JP2009281789A - Temperature measuring instrument and method for fitting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature measuring instrument and its fitting method, which enable a reduction in fitting execution time to an inspection object, and accurate detection of the temperature of the inspection object. <P>SOLUTION: The temperature measuring instrument includes an optical fiber 3 equipped with a plurality of diffraction grating sections 33 formed at intervals in its core 31, and pads 6 which bury at least parts where the grating sections 33 are formed of the optical fiber 3, and are fixed to the temperature measuring object 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature measurement device suitable for use in temperature distribution measurement using an optical fiber and a method for attaching the temperature measurement device.

Conventionally, in a boiler tube used in a thermal power plant or the like, temperature monitoring is performed in order to prevent steam leakage from a stress concentration portion due to thermal elongation.
In such measurement of the metal temperature of the boiler tube, measurement using a thermocouple has become the mainstream. Thermocouples are sensors that are most frequently used in temperature measurement, and have the advantage that the most suitable thermocouple can be selected from a variety of thermocouples using a wide variety of materials depending on the intended use.

  Temperature measurement using a thermocouple is performed by bringing a welding end, which is a welded end of two different types of metal wires that make up the thermocouple, into contact with a temperature measurement target and generating heat between the other ends. This is done by measuring power. The above-described thermoelectromotive force, that is, the output voltage of the thermocouple is affected by the temperature difference between the above-described one end and the other end. Therefore, the temperature of the terminal part of the measuring instrument to which the other end of the thermocouple is connected is measured, and the measured temperature is corrected based on the measured temperature, whereby the above-mentioned weld end, that is, the temperature sensitive The temperature of the part to be measured temperature contact point is specified.

However, thermocouples can only measure the temperature at one location for one sensor, so a signal line is required for each thermocouple that connects the thermocouple and the measuring instrument and inputs the output voltage to the measuring instrument. Therefore, there is a problem that it takes time to install a large number of thermocouples.
Furthermore, since the thermocouple used for measuring the metal temperature of the boiler tube requires corrosion resistance, a thermocouple having a high unit price is used. Therefore, there is a problem that it is not suitable for multipoint measurement that requires a large number of thermocouples.

  In order to solve the above-mentioned problem, a method for detecting temperature using a temperature sensor other than a thermocouple has been proposed. For example, the wavelength distribution of scattered light generated in an optical fiber cable changes with temperature. A temperature detection method has been proposed (see, for example, Patent Document 1).

  Further, a fiber Bragg grating (hereinafter referred to as “FBG”) optical fiber temperature sensor using an optical fiber having a diffraction grating formed in a part of a core is also known. The optical fiber used for the FBG optical fiber temperature sensor is formed by alternately repeating a portion having a high refractive index and a portion having a low refractive index at a constant interval in the longitudinal direction, that is, periodically. .

The above-described periodic structure is formed by irradiating the core of the optical fiber with ultraviolet (UV) light having a wavelength of about 250 nm.
Generally, when the core is irradiated with ultraviolet light, the refractive index changes due to a change in the light-induced refractive index, and the changed refractive index is maintained even after the ultraviolet light irradiation is stopped. Therefore, in the above-described periodic structure, a structure in which the refractive index is periodically changed is written in the core by forming the interference fringes of ultraviolet light in the region where the core of the optical fiber is disposed.

This structure in which the refractive index changes periodically functions as a diffraction grating that reflects light of wavelength λ _B = 2nΛ and transmits light of other wavelengths. Here, n is the refractive index of the optical fiber, and Λ is the period of the diffraction grating.
Such a structure in which the refractive index changes periodically, that is, a diffraction grating is formed at a plurality of points of an optical fiber cable, and the optical fiber cable is laid on a measurement object, so that a plurality of points can be obtained with one optical fiber cable. It is known that the temperature of can be measured.

