Telescopic joint

Abstract

To provide a telescopic joint which can detect deterioration of a heat insulation function in a wide range of a heat insulation part.SOLUTION: A telescopic joint 20 connects an upstream side duct 11 and a downstream side duct 12, in which a fluid circulates, with each other and allows the fluid to circulate therein. The telescopic joint 20 includes: a bellows material 23 which is provided between the upstream side duct 11 and the downstream side duct 12 and prevents outflow of the fluid; a heat insulation part 30 which is provided at the inner side of the bellows material 23 and insulates heat of the fluid; and FBG sensors 40, 41, 42 provided at the outer side of the heat insulation part 30.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention relates to expansion joints. [Background technology]

[0002] Expansion joints are used at the connections of ducts that transport fluids such as high-temperature gases and are installed in facilities such as thermal power plants and chemical plants, for the purpose of absorbing displacement, vibration, stress, and the like that occurs in the duct itself. One example of a conventional expansion joint is known, for example, from the expansion joint described in Patent Document 1. This expansion joint is formed by connecting a pair of flanges formed so as to be connectable to a duct with a cylindrical non-metallic bellows material having expansion and contraction flexibility and a thermal insulation section, and multiple thermal fuses are arranged in the thermal insulation section, and a decrease in the thermal insulation function of the thermal insulation section is detected by detecting a disconnection state of these thermal fuses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-27189 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the expansion joint described in Patent Document 1, the number of thermal fuses that can be installed in the thermal insulation section is limited due to issues with the layout of the conductors connected to the thermal fuses and the number of detection channels, so there is a problem in that there are parts in the thermal insulation section where a decrease in the thermal insulation function cannot be detected.

[0005] The present invention has been made to solve such problems, and has an object to provide an expansion joint that is capable of detecting a decrease in the insulating function over a wide area of ​​the insulating section. [Means for solving the problem]

[0006] In order to solve the above problems, the expansion joint of the present invention is an expansion joint that connects a first duct and a second duct through which a fluid flows and through which the expansion joint comprises an outflow prevention section that is arranged between the first duct and the second duct and has elasticity to prevent the outflow of the fluid, an insulating section that is arranged inside the outflow prevention section to insulate the fluid from heat, and an optical fiber temperature sensor that has a temperature measurement section arranged at least either outside the insulating section or inside the insulating section.

[0007] The optical fiber temperature sensor may also have a plurality of temperature measuring units. The optical fiber temperature sensor may also be housed in a tubular protective member. The optical fiber temperature sensor may be provided in at least one of the outflow prevention section, the heat insulating section, or between the outflow prevention section and the heat insulating section. Furthermore, a plurality of optical fiber temperature sensors may be provided along the circumferential direction of the outflow prevention portion. The optical fiber temperature sensor may be wound multiple times in the circumferential direction of the outflow prevention portion. The optical fiber temperature sensor may be provided along the circumferential direction of the outflow prevention portion, with at least a portion of the sensor meandering. Effect of the Invention

[0008] The expansion joint of the present invention comprises an outflow prevention section that is arranged between the first duct and the second duct and has elasticity to prevent the outflow of fluid, an insulating section that is arranged inside the outflow prevention section to insulate the heat of the fluid, and an optical fiber temperature sensor that is arranged at least either in the insulating section, outside the insulating section, or inside the insulating section, so that a deterioration in the insulating function can be detected over a wide range of the insulating section. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a non-metallic expansion joint in accordance with a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the upstream duct, downstream duct, and expansion joint shown in FIG. [Diagram 3] FIG. 1 is a cross-sectional view of a protective tube and an FBG sensor cut along a radial direction. [Figure 4] FIG. 1 is a schematic diagram of an expansion joint and an FBG sensor. [Diagram 5] FIG. 11 is a schematic diagram of an expansion joint and an FBG sensor according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a schematic diagram of an expansion joint and an FBG sensor according to a third embodiment of the present invention. [Figure 7] FIG. 11 is an enlarged schematic cross-sectional view showing one radial half of a cross section of an upstream duct, a downstream duct, and an expansion joint according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Embodiment 1 Hereinafter, an expansion joint according to a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a non-metallic expansion joint according to the first embodiment. In the first embodiment, a duct structure 1 arranged in a thermal power generation facility or the like has a cylindrical upstream duct 11 and a downstream duct 12 through which a high-temperature fluid such as exhaust gas flows. An expansion joint 20, which is a non-metallic expansion joint provided in the duct structure 1, is arranged between the upstream duct 11 and the downstream duct 12 to connect the two ducts and prevent the internal fluid from flowing out. In addition, the expansion joint 20 absorbs the variation in the gap between the upstream duct 11 and the downstream duct 12 due to the expansion and contraction of the upstream duct 11 and the downstream duct 12, and absorbs vibrations generated in the upstream duct 11 and the downstream duct 12 due to the flow of the fluid. Note that the expansion joint 20 shown in FIG. 1 is exemplified as being cylindrical, but the actual shape is not limited to this, and it is common to have a structure that matches the shape of the duct structure to be connected, and for example, a square tube shape can also be used.

