Piping system for cryogenic fluid

Abstract

To prevent a human body from coming into contact with a surface of a single pipe with a temperature drop.SOLUTION: A piping system (1) for cryogenic fluid comprises: a heat insulating pipe (2) including an inner pipe (21) through which the cryogenic fluid flows and an outer pipe (22) that houses the inner pipe (21) via a heat insulating layer (23); a single pipe (3) connected to the heat insulating pipe (2), and through which the cryogenic fluid flows; and a mesh cover (10) including a wire mesh layer (11) that surrounds an outer peripheral surface of the single pipe (3) while being spaced apart from the outer peripheral surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a piping system through which cryogenic fluid flows.

Background Art

[0002] As piping through which cryogenic fluid flows, the one disclosed in Patent Document 1 below is known. Specifically, Patent Document 1 discloses a double pipe having a vacuum insulation structure for flowing liquefied hydrogen while keeping it cold. This double pipe has an inner pipe and an outer pipe. A vacuum layer for blocking heat transfer is formed between the inner pipe and the outer pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in a liquefied hydrogen facility for storing or transporting liquefied hydrogen, not only the double pipe as described above but also a single pipe can be used. The single pipe can be used, for example, as part of a vent line for discharging hydrogen gas generated by the heat input of liquefied hydrogen, that is, boil-off gas. However, the temperature of the boil-off gas passing through the vent line may become extremely low close to the temperature range of liquefied hydrogen. When such extremely low-temperature boil-off gas flows through the single pipe, the surface temperature of the single pipe drops significantly. Therefore, it is desirable to take measures to prevent the human body from coming into contact with the surface (outer surface) of the single pipe. Similar measures are desirably applied not only to the vent line of the liquefied hydrogen facility but also to various single pipes through which cryogenic fluid flows.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a piping system for cryogenic fluid capable of preventing the human body from coming into contact with the surface of a single pipe with a reduced temperature.

Means for Solving the Problem

[0006] As a solution to the above problems, a cryogenic fluid piping system according to one aspect of the present disclosure includes a heat-insulated pipe including an inner pipe through which a cryogenic fluid flows and an outer pipe that houses the inner pipe via a heat-insulation layer, a single pipe connected to the heat-insulated pipe through which the cryogenic fluid flows, and a mesh cover including a wire mesh layer that surrounds the outer peripheral surface of the single pipe with a space therebetween.

[0007] In addition, a cryogenic fluid piping system according to another aspect of the present disclosure includes a single pipe through which a cryogenic fluid flows, a heater connected to the single pipe that heats the cryogenic fluid, and a mesh cover including a wire mesh layer that surrounds the outer peripheral surface of the single pipe with a space therebetween.

Advantages of the Invention

[0008] According to the cryogenic fluid piping system of the present disclosure, it is possible to prevent a human body from coming into contact with the surface of the single pipe whose temperature has decreased.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] Hereinafter, based on the drawings, embodiments of the cryogenic fluid piping system of the present disclosure will be described in detail. The cryogenic fluid piping system of the present disclosure is a system including a pipe through which a cryogenic fluid flows. The cryogenic fluid is a cryogenic fluid that is difficult for a person to directly touch, such as a cryogenic liquid such as liquefied hydrogen or liquid helium, or a cryogenic gas generated by vaporization of the cryogenic liquid.

[0011] [Configuration of the piping system] FIG. 1 is a side view schematically showing the configuration of a cryogenic fluid piping system 1 (hereinafter, also simply referred to as the piping system 1) according to an embodiment of the present disclosure. The piping system 1 shown in this figure is applied to a liquefied hydrogen facility for storing or transporting liquefied hydrogen. More specifically, in this embodiment, the piping system 1 is applied to a vent line that discharges the cryogenic hydrogen gas generated by vaporization of liquefied hydrogen, that is, boil-off gas, while heating it. The piping system 1 includes a heat-insulating pipe 2, a single pipe 3, a valve 4, a heater 5, and a discharge pipe 6. The boil-off gas is led out from the heat-insulating pipe 2 on the left side of FIG. 1, passes through the single pipe 3 and the like, and is then discharged from the discharge pipe 6 on the right side of FIG. 1. In the following description, the upstream and downstream are based on the flow direction of the boil-off gas flowing in such a direction.

