Manufacturing method for double pipe, and double pipe

Abstract

To efficiently manufacture a double pipe that requires the arrangement of an accessory between an inner pipe and an outer pipe.SOLUTION: A vacuum heat insulation double pipe 1 includes an inner pipe 2 for passing fluid, an outer pipe 3 covering the inner pipe 2, and a vacuum heat insulation layer 4 that is an annular space layer between the inner pipe 2 and the outer pipe 3. The outer pipe 3 comprises an outer pipe body 31, and an outer pipe piece 32 covering an opening part 6 of the outer pipe body 31. At the time of manufacturing the vacuum heat insulation double pipe 1, an accessory 5 is attached to an inner surface 32A of the outer pipe piece 32 in advance. Next, the inner pipe 2 is covered with the outer pipe piece 32 and the outer pipe body 31. In other words, the outer pipe body 31 is externally fitted to the inner pipe 2, and the opening part 6 is covered with the outer pipe piece 32 equipped with the accessory 5. The outer pipe piece 32 is attached to the outer pipe body 31 so as to comprise an overlap part OL in which a peripheral edge part 32E of the outer pipe piece 32 overlaps with the outer pipe body 31 from the outside.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a double tube including an inner tube, an outer tube covering the inner tube, and an annular space layer between the inner tube and the outer tube, and a method for manufacturing the same.

Background Art

[0002] A double tube including an inner tube, an outer tube, and an annular space layer between the inner tube and the outer tube may be used, for example, as a transfer pipe for low-temperature liquefied gas. In this case, the annular space layer is evacuated to form a vacuum insulation layer. Necessary accessories are arranged in the annular space layer. The accessories include an axial stop member that regulates the axial relative movement between the inner tube and the outer tube, an inner tube support member that supports the inner tube in the radial direction, and the like. Patent Document 1 discloses a method for manufacturing a double tube in which an outer tube is fitted onto an inner tube with accessories attached in advance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when adopting the manufacturing method of Patent Document 1, when fitting the outer tube, it is necessary to perform an operation while avoiding interference between the accessories attached to the inner surface of the outer tube and the accessories pre-mounted on the inner tube, and there is a problem that the workability is poor. Further, in the case of a vacuum-insulated double tube, it is necessary to attach an end seal near the terminal of the inner tube for sealing the vacuum insulation layer. In this case, there is also a problem that the outer tube with accessories attached cannot be externally fitted onto the inner tube.

[0005] An object of the present disclosure is to provide a method for efficiently manufacturing a double tube that requires arranging accessories between an inner tube and an outer tube, and a double tube that can be efficiently manufactured.

Means for Solving the Problem

[0006] A method for manufacturing a double tube according to one aspect of the present disclosure is a method for manufacturing a double tube including an inner tube through which a fluid flows, an outer tube covering the inner tube, and an annular space layer between the inner tube and the outer tube, the method including attaching an accessory to an inner surface of an outer tube piece that constitutes a part of the outer tube, covering the inner tube with the outer tube piece and an outer tube body that constitutes the remaining part of the outer tube, and attaching the outer tube piece to the outer tube body in a state where at least a part of a peripheral edge portion of the outer tube piece overlaps the outer tube body.

[0007] A double tube according to another aspect of the present disclosure is a double tube including an inner tube through which a fluid flows, an outer tube covering the inner tube, an annular space layer between the inner tube and the outer tube, and an accessory disposed in the annular space layer, the outer tube including an outer tube piece that is a part of the outer tube and an outer tube body that is the remaining part of the outer tube, the accessory being attached to an inner surface of the outer tube piece, and at least a part of a peripheral edge portion of the outer tube piece being attached in a state of overlapping the outer tube body.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a method for efficiently manufacturing a double tube that requires an accessory to be disposed between an inner tube and an outer tube, and a double tube that can be efficiently manufactured.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0010] Hereinafter, embodiments of the double tube and its manufacturing method according to the present disclosure will be described in detail with reference to the drawings. The double tube targeted by the present disclosure has a structure including an inner tube, an outer tube, and an annular space layer between the inner tube and the outer tube. For example, the inner tube and the outer tube are arranged coaxially. Such a double tube is used as a transfer pipe for cryogenic liquefied gas. For example, when transferring cryogenic liquefied gas such as liquefied hydrogen (LH2), the annular space layer is evacuated to form a vacuum insulation layer. By using a vacuum-insulated double tube, it is possible to suppress the generation of boil-off gas of the liquefied gas, icing on the tube surface, and the generation of liquefied air. In the embodiments shown below, a vacuum-insulated double tube is exemplified as the double tube according to the present disclosure. Of course, the present disclosure is not limited to vacuum-insulated double tubes and can also be applied to other double tubes without a vacuum insulation structure.

[0011] [Basic Embodiment] FIG. 1 is an axial sectional view of a vacuum insulated double tube 1 (double tube) according to a basic embodiment of the present disclosure. In FIG. 1, the vicinity of the terminal 10 of the vacuum insulated double tube 1 is shown. The vacuum insulated double tube 1 includes an inner tube 2, an outer tube 3, a vacuum insulation layer 4, and accessories 5. The object to be transferred by the vacuum insulated double tube 1 is liquefied hydrogen.

[0012] The inner tube 2 is a tube through which a low-temperature fluid to be transferred flows. In the present embodiment, liquefied hydrogen flows through the inner tube 2. The terminal of the inner tube 2 is sealed by a terminal sealing portion 21 with a cap. The outer tube 3 is a tube that covers the inner tube 2 and is arranged coaxially with the inner tube 2. The vacuum insulation layer 4 is an annular space layer between the inner tube 2 and the outer tube 3 and is a layer formed by evacuation. By removing heat carriers by evacuation, the annular space layer between the inner tube 2 and the outer tube 3 functions as the vacuum insulation layer 4. At the edge 301 of the outer tube 3, an end seal 302 is attached to the inner tube 2, and the edge of the vacuum insulation layer 4 is sealed.

