Triple-shell tank

Abstract

To provide a structure with excellent workability during construction in a triple-shell tank with an inner tank, intermediate tank, and outer tank.SOLUTION: A triple-shell tank 1 comprises an inner tank 4, an intermediate tank 3, and an outer tank 2. The inner tank 2 includes an inner tank side plate 42 assembled by stacking a plurality of annular tiers formed by a plurality of inner tank side plate pieces 42P arranged in a circular pattern. The intermediate tank 3 includes an intermediate tank side plate 32 assembled by stacking a plurality of annular tiers formed by a plurality of intermediate tank side plate pieces 32P arranged in a circular pattern. The annular tier of the intermediate tank side plate 32 includes a bottom tier formed by a height-adjusting intermediate tank side plate piece 32P1 having a height corresponding to height difference between an inner tank bottom plate 41 and an intermediate tank bottom plate 31, and a second tier above the lowest tier formed by an intermediate tank side plate piece 32P2 positioned at the same height as the bottom tier inner tank side plate piece 42 P1 in the annular tier of the inner tank side plate 42.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a triple-shell tank for storing cryogenic liquefied gas. [Background technology]

[0002] Flat-bottom tanks with a multi-shell structure are known as facilities for storing low-temperature liquefied gas. Patent Document 1 discloses a flat-bottom tank with a triple-shell structure that includes an inner tank, an intermediate tank, and an outer tank. In constructing a triple-shell tank, it is desirable to construct the inner tank, intermediate tank, and outer tank in parallel rather than sequentially, in order to shorten the construction period. In this case, construction entrances are opened in the side panels of the inner tank, intermediate tank, and outer tank to allow for the transport of construction materials and equipment and for workers to enter and exit the tank.

[0003] Generally, the side panels of the inner, middle, and outer tanks are assembled by stacking multiple annular rows formed by arranging side panel pieces in a circular pattern. The construction opening is opened by temporarily removing one or more of the side panel pieces after the annular rows are formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 55-20937 Summary of the Invention [Problem to be solved by the invention]

[0005] In a triple-shell tank, the middle tank completely covers the inner tank, and the outer tank completely covers the middle tank. Because an insulation layer is interposed between the bottom plates of adjacent tanks, there is a difference in height between the bottom plates of each tank. This also creates a difference in height between the lowest level of each tank's side plate. Therefore, when opening a construction opening in each side plate by removing a side plate piece, a step may occur between adjacent construction openings. This step can hinder smooth work execution.

[0006] The object of the present disclosure is to provide a triple-shell tank having an inner tank, an intermediate tank, and an outer tank, with a structure that is easy to install. [Means for solving the problem]

[0007] A triple-shell tank according to one aspect of the present disclosure is a triple-shell tank comprising an inner tank, an intermediate tank covering the inner tank, and an outer tank covering the intermediate tank, wherein the inner tank includes inner tank side plates, an inner tank roof, and an inner tank bottom plate assembled by stacking multiple annular stages formed by arranging multiple inner tank side plate pieces in a ring shape, and the intermediate tank includes intermediate tank side plates, an intermediate tank roof, and an intermediate tank bottom plate assembled by stacking multiple annular stages formed by arranging multiple intermediate tank side plate pieces in a ring shape, and the annular stages of the intermediate tank side plates include a lowest stage formed by intermediate tank side plate pieces for height adjustment having a height corresponding to the difference in height between the inner tank bottom plate and the intermediate tank bottom plate, and a second stage above the lowest stage formed by intermediate tank side plate pieces arranged at the same height position as the inner tank side plate piece of the lowest stage in the annular stages of the inner tank side plate. [Effects of the Invention]