[0012] The heat-insulating pipe 2 is connected to other pipes or equipment through which liquefied hydrogen flows. In at least the upstream portion of such a heat-insulating pipe 2, a fluid containing liquefied hydrogen may flow. That is, the fluid flowing through the upstream portion of the heat-insulating pipe 2 can be liquefied hydrogen or a gas-liquid two-phase fluid in which liquefied hydrogen and boil-off gas are mixed. On the other hand, in the downstream portion of the heat-insulating pipe 2 shown in FIG. 1, due to the influence of heat input from the single pipe 3, the vaporization of liquefied hydrogen proceeds, and the proportion of liquefied hydrogen decreases. For this reason, the fluid flowing through the downstream portion of the heat-insulating pipe 2 is basically boil-off gas (hydrogen gas) or a gas-liquid two-phase fluid in which liquefied hydrogen and boil-off gas are mixed. In any case, the temperature of the fluid is close to the temperature at which liquefied hydrogen vaporizes (the boiling point of hydrogen). In other words, the fluid flowing through the downstream portion of the heat-insulating pipe 2 shown in FIG. 1, that is, the fluid introduced from the heat-insulating pipe 2 into the single pipe 3, is an extremely low-temperature fluid close to the boiling point of hydrogen (about -253°C at normal pressure). Although the extremely low-temperature fluid introduced into the upstream end of the single pipe 3 may contain liquefied hydrogen, in this embodiment, it is assumed that an extremely low-temperature fluid that does not contain liquefied hydrogen, that is, boil-off gas, is introduced into the upstream end of the single pipe 3.

[0013] The heat-insulating pipe 2 includes an inner pipe 21 through which a fluid containing the above-mentioned extremely low-temperature boil-off gas flows, and an outer pipe 22 arranged concentrically outside the inner pipe 21. A heat-insulating layer 23 is formed between the inner pipe 21 and the outer pipe 22. In other words, the outer pipe 22 houses the inner pipe 21 via the heat-insulating layer 23. In this embodiment, the heat-insulating layer 23 is a space communicating with a suction source such as a vacuum pump. By evacuating the heat-insulating layer 23 with this suction source, heat input (heat transfer) from the outer pipe 22 to the inner pipe 21 is significantly suppressed. Note that the heat-insulating layer 23 may be a layer filled with a heat-insulating material such as foamed urethane.

[0014] The single pipe 3 is disposed between the downstream end of the heat-insulating pipe 2 and the heater 5. The single pipe 3 is divided into a plurality of pipes in the axial direction. In the case of this embodiment, the single pipe 3 is divided into a first pipe 3A and a second pipe 3B with the valve 4 as a boundary. That is, the single pipe includes a first pipe 3A connecting the heat-insulating pipe 2 and the valve 4, and a second pipe 3B connecting the valve 4 and the heater 5.

[0015] The first pipe 3A has a cylindrical pipe wall 31 that defines a flow path communicating with the inner pipe 21 of the heat insulation pipe 2. There is no case body corresponding to the outer pipe 22 of the heat insulation pipe 2 on the outside of the pipe wall 31, and the surface (outer peripheral surface) of the pipe wall 31 is exposed to the outside air. The structure of the second pipe 3B is the same as that of the first pipe 3A.

[0016] The single pipe 3 is supported by a support 7 at an appropriate position in the axial direction. The support 7 is a support column erected on a base B made of grating or ground. The single pipe 3 is fixed on the support 7 via a fixture 7a attached to the upper end of the support 7.

[0017] The valve 4 is a valve that is opened when performing a venting operation to discharge boil-off gas to the outside air. The valve 4 includes a valve body 41 that houses a valve element for opening and closing, an upstream flange 42 provided on the upstream side of the valve body 41, and a downstream flange 43 provided on the downstream side of the valve body 41. The flange 32 at the downstream end of the single pipe 3 (the first pipe 3A) on the upstream side of the valve 4 is coupled to the upstream flange 42, and the flange 33 at the upstream end of the single pipe 3 (the second pipe 3B) on the downstream side of the valve 4 is coupled to the downstream flange 43.

[0018] The single pipe 3 and the valve 4 are each covered by mesh covers 10 and 20. The mesh covers 10 and 20 are covers mainly made of wire mesh. The structure thereof will be described in detail.