[0013] The accessories 5 are various components arranged in the vacuum insulation layer 4. The accessories 5 are, for example, an axial stop that restricts the axial relative movement between the inner tube 2 and the outer tube 3, a sliding plate that slidably supports the inner tube 2, an inner tube support that supports the inner tube 2 in the radial direction, and the like. Specific examples of the axial stop are described later in the first embodiment (FIGS. 3 and 4), specific examples of the sliding plate are described later in the second embodiment (FIG. 5), and specific examples of the inner tube support are described later in the third to sixth embodiments (FIGS. 5 to 10).

[0014] The outer tube 3 is composed of an outer tube main body 31 and an outer tube piece 32. That is, a part of the single outer tube 3 is the outer tube piece 32, and the remaining part is composed of the outer tube main body 31. An accessory 5 is attached to the inner surface 32A of the outer tube piece 32. The outer tube piece 32 is attached to the outer tube main body 31 in a manner having an overlapping portion OL in which the peripheral edge portion of the outer tube piece 32 overlaps the outer tube main body 31 in the radial direction. The outer tube piece 32 is overlapped from the radially outer side with respect to the outer tube main body 31 and is fixed by a welded portion Wd formed by fillet welding on the peripheral edge portion.

[0015] Figure 2 is an axial cross-sectional view showing a manufacturing method of the vacuum-insulated double tube 1 of the basic embodiment. When manufacturing the vacuum-insulated double tube 1, an opening 6 is formed in the outer tube main body 31. The opening 6 is provided at a position corresponding to the attachment position 2P of the accessory 5 in the inner tube 2 or the vacuum insulation layer 4. That is, in a state where the inner tube 2 is inserted into the outer tube 3 to a predetermined position, the opening 6 is provided at the position where the accessory 5 should be arranged. The opening 6 can be provided in the form of a window portion obtained by cutting a part of the outer tube main body 31 in the axial direction and the circumferential direction, or in the form of a dividing portion obtained by completely dividing the outer tube main body 31.

[0016] The outer tube piece 32 has a size that completely covers and hides the opening 6, and has the same material and the same thickness as the outer tube main body 31. Note that the outer tube piece 32 may be made of a material different from that of the outer tube main body 31 or may have a different thickness. An accessory 5 to be arranged in the vacuum insulation layer 4 is pre-attached to the inner surface 32A of the outer tube piece 32. In particular, no accessory 5 is attached to the surface of the inner tube 2. When the accessory 5 is composed of a combination of a plurality of parts, a part of the accessory 5 may be pre-attached to the surface of the inner tube 2. However, an end seal 302 for sealing the edge of the vacuum insulation layer 4 is attached near the terminal of the inner tube 2. A terminal sealing portion 21 for sealing the terminal of the inner tube 2 is also attached. After these attachments, an airtightness inspection of the inner tube 2 is performed. The above is the preparation process for assembling the vacuum-insulated double tube 1.

[0017] Subsequently, a step of covering the inner tube 2 with the outer tube main body 31 and the outer tube piece 32 is performed. Specifically, first, the outer tube main body 31 is externally fitted onto the inner tube 2. Since no accessories 5 are attached to the inner surface of the outer tube main body 31, this external fitting operation can be easily performed. That is, even if the end seal 302 is attached to the inner tube 2 in advance, the outer tube main body 31 can be externally fitted onto the inner tube 2. When the end seal 302 is attached by retrofitting after the above external fitting, a step of reinspecting the airtightness of the inner tube 2 after the attachment becomes essential, and the workability decreases. Thereafter, the outer tube piece 32 equipped with the accessories 5 in advance is arranged so as to close the opening 6 of the outer tube main body 31. This arrangement operation is performed in such a manner that the outer tube piece 32 closes the opening 6 of the outer tube main body 31 from the outside as indicated by the arrow in FIG. 2.

[0018] After the above covering step, a step of attaching the outer tube piece 32 to the outer tube main body 31 is performed. The outer tube piece 32 closes the opening 6 and is positioned in a state where the peripheral edge portion 32E of the outer tube piece 32 overlaps near the opening edge 6E of the outer tube main body 31. This positioning includes position adjustment for arranging the accessory 5 at a predetermined position within the vacuum heat insulation layer 4. If the accessory 5 is attached to the outer tube 3 in advance and externally fitted onto the inner tube 2, it is extremely difficult to adjust the position of the accessory 5. In the present embodiment, by performing position adjustment for attaching the outer tube piece 32 to the outer tube main body 31, it is possible to easily perform position adjustment of the accessory 5.

[0019] After the position adjustment of the accessory 5, the outer tube piece 32 is fixed to the outer tube main body 31 by welding. Specifically, the peripheral edge portion 32E of the outer tube piece 32 is fillet welded to the surface near the opening edge 6E of the outer tube main body 31. As a result, as shown in FIG. 1, an overlapping portion OL is formed in the region near the opening edge 6E of the outer tube main body 31, where the region near the peripheral edge portion 32E of the outer tube piece 32 is overlapped from the radially outer side, and a welded portion Wd is formed on the peripheral edge portion 32E.

[0020] The overlapping portion OL is not limited to the overlapping mode as long as the outer tube piece 32 and the outer tube body 31 overlap with each other in the radial direction with a predetermined width. The outer tube piece 32 and the outer tube body 31 may directly overlap, or there may be an intervening substance or a coating layer between the two. Further, as long as the airtightness of the vacuum heat insulation layer 4 is ensured, a part of the peripheral edge portion 32E of the outer tube piece 32 does not have to overlap with the outer tube body 31. Furthermore, although the peripheral edge portion 32E does not overlap, a mode in which the welded portion Wd overlaps with the outer tube body 31 may be adopted. That is, the overlapping portion OL may be constituted by the overlap between the welded portion Wd and the outer tube body 31.

