JPS59119259A - Automatic ultrasonic flaw detector for tube wall - Google Patents

Abstract

PURPOSE:To perform calibrating operation at an optional point of time by incorporating a test piece for calibration and directing an ultrasonic wave from a probe freely to a tube to be inspected or the test piece for calibration. CONSTITUTION:An ultrasonic flaw detector has the double structure of an external cylinder 6 and a cylindrical member 5 and is fixed in a pressure tube by a fixing mechanism 1. The cylindrical member 5 is axially movable and an inspecting device body 2 which is rotated by a rotation driving mechanism 4 is positioned at the upper part. The inspecting device body 2 is fitted with ultrasonic wave probes 15a and 15b, acoustic mirrors 3a and 3b, test pieces 18a and 18b for calibration, and a direction change driving mechanism which changes directions of the acoustic mirrors 3a and 3b. The probe 15a detects a circumferential flaw and the probe 15b detects an axial flaw. The test pieces 18a and 18b are made by cutting the same material with the tube 1 and artificial flaws 34 and 35 are cut. The direction change driving mechanism for the acoustic mirrors and a moving mechanism for the test pieces are operated remotely from a control panel 12 to switch an inspection and a calibration state instantaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus that is inserted into the inside of a tube to be inspected and performs ultrasonic flaw detection on the tube wall, and more particularly relates to a continuously rotating automatic ultrasonic flaw detection apparatus with a built-in calibration function. It is something. Although not particularly limited, the present invention is a device suitable for automatically inspecting the wall surface of a long tubular body that is difficult for humans to access, such as the pressure pipe of a pressure tube nuclear reactor. be.

Hereinafter, the prior art and the present invention will be explained by taking as an example the case of inspecting a pressure tube of a pressure tube type nuclear reactor. As with other nuclear reactors, pressure tube reactors also require regular inspections during their service life, but the area around the pressure tubes is under a radiation environment, so humans are not required to perform inspections during inspections. Cannot stay close for long periods of time. For this reason, at present, when performing ultrasonic flaw detection inspection on pressure pipes, the ultrasonic flaw detection inspection is performed from inside the pressure pipe using a remote automatic operation type inspection device.

In order to ensure the reliability of inspection data in such ultrasonic flaw detection, it is necessary to calibrate the inspection device from time to time using a calibration test piece.

Conventional inspection devices of this type do not have a built-in calibration mechanism, and therefore require very long and labor-intensive work for calibration. In other words, equipment used inside pressure pipes becomes contaminated with radioactive materials, so inspectors must handle the equipment carefully, wearing rubber gloves and masks. In addition, with conventional equipment, the equipment is calibrated before inspection, the equipment is installed in the pressure pipe for several tens of minutes, then the equipment is inspected, and the equipment is removed from the pressure pipe for several tens of minutes. Since calibration cannot be performed, calibration is performed before and after the inspection (limited to 30 seconds), which increases the time interval between calibrations, and because calibration cannot be performed under the same radiation conditions as during the inspection, the reliability of the inspection data may be affected. The drawback was that it was not always sufficient.

Furthermore, with conventional automatic ultrasonic flaw detection VZ systems, if the probe is continuously rotated in one direction, the cable connected to the probe that transmits the ultrasonic flaw detection signal will be twisted and cut. Therefore, the structure had to be inspected by repeated rotations. For this reason, the driving speed of the inspection device cannot be increased above a certain speed, and when inspecting a long tube (approximately 5 tIl) such as a pressure tube, it takes a long time. In addition, in order to shorten the inspection time,
There is also equipment that inspects the entire circumference of the pipe to be inspected at once by arranging a large number of probes in the circumferential direction, and the probes move only in the axial direction. Although it is faster, it is also very expensive and impractical.

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art, to provide a tube that allows for extremely easy calibration work, extremely high reliability of inspection data, and that can significantly shorten the time required for inspection. Our objective is to provide automatic ultrasonic wall flaw detection equipment.

