Back shield gas supply device, multi-wall pipe welding method, and multi-wall pipe manufacturing method

Abstract

To provide a back shield gas supply device that can fill a back shield gas between an inner pipe and an outer pipe when the outer pipe of a multiple pipe is welded, and to provide a method for welding a multiple pipe and a method for manufacturing a multiple pipe.SOLUTION: A back shield gas supply device 100 for supplying a back shield gas into a multiple pipe DP including an inner pipe IP and an outer pipe OP into which the inner pipe IP is inserted includes: a supply tube 10 for supplying a back shield gas into a multiple pipe DP.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a back shielding gas supply device, a method for welding a multi-layer pipe, and a method for manufacturing a multi-layer pipe. [Background technology]

[0002] When the tubular members are welded together, the inside of the tubular members is filled with a back shield gas. Patent Document 1 discloses a technique in which a gas supply tube is inserted from a hole provided in the side surface of a tubular member, and a back shield gas is sprayed from a gas spray nozzle provided at the end of the gas supply tube. Patent Document 2 discloses a technique in which a seal member is disposed inside a tubular member, thereby filling the inside of the tubular member with a back shield gas. Patent Document 3 discloses a technique in which a foaming agent is filled inside a tubular member, thereby filling the inside of the tubular member with a back shielding gas. Patent Document 4 discloses a method for welding a double-pipe structure having an inner pipe and an outer pipe, in which the inner pipes are first welded together using a laser beam, and then a filler material is fitted into the groove of the outer pipe, and the outer pipes are welded together by TIG welding while flowing an inert gas between the inner pipe and the outer pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-146771 A [Patent Document 2] JP 2014-97527 A [Patent Document 3] International Publication No. 2010 / 150422 [Patent Document 4] Japanese Patent Application Publication No. 10-34373 Summary of the Invention [Problem to be solved by the invention]

[0004] When welding outer tubes together in a multi-tube structure, there is a need to fill the gap between the inner tube and the outer tube around the welded part with back shielding gas. However, the techniques in Patent Documents 1 to 3 are based on the premise of welding a single tube, and cannot be used for multi-tube. The technique in Patent Document 4 does not specify a specific method for supplying inert gas between the inner tube and the outer tube around the welded part.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a back shielding gas supply device that can fill the space between an inner tube and an outer tube when welding the outer tube of a multi-wall pipe, a welding method for a multi-wall pipe, and a manufacturing method for a multi-wall pipe. [Means for solving the problem]

[0006] <1> A back shielding gas supplying device according to aspect 1 of the present invention is a back shielding gas supplying device for supplying a back shielding gas to one or more layers of a multi-layer tube including an inner tube and one or more outer tubes into which the inner tube is inserted, and is characterized in that it includes a supply tube for supplying the back shielding gas to the multi-layer tube.

[0007] According to this invention, a supply tube is provided for supplying the back shielding gas to the multi-wall pipe, whereby, when the outer pipe is welded, the back shielding gas can be supplied to the multi-wall pipe by the supply tube.

[0008] <2> A back shielding gas supplying apparatus according to a second aspect of the present invention is characterized in that, in the back shielding gas supplying apparatus according to the first aspect, the supply tube is disposed between the inner pipe and the outer pipe.

[0009] According to the present invention, the supply tube is disposed between the inner tube and the outer tube, whereby, when the outer tube is welded, the supply tube can supply the back shielding gas between the inner tube and the outer tube.

[0010] <3> A back shielding gas supplying apparatus according to a third aspect of the present invention is the back shielding gas supplying apparatus according to the first or second aspect, characterized in that the supply tube is detachably attached to the inner tube.

[0011] According to this invention, the supply tube is detachably attached to the inner tube. As a result, for example, by inserting the inner tube into the outer tube with the supply tube attached to the inner tube, the supply tube can be disposed between the inner tube and the outer tube. This makes it easier to dispose the supply tube between the inner tube and the outer tube.

[0012] <4> A back shielding gas supply device according to a fourth aspect of the present invention is a back shielding gas supply device according to any one of the first to third aspects, characterized in that the supply tube is maintained wound around the inner tube by a detachable part, and the detachable part releases the state in response to the supply tube being pulled.

[0013] According to this invention, the supply tube is maintained in a state where it is wound around the inner tube by the detachable part, and the state is released in response to pulling of the supply tube, which makes it easy to remove the supply tube from between the inner tube and the outer tube after welding of the outer tube.

[0014] <5> A back shield gas supply apparatus according to a fifth aspect of the present invention is a back shield gas supply apparatus according to any one of the first to fourth aspects, characterized in that the supply tube includes an outlet for ejecting the back shield gas.

[0015] According to the present invention, the supply tube includes an outlet for ejecting the back shielding gas, whereby the back shielding gas can be rapidly filled into the inside of the outer tube.

[0016] <6> A back shielding gas supply device according to a sixth aspect of the present invention is a back shielding gas supply device according to the fifth aspect, characterized in that the supply tube has a plurality of the nozzles arranged along the circumferential direction of the inner surface of the outer tube.