On the other hand, since the diffraction grating in the optical fiber disappears in a high temperature range (for example, about 300 ° C. to about 350 ° C.), in order to protect the diffraction grating serving as the sensor unit, the optical fiber is made of a metal tube having excellent heat resistance. The covering technique is also known.
Japanese Patent Laid-Open No. 9-257597

However, in the temperature measurement using the optical fiber described above, since the contact area between the cylindrical optical fiber and the inspection target (for example, a boiler tube) is narrow, a temperature difference is likely to occur between the optical fiber and the inspection target. However, there is a problem that the temperature measurement accuracy is lowered.
Furthermore, since the contact area between the optical fiber and the inspection object is small, it is difficult to fix the optical fiber to the inspection object, and the optical fiber may be peeled off from the inspection object, and the temperature of the inspection object may not be accurately detected.

  The present invention has been made to solve the above-described problems, and is a temperature measuring device and a temperature measuring device that can reduce the time required for mounting on an inspection object and accurately detect the temperature of the inspection object. It aims at providing the attachment method of.

In order to achieve the above object, the present invention provides the following means.
The temperature measuring device of the present invention includes an optical fiber in which a plurality of diffraction grating portions are formed at intervals in a core, and at least a portion where the diffraction grating portion is formed in the optical fiber, and temperature measurement. And a pad to be fixed to the object.

According to the present invention, since the optical fiber is fixed to the measuring object together with the pad, the fixing to the measuring object becomes easier as compared with the method of directly fixing the optical fiber to the measuring object.
Furthermore, the optical fiber and the measurement target can be brought into close contact with each other through the pad, and an increase in temperature difference between the optical fiber and the measurement target can be suppressed.

  Since at least the portion of the optical fiber in which the diffraction grating portion is formed is embedded in the pad, in other words, since the other portions are not embedded in the pad, all of the optical fiber is embedded in the pad or the like. Compared to the case, the portion of the optical fiber not embedded in the pad can be bent freely. Therefore, even if the surface on which the pad in the measurement target is attached is a curved surface, the optical fiber and the pad can be easily fixed to the measurement target.

  The temperature measuring device of the present invention is formed in an optical fiber having a plurality of diffraction grating portions formed at intervals in a core, a substantially cylindrical protective tube through which the optical fiber is inserted, and a temperature measurement target. A fixing portion for fixing the protective tube arranged in the groove portion to the measurement object is provided.

  According to the present invention, since the optical fiber inserted into the protective tube is disposed in the groove formed in the measurement target, the measurement is performed in comparison with the configuration in which the optical fiber inserted into the protective tube is simply disposed in the measurement target. The contact area with the object, in other words, the heat transfer area increases. Therefore, the expansion of the temperature difference between the optical fiber and the measurement object can be suppressed.

  Furthermore, since the protective tube and the optical fiber are fixed in a state where they are arranged in the groove portion, the optical fiber can be fixed to the measurement object easily and reliably compared to a fixing method that does not use the groove portion.

  In the above invention, it is desirable that the measurement object is a substantially cylindrical member, and the groove portion is formed to extend along the longitudinal direction of the measurement object.

  According to the present invention, since the optical fiber can be arranged along the longitudinal direction of the substantially cylindrical measuring object, the temperature distribution in the longitudinal direction of the measuring object can be measured.

  In the above invention, it is preferable that the measurement object is a substantially cylindrical member, and the groove portion is formed to extend spirally on the cylindrical surface of the measurement object.

  According to the present invention, since the optical fiber can be spirally arranged on the cylindrical surface of the measurement target, the temperature distribution on the cylindrical surface of the measurement target can be measured.

  The temperature measuring device mounting method of the present invention includes an embedding step of embedding a portion of the optical fiber including at least a diffraction grating portion formed in a core in a pad formed in a plate shape, and measuring the pad And a fixing step for fixing to the substrate.

According to the present invention, since the optical fiber is fixed to the measuring object together with the pad, the fixing to the measuring object becomes easier as compared with the method of directly fixing the optical fiber to the measuring object.
Furthermore, the optical fiber and the measurement target can be brought into close contact with each other through the pad, and an increase in temperature difference between the optical fiber and the measurement target can be suppressed.

