Heat insulation pipe

Abstract

To suppress heat input from a branch pipe to a main pipe with a simple structure.SOLUTION: A heat insulation pipe (1) includes: a main pipe (2) including an inner pipe (21) and an outer pipe (22) which are disposed sandwiching a vacuum layer (23) therebetween; a branch pipe (3) branched downward from the inner pipe (21); a valve (4) provided at the branch pipe (3); and a thermal isolator (5) which covers an upstream side portion with respect to the valve (4) in the branch pipe (3) to form a vacuum space (S1) around the branch pipe (3). The branch pipe (3) includes: an upstream pipe (31) communicating with the inner pipe (21); a riser pipe (32) rising upward from a downstream end of the upstream pipe (31); and a downstream pipe (33) connecting a downstream end of the riser pipe (32) with the valve (4). The thermal isolator (5) includes at least a part at the upstream side of the riser pipe (32) and the upstream pipe (31).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to insulated piping utilizing vacuum insulation. [Background technology]

[0002] One type of thermally insulated piping is known from Patent Document 1 below. Specifically, the piping in Patent Document 1 is a double-structured piping (double pipe) having an inner pipe and an outer pipe for flowing a cryogenic fluid. A vacuum layer is formed between the inner pipe and the outer pipe. The action of this vacuum layer significantly suppresses heat input (heat transfer) from the outer pipe to the inner pipe, and keeps the cryogenic fluid inside the inner pipe cool. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-20914 Summary of the Invention [Problem to be solved by the invention]

[0004] The piping described in Patent Document 1, i.e., a double pipe including an inner pipe and an outer pipe, can be used as a transfer line for transferring cryogenic fluids such as liquefied hydrogen. On the other hand, when the double pipe is not used as a transfer line, a branch pipe branching off from the double pipe (main pipe) may be installed for purposes such as draining the cryogenic fluid from the double pipe during maintenance, for example. However, adding such a branch pipe is likely to increase the amount of heat input to the main pipe. If the amount of heat input to the main pipe increases, it may become impossible to maintain the cryogenic fluid in the main pipe at the desired low temperature range.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a thermally insulated pipe that can suppress heat input from a branch pipe to a main pipe with a simple configuration. [Means for solving the problem]

[0006] In order to solve the above problem, an insulated pipe according to one aspect of the present disclosure comprises a mother pipe including an inner pipe and an outer pipe arranged with a vacuum layer between them, a branch pipe branching downward from the inner pipe, a valve provided in the branch pipe, and an insulator covering a portion of the branch pipe upstream of the valve and forming a vacuum space around the branch pipe, wherein the branch pipe includes an upstream pipe communicating with the inner pipe, a riser pipe rising upward from the downstream end of the upstream pipe, and a downstream pipe connecting the downstream end of the riser pipe and the valve, and the insulator encloses at least a portion of the upstream side of the riser pipe and the upstream pipe. [Effects of the Invention]

[0007] According to the thermally insulated piping of the present disclosure, heat input from the branch pipe to the main pipe can be suppressed with a simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a structure of a thermally insulated pipe according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a branch pipe of the thermal insulation pipe. [Figure 3] This is a diagram equivalent to Figure 1 showing the situation when liquefied hydrogen is drained from the mother pipe using the branch pipe. [Figure 4] FIG. 10 is a view equivalent to FIG. 1, showing a modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Insulated piping structure] FIG. 1 is a cross-sectional view showing the structure of a thermally insulated pipe 1 according to an embodiment of the present disclosure. In FIG. 1, "up" refers to the vertically upward direction, and "down" refers to the vertically downward direction. The thermally insulated pipe 1 shown in this figure is a pipe for flowing a cryogenic fluid, and includes a main pipe 2, a branch pipe 3, a valve 4, and an insulator 5. The main pipe 2 is a pipe through which the cryogenic fluid flows. The branch pipe 3 is a pipe branched downward from the main pipe 2. The valve 4 is an on-off valve provided midway in the branch pipe 3. The insulator 5 is a container body that insulates a portion of the upstream side of the branch pipe 3. In this embodiment, the cryogenic fluid flowing through the main pipe 2 is liquefied hydrogen LH, which is hydrogen gas liquefied.

