JP4881212B2 - Material thickness monitoring system and material thickness measuring method - Google Patents

Description

  The present invention relates to a material thickness monitoring system and a material thickness measurement method for detecting the arrival time of an ultrasonic signal incident in a material and a resonance phenomenon with an optical fiber sensor and measuring the material thickness, and particularly during plant operation. The present invention also relates to a material thickness monitoring system and a material thickness measurement method that can measure and monitor the thickness of equipment constituent materials and at the same time efficiently and accurately measure the material thickness.

  In the past, steam pipe failures that occurred in nuclear power plants and thermal power plants in Japan and overseas have reduced the pipe wall thickness due to erosion and corrosion caused by steam inside the piping, resulting in insufficient structural strength. It is said that having been a direct cause. For this reason, the importance of ensuring the reliability of these pipes and the importance of inspection methods have been recognized again.

  As a pipe thickness inspection method that has been widely used, a method based on an ultrasonic method is generally used. In this ultrasonic method, there has been proposed a method for improving the thinned portion of the pipe and the thickness measurement accuracy by ultrasonic signal processing (see, for example, Patent Document 1). In addition, an accurate pipe thickness measurement method using ultrasonic waves in a narrow place or an eccentric pipe has been proposed (for example, see Patent Documents 2 and 3). Many proposals have been made, such as an efficient ultrasonic pipe measuring device (for example, see Patent Document 2) by performing measurement by scanning the surface of the pipe two-dimensionally.

  However, the various measurement methods described above are basically premised on being implemented as part of nondestructive inspection before the plant is started or stopped, such as an operating thermal power plant. In addition, there is a difficulty that cannot be handled in a high temperature state where high-temperature steam is circulating in the pipe. Moreover, in the above measurement method, the thickness distribution is obtained in order to identify the portion where the thinning occurs most, but for that purpose, it is necessary to measure multiple points (usually several hundred points). There is also a problem that requires a long measurement time.

  On the other hand, an attempt to measure the pipe wall thickness using a resonance phenomenon by electromagnetic ultrasonic waves has also been proposed (see, for example, Patent Document 4). However, in this measuring device, since the position of the ultrasonic wave is changed by the carriage, the device configuration becomes very large and the manufacturing cost of the device becomes enormous. At the same time, as with the ultrasonic method described above, it can cope with high temperature conditions. In addition, there is a drawback that much time is required for the measurement.

  Furthermore, there is an attempt to predict the amount of thinning by a system incorporating a thinning rate evaluation formula (see, for example, Patent Document 5). This method makes it possible to predict pipe thinning efficiently, but the progress mechanism of pipe erosion and corrosion phenomena is very complex, and it is predicted in consideration of subtle differences in plant operating conditions. It is difficult to do, and there is a problem in measurement accuracy.

In recent years, the application of optical fibers has been expanded mainly in the communication field, and there is a tendency that the reliability is improved and the cost is lowered. For this reason, application products and services using the advantages of optical fibers as information transmission media are being actively developed. Among them, an FBG (Fiber Bragg Grating) type optical fiber element is attracting attention as a sensor for detecting strain, temperature, and the like (see, for example, Patent Documents 6 and 7). In addition, since the electrical noise is small and the sensitivity is very high, application as a sensor that detects minute environmental changes such as magnetism, vibration, and sound has been studied (for example, see Patent Documents 8 and 9). On the other hand, as another method for measuring dynamic vibration (strain rate) using an optical fiber, a method using a laser Doppler phenomenon has been proposed. In particular, when the bending portion is vibrated (strained) with the optical fiber bent and attached to the object, the wavelength change between the input light and the output light passing through the fiber corresponds to the strain rate, There is also a report that broadband vibration can be measured with high sensitivity (see, for example, Patent Document 10). Although some measuring devices using these optical fibers have been studied for measurement at high temperatures up to about 600 ° C, they are limited to strain, displacement, vibration, temperature, etc. Nothing has been done yet.
JP 2004-163250 A JP 2002-48769 A JP 2003-270217 A Japanese Patent Laid-Open No. 9-281087 Japanese Patent Laid-Open No. 2001-12698 JP-A-10-141922 Japanese Patent Laid-Open No. 11-51783 JP 2003-130934 A JP 2004-12280 A Japanese Patent Application No. 2003-508894 Specification

