JPH0192607A - Tank plate inspecting device - Google Patents

Abstract

PURPOSE:To easily and smoothly inspect the plate thickness state of a tank plate by using a noncontract type ultrasonic wave generator and an ultrasonic wave detector. CONSTITUTION:The inspecting device 10 runs on the surface of the bottom plate 1 of a tank by itself with wheels 12A and 12B provided to a casing 11. The inspecting device 10 has the ultrasonic wave generator 13, ultrasonic wave detector 14, a data analyzing and storing circuit 15, a control circuit 16, a power circuit 17, and a wheel driving motor 18 incorporated in the casing 11. Laser light L1 from the ultrasonic wave generator 13 is projected on the surface of the tank bottom plate 1 as a body to be inspected to generate an ultrasonic wave in the surface of the tank bottom plate 1. The ultrasonic wave is propagated in the plate and reflected by the bottom surface of the tank bottom plate 1 to return to the surface. Consequently, the ultrasonic wave detector 14 performs detection by the intervention of the laser light L2. Data is analyzed by the data analyzing and storing circuit 15 to measure the plate thickness of the tank bottom plate 1 according to its reflection time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tank plate inspection device for inspecting the thickness of bottom plates, side plates, etc. of tanks for storing petroleum products, LNG, chemicals, etc.

[Prior Art] When the thickness of the bottom plate, side plate, etc. of a tank becomes thin due to corrosion or the like, there is a risk that the contents may leak. For this reason, depending on the contents, periodic board thickness inspections are required by law.

Conventionally, tank plate inspection equipment has been used to measure tank plate thickness by generating ultrasonic waves in each part of the tank plate and measuring the time it takes for the ultrasonic waves to propagate within the thickness of the tank plate. has been done. This tank plate inspection device includes an ultrasonic generator that generates ultrasonic waves on the tank plate, and an ultrasonic detector that detects the ultrasonic waves propagated within the thickness of the tank plate.

[Problems to be Solved by the Invention] However, in the conventional tank plate inspection device described above, the transmitting end of the ultrasonic generator is brought into contact with the surface of the tank plate, and the receiving end of the ultrasonic detector is brought into contact with the surface of the tank plate. It is a contact type. For this reason, (1) a couplant such as water is required to efficiently transmit ultrasonic waves into the subject, and post-treatment of this couplant is also required. In addition, (1) Since the unevenness of the surface of the object to be examined affects the measurement results, pretreatment to remove the unevenness of the surface and smooth the measurement surface such as polishing is necessary.

SUMMARY OF THE INVENTION An object of the present invention is to enable inspection of the thickness of a tank plate easily and smoothly.

[Means for solving the problem] The present invention generates ultrasonic waves in each part of the tank plate, and measures the time it takes for the ultrasonic waves to propagate within the thickness of the tank plate, thereby determining the thickness of the tank plate. A tank plate inspection device that measures tank plate includes an ultrasonic generator that generates ultrasonic waves in a non-contact manner to the tank plate, and an ultrasonic detector that detects ultrasonic waves propagated within the thickness of the tank plate in a non-contact manner. It is designed to have the following.

[Function] In the tank plate inspection device of the present invention, ultrasonic waves are generated in each part of the tank plate in a non-contact manner by an ultrasonic generator, and the ultrasonic waves propagated within the thickness of the tank plate are detected by ultrasonic waves. The ultrasonic wave propagates through the thickness of the tank plate without contact, and the thickness of the tank plate is measured by using the known ultrasonic propagation speed within the tank plate. I will do it.

Here, since the ultrasonic generator and ultrasonic detector are non-contact type, ■ no couplant is required, and ■ there is no need to smooth out the irregularities on the surface of the specimen in advance, allowing the plate to be easily and smoothly removed. Thickness can be inspected.

[Example] Fig. 1 is a schematic diagram showing an inspection device according to the first embodiment of the present invention, Fig. 2 is a schematic diagram showing the principle of plate thickness measurement of the present invention, and Fig. 3 is a schematic diagram showing the inspection device according to the first embodiment of the present invention.
The figure is a schematic diagram showing the detection principle of the ultrasonic detector, and FIG. 4 is a schematic diagram showing another detection principle of the ultrasonic detector.

