Termination structure of vacuum heat insulating multiple pipe

Abstract

To provide a termination structure of a vacuum heat insulating multiple pipe that is excellent in adaptability to subsequent work on a vacuum heat insulating multiple pipe during operation.SOLUTION: A termination structure TR1 of a vacuum heat insulating multiple pipe 1 includes an inner pipe 2 through which low-temperature fluid flows, an outer pipe 3 covering the inner pipe 2, and a vacuum heat insulating layer 4 between the inner pipe 2 and the outer pipe 3. The termination structure TR1 comprises a protruding end part 22 of the inner pipe 2 including a protruding portion 22A that protrudes outward beyond an edge 3E of the outer pipe 3, a cold insulation chamber 6 that covers the protruding end part 22 and the edge 3E of the outer pipe 3, and a blocking mechanism 5 that separates an internal space S0 of a body part 21 of the inner pipe 2 covered by the outer pipe 3 from an internal space S3 of the protruding end part 22.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an end structure of a vacuum insulated multi-wall pipe including an inner pipe through which a cryogenic fluid flows, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe. [Background technology]

[0002] A vacuum insulated multi-wall pipe is sometimes used as a transfer pipe for low-temperature liquefied gas. The vacuum insulated multi-wall pipe includes an outer pipe, an inner pipe disposed within the outer pipe, and a vacuum insulation layer between the inner pipe and the outer pipe. In a transfer facility for low-temperature liquefied gas, a transfer pipeline is formed by connecting a plurality of vacuum insulated multi-wall pipes having a pipe length sufficient for transfer. Patent Document 1 discloses a technique for connecting vacuum insulated double-wall pipes on-site. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 8-20033 Summary of the Invention [Problem to be solved by the invention]

[0004] The vacuum insulation multi-layer pipe installed in the transfer facility may be subjected to subsequent work such as additional installation of the vacuum insulation multi-layer pipe or inspection during operation of the facility. For this reason, it is desirable to provide the vacuum insulation multi-layer pipe with a termination structure that can easily handle the subsequent work.

[0005] An object of the present disclosure is to provide a termination structure for a vacuum insulated multi-wall pipe that is highly adaptable to subsequent work. [Means for solving the problem]

[0006] The termination structure of a vacuum insulated multi-pipe according to one aspect of the present disclosure is a termination structure of a vacuum insulated multi-pipe including an inner pipe through which a low-temperature fluid flows, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, and is equipped with a protruding end of the inner pipe including a protruding portion that protrudes outward beyond an end edge of the outer pipe, a cold insulation cover covering the protruding portion and the end edge of the outer pipe, and a blocking mechanism located between a main body portion of the inner pipe covered by the outer pipe and the protruding end, separating the main body portion of the inner pipe from the protruding end. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a termination structure for a vacuum insulated multi-wall pipe that is highly adaptable to subsequent work. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an end structure of a triple-block type vacuum thermally insulated multi-wall pipe according to a first embodiment of the present disclosure. [Diagram 2] 2(A) and (B) are diagrams showing a procedure for connecting an additional vacuum thermal insulation multi-wall pipe to an end of the vacuum thermal insulation multi-wall pipe of the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an end structure of a double-block type vacuum thermal insulation multi-wall pipe according to the second embodiment. [Figure 4] FIG. 4 is a diagram showing an end structure of a vacuum thermally insulated multi-wall pipe according to a modified example of the second embodiment. [Diagram 5] FIG. 5 is a diagram showing an end structure of a single-block type vacuum thermal insulation multi-wall pipe according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the end structure of the vacuum insulated multi-wall pipe according to the present disclosure will be described in detail with reference to the drawings. In facilities that handle extremely low-temperature liquefied gases such as liquefied natural gas (LNG) and liquefied hydrogen (LH2), vacuum insulated multi-wall pipes are sometimes used as transport piping for the liquefied gas. By using the vacuum insulated multi-wall pipe, it is possible to suppress the generation of boil-off gas and the formation of ice on the piping surface, and for example, in the case of liquefied hydrogen, it is possible to suppress the generation of liquefied air on the piping surface.

[0010] In a liquefied gas facility, for example, based on a future facility expansion plan, it may be necessary to provide a terminal structure at the end of the transfer pipe in preparation for pipe extension. When a vacuum insulated multi-wall pipe is used as the transfer pipe, the construction of the terminal structure is also required. The terminal structure is required to be able to easily connect the vacuum insulated multi-wall pipe for extension and inspect the existing vacuum insulated multi-wall pipe, and to suppress heat input from the terminal structure part to the existing vacuum insulated multi-wall pipe. In particular, when transferring liquefied hydrogen, it is also essential to be able to suppress the formation of ice and the generation of liquefied air at the terminal structure part. Various embodiments of the terminal structure of the vacuum insulated multi-wall pipe that can meet the above requirements will be described below.