  As described above, various pipe thickness measurements have been attempted by the ultrasonic method or the electromagnetic ultrasonic method. However, each pipe wall thickness measuring device / method is basically developed on the assumption that it is implemented as part of non-destructive inspection before the plant is started or stopped, such as a thermal power plant. There is a problem that cannot be handled in a high temperature state where high temperature steam is circulating in the pipe. In addition, it is necessary to provide a drive mechanism for scanning the ultrasonic probe, so that the apparatus configuration is often large, and the manufacturing cost of the measuring apparatus increases. Furthermore, in order to identify the part where the thinning occurs most in the material to be measured, in the method for obtaining the thickness distribution, it is necessary to measure multiple points (hundreds of points), requiring a lot of measurement time. There is a problem that there is.

  In addition, a system that predicts the amount of thinning from the thinning rate evaluation formula has also been tried, but the pipe erosion and corrosion phenomena are very complex, and it is not possible to predict differences due to subtle differences in plant operating conditions. There is a problem that it is difficult and measurement accuracy is low.

  In addition, material inspection systems using optical fiber elements have been put into practical use, but the use of optical fiber elements is limited to measuring strain, displacement, vibration, temperature, etc., and is applied to the measurement of pipe wall thickness. There is nothing.

  The present invention was made to solve the above-described problems of the prior art, and an ultrasonic wave was incident on the material, and the signal was received by a sensor using an optical fiber to measure the material thickness of a pipe or the like. Is. It is also possible to provide a material thickness monitoring system and a material thickness measuring method that can measure and monitor the material thickness even during plant operation, and at the same time efficiently and accurately measure the material thickness. Objective.

  In order to achieve the above object, the present invention is provided with the following means.

That is, the material thickness monitoring system according to the present invention is for supplying an optical fiber sensor that is spirally wound around the surface of a material whose thickness is to be measured, and for supplying light into the optical fiber sensor. A light source, an ultrasonic oscillation device that is disposed at the center of the optical fiber sensor that is attached in a spirally wound state, and injects ultrasonic waves into the material, and detects reflected waves of the ultrasonic waves A photoelectric conversion device for converting a shift amount between the light having a wavelength changed by the light transmitted through the optical fiber sensor and the wavelength of the light when supplied to an electrical signal, and a predetermined optical fiber sensor. and the ultrasonic speed of data in the context and various the material of the shift amount and the incident ultrasound frequencies wavelength at, based on the electric signal obtained by converting the shift amount An arithmetic unit for calculating a RyoAtsu is characterized by and a control computer for controlling all the devices described above.

  Further, in the material thickness monitoring system, the ultrasonic wave oscillating device that makes an ultrasonic wave enter the material is configured to use a falling ball ultrasonic oscillating device that makes an ultrasonic wave generated when a falling sphere collides with the material. It is also possible to do.

  Furthermore, in the material thickness monitoring system, it is also possible to use a variable frequency ultrasonic oscillator that can change the frequency of the incident ultrasonic waves as an ultrasonic transmission device that makes ultrasonic waves enter the material. It is.

  In the material thickness monitoring system, as the variable frequency ultrasonic oscillating device, an iron core around which a coil is wound is erected on the surface of a material whose thickness is to be measured, and a voltage having a predetermined frequency is applied to the coil. It is also possible to configure using an electromagnetic ultrasonic oscillation device that generates electromagnetic ultrasonic waves by applying.

  Further, in the material thickness monitoring system, as the frequency variable type ultrasonic oscillating device, a piezoelectric element ultrasonic wave that generates an ultrasonic wave of a predetermined frequency by applying a voltage to the piezoelectric element and converting it to vibration (mechanical energy). It is also possible to configure using an oscillation device.

  Further, in the material thickness monitoring system, a falling ball ultrasonic oscillator capable of generating an ultrasonic wave whose frequency is changed by changing a material or a diameter of a sphere is used as the variable frequency ultrasonic oscillator. It is also possible to configure.

  Furthermore, in the material thickness monitoring system, it is preferable that the ultrasonic oscillator causes an ultrasonic wave in a frequency range of 10 kHz to 100 MHz to enter the material. By setting the frequency range of the ultrasonic wave incident on the material within the above range without excessively increasing, the absorption of the ultrasonic wave is reduced, and high-accuracy measurement is possible.