  Since at least the portion of the optical fiber in which the diffraction grating portion is formed is embedded in the pad, in other words, since the other portions are not embedded in the pad, all of the optical fiber is embedded in the pad or the like. Compared to the case, the portion of the optical fiber not embedded in the pad can be bent freely. Therefore, even if the surface on which the pad in the measurement target is attached is a curved surface, the optical fiber and the pad can be easily fixed to the measurement target.

  According to the temperature measuring device and the method for attaching the temperature measuring device of the present invention, the optical fiber is fixed to the measuring object together with the pad, so that the installation time for the inspection object is shortened and the temperature of the inspection object is accurately set. The effect that it can detect can be show | played. Further, since at least the portion of the optical fiber in which the diffraction grating portion is formed is embedded in the pad, it is easy to attach the optical fiber and the pad to the inspection object, and the effect that the installation time can be shortened. Play.

  According to the temperature measuring device and the method of attaching the temperature measuring device of the present invention, the optical fiber inserted through the protective tube is disposed in the groove formed in the measurement target, so that the installation time for the inspection target is shortened. The effect that the temperature of the inspection object can be accurately detected can be achieved.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the invention of the present application will be described by applying it to a temperature measuring device used for temperature measurement such as an evaporator tube, a furnace wall, a nozzle, a superheater, and a reheater in a boiler of a thermal power plant. .
FIG. 1 is a cross-sectional view for explaining the outline of the configuration of the temperature measuring apparatus according to the present embodiment.
As shown in FIG. 1, an optical fiber sensor (optical fiber) 3 and a measuring instrument 4 for detecting the temperature of a boiler tube (measurement target) 2 such as an evaporation tube and an optical fiber sensor 3 are inserted into the temperature measuring device 1. A protective tube 5 and a pad 6 in which the optical fiber sensor 3 is embedded and fixed to the boiler tube 2 are provided.

As shown in FIG. 1, the optical fiber sensor 3 includes a core 31 that conveys light and a clad 32 that covers the periphery of the core 31, and a plurality of diffraction grating portions spaced apart in the longitudinal direction from the core 31. 33 is formed.
Thus, by providing the several diffraction grating part 33 in one optical fiber sensor 3, highly accurate multipoint temperature measurement can be performed.

FIG. 2 is a schematic diagram illustrating the configuration of the diffraction grating portion formed in the core of the optical fiber sensor in FIG.
As shown in FIG. 2, the diffraction grating portion 33 is a portion where the refractive index in the core 31 periodically changes and is a portion that functions as a temperature sensor in the optical fiber sensor 3. As described above, the diffraction grating portion 33 is formed by irradiating the core 31 with ultraviolet light having a wavelength of about 250 nm.

The measuring instrument 4 measures temperature together with the optical fiber sensor 3 as shown in FIG. The principle of temperature measurement in the optical fiber sensor 3 and the measuring instrument 4 will be described later.
The end of the optical fiber sensor 3 is connected to the measuring instrument 4, and the measuring instrument 4 causes incident light used for temperature measurement to enter the core 31 of the optical fiber sensor 3 and reflected light reflected by the diffraction grating section 33. Is incident on the measuring instrument 4.

FIG. 3 is a cross-sectional view illustrating the configuration of the protective tube of FIG.
The protective tube 5 is a cylindrical member into which the optical fiber sensor 3 is inserted, and is a member formed from a metal material having heat resistance. Further, the protective tube 5 is disposed so as to cover the optical fiber sensor 3 including a portion embedded in the pad 6.
By inserting the optical fiber sensor 3 into the protective tube 5 in this way, the optical fiber sensor 3 can be protected from high temperatures. In other words, the diffraction grating portion 33 of the optical fiber sensor 3 is prevented from disappearing due to a high temperature, and temperature measurement using the optical fiber sensor 3 can be performed even in the high temperature region.

FIG. 4 is a diagram for explaining the arrangement of the pad of FIG. 1 and the optical fiber sensor embedded in the pad.
The pad 6 is a quadrangular columnar member fixed to the boiler tube 2 while a portion where the diffraction grating portion 33 is formed in the optical fiber sensor 3 is embedded. Examples of the material for forming the pad 6 include a material having a thermal expansion coefficient equivalent to that of the boiler tube 2, such as stainless steel (SUS347).