[0011] The expansion joint 20 has a flange 21 connected to the upstream duct 11, a flange 22 connected to the downstream duct 12, and a bellows material 23 provided between the flanges 21 and 22 to airtightly connect these flanges. The pair of flanges 21, 22 and the bellows material 23 are configured in a cylindrical shape to match the cylindrical shapes of the upstream duct 11 and the downstream duct 12. The upstream duct 11 is formed with a duct flange 14, and the flange 21 is formed to correspond to the duct flange 14. The expansion joint 20 and the upstream duct 11 are airtightly connected by connecting the flange 21 and the duct flange 14 (for example, fastening with bolts, etc.). The downstream duct 12 is formed with a duct flange 15, and the flange 22 is formed to correspond to the duct flange 15. The expansion joint 20 and the downstream duct 12 are airtightly connected by connecting the flange 22 and the duct flange 15 (for example, fastening with bolts, etc.). Furthermore, the flanges 21 and 22 can be made of any metal such as stainless steel. The bellows material 23 has a dimension required for the distance between both ends of the expansion joint 20 (the connection surfaces with the upstream duct 11 and the downstream duct 12) to be sufficiently longer than the separation distance between the upstream duct 11 and the downstream duct 12 to be connected. Then, by attaching the expansion joint 20 between the upstream duct 11 and the downstream duct 12 with the bellows material 23 in a slackened state, the thermal expansion and contraction, vibration, etc. of both ducts are absorbed.

[0012] Fig. 2 is a schematic cross-sectional view of the upstream duct 11, downstream duct 12, and expansion joint 20 shown in Fig. 1. A baffle plate 13 formed as a cylindrical body with a tip smaller than the inner diameter of the downstream duct 12 is provided on the downstream side of the upstream duct 11. This baffle plate 13 can be made of a metal such as stainless steel. The expansion joint 20 is disposed so that the presence of the baffle plate 13 prevents it from being directly exposed to the fluid passing through the upstream duct 11 and flowing in the direction of arrow A.

[0013] The expansion joint 20 has a bellows material 23 disposed between the flanges 21 and 22 at the outermost radial position to prevent outflow of the fluid flowing through the upstream duct 11 and the downstream duct 12. The bellows material 23 is constructed by stacking four layered members, namely, a first bellows member 24, a second bellows member 25, a third bellows member 26, and a fourth bellows member 27, in that order from the outer radial position. The bellows material 23 is constructed so as to have flexibility to expand and contract along the outflow direction of the fluid indicated by the arrow A and along a direction intersecting the outflow direction. The bellows material 23 constitutes an expandable portion.

[0014] The first bellows member 24, the second bellows member 25, the third bellows member 26, and the fourth bellows member 27 constituting the bellows material 23 may include any layer such as a sealing layer for preventing the outflow of fluid, a reinforcing layer for reinforcing the strength of the bellows material 23, and a protective layer for protecting the bellows material 23 from the surrounding environment such as the outside air, moisture, and ultraviolet rays, and the bellows material 23 may be formed by combining such any layer in any suitable order. The bellows material 23 is not limited to a four-layer structure, and may be, for example, a structure of one to three layers, or a structure of five or more layers. The first bellows member 24, the second bellows member 25, the third bellows member 26, and the fourth bellows member 27 may be formed by appropriately adopting any known material, such as PTFE (polytetrafluoroethylene), inorganic fiber cloth such as glass cloth, metal fiber cloth, and film-like resin.