[0021] According to the basic embodiment described above, the accessory 5 is attached in advance to the inner surface 32A of the outer tube piece 32, and the procedure of covering the inner tube 2 with the outer tube piece 32 and the outer tube body 31 is taken. For this reason, it is possible to perform an operation of inserting the inner tube 2 into the outer tube body 31 in a state where the accessory 5 is not mounted on the inner surface, and then retrofitting the outer tube piece 32 equipped with the accessory 5 to the opening 6 of the outer tube body 31. Therefore, the operation of arranging the inner tube 2 inside the outer tube 3 is not hindered by the accessory 5. Further, since the peripheral edge portion 32E of the outer tube piece 32 is attached in a state of overlapping the outer tube body 31, it is easy to ensure the airtightness of the vacuum heat insulation layer 4. Furthermore, since the outer tube piece 32 is attached from the outside of the outer tube body 31, the operation of attaching the outer tube piece 32 to the outer tube body 31 can be simplified after the inner tube 2 is inserted into the outer tube body 31. Hereinafter, various embodiments of the vacuum heat insulation double tube 1 embodying the above-described basic embodiment will be described.

[0022] [First Embodiment] FIG. 3 is an axial cross-sectional view of a vacuum heat insulation double tube 1A according to a first embodiment of the present disclosure. The vacuum heat insulation double tube 1A includes an inner tube 2 made of a metal such as stainless steel and an outer tube 3A, and a vacuum heat insulation layer 4 between the inner tube 2 and the outer tube 3A. The outer tube 3A is composed of an outer tube body 31 and a backing plate 33 (plate) corresponding to the above-described outer tube piece 32. In the first embodiment, an example in which the accessory 5 is an axial stop 5A is shown. The axial stop 5A regulates the axial movement of the inner tube 2 with respect to the outer tube 3A.

[0023] The shaft stop 5A includes an inner tube shaft stop member 51 (a part of the accessory) and an outer tube shaft stop member 52 (the remaining part of the accessory). The inner tube shaft stop member 51 is a member pre-attached to the surface of the inner tube 2, and is composed of a first bracket 511 and a first pressing plate 512 made of a metal material, and a heat insulation spacer 513 made of a heat insulation material. The first bracket 511 is a rectangular plate having a predetermined thickness, and is welded to the outer peripheral surface of the inner tube 2 along the tube axis direction of the inner tube 2. The first pressing plate 512 is a flat plate welded to the outer peripheral surface of the inner tube 2 so that the back side is supported by the first bracket 511, and has a pressing surface formed by a plane extending in the circumferential direction of the inner tube 2 on the surface side. The heat insulation spacer 513 is attached to the pressing surface of the first pressing plate 512 and has a rectangular parallelepiped shape.

[0024] The outer tube shaft stop member 52 is a member pre-attached to the inner surface 33A of the contact plate 33, and includes a second bracket 521 and a second pressing plate 522 made of a metal material. The second bracket 521 is a rectangular plate having a predetermined thickness, and is welded to the inner surface 33A of the contact plate 33 along the tube axis direction of the outer tube 3A. The second pressing plate 522 is a flat plate welded to the inner surface 33A of the contact plate 33 so that the back side is supported by the second bracket 521, and has a pressing surface formed by a plane extending in the circumferential direction of the outer tube 3A on the surface side.

[0025] As shown in FIG. 3, the contact plate 33 is attached to the outer tube body 31 such that the second pressing plate 522 faces the first pressing plate 512 at a predetermined interval, that is, the pressing surfaces of each other face each other. The heat insulation spacer 513 is in a state of being tightly sandwiched between the first pressing plate 512 and the second pressing plate 522. Due to the interposition of the heat insulation spacer 513, the heat input from the outer tube 3A to the inner tube 2 is suppressed. The contact plate 33 is attached to the outer tube body 31 so as to form an overlapping portion OL in which a region near the peripheral edge 33E thereof overlaps the outer tube body 31. A welded portion Wd by fillet welding is formed at the peripheral edge 33E of the contact plate 33.

[0026] In the example of Fig. 3, an axial stop 5A is illustrated, where the inner tube 2 is assumed to move relatively only in one axial direction (rightward in Fig. 3). If it is assumed that the inner tube 2 moves relatively only leftward, the facing direction between the inner tube axial stop member 51 and the outer tube axial stop member 52 is reversed left and right from Fig. 3. Further, when it is assumed that the inner tube 2 moves relatively in both left and right directions, pairs of inner tube axial stop members 51 and outer tube axial stop members 52 with different facing directions are arranged. Alternatively, a configuration is adopted in which heat insulation spacers 513 are respectively attached to both surfaces of one first pressing plate 512, and a second pressing plate 522 is provided so as to face each of them.

[0027] Figs. 4(A) to 4(C) are diagrams for explaining a method of manufacturing the vacuum insulated double tube 1A. As shown in Fig. 4(A), a window portion 61 for retrofitting a backing plate 33 is formed in the outer tube body 31. The window portion 61 corresponds to the opening 6 in the basic embodiment of Fig. 1. The window portion 61 is provided in the outer tube body 31 so as to open at the attachment position 2P of the axial stop 5A as an accessory. In Fig. 4(A), an example is shown in which four window portions 61 each formed of a rectangular opening in side view are formed at equal intervals in the circumferential direction of the outer tube body 31. An operation of fitting such an outer tube body 31 onto the inner tube 2 or inserting the inner tube 2 into the outer tube body 31 is performed.

[0028] Fig. 4(C) is a plan view of the backing plate 33 to which the outer tube axial stop member 52 is attached in advance. The backing plate 33 is an arc-shaped flat plate having a size to completely close the window portion 61. That is, the backing plate 33 has a peripheral edge portion 33E that extends outward in the axial direction and the circumferential direction from the opening edge 61E of the window portion 61, also for the formation of the overlapping portion OL in Fig. 3.

[0029] Fig. 4(B) is a diagram showing an attachment mode of the backing plate 33 equipped with the outer tube axial stop member 52 to the window portion 61 of the outer tube body 31. The backing plate 33 is attached from the radially outer side of the outer tube body 31 so that the outer tube axial stop member 52 is fitted into the window portion 61. By this fitting, the inner tube 2 is covered by the outer tube body 31 and the backing plate 33.