[0011] [First embodiment] FIG. 1 is a schematic diagram showing an end structure TR1 of a vacuum thermal insulation multi-wall pipe according to the first embodiment. FIG. 1 illustrates an end structure TR1 applied to an end 1E of a vacuum thermal insulation double-wall pipe 1 having an inner pipe 2, an outer pipe 3, and a vacuum thermal insulation layer 4 as a vacuum thermal insulation multi-wall pipe. The object of transport of the vacuum thermal insulation double-wall pipe 1 in the first embodiment is liquefied hydrogen (LH2). The vacuum thermal insulation double-wall pipe 1 is connected to a liquefied hydrogen supply source 1T and transports the liquefied hydrogen to a required location. The liquefied hydrogen supply source 1T is, for example, a liquefied hydrogen storage tank that stores liquefied hydrogen, an onboard tank of a liquefied hydrogen transport ship, a liquefied hydrogen production plant, or the like.

[0012] The inner pipe 2 is a pipe through which the low-temperature fluid to be transported flows. In the first embodiment, liquefied hydrogen flows through the inner pipe 2. The outer pipe 3 is a pipe that covers the inner pipe 2 and is arranged coaxially with the inner pipe 2. The vacuum insulation layer 4 is a space layer between the inner pipe 2 and the outer pipe 3, and is a layer formed by drawing a vacuum. By removing the heat carrier by drawing a vacuum, the space layer between the inner pipe 2 and the outer pipe 3 functions as an insulation layer.

[0013] The end 1E of the vacuum insulated double pipe 1 is an end 1E where cutting work is expected to be performed for some reason, such as when a new vacuum insulated double pipe 1 is planned to be installed or when an inspection of the existing vacuum insulated double pipe 1 is planned. The end 1E is provided with a end structure TR1 designed for the installation work. The end structure TR1 includes the protruding end 22 of the inner pipe 2, a cutoff mechanism 5, and a cold insulation chamber 6 (cold insulation cover).

[0014] The protruding end 22 corresponds to the terminal of the inner pipe 2, including a protruding portion 22A that protrudes outward beyond the edge 3E of the outer pipe 3 at the end 1E. During an expansion operation, the inner pipe 2 of the vacuum insulated double pipe 1 to be expanded is connected to the protruding end 22. An end seal 31 is attached to the edge 3E of the outer pipe 3 to fill the gap between the edge 3E and the outer peripheral surface of the protruding end 22. The attachment of the end seal 31 maintains the airtightness of the vacuum insulation layer 4. A cap portion 25 is attached to the edge of the protruding end 22 by welding or the like so as not to be detachable from the edge, and the opening of the edge is sealed.

[0015] The shutoff mechanism 5 is located between the main body 21 and the protruding end 22 of the inner pipe 2, and is a mechanism for separating the main body 21 and the protruding end 22. More specifically, the shutoff mechanism 5 is a mechanism for spatially isolating the internal space S0 of the main body 21 of the inner pipe 2 from the internal space S3 of the protruding end 22. The main body 21 is a part covered by the outer pipe 3 of the inner pipe 2, and is an operational part that actually transfers liquefied hydrogen. The shutoff mechanism 5 includes a first valve 51, a second valve 52, and a third valve 53 arranged at intervals in the axial direction of the inner pipe 2, and a first connecting pipe 23 and a second connecting pipe 24 that connect these valves to each other. In the first embodiment, a triple block structure in which three valves, that is, three spatial blocks, are arranged between the main body 21 and the protruding end 22 of the inner pipe 2 is exemplified.

[0016] The first valve 51, the second valve 52, and the third valve 53 are formed of ball valves, butterfly valves, gate valves, or the like, and switch between blocking and opening the adjacent internal spaces of the inner pipe 2 at the valve arrangement positions. The first connecting pipe 23 connects between the first valve 51 and the second valve 52. The second connecting pipe 24 connects between the second valve 52 and the third valve 53. By opening and closing the first valve 51, communication between the internal space S0 of the main body 21 and the internal space S1 of the first connecting pipe 23 is switched between being connected and blocked. By opening and closing the second valve 52, communication between the internal space S1 of the first connecting pipe 23 and the internal space S2 of the second connecting pipe 24 is switched between being connected and blocked. By opening and closing the third valve 53, communication between the internal space S2 of the second connecting pipe 24 and the internal space S3 of the protruding end 22 is switched between being connected and blocked.

