Pipe connection structure and pipe system

Abstract

To simplify a structure of a connection part of a vacuum heat insulation pipe.SOLUTION: A pipe connection structure 1 connects terminals of a first pipe 2A and a second pipe 2B, each of which includes an inner pipe 21, an outer pipe 22, and a vacuum heat insulation layer 23. The connection structure 1 comprises: a pipe connection part 24 located at the terminal of each of the first pipe 2A and the second pipe 2B and including a protruding end part 25 of the inner pipe 21 that protrudes beyond an edge 22E of the outer pipe 22, and a flange connection part 26 between the protruding end parts 25; a heat insulating material 3 that covers a heat insulating area TA, which is an outer pipe surface area having a predetermined length extending from the edge 22E of the outer pipe 22 in a pipe axis direction F of the outer pipe, and also covers the pipe connection part 24; a cover 4 that covers the heat insulating material 3; and a receptacle 5 that is arranged inside the cover 4, and receives liquefied air LA generated from the pipe connection part 24.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a connection structure for connecting ends of piping that includes an inner pipe, an outer pipe, and a vacuum insulation layer, and to a piping system that includes the connection structure. [Background technology]

[0002] In piping that transports cryogenic fluid, it is preferable to have a structure that allows the piping to be partially separated. For example, equipment such as a pump may be connected to the piping. When performing maintenance or replacement of the equipment, it is desirable to separate the equipment from the piping so that the cryogenic fluid remaining in the piping does not leak into the equipment. The same applies to replacement or maintenance of the piping itself. Patent Document 1 discloses a piping connection structure in which a flange connection portion is provided on the piping and the circumferential surface of the flange connection portion is covered with a sealing member to prevent leakage. When it is necessary to separate the equipment, the flange connection portion can be used to sever the connection between the equipment and the piping. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-239310 Summary of the Invention [Problem to be solved by the invention]

[0004] When the cryogenic fluid to be transported is a fluid that generates liquefied air, such as liquefied hydrogen, a vacuum insulated pipe is used as the piping, which includes an inner pipe, an outer pipe, and a vacuum insulation layer. When a connection that allows for disconnection is provided to the vacuum insulated pipe, the structure becomes complicated due to the multiple pipe structure.

[0005] An object of the present disclosure is to provide a piping connection structure that can simplify the connection portion of a vacuum insulated piping, and a piping system that includes the connection structure. [Means for solving the problem]

[0006] A piping connection structure according to one aspect of the present disclosure is a piping connection structure that connects the ends of a first pipe and a second pipe, each of which includes an inner pipe through which a cryogenic fluid passes, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, and is provided with a piping connection portion that includes a protruding end portion of the inner pipe located at each of the ends of the first pipe and the second pipe and protruding beyond the end edge of the outer pipe, and a flange connection portion between the protruding end portions, an insulating material that covers an insulating area, which is an outer pipe surface area of ​​a predetermined length from the end edge of the outer pipe at the end in the axial direction of the outer pipe, and also covers the piping connection portion, a cover that covers the insulating material, and a receiving member that is arranged inside the cover and receives liquefied air generated from the piping connection portion.

[0007] A piping system according to another aspect of the present disclosure includes the above-described piping connection structure and a container that defines a space into which the other end of the first piping or the second piping opposite the terminal end enters, the space requiring maintenance work. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a piping connection structure that can simplify the connection portion of a vacuum insulated piping, and a piping system that includes the connection structure. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a pipe connection structure according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing a pipe connection structure according to a second embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing a pipe connection structure according to a third embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a pipe connection structure according to a fourth embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing a pipe connection structure according to a fifth embodiment. [Figure 6]FIG. 6 is a cross-sectional view showing a pipe connection structure according to a sixth embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing a pipe connection structure according to a seventh embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing a pipe connection structure according to a modified example of the seventh embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a pipe connection structure according to the eighth embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a pipe connection structure according to a ninth embodiment. [Figure 11] FIG. 11 is a diagram showing an operational state of the piping system according to the embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of control of a piping system. DETAILED DESCRIPTION OF THE INVENTION

[0010] Various embodiments of the piping connection structure according to the present disclosure will be described in detail below with reference to the drawings. In facilities that handle cryogenic fluids, vacuum insulated multi-layer pipes are sometimes used as piping for transferring the cryogenic fluid. By using vacuum insulated multi-layer pipes, the generation of boil-off gas and the formation of ice on the piping surface can be suppressed. Furthermore, when the object to be transferred is a cryogenic fluid, the generation of liquefied air on the piping surface can be suppressed. A cryogenic fluid is a fluid in a temperature range that liquefies the surrounding air, or a fluid in a temperature range that liquefies the oxygen or nitrogen contained in the surrounding air. Examples of cryogenic fluids include liquefied hydrogen (LH2) and liquefied helium (LHe). Alternatively, the cryogenic fluid may be hydrogen gas or helium gas in a cryogenic temperature range.

[0011] Cryogenic fluid-related facilities include various types of equipment connected to piping. Typical examples include pumps that generate the transport force for liquefied gas and compressors that adjust pressure. It is desirable to provide a structure that can isolate the equipment from the piping to prevent the cryogenic fluid remaining in the piping from leaking into the equipment during maintenance or replacement. Furthermore, there may be sections of the piping that require replacement or maintenance. It is desirable to be able to isolate these sections from other sections of piping. One method for achieving this isolation structure is to provide a mechanical intermediate connector that can be disassembled and reassembled, allowing the piping to be disconnected at the intermediate connector. When the piping is a vacuum-insulated multi-wall pipe, the cold insulation structure at the connector must be designed in a way that prevents liquefied air from being generated at the connector. Furthermore, when the cryogenic fluid is liquefied hydrogen, measures must also be taken to prevent liquefied air from being generated at the connector. Mechanical intermediate connectors can also be used to isolate backup piping, which is not used during normal operation, from the operational piping and connect the backup piping to the operational piping when needed. Various embodiments of a connection structure made of a vacuum insulated multi-wall pipe that can meet the above requirements will be described below.