[0008] According to the present disclosure, a triple-shell tank having an inner tank, an intermediate tank, and an outer tank can be provided with a structure that is easy to install. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a vertical cross-sectional view showing an example of a triple-shell tank according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing the details of the vicinity of the lower end of the side plate of each vessel of the triple-shell tank. [Figure 3] FIG. 3 is a diagram showing the stacked state of the annular steps formed by the side plate pieces, exploded into the inner tank side plate, the intermediate tank side plate, and the outer tank side plate. [Figure 4] FIG. 4 is a cross-sectional view showing the opened state of the construction openings in the inner tank side plate, the intermediate tank side plate, and the outer tank side plate. [Figure 5]FIG. 5 is a cross-sectional view showing the installation state of the inner tank anchor straps and the intermediate tank anchor straps. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a triple-shell tank according to the present disclosure will be described in detail below with reference to the drawings. The triple-shell tank to be constructed according to the present disclosure is a flat-bottom tank with a triple-shell structure that is installed above ground and stores low-temperature liquefied gas. The liquefied gas stored therein is, for example, liquefied hydrogen or liquid helium.

[0011] [Triple-shell tank structure] The structure of a triple-shell tank 1 of this embodiment will be described based on the longitudinal cross-sectional view shown in Fig. 1. Fig. 1 illustrates a triple-shell tank 1 that stores liquid hydrogen LH. The triple-shell tank 1 includes a tank foundation 10, an outer tank 2 erected on the tank foundation 10, an intermediate tank 3 covered by the outer tank 2, and an inner tank 4 covered by the intermediate tank 3. The outer tank 2, intermediate tank 3, and inner tank 4 all have a circular shape when viewed from above, and are arranged concentrically.

[0012] The tank foundation 10 is a concrete layer that forms the foundation of the triple-shell tank 1. The tank foundation 10 is larger in size than the outer diameter of the outer tank 2. The outer tank 2 is a sealed body made of metal such as carbon steel, and includes an outer tank bottom plate 21, outer tank side plates 22, and an outer tank roof 23. The outer tank bottom plate 21 is laid directly on top of the tank foundation 10 and has a disk-like shape. The outer tank side plates 22 are erected from the periphery of the outer tank bottom plate 21 and have a cylindrical shape. The outer tank roof 23 is attached to the upper end of the cylindrical outer tank side plate 22 so as to close the upper opening of the outer tank side plate 22, and has a dome-like shape.

[0013] The intermediate tank 3 is a sealed body made of metal such as SUS, and is disposed inside the outer tank 2. The intermediate tank 3 includes an intermediate tank bottom plate 31, intermediate tank side plates 32, and an intermediate tank roof 33. The intermediate tank bottom plate 31 has a disk-like shape with a smaller diameter than the outer tank bottom plate 21. The intermediate tank side plates 32 stand upright from the periphery of the intermediate tank bottom plate 31 and have a cylindrical shape. The intermediate tank roof 33 is attached to the upper end of the intermediate tank side plates 32 and has a dome-like shape.

[0014] A first-level concrete layer 24, a first ring portion 25, and an outer bottom cold insulation layer 26 are interposed between the outer tank bottom plate 21 and the intermediate tank bottom plate 31. The first-level concrete layer 24 is a flat concrete layer constructed on the outer tank bottom plate 21. The first ring portion 25 is a high-strength concrete layer arranged in a ring shape around the periphery of the first-level concrete layer 24. A reinforced concrete layer 251 is arranged in the first ring portion 25 at a location that directly bears the load of the intermediate tank side plate 32. The outer bottom cold insulation layer 26 is an insulating layer arranged on top of the first-level concrete layer 24 and inside the first ring portion 25. The first ring portion 25 can be formed of an array of insulating concrete blocks, such as perlite concrete blocks. The outer bottom cold insulation layer 26 can be formed of an array of insulating inorganic blocks, such as foam glass. Lightweight aerated concrete plates, for example, can be laid on top of the outer bottom cold insulation layer 26.

[0015] The inner tank 4 is a tank that actually stores liquid, and is a sealed body made of metal such as SUS, and is disposed inside the intermediate tank 3. The inner tank 4 includes an inner tank bottom plate 41, inner tank side plates 42, and an inner tank roof 43. The inner tank bottom plate 41 has a disk-like shape with a smaller diameter than the intermediate tank bottom plate 31. The inner tank side plates 42 stand upright from the periphery of the inner tank bottom plate 41 and have a cylindrical shape. The inner tank roof 43 is attached to the upper end of the inner tank side plates 42 and has a dome-like shape. Liquid hydrogen LH is stored inside the inner tank 4.