[0010] The header pipe 2 is a double pipe with a vacuum insulation structure. That is, the header pipe 2 includes an inner pipe 21 through which liquefied hydrogen LH flows, and an outer pipe 22 arranged outside the inner pipe 21. In this embodiment, the inner pipe 21 and the outer pipe 22 are arranged concentrically. A vacuum layer 23 is formed between the inner pipe 21 and the outer pipe 22. The vacuum layer 23 is evacuated by a suction source P1 formed by a vacuum pump or the like. However, the suction source P1 may be used only during the manufacture of the thermally insulated piping 1 and removed when the thermally insulated piping 1 is in operation. The vacuum layer 23 significantly suppresses heat input (heat transfer) from the outer pipe 22 to the inner pipe 21, thereby maintaining the temperature of the liquefied hydrogen LH in the inner pipe 21 at an extremely low temperature (for example, around −253°C) at which the liquid phase can be maintained.

[0011] The branch pipe 3 is a single pipe that communicates with the inner pipe 21 of the main pipe 2. Specifically, the branch pipe 3 includes an upstream pipe 31 that extends downward from the bottom of the inner pipe 21, a riser pipe 32 that rises upward from the downstream end of the upstream pipe 31, a downstream pipe 33 that connects the downstream end of the riser pipe 32 to the valve 4, and an extension pipe 34 that extends further downstream from the valve 4.

[0012] FIG. 2 is an enlarged cross-sectional view of the branch pipe 3. For convenience, the boundaries between the elements of the branch pipe 3 are indicated by dashed lines in FIG. 2. As shown in FIGS. 1 and 2, the upstream pipe 31 includes a first descending portion 31a extending straight downward from the bottom of the inner pipe 21, and a first bent portion 31b extending from the downstream end (lower end) of the first descending portion 31a while bending in a U-shape. The riser pipe 32 is formed to extend straight upward from the downstream end of the first bent portion 31b to the downstream pipe 33. In other words, the riser pipe 32 is a pipe that extends in the up-down direction (vertical direction) from the downstream end of the upstream pipe 31 (first bent portion 31b) to the upstream end of the downstream pipe 33 (second bent portion 33a, described later). The downstream pipe 33 includes a second bent portion 33a that extends while bending in an inverted U shape from the downstream end (upper end) of the riser pipe 32, a second falling portion 33b that extends straight downward from the downstream end of the second bent portion 33a, and a horizontal portion 33c that extends horizontally from the downstream end (lower end) of the second falling portion 33b toward the valve 4. Note that, as shown in Fig. 2, in this embodiment, the portion that rises straight upward between the first bent portion 31b and the second bent portion 33a is defined as the riser pipe 32, and therefore the axial length, i.e., the vertical dimension, of the riser pipe 32 is equal to or less than the distance L1 between the inner circumferences of the first bent portion 31b and the second bent portion 33a.

[0013] The insulator 5 is joined by welding to the bottom of the outer pipe 22 of the main pipe 2. The shape of the insulator 5 is not particularly limited, but in this embodiment, the insulator 5 integrally includes a vertically extending peripheral wall 51 joined to the outer pipe 22 and a bottom wall 52 closing the lower end opening of the peripheral wall 51. The outer pipe 22 is cut out on the inside of the peripheral wall 51. This creates an airtight vacuum space S1 inside the insulator 5, which is continuous with the vacuum layer 23 of the main pipe 2. The vacuum space S1 is a space that accommodates a portion of the upstream side of the branch pipe 3, and is evacuated by the same suction source P1 as the vacuum layer 23. In other words, the insulator 5 is a container that forms the vacuum space S1 for thermal insulation around the branch pipe 3. Note that the degree of airtightness between the insulator 5 and the main pipe 2 does not need to be perfect.

[0014] The insulator 5, i.e., the vacuum space S1, accommodates the branch pipe 3 in a region upstream of the valve 4. Specifically, in this embodiment, the upstream pipe 31, the riser pipe 32, and a portion of the upstream side of the downstream pipe 33 are each accommodated in the insulator 5. The upstream pipe 31 and the riser pipe 32 are entirely accommodated in the insulator 5. In contrast, only a portion of the downstream pipe 33, excluding a region close to the valve 4, is accommodated in the insulator 5. That is, the downstream pipe 33 is accommodated in its entirety in the insulator 5 only in its entirety in the second bent portion 33a and the second falling portion 33b, and in a portion of the upstream side of the horizontal portion 33c. Meanwhile, a portion of the downstream side of the horizontal portion 33c is disposed outside the insulator 5. In other words, the downstream pipe 33 has an exposed portion R1 near the valve 4 that is exposed to the outside of the insulator 5.