[0012] Fig. 1 is a cross-sectional view schematically illustrating a pipe connection structure 1 according to a first embodiment. Fig. 1 illustrates a pipe connection structure 1 that connects the ends of a first pipe 2A and a second pipe 2B, each made of a vacuum insulated double pipe, as an example of a vacuum insulated multi-pipe. The pipe connection structure 1 includes a pipe connection portion 24, a heat insulating material 3, a cover 4, and a tray 5 as a receiving member.

[0013] The first pipe 2A and the second pipe 2B are pipes that constitute part or all of a piping line that transports a cryogenic fluid in cryogenic fluid-related equipment. The transported cryogenic fluid is a liquefied gas that generates liquefied air. In this embodiment, the liquefied gas is assumed to be liquefied hydrogen. The pipe connection structure 1 may be, for example, a portion that connects a first end 2AE of the first pipe 2A to a second end 2BE of the second pipe 2B at any intermediate position of the piping line. In this case, the first end 2AE and the second end 2BE are not the ends of the piping line itself, but a pair of ends created by dividing the piping line in the middle. When one piping line is composed of the first pipe 2A and the other piping line is composed of the second pipe 2B, the pipe connection structure 1 is a portion that connects the ends of the piping lines.

[0014] The first pipe 2A and the second pipe 2B include an inner pipe 21, an outer pipe 22, and a vacuum insulation layer 23. The inner pipe 21 is a pipe through which the cryogenic fluid to be transported, in this embodiment, liquefied hydrogen, passes. Part or all of the inner pipe 21 may be operated so that liquefied hydrogen does not pass through it at all times. The outer pipe 22 is a pipe that covers the inner pipe 21 and is arranged coaxially with the inner pipe 21. The vacuum insulation layer 23 is a space layer between the inner pipe 21 and the outer pipe 22, and is a layer formed by drawing a vacuum. By removing heat carriers by drawing a vacuum, the space layer between the inner pipe 21 and the outer pipe 22 functions as an insulation layer.

[0015] The pipe connection portion 24 connects the inner pipes 21 of the first pipe 2A and the second pipe 2B. The pipe connection portion 24 includes a protruding end portion 25 of the inner pipe 21 and a flange connection portion 26. The protruding end portions 25 are located at the first end 2AE of the first pipe 2A and the second end 2BE of the second pipe 2B. The protruding end portions 25 are ends of the inner pipe 21 that protrude outward beyond the edge 22E of the outer pipe 22. In other words, the first end 2AE and the second end 2BE form a single-pipe structure consisting of only the inner pipe 21. An end seal 221 is attached to the edge 22E to fill the gap between the edge 22E and the outer peripheral surface of the protruding end portion 25. The attachment of the end seal 221 maintains the airtightness of the vacuum insulation layer 23.

[0016] The flange connection portion 26 mechanically connects the protruding end portions 25 of the first pipe 2A and the second pipe 2B. A first flange 26A is attached to the edge of the protruding end portion 25 of the first pipe 2A, and a second flange 26B is attached to the edge of the protruding end portion 25 of the second pipe 2B. The flange connection portion 26 is formed, for example, by fastening the first flange 26A and the second flange 26B together with bolts and nuts.

[0017] The heat insulating material 3 covers the pipe connection portion 24 and a predetermined heat insulating area TA to keep the pipe connection portion 24 cool. The heat insulating material 3 may be a closed-cell resin heat insulating material made of a resin material such as polyethylene or polyurethane. The heat insulating area TA is a surface area of ​​the outer pipe 22 that extends a predetermined length in the pipe axis direction F from the end edges 22E of the outer pipe 22 at the first end 2AE and the second end 2BE away from the pipe connection portion 24. The heat insulating area TA is an area set to suppress heat input from the outside to the pipe connection portion 24.

[0018] The layer of insulating material 3 can be formed, for example, by wrapping a sheet or tape of the resin insulating material. In this case, the sheet or tape is wrapped around the pipe connection portion 24 and the insulating area TA. The layer of insulating material 3 may also be formed by assembling block pieces of predetermined size made of resin insulating material, filling in small pieces of resin insulating material, wrapping the small pieces in a net or the like and winding them, or the like. In FIG. 1, the insulating material 3 is depicted as being disposed in a portion of the cover 4. This is to clearly show the pipe connection portion 24; in reality, most of the space within the cover 4 is filled with insulating material 3.

[0019] The cover 4 covers the insulation material 3. As a result of covering the insulation material 3, the cover 4 covers the periphery of the pipe connection portion 24 and the insulated area TA. Covering the insulation material 3 with the cover 4 has advantages such as waterproofing the insulation material 3, maintaining its shape and protecting it, improving its cold insulation effect, and trapping liquefied air. The shape of the cover 4 is not limited as long as it has a cavity to accommodate the insulation material 3 installed to the required thickness. For example, the cover 4 may be cylindrical or rectangular. The material of the cover 4 is a metal or hard resin that is resistant to cold and heat. To ensure ease of assembly and disassembly to the pipe connection portion 24, it is desirable to use a split cover 4, such as one that splits into two.

[0020] The tray 5 receives the liquefied air LA generated from the pipe connection part 24. The tray 5 is disposed inside the cover 4. The pipe connection part 24 does not have an outer pipe 22, and there is no vacuum insulation layer 23 either. Therefore, when liquefied hydrogen passes through the pipe connection part 24, it liquefies the air around the pipe connection part 24. The tray 5 is disposed below the pipe connection part 24, and receives the liquefied air LA hanging down from the pipe connection part 24.

