traveling carriage 14 to which the nozzle 1 is attached by an LM guide and a rack and pinion.
The slide base 15 that moves in the axial direction is mounted, and the flaw detection arm 16 arranged in the radial direction of the nozzle 1 is supported at the tip of the slide base 15 so as to be movable in the axial direction of the nozzle 1. A probe mount 17 that moves along the flaw detection arm 16 with an LM guide and a rack and pinion is attached to the flaw detection arm 16 at a right angle to the flaw detection arm 16, and the probe attachment base 17 has an irradiation angle. 0,45,60
3 ultrasonic probe 18, 18a, 1
8b is attached. A pressing cylinder 19 is connected between the slide base 15 and the flaw detection arm 16, and the three flaw detection arms 16 each have three probes 18, 18a, 1a.
8b can be pressed against the weld 3 of the nozzle 1.

Further, these probes 18, 18a, 18b
As shown in FIG. 5, is attached to a probe mount 17 via a gimbal mechanism 20 so that the tip surface can be tilted in any direction.

Therefore, the traveling carriage 14 is used for flaw detection.
Rotation around the X-axis for traveling along the outer circumference of the nozzle 1, traveling along the Y-axis for moving the probe mounting base 17 along the flaw detection arm 16, and X-axis for moving the slide base 15 in the nozzle axial direction. The probe 18 for ultrasonic flaw detection, 18a,
18b is pressed against the welded portion 3 on the outer circumference of the nozzle, which is a flaw detection portion, so as to follow the saddle shape, and an ultrasonic flaw detection test is automatically performed.

[0008]

However, when an ultrasonic beam is injected in the direction perpendicular to the welding line in the flaw detection device 10 for flaw detection, as shown in FIG. 6 (a), three probes 18 are provided. , 18a, 18b, the probe 18 attached in the radial direction of the nozzle 1 does not change its incident direction even if it moves in the Y-axis direction along the flaw detection arm 16 between the flaw detection ranges L, but on both sides. The attached probes 18a and 18b are displaced from the flaw detection range L by an angle α with respect to the radial direction on the outer side A, and on the inner side B of the flaw detection range L by an angle β with respect to the incident direction. Therefore, there is a problem that the detection accuracy of the defect position is affected by the spread of the ultrasonic beam.

Further, in the case where the beam is incident on the flaw detection device 10 in parallel with the welding line to detect a flaw, the flaw detection device 10 is also shown in FIG.
As shown in FIG. 3, among the three probes 18, 18 a, 18 b, the probes 1 mounted on both sides of the nozzle 1 in the radial direction are shown.
8a and 18b, in the outer side A of the flaw detection range L, the incident direction is deviated from the radial direction by an angle α, and the intermediate portion C is deviated by an angle γ. There is a problem of being affected by the spread.

The present invention has been made in view of the above prior art, and provides a flaw detection device for a nozzle welded portion capable of performing flaw detection with high accuracy without being affected by the spread of the beam emitted from the probe. Is what you are trying to do.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, a nozzle welded portion flaw detection apparatus of the present invention is an apparatus for flaw detection of a nozzle welded portion welded to an equipment body. A possible traveling carriage, and a flaw detection arm that is erected in the radial direction of the nozzle of this traveling carriage and that is movable toward the equipment body side, and a plurality of movable along the flaw detection arm that are arranged side by side in the direction perpendicular to the nozzle radiation. Probe, a rotation mechanism that is provided on one of these probes that is not located on the center line of the flaw detection arm and that rotates about a rotation axis that is perpendicular to the probe surface of the probe, and a probe that includes these rotation mechanisms. The control means of the rotating mechanism controls the rotational position of the probe surface at the tip of the probe by moving the probe in the radial direction of the nozzle.

[0012]

According to this flaw detection apparatus for the nozzle welded portion, when the traveling carriage is made to travel along the outer periphery of the nozzle and a plurality of probes are moved along the flaw detection arm attached to the traveling carriage, A rotating mechanism provided on a part of the probe that is not on a concentric circle centered on the center axis of the nozzle is controlled by the controller to rotate the probe surface of the tip of the probe about an axis perpendicular to this, depending on the movement position in the nozzle radial direction. Therefore, regardless of the movement position, flaw detection can be performed by optimizing the incident direction of ultrasonic waves of all the probe shells.

As a result, the detection accuracy of the defect position is improved, and the flaw detection can be performed with high accuracy without lowering the accuracy due to the spread of the beam such as ultrasonic waves.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view and a sectional view of a probe portion of an embodiment of a flaw detection device for a nozzle welded portion of the present invention. The flaw detection device 30 for the nozzle welded portion is the probe 1
The structure is the same as that of the flaw detector 10 already described with reference to FIG. 4 except for the structure of the mounting portions of 8, 18a, and 18b, and the description of the same portions will be omitted.