[0015] As described above, the downstream pipe 33 is disposed from the inside to the outside of the insulator 5. For this layout, a through hole is formed in the peripheral wall 51 of the insulator 5, and the downstream pipe 33 is disposed so as to extend from the inside to the outside of the insulator 5 through this through hole.

[0016] The downstream pipe 33 is joined to the insulator 5 by welding. That is, the periphery of the through hole in the peripheral wall 51 is welded to the peripheral surface of the downstream pipe 33 via a weld bead W1, thereby joining the downstream pipe 33 and the insulator 5 to each other. To ensure the airtightness of the insulator 5, the weld bead W1 is formed around the entire circumference of the downstream pipe 33.

[0017] [Example of branch pipe usage] In this embodiment, the branch pipe 3 is used as a drain pipe for withdrawing liquefied hydrogen LH from the mother pipe 2. For example, during maintenance of a liquefied hydrogen facility including the thermally insulated piping 1, it may be necessary to discharge liquefied hydrogen LH from at least a portion of the mother pipe 2. In such cases, if the branch pipe 3 (drain pipe) is used, the liquefied hydrogen LH can be discharged from the mother pipe 2 in a shorter time than, for example, a method of vaporizing the liquefied hydrogen LH by introducing gas into the mother pipe 2. When discharging liquefied hydrogen LH using the branch pipe 3, as shown in FIG. 3 , the valve 4 is opened, and the downstream pipe 33 of the branch pipe 3 is connected to the extension pipe 34. As a result, the liquefied hydrogen LH in the mother pipe 2 passes through the upstream pipe 31, riser pipe 32, downstream pipe 33, and extension pipe 34 of the branch pipe 3 in that order, and is discharged to a predetermined destination while being appropriately vaporized.

[0018] On the other hand, when the header pipe 2 is used as a transfer line for liquefied hydrogen LH, or the like, during facility operation, the valve 4 is closed as shown in Figure 1. The valve 4 and the exposed portion R1 of the downstream pipe 33 are located outside the insulator 5 and are exposed to the outside air, and therefore function as a heat input source. The heat input from the valve 4 and the exposed portion R1 vaporizes the liquefied hydrogen LH, and the inside of the downstream pipe 33 becomes filled with vaporized liquefied hydrogen LH, that is, hydrogen gas GH. Because the valve 4 is closed, the hydrogen gas GH is pressurized inside the downstream pipe 33. As will be described in detail later, the pressurized hydrogen gas GH keeps the liquid level of the liquefied hydrogen LH drawn from the header pipe 2 midway up the riser pipe 32. In other words, a boundary B1 between the liquefied hydrogen LH and the hydrogen gas GH is formed midway up the riser pipe 32.

[0019] [Action and effect] As described above, in this embodiment, the insulator 5 for vacuum insulation is provided around the area of ​​the branch pipe 3 upstream of the valve 4. The insulator 5 encompasses a portion of the upstream side of the branch pipe 3, that is, the entire upstream pipe 31 and riser pipe 32, and a portion of the upstream side of the downstream pipe 33. Conversely, the exposed portion R1, which is a portion of the downstream side of the downstream pipe 33, and the above-mentioned valve 4 are both located outside the insulator 5. This configuration has the advantage of being able to suppress heat input from the branch pipe 3 to the mother pipe 2 with a simple configuration.

[0020] That is, in this embodiment, the exposed portion R1 of the downstream pipe 33 and the valve 4 are both disposed outside the insulator 5, and as a result, the liquefied hydrogen LH is vaporized due to the influence of heat input from the exposed portion R1 and the valve 4, and the interior of the downstream pipe 33 is filled with vaporized liquefied hydrogen LH, i.e., hydrogen gas GH. Meanwhile, the interior of the upstream pipe 31 is filled with liquefied hydrogen LH drawn out from the inner pipe 21 of the mother pipe 2. As a result of the different phases of hydrogen on the upstream and downstream sides of the riser pipe 32, both liquefied hydrogen LH and hydrogen gas GH are present inside the riser pipe 32. Moreover, in the riser pipe 32, the low-density hydrogen gas GH collects at the top, and the high-density liquefied hydrogen LH collects at the bottom, so a boundary B1 between the liquefied hydrogen LH and hydrogen gas GH is formed midway along the riser pipe 32. In other words, the liquefied hydrogen LH and hydrogen gas GH are arranged separately above and below the boundary B1. In this way, by balancing the liquefied hydrogen LH and hydrogen gas GH midway through the riser pipe 32, it is possible to prevent the hydrogen gas GH from flowing into the upstream pipe 31, and it is possible to prevent the hydrogen gas GH from flowing into the inner pipe 21 of the main pipe 2 through the upstream pipe 31.

