Pipe unit for liquefied gas and method for assembling the same

Abstract

A pipe unit (1) for transporting liquefied gas has: a first double pipe (3A) having a first inner pipe (5A) through which the liquefied gas passes and a first outer pipe (9A) covering the first inner pipe (5A) with a vacuum layer (7) interposed; a second double pipe (3B) having a second inner pipe (5B) through which the liquefied gas passes and a second outer pipe (9B) covering the second inner pipe (5B) with a vacuum layer (7) interposed, the second inner pipe (5B) being connected to the first inner pipe (5A); a cover pipe (13) covering a connecting portion (11) of the first inner pipe (5A) and the second inner pipe (5B) with a vacuum layer (23) interposed; and a communication path (35) communicating the vacuum layer (7) of the first double pipe (3A), the vacuum layer (7) of the second double pipe (3B), and the vacuum layer (7) in the cover pipe (13).

Description

[0001] Related applications

[0002] This application claims priority to Japanese Patent Application No. 2024-028624, filed on February 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to piping units for liquefied petroleum gas and methods for assembling them. Background Technology

[0004] Previously, for piping used to transport liquefied gases such as liquefied natural gas and liquefied hydrogen, a solution using a double-layered vacuum insulated pipe has been proposed (for example, see Patent Document 1). This double-layered piping has a structure in which an outer pipe covers an inner pipe through a vacuum insulation layer, thus achieving high insulation performance and effectively suppressing the temperature rise of the low-temperature liquefied gas flowing inside the inner pipe.

[0005] Typically, such double-layer piping is manufactured by dividing the piping system into multiple blocks, which are then connected to form a piping unit. This configuration creates a vacuum layer in each block, making it easier to pinpoint the cause of vacuum degradation after installation and use.

[0006] Furthermore, double-layer piping has auxiliary components between the inner and outer pipes for support and maintaining the gap. In liquefied gas double-layer piping, a high vacuum is required between the inner and outer pipes, making the installation of piping units composed of double-layer piping complex. Therefore, conventionally, after assembling the individual double-layer piping components, they were transported to the installation site, where installation could be completed with simple operations such as connecting the double-layer piping to each other. This allows for high-precision and high-efficiency assembly and installation of double-layer piping units, which require highly skilled personnel.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2022-064652 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, when re-vacuuming a double-layered piping unit already installed in a designated facility, depending on the location of the cause of vacuum deterioration, there may be situations requiring large-scale scaffolding or difficulties in connecting vacuum pumps. Furthermore, when re-vacuuming the entire double-layered piping system for routine maintenance, it is necessary to connect vacuum pumps to each of multiple sections. In addition, such equipment contains numerous double-layered piping units, resulting in a large number of vacuum spaces requiring re-vacuuming. Therefore, in large-scale double-layered piping systems, the period for confirming vacuum deterioration and re-vacuuming operations may become lengthy.

[0012] The purpose of this disclosure is to address the aforementioned issues by enabling more efficient re-vacuuming operations for double-layer piping units that are constructed by dividing them into multiple blocks.

[0013] Methods for solving problems

[0014] To achieve the above objectives, the liquefied gas piping unit disclosed herein is used for transporting liquefied gas, wherein the liquefied gas piping unit comprises: a first double-layer piping having a first inner pipe through which the liquefied gas passes and a first outer pipe covering the first inner pipe with a vacuum layer; a second double-layer piping having a second inner pipe through which the liquefied gas passes and a second outer pipe covering the second inner pipe with a vacuum layer, the second inner pipe being connected to the first inner pipe; a cover pipe covering the connection portion between the first inner pipe and the second inner pipe with a vacuum layer; and a connecting passage connecting the vacuum layer of the first double-layer piping, the vacuum layer of the second double-layer piping, and the vacuum layer inside the cover pipe.

[0015] Furthermore, any combination of at least two constituent elements disclosed in the claims and / or description and / or drawings is included in this disclosure. In particular, any combination of two or more claims recited in the claims is included in this disclosure. Attached Figure Description

[0016] This disclosure will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of this disclosure. The scope of this disclosure is determined by the appended claims. In the drawings, the same part numbers in the plurality of drawings denote the same parts.

[0017] Figure 1 This is a longitudinal sectional view showing a schematic structure of a liquefied gas piping unit according to one embodiment of the present disclosure.

[0018] Figure 2 It is shown Figure 1 A simplified flowchart of the assembly method for liquefied gas piping units.