[0016] A second-level concrete layer 34, a second ring portion 35, and an inner bottom cold insulation layer 36 are interposed between the intermediate tank bottom plate 31 and the inner tank bottom plate 41. The second-level concrete layer 34 is constructed on the intermediate tank bottom plate 31. The second ring portion 35 is a high-strength concrete layer arranged in a ring shape around the periphery of the second-level concrete layer 34. A reinforced concrete layer 351 is arranged in the second ring portion 35 at a location that directly bears the load of the inner tank side plate 42. The inner bottom cold insulation layer 36 is an insulating layer arranged on the second-level concrete layer 34 and inside the second ring portion 35. For example, the second ring portion 35 can be made of perlite concrete blocks, and the inner bottom cold insulation layer 36 can be made of foam glass blocks. A lightweight aerated concrete plate, for example, can be laid on the inner bottom cold insulation layer 36.

[0017] A gap of a predetermined width is provided between the inner tank 4 and the intermediate tank 3, and between the intermediate tank 3 and the outer tank 2. A first space between the tanks 11, which is the gap between the inner tank 4 and the intermediate tank 3, and a second space between the tanks 12, which is the gap between the intermediate tank 3 and the outer tank 2, are filled with a heat insulating material. Perlite or glass wool can be used as the heat insulating material. The first space between the tanks 11 is filled with a low-boiling-point gas, such as hydrogen gas, that has the same boiling point as the liquid hydrogen LH stored in the inner tank 4. The second space between the tanks 12 is filled with, for example, nitrogen gas.

[0018] [Details of the side panels of each tank] Fig. 2 is a cross-sectional view showing the details of the lower ends of the outer tank side plate 22, intermediate tank side plate 32, and inner tank side plate 42 of the triple-shell tank 1. Fig. 3 is an exploded view showing the construction of each tank's side plate, with the outer tank side plate 22, intermediate tank side plate 32, and inner tank side plate 42. The outer tank side plate 22, intermediate tank side plate 32, and inner tank side plate 42 are assembled by stacking multiple annular stages formed by arranging multiple side plate pieces 22P, 32P, and 42P in a circular ring shape. Figs. 2 and 3 show examples of stacking the annular stages.

[0019] The inner tank side plate 42 is assembled using multiple inner tank side plate pieces 42P, each consisting of a rectangular plate curved gently in an arc. More specifically, multiple inner tank side plate pieces 42P are arranged in an annular shape, and adjacent side plate pieces 42P are welded together to form a single annular step. The inner tank side plate 42 is constructed by stacking multiple such annular steps.

[0020] 2 and 3 is a side plate piece that constitutes the lowest annular stage of the inner tank side plate 42, erected directly above the outer periphery of the inner tank bottom plate 41. The inner tank side plate piece 42P2 is a side plate piece that constitutes the second annular stage stacked on top of the lowest stage. The inner tank side plate pieces 42P1 and 42P2 are also welded between the lowest annular stage and the second annular stage, i.e., they are welded together.

[0021] Thereafter, the inner tank side plate piece 42P3 and the inner tank side plate pieces above it are used to stack the third and upper annular tiers of the inner tank side plate 42 to the designed height. The inner tank side plate pieces 42P1 to 42P3 are of the same or similar size. Note that side plate pieces for adjusting the height and for filling in the remaining space after equal division may be of a size different from the regular size.

[0022] The intermediate tank side plate 32 and the outer tank side plate 22 are also assembled by stacking multiple annular stages, each formed by arranging multiple side plate pieces in an annular shape. The lowest annular stage of the intermediate tank side plate 32 is formed by arranging intermediate tank side plate pieces 32P1 in an annular shape directly above the outer periphery of the intermediate tank bottom plate 31. This lowest annular stage also serves as a height-adjusting side plate piece to match the height of the second annular stage of the intermediate tank side plate 32, constructed with intermediate tank side plate pieces 32P2, and the lowest annular stage of the inner tank side plate 42 described above.

