JP5624271B2 - Piping thickness measurement method and apparatus - Google Patents

Description

  The present invention relates to a pipe thickness measurement method and apparatus in a nuclear power plant or a thermal power plant, and in particular, to determine whether there is an abnormality such as pipe thinning due to high-temperature steam, pipe corrosion in a chemical plant or a garbage incineration plant. The present invention relates to a thickness measuring method and apparatus therefor.

  Conventionally, pipe thinning and corrosion have been inspected using an ultrasonic flaw detector, an X-ray transmission device, or the like during periodic inspection. In the ultrasonic flaw detection method, a probe that transmits and receives ultrasonic waves is pressed against the surface of a test object, and ultrasonic waves of various frequencies are propagated inside.

  And the ultrasonic wave which reflected and returned by the defect in a to-be-tested object and a back surface is received, and the state inside a to-be-tested object is grasped | ascertained. The defect position is measured from the time taken from transmission to reception of the ultrasonic wave, and the size of the defect is obtained by measuring the height of the received echo and the range in which the defect echo appears.

  Ultrasonic inspection methods are mainly applied to the detection of material thickness and lamination in nuclear power plants, and detection of cracks occurring in welded and melted parts due to welding and cracks in heat affected parts. . In addition, for the weld overlay that is performed as a reinforcement for the nozzle opening, branch, and pipe joint around the reactor pressure vessel, for the base metal directly under the weld overlay, the melted portion, and the weld overlay, This inspection is applied (see Non-Patent Document 1).

  In addition, there is an X-ray transmission method that can detect pipe thinning without removing the heat insulating material. With an X-ray CT scanner or the like, X-ray CT data can be processed at high speed using a high-performance computer. The difference in the line transmittance can be taken as a tomographic image, and an image of the entire object can be projected.

  Recently, the applicant of the present application has developed a sheet-shaped color scintillator (fluorescent screen) that emits light in three primary colors of red (R), green (G), and blue (B), and the light emission ratio changes according to the amount of transmission, and a CCD camera. We have devised a method that can simultaneously photograph materials with different X-ray transmittances with a simple system that is combined, and is applied to pipe thinning observation and contamination inspection in thermal power, nuclear power plants and petroleum, chemical complexes. .

As another pipe thinning measurement method, there is a method in which an electromagnetic ultrasonic oscillator (EMAT) and an optical fiber sensor (FOD sensor) are combined. This uses an electromagnetic ultrasonic transducer (EMAT) to directly excite ultrasonic waves in the pipe by the action of electromagnetic force, and detect and analyze the resonance waves with a FOD (Fiber-optic Doppler) sensor. This is a method for obtaining information on the thickness of the sample and internal defects (see Non-Patent Documents 2 to 5).
Kiichiro Uchigasaki et al .: “Nuclear Power and Design Technology” Taiga Publishing (1980), p226-250 Takahashi, Sasaki et al. “Thickness measurement technique of metal pipes by electromagnetic ultrasonic method using optical fiber sensor (1st report)” TRP-04987 (2006) Sasaki, Takahashi, et al. "Metal thickness measurement by electromagnetic ultrasonic resonance using optical fiber Doppler sensor" Symposium on Welded Structure Symposium 2006 (November 2006) Takahashi, Sasaki et al. "Metal pipe thickness measurement by electromagnetic ultrasonic resonance method using optical fiber Doppler" Material of "The 1st Joint Lecture on Inspection / Evaluation / Maintenance" Maintenance Society (January 2008) Yamaya, Takahashi, Ahiko “Measurement Technology of Pipe Thinning in Thermal Power Plants” Toshiba Review, Vol.63, No.4 (2008) pp.41-44

  FIG. 1 shows an optical fiber sensor system used for conventional thickness measurement. This system detects the optical fiber vibration velocity using the optical Doppler effect, and has a configuration combining a Mach-Zehnder interference system and a heterodyne detection method in order to accurately detect the optical fiber vibration velocity.

  Major components include special parts such as narrow linewidth semiconductor lasers, optical modulators, and heterodyne detection circuits. These parts are expensive and large in size, so the entire system is expensive and compact. There is a difficult problem.