[0019] Figure 3 It is shown Figure 2 A longitudinal sectional view of an example of the state of a liquefied gas piping unit in the vacuum destruction step of the assembly method.

[0020] Figure 4 This is a longitudinal sectional view showing a schematic structure of a liquefied gas piping unit according to other embodiments of the present disclosure.

[0021] Figure 5 It is shown Figure 4 A simplified flowchart of the assembly method for liquefied gas piping units.

[0022] Figure 6 The diagram illustrates the structure of a liquefied gas piping unit according to one embodiment of the present disclosure, which facilitates re-vacuuming in the field.

[0023] Figure 7 It is shown Figure 6 A diagram showing the details of Part VII. Detailed Implementation

[0024] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. Figure 1 A liquefied gas piping unit 1 according to one embodiment of the present disclosure is shown. In the following description, this liquefied gas piping unit 1 will be simply referred to as "piping unit 1". Piping unit 1 is used for the transportation of liquefied gas. Piping unit 1 has a plurality of interconnected double-layer pipes 3. That is, piping unit 1 is composed of a plurality of blocks, i.e., double-layer pipes 3. Each double-layer pipe 3 has an inner pipe 5 through which liquefied gas passes and an outer pipe 9 covering the inner pipe 5 through a vacuum layer 7. Piping unit 1 also has a cover pipe 13 covering the connection portion 11 between the double-layer pipes 3. In the following description, the vacuum layer 7 formed on the double-layer pipes 3 will be referred to as "piping vacuum layer 7".

[0025] In this specification, one of the two interconnected double-layer pipes 3 is referred to as "first double-layer pipe 3A", and the other double-layer pipe 3 is referred to as "second double-layer pipe 3B". Furthermore, the inner pipe 5 and outer pipe 9 of the first double-layer pipe 3A are referred to as "first inner pipe 5A" and "first outer pipe 9A", respectively, and the inner pipe 5 and outer pipe 9 of the second double-layer pipe 3B are referred to as "second inner pipe 5B" and "second outer pipe 9B", respectively. However, since the first double-layer pipe 3A and the second double-layer pipe 3B can have the same structure, they are simply referred to as "double-layer pipe 3", "inner pipe 5", and "outer pipe 9" when describing common aspects of these double-layer pipes 3.

[0026] Piping unit 1 is used, for example, in liquefied gas storage facilities such as liquefied gas storage ships or land-based liquefied gas storage bases. In this specification, "liquefied gas storage ship" refers to a vessel with the function of storing liquefied gas. Besides liquefied gas transport ships, liquefied gas storage ships also include, for example, liquefied gas fuel ships and fuel ships that supply liquefied gas to other ships. However, liquefied gas storage facilities are not limited to ships as long as they have the structure and function of storing liquefied gas; for example, they can also be land-based liquefied gas storage facilities or facilities that utilize liquefied gas.

[0027] The liquefied gas transported by piping unit 1 is, for example, liquefied petroleum gas (LPG, approximately -45°C), liquefied ethylene gas (LEG, approximately -100°C), liquefied natural gas (LNG, approximately -160°C), liquefied hydrogen (LH2, approximately -250°C), or liquefied helium (LHe, approximately -270°C). In this embodiment, liquefied hydrogen is transported via piping unit 1.

[0028] The first double-layer piping 3A and the second double-layer piping 3B are connected by connecting the first inner pipe 5A of the first double-layer piping 3A to the second inner pipe 5B of the second double-layer piping 3B. Specifically, in each double-layer piping 3, the end of the inner pipe 5 protrudes from the outer pipe 9, and the end of the first inner pipe 5A protruding from the first outer pipe 9A is connected to the end of the second inner pipe 5B protruding from the second outer pipe 9B. In the following description, the end of the first inner pipe 5A protruding from the first outer pipe 9A is referred to as "first protrusion 15A", and the end of the second inner pipe 5B protruding from the second outer pipe 9B is referred to as "second protrusion 15B". In addition, in this specification, the interconnected first protrusion 15A and second protrusion 15B are collectively referred to as "connection portion 11". In this embodiment, the first protrusion 15A and the second protrusion 15B are connected by welding. However, the first protrusion 15A and the second protrusion 15B can also be connected by other means.

