Piping for low-temperature fluid

Abstract

This piping for a low-temperature fluid comprises a piping body, an end seal, a heat insulating layer, and a gas barrier. The piping body is metallic piping through which a low-temperature fluid flows. The end seal is protruding outward in the radial direction of the piping body from the circumferential surface of the piping body. The heat insulating layer covers the piping body and includes a layer end portion which faces the end seal. The gas barrier covers the heat insulating layer and includes a welded portion which is welded to the end seal.

Description

Piping for cryogenic fluids

[0001] The present disclosure relates to cryogenic fluid piping for transporting cryogenic fluid.

[0002] Pipes carrying cryogenic fluids are insulated. For example, in pipes carrying liquefied hydrogen, insulation is wrapped around the pipe, and the insulation is then covered with a gas barrier. The insulation reduces heat input to the pipe. The gas barrier prevents outside air from entering the insulation, preventing the generation of liquefied air.

[0003] At the terminal end or intermediate joint of the pipe, the insulation layer is removed to expose the pipe. End seals are attached to the end of the insulation in the exposed portion of the pipe, as in Patent Document 1, for example. The end seals prevent outside air from entering the insulation from the end. The sealing performance of the end seals must be maintained for a long period of time. However, the sealing performance of the end seals can be reduced due to breakage or gaps caused by differences in thermal contraction between the end seal and the mating member that comes into contact with the end seal.

[0004] Japanese Utility Model Application Publication No. 54-63259

[0005] An object of the present disclosure is to provide a cryogenic fluid piping that can maintain the sealing performance of the end seal.

[0006] A low-temperature fluid pipe according to one aspect of the present disclosure comprises a metal pipe body through which a low-temperature fluid passes, an end seal protruding radially outward from the outer peripheral surface of the pipe body, an insulating layer surrounding the pipe body and including a layer end portion facing the end seal, and a gas barrier surrounding the insulating layer and including a welding portion welded to the end seal.

[0007] According to the present disclosure, it is possible to provide a cryogenic fluid pipe capable of maintaining the sealing performance of the end seal.

[0008] FIG. 1 is a cross-sectional view showing a first embodiment of cryogenic fluid piping according to the present disclosure. FIG. 2 is a perspective view of the cryogenic fluid piping of FIG. 1. FIG. 3 is a cross-sectional view of a welded portion between an end seal and a gas barrier, with an enlarged cross-sectional view of the welded portion added. FIG. 4 is a perspective view showing an example of a gas barrier construction process. FIG. 5A is a perspective view showing another example of a gas barrier construction process. FIG. 5B is a cross-sectional view taken along line VB-VB of FIG. 5A. FIG. 6 is a cross-sectional view showing a second embodiment of cryogenic fluid piping according to the present disclosure. FIG. 7 is a cross-sectional view showing a third embodiment of cryogenic fluid piping according to the present disclosure. FIG. 8 is a cross-sectional view showing a fourth embodiment of cryogenic fluid piping according to the present disclosure.

[0009] Hereinafter, with reference to the drawings, an embodiment of a cryogenic fluid pipe according to the present disclosure will be described in detail. The cryogenic fluid pipe according to the present disclosure is a pipe through which a cryogenic fluid is passed for purposes such as transportation. The cryogenic fluid includes not only cryogenic fluids such as liquefied natural gas (LNG) but also cryogenic fluids having even lower liquefaction temperatures. A cryogenic fluid is a fluid in a temperature range that liquefies the surrounding air or a fluid in a temperature range that liquefies oxygen or nitrogen contained in the surrounding air. Examples of the cryogenic fluid include liquefied hydrogen and liquefied helium. The cryogenic fluid may be hydrogen gas or helium gas in an extremely low temperature range.

[0010] [First embodiment] Fig. 1 is a cross-sectional view showing a cryogenic fluid pipe 1 according to a first embodiment of the present disclosure, and Fig. 2 is a perspective view of the cryogenic fluid pipe 1 of Fig. 1. The cryogenic fluid pipe 1 includes a pipe body 2, a heat insulating layer 3, end seals 4, and a gas barrier 5. The gas barrier 5 includes a welded portion 6. The pipe body 2 is covered with the heat insulating layer 3. The heat insulating layer 3 is covered with the gas barrier 5.

[0011] 1 and 2 show the end portion of the cryogenic fluid pipe 1 where an intermediate connection or termination is performed. In this end portion, the pipe body 2 is exposed in the pipe axis direction AX by a predetermined length beyond the insulating layer 3. In addition, in this end portion, a predetermined region in the pipe axis direction AX, including the layer end portion 31, which is the edge of the insulating layer 3, is exposed and not covered by the gas barrier 5. The portion of the insulating layer 3 that is not covered by the gas barrier 5 is covered by an end seal 4. The exposed portions of the pipe body 2 and the end seal 4 are covered by an insulating cover 7. The insulating cover 7 is a member that insulates the intermediate connection portion, the terminal end, etc. of the cryogenic fluid pipe 1. The insulating cover 7 is detachably attached to the intermediate connection portion or the terminal end.