The present invention, devised to achieve the above objects, incorporates a test piece for calibration in the main body of the inspection device, and changes the direction of the ultrasonic waves emitted from the ultrasonic probe to the direction of the tube to be inspected or to the calibration test piece. By using a 414-piece structure that can be freely switched in the direction of the test piece, calibration work can be performed at any time with the inspection device main body installed inside the pipe to be inspected. This is an automatic ultrasonic flaw detection device for pipe walls that is designed to perform ultrasonic flaw detection by continuously rotating an ultrasonic probe in one direction by transmitting signals, power, etc. To summarize, the present invention is characterized in that it has a built-in calibration groove Ia and that ultrasonic flaw detection can be performed in a continuous rotation manner.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is an explanatory diagram showing a schematic structure of an automatic ultrasonic flaw detection device inserted into a pressure tube of a pressure tube nuclear reactor. The ultrasonic flaw detection device is used in a pressure tube reactor to detect flaws in the pressure tube by handling the fuel assembly from the pressure tube 1 and then inserting it into the pressure tube 1 from below. , has a double structure with a cylindrical member 5 located inside thereof and forming a sealed structure, and is fixed inside the pressure pipe 1 by a fixing device 4I410 equipped with a sealing material 9. The cylindrical member 5 is movable in the axial direction by engagement between a pinion 7 incorporated therein and a rack 8 attached to the inner surface of the outer cylinder 6. Further, an inspection device main body 2 is located coaxially with the upper part of the cylindrical member 5, and the inspection device main body 2 is rotatably supported on the cylindrical member 5, and has a rotary drive mechanism 4.
It is rotatable in the circumferential direction. As a result, due to the combination of the above-mentioned mechanisms, the inspection device main body 2 is movable in the axial direction inside the pressure pipe 1 and is also rotatable in the circumferential direction. The movement of these inspection devices can be controlled remotely from a control panel 12 connected via a cable 11, which allows the axial position and circumferential direction of the inspection device body 2 to be freely controlled. , the pressure pipe 1 is inspected. Incidentally, at the time of inspection, reactor secondary cooling water (light water) is contained inside the pressure pipe 1.

Now, the internal structure of the inspection device body is shown in Figure 2.
< is. This embodiment is an example in which an ultrasonic probe and its related members are each incorporated in two phases. The inspection device main body 2 has a rotatable structure with a rotary drive shaft 31 fixed to its lower end, and the rotary drive shaft 31 is connected to a motor 33 via a speed reducer 32. Inspection device body 2
Inside, there are ultrasonic probes 15a, 151) mounted at approximately 180° symmetrical positions with respect to the central axis and emitting ultrasonic waves downward in the axial direction, and an acoustic transducer equipped with a reflective surface that reflects the ultrasonic waves. Mirrors 3a, 3b and each acoustic mirror 3
A calibration test piece 18a installed near a and 3b,
18b, and a direction changing drive mechanism that changes the direction of the acoustic mirrors 3a, 3b. Here, the ultrasonic probe 15a is used to detect flaws occurring in the circumferential direction of the pressure pipe 1, while the ultrasonic probe 15b is used to detect flaws in the axial direction. be. These ultrasound probes 1
The acoustic mirrors 5a, 15b and the acoustic mirrors 3a, 3b are arranged so that their respective central axes are aligned.

Acoustic mirrors 3a and 3b are ultrasound probes 15a.

151) so that the ultrasonic waves emitted from the pressure pipe can be incident at an angle of incidence suitable for ultrasonic flaw detection of pressure pipes, so that the reflecting surface is finished inclined at an appropriate angle.

Further, the calibration test pieces 18a and 18b are cut out from the same material as the pressure pipe 1, which is the object to be inspected, and have artificial flaws 34 and 35 carved on their surfaces, respectively. The solid line indicates an artificial flaw processed on the front surface (corresponding to the inner surface of the pressure tube) of the calibration test piece 18a, 181), and the broken line indicates an artificial flaw processed on the rear surface (corresponding to the outer surface of the pressure tube). )
This shows the artificial flaws that have been processed. In the case of ultrasonic flaw detection, even if the flaw is the same size, the detection sensitivity is different for flaws on the inner surface of the pressure pipe and flaws on the outer surface, so in order to perform calibration for flaws on either side, Artificial flaws 34 and 35 for calibration are provided in each case.

The acoustic mirror direction changing drive mechanism and the associated calibration test piece moving mechanism are as follows.

In order to make it easier to understand, Figures 3 to 5 depict this part. Each acoustic mirror 3a
, 3b are attached to the gear 20a.

20b is rotatable by meshing with a large gear 21 located at the center, and the large gear 21 has a cam 19 integrated therewith.
and is connected to the motor 26 via a mirror drive shaft 29 and a reduction gear 27. The motor 26 is the inspection device main body 2
By driving the motor 26 (φ), the mirror drive shaft 29, and by extension the acoustic mirror 3a,
3b can be rotationally driven. Gears 20a, 2
0b and the large gear 21 have teeth only on a part of their outer peripheries, and even if the large gear 21 rotates any further after they are disengaged from each other, the gear 20a remains closed.