[0017] The cold-storage chamber 6 is attached to the end 1E of the vacuum-insulated double pipe 1 so as to cover the protruding portion 22A of the protruding end portion 22 of the inner pipe 2 and the edge 3E of the outer pipe 3. The cold-storage chamber 6 has a cavity capable of accommodating the protruding portion 22A including the cap portion 25 and the edge 3E of the outer pipe 3. The cold-storage chamber 6 is attached to the outer pipe 3 with a seal structure (not shown) so that the cavity can be evacuated and gas replaced. The cold-storage chamber 6 is provided with a purge terminal 61. The purge terminal 61 can be used to evacuate the internal space S4 of the cold-storage chamber 6 and replace it with an inert gas. By evacuating the internal space S4, a vacuum insulation structure can be constructed even in the area of ​​the protruding portion 22A.

[0018] The purpose of installing the cold insulation chamber 6 is to keep the protruding portion 22A protruding from the edge 3E of the outer pipe 3 cool, to suppress heat input from the protruding portion 22A to the main body 21 of the inner pipe 2, and to protect the protruding portion 22A. The cold insulation can suppress the formation of ice and liquefied air on the outer circumferential surface of the protruding end 22. As a result of the cold insulation, the heat input is also suppressed. Furthermore, the cover of the cold insulation chamber 6 prevents the protruding portion 22A from being exposed to rainwater or wind and snow, and prevents flying objects, plants and animals from interfering with the protruding portion 22A.

[0019] The end structure TR1 includes a first nozzle 71, a second nozzle 72, and a third nozzle 73 for purging. The first nozzle 71 is a nozzle for purging the internal space S1 of the first connecting pipe 23. Through the first nozzle 71, it is possible to exhaust gas present in the internal space S1 and introduce replacement gas into the internal space S1. Similarly, the second nozzle 72 is a nozzle for purging the internal space S2 of the second connecting pipe 24, and the third nozzle 73 is a nozzle for purging the internal space S3 of the protruding end 22. The first, second, and third nozzles 71, 72, and 73 may be configured with a plurality of nozzles. Note that any of the nozzles 71, 72, and 73, for example, the first nozzle 71 may be omitted. The third nozzle 73 may be branched from either the part covered by the outer tube 3 of the protruding end 22 or the protruding part 22A.

[0020] FIG. 1 shows the fluid-filled state of the internal spaces S0 to S3 during operation of the vacuum insulated double pipe 1. The first valve 51, the second valve 52, and the third valve 53 are closed. Liquefied hydrogen (LH2) flows through the internal space S0 of the main body 21 of the inner pipe 2. The internal spaces S1, S2, and S3 are filled with hydrogen gas (GH2). If the internal spaces S1, S2, and S3 are filled with a gas other than helium gas, for example, an inert gas such as nitrogen gas, the gas will liquefy or solidify due to the cold heat of the liquefied hydrogen in the main body 21. In addition, if the internal spaces S1, S2, and S3 are filled with a gas containing oxygen, such as air, the possibility of hydrogen leakage from the first valve 51 cannot be reduced to zero, and a mixed gas of hydrogen and oxygen may be generated, making it difficult to ensure explosion-proof properties. If the gas filled into the internal spaces S1, S2, and S3 is hydrogen gas, the problems of liquefaction, solidification, and generation of a mixed gas can be avoided.

[0021] <Example of expansion work> 2(A) and (B) are diagrams showing the procedure for connecting an additional vacuum insulated double pipe to the end 1E of the vacuum insulated double pipe 1 of the first embodiment. In FIG. 2(A), a cut line C1 for cutting the protruding end 22 of the inner pipe 2 and a cut line C2 for cutting the cold storage chamber 6 are added. Before cutting along the cut lines C1 and C2, the internal spaces S2 and S3 are purged. As shown in FIG. 1, the internal spaces S2 and S3 are filled with hydrogen gas. In particular, in order to avoid contact between the hydrogen gas in the internal space S3 and the surrounding air due to the cutting of the protruding end 22, a purge is performed to replace the hydrogen gas in the internal space S3 with nitrogen gas (GN2). Note that other inert gases may be used as replacement gases instead of nitrogen gas.

[0022] Specifically, the third valve 53 is opened, and the purging is performed using the second nozzle 72 and the third nozzle 73. The first valve 51 and the second valve 52 are kept closed, and the internal space S1 of the first connecting pipe 23 is maintained in a state in which hydrogen gas is sealed therein. The main body 21 of the inner pipe 2 is maintained in an operational state in which liquefied hydrogen is circulated. Nitrogen gas is supplied from the second nozzle 72 to the internal space S2 of the second connecting pipe 24. The supplied nitrogen gas and the existing hydrogen gas become a mixed gas in the internal space S2. The mixed gas passes through the third valve 53, enters the internal space S3 of the protruding end 22, and is discharged from the third nozzle 73. When it is confirmed that the internal spaces S2 and S3 are filled with nitrogen gas based on the measurement result of the gas concentration meter (not shown) installed in the third nozzle 73, the third valve 53 is closed. By this purging, even if hydrogen gas leaks from the second valve 52, the leaked hydrogen gas can be discharged from the third nozzle 73. Conversely to the above, a mode in which nitrogen gas is supplied from the third nozzle 73 to the internal space S2 and the mixed gas is discharged from the second nozzle 72 may also be adopted.