  This system has a function for specifying a signal frequency on both the transmitting side (EMAT) and the receiving side (FOD). In basic verification level testing, it is necessary to be able to check both the transmit and receive frequencies. However, if it can be confirmed that there is no frequency shift due to input and reflection, only one of the frequency check functions is sufficient in the practical application stage. In the case of this apparatus configuration, the apparatus on the optical measurement side is expensive and large, and by reducing this, the apparatus can be downsized and the cost can be significantly reduced.

  In addition, in the conventional system, it is necessary to match the fiber lengths of the “sensor side” and “reference light side” of the Mach-Zehnder interference system to the same length, and the “length adjusting fiber” is the same length as the sensor fiber length. Had to be prepared in advance.

  On the other hand, it is possible to measure multiple points with different sensor fiber lengths. In this case, it is necessary to prepare multiple “length adjustment fibers” for each measurement point and replace each measurement. There is a problem that the measurement work in the field is troublesome.

  The present invention has been made in consideration of the above-mentioned points. A pipe thickness measuring method and apparatus that do not require a length adjusting fiber in the optical Doppler method and that can be configured in a small system using inexpensive general-purpose parts. The purpose is to provide.

  In order to solve the above problems, the present invention provides the following method and apparatus invention.

First, the method invention
An active sensor in which an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band and an optical fiber sensor that detects dynamic distortion of a measurement object is integrated is prepared,
The active sensor is attached to the pipe that is the measurement object,
Input the ultrasonic wave or vibration designated at a predetermined frequency between 0 and 10 MHz in the thickness direction of the pipe, detect the reflected wave of the input ultrasonic wave or vibration or a synthesized wave thereof,
Measure the thickness of the measurement object based on resonance by the pipe in the detected ultrasonic or vibration signal,
In the pipe thickness measurement method ,
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe Determine the thickness d of the pipe by the following formula,
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
The optical fiber sensor changes the phase of light propagating inside the optical fiber due to vibration, detects vibration from the optical polarization state that changes due to the phase change,
The method for measuring the thickness of a pipe, wherein the method for detecting a change in polarization of the optical fiber sensor is based on an optical vibration sensor using a technique for detecting an angle change of a polarization axis ,
It is.

The invention of the device
An active sensor that integrates an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
A pipe thickness measuring device characterized by comprising:
The optical fiber sensor detects the vibration from the optical polarization state that changes due to the phase change of the light propagating inside the optical fiber due to the vibration,
A method for detecting a polarization change of the optical fiber sensor is an optical vibration sensor using a technique for detecting an angle change of a polarization axis.
It is.

(Summary of Invention)
In the pipe thickness measurement method according to the present invention, an active sensor is attached to a measurement object, and an ultrasonic wave or vibration designated at a predetermined frequency between 0 to 10 MHz is input in the pipe thickness direction, A reflected wave of a sound wave or a vibration or a synthesized wave thereof is detected, and the thickness of the measurement object is measured based on resonance by the pipe in the detected ultrasonic wave or vibration signal.

  In the thickness measuring device according to the present invention, an electromagnetic oscillator capable of sweeping a frequency in a predetermined frequency band and an optical fiber sensor for detecting a dynamic distortion of a predetermined frequency are integrated to transmit and receive. Therefore, a thin sensor capable of performing resonance detection using a signal having a wide frequency bandwidth can be realized. Since the optical fiber sensor is a broadband optical vibration sensor, dynamic distortion can be detected with high sensitivity in a wide frequency band from 0 Hz to several MH.

  With this configuration, it is possible to perform diagnosis according to the size and thickness of pipes that are different for each industry and model. Further, by adopting a polarization interference type optical vibration sensor, a length adjusting fiber becomes unnecessary, and the optical sensor can be arranged on one fiber from the LD module. For this reason, a length adjusting fiber is not required, and it can be easily adapted to sensor lengths having different lengths.

  In addition, a system configuration using general-purpose parts is possible, and a system configuration can be simply made with commercially available DFB lasers, optical parts, amplifiers, etc., so that the size of the apparatus can be reduced and the part cost can be reduced.

  As described above, according to the present invention, power can be supplied to the coil portion to actively measure the behavior of ultrasonic waves in the thickness direction, and the thickness can be measured. Thus, it is possible to measure the thickness by passively monitoring the accumulation of dynamic strain received by the optical fiber group attached to the pipe surface due to the occurrence of pipe vibration or cavitation. Since these two methods can be applied at the same time, it is possible to increase the probability of detecting an abnormal thickness or thinning of the pipe.