20b has a shape that does not rotate and remains oriented in a fixed direction. In addition, the cam 19
has a first cam surface and a second cam surface on its top and side surfaces. The calibration test piece 18a is the spring 17a.
The first cam surface is pressed downward and comes into contact with the first cam surface, and can be moved in the axial direction accordingly. On the other hand, the calibration test piece 18b is pressed toward the center by the spring 17b, comes into contact with the second cam surface, and is movable in the radial direction of the pressure tube 1 in accordance with the movement of the cam 19. With this structure, simply by rotating the motor 26 by remote control from the control panel 12, it becomes possible to immediately switch between the inspection state and the calibration state.

Ultrasonic probe 1! ia, 151) signal transmission cables 14a, 14b and the power transmission cable 13 to the motor 26 pass through the interior of the mirror drive shaft 29 to a rotating side sliding contact formed on the outer circumferential surface of the rotation drive shaft 31. 27
Connected to 1. An annular sliding contact main body 23 is located on the outer periphery of the rotating sliding contact 24 and is arranged to surround it, and the rotating sliding contact is connected to the fixed sliding contact 22 formed on the inner peripheral surface of the rotating sliding contact 24. 24 makes contact. It will be connected to an external device via a multicore cable 25 via these sliding contacts. Therefore, even if the inspection device main body 2 rotates, each cable 13.14a, 14b does not twist, and the electrical connection with the external device is maintained through contact between the fixed side sliding contact 22 and the rotating side sliding contact 24. will be achieved. Note that numerals 28 and 30 are seal rings for keeping the inside airtight.

Next, the operation of this device will be explained. The state shown in FIG. 2 is a state in which the reflective surfaces of the acoustic mirrors 3a, 3t+ are directed toward the inner surface of the pressure pipe 1, and the pressure pipe 1 is being inspected. To calibrate the device from this state, the mirror drive shaft 29 can be rotated counterclockwise by the motor 26 when viewed from above. Cam 19 and calibration test piece 18
Figure 6 shows the movement of gear 21 and acoustic mirrors 3a and 3b.
The movements of the cam 19 and the calibration test piece 18b are schematically shown in FIG. 7 and FIG. 8, respectively. Mirror drive 11i
When the Il 129 rotates, the large gear 21 also rotates counterclockwise, and the gear 2 meshing with the large gear 21 rotates accordingly.
0a and 2011 will each rotate clockwise. Therefore, the acoustic mirrors 3a and 3b mounted and fixed on the respective gears 20a and 20b also rotate.
(see), their reflective surfaces point in the direction of the artificial flaws 34 and 35 of the corresponding calibration test pieces 18a and 181) (as described above, the structure of the gears 20a and 20b is such that the teeth are machined on the entire circumference). When the reflective surfaces of the acoustic mirrors 3a and 3b face the center position of the artificial flaw 34.35,
Even if the gear 21 rotates further, the acoustic mirrors 3a, 3b
The teeth are cut in the middle so that the acoustic mirrors 3a and 3b stop rotating at that position (see Fig. 7 C to E). When the calibration test piece 18a, 1 is
8b is also moved. That is, as shown in FIG. 6, when the cam 19 rotates, the calibration test piece in contact with the first cam surface moves upward as shown by the arrow (see E in the same figure). 〉.Also, as shown in Fig. 8, the calibration test piece 18b in contact with the second cam surface is moved in the direction of the arrow, that is, in the right-hand direction in the drawing.
(See figure E). To explain these operations collectively, in FIGS. 6 to 8, when the calibration operation is started,
First, as shown in A and B, the large gear 21 rotates and the gear 2
0a and 2Gb, and the acoustic mirrors 3a and 3b mounted thereon are used as calibration test pieces 18a and 18b.
turn it towards. Even if the large gear 21 continues to rotate, the acoustic mirrors 3a and 3b do not move as shown in C, and calibration is performed using the artificial flaw on the front surface shown by the solid line. The large gear 21 further rotates, and D.

As shown in E, the calibration test piece 18a is
, 18b is moved, a calibration is performed due to the artificial flaw on the rear surface shown in dashed lines. In this way, the rotation of the acoustic mirrors 3a, 3b and the calibration test pieces 18a, 18b
The ultrasonic probes 15a, 1! move in the axial direction or radial direction, respectively, to the artificial flaws carved on the front or rear surfaces of the ultrasonic probes 15a, 1! The ultrasonic waves emitted from the ib hit the ib, allowing the device to be calibrated. The mirror drive shaft 29 is designed to stop when the calibration operation of the system is completed, and once the calibration is completed,
By performing the above-mentioned operations in reverse order, the inspection state can be returned to, so that the ultrasonic flaw detection of the pressure pipe can be performed immediately. As mentioned above, the ultrasonic probe 15a,
The signal transmission cables 14a, 141) of 15b and the power transmission cable 13 to the motor 26 pass through the interior of the mirror drive shaft 29 and are connected to the rotating side sliding contact 24.
The end of the cable is connected to the control panel 12 with a multi-core cable 25 connected to the sliding contact 22 on the fixed side, so even if the inspection device main body 2 is continuously rotated in one direction, the cable will not be connected. Ultrasonic signals and motor power can be transmitted without twisting. Therefore, ultrasonic flaw detection of the pressure pipe 1 can be performed by continuously rotating the inspection device main body 2 in one direction at high speed.