[0023] After the above purging is completed, the cold storage chamber 6 is first cut along the cut line C2. The cut line C2 is set at a position closer to the edge 3E than the cut line C1 of the inner pipe 2. The remaining chamber 6A, which is the cut remaining part of the cold storage chamber 6, is utilized as a part of the cover that covers the joint part of the inner pipe 2 after the expansion. Next, the protruding end 22 is cut along the cut line C1. A part of the protruding part 22A is removed by this cutting. The nitrogen gas in the internal space S3 is dissipated into the atmosphere by this cutting, and air (Air) enters the internal space S3. Note that, unlike the example of FIG. 2, the cut line C1 may be set at a position closer to the edge 3E than the cut line C2. Furthermore, the cut line C2 may be set closer to the third valve 53 than the edge 3E.

[0024] The additional vacuum insulated double pipe 10, which is joined to the end 1E of the existing vacuum insulated double pipe 1, comprises an inner pipe 20, an outer pipe 30, and a vacuum insulation layer 40. These have substantially the same configuration as the inner pipe 2, the outer pipe 3, and the vacuum insulation layer 4 of the vacuum insulated double pipe 1. The vacuum insulated double pipe 10 comprises an end portion facing the end 1E, in which the inner pipe 20 has a protruding end portion 202 that protrudes outward beyond the edge 30E of the outer pipe 30.

[0025] FIG. 2(B) shows a state in which an additional vacuum insulated double pipe 10 is added to the end 1E of the existing vacuum insulated double pipe 1. The edges of the protruding end 22 of the existing inner pipe 2 and the protruding end 202 of the additional inner pipe 20 are welded to each other to form an inner pipe connection J1. The end of the additional vacuum insulated double pipe 10 is covered with an additional chamber 6B. The edge of the additional chamber 6B is welded to the edge of the remaining chamber 6A to form a chamber connection J2. The welded body of the remaining chamber 6A and the additional chamber 6B forms a joint cover 60 that provides a closed space S40 that covers the inner pipe connection J1 and the edges 3E and 30E.

[0026] After the inner pipe connection part J1 and the chamber connection part J2 are formed, nitrogen gas is supplied from the third nozzle 73 to the internal space S3. This nitrogen gas supply replaces the air in the internal space S3 of the protruding end part 22 and the internal space of the additional inner pipe 20 with nitrogen gas. In addition, the closed space S40 of the joint cover 60 is evacuated using the purge terminal 61. As a result, the joint cover 60 serves as the outer pipe 3 at the inner pipe connection part J1, and the closed space S40 serves as the vacuum insulation layer 4.

[0027] During start-up work after the expansion, the nitrogen gas in the internal space S2 of the second connecting pipe 24, the internal space S3 of the protruding end 22, and the internal space of the expanded inner pipe 20 is replaced with hydrogen gas. Then, the first valve 51, the second valve 52, and the third valve 53 are opened, and liquefied hydrogen flows from the main body 21 of the inner pipe 2 into the inner pipe 20 of the expanded vacuum insulated double pipe 10.

[0028] According to the termination structure TR1 of the first embodiment described above, the protruding end 22 of the inner pipe 2 is provided at the termination 1E of the vacuum thermal insulation double pipe 1. The protruding end 22 includes a protruding portion 22A that protrudes outward from the edge 3E of the outer pipe 3. By providing the protruding portion 22A, the connection work with the inner pipe 20 of the vacuum thermal insulation double pipe 10 for expansion can be facilitated. In addition, the protruding portion 22A is covered with the cold storage chamber 6, and the protruding end 22 and the main body portion 21 of the inner pipe 2 are spatially blocked by the blocking mechanism 5. For this reason, not only is the protruding portion 22A mechanically protected, but also heat input from the protruding portion 22A to the main body portion 21, icing on the surface of the protruding portion 22A, and generation of liquefied air can be suppressed.

[0029] In particular, in the first embodiment, three spatial blocks, the first valve 51, the second valve 52, and the third valve 53, are interposed between the main body 21 and the protruding end 22 of the inner pipe 2. Such a triple block structure provides various advantages at the end 1E of the vacuum insulated double pipe 1 that transports liquefied hydrogen. That is, two internal spaces S1 and S2 of the first connecting pipe 23 and the second connecting pipe 24 exist between the main body 21 of the inner pipe 2, through which liquefied hydrogen flows during operation, and the protruding end 22. These two internal spaces S1 and S2 function as buffer spaces for the liquefied hydrogen present in the internal space S0 of the main body 21.

