JP2014139590A - Material deterioration diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve long-term reliability for diagnosis using an ultrasonic optical probe.SOLUTION: A material deterioration diagnostic device comprises: a sheet material 22 on a first surface of which is bonded to the surface of a metallic material by an adhesive 31; an optical fiber 21 which is coated with gold, nickel or silica and adhered to a second surface of the sheet material 22 by an adhesive 23; an oscillator 1 provided on the optical fiber 21 for imparting oscillation into the metallic material; an optical interferometer 4 for converting the oscillation of light transmitting through the optical fiber 21 according to the oscillation in the metallic material into an electric signal; and a measurement and control part 5 for calculating the thickness of the metallic material based on the electric signal to determine the degree of deterioration of the metallic material. A metal paste, a glass paste or a ceramic-based adhesive is used as the adhesive 31.

Description

  The present invention relates to a material deterioration diagnosis apparatus that performs material deterioration diagnosis.

  Ultrasonic flaw detection is used for pipe thinning and corrosion 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 required from transmission to reception of the ultrasonic wave, and the size of the defect is obtained by measuring the intensity of the received echo and the range in which the defect echo appears.

  The ultrasonic inspection method is used in nuclear power plants to measure the thickness of materials and to detect welding defects such as lamination. In addition, such an inspection method is also used in the inspection of a weld overlay that reinforces nozzle openings, branches, and pipe joints around the reactor pressure vessel (see, for example, Non-Patent Document 1).

  It has been found that in power plants, thinning tends to occur easily in the elbow part of the piping, the downstream side of the orifice, and the like due to flow accelerated corrosion (FAC) and erosion. Based on such knowledge, a standard (JSME S CA1-2005) for pipe thinning management has been established by the Japan Society of Mechanical Engineers. As a standardized pipe thinning management technique, pipe thickness measurement using an ultrasonic thickness measuring instrument is performed. However, this method requires a great deal of time and cost because it is necessary to disassemble / restore the heat insulating material covering the pipe every time measurement is performed.

  Therefore, in order to realize low-cost thinning management, an embedded type fixed point measuring sensor has been developed. For example, an ultrasonic optical probe in which an electromagnetic ultrasonic transducer (EMAT) and an optical fiber vibration sensor are combined is known. The optical fiber vibration sensor is polyimide-coated and attached to the pipe surface using a polyimide-based adhesive. The electromagnetic ultrasonic oscillator directly excites the ultrasonic wave in the pipe by the action of electromagnetic force, and the resonance wave of the excited ultrasonic wave is detected by the optical fiber vibration sensor. Then, by analyzing the detection result, information on the thickness of the pipe and internal defects can be obtained (for example, see Non-Patent Documents 2 to 4).

  When applying such technology to thinning management of water supply system piping at power plants, sensor mounting locations are required to have long-term durability and heat resistance exceeding 300 ° C. The mounting used has only achieved a heat resistance of about 250 ° C. to 300 ° C. at best.

Kiichiro Uchigasaki et al .: “Nuclear Power and Design Technology” Taiga Publishing (1980), pp.226-250 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

  It is an object of the present invention to provide a material deterioration diagnostic apparatus that can improve the long-term reliability of diagnosis using an ultrasonic optical probe.

  The material deterioration diagnosis apparatus according to one aspect of the present invention is coated with a sheet material in which a first surface is bonded to a surface of a metal material with a first adhesive, gold, nickel, or silica, and the second adhesive with the above-mentioned An optical fiber bonded to the second surface of the sheet material; an oscillator provided on the optical fiber that applies vibration to the metal material; and transmits the optical fiber according to the vibration in the metal material. An optical interferometer that converts fluctuations of light into an electrical signal, and a measurement / control unit that calculates the thickness of the metallic material based on the electrical signal and determines the degree of deterioration of the metallic material. The first adhesive is a metal paste, a glass paste, or a ceramic adhesive.

  A material deterioration diagnosis apparatus according to an aspect of the present invention includes a metal mesh joined to a surface of a metal material by partial welding, an optical fiber that is bonded to the metal mesh and receives light from a light source, and an optical fiber on the optical fiber. An oscillator that provides vibration in the metal material, an optical interferometer that converts fluctuations of light transmitted through the optical fiber according to the vibration in the metal material into an electric signal, and the electric signal And a measurement / control unit that calculates the thickness of the metallic material based on the above and determines the degree of deterioration of the metallic material.

  According to the present invention, it is possible to improve long-term reliability of diagnosis using an ultrasonic optical probe.