  The essence of the present invention is to provide a pipe thickness measuring method and apparatus capable of monitoring the deterioration state (thinning and corrosion) of a high-temperature pipe without stopping the plant and capable of inspecting a wide range in a short time. It is to be.

  The system that monitors erosion and corrosion thinning at the elbow and orifice of the steam pipe will shorten the periodical inspection and improve the advanced maintenance service. Furthermore, the apparatus is reduced in size and cost, and the practicality is improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIGS. 1A, 1B and 1C are diagrams for explaining the principle of a thickness measurement method using ultrasonic waves. First, as shown in FIG. 1 (a), ultrasonic waves in the thickness direction are generated on the object of thickness measurement. For example, when an alternating current in a frequency range of 0 to 10 MHz is input to a coil wound around a permanent magnet in the vibrator 300, a longitudinal wave in the thickness direction of the pipe wall of the pipe 10 can be input. The alternating current is variable in frequency using a function generator (not shown), and can sweep a predetermined frequency band.

  At this time, when a relationship of “λ = 2d” is established between the thickness d of the pipe 10 and the wavelength λ of the ultrasonic wave, the incident wave and the reflected wave resonate, and the amplitude of the output wave increases rapidly. Therefore, the thickness d of the object can be measured by calculating backward from the resonance frequency λ.

の条件を満たすときに超音波が共振する。これを超音波の周波数fを用いて書き直せば、下記式（２）のようになる。

ここで、ν: 音速
したがって、共振する周波数ｆ_ｎおよび音速νが分かれば、下記式（３）によって板厚ｄを逆算することができる。
ｄ＝ｎ・ν／（２・ｆ_ｎ） 式（３）
ここで、ｎ：正の整数（１，２，３，・・・） As shown in FIG. 1B, for example, when the pipe is made of a steel plate having a thickness of 15 mm, resonance occurs when an ultrasonic wave of 500 kHz is input. If the thickness becomes thicker than this, the frequency decreases, and if the thickness becomes thinner, the frequency increases. That is, if the thickness of the metal plate is d and the wavelength of the ultrasonic wave is λ,

The ultrasonic wave resonates when the above condition is satisfied. If this is rewritten using the ultrasonic frequency f, the following equation (2) is obtained.

Here, ν: sound speed Therefore, if the resonating frequency f _n and sound speed ν are known, the plate thickness d can be calculated backward by the following equation (3).
d = n · ν / (2 · f _n ) Formula (3)
Where n is a positive integer (1, 2, 3,...)

  As an oscillator, in addition to using an electromagnet coil, a piezoelectric (piezo) element or the like may be used for oscillation. Using a piezoelectric element tends to provide strong oscillation at low power.

  As shown in Fig. 1 (b), an optical fiber with a winding number of 50 is applied to the metal surface with an instantaneous adhesive on a SUS304 plate with a diameter of 200 mm and a thickness of 5, 7, 10, 15, 20, 25, 30 mm. A fixed optical fiber sensor was constructed. Then, using a frequency synthesizer, a sine wave is generated in increments of 1 kHz from 50 kHz to 500 kHz, and the signal obtained by applying to the optical fiber sensor is amplified to 150 Vp-p by an amplifier. The output of the optical fiber sensor at each frequency From the waveform, resonance signals were obtained only at wavelengths corresponding to the plate thickness at each plate thickness.

  As shown in the graph of FIG. 1 (c), an experimental value proving the above equation (2) was obtained between the frequency of the input wave and the reciprocal of the plate pressure. The frequency variable means is configured to freely set the frequency of the input wave as a function generator or a combination circuit (not shown) of the function generator and amplifier, and it is desirable that the intensity can be set freely.

  FIGS. 2A, 2B, and 2C are diagrams illustrating the configuration and operating principle of a FOD (Fiber-optic Doppler) sensor. FIG. 2A shows the connection relationship between the sensor unit 200 and the detection unit 400. The sensor unit 200 has a shape in which an optical fiber is wound in a plane spiral shape as shown in FIG. Light is sent from the light source LS of the detection unit 400 to the unit 200 and received by the detector DET. The sensor unit 200 is configured by a single optical fiber sensor in FIG. 2, but may be configured by a plurality of sensors as described later.