[0030] As described above, cutting and welding work that generates fire is performed on the protruding end 22 during the expansion. Since liquefied hydrogen or hydrogen gas is flammable, it is desirable to interpose a space filled with an inert gas between the main body 21 and the protruding end 22. By adopting the triple block structure of this embodiment, as shown in FIG. 2(A), it is possible to fill the internal space S1 with hydrogen gas and the internal space S2 with nitrogen gas. Since the internal space S2 adjacent to the internal space S3 of the protruding end 22 is in a nitrogen gas atmosphere, work that generates fire can be performed on the protruding end 22. In addition, if the internal space S1 adjacent to the internal space S0 of the main body 21 through which liquefied hydrogen flows is, for example, in a nitrogen gas atmosphere, the nitrogen gas may solidify due to the cold heat of the liquefied hydrogen, and a problem may occur in which solidified nitrogen adheres to the first valve 51. However, in this embodiment, the internal space S1 in which the hydrogen gas atmosphere is set to be adjacent to the internal space S0, so that the above problem can be avoided.

[0031] [Second embodiment] FIG. 3 is a diagram showing a schematic diagram of an end structure TR2 of a vacuum insulated double pipe 1 according to the second embodiment. The end structure TR2 is applied to the end 1E of a vacuum insulated double pipe 1 having an inner pipe 2, an outer pipe 3, and a vacuum insulation layer 4, as in the first embodiment. The difference from the first embodiment is that the cutoff mechanism 5A is composed of a first valve 51A and a second valve 52A arranged at an interval from each other in the pipe axis direction of the inner pipe 2, and one connecting pipe 26 that communicates between these valves. In the second embodiment, a double block structure in which two valves, that is, two space blocks, are arranged between the main body 21 and the protruding end 22 of the inner pipe 2 is illustrated.

[0032] The first valve 51A is opened or closed to switch between communication and cut-off between the internal space S0 of the main body 21 and the internal space S11 of the connecting pipe 26. The second valve 52A is opened or closed to switch between communication and cut-off between the internal space S11 of the connecting pipe 26 and the internal space S12 of the protruding end 22. The protruding end 22 includes a protruding portion 22A that protrudes outward beyond the edge 3E of the outer pipe 3 at the terminal end 1E, and the opening of the edge is sealed by a cap portion 25. An end seal 31 is attached to the edge 3E of the outer pipe 3.

[0033] The cold storage chamber 6 is attached to the end 1E of the vacuum insulated double pipe 1 so as to cover the protruding portion 22A and the edge 3E of the outer pipe 3. The internal space S13 of the cold storage chamber 6 is subjected to evacuation, inert gas replacement, etc. Also, a first nozzle 71A for purging the internal space S11 of the connecting pipe 26 and a second nozzle 72A for purging the internal space S12 of the protruding end 22 are provided.

[0034] When the vacuum insulated double pipe 1 is used for the transfer of liquefied hydrogen, the first valve 51A and the second valve 52A are closed during operation, and liquefied hydrogen flows through the internal space S0 of the main body 21 of the inner pipe 2. The internal spaces S11 and S12 are filled with hydrogen gas. During the expansion work, nitrogen gas is introduced from the second nozzle 72A, and the hydrogen gas in the internal space S12 is replaced with nitrogen gas. In this case, it is desirable to strictly manage the sealing property of the second valve 52A so that the hydrogen gas in the internal space S11 does not flow into the internal space S12 through the second valve 52A. Thereafter, as in the first embodiment, the cold storage chamber 6 and the protruding end 22 are cut in sequence, and the vacuum insulated double pipe for expansion is welded and connected. When the vacuum insulated double pipe 1 is used for the transfer of liquefied natural gas, the internal spaces S11 and S12 may be filled with an inert gas such as nitrogen gas.

[0035] FIG. 4 is a diagram showing a termination structure TR2A of the vacuum heat-insulating double pipe 1 according to a modified example of the second embodiment. When liquefied hydrogen is circulated through the main body 21 of the inner pipe 2, it is necessary to fill the internal space S11 of the connecting pipe 26 adjacent to the internal space S0 of the main body 21 with hydrogen gas. This is because, for example, if nitrogen gas is filled into the internal space S11, a problem may occur in which solidified nitrogen adheres to the first valve 51A due to the cold heat of the liquefied hydrogen. It is desirable to avoid cutting and welding the protruding end 22 adjacent to the connecting pipe 26 containing hydrogen gas during the extension process, which may generate fire. The termination structure TR2A has a structure that takes this into consideration.

