Loading system

Abstract

A loading system 1A for liquefied hydrogen includes a loading arm 11, a recovery line 5, a pressure holding line 6, and a purge line 7. The loading arm 11 includes a plurality of swivel joints 13. Each of the swivel joints 13 has a first seal member for separating a flow passage for the liquefied hydrogen and a recovery area, a second seal member for separating the recovery area and a pressure holding chamber, and a third seal member for separating the pressure holding chamber and a purge area. The recovery line 5 passes through the recovery area of each of the swivel joints 13, the pressure holding line 6 passes through the pressure holding chamber of the swivel joint 13, and the purge line 7 passes through the purge area of the swivel joint 13. The purge line 7 is provided with a hydrogen concentration meter 91 on the downstream side of the swivel joints 13.

Description

Cargo handling system

[0001] The present disclosure relates to a cargo handling system for liquefied hydrogen.

[0002] In recent years, loading arms for liquefied hydrogen installed at ports and the like have been under development. Such loading arms incorporate a plurality of swivel joints that rotatably connect double pipes through which liquefied hydrogen flows. For example, Patent Document 1 discloses a swivel joint 100 as shown in FIG. 7.

[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. By connecting the first half 200 and the second half 300, a flow path for liquefied hydrogen is formed by the first inner pipe 210 of the first half 200 and the second inner pipe 310 of the second half 300.

[0004] The first half 200 includes, in addition to the 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-shaped 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.

[0005] The second half 300 includes, in addition to the 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-shaped 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.

[0006] 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.

[0007] 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.

[0008] Japanese Patent Publication No. 2017-19531

[0009] Prior to this application, the applicant provided an improved swivel joint (Japanese Patent Application No. 2024-175695). The swivel joint includes a first sealing member that separates a flow path for liquefied hydrogen from a recovery area, a second sealing member that separates the recovery area from a pressure-holding chamber, and a third sealing member that separates the pressure-holding chamber from a purge area. A pressure-holding gas, which is helium gas or hydrogen gas, is supplied to the pressure-holding chamber, and a purge gas, which is nitrogen gas or helium gas, is supplied to the purge area. Although not described in Japanese Patent Application No. 2024-175695, it is desirable to supply the same hydrogen gas as the recovery gas to the recovery area.

[0010] In such a swivel joint, even if liquefied hydrogen that has leaked beyond the first sealing member vaporizes and enters the pressure-holding chamber beyond the second sealing member, a purge area exists between the pressure-holding chamber and the outside, thus reducing the risk of the leaked hydrogen gas leaking to the outside.

[0011] Incidentally, in a loading arm incorporating multiple swivel joints and a gas supply system, as described above, although the risk of leaked hydrogen gas leaking to the outside is reduced by the presence of a purge area at each swivel joint, it is desirable to detect when leaked hydrogen gas enters the purge area, or in other words, when the possibility of leaked hydrogen gas leaking to the outside has increased.

[0012] Therefore, the present disclosure aims to provide a cargo handling system capable of detecting the intrusion of leaked hydrogen gas into the purge area of ​​a swivel joint.

[0013] This disclosure provides a loading system for liquefied hydrogen, comprising: a loading arm including a plurality of swivel joints, each having a first sealing member separating the flow path for liquefied hydrogen from a recovery area, a second sealing member separating the recovery area from a pressure-holding chamber, and a third sealing member separating the pressure-holding chamber from a purge area; a recovery line through which a recovery gas, which is hydrogen gas, flows, passing through the recovery area of ​​the plurality of swivel joints; a pressure-holding line through which a pressure-holding gas, which is helium gas or hydrogen gas, flows, passing through the pressure-holding chamber of the plurality of swivel joints; a purge line through which a purge gas, which is nitrogen gas or helium gas, flows, passing through the purge area of ​​the plurality of swivel joints; and a hydrogen concentration meter provided on the purge line downstream of the plurality of swivel joints.

[0014] According to this disclosure, a cargo handling system is provided that can detect the intrusion of leaked hydrogen gas into the purge area of ​​a swivel joint.

[0015] This is a schematic diagram of the cargo handling system according to the first embodiment. This is a cross-sectional view of a swivel joint. This is a cross-sectional view along line III-III in Figure 2. This is an enlarged view of the main part of Figure 2. This is a schematic diagram of the cargo handling system according to the second embodiment. This is a schematic diagram of the cargo handling system according to another embodiment. This is a cross-sectional view of a conventional swivel joint.