[0015] The expansion joint 20 also has a heat insulating section 30 on the radially inner side of the bellows material 23. The heat insulating section 30 insulates the heat of the fluid flowing through the expansion joint 20 and prevents the heat of the fluid from being directly transmitted to the bellows material 23 provided on the radially outer side. The heat insulating section 30 is configured by stacking five layers of heat insulating members, namely, a first heat insulating member 31, a second heat insulating member 32, a third heat insulating member 33, a fourth heat insulating member 34, and a fifth heat insulating member 35, in order from the radially outer side. The first heat insulating member 31, the second heat insulating member 32, the third heat insulating member 33, the fourth heat insulating member 34, and the fifth heat insulating member 35 constituting the heat insulating section 30 may include any layer as a heat insulating layer for satisfying conditions such as heat insulating performance, and the heat insulating section 30 may be formed by combining such any layer in any suitable order. The heat insulating section 30 is not limited to a configuration in which five layers of members are stacked, and may be configured, for example, by 1 to 4 layers of members, or by 6 or more layers of members. The first insulating member 31, the second insulating member 32, the third insulating member 33, the fourth insulating member 34, and the fifth insulating member 35 constituting the insulating section 30 can be formed by appropriately adopting any known material. The first insulating member 31, the second insulating member 32, the third insulating member 33, the fourth insulating member 34, and the fifth insulating member 35 may be formed, for example, by wrapping inorganic fiber felt such as glass felt, alumina felt, or alumina felt with inorganic fiber cloth such as glass cloth, ceramic cloth, or alumina cloth, and optionally wrapping this with a net (mesh, etc.) woven with stainless steel copper wire, Inconel copper wire, etc., or alternatively, by wrapping with organic fiber or organic film such as PTFE, etc.

[0016] A protective tube 37 made of stainless steel is wound around the radial outside of the first insulating member 31 of the expansion joint 20, and an FBG sensor 41 is inserted inside the protective tube 37. A protective tube 37 is wound around the radial outside of the second insulating member 32, on the side closer to the downstream duct 12 than the FBG sensor 41, and an FBG sensor 40 is inserted inside the protective tube 37. A protective tube 37 is wound around the radial outside of the second insulating member 32, on the side closer to the upstream duct 11 than the FBG sensor 41, and an FBG sensor 42 is inserted inside the protective tube 37. That is, the FBG sensors 40, 41, and 42 are disposed on the radial outside of the insulating section 30 and on the radial inside of the bellows material 23. The FBG sensors 40, 41, and 42 are temperature sensors configured by forming a plurality of diffraction gratings in the core portion of an optical fiber by laser processing.

[0017] The protective tube 37 and the FBG sensors 40, 41, 42 are drawn out from the joint between the flange 21 and the bellows material 23 to the outside of the expansion joint 20. The FBG sensors 40, 41, 42 constitute optical fiber temperature sensors, and the protective tube 37 constitutes a tubular protective member.

[0018] 3 is a cross-sectional view taken along a radial direction of the protective tube 37 and the FBG sensors 40, 41, 42 according to the embodiment 1. That is, the FBG sensors 40, 41, 42 are housed in the protective tube 37 made of stainless steel and are wound around the radial outside of the thermal insulation section 30 shown in FIG.

[0019] FIG. 4 is a schematic diagram of the expansion joint 20 and the FBG sensors 40, 41, 42 according to the first embodiment. For ease of explanation, FIG. 4 omits the illustration of some of the configuration of the expansion joint 20, such as the flanges 21, 22, the bellows material 23, and the protective tube 37. The FBG sensor 40, the FBG sensor 41, and the FBG sensor 42 are provided in this order from the downstream side with respect to the flow direction of the fluid indicated by the arrow A. The FBG sensors 40, 41, 42 are wound in parallel to each other with intervals between them along the circumferential direction on the radially outer side of the thermal insulation section 30 of the expansion joint 20. That is, the FBG sensors 40, 41, 42 are wound in parallel to each other with intervals between them along the circumferential direction on the radially inner side of the bellows material 23 (see FIG. 2).

[0020] The FBG sensors 40, 41, and 42 are optical fibers having a cladding portion whose surface is covered with polyimide resin and a core portion disposed inside the cladding portion, and are optical fiber temperature sensors having a plurality of diffraction gratings 43 (refractive index modulation) formed in the core portion by laser processing at predetermined intervals in the extending direction of the optical fiber. Note that the diffraction gratings 43 are also provided in the portions of the FBG sensors 40, 41, and 42 that are hidden by the expansion joint 20 and depicted by dashed lines in FIG. 4. That is, each of the FBG sensors 40, 41, and 42 has a plurality of diffraction gratings 43 on one optical fiber. Note that the diffraction gratings 43 constitute a temperature measuring unit.

[0021] The FBG sensors 40, 41, and 42 are connected to an interrogator 44 provided outside the expansion joint 20. The interrogator 44 has a light source device that makes light incident on the FBG sensors 40, 41, and 42, and a light wavelength measurement device that measures and analyzes the wavelength of the light reflected from each diffraction grating 43, and is disposed in an appropriate weatherproof case.