[0012] The pipe body 2 is a metallic cylindrical body through which a cryogenic fluid passes. The pipe body 2 has a sealed cylindrical passage 2H inside. The pipe body 2 can be a single pipe made of, for example, stainless steel or aluminum. A cryogenic fluid passes through the passage 2H of the pipe body 2 for purposes such as transporting, storing, and keeping the cryogenic fluid cold. Vacuum insulated multi-layer pipes are sometimes used for transporting cryogenic fluids, particularly cryogenic fluids such as liquefied hydrogen. As described later with reference to FIG. 7 , this disclosure does not exclude the use of vacuum insulated multi-layer pipes as a pipe through which a cryogenic fluid passes. However, using a pipe body 2 made of a metallic single pipe eliminates the need for establishing and releasing a vacuum environment when forming and dismantling intermediate connections and terminals of the cryogenic fluid pipe 1, thereby reducing the amount of construction work. Furthermore, using a pipe body 2 made of a metallic single pipe can reduce the weight of the cryogenic fluid pipe 1 compared to, for example, a vacuum insulated multi-layer pipe.

[0013] The insulating layer 3 surrounds the pipe body 2 and insulates the pipe body 2. There are no particular limitations on the insulating material used for the insulating layer 3, and materials commonly used as insulating materials can be used. For example, the insulating material can be a petroleum-based synthetic rubber material such as ethylene propylene rubber, an organic polymer material such as polyurethane foam or polyethylene foam, a fibrous material such as glass fiber or glass wool, or an inorganic material such as perlite, foam glass, or aerogel. The insulating layer 3 can be formed of multiple types of insulating materials or a single insulating material, and can also include a material without insulating function. For example, the insulating layer 3 can be formed around the pipe body 2 by wrapping a sheet-like insulating material around the outer periphery of the pipe body 2.

[0014] The end seals 4 cover the exposed portions near the ends of the heat insulating layer 3. The end seals 4 can be made of, for example, stainless steel or aluminum. It is desirable to make the pipe body 2 and the end seals 4 from the same metal material. In this case, the thermal expansion coefficients of both are the same, and internal stresses in the pipe body 2 and the end seals 4 that occur due to temperature changes can be suppressed.

[0015] The end seal 4 includes a plate portion 41 and a tubular portion 42. The plate portion 41 includes a hole portion 4H through which the piping main body 2 passes, and has a disk shape extending radially outward from the piping main body 2. In other words, the plate portion 41 protrudes radially outward from the outer peripheral surface of the piping main body 2 when attached to the piping main body 2. The layer end portion 31 of the thermal insulation layer 3 has a cross section that faces parallel to the plate portion 41. The plate portion 41 abuts the layer end portion 31. In this embodiment, the plate portion 41 is attached to the outer peripheral surface of the piping main body 2 by welding. In other words, with the piping main body 2 inserted through the hole portion 4H, the periphery of the hole portion 4H of the plate portion 41 is welded to the piping main body 2. The plate portion 41 may be formed integrally with the piping main body 2 by machining or the like.

[0016] The cylindrical portion 42 has a cylindrical shape that extends in the pipe axis direction AX of the pipe main body 2 and surrounds the pipe main body 2. The cylindrical portion 42 covers a portion of the heat insulating layer 3 from the layer end portion 31 by a predetermined length in the pipe axis direction AX. The cylindrical portion 42 includes one end 421 located on the plate portion 41 side and the other end 422 located on the edge 5E side of the gas barrier 5. In this embodiment, the inner circumferential surface of the one end 421 is welded to the outer circumferential surface of the plate portion 41. The welded portion of the inner circumferential surface of the one end 421 may be the one end region including the one end 421 and the vicinity of the one end 421. Note that the cylindrical portion 42 may be formed integrally with the plate portion 41 by machining or the like. The other end 422 extends beyond the edge 5E of the gas barrier 5 and into the inside of the gas barrier 5 in the direction from the plate portion 41 to the gas barrier 5 in the pipe axis direction AX. The other end region including the other end 422 and the vicinity of the other end 422 overlapping with the gas barrier 5 is welded to the gas barrier 5 .

[0017] The gas barrier 5 surrounds the heat insulating layer 3 and isolates it from the outside air. In other words, the gas barrier 5 covers the outer peripheral surface of the heat insulating layer 3, thereby preventing outside air from entering the heat insulating layer 3. The gas barrier 5 can be made of an air-impermeable metal-resin composite sheet, a resin sheet, a metal sheet, or the like. Specific examples of preferred gas barriers 5 will be described later with reference to FIG. 3.

[0018] The gas barrier 5 includes a welded portion 6 welded to the end seal 4. In the low-temperature fluid piping 1, the insulating layer 3 at the end portion not covered by the gas barrier 5 is covered with the end seal 4 as described above. The welded portion 6 joins the gas barrier 5 and the tubular portion 42 of the end seal 4 together in an airtight manner. The welded portion 6 is a joint where the constituent material of the gas barrier 5 and the constituent material of the end seal 4 come into direct contact and are joined together without using an intermediary such as an adhesive.