  FIG. 2 (c) shows the operating principle of the FOD, and the optical fiber sensor is being propagated by light reflection at the boundary between the core at the center of the optical fiber and the cladding disposed outside thereof. The distortion and vibration caused by the deformation of the optical fiber are regarded as the Doppler effect. This sensor is desirably small, thin and flexible.

  FIG. 3 is a diagram for explaining the structure of an active sensor, that is, an optical fiber sensor 200 in which a vibration exciter 300 is combined. FIG. 3 shows an example of a “multi-point patch type sensor” in which an oscillator (ultrasonic excitation mechanism) and a plurality of optical fiber sensors are integrated.

  In the configuration example of FIG. 3, as shown in the cross-sectional view shown at the top of the figure, an oscillator having a permanent magnet 310 and an electromagnetic coil 320 is fixed on the optical fiber sensor 200 with an adhesive 330 or the like, and the active sensor And a plurality of active sensors 220 are prepared and attached on the substrate 210. In the case of FIG. 3, a multi-point patch type active sensor having nine active sensors (3 × 3 matrisk arrangement) of about 30 mmφ in a size of 100 mm square is configured.

  By adopting such a multi-point patch type sensor, the sensor can be attached to a high-temperature pipe curved surface portion or the like, and it is easy to inspect a portion where pipe thinning is assumed.

  The multi-point patch type active sensor 220 is integrated with a base material such as high-temperature adhesive, silicon rubber, silicon sheet, metal member, etc. Paste in a dot matrix. The mounting method is by high temperature adhesive or thermal spraying. In the case of an FOD sensor, an anisotropy may be imparted by winding it in the shape of a mosquito coil (vortex) around an oscillator or by winding it in an elliptical shape.

  The optical fiber sensor 200 is capable of sensing up to a high temperature (up to about 750 ° C.) by applying a heat-resistant coating such as gold, nickel, silica, and polyimide and a protective treatment with a thin tube.

  In order to provide long-term reliability for this multi-point patch type sensor, the sensing area is reduced by reducing the size of the oscillator element, the distance between sensors in the matrix arrangement is optimized, the connections between sensors, and the thickness at the time of multi-point measurement mapping It is necessary to consider the measurement resolution, the temperature dependence of the adhesive strength of the protective sheet, the degree of contraction at the elbow portion of the flexible sensor, and the like.

  In addition, regarding the thickness measurement accuracy, the power of the ultrasonic wave from the oscillator (amplifier capability of the function generator, the magnetic force of the electromagnetic coil core, the number of turns of the coil, the piezoelectric element performance), the sensitivity of the optical fiber sensor itself (the number of turns of the sensor) , And design in consideration of heat resistance.

  The optical fiber sensor configured as described above is attached to a pipe elbow or an orifice downstream where erosion or corrosion is likely to occur during construction or periodic inspection. Thereby, the piping abnormality can be monitored even during operation without removing the heat insulating material of the piping.

  FIG. 4 is a diagram for explaining a schematic configuration when a pipe deterioration diagnosis apparatus is configured using the thickness measuring apparatus of the present invention, and corresponds to a multi-point patch type optical fiber sensor 200 for active sensing. The monitoring system is shown.

  The oscillation controller 401 has a switching mechanism (ultrasonic excitation input system) that can arbitrarily select an input location from a plurality of integrated sensors, and a switching mechanism that can arbitrarily select an input point from a remote point is added. , It is possible to determine where the thickness in the patch is being monitored.

  In addition, as shown in FIG. 3, when an ultrasonic transmission mechanism is provided at each of the vertically upper portions of the optical fiber sensors 220 arranged in the base 210, the control system at the remote point can: a) frequency sweep, b) Input point switching and c) Input voltage switching. An optical detector 402 for detecting dynamic distortion from the output of the optical fiber sensor 220 is also incorporated in the monitoring system.

  The computer 403 as a diagnostic means uses a diagnostic database 404 based on the basic data shown in FIG. 1 (c), and uses a signal processing program for deriving a wall thickness value at high speed from the acquired sampling signal. Perform site mapping.