1 is a schematic configuration diagram of a material deterioration diagnosis apparatus according to a first embodiment of the present invention. It is a schematic block diagram of EMAT which concerns on the 1st Embodiment. It is a schematic block diagram of the optical fiber sensor part which concerns on the 1st Embodiment. It is a figure explaining the attachment method of the ultrasonic optical probe which concerns on the 1st Embodiment. It is a figure which shows an example of the attachment to piping of the material deterioration diagnostic apparatus which concerns on the 1st Embodiment. It is a schematic block diagram of the optical fiber sensor part which concerns on the 2nd Embodiment of this invention. It is a figure explaining the attachment method of the ultrasonic optical probe which concerns on the 2nd Embodiment.

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

  (First Embodiment) FIG. 1 shows a schematic configuration of a material deterioration diagnosis apparatus according to a first embodiment of the present invention. The material deterioration diagnostic apparatus includes an electromagnetic ultrasonic oscillator (hereinafter referred to as EMAT) 1, an optical fiber sensor unit 2, a light source 3, an optical interferometer 4, a measurement / control unit 5, a waveform signal generator 6, and an amplifier 7. . The ultrasonic optical probe constituted by the EMAT 1 and the optical fiber sensor unit 2 is disposed on the surface of the metal 8 to be measured for thickness. The thickness measurement target is, for example, a piping of a nuclear power plant or a thermal power plant. The waveform signal generator 6 and the amplifier 7 supply a high-frequency current to the EMAT 1 based on the control of the measurement / control unit 5.

  FIG. 2 shows a schematic configuration of EMAT1. The EMAT 1 includes an electric coil 12 connected to the amplifier 7 and supplied with a high-frequency current, and a permanent magnet 11 placed on the electric coil 12. The material of the permanent magnet 11 is, for example, samarium cobalt. Since samarium cobalt has a demagnetization point between 350 and 400 ° C., it is preferably used in an environment of 350 ° C. or less.

  The permanent magnet 11 may be plated (plated) to prevent oxidation and the electric coil 12 may be coated with polyimide. In this way, the oscillation power can be maintained even at high temperatures.

  The upper surface of the optical fiber sensor unit 2 is shown in FIG. 3A, and the side surface is shown in FIG. As shown in FIG. 3A, in the optical fiber sensor unit 2, the optical fiber 21 is spirally wound into a circular flat plate. One end on the inner side of the optical fiber 21 is connected to the optical interferometer 4, and the other end on the outer side is connected to the light source 3. The optical fiber 21 receives the reference laser light from the light source 3. Further, the optical interferometer 4 detects the fluctuation of the light transmitted through the optical fiber 21. The optical fiber 21 is coated with a metal such as gold or nickel, or silica.

  Although not shown, the connection relationship between the optical interferometer 4 and the light source 3 with respect to the optical fiber may be reversed.

  As shown in FIG. 3B, the optical fiber 21 is attached to the sheet material 22 using an adhesive 23. For the sheet material 22, for example, a flexible sheet material that does not contain metal such as silicon foil, glass foil, ceramic foil, and the like can be used. The adhesive 23 for bonding the optical fiber 21 and the sheet material 22 differs depending on the material for coating the optical fiber 21. For example, when the optical fiber 21 is coated with gold, a gold paste is used for the adhesive 23. Further, when the optical fiber 21 is nickel-coated, a gold paste or a silver paste is used for the adhesive 23. Alternatively, when the optical fiber 21 is coated with silica, a glass paste is used for the adhesive 23.

  As shown in FIG. 3C, the optical fiber 21 may be sandwiched between the sheet material 22 and the resin sheet 24. The optical fiber 21 is fixed by filling the adhesive 23 between the sheet material 22 and the resin sheet 24. For the resin sheet 24, a heat-resistant resin sheet such as heat-resistant epoxy, polybenzimidazole, mica-reinforced polytetrafluoroethylene, and aromatic polyester can be used.

  Next, a method for attaching the ultrasonic optical probe to the surface of the metal 8 will be described with reference to longitudinal sections of the ultrasonic optical probe shown in FIGS. 4 (a) and 4 (b).

  First, as shown in FIG. 4A, a sheet material 22 having an optical fiber 21 bonded to one surface (second surface) using an adhesive 23 is prepared. And the other surface (1st surface) of this sheet material is adhere | attached on the surface of the metal 8 (for example, carbon steel) using the adhesive agent 31 with high heat resistance. Here, it is assumed that the metal 8 is a pipe and the surface is a curved surface. The adhesive 31 that bonds the sheet material 22 and the metal 8 differs depending on the material of the sheet material 22. For example, when the sheet material 22 is a silicon foil, a metal paste is used for the adhesive 31. As the metal paste, for example, a paste having a heat resistance of about 500 ° C. such as a silver paste can be used.