  Moreover, in the said material thickness monitoring system, it is preferable that the optical fiber sensor stuck on the said material surface is stuck on the material surface in the state wound by the spiral shape. By sticking the optical fiber sensor in a spiral shape on the surface of the material, the Doppler effect at the curved portion increases the strain change rate corresponding to the reflected ultrasonic wave, enabling high-precision measurement. It becomes possible.

  Further, in the material thickness monitoring system, in the target material for measuring the material thickness, an ultrasonic oscillation source and an optical fiber sensor for detecting the ultrasonic wave are provided on the same surface side of the material. Is also possible.

  Further, in the material thickness monitoring system, in the target material for measuring the material thickness, an ultrasonic oscillation source is disposed on the surface side of the material, and an optical fiber sensor for detecting the ultrasonic wave is provided on the back surface of the material. It is also possible to arrange it on the side.

In the method for measuring the material thickness according to the present invention, an ultrasonic wave is incident on the material from the center portion of the optical fiber sensor attached in a spiral shape on the surface of the material to be measured for thickness. , the optical fiber sensor disposed around the incident point of the ultrasonic wave is incident light wave of predetermined wavelength, the light wave wavelength is changed by the reflection wave of the ultrasonic wave detected by the optical fiber sensor, the dynamic of the wavelength change The material thickness is calculated from the speed of the strain change.

  The operation of converting the wavelength change of the optical signal from the optical fiber sensor into a dynamic strain change is performed by, for example, an optical fiber laser Doppler velocimeter (FLV: Fiber-opt Laser Doppler Velocimeter).

  Furthermore, in the method for measuring the material thickness, when a pulsed ultrasonic wave is incident on the material, a phenomenon that the ultrasonic wave periodically increases due to a reflected wave from the back surface of the material is used. It is preferable to obtain the material thickness from the peak time interval (frequency).

  Further, in the method for measuring the material thickness, when the frequency of the ultrasonic wave incident on the material is continuously changed, the material thickness can be obtained from a specific frequency at which the incident wave and the reflected wave resonate. preferable.

  According to the material thickness monitoring system and the material thickness measurement method according to the present invention, even when a nuclear power plant, a thermal power plant, or the like is in operation, monitoring of the thickness of equipment components such as high-temperature pipes is long. It becomes possible to carry out continuously over a period of time, and the material thickness can be measured efficiently and with high accuracy. In particular, since the above-mentioned continuous monitoring is possible even while the plant is in operation, the soundness of equipment components such as piping can be ensured, and the equipment components can be repaired and replaced easily and safely. Can be specified.

<Configuration of Example>
Below, one Example of the material thickness monitoring system which concerns on this invention is described with reference to FIGS.

  FIG. 1 is a block diagram illustrating a configuration of a material thickness monitoring system according to the present embodiment. This material thickness monitoring system includes an optical fiber sensor 3 attached to the surface of a material 1 whose thickness is to be measured, and a light source 2 for supplying laser light having a predetermined wavelength into the optical fiber sensor 3. An ultrasonic oscillation device 4 that causes ultrasonic waves to enter the material, a photoelectric conversion device 5 that converts laser light transmitted through the optical fiber sensor 3 into an electrical signal, and an electrical signal obtained by this photoelectric conversion device An amplifier 6, an arithmetic unit 7 for calculating a material thickness from the amplified electric signal, an output unit 8 for outputting a calculation result of the material thickness, and the devices 2 to 8 are controlled. It comprises a control computer (computer) 9 as a controller.

  One end of the optical fiber sensor 3 is supplied with laser light of a predetermined wavelength from the light source 2 attached to one side, while the other end side (output side) of the optical fiber sensor is connected to the photoelectric conversion device 5. Yes. In this photoelectric conversion device 5, the wavelength of the laser light emitted from the light source 2 is compared with the wavelength of the laser light after passing through the optical fiber sensor 3, and the “deviation” (optical signal) and intensity of the wavelength are electrically measured. Convert to signal. The electric signal from the photoelectric conversion device 5 is amplified by the amplifier 6. The amplified electrical signal is digitally processed by the arithmetic unit 7 and then the material thickness is calculated using the database 7a. The calculation result of the obtained material thickness is output by the output device 8. All these processing operations are controlled by the control computer 9.