  FIG. 5 shows an actual application of the multi-point patch type active sensor according to the present invention. As shown in FIG. 5, the multi-point patch type active sensor 200 utilizes the durability and corrosion resistance of the optical sensor in addition to monitoring at regular intervals such as during regular inspections, and suddenly appears impact. It can also be used as a system that passively monitors signals and abnormal vibrations that are not recognized in steady state.

  At this time, the waveform analysis means (1) frequency analysis focusing on sudden behavior in the high frequency region (discrimination from stationary noise), (2) observation of standing wave behavior in the low frequency region (discrimination from stationary noise), (3) It has three functions of “steady” and “unsteady” observations using a neural network, etc., reads actual machine data recorded in the actual pipe high stress load section (actual machine environment) from the diagnostic database, and passive signals The pipe thinning or abnormality is determined by comparing with the result of the processing method.

  In the present invention, the polarization property of light propagating in the optical fiber is used. Polarization represents the vibration state of light and is applied to an optical fiber vibration sensor or the like by utilizing the characteristics of laser (LD) light having strong polarization characteristics.

  In this system, a laser that oscillates at a single frequency, such as a commercially available DFB (Distributed Feedback) laser, can be used as the laser light source. The output light from the DFB laser is propagated to the sensor fiber after the polarization is adjusted by the polarization controller. In the sensor unit, the waveguide is distorted by the vibration of the optical fiber, and the phase of the polarization changes.

  There is little dependency on the polarization state of the light propagating to the sensor fiber and the phase change of the polarization due to the distortion of the waveguide due to the vibration of the optical fiber. Therefore, the polarization state adjusted by the polarization controller is linear, circular. The polarization state may be any of elliptical and elliptical states, or the state of random polarization in which these polarization states change randomly with respect to time.

  After the light is adjusted again using optical polarization control, it is separated into a parallel component and a vertical component by the polarization branching module. The phase change in the sensor unit can be detected as the light intensity by causing interference with the polarization maintaining coupler after matching with the direction. This light intensity change can be directly observed with an oscilloscope after being converted into an electrical signal using an optical / electrical conversion module.

  As another method for detecting the change in polarization phase, if the light whose polarization phase has changed in the sensor fiber is converted to linearly polarized light using optical polarization control, the phase change will change in the polarization axis angle due to vibration. Therefore, the light can be detected as a change in light intensity by passing the light through a polarizer such as a polarizer.

  FIG. 6 is a diagram for explaining the measurement principle of the pipe thickness measuring device using the optical Doppler method. FIG. 7 is a diagram for explaining the measurement principle of the pipe thickness measuring apparatus using the polarization interference method. In FIG. 7, as the optical fiber used, a high refractive index difference optical fiber coated with polyimide is used in the sensor portion, and a normal single mode optical fiber is used in the connection portion to the sensor.

  A polarization maintaining fiber is used in the optical system after the polarization branching module. Polarization-maintaining optical fiber is an optical fiber with excellent optical polarization state retention, which allows the parallel and vertical polarization components branched by the polarization branching module to propagate without changing in the optical fiber and is stable efficiently. It is used to perform interference in the state.

  Since ordinary optical fibers have poor polarization maintenance, the polarization accuracy of the parallel and vertical polarization components branched by the polarization branching module changes randomly during propagation through the optical fiber, and a stable interference state cannot be obtained. A problem occurs.

  The measurement system using the polarization interference method has the advantage that “length adjustment fiber is not required” compared to the optical Doppler method. Since the optical sensor can be arranged on one fiber from the laser light source (LD module), a length adjusting fiber is not necessary, and it can be easily adapted to sensor lengths having different lengths.

  Furthermore, with this polarization interference method, a system configuration using general-purpose components is possible. Unlike conventional optical Doppler methods, special optical components and complicated detection circuits are not required. Since the system can be configured simply and inexpensively with parts, amplifiers, etc., the apparatus can be downsized and the parts cost can be reduced.

  However, the polarization plane must be adjusted for each measurement. The polarization state adjustment method requires some external vibration source, and manually adjusts the signal from the vibration source so that the sensor reception sensitivity is maximized. Therefore, it is unsuitable for detecting sudden signals such as destructive sound (AE) and shock waves that do not know when a signal is generated, and for long-term monitoring. Therefore, in order to put the measurement using the polarization interference method into practical use, it is necessary to verify it in comparison with the optical Doppler method.