[0019] A gap may occur at the contact point between the gas barrier 5 and the end seal 4 due to the difference in thermal expansion coefficients between the two. However, by welding the gas barrier 5 and the end seal 4 to each other at the welded portion 6, airtightness is ensured at the contact point between the gas barrier 5 and the end seal 4 regardless of the difference in thermal expansion coefficients between the two. As a result, the insulating layer 3 is sealed by the outer surface of the piping body 2, the end seal 4, and the gas barrier 5. Therefore, the intrusion of outside air into the insulating layer 3 can be suppressed for a long period of time. When the low-temperature fluid passed through the piping body 2 is liquefied hydrogen, if air intrudes into the insulating layer 3, liquefaction may occur due to the cold from the piping body 2. In this embodiment, the insulating layer 3 is sealed, which suppresses the generation of liquefied air. Furthermore, the mechanical strength can be increased compared to when the gas barrier 5 and the end seal 4 are joined with an adhesive.

[0020] <Details of Gas Barrier and Welded Portion> Figure 3 is a cross-sectional view of the welded portion 6 between the end seal 4 and the gas barrier 5, with an enlarged cross-sectional view of the welded portion 6 added. The gas barrier 5 includes a resin layer in the surface portion that becomes the welded portion 6, and this resin layer is welded to the end seal 4. The gas barrier 5 is made of a flexible film formed by laminating aluminum foil and a resin film. Specifically, the gas barrier 5 includes, for example, an outer resin layer 51, an inner resin layer 52, a first aluminum foil layer 53, a second aluminum foil layer 54, and an adhesive layer 55. Note that the number of resin layers and the number of aluminum foil layers included in the gas barrier 5 are merely examples.

[0021] The outer resin layer 51 is located as the outermost layer of the gas barrier 5 when the gas barrier 5 is attached to the insulating layer 3. The outer side when the gas barrier 5 is attached to the insulating layer 3 refers to the side facing from the insulating layer 3 to the gas barrier layer in the radial direction of the cryogenic fluid pipe 1, and the inner side refers to the opposite side. The outer resin layer 51 functions as a protective layer that protects, for example, the insulating layer 3 from external forces. The outer resin layer 51 can be made of a resin film such as nylon or polyethylene terephthalate. If fire resistance is required for the outer resin layer 51, an engineering plastic may be used for the outer resin layer 51. If heat welding processing is required for the outer resin layer 51, a thermoplastic resin may be used for the outer resin layer 51.

[0022] The inner resin layer 52 is located as the innermost layer of the gas barrier 5 when the gas barrier 5 is attached to the heat insulating layer 3. The inner resin layer 52 is a layer that comes into contact with the tubular portion 42 of the end seal 4, and is a layer that forms the welded portion 6 by thermal welding. A thermoplastic resin film such as polyethylene or polypropylene can be used as the inner resin layer 52. If fire resistance is required for the inner resin layer 52, an engineering plastic may be used as the inner resin layer 52.

[0023] The first aluminum foil layer 53 and the second aluminum foil layer 54 are positioned between the outer resin layer 51 and the inner resin layer 52. The first aluminum foil layer 53 and the second aluminum foil layer 54 function as gas barrier layers that prevent outside air from penetrating the thermal insulation layer 3. In the gas barrier 5, either the first aluminum foil layer 53 or the second aluminum foil layer 54 may be omitted, resulting in a single-layer gas barrier layer. However, to ensure redundancy, a two-layer gas barrier layer, as in this embodiment, or a gas barrier layer with three or more layers is desirable. Metal foils other than aluminum foil may also be used as the gas barrier layer included in the gas barrier 5. Furthermore, a resin film with excellent gas barrier properties may also be used as the gas barrier layer included in the gas barrier 5. Examples of the resin film that can be used include vinyl alcohol-based resin films such as EVOH (ethylene-vinyl alcohol copolymer).

[0024] The adhesive layer 55 is disposed between the outer resin layer 51 and the first aluminum foil layer 53, between the first aluminum foil layer 53 and the second aluminum foil layer 54, and between the second aluminum foil layer 54 and the inner resin layer 52, respectively, to bond these adjacent layers together. The adhesive layer 55 may be an adhesive or a thermoplastic resin film for heat welding. When the latter is used as the adhesive layer 55, the thermoplastic resin film is heated to a temperature above the melting point of the resin material of the thermoplastic resin film during the production of the gas barrier 5, and heat-welded to the adjacent layers. In this embodiment, heat welding is performed by heating at least one of the two joining portions to be joined, melting the joining portions and bringing them into contact with each other. The joining portions are then cooled while still in contact, thereby joining the joining portions together. When bringing the joining portions into contact with each other, pressure may be applied by pressing the joining portions together.