  FIG. 2 is a block diagram showing a high-temperature pipe thickness monitoring system when the material thickness monitoring system according to the embodiment is applied to the measurement of the thickness of the high-temperature pipe of the steam turbine power plant. The high-temperature pipe thickness monitoring system includes an optical fiber sensor 3 attached to the outer surface of the pipe 10 that is a target for thickness measurement, and a laser beam having a predetermined wavelength supplied to the optical fiber sensor 3. Obtained by the light source 2, the ultrasonic oscillation device 4 that makes ultrasonic waves enter the pipe 10, the photoelectric conversion device 5 for converting the laser light transmitted through the optical fiber sensor 3 into an electrical signal, and the photoelectric conversion device 5. An amplifier 6 for amplifying the electrical signal, an arithmetic unit 7 for calculating the material thickness from the amplified electrical signal, a wavelength shift (shift amount) in the fiber sensor determined in advance and the incident super A database 7a in which the relationship with the frequency of sound waves, ultrasonic velocity data in various materials, and the like are stored, an output device 8 for outputting and displaying the calculation result of the material thickness, and the devices 2 to 8 are provided. And a Gosuru control computer 9.

  As shown in FIG. 4, the optical fiber sensor 3 has a core portion 11 at the center through which laser light passes, and the optical path including the core portion 11 has a thin quartz wire 12 having a cross-sectional diameter of about 100 to 500 μm. It is composed of A gold (Au) coating layer 13 having a thickness of several μm to several tens of μm is integrally formed on the outer surface of the quartz wire 12.

  As shown in FIGS. 3 and 5, the optical fiber sensor 3 having the gold coating layer 13 is wound into an arc shape (spiral shape) and then embedded in the NiCr-based steel coating layer 14. It is affixed and fixed to the outer surface.

  As the light source 2, a light source that generates infrared rays having a wavelength of about 1550 nm, which is generally used in the communication field, is used. As shown in FIG. 2, the ultrasonic oscillator 4 that causes ultrasonic waves to enter the pipe 10 is an electromagnetic ultrasonic generator that includes a magnet 17 at the top after a coil 16 is wound around the iron core 15. The iron core 15 is disposed in the central portion or the vicinity of the periphery of the optical fiber sensor 3 wound in a spiral shape, and is directly or indirectly connected to the pipe 10 via the contact medium 18. The coil terminal is connected to a function generator 19, and is configured so that the function generator 19 can change and adjust the frequency of the voltage applied to the coil 16. The photoelectric conversion device 5 is a high-speed photodetector that can handle a frequency of 10 MHz.

  Next, an example of a method for measuring a material thickness using the material thickness monitoring system according to the present embodiment will be described in more detail with reference to FIGS.

FIG. 6 shows a schematic diagram of the wavelength change before and after passing through the optical fiber sensor 3 attached spirally to the surface of the material 10 (for example, carbon steel pipe) that is the object of thickness measurement. As shown in FIG. 6, in the optical fiber sensor 3 attached to the surface of the material 10 in a spiral shape, the strain rate generated in the material 10 ( ε _x ; strain rate in the x direction, ε _y ; y direction) And a wavelength shift λ _x as shown in the following (formula 1) occurs due to the Doppler effect at the curved portion.
[Equation 1]
λ _x = n _eq · N · π · R _av ( ε _x + ε _y ) / λ ₀ (Equation 1)
n _eq ; Refractive index in fiber N; Number of turns R _av ; Average winding diameter λ ₀ ; Wavelength of incident light

For example, the ultrasonic wave that has entered the pipe 10 from the ultrasonic oscillator 4 is reflected by the back surface (reflecting surface) opposite to the incident surface, and reaches the incident surface again. The ultrasonic wave that reaches the incident surface is reflected again by the incident surface, and the incidence and reflection are repeated. That is, if the optical fiber sensor 3 is attached to the incident surface or the reflecting surface of the pipe 10 in a spiral shape, a phenomenon in which the strain is generated in the pipe corresponding to the reflected ultrasonic wave and the strain rate is increased periodically. Repeated. This frequency (1 / cycle) f _m, as shown in the following (Equation 2), corresponding to the pipe to the thickness t and the ultrasonic speed of sound v in the pipe. Therefore, if the speed of ultrasonic waves in the pipe is measured, the pipe thickness can be calculated by measuring the frequency at which the strain rate increases.

