Swivel joints and joint systems

Abstract

This invention provides a swivel joint that can reduce the risk of leaked hydrogen gas escaping to the outside. [Solution] A swivel joint 1 according to one embodiment includes a first half 2 and a second half 3. The first half 2 includes a first inner pipe 21, a first outer pipe 22, a first closure body 24, and a holder 25, and the second half 3 includes a second inner pipe 31, a second outer pipe 32, and a second closure body 34. An outer flange 35 provided on the second outer pipe 32 is fastened to the holder 25. A first sealing member 71 and a second sealing member 72 are arranged between the first inner flange 23 and the second inner flange 33, and a third sealing member 73 with a U-shaped cross-section that opens radially inward is arranged so as to be interposed around the first inner flange 23 and the second inner flange 33 and on the route from the pressure-holding chamber 4B formed between the first closure body 24 and the second closure body 34 to the outer sealing member 74.

Description

Technical Field

[0001] The present disclosure relates to a swivel joint and a joint system including the swivel joint.

Background Art

[0002] In recent years, loading arms for liquefied hydrogen installed in harbors and the like have been under development. Such loading arms incorporate a swivel joint that rotatably connects double pipes through which liquefied hydrogen flows. For example, Patent Document 1 discloses a swivel joint 100 as shown in FIG. 4.

[0003] Specifically, the swivel joint 100 of Patent Document 1 includes a first half 200 on the rotating side and a second half 300 on the fixed side. The first half 200 includes a first inner pipe 210, a first outer pipe 220, a first closing body 240, and a holder 250. The first outer pipe 220 houses the first inner pipe 210. A first inner flange 230 is provided at the end of the first inner pipe 210. The first closing body 240 has a bellows cross-section and connects the first inner flange 230 and the end of the first outer pipe 220. The holder 250 rotatably holds the first outer pipe 220 via a bearing 510.

[0004] The second half 300 includes a second inner pipe 310, a second outer pipe 320, and a second closing body 340. The second outer pipe 320 houses the second inner pipe 310. A second inner flange 330 is provided at the end of the second inner pipe 310. The second closing body 340 has a bellows cross-section and connects the second inner flange 330 and the end of the second outer pipe 320. An outer flange 350 is provided at the end of the second outer pipe 320, and the outer flange 350 is fastened to the holder 250 of the first half 200 by bolts 520.

[0005] A pressure-holding chamber 400 is formed around the first inner flange 230 and the second inner flange 330, and between the first closure body 240 and the second closure body 340. Helium gas, which does not solidify at the temperature of liquefied hydrogen, is supplied to the pressure-holding chamber 400 through a plug 800 attached to the holder 250, and through the gap between the first outer tube 220 and the holder 250.

[0006] Between the first inner flange 230 and the second inner flange 330, a first sealing member 610 and a second sealing member 620 are positioned to prevent leakage of liquefied hydrogen. The first half 200 is provided with a recovery line 700 that guides leaked hydrogen gas, generated by the vaporization of liquefied hydrogen that has leaked beyond the first sealing member 610, to the outside from between the first sealing member 610 and the second sealing member 620.

[0007] Furthermore, an outer sealing member 630 is positioned between the first outer tube 220 and the holder 250 to prevent air and water from entering the gap between the first outer tube 220 and the holder 250. The pressure in the pressure-holding chamber 400 is kept higher than atmospheric pressure, thereby preventing air and water from entering the pressure-holding chamber 400 from the outside. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-19531 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, in the swivel joint 100 that connects the double pipes through which liquefied hydrogen flows, lubricants such as grease cannot be used on the bearing 510. Therefore, instead of an O-ring, a U-shaped seal member with a cross-section that opens radially outward is used as the outer seal member 630. Conversely, the first seal member 610 and the second seal member 620 are U-shaped seal members with a cross-section that opens radially inward.