When the sheet material 22 is a glass foil, a glass paste is used for the adhesive 31. The glass paste has a heat resistance of about 380 ° C. As the glass paste, for example, one containing SiO ₂ , B ₂ O ₃ , PbO, one containing SiO ₂ , ZnO, or RO can be used.

  When the sheet material 22 is a ceramic foil, a ceramic high temperature adhesive such as a heat resistant inorganic adhesive (Nissela coat) is used for the adhesive 31. The ceramic high temperature adhesive has a heat resistance of about 700 ° C.

  And as shown in FIG.4 (b), the electric coil 12 and the permanent magnet 11 are arrange | positioned in order on the optical fiber 21. As shown in FIG. Usually, the permanent magnet 11 is fixed to the metal 8 by magnetic force, and the electric coil 12 is fixed by being sandwiched between the permanent magnet 11 and the optical fiber 21. However, even if it is fixed with an adhesive or the like to prevent displacement. Good.

  A method of measuring the thickness of the metal 8 using the ultrasonic optical probe attached to the metal 8 in this way will be described. When a high-frequency current flows, the electric coil 12 vibrates the metal 8 by Lorentz force or magnetostriction generated along with the electromagnetic induction action, and generates electromagnetic ultrasonic waves inside the metal 8. The waveform signal generator 6 changes the frequency of the alternating current applied to the electric coil, and sweeps the frequency of the generated electromagnetic ultrasonic wave in a desired frequency band.

  The vibration inside the metal 8 is transmitted to the optical fiber sensor unit 2 on the same principle as the strain measurement of the high-temperature strain gauge. When vibration reaches the optical fiber sensor unit 2 in a state where the reference laser beam is input from the light source 3, the optical fiber 21 is slightly expanded and contracted, and the Doppler effect and the polarization plane change occur in the laser beam. The frequency of the ultrasonic wave propagating in the metal 8 can be measured by the optical interferometer 4 converting this fluctuation (stretching speed) into a voltage value by photoelectric conversion.

  The frequency of vibration generated inside the metal 8 to be measured for thickness can be selected by the waveform signal generator 6 from 1 Hz to 10 MHz according to the thickness of the metal. The measurement / control unit 5 detects vibration with a frequency of 1 Hz to 20 kHz and ultrasonic vibration with a frequency of 20 kHz to 10 MHz via the optical fiber 21 and the optical interferometer 4.

  When the frequency of the electromagnetic ultrasonic wave is swept and the relationship of λ = 2d is established between the thickness d of the metal 8 and the wavelength λ of the electromagnetic ultrasonic wave, the incident wave and the reflected wave resonate, and the amplitude of the output wave is large. Become. This relationship can be expressed as f = v / 2d using the ultrasonic frequency f and sound velocity v. Therefore, the thickness of the metal 8 can be obtained from the resonance frequency and the speed of sound. For example, in the case of a 9 mm thick steel plate, resonance occurs when an ultrasonic wave of 300 kHz is input.

  In FIG. 5, an example of the attachment to piping of the material deterioration diagnostic apparatus which concerns on this embodiment is shown. By attaching the ultrasonic optical probe 40 constituted by the EMAT 1 and the optical fiber sensor unit 2 to the outer surface of the pipe 41, the measurement / control unit 5 analyzes the resonance ultrasonic signal that has been multiple-reflected from the inner surface and the outer surface of the pipe 41, The thickness of the pipe 41 is measured. The material of the pipe 41 is, for example, carbon steel. As described above, the sheet material 22 to which the optical fiber 21 is bonded is bonded to the pipe 41 using an adhesive (adhesive 31). It is preferable that the ultrasonic optical probe 40 is attached to a portion that is considered to be statistically likely to be thinned, such as the elbow portion of the pipe 41 or the downstream of the orifice portion.

  The measurement / control unit 5 has a diagnostic database including a determination threshold regarding deterioration such as corrosion and thinning of the pipe 41, and results of the original waveform received from the optical interferometer 4 and the signal processing performed on the original waveform And the diagnosis database are collated to determine the degree of deterioration of the pipe 41.

  The ultrasonic optical probe 40 is embedded in advance between the pipe 41 and the heat insulating material 42, thereby enabling online thickness measurement (determination of deterioration). In measuring the thickness of the pipe 41, it is not necessary to dismantle / restore the heat insulating material 42. Therefore, the safety of the plant and the equipment operation rate can be increased.

In the pipe thinning management standard, the position of the pipe thickness measurement point is determined according to the pipe diameter. When the pipe size is 150 A (outer diameter: about 165 mm) or more, eight locations ( When the size is less than 150A, there are four locations in the circumferential direction (90 ° intervals).
Moreover, about the axial direction of piping, it is decided to measure the thickness of piping at the space | interval below the outer diameter length of piping.