[0025] Constructing the gas barrier 5 from a flexible film laminated with metal foil and resin film, as in this embodiment, offers the following advantages. First, the gas barrier 5 can be joined to the end seal 4 at the welded portion 6 by heat welding. In this embodiment, the gas barrier 5 can be heat-welded to the end seal 4 simply by applying heat equal to or higher than the melting point of the resin constituting the inner resin layer 52. This makes the installation work relatively easy. In addition, because the joining is by welding, the joint between the gas barrier 5 and the end seal 4 is also airtight. Furthermore, because the flexible film laminated with metal foil and resin film is a relatively lightweight material, the weight of the cryogenic fluid piping 1 can be reduced compared to, for example, a vacuum insulated multi-wall pipe.

[0026] The use of the flexible film also contributes to durability and excellent maintainability. When a low-temperature fluid is passed through the pipe body 2, the temperature inside the gas barrier 5 drops, and negative pressure is created due to condensation of the air. In this embodiment, the high airtightness due to the welded portion 6 makes it easier to create negative pressure inside the gas barrier 5. This negative pressure causes stress to act on the gas barrier 5, pulling it radially inward. If the gas barrier 5 is a relatively rigid structure, there is a concern that the gas barrier 5 may be damaged by this stress. However, a gas barrier 5 made of the flexible film can flexibly deform even when stress associated with negative pressure acts on it, and is therefore highly durable.

[0027] Furthermore, if the gas barrier 5 is made of a flexible film, defects such as pinholes and tears that occur in the gas barrier 5 can be easily found. As described above, when a low-temperature fluid is circulated through the piping body 2, the gas barrier 5 is deformed due to the negative pressure. However, if the above-mentioned defect occurs, the airtightness is destroyed and the gas barrier 5 does not deform. In other words, if the gas barrier 5 does not deform due to the negative pressure, it can be assumed that some kind of defect has occurred in the gas barrier 5. Therefore, maintainability can be improved.

[0028] <Formation of a rough surface layer on the end seal> Figure 3 shows an enlarged view of a more preferred embodiment of the welded portion 6. The end seal 4 has a roughened surface layer 43 in the area facing the welded portion 6. The area of ​​the end seal 4 facing the welded portion 6 may be smooth, but by forming a roughened surface layer 43 in the welded portion 6, the bonding strength between the end seal 4 and the gas barrier 5 and the airtightness of the welded portion 6 can be further improved.

[0029] The rough surface layer 43 is formed on the outer peripheral surface of the tubular portion 42 in a region near the other end 422 of the tubular portion 42, and includes a plurality of minute protrusions 44 and recesses 45. The recesses 45 preferably have a wedge-shaped cross section that is wide near the bottom and narrow near the opening. The melted portion 52A of the inner resin layer 52 melted during the thermal welding process enters the recesses 45. Due to the characteristics described above, the engagement between the melted portion 52A and the recesses 45 creates an anchor effect, firmly bonding the rough surface layer 43 and the welded portion 6.

[0030] There are no particular limitations on the means for forming the roughened surface layer 43. For example, the roughened surface layer 43 can be formed by chemical etching using a chemical solution, shot blasting using fine particles, sanding using a roughening tool, or the like. In the case of an end seal 4 made of an iron-based material, the above-mentioned chemical etching is performed by immersing the region near the other end 422 of the cylindrical portion 42 in a phosphate-based chemical solution for a predetermined period of time.

[0031] <Heat transfer path of end seal> The end seal 4 covers the exposed portion of the insulating layer 3 near the layer end 31, which is not exposed from the gas barrier 5. The installation of the end seal 4 suppresses the generation of liquefied air that accompanies the intrusion of outside air into the insulating layer 3. In addition to this effect, the geometric characteristics of the end seal 4 of this embodiment have the advantage of being able to suppress heat transfer from the piping main body 2 to the gas barrier 5, as well as heat input from the gas barrier 5 to the piping main body 2.

[0032] As described above, the end seal 4 covers the exposed portion of the thermal insulation layer 3, and therefore also serves as a component connecting the piping main body 2 and the gas barrier 5. Therefore, the end seal 4 can serve as a heat transfer path between the piping main body 2 and the gas barrier 5. That is, the cold heat of the piping main body 2 during the flow of liquid hydrogen can be transferred to the gas barrier 5 through the end seal 4. In this case, the temperature of the welded portion 6 between the end seal 4 and the gas barrier 5 decreases, which may cause the gas barrier 5 to peel off. Conversely, the gas barrier 5, which is exposed to the outside air, can become a heat source, and heat may be input from the gas barrier 5 to the piping main body 2 through the end seal 4. In this case, boil-off gas of the liquefied hydrogen may be generated within the piping main body 2.