[0010] In the swivel joint 100 of Patent Document 1, a recovery line 700 is provided and the pressure in the pressure-holding chamber 400 is kept higher than atmospheric pressure, but leaked hydrogen gas may enter the pressure-holding chamber 400. In this case, since the outer sealing member 630 is a U-shaped sealing member with an opening radially outward, there is a concern that the leaked hydrogen gas that has entered the pressure-holding chamber 400 may leak to the outside beyond the outer sealing member 630.

[0011] Therefore, the present disclosure aims to provide a swivel joint and a joint system including the swivel joint that can reduce the risk of leaked hydrogen gas leaking to the outside. [Means for solving the problem]

[0012] This disclosure relates to a swivel joint for connecting double pipes through which liquefied hydrogen flows from one side, comprising: a first half including a first inner pipe having a first inner flange, a first outer pipe housing the first inner pipe, a first closure body connecting the first inner flange and the first outer pipe, and a holder for rotatably holding the first outer pipe; a second half including a second inner pipe having a second inner flange, a second outer pipe housing the second inner pipe and having an outer flange fastened to the holder, and a second closure body connecting the second inner flange and the second outer pipe; and a first sealing member having a U-shaped cross-section and opening radially inward, disposed between the first inner flange and the second inner flange; and A swivel joint is provided, comprising: a second seal member having a U-shaped cross-section and opening radially inward, positioned outside the first seal member and between the first inner flange and the second inner flange; an outer seal member having a U-shaped cross-section and opening radially outward, which prevents outside air and water from entering the gap between the first outer tube and the holder; and a third seal member having a U-shaped cross-section and opening radially inward, which is positioned between the first outer tube, the outer flange, and the holder and the first outer tube, interposed on the route from the pressure-holding chamber formed around the first inner flange and the second inner flange and between the first and second closure bodies to the outer seal member.

[0013] This disclosure also provides a joint system comprising the swivel joint described above, a first gas supply pipe connected to the first gas supply passage of the swivel joint and equipped with a first pressure regulating valve, and a second gas supply pipe connected to the second gas supply passage of the swivel joint and equipped with a second pressure regulating valve, wherein the second pressure regulating valve controls the pressure in the purge area to be higher than atmospheric pressure, and the first pressure regulating valve controls the pressure in the pressure holding chamber to be higher than the pressure in the purge area. [Effects of the Invention]

[0014] This disclosure provides a swivel joint that can reduce the risk of leaked hydrogen gas leaking to the outside, and a joint system including the swivel joint. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram of a joint system including a swivel joint according to one embodiment. [Figure 2] This is a cross-sectional view along line II-II in Figure 1. [Figure 3] This is an enlarged view of the main part of Figure 1. [Figure 4] This is a cross-sectional view of a conventional swivel joint. [Modes for carrying out the invention]

[0016] Figure 1 shows a joint system 10 including a swivel joint 1 according to one embodiment. For example, the swivel joint 1 is incorporated into a loading arm for liquefied hydrogen.

[0017] The joint system 10 includes, in addition to the swivel joint 1, a recovery pipe 81 and a first gas supply pipe 82 as shown in Figure 2, and a second gas supply pipe 84 and a discharge pipe 86 as shown in Figure 1. Leaked hydrogen gas, described later, is recovered from the swivel joint 1 through the recovery pipe 81, and pressure-retaining gas is supplied to the swivel joint 1 through the first gas supply pipe 82. Purge gas is also supplied to the swivel joint 1 through the second gas supply pipe 84, and the purge gas is discharged from the swivel joint 1 through the discharge pipe 86.

[0018] The pressure-holding gas is either helium or hydrogen. If the pressure-holding gas is helium, the purge gas is nitrogen; if the pressure-holding gas is hydrogen, the purge gas is either nitrogen or helium.

[0019] The swivel joint 1 rotatably connects double pipes through which liquefied hydrogen flows. For example, each double pipe is a vacuum double pipe in which a vacuum is maintained between a conduit in contact with liquefied hydrogen and a housing pipe that houses the conduit.

[0020] Specifically, the swivel joint 1 includes a movable-side first half 2 provided at the tip of a first double pipe, which is one of the double pipes, and a fixed-side second half 3 provided at the tip of a second double pipe, which is the other double pipe.