[0016] <First Embodiment> Figure 1 shows a cargo handling system 1A for liquefied hydrogen according to the first embodiment. The cargo handling system 1A includes a loading arm 11 installed in a port or the like, a recovery line 5, a pressure holding line 6, and a purge line 7 which constitute a gas supply system to the loading arm 11 and a gas discharge system from the loading arm 11, and a control device 8.

[0017] The loading arm 11 has a multi-joint structure and includes a plurality of double-walled tubes 12 through which liquefied hydrogen flows, and a plurality of swivel joints 13 that rotatably connect the double-walled tubes 12 to each other. For example, each double-walled tube 12 is a vacuum double-walled tube in which a vacuum is maintained between a conduit that is in contact with the liquefied hydrogen and a housing tube that houses the conduit.

[0018] A fixed joint 14 is provided at the tip of the loading arm 11. For example, the fixed joint 14 is connected to a fixed joint of a liquefied hydrogen carrier, and unloading from or loading onto the liquefied hydrogen carrier is performed through the loading arm 11.

[0019] As shown in Figure 2, each swivel joint 13 includes a movable first half 2 provided at the tip of the first double pipe, which is one of the double pipes 12, and a fixed second half 3 provided at the tip of the second double pipe, which is the other double pipe 12. By connecting the first half 2 and the second half 3, a flow path 10 for liquefied hydrogen is formed by the first inner pipe 21 of the first half 2 (described later) and the second inner pipe 31 of the second half 3 (described later).

[0020] The first half 2 includes a first inner pipe 21 and a first outer pipe 22 that houses the first inner pipe 21. The base end of the first inner pipe 21 is joined to the conduit of the first double pipe by welding or the like, and the base end of the first outer pipe 22 is joined to the housing pipe of the first double pipe by welding or the like. In the first inner pipe 21 and the first outer pipe 22, the base end is the end opposite to the second half 3, and the end is the end on the second half 3 side.

[0021] 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 base end of the second inner pipe 31 is joined to the conduit of the second double pipe by welding or the like, and the base end of the second outer pipe 32 is joined to the housing pipe of the second double pipe by welding or the like. In the second inner pipe 31 and the second outer pipe 32, the base end is the end opposite to the first half 2, and the end is the end on the first half 2 side.

[0022] Furthermore, the first half 2 includes a cylindrical holder 25 that rotatably holds the first outer tube 22 via bearings 17 and 18. On the other hand, the end of the second outer tube 32 of the second half 3 is provided with an outer flange 35 that extends radially outward from the end. The outer flange 35 is fastened to the holder 25 by a plurality of bolts 16. That is, the outer flange 35 is provided with a plurality of through holes for the bolts 16, and the holder 25 is provided with a plurality of screw holes that engage with the bolts 16. However, instead of screw holes, the holder 25 may be provided with a plurality of through holes for the bolts 16, and nuts may be used.

[0023] 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 4, an annular first sealing member 4a and a second sealing member 4b are arranged.

[0024] 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 on the inner peripheral edge of the sealing surface of the first inner flange 23. The first sealing member 4a is held within the notch, and the ring 15 is fitted onto the end of the first inner pipe 21 so as to cover the first sealing member 4a from the inside. On the other hand, the second sealing member 4b, which is positioned outside the first sealing member 4a, is held within an annular groove formed on the sealing surface of the first inner flange 23.

[0025] However, the holding structure for the first sealing member 4a and the second sealing member 4b is not limited to this and can be modified as appropriate. For example, instead of the notch and ring 15 for holding the first sealing member 4a, an annular groove may be formed on the sealing surface of the first inner flange 23, and the first sealing member 4a may be held within the annular groove. Alternatively, one or both of the notch for holding the first sealing member 4a and the annular groove for holding the second sealing member 4b may be formed on the sealing surface of the second inner flange 33 facing the first inner flange 23.

[0026] The portion between the first sealing member 4a and the second sealing member 4b 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 4a. In other words, the first sealing member 4a separates the flow path 10 for liquefied hydrogen from the recovery area 4A.

[0027] In the first half 2, the inner circumferential surface of the first outer tube 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 circumferential surface of the second outer tube 32 is connected to the non-sealing surface of the second inner flange 33 by the second closure body 34.

