Method for producing double pipe, and double pipe

Abstract

Provided is a method for producing a double pipe that is provided with an inner pipe through which a fluid flows, an outer pipe which covers the inner pipe, and an annular space layer which is between the inner pipe and the outer pipe. The method comprises: attaching an attachment to an inner surface of an outer pipe piece that constitutes a part of the outer pipe; covering the inner pipe with the outer pipe piece and an outer pipe body that constitutes 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 a peripheral edge part of the outer pipe piece overlaps with the outer pipe body.

Description

Double pipe manufacturing method and double pipe

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

[0002] A double-walled pipe including an inner pipe, an outer pipe, and an annular space layer between the inner pipe and the outer pipe may be used, for example, as a pipe for transporting low-temperature liquefied gas. In this case, the annular space layer is evacuated to form a vacuum insulation layer. Required accessories are placed in the annular space layer. The accessories include an axial stop material that restricts relative axial movement between the inner pipe and the outer pipe, and an inner pipe support material that supports the inner pipe in the radial direction. Patent Document 1 discloses a method for manufacturing a double-walled pipe in which an outer pipe is fitted into an inner pipe to which accessories have been previously attached.

[0003] However, when the manufacturing method described in Patent Document 1 is adopted, the fitting of the outer pipe requires work to avoid interference between the accessories attached to the inner surface of the outer pipe and the accessories already attached to the inner pipe, resulting in poor workability. Furthermore, in the case of a vacuum-insulated double-walled pipe, an end seal must be attached near the end of the inner pipe to seal the vacuum insulation layer. In this case, there is also the problem that the outer pipe with the attached accessories cannot be fitted onto the inner pipe.

[0004] Japanese Patent Application Laid-Open No. 2021-156272

[0005] The present disclosure aims to provide a method for efficiently manufacturing a double pipe that requires the placement of accessories between an inner pipe and an outer pipe, as well as a double pipe that can be efficiently manufactured.

[0006] A method for manufacturing a double pipe according to one aspect of the present disclosure is 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, and includes attaching an accessory to the inner surface of an outer pipe piece that constitutes a part of the outer pipe, enveloping the inner pipe with the outer pipe piece and an outer pipe body that constitutes the remainder of the outer pipe, and attaching the outer pipe piece to the outer pipe body in a state where at least a portion of the peripheral edge of the outer pipe piece overlaps the outer pipe body.

[0007] A double pipe according to another aspect of the present disclosure is a double pipe comprising an inner pipe through which a fluid flows, an outer pipe covering the inner pipe, an annular space layer between the inner pipe and the outer pipe, and an accessory disposed in the annular space layer, wherein the outer pipe includes an outer pipe piece which is a part of the outer pipe, and an outer pipe body which is the remainder of the outer pipe, and the accessory is attached to the inner surface of the outer pipe piece, and at least a portion of the peripheral edge of the outer pipe piece is attached so as to overlap the outer pipe body.

[0008] According to the present disclosure, it is possible to provide a method for efficiently manufacturing a double pipe that requires the placement of accessories between the inner pipe and the outer pipe, as well as a double pipe that can be efficiently manufactured.

[0009] FIG. 1 is an axial cross-sectional view of a double pipe according to a basic embodiment of the present disclosure. FIG. 2 is an axial cross-sectional view illustrating a manufacturing method for a double pipe according to a basic embodiment. FIG. 3 is an axial cross-sectional view of a double pipe according to a first embodiment of the present disclosure. FIGS. 4(A) to 4(C) are views for explaining a manufacturing method for a double pipe according to the first embodiment. FIG. 5(A) is a cross-sectional view perpendicular to the axial direction of a double pipe according to a second embodiment, and FIG. 5(B) is a cross-sectional view illustrating a manufacturing method for a double pipe according to the second embodiment. FIG. 6(A) is an axial cross-sectional view of a double pipe according to a third embodiment, and FIG. 6(B) is a cross-sectional view taken along line VIB-VIB of FIG. 6(A). FIGS. 7(A) and 7(B) are axial cross-sectional views for explaining a manufacturing method for a double pipe according to a fourth embodiment. FIG. 8(A) is a cross-sectional view taken along line VIIIA-VIIIA of FIG. 7(B), and FIG. 8(B) is a cross-sectional view perpendicular to the axial direction for explaining a manufacturing method for a double pipe according to the fourth embodiment. Fig. 9(A) is an axial cross-sectional view of a double pipe according to a fifth embodiment, Fig. 9(B) is a cross-sectional view taken along line IXB-IXB in Fig. 9(A), and Figs. 9(C) and (D) are cross-sectional views taken along a direction perpendicular to the axial direction for explaining a method for manufacturing a double pipe according to the fifth embodiment. Fig. 10(A) is an axial cross-sectional view of a double pipe according to a sixth embodiment, and Fig. 10(B) is a cross-sectional view taken along line XB-XB in Fig. 10(A).