[0029] The cover tube 13 covers the connection portion 11 between the first inner tube 5A and the second inner tube 5B. The cover tube 13 covers the connection portion 11 in a sealable manner. In this embodiment, as shown in the illustrated example, the cover tube 13 extends beyond the "connection portion 11" to cover the ends of the first outer tube 9A and the second outer tube 9B. This ensures a sufficient heat conduction distance and improves insulation. However, the shape of the cover tube 13 is not limited to the illustrated example. For example, the outer diameter of the cover tube 13 may be the same as the outer diameter of the first outer tube 9A and the second outer tube 9B. In this case, for example, it may be configured such that a step is formed at the ends of the first outer tube 9A and the second outer tube 9B to reduce the outer diameter, and this stepped portion is inserted and connected to the cover tube 13.

[0030] Each outer tube 9 is provided with an outer tube vacuum port 17 for evacuating the space between it and the inner tube 5 to form a piping vacuum layer 7. The outer tube vacuum port 17 is located on the portion of each outer tube 9 not covered by the cover tube 13. In this example, the outer tube vacuum port 17 is formed by an opening 19 penetrating the tube wall of the outer tube 9 and a sealing shut-off valve 21 installed in the opening 19.

[0031] Additionally, a vacuum port 25 is provided in the shroud 13 for evacuating its internal space to form a vacuum layer 23. In the following description, the vacuum layer 23 formed inside the shroud 13 will be referred to as the "shroud vacuum layer 23". In the illustrated example, the shroud vacuum port 25 is located approximately at the center of the axial direction of the shroud 13. However, the location of the shroud vacuum port 25 is not limited to this example. In this example, the shroud vacuum port 25 is formed by an opening 27 penetrating the wall of the shroud 13 and a sealing valve 29 installed in the opening 27.

[0032] In this embodiment, the cover pipe 13 comprises a plurality of segments 31. Specifically, in this example, the cover pipe 13 is formed from two segments 31 cut in half with a plane including its axis. By forming the cover pipe 13 from the segments 31, the assembly operation of the piping unit 1, which will be detailed later, becomes easier. However, it is not necessary to form the cover pipe 13 from the segments 31; it can also be formed as a single pipe. Furthermore, when the cover pipe 13 is formed from a plurality of segments 31, the segmentation method is not limited to the example described above.

[0033] The piping unit 1 of this embodiment has a connecting passage 35 that connects the piping vacuum layer 7 of the first double-layer piping 3A, the piping vacuum layer 7 of the second double-layer piping 3B, and the cover pipe vacuum layer 23. Specifically, in this embodiment, the connecting passage 35 is formed in the portion of the first outer pipe 9A and the second outer pipe 9B covered by the cover pipe 13. More specifically, the connecting passage 35 is formed by connecting holes 39 formed in the pipe walls of the first outer pipe 9A and the second outer pipe 9B, which can be closed by sealing bolts 37. As will be detailed later, during the assembly of the piping unit 1, each connecting hole 39 is closed by the sealing bolts 37 shown by the dashed lines in the figure, but when the piping unit 1 is assembled, the sealing bolts 37 are removed, leaving each connecting hole 39 open. Alternatively, the connecting holes 39 can also be closed by installing a vacuum flange instead of by using sealing bolts.

[0034] Next, the assembly method of the piping unit 1 of this embodiment described above will be explained. In addition, in the following description, each step will sometimes be referred to as "...step SN" (N: integer) as needed, but "N" is a number added to facilitate the distinction between each step, and does not necessarily indicate the time sequence relationship between the steps unless otherwise specified.

[0035] like Figure 2 As shown, the assembly method of this embodiment includes the following steps: preparing a required number, for example, two double-layer pipes 3; connecting the first inner pipe 5A and the second inner pipe 5B; breaking the vacuum layer 7 of the pipes of the first double-layer pipe 3A and the second double-layer pipe 3B; then covering the connection portion 11 with a cover pipe 13; and evacuating a vacuum from at least one of the cover pipe 13, the first outer pipe 9A, and the second outer pipe 9B. In the following description, these steps will be referred to sequentially as "double-layer pipe preparation step S1", "inner pipe connection step S2", "vacuum breaking step S3", "covering step S4", and "vacuum evacuation step S5".

[0036] In the double-layer piping preparation step S1, after assembling the inner pipe 5 and the outer pipe 9, the space between the inner pipe 5 and the outer pipe 9 is evacuated while the connecting passage 35 is closed to create the double-layer piping 3. When assembling the inner pipe 5 and the outer pipe 9, appropriate structural components such as spacers to ensure the distance between the inner pipe 5 and the outer pipe 9, and expansion joints such as bellows to absorb the difference in thermal shrinkage between the inner pipe 5 and the outer pipe 9 can be used as needed. In this example, the connecting passage 35 is closed by inserting a sealing plug 37 into the connecting hole 39. Vacuuming is performed by connecting a vacuum pump to the vacuum port provided on the outer pipe 9. A piping vacuum layer 7 is formed by evacuating the vacuum.