[0021] If the riser pipe 32 were omitted, for example, if the downstream end of the upstream pipe 31 were connected to the valve 4 by a horizontal pipe, a clear gas-liquid boundary would not be formed, and the low-density hydrogen gas GH would tend to move upward, which could result in the hydrogen gas GH flowing through the upstream pipe 31 into the inner pipe 21. Such an inflow of hydrogen gas GH would increase the temperature of the liquefied hydrogen LH inside the inner pipe 21 and, in some cases, could cause the liquefied hydrogen LH to vaporize. In other words, omitting the riser pipe 32 would increase the amount of heat input to the header pipe 2 and could raise the temperature of the liquefied hydrogen LH therein. In contrast, in this embodiment, in which the riser pipe 32 is provided midway through the branch pipe 3, heat input to the header pipe 2 can be prevented by utilizing the gas-liquid boundary B1 formed midway through the riser pipe 32, and the liquefied hydrogen LH in the header pipe 2 can be maintained at a sufficiently low temperature.

[0022] Moreover, in this embodiment in which the valve 4 is used as a heat input source, there is no need to house the valve 4 inside the insulator 5. This means that there is no need to use a valve with a special structure that can be used in a vacuum environment as the valve 4. Therefore, it is possible to prevent the structure of the insulated piping 1, including the valve 4, from becoming complicated, and it is possible to reduce the amount of heat input to the mother pipe 2 described above with a relatively simple configuration.

[0023] Furthermore, in this embodiment, not only the valve 4 but also the exposed portion R1 of the adjacent downstream pipe 33 is positioned outside the insulator 5, so that the heat input from the exposed portion R1 of the downstream pipe 33 promotes the vaporization of the liquefied hydrogen LH, thereby enabling the generation of hydrogen gas GH with a pressure that balances with the liquefied hydrogen LH inside the riser pipe 32.

[0024] In addition, in this embodiment, the insulator 5 is joined to the outer pipe 22 of the main pipe 2 by welding, and cooperates with the main pipe 2 to form a vacuum space S1 that is continuous with the vacuum layer 23. With this configuration, the vacuum layer 23 of the main pipe 2 and the inside (vacuum space S1) of the insulator 5 can be evacuated using a common suction source P1, and the main pipe 2 and branch pipes 3 can be sufficiently insulated (kept cold) as a result of this evacuation.

[0025] [Variations] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the present disclosure.

[0026] For example, in the above embodiment, the insulator 5 is formed to enclose the branch pipe 3 excluding the exposed portion R1 of the downstream pipe 33, i.e., the entire upstream pipe 31 and riser pipe 32 and a portion of the upstream side of the downstream pipe 33. However, the insulator 5 only needs to vacuum insulate the branch pipe 3 so that the boundary B1 between the liquefied hydrogen LH and the hydrogen gas GH is formed midway through the riser pipe 32, and the range of insulation by the insulator 5 can be changed in various ways depending on the situation. For example, if the downstream pipe 33 is short, the insulator 5 may be formed to enclose only the upstream pipe 31 and the riser pipe 32 (but not the downstream pipe 33).

[0027] Furthermore, the thermal insulation range of the riser pipe 32 by the adiabatic unit 5 does not necessarily have to be the entire riser pipe 32, i.e., the range from the start point of the riser pipe 32, which is the boundary with the upstream pipe 31, to the end point of the riser pipe 32, which is the boundary with the downstream pipe 33, but may be limited to a portion of the upstream side of the riser pipe 32. Minimizing the thermal insulation range in this way has the advantage of reducing the volume of the adiabatic unit 5 as much as possible. On the other hand, enclosing the entire riser pipe 32 within the adiabatic unit 5, as in the above embodiment, has the advantage of being able to accurately insulate the liquefied hydrogen LH even when the heat input fluctuates and the position of the boundary B1 between the liquefied hydrogen LH and the hydrogen gas GH fluctuates vertically. Note that if the riser pipe 32 is sufficiently long, simply covering a portion of the upstream side of the riser pipe 32 with the adiabatic unit 5 can accommodate fluctuations in the position of the boundary B1.