  FIG. 8 is a diagram illustrating a detection waveform based on the optical Doppler method and a detection waveform based on the polarization interference method for the purpose of verification, and illustrates a waveform in a resonance state. FIG. 9 is a diagram showing the frequency spectrum of the detection waveform by the optical Doppler method and the detection waveform by the polarization interference method, and shows the resonance frequency spectrum.

  This waveform detection uses a steel tube made of carbon steel (SS400) with a thickness of t = 15 mm, an optical fiber sensor with an outer diameter of 20 mm, EMAT has a transverse wave generation type structure, an outer diameter of an electric coil of 20 mm, and a permanent magnet with a size of φ10 A neodymium magnet with a thickness of 5 mm was used.

  From these detection results, it can be seen that both FIG. 8 and FIG. 9 have the same reception waveform at resonance and the same resonance vibration frequency of 184 kHz. However, the S / N ratio of the resonance frequency spectrum of the polarization interference method is somewhat inferior to that of the optical Doppler method, and there are a plurality of noise peaks in addition to the resonance frequency (184 kHz). The cause of these noise peaks is considered to be due to the influence of waveform noise or the like due to fluctuations in the polarization plane during frequency sweep measurement.

  FIG. 10 is a diagram illustrating measurement points and measurement results in a 250A piping elbow that is a detection target. FIG. 10 shows the detection result of the measurement plate thickness value by the polarization interference method in contrast with that of the optical Doppler method.

  That is, the measurement accuracy of the polarization interference method was confirmed using a 250A piping elbow test piece. The material is STPT370. The size of the sensor used for the test is 15mm outside diameter (20mm for the part with low sensitivity), the EMAT is a transverse wave generation type structure with an outer diameter of the electric coil of 25mm, the permanent magnet is 10mm in diameter and 5mm in thickness A neodymium magnet was used. The measurement points are the elbow bending outer side 10a, side surface 10b, and inner side 10c at three locations on the half circumference of the pipe end. The frequency sweep interval is 0.5 kHz for all of the measurement points 10a, 10b, and 10c.

  The detection result is a value outside the plate thickness measurement point based on the obtained resonance frequency, and the plate thickness value is obtained by correcting the sound velocity in the metal. As a result, the thickness values of both were in the range of 0.1 mm, and it was confirmed that the thickness measurement by the polarization interference method could be accurately performed on the surface of the pipe elbow having two curvatures.

被測定体はJIS RB-E試験体を模した構造であり、材質はSUS304である。測定に用いたセンサの大きさは外径15mm、ＥＭＡＴは横波発生タイプ構造で、電気コイルの外径20mm、永久磁石は大きさφ10、厚さ5mmのネオジウム磁石を用いた。掃引周波数間隔は、厚さt=5mm、9mm、13mmは1kHz間隔、厚さt=15mm、19mm、23mmは0.5kHz間隔で掃引した。 Table 1 below compares the plate thickness measurement results from the detection waveform by the optical Doppler method and the detection waveform by the polarization interference method.

The object to be measured has a structure simulating a JIS RB-E test body, and the material is SUS304. The sensor used for the measurement had an outer diameter of 15 mm, EMAT had a transverse wave generation type structure, an outer diameter of the electric coil of 20 mm, a permanent magnet used a neodymium magnet having a size of φ10 and a thickness of 5 mm. As for the sweep frequency interval, thickness t = 5 mm, 9 mm, and 13 mm were swept at 1 kHz intervals, and thickness t = 15 mm, 19 mm, and 23 mm were swept at 0.5 kHz intervals.

  As a result, the thickness values of both were in the range of 0.1 mm, and the linearity was also good, so it was confirmed that the thickness measurement by the polarization interference method could be performed accurately. Further, since the measurable frequency band has a resonance peak from 100 kHz to 500 kHz as shown in this measurement result, the frequency band necessary for the plate thickness measurement can be measured.

  In addition, sensing using an optical fiber enables simultaneous monitoring over a long distance and a wide range, and is effective as a screening technique for identifying the location of an abnormal site and performing a precise diagnosis.