FIG. 5 is a diagram illustrating the configuration of the divided body in the pad of FIG.
As shown in FIGS. 4 and 5, the pad 6 is provided with a pair of square plate-like divided bodies 61, 61, and the pad 6 is formed by welding the pair of divided bodies 61, 61 together.
As shown in FIG. 5, a groove 62 in which the optical fiber sensor 3 inserted through the protective tube 5 is disposed is formed on the mating surface where the split bodies 61 come into contact with each other. The groove part 62 is formed to extend substantially in parallel along one side of the divided body 61.
Furthermore, the surface of the groove 62 is formed so as to be in close contact with the protective tube 5, in other words, without any unevenness.

6 is a top view for explaining the arrangement of the pads in FIG. 1, and FIG. 7 is a cross-sectional view for explaining the arrangement of the pads in FIG.
As shown in FIG. 6, the pads 6 are discretely arranged only at the temperature measurement points in the boiler tube 2. In other words, the diffraction grating portion 33 in the optical fiber sensor 3 is also discretely formed only at the temperature measurement points in the boiler tube 2.
Further, as shown in FIG. 7, the pad 6 is disposed in close contact with the outer peripheral surface of the boiler tube 2, and is welded to the boiler tube 2 at a side extending along the optical fiber sensor 3 of the pad 6. As the welding, TIG (Tungsten Inert Gas) welding that is also used for bonding the pad-type thermocouple and the boiler tube 2 can be exemplified.

Next, a method for attaching the temperature measuring device 1 to the boiler tube 2 will be described.
First, as shown in FIG. 3, the optical fiber sensor 3 is inserted through the protective tube 5. Thereafter, as shown in FIG. 4, the optical fiber sensor 3 and the protective tube 5 are disposed between the pair of split bodies 61 and 61, and the split bodies 61 and 61 are welded, so that the optical fiber sensor 3 is attached to the pad 6. Buried (buried process).
At this time, the optical fiber sensor 3 and the protective tube 5 are disposed in the groove 62 formed in the divided body 61, and the optical fiber sensor 3, the protective tube 5 and the divided body 61 are in close contact with each other.

  Thereafter, as shown in FIGS. 6 and 7, the pad 6 is fixed to the boiler tube 2 by welding (fixing step). Since the pad 6 is in close contact with the boiler tube 2, the optical fiber sensor 3, the protective tube 5, and the boiler tube 2 are in close contact via the pad 6.

Next, temperature measurement of the boiler tube 2 in the above-described temperature measurement apparatus 1 will be described.
When measuring the temperature of the boiler tube 2, first, as shown in FIG. 1, the pad 6 in which the optical fiber sensor 3 is embedded is welded and fixed to a temperature measurement point in the boiler tube 2.

  Thereafter, incident light enters the core 31 of the optical fiber sensor 3 from the measuring instrument 4, and the reflected light reflected by the diffraction grating portion 33 is measured by the measuring instrument 4. The measuring instrument 4 calculates the distortion of the diffraction grating unit 33 based on the wavelength of the incident reflected light, and calculates the temperature of the diffraction grating unit 33 from the calculated distortion of the diffraction grating unit 33.

The wavelength λ _B of the reflected light is expressed as λ _B = 2nΛ using the refractive index n of the core 31 and the diffraction grating period Λ of the diffraction grating portion 33. Therefore, when the diffraction grating portion 33 is distorted and the diffraction grating period changes to Λ1, the wavelength of the reflected light also changes to λ1 _B = 2nΛ1 according to the above formula.
Further, when the distortion in the diffraction grating portion 33 is distortion due to thermal expansion of the optical fiber sensor 3, the temperature in the diffraction grating portion 33 is set based on the thermal expansion coefficient of the optical fiber sensor 3 and the distortion of the diffraction grating portion 33. Can be calculated.