[0037] In the inner tube connection step S2, the first inner tube 5A and the second inner tube 5B are connected by connecting the first protrusion 15A of the first inner tube 5A to the second protrusion 15B of the second inner tube 5B. As described above, the connection between the first protrusion 15A and the second protrusion 15B is performed, for example, by welding, but it can also be performed by other methods.

[0038] In vacuum breaking step S3, the connecting passages 35 of the first double-layer pipe 3A and the second double-layer pipe 3B are opened to break the vacuum layer 7 of each pipe. In this example, as... Figure 3As shown, vacuum breaking is performed as follows: the operating device 41 is installed on the sealing valve 21 of the vacuum port 17 of the outer tube; the operating device 41 is operated to open the sealing valve 21; and the sealing plug 37 inserted into the communication hole 39 of the outer tube 9 is removed. More specifically, the operating device 41 is operated to open the sealing valve 21, and dry gas is supplied to the vacuum layer 7 from the dry gas cylinder connected to the operating device 41. If the vacuum layer 7 reaches atmospheric pressure or above, the sealing plug 37 is opened. During this operation, it is preferable to continuously supply a small flow of dry gas to prevent moisture from entering. By performing vacuum breaking in this sequence, the sealing plug 37 can be easily removed to open the communication path 35. Furthermore, the method of vacuum breaking is not limited to the example described above; for example, it can also be performed simply by removing the sealing plug 37 inserted into the communication hole 39 of the outer tube 9.

[0039] In this embodiment, during further vacuum breaking, dry gas is introduced into the piping vacuum layer 7. Specifically, in this example, the aforementioned vacuum breaking operation is performed with the dry gas supply source 43 connected to the operating device 41. In this embodiment, nitrogen is used as the dry gas, but the type of dry gas is not limited to this. Furthermore, in the illustrated example, a dry gas cylinder is used as the dry gas supply source 43, but the dry gas supply source 43 is not limited to this; for example, it could also be a gasbag sealed with dry gas.

[0040] Then, in the covering step S4, after covering the connection portion 11 between the first inner tube 5A and the second inner tube 5B with the cover tube 13, in the vacuuming step S5, vacuuming is performed from at least one of the cover tube 13, the first outer tube 9A, and the second outer tube 9B. In this embodiment, a vacuum pump is connected to the vacuum port 25 of the cover tube, and vacuuming is performed from the cover tube 13. In this embodiment, by forming a connecting path 35, vacuuming is performed from only one of the cover tube 13, the first outer tube 9A, and the second outer tube 9B, thereby forming the first double-layer piping 3A, the second double-layer piping 3B, and all the vacuum layers of the cover tube 13, and making these vacuum layers interconnected. However, vacuuming can also be performed from the first outer tube 9A or the second outer tube 9B. Alternatively, vacuuming can be performed from two of the cover tube 13, the first outer tube 9A, and the second outer tube 9B.

[0041] Figure 4 A liquefied gas piping unit 1 is shown as another embodiment of this disclosure. In the following description, the description will primarily focus on [the gas] and [other components]. Figures 1-3 The differences between the embodiments described together will be explained, while the description of structures common to the embodiments will be omitted.

[0042] In this embodiment, the connecting path 35 is formed by connecting pipes 45 that connect the portions of the first outer pipe 9A and the second outer pipe 9B that are not covered by the cover pipe 13 to the cover pipe 13. In this example, an on / off valve 47 is provided in each connecting pipe 45.

[0043] Next, the assembly method of the piping unit 1 according to other embodiments described above will be described. In the following description, only the methods of assembly with and will be discussed. Figures 1-3 The differences between the embodiments described together will be explained, while the description of structures common to the embodiments will be omitted.

[0044] like Figure 5 As shown, the assembly method of this embodiment includes the following steps: preparing the required quantity, for example, two double-layer pipes 3; connecting a portion of the cover pipe 13, the first double-layer pipe 3A, and the second double-layer pipe 3B using a connecting pipe 45; connecting the first inner pipe 5A and the second inner pipe 5B; covering the connection portion 11 of the first inner pipe 5A and the second inner pipe 5B with the remaining portion of the cover pipe 13; evacuating the internal space of the cover pipe 13; and opening the connecting pipe 45. In the following description, these steps will be referred to sequentially as "double-layer pipe preparation step S11", "double-layer pipe connection step S12", "inner pipe connection step S13", "covering step S14", "cover pipe evacuation step S15", and "connecting pipe opening step S16".