[0017] According to this invention, the supply tube has a plurality of outlets provided along the circumferential direction of the inner circumferential surface of the outer tube, whereby the back shielding gas can be evenly filled inside the outer tube.

[0018] <7> A back shielding gas supply apparatus according to a seventh aspect of the present invention is characterized in that, in the back shielding gas supply apparatus according to the fifth or sixth aspect, a portion of the supply tube is wound around the inner tube, and the multiple nozzles are provided in the portion of the supply tube wound around the inner tube.

[0019] According to this invention, a portion of the supply tube is wound around the inner tube. The multiple nozzles are provided in the portion of the supply tube wound around the inner tube. This allows the multiple nozzles to be arranged along the circumferential direction of the inner tube. This allows the back shield gas to be more evenly filled inside the outer tube.

[0020] <8> The back shielding gas supply device of aspect 8 of the present invention is a back shielding gas supply device of any one of aspects 1 to 7, characterized in that a ring-shaped base having a portion of its circumference cut out is provided on the outer circumferential surface of the inner tube, and the supply tube is passed through a portion of the inner tube in its circumference.

[0021] According to this invention, a ring-shaped seat with a circumferentially cut-out portion is provided on the outer peripheral surface of the inner tube. The supply tube passes through the circumferentially cut-out portion of the inner tube. This makes it easy to position the supply tube between the inner tube and the outer tube, even when a seat is provided on the outer peripheral surface of the inner tube.

[0022] <9> A back shielding gas supply device according to a ninth aspect of the present invention is a back shielding gas supply device according to any one of aspects 1 to 8, characterized in that a base is provided on the outer peripheral surface of the inner tube, and the supply tube passes through a part of the base that is thinner than the remaining parts of the base.

[0023] According to this invention, a pedestal is provided on the outer peripheral surface of the inner tube. The supply tube passes through a part of the pedestal that is thinner than the remaining part of the pedestal. This makes it easy to position the supply tube between the inner tube and the outer tube, even when the pedestal is provided on the outer peripheral surface of the inner tube.

[0024] <10> A back shielding gas supplying apparatus according to a tenth aspect of the present invention is the back shielding gas supplying apparatus according to any one of the first to ninth aspects, characterized in that a first protrusion streak and a second protrusion streak are provided on an inner peripheral surface of the outer tube along an axial direction of the outer tube, and the supply tube is passed between the first protrusion streak and the second protrusion streak.

[0025] According to this invention, the first and second ridges are provided on the inner circumferential surface of the outer tube along the tube axis direction of the outer tube. The supply tube is passed between the first and second ridges. This makes it easy to arrange the supply tube between the inner tube and the outer tube, even when the first and second ridges are provided on the inner circumferential surface of the outer tube.

[0026] <11> The back shielding gas supply device of aspect 11 of the present invention is a back shielding gas supply device of any one of aspects 1 to 10, characterized in that a notch is provided on the inner surface of the end of the outer tube, and the end of the supply tube is positioned at a position of the inner tube corresponding to the notch.

[0027] According to this invention, a notch is provided on the inner circumferential surface of the end of the outer tube. The end of the supply tube is disposed at a position on the inner tube corresponding to the notch. This makes it easier to fill the part of the outer tube where the notch is provided, i.e., the part of the inner circumferential surface of the outer tube where the first and second protrusions are not provided, with back shielding gas.

[0028] <12> A back shielding gas supplying apparatus according to a twelfth aspect of the present invention is characterized in that, in the back shielding gas supplying apparatus according to any one of aspects 1 to 11, the supply tube is detachably attached to the outer tube.

[0029] According to this invention, the supply tube is detachably attached to the outer tube, which makes it easier to insert the inner tube into the outer tube, for example.

[0030] <13> The method for welding a multi-wall pipe according to aspect 13 of the present invention is characterized by comprising an attachment step of attaching a supply tube capable of supplying a back shielding gas to an inner pipe, an insertion step of inserting the inner pipe with the supply tube attached thereto into an outer pipe, an ejection step of ejecting the back shielding gas from the supply tube, an outer pipe welding step of welding the outer pipe, and a removal step of removing the supply tube attached to the inner pipe.

[0031] According to this invention, there is provided an inserting step of inserting the inner tube to which the supply tube is attached into the outer tube, which makes it easier to position the supply tube between the inner tube and the outer tube. The method further includes a step of ejecting the back shield gas from the supply tube, thereby filling the inside of the outer tube with the back shield gas. The method further includes a removal step of removing the supply tube attached to the inner tube, which can prevent the supply tube from being left behind between the inner tube and the outer tube after the outer tube is welded.

[0032] <14> A method for welding a multi-wall pipe according to a fourteenth aspect of the present invention is the method for welding a multi-wall pipe according to the thirteenth aspect, characterized in that in the inserting step, one of the inner pipe and the outer pipe is fixed.

[0033] According to this invention, in the inserting step, one of the inner tube and the outer tube is fixed, which makes it easier to insert the inner tube into the outer tube.

[0034] <15> The manufacturing method of a multi-tube according to aspect 15 of the present invention is characterized by comprising an attachment step of attaching a supply tube capable of supplying a back shielding gas to an inner tube, and an insertion step of inserting the inner tube with the supply tube attached into an outer tube.