[0022] Next, the operation of the expansion joint 20 according to the present embodiment 1 will be described. The thermal power generation facility of the present embodiment 1 has a duct structure 1 provided with the expansion joint 20 shown in Fig. 1. During operation of this thermal power generation facility, an interrogator 44 shown in Fig. 4 causes light to be incident on the FBG sensors 40, 41, and 42, and measures and analyzes the wavelengths of the light reflected from each diffraction grating 43.

[0023] During operation of the duct structure 1, if damage occurs to a part of the heat insulating part 30 of the expansion joint 20 shown in FIG. 2 due to aging, abnormal operation, interference of foreign matter in the fluid, or the like, the heat insulating performance of blocking the heat of the fluid flowing inside is reduced. Therefore, the temperature of the heat insulating part 30, the bellows material 23, and the surroundings thereof on the radially outer side of the part where the heat insulating performance of the heat insulating part 30 has been reduced rises more than before the heat insulating performance was reduced. This causes the temperature of the diffraction grating 43 (see FIG. 4) disposed near the part where the heat insulating performance of the heat insulating part 30 has been reduced to rise. The temperature rise of the diffraction grating 43 causes the wavelength of the reflected light from the diffraction grating 43 to change. The interrogator 44 measures the wavelength of this reflected light, compares the change in wavelength with the wavelength before the change, and analyzes it, thereby making it possible to detect which of the diffraction gratings 43 provided in the FBG sensors 40, 41, and 42 has experienced a temperature change. Then, it is possible to identify that the heat insulating part 30 has deteriorated near the diffraction grating 43 where the temperature change occurred. That is, it is possible to identify the location of the expansion joint 20 where deterioration of the heat insulating section 30 has occurred.

[0024] In addition, damage may occur to a part of the bellows material 23 of the expansion joint 20 shown in FIG. 2 due to heat, external force, or the like, and the airtightness of the bellows material 23 may be impaired. In this case, the internal fluid or external air flows inside and outside the bellows material 23 at the location where the damage occurred, and the temperature of the heat insulating section 30 located radially inside the location where the damage occurred and its surroundings may rise or fall compared to before the damage occurred. This causes the temperature of the diffraction grating 43 (see FIG. 4) disposed near the location where the damage occurred to rise or fall. The rise or fall in temperature of the diffraction grating 43 changes the wavelength of the reflected light from the diffraction grating 43. The interrogator 44 compares the change in the wavelength of the reflected light with the wavelength before the change and analyzes it, thereby making it possible to detect which of the diffraction gratings 43 of the FBG sensors 40, 41, and 42 has experienced the temperature change. Then, it is possible to identify that the damage to the bellows material 23 has occurred near the diffraction grating 43 where the temperature change occurred. In other words, it is possible to identify the location of the expansion joint 20 where the damage to the bellows material 23 has occurred.

[0025] In the first embodiment, the FBG sensors 40, 41, and 42 are provided with diffraction gratings 43 having a temperature change detection function at multiple locations in each optical fiber. Therefore, unlike a conventional expansion joint in which a conductor is wired to each of multiple temperature fuses provided in the heat insulating section to detect a temperature change in the heat insulating section, the temperature can be detected by the diffraction gratings 43 provided at multiple locations in each of the FBG sensors 40, 41, and 42, and since there is no need to wire each of the diffraction gratings 43, it is possible to detect a deterioration in the heat insulating function of the heat insulating section 30 and damage to the bellows material 23 over a wider range while reducing the installation space for the temperature detection means.

[0026] In the first embodiment, the FBG sensors 40, 41, 42 are disposed radially outside the heat insulating section 30 and radially inside the bellows material 23. That is, the FBG sensors 40, 41, 42 are disposed between the heat insulating section 30 and the bellows material 23. The positions of the FBG sensors 40, 41, 42 are suitable for detecting a decrease in the heat insulating function of the heat insulating section 30, and are also suitable for detecting the effect of heat on the bellows material 23 due to a decrease in the heat insulating function of the heat insulating section 30.

[0027] 3, the FBG sensors 40, 41, 42 are inserted into the protective tube 37 and are housed and protected in the protective tube 37. By being housed in the protective tube 37, the FBG sensors 40, 41, 42 are protected from friction and pressure with the bellows material 23 and the thermal insulation section 30 caused by the expansion and contraction of the expansion joint 20, and the possibility of failure such as disconnection can be reduced.

[0028] In the first embodiment, the protective tube 37 housing the FBG sensors 40, 41, 42 is made of stainless steel, which has a higher thermal conductivity than the polyimide resin that covers the surface of the cladding. Therefore, compared to a case where the FBG sensors 40, 41, 42 are not housed in the protective tube 37, there is an advantage that a temperature change occurring at a certain point of the expansion joint 20 is more easily transmitted to the diffraction grating 43 located at a position away from the point where the temperature change occurs, and each diffraction grating 43 can more easily detect temperature changes over a wider range.