[0045] In the double-layer piping preparation step S11, after assembling the inner pipe 5 and the outer pipe 9, the space between the inner pipe 5 and the outer pipe 9 is evacuated to create the double-layer piping 3. When assembling the inner pipe 5 and the outer pipe 9, structural components such as spacers to ensure the distance between the inner pipe 5 and the outer pipe 9, and expansion-reducing components such as bellows to absorb the difference in thermal shrinkage between the inner pipe 5 and the outer pipe 9 can be used as needed.

[0046] In the double-layer piping connection step S12, a portion of the cover pipe 13, the first double-layer piping 3A, and the second double-layer piping 3B are connected via a closed connecting pipe 45. In this example, the closed state of the connecting pipe 45 is achieved by closing the on / off valve 47. The "part of the cover pipe 13" connected in the double-layer piping connection step S12 is, for example, one of the segments 31 in the case where the cover pipe 13 is formed by multiple segments 31. Furthermore, the connection between the connecting pipe 45 and the aforementioned pipes is, for example, performed by a weld-based connection, but other methods may also be used.

[0047] In the inner tube connection step S13, the first inner tube 5A and the second inner tube 5B are connected by connecting the first protrusion 15A of the first inner tube 5A and the second protrusion 15B of the second inner tube 5B. As described above, the connection between the first protrusion 15A and the second protrusion 15B is performed, for example, by welding, but it can also be performed by other methods.

[0048] In the covering step S14, the remaining portion of the cover tube 13 is used to cover the connection portion 11 between the first inner tube 5A and the second inner tube 5B. Here, "the remaining portion of the cover tube 13" refers to all the segments 31 other than the segments 31 connected to the connecting tube 45, for example, in the case where the cover tube 13 is formed by multiple segments 31.

[0049] In the vacuuming step S15, a vacuum pump is connected to the vacuum port 25 of the cover tube to evacuate the cover tube 13, thereby forming the internal space of the cover tube 13 into a vacuum layer 23.

[0050] In the connecting pipe opening step S16, the closed connecting pipe 45 is opened. In this example, the connecting pipe 45 is opened by opening the on / off valve 47, forming a connecting path 35, which enables the first double-layer piping 3A, the second double-layer piping 3B, and all the vacuum layers of the cover pipe 13 to be connected.

[0051] and Figure 2 and Figure 3 The methods of the embodiments shown are different, according to Figure 5 The method of this embodiment shown can connect the vacuum layers without breaking the vacuum of the double-layer piping 3. Therefore, during assembly, there is no risk of moisture flowing into the piping vacuum layer 7, and the step of suppressing moisture inflow during vacuum breaking as described above can be omitted.

[0052] Next, a method for efficiently re-vacuuming the piping unit 1 set up by the above method will be described. Figure 6 This diagram illustrates the structure that facilitates the re-vacuuming of piping unit 1 at the site. For simplicity, detailed illustrations of piping unit 1 and other elements are omitted. The re-vacuuming method of this embodiment is a method for re-vacuuming multiple piping units 1, and includes the following steps: guiding the vacuum layers 7 and 23 within the multiple piping units 1 to a shared work area, and using a shared vacuum pump P to evacuate the vacuum layers 7 and 23 within the piping unit 1.

[0053] exist Figure 6In the example shown, in an LPG storage facility that serves as an example of an LPG piping system, multiple piping units 1 are installed on upper and lower piping racks 51 located at a height above ground level GL. However, the arrangement of the multiple piping units 1 is not limited to the example shown. The multiple piping units 1 on each floor are connected by... Figure 2 or Figure 5 They can be interconnected by any of the methods mentioned and described above. The number of interconnected piping units 1 can be arbitrarily determined.

[0054] For each vacuum space formed by multiple interconnected piping units 1, a representative vacuum evacuation point is predetermined. The representative vacuum evacuation point could be, for example, a... Figure 1 The outer tube vacuum port 17 and the cover tube vacuum port 25 of the piping unit 1. Alternatively, the vacuuming point can also be a dedicated vacuum port separately provided on the outer tube 9 or the cover tube 13. In addition, the vacuuming point can also be a part where the vacuuming piping 53 is directly connected to the outer tube 9 or the cover tube 13 by means of welding, for example.