[0019] The heater 5 is a heat exchanger connected to the downstream end of the single pipe 3 (the second pipe 3B). The heater 5 heats the boil-off gas derived from the single pipe 3 using a predetermined heat medium. The heat medium used in the heater 5 is not particularly limited as long as it can heat the boil-off gas. For example, normal temperature air can be used as the heat medium. The boil-off gas is heated by heat exchange in the process of passing through the heater 5 and is heated to a temperature close to normal temperature, for example.

[0020] The discharge pipe 6 includes a connection part 61 connected to the downstream side of the heater 5, and a vertical pipe part 62 extending upward from the downstream end of the connection part 61. The boil-off gas heated by the heater 5 is discharged to the outside air from the exhaust port at the downstream end of the vertical pipe part 62.

[0021] [Details of the Mesh Cover] FIG. 2 is a cross-sectional view schematically showing the structure of the mesh cover 10 covering the single pipe 3. As shown in this figure, the mesh cover 10 includes a plurality of wire mesh layers 11 surrounding the single pipe 3 concentrically, and a fixture 12 holding each wire mesh layer 11 on the outside of the single pipe 3.

[0022] As shown in FIG. 3, the wire mesh layer 11 is formed by rounding a sheet-shaped wire mesh in which metal wire rods 110 are woven together in a predetermined pattern into a circular shape. When the wire mesh is rounded, the edges of the wire meshes that abut against each other are fixed to each other using a fixture such as a wire. Thereby, the wire mesh is held in a rounded state, and a circular wire mesh layer 11 is formed. The wire mesh layer 11 (wire rod 110) is made of a low-temperature steel that is difficult to embrittle even under low-temperature conditions, for example, austenitic stainless steel. Note that the wire mesh layer 11 as described above is not necessarily highly rigid, and may be deformed by its own weight or the like. In other words, the circle presented by the wire mesh layer 11 does not necessarily have to be a precise circle, and may be a somewhat deformed circle caused by the deformation as described above. Also, the centers of the plurality of wire mesh layers 11 may be slightly offset from each other.

[0023] The plurality of wire mesh layers 11 are made to have different diameters. In this embodiment, three types of wire mesh layers 11 with different diameters are used. That is, the plurality of wire mesh layers 11 include a first wire mesh layer 11A, a second wire mesh layer 11B having a larger diameter than the first wire mesh layer 11A, and a third wire mesh layer 11C having a larger diameter than the second wire mesh layer 11B. The first to third wire mesh layers 11A to 11C are arranged to be concentrically arranged with a space in the radial direction outside the single pipe 3. Note that hereinafter, when referring to the first to third wire mesh layers 11A to 11C without distinction, they may simply be referred to as the wire mesh layer 11.

[0024] The first wire mesh layer 11A is arranged so as to surround the outer peripheral surface of the pipe wall 31 of the single pipe 3 with a gap therebetween. The second wire mesh layer 11B is arranged so as to surround the first wire mesh layer 11A with a gap therebetween. The third wire mesh layer 11C is arranged so as to surround the second wire mesh layer 11B with a gap therebetween. However, the single pipe 3 and the first wire mesh layer 11A do not necessarily need to have a gap over the entire circumference, and a part of the first wire mesh layer 11A may be in contact with the single pipe 3. This also applies to the relationship between the first wire mesh layer 11A and the second wire mesh layer 11B, and the relationship between the second wire mesh layer 11B and the third wire mesh layer 11C.

[0025] FIG. 4 is an enlarged cross-sectional view showing a part of FIG. 2 in an enlarged manner. As shown in FIGS. 4 and 2, the fixture 12 has a base portion 121 wound around the pipe wall 31 of the single pipe 3 and a plurality of support portions 122 radially extending outward in the radial direction from the base portion 121. Note that the fixture 12 may be provided at a plurality of locations in the axial direction separated from each other in the mesh cover 10 so that the wire mesh layer 11 is supported at a plurality of locations in the axial direction via the fixture 12.

[0026] In the present embodiment, both the base portion 121 and the support portion 122 are made of wire. That is, the base portion 121 is formed by a wire wound around the single pipe 3, and the support portion 122 is formed by a wire intertwined so as to extend radially outward from the base portion 121. The material of the wire forming these base portion 121 and support portion 122, that is, the material of the fixture 12, is the same low-temperature steel as that of the wire mesh layer 11. In FIGS. 2 and 4, although there is a slight gap between the outer peripheral surface of the single pipe 3 and the base portion 121, this is for convenience, and actually the base portion 121 is firmly wound around the single pipe 3 so as not to move relative to the single pipe 3.