[0036] The termination structure TR2A is the same as the termination structure TR2 in FIG. 3, except for the sealing structure of the edge opening of the protruding end 22 and the cold insulation cover 62 that covers the protruding portion 22A. The structure related to the differences will be described below. The protruding end 22 has a flange-type sealing portion instead of the cap portion 25. An edge flange 22F is provided on the periphery of the edge opening of the protruding end 22. The edge opening is sealed by attaching a bolt-fastened flange lid 27 to the edge flange 22F. That is, the internal space S12 is made a closed space by attaching the flange lid 27 to the edge flange 22F, and the internal space S12 can be opened by removing the flange lid 27.

[0037] The cold insulation cover 62 is a casing having a cavity capable of accommodating the protruding portion 22A having a flange-type sealing portion consisting of the edge flange 22F and the flange lid 27, and the edge 3E of the outer pipe 3. The cold insulation cover 62 has an attachment opening having a flange portion 63. A receiving flange 32 is attached to the outer periphery of the outer pipe 3 at the end 1E of the vacuum insulated double pipe 1. The cold insulation cover 62 is fitted onto the end 1E so that the flange portion 63 of the cold insulation cover 62 faces the receiving flange 32. Thereafter, the flange portion 63 is fixed to the receiving flange 32 by bolting or the like. In other words, the cold insulation cover 62 can be attached to and detached from the outer pipe 3 by fastening and releasing the bolts.

[0038] An example of the work of adding a vacuum insulated double pipe in the termination structure TR2A of FIG. 4 will be described. In this case, a flange is attached to the edge of the inner pipe of the double pipe to be added. In the case of the vacuum insulated double pipe 10 for addition shown in FIG. 2(A), the edge of the protruding end 202 of the inner pipe 20 is provided with an edge flange the same as the edge flange 22F shown in FIG. 4. During operation of the vacuum insulated double pipe 1, liquefied hydrogen flows through the internal space S0 of the main body 21 of the inner pipe 2, and hydrogen gas is filled in the internal spaces S11 and S12. The internal space S13 of the cold insulation cover 62 is evacuated, nitrogen gas is sealed in, and the like. It is also possible to adopt a cold insulation structure in which a cold insulation sheet is wrapped around the protruding end 22 and then the cold insulation cover 62 is fitted on the outside.

[0039] During the expansion work, a purging work is performed using the second nozzle 72A to replace the hydrogen gas in the internal space S12 with nitrogen gas. Of course, the first valve 51A and the second valve 52A are closed. Next, the bolts of the flange portion 63 are released and the cold insulation cover 62 is removed. After that, the flange cover 27 is removed from the edge flange 22F of the protruding end portion 22. These operations result in an expansion standby state. Next, the inner pipe 20 of the vacuum insulated double pipe 10 for expansion is flange-connected to the edge flange 22F of the protruding end portion 22. Furthermore, a joint cover that covers the inner pipe connection portion is attached using the receiving flange 32, etc.

[0040] According to the termination structure TR2A relating to the modified example of the second embodiment, the cold insulation cover 62 is detachable from the outer pipe 3, and the protruding end 22 has a flange-type sealing portion. Therefore, the internal space S12 of the protruding end 22 can be opened and sealed, that is, the inner pipe 20 can be extended, without cutting or welding the protruding end 22. Therefore, even if hydrogen gas is present in the internal space S11 of the connecting pipe 26 adjacent to the internal space S12, the termination structure TR2A does not require work involving fire when extending the pipe, so explosion-proof properties can be ensured.

[0041] [Third embodiment] 5 is a schematic diagram showing the end structure TR3 of the vacuum insulated double pipe 1 according to the third embodiment. The end structure TR3 is applied to the end 1E of the vacuum insulated double pipe 1 having the inner pipe 2, the outer pipe 3, and the vacuum insulation layer 4, as in the first and second embodiments. The difference from the first and second embodiments is that the cutoff mechanism 5B is composed of one valve 51B. That is, the third embodiment illustrates a single block structure in which only one valve 51B is disposed between the main body 21 and the protruding end 22 of the inner pipe 2.

[0042] By opening and closing the valve 51B, the communication between the internal space S0 of the main body 21 and the internal space S11 of the connecting pipe 26 is switched between open and closed. The protruding end 22 includes a protruding portion 22A that protrudes outward from the end edge 3E of the outer pipe 3 at the end 1E, and the opening of the end edge is sealed with a cap portion 25. The flange-type sealing portion shown in FIG. 4 may be used instead of the cap portion 25. An end seal 31 is attached to the end edge 3E of the outer pipe 3. The cold storage chamber 6 is attached to the end 1E of the vacuum insulated double pipe 1 so as to cover the protruding portion 22A and the end edge 3E of the outer pipe 3. A nozzle 71B is attached to the protruding end 22 for purging the internal space S21 of the protruding end 22.