[0029] In addition, in the first embodiment, when winding the FBG sensors 40, 41, 42 around the thermal insulation section 30 of the expansion joint 20 in assembling the expansion joint 20 shown in FIG. 2, the protective tube 37 is first wound around the thermal insulation section 30, and then the FBG sensors 40, 41, 42 are inserted into the protective tube 37. This allows the FBG sensors 40, 41, 42 to be easily wound around the thermal insulation section 30. Furthermore, when replacing the FBG sensors 40, 41, 42 due to reasons such as the occurrence of a failure of the FBG sensors 40, 41, 42 during operation of the duct structure 1, the FBG sensors 40, 41, 42 to be replaced are removed from the protective tube 37 while the protective tube 37 is left in place, and new FBG sensors 40, 41, 42 are inserted into the protective tube 37. This makes it possible to easily replace the FBG sensors 40, 41, 42, without the need to dismantle the bellows material 23 and the thermal insulation section 30 of the expansion joint 20, as compared to when the protective tube 37 is not provided.

[0030] In this way, the expansion joint 20 according to the first embodiment is an expansion joint 20 that connects between the upstream duct 11 and the downstream duct 12 through which a fluid flows and through which a fluid flows, and is equipped with a bellows material 23 that is provided between the upstream duct 11 and the downstream duct 12 and has elasticity to prevent the outflow of the fluid, a thermal insulation section 30 that is provided inside the bellows material 23 to insulate the heat of the fluid, and FBG sensors 40, 41, 42 provided outside the thermal insulation section 30, so that a deterioration in the thermal insulation function can be detected over a wide range of the thermal insulation section 30.

[0031] Furthermore, since the FBG sensors 40, 41, 42 each have multiple diffraction gratings 43, each of the FBG sensors 40, 41, 42 can detect a decrease in the insulating function at multiple locations, making it possible to detect a decrease in the insulating function over a wider range in the insulating section 30 while reducing the number of FBG sensors 40, 41, 42 installed.

[0032] In addition, since the FBG sensors 40, 41, and 42 are housed in the protective tube 37, this has the advantage of reducing the possibility of failure such as disconnection of the FBG sensors 40, 41, and 42, making it easier for each diffraction grating 43 to detect temperature changes over a wider range, and allowing the FBG sensors 40, 41, and 42 to be easily installed and replaced.

[0033] Furthermore, since the FBG sensors 40, 41, and 42 are provided between the bellows material 23 and the heat insulating section 30, any deterioration in the heat insulating function of the heat insulating section 30 can be effectively detected.

[0034] Furthermore, since the three FBG sensors 40, 41, and 42 are provided along the circumferential direction of the bellows material 23, the temperatures of a plurality of locations in the heat insulating section 30 can be detected with a simple configuration.

[0035] In the first embodiment, stainless steel is used as the material for protective tube 37, but copper may be used as the material for protective tube 37. This increases the thermal conductivity of protective tube 37 compared to the case where stainless steel is used as the material for protective tube 37, making it easier for each diffraction grating 43 to detect temperature changes over a wider range. In addition, the material for protective tube 37 is not limited to these, and carbon steel, alloy steel, aluminum alloy, etc. may be used as appropriate.

[0036] In the first embodiment, the FBG sensors 40 , 41 , and 42 are housed in the protective tube 37 , but if the protective tube 37 is not necessary, the FBG sensors 40 , 41 , and 42 may be attached directly to the thermal insulation section 30 .

[0037] In the first embodiment, three FBG sensors 40, 41, and 42 are provided, but at least one FBG sensor may be provided, and four or more FBG sensors may be provided. Furthermore, in the FBG sensors 40, 41, and 42, a plurality of diffraction gratings 43 are configured on one optical fiber, but at least one diffraction grating 43 may be configured.

[0038] Embodiment 2 Next, an expansion joint according to a second embodiment of the present invention will be described. In the following embodiments, the same reference characters as those in Fig. 1 to Fig. 4 denote the same or similar components, and detailed descriptions thereof will be omitted. The expansion joint according to the second embodiment differs from the first embodiment in that the FBG sensor is arranged in a spiral shape. 5 is a schematic diagram of an FBG sensor 40 provided in an expansion joint 20 according to the second embodiment. For ease of explanation, FIG. 5 omits the illustration of some components of the expansion joint 20, such as the flanges 21 and 22, the bellows material 23, and the protective tube 37. The FBG sensor 40 is disposed on the radially outer side of the thermal insulation section 30 of the expansion joint 20, wound three times in a clockwise spiral shape as viewed from the downstream side in the flow direction of the fluid indicated by the arrow A. That is, the FBG sensor 40 is disposed on the radially inner side of the bellows material 23 (see FIG. 2), wound three times in a spiral shape along the circumferential direction.