[0010] Hereinafter, embodiments of a double pipe and a manufacturing method thereof according to the present disclosure will be described in detail with reference to the drawings. The double pipe according to the present disclosure has a structure including an inner pipe, an outer pipe, and an annular space layer between the inner pipe and the outer pipe. For example, the inner pipe and the outer pipe are arranged coaxially. Such a double pipe is used as a transport pipe for cryogenic liquefied gas. For example, liquefied hydrogen (LH2O) ２ When transferring a cryogenic liquefied gas such as liquefied gas (e.g., liquefied air), the annular space layer is evacuated to form a vacuum insulation layer. By using a vacuum insulated double pipe, it is possible to suppress the generation of boil-off gas of the liquefied gas, ice formation on the pipe surface, and the generation of liquefied air. In the embodiments shown below, a vacuum insulated double pipe is exemplified as the double pipe according to the present disclosure. Of course, the present disclosure is not limited to vacuum insulated double pipes, and can also be applied to other double pipes that do not have a vacuum insulation structure.

[0011] [Basic embodiment] Fig. 1 is an axial cross-sectional view of a vacuum insulated double pipe 1 (double pipe) according to a basic embodiment of the present disclosure. Fig. 1 shows the vicinity of an end 10 of the vacuum insulated double pipe 1. The vacuum insulated double pipe 1 comprises an inner pipe 2, an outer pipe 3, a vacuum insulation layer 4, and an accessory 5. The object to be transported through the vacuum insulated double pipe 1 is liquefied hydrogen.

[0012] The inner pipe 2 is a pipe through which the cryogenic fluid to be transported flows. In this embodiment, liquefied hydrogen flows through the inner pipe 2. The end of the inner pipe 2 is sealed with an end sealing portion 21 made of a cap. The outer pipe 3 is a pipe that covers the inner pipe 2 and is arranged coaxially with the inner pipe 2. The vacuum insulation layer 4 is an annular space layer between the inner pipe 2 and the outer pipe 3, and is formed by drawing a vacuum. Heat carriers are removed by drawing a vacuum, so that the annular space layer between the inner pipe 2 and the outer pipe 3 functions as the vacuum insulation layer 4. An end seal 302 is attached to the inner pipe 2 at the edge 301 of the outer pipe 3, sealing the edge of the vacuum insulation layer 4.

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

[0014] The outer pipe 3 is composed of an outer pipe main body 31 and an outer pipe piece 32. That is, a portion of one outer pipe 3 is composed of the outer pipe piece 32, and the remaining portion is composed of the outer pipe main body 31. An accessory 5 is attached to an inner surface 32A of the outer pipe piece 32. The outer pipe piece 32 is attached to the outer pipe main body 31 in a manner that an overlapping portion OL is formed in which the peripheral portion of the outer pipe piece 32 overlaps the outer pipe main body 31 in the radial direction. The outer pipe piece 32 overlaps the outer pipe main body 31 from the radial outside, and is fixed by a welded portion Wd formed by fillet welding to the peripheral portion.

[0015] 2 is an axial cross-sectional view showing a manufacturing method of the vacuum insulated double pipe 1 of the basic embodiment. When manufacturing the vacuum insulated double pipe 1, an opening 6 is formed in the outer pipe body 31. The opening 6 is opened at a position corresponding to the attachment position 2P of the accessory 5 in the inner pipe 2 or the vacuum insulation layer 4. In other words, the opening 6 is provided at the position where the accessory 5 should be placed when the inner pipe 2 is inserted into the outer pipe 3 to a predetermined position. The opening 6 can be provided in the form of a window portion obtained by cutting out a portion of the outer pipe body 31 in the axial and circumferential directions, or in the form of a divided portion where the outer pipe body 31 is completely divided.

[0016] The outer pipe piece 32 is sized to completely cover the opening 6 and is made of the same material and thickness as the outer pipe body 31. The outer pipe piece 32 may be made of a different material or thickness than the outer pipe body 31. The accessories 5 to be placed in the vacuum insulation layer 4 are pre-attached to the inner surface 32A of the outer pipe piece 32. No accessories 5 are attached to the surface of the inner pipe 2. If the accessories 5 are made up of a combination of multiple parts, some of the accessories 5 may be pre-attached to the surface of the inner pipe 2. However, an end seal 302 is attached near the end of the inner pipe 2 to seal the edge of the vacuum insulation layer 4. An end seal 21 is also attached to the end of the inner pipe 2. After these are attached, the inner pipe 2 is inspected for airtightness. These are the preparatory steps for assembling the vacuum insulation double pipe 1.

[0017] Next, the process of encasing the inner pipe 2 with the outer pipe body 31 and the outer pipe piece 32 is performed. Specifically, first, the outer pipe body 31 is fitted onto the inner pipe 2. This fitting process can be easily performed because no accessories 5 are attached to the inner surface of the outer pipe body 31. In other words, the outer pipe body 31 can be fitted onto the inner pipe 2 even if the end seal 302 has already been attached to the inner pipe 2. Note that if the end seal 302 is attached after the fitting process, a process of re-inspecting the airtightness of the inner pipe 2 after the fitting is required, which reduces workability. Then, the outer pipe piece 32, which has already been equipped with the accessories 5, is positioned to block the opening 6 of the outer pipe body 31. This positioning process is performed in a manner such that the outer pipe piece 32 blocks the opening 6 of the outer pipe body 31 from the outside, as indicated by the arrow in FIG. 2 .