[0021] The first half 2 includes a first inner pipe 21 and a first outer pipe 22 that houses the first inner pipe 21. The conduit of the first double pipe is joined to the base end of the first inner pipe 21 by welding or the like, and the housing pipe of the first double pipe is joined to the base end of the first outer pipe 22 by welding or the like. In the first inner pipe 21 and the first outer pipe 22, the base end is the end on the side opposite to the second half 3, and the end is the end on the side of the second half 3.

[0022] Similarly, the second half 3 includes a second inner pipe 31 and a second outer pipe 32 that houses the second inner pipe 31. The conduit of the second double pipe is joined to the base end of the second inner pipe 31 by welding or the like, and the housing pipe of the second double pipe is joined to the base end of the second outer pipe 32 by welding or the like. In the second inner pipe 31 and the second outer pipe 32, the base end is the end on the side opposite to the first half 2, and the end is the end on the side of the first half 2.

[0023] Furthermore, the first half 2 includes a cylindrical holder 25 that rotatably holds the first outer pipe 22 via bearings 61, 62. On the other hand, an outer flange 35 that extends radially outward from the end of the second outer pipe 32 of the second half 3 is provided at the end. The outer flange 35 is fastened to the holder 25 by a plurality of bolts 12. That is, a plurality of insertion holes for the bolts 12 are provided in the outer flange 35, and a plurality of screw holes that are respectively screwed with the bolts 12 are provided in the holder 25. However, instead of the screw holes, a plurality of insertion holes for the bolts 12 may be provided in the holder 25, and nuts may be used.

[0024] The end of the first inner pipe 21 is provided with a first inner flange 23 that extends radially outward from that end, and the end of the second inner pipe 31 is provided with a second inner flange 33 that extends radially outward from that end. The first inner flange 23 and the second inner flange 33 face each other, and between the first inner flange 23 and the second inner flange 33, as shown in Figure 3, an annular first sealing member 71 and a second sealing member 72 are arranged.

[0025] More specifically, a step is formed between the end surface of the first inner pipe 21 and the sealing surface of the first inner flange 23 that faces the second inner flange 33, and a notch of the same depth as the step is formed in the inner peripheral edge of the sealing surface of the first inner flange 23. The first sealing member 71 is held within the notch, and the ring 11 is fitted onto the end of the first inner pipe 21 so as to cover the first sealing member 71 from the inside. On the other hand, the second sealing member 72, which is positioned outside the first sealing member 71, is held within an annular groove formed in the sealing surface of the first inner flange 23.

[0026] However, the holding structure for the first sealing member 71 and the second sealing member 72 is not limited to this and can be modified as appropriate. For example, instead of the notch and ring 11 for holding the first sealing member 71, an annular groove may be formed on the sealing surface of the first inner flange 23, and the first sealing member 71 may be held within the annular groove. Alternatively, one or both of the notch for holding the first sealing member 71 and the annular groove for holding the second sealing member 72 may be formed on the sealing surface of the second inner flange 33 facing the first inner flange 23.

[0027] In the first half 2, the inner surface of the first outer pipe 22 is connected to the non-sealing surface of the first inner flange 23 by the first closure body 24, and in the second half 3, the inner surface of the second outer pipe 32 is connected to the non-sealing surface of the second inner flange 33 by the second closure body 34. A pressure-holding chamber 4B is formed around the first inner flange 23 and the second inner flange 33 and between the first closure body 24 and the second closure body 34.

[0028] In this embodiment, the first closure body 24 is joined to the inner circumferential surface of the first outer tube 22 near its end, but the first closure body 24 may be joined to the inner circumferential surface of the first outer tube 22 at its end. Similarly, in this embodiment, the second closure body 34 is joined to the inner circumferential surface of the second outer tube 32 near its end, but the second closure body 34 may be joined to the inner circumferential surface of the second outer tube 32 at its end.