[0030] With the heat insulating spacer 513 and the second pressing plate 522 in contact, fillet welding is performed on the peripheral edge 33E of the backing plate 33, and the backing plate 33 is fixed to the surface of the outer tube body 31.

[0031] [Second Embodiment] FIG. 5(A) is a cross-sectional view in a direction orthogonal to the axial direction of the vacuum heat insulating double tube 1B according to the second embodiment. The vacuum heat insulating double tube 1B includes coaxially arranged inner tube 2 and outer tube 3B, and a vacuum heat insulating layer 4 between the inner tube 2 and the outer tube 3B. The outer tube 3B consists of an outer tube body 31 and a backing plate 34 (plate) corresponding to the outer tube piece 32 of the basic embodiment. In the second embodiment, an example of the accessory 5 is a sliding plate 5B that allows the inner tube 2 to slide inside the outer tube 3B, and a slide support 53 that supports the inner tube 2.

[0032] In a double tube, there may be a case where a support structure that supports the inner tube without deliberately restraining it is required. For example, supporting the inner tube so that it can move in the left-right direction at a bent portion in the horizontal plane of the pipe, or supporting the inner tube so that it can move in the up-down direction at a bent portion in the vertical plane, etc. The sliding plate 5B shown in FIG. 5 corresponds to the former support structure.

[0033] As shown in FIG. 5(A), the inner tube 2 is supported from below by the slide support 53. The slide support 53 is fixed to the outer peripheral surface of the inner tube 2 and is made of a heat insulating material in order to suppress heat conduction between the inner tube 2 and the outer tube 3B. The slide support 53 is simply placed on the sliding plate 5B. That is, the lower end surface of the slide support 53 is not fixed to the sliding plate 5B. Therefore, the inner tube 2 can slide in the left-right direction on the sliding plate 5B together with the slide support 53. The sliding plate 5B is attached to the inner surface of the backing plate 34. The backing plate 34 is fixed to the outer tube body 31 by a welded portion Wd. When the inner tube 2 is to be movable in the up-down direction, the slide support 53 and the sliding plate 5B are arranged on the side of the inner tube 2.

[0034] FIG. 5(B) is a cross-sectional view showing a method for manufacturing the vacuum insulation double tube 1B. A window portion 62 is formed in the outer tube body 31 at a position corresponding to the arrangement position of the slide support 53. On the other hand, a sliding plate 5B is pre-attached to the inner surface of the backing plate 34. The backing plate 34 has a size larger than the opening size of the window portion 62. Therefore, when the backing plate 34 is overlapped with the window portion 62 from the outside, an overlapping portion OL can be formed in which the vicinity of the opening edge 62E of the window portion 62 and the vicinity of the peripheral edge portion 34E of the backing plate 34 overlap in the radial direction.

[0035] First, the outer tube body 31 having the window portion 62 is externally fitted to the inner tube 2 with the slide support 53 mounted at a predetermined position. After this external fitting, the slide support 53 may be attached to the inner tube 2 through the window portion 62. Next, the backing plate 34 equipped with the sliding plate 5B is overlapped with the window portion 62 so that the overlapping portion OL is formed at the peripheral edge portion 34E. By this overlapping, the sliding plate 5B comes into contact with the lower surface of the slide support 53. Thereafter, the peripheral edge portion 34E is fillet welded to the outer tube body 31.

[0036] According to the second embodiment, it is possible to externally fit the outer tube body 31 to the inner tube 2 and attach the backing plate 34 equipped with the sliding plate 5B to the window portion 62 of the outer tube body 31. Therefore, the external fitting operation of the outer tube body 31 is easy, and the sliding plate 5B can be accurately attached to a predetermined position within the vacuum insulation layer 4.

[0037] [Third Embodiment] FIG. 6(A) is an axial cross-sectional view of the vacuum-insulated double tube 1C according to the third embodiment, and FIG. 6(B) is a cross-sectional view taken along line VIB-VIB of FIG. 6(A). The vacuum-insulated double tube 1C includes a coaxially arranged inner tube 2 and outer tube 3C, and a vacuum insulation layer 4 between the inner tube 2 and the outer tube 3C. The outer tube 3C is composed of an outer tube main body 31 and a backing plate 35 (plate). In the third embodiment, an example is shown in which the member corresponding to the accessory 5 in FIG. 1 is an inner tube support 5C that supports the inner tube 2 in the radial direction. Also shown is an example in which the backing plate 35 is attached to the outer tube main body 31 with all the components constituting the inner tube support 5C mounted on the backing plate 35.

[0038] The inner tube support 5C includes a heat insulation support 54, and a support base 541 and a fixing fitting 542 for fixing the heat insulation support 54 to a metal backing plate 35. The heat insulation support 54 is made of a heat insulating material and is a member that directly supports the inner tube 2. The heat insulation support 54 includes an arc support surface 54A that abuts against the outer peripheral surface of the inner tube 2 via a radiation shield 22 described later, and a seat surface 54B located on the back surface side of the arc support surface 54A.

[0039] The support base 541 is a member that serves as a mounting seat for the heat insulation support 54 and is fixed to the backing plate 35 by welding or the like. The fixing fitting 542 is a member for fixing the heat insulation support 54 to the support base 541. The fixing fitting 542 is an L-shaped fitting and has a fixing surface for the support base 541 and a fixing surface for the heat insulation support 54. Note that the support base 541 may be omitted, the fixing fitting 542 may be directly attached to the backing plate 35, and the heat insulation support 54 may be supported by the fixing fitting 542.

[0040] The heat insulation supports 54 mounted on the backing plate 35 are arranged at four locations at 90-degree intervals in the circumferential direction of the outer tube main body 31. A radiation shield 22 made of aluminum foil or the like is wound around the outer peripheral surface of the inner tube 2. The radiation shield 22 serves to thermally shield the inner tube 2 so that the radiant heat from the outer tube 3C does not reach the inner tube 2. The four heat insulation supports 54 arranged in the circumferential direction support the inner tube 2 around which the radiation shield 22 is wound. Note that in other embodiments, a layer of the radiation shield 22 may also be formed on the outer peripheral surface of the inner tube 2.