That is, if the relationship between the frequency of the ultrasonic wave incident in advance and the wavelength shift (shift amount) of the laser beam measured by the optical fiber sensor 3 at that time is obtained, the wavelength shift (shift amount) is reversed. Therefore, the resonance frequency is obtained in the pipe. And piping thickness can be calculated | required from this resonance frequency based on (Formula 2).
[Equation 2]
f _m = v / m (2 × t) (Formula 2)
v: Ultrasonic velocity in pipe material t: Pipe thickness m: Number of reflections on the opposite side of incidence

On the other hand, as another measurement method, there is a method using an ultrasonic resonance phenomenon. That is, if the _n-th resonance frequency of the ultrasonic wave generated in the pipe is f _n , the following (Equation 3) is established.
[Equation 3]
f _n = n × v / (2 × t)
n: nth order resonance frequency (Equation 3)

FIG. 7 shows, as a representative example, the primary resonance frequency of the longitudinal wave (5.7 × 10 ³ m / s) in carbon steel and the transverse wave (3.1 × 10 ³ m / s) of carbon steel and the carbon steel. The relationship with thickness is shown. If the relationship shown in FIG. 7 is used, the thickness t of the pipe 10 made of carbon steel can be measured by measuring the resonance frequency.

  FIG. 8 is a perspective view schematically showing a method for measuring the thickness distribution of the pipe 10. A plurality of optical fiber sensors 3 are attached and fixed to the pipe 10 in a state of being wound in a curved shape (spiral shape). The thickness distribution of the pipe 10 is measured by measuring the thickness of the material at the incident position while changing the ultrasonic incident position using the plurality of optical fiber sensors 3, 3-arranged in this way. . Further, if the measurement is performed with the incident position of the ultrasonic wave fixed, a probability distribution of the thickness of each part appears. The thickness distribution can be obtained by using a value having a large probability. Specifically, as shown by the equal thickness distribution line illustrated on the surface of the pipe 10 shown in FIG. 8, the thickness distribution of the pipe 10 can be obtained efficiently.

<Operation of Example>
Operations of the material thickness monitoring system and the material thickness measurement method according to the present embodiment will be described with reference to FIGS.

FIG. 9 shows the operation of the ultrasonic oscillator 4 that causes ultrasonic waves to enter the pipe 10 in the material thickness monitoring system shown in FIGS. 2 to 5. The frequency fv of the voltage applied to the coil 16 and the incident ultrasonic waves are shown in FIG. It is a graph which shows the relationship with the frequency fu. As shown in FIG. 2, the ultrasonic oscillator 4 of the above system is an electromagnetic ultrasonic generator having a magnet 17 on the iron core after the coil 16 is wound around the iron core 15, and the coil 16 has a function. The generator 19 is connected. FIG. 9 shows the relationship with the frequency f _{u of the} ultrasonic wave incident on the material (pipe 10) when the voltage frequency f _V of the function generator 19 is changed. From these relationship diagrams, f _V and f _u have a first-order proportional correspondence, and it is possible to obtain the resonance frequency by changing the frequency f _V of the voltage applied to the coil 16. . That is, the wavelength of the ultrasonic wave incident on the material is continuously changed, and when the integral multiple of the half wavelength is equal to the plate thickness, the incident wave and the reflected wave resonate to generate a stationary wave. The degree of corrosion can be easily grasped even during plant operation from the strength of measurement or resonance.

  FIG. 10 is a graph illustrating an example of a signal obtained by the optical fiber sensor 3 when an ultrasonic pulse is incident on the material (for example, carbon steel pipe) 10. That is, the ultrasonic pulse incident on the material is reflected on the bottom surface (back surface) of the pipe, and thereafter, reflection on the surface of the pipe and reflection on the back surface and the surface are repeated. At this time, in the optical fiber sensor 3 affixed to the pipe surface, the strain rate increases due to the ultrasonic waves reflected on the surface, and therefore, tends to increase at a certain period. That is, this period corresponds to the time for the ultrasonic wave to reach the surface from the pipe surface to the bottom surface and further from the bottom surface to the surface. Therefore, if the sound speed of the ultrasonic wave is found, the pipe thickness can be calculated from this cycle.