[0028] A pressure-holding chamber 4B is formed around the first inner flange 23 and the second inner flange 33, and between the first closing body 24 and the second closing body 34. In other words, the second sealing member 4b separates the recovery area 4A from the pressure-holding chamber 4B.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] An annular outer sealing member 4d is positioned between the annular projection 22b and the end face of the holder 25. The outer sealing member 4d 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.

[0034] A third sealing member 4c is positioned between the end surface of the first outer tube 22 and the outer flange 35. The portion between the outer sealing member 4d and the third sealing member 4c in 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 is the purge area 4C. In other words, the third sealing member 4c separates the pressure-holding chamber 4B from the purge area 4C.

[0035] As shown in Figure 3, the second inner flange 33 is provided with two recovery passages 41 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 43 extending from the inner circumferential surface of the second outer pipe 32 to the outer circumferential surface of the outer flange 35.

[0036] In this embodiment, the recovery paths 41 and 43 are arranged alternately at 90-degree intervals around the central axis of the second inner pipe 31, but the positions of the recovery paths 41 and 43 can be changed as appropriate. Two recovery pipes 42 are arranged inside the pressure-holding chamber 4B, connecting the recovery path 41 and the recovery path 43, respectively. One set of recovery path 41, recovery pipe 42, and recovery path 43 constitutes a recovery gas supply path, and the other set of recovery path 41, recovery pipe 42, and recovery path 43 constitutes a recovery gas discharge path.

[0037] Furthermore, the second outer pipe 32 and the outer flange 35 are provided with two pressure-retaining passages 44 that extend from the inner circumferential surface of the second outer pipe 32 to the outer circumferential surface of the outer flange 35. One pressure-retaining passage 44 constitutes a pressure-retaining gas supply passage that communicates with the pressure-retaining chamber 4B, and the other pressure-retaining passage 44 constitutes a pressure-retaining gas discharge passage that communicates with the pressure-retaining chamber 4B.

[0038] In this embodiment, each of the bearings 17 and 18 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. In addition, as shown in Figure 2, the holder 25 is provided with a ball insertion hole 45 for bearing 17 and a ball insertion hole 47 for bearing 18. However, each of the bearings 17 and 18 may be a cross roller bearing or other type of bearing.

[0039] The ball insertion hole 45 is a screw hole, and a plug 46 is installed in the ball insertion hole 45. The plug 46 is hollow, and the ball insertion hole 45 and the plug 46 constitute a purge gas supply path that communicates with the purge area 4C.

[0040] Similarly, the ball insertion hole 47 is a screw hole, and a plug 48 is installed in the ball insertion hole 47. The plug 48 is hollow, and the ball insertion hole 47 and the plug 48 constitute a purge gas discharge passage that communicates with the purge area 4C.

[0041] Returning to FIG. 1, the recovery line 5 passes through the recovery area 4A of all the swivel joints 13, the pressure-holding line 6 passes through the pressure-holding chamber 4B of all the swivel joints 13, and the purge line 7 passes through the purge area 4C of all the swivel joints 13. A recovery gas flows in the recovery line 5, a pressure-holding gas flows in the pressure-holding line 6, and a purge gas flows in the purge line 7.

[0042] The recovery gas is hydrogen gas, and the pressure-holding gas is helium gas or hydrogen gas. When the pressure-holding gas is helium gas, the purge gas is nitrogen gas, and when the pressure-holding gas is hydrogen gas, the purge gas is nitrogen gas or helium gas.

[0043] In the present embodiment, the recovery line 5 connects the recovery areas 4A of all the swivel joints 13 in parallel, the pressure-holding line 6 connects the pressure-holding chambers 4B of all the swivel joints 13 in parallel, and the purge line 7 connects the purge areas 4C of all the swivel joints 13 in series.

[0044] More specifically, the recovery line 5 includes a recovery gas supply line 51 located upstream of all the swivel joints 13 and a recovery gas discharge line 52 located downstream of all the swivel joints 13. The recovery gas supply line 51 has an upstream main flow path and the same number of upstream branch paths as the swivel joints 13, and the recovery gas discharge line 52 has a downstream main flow path and the same number of downstream branch paths as the swivel joints 13.