[0023] There is a height difference between the inner tank bottom plate 41 on which the inner tank side plate 42 is erected and the intermediate tank bottom plate 31 on which the intermediate tank side plate 32 is erected. This height difference is created by constructing the inner bottom cold insulation layer 36 and the second-level concrete layer 34 (not shown in FIG. 2 ) on the intermediate tank bottom plate 31, and then laying the inner tank bottom plate 41 on top of them. The lowest intermediate tank side plate piece 32P1 has a height corresponding to the height difference between the inner tank bottom plate 41 and the intermediate tank bottom plate 31. Note that the height difference does not need to strictly match the height size of the intermediate tank side plate piece 32P1. A slight size difference is permissible as long as no significant step is created between the upper end surface of the intermediate tank side plate piece 32P1 and the inner tank bottom plate 41 when openings for construction work (described later) are opened in the inner tank side plate 42 and the intermediate tank side plate 32.

[0024] The second, third, and subsequent annular steps of the intermediate tank side plate 32, formed by the intermediate tank side plate pieces 32P2, 32P3, and so on, are stacked on top of the lowest annular step formed by the height-adjusting intermediate tank side plate piece 32P1. The second annular step (intermediate tank side plate piece 32P2) of the intermediate tank side plate 32 is located at the same height as the lowest annular step (inner tank side plate piece 42P1) of the inner tank side plate 42. Here, "the same height" includes not only the exact same height, but also a range that can be treated as substantially the same height. Therefore, even if there is a slight difference between the height positions of the intermediate tank side plate piece 32P2 and the inner tank side plate piece 42P1, this falls within the category of "the same height."

[0025] The lowest annular step of the outer tank side plate 22 is formed by arranging outer tank side plate pieces 22P1 in a circular ring shape directly above the outer periphery of the outer tank bottom plate 21. The height of the outer tank side plate pieces 22P1 can be selected according to the height difference between the outer tank bottom plate 21 and the inner tank bottom plate 41. A second annular step is formed above the lowest annular step by arranging outer tank side plate pieces 22P2 in a circular ring shape. The second annular step of the outer tank side plate 22 formed by the outer tank side plate pieces 22P2 is at approximately the same height as the intermediate tank side plate piece 32P2 that constitutes the second annular step of the intermediate tank side plate 32. Subsequently, the third, fourth, etc. annular steps of the outer tank side plate 22 are stacked up using outer tank side plate pieces 22P3, 22P4, etc.

[0026] In this embodiment, the side plate pieces 22P, 32P, and 42P used to construct each side plate 22, 32, and 42 have rectangular shapes with the same or similar heights and circumferential widths. The sizes of these side plate pieces 22P, 32P, and 42P can be selected based on the size of a single piece that can be manufactured. For example, the intermediate tank side plate piece 32P and the inner tank side plate piece 42P, both made of stainless steel, can be the same size, and the outer tank side plate piece 22P, made of carbon steel, can be slightly smaller or larger than these side plate pieces 32P and 42P. Of course, the three side plate pieces 22P, 32P, and 42P may be the same size, or the side plate pieces 32P and 42P may be different sizes.

[0027] [About the opening of the construction entrance] In constructing the triple-shell tank 1, if a construction method is adopted in which the tanks are constructed sequentially from the innermost tank, such as starting construction of the intermediate tank 3 after completing the inner tank 4, and then constructing the outer tank 2 after completing the intermediate tank 3, the construction period will be longer. In contrast, if the outer tank 2, intermediate tank 3, and inner tank 4 are constructed in parallel, work efficiency can be improved by allowing scaffolding and cranes to be shared for the construction of multiple tanks, which will ultimately contribute to shortening the construction period. In this case, it will be necessary to open construction entrances in the outer tank side plate 22, intermediate tank side plate 32, and inner tank side plate 42 for the transport of construction materials and equipment and for workers to enter and exit.