[0028] In the above embodiment, the riser pipe 32 is formed to extend straight in the up-down direction (vertical direction), but the riser pipe 32 may extend in the up-down direction (vertical direction) as long as it extends in the up-down direction, and may be inclined with respect to the up-down direction (vertical direction). The same applies to the first falling portion 31a of the upstream pipe 31 and the second falling portion 33b of the downstream pipe 33. In the above embodiment, the portion downstream of the second falling portion 33b is the horizontal portion 33c extending in the horizontal direction, but the portion downstream of the second falling portion 33b may extend in any direction other than the horizontal direction.

[0029] In the above embodiment, the outer pipe 22 of the main pipe 2 and the insulator 5 are integrated by welding, but the integration method is not limited to welding as long as a predetermined level of sealing can be ensured. The same applies to the joining of the downstream pipe 33 and the insulator 5.

[0030] In the above embodiment, the insulator 5 is formed integrally with the outer pipe 22 of the main pipe 2, but the insulator 5 may also be configured by a container body independent of the main pipe 2. That is, an insulator separate from the main pipe 2 may be provided in the vicinity of the main pipe 2 so that the vacuum space S1 inside the insulator 5 and the vacuum layer 23 of the main pipe 2 are independent of each other, and a part of the upstream side of the branch pipe 3 may be housed inside this insulator. In this case, it is preferable that a suction source for evacuating the inside of the insulator (vacuum space) be provided separately from the suction source P1 for evacuating the vacuum layer 23 of the main pipe 2.

[0031] In the above embodiment, the downstream pipe 33 including the falling portion 33b is provided between the riser pipe 32 of the branch pipe 3 and the valve 4, but the falling portion 33b is not essential to the downstream pipe 33. For example, as shown in Fig. 4, the downstream pipe 133 may be formed so as to extend horizontally from the downstream end (upper end) of the riser pipe 32. In any case, the downstream pipe of the branch pipe 3 may be any pipe that connects the downstream end of the riser pipe 32 and the valve 4, and the route of the downstream pipe is not particularly limited.

[0032] In the above embodiment, an example in which the present disclosure is applied to an insulated pipe 1 for flowing liquefied hydrogen is described, but the present disclosure can also be applied to an insulated pipe for flowing a cryogenic liquid other than liquefied hydrogen, such as liquid helium, liquid nitrogen, liquid oxygen, liquefied ammonia, liquefied natural gas (LNG), etc.

[0033] Furthermore, the present disclosure can be applied to any insulated piping that carries a fluid whose density decreases with increasing temperature, and is not limited to piping that carries a cryogenic liquid. For example, the present disclosure can also be applied to piping that carries a gas such as low-temperature hydrogen gas. In such piping that carries a cryogenic gas, a branch pipe may be branched off from a main pipe for gas purging, for example, to replace the gas in the piping with an inert gas. In such cases, the low-temperature gas in the main pipe may be unnecessarily heated due to heat input from a valve or the like installed in the branch pipe. The present disclosure is also useful for preventing heat input from the branch pipe to the main pipe in such cases. In other words, the present disclosure is widely applicable to insulated piping that carries any fluid whose density decreases with increasing temperature, regardless of whether the fluid is a liquid or a gas. In this case, if the branch pipe is insulated (cooled) using a configuration similar to that of the above embodiment, a low-temperature, high-density fluid (high-density fluid) and a low-density fluid (low-density fluid) that has been heated due to heat input from a valve or the like can be balanced midway up the riser pipe of the branch pipe, thereby preventing heat input to the main pipe.

[0034] [summary] The above-described embodiments and their modifications include the following disclosures.

[0035] A thermally insulated pipe according to a first aspect of the present disclosure includes a mother pipe including an inner pipe and an outer pipe disposed on either side of a vacuum layer, a branch pipe branching downward from the inner pipe, a valve provided in the branch pipe, and an insulator covering a portion of the branch pipe upstream of the valve and forming a vacuum space around the branch pipe. The branch pipe includes an upstream pipe communicating with the inner pipe, a riser pipe rising upward from the downstream end of the upstream pipe, and a downstream pipe connecting the downstream end of the riser pipe to the valve. The insulator encloses at least a portion of the upstream side of the riser pipe and the upstream pipe.