[0027] The plurality of support portions 122 are each fastened to the base portion 121 at the fastening point P1 (FIG. 4). Further, each support portion 122 is fastened to the first to third wire mesh layers 11A to 11C at three radially spaced fastening points P2 to P4. That is, the first wire mesh layer 11A is fixed to the support portion 122 at the fastening point P2, the second wire mesh layer 11B is fixed to the support portion 122 at the fastening point P3, and the third wire mesh layer 11C is fixed to the support portion 122 at the fastening point P4. In this way, the first to third wire mesh layers 11A to 11C are arranged concentrically outside the single pipe 3 by being fixed to the support portion 122 at three radially spaced fastening points P2 to P4. In other words, the support portion 122 has a function as a spacer for maintaining the interval between adjacent wire mesh layers 11 in the radial direction.

[0028] FIG. 5 is a schematic cross-sectional view showing the positional relationship of the first to third wire mesh layers 11A to 11C. As shown in this figure, the first to third wire mesh layers 11A to 11C are arranged such that their meshes are shifted from each other in the radial view. That is, the first to third wire mesh layers 11A to 11C each have a large number of mesh holes h1 partitioned by the intertwined wire rods 110. And the first to third wire mesh layers 11A to 11C are arranged while being angularly shifted in the circumferential direction so that the centers of the respective mesh holes h1, that is, the meshes are shifted from each other in the radial view.

[0029] The mesh cover 10 having the above structure is arranged in series along the axial direction of the single pipe 3 as shown in FIG. 1. That is, the mesh cover 10 is manufactured so that its axial dimension becomes equal to or less than a predetermined upper limit value due to the specifications of the raw wire mesh or manufacturing convenience. By preparing a plurality of such mesh covers 10 and arranging them in the axial direction, the single pipe 3 is covered with the mesh cover 10 over substantially the entire axial direction. A pair of adjacent mesh covers 10 are fixed to each other using a binding member 15 made of a wire or the like.

[0030] More specifically, in the present embodiment, a valve 4 is present between the first pipe 3A and the second pipe 3B of the single pipe 3. Therefore, the mesh covers 10 are prepared separately for the first pipe 3A and the second pipe 3B. That is, at least one mesh cover 10 is prepared for the first pipe 3A, and at least one mesh cover 10 is prepared for the second pipe 3B. The axial dimensions of the respective mesh covers 10 may be the same as each other or different from each other. Note that a separate mesh cover 20 is prepared for the valve 4, and this mesh cover 20 will be described again later.

[0031] The number of mesh covers 10 used can be appropriately set according to the respective axial lengths of the first pipe 3A and the second pipe 3B. For example, when the axial length of the first pipe 3A (second pipe 3B) is equal to or less than the upper limit dimension in the axial direction of the mesh cover 10, basically one mesh cover 10 for the first pipe 3A (second pipe 3B) is sufficient. On the other hand, when the axial length of the first pipe 3A (second pipe 3B) is greater than the upper limit dimension in the axial direction of the mesh cover 10, a plurality of mesh covers 10 are required for the first pipe 3A (second pipe 3B). FIG. 1 shows an example in which a plurality of mesh covers 10 are attached to the downstream second pipe 3B. The plurality of mesh covers 10 are arranged adjacent to each other along the axial direction of the second pipe 3B so as to continuously cover the second pipe 3B. Although not shown for convenience in FIG. 1, it is also possible to attach a plurality of mesh covers 10 to the first pipe 3A in the same manner.

[0032] As described above, in the present embodiment, a plurality of mesh covers 10 having an axial dimension equal to or less than a predetermined value are prepared, and the mesh covers 10 are attached in series to the first pipe 3A and the second pipe 3B before and after the valve 4, respectively. Thereby, the single pipe 3 composed of both pipes 3A and 3B is entirely covered by the mesh covers 10.

[0033] The mesh cover 10 on the most upstream side of the single pipe 3 (the first pipe 3A) is arranged such that the upstream end of its wire mesh layer 11 abuts against the vertical wall W1 on the downstream side of the heat insulating pipe 2. Similarly, the mesh cover 10 on the most downstream side of the single pipe 3 (the second pipe 3B) is arranged such that the downstream end of its wire mesh layer 11 abuts against the vertical wall W2 on the upstream side of the heater 5.