[0028] FIG. 4 is a cross-sectional view showing the openings of the construction openings in the inner tank side plate, intermediate tank side plate, and outer tank side plate. During construction of the triple-shell tank 1, the first opening OP1 is opened when the outer tank side plate 22 is constructed, the second opening OP2 is opened when the intermediate tank side plate 32 is constructed, and the third opening OP3 is opened when the inner tank side plate 42 is constructed. These openings OP1, OP2, and OP3 are temporarily opened for construction purposes, and are sealed after their use, starting from the inside. That is, the third opening OP3 is sealed after work inside the inner tank 4 is completed, the second opening OP2 is sealed after work inside the intermediate tank 3 is completed, and then the first opening OP1 is sealed after work inside the outer tank 2 is completed. Note that FIG. 4 also shows the intermediate tank annulus 311 and the inner tank annulus 411, which form the outer peripheral edges of the intermediate tank bottom plate 31 and the inner tank bottom plate 41.

[0029] The first opening OP1, the second opening OP2, and the third opening OP3 are opened by removing one or more of the side plate pieces 22P, 32P, and 42P constituting the annular sections of each side plate 22, 32, and 42. In FIG. 4, the first opening OP1 is opened by removing the outer tank side plate pieces 22P1 and 22P2 from the bottom and second annular sections of the annular sections constituting the outer tank side plate 22. The second opening OP2 is opened by removing the intermediate tank side plate piece 32P2 from the second annular section above the bottom height-adjusting section of the annular sections constituting the intermediate tank side plate 32. The third opening OP3 is opened by removing the inner tank side plate piece 42P1 from the bottom annular section of the annular sections constituting the inner tank side plate 42.

[0030] These openings OP1, OP2, and OP3 are opened at positions that overlap each other circumferentially around the triple-shell tank 1. Furthermore, because the side panel pieces 22P2, 32P2, and 42P1, which are located at approximately the same height, are removed, the openings OP1, OP2, and OP3 are also at the same height. In particular, the height difference between the intermediate tank bottom plate 31 and the inner tank bottom plate 41 is eliminated by the presence of the lowest height-adjusting intermediate tank side panel piece 32P1, allowing the second opening OP2 and the third opening OP3 to be opened without any steps. The formation of these openings OP1, OP2, and OP3 ensures a construction access that ensures a horizontal and linear work flow in the radial direction of the triple-shell tank 1. The first opening OP1, second opening OP2, and third opening OP3 are sealed by fitting the previously removed side panel pieces 22P1, 22P2, 32P2, and 42P1 into the respective openings and securing them by welding or other means.

[0031] [Installing anchor straps] Next, an example will be shown in which anchor straps are attached to the intermediate tank side plate 32 and the inner tank side plate 42 to reinforce these side plates 32, 42. Figure 5 is a cross-sectional view showing the triple-shell tank 1 shown in Figures 2 to 4 with the inner tank anchor straps 5 and intermediate tank anchor straps 6 attached.

[0032] The inner tank anchor strap 5 has an upper end 51 (one end) connected to the inner tank side plate 42 and a lower end 52 (other end) connected to the intermediate tank side plate 32 and the intermediate tank bottom plate 31. The intermediate tank anchor strap 6 has an upper end 61 (one end) connected to the intermediate tank side plate 32 and a lower end 62 (other end) fixed to the tank foundation 10. The inner tank anchor straps 5 and intermediate tank anchor straps 6 are arranged so that about five to six of them are lined up in the circumferential direction per side plate piece 22P, 32P. The installation of the anchor straps 5, 6 can improve the strength and earthquake resistance of the intermediate tank side plate 32 and the inner tank side plate 42.

[0033] More specifically, the upper end 51 of the inner tank anchor strap 5 is connected to the inner tank side plate piece 42P1 that constitutes the lowest part of the inner tank side plate 42. The upper end 51 is attached to the inner tank side plate piece 42P1 so that it can slide relative to the inner tank side plate piece 42P1 to some extent. This is to allow for some degree of expansion, contraction, and swinging of the inner tank 4. Meanwhile, the lower end 52 is fixed to a bracket 53 made of a rectangular plate. A side edge 531 of the bracket 53 is welded to the inner circumferential surface of the intermediate tank side plate piece 32P1 for height adjustment that constitutes the lowest part of the intermediate tank side plate 32. Furthermore, the lower edge 532 of the bracket 53 is welded to the intermediate tank bottom plate 31.