The inspection device 10 can run on the surface of the tank bottom plate 1 using wheels 12A and 12B provided on the casing 11, as shown in FIG. The inspection device 10 includes, inside a casing 11, an ultrasonic generation laser (ultrasonic generator) 13, an ultrasonic detector 14. Data analysis/memory circuit 15, control circuit 1
6. Built-in power supply circuit 17 and wheel drive motor 18.

19A-19G are cable pulls for power supply, signal transmission, etc.

The plate thickness measurement principle of the inspection device 10 is as follows (Second
(see figure).

(A) Laser light L1 from the ultrasonic generation laser 13
By irradiating the surface of the tank bottom plate 1 as a subject, ultrasonic waves are generated on the surface of the tank bottom plate 1. The mechanisms of ultrasonic generation are: 1) the radiation pressure of the laser beam, 2) the thermal stress generated on the material surface, and 2) the force of material evaporation. The inspection device 10 transmits a signal from a light receiving element provided near the laser optical axis of the ultrasonic generation laser 13, that is, a laser irradiation time signal, to the data analysis/storage circuit 15.

(B) The ultrasonic waves generated on the surface of the tank bottom plate 1 in (A) above propagate inside the plate thickness, are reflected on the back surface of the tank bottom plate 1, and return to the surface again. The inspection device 1o detects ultrasonic waves (longitudinal waves) returning to the surface of the tank bottom plate 1 using an ultrasonic detector 1.
4 through the laser beam L2. Inspection device 1
0 performs data analysis/data analysis on the detection information of the ultrasonic detector 14.
The information is transmitted to the memory circuit 15.

(C) The data analysis/storage circuit 15 measures the time to when the ultrasonic detector 14 detects a longitudinal wave, with the laser irradiation time as a reference. Here, the longitudinal wave propagation velocity (sound velocity) C inside the tank bottom plate 1 as the object to be inspected is known in front of the vehicle. Therefore, the thickness of the tank bottom plate 1 is C-t
o/2 and stored in the data analysis/storage circuit 15. In addition, since the longitudinal waves repeat reciprocation until they are attenuated on the front and back surfaces of the tank bottom plate 1, the thickness of the tank bottom plate 1 can also be detected by the inter-plane spacing of the longitudinal waves.

(D) The inspection device 10 drives and controls the wheel drive motor 18 using a motor drive signal issued by the control circuit 16, and transmits the motor drive signal to the data analysis/storage circuit 15. Thereby, the inspection device 10 stores the positional information of each part of the tank bottom plate l in the data analysis/storage circuit 15 together with the plate thickness information of (C) above, thereby making it possible to measure the plate thickness of each part of the tank bottom plate l.

In addition, as the ultrasonic generation laser 13, a giant pulse laser (for example, a Nd:YAG laser, equipped with a Q switch, and an output of 0.05 J or less) is used.

Further, as the ultrasonic detector 14, one based on a laser interference method such as a stabilized Michelson interference method (see FIG. 3) or a heterodyne interference method (see FIG. 4) is used.

The stabilized Michelson interference method will be explained. Laser light from a laser 21 (e.g. He-N e laser, output 10 mW) is transmitted through lenses 22A and 22B.
, the noise reduction and coherence of the laser beam are improved by passing through the aperture 23A,
It is sent to the beam splitter 24. The laser beam is split into two beams by the beam splitter 24, one of which is reflected by a reflecting mirror 26 attached to the surface of the piezo element 25 and returns to the beam splitter 24. The other beam is reflected by the measurement surface of the tank bottom plate 1 and is reflected by the beam splitter 24.
Return to These two beams combine with each other to create interference fringes, and a part of the beam that created these interference fringes is transmitted to the aperture 2.
3B and is sent to the photodetector 27. That is, a minute displacement caused by the ultrasonic waves on the surface of the tank bottom plate 1 results in a movement change in the interference fringes, and the photodetector 27 can detect the change. The output signal of the photodetector 27 is sent to a signal amplifier 28
The data is incremented by i1 and sent to the data analysis/storage circuit 15 mentioned above. A portion of the signal from the signal amplifier 28 passes through a low-pass filter 29 and is sent to the piezo element 25 to drive the piezo element 25. This eliminates low-frequency vibrations transmitted from the outside, low-frequency vibrations generated by the measuring instrument itself, and changes in the optical path of the laser beam due to atmospheric fluctuations.
above) can be detected. In addition, 220-22E
is a lens.