[0035] According to this invention, the method includes a mounting step of mounting a supply tube capable of supplying back shielding gas to an inner tube, and an inserting step of inserting the inner tube with the supply tube mounted thereon into the outer tube. That is, the inner tube is inserted into the outer tube with the supply tube mounted thereon. This makes it easy to arrange the supply tube between the inner tube and the outer tube. Therefore, it is easy to manufacture a multi-tube capable of supplying back shielding gas between the inner tube and the outer tube.

[0036] <16> A method for welding a multi-wall pipe according to aspect 16 of the present invention is a method for welding a multi-wall pipe including an inner pipe to which a supply tube capable of supplying a back shielding gas is attached, and an outer pipe into which the inner pipe is inserted, and is characterized in that it comprises an ejection step for ejecting the back shielding gas from the supply tube, and an outer pipe welding step for welding the outer pipe.

[0037] According to this invention, the method includes a step of ejecting the back shielding gas from the supply tube. That is, the back shielding gas is ejected from the supply tube disposed between the inner tube and the outer tube. This makes it easier to supply the back shielding gas between the inner tube and the outer tube when welding the outer tube. Effect of the Invention

[0038] According to the present invention, it is possible to provide a back shielding gas supply device capable of filling the space between an inner tube and an outer tube when welding the outer tube of a multi-layer pipe, a welding method for a multi-layer pipe, and a manufacturing method for a multi-layer pipe. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a conceptual diagram of a welding operation for multiple pipes. [Diagram 2] 2 is a first example of a cross-sectional view taken along line II-II of FIG. 1. [Diagram 3] 2 is a second example of a cross-sectional view taken along line II-II of FIG. 1. [Figure 4] 4 is an enlarged cross-sectional view of the vicinity of a welded portion between multiple pipes, as viewed from the IV direction shown in FIG. 1. [Diagram 5] 13 is a diagram showing a state in which the detachable part is broken by pulling the supply tube. FIG. [Figure 6] This is a first example of the location of the detachable part. [Figure 7] 2 is a second example of the location of the detachable part. [Figure 8] FIG. 13 is a diagram showing a state in which the supply tube comes into contact with the base. [Figure 9] FIG. 13 is a conceptual diagram of a welding operation for modified multi-wall pipes. [Figure 10] 10 is a cross-sectional view taken along the line XX in FIG. 9. [Figure 11] 10 is an enlarged cross-sectional view of the vicinity of a welded portion between modified examples of multi-wall pipes, as viewed from the XI direction shown in FIG. 9 . FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, a back shield gas supply device 100, a method for welding a multi-wall pipe DP, and a method for manufacturing a multi-wall pipe DP according to an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, the back shielding gas supplying device 100 according to this embodiment supplies a back shielding gas to one or more layers of a multi-tube DP including an inner tube IP and one or more outer tubes OP into which the inner tube IP is inserted, when the ends of the multi-tube DP including the inner tube IP and one or more outer tubes OP are welded together by a welding torch T. In this embodiment, the multi-tube DP is a double tube including an inner tube IP and one outer tube OP. That is, in this embodiment, the back shielding gas supplying device 100 supplies a back shielding gas between the inner tube IP and the outer tube OP shown in Fig. 1. In this embodiment, the back shielding gas is, for example, argon gas.

[0041] In this embodiment, as shown in FIG. 1, a ring-shaped pedestal IPs with a portion cut out in the circumferential direction is provided on the outer peripheral surface of the inner pipe IP. A plurality of pedestals IPs are provided at intervals along the longitudinal direction of the inner pipe IP. The interval between the pedestals IPs on the inner pipe IP is, for example, about 2 m to 3 m. The pedestals IPs contact the inner peripheral surface of the outer pipe OP. In this way, the pedestals IPs secure a gap between the outer peripheral surface of the inner pipe IP and the inner peripheral surface of the outer pipe OP in a portion of the inner pipe IP where the pedestals IPs are not provided. Note that an SI material (super insulation material) may be provided along the outer peripheral surface of the inner pipe IP in the gap between the outer peripheral surface of the inner pipe IP and the inner peripheral surface of the outer pipe OP. In the multiple pipe DP according to this embodiment, the seat IPs is preferably provided at a location at least 300 mm away from the ends of the inner pipe IP and the outer pipe OP. Details will be described below together with the location of the detachable part 20.

[0042] In this embodiment, the base IPs is partially cut out in the circumferential direction of the inner pipe IP, as shown in Fig. 2. Hereinafter, the cut-out part of the base IPs is referred to as a cut-out part IPsc. Alternatively, the base IPs has a part that is thinner than the other part of the base IPs, as shown in Fig. 3. Hereinafter, the part of the base IPs that is thinner is referred to as a thin-walled part IPst. In this embodiment, the cutout width of the cutout portion IPsc, i.e., the dimension A of the cutout portion IPsc in the circumferential direction of the inner pipe IP shown in Fig. 2, is about 30 mm, for example. The width of the thin-walled portion IPst, i.e., the dimension B of the thin-walled portion IPst in the circumferential direction of the inner pipe IP shown in Fig. 3, is about 30 mm, for example.