[0041] A method for manufacturing the vacuum insulation double tube 1C will be described. In the outer tube body 31, a window portion 63 is formed at a position where the inner tube 2 is supported. In the present embodiment, four window portions 63 arranged at intervals of 90 degrees in the circumferential direction are provided. Regarding the inner tube 2, no special accessories are attached, and only the winding of the radiation shield 22 is performed. When an aluminum foil is used as the radiation shield 22, about 20 winding layers are formed on the surface of the inner tube 2. All the components constituting the inner tube support 5C are attached to the backing plate 35.

[0042] The outer tube body 31 having the window portion 63 is externally fitted to the inner tube 2 with the winding layer of the radiation shield 22. Next, the backing plate 35 equipped with the inner tube support 5C is overlapped with the window portion 63 so that the overlapping portion OL is formed at the peripheral edge portion 35E. By this overlapping, the arc support surface 54A of the heat insulation support 54 abuts on the outer peripheral surface of the inner tube 2 via the radiation shield 22. Thereafter, the peripheral edge portion 35E is fillet welded near the opening edge 62E of the window portion 63 in the outer tube body 31. Thereby, a welded portion Wd is formed at the peripheral edge portion 35E, and the backing plate 35 is fixed to the outer tube body 31. The same operation is performed for the four window portions 63.

[0043] According to the third embodiment, after all the components constituting the inner tube support 5C are equipped on the backing plate 35, the outer tube body 31 is externally fitted to the inner tube 2, and then the backing plate 35 is attached to the window portion 63. That is, since the arrangement of the inner tube support 5C is completed only by attaching the backing plate 35 to the window portion 63, the workability can be further improved. In addition, since no component attachment work by welding is performed on the inner tube 2, the airtight inspection work locations associated with welding can be reduced. Further, since the radiation shield 22 can be wound around the cylindrical inner tube 2 having no accessories on the surface, the winding work can be greatly simplified.

[0044] [Fourth Embodiment] FIG. 7(A) and FIG. 7(B) are axial cross-sectional views for explaining a manufacturing method of the vacuum insulated double tube 1D according to the fourth embodiment, and FIG. 8(A) is a cross-sectional view taken along line VIIIA-VIIIA of FIG. 7(B). The vacuum insulated double tube 1D includes a coaxially arranged inner tube 2 and outer tube 3D, and a vacuum insulation layer 4 between the inner tube 2 and the outer tube 3D. The outer tube 3D consists of an outer tube main body 31 and a pair of split tubes 36A, 36B (split pieces). That is, the members corresponding to the outer tube piece 32 in the basic embodiment of FIG. 1 are the first split tube 36A and the second split tube 36B in the fourth embodiment. The accessory exemplified in the fourth embodiment is an inner tube support 5D that supports the inner tube 2 in the radial direction.

[0045] As shown in FIG. 7(A), the outer tube main body 31 is provided with a dividing portion 64 that is divided at the attachment position of the inner tube support 5D. Substantially, the dividing portion 64 can be formed by arranging a pair of outer tube main bodies 31 such that their edges 31E face each other with a predetermined interval in the axial direction. The split tubes 36A, 36B are attached to the pair of outer tube main bodies 31 so as to connect the dividing portion 64. That is, as shown in FIG. 7(B), in the axial direction, the split tubes 36A, 36B have a length longer than that of the dividing portion 64. The split tubes 36A, 36B are attached to the pair of outer tube main bodies 31 such that near both edges 36E, there are overlapping portions OL that overlap the vicinity of the edges 31E of the pair of outer tube main bodies 31 from the outside, and cover the dividing portion 64. Note that instead of the split tubes 36A, 36B, the dividing portion 64 may be connected by three or more split pieces.

[0046] Referring to FIG. 8(A), the inner tube support 5D includes a heat insulation support 55 that supports the inner tube 2, and a fixing fitting 551 that holds the heat insulation support 55 on the second split tube 36B. The heat insulation support 55 is a plate made of a heat insulating material having a predetermined thickness in the axial direction, and has a housing portion 552, a bottom portion 553, a pair of side portions 554, and a notch portion 555.

[0047] The accommodating portion 552 is a U-shaped groove that accommodates the inner tube 2. The bottom portion 553 is the portion that abuts against the inner surface of the second split tube 36B, and is clamped by a pair of fixing brackets 551 arranged in the axial direction. The fixing brackets 551 are fixed to the inner surface of the second split tube 36B and hold the bottom portion 553. The pair of side portions 554 are portions that extend obliquely upward from the bottom portion 553, and serve as spacers that fill the space between the side portion of the inner tube 2 and the outer tube 3D. The notch portion 555 is a portion formed by notching a part of the heat insulation support 55 radially inward.

[0048] The first split tube 36A and the second split tube 36B are formed into a cylindrical body by butting and welding the circumferential edges thereof. A backing metal 361 is attached inside the butting connection portion 36J of both. The notch portion 555 is provided to avoid interference with the backing metal 361 and prevent the heat during welding from reaching the heat insulation support 55. Note that, since the backing metal 361 becomes a protrusion inside the outer tube 3D, it also serves to prevent the heat insulation support 55 from rotating around the inner tube 2.

[0049] Referring further to FIG. 8(B), a manufacturing method of the vacuum insulated double tube 1D will be described. As shown in FIG. 7(A), a dividing portion 64 in which the outer tube body 31 is completely separated is formed in the outer tube body 31. The inner tube 2 is externally fitted with a pair of outer tube bodies 31 in a state where no special accessories are attached. Note that the radiation shield 22 shown in the third embodiment may be wound around the surface of the inner tube 2 in advance. An inner tube support 5D is attached in advance to the inner surface of the second split tube 36B. That is, the fixing bracket 551 is welded to the inner surface of the second split tube 36B, and the heat insulation support 55 is held by the fixing bracket 551. No components are attached to the first split tube 36A in particular.