[0034] When opening a construction opening such as the second opening OP2 in the intermediate tank side plate 32, the intermediate tank side plate piece 32P1 is not temporarily removed. Therefore, the installation of the bracket 53, i.e., the inner tank anchor strap 5, is not obstructed. For the inner tank side plate piece 42P1 that is removed to open the third opening OP3, the bracket 53 with half the length of the inner tank anchor strap 5 attached is welded to the intermediate tank side plate piece 32P1. Then, when the inner tank side plate piece 42P1 is fitted into the third opening OP3, the remaining half is added to complete the inner tank anchor strap 5. The length of the inner tank anchor strap 5 is set according to the allowable displacement of the inner tank 4, so the upper end 51 of the inner tank anchor strap 5 may be attached to the inner tank side plate piece 42P2 that forms the second annular section.

[0035] The upper end 61 of the intermediate tank anchor strap 6 is connected to the intermediate tank side plate piece 32P2 that constitutes the second annular step from the bottom of the intermediate tank side plate 32. The upper end 61 is attached to the intermediate tank side plate piece 32P2 so that it can slide relatively to a certain extent. The lower end 62 is fixed to an anchor box 63 embedded in the tank foundation 10 (foundation structure). The attachment of the intermediate tank anchor strap 6 to the intermediate tank side plate piece 32P2, which is temporarily removed to open the second opening OP2, is the same as for the inner tank anchor strap 5 described above. The length of the intermediate tank anchor strap 6 is also set depending on the allowable displacement of the intermediate tank 3, etc. Therefore, the upper end 61 may be attached to the intermediate tank side plate piece 32P1 or 32P3 that constitutes the lowest or third annular step.

[0036] In the triple-shell tank 1 according to the present disclosure described above, the outer tank side plate 22, the intermediate tank side plate 32, and the inner tank side plate 42 are constructed by stacking annular stages formed by arranging side plate pieces 22P, 32P, and 42P in an annular shape. The height-adjusting intermediate tank side plate piece 32P1 that constitutes the lowest stage of the intermediate tank side plate 32 has a height that compensates for the height difference between the inner tank bottom plate 41 and the intermediate tank bottom plate 31. Therefore, the intermediate tank side plate piece 32P2 that constitutes the second annular stage of the intermediate tank side plate 32 and the inner tank side plate piece 42P1 that constitutes the lowest annular stage of the inner tank side plate 42 can be positioned at the same height. Therefore, when opening construction openings in the intermediate tank side plate 32 and the inner tank side plate 42, by removing the intermediate tank side plate piece 32P2 and the inner tank side plate piece 42P1 that are positioned to overlap circumferentially, it is possible to open the second opening OP2 and the third opening OP3 without any steps or with steps that are so small that they can be ignored.

[0037] Furthermore, if the lowest intermediate tank side plate piece 32P1 of the intermediate tank side plate 32 is set not to be removed when the second opening OP2 is opened, the intermediate tank side plate piece 32P1 can be used to fix the lower end 52 of the inner tank anchor strap 5. Therefore, the installation work of the inner tank anchor strap 5 can be made more efficient.

[0038] Summary of this disclosure The specific embodiments described above include disclosures having the following configurations.

[0039] The triple-shell tank according to the present disclosure is a triple-shell tank comprising an inner tank, an intermediate tank covering the inner tank, and an outer tank covering the intermediate tank, wherein the inner tank includes inner tank side plates, an inner tank roof, and an inner tank bottom plate assembled by stacking multiple annular stages formed by arranging multiple inner tank side plate pieces in a circular ring, and the intermediate tank includes intermediate tank side plates, an intermediate tank roof, and an intermediate tank bottom plate assembled by stacking multiple annular stages formed by arranging multiple intermediate tank side plate pieces in a circular ring, and the annular stages of the intermediate tank side plates include a lowest stage formed by intermediate tank side plate pieces for height adjustment having a height corresponding to the difference in height between the inner tank bottom plate and the intermediate tank bottom plate, and a second stage above the lowest stage formed by intermediate tank side plate pieces arranged at the same height position as the inner tank side plate piece of the lowest stage in the annular stages of the inner tank side plate.