In the flaw detection device 30 for the nozzle welded portion, among the probes mounted on the probe mounting base 17 movable along the flaw detection arm 16, a concentric circle centered on the central axis of the nozzle 1 ( The rotating mechanism 31 is provided on the probes 18a and 18b on both sides which are mounted so as to be displaced from the radial direction).

The rotating mechanism 31 rotates around an axis (rotating axis in the nozzle axis direction) parallel to the central axis (X axis) of the nozzle 1 (around an axis perpendicular to the tip sensing surfaces of the probes 18a and 18b). The probes 18a and 18b are each rotated. In the rotating mechanism 31, a base 32 is attached to the probe mount 17, and a rotating shaft of a ring gear 34 is rotatably attached to the base 32 via a bearing 33.

An outer frame 21 of the gimbal mechanism 20 is integrally attached to the ring gear 34, and the gimbal mechanism 20 is attached.
Is rotatable about an axis perpendicular to the probe surfaces of the tips of the probes 18a and 18b (a rotation axis parallel to the nozzle axis direction). A DC gear motor 35 having a pinion that meshes with the ring gear 34 is attached to the base 32, and a potentiometer 36 having a pinion that meshes with the ring gear 34 is attached to the base 32. The DC gear motor 35 and the potentiometer 36 are connected to the control device 37, and the probe 1
The detection signals of the moving positions of 8, 18a, 18b are input,
Based on this, the rotation angles of the probes 18a and 18b are controlled and set.

An inner frame 22 is arranged inside the outer frame 21 of the gimbal mechanism 20, both sides of the inner frame 22 are rotatably attached to the outer frame 21 by pins 23, and further, the inner frame 22.
The probe 18a (18b) is arranged inside the
It is rotatably attached to the inner frame 22 by the pins 24 on both sides in a direction orthogonal to the pin 23 that supports (see also FIG. 5).

Therefore, the tip of the probe 18a (18b) can be oriented at any angle by the gimbal mechanism 20, and the probe 1 can be rotated by the rotating mechanism 31.
The tip probe surfaces of 8a and 18b can be rotated about an axis perpendicular thereto (about a rotation axis parallel to the nozzle axis direction (X axis direction)), and the rotation amount of this probe 18a (18b) can be changed. It can be arbitrarily set by the controller 37 by the potentiometer 36 and the DC gear motor 35.

In the flaw detection device 30 for the nozzle welded portion provided with such a rotating mechanism 31, when the flaw detection of the welded portion 3 of the nozzle 1 is performed, the traveling wheel 11 made of the permanent magnet of the traveling carriage 14 is driven by the drive mechanism. In addition, the guide wheel 12 made of a permanent magnet is made to travel along the inclined surface of the shoulder portion of the nozzle 1 in combination to cause the traveling travel, and thereby the traveling carriage 14 travels along the outer periphery of the nozzle 1. Rotation around the X-axis, traveling along the Y-axis, which is movement of the probe mount 17 along the flaw detection arm 16 by a drive mechanism (not shown) in the nozzle radial direction, and slide base 15
Is combined with traveling along the X-axis, which is moved in the nozzle axial direction by a drive mechanism (not shown), so as to follow the saddle-shaped welded portion 3 of the outer periphery of the nozzle 1 welded to the reactor pressure vessel 2 and the probe. The mount 17 is moved.

When the probe mount 17 is moved along the flaw detection arm 16 in the Y-axis direction, the incident direction of the probe 18a (18b) with respect to the movement position in the Y-axis direction is made to coincide with the center of the nozzle. The required rotation angle is obtained, for example, the angles are obtained as α, β, γ with respect to the moving positions A, B, C, and the moving position is detected by an encoder in the drive mechanism of the probe mount 17. , The controller 37 adjusts the potentiometer 36 and DC so that the angle corresponds to this moving position.
The gear motor 35 controls the amount of rotation of the probe 18a (18b).

With the amount of rotation of the probe 18a (18b) set in this way, the ultrasonic welding flaw detection probes 18, 18a, and 18b are welded to the welding portion 3 on the outer periphery of the nozzle, which is the flaw detection portion, by the pressing cylinder 19. The ultrasonic flaw detection test is performed by pressing the flaw detection arm 16 together with the flaw detection arm 16. When changing the flaw detection position along the Y-axis direction, the probe 18a (18
The ultrasonic detection test is repeated by setting the incident direction of b) toward the center of the nozzle to detect the entire welded portion 3.