The heteroline interference method will be explained. laser 31
Laser light (frequency fO) from (for example, a He-Ne laser, output 10 mW) is sent to the Bragg cell 32. Let fs be the frequency of the sound wave within the cell material in the Bragg cell 32. The beam from the Bragg cell 32 is divided into a straight beam (frequency fO) without frequency change and a diffracted beam (frequency fO−fs). The straight beam is reflected by the measurement surface of the tank bottom plate 1 and returns to the Bragg cell 32. The diffracted beam is reflected by reflecting mirrors 33A and 33B and returns to Bragg cell 32. The beam reflected by the measurement surface of the tank bottom plate 1 is diffracted by the Bragg cell 32 and has a frequency of fo+fs, and is sent to the photodetector . In addition, the beams reflected by the reflecting mirrors 33A and 33B are transmitted to the Bragg cell 3.
2 and is sent to the photodetector 34 at a frequency fO-fs. When the measurement surface of the tank bottom plate 1 is vibrated by ultrasonic waves,
Due to the Doppler shift, the frequency becomes fO+fs+fm. Therefore, the photodetector data analysis/storage circuit 15
sent to. This allows ultrasonic waves to be detected. In addition,
35 is an oscillation circuit, and 36 is a lens.

Note that the laser beam L1 of the ultrasonic generation laser 13 and the laser beam L2 of the ultrasonic detection laser 21.31
The measurement surface of the tank bottom plate 1 can be scanned over a wide range using a polygon mirror or a flat reflector.

According to the first embodiment, since the ultrasonic generation laser 13 and the ultrasonic detector 14 are non-contact type, (1) no couplant is required, and (2) irregularities on the surface of the subject are smoothed in advance. It is possible to easily and smoothly inspect the plate thickness condition without any need.

Further, since the ultrasonic wave generation laser 13 and the ultrasonic detector 14 generate/detect ultrasonic waves using laser light, the thickness condition of a tank plate made of any material other than metal can be inspected.

FIG. 5 is a schematic diagram showing how the inspection device according to the second embodiment of the present invention is used, and FIG. 6 is a schematic diagram showing the inspection device according to the second embodiment of the present invention.

The inspection device 50 is installed in a nozzle 3 such as an inspection hole provided in the tank roof plate 2. The inspection device 50 includes a laser beam L1 for generating ultrasonic waves and a laser beam L for detecting ultrasonic waves.
2 are rotated by the corresponding reflector drive motors 52A and 52B, and the laser beams L1 and L2 are scanned two-dimensionally over a wide range at high speed on the tank bottom plate 1. Inspect the thickness of the bottom plate 1. The motors 52A and 52B are driven and controlled by a motor drive signal issued by the control circuit 16. 19G, 1
9H is a power supply cable, and 51C151D is a reflecting mirror.

In addition, the parts in the inspection device 50 that are substantially the same as those in the inspection device 1O are given the same reference numerals, and the description thereof will be omitted.

FIG. 7 is a schematic diagram showing how the inspection device according to the third embodiment of the present invention is used, and FIG. 8 is a schematic diagram showing the inspection device according to the third embodiment of the present invention.

The inspection device 60 is movably supported by a device suspension cable 5 whose both ends are temporarily connected to the tank side plate 4 via wheels 61A and 61B. Even when internal parts 62 such as steam coils are disposed on the surface of the tank bottom plate 1, the inspection device 60 can smoothly move above the tank bottom plate 1 by controlling the drive of the wheel drive motor 63. Similar to the inspection device 50, the inspection device 60 is provided with a polygon mirror and a reflector to transmit the ultrasonic generation laser beam L1 and the ultrasonic detection laser beam L2 to the tank bottom plate 1 over a wide range at high speed in two dimensions. Scan the
The thickness condition of the tank bottom plate 1 can be inspected. In addition, the parts in the inspection device 60 that are substantially the same as those in the inspection device 10 are given the same reference numerals, and the description thereof will be omitted.

