Low-temperature underground tank

Abstract

To provide a low-temperature underground tank having a wide pump barrel pit and capable of suppressing expansion of corrugation intervals.SOLUTION: A low-temperature underground tanks comprises a pump barrel pit into which a pump barrel is inserted, and a membrane retaining liquefied gas therein. The membrane comprises a membrane opening through which the pump barrel penetrates and which has a smaller area than a horizontal cross section of the pump barrel pit, and a number of corrugations of convex cross-section at least one of which passes over the pump barrel pit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to cryogenic underground tanks. [Background technology]

[0002] A thin stainless steel membrane is attached to the entire surface of the bottom of a cryogenic underground tank that stores low-temperature liquefied gas such as LNG. This membrane has numerous corrugations with a convex cross section. When the membrane is cooled by the low-temperature liquefied gas and contracts, each corrugation expands in response to the contraction of the membrane, preventing damage to the membrane.

[0003] Furthermore, the liquefied gas stored in the cryogenic underground tank is discharged to the outside by a pump barrel. The pump barrel extends vertically inside the cryogenic underground tank and draws in the liquefied gas from a suction port located at the bottom end. A pump barrel pit into which the lower end of the pump barrel is inserted may be formed at the bottom of the cryogenic underground tank (see Patent Document 1). By forming a pump barrel pit in the cryogenic underground tank, the amount of liquefied gas remaining after the liquefied gas is discharged can be reduced. The pump barrel pit is positioned to avoid the corrugations formed in the membrane. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-108198 Summary of the Invention [Problem to be solved by the invention]

[0005] When liquefied gas is not stored in the cryogenic underground tank, workers may enter the pump barrel pit and perform work on the lower end of the pump barrel. To perform work efficiently, it is desirable for the pump barrel pit to be large. However, if the pump barrel pit is widened, the spacing between the corrugations around the pump barrel pit increases, which may cause the membrane to be unable to withstand contraction due to cooling.

[0006] Therefore, an object of the present disclosure is to provide a low-temperature underground tank that has a spacious pump barrel pit and can suppress the expansion of corrugation spacing. [Means for solving the problem]

[0007] A low-temperature underground tank according to one embodiment of the present disclosure comprises a pump barrel pit into which a pump barrel is inserted, and a membrane that holds liquefied gas therein, the membrane including a membrane opening hole through which the pump barrel passes and which has an area smaller than the horizontal cross section of the pump barrel pit, and a number of corrugations with a convex cross section, at least one of which passes over the pump barrel pit. [Effects of the Invention]

[0008] According to the above configuration, it is possible to provide a low-temperature underground tank that has a spacious pump barrel pit and can suppress the expansion of the corrugation spacing. [Brief explanation of the drawings]

[0009] [Figure 1] Figure 1 is a vertical cross-sectional view of the bottom of a cryogenic underground tank. [Figure 2] Figure 2 is a plan view of the bottom of a cryogenic underground tank. [Figure 3] FIG. 3 is a perspective view of the pump barrel pit and the pit top plate. DETAILED DESCRIPTION OF THE INVENTION

[0010] A cryogenic underground tank 100 according to an embodiment will be described below. FIG. 1 is a vertical cross-sectional view of the bottom of the cryogenic underground tank 100. The cryogenic underground tank 100 is partially or completely buried underground and stores cryogenic liquefied gas such as LNG. As shown in FIG. 1, the cryogenic underground tank 100 includes a pump barrel pit 10, a membrane 20, and a pit top plate 30. These components will be described below in order.

[0011] <Pump barrel pit> The pump barrel pit 10 is a hole into which the lower end portion of the pump barrel 90 that discharges liquefied gas is inserted. The pump barrel pit 10 is located at the bottom of the cryogenic underground tank 100, and is recessed downward and open upward. FIG. 2 is a plan view of the bottom of the cryogenic underground tank 100. As shown in FIG. 2, the pump barrel pit 10 is circular in plan view, and the horizontal cross section of the pump barrel pit 10 is also circular. As shown in FIG. 1, the pump barrel pit 10 is defined by a pit body 11.

[0012] FIG. 3 is a perspective view of the pit body 11 and a pit upper plate 30, which will be described later. As shown in FIG. 3, the pit body 11 is formed in a cup shape and includes a cylindrical side portion 12 and a bottom portion 13 located below the side portion 12. The material of the pit body 11 is a metal, which has a smaller linear expansion coefficient than the material of the membrane 20, which will be described later. Therefore, when exposed to low-temperature liquefied gas, the pit body 11 is less likely to shrink than the membrane 20. The material of the pit body 11 is, for example, 9% nickel steel, 36% nickel stainless steel, or the like.