According to the above configuration, since the optical fiber sensor 3 is fixed to the boiler tube 2 together with the pad 6 by welding, the optical fiber sensor 3 is fixed to the boiler tube 2 as compared with the method of directly fixing the optical fiber sensor 3 to the boiler tube 2. Becomes easier. Therefore, the construction time for attaching the temperature measuring device 1 to the boiler tube 2 can be shortened.
Furthermore, since the optical fiber sensor 3 and the boiler tube 2 can be brought into close contact with each other via the pad 6, an increase in temperature difference between the optical fiber sensor 3 and the boiler tube 2 can be suppressed. Therefore, the temperature of the boiler tube 2 can be detected accurately.

  Since the portion where the diffraction grating portion 33 in the optical fiber sensor 3 is formed is embedded in the pad 6, in other words, since the other portion is not embedded in the pad 6, all of the optical fiber sensor 3 is padded. Compared with the case where it is embedded in 6, the portion of the optical fiber sensor 3 which is not embedded in the pad 6 can be bent freely. Therefore, even if the surface on which the pad 6 is attached in the boiler tube 2 is a curved surface, the optical fiber sensor 3 and the pad 6 can be easily fixed to the measurement object.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.
The basic configuration of the temperature measurement device of this embodiment is the same as that of the first embodiment, but differs from the first embodiment in the method of fixing the optical fiber sensor to the boiler tube. Therefore, in the present embodiment, only the configuration relating to the fixing of the optical fiber sensor will be described with reference to FIGS. 8 and 9, and the description of the other configurations and the like will be omitted.
FIG. 8 is a top view for explaining a configuration relating to fixing of the optical fiber sensor to the boiler tube in the temperature measuring device according to the present embodiment, and FIG. 9 relates to fixing of the optical fiber sensor to the boiler tube of FIG. It is a sectional view explaining composition.
In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIGS. 8 and 9, the optical fiber sensor 3 and the protective tube 5 in the temperature measuring device 101 of the present embodiment are arranged in the groove portion 102 formed in the boiler tube 2, and then the groove portion 102 is fixed by the fixing portion 103. It is fixed to.

  The groove portion 102 is a groove portion 102 that extends substantially linearly in the longitudinal direction of the boiler tube 2, and the surface of the groove portion 102 is formed so as to be in close contact with the protective tube 5, in other words, without any irregularities. ing.

The fixed portion 103 is, for example, a wire formed of stainless steel or a string-like member formed of glass wool, and the surroundings of the boiler tube 2 with the optical fiber sensor 3 and the protective tube 5 disposed in the groove portion 102. It can be wrapped around.
Here, the fixed portion 103 is wound around a portion of the optical fiber sensor 3 where the diffraction grating portion 33 is not provided.

  According to said structure, in order to arrange | position the optical fiber sensor 3 penetrated by the protective tube 5 in the groove part 102 formed in the boiler tube 2, the optical fiber sensor 3 simply penetrated by the protective tube 5 in the boiler tube 2 is provided. Compared with the structure which arrange | positions, the contact area with the boiler tube 2, in other words, a heat-transfer area increases. Therefore, the expansion of the temperature difference between the optical fiber sensor 3 and the boiler tube 2 can be suppressed. Therefore, the temperature of the boiler tube 2 can be detected accurately.

  On the other hand, since the protective tube 5 and the optical fiber sensor 3 are fixed in a state where they are arranged in the groove 102, the optical fiber sensor 3 is fixed to the boiler tube 2 easily and surely as compared with a fixing method that does not use the groove 102. can do. Therefore, the installation construction time of the optical fiber sensor 3 to the boiler tube 2 can be shortened. Furthermore, since the optical fiber sensor 3 can be disposed along the longitudinal direction of the substantially cylindrical boiler tube 2, the temperature distribution in the longitudinal direction of the boiler tube 2 can be measured.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
The basic configuration of the temperature measurement device of this embodiment is the same as that of the first embodiment, but differs from the first embodiment in the method of fixing the optical fiber sensor to the boiler tube. Therefore, in the present embodiment, only the configuration relating to the fixing of the optical fiber sensor will be described using FIG. 10, and the description of the other configurations and the like will be omitted.
FIG. 10 is a top view for explaining the configuration relating to the fixing of the optical fiber sensor to the boiler tube in the temperature measuring device according to the present embodiment.
In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 10, the optical fiber sensor 3 and the protective tube 5 in the temperature measuring device 201 of this embodiment are fixed to the groove portion 202 by the fixing portion 103 after being arranged in the groove portion 202 formed in the boiler tube 2. ing.