[0021] The tray 5 is made of a material that can withstand extremely low temperatures. For example, the tray 5 can be made of a closed-cell insulation material using an EPDM synthetic rubber-based material. The tray 5 has the shape of a container with an open top and includes a bottom plate 51 and side plates 52. The bottom plate 51 is flat and faces the pipe connection portion 24 from below. The side plates 52 rise from the periphery of the bottom plate 51. However, the shape of the tray 5 is not particularly limited as long as it can store a predetermined amount of liquefied air LA. For example, the tray 5 may have a semicircular cross section perpendicular to the pipe axis direction F. The liquefied air LA received in the tray 5 eventually evaporates. The evaporated air can be cooled again at the pipe connection portion 24 and become liquefied air LA. In other words, a cycle of liquefaction and evaporation of air occurs within the cover 4. When the liquefied air LA is evaporated in an open space, an oxygen-rich region may be formed due to the fact that nitrogen evaporates faster than oxygen. In this embodiment, the liquefied air LA is vaporized within the cover 4, so that an oxygen-rich region can be confined.

[0022] The tray 5 has a length longer than the pipe connection portion 24 in the pipe axis direction F. That is, the tray 5 is arranged straddling below at least a portion of the insulating area TA and below the pipe connection portion 24. The liquefied air LA is generated exclusively in the pipe connection portion 24. By arranging the tray 5 with a size longer than the pipe connection portion 24, it is easier to receive the liquefied air LA without leakage.

[0023] The pipe connection structure 1 of the first embodiment includes a flange connection portion 26 between the protruding ends 25 of the inner pipes 21. Therefore, the first pipe 2A and the second pipe 2B, which are vacuum-insulated pipes, can be mechanically disconnected at the flange connection portion 26. To disconnect the first pipe 2A and the second pipe 2B, the cover 4 is removed, and the insulating material 3 wrapped around the pipe connection portion 24 is removed to expose the flange connection portion 26. After disassembling the flange connection portion 26, the first flange 26A or the second flange 26B is sealed. This procedure allows the flange connection portion 26 to be used for disconnecting the first pipe 2A or the second pipe 2B during maintenance, replacement, or other work on equipment connected to the first pipe 2A or the second pipe 2B. After the work is completed, the flange connection portion 26 is reassembled to connect the first pipe 2A and the second pipe 2B, and the insulating material 3 and the cover 4 are then sequentially reinstalled. By providing the insulating material 3 and the cover 4 as a structure that can be easily attached and detached to and from the pipe connection portion 24, workability is improved.

[0024] Furthermore, according to the piping connection structure 1, the heat insulating area TA and the piping connection portion 24 are covered with the heat insulating material 3, so that the portion of the piping connection portion 24 where the inner pipe 21 is exposed and the surrounding area can be kept cool. This reduces heat input to the piping connection portion 24, which is a single piping for only the inner pipe 21. Furthermore, the tray 5 arranged inside the cover 4 receives the liquefied air LA generated from the piping connection portion 24. This prevents the liquefied air LA from dripping out of the piping connection portion 24 and allows it to evaporate within the cover 4. As described above, the piping connection structure 1 of the first embodiment allows the vacuum insulated piping to be temporarily disconnected, while also properly keeping the piping connection portion 24 cool and disposing of the liquefied air LA.

[0025] 2 is a cross-sectional view showing a pipe connection structure 1A according to a second embodiment. The second embodiment shows an example in which the liquefied air LA received by the tray 5 is actively vaporized. The pipe connection structure 1A further includes a vaporizer 6 in addition to the pipe connection part 24, the heat insulating material 3, the cover 4, and the tray 5 similar to those of the connection structure 1 of the first embodiment. The vaporizer 6 vaporizes the liquefied air LA received by the tray 5.

[0026] The vaporizer 6 includes a heat exchange pipe 61 and heat dissipation fins 62. The heat exchange pipe 61 is a serpentine metal pipe capable of carrying a fluid. The heat dissipation fins 62 protrude from the outer periphery of the heat exchange pipe 61. The heat dissipation fins 62 may be blade-shaped or corrugated fins. The addition of the heat dissipation fins 62 provides the heat exchange pipe 61 with high heat exchange performance. A drainage pipe 53 is attached to the bottom plate 51 of the tray 5. The tip of the drainage pipe 53 extends outside the cover 4 and is attached to a joint 53J. One end 611 of the heat exchange pipe 61 is connected to the joint 53J. In other words, the heat exchange pipe 61 and the drainage pipe 53 are in communication with each other. The other end 612 of the heat exchange pipe 61 is open to the atmosphere.

[0027] The liquefied air LA received by the tray 5 is taken into one end 611 of the heat exchange pipe 61 through the drain pipe 53. While passing through the heat exchange pipe 61, the liquefied air LA exchanges heat with the outside air through the surface of the heat exchange pipe 61 and the heat dissipation fins 62. Due to this heat exchange, the liquefied air LA in the heat exchange pipe 61 is gradually vaporized as it heads toward the other end 612. Air is dissipated from the other end 612. That is, the liquefied air LA received by the tray 5 can be returned to a gaseous state and dissipated into the atmosphere.

[0028] In the upstream region of the heat exchange pipe 61, new liquefied air can be generated from around the heat exchange pipe 61 by the cold energy of the introduced liquefied air LA. To prevent the liquefied air from scattering, the vaporizer 6 may be installed inside a chamber. As the vaporizer 6, a device in which only the heat exchange pipe 61 or the heat exchange pipe 61 with heat dissipation fins 62 is arranged inside a chamber to which a fluid for heat exchange is supplied may be used. Also, a heat exchange device in an embodiment in which a flow path for passing the liquefied air LA is formed in a metal block may be used as the vaporizer 6.

[0029] 3 is a cross-sectional view showing a piping connection structure 1B according to a third embodiment. The third embodiment shows an example in which measures are taken to prevent liquid leakage from flange connection portion 26. In addition to the piping connection portion 24, heat insulating material 3, cover 4, tray 5, and vaporizer 6 similar to those of connection structure 1A of the second embodiment, piping connection structure 1B further includes a flange cap 54, a diffusion tube 55, an air supply tube 56, and a gas sensor 57.