The figure explaining the measurement principle of the thickness measuring method using the ultrasonic wave by this invention. The figure explaining the operation principle of the conventional FOD (Fiber-optic Doppler) sensor. The figure explaining the structure of the active sensor (multi-point patch type) used for this invention. The figure explaining the schematic structure of the apparatus which performs the deterioration diagnosis of piping using a thickness measurement result. The figure explaining the mode of an actual machine application of the active sensor and thickness measuring apparatus used for this invention. The figure explaining the principle of operation of the pipe thickness measuring device by an optical Doppler system. The figure explaining the operation | movement principle of the pipe thickness measuring apparatus by the polarization interference system used for this invention. The figure which compares the detection waveform by an optical Doppler system with the detection waveform by a polarization interference system. The figure which compares the frequency spectrum of the detection waveform by an optical Doppler system, and the detection waveform by a polarization interference system. The figure explaining the measurement point and measurement result of a 250A piping elbow (measurement object).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piping 11 Elbow 12 Orifice downstream part piping 13 Orifice 14 Orifice upstream part piping 100 Light sending part 200 (Multi-point patch type) Optical fiber sensor 200 'Length adjustment fiber 210 Base material 220 Active sensor 300 Exciter 310 Permanent magnet 320 Electromagnetic coil 330 Spacer 400 Optical receiver 401 Oscillation controller 402 Optical detector 403 Diagnostic means 404 Diagnostic database 500 Oscilloscope SMF Single mode fiber PMF Polarization maintaining fiber

Claims (8)