[0045] A first recovery control valve 53 is provided in the upstream main flow path of the recovery gas supply line 51, and a second recovery control valve 54 is provided in the downstream main flow path of the recovery gas discharge line 52. Further, a pressure gauge 5a is provided upstream of the first recovery control valve 53 in the upstream main flow path of the recovery gas supply line 51, and a pressure gauge 5b is provided upstream of the second recovery control valve 54 in the downstream main flow path of the recovery gas discharge line 52.

[0046] In the present embodiment, each of the first recovery control valve 53 and the second recovery control valve 54 is an electromagnetic on-off valve. However, each of the first recovery control valve 53 and the second recovery control valve 54 may be an air-operated valve.

[0047] The pressure-holding line 6 includes a pressure-holding gas supply line 61 located upstream of all the swivel joints 13 and a pressure-holding gas discharge line 62 located downstream of all the swivel joints 13. The pressure-holding gas supply line 61 has an upstream main flow path and the same number of upstream branch paths as the swivel joints 13, and the pressure-holding gas discharge line 62 has a downstream main flow path and the same number of downstream branch paths as the swivel joints 13.

[0048] A first pressure-holding control valve 63 is provided in the upstream main flow path of the pressure-holding gas supply line 61, and a second pressure-holding control valve 64 is provided in the downstream main flow path of the pressure-holding gas discharge line 62. Further, a pressure gauge 6a is provided upstream of the first pressure-holding control valve 63 in the upstream main flow path of the pressure-holding gas supply line 61, and a pressure gauge 6b is provided upstream of the second pressure-holding control valve 64 in the downstream main flow path of the pressure-holding gas discharge line 62.

[0049] In the present embodiment, each of the first pressure-holding control valve 63 and the second pressure-holding control valve 64 is an electromagnetic on-off valve. However, each of the first pressure-holding control valve 63 and the second pressure-holding control valve 64 may be an air-operated valve.

[0050] Furthermore, in the present embodiment, the downstream portion of the recovered gas discharge line 52 and the downstream portion of the pressure-holding gas discharge line 62 merge with each other to form a common line, and a manual on-off valve 92 is provided in this common line. The on-off valve 92 is opened by an operator performing connection work of the loading arm 11 or the like during cargo handling, that is, during loading or unloading, and is closed outside of cargo handling.

[0051] The purge line 7 includes a purge gas supply line 71 located upstream of all the swivel joints 13, a plurality of intermediate lines 72 interposed between all the swivel joints 13, and a purge gas discharge line 73 located downstream of all the swivel joints 13.

[0052] A manually operated flow control valve 74 is provided in the purge gas discharge line 73. A pressure gauge 7a is provided in the purge gas supply line 71, and a pressure gauge 7b is provided upstream of the flow control valve 74 in the purge gas discharge line 73. Furthermore, a hydrogen concentration meter 91 is provided downstream of the flow control valve 74 in the purge gas discharge line 73.

[0053] The first recovery control valve 53, the second recovery control valve 54, the first pressure holding control valve 63, the second pressure holding control valve 64, and the pressure gauges 5a, 5b, 6a, 6b, 7a, and 7b are electrically connected to the control device 8. Note that in Figure 1, some signal lines are omitted for the sake of simplicity.

[0054] The control device 8 includes a processing circuit 81 that controls the first recovery control valve 53, the second recovery control valve 54, the first pressure holding control valve 63, and the second pressure holding control valve 64, and a user interface 82 having a display screen that functions as an input and display. The user interface 82 is, for example, a touchscreen. However, instead of the control device 8 including the user interface 82, the input and display may be electrically connected to the control device 8.

[0055] With respect to the control device 8, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0056] Regarding the recovery line 5, the processing circuit 81 opens the second recovery control valve 54 during cargo handling and closes the second recovery control valve 54 when not handling cargo. In addition, the processing circuit 81 normally keeps the first recovery control valve 53 closed and opens the first recovery control valve 53 when the pressure Pr between the first recovery control valve 53 and the second recovery control valve 54 in the recovery line 5, as measured by the pressure gauge 5b, becomes negative.

[0057] Before handling the load, the loading arm 11 is cooled down. By controlling the first recovery control valve 53 as described above, it is possible to suppress the leakage of gas from the liquid hydrogen flow path 10 or the pressure holding chamber 4B into the recovery area 4A due to the contraction of gas in the recovery area 4A of the swivel joint 13 when the loading arm 11 is cooled down.