[0033] Referring to FIG. 1 , the end seal 4 includes a disk-shaped plate portion 41 and a cylindrical portion 42 extending in the axial direction AX of the piping body 2. FIG. 1 also shows a heat transfer path HP formed by the end seal 4. Because the end seal 4 includes not only the plate portion 41 but also the cylindrical portion 42, the heat transfer path HP also includes a portion extending in the axial direction AX. In other words, the heat transfer path HP is longer by the length of the cylindrical portion 42 than when the end seal 4 is configured only with a portion corresponding to the plate portion 41. In other words, in the cryogenic fluid piping 1 of the present disclosure, in order to lengthen the heat transfer path HP, the layer end portion 31 of the insulating layer 3 protrudes in the axial direction AX beyond the edge 5E of the gas barrier 5, and the end seal 4 includes a cylindrical portion 42 that covers the protruding portion. Because the cryogenic fluid piping 1 of the present disclosure has a longer heat transfer path HP as described above, cold from the piping body 2 is less likely to be transferred to the gas barrier 5. Therefore, peeling of the gas barrier 5 due to cooling of the welded portion 6 can be suppressed. In addition, heat input from the gas barrier 5 to the pipe body 2 can also be suppressed.

[0034] In this embodiment, the heat transfer path HP is lengthened by providing the cylindrical portion 42 in the end seal 4. Instead of the flat cylindrical portion 42, a cylindrical portion shaped like a bellows or a cylindrical portion with a rectangular cross section and continuous concaves and convexes may be used to lengthen the heat transfer path HP of the low-temperature fluid piping 1.

[0035] <Decompression of the insulation layer> In this embodiment, the insulation layer 3 is covered with the gas barrier 5, the plate portion 41 of the end seal 4 is joined to the piping body 2 by welding, and the other end 422 of the tubular portion 42 is joined to the gas barrier 5 by the welded portion 6. Therefore, the insulation layer 3 is disposed in a space sealed by the outer peripheral surface of the piping body 2, the end seal 4, and the gas barrier 5. In other words, the insulation layer 3 is disposed in a space with a high airtightness. Therefore, the space in which the insulation layer 3 is disposed may be decompressed.

[0036] By reducing the pressure in the space in which the insulating layer 3 is disposed, the insulating effect of the insulating layer 3 can be further enhanced. When the end seals 4 and the gas barrier 5 are joined with an adhesive, drawing a vacuum to reduce the pressure in the space in which the insulating layer is disposed can cause a problem of outgassing from the adhesive. However, in this embodiment, the end seals 4 and the gas barrier 5 are joined by the welded portion 6, so the problem of outgassing does not occur.

[0037] <Gas Barrier Installation Process> Figure 4 is a perspective view showing an example of a gas barrier 5 installation process. The installation process includes steps P1 to P3, which are carried out sequentially. In step P1, the insulating layer 3 is installed on the piping body 2, and the end seal 4 is attached to the layer end 31 of the insulating layer 3. In step P2, a sheet-like gas barrier 5 is prepared. The gas barrier 5 has a size that allows it to circumferentially enclose the exposed insulating layer 3. The gas barrier 5 is wrapped around the insulating layer 3 so that its end region in the pipe axis direction AX overlaps with part of the tubular portion 42 of the end seal 4.

[0038] In process P3, the gas barrier 5 is welded. An overlapping portion is formed where one end 501 and the other end 502 in the circumferential direction of the gas barrier 5 overlap. The overlapping portion is heated to thermally weld the inner resin layers 52 shown in FIG. 3 to each other, i.e., the inner resin layer 52 at the one end 501 to the inner resin layer 52 at the other end 502. This thermal welding forms an axial weld portion 61 extending in the tube axis direction AX in the gas barrier 5. Instead of thermally welding the inner resin layers 52 by butting them together, the inner resin layer 52 at one of the one end 501 and the other end 502 may be thermally welded to the outer resin layer 51 at the other end. That is, the gas barrier 5 may be wrapped around the heat insulating layer 3 so that the one end 501 and the other end 502 overlap in the radial direction, and the overlapping portion at the one end 501 and the other end 502 may be heated to thermally weld them. As described above, the end of the gas barrier 5 in the tube axis direction AX is heat-welded to the end seal 4, forming a circumferentially extending welded portion 6. The formation of the circumferential welded portion 6 and the axial welded portion 61 improves the airtightness of the gas barrier 5.

[0039] In process P3, one end 501 and the other end 502 of the gas barrier 5 may be heat-welded in advance to form a cylindrical shape, and then the cylindrical gas barrier 5 may be placed on the insulating layer 3. When encasing the insulating layer 3 with the gas barrier 5, air may be trapped between the outer peripheral surface of the insulating layer 3 and the inner peripheral surface of the gas barrier 5. To prevent air trapping, in process P3, a step of sucking out air between the insulating layer 3 and the gas barrier 5 may be performed, and then the gas barrier 5 may be heat-welded to make it airtight. In this case, the welding of some of the circumferential welded portions 6 and the axial welded portions 61 may be left incomplete, and after air is sucked out from the unwelded portions, the unwelded portions may be heat-welded to make the gas barrier 5 airtight. When the insulating layer 3 has a long length in the tube axis direction AX, multiple sheet-like gas barriers 5 may be arranged in the tube axis direction AX and connected to each other by heat fusion.