[0029] The first closure body 24 has a bellows-like cross-section and has a plurality of annular grooves arranged radially. Each annular groove is recessed along the first inner tube 21 in a direction away from the second half 3. In this embodiment, there are two annular grooves, but there may be one or three or more annular grooves.

[0030] Similarly, the second closure body 34 has a bellows-like cross-section and has a plurality of annular grooves arranged radially. Each annular groove is recessed along the second inner tube 31 in a direction away from the first half 2. In this embodiment, there are two annular grooves, but there may be one or three or more annular grooves.

[0031] In this embodiment, a portion of the end face of the first outer tube 22 extends radially outward for a predetermined length, forming a thickened portion 22a that overlaps with the holder 25. Furthermore, an annular projection 22b is provided at the base end of the thickened portion 22a, projecting radially outward to form a gap between it and the end face of the holder 25 that faces away from the outer flange 35.

[0032] An annular outer sealing member 74 is positioned between the annular projection 22b and the end face of the holder 25. The outer sealing member 74 is a U-shaped sealing member with a cross-section that opens radially outward, and prevents air and water from entering the gap between the outer circumferential surface of the thickened portion 22a of the first outer tube 22 and the inner circumferential surface of the holder 25.

[0033] Each of the first sealing member 71 and the second sealing member 72 described above is a sealing member with a U-shaped cross-section that opens radially inward. The portion between the first sealing member 71 and the second sealing member 72 in the gap between the sealing surface of the first inner flange 23 and the sealing surface of the second inner flange 33 is a recovery area 4A for recovering leaked hydrogen gas, which is vaporized liquefied hydrogen that has leaked beyond the first sealing member 71.

[0034] The second inner flange 33 is provided with two recovery passages 51 extending from the recovery area 4A to the outer circumferential surface of the second inner flange 33, and the second outer pipe 32 and outer flange 35 are provided with two recovery passages 53 extending from the inner circumferential surface of the second outer pipe 32 to the outer circumferential surface of the outer flange 35.

[0035] In this embodiment, the recovery paths 51 and 53 are arranged alternately at 90-degree intervals around the central axis of the second inner pipe 31, but the positions of the recovery paths 51 and 53 can be changed as appropriate. Also, the number of recovery paths 51 and 53 may be one or three or more.

[0036] Furthermore, two recovery pipes 52 are located within the pressure-holding chamber 4B, connecting recovery passage 51 and recovery passage 53, respectively. In addition, the aforementioned recovery pipe 81 is connected to each recovery passage 53. Therefore, the leaked hydrogen gas described above flows from the recovery area 4A through recovery passage 51, recovery pipes 52 and 53 to recovery pipe 81.

[0037] The second outer pipe 32 and the outer flange 35 are provided with two first gas supply passages 54 that communicate with the pressure-holding chamber 4B. However, the number of first gas supply passages 54 may be one or three or more.

[0038] Each first gas supply passage 54 extends from the inner circumferential surface of the second outer pipe 32 to the outer circumferential surface of the outer flange 35, and the first gas supply pipe 82 described above is connected to each first gas supply passage 54. Therefore, pressure-retaining gas can be supplied from the first gas supply pipe 82 to the pressure-retaining chamber 4B through the first gas supply passage 54.

[0039] In this embodiment, the third seal member 73 is positioned between the first outer pipe 22 and the outer flange 35 so as to be interposed on the route from the pressure-holding chamber 4B to the outer seal member 74. Furthermore, in this embodiment, the third seal member 73 is interposed between the bearings 61, 62 and the pressure-holding chamber 4B. The portion between the outer seal member 74 and the third seal member 73 in the gap between the outer circumferential surface of the thickened portion 22a of the first outer pipe 22 and the inner circumferential surface of the holder 25 is the purge area 4C.

[0040] In this embodiment, each of the bearings 61 and 62 is a ball bearing and contains a plurality of balls arranged in the circumferential direction. The outer circumferential surface of the thickened portion 22a of the first outer tube 22 and the inner circumferential surface of the holder 25 have annular grooves with a semicircular cross-section that are continuous in the circumferential direction and guide the balls. The holder 25 is also provided with a ball insertion hole 63 for bearing 61 and a ball insertion hole 65 for bearing 62.