[0018] After the above-described wrapping process, a process of attaching the outer pipe body 31 to the outer pipe piece 32 is performed. The outer pipe piece 32 is positioned so that it closes the opening 6 and the peripheral edge 32E of the outer pipe piece 32 overlaps the vicinity of the opening edge 6E of the outer pipe body 31. This positioning includes adjusting the position of the accessory 5 to a predetermined position within the vacuum insulation layer 4. If the accessory 5 is attached to the outer pipe 3 in advance and then fitted onto the inner pipe 2, it is extremely difficult to adjust the position of the accessory 5. In this embodiment, by adjusting the attachment position of the outer pipe piece 32 to the outer pipe body 31, it is possible to easily adjust the position of the accessory 5.

[0019] After adjusting the position of the accessory 5, the outer pipe piece 32 is fixed to the outer pipe main body 31 by welding. Specifically, the peripheral edge 32E of the outer pipe piece 32 is fillet welded to the surface of the outer pipe main body 31 near the opening edge 6E. 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 pipe main body 31, where the region near the peripheral edge 32E of the outer pipe piece 32 is overlapped from the radial outside, and a welded portion Wd is formed in the peripheral edge 32E.

[0020] The overlapping portion OL is not limited to a specific overlapping configuration, as long as the outer pipe piece 32 and the outer pipe body 31 overlap by a predetermined radial width. The outer pipe piece 32 and the outer pipe body 31 may overlap directly, or an inclusion or coating layer may be present between them. Furthermore, as long as the airtightness of the vacuum insulation layer 4 is ensured, a portion of the peripheral edge 32E of the outer pipe piece 32 and the outer pipe body 31 may not overlap. Furthermore, a configuration in which the peripheral edge 32E does not overlap, but the welded portion Wd overlaps the outer pipe body 31, is also acceptable. That is, the overlapping portion OL may be formed by the overlap between the welded portion Wd and the outer pipe body 31.

[0021] According to the basic embodiment described above, the accessory 5 is attached to the inner surface 32A of the outer pipe piece 32 in advance, and then the outer pipe piece 32 and the outer pipe body 31 encase the inner pipe 2. This allows the inner pipe 2 to be inserted into the outer pipe body 31 without the accessory 5 attached to its inner surface, and then the outer pipe piece 32 equipped with the accessory 5 can be later attached to the opening 6 of the outer pipe body 31. Therefore, the accessory 5 does not interfere with the process of placing the inner pipe 2 inside the outer pipe 3. Furthermore, since the peripheral edge 32E of the outer pipe piece 32 is attached to the outer pipe body 31 so as to overlap the outer pipe body 31, it is easy to ensure the sealing of the vacuum insulation layer 4. Furthermore, since the outer pipe piece 32 is attached from the outside of the outer pipe body 31, the process of attaching the outer pipe piece 32 to the outer pipe body 31 after inserting the inner pipe 2 into the outer pipe body 31 is simplified. Various embodiments of the vacuum insulated double pipe 1 that embody the basic embodiment described above will be described below.

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

[0023] The shaft stop 5A includes an inner pipe shaft stop material 51 (part of the accessory) and an outer pipe shaft stop material 52 (the remainder of the accessory). The inner pipe shaft stop material 51 is a component that is pre-attached to the surface of the inner pipe 2 and is composed of a first bracket 511 and a first support plate 512 made of a metal material, and an insulating spacer 513 made of an insulating material. The first bracket 511 is a rectangular plate with a predetermined thickness and is welded to the outer surface of the inner pipe 2 along the axial direction of the inner pipe 2. The first support plate 512 is a flat plate welded to the outer surface of the inner pipe 2 so that its back side is supported by the first bracket 511. On its front side, it has a support surface consisting of a flat surface extending circumferentially around the inner pipe 2. The insulating spacer 513 is attached to the support surface of the first support plate 512 and has a rectangular parallelepiped shape.

[0024] The outer tube shaft stopping member 52 is a component that is attached in advance to the inner surface 33A of the backing plate 33, and includes a second bracket 521 and a second support plate 522 made of metal. The second bracket 521 is a rectangular plate with a predetermined thickness, and is welded to the inner surface 33A of the backing plate 33 so as to extend along the tube axis direction of the outer tube 3A. The second support plate 522 is a flat plate welded to the inner surface 33A of the backing plate 33 so that its back side is supported by the second bracket 521, and has a support surface on its front side that is a flat surface extending in the circumferential direction of the outer tube 3A.

[0025] As shown in Figure 3, the backing plate 33 is attached to the outer pipe body 31 so that the second support plate 522 faces the first support plate 512 at a predetermined distance, that is, so that their support surfaces face each other. The insulating spacer 513 is tightly sandwiched between the first support plate 512 and the second support plate 522. The presence of the insulating spacer 513 suppresses heat input from the outer pipe 3A to the inner pipe 2. The backing plate 33 is attached to the outer pipe body 31 so that an area near its peripheral edge 33E forms an overlapping portion OL with the outer pipe body 31. A welded portion Wd is formed by fillet welding on the peripheral edge 33E of the backing plate 33.

[0026] The example in Figure 3 illustrates an axial stop 5A in which it is assumed that the inner pipe 2 will move relatively only in one axial direction (to the right in Figure 3). If it is assumed that the inner pipe 2 will move relatively only to the left, the opposing direction of the inner pipe axial stop member 51 and the outer pipe axial stop member 52 is reversed from left to right compared to Figure 3. Furthermore, if it is assumed that the inner pipe 2 will move relatively both left and right, a pair of inner pipe axial stop members 51 and outer pipe axial stop members 52 with opposing directions is provided. Alternatively, a configuration may be adopted in which insulating spacers 513 are attached to both sides of a single first support plate 512, and second support plates 522 are provided to face these, respectively.