[0043] The cutouts IPsc or thin-walled portions IPst are provided in all of the multiple pedestals IPs provided along the longitudinal direction of the inner pipe IP. In addition, the cutouts IPsc or thin-walled portions IPst are arranged in a straight line in the multiple pedestals IPs. This allows a supply tube 10, which will be described later, to be placed in the cutouts IPsc or thin-walled portions IPst. During the welding operation of the multi-wall pipe DP, it is preferable that the cutouts IPsc or thin-walled portions IPst are located at the top as shown in Figures 2 and 3 (details will be described later).

[0044] As shown in FIG. 1, the back shield gas supply device 100 includes a supply tube 10. The supply tube 10 is a tube disposed between an inner pipe IP and an outer pipe OP. One end of the supply tube 10 is disposed at a joint between the multiple pipes DP, and the other end is connected to a gas tank or the like (not shown). The supply tube 10 is supplied with a back shield gas from a gas tank or the like (not shown). As a result, the supply tube 10 supplies the back shield gas between the inner pipe IP and the outer pipe OP of the multiple pipes DP. The outer diameter of the supply tube 10 is preferably, for example, 80% or less of the dimension of the gap between the inner pipe IP and the outer pipe OP. The inner diameter of the supply tube 10 is preferably, for example, a diameter that can keep the flow rate of the back shield gas at 0.6 L / min or more when the length of the supply tube 10 is 100 m.

[0045] In this embodiment, one end of the supply tube 10 is wound around the inner pipe IP as shown in Fig. 4. A portion of the supply tube 10 is kept wound around the outer circumferential surface of the inner pipe IP during the welding operation of the multi-wall pipe DP. In this embodiment, the supply tube 10 is detachably attached to the inner pipe IP. Specifically, as shown in Fig. 4, the supply tube 10 is maintained in a state of being wound around the inner pipe IP by a detachable part 20. The detachable part 20 is, for example, an aluminum tape. A loop formed by winding one end of the supply tube 10 around the inner pipe IP is fixed by the detachable part 20, which is the aluminum tape.

[0046] When the supply tube 10 is pulled, the detachable part 20 releases the supply tube 10 from the state where it is wound around the inner tube IP. Specifically, by pulling the other end of the supply tube 10 in a direction away from one end of the supply tube 10, the detachable part 20 breaks as shown in FIG. 5. This releases the supply tube 10 from the state where it is wound around the inner tube IP. This makes the supply tube 10 detachable from the inner tube IP.

[0047] As described above, the supply tube 10 is removed from the inner tube IP by being pulled. Therefore, it is preferable that the supply tube 10 has sufficient resistance to the pulling force. That is, the material of the supply tube 10 is preferably, for example, a polyurethane tube, and a nylon tube may also be used.

[0048] 4, the supply tube 10 includes an outlet 10n for ejecting the back shield gas. Specifically, the supply tube 10 has a plurality of outlets 10n provided along the circumferential direction of the inner peripheral surface of the outer tube OP. In other words, the plurality of outlets 10n are provided in a part of the supply tube 10 wound around the inner tube IP.

[0049] The nozzles 10n are formed, for example, by drilling through holes with a diameter of about 0.5 mm in the supply tube 10 with a drill bit or the like. In this case, it is preferable that a plurality of nozzles 10n are provided at intervals of about 20 mm along the length of the supply tube 10 in the supply tube 10 in a state where it is not wound around the inner tube IP. Note that the above dimensions are merely examples, and any other dimensions may be used.

[0050] (Location of supply tube 10) Next, a specific location of the supply tube 10 between the inner pipe IP and the outer pipe OP will be described. First, a location of the supply tube 10 other than the part wound around the inner pipe IP will be described. That is, the supply tube 10 is arranged so as to pass through the notch portion IPsc or the thin portion IPst provided in the base IPs, as shown in FIG. 2 or FIG.

[0051] Here, the weight of the inner pipe IP may reduce the size of the gap between the outer peripheral surface of the inner pipe IP and the inner peripheral surface of the outer pipe OP below the multiple pipe DP. In this case, if the cut-out portion of the pedestal IPs or the thin portion of the pedestal IPs is located below the multiple pipe DP, the supply tube 10 may be pinched between the outer peripheral surface of the inner pipe IP and the inner peripheral surface of the outer pipe OP, making it impossible to pull the supply tube 10 to remove it. For this reason, as described above, it is preferable that the cut-out portion of the pedestal IPs or the thin portion of the pedestal IPs is located above the multiple pipe DP.

[0052] Next, the location of the part of the supply tube 10 wound around the inner pipe IP will be described. As described above, a part of the supply tube 10 wound around the inner pipe IP is provided with a plurality of nozzles 10n at intervals. This allows the back shield gas supplied from the other end of the supply tube 10 to be evenly filled around the outer circumferential surface of the inner pipe IP through the nozzles 10n.