[0013] As shown in Figure 1, the pit body 11 is inserted into a recess formed in a concrete bottom slab 14, and cold insulation material 15 is positioned between the pit body 11 and the bottom slab 14. The pit body 11 serves to prevent liquefied gas in the pump barrel pit 10 from leaking into the cold insulation material 15 and the bottom slab 14. Furthermore, because the horizontal cross section of the pump barrel pit 10, i.e., the horizontal cross section of the pit body 11, is circular, higher strength can be obtained compared to cases where the horizontal cross section is not circular. As a result, the thickness of the pit body 11 can be reduced.

[0014] <Membrane> The membrane 20 is a thin plate that extends over the surface of the bottom and sidewalls of the cryogenic underground tank 100, and holds the liquefied gas, which is the stored liquid, inside. The membrane 20 ensures airtightness and liquidtightness against the liquefied gas. As shown in FIG. 1, at the bottom of the cryogenic underground tank 100, the membrane 20 is located above the bottom plate 14, and a cold insulation material 15 is located between the membrane 20 and the bottom plate 14. The membrane 20 serves to prevent the liquefied gas in the cryogenic underground tank 100 from leaking into the cold insulation material 15 and the bottom plate 14. The membrane 20 is made of a metal material, such as SUS304.

[0015] As shown in Figure 2, the membrane 20 includes a membrane opening 21 and numerous corrugations 22. The membrane opening 21 is located above the pump barrel pit 10, and the pump barrel 90 passes through it. The membrane opening 21 has an area smaller than the horizontal cross section of the pump barrel pit 10. Therefore, the area surrounding the membrane opening 21 is located above the pump barrel pit 10. Furthermore, if the vertical direction on the paper surface of Figure 2 is referred to as the "first direction," and the horizontal direction on the paper surface perpendicular to the first direction is referred to as the "second direction," the membrane opening 21 is substantially rectangular, with the dimension Y in the first direction being greater than the dimension X in the second direction.

[0016] The corrugations 22 are portions formed on the membrane 20 that have a convex cross section. The corrugations 22 expand when the membrane 20 is cooled by the liquefied gas and contracts, thereby preventing damage to the membrane 20. The membrane 20 of this embodiment includes a plurality of corrugations 22 extending in a first direction and a plurality of corrugations 22 extending in a second direction. To prevent partial stress from being applied to the membrane 20 when it contracts, the corrugations 22 extending in the first direction are preferably positioned so that they are spaced apart at intervals not greater than a certain level in the second direction, and the corrugations 22 extending in the second direction are preferably positioned so that they are spaced apart at intervals not greater than a certain level in the first direction.

[0017] In this embodiment, of the many corrugations 22 included in the membrane 20, two corrugations 22 that are adjacent to both sides of the membrane opening hole 21 in the second direction and extend in the first direction pass over the pump barrel pit 10. In other words, these two corrugations 22 pass over the pump barrel pit 10 near the membrane opening hole 21. Therefore, the distance in the second direction between the two corrugations 22 that pass over the pump barrel pit 10 is smaller than the dimension of the pump barrel pit 10 in the second direction.

[0018] Furthermore, in this embodiment, the dimension Y in the first direction of the membrane opening hole 21 is larger than the dimension X in the second direction, so that there are relatively wide areas at both ends of the membrane opening hole 21 in the first direction that do not interfere with the pump barrel 90. Therefore, workers can easily enter and exit the pump barrel pit 10 through these areas.

[0019] In this embodiment, two corrugations 22 pass over the pump barrel pit 10, but the number may be one, or three or more. When at least one corrugation 22 is arranged to pass over the pump barrel pit 10, it is possible to suppress an increase in the spacing between adjacent corrugations 22 across the pump barrel pit 10 (in this embodiment, the spacing in the second direction). Therefore, even if the interior of the pump barrel pit 10 is enlarged, it is possible to suppress an increase in the spacing between the corrugations 22.

[0020] <Pit top plate> The pit top plate 30 is a member located on the pit main body 11. As shown in FIG. 3, the pit top plate 30 is annular. The outer peripheral edge 31 of the pit top plate 30 is located outward from the side surface 12 of the pit main body 11, i.e., outward from the pump barrel pit 10. The inner peripheral edge 32 of the pit top plate 30 is located inward from the side surface 12 of the pit main body 11, i.e., above the pump barrel pit 10. Therefore, the top plate opening hole 33 formed by the inner peripheral edge 32 of the pit top plate 30 is located above the pump barrel pit 10, and the pump barrel 90 passes through it.

[0021] In this embodiment, the upper plate opening 33 of the pit upper plate 30 has the same shape and size as the membrane opening 21 (see FIG. 2) of the membrane 20. Furthermore, the membrane opening 21 of the membrane 20 is located above the upper plate opening 33 of the pit upper plate 30. In other words, the pit upper plate 30 is in contact with the underside of the membrane 20 in an area surrounding the membrane opening 21. Therefore, the pit upper plate 30 is located above the pump barrel pit 10 of the membrane 20, and suppresses distortion of the membrane 20 due to its own weight in this area.