[0039] The FBG sensor 40 is provided with a plurality of diffraction gratings 43 formed in the core portion by laser processing at predetermined intervals in the extending direction of the optical fiber. As a result, a plurality of diffraction gratings 43 are arranged in both the fluid flow direction indicated by the arrow A and the circumferential direction of the heat insulating portion 30 of the expansion joint 20. Note that a diffraction grating 43 is also arranged in the part of the FBG sensor 40 hidden by the expansion joint 20 and indicated by the dashed line in Fig. 5. The other configurations are the same as those of the first embodiment.

[0040] In the second embodiment, one FBG sensor 40 is wound spirally around the insulating section 30 multiple times, so that the diffraction grating 43 can be arranged over the entire insulating section 30. This allows the number of FBG sensors to be reduced compared to the first embodiment, which has the advantage of reducing the number of parts and the space required for the FBG sensor 40 to be pulled out from the expansion joint 20.

[0041] In this way, the FBG sensor 40 of the expansion joint 20 according to the second embodiment is wound three times around the circumferential direction of the bellows material 23, so that a single FBG sensor 40 can be used to provide a diffraction grating 43 over the entire insulating section 30.

[0042] In the second embodiment, the FBG sensor 40 is wound three times in a clockwise spiral as viewed from the direction of fluid flow indicated by the arrow A, but it may be wound counterclockwise as viewed from the direction of fluid flow, or the number of turns of the FBG sensor 40 may be any other number. In addition to the FBG sensor 40, at least one other FBG sensor may be arranged in a spiral shape.

[0043] Embodiment 3 Next, a description will be given of an expansion joint according to a third embodiment of the present invention. The expansion joint according to the third embodiment differs from the first embodiment in that the FBG sensor is disposed in a serpentine manner. FIG. 6 is a schematic diagram of an FBG sensor 40 provided in an expansion joint 20 according to the third embodiment. For convenience of explanation, FIG. 6 omits the illustration of some of the configurations of the expansion joint 20, such as the flanges 21 and 22, the bellows material 23, and the protective tube 37. The FBG sensor 40 is provided along the circumferential direction on the radially outer side of the thermal insulation part 30 of the expansion joint 20. The FBG sensor 40 has curved parts 45 that protrude alternately in the direction along the fluid flow direction indicated by the arrow A. The FBG sensor 40 is provided along the circumferential direction on the radially inner side of the bellows material 23 (see FIG. 2), and is disposed while meandering in the direction indicated by the arrow A. The FBG sensor 40 is provided with a plurality of diffraction gratings 43 formed in the core part by laser processing at predetermined intervals in the direction in which the optical fiber extends. As a result, a plurality of diffraction gratings 43 are provided in both the fluid flow direction indicated by the arrow A and the circumferential direction of the thermal insulation part 30 of the expansion joint 20. 6, a diffraction grating 43 is also provided in the portion of the FBG sensor 40 which is hidden by the expansion joint 20 and is indicated by a dashed line. The other configurations are the same as those of the first embodiment.

[0044] In the third embodiment, a single FBG sensor 40 is arranged in a serpentine manner along the circumferential direction of the bellows material 23, so that the diffraction grating 43 can be arranged over the entire insulating section 30. This allows the number of FBG sensors to be reduced compared to the first embodiment, which has the advantage of reducing the number of parts and the space required for the FBG sensor to be pulled out from the expansion joint 20.

[0045] In this way, the FBG sensor 40 of the expansion joint 20 according to the third embodiment is arranged in a serpentine shape at least partially along the circumferential direction of the insulating section 30, so that a single FBG sensor 40 can provide a diffraction grating 43 over the entire insulating section 30.

[0046] In the third embodiment, one FBG sensor 40 is arranged in a meandering manner so as to have curved portions 45 that alternately protrude along the flow direction of the fluid indicated by the arrow A, but such an arrangement of the FBG sensor 40 is merely an example, and the FBG sensor 40 may be arranged in other forms. For example, the FBG sensor 40 may be arranged to have bent portions instead of the curved portions 45, the FBG sensors 40 may cross at the curved portions 45, or two or more FBG sensors arranged in a meandering manner may be arranged.