FIG. 9 is a schematic diagram showing an inspection apparatus according to a fourth embodiment of the present invention.

The inspection device 70 differs from the inspection device 10 in that it employs an ultrasonic detection method using electromagnetic induction. That is, in this inspection device 70, the ultrasonic generation laser 13
When the ultrasonic waves propagated inside the tank bottom plate l by the laser beam L1 irradiated by the lamp return to the surface, the DC electromagnet 7
The subject undergoes mechanical displacement in the static magnetic field (B) given by 1, and an electromotive force based on Fleming's right-hand rule is generated, generating an eddy current (Ie). When an eddy current is generated, a magnetic field is generated according to the frequency of the eddy current, and the receiving coil (ultrasonic detector) 72 receives this magnetic field as a voltage signal. The information received by the receiving coil 72 is transmitted to the data analysis/storage circuit 15. Inspection device 70
Also, the ultrasonic generating laser 13 generates ultrasonic waves using laser light, and the receiving coil 72 detects the ultrasonic waves by operating electromagnetic induction, so that the thickness state of the tank bottom plate l can be inspected without contact. However, the application of this inspection device 70 is limited to cases where the subject is made of a conductive material. In addition, the parts in the inspection device 70 that are substantially the same as those in the inspection device 10 are given the same reference numerals, and the description thereof will be omitted.

The present invention is not limited to tank bottom plates, but can also be applied to inspection of the thickness of tank side plates and the like in the same manner as for tank bottom plates.

Further, the ultrasonic waves used in the inspection operation of the present invention may be longitudinal waves and/or transverse waves, but longitudinal waves are more preferable.

[Effects of the Invention] As described above, according to the present invention, the thickness state of a tank plate can be easily and smoothly inspected by using a non-contact type ultrasonic generator and an ultrasonic detector.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the inspection device according to the first embodiment of the present invention, FIG. 2 is a schematic diagram showing the principle of plate thickness measurement of the present invention, and FIG.
The figure is a schematic diagram showing the detection principle of an ultrasonic detector, FIG. 4 is a schematic diagram showing another detection principle of the ultrasonic detector, and FIG. 5 is a usage state of the inspection device according to the second embodiment of the present invention. 6 is a schematic diagram showing the inspection device according to the second embodiment of the present invention. FIG. 7 is a schematic diagram showing the usage state of the inspection device according to the third embodiment of the present invention. The figure is a schematic diagram showing an inspection apparatus according to a third embodiment of the present invention, and FIG. 9 is a schematic diagram showing an inspection apparatus according to a fourth embodiment of the present invention. 10... Inspection device, 13... Ultrasonic generation laser (ultrasonic generator), 1
4... Ultrasonic detector, 50.60.70... Inspection device, 72... Receiving coil (ultrasonic detector). Agent Patent Attorney Osamu Shiokawa 1 Figure 2 ot. 3rd circle, Figure 5, 6th circle, Figure 7, Figure 8

Claims (4)

[Claims] (1) In a tank plate inspection device that measures the thickness of a tank plate by generating ultrasonic waves in each part of the tank plate and measuring the time it takes for the ultrasonic waves to propagate within the thickness of the tank plate, 1. A tank comprising: an ultrasonic generator that generates ultrasonic waves in a non-contact manner; and an ultrasonic detector that detects ultrasonic waves propagated within the thickness of a tank plate in a non-contact manner. Board inspection equipment. (2) The tank plate inspection device according to claim 1, wherein the ultrasonic generator irradiates the surface of the tank plate with laser light to generate ultrasonic waves on the tank plate. (3) The tank plate inspection device according to claim 1, wherein the ultrasonic detector detects minute displacements caused by ultrasonic waves on the surface of the tank plate using laser interferometry. (4) The tank plate inspection device according to claim 1, wherein the ultrasonic detector detects minute displacements caused by ultrasonic waves on the surface of the tank plate using an electromagnetic induction method.