[0040] Figure 5A is a perspective view showing another example of the construction process for the gas barrier 5, and Figure 5B is a cross-sectional view taken along line VB-VB in Figure 5A. Here, an example is shown that is advantageous when the pipe diameter of the piping body 2 is large. A sheet-like first gas barrier 5A and second gas barrier 5B are used as the gas barrier 5 that covers the heat insulating layer 3. The first gas barrier 5A covers one half of the circumferential surface of the heat insulating layer 3, and the second gas barrier 5B covers the other half.

[0041] In the example shown in FIG. 5A , two circumferential ends 503 of the first gas barrier 5A and two circumferential ends 504 of the second gas barrier 5B are butted together and thermally welded to form a pair of axial welds 62. The axial welds 62 may be left protruding radially outward, or may be folded along the circumferential surface of the gas barrier 5 and thermally welded or taped. The insulating layer 3 may be wrapped with three or more gas barrier sheets, and adjacent gas barrier sheets may be thermally welded to each other. If the pipe diameter of the piping body 2 is large, the outer diameter of the insulating layer 3 also becomes large. In this case, wrapping the insulating layer 3 with a single gas barrier sheet may be difficult. Wrapping the insulating layer 3 with multiple gas barrier sheets can facilitate the installation of the gas barrier 5.

[0042] 6 is a cross-sectional view showing a cryogenic fluid piping 1A according to a second embodiment. The cryogenic fluid piping 1A includes a piping body 2, a heat insulating layer 3, an end seal 40, and a gas barrier 5. The second embodiment differs from the first embodiment in that the end seal 40 does not have a portion corresponding to the cylindrical portion 42 extending in the pipe axis direction AX.

[0043] The end seal 40 includes a hole 40H through which the piping body 2 passes, and has a disk shape extending radially outward from the piping body 2. The piping body 2 is inserted into the hole 40H, and the periphery of the hole 40H is welded to the piping body 2. The outer surface of the end seal 40 in the pipe axis direction AX is flush with the edge 5E of the gas barrier 5. The inner surface of the end seal 40 in the pipe axis direction AX abuts against the layer end 31 of the thermal insulation layer 3. The exposed portion of the piping body 2 is covered with the thermal insulation cover 7.

[0044] In the second embodiment, the outer peripheral edge of the end seal 40 is welded to the gas barrier 5. The gas barrier 5 has a welded portion 60 welded to the end seal 40 on its inner surface near the edge 5E. The configuration of the welded portion 60 is substantially the same as in the first embodiment. The inner resin layer 52 of the gas barrier 5 is heat-welded to the outer peripheral edge of the end seal 40, thereby forming the welded portion 60. The welding of the hole 40H and the formation of the welded portion 60 improve the airtightness of the space in which the insulating layer 3 is disposed by the end seal 40. This prevents outside air from entering the insulating layer 3. The outer peripheral edge of the end seal 40 may be formed as a rough surface layer 43, as shown in FIG. 3 .

[0045] [Third embodiment] Figure 7 is a cross-sectional view showing a cryogenic fluid piping 1B according to a third embodiment. The cryogenic fluid piping 1B includes an inner pipe 21 as a piping body, a heat insulating layer 30, an outer pipe 22 as a vacuum jacket, and a gas barrier 50. The inner pipe 21 is a metal pipe through which a cryogenic fluid passes. The outer pipe 22 is disposed coaxially with the inner pipe 21 and covers the inner pipe 21 with a radial space therebetween. The inner pipe 21 and the outer pipe 22 constitute a vacuum double pipe 20. The space between the inner pipe 21 and the outer pipe 22 is decompressed to form a vacuum insulation space.

[0046] The cryogenic fluid piping 1B includes an exposed portion PA where the outer pipe 22 has been removed and the inner pipe 21 has been exposed. The exposed portion PA is, for example, a portion where the inner pipes 21 are connected to each other in an intermediate joint that connects a pair of vacuum double pipes 20. In the intermediate joint, the outer pipe 22 is removed to connect the inner pipes 21 to each other by welding or the like, and a predetermined length of the inner pipe 21 is exposed in the pipe axis direction AX. A sealant 221 is attached to an end 22E of the outer pipe 22, maintaining airtightness of the space between the inner pipe 21 and the outer pipe 22.

[0047] The insulating layer 30 covers the exposed portion PA of the inner pipe 21 and the vicinity of the end 22E of the outer pipe 22. The insulating layer 30 insulates the inner pipe 21 mainly at the exposed portion PA. As a result, the outer pipe 22 covers the outer periphery of the inner pipe 21 except for the exposed portion PA through a reduced pressure space, insulating the inner pipe 21. The insulating layer 30 can be formed, for example, by wrapping a sheet-like insulating material around the exposed portion PA so that it spans the ends 22E of a pair of opposing outer pipes 22. In the third embodiment, as shown by dotted lines in FIG. 7 , the sealing material 221 adjacent to the insulating layer 30 in the pipe axis direction AX and the end 22E of the outer pipe 22 radially adjacent to the insulating layer 30 form end seals 4A that seal the layer ends of the insulating layer 30.