As described above, since the flaw detection can be performed by making the incident direction of the probe 18a (18b) coincident with the center of the nozzle, even if the flaw is detected by the flaw detection, its position can be accurately known. .

For the probe 18b, the probe 1 is used.
It goes without saying that it is rotated in the same direction as that of 8a but in the opposite direction.

In the flaw detector 30 for the nozzle welded portion constructed as described above, of the probes 18, 18a, 18b mounted on the probe mount 17, two probes arranged so as to be displaced from the nozzle radiation direction are used. A rotating mechanism 3 is provided so that the tentacles 18a and 18b can be rotated around a rotation axis parallel to the central axis of the nozzle.
1, and the rotation angle of the probe arm 16 depends on the position on the probe arm 16.
The C gear motor 35 can be set so as to face the center of the nozzle. For example, as shown in FIG. 2, the positions of A and B and the welding of the nozzle 1 representing the case where the beam is incident perpendicularly to the welding line of the nozzle 1 are shown. It is possible to detect flaws by always making the incident direction of the beam coincide with the center of the nozzle regardless of the position of C, which represents the case where the beam is incident parallel to the line.

Therefore, according to the flaw detection device 30 for the nozzle welded portion, the presence or absence of a defect is conventionally detected by utilizing the spread of the beam. It is possible to accurately detect the existing position.

[0027]

As described above in detail with reference to the embodiment, according to the flaw detection device for a nozzle welded portion of the present invention,
When moving the traveling carriage along the outer circumference of the nozzle and moving multiple probes along the flaw detection arm attached to this traveling carriage, place the probe on a concentric circle centered on the nozzle center axis. The rotating mechanism provided for the non-existing device is designed to control the rotation of the probe surface of the probe tip about an axis perpendicular to this by the moving position in the nozzle radial direction, so that all probes can be moved regardless of the moving position. The flaw detection test can be performed by optimizing the incident direction of ultrasonic waves on the tentacle shell.

As a result, the detection accuracy of the defect position is improved, high-accuracy flaw detection can be performed without lowering the accuracy due to the spread of the beam such as ultrasonic waves, and the existence position of the defect can be increased as well as the presence or absence of the defect. It can be detected accurately.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view of a probe portion of an embodiment of a flaw detection device for a nozzle welded portion of the present invention.

FIG. 2 is an explanatory view of a beam incident direction by a flaw detection device for a nozzle welded portion according to the present invention, where A and B indicate a case where an ultrasonic beam is incident in a direction perpendicular to a welding line for flaw detection, and C indicates a welding line. The case is shown in which the beam is incident parallel to and the flaw detection is performed.

FIG. 3 is an explanatory perspective view and an explanatory development view of a welded portion between a reactor pressure vessel and a nozzle, which is an example of an object to be inspected by the inspection apparatus for a nozzle welded portion of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional flaw detection apparatus for a nozzle welded portion mounted on a nozzle.

FIG. 5 is a front view showing a probe mounting structure of a conventional flaw detection device for a nozzle welded portion.

6A and 6B are explanatory views of a beam incident direction by a conventional flaw detection apparatus for a nozzle welded portion, in which FIG. 6A shows a case where an ultrasonic beam is incident in a direction perpendicular to a welding line for flaw detection, and FIG. The case where the beam is incident parallel to the line for flaw detection is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle 2 Reactor pressure vessel (equipment main body) 3 Welding part 30 Nozzle welding part flaw detector 11 Traveling wheel 12 Guide wheel 13 Supporting wheel 14 Traveling trolley 15 Slide platform 16 Testing arm 17 Probe mount 18, 18, a, 18b Probe 19 Pressing cylinder 20 Gimbal mechanism 21 Outer frame 22 Inner frame 23, 24 pin 31 Rotating mechanism 32 Base 33 Bearing 34 Ring gear 35 DC gear motor 36 Potentiometer A, B, C Moving position of the probe L Detecting range X-axis nozzle Center axis Y axis Nozzle radial direction α, β, γ Beam deviation angle

Claims (1)

[Claims] 1. A device for detecting a welded portion of a nozzle welded to a main body of a device, wherein a traveling carriage capable of following the outer periphery of the nozzle and a traveling carriage that is erected in a radial direction of the nozzle of the traveling carriage. A flaw detection arm that can move toward the equipment body, a plurality of probes that can move along this flaw detection arm and are arranged side by side in the direction perpendicular to the nozzle radiation, and those that are not on the flaw detection arm center line The rotation mechanism that rotates about a rotation axis that is perpendicular to the tip probe surface of the probe and the probe equipped with these rotation mechanisms moves the probe in the nozzle radial direction to determine the rotation position of the tip probe surface of the probe. And a control unit for controlling the rotating mechanism for controlling the above.