[0034] Openings A1 are appropriately formed in the mesh cover 10 to avoid interfering objects protruding radially from the single pipe 3. Specifically, in the present embodiment, the second pipe 3B of the single pipe 3 is supported from below by a support 7 extending in the vertical direction. Therefore, openings A1 for avoiding the support 7 are formed at the bottom of the mesh cover 10 in the region where the support 7 is located. The openings A1 are formed by partially cutting out the bottoms of the respective wire mesh layers 11A to 11C (FIG. 2) in the mesh cover 10.

[0035] Here, as described above, in the present embodiment, not only the mesh cover 10 covering the single pipe 3 but also a mesh cover 20 (valve mesh cover) covering the valve 4 is prepared. The mesh cover 20 covering the valve 4 and the plurality of mesh covers 10 covering the single pipe 3 described above are arranged to be aligned in the axial direction with almost no break. In other words, in the present embodiment, a section from the heat insulating pipe 2 to the heater 5 is continuously covered by a plurality of mesh covers combining the mesh cover 10 for the single pipe 3 and the mesh cover 20 for the valve 4.

[0036] The mesh cover 20 for the valve 4 has the same structure as the mesh cover 10 for the single pipe 3. That is, the mesh cover 20 has a plurality of wire mesh layers that concentrically surround the valve 4 and correspond to the first to third wire mesh layers 11A to 11C (FIG. 2) described above. The mesh cover 20 and the mesh covers 10 before and after it are fixed to each other using a binding member 16 made of wire or the like. In the present embodiment, the outer diameter of the mesh cover 20 for the valve 4 is larger than the outer diameter of the mesh cover 10 for the single pipe 3. However, the outer diameter of the mesh cover 20 for the valve 4 may be appropriately set according to the shape of the valve 4 or the like, and may be the same as the outer diameter of the mesh cover 10 for the single pipe 3.

[0037] An opening A2 (FIG. 1) for avoiding the neck portion 41a of the valve 4 is formed in the upper part of the mesh cover 20. This opening A2 is formed by partially notching each wire mesh layer of the mesh cover 20, similar to the opening A1 of the mesh cover 10 for the single pipe 3 described above.

[0038] [Function and Effect] As described above, in the present embodiment, a mesh cover 10 including a wire mesh layer 11 that covers the single pipe 3 from the outside is attached to the single pipe 3 through which the cryogenic boil-off gas derived from the heat-insulating pipe 2 flows. According to such a configuration, there is an advantage that it is possible to prevent a human body from being suppressed on the surface (outer peripheral surface) of the single pipe 3 that has been cooled by the flow of the boil-off gas.

[0039] That is, during the venting operation of discharging boil-off gas to the outside air through the single pipe 3 or the like, the surface temperature of the single pipe 3 can drop to an extremely low temperature close to the temperature range of liquefied hydrogen. At this time, if the surface of the single pipe 3 is completely exposed, there is a risk that the human body may directly touch the surface of the single pipe 3. In contrast, in this embodiment, since the mesh cover 10 including the wire mesh layer 11 is attached to the single pipe 3, the wire mesh layer 11 can suppress the human body from touching the single pipe 3. Here, the wire mesh layer 11 is a porous layer located at a position away from the surface (outer peripheral surface) of the single pipe 3 and having a large surface area. Therefore, the temperature of the wire mesh layer 11 is maintained at a temperature sufficiently higher than the surface temperature of the single pipe 3. Therefore, if such a mesh cover 10 including the wire mesh layer 11 is attached to the single pipe 3, even if the human body approaches the single pipe 3, it is only necessary for the body to touch the relatively high-temperature wire mesh layer 11, and the body can be prevented from touching the extremely low-temperature surface such as the surface of the single pipe 3.

[0040] In particular, in this embodiment, since the extremely low-temperature boil-off gas generated by the vaporization of liquefied hydrogen flows through the single pipe 3, the surface temperature of the single pipe 3 may drop to a temperature at which liquefied air is generated. Furthermore, if liquefied air is generated on the surface of the single pipe 3, the liquefied air may flow down below the single pipe 3. Since liquefied air is an extremely low-temperature liquid of about -200°C, it is not desirable for such extremely low-temperature liquefied air to flow down and scatter. In contrast, in this embodiment where the single pipe 3 is covered with the mesh cover 10, even if liquefied air flows down from the single pipe 3, a part of the flowing-down liquefied air can be received by the mesh cover 10, and the scattering of the liquefied air can be prevented. That is, in the process of the liquefied air flowing down from the single pipe 3 passing through the wire mesh layer 11, by receiving a part of the liquefied air with the wire 110 of the wire mesh layer 11, the liquefied air can be prevented from scattering downward in a droplet state.