[0027] 4A to 4C are diagrams illustrating a manufacturing method for a vacuum insulated double pipe 1A. As shown in FIG. 4A, a window 61 is formed in the outer pipe body 31 for later attachment of a backing plate 33. The window 61 corresponds to the opening 6 in the basic embodiment of FIG. 1. The window 61 is provided in the outer pipe body 31 so as to open at the attachment position 2P for the shaft stop 5A, which serves as an accessory. FIG. 4A shows an example in which four window portions 61, each having a rectangular opening in side view, are formed at equal intervals around the circumference of the outer pipe body 31. The outer pipe body 31 is then fitted onto the inner pipe 2, or the inner pipe 2 is inserted into the outer pipe body 31.

[0028] 4(C) is a plan view of the backing plate 33 to which the outer tube shaft stopping member 52 has been attached in advance. The backing plate 33 is an arc-shaped flat plate sized to completely cover the window portion 61. That is, the backing plate 33 has a peripheral edge portion 33E that extends outward in the axial and circumferential directions beyond the opening edge 61E of the window portion 61, in order to form the overlapping portion OL in FIG. 3 .

[0029] 4(B) is a diagram showing how the backing plate 33 equipped with the outer pipe shaft stopping member 52 is attached to the window portion 61 of the outer pipe main body 31. The backing plate 33 is attached from the radial outside of the outer pipe main body 31 so that the outer pipe shaft stopping member 52 is fitted into the window portion 61. This fitting results in the inner pipe 2 being enveloped by the outer pipe main body 31 and the backing plate 33.

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

[0031] [Second Embodiment] Figure 5(A) is a cross-sectional view of a vacuum insulated double pipe 1B according to a second embodiment, taken in a direction perpendicular to the axial direction. The vacuum insulated double pipe 1B includes an inner pipe 2 and an outer pipe 3B that are coaxially arranged, and a vacuum insulation layer 4 between the inner pipe 2 and the outer pipe 3B. The outer pipe 3B comprises an outer pipe body 31 and a backing plate 34 (plate) that corresponds to the outer pipe piece 32 of the basic embodiment. In the second embodiment, an example is shown in which the accessory 5 is a sliding plate 5B that allows the inner pipe 2 to slide inside the outer pipe 3B, and a slide support 53 that supports the inner pipe 2.

[0032] In double-wall pipes, a support structure that supports the inner pipe without restraining it may be required. For example, the inner pipe may be supported so that it can move left and right at a bend in a horizontal plane, or so that it can move up and down at a bend in a vertical plane. The sliding plate 5B shown in Figure 5 corresponds to the former support structure.

[0033] As shown in FIG. 5A , the inner pipe 2 is supported from below by slide supports 53. The slide supports 53 are fixed to the outer peripheral surface of the inner pipe 2 and are made of a heat insulating material to suppress heat conduction between the inner pipe 2 and the outer pipe 3B. The slide supports 53 are simply placed on the sliding plate 5B. In other words, the lower end surfaces of the slide supports 53 are not fixed to the sliding plate 5B. This allows the inner pipe 2 to slide left and right on the sliding plate 5B together with the slide supports 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 pipe body 31 at the welded portion Wd. Note that if the inner pipe 2 is to be movable up and down, the slide supports 53 and the sliding plate 5B are positioned to the sides of the inner pipe 2.

[0034] 5(B) is a cross-sectional view showing a manufacturing method of the vacuum insulated double pipe 1B. A window 62 is opened in the outer pipe body 31 at a location corresponding to the arrangement position of the slide support 53. Meanwhile, 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 62. Therefore, when the backing plate 34 is placed over the window 62 from the outside, an overlapping portion OL can be formed in which the vicinity of the opening edge 62E of the window 62 and the vicinity of the peripheral edge 34E of the backing plate 34 overlap in the radial direction.

[0035] First, the outer pipe body 31 having the window 62 is fitted onto the inner pipe 2 with the slide support 53 attached in a predetermined position. After this fitting, the slide support 53 may be attached to the inner pipe 2 through the window 62. Next, the backing plate 34 equipped with the sliding plate 5B is overlapped onto the window 62 so that an overlapping portion OL is formed on the peripheral edge 34E. This overlapping brings the sliding plate 5B into contact with the underside of the slide support 53. Thereafter, the peripheral edge 34E is fillet welded to the outer pipe body 31.

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

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

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

[0039] The support base 541 is a member that serves as an attachment seat for the heat insulating support 54, and is fixed to the backing plate 35 by welding or the like. The fixing bracket 542 is a member for fixing the heat insulating support 54 to the support base 541. The fixing bracket 542 is an L-shaped bracket, and has a fixing surface for the support base 541 and a fixing surface for the heat insulating support 54. It is also possible to omit the support base 541 and attach the fixing bracket 542 directly to the backing plate 35 so that the heat insulating support 54 is supported by the fixing bracket 542.

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

[0041] A method for manufacturing the vacuum insulated double pipe 1C will now be described. A window 63 is opened in the outer pipe body 31 at a position where the inner pipe 2 is supported. In this embodiment, four windows 63 are provided, spaced circumferentially at 90-degree intervals. No special accessories are attached to the inner pipe 2; only the radiation shield 22 is wound around it. When aluminum foil is used as the radiation shield 22, approximately 20 layers are wound around the surface of the inner pipe 2. All of the components that make up the inner pipe support 5C are attached to the backing plate 35.