[0030] The flange cap 54 is a dish-shaped member with an open bottom. The flange cap 54 is attached to the tray 5 so as to cover the top opening. That is, the flange cap 54 and the tray 5 form the housing 50 that encloses the pipe connection portion 24, including the flange connection portion 26. Note that a housing 50 in which the flange cap 54 and the tray 5 are pre-integrated may also be used. The diffusion pipe 55 extends from the top of the flange cap 54 and penetrates the cover 4. The diffusion pipe 55 is a conduit that discharges the vaporized gas of liquefied hydrogen LH from the housing 50. A joint portion 55J is attached to the tip of the diffusion pipe 55. The gas supply pipe 56 is a conduit that guides the vaporized gas of liquefied hydrogen LH to a predetermined processing device. One end of the gas supply pipe 56 is connected to the joint portion 55J. That is, the interior of the housing 50, the diffusion pipe 55, and the gas supply pipe 56 are connected to each other. As a modified example, the gas supply pipe 56 may be omitted. Also, the diffusion pipe 55 and the gas supply pipe 56 may be integrated into one pipe. The gas sensor 57 measures the hydrogen gas concentration inside the housing 50.

[0031] Because the flange connection 26 is a mechanical connection, the possibility of leakage of liquefied hydrogen LH is extremely low, but it is more likely to occur than with a welded connection. By enclosing the flange connection 26 in the housing 50, even if leakage of liquefied hydrogen LH does occur from the flange connection 26, it is possible to prevent hydrogen gas from scattering into the surrounding area. The leaked liquefied hydrogen LH is immediately vaporized and guided from the diffusion pipe 55 through the gas supply pipe 56 to a predetermined processing device. Meanwhile, the liquefied air LA received in the tray 5 is discharged from the housing 50 through the drain pipe 53. The discharged liquefied air LA is vaporized in the vaporizer 6 and dispersed into the atmosphere.

[0032] According to the piping connection structure 1B, the liquefied hydrogen LH leaking from the flange connection portion 26 and the liquefied air LA generated at the piping connection portion 24 can be separated and discharged from inside the cover 4. That is, the vaporized gas of the liquefied hydrogen LH can be discharged from the diffusion pipe 55, and the liquefied air LA can be discharged from the drain pipe 53. It is not desirable to allow the liquefied hydrogen LH to continue leaking from the flange connection portion 26. It is desirable to construct a system that immediately issues an alert when the gas sensor 57 detects a predetermined concentration of hydrogen gas.

[0033] 4 is a cross-sectional view showing a piping connection structure 1C according to a fourth embodiment. The fourth embodiment is also an example of implementing measures to prevent leakage from flange connection portion 26, but shows an example of a configuration that minimizes contact between leaked liquefied hydrogen LH and the air inside cover 4. In addition to the piping connection portion 24, heat insulating material 3, cover 4, tray 5, and vaporizer 6 similar to those of connection structure 1A of the second embodiment, piping connection structure 1C further includes a flange cap 58, a diffusion pipe 55A, and an air supply pipe 56.

[0034] Unlike the flange cap 54 in the third embodiment, the flange cap 58 only covers the periphery of the flange connection portion 26. In other words, the flange cap 58 surrounds the vicinity of the flange connection portion 26 separately from the tray 5. The diffusion pipe 55A extends from the top of the flange cap 58 and penetrates the cover 4. The diffusion pipe 55A discharges vaporized liquefied hydrogen LH that leaks from the flange connection portion 26 from the flange cap 58. A joint portion 55J is attached to the tip of the diffusion pipe 55A. One end of the air supply pipe 56 is connected to the joint portion 55J. The diffusion pipe 55A and the air supply pipe 56 are connected to each other inside the flange cap 58.

[0035] According to the piping connection structure 1C, only the flange connection portion 26, which has a higher possibility of leakage of liquefied hydrogen LH than other portions, is covered by the flange cap 58. In other words, within the cover 4, only the flange connection portion 26 and the space around it are isolated from the space within the cover 4. Therefore, even if liquefied hydrogen LH leaks from the flange connection portion 26, the vaporized gas of the liquefied hydrogen LH can be diffused to the outside through the diffusion pipe 55A. In other words, the leaked liquefied hydrogen LH can be diffused to the outside as a vaporized gas without coming into contact with the air, particularly oxygen, inside the cover 4. Meanwhile, the liquefied air LA generated at the piping connection portion 24 is received by the receiver 5 and diffused into the atmosphere through the drain pipe 53 and the vaporizer 6.

[0036] FIG. 5 is a cross-sectional view showing a pipe connection structure 1D according to a fifth embodiment. In the fifth embodiment, the cover 4 also functions as a receiving member for receiving liquefied air LA. The pipe connection structure 1D includes a pipe connection portion 24, a heat insulating material 3, and a cover 4. The cover 4 does not include the tray 5 shown in the above embodiment. Instead, a lower region 41 of the cover 4 serves as a substitute for the tray 5. The lower region 41 receives the liquefied air LA generated at the pipe connection portion 24. The lower region 41 is located below the pipe connection portion 24 and is a container-like portion capable of storing liquid, so it can function as the tray 5. It is desirable to improve the sealing of at least the lower region 41 of the cover 4 to prevent leakage of the liquefied air LA from the cover 4. Furthermore, to prevent ice and frost from forming on the surface of the cover 4, it is desirable to attach a heat insulating material to the inner surface of the cover 4 without any gaps.

[0037] According to the piping connection structure 1D, the cover 4 also functions as a receiving member for the liquefied air LA. Therefore, it is possible to provide a piping connection structure 1D with simplified components. In the piping connection structure 1D, the drain pipe 53 and the vaporizer 6 attached to the tray 5 as exemplified in the second to fourth embodiments may be attached to the lower region 41. Furthermore, the flange cap 58 exemplified in the fourth embodiment may be applied to the flange connection portion 26. These points are the same in the embodiments described below.