[0041] The above-described effect of preventing the scattering of liquefied air increases as the mesh of the wire mesh layer 11 becomes finer. Utilizing this, the fineness of the mesh may be changed depending on the location of the pipe. For example, for the mesh cover applied to the single pipe located at a position higher than a person's height, the mesh of the wire mesh layer may be set to be finer.

[0042] Also, in the present embodiment, the mesh cover 10 includes a plurality of wire mesh layers 11 (first to third wire mesh layers 11A to 11C) arranged at intervals in the radial direction on the outer side of the single pipe 3. In this way, when covering the single pipe 3 with a plurality of wire mesh layers 11, the above-described effects, that is, effects such as suppressing contact with the single pipe 3, can be enhanced more than when using a single wire mesh layer 11.

[0043] Specifically, the plurality of wire mesh layers 11 are each formed in a circular shape surrounding the single pipe 3 and are arranged concentrically. According to such a configuration, by combining a plurality of mutually independent wire mesh layers 11 having similar shapes, the mesh cover 10 including the wire mesh layer 11 can be easily and appropriately constructed.

[0044] Furthermore, the plurality of wire mesh layers 11 are arranged such that their meshes are offset from each other in a radial view. According to such a configuration, since the route for accessing the surface of the single pipe 3 through the meshes (mesh holes h1) of each wire mesh layer 11 becomes complicated, even if a thin body part such as a finger approaches the single pipe 3, it can be suppressed from touching the surface of the single pipe 3. Also, when liquefied air flows down from the single pipe 3, the liquefied air can be made to abut against the wire 110 of any one of the wire mesh layers 11 with a high probability, thereby promoting the atomization of the liquefied air.

[0045] Also, in the present embodiment, the mesh cover 10 includes a holder 12 that functions as a spacer for maintaining the interval between adjacent wire mesh layers 11 in the radial direction. According to such a configuration, the plurality of wire mesh layers 11 can be attached to the single pipe 3 while maintaining a constant interval between them.

[0046] Further, in the present embodiment, a heater 5 is connected to the downstream end of the single pipe 3. According to such a configuration, since the boil-off gas derived from the single pipe 3 is heated by the heater 5, the temperature of the boil-off gas discharged to the outside air through the discharge pipe 6 from the heater 5 can be brought close to the temperature of the outside air, and the influence caused by the discharge of the boil-off gas can be suppressed to a low level.

[0047] Moreover, according to the present embodiment in which the mesh cover 10 is attached to the single pipe 3 for discharging the boil-off gas to the outside air as described above, the degree to which the heat input from the outside air to the single pipe 3 is inhibited can be made smaller compared to, for example, the case where the single pipe 3 is completely covered with a cylindrical body. As a result, the temperature of the boil-off gas significantly rises in the process of passing through the single pipe 3, so that the temperature of the boil-off gas discharged from the downstream end of the single pipe 3 through the heater 5 to the outside air can be brought closer to the temperature of the outside air.

[0048] Also, in the present embodiment, a plurality of mesh covers 10 are arranged in series along the axial direction of the single pipe 3. According to such a configuration, by preparing the number of mesh covers 10 corresponding to the axial length of the single pipe 3, the single pipe 3 can be appropriately covered with the mesh covers 10 over the necessary range. In addition, since the axial dimension of each mesh cover 10 can be suppressed below a predetermined upper limit, the production of the mesh cover 10 can be facilitated.

[0049] Furthermore, in the present embodiment, a mesh cover 20 (valve mesh cover) is also attached to the valve 4 in the middle of the single pipe 3. According to such a configuration, by covering the single pipe 3 and the valve 4 with separate mesh covers 10 and 20, any contact of the human body with the single pipe 3 and the valve 4 can be suppressed.