[0042] The outer pipe body 31 having the window portion 63 is fitted onto the inner pipe 2 with the wound layer of the radiation shield 22. Next, the backing plate 35 equipped with the inner pipe support 5C is overlapped onto the window portion 63 so that an overlapping portion OL is formed at the peripheral edge portion 35E. This overlapping allows the arcuate support surface 54A of the heat insulation support 54 to abut against the outer peripheral surface of the inner pipe 2 with the radiation shield 22 interposed therebetween. Thereafter, the peripheral edge portion 35E is fillet welded to the outer pipe body 31 near the opening edge 62E of the window portion 63. This forms a weld Wd at the peripheral edge portion 35E, and the backing plate 35 is fixed to the outer pipe body 31. Similar operations are performed for the four window portions 63.

[0043] According to the third embodiment, all of the components constituting the inner pipe support 5C are mounted on the backing plate 35, and after the outer pipe body 31 is fitted onto the inner pipe 2, the backing plate 35 is attached to the window 63. In other words, the arrangement of the inner pipe support 5C is completed simply by attaching the backing plate 35 to the window 63, which further improves workability. In addition, since no component attachment work by welding is performed on the inner pipe 2, the number of locations for airtightness inspection work associated with welding can be reduced. Furthermore, since the radiation shield 22 can be wrapped around the cylindrical inner pipe 2 with no accessories on its surface, the wrapping work can be greatly simplified.

[0044] [Fourth Embodiment] Figures 7(A) and 7(B) are axial cross-sectional views illustrating a manufacturing method for a vacuum insulated double pipe 1D according to a fourth embodiment, and Figure 8(A) is a cross-sectional view taken along line VIIIA-VIIIA in Figure 7(B). The vacuum insulated double pipe 1D includes a coaxially arranged inner pipe 2 and outer pipe 3D, and a vacuum insulation layer 4 between the inner pipe 2 and the outer pipe 3D. The outer pipe 3D comprises an outer pipe body 31 and a pair of split pipe halves 36A and 36B (segments). In other words, in the fourth embodiment, the components corresponding to the outer pipe piece 32 in the basic embodiment of Figure 1 are the first split pipe half 36A and the second split pipe half 36B. The accessory illustrated in the fourth embodiment is an inner pipe support 5D that radially supports the inner pipe 2.

[0045] As shown in FIG. 7A , the outer pipe body 31 is provided with a divided portion 64 at the attachment position of the inner pipe support 5D. Essentially, the divided portion 64 can be formed by arranging a pair of outer pipe bodies 31 so that their end edges 31E face each other at a predetermined axial distance. The split pipe halves 36A, 36B are attached to the pair of outer pipe bodies 31 so as to connect the divided portion 64. That is, as shown in FIG. 7B , the split pipe halves 36A, 36B are longer in the axial direction than the divided portion 64. The split pipe halves 36A, 36B are attached to the pair of outer pipe bodies 31 so that the vicinity of both end edges 36E form overlapping portions OL that overlap the end edges 31E of the pair of outer pipe bodies 31 from the outside and so as to cover the divided portion 64. Note that instead of the split pipe halves 36A, 36B, three or more split pieces may be used to connect the divided portion 64.

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

[0047] The accommodation portion 552 is a U-shaped groove that accommodates the inner pipe 2. The bottom portion 553 abuts against the inner surface of the second split pipe half 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 pipe half 36B and hold the bottom portion 553. The pair of side portions 554 extend obliquely upward from the bottom portion 553 and serve as spacers that fill the gap between the side portions of the inner pipe 2 and the outer pipe 3D. The cutout portion 555 is formed by cutting a portion of the insulation support 55 radially inward.

[0048] The first and second pipe halves 36A and 36B are butt-welded together at their circumferential edges to form a cylindrical body. A backing metal 361 is attached to the inside of the butt joint 36J between the first and second pipe halves. The notch 555 is provided to avoid interference with the backing metal 361 and to prevent heat from reaching the heat insulating support 55 during welding. The backing metal 361 forms a protrusion inside the outer pipe 3D, and therefore also serves to prevent the heat insulating support 55 from rotating twice around the inner pipe.

[0049] A manufacturing method for the vacuum insulated double pipe 1D will be described with further reference to FIG. 8B. As shown in FIG. 7A, a dividing section 64 is formed in the outer pipe body 31, where the outer pipe body 31 is completely separated. A pair of outer pipe bodies 31 is fitted onto the inner pipe 2 without any particular accessories attached. The radiation shield 22 described in the third embodiment may be wrapped around the surface of the inner pipe 2. An inner pipe support 5D is attached to the inner surface of the second split pipe half 36B in advance. A fixing bracket 551 is welded to the inner surface of the second split pipe half 36B, and the fixing bracket 551 holds the insulation support 55. No particular parts are attached to the first split pipe half 36A.