[0022] Furthermore, as described above, the two corrugations 22 pass over the pump barrel pit 10, and the pit top plate 30 is in contact with the underside of the membrane 20 in the area corresponding to the two corrugations 22. In other words, the pit top plate 30 covers the corrugations 22 from below. This prevents the liquefied gas stored in the low-temperature underground tank 100 from passing through the two corrugations 22 and leaking into the cold insulation material 15 and the bottom slab 14. In this embodiment, the pit top plate 30 is supported on the bottom slab 14 via support members 34.

[0023] <Effects of the embodiment> As described above, the low-temperature underground tank according to the embodiment comprises a pump barrel pit into which a pump barrel is inserted, and a membrane that holds liquefied gas therein, and the membrane includes a membrane opening hole through which the pump barrel passes and which has an area smaller than the horizontal cross section of the pump barrel pit, and a number of corrugations with a convex cross section, at least one of which passes over the pump barrel pit.

[0024] According to this configuration, at least one corrugation passes over the pump barrel pit, so even if the pump barrel pit is widened, the increase in the spacing between adjacent corrugations across the pump barrel pit can be suppressed.

[0025] In addition, the low-temperature underground tank according to the embodiment further includes a pit upper plate that contacts the lower surface of the membrane in an area that includes the corrugation that passes over the pump barrel pit.

[0026] With this configuration, the pit body covers the corrugation passing over the pump barrel pit from below, preventing liquefied gas stored in the low-temperature underground tank from leaking through the corrugation into the ice insulation and bottom plate.

[0027] In addition, in the low-temperature underground tank of the embodiment, the pit upper plate is annular and contacts the underside of the membrane in the area surrounding the membrane opening hole, with its outer peripheral edge located outward from the pump barrel pit and its inner peripheral edge located above the pump barrel pit.

[0028] With this configuration, the pit upper plate supports the area of ​​the membrane located above the pump barrel pit and is submerged in the liquid, so it is only necessary to suppress distortion due to the membrane's own weight in that area, and no reinforcing structure is required to support the liquid pressure.

[0029] In addition, in the low-temperature underground tank according to the embodiment, the material of the pit body that defines the pump barrel pit has a linear expansion coefficient smaller than that of the material of the membrane.

[0030] Since it is difficult to form corrugations in the pit body like in the membrane, if the pit body is made of the same material as the membrane, deformation due to cooling will be large. In contrast, in the above configuration, the pit body material has a smaller linear expansion coefficient than the membrane material, so deformation of the pit body can be suppressed, and the impact on the membrane can also be reduced.

[0031] In addition, in the low-temperature underground tank according to the embodiment, the horizontal cross section of the pump barrel pit is circular.

[0032] With this configuration, the strength of the pump barrel pit can be improved and the thickness of the pit body can be reduced compared to when the horizontal cross section of the pump barrel pit is not circular.

[0033] In addition, in the low-temperature underground tank of the embodiment, the dimension of the membrane opening hole in a first direction, which is the direction in which the corrugation passing over the pump barrel pit extends, is larger than the dimension in a second direction perpendicular to the first direction.

[0034] This configuration makes it possible to increase the area of ​​the membrane openings while suppressing the increase in the gap between adjacent corrugations on either side of the pump barrel pit, thereby making it easier for workers to enter and exit the pump barrel pit. [Explanation of symbols]

[0035] 10 Pump Barrel Pit 11 Pit body 20 membranes 21 Membrane opening hole 22 Corrugation 30 Pit top plate 31 outer edge 32 inner periphery 90 pump barrels 100 Low-temperature underground tank

Claims

1. a pump barrel pit into which the pump barrel is inserted; a membrane for holding a liquefied gas therein; The membrane includes a membrane opening hole through which the pump barrel passes and which is smaller in area than the horizontal cross section of the pump barrel pit, and a number of corrugations with a convex cross section, at least one of which passes over the pump barrel pit.

2. 2. The cryogenic underground tank according to claim 1, further comprising a pit top plate in contact with the lower surface of the membrane in an area including a corrugation passing over the pump barrel pit.

3. 3. The low-temperature underground tank described in claim 2, wherein the pit upper plate is annular and contacts the underside of the membrane in an area surrounding the membrane opening hole, with its outer peripheral edge located outward from the pump barrel pit and its inner peripheral edge located above the pump barrel pit.

4. 4. The low-temperature underground tank according to claim 1, wherein the material of the pit body defining the pump barrel pit has a linear expansion coefficient smaller than that of the material of the membrane.

5. 5. A cryogenic underground tank according to claim 1, wherein the horizontal cross section of the pump barrel pit is circular.

6. A low-temperature underground tank as described in any one of claims 1 to 5, wherein the dimension of the membrane opening hole in a first direction, which is the direction in which the corrugation passing over the pump barrel pit extends, is larger than the dimension in a second direction perpendicular to the first direction.

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