[0055] This indicates the connection between the vacuuming section and the vacuuming piping 53. Figure 6 Three vacuum piping units 53 are shown. More specifically, the vacuum piping units 53 are connected to an upper piping unit 1, a lower piping unit 1, and a piping unit 1 (not shown), respectively. Additionally, as... Figure 7 As shown in the detailed diagram, the vacuum piping 53, connected to a piping unit 1 on the upper level, is connected to a cover pipe 13 representing the vacuuming location. These multiple vacuum piping 53 extend to a common work area. In this example, each vacuum piping 53 extends to a common work area near the ground GL. The term "work area" here refers to each site where the re-vacuuming operation of piping unit 1 is performed using a vacuum pump. The "common work area" refers to a work area where the re-vacuuming operation of multiple piping units 1 can be performed sequentially or simultaneously without moving the vacuum pump. There can be multiple work areas, and the number of work areas can be arbitrarily determined based on considerations such as the number of piping units, their configuration, and ease of maintenance. The location of the work area is not limited to the ground level and can also be located in corridors, scaffolding, etc., within the liquefied gas storage equipment.

[0056] The vacuum piping 53 has an access vacuum port 55 for connecting the vacuum pump P. A vacuum valve is provided at the access vacuum port 55. The vacuum valve can be, for example, an angle vacuum valve, a linear vacuum valve, or a shut-off valve. Multiple access vacuum ports 55 are arranged adjacently in a common work area. The vacuum pump P can be sequentially connected to multiple access vacuum ports 55 adjacent to each other in a common work area to continuously re-evacuate multiple vacuum spaces formed by the interconnected vacuum layers 7 and 23. Alternatively, the vacuum pump P can be simultaneously connected to multiple access vacuum ports 55 adjacent to each other in a common work area to simultaneously re-evacuate multiple vacuum spaces formed by the interconnected vacuum layers 7 and 23.

[0057] The vacuum port 55 for connection does not necessarily need to be located near the ground GL, but if it is located in a work area near the ground GL, vacuuming operations can be performed without lifting the vacuum pump onto beams, columns, or pipe racks. Therefore, the movement of the vacuum pump P is minimized and easy, and the previously required access corridor or maintenance platform for maintenance is no longer needed on the pipe rack 51, thus simplifying maintenance and improving equipment safety. Furthermore, re-vacuuming can be performed from the designated vacuuming point, which can also be omitted. Figure 6 The illustrated vacuum piping 53 and the vacuum port 55 are shown.

[0058] The first embodiment of the liquefied gas piping unit 1 disclosed herein is a piping unit 1 for conveying liquefied gas, comprising: a first double-layer piping 3A having a first inner pipe 5A through which the liquefied gas passes and a first outer pipe 9A covering the first inner pipe 5A with a vacuum layer; a second double-layer piping 3B having a second inner pipe 5B through which the liquefied gas passes and a second outer pipe 9B covering the second inner pipe 5B with a vacuum layer, the second inner pipe 5B being connected to the first inner pipe 5A; a cover pipe 13 covering the connection portion 11 of the first inner pipe 5A and the second inner pipe 5B with a vacuum layer; and a connecting passage 35 connecting the vacuum layer of the first double-layer piping 3A, the vacuum layer of the second double-layer piping 3B, and the vacuum layer inside the cover pipe 13.

[0059] According to this structure, in a piping unit with multiple double-layer piping 3, the connected double-layer piping and the vacuum layer inside the casing are connected by a connecting path, thus enabling re-vacuuming from any pipe instead of every single pipe. Therefore, the re-vacuuming operation can be made more efficient.

[0060] The second embodiment of the liquefied gas piping unit 1 disclosed herein is based on the first embodiment of the liquefied gas piping unit 1, wherein the connecting passage 35 is formed in the portions of the first outer pipe 9A and the second outer pipe 9B covered by the cover pipe 13. According to this structure, the re-vacuuming operation is made more efficient through a simple construction.

[0061] The third embodiment of the liquefied gas piping unit 1 disclosed herein is based on the second embodiment of the liquefied gas piping unit 1, wherein the connecting passage 35 is formed by connecting holes 39 formed in the walls of the first outer pipe 9A and the second outer pipe 9B, which can be closed by sealing bolts 37. According to this structure, the connecting passage 35 can be temporarily evacuated by closing the sealing bolts 37, thus enabling re-vacuuming during the assembly process via short-term vacuum breaking, thereby improving the efficiency of the assembly operation.