[0038] 6 is a cross-sectional view showing a pipe connection structure 1E according to a sixth embodiment. The sixth embodiment shows an example in which measures are taken to prevent liquefied air LA from flowing out from a cover 4. The pipe connection structure 1E further includes an outer receiving member 42 in addition to a pipe connection portion 24, a heat insulating material 3, and a cover 4 that functions as a receiving member, which are similar to those of the connection structure 1D of the fifth embodiment.

[0039] The outer receiving member 42 is disposed below the cover 4. The outer receiving member 42 is a container having an upper opening that is larger than the size of the cover 4. For example, the outer receiving member 42 has a tray-like shape. Even if the liquefied air LA leaks out from the cover 4, the liquefied air LA is received by the outer receiving member 42. Therefore, the dispersion of the liquefied air LA that has leaked out from the cover 4 can be suppressed.

[0040] A situation may occur in which a large amount of liquefied air LA accumulates inside the cover 4. If the cover 4 is formed from sheet metal or the like, the cover 4 will not be completely sealed. In this case, the liquefied air LA accumulated inside the cover 4 will overflow. As shown by the dotted line in Figure 6, even if a tray 5 is placed inside the cover 4, the liquefied air LA may overflow from the tray 5 and then overflow from the cover 4. It is also possible that secondary liquefied air LA will be generated from the surface of the lower region 41 due to the cold heat of the liquefied air LA accumulated inside the cover 4. The outer receiving member 42 receives the liquefied air LA that flows out of the cover 4 due to such factors. The received liquefied air LA will eventually evaporate.

[0041] 7 is a cross-sectional view showing a pipe connection structure 1F according to a seventh embodiment. The seventh embodiment shows an example in which a cover 4 is provided with measures to prevent intake noise. The pipe connection structure 1F further includes an opening 7 provided in the cover 4 in addition to the pipe connection portion 24, heat insulating material 3, cover 4, and tray 5 similar to those of the connection structure 1 of the first embodiment. The opening 7 allows air to enter the cover 4 from the outside.

[0042] The cover 4 is a housing made of a split structure or the like, which encloses the periphery of the pipe connection portion 24 and creates a sealed space. However, the degree of sealing is not perfect. In such a cover 4, minute gaps exist that allow air to circulate inside and outside the cover 4. For example, when the cover 4 is constructed by assembling sheet metal materials, minute gaps exist at the joints between the sheet metal materials. When liquefied air LA is generated inside the cover 4, the air condenses, causing a drop in the air pressure inside the cover 4. In this case, outside air enters the cover 4 through the gaps to fill the pressure difference. At this time, intake noise occurs due to the small gaps through which the outside air enters. This intake noise can become unintended noise.

[0043] The opening 7 is made up of an intake pipe 71 and a check valve 72. The intake pipe 71 is a pipe with one end opening into the cover 4 and the other end opening to the outside air. The check valve 72 is located in the middle of the intake pipe 71 and allows air to pass only in the direction from the outside air toward the inside of the cover 4. When the air pressure drops due to the evaporation of the liquefied air LA inside the cover 4, outside air is actively taken into the cover 4 through the intake pipe 71. This makes it difficult for air to flow through tiny gaps that would cause intake noise. Therefore, the generation of intake noise can be suppressed.

[0044] The opening 7 may be configured such that the check valve 72 is not provided and only the intake pipe 71 is attached to the cover 4. Even in this case, as shown in Fig. 7, it is desirable that the opening at the outside air side end of the intake pipe 71 be positioned facing downward to prevent rainwater from entering. Furthermore, the opening 7 may be a hole having an opening area that is sufficiently larger than the minute gaps that inevitably occur in the cover 4, as long as the airtightness of the cover 4 is not significantly impaired.

[0045] FIG. 8 is a cross-sectional view showing a pipe connection structure 1G according to a modification of the seventh embodiment. The pipe connection structure 1G is an example in which the above-described pipe connection structure 1F is modified to have a vertical arrangement. In the pipe connection structure 1F, the first pipe 2A and the second pipe 2B extend in the horizontal X direction. In contrast, in the pipe connection structure 1G, the first pipe 2A and the second pipe 2B extend in the Z direction, which is perpendicular to both the X and Y directions. The components of the pipe connection structure 1G are the same as those of the pipe connection structure 1F in FIG. 7. The tray 5 is attached to the second pipe 2B located below. The opening 7 is attached to the bottom surface of the cover 4. The opening 7 may be attached to any location on the cover 4 as long as measures are taken to prevent rainwater from entering. The pipe connection structures of the above-described first to sixth embodiments and the embodiments described below may be modified to have a vertical arrangement like the pipe connection structure 1G.

[0046] 9 is a cross-sectional view showing a pipe connection structure 1H according to an eighth embodiment. The eighth embodiment shows an example in which an innovative arrangement of the insulating material 3 is employed. The pipe connection structure 1H includes a pipe connection portion 24, insulating material 3, cover 4, and tray 5 similar to those of the connection structure 1 of the first embodiment. The insulating material 3 includes a first insulating material 31 and a second insulating material 32.

[0047] The first insulating material 31 covers the insulating area TA and the pipe connection portion 24 in the upper region of the tray 5. In other words, the first insulating material 31 covers the insulating area TA shown in FIG. 1 within the width of the tray 5. The first insulating material 31 may extend beyond the width of the tray 5 to cover the upper region of the tray 5. The second insulating material 32 includes a lower insulating material 33 and a pair of left and right side insulating materials 34. The lower insulating material 33 is disposed between the underside of the tray 5 and the bottom wall of the cover 4. The side insulating materials 34 are disposed between the side of the tray 5 and the side wall of the cover 4. The lower insulating material 33 may be the same length as the width of the tray 5, and the side insulating materials 34 may reach the bottom wall of the cover 4. The first insulating material 31 and the second insulating material 32 may each be divided into smaller pieces than shown in FIG. 9.