[0050] Next, as shown in FIG. 7(B), the second split tube 36B is disposed at the dividing portion 64 so that an overlapping portion OL is formed with respect to the pair of outer tube bodies 31. At this time, the accommodating portion 552 of the heat insulation support 55 is fitted into the inner tube 2. Subsequently, with the backing metal 361 attached to the inner surface, the circumferential edge 36E1 of the first split tube 36A and the circumferential edge 36E2 of the second split tube 36B are butted against each other. As a result, the inner tube 2 is covered with the pair of outer tube bodies 31 and the split tubes 36A and 36B. Thereafter, the butting connection portion 36J of the edges 36E1 and 36E2 is welded to form a cylindrical body covering the dividing portion 64. Finally, the axial edges 36E of the first split tube 36A and the second split tube 36B are fillet welded to the surface of the outer tube body 31.

[0051] According to the fourth embodiment, the second split tube 36B with accessories, that is, the inner tube support 5D attached thereto, can be attached to the outer tube body 31 with the inner tube 2 completely exposed at the dividing portion 64 of the outer tube body 31. For this reason, it becomes easy to check the surface state of the inner tube 2 and the attachment position of the inner tube support 5D. In addition, since the operation of drilling an opening for the window portion in the outer tube body 31 is not required, the preparation work of the outer tube body 31 becomes easy.

[0052] [Fifth Embodiment] FIG. 9(A) is an axial cross-sectional view of the vacuum insulated double tube 1DA according to the fifth embodiment, and FIG. 9(B) is a cross-sectional view taken along line IXB-IXB of FIG. 9(A). The vacuum insulated double tube 1DA is a modified example of the inner tube support 5D of the previous fourth embodiment, and the rest is the same as the vacuum insulated double tube 1D.

[0053] The vacuum insulated double tube 1DA includes an inner tube 2, an outer tube 3D, and a vacuum insulation layer 4. The outer tube 3D includes an outer tube body 31 and a pair of split tubes 36A and 36B. The inner tube support 5DA included in the vacuum insulated double tube 1DA includes a floating stopper 56 in addition to the heat insulation support 55. The floating stopper 56 is made of a heat insulating material and restricts the inner tube 2 from rising from the accommodating portion 552 of the heat insulation support 55. The floating stopper 56 has a radial width that fills the gap between the upper portion of the inner tube 2 and the inner surface of the first split tube 36A.

[0054] The floating stopper 56 includes an inner tube pressing portion 561 and a fitting portion 562. The inner tube pressing portion 561 covers the outer peripheral surface of the inner tube 2 and restricts the upward movement of the inner tube 2. The fitting portion 562 is disposed on both sides of the inner tube pressing portion 561 and is a portion that is fitted to the heat insulation support 55.

[0055] Figs. 9(C) and (D) are cross-sectional views in a direction orthogonal to the axial direction for explaining the manufacturing method of the vacuum heat insulation double tube 1DA. Fig. 9(C) shows a state in which the heat insulation support 55 is attached to the inner surface of the second half split tube 36B via the fixing fitting 551, and the inner tube 2 is supported by the heat insulation support 55. Subsequently, as shown in Fig. 9(D), the floating stopper 56 is attached to the heat insulation support 55. Thereby, a state is formed in which the inner tube pressing portion 561 abuts or is close to the outer peripheral surface of the inner tube 2, and the fitting portion 562 is fitted into the side portion 554 of the heat insulation support 55.

[0056] After that, the first half split tube 36A is butted against the second half split tube 36B so as to wrap the floating stopper 56. In this state, the butting connection portion 36J between the circumferential edge 36E1 of the first half split tube 36A and the circumferential edge 36E2 of the second half split tube 36B is butt-welded using the backing metal 361. Finally, the axial edges 36E of the first half split tube 36A and the second half split tube 36B are fillet-welded to the surface of the outer tube body 31. When the floating stopper 56 abuts against the second half split tube 36B, the floating is restricted.

[0057] [Sixth Embodiment] FIG. 10(A) is an axial sectional view of the vacuum insulated double tube 1E according to the sixth embodiment, and FIG. 10(B) is a sectional view taken along line XB-XB of FIG. 10(A). The vacuum insulated double tube 1E includes a coaxially arranged inner tube 2 and outer tube 3E, and a vacuum insulation layer 4 between the inner tube 2 and the outer tube 3E. The outer tube 3E consists of an outer tube main body 31 and a pair of split tubes 37A, 37B (split pieces). The accessory exemplified in the sixth embodiment is an inner tube support 5E that supports the inner tube 2 in the radial direction, similar to the inner tube support 5C exemplified in the third embodiment of FIG. 6. In the third embodiment, an example of attaching the inner tube support 5C to the plate 35 that closes the window portion 63 was shown, but in the sixth embodiment, an example of attaching the inner tube support 5E to the split tubes 37A, 37B is shown.

[0058] The inner tube support 5E includes a heat insulation support 57, and a support base 571 and a fixing fitting 572 for fixing the heat insulation support 54 to the metal split tubes 37A, 37B. The heat insulation support 57 is made of a heat insulating material and is a member that directly supports the inner tube 2. The heat insulation support 57 supports the inner tube 2 around which the radiation shield 22 is wound. The support base 571 is a member that serves as a mounting seat for the heat insulation support 57 and is fixed to the inner surface of the first split tube 37A or the second split tube 37B by welding or the like. The fixing fitting 572 is a member for fixing the heat insulation support 57 to the support base 571.

[0059] The inner tube supports 5E are arranged at four locations at 90-degree intervals in the circumferential direction of the inner tube 2. Two inner tube supports 5E are pre-attached to each of the first split tube 37A and the second split tube 37B. The first split tube 37A and the second split tube 37B are formed into a cylindrical body by butting and welding the circumferential edges together. A backing plate 371 is attached inside the butting connection portion 37J of the two.