[0036] According to this first aspect, the valve connected to the downstream pipe of the branch pipe is located outside the adiabatic unit. Therefore, the temperature of the fluid in the downstream pipe rises due to the heat input from the valve, and the density of the fluid decreases. Meanwhile, the upstream pipe is filled with a low-temperature, high-density fluid drawn from the inner pipe of the mother pipe. As a result of the difference in fluid density between the upstream and downstream sides of the riser pipe, both high-density and low-density fluids exist inside the riser pipe. Furthermore, in the riser pipe, the low-density fluid collects at the top and the high-density fluid collects at the bottom, forming a boundary between the high-density and low-density fluids along the riser pipe. At this time, at least a portion (lower portion) of the upstream side of the riser pipe is vacuum insulated within the adiabatic unit, so the high-density fluid in the lower portion of the riser pipe is kept cool and maintained at a high density. By balancing the high-density and low-density fluids along the riser pipe, it is possible to prevent the relatively high-temperature low-density fluid from flowing into the upstream pipe and the low-density fluid from flowing into the inner pipe of the mother pipe through the upstream pipe. In other words, the boundary between the high-density fluid and the low-density fluid formed midway through the riser pipe can be utilized to prevent heat input to the main pipe, and the fluid in the main pipe can be maintained at a sufficiently low temperature.

[0037] Furthermore, in this embodiment, in which a valve is used as a heat input source, there is no need to house the valve inside the insulated vessel. This means that there is no need to use a valve with a special structure that can be used in a vacuum environment. Therefore, the structure of the insulated piping including the valve can be prevented from becoming complicated, and the amount of heat input to the mother pipe can be reduced with a relatively simple configuration.

[0038] A second aspect of the insulated piping is the insulated piping of the first aspect, wherein the insulator encloses the entire riser pipe.

[0039] In this way, when the entire riser pipe is housed inside the insulator, the high-density fluid can be accurately kept cold even if the heat input fluctuates and the position of the boundary between the high-density fluid and the low-density fluid moves up and down.

[0040] The insulated piping of a third aspect is the insulated piping of the second aspect, wherein the insulator encompasses a portion of the upstream side of the downstream pipe, and a portion of the downstream side of the downstream pipe is exposed to the outside of the insulator.

[0041] According to the third aspect, not only the valve but also a part of the downstream pipe adjacent to the valve is arranged outside the insulator. Therefore, the heat input from this part raises the temperature of the fluid, and as a result, a low-density fluid having a pressure that balances with the high-density fluid inside the riser pipe can be appropriately generated.

[0042] A fourth aspect of the insulated piping is any of the first to third aspects, wherein the insulator is airtightly connected to the outer pipe, and the vacuum space is continuous with the vacuum layer.

[0043] According to this fourth aspect, the vacuum layer of the main pipe and the inside (vacuum space) of the insulator can be evacuated using a common suction source, and as a result of this evacuation, the main pipe and branch pipes can be sufficiently insulated (kept cold). [Explanation of symbols]

[0044] 1. Insulated piping 2 Main tube 3 branch pipes 4 valves 5. Insulator 21 Inner tube 22 Outer tube 23 Vacuum layer 31 Upstream pipe 32 riser pipe 33 Downstream pipe S1 vacuum space

Claims

1. a mother pipe including an inner pipe and an outer pipe arranged with a vacuum layer therebetween; a branch pipe branching downward from the inner pipe; a valve provided in the branch pipe; an insulator that covers a portion of the branch pipe upstream of the valve and forms a vacuum space around the branch pipe, the branch pipe includes an upstream pipe communicating with the inner pipe, a riser pipe rising upward from a downstream end of the upstream pipe, and a downstream pipe connecting the downstream end of the riser pipe and the valve, The insulated piping, wherein the insulator contains at least a portion of the upstream side of the riser pipe and the upstream pipe.

2. The thermally insulated pipe according to claim 1, The insulated piping includes the insulator enclosing the entire riser pipe.

3. The thermally insulated pipe according to claim 2, the insulator encompasses a portion of the upstream side of the downstream pipe; A part of the downstream side of the downstream pipe is exposed to the outside of the insulator.

4. The thermally insulated pipe according to any one of claims 1 to 3, the insulator is airtightly connected to the outer pipe, The vacuum space is a heat-insulating pipe that is continuous with the vacuum layer.

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