[0043] When the vacuum insulated double pipe 1 is used to transport liquefied hydrogen, the valve 51B is closed during operation, and liquefied hydrogen flows through the internal space S0 of the main body 21 of the inner pipe 2. The internal space S21 of the protruding end 22 is filled with hydrogen gas. The internal space S22 of the cold-storage chamber 6 is subjected to evacuation, inert gas replacement, and the like. During expansion work, the cold-storage chamber 6 and the protruding end 22 are cut in order, and welded to the vacuum insulated double pipe to be expanded.

[0044] According to the termination structure TR3 of the third embodiment, the protruding end 22 of the inner pipe 2 is provided at the termination 1E of the vacuum thermal insulation double pipe 1. The presence of this protruding end 22 can facilitate subsequent work such as the addition of the vacuum thermal insulation double pipe 1 and inspection of the inner pipe 2. In addition, the protruding portion 22A of the protruding end 22 is covered by the cold storage chamber 6, and the protruding end 22 and the main body 21 of the inner pipe 2 are spatially blocked by the blocking mechanism B (valve 51B). This not only provides mechanical protection for the protruding portion 22A, but also suppresses heat input from the protruding portion 22A to the main body 21 and ice formation on the surface of the protruding portion 22A.

[0045] [Summary of this disclosure] The specific embodiments described above include disclosures having the following configurations.

[0046] The termination structure of a vacuum insulated multi-pipe according to a first aspect of the present disclosure is a termination structure of a vacuum insulated multi-pipe including an inner pipe through which a low-temperature fluid flows, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, and is equipped with a protruding end of the inner pipe including a protruding portion protruding outward beyond an end edge of the outer pipe, a cold insulation cover covering the protruding end and the end edge of the outer pipe, and a blocking mechanism located between a main body portion of the inner pipe covered by the outer pipe and the protruding end, separating the main body portion of the inner pipe from the protruding end.

[0047] According to the first aspect, a protruding end of the inner pipe is provided at the end of the vacuum thermal insulation multi-wall pipe. The presence of this protruding end facilitates subsequent work such as the installation of additional vacuum thermal insulation multi-wall pipes and inspection of the inner pipe. The protruding portion is covered with a cold insulation cover, and the protruding end and the main body of the inner pipe are separated by a blocking mechanism. This not only provides mechanical protection for the protruding portion, but also suppresses heat input from the protruding end to the main body of the inner pipe and ice formation on the surface of the protruding portion.

[0048] The termination structure of a vacuum insulated multi-pipe in the second aspect is the termination structure of the first aspect, in which the cold insulation cover includes a cavity that accommodates the protruding portion and the end edge of the outer pipe, and is a cold insulation chamber that is attached to the outer pipe in a state where the cavity can be evacuated.

[0049] According to the second aspect, a vacuum insulation structure can be constructed even in the region of the protruding portion at the end of the vacuum insulation multi-wall pipe. Therefore, even if the fluid flowing through the inner pipe is an extremely low-temperature fluid that liquefies air, the occurrence of liquefied air and ice formation on the surface of the protruding portion can be suppressed.

[0050] The termination structure of a vacuum insulated multi-wall pipe according to a third aspect is the termination structure of the first or second aspect, wherein the blocking mechanism includes a first valve and a second valve arranged at intervals in the axial direction of the inner pipe, and a connecting pipe connecting between the first valve and the second valve.

[0051] According to the third aspect, two spatial blocks, the first valve and the second valve, are interposed between the main body and the protruding end of the inner pipe. This makes it possible to further suppress the transfer of cold energy from the low-temperature fluid flowing through the main body of the inner pipe to the protruding end and the input of heat from the protruding end to the main body. In addition, when installing additional vacuum insulated multi-wall pipes, the internal space of the connecting pipe can be used as a buffer space, improving the workability of the installation work.

[0052] The termination structure of a vacuum insulated multi-pipe according to a fourth aspect is the termination structure of the first or second aspect, wherein the blocking mechanism includes a first valve, a second valve and a third valve arranged at intervals from each other in the axial direction of the inner pipe, a first connecting pipe connecting the first valve and the second valve, and a second connecting pipe connecting the second valve and the third valve.