[0041] However, each of the bearings 61 and 62 may be a cross roller bearing or other type of bearing. If each of the bearings 61 and 62 is a cross roller bearing, the holder 25 is divided axially along the first outer tube 22 at the centers of each of the bearings 61 and 62.

[0042] The ball insertion hole 63 is a screw hole, and a plug 64 is installed in the ball insertion hole 63. The plug 64 is hollow, and the ball insertion hole 63 and the plug 64 constitute a second gas supply passage 26 that communicates with the purge area 4C, which is provided in the holder 25.

[0043] The plug 64 is connected to the second gas supply pipe 84 described above. Therefore, purge gas can be supplied from the second gas supply pipe 84 to the purge area 4C through the second gas supply passage 26.

[0044] Similarly, the ball insertion hole 65 is a screw hole, and a plug 66 is attached to the ball insertion hole 65. The plug 66 is hollow, and the ball insertion hole 65 and the plug 66 constitute a discharge passage 27 that communicates with the purge area 4C, which is provided in the holder 25.

[0045] The aforementioned exhaust pipe 86 is connected to the plug 66. As a result, purge gas flows from the purge area 4C through the exhaust passage 27 to the exhaust pipe 86.

[0046] In the swivel joint 1 with the configuration described above, even if leaked hydrogen gas penetrates the pressure-holding chamber 4B beyond the second seal member 72, the third seal member 73 on the route from the pressure-holding chamber 4B to the outer seal member 74 is open radially inward, thus preventing the leaked hydrogen gas from exceeding the third seal member 73. Therefore, the risk of leaked hydrogen gas leaking to the outside can be reduced.

[0047] Furthermore, by using helium gas as the pressure-retaining gas supplied to the pressure-retaining chamber 4B, and using nitrogen gas as the purge gas that is prone to leaking from the outer sealing member 74, the consumption of expensive helium gas can be reduced.

[0048] Furthermore, in this embodiment, since the holder 25 is provided with a discharge passage 27, the intrusion of leaked hydrogen gas into the purge area 4C can be detected by measuring the hydrogen concentration in the purge gas discharged through the discharge passage 27.

[0049] Next, with reference to Figure 1, the configuration of the joint system 10 will be described in more detail. The first gas supply pipe 82 is provided with a first pressure regulating valve 83, and the second gas supply pipe 84 is provided with a second pressure regulating valve 85.

[0050] A pressure gauge 92 is provided in the second gas supply pipe 84 to detect the pressure in the purge area 4C. The second pressure regulating valve 85 is controlled so that the pressure in the purge area 4C detected by the pressure gauge 92 is higher than atmospheric pressure. For example, the pressure in the purge area 4C is maintained within the range of 1 kPaG to 10 kPaG.

[0051] A pressure gauge 91 is provided in the first gas supply pipe 82 to detect the pressure in the pressure-holding chamber 4B. The first pressure regulating valve 83 is controlled so that the pressure in the pressure-holding chamber 4B detected by the pressure gauge 91 is higher than the pressure in the purge area 4C. For example, the pressure in the pressure-holding chamber 4B is maintained within the range of 2 kPaG to 100 kPaG.

[0052] As described above, the first pressure regulating valve 83 and the second pressure regulating valve 85 are controlled to prevent leakage of purge gas from the purge area 4C to the pressure holding chamber 4B in the swivel joint 1. This prevents the solidification of nitrogen gas in the pressure holding chamber 4B when the purge gas is nitrogen gas.

[0053] <Variation> This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0054] For example, a notch for holding the third sealing member 73 may be formed on the end surface of the second outer tube 32, and the third sealing member 73 may be positioned between the first outer tube 22 and the second outer tube 32.