[0053] When welding the outer pipes OP of the multi-pipe DP together, the space between the inner pipe IP and the outer pipe OP is filled with back shielding gas by the supply tube 10. If the distance between the welded portion of the outer pipe OP, i.e., the end of the outer pipe OP, and the part of the supply tube 10 wrapped around the inner pipe IP, is short, there is a risk that the supply tube 10 will melt during the welding operation of the outer pipe OP. For this reason, for example, when the supply tube 10 is a polyurethane tube, it is desirable to set the surface temperature that the supply tube 10 receives due to radiant heat during welding to be equal to or lower than 200° C., which is the melting point of polyurethane tubes. To meet this requirement, as shown in FIG. 4, it is preferable that the distance D between the part of the supply tube 10 wound around the inner tube IP and the end of the outer tube OP is 50 mm or more.

[0054] (Location of the detachable part 20) Next, the location of the detachable part 20 that secures the supply tube 10 will be described. As described above, the supply tube 10 is secured to the inner tube IP by the detachable part 20. The detachable part 20 breaks when the supply tube 10 is pulled. In this way, the detachable part 20 enables the supply tube 10 to be detached from the inner tube IP. For this reason, it is preferable that the detachable part 20 is disposed in a position where it is likely to break when the supply tube 10 is pulled.

[0055] Here, the portion of the supply tube 10 wound around the inner pipe IP is positioned as follows: That is, for example, as shown in Fig. 4 or 5, when viewed from the end of the multiple pipe DP that is to be welded, the portion of the supply tube 10 wound around the inner pipe IP is positioned so that the supply tube 10 moves counterclockwise around the axis of the inner pipe IP from the side closer to the other end toward one end of the supply tube 10.

[0056] At this time, the portion of the supply tube 10 that passes through the pedestal IPs located at the position closest to the detachable part 20 is preferably disposed at a position that ensures a distance C from at least the notched part IPsc or the thin-walled part IPst of the pedestal IPs when viewed from one end side of the supply tube 10, as shown in, for example, Figures 2 to 4. Moreover, it is more preferable that the detachable part 20 is disposed at a position shifted about 10° to 30° in the clockwise direction from the upper end of the multiple tube DP when viewed from one end side of the supply tube 10, as shown in Figure 7.

[0057] Here, when the supply tube 10 is pulled and the supply tube 10 comes into contact with the base IPs as shown in Fig. 8, it becomes difficult for the supply tube 10 to apply a force in a direction that breaks the detachable part 20. For this reason, in order to make it easier for the detachable part 20 to break when the supply tube 10 is pulled, it is preferable that the distance E between the part of the supply tube 10 wound around the inner tube IP and the base IPs be 250 mm or more as shown in Fig. 4, for example. As described above, the distance D between the part of the supply tube 10 wound around the inner tube IP and the end of the outer tube OP is preferably 50 mm or more.

[0058] In order to satisfy these requirements, it is preferable that the distance F (see FIG. 4) between the ends of the inner pipe IP and the outer pipe OP and the base IPs is at least 300 mm. In other words, as described above, it is preferable that the base IPs is provided at a location at least 300 mm away from the ends of the inner pipe IP and the outer pipe OP.

[0059] (Welding method for multi-layer DP pipes) Next, a method for welding a multi-wall pipe DP according to the present embodiment will be described. That is, a method for welding a multi-wall pipe DP including an inner pipe IP to which a supply tube 10 capable of supplying back shielding gas is attached and an outer pipe OP into which the inner pipe IP is inserted will be described. The method for welding a multi-wall pipe DP according to this embodiment includes an attachment step, an insertion step, an inner pipe welding step, a jetting step, an outer pipe welding step, and a removal step.

[0060] (Installation steps) The mounting step is a process of mounting the supply tube 10 capable of supplying back shielding gas to the inner pipe IP. That is, first, one end of the supply tube 10 provided with the nozzle 10n is wound around the inner pipe IP. Next, the supply tube 10 is fixed to the inner pipe IP by wrapping the detachable part 20, which is an aluminum tape, around the supply tube 10. Then, the part of the supply tube 10 other than the part wrapped around the inner pipe IP is placed in the cutout part IPsc or the thin part IPst of the base IPs arranged along the axial direction of the inner pipe IP.

[0061] (Insertion step) The insertion step is a process of inserting the inner pipe IP to which the supply tube 10 is attached into the outer pipe OP. In the insertion step, first, one of the inner pipe IP and the outer pipe OP is fixed. In this state, the other of the inner pipe IP and the outer pipe OP is moved toward the fixed one of the inner pipe IP and the outer pipe OP. In this way, the inner pipe IP is inserted into the outer pipe OP.

[0062] (Inner pipe welding step) The inner pipe welding step is a step of welding the inner pipes IP of the multi-pipe DP together. In the inner pipe welding step, the inner pipes IP are welded together, for example, by TIG welding. After the inner pipes IP are connected together by the inner pipe welding step, the outer pipes OP are welded together by the following steps.

[0063] (Ejection step) The ejection step is a process of ejecting the back shielding gas from the supply tube 10. This fills the gap between the inner pipe IP and the outer pipe OP with the back shielding gas. At the time of the ejection step, it is preferable that the ends of the outer pipe OP are in close contact with each other. If an SI material is provided on the outer peripheral surface of the inner pipe IP, aluminum tape may be wrapped around the SI material before the ejection step in order to protect the SI material located directly below the welded portion of the outer pipe OP.