FIG. 11 is a graph showing the strain rate when the frequency f _u of the ultrasonic wave incident on the pipe 10 is changed by changing the voltage frequency f _V of the function generator 19. FIG. 11 shows a phenomenon in which the strain rate periodically increases, and the periodic increase in the strain rate is caused by the resonance phenomenon occurring in the pipe, and the frequency corresponding to the peak position. Is the resonance frequency. Then, as described in detail in FIG. 7, since the resonance frequency and the pipe thickness correspond with a certain correlation, the pipe thickness can be easily calculated by measuring the resonance frequency. In addition, although the example which used EMAT (Electro Magnetic Acoustic Transducer) using an electromagnet as an ultrasonic oscillator was demonstrated, it is not restricted to this, You may use a piezoelectric element. In short, as long as the frequency of the generated ultrasonic wave can be controlled by an electric signal and the ultrasonic wave can be easily propagated to the object to be measured, it does not stick to that type.

  As described above, in the description of the material thickness monitoring apparatus of the present invention, the explanation has been given by taking the piping mainly made of carbon steel as an example, but if the sound velocity of the ultrasonic wave in the material in the above (Equation 2) is found. Independent of the material. Further, the thickness measurement is not limited to piping, and may be a simple plate-like member.

<Effect of Example>
According to the material thickness monitoring system and the material thickness measuring method according to the present embodiment, practical effects as listed below are exhibited.
(1) A gold coating layer excellent in heat resistance and corrosion resistance is formed on the surface of each optical fiber sensor 3 attached to the surface of the pipe 10 to be subjected to thickness measurement, and the pipe 10 is made of carbon steel. Since the NiCr steel material is applied to the surface of the pipe 10 by thermal spraying, the main part of the system has excellent heat resistance, and the pipe thickness can be measured at a high temperature up to about 600 ° C.
(2) By repeating this pipe thickness measurement operation in a high temperature state, monitoring the thickness of equipment components such as pipes over a long period of time, even when a nuclear power plant, a thermal power plant or the like is in operation. It becomes possible to carry out continuously.
(3) Since the above-mentioned continuous monitoring is possible even during operation of the plant, the soundness of equipment components such as piping can be ensured, and there is no need for wasteful repair and replacement of equipment components. Easy to identify.
(4) The material thickness of the pipe or the like can be easily calculated using the phenomenon that the strain rate of the light transmitted through the optical fiber sensor attached to the surface of the material such as the pipe increases periodically. (5) The thickness distribution of the pipe can be obtained by attaching a large number of optical fibers to the surface of the material such as the pipe or repeating the measurement while changing the ultrasonic incident position into the pipe or the like.

The block diagram which shows the structure of one Example of the material thickness monitoring system which concerns on this invention. The block diagram which shows the structural example of the high temperature piping thickness monitoring system at the time of applying the material thickness monitoring system which concerns on this invention to the thickness measurement of the high temperature piping of a steam turbine power plant. The top view which shows the attachment state of an optical fiber sensor in a high-temperature piping thickness monitoring system. It is sectional drawing which shows the cross-sectional structure of an optical fiber sensor, and is IV-IV arrow sectional drawing in FIG. It is sectional drawing which shows the structure which fixes the optical fiber sensor wound by the spiral to the piping surface, and is VV arrow sectional drawing in FIG. The graph which shows the wavelength change of the light which permeate | transmitted the optical fiber sensor attached to the material surface in the state wound by the spiral shape. The graph which shows the relationship between the primary resonant frequency of the longitudinal wave and the transverse wave which propagate in carbon steel, and carbon steel thickness. The perspective view which shows typically the measuring method of the thickness distribution of carbon steel piping. The graph which shows the relationship between the frequency fv of the voltage applied to a coil, and the frequency fu of the ultrasonic wave which injects into a material in the ultrasonic oscillation apparatus of a material thickness monitoring system. The graph which shows an example of the signal obtained with the optical fiber sensor in the case of entering an ultrasonic pulse in material. Graph showing strain rate in the case of changing the frequency f _u of the ultrasonic wave incident on the pipe by changing the voltage frequency f _V of the function generator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thickness measuring material 2 Light source 3 Optical fiber sensor 4 Ultrasonic oscillator 5 Photoelectric conversion device 6 Amplifier 7 Arithmetic device 7a Database 8 Output device 9 Control computer 10 Piping (Thickness measuring material)
DESCRIPTION OF SYMBOLS 11 Core part 12 Quartz wire 13 Gold (Au) coating layer 14 NiCr-type steel coating layer 15 Iron core 16 Coil 17 Magnet 18 Contact medium 19 Function generator