[0058] With respect to the purge line 7, the flow control valve 74 is opened by the worker to such an extent that the pressure Pp on the upstream side of the flow control valve 74 in the purge line 7 is higher than atmospheric pressure. For example, the pressure Pp is between 1 kPaG and 10 kPaG.

[0059] With respect to the pressure holding line 6, the processing circuit 81 controls the first pressure holding control valve 63 and the second pressure holding control valve 64 so that the pressure Ph between the first and second pressure holding control valves 63 in the pressure holding line 6, as measured by the pressure gauge 6b, is maintained within a certain range. This certain range is higher than the pressure Pp upstream of the flow control valve 74 in the purge line 7. For example, this certain range is a predetermined range within the range of 2 kPaG to 100 kPaG.

[0060] By controlling the first pressure-holding control valve 63 and the second pressure-holding control valve 64 as described above, the pressure in the pressure-holding chambers 4B of all swivel joints 13 can be maintained within the specified range. Moreover, since the specified range is higher than the pressure Pp upstream of the flow control valve 74 in the purge line 7, it is possible to prevent purge gas from entering the pressure-holding chamber 4B from the purge area 4C in each swivel joint 13. As a result, if the purge gas is nitrogen gas, solidification of the nitrogen gas in the pressure-holding chamber 4B can be prevented.

[0061] In the cargo handling system 1A with the configuration described above, a hydrogen concentration meter 91 is installed on the purge line 7 downstream of the swivel joint 13. Therefore, if leaked hydrogen gas enters the purge area 4C of the swivel joint 13, the hydrogen concentration measured by the hydrogen concentration meter 91 will rise. Consequently, it is possible to detect that leaked hydrogen gas has entered the purge area 4C of the swivel joint 13, or in other words, that there is a high possibility of leaked hydrogen gas leaking to the outside. When the hydrogen concentration measured by the hydrogen concentration meter 91 exceeds a threshold, the processing circuit 81 displays this information on the display screen of the user interface 82.

[0062] Furthermore, in this embodiment, since the purge line 7 connects the purge areas 4C of all swivel joints 13 in series, the intrusion of leaked hydrogen gas into the purge areas 4C of all swivel joints 13 can be detected by a single hydrogen concentration meter 91.

[0063] <Second Embodiment> Figure 5 shows the cargo handling system 1B according to the second embodiment. In this embodiment, the same reference numerals are used for the same components as in the first embodiment, and redundant explanations are omitted.

[0064] In this embodiment, a recovery pressure reducing valve 55 is provided in place of the first recovery control valve 53 in the upstream main flow path of the recovery gas supply line 51, and a manually operated on-off valve 56 is provided in place of the second recovery control valve 54 in the downstream main flow path of the recovery gas discharge line 52. The on-off valve 56 is opened during cargo handling by workers performing tasks such as connecting the loading arm 11, and closed when not in use.

[0065] The recovery pressure reducing valve 55 automatically opens and closes in response to the pressure downstream of the recovery pressure reducing valve 55 in the recovery line 5. In other words, the recovery pressure reducing valve 55 opens when the pressure downstream of the recovery pressure reducing valve 55 is less than the set pressure α, and closes when the pressure downstream of the recovery pressure reducing valve 55 is greater than the set pressure α. For example, the set pressure α is equal to atmospheric pressure.

[0066] Furthermore, in this embodiment, a pressure reducing valve 65 is provided in place of the first pressure holding control valve 63 in the upstream main flow path of the pressure holding gas supply line 61, and a pressure holding relief valve 66 is provided in place of the second pressure holding control valve 64 in the downstream main flow path of the pressure holding gas discharge line 62.

[0067] The pressure reducing valve 65 automatically opens and closes in response to the pressure downstream of the pressure reducing valve 65 in the pressure holding line 6. In other words, the pressure reducing valve 65 opens when the pressure downstream of the pressure reducing valve 65 is less than the set pressure β1, and closes when the pressure downstream of the pressure reducing valve 65 is greater than the set pressure β1.

[0068] The pressure-holding relief valve 66 automatically opens and closes in response to the pressure upstream of the pressure-holding relief valve 66 in the pressure-holding line 6. In other words, the pressure-holding relief valve 66 opens when the pressure upstream of the pressure-holding relief valve 66 is greater than the relief pressure β2, and closes when the pressure upstream of the pressure-holding relief valve 66 is less than the relief pressure β2.