An active sensor in which an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band and an optical fiber sensor that detects dynamic distortion of a measurement object is integrated is prepared,
The active sensor is attached to the pipe that is the measurement object,
Input the ultrasonic wave or vibration designated at a predetermined frequency between 0 and 10 MHz in the thickness direction of the pipe, detect the reflected wave of the input ultrasonic wave or vibration or a synthesized wave thereof,
Measure the thickness of the measurement object based on resonance by the pipe in the detected ultrasonic or vibration signal,
In the pipe thickness measurement method ,
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe Determine the thickness d of the pipe by the following formula,
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
The optical fiber sensor changes the phase of light propagating inside the optical fiber due to vibration, detects vibration from the optical polarization state that changes due to the phase change,
The method for detecting the polarization change of the optical fiber sensor is based on an optical vibration sensor that detects the change in the angle of the polarization axis.
A method for measuring the thickness of a pipe, characterized by that . In the pipe thickness measuring method according to claim 1,
Further, the pipe deterioration degree determination method is characterized in that the deterioration degree of the pipe is determined by comparing the thickness of the measurement object with a diagnosis database having a determination threshold regarding deterioration such as corrosion or thinning of the pipe. . An active sensor that integrates an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
A pipe thickness measuring device comprising:
The optical fiber sensor is a pipe thickness measurement device that detects vibration from a light polarization state that changes due to the phase change of light propagating inside the optical fiber due to vibration,
A pipe thickness measuring apparatus, wherein the method for detecting a change in polarization of the optical fiber sensor is an optical vibration sensor using a technique for detecting an angle change of a polarization axis. An active sensor integrated with an electromagnetic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
A pipe thickness measuring device characterized by comprising:
The optical fiber sensor detects the vibration from the optical polarization state that changes due to the phase change of the light propagating inside the optical fiber due to the vibration,
The method of detecting the polarization change of the optical fiber sensor is a polarization interference optical vibration sensor,
The optical vibration sensor includes a laser light source having a strong polarization characteristic, a polarization controller that adjusts the polarization of output light from the laser light source, and an interferometer device unit for measuring the phase change of the polarization. A light-damaging fiber sensor that is fixed to the pipe and forms a waveguide for the light from the polarization controller to the interferometer unit, and the optical fiber sensor is moved to the waveguide by vibration of the pipe. In the pipe thickness measuring device designed to detect the generated strain ,
A pipe thickness measuring device, wherein polarization of output light from the laser light source is adjusted to circularly polarized light using a controller. An active sensor integrated with an electromagnetic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
A pipe thickness measuring device characterized by comprising:
The optical fiber sensor detects the vibration from the optical polarization state that changes due to the phase change of the light propagating inside the optical fiber due to the vibration,
The method of detecting the polarization change of the optical fiber sensor is a polarization interference optical vibration sensor,
The optical vibration sensor includes a laser light source having a strong polarization characteristic, a polarization controller that adjusts the polarization of output light from the laser light source, and an interferometer device unit for measuring the phase change of the polarization. A light-damaging fiber sensor that is fixed to the pipe and forms a waveguide for the light from the polarization controller to the interferometer unit, and the optical fiber sensor is moved to the waveguide by vibration of the pipe. In the pipe thickness measuring device designed to detect the generated strain ,
A pipe thickness measuring device, wherein polarization of output light from the laser light source is adjusted to random polarization using a controller. An active sensor that integrates an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
With
The optical fiber sensor changes the phase of light propagating inside the optical fiber due to vibration, detects vibration from the optical polarization state that changes due to the phase change,
A polarization controller that forms a polarized light by controlling the polarization of the laser light whose phase has been changed by the optical fiber sensor, and a polarization converter that converts the change state of the polarized light as a light intensity change A photoelectric conversion module (PDM) that photoelectrically converts a change in light intensity converted by the polarization converter, and detects a phase change of the optical fiber sensor as a light intensity;
The polarization converter of the interferometer device unit includes a polarization branching module that separates the polarized light into a parallel component and a vertical component, and a polarization plane of the vertical component of the polarized light rotated by 90 degrees to be the same as the parallel component In the pipe thickness measuring device that is composed of a polarization maintaining coupler that interferes with the direction of the polarization plane ,
A polarization maintaining fiber is employed between the laser light source and the polarization controller or between the polarization branching module and the polarization auxiliary coupler to suppress fluctuations in the polarization plane. Pipe thickness measuring device. An active sensor that integrates an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
With
The optical fiber sensor changes the phase of light propagating inside the optical fiber due to vibration, detects vibration from the optical polarization state that changes due to the phase change,
A polarization controller that forms a polarized light by controlling the polarization of the laser light whose phase has been changed by the optical fiber sensor, and a polarization converter that converts the change state of the polarized light as a light intensity change A photoelectric conversion module (PDM) that photoelectrically converts a change in light intensity converted by the polarization converter, and detects a phase change of the optical fiber sensor as a light intensity;
The polarization converter of the interferometer device unit includes a polarization branching module that separates the polarized light into a parallel component and a vertical component, and a polarization plane of the vertical component of the polarized light rotated by 90 degrees to be the same as the parallel component In the pipe thickness measuring device that is composed of a polarization maintaining coupler that interferes with the direction of the polarization plane ,
The pipe thickness measuring device, wherein the polarization branching module can adjust a polarization plane so that a sensor output is maximized by a combination of polarization planes before and after the optical fiber sensor. An active sensor that integrates an ultrasonic oscillator that sweeps and outputs within a predetermined frequency band, and an optical fiber sensor that detects dynamic distortion of the measurement object;
By the active sensor, when the input ultrasound or vibration in the thickness direction with respect to the measurement object is a pipe, the resonance frequency f _n of the pipe in the reflection wave or the detection signal of the composite wave from the pipe A thickness measuring means for calculating the thickness d of the pipe by the following formula;
d = n · ν / (2 · f _n )
Where n is a positive integer (1, 2, 3,...)
ν: speed of sound in the pipe
With
The optical fiber sensor changes the phase of light propagating inside the optical fiber due to vibration, detects vibration from the optical polarization state that changes due to the phase change,
A polarization controller that forms a polarized light by controlling the polarization of the laser light whose phase has been changed by the optical fiber sensor, and a polarization converter that converts the change state of the polarized light as a light intensity change A photoelectric conversion module (PDM) that photoelectrically converts a change in light intensity converted by the polarization converter, and detects a phase change of the optical fiber sensor as a light intensity;
The polarization converter of the interferometer device unit includes a polarization branching module that separates the polarized light into a parallel component and a vertical component, and a polarization plane of the vertical component of the polarized light rotated by 90 degrees to be the same as the parallel component In the pipe thickness measuring device that is composed of a polarization maintaining coupler that interferes with the direction of the polarization plane ,
An apparatus for measuring a thickness of a pipe, wherein the optical fiber of the optical fiber sensor is replaced with the polarization maintaining coupler.

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