[0064] (Outer pipe welding step) The outer pipe welding step is a process of welding the outer pipes OP. In the outer pipe welding step, the outer pipes OP are welded together by, for example, TIG welding. In this way, the multiple pipes DP are connected together.

[0065] (Removal steps) The removal step is a process of removing the supply tube 10 attached to the inner tube IP. That is, the supply tube 10 is pulled to break the detachable portion 20, and the supply tube 10 is removed from between the inner tube IP and the outer tube OP. Through the above steps, the multi-wall pipe DP is welded.

[0066] (Manufacturing method of multi-tube DP) Next, a method for manufacturing the multiple tube DP according to this embodiment will be described. The method for manufacturing the multiple tube DP includes a mounting step and an insertion step. The attachment step is a step of attaching the supply tube 10 capable of supplying the back shielding gas to the inner pipe IP. The attachment step is the same as the step explained in the welding method for the multi-pipe DP. The insertion step is a step of inserting the inner pipe IP, to which the supply tube 10 is attached, into the outer pipe OP. The insertion step is the same as the step described in the method for welding the multiple pipes DP. Through the above steps, the multi-tube DP is manufactured.

[0067] As described above, the back shield gas supply device 100 according to the present embodiment includes the supply tube 10 that supplies the back shield gas to the multi-wall pipe DP. This allows the back shield gas to be supplied to the multi-wall pipe DP by the supply tube 10 when the outer pipe OP is welded.

[0068] In addition, the supply tube 10 is disposed between the inner pipe IP and the outer pipe OP. This allows the supply tube 10 to supply back shield gas between the inner pipe IP and the outer pipe OP when welding the outer pipe OP.

[0069] In addition, the supply tube 10 is detachably attached to the inner tube IP. With this, for example, by inserting the inner tube IP into the outer tube OP while the supply tube 10 is attached to the inner tube IP, the supply tube 10 can be disposed between the inner tube IP and the outer tube OP. This makes it easier to dispose the supply tube 10 between the inner tube IP and the outer tube OP.

[0070] The supply tube 10 is maintained in a state of being wound around the inner pipe IP by the detachable part 20. The state is released in response to the supply tube 10 being pulled. This makes it possible to easily remove the supply tube 10 from between the inner pipe IP and the outer pipe OP after welding the outer pipe OP.

[0071] The supply tube 10 also includes an outlet 10n for ejecting the back shielding gas, so that the back shielding gas can be quickly filled into the outer tube OP.

[0072] Further, the supply tube 10 has a plurality of nozzles 10n provided along the circumferential direction of the inner peripheral surface of the outer tube OP, thereby making it possible to uniformly fill the inside of the outer tube OP with the back shielding gas.

[0073] In addition, a portion of the supply tube 10 is wound around the inner tube IP. The multiple nozzles 10n are provided in the portion of the supply tube 10 wound around the inner tube IP. This allows the multiple nozzles 10n to be arranged along the circumferential direction of the inner tube IP. This allows the back shield gas to be filled more evenly inside the outer tube OP.

[0074] In addition, a ring-shaped seat IPs with a portion cut out in the circumferential direction is provided on the outer peripheral surface of the inner pipe IP. The supply tube 10 passes through the portion cut out in the circumferential direction of the inner pipe IP. This makes it easy to arrange the supply tube 10 between the inner pipe IP and the outer pipe OP, even if the seat IPs is provided on the outer peripheral surface of the inner pipe IP.

[0075] In addition, a pedestal IPs is provided on the outer peripheral surface of the inner pipe IP. The supply tube 10 passes through a part of the pedestal IPs that is thinner than the remaining part of the pedestal IPs. This makes it easier to arrange the supply tube 10 between the inner pipe IP and the outer pipe OP, even if the pedestal IPs is provided on the outer peripheral surface of the inner pipe IP.

[0076] Furthermore, the method for welding a multi-wall pipe DP according to the present embodiment includes an inserting step of inserting the inner pipe IP to which the supply tube 10 is attached into the outer pipe OP. This makes it easier to arrange the supply tube 10 between the inner pipe IP and the outer pipe OP. The method includes a jetting step for jetting the back shield gas from the supply tube 10. This allows the back shield gas to fill the inside of the outer tube OP. The method includes a removal step for removing the supply tube 10 attached to the inner pipe IP. This makes it possible to prevent the supply tube 10 from being left behind between the inner pipe IP and the outer pipe OP after the outer pipe OP is welded.

[0077] In the insertion step, either the inner pipe IP or the outer pipe OP is fixed, which makes it easier to insert the inner pipe IP into the outer pipe OP.

[0078] In addition, the manufacturing method of the multi-tube DP according to the present embodiment includes an attachment step of attaching the supply tube 10 capable of supplying back shielding gas to the inner tube IP, and an insertion step of inserting the inner tube IP to which the supply tube 10 is attached into the outer tube OP. That is, the inner tube IP is inserted into the outer tube OP with the supply tube 10 attached to the inner tube IP. This makes it easier to arrange the supply tube 10 between the inner tube IP and the outer tube OP. Therefore, it is easier to manufacture the multi-tube DP capable of supplying back shielding gas between the inner tube IP and the outer tube OP.