[0069] The set pressure β1 of the pressure-reducing valve 65 is smaller than the relief pressure β2 of the pressure-reducing valve 66 (β2 > β1). Also, the set pressure β1 of the pressure-reducing valve 65 is set higher than the set pressure γ1 of the purge pressure-reducing valve 75, which will be described later. For example, the set pressure β1 of the pressure-reducing valve 65 is 2 kPaG or higher, and the relief pressure β2 of the pressure-reducing valve 66 is 100 kPaG or lower.

[0070] Furthermore, in this embodiment, a purge pressure reducing valve 75 is provided in the purge gas supply line 71, and a purge relief valve 76 is provided in the purge gas discharge line 73 instead of a flow control valve 74.

[0071] The purge pressure reducing valve 75 automatically opens and closes in response to the pressure downstream of the purge pressure reducing valve 75 in the purge line 7. In other words, the purge pressure reducing valve 75 opens when the pressure downstream of the purge pressure reducing valve 75 is less than the set pressure γ1, and closes when the pressure downstream of the purge pressure reducing valve 75 is greater than the set pressure γ1.

[0072] The purge relief valve 76 automatically opens and closes in response to the pressure upstream of the purge relief valve 76 in the purge line 7. In other words, the purge relief valve 76 opens when the pressure upstream of the purge relief valve 76 is greater than the relief pressure γ2, and closes when the pressure upstream of the purge relief valve 76 is less than the relief pressure γ2.

[0073] The set pressure γ1 of the purge pressure reducing valve 75 is greater than the relief pressure γ2 of the purge relief valve 76 (γ1 > γ2). Also, the relief pressure γ2 of the purge relief valve 76 is set higher than atmospheric pressure. For example, the relief pressure γ2 of the purge relief valve 76 is 1 kPaG or more, and the set pressure γ1 of the purge pressure reducing valve 75 is 10 kPaG or less.

[0074] In this embodiment, as in the first embodiment, a hydrogen concentration meter 91 is provided on the purge line 7 downstream of the swivel joint 13. Therefore, if leaked hydrogen gas enters the purge area 4C of the swivel joint 13, the hydrogen concentration measured by the hydrogen concentration meter 91 will increase. Consequently, it is possible to detect the intrusion of leaked hydrogen gas into the purge area 4C of the swivel joint 13, or in other words, an increased possibility of leaked hydrogen gas leaking to the outside.

[0075] Furthermore, in this embodiment, a pressure reducing valve 65 is provided in the pressure holding gas supply line 61 and a pressure holding relief valve 66 is provided in the pressure holding gas discharge line 62, so that the pressure in the pressure holding chambers 4B of all swivel joints 13 can be maintained within the range between the set pressure β1 of the pressure reducing valve 65 and the relief pressure β2 of the pressure holding relief valve 66.

[0076] Furthermore, in this embodiment, since the set pressure β1 of the pressure-reducing valve 65 is set higher than the set pressure γ1 of the purge pressure-reducing valve 75, it is possible to prevent the intrusion of purge gas from the purge area 4C into the pressure-reducing chamber 4B at each swivel joint 13. As a result, if the purge gas is nitrogen gas, it is possible to prevent the solidification of nitrogen gas in the pressure-reducing chamber 4B.

[0077] Furthermore, in this embodiment, since a recovery pressure reducing valve 55 is provided in the recovery gas supply line 51, when the set pressure α of the recovery pressure reducing valve 55 is equal to atmospheric pressure, it is possible to suppress the leakage of gas from the flow path 10 or pressure holding chamber 4B for liquefied hydrogen into the recovery area 4A due to the contraction of gas in the recovery area 4A of the swivel joint 13 during the cool-down of the loading arm 11 before cargo handling.

[0078] <Other Embodiments> This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0079] For example, in either the first or second embodiment, the purge line 7 may connect the purge areas 4C of all swivel joints 13 in parallel. In other words, the purge line 7 may include a purge supply line having an upstream main channel and a plurality of upstream branch channels, and a purge discharge line having a downstream main channel and a plurality of downstream branch channels. In this case, a hydrogen concentration meter 91 may be provided in each of the downstream branch channels, or a hydrogen concentration meter 91 may be provided only in the downstream main channel.

[0080] Furthermore, in either the first or second embodiment, the pressure holding line 6 may connect all the pressure holding chambers 4B of the swivel joints 13 in series.