[0050] Next, as shown in FIG. 7B , the second pipe half 36B is disposed in the separation section 64 so as to form an overlapping portion OL with the pair of outer pipe bodies 31. At this time, the housing portion 552 of the insulation support 55 is fitted into the inner pipe 2. Next, with the backing metal 361 attached to the inner surface, the circumferential edge 36E1 of the first pipe half 36A is butted against the circumferential edge 36E2 of the second pipe half 36B. As a result, the inner pipe 2 is surrounded by the pair of outer pipe bodies 31 and the pipe halves 36A and 36B. The butt joint portion 36J of the edges 36E1 and 36E2 is then welded to form a cylindrical body covering the separation section 64. Finally, the axial edges 36E of the first pipe half 36A and the second pipe half 36B are fillet welded to the surface of the outer pipe body 31.

[0051] According to the fourth embodiment, the outer pipe piece with accessories, i.e., the second split pipe half 36B with the inner pipe support 5D attached, can be attached to the outer pipe body 31 with the inner pipe 2 completely exposed at the divided portion 64 of the outer pipe body 31. This makes it easy to check the surface condition of the inner pipe 2 and the attachment position of the inner pipe support 5D. In addition, since the work of drilling a window opening in the outer pipe body 31 is not required, the preparation work of the outer pipe body 31 is easy.

[0052] [Fifth embodiment] Fig. 9(A) is an axial cross-sectional view of a vacuum thermally insulated double pipe 1DA according to a fifth embodiment, and Fig. 9(B) is a cross-sectional view taken along line IXB-IXB in Fig. 9(A). The vacuum thermally insulated double pipe 1DA is a modified example of the inner pipe support 5D of the fourth embodiment, and the remaining parts are the same as those of the vacuum thermally insulated double pipe 1D.

[0053] The vacuum insulated double pipe 1DA includes an inner pipe 2, an outer pipe 3D, and a vacuum insulation layer 4. The outer pipe 3D is composed of an outer pipe body 31 and a pair of split pipe halves 36A and 36B. The inner pipe support 5DA provided in the vacuum insulated double pipe 1DA includes a floating stopper 56 in addition to the insulating support 55. The floating stopper 56 is made of insulating material and prevents the inner pipe 2 from floating up from the housing portion 552 of the insulating support 55. The floating stopper 56 has a radial width that fills the gap between the top of the inner pipe 2 and the inner surface of the first split pipe half 36A.

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

[0055] 9(C) and 9(D) are cross-sectional views taken perpendicular to the axial direction to illustrate a manufacturing method for the vacuum insulated double pipe 1DA. Fig. 9(C) shows a state in which an insulating support 55 is attached to the inner surface of the second split pipe half 36B via a fixing bracket 551, and the inner pipe 2 is supported by the insulating support 55. Next, as shown in Fig. 9(D), a floating stopper 56 is attached to the insulating support 55. This brings the inner pipe pressing portion 561 into contact with or close to the outer circumferential surface of the inner pipe 2, and the fitting portion 562 is fitted into the side portion 554 of the insulating support 55.

[0056] Thereafter, the first pipe half 36A is butted against the second pipe half 36B so as to encase the floating stopper 56. In this state, the butt joint 36J between the circumferential edge 36E1 of the first pipe half 36A and the circumferential edge 36E2 of the second pipe half 36B is butt-welded using a backing metal 361. Finally, the axial edges 36E of the first pipe half 36A and the second pipe half 36B are fillet-welded to the surface of the outer pipe body 31. The floating stopper 56 abuts against the second pipe half 36B, thereby restricting floating.

[0057] Sixth Embodiment Figure 10(A) is an axial cross-sectional view of a vacuum insulated double pipe 1E according to a sixth embodiment, and Figure 10(B) is a cross-sectional view taken along line XB-XB in Figure 10(A). The vacuum insulated double pipe 1E includes a coaxially arranged inner pipe 2 and outer pipe 3E, and a vacuum insulation layer 4 between the inner pipe 2 and the outer pipe 3E. The outer pipe 3E comprises an outer pipe body 31 and a pair of split pipe halves 37A and 37B (segments). The accessory illustrated in the sixth embodiment is an inner pipe support 5E that radially supports the inner pipe 2, similar to the inner pipe support 5C illustrated in the third embodiment of Figure 6. While the third embodiment illustrated an example in which the inner pipe support 5C is attached to a backing plate 35 that covers the window portion 63, the sixth embodiment illustrates an example in which the inner pipe support 5E is attached to the split pipe halves 37A and 37B.

[0058] The inner pipe support 5E includes a heat insulating support 57, a support base 571, and a fixing bracket 572 for fixing the heat insulating support 57 to the metal pipe halves 37A and 37B. The heat insulating support 57 is made of a heat insulating material and directly supports the inner pipe 2. The heat insulating support 57 supports the inner pipe 2 wrapped with the radiation shield 22. The support base 571 is a mounting seat for the heat insulating support 57 and is fixed to the inner surface of the first pipe half 37A or the second pipe half 37B by welding or the like. The fixing bracket 572 is a member for fixing the heat insulating support 57 to the support base 571.

[0059] The inner pipe supports 5E are arranged at four locations at 90-degree intervals around the circumferential direction of the inner pipe 2. Two inner pipe supports 5E are pre-attached to each of the first and second pipe halves 37A and 37B. The first and second pipe halves 37A and 37B are formed into a cylindrical body by butt-welding their circumferential edges together. A backing metal 371 is attached to the inside of the butt joint 37J between the two pipe halves.