  In the present embodiment, the flexible sheet material 22 to which the optical fiber 21 coated with metal or silica is bonded is attached to the metal surface of the thickness measurement target such as a pipe with the adhesive 23 having high heat resistance. Bonding strength is higher than when attaching to a metal surface with a simple polyimide varnish, and reliability such as heat resistance and durability can be improved over a long period of time.

  Moreover, since the flexible sheet material which does not contain metals, such as silicon foil, glass foil, and ceramic foil, is used for the sheet material 22, compared with the case where metal foil is used for the sheet material 22, electromagnetic field shielding is reduced. It is possible to improve the diagnostic accuracy of the material deterioration diagnostic apparatus.

  (Second Embodiment) FIG. 6 shows a schematic configuration of an ultrasonic optical probe of a material deterioration diagnosis apparatus according to a second embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 3 in that the optical fiber 21 is bonded to the metal mesh 25. In FIG. 6, the same parts as those of the first embodiment shown in FIG. The material of the metal mesh 25 is, for example, iron.

  Next, a method of attaching the ultrasonic optical probe having the optical fiber sensor portion 2 having the configuration as shown in FIG. 6 to the surface of the metal 8 will be described with reference to the ultrasonic waves shown in FIGS. 7 (a), (b), and (c). This will be described using a longitudinal section of an optical probe or the like.

  First, as shown in FIG. 7A, a metal mesh 25 to which an optical fiber 21 is bonded using an adhesive 23 is placed on the surface of a metal 8 (for example, carbon steel). Here, the metal 8 is a pipe, and the surface is a curved surface. When the metal mesh 25 is pressed against the surface of the metal 8, convex portions (not shown) of the metal mesh 25 make point contact with the surface of the metal 8. At this time, the metal mesh 25 and the metal 8 surface may be temporarily fixed with an adhesive or the like.

  Subsequently, as shown in FIG. 7B, using a welding power source (not shown), a current is passed through the metal mesh 25 to melt the convex portions of the metal mesh 25 that are in point contact with the surface of the metal 8. Thereby, the metal mesh 25 and the metal 8 are partially welded, and the metal mesh 25 is joined to the metal 8.

  Then, as shown in FIG. 7C, the electric coil 12 and the permanent magnet 11 are sequentially arranged on the optical fiber 21. Usually, the permanent magnet 11 is fixed to the metal 8 by magnetic force, and the electric coil 12 is fixed by being sandwiched between the permanent magnet 11 and the optical fiber 21. However, even if it is fixed with an adhesive or the like to prevent displacement. Good.

  In this embodiment, since the metal mesh 25 to which the optical fiber 21 is bonded is attached to the metal surface of a thickness measurement target such as a pipe by partial welding, the bonding strength is higher than the case where the metal mesh 25 is attached to the metal surface with an adhesive. Reliability such as durability and durability can be improved over a long period of time.

  Further, since the optical fiber 21 is bonded to the metal mesh 25, the electromagnetic field shielding can be reduced by the mesh structure as compared with the case where the optical fiber 21 is bonded to the metal foil. Diagnosis accuracy can be improved.

  In the first and second embodiments, the material of the piping to be subjected to deterioration diagnosis is not limited to a magnetic body such as carbon steel, and may be a non-magnetic body. As in the first embodiment, when the sheet material 22 bonded to the pipe does not contain metal, the permanent magnet 11 is not fixed by magnetic force. Fix it.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 EMAT
2 Optical fiber sensor unit 3 Light source 4 Optical interferometer 5 Measurement / control unit 6 Waveform signal generator 7 Amplifier 8 Metal 11 Permanent magnet 12 Electric coil 21 Optical fiber 22 Sheet material 23 Adhesive 24 Resin sheet 25 Metal mesh 31 Adhesive

Claims (2)

A metal mesh joined to the surface of the metal material by partial welding;
An optical fiber that is bonded to the metal mesh and receives light from a light source;
An oscillator which is provided on the optical fiber and which vibrates in the metal material;
An optical interferometer that converts fluctuations of light transmitted through the optical fiber in response to vibration in the metal material into an electrical signal;
A measurement / control unit that calculates the thickness of the metal material based on the electrical signal and determines the degree of deterioration of the metal material;
A material deterioration diagnosis device comprising: When the optical fiber is gold-coated, the optical fiber is bonded to the metal mesh with a gold paste,
When the optical fiber is nickel-coated, the optical fiber is bonded to the metal mesh with a gold paste or a silver paste,
2. The material deterioration diagnosis apparatus according to claim 1, wherein when the optical fiber is silica-coated, the optical fiber is bonded to the metal mesh with a glass paste.

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