[0081] Furthermore, as shown in the cargo handling system 1C in Figure 6, the upstream main passage of the recovered gas supply line 51 and the upstream main passage of the pressure-retaining gas supply line 61 may be connected by a relay line 93, and a manually operated on-off valve 94 may be provided in the relay line 93, so that the gas in the pressure-retaining chamber 4B of each swivel joint 13 can be temporarily replaced with hydrogen gas before cargo handling. This configuration is also applicable to the second embodiment.

[0082] <Summary> In a first aspect, the present disclosure provides a loading system for liquefied hydrogen, comprising: a loading arm including a plurality of swivel joints, each having a first sealing member separating the flow path for liquefied hydrogen from a recovery area, a second sealing member separating the recovery area from a pressure-holding chamber, and a third sealing member separating the pressure-holding chamber from a purge area; a recovery line through which a recovery gas, which is hydrogen gas, flows, passing through the recovery area of ​​the plurality of swivel joints; a pressure-holding line through which a pressure-holding gas, which is helium gas or hydrogen gas, flows, passing through the pressure-holding chamber of the plurality of swivel joints; a purge line through which a purge gas, which is nitrogen gas or helium gas, flows, passing through the purge area of ​​the plurality of swivel joints; and a hydrogen concentration meter provided on the purge line downstream of the plurality of swivel joints.

[0083] With the above configuration, a hydrogen concentration meter is installed on the purge line downstream of the swivel joint. Therefore, if leaked hydrogen gas enters the purge area of ​​the swivel joint, the hydrogen concentration measured by the hydrogen concentration meter will increase. Consequently, it is possible to detect the intrusion of leaked hydrogen gas into the purge area of ​​the swivel joint, or in other words, an increased likelihood of leaked hydrogen gas leaking to the outside.

[0084] In a second embodiment, the purge line may connect the purge areas of the plurality of swivel joints in series, as in the first embodiment. With this configuration, the intrusion of leaked hydrogen gas into the purge areas of all swivel joints can be detected with a single hydrogen concentration meter.

[0085] In a third embodiment, in the first or second embodiment, the cargo handling system may include a first pressure-holding control valve provided in the pressure-holding line upstream of the plurality of swivel joints, a second pressure-holding control valve provided in the pressure-holding line downstream of the plurality of swivel joints, and a processing circuit that controls the first pressure-holding control valve and the second pressure-holding control valve so that the pressure between the first pressure-holding control valve and the second pressure-holding control valve in the pressure-holding line is maintained within a certain range. With this configuration, the pressure in the pressure-holding chambers of all swivel joints can be maintained within a certain range.

[0086] In a fourth aspect, in the third aspect, the above-described cargo handling system includes a flow control valve provided in the purge line downstream of the plurality of swivel joints, wherein the flow control valve is adjusted to an opening such that the pressure upstream of the flow control valve in the purge line is higher than atmospheric pressure, and the certain range may be higher than the pressure upstream of the flow control valve in the purge line. With this configuration, it is possible to prevent the intrusion of purge gas from the purge area into the pressure-holding chamber. This prevents the solidification of nitrogen gas in the pressure-holding chamber when the purge gas is nitrogen gas.

[0087] In a fifth embodiment, in any of the first to fourth embodiments, the cargo handling system may include a recovery control valve provided in the recovery line upstream of the plurality of swivel joints, and a processing circuit that opens the recovery control valve when the pressure downstream of the recovery control valve in the recovery line becomes negative. With this configuration, during the cool-down of the loading arm before cargo handling, it is possible to suppress the leakage of gas from the flow path or pressure-holding chamber for liquefied hydrogen into the recovery area due to the contraction of gas in the recovery area of ​​the swivel joint.

[0088] In a sixth embodiment, in the first or second embodiment, the cargo handling system may include a pressure reducing valve provided on the pressure holding line upstream of the plurality of swivel joints, and a pressure relief valve provided on the pressure holding line downstream of the plurality of swivel joints. With this configuration, the pressure in the pressure holding chambers of all swivel joints can be maintained within a range between the set pressure of the pressure reducing valve and the relief pressure of the pressure relief valve.