[0060] A manufacturing method for the vacuum insulated double pipe 1E will now be described. The outer pipe body 31 is formed with a separation section 65 where the outer pipe body 31 is completely separated. No support-related accessories are attached to the inner pipe 2; only the radiation shield 22 is wrapped around it. After fitting the pair of outer pipe bodies 31 onto the inner pipe 2, a first pipe half 37A and a second pipe half 37B, each equipped with an inner pipe support 5E, are butted together to cover the separation section 64. At this time, an overlapping section OL is formed, where the axial edges 37E of the pipe halves 37A and 37B overlap the edges 31E of the pair of outer pipe bodies 31 from the outside. Then, with a backing metal 371 attached to the inner surface, the butt joints 37J of the pipe halves 37A and 37B are welded. Finally, the axial edges 37E of the first pipe half 37A and the second pipe half 37B are fillet-welded to the surface of the outer pipe body 31.

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

[0062] A method for manufacturing a double pipe according to a first aspect of the present disclosure is 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, and includes attaching an accessory to the inner surface of an outer pipe piece that constitutes a part of the outer pipe, enveloping the inner pipe with the outer pipe piece and an outer pipe body that constitutes the remainder of the outer pipe, and attaching the outer pipe piece to the outer pipe body so that at least a portion of the peripheral edge of the outer pipe piece overlaps the outer pipe body.

[0063] According to the first aspect, accessories are attached to the inner surface of the outer pipe piece in advance, and then the outer pipe piece and the outer pipe body are used to encase the inner pipe. This allows the outer pipe body without accessories attached to its inner surface to be fitted onto the inner pipe, and then the outer pipe piece with the accessories attached can be attached to the outer pipe body later. This reduces the possibility that the accessories will interfere with the process of placing the inner pipe inside the outer pipe. Furthermore, since the outer pipe piece is attached with its peripheral edge overlapping the outer pipe body, it is easy to ensure the sealing of the annular space.

[0064] The manufacturing method for a double pipe according to the second aspect is the same as the manufacturing method of the first aspect, in which the peripheral portion of the outer pipe piece is attached to the outer pipe body in an overlapping state, i.e., the outer pipe piece is attached to the outer pipe body by overlapping it from the outside.

[0065] According to the second aspect, the outer pipe piece can be attached from the outside of the outer pipe body, which simplifies the process of attaching the outer pipe piece to the outer pipe body after fitting the outer pipe body onto the inner pipe.

[0066] A third aspect of the double-pipe manufacturing method is the same as the first or second aspect, except that the outer pipe body has a window portion, and the outer pipe piece is a plate sized to cover the window portion, and attaching the outer pipe piece to the outer pipe body means attaching the plate to the window portion.

[0067] According to the third aspect, the accessory can be positioned in a predetermined position simply by attaching a plate with the accessory to the window of the outer tube body. Furthermore, the positional relationship between the accessory and the inner tube surface can be confirmed through the window while attaching the plate to the window. Therefore, the accessory can be easily attached to the predetermined position with high accuracy.

[0068] The fourth aspect of the method for manufacturing a double pipe is the same as the third aspect, except that part of the accessory is attached to the surface of the inner pipe at the opening position of the window portion, and the plate is attached to the window portion with the remainder of the accessory attached to the plate.

[0069] According to the fourth aspect, the plate equipped with the remaining accessories can be attached to the window while checking the positional relationship with the accessories attached to the inner pipe through the window. Therefore, it is possible to fix the plate to the window after adjusting the position of the accessories on the outer pipe relative to the accessories on the inner pipe, making it easier to manufacture a double-walled pipe with the designed performance. The fourth aspect is suitable when the accessories are, for example, axial stops that restrict relative axial movement between the inner pipe and the outer pipe.

[0070] A fifth aspect of the manufacturing method for a double pipe is the same as the third aspect, except that the plate is attached to the window portion in a state where all of the accessories are attached to the plate.

[0071] According to the fifth aspect, the inner pipe is inserted into the outer pipe without attaching any accessories, and the arrangement of the accessories in the annular space layer is completed simply by attaching the plate to the window portion. This further improves workability. Furthermore, if a surface layer needs to be formed on the surface of the inner pipe, the surface layer can be formed by wrapping a sheet around the surface of the inner pipe when no accessories are present, improving workability. The fifth aspect is suitable when the accessory is, for example, an inner pipe support that supports the inner pipe in the radial direction.

[0072] A sixth aspect of the method for manufacturing a double pipe is the same as the first or second aspect, except that the outer pipe body has a divided portion at the attachment position of the accessory, and attaching the outer pipe piece to the outer pipe body means attaching the outer pipe piece so as to connect the divided portion.

[0073] According to the sixth aspect, the outer pipe piece with accessories can be attached to the outer pipe body with the inner pipe completely exposed at the divided portion of the outer pipe body. This makes it easy to check the surface condition of the inner pipe. Furthermore, since the work of drilling a window opening in the outer pipe body is not required, the preparation work of the outer pipe body is easy.

[0074] A seventh aspect of the manufacturing method for a double pipe is the same as the sixth aspect, except that the outer pipe piece is made up of a plurality of segments divided circumferentially, and the accessory is attached to the inner surface of at least one of the segments.

[0075] According to the seventh aspect, the work of joining the divided portions of the outer pipe body can be completed by assembling the divided pieces of the outer pipe piece, thereby improving workability.