[0050] [Modification Example] In the above embodiment, as the mesh cover 10 covering the single tube 3, one prepared including a plurality of independent wire mesh layers 11 formed in a circular shape surrounding the single tube 3 was used. Instead of this, as shown in FIG. 6, it is also possible to construct a mesh cover 210 including a plurality of wire mesh layers 211 surrounding the outer peripheral surface of the single tube 3 by winding a wire mesh around the outer peripheral surface of the single tube 3 in a spiral shape. Specifically, in the example of FIG. 6, as the plurality of wire mesh layers 211, a first wire mesh layer 211A, a second wire mesh layer 211B outside thereof, and a third wire mesh layer 211C outside thereof are formed. These first to third wire mesh layers 211A to 211C are continuous in this order from the side closer to the outer peripheral surface of the single tube 3. That is, each divided region obtained by virtually dividing the wire mesh wound in a spiral shape by 360° in the circumferential direction corresponds to the first to third wire mesh layers 211A to 211C, respectively. The first to third wire mesh layers 211A to 211C are held at a constant interval in the radial direction from each other by a holder 212 (spacer) similar to the holder 12 (FIGS. 2 and 4) used in the above embodiment.

[0051] In addition, when winding the wire mesh in a spiral shape as described above, the winding may be performed while slightly shifting the axial position little by little. That is, a mesh cover including a plurality of wire mesh layers surrounding the single tube may be constructed by winding a wire mesh around the single tube in a spiral shape.

[0052] In the above embodiment, on the premise that the outer diameter of the outermost wire mesh layer 11 (third wire mesh layer 11C) in the most upstream mesh cover 10 is smaller than the outer diameter of the outer tube 22 in the heat insulating tube 2, the mesh cover 10 is arranged such that the end of the wire mesh layer 11 abuts against the vertical wall W1 of the heat insulating tube 2. However, the outermost diameter of the wire mesh layer 11 may be larger than the outer diameter of the outer tube 22. In this case, since a ring-shaped gap is generated in the axial direction view between the upstream end of the wire mesh layer 11 and the downstream end of the outer tube 22, a ring-shaped wire mesh for filling this gap may be additionally attached. This also applies to the relationship between the most downstream mesh cover 10 and the warmer 5.

[0053] In the above embodiment, the heater 5 is provided between the single pipe 3 (the second pipe 3B) and the discharge pipe 6, but the heater 5 may be omitted. That is, the single pipe 3 and the discharge pipe 6 may be directly connected.

[0054] In the above embodiment, the valve 4 is attached in the middle of the single pipe 3, that is, between the first pipe 3A and the second pipe 3B of the single pipe 3, but a similar valve may be attached to the end of the single pipe 3.

[0055] [Summary] The above embodiment and its modifications include the following disclosures.

[0056] The cryogenic fluid piping system according to the first aspect of the present disclosure includes a heat-insulating pipe including an inner pipe through which a cryogenic fluid flows and an outer pipe that houses the inner pipe via a heat-insulating layer, a single pipe connected to the heat-insulating pipe through which the cryogenic fluid flows, and a mesh cover including a wire mesh layer that surrounds the outer peripheral surface of the single pipe with a space therebetween.

[0057] According to this first aspect, since the mesh cover including the wire mesh layer surrounding the single pipe is attached to the single pipe, even if the cryogenic fluid flows through the single pipe and the temperature of the surface (outer peripheral surface) of the single pipe drops significantly, the wire mesh layer can prevent the human body from coming into contact with the surface of the single pipe with the reduced temperature.

[0058] The cryogenic fluid piping system according to the second aspect further includes a heater for heating the cryogenic fluid in the first aspect, and the single pipe connects the heat-insulating pipe and the heater.

[0059] According to this second aspect, since the cryogenic fluid derived from the single pipe is heated by the heater, the influence exerted by the cryogenic fluid can be suppressed to a low level on the downstream side of the heater.

[0060] The cryogenic fluid piping system according to the third aspect includes, in the first or second aspect, the mesh cover including a plurality of the wire mesh layers arranged at intervals in the radial direction outside the single pipe.

[0061] When covering the single pipe with a plurality of wire mesh layers as in this third aspect, the above-described effect of suppressing contact with the single pipe can be enhanced more than when using a single wire mesh layer.

[0062] In the cryogenic fluid piping system according to the fourth aspect, in the third aspect, the plurality of wire mesh layers are each formed in a circular shape surrounding the single pipe and are arranged concentrically.

[0063] According to this fourth aspect, by combining a plurality of mutually independent wire mesh layers having similar shapes, a mesh cover including the wire mesh layers can be easily and appropriately constructed.

[0064] In the cryogenic fluid piping system according to the fifth aspect, in the third or fourth aspect, the plurality of wire mesh layers are arranged such that their meshes are offset from each other in a radial view.