[0053] According to the fourth aspect, three spatial blocks, the first valve, the second valve, and the third valve, are interposed between the main body and the protruding end of the inner pipe. Therefore, heat transfer between the main body and the protruding end of the inner pipe can be further suppressed. In addition, the two internal spaces of the first connecting pipe and the second connecting pipe can be used as buffer spaces between the main body and the protruding end of the inner pipe. Therefore, even if the fluid flowing through the inner pipe is a liquefied gas that is flammable and has the cold heat to liquefy air, it is possible to use the two buffer spaces to prevent it from affecting various operations on the protruding end.

[0054] The termination structure of a vacuum insulated multi-wall pipe in accordance with the fifth aspect is the termination structure of the third aspect, wherein the protruding end has an opening at the edge of the protruding portion and a flange-type sealing portion that seals the opening, and the cold insulation cover has a cavity that accommodates the protruding portion including the sealing portion and the edge of the outer pipe.

[0055] According to the fifth aspect, the protruding end has a flange-type sealing portion. Therefore, by removing the cold insulation cover and opening the sealing portion, it is possible to perform additional connection of the inner pipe and inspection of the inner pipe. In other words, the internal space of the protruding end can be opened and sealed without cutting or welding the protruding end. Therefore, even if the low-temperature fluid is a liquid that requires explosion-proof measures such as liquefied hydrogen, work on the protruding end can be performed while ensuring explosion-proof properties.

[0056] The sixth aspect of the termination structure of a vacuum insulated multi-wall pipe is the termination structure of the fourth aspect, wherein the protruding end has a cap portion that is non-detachably attached to the edge of the protruding portion, and the cold storage cover has a cavity that accommodates the protruding portion including the cap portion and the edge of the outer pipe.

[0057] According to the sixth aspect, the edge of the protruding portion is sealed with a cap, so that the inner and outer spaces of the protruding end can be completely separated. Also, since there are two buffer spaces between the main body of the inner pipe and the protruding end, even if the low-temperature fluid is liquefied hydrogen, work that may generate fire can be performed on the protruding end. For example, when opening the internal space of the protruding end, work can be performed such as cutting the protruding end or welding an additional inner pipe to the protruding end. [Explanation of symbols]

[0058] 1. Vacuum insulated double pipe (vacuum insulated multi-pipe) 1E Termination 2 Inner tube 21 Main body 22 Projecting end 22F Edge flange 23 First connecting pipe 24 Second connecting pipe 25 Cap section 26 Connecting pipe 27 Flange lid (flange type sealing part) 3 outer tube 3E Edge 4. Vacuum insulation layer 5, 5A, 5B cutoff mechanism 51, 51A First valve 52, 52A Second valve 53 Third valve 6 Cooling chamber (cooling cover) 62 Cooling cover TR1, TR2, TR2A, TR3 termination structure S0, S1, S2, S3 interior space

Claims

1. A termination structure of a vacuum insulation multi-wall pipe including an inner pipe through which a low-temperature fluid flows, an outer pipe covering the inner pipe, and a vacuum insulation layer between the inner pipe and the outer pipe, a protruding end portion of the inner tube including a protruding portion protruding outward beyond an edge of the outer tube; a cold insulation cover covering the protruding portion and an end edge of the outer tube; A termination structure for a vacuum insulated multi-pipe, comprising: a blocking mechanism positioned between a main body portion of the inner pipe covered by the outer pipe and the protruding end portion, which separates the main body portion of the inner pipe from the protruding end portion.

2. The end structure of the vacuum insulation multi-wall pipe according to claim 1, The cold insulation cover is a cold insulation chamber that includes a cavity that accommodates the protruding portion and the end edge of the outer pipe and is attached to the outer pipe in a state where the cavity can be evacuated.

3. The end structure of the vacuum insulation multi-wall pipe according to claim 1, The shutoff mechanism includes a first valve and a second valve arranged at intervals in the axial direction of the inner pipe, and a connecting pipe connecting the first valve and the second valve.

4. The end structure of the vacuum insulation multi-wall pipe according to claim 1, The shutoff mechanism includes a first valve, a second valve, and a third valve arranged at intervals in the axial direction of the inner pipe, a first connecting pipe connecting the first valve and the second valve, and a second connecting pipe connecting the second valve and the third valve.

5. The end structure of the vacuum insulation multi-wall pipe according to claim 3, The protruding end portion has an opening at an edge of the protruding portion and a flange-type sealing portion that seals the opening, The cold insulation cover has a cavity that accommodates the protruding portion including the sealing portion and an end edge of the outer pipe, in a termination structure of a vacuum insulated multi-wall pipe.

6. The end structure of the vacuum insulation multi-wall pipe according to claim 4, the protruding end portion has a cap portion non-removably attached to an edge of the protruding portion; The cold insulation cover has a cavity that accommodates the protruding portion including the cap portion and an end edge of the outer pipe, forming an end structure of a vacuum insulated multi-wall pipe.

Images