[0047] Embodiment 4 Next, a description will be given of an expansion joint according to a fourth embodiment of the present invention. In the expansion joint according to the fourth embodiment, the position of the FBG sensor is changed from that in the first embodiment. 7 is an enlarged schematic cross-sectional view showing one half in the radial direction of the cross sections of the upstream duct 11, the downstream duct 12, and the expansion joint 20 according to embodiment 4. An example of the arrangement of the FBG sensor will be described below with reference to FIG.

[0048] As a first arrangement example, the FBG sensors 40a, 41a, and 42a are arranged on the radially inner side of the heat insulating section 30. As a second arrangement example, the FBG sensors are arranged between the layers constituting the heat insulating section 30, for example, the FBG sensors 40b, 41b, and 42b are arranged between the third heat insulating member 33 and the fourth heat insulating member 34. As a third arrangement example, the FBG sensors 40c, 41c, and 42c are arranged on the radially outer side of the bellows material 23. Note that the FBG sensors 40a, 41a, and 42a, the FBG sensors 40b, 41b, and 42b, and the FBG sensors 40c, 41c, and 42c are arranged correspondingly on the other half of the radial direction not shown in FIG. 7. In addition, as a fourth arrangement example, the FBG sensor 40d is arranged at a position separated from the outer diameter part of the bellows material 23 using a support member not shown. The other configurations are the same as those of the first embodiment.

[0049] When the FBG sensors 40a, 41a, and 42a are disposed radially inside the heat insulating section 30, which is the space through which the fluid flows, as in the first arrangement example, the temperature change of the fluid can be directly detected. When the FBG sensors 40b, 41b, and 42b are disposed inside the heat insulating section 30, as in the second arrangement example, the temperature change due to the deterioration of the heat insulating function at the radial inside of the heat insulating section 30 can be easily detected. When the FBG sensors 40c, 41c, and 42c are disposed radially outside the bellows material 23, as in the third arrangement example, the temperature change due to the influence of heat applied to the bellows material 23 from outside the expansion joint 20 can be easily detected, and after the expansion joint 20 is disposed in the upstream duct 11 and the downstream duct 12, the FBG sensors 40c, 41c, and 42c can be easily attached to the expansion joint 20. When the FBG sensor 40d is disposed at a position separated from the outer diameter portion of the bellows material 23 as in the fourth arrangement example, the temperature state around the expansion joint 20 can be detected.

[0050] In this way, the expansion section of the expansion joint 20 according to the fourth embodiment has the bellows material 23 that prevents the outflow of fluid, and the insulation section 30 that is provided inside the bellows material 23 and insulates against the heat of the fluid. Since the FBG sensor can be provided at any position, it is possible to detect temperature changes at any point in and around the expansion joint 20.

[0051] The FBG sensor arrangements in the first to fourth arrangement examples of the fourth embodiment and the FBG sensor arrangement in the first embodiment can be used in appropriate combination as necessary.

[0052] Embodiment 5. Next, a description will be given of an expansion joint according to a fifth embodiment of the present invention. In the expansion joint according to the fifth embodiment, the material of the protective pipe is changed from that in the first embodiment. In the fifth embodiment, the protective tube 37 shown in Fig. 3 is made of polytetrafluoroethylene (PTFE) instead of the stainless steel of the first embodiment. The other configurations are the same as those of the first embodiment.

[0053] PTFE has a smaller coefficient of friction than general metals, and therefore, by using PTFE for the protective tube 37, the FBG sensors 40, 41, 42 can be easily inserted or removed, and the possibility of damaging the FBG sensors 40, 41, 42 during the insertion or removal is reduced.

[0054] In addition, PTFE has a lower thermal conductivity than general metals, which has the advantage that a temperature change occurring in the heat insulating part 30 or the bellows material 23 is unlikely to be transmitted to a distant location via the protective tube 37, making it easier for the FBG sensors 40, 41, 42 to clearly identify the position on the heat insulating part 30 or the bellows material 23 where the temperature change has occurred.

[0055] In this way, the FBG sensors 40, 41, 42 of the expansion joint 20 according to the fifth embodiment are housed in the protective tube 37 made of PTFE, which has the advantage that the FBG sensors 40, 41, 42 can be easily inserted or removed.

[0056] The non-metallic material of the protective tube 37 is not limited to PTFE, and a resin other than PTFE may be used. For example, a resin material such as polyether ether ketone, polyphenylene sulfide, or heat-resistant rubber such as heat-resistant silicone rubber may be appropriately used. In addition, by using the same material for the protective tube 37 and the bellows material 23, the thermal conductivity of the protective tube 37 and the bellows material 23 become the same, so that the possibility that the bellows material 23 will be excessively affected by the heat conducted to the protective tube 37 can be reduced.