[0040] In this triple-shell tank, the intermediate tank side plates and the inner tank side plates are assembled by stacking annular sections formed by arranging inner tank side plate pieces and intermediate tank side plate pieces, respectively, in an annular shape. The height-adjustable intermediate tank side plate piece that constitutes the lowest section of the intermediate tank side plate has a height size that corresponds to the height difference between the inner tank bottom plate and the intermediate tank bottom plate. Therefore, the intermediate tank side plate piece that constitutes the second annular section of the intermediate tank side plate and the inner tank side plate piece that constitutes the lowest annular section of the inner tank side plate can be positioned at the same height. Openings for construction work may be opened in the intermediate tank side plates and the inner tank side plates. In this case, by removing the intermediate tank side plate pieces and the inner tank side plate pieces that are circumferentially overlapping, a construction opening with no step or a step so small that it can be ignored can be opened.

[0041] The above-mentioned triple-shell tank may further include an inner tank anchor strap having one end connected to the inner tank side plate and the other end connected to the lowermost intermediate tank side plate piece.

[0042] With this triple-shell tank, the inner tank anchor straps can be installed using the intermediate tank side plate pieces for height adjustment. Construction openings can be opened in the intermediate tank side plates without removing the lowest intermediate tank side plate piece for height adjustment. In other words, since there is no need to consider removing the intermediate tank side plate piece for height adjustment, the installation work for the inner tank anchor straps can be made more efficient.

[0043] The above-mentioned triple-shell tank may further include an intermediate tank anchor strap having one end connected to the second-stage intermediate tank side plate piece and the other end connected to a foundation structure of the triple-shell tank.

[0044] According to this triple-shell tank, the strength of the intermediate tank side plate can be reinforced by the intermediate tank anchor straps. [Explanation of symbols]

[0045] 1. Triple-shell tank 10 Tank foundation (foundation structure) 2 Outer tank 21 Outer tank bottom plate 22 Outer tank side plate 22P (22P1~22P4) Outer tank side plate piece 23 Outer tank roof 3 Intermediate tank 31 Intermediate tank bottom plate 32 Intermediate tank side plate 32P (32P1~32P4) Intermediate tank side panel piece 32P1 Height-adjustable intermediate tank side plate piece 33 Intermediate tank roof 4 Inner tank 41 Inner tank bottom plate 42 Inner tank side plate 42P (42P1~42P3) Inner tank side plate piece 43 Inner tank roof 5 Inner tank anchor strap 6 Intermediate tank anchor strap

Claims

1. A triple-shell tank comprising an inner tank, an intermediate tank covering the inner tank, and an outer tank covering the intermediate tank, the inner tank includes an inner tank side plate, an inner tank roof, and an inner tank bottom plate assembled by stacking a plurality of annular stages formed by arranging a plurality of inner tank side plate pieces in an annular shape, the intermediate tank includes intermediate tank side plates, an intermediate tank roof, and an intermediate tank bottom plate assembled by stacking a plurality of annular stages formed by arranging a plurality of intermediate tank side plate pieces in an annular shape, The annular step of the intermediate tank side plate is a lowermost section formed of intermediate tank side plate pieces for height adjustment, the height of which corresponds to the height difference between the inner tank bottom plate and the intermediate tank bottom plate; a second stage above the lowest stage, which is formed of intermediate tank side plate pieces arranged at the same height as the inner tank side plate piece of the lowest stage in the annular stage of the inner tank side plate; A triple-shell tank containing

2. The triple-shell tank according to claim 1, The triple-shell tank further comprises an inner tank anchor strap, one end of which is connected to the inner tank side plate and the other end of which is connected to the lowermost intermediate tank side plate piece.

3. The triple-shell tank according to claim 1 or 2, The triple-shell tank further comprises an intermediate tank anchor strap, one end of which is connected to the second-stage intermediate tank side panel piece and the other end of which is connected to a foundation structure of the triple-shell tank.

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