Claims (11)

An optical fiber sensor attached in a spirally wound state on the surface of the material whose thickness is to be measured, a light source for supplying light into the optical fiber sensor, and a spirally wound state An ultrasonic oscillation device that is disposed in the center of an optical fiber sensor that is attached, and that makes an ultrasonic wave enter the material; and an optical fiber sensor that is a light whose wavelength is changed by detecting a reflected wave of the ultrasonic wave A photoelectric conversion device for converting the shift amount between the light transmitted through the light and the wavelength of the light when supplied to an electrical signal, the shift amount of the wavelength in the optical fiber sensor determined in advance and the incident ultrasonic wave controlling the ultrasonic velocity of the data in relation and various the material of the frequency, an arithmetic unit for calculating a material thickness based on the electrical signal obtained by converting the shift amount, all equipment described above Material thickness monitoring system comprising: the patronized computer, a. 2. The material thickness monitoring system according to claim 1, wherein a frequency variable type ultrasonic oscillation device in which a frequency of an incident ultrasonic wave is variable is used as an ultrasonic wave transmission device that causes an ultrasonic wave to enter the material. As the variable frequency ultrasonic oscillating device, an iron core having a coil wound is erected on the surface of a material to be measured for thickness, and an electromagnetic ultrasonic wave is generated by applying a voltage of a predetermined frequency to the coil. 3. The material thickness monitoring system according to claim 2, wherein an electromagnetic ultrasonic oscillator is used. A piezoelectric element ultrasonic oscillator that generates ultrasonic waves of a predetermined frequency by applying a voltage to a piezoelectric element and converting it into vibration (mechanical energy) is used as the variable frequency ultrasonic oscillator. Item 2. The material thickness monitoring system according to Item 2. 2. The material thickness monitoring system according to claim 1, wherein the ultrasonic oscillator makes an ultrasonic wave in a frequency region of 10 kHz to 100 MHz enter the material. 3. The optical fiber sensor obtained in advance, further comprising: an amplifier that amplifies an electric signal obtained by the photoelectric conversion device converting the shift amount; and an output device that outputs the calculation result of the material thickness. 2. The relationship between the amount of shift of the wavelength inside and the frequency of the incident ultrasonic wave and the ultrasonic velocity data in various materials are stored in a database readable by the arithmetic unit. The material thickness monitoring system described. 7. The material thickness according to claim 6, wherein in the target material for measuring the material thickness, an ultrasonic oscillation source and an optical fiber sensor for detecting the ultrasonic wave are provided on the same surface side of the material. Monitoring system. In the target material for measuring the material thickness, an ultrasonic oscillation source is disposed on the surface side of the material, and an optical fiber sensor for detecting the ultrasonic wave is disposed on the back surface side of the material. The material thickness monitoring system according to claim 6. While be incident ultrasonic waves on the surface of the material to be measured in thickness from the center portion of the optical fiber sensor is stuck in a state wound in a spiral in the material, wherein disposed about the point of incidence of the ultrasonic A light wave of a predetermined wavelength is incident on the optical fiber sensor, the light wave whose wavelength is changed by the reflected wave of the ultrasonic wave is detected by the optical fiber sensor, and the change in the wavelength is converted into a dynamic strain change, and the speed of the strain change. A method for measuring a material thickness, comprising calculating the material thickness from When a pulsed ultrasonic wave is incident on the material, the phenomenon that the ultrasonic wave periodically increases due to the reflected wave from the back surface of the material, and the material thickness is obtained from the time interval of the ultrasonic peak. The material thickness measuring method according to claim 9. 10. The material thickness according to claim 9, wherein the material thickness is obtained from a specific frequency at which the incident wave and the reflected wave resonate when the frequency of the ultrasonic wave incident on the material is continuously changed. Measuring method.

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