[0055] Alternatively, the third seal member 73 does not necessarily have to be located between the bearings 61, 62 and the pressure-holding chamber 4B, but may be located between the bearings 61, 62 and the outer seal member 74. For example, the height of the annular projection 22b of the first outer tube 22 may be increased, and the third seal member 73 may be located inside the outer seal member 74, that is, between the first outer tube 22 and the holder 25. However, in this case, there is a possibility that leaked hydrogen gas may leak to the outside through the structural part for the bearings 61, 62 in the holder 25 (plugs 64, 66 in the above embodiment). In contrast, if the third seal member 73 is located between the bearings 61, 62 and the pressure-holding chamber 4B as in the above embodiment, the possibility of leaked hydrogen gas leaking to the outside through the structural part for the bearings 61, 62 in the holder 25 can be eliminated.

[0056] <Summary> In a first aspect, the present disclosure provides a swivel joint for connecting two double pipes through which liquefied hydrogen flows, comprising: a first half including a first inner pipe having a first inner flange, a first outer pipe housing the first inner pipe, a first closure body connecting the first inner flange and the first outer pipe, and a holder for rotatably holding the first outer pipe; a second half including a second inner pipe having a second inner flange, a second outer pipe housing the second inner pipe and having an outer flange fastened to the holder, and a second closure body connecting the second inner flange and the second outer pipe; and a first sealing member having a U-shaped cross-section and opening radially inward, disposed between the first inner flange and the second inner flange; and the A swivel joint is provided, comprising: a second seal member having a U-shaped cross-section and opening radially inward, positioned outside the first seal member and between the first inner flange and the second inner flange; an outer seal member having a U-shaped cross-section and opening radially outward, which prevents outside air and water from entering the gap between the first outer tube and the holder; and a third seal member having a U-shaped cross-section and opening radially inward, which is positioned between the first outer tube, the outer flange, and the holder and the first outer tube, interposed on the route from the pressure-holding chamber formed around the first inner flange and the second inner flange and between the first and second closure bodies to the outer seal member.

[0057] With the above configuration, even if liquefied hydrogen that has leaked beyond the first sealing member vaporizes and enters the pressure-holding chamber beyond the second sealing member, the third sealing member on the route from the pressure-holding chamber to the outer sealing member is open radially inward, thus preventing the leaked hydrogen gas from exceeding the third sealing member. Therefore, the risk of leaked hydrogen gas leaking to the outside can be reduced.

[0058] In a second embodiment, the holder may rotatably hold the first outer tube via a bearing, and the third sealing member may be located between the bearing and the pressure-holding chamber. This configuration eliminates the possibility of leaked hydrogen gas leaking to the outside through the bearing structure in the holder.

[0059] In a third embodiment, in the first or second embodiment, helium gas or hydrogen gas may be supplied to the pressure-holding chamber, and nitrogen gas may be supplied to the purge area between the outer seal member and the third seal member. With this configuration, by using nitrogen gas as the purge gas that is prone to leaking from the outer seal member, the consumption of expensive helium gas can be reduced.

[0060] In a fourth embodiment, in the first or second embodiment, for example, hydrogen gas may be supplied to the pressure-holding chamber and helium gas may be supplied to the purge area between the outer seal member and the third seal member.

[0061] In a fifth embodiment, in any of the first to fourth embodiments, the second outer tube and the outer flange may be provided with a first gas supply passage communicating with the pressure-holding chamber, and the holder may be provided with a second gas supply passage communicating with the purge area between the outer seal member and the third seal member. With this configuration, pressure-holding gas can be supplied to the pressure-holding chamber through the first gas supply passage, and purge gas can be supplied to the purge area through the second gas supply passage.

[0062] In a sixth embodiment, in the fifth embodiment, the holder may be provided with a discharge passage that communicates with the purge area. With this configuration, the intrusion of leaked hydrogen gas into the purge area can be detected by measuring the hydrogen concentration in the purge gas discharged through the discharge passage.

[0063] In a seventh aspect, the Disclosure provides a joint system comprising a swivel joint according to the fifth or sixth aspect, a first gas supply pipe connected to the first gas supply passage of the swivel joint and equipped with a first pressure regulating valve, and a second gas supply pipe connected to the second gas supply passage of the swivel joint and equipped with a second pressure regulating valve, wherein the second pressure regulating valve controls the pressure in the purge area to be higher than atmospheric pressure, and the first pressure regulating valve controls the pressure in the pressure holding chamber to be higher than the pressure in the purge area.