[0079] The method also includes an ejection step of ejecting the back shielding gas from the supply tube 10. That is, the back shielding gas is ejected from the supply tube 10 disposed between the inner pipe IP and the outer pipe OP. This makes it easier to supply the back shielding gas between the inner pipe IP and the outer pipe OP when welding the outer pipe OP.

[0080] (Modification of multi-tube DP) Next, a modified example of the multi-tube DP according to this embodiment will be described with reference to FIGS. In this modification, the same components as those in the above-described embodiment are denoted by the same reference numerals, and their description will be omitted, with only the differences being described. The multiple pipe DP according to the modified example differs from the above-described embodiment in the structure for ensuring a gap between the outer circumferential surface of the inner pipe IP and the inner circumferential surface of the outer pipe OP.

[0081] That is, in the multi-wall pipe DP according to the modified example, ribs OPp are provided on the inner peripheral surface of the outer pipe OP along the pipe axis direction of the outer pipe OP, as shown in Fig. 9. A plurality of ribs OPp are provided on the inner peripheral surface of the outer pipe OP at intervals in the circumferential direction of the outer pipe OP, as shown in Fig. 10. The tips of the ribs OPp contact the outer peripheral surface of the inner pipe IP. This ensures a gap between the outer peripheral surface of the inner pipe IP and the inner peripheral surface of the outer pipe OP in areas other than the ribs OPp.

[0082] In the multi-wall pipe DP according to the modified example, the supply tube 10 is disposed so as to pass between a first ridge OPp1, which is one of the plurality of ridges OPp provided as described above, and a second ridge OPp2, which is a ridge OPp located adjacent to the first ridge OPp1. During welding of the multi-wall pipe DP, the portion between the first ridge OPp1 and the second ridge OPp2, where the supply tube 10 is disposed, is preferably located above.

[0083] As shown in Fig. 11, a notch OPc is provided on the inner peripheral surface of the end of the outer pipe OP according to the modified example. The notch OPc refers to a portion of the end of the outer pipe OP where the protrusion OPp is cut out. The notch OPc is formed by machining the end of the outer pipe OP by countersinking, thereby removing the protrusion OPp provided on the end of the outer pipe OP. In the modified multi-pipe DP, the end of the supply tube 10 is located at the position of the inner pipe IP, corresponding to the notch OPc.

[0084] As described above, in the multi-wall pipe DP according to the modified example, the first ridges OPp1 and the second ridges OPp2 are provided on the inner circumferential surface of the outer pipe OP along the pipe axis direction of the outer pipe OP. The supply tube 10 is passed between the first ridges OPp1 and the second ridges OPp2. This makes it easier to arrange the supply tube 10 between the inner pipe IP and the outer pipe OP, even if the first ridges OPp1 and the second ridges OPp2 are provided on the inner circumferential surface of the outer pipe OP.

[0085] Further, a notch OPc is provided on the inner peripheral surface of the end portion of the outer tube OP. The end portion of the supply tube 10 is disposed at a position corresponding to the notch OPc at the position of the inner tube IP. This makes it easier to fill the part of the outer tube OP where the notch OPc is provided, i.e., the part of the inner peripheral surface of the outer tube OP where the first protrusion OPp1 and the second protrusion OPp2 are not provided, with the back shielding gas.

[0086] (Modification of attachment of supply tube 10) Next, a modified example of the attachment of the supply tube 10 according to this embodiment will be described. In this modification, the same components as those in the above-described embodiment are denoted by the same reference numerals, and their description will be omitted, with only the differences being described. In a variant of the attachment of the supply tube 10, the supply tube 10 is detachably attached to the outer tube OP.

[0087] Specifically, both ends of the supply tube 10 are attached to the inner circumferential surface of the outer tube OP by sticking them with tape or the like. At this time, tension is generated between both ends of the supply tube 10, so that the portions of the supply tube 10 other than both ends do not become loose. In this way, when the supply tube 10 is attached to the inner peripheral surface of the outer tube OP in advance, the attachment step is performed after the above-mentioned insertion step. That is, after the inner tube IP is inserted into the outer tube OP to which the supply tube 10 is attached in advance, the tape that attached the supply tube 10 to the outer tube OP is removed. Then, one end of the supply tube 10 is wrapped around the inner tube IP and fixed by the attachment / detachment part 20. The above-mentioned modified attachment of the supply tube 10 can be applied to both the multiple pipe DP described above in this embodiment and the modified multiple pipe DP.

[0088] As described above, according to the modified embodiment of the supply tube 10, the supply tube 10 is detachably attached to the outer tube OP. This makes it easier to insert the inner tube IP into the outer tube OP, for example.

[0089] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the detachable portion 20 may be fixed using adhesive, hook-and-loop fastener, or tube joint other than aluminum tape. The supply tube 10 may be made of any tubing material other than polyurethane and nylon tubing.