[0048] The first insulating material 31 layer can be formed by winding, for example, a sheet or tape of resin insulating material concentrically or spirally around the pipe connection 24 as the winding axis. The side insulating material 34 layer can be formed by a similar winding operation. The lower insulating material 33 layer can be formed by stacking or interposing sheets or block pieces of resin insulating material.

[0049] According to the piping connection structure 1H, the liquefied air LA generated at the piping connection portion 24 can be guided to the tray 5 along the first insulating material 31. The first insulating material 31 covers the piping connection portion 24 and the insulating area TA within the opening range of the tray 5. The lower end portion of the first insulating material 31 fits into the tray 5. Therefore, the liquefied air LA generated at the piping connection portion 24 is guided by the first insulating material 31 and enters the tray 5. This makes it easier for the tray 5 to receive the liquefied air LA without leakage.

[0050] Furthermore, the arrangement of the second insulating material 32 can prevent frost from forming on the surface of the cover 4. That is, a lower insulating material 33 is interposed between the lower surface of the tray 5 and the bottom wall of the cover 4, and a side insulating material 34 is interposed between the side surface of the tray 5 and the side wall of the cover 4. Therefore, even if the tray 5 becomes extremely cold due to the accumulation of liquefied air LA, the cold heat is unlikely to be transferred to the bottom wall and side wall of the cover 4. Therefore, it is possible to prevent frost from forming on the surface of the cover 4.

[0051] 10 is a cross-sectional view showing a piping connection structure 1I according to a ninth embodiment. The ninth embodiment shows an example in which an inclusion is attached to a flange connection portion 26. The piping connection structure 1I further includes a spacer 8 in addition to the piping connection portion 24, the heat insulating material 3, the cover 4, and the tray 5 similar to those of the connection structure 1 of the first embodiment.

[0052] The spacer 8 is interposed between the first flange 26A attached to the first end 2AE of the first pipe 2A and the second flange 26B attached to the second end 2BE of the second pipe 2B. The flange connection portion 26S of the ninth embodiment is composed of the first flange 26A, the second flange 26B, and the spacer 8 sandwiched between these flanges. The interposition of the spacer 8 ensures a space between the first flange 26A and the second flange 26B for incorporating desired members.

[0053] One example of the spacer 8 is a ring spacer having an opening that connects the inner pipes 21 of the first pipe 2A and the second pipe 2B. Another example of the spacer 8 is a sealing spacer that physically separates the first pipe 2A and the second pipe 2B. When the pipe connection structure 1I is in operation, that is, when liquefied hydrogen LH is being transferred, the ring spacer may be inserted, and when not in operation or during maintenance, the ring spacer may be replaced with the sealing spacer.

[0054] 11 is a diagram showing an operating state of a piping system PS according to an embodiment of the present disclosure. The piping system PS includes a first pipe 2A and a second pipe 2B, a sealing spacer 81, a container 9, and a valve 91. The first pipe 2A and the second pipe 2B are connected by a pipe connection part 24 to form a piping line 10 for transporting liquefied hydrogen LH. The pipe connection part 24 is a connection part between the protruding end parts 25 of the inner pipes 21 exemplified in the first to ninth embodiments described above.

[0055] The container 9 defines a space requiring maintenance work. The container 9 may be, for example, an equipment room that houses equipment such as a pump or compressor for pumping liquefied hydrogen LH, or a tank that stores liquefied hydrogen LH. The container 9 is connected to the other ends of the first pipe 2A and the second pipe 2B, opposite the ends that form the pipe connection portion 24. The sealing spacer 81 is a member corresponding to the spacer 8 exemplified in the pipe connection structure 1I of the ninth embodiment, and blocks the pipe line 10 at the pipe connection portion 24. The valve 91 opens and closes the first pipe 2A and the second pipe 2B. The valve 91 is disposed on the pipe opposite the pipe connected to the container 9, across the pipe connection portion 24. The valve 91 and the sealing spacer 81 enable doubly isolating the container 9 from the pipes.

[0056] 11 shows a state in which a pair of valves 91 are closed, and the container 9 and the first pipe 2A and second pipe 2B directly connected to the container 9 are isolated from the piping line 10 by a pair of sealing spacers 81. In other words, the first pipe 2A and the second pipe 2B leading to the container 9 requiring maintenance are physically isolated at the pipe connection part 24. This allows workers to more safely perform maintenance and other work on the container 9. Furthermore, this isolation prevents liquefied hydrogen LH or its vaporized gas remaining in the piping line 10 from flowing into the container 9.

[0057] An example of the procedure for performing maintenance work on a container 9 in the piping system PS is as follows: A pair of valves 91 sandwiching the container 9 is closed. Next, the piping line 10 between the pair of valves 91 is purged with a purge gas such as nitrogen gas. After the replacement, a sealing spacer 81 is interposed in the flange connection portion 26 of the piping connection portion 24. If a ring spacer is interposed in the flange connection portion 26 during operation, the ring spacer is replaced with the sealing spacer 81. This prevents hydrogen gas remaining in the piping line 10 and valves 91 other than the cut-off section from entering the container 9. Thereafter, a worker performs maintenance work on the container 9.

[0058] According to the piping system of this embodiment, a piping line 10 made up of a first piping 2A and a second piping 2B made of vacuum insulated double pipes is provided with a piping connection section 24 including a flange connection section 26 between the protruding ends 25 of the inner pipes 21. This allows the piping leading to a container 9 requiring maintenance to be physically disconnected at the piping connection section 24. This improves the ease of maintenance of the container 9.

[0059] Fig. 12 is a cross-sectional view showing a piping connection structure 1J applicable to the above-mentioned piping system PS. The embodiment in Fig. 12 shows an example including a mechanism for closing a valve 91 in the event of a leak of liquefied hydrogen LH. In addition to the piping connection part 24, heat insulating material 3, cover 4, tray 5, and spacer 8 similar to those of the piping connection structure 1I of the ninth embodiment, the piping connection structure 1J further includes a drain pipe 53A, a gas sensor 57A, and a valve control part 92.