[0062] The fourth embodiment of the liquefied gas piping unit 1 disclosed herein is based on the first embodiment of the liquefied gas piping unit 1, wherein the connecting passage 35 is formed by a connecting pipe 45 that connects the portions of the first outer pipe 9A and the second outer pipe 9B not covered by the cover pipe 13 to the cover pipe 13, and an on / off valve 47 is provided in the connecting pipe 45. According to this structure, vacuum destruction is not required during the assembly process of the piping unit 1, and the intrusion of moisture into the vacuum layer can be suppressed.

[0063] The assembly method of the first embodiment of the liquefied gas piping unit 1 disclosed herein is a method for assembling the second or third embodiment of the liquefied gas piping unit 1, wherein the assembly method of the liquefied gas piping unit 1 includes the following steps: combining the first inner pipe 5A and the first outer pipe 9A, and evacuating the space between the first inner pipe 5A and the first outer pipe 9A to form the vacuum layer while the connecting passage 35 is closed, thereby preparing the first double-layer piping 3A; combining the second inner pipe 5B and the second outer pipe 9B, and evacuating the space between the first inner pipe 5A and the first outer pipe 9A to form the vacuum layer while the connecting passage 35 is closed. The space between the second inner tube 5B and the second outer tube 9B is evacuated to form the vacuum layer, thereby preparing the second double-layer piping 3B; the first inner tube 5A and the second inner tube 5B are connected; the connecting passage 35 is opened to break the vacuum layer of the first double-layer piping 3A and the second double-layer piping 3B; after the vacuum is broken, the connection portion 11 of the first inner tube 5A and the second inner tube 5B is covered by the cover tube 13; and a vacuum is evacuated from at least one of the cover tube 13, the first outer tube 9A and the second outer tube 9B.

[0064] According to this structure, the connecting passage 35 can be temporarily evacuated by sealing the sealing bolt 37, so that the assembly process can be re-vacuumed by short-term vacuum breaking, which can make the assembly operation more efficient.

[0065] The assembly method of the liquefied gas piping unit 1 according to the second aspect of this disclosure is based on the assembly method of the first aspect, wherein the vacuum breaking includes the step of allowing dry gas to flow into the vacuum layer. According to this structure, by allowing dry gas to flow into the vacuum layer, the intrusion of moisture into the vacuum layer can be suppressed.

[0066] The assembly method of the liquefied gas piping unit 1 according to the third aspect of this disclosure is a method for assembling the liquefied gas piping unit 1 according to the fourth aspect. The assembly method of the liquefied gas piping unit 1 includes the following steps: combining the first inner pipe 5A and the first outer pipe 9A; evacuating the space between the first inner pipe 5A and the first outer pipe 9A to form the vacuum layer, thereby preparing the first double-layer piping 3A; combining the second inner pipe 5B and the second outer pipe 9B; and assembling the space between the second inner pipe 5B and the second outer pipe 9A... The space between pipes 9B is evacuated to form the vacuum layer, thereby preparing the second double-layer piping 3B; a portion of the cover pipe 13, the first double-layer piping 3A, and the second double-layer piping 3B are connected using the closed connecting pipe 45; the first inner pipe 5A is connected to the second inner pipe 5B; the remaining portion of the cover pipe 13 covers the connection portion 11 of the first inner pipe 5A and the second inner pipe 5B; the internal space of the cover pipe 13 is evacuated; and the connecting pipe 45 is opened.

[0067] According to this structure, the assembly process of piping unit 1 does not require vacuum destruction, thus preventing moisture from entering the vacuum layer.

[0068] The re-vacuuming method of the first embodiment of the present disclosure is a method for re-vacuuming the liquefied gas piping unit 1 of any of the first to fourth embodiments. The re-vacuuming method of the liquefied gas piping unit 1 includes the following steps: guiding the vacuum layer in the plurality of liquefied gas piping units 1 to a common work site, and using a common vacuum pump to evacuate the vacuum layer in the liquefied gas piping unit 1.

[0069] According to this structure, for example, by centrally configuring the access vacuum ports of multiple re-vacuuming pipes, the vacuum layers in multiple piping units 1 can be accessed in a common work area, thus enabling efficient re-vacuuming of multiple vacuum spaces without moving the vacuum pump or with minimal movement of the vacuum pump.

[0070] The liquefied gas piping system of the first aspect of this disclosure has a plurality of liquefied gas piping units 1 of any of the first to fourth aspects, wherein the liquefied gas piping system has: a vacuum piping 53 connected to at least one of the liquefied gas piping units 1 to guide the vacuum layer in the plurality of liquefied gas piping units 1 to a common work area; and a vacuum port 55 provided in the vacuum piping 53 and configured to be connected to a vacuum pump in the common work area.