[0089] In a seventh aspect, in the sixth aspect, the cargo handling system comprises a purge pressure reducing valve provided on the purge line upstream of the plurality of swivel joints, and a purge relief valve provided on the purge line downstream of the plurality of swivel joints, wherein the relief pressure of the purge relief valve is set higher than atmospheric pressure, and the set pressure of the pressure-reducing valve may be set higher than the set pressure of the purge pressure reducing valve. This configuration prevents the intrusion of purge gas from the purge area into the pressure-reducing chamber. As a result, if the purge gas is nitrogen gas, solidification of the nitrogen gas in the pressure-reducing chamber can be prevented.

[0090] In an eighth aspect, in any of the first, second, sixth, and seventh aspects, the cargo handling system may be provided with a recovery pressure reducing valve installed in the recovery line upstream of the plurality of swivel joints. With this configuration, when the set pressure of the recovery pressure reducing valve is equal to atmospheric pressure, it is possible to suppress the leakage of gas from the flow path or pressure holding chamber for liquefied hydrogen into the recovery area due to the contraction of gas in the recovery area of ​​the swivel joint during the cool-down of the loading arm before cargo handling.

[0091] 1A, 1B Cargo handling system 10 Flow path 11 Loading arm 12 Double pipe 13 Swivel joint 4a First seal member 4b Second seal member 4c Third seal member 4d Fourth seal member 4A Recovery area 4B Pressure holding chamber 4C Purge area 5 Recovery line 53 First recovery control valve 54 Second recovery control valve 55 Recovery pressure reducing valve 56 On / off valve 6 Pressure holding line 63 First pressure holding control valve 64 Second pressure holding control valve 65 Pressure holding pressure reducing valve 66 Pressure holding relief valve 7 Purge line 74 Flow control valve 75 Purge pressure reducing valve 76 Purge relief valve 8 Control device 81 Processing circuit 82 User interface 91 Hydrogen concentration meter

Claims

1. A loading and unloading system for liquefied hydrogen, comprising: a loading arm including a plurality of swivel joints, each having a first sealing member that separates the flow path for liquefied hydrogen from a recovery area, a second sealing member that separates the recovery area from a pressure-holding chamber, and a third sealing member that separates the pressure-holding chamber from a purge area; a recovery line through which a recovery gas, which is hydrogen gas, flows, passing through the recovery area of ​​the plurality of swivel joints; a pressure-holding line through which a pressure-holding gas, which is helium gas or hydrogen gas, flows, passing through the pressure-holding chamber of the plurality of swivel joints; a purge line through which a purge gas, which is nitrogen gas or helium gas, flows, passing through the purge area of ​​the plurality of swivel joints; and a hydrogen concentration meter provided on the purge line downstream of the plurality of swivel joints.

2. The cargo handling system according to claim 1, wherein the purge line connects the purge areas of the plurality of swivel joints in series.

3. A cargo handling system according to claim 1 or 2, comprising: a first pressure-holding control valve provided in the pressure-holding line upstream of the plurality of swivel joints; a second pressure-holding control valve provided in the pressure-holding line downstream of the plurality of swivel joints; and a processing circuit that controls the first pressure-holding control valve and the second pressure-holding control valve so that the pressure between the first pressure-holding control valve and the second pressure-holding control valve in the pressure-holding line is maintained within a certain range.

4. The cargo handling system according to claim 3, further comprising a flow control valve provided in the purge line downstream of the plurality of swivel joints, wherein the flow control valve is adjusted to an opening such that the pressure upstream of the flow control valve in the purge line is higher than atmospheric pressure, and the certain range is higher than the pressure upstream of the flow control valve in the purge line.

5. The cargo handling system according to claim 1 or 2, comprising: a recovery control valve provided in the recovery line upstream of the plurality of swivel joints; and a processing circuit that opens the recovery control valve when the pressure downstream of the recovery control valve in the recovery line becomes negative.

6. The cargo handling system according to claim 1 or 2, further comprising: a pressure reducing valve provided in the pressure holding line upstream of the plurality of swivel joints; and a pressure relief valve provided in the pressure holding line downstream of the plurality of swivel joints.

7. The cargo handling system according to claim 6, further comprising: a purge pressure reducing valve provided on the purge line upstream of the plurality of swivel joints; and a purge relief valve provided on the purge line downstream of the plurality of swivel joints, wherein the relief pressure of the purge relief valve is set higher than atmospheric pressure, and the set pressure of the pressure holding valve is set higher than the set pressure of the purge pressure reducing valve.

8. The cargo handling system according to claim 1 or 2, further comprising a recovery pressure reducing valve provided in the recovery line upstream of the plurality of swivel joints.

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