[0057] In the first to fifth embodiments, the number of FBG sensors, the number of diffraction gratings of the FBG sensors, and the positions of the diffraction gratings may be determined according to the required temperature detection positions in the expansion joint 20. For example, the FBG sensors and diffraction gratings may be arranged so as to be able to detect temperature changes throughout the heat insulating section 30 and the bellows material 23, or the FBG sensors and diffraction gratings may be arranged so as to be able to detect temperature changes at certain locations in the heat insulating section 30 or the bellows material 23. The FBG sensors and diffraction gratings may also be arranged on the flanges 21 and 22 of the expansion joint 20 or on the frame portion.

[0058] In addition, the FBG sensors 40, 41, 42 in the first to fifth embodiments may be attached in any manner, such as by sewing the protective tube 37 to the target member such as the insulating section 30, or by binding the protective tube 37 to the target member such as the insulating section 30 with a wire.

[0059] The components included in the first to fifth embodiments of the present invention and the components included in the variations thereof can be used in any suitable combination.

[0060] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0061] Various aspects of the present disclosure are summarized below as appendices.

[0062] (Appendix 1) An expansion joint that connects a first duct and a second duct through which a fluid flows, and through which the fluid flows, an outflow prevention part that is provided between the first duct and the second duct and has elasticity to prevent the outflow of the fluid; a heat insulating portion provided inside the outflow prevention portion and insulating the heat of the fluid; the heat insulating portion, and an optical fiber temperature sensor provided at least one of an outer side of the heat insulating portion and an inner side of the heat insulating portion; An expansion joint comprising: (Appendix 2) 2. The expansion joint according to claim 1, wherein the optical fiber temperature sensor has a plurality of the temperature measurement portions. (Appendix 3) 3. The expansion joint according to claim 1 or 2, wherein the optical fiber temperature sensor is housed in a tubular protective member. (Appendix 4) 4. The expansion joint according to any one of claims 1 to 3, wherein the optical fiber temperature sensor is provided in at least one of the outflow prevention section, the heat insulating section, or between the outflow prevention section and the heat insulating section. (Appendix 5) 5. The expansion joint according to claim 1, wherein a plurality of the optical fiber temperature sensors are provided along a circumferential direction of the outflow prevention portion. (Appendix 6) 6. The expansion joint according to any one of claims 1 to 5, wherein the optical fiber temperature sensor is wound a plurality of times in a circumferential direction of the outflow prevention part. (Appendix 7) 7. The expansion joint according to any one of claims 1 to 6, wherein the optical fiber temperature sensor is provided in such a way that at least a portion of the optical fiber temperature sensor meanders along the circumferential direction of the outflow prevention part. [Explanation of symbols]

[0063] 11 upstream duct (first duct), 12 downstream duct (second duct), 23 bellows material (flow prevention section), 30 heat insulation section, 37 protective tube (tubular protective member), 40 FBG sensor (optical fiber temperature sensor), 41 FBG sensor (optical fiber temperature sensor), 42 FBG sensor (optical fiber temperature sensor), 43 diffraction grating (temperature measurement section).

Claims

1. An expansion joint that connects a first duct and a second duct through which a fluid flows, and through which the fluid flows, an outflow prevention part that is provided between the first duct and the second duct and has elasticity to prevent the outflow of the fluid; a heat insulating portion provided inside the outflow prevention portion and insulating the heat of the fluid; the heat insulating portion, and an optical fiber temperature sensor provided at least one of an outer side of the heat insulating portion and an inner side of the heat insulating portion; An expansion joint comprising:

2. The expansion joint according to claim 1 , wherein the optical fiber temperature sensor has a plurality of temperature measurement portions.

3. 3. The expansion joint according to claim 1 or 2, wherein the optical fiber temperature sensor is housed in a tubular protective member.

4. The expansion joint according to claim 1 or 2, wherein the optical fiber temperature sensor is provided in at least one of the outflow prevention section, the heat insulating section, or a section between the outflow prevention section and the heat insulating section.

5. The expansion joint according to claim 1 or 2, wherein a plurality of the optical fiber temperature sensors are provided along a circumferential direction of the outflow prevention portion.

6. The expansion joint according to claim 1 or 2, wherein the optical fiber temperature sensor is wound a plurality of times in a circumferential direction of the outflow prevention portion.

7. The expansion joint according to claim 1 or 2, wherein the optical fiber temperature sensor is provided along a circumferential direction of the outflow prevention portion, and at least a portion of the optical fiber temperature sensor is provided in a serpentine manner.

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