[0090] In addition, the portion of the supply tube 10 wound around the inner pipe IP may be positioned such that, when viewed from the end of the multiple pipes DP that is to be welded, the portion of the supply tube 10 wound around the inner pipe IP moves in a clockwise direction around the axis of the inner pipe IP from the side closer to the other end of the portion of the supply tube 10 wound around the inner pipe IP toward one end of the supply tube 10. In this case, the detachable portion 20 is preferably positioned, for example, at a position overlapping at least the notch portion IPsc or the thin-walled portion IPst of the base IPs when viewed from one end of the supply tube 10, and more preferably positioned at a position shifted approximately 10° to 30° counterclockwise from the upper end of the multiple tube DP when viewed from one end of the supply tube 10. In this embodiment, the multi-tube DP is described as a double tube including an inner tube IP and one outer tube OP, but the back shielding gas supply device 100 of this embodiment may also be used to supply back shielding gas to a triple tube or a multi-tube having even more layers.

[0091] In addition, within the scope of the invention, the components in the above-described embodiments may be replaced with well-known components, and the above-described modified examples may be combined as appropriate. [Explanation of symbols]

[0092] 10 Supply Tube 10n spout 20 Detachable part 100 Back shield gas supply device A, B dimensions C, D, E, F distance DP multiple tube IP inner tube IPs Pedestal IPsc notch IPst thin section OP outer tube OPc cutout OPp protrusion OPp1 1st protrusion OPp2 2nd protrusion T welding torch

Claims

1. A back shield gas supply device for supplying a back shield gas to one or more layers of a multi-layer tube including an inner tube and one or more outer tubes into which the inner tube is inserted, the inner tubes being welded to each other and the outer tubes being welded to each other, comprising: a supply tube for supplying the back shield gas to the multiple tubes, the supply tube is disposed between the inner tube and the outer tube; A detachable portion is further provided, The supply tube is maintained in a state of being wound around the inner tube by the detachable portion, The detachable unit releases the state in response to the supply tube being pulled. A back shield gas supply device.

2. The supply tube is removably attached to the inner tube.

2. The back shield gas supply device according to claim 1,

3. The supply tube includes an outlet for ejecting the back shield gas.

2. The back shield gas supply device according to claim 1,

4. a ring-shaped seat having a circumferentially cut-out portion provided on an outer circumferential surface of the inner tube; The supply tube is passed through a portion of the inner tube in the circumferential direction.

2. The back shield gas supply device according to claim 1,

5. A seat is provided on an outer circumferential surface of the inner tube, The supply tube is passed through a portion of the base, the portion being thinner than the remaining portion of the base.

2. The back shield gas supply device according to claim 1,

6. a first protrusion rib and a second protrusion rib are provided on an inner peripheral surface of the outer tube along an axial direction of the outer tube, The supply tube is passed between the first protrusion and the second protrusion.

2. The back shield gas supply device according to claim 1,

7. A notch is provided on the inner peripheral surface of the end of the outer tube, an end of the supply tube is disposed at a position of the inner tube corresponding to the notch; 2. The back shield gas supply device according to claim 1,

8. The supply tube is removably attached to the outer tube.

2. The back shield gas supply device according to claim 1,

9. A back shield gas supplying device for supplying a back shield gas to one or more layers of a multi-tube including an inner tube and one or more outer tubes into which the inner tube is inserted, comprising: a supply tube for supplying the back shield gas to the multiple tubes; Equipped with the supply tube is disposed between the inner tube and the outer tube; the supply tube includes an outlet for ejecting the back shield gas, The supply tube has a plurality of the ejection ports provided along a circumferential direction of an inner circumferential surface of the outer tube. A back shield gas supply device.

10. a portion of the supply tube is wound around the inner tube; The plurality of ejection ports are provided in a portion of the supply tube that is wound around the inner tube.

10. The back shield gas supply device according to claim 9.

11. a mounting step of mounting a supply tube capable of supplying a back shield gas to an outer circumferential surface of the inner tube; an inserting step of inserting the inner tube having the supply tube attached to the outer peripheral surface thereof into the outer tube; a jetting step of jetting the back shield gas from the supply tube to between the inner tube and the outer tube; an outer pipe welding step of welding the outer pipe; a removing step of removing the supply tube attached to the inner tube; A method for welding multiple pipes comprising the steps of:

12. In the inserting step, one of the inner tube and the outer tube is fixed. The method for welding multiple pipes according to claim 11.

13. a mounting step of mounting a supply tube capable of supplying a back shield gas for welding the outer tube to an outer peripheral surface of the inner tube; an inserting step of inserting an inner tube having the supply tube attached to the outer peripheral surface thereof into the outer tube; a jetting step of jetting the back shield gas from the supply tube to between the inner tube and the outer tube; A method for manufacturing a multi-layer pipe, comprising:

14. A method for welding a multi-wall pipe, comprising: an inner pipe having a supply tube capable of supplying a back shielding gas attached to an outer peripheral surface thereof; and an outer pipe into which the inner pipe is inserted, the supply tube being disposed between the inner pipe and the outer pipe, the method comprising the steps of: a jetting step of jetting the back shield gas from the supply tube to between the inner tube and the outer tube; an outer pipe welding step of welding the outer pipe; A method for welding multiple pipes comprising the steps of:

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