[0048] The gas barrier 50 covers the outer periphery of the thermal insulation layer 30 and isolates the thermal insulation layer 30 from the outside air. The gas barrier 50 can be made of a non-breathable metal-resin composite sheet, a resin sheet, a metal sheet, or the like. For example, a laminate film of aluminum foil and a resin film, as illustrated in FIG. 3, may be used as the gas barrier 50. The gas barrier 50 includes a welded portion 63 welded to the end 22E of the outer tube 22 as the end seal 4A. The welded portion 63 is located at the end 56 of the gas barrier 50 in the tube axis direction AX. The welded portion 63 can be formed by heat-welding a resin layer included in the gas barrier 50 to the surface of the outer tube 22. The area of ​​the end seal 4A facing the welded portion 63 may be processed to have a roughened surface layer 43, as illustrated in FIG. 3.

[0049] Covering the insulating layer 30 with the gas barrier 50 including the welded portion 63 can prevent outside air from entering the insulating layer 30. A gap can occur at the contact point between the gas barrier 50 and the outer pipe 22 due to the difference in thermal expansion coefficients between the two. However, the gas barrier 50 is welded to the outer pipe 22 by the welded portion 63. Therefore, even if there is a difference in thermal expansion coefficients, the airtightness of the contact point between the gas barrier 50 and the outer pipe 22 is ensured, and outside air can be prevented from entering the insulating layer 30 for a long period of time. Furthermore, mechanical strength can be increased compared to when the gas barrier 50 and the outer pipe 22 are joined with an adhesive.

[0050] [Fourth embodiment] Figure 8 is a cross-sectional view showing a cryogenic fluid piping 1C according to a fourth embodiment. The cryogenic fluid piping 1C is a piping connected to a piping device 8, and includes a piping main body 20A, a heat insulating layer 300, and a gas barrier 50A. The piping main body 20A is a metal piping through which a cryogenic fluid passes. The heat insulating layer 300 covers the outer periphery of the piping main body 20A and insulates the piping main body 20A. The gas barrier 50A covers the outer periphery of the heat insulating layer 300 and isolates the heat insulating layer 300 from the outside air.

[0051] The piping device 8 is, for example, a pump or compressor that sends liquid hydrogen to the piping body 2, or a heat exchanger that uses liquid hydrogen as a heat medium. The piping device 8 is covered with a vacuum jacket 81 to keep it cool or to prevent the generation of liquefied air. An edge 57 of the gas barrier 50A is welded to the vacuum jacket 81. For example, a laminate film of aluminum foil and a resin film can be used as the gas barrier 50A, and the edge 57 can be heat-welded to the vacuum jacket 81.

[0052] In the fourth embodiment, the portion of the vacuum jacket 81 that abuts against the layer end portion 310 of the insulating layer 300 serves as an end seal. The edge 57 of the gas barrier 50A is welded to the vacuum jacket 81, thereby making the insulating layer 300 airtight.

[0053] [Summary of the Disclosure] The specific embodiments described above include disclosures having the following configurations.

[0054] A low-temperature fluid pipe according to a first aspect of the present disclosure comprises a metal pipe body through which a low-temperature fluid passes, an end seal protruding radially outward from the outer peripheral surface of the pipe body, an insulating layer surrounding the pipe body and including a layer end portion facing the end seal, and a gas barrier surrounding the insulating layer and including a welded portion welded to the end seal.

[0055] According to the first aspect, the insulating layer is surrounded by a gas barrier and the layer ends are covered by end seals, thereby preventing outside air from entering the insulating layer. A gap may form at the contact point between the end seal and the gas barrier due to the difference in the thermal expansion coefficients of the two. However, in the above aspect, the gas barrier includes a welded portion welded to the end seal. Therefore, even if there is a difference in the thermal expansion coefficients, the airtightness of the contact point between the end seal and the gas barrier is ensured, preventing outside air from entering for a long period of time. Furthermore, mechanical strength can be increased compared to when the end seal and the gas barrier are joined with an adhesive.

[0056] A cryogenic fluid pipe according to a second aspect is the cryogenic fluid pipe of the first aspect, wherein the gas barrier includes a resin layer at least on the surface portion of the welded portion, and the resin layer is welded to the end seal.

[0057] According to the second aspect, the resin layer of the gas barrier can be melted to weld the gas barrier to the end seal, thereby improving the workability of the welded portion compared to welding or the like.

[0058] A cryogenic fluid pipe according to a third aspect is the cryogenic fluid pipe according to the first or second aspect, wherein the end seal has a roughened surface layer in an area facing the welded portion.

[0059] According to the third aspect, the anchor effect based on the presence of the rough surface layer can further improve the bonding strength and airtightness between the end seal and the gas barrier at the welded portion.

[0060] The low-temperature fluid piping of the fourth aspect is a low-temperature fluid piping of any of the first to third aspects, wherein the insulating layer is sealed by the outer surface of the piping body, the end seal, and the gas barrier, and is arranged in a reduced-pressure space.