[0060] A method for manufacturing a vacuum-insulated double tube 1E will be described. In the outer tube body 31, a dividing portion 65 is formed where the outer tube body 31 is completely separated. No accessories related to the support are attached to the inner tube 2, and only the radiation shield 22 is wound around it. After fitting a pair of outer tube bodies 31 onto the inner tube 2, the first half-cracked tube 37A and the second half-cracked tube 37B each equipped with an inner tube support 5E are butted against each other so as to cover the dividing portion 64. At this time, an overlapping portion OL is formed where the vicinity of the axial edge 37E of the half-cracked tubes 37A and 37B overlaps the vicinity of the edge 31E of the pair of outer tube bodies 31 from the outside. Then, with the backing plate 371 attached to the inner surface, the butting connection portion 37J of the half-cracked tubes 37A and 37B is welded. Finally, the axial edges 37E of the first half-cracked tube 37A and the second half-cracked tube 37B are fillet welded to the surface of the outer tube body 31.

[0061] [Summary of the Present Disclosure] The specific embodiments described above include the following disclosed configurations.

[0062] A method for manufacturing a double tube according to a first aspect of the present disclosure is a method for manufacturing a double tube including an inner tube through which a fluid flows, an outer tube covering the inner tube, and an annular space layer between the inner tube and the outer tube, the method including attaching an accessory to the inner surface of an outer tube piece constituting a part of the outer tube, covering the inner tube with the outer tube piece and an outer tube body constituting the remaining part of the outer tube, and attaching the outer tube piece to the outer tube body in a state where at least a part of the peripheral edge of the outer tube piece overlaps the outer tube body.

[0063] According to the first aspect, an accessory is attached in advance to the inner surface of the outer tube piece, and a procedure is taken to cover the inner tube with the outer tube piece and the outer tube body. For this reason, it becomes possible to perform an operation of fitting the outer tube body in a state where no accessory is attached to the inner surface onto the inner tube and then retrofitting the outer tube piece with the accessory to the outer tube body. Therefore, the possibility that the operation of arranging the inner tube inside the outer tube is hindered by the accessory can be suppressed. Also, since the peripheral edge of the outer tube piece is attached in a state of overlapping the outer tube body, it is easy to ensure the sealing performance of the annular space layer.

[0064] In the manufacturing method of the double tube according to the second aspect, in the manufacturing method of the first aspect, attaching the peripheral edge portion of the outer tube piece in a state overlapping the outer tube main body means attaching it by overlapping from the outside with respect to the outer tube main body.

[0065] According to the second aspect, the operation of attaching the outer tube piece from the outside of the outer tube main body can be performed. Therefore, after fitting the outer tube main body onto the inner tube, the operation of attaching the outer tube piece to the outer tube main body can be simplified.

[0066] In the manufacturing method of the double tube according to the third aspect, in the manufacturing method of the first or second aspect, the outer tube main body has a window portion, and the outer tube piece is a plate having a size to close the window portion, and attaching the outer tube piece to the outer tube main body means attaching the plate to the window portion.

[0067] According to the third aspect, by simply attaching a plate with accessories to the window portion of the outer tube main body, a state in which the accessories are arranged at a predetermined position can be formed. Further, it is possible to attach the plate to the window portion while checking the positional relationship between the accessories and the surface of the inner tube through the window portion. Therefore, it becomes easier to accurately attach the accessories to a predetermined position determined in advance.

[0068] In the manufacturing method of the double tube according to the fourth aspect, in the manufacturing method of the third aspect, a part of the accessory is attached to the surface of the inner tube at the opening position of the window portion, and the plate is equipped with the remaining part of the accessory, and the plate is attached to the window portion in this state.

[0069] According to the fourth aspect, through the window portion, while checking the positional relationship with the accessories attached to the inner tube, a plate equipped with the remaining accessories can be attached to the window portion. Therefore, after adjusting the position of the accessories on the outer tube side with respect to the accessories on the inner tube side, it becomes possible to fix the plate to the window portion, and it becomes easier to manufacture a double tube having the performance as designed. The fourth aspect is suitable when the accessory is, for example, an axial stop that restricts the relative movement in the axial direction between the inner tube and the outer tube.

[0070] The manufacturing method of the double tube according to the fifth aspect is, in the manufacturing method of the third aspect, to attach the plate to the window portion with all of the accessories mounted on the plate.

[0071] According to the fifth aspect, without attaching the accessories to the inner tube, by simply inserting it into the outer tube and attaching the plate to the window portion, the arrangement of the accessories in the annular space layer is completed. Therefore, the workability can be further improved. Further, when it is necessary to form some surface layer on the surface of the inner tube, the surface layer can be formed by winding a sheet around the surface of the inner tube in a state where no accessory exists, and the workability becomes good. The fifth aspect is suitable when the accessory is, for example, an inner tube support that supports the inner tube in the radial direction.

[0072] The manufacturing method of the double tube according to the sixth aspect is, in the manufacturing method of the first or second aspect, the outer tube body has a dividing portion divided at the attachment position of the accessory, and attaching the outer tube piece to the outer tube body is to attach the outer tube piece so as to connect the dividing portion.

[0073] According to the sixth aspect, with the inner tube completely exposed at the dividing portion of the outer tube body, the outer tube piece with the accessory can be attached to the outer tube body. For this reason, it becomes easy to check the surface state of the inner tube. Further, since the work of drilling a window portion opening in the outer tube body becomes unnecessary, the preparation work of the outer tube body becomes easy.

[0074] The manufacturing method of the double tube according to the seventh aspect is, in the manufacturing method of the sixth aspect, the outer tube piece is composed of a plurality of divided pieces divided in the circumferential direction, and the accessory is attached to at least one inner surface of the plurality of divided pieces.

[0075] According to the seventh aspect, the work of connecting the dividing portion of the outer tube body can be completed by assembling the divided pieces of the outer tube piece. Therefore, the workability can be made good.