A preferred embodiment of the present invention has been described in detail above.
The present invention is not limited to this structure, and various modifications are possible. In this example, two sets of probes are provided, one for detecting flaws occurring in the axial direction of the tube and the other for detecting flaws occurring in the circumferential direction. Depending on the situation, you may only need ~silk, or you may have three or more pairs. In addition, artificial flaws were provided on the front and rear surfaces of the calibration test piece so that calibration could be performed for each artificial flaw, making the IN 41! It took
Depending on the purpose of the inspection, such as finding only flaws on the inner surface of the pipe to be inspected, or conversely finding flaws only on the outer surface, it may be necessary to engrave only one of the flaws on the calibration test piece. In that case, the mechanism can be considerably simplified. On the other hand, in order to carry out calibration even more strictly, there are cases where a plurality of various large-sized flaws are formed on the calibration test piece, and in such a case, the mechanism may become quite complicated.

Since the present invention is an automatic ultrasonic flaw detection device for tube walls configured as described above, it can achieve the following excellent effects. First, a calibration test piece is built in near the ultrasonic probe, and calibration can be performed whenever necessary4.
Since it is made of M construction, it is possible to calibrate not only immediately before or after the inspection, but also during the inspection if necessary, which greatly improves the reliability of the inspection data, and the calibration work is extremely simple. It is particularly effective in environments where the equipment is contaminated with radioactive materials, reducing the time required for calibration to less than one-tenth of the time required using conventional equipment, and it is possible to reduce the time required for calibration using conventional equipment. Even if the characteristics of the device system change somewhat due to the influence of the line, calibration can be performed under the same conditions as during the inspection, so the reliability of the inspection data is further improved. In addition, since it is possible to perform inspection while continuously rotating the ultrasonic probe, it is possible to obtain a device that is much cheaper than conventional ultrasonic flaw detection equipment equipped with multi-channel probes. The inspection speed can be more than twice as fast as that of a repeating rotation type ultrasonic flaw detector. Combining the various effects mentioned above, the reliability of inspection data is significantly increased compared to conventional inspection equipment, and at the same time, the time required for inspection is less than half that of conventional inspection equipment. Since it provides a flaw detection device, it can be said to be extremely effective.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention, Fig. 2 is an TI explanatory diagram showing details of the inspection device main body and its drive section, Fig. 3 is an explanatory diagram of the acoustic mirror deflection drive mechanism, and Fig. 4 The figure is a plan view, FIG. 5 is a rear view, and FIGS. 6, 7, and 8 are explanatory diagrams of the operation. 1... Pressure pipe, 2... Inspection device main body, 3a, 3b.
...Acoustic mirror, 15a, 15b...Ultrasonic probe, 18a, 1811...Calibration test piece, 22...
- Fixed side sliding contact, 24...Rotating side sliding contact. Patent applicant: Power Reactor and Nuclear Fuel Development Corporation
Japan Cloud Claimer Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1. A cylindrical member that is inserted into the inside of the tube to be inspected and is movable in its axial direction; An ultrasonic flaw detection device having an inspection device main body that is rotatable in the circumferential direction inside the inspection device main body, the inspection device main body having a
a free-time acoustic probe, a rotatable acoustic mirror positioned so that the ultrasonic waves emitted from the ultrasonic probe hit a reflecting surface, a calibration test piece, and a direction change for changing the direction of the acoustic mirror. a drive mechanism, and has a structure in which the direction of the reflected ultrasonic waves can be freely switched in the direction of the tube to be inspected or in the direction of the calibration test piece by rotating the acoustic mirror by the direction changing drive mechanism; On the rotation support part of the inspection device main body,
An automatic ultrasonic wave detector for pipe walls characterized in that a sliding contact is provided for electrical connection between the inspection device body and the outside, so that ultrasonic flaw detection can be performed while the inspection device body rotates continuously in one direction. Flaw detection equipment.