[0061] According to the fourth aspect, the area where the insulating layer is placed is in a reduced-pressure environment, thereby improving the insulating effect on the piping. Furthermore, if the end seal and the gas barrier are joined with an adhesive, drawing a vacuum to reduce the pressure in the area where the insulating layer is placed can cause problems with outgassing from the adhesive. However, in this aspect, the end seal and the gas barrier are joined by welding, so the problem of outgassing does not occur.

[0062] The cryogenic fluid piping of the fifth aspect is a cryogenic fluid piping of any of the first to fourth aspects, wherein the end seal has a hole portion that passes through the piping body, is a plate-shaped end seal plate portion that extends radially outward from the piping body and contacts the layer end portion of the insulation layer, and is a cylindrical end seal cylindrical portion that surrounds the piping body, is connected to the end seal plate portion at one end region and has the other end region welded to the welding portion of the gas barrier.

[0063] According to the fifth aspect, not only the end seal plate portion but also the end seal cylindrical portion is interposed between the pipe body and the gas barrier. This lengthens the heat transfer path between the pipe body and the gas barrier, making it difficult for the cold heat of the pipe body to be transferred to the gas barrier. This prevents the gas barrier from peeling off due to the cooling of the welded portion. It also prevents heat input to the pipe body from the gas barrier exposed to the outside air.

[0064] A cryogenic fluid pipe according to a sixth aspect is any of the cryogenic fluid pipes of the first to fifth aspects, wherein the cryogenic fluid passed through the pipe body is liquefied hydrogen.

[0065] Liquefied hydrogen has cold energy that generates liquefied air. If the sealing ability of the end seal is reduced and outside air penetrates the insulation layer and comes into contact with the piping body, liquefied air will be generated. According to the sixth aspect, the sealing ability of the end seal is ensured by the welded portion, so the generation of liquefied air can be suppressed.

[0066] A seventh aspect of the cryogenic fluid piping comprises a metal piping body through which a cryogenic fluid passes, an insulating layer covering the outer periphery of a first portion of the piping body, a vacuum jacket covering the outer periphery of a second portion of the piping body that is different from the first portion through a reduced pressure space, and a gas barrier covering the outer periphery of the insulating layer and including a welding portion welded to the vacuum jacket.

[0067] According to the seventh aspect, the insulating layer is covered with a gas barrier that includes a welded portion to the vacuum jacket, thereby preventing outside air from entering the insulating layer. A gap may occur at the contact point between the gas barrier and the vacuum jacket due to the difference in thermal expansion coefficients between the two. However, in the above aspect, the gas barrier includes a welded portion that is welded to the vacuum jacket. Therefore, even if there is a difference in thermal expansion coefficients, airtightness is ensured at the contact point between the gas barrier and the vacuum jacket, preventing outside air from entering for a long period of time. Furthermore, mechanical strength can be increased compared to when the gas barrier and the vacuum jacket are joined with an adhesive.

[0068] The cryogenic fluid piping according to an eighth aspect is the cryogenic fluid piping of the seventh aspect, wherein the gas barrier includes a resin layer at least on the surface portion of the welded portion, and the resin layer is welded to the vacuum jacket.

[0069] According to the eighth aspect, the resin layer of the gas barrier can be melted to weld the gas barrier to the vacuum jacket, thereby improving the workability of the welded portion compared to welding or the like.

[0070] A cryogenic fluid pipe according to a ninth aspect is the cryogenic fluid pipe of the seventh or eighth aspect, wherein the end seal has a roughened surface layer in an area facing the welded portion.

[0071] According to the ninth aspect, the anchor effect based on the presence of the rough surface layer can further improve the bonding strength and airtightness between the gas barrier and the vacuum jacket at the welded portion.

Claims

1. A pipe for cryogenic fluid comprising: a metallic pipe body through which a cryogenic fluid passes; an end seal protruding radially outward from the outer peripheral surface of the pipe body; an insulating layer surrounding the pipe body and including a layer end portion facing the end seal; and a gas barrier surrounding the insulating layer and including a welded portion welded to the end seal.

2. The low-temperature fluid piping according to claim 1, wherein the gas barrier includes a resin layer at least on the surface of the welded portion, and the resin layer is welded to the end seal.

3. A cryogenic fluid pipe as claimed in claim 1, wherein the end seal has a roughened surface layer in the area facing the welded portion.

4. A low-temperature fluid piping as claimed in claim 1, wherein the heat insulating layer is sealed by the outer peripheral surface of the piping body, the end seal and the gas barrier, and is disposed in a reduced pressure space.

5. A piping for cryogenic fluid according to any one of claims 1 to 4, wherein the end seal comprises: a plate-shaped end seal plate portion having a hole portion penetrating the piping body and extending radially outward from the piping body, the end seal plate portion being in contact with an end portion of the insulating layer; and a cylindrical end seal tubular portion surrounding the piping body, the end seal tubular portion being connected to the end seal plate portion at one end region and having the other end region welded to the welded portion of the gas barrier.

6. The cryogenic fluid piping according to claim 1, wherein the cryogenic fluid passed through the piping body is liquefied hydrogen.

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