[0060] One end of drain pipe 53A is connected to tray 5, and the other end is open to the atmosphere. Drain pipe 53A is a pipe that discharges liquefied air LA from tray 5. Drain pipe 53A may be replaced with vaporizer 6 illustrated in FIG. 2 and elsewhere. Gas sensor 57A detects the concentration of hydrogen gas in the fluid flowing through drain pipe 53A. Gas sensor 57A has a probe portion disposed at an arbitrary position on drain pipe 53A. Valve control unit 92 opens and closes valve 91 based on the measurement results of gas sensor 57A.

[0061] During normal operation, the tray 5 receives liquefied air LA generated from the pipe connection 24. This liquefied air LA is discharged through the drain pipe 53A. The gas sensor 57A does not detect hydrogen gas. In contrast, if a leak of liquefied hydrogen LH occurs at the pipe connection 24, the liquefied air LA will flow through the drain pipe 53A with some hydrogen gas mixed in. Therefore, the gas sensor 57A detects hydrogen gas. When the gas sensor 57A measures hydrogen gas exceeding a predetermined concentration, the valve control unit 92 closes the valve 91. Closing the valve 91 stops the supply of liquefied hydrogen LH to the pipe connection 24 where the leak is occurring. Instead of the valve control unit 92, a monitor or alarm may be installed to notify an instruction to close the valve 91.

[0062] Summary of this disclosure The specific embodiments described above include disclosures having the following configurations.

[0063] A piping connection structure according to a first aspect of the present disclosure is a piping connection structure that connects the ends of a first pipe and a second pipe, each of which includes an inner pipe through which a cryogenic fluid passes, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, and is provided with a piping connection portion that includes a protruding end portion of the inner pipe located at the end of each of the first pipe and the second pipe and protruding beyond the end edge of the outer pipe, and a flange connection portion between the protruding end portions, an insulating material that covers an insulating area, which is an outer pipe surface area of ​​a predetermined length from the end edge of the outer pipe at the end in the axial direction of the outer pipe, and also covers the piping connection portion, a cover that covers the insulating material, and a receiving member that is arranged inside the cover and receives liquefied air generated from the piping connection portion.

[0064] According to the first aspect, a flange connection is provided between the protruding ends of the inner pipes. Therefore, the first and second pipes, which are vacuum insulated pipes, can be separated at the flange connection. Furthermore, because the insulated area and the pipe connection are covered with insulating material, the exposed portion of the inner pipe at the pipe connection and its surrounding area can be kept cold. Furthermore, a receiving member disposed inside the cover receives the liquefied air generated from the pipe connection. Therefore, the liquefied air is prevented from dripping out of the pipe connection and can be evaporated within the cover. As described above, according to the first aspect, the vacuum insulated pipe can be separated, while still allowing the pipe connection to be kept cold and the liquefied air to be properly disposed of.

[0065] A piping connection structure according to a second aspect is the connection structure of the first aspect, wherein the receiving member is a receiving tray disposed below the piping connection portion inside the cover.

[0066] According to the second aspect, a tray disposed inside the cover receives the liquefied air generated from the pipe connection portion. The second aspect has the advantage that the tray is disposed inside the cover, which is a simple structure, yet can easily receive the liquefied air.

[0067] The piping connection structure of the third aspect is the connection structure of the second aspect, wherein the tray has a length in the pipe axis direction that is longer than the piping connection portion, and is positioned across from below at least a portion of the insulation area and below the piping connection portion.

[0068] According to the third aspect, since the tray has the above size, it is easy to receive the liquefied air without leakage.

[0069] A pipe connection structure according to a fourth aspect is the connection structure of the first aspect, wherein the receiving member is a lower region of the cover.

[0070] According to the fourth aspect, the cover can also function as a receiving member for receiving liquefied air, thereby simplifying the pipe connection structure.

[0071] A pipe connection structure according to a fifth aspect is the connection structure of any of the first to fourth aspects, further comprising an outer receiving member that is disposed below the cover and receives liquefied air flowing out from the cover.

[0072] According to the fifth aspect, even if liquefied air leaks out from the cover, the outer receiving member can receive the liquefied air, thereby preventing the liquefied air from scattering.

[0073] A pipe connection structure according to a sixth aspect is the connection structure of any one of the first to fifth aspects, further comprising an evaporation device that evaporates the liquefied air received by the receiving member.

[0074] According to the sixth aspect, the liquefied air can be returned to a gaseous state and released into the atmosphere.

[0075] A piping connection structure according to a seventh aspect is the connection structure of the sixth aspect, in which the vaporizer is a heat exchange pipe including a heat exchange function, one end of the heat exchange pipe is connected to the receiving member, and the other end of the heat exchange pipe is open to the atmosphere.

[0076] According to the seventh aspect, the liquefied air collected by the receiving member can be sent to the heat exchange pipe, and after the liquefied air is vaporized in the heat exchange pipe, it can be released from the other end of the heat exchange pipe.

[0077] A piping connection structure according to an eighth aspect is the connection structure according to any one of the first to seventh aspects, wherein the cover is a housing that creates a sealed space and includes an opening that takes air into the cover from the outside.

[0078] According to the eighth aspect, an opening is provided as an air intake port into the cover. Therefore, when the liquefied air evaporates and the air pressure inside the cover drops, air can be actively taken into the cover through the opening. Therefore, the generation of intake noise caused by the drop in air pressure inside the cover can be suppressed.

[0079] A piping connection structure according to a ninth aspect is the connection structure of any one of the first to seventh aspects, further comprising a flange cap that covers the flange connection portion, and a diffusion pipe that extends from an upper portion of the flange cap.