[0065] According to this fifth aspect, since the route for accessing the surface of the single pipe through the meshes of each wire mesh layer becomes complicated, even if a thin body part such as a finger approaches the single pipe, it can be suppressed from touching the surface of the single pipe.

[0066] In the cryogenic fluid piping system according to the sixth aspect, in the third to fifth aspects, the mesh cover further includes a spacer that maintains the interval between the radially adjacent wire mesh layers.

[0067] According to this sixth aspect, a plurality of wire mesh layers can be attached to the single pipe while maintaining a constant interval between them.

[0068] In the cryogenic fluid piping system according to the seventh aspect, in the first to sixth aspects, it includes a plurality of the mesh covers arranged in series along the axial direction of the single pipe.

[0069] According to this seventh aspect, by preparing a number of mesh covers corresponding to the axial length of the single pipe, the single pipe can be appropriately covered with the mesh covers over the required range. Further, since the axial dimension of each mesh cover can be suppressed below a predetermined upper limit, the production of the mesh cover can be facilitated.

[0070] The cryogenic fluid piping system according to the eighth aspect further includes, in the seventh aspect, a valve attached to the single pipe and a valve mesh cover including a wire mesh layer surrounding the valve.

[0071] According to this eighth aspect, by covering the single pipe and the valve with separate mesh covers, contact of the human body with the single pipe and the valve can be suppressed.

[0072] The cryogenic fluid piping system according to the ninth aspect of the present disclosure includes a single pipe through which a cryogenic fluid flows, a heater connected to the single pipe for heating the cryogenic fluid, and a mesh cover including a wire mesh layer surrounding the outer peripheral surface of the single pipe with a space therebetween.

[0073] According to this ninth aspect, the same effects as those of the first aspect described above can be obtained.

Description of Reference Numerals

[0074] 1 Cryogenic fluid piping system 2 Heat insulation pipe 3 Single pipe 4 Valve 5 Heater 10 Mesh cover 11 Wire mesh layer 12 Holder (spacer) 21 Inner pipe 22 Outer pipe 23 Heat insulation layer 20 Mesh cover (valve mesh cover)

Claims

1. A heat-insulated pipe including an inner pipe through which an extremely low temperature fluid flows and an outer pipe that houses the inner pipe via a heat-insulating layer, A single pipe connected to the heat-insulated pipe through which the extremely low temperature fluid flows, A mesh cover including a wire mesh layer that surrounds the outer peripheral surface of the single pipe with a space therebetween, for a piping system for an extremely low temperature fluid.

2. In the piping system for an extremely low temperature fluid according to Claim 1, Further comprising a heater for heating the extremely low temperature fluid, The single pipe connects the heat-insulated pipe and the heater, for a piping system for an extremely low temperature fluid.

3. In the piping system for an extremely low temperature fluid according to Claim 1, The mesh cover includes a plurality of the wire mesh layers arranged at intervals in the radial direction outside the single pipe, for a piping system for an extremely low temperature fluid.

4. In the piping system for an extremely low temperature fluid according to Claim 3, The plurality of wire mesh layers are each formed in a circular shape surrounding the single pipe and are arranged concentrically, for a piping system for an extremely low temperature fluid.

5. In the piping system for an extremely low temperature fluid according to Claim 3 or 4, The plurality of wire mesh layers are arranged such that their meshes are offset from each other in a radial view, for a piping system for an extremely low temperature fluid.

6. In the piping system for an extremely low temperature fluid according to Claim 3 or 4, The mesh cover further includes a spacer for maintaining the interval between the radially adjacent wire mesh layers, for a piping system for an extremely low temperature fluid.

7. In the piping system for an extremely low temperature fluid according to any one of Claims 1 to 4, Comprising a plurality of the mesh covers arranged in series along the axial direction of the single pipe, for a piping system for an extremely low temperature fluid.

8. In the piping system for an extremely low temperature fluid according to Claim 7, A valve attached to the single pipe, Further comprising a valve mesh cover including a wire mesh layer surrounding the valve, for a piping system for an extremely low temperature fluid.

9. A single pipe through which an extremely low temperature fluid flows, A heater connected to the single pipe for heating the extremely low temperature fluid, A mesh cover including a wire mesh layer that surrounds the outer peripheral surface of the single pipe with a space therebetween, for a piping system for an extremely low temperature fluid.

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