[0071] Based on this structure, similar to the above-mentioned revacuuming method, it is possible to access the vacuum layers in multiple piping units 1 in a common work area, thus enabling efficient revacuuming of multiple vacuum spaces.

[0072] As described above, preferred embodiments of the present disclosure have been illustrated with reference to the accompanying drawings, but various additions, modifications, or deletions can be made without departing from the spirit of the present disclosure. Therefore, such structures are also included within the scope of the present disclosure.

Claims

1. A piping unit for liquefied petroleum gas (LPG), used for transporting LPG, wherein, This liquefied gas piping unit has the following features: The first double-layer piping has a first inner pipe through which the liquefied gas passes and a first outer pipe covering the first inner pipe through a vacuum layer; The second double-layer piping has a second inner pipe through which the liquefied gas passes and a second outer pipe covering the second inner pipe through a vacuum layer, the second inner pipe being connected to the first inner pipe; A cover tube, which covers the connection between the first inner tube and the second inner tube through a vacuum layer; and A connecting path that connects the vacuum layer of the first double-layer piping, the vacuum layer of the second double-layer piping, and the vacuum layer inside the casing.

2. The liquefied gas piping unit according to claim 1, wherein, The connecting path is formed in the portion of the first outer tube and the second outer tube that is covered by the cover tube.

3. The liquefied gas piping unit according to claim 2, wherein, The connecting route is formed by connecting holes in the walls of the first outer pipe and the second outer pipe that can be sealed by a sealing bolt.

4. The liquefied gas piping unit according to claim 1, wherein, The connection route forms a connecting pipe that connects the portions of the first outer pipe and the second outer pipe not covered by the cover pipe to the cover pipe. An on / off valve is provided on the connecting pipe.

5. A method for assembling a liquefied petroleum gas (LPG) piping unit, comprising assembling the LPG piping unit as described in claim 2 or 3, wherein, The assembly method for this liquefied gas piping unit includes the following steps: The first inner pipe and the first outer pipe are combined, and the space between the first inner pipe and the first outer pipe is evacuated to form the vacuum layer while the connecting path is closed, thereby preparing the first double-layer piping. The second inner pipe and the second outer pipe are combined, and the space between the second inner pipe and the second outer pipe is evacuated to form the vacuum layer while the connecting path is closed, thereby preparing the second double-layer piping. Connect the first inner tube to the second inner tube; Open the connecting path to break the vacuum layer of the first double-layer piping and the second double-layer piping; After the vacuum is broken, the connecting portion between the first inner tube and the second inner tube is covered by the cover tube; and A vacuum is drawn from at least one of the cover tube, the first outer tube, and the second outer tube.

6. The assembly method of the liquefied gas piping unit according to claim 5, wherein, The vacuum disruption process includes the following steps: allowing dry gas to flow into the vacuum layer.

7. A method for assembling a liquefied petroleum gas (LPG) piping unit, comprising assembling the LPG piping unit of claim 4, wherein, The assembly method for this liquefied gas piping unit includes the following steps: The first inner tube and the first outer tube are combined, and the space between the first inner tube and the first outer tube is evacuated to form the vacuum layer, thereby preparing the first double-layer piping; The second inner tube and the second outer tube are combined, and the space between the second inner tube and the second outer tube is evacuated to form the vacuum layer, thereby preparing the second double-layer piping; A portion of the cover pipe, the first double-layer piping, and the second double-layer piping are connected using the connecting pipe in a closed state; Connect the first inner tube to the second inner tube; The remaining portion of the cover tube is used to cover the connection between the first inner tube and the second inner tube; The internal space of the cover tube is evacuated; and Open the connecting tube.

8. A method for re-vacuuming a liquefied gas piping unit, comprising re-vacuuming a plurality of liquefied gas piping units as described in claim 1, wherein, The vacuum layers within the multiple liquefied gas piping units are guided to a shared work area, and a shared vacuum pump is used to evacuate the vacuum layers within the liquefied gas piping units.

9. A liquefied petroleum gas (LPG) piping system comprising a plurality of LPG piping units as described in claim 1, wherein, This liquefied gas piping system has the following features: Vacuum piping, which is connected to at least one of the liquefied gas piping units, guides the vacuum layer within the plurality of liquefied gas piping units to a common work area; as well as A vacuum port is provided in the vacuum piping and configured to connect to the vacuum pump in the shared work area.

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