[0076] The double pipe of the eighth aspect is a double pipe comprising an inner pipe through which a fluid flows, an outer pipe covering the inner pipe, an annular space layer between the inner pipe and the outer pipe, and an accessory arranged in the annular space, wherein the outer pipe includes an outer pipe piece which is a part of the outer pipe, and an outer pipe body which is the remainder of the outer pipe, and the accessory is attached to the inner surface of the outer pipe piece, and at least a portion of the peripheral edge of the outer pipe piece is attached so as to overlap the outer pipe body.

[0077] According to the eighth aspect, the outer pipe that covers the inner pipe is composed of the outer pipe piece with accessories already attached to its inner surface and the outer pipe body. This makes it possible to insert the inner pipe into the outer pipe body without accessories attached to its inner surface, and then later attach the outer pipe piece with the accessories to the outer pipe body. This makes it possible to provide a double pipe that is easy to manufacture.

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

[0079] A double pipe according to a 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 can be provided in which an axial stop member or an inner pipe support member is disposed in the annular space layer, and the inner pipe and outer pipe can be easily assembled.

[0081] A double pipe according to an eleventh aspect is the double pipe according to any one of the eighth to tenth aspects, wherein the peripheral edge of the outer pipe piece is attached to the outer pipe body in a state where it overlaps the outer pipe body from the outside.

[0082] According to the eleventh aspect, it is possible to provide a double pipe in which the outer pipe piece can be easily attached to the outer pipe body after the outer pipe body has been fitted onto the inner pipe.

[0083] A double-walled pipe according to a twelfth aspect is the double-walled pipe of the eleventh aspect, wherein the peripheral edge portion is attached to the surface of the outer pipe body by a fillet weld.

[0084] According to the twelfth aspect, the outer pipe piece can be attached to the outer pipe body by a simple welding technique.

[0085] DESCRIPTION OF SYMBOLS 1 Vacuum insulated double pipe (double pipe) 2 Inner pipe 2P Mounting position 3 Outer pipe 31 Outer pipe body 32 Outer pipe piece 32E, 33E, 34E Peripheral edge 33, 34, 35 Backing plate (outer pipe piece / plate) 36A, 37A First half-split pipe (divided piece) 36B, 37B Second half-split pipe (divided piece) 4 Vacuum insulation layer (annular space layer) 5 Accessories 5A Axial stop (accessory) 51 Inner pipe axial stop material (part of accessory) 52 Outer pipe axial stop material (remaining part of accessory) 5B Sliding plate (accessory) 5C, 5D, 5E Inner pipe support (accessory) 6 Opening 61, 62, 63 Window portion 64 Divided portion OL Overlap portion

Claims

1. A method for manufacturing a double pipe having 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, comprising: attaching an accessory to the inner surface of an outer pipe piece that constitutes part of the outer pipe; covering the inner pipe with the outer pipe piece and an outer pipe main body that constitutes the remainder of the outer pipe; and attaching the outer pipe piece to the outer pipe main body in a state in which at least a portion of the peripheral edge of the outer pipe piece overlaps the outer pipe main body.

2. A method for manufacturing a double-walled pipe as described in claim 1, wherein attaching the peripheral portion of the outer pipe piece to the outer pipe body in an overlapping state means attaching the outer pipe piece to the outer pipe body by overlapping it from the outside.

3. A method for manufacturing a double-pipe as described in claim 1 or 2, wherein the outer pipe body has a window portion, the outer pipe piece is a plate having a size that covers the window portion, and attaching the outer pipe piece to the outer pipe body means attaching the plate to the window portion.

4. A method for manufacturing a double-walled pipe as described in claim 3, comprising the steps of: 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 to the window portion with the remainder of the accessory attached to the plate.

5. A method for manufacturing a double-walled pipe as claimed in claim 3, wherein the plate is attached to the window portion with all of the accessories attached to the plate.

6. A method for manufacturing a double pipe as described in claim 1 or 2, wherein the outer pipe body has a divided portion at the attachment position of the accessory, and attaching the outer pipe piece to the outer pipe body means attaching the outer pipe piece so as to connect the divided portion.

7. A method for manufacturing a double-walled pipe as described in claim 6, wherein the outer pipe piece is composed of a plurality of segments divided in the circumferential direction, and the accessory is attached to the inner surface of at least one of the plurality of segments.

8. A double pipe comprising an inner pipe through which a fluid flows, an outer pipe covering the inner pipe, an annular space layer between the inner pipe and the outer pipe, and an accessory disposed in the annular space layer, wherein the outer pipe includes an outer pipe piece which is a part of the outer pipe, and an outer pipe body which is the remainder of the outer pipe, the accessory is attached to the inner surface of the outer pipe piece, and at least a portion of the peripheral edge of the outer pipe piece is attached so as to overlap the outer pipe body.

9. A double pipe as claimed in claim 8, wherein the accessory is an axial stop which restricts relative axial movement between the inner pipe and the outer pipe.

10. A double pipe according to claim 8, wherein the accessory is an inner pipe support that supports the inner pipe in the radial direction.

11. A double-walled pipe according to any one of claims 8 to 10, wherein the peripheral portion of the outer pipe piece is attached to the outer pipe body in an overlapping state from the outside.

12. A double-walled pipe as claimed in claim 11, further comprising a fillet weld between the side surface of the peripheral edge and the surface of the outer pipe body.

Images