[0064] According to the above configuration, the swivel joint can prevent the intrusion of purge gas from the purge area into the pressure-holding chamber. This prevents the solidification of nitrogen gas within the pressure-holding chamber when the purge gas is nitrogen gas. [Explanation of symbols]

[0065] 1 Swivel Joint 10 Joint System 12 volts 2 First Half 21 1st inner pipe 22 First outer tube 23 First Inner Flange 24 First obstructor 25 holder 26 Second gas supply line 27 Exhaust channel 3. Second Half 31 2nd inner pipe 32 Second outer tube 33 Second inner flange 34 Second occlusion body 35 Outer flange 4A Collection Area 4B Pressure-retaining chamber 4C Purge Area 51, 53 Recovery Route 52 Recovery pipe 54. First Gas Supply Line 61, 62 Bearings 63, 65 Ball insertion holes 64,66 plugs 71 First sealing member 72 Second sealing member 73 Third sealing member 74 Outer sealing member 81 Recovery pipe 82 First gas supply pipe 83. First pressure regulating valve 84 Second gas supply pipe 85. Second pressure regulating valve 86 Discharge pipe

Claims

1. A swivel joint that connects two double-walled pipes through which liquefied hydrogen flows. A first half includes a first inner tube provided with a first inner flange, a first outer tube housing the first inner tube, a first closing body connecting the first inner flange and the first outer tube, and a holder that rotatably holds the first outer tube. A second half includes a second inner tube having a second inner flange, a second outer tube having an outer flange that houses the second inner tube and is fastened to the holder, and a second closing body connecting the second inner flange and the second outer tube, A first sealing member with a U-shaped cross-section that opens radially inward is positioned between the first inner flange and the second inner flange, A second seal member, which has a U-shaped cross-section and opens radially inward, is positioned outside the first seal member and between the first inner flange and the second inner flange, An outer sealing member with a U-shaped cross-section that opens radially outward prevents air and water from entering the gap between the first outer tube and the holder from the outside, A third seal member, which has a U-shaped cross-section and opens radially inward, is positioned between the first outer tube, the outer flange, and the holder and the first outer tube, so as to be interposed on the route from the pressure-holding chamber formed around the first inner flange and the second inner flange and between the first and second closure bodies to the outer seal member, A swivel joint equipped with [a specific feature].

2. The holder rotatably holds the first outer tube via a bearing, The swivel joint according to claim 1, wherein the third sealing member is located between the bearing and the pressure-holding chamber.

3. Helium gas or hydrogen gas is supplied to the aforementioned pressure-holding chamber. The swivel joint according to claim 1 or 2, wherein nitrogen gas is supplied to the purge area between the outer sealing member and the third sealing member.

4. Hydrogen gas is supplied to the aforementioned pressure-holding chamber. The swivel joint according to claim 1 or 2, wherein helium gas is supplied to the purge area between the outer sealing member and the third sealing member.

5. The second outer pipe and the outer flange are provided with a first gas supply passage that communicates with the pressure-holding chamber. The swivel joint according to claim 1 or 2, wherein the holder is provided with a second gas supply passage that communicates with the purge area between the outer sealing member and the third sealing member.

6. The swivel joint according to claim 5, wherein the holder is provided with a discharge passage that communicates with the purge area.

7. The swivel joint described in claim 5, A first gas supply pipe, which is connected to the first gas supply passage of the swivel joint and is equipped with a first pressure regulating valve, The system comprises a second gas supply pipe, which is connected to the second gas supply passage of the swivel joint and is equipped with a second pressure regulating valve, The second pressure regulating valve is controlled so that the pressure in the purge area becomes higher than atmospheric pressure. The first pressure regulating valve is a joint system that controls the pressure in the pressure holding chamber to be higher than the pressure in the purge area.

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