[0076] The double pipe according to the eighth aspect includes an inner pipe through which a fluid flows, an outer pipe that covers the inner pipe, an annular space layer between the inner pipe and the outer pipe, and accessories disposed in the annular space. The outer pipe includes an outer pipe piece that is a part of the outer pipe and an outer pipe body that is the remainder of the outer pipe. The accessory is attached to the inner surface of the outer pipe piece, and at least a part of the peripheral edge of the outer pipe piece is attached in a state of overlapping the outer pipe body.

[0077] According to the eighth aspect, the outer pipe that covers the inner pipe is constituted by the outer pipe piece with the accessory attached to the inner surface in advance and the outer pipe body. Therefore, it is possible to perform an operation of inserting the inner pipe through the outer pipe body whose inner surface is not equipped with the accessory and then retrofitting the outer pipe piece with the accessory to the outer pipe body. Accordingly, a double pipe that is easy to manufacture can be provided.

[0078] The double pipe according to the ninth aspect is the double pipe according to the eighth aspect, wherein the accessory is an axial stop that restricts the axial relative movement between the inner pipe and the outer pipe.

[0079] The double pipe according to the tenth aspect is the double pipe according to the eighth aspect, wherein the accessory is an inner pipe support that supports the inner pipe in the radial direction.

[0080] According to the ninth and tenth aspects, a double pipe in which the inner pipe and the outer pipe can be easily assembled by arranging an axial stop material or an inner pipe support material in the annular space layer can be provided.

[0081] The double pipe according to the eleventh aspect is the double pipe according to the eighth to tenth aspects, wherein the peripheral edge of the outer pipe piece is attached in a state of overlapping the outer pipe body from the outside.

[0082] According to the eleventh aspect, a double pipe can be provided in which the operation of attaching the outer pipe piece to the outer pipe body can be easily performed after fitting the outer pipe body onto the inner pipe.

[0083] The double tube according to the 12th aspect is the double tube of the 11th aspect, wherein the peripheral portion is attached to the surface of the outer tube body by a welded portion formed by fillet welding.

[0084] According to the 12th aspect, the outer tube piece can be attached to the outer tube body by a simple welding method.

Explanation of Reference Numerals

[0085] 1 Vacuum Insulated Double Tube (Double Tube) 2 Inner Tube 2P Attachment Position 3 Outer Tube 31 Outer Tube Body 32 Outer Tube Piece 32E, 33E, 34E Peripheral Portion 33, 34, 35 Fitting Plate (Outer Tube Piece / Plate) 36A, 37A First Half-Cracked Tube (Split Piece) 36B, 37B Second Half-Cracked Tube (Split Piece) 4 Vacuum Insulation Layer (Annular Space Layer) 5 Accessories 5A Axial Stop (Accessory) 51 Inner Tube Axial Stop Material (Part of the Accessory) 52 Outer Tube Axial Stop Material (Remaining Part of the Accessory) 5B Sliding Plate (Accessory) 5C, 5D, 5E Inner Tube Support (Accessory) 6 Opening 61, 62, 63 Window Portion 64 Division Portion OL Overlapping Portion

Claims

1. A method for manufacturing a double pipe comprising an inner pipe through which a fluid flows, an outer pipe covering the inner pipe, and an annular space layer between the inner pipe and the outer pipe, attaching an accessory to the inner surface of an outer pipe piece that forms part of the outer pipe, covering the inner pipe with the outer pipe piece and an outer pipe body that forms the remainder of the outer pipe, and attaching the outer pipe piece to the outer pipe body in a state where at least a part of the peripheral edge of the outer pipe piece overlaps the outer pipe body. A method for manufacturing a double pipe.

2. In the method for manufacturing a double pipe according to Claim 1, attaching the peripheral edge of the outer pipe piece in a state where it overlaps the outer pipe body means attaching it by overlapping from the outside with respect to the outer pipe body. A method for manufacturing a double pipe.

3. In the method for manufacturing a double pipe according to Claim 1 or 2, the outer pipe body has a window portion, the outer pipe piece is a plate having a size to close the window portion, and attaching the outer pipe piece to the outer pipe body means attaching the plate to the window portion. A method for manufacturing a double pipe.

4. In the method for manufacturing a double pipe according to Claim 3, attaching a part of the accessory to the surface of the inner pipe at the opening position of the window portion, and attaching the plate equipped with the remainder of the accessory to the window portion. A method for manufacturing a double pipe.

5. In the method for manufacturing a double pipe according to Claim 3, attaching the plate equipped with all of the accessory to the window portion. A method for manufacturing a double pipe.

6. In the method for manufacturing a double pipe according to Claim 1 or 2, the outer pipe body has a divided portion divided at the attachment position of the accessory, A method for manufacturing a double tube, wherein attaching the outer tube piece to the outer tube body is to attach the outer tube piece so as to connect the divided portions.

7. In the method for manufacturing a double tube according to claim 6, the outer tube piece is composed of a plurality of divided pieces divided in the circumferential direction, A method for manufacturing a double tube, wherein the accessory is attached to the inner surface of at least one of the plurality of divided pieces.

8. an inner tube through which a fluid flows, an outer tube covering the inner tube, an annular space layer between the inner tube and the outer tube, and an accessory disposed in the annular space layer, the double tube comprising: the outer tube includes an outer tube piece that is a part of the outer tube and an outer tube body that is the remaining part of the outer tube, the accessory is attached to the inner surface of the outer tube piece, A double tube, wherein at least a part of the peripheral edge of the outer tube piece is attached in a state of overlapping the outer tube body.

9. In the double tube according to claim 8, the accessory is an axial stop that restricts the axial relative movement between the inner tube and the outer tube.

10. In the double tube according to claim 8, the accessory is an inner tube support that supports the inner tube in the radial direction.

11. In the double tube according to any one of claims 8 to 10, A double tube, wherein the peripheral edge of the outer tube piece is attached in a state of overlapping the outer tube body from the outside.

12. In the double tube according to claim 11, A double tube, comprising a fillet weld portion between the side surface of the peripheral edge portion and the surface of the outer tube body.

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