  The groove portion 202 is a groove portion 202 extending spirally along the cylindrical surface of the boiler tube 2, and the surface of the groove portion 202 is formed so as to be in close contact with the protective tube 5, in other words, without any irregularities. Yes.

  According to said structure, in order to arrange | position the optical fiber sensor 3 penetrated by the protective tube 5 in the groove part 202 formed in the boiler tube 2, the optical fiber sensor 3 simply penetrated by the protective tube 5 in the boiler tube 2 is provided. Compared with the structure which arrange | positions, the contact area with the boiler tube 2, in other words, a heat-transfer area increases. Therefore, the expansion of the temperature difference between the optical fiber sensor 3 and the boiler tube 2 can be suppressed. Therefore, the temperature of the boiler tube 2 can be detected accurately.

  On the other hand, since the protective tube 5 and the optical fiber sensor 3 are fixed in a state where they are disposed in the groove 202, the optical fiber sensor 3 can be fixed to the boiler tube 2 easily and reliably compared to a fixing method that does not use the groove 202. can do. Therefore, the installation construction time of the optical fiber sensor 3 to the boiler tube 2 can be shortened. Furthermore, since the optical fiber sensor 3 can be spirally disposed on the cylindrical surface of the boiler tube 2, the temperature distribution on the cylindrical surface of the boiler tube 2 can be measured.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a sectional view explaining the outline of the composition of the temperature measuring device concerning a 1st embodiment of the present invention. It is a schematic diagram explaining the structure of the diffraction grating part formed in the core of the optical fiber sensor of FIG. FIG. 2 is a cross-sectional view illustrating the configuration of the protective tube in FIG. 1. It is a figure explaining arrangement | positioning of the optical fiber sensor embedded in the pad of FIG. 1, and a pad. It is a figure explaining the structure of the division body in the pad of FIG. FIG. 2 is a top view for explaining the arrangement of pads in FIG. 1. FIG. 7 is a cross-sectional view for explaining the arrangement of pads in FIG. 6. It is a top view explaining the structure regarding fixation of the optical fiber sensor to the boiler tube in the temperature measuring device which concerns on the 2nd Embodiment of this invention. It is a sectional view explaining composition about fixation of an optical fiber sensor to a boiler tube of Drawing 7. It is a top view explaining the structure regarding fixation of the optical fiber sensor to the boiler tube in the temperature measuring device which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

1,101,201 Temperature measuring device 2 Boiler tube (measuring object)
3 Optical fiber sensor (optical fiber)
6 Pad 31 Core 33 Diffraction grating part 102, 202 Groove part 103 Fixed part

Claims (5)

An optical fiber having a plurality of diffraction grating portions formed at intervals in a core;
A pad in which at least the diffraction grating portion of the optical fiber is formed is embedded, and a pad fixed to a temperature measurement target;
A temperature measuring device characterized in that is provided. An optical fiber having a plurality of diffraction grating portions formed at intervals in a core;
A substantially cylindrical protective tube through which the optical fiber is inserted;
A fixing portion for fixing the protective tube disposed in the groove formed in the temperature measurement target to the measurement target;
A temperature measuring device characterized in that is provided. The measurement object is a substantially cylindrical member,
The temperature measuring device according to claim 2, wherein the groove portion is formed to extend along a longitudinal direction of the measurement target. The measurement object is a substantially cylindrical member,
The temperature measuring device according to claim 2, wherein the groove is formed to extend spirally on the cylindrical surface of the measurement target. An embedding step of embedding a portion of the optical fiber including at least a diffraction grating portion formed in a core in a pad formed in a plate shape;
A fixing step of fixing the pad to a measurement object;
A method for attaching a temperature measuring device, wherein:

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