[0080] According to the ninth aspect, even if the cryogenic fluid leaks from the flange connection, the cryogenic fluid can be diffused to the outside through the diffusion pipe. Therefore, the leaked cryogenic fluid can be diffused to the outside as vaporized gas without coming into contact with the gas inside the cover.

[0081] The piping connection structure of the tenth aspect is the connection structure of the second or third aspect, and further comprises a flange cap which, together with the tray, forms a housing that surrounds the flange connection portion, a diffusion pipe extending from the top of the flange cap, and a drain pipe that draws liquefied air from the tray.

[0082] According to the tenth aspect, the liquefied air and the cryogenic fluid leaking from the flange connection can be discharged separately from inside the cover. That is, the vaporized gas of the cryogenic fluid can be discharged from the diffusion pipe, and the liquefied air can be discharged from the drain pipe.

[0083] The piping connection structure of the 11th aspect is the connection structure of the third aspect, in which the insulating material includes a first insulating material covering the insulating area and the piping connection portion in the upper region of the tray, and a second insulating material arranged in the lateral and lower regions of the tray.

[0084] According to the eleventh aspect, liquefied air generated at the pipe connection portion can be guided to the tray through the first insulating material. Furthermore, the arrangement of the second insulating material can suppress the formation of frost on the surface of the cover.

[0085] The piping connection structure of the 12th aspect is the connection structure of the 1st to 11th aspects, wherein the flange connection portion includes a first flange attached to the end of the first piping, a second flange attached to the end of the second piping, and a spacer interposed between the first flange and the second flange.

[0086] According to the twelfth aspect, the spacer ensures a space between the first flange and the second flange for incorporating a desired member. For example, a sealing member that physically separates the first pipe from the second pipe can be disposed at the location where the spacer is provided afterward.

[0087] A piping system according to a thirteenth aspect comprises the above-described piping connection structure and a container that defines a space to which the other end of the first piping or the second piping opposite the terminal end is connected, the space requiring maintenance work.

[0088] According to the thirteenth aspect, a piping connection structure including a flange connection portion between the inner pipes is provided in a multi-pipe piping including an inner pipe and an outer pipe leading to a container. This allows the piping leading to a container requiring maintenance to be physically disconnected at the flange connection portion. This makes it possible to prevent the cryogenic fluid remaining in the piping from flowing into the container during maintenance of the container. [Explanation of symbols]

[0089] 1. 1A~1J Piping connection structure 2A, 2B 1st piping, 2nd piping 2AE, 2BE 1st termination, 2nd termination 2BE 21 Inner tube 22 Outer tube 22E Edge 23 Vacuum insulation layer 24 Pipe connection 25 Projecting end 26 Flange connection 26A, 26B 1st flange, 2nd flange 3. Insulation 31, 32 First insulation material, second insulation material 4 Cover 41 Lower area 42 outer support member 5. Receptacle (receptacle part) 50 cabinets 53 Drainage tube 55 Diffusion tube 6 Vaporizer 61 Heat exchange pipe 611, 612 One end, other end 62 Heat dissipation fin (heat exchange function) 7 Openings 8 spacers TA Insulation Area

Claims

1. A pipe connection structure for connecting terminals of a first pipe and a second pipe, each of which includes an inner pipe through which a cryogenic fluid passes, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, a pipe connection portion including a protruding end portion of the inner pipe located at each end of the first pipe and the second pipe and protruding beyond an edge of the outer pipe, and a flange connection portion between the protruding end portions; a heat insulating material covering an insulating area, which is an outer pipe surface area having a predetermined length from the end edge of the outer pipe in the pipe axis direction of the outer pipe, and covering the pipe connection portion; a cover that covers the heat insulating material; a receiving member disposed inside the cover for receiving liquefied air generated from the piping connection portion.

2. The piping connection structure according to claim 1, A pipe connection structure, wherein the receiving member is a tray arranged below the pipe connection portion inside the cover.

3. The piping connection structure according to claim 2, A piping connection structure in which the tray has a length longer than the piping connection portion in the pipe axis direction and is positioned across from below at least a portion of the insulation area and below the piping connection portion.

4. The piping connection structure according to claim 1, The receiving member is a lower region of the cover, in this piping connection structure.

5. The piping connection structure according to any one of claims 1 to 4, The piping connection structure further comprises an outer receiving member disposed below the cover and configured to receive the liquefied air flowing out from the cover.

6. The piping connection structure according to any one of claims 1 to 4, The pipe connection structure further includes a vaporizer that vaporizes the liquefied air received by the receiving member.

7. The pipe connection structure according to claim 6, the vaporizer is a heat exchange pipe having a heat exchange function; A piping connection structure, wherein one end of the heat exchange pipe is connected to the receiving member, and the other end of the heat exchange pipe is open to the atmosphere.

8. The piping connection structure according to any one of claims 1 to 4, The cover is a housing that creates a sealed space and includes an opening that allows air to enter the cover from the outside, and is a piping connection structure.

9. The piping connection structure according to any one of claims 1 to 4, The piping connection structure further comprises a flange cap that covers the flange connection portion, and a diffusion pipe that extends from an upper portion of the flange cap.

10. The piping connection structure according to claim 2, A piping connection structure further comprising a flange cap that, together with the tray, forms a housing that surrounds the flange connection portion, a diffusion pipe extending from the top of the flange cap, and a drain pipe that draws liquefied air from the tray.

11. The piping connection structure according to claim 3, A piping connection structure in which the insulation material includes a first insulation material covering the insulation area and the piping connection portion in the upper region of the tray, and a second insulation material arranged in the side and lower regions of the tray.

12. The piping connection structure according to any one of claims 1 to 4, A piping connection structure, wherein the flange connection portion includes a first flange attached to an end of the first piping, a second flange attached to an end of the second piping, and a spacer interposed between the first flange and the second flange.

13. The piping connection structure according to any one of claims 1 to 4, A piping system comprising: a container that defines a space to which the other end opposite the terminal end of the first pipe or the second pipe is connected, the space requiring maintenance work.

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