Triple-shell tank construction method

Abstract

To contribute to shortening the construction period by optimizing an opening mode of the construction entrance for the construction of triple-shell tanks with inner, intermediate, and outer tanks.SOLUTION: In a construction method of a triple-shell tank, a first construction opening is opened when an outer tank side panel is constructed, a second construction opening when an inner tank side panel is constructed, and a third construction opening when an intermediate tank side panel is constructed, respectively, as an entrance and exit for construction. The second construction opening is sealed after completion of work inside the inner tank, then the third construction opening is sealed after completion of work inside the intermediate tank, and then the first construction opening is sealed after completion of work inside the outer tank. The first construction opening, the second construction opening, and the third construction opening are opened at positions where at least part of them overlap each other in the circumferential and height directions of the triple shell tank, and when the opening area of the first construction opening is AR1 and that of the second construction opening is AR2, the first construction opening and the second construction opening are opened so as to satisfy a relationship AR1≥AR2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Flat-bottom tanks with a multi-shell structure are known as facilities for storing low-temperature liquefied gas. The construction of this type of multi-shell tank generally requires a long construction period, as the structure itself is large-scale and requires the application of thermal insulation and other features. For example, Patent Documents 1 and 2 disclose construction methods for double-shell tanks with an inner and outer tank, with the aim of shortening the construction period. In recent years, flat-bottom tanks with a triple-shell structure, which have an intermediate tank between the inner and outer tanks, have been considered as storage facilities for cryogenic liquefied gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6127453 [Patent Document 2] Patent No. 5672787 Summary of the Invention [Problem to be solved by the invention]

[0004] In the construction of triple-shell tanks, it is desirable to build the inner, intermediate, and outer tanks in parallel rather than sequentially, in order to shorten the construction period. In this case, construction entrances must be opened in the side panels of the inner, intermediate, and outer tanks to allow the loading and unloading of construction materials and equipment, and for workers to enter and exit. If these entrances are not properly located in the side panels, it may hinder the smooth progress of work and hinder the shortening of the construction period.

[0005] The object of the present disclosure is to provide a construction method that can optimize the opening of construction ports and contribute to shortening construction time when constructing a triple-shell tank having an inner tank, an intermediate tank, and an outer tank. [Means for solving the problem]

[0006] A construction method for a triple-shell tank according to one aspect of the present disclosure is a construction method for a triple-shell tank including an inner tank, an intermediate tank, and an outer tank, each having a roof and a side plate, and includes the steps of opening a first construction port in the outer tank side plate when the outer tank side plate is constructed, a second construction port in the inner tank side plate when the inner tank side plate is constructed, and a third construction port in the intermediate tank side plate when the intermediate tank side plate is constructed, as construction entrances and exits, sealing the second construction port after work inside the inner tank is completed, then sealing the third construction port after work inside the intermediate tank is completed, and then sealing the first construction port after work inside the outer tank is completed, wherein the first construction port, the second construction port, and the third construction port are opened at positions where they at least partially overlap each other in the circumferential and vertical directions of the triple-shell tank, and when the opening area of ​​the first construction port is AR1 and the opening area of ​​the second construction port is AR2, AR1≧AR2 The first construction entrance and the second construction entrance are opened so as to satisfy the relationship. [Effects of the Invention]

[0007] According to the present disclosure, when constructing a triple-shell tank having an inner tank, an intermediate tank, and an outer tank, it is possible to provide a construction method that optimizes the opening mode of the construction entrance and contributes to shortening the construction period. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a vertical cross-sectional view showing the structure of a triple-shell tank to which the present disclosure is applied. [Figure 2] 2A and 2B are diagrams showing a first embodiment of the construction entrance opening, in which FIG. 2A is a vertical cross-sectional view of the construction entrance opening location, and FIG. 2B is a horizontal cross-sectional view. [Figure 3] FIG. 3 shows a second embodiment of the construction entrance opening, where FIG. 3(A) is a vertical cross-sectional view of the construction entrance opening location, and FIG. 3(B) is a horizontal cross-sectional view. [Figure 4]4A and 4B are diagrams showing a third embodiment of the construction entrance opening, in which FIG. 4A is a vertical cross-sectional view of the construction entrance opening location, and FIG. 4B is a horizontal cross-sectional view. [Figure 5] FIG. 5 is a view showing the construction port opening mode of the third embodiment, exploded into the inner tank side plate, the intermediate tank side plate, and the outer tank side plate. [Figure 6] FIG. 6 is a cross-sectional view showing a modified example of the third embodiment. [Figure 7] FIG. 7 is a process chart showing an example of a construction method for a triple-shell tank to which the construction entrance opening method according to the present disclosure is applied. [Figure 8] FIG. 8 is a diagram showing one step of the construction method for the triple-shell tank, using a cross section of half of the tank. [Figure 9] FIG. 9 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 10] FIG. 10 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 11] FIG. 11 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 12] FIG. 12 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 13] FIG. 13 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 14] FIG. 14 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 15] FIG. 15 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 16] FIG. 16 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 17] FIG. 17 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 18] FIG. 18 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 19] FIG. 19 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 20]FIG. 20 is a diagram showing one step of the construction method for the triple-shell tank. [Figure 21] FIG. 21 is a diagram showing one step of the construction method for the triple-shell tank. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a triple-shell tank construction method according to the present disclosure will be described in detail 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 stored liquefied gas is, for example, liquefied hydrogen or liquid helium.

[0010] [Triple-shell tank structure] First, the structure of a triple-shell tank 1, which is the subject of construction of the present disclosure, will be described based on the longitudinal cross-sectional view shown in Figure 1. Figure 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 contained in the outer tank 2, and an inner tank 4 contained in 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.

[0011] 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 plate 22 stands upright from the periphery of the outer tank bottom plate 21 and has 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.

[0012] 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.

[0013] Between the outer tank bottom plate 21 and the intermediate tank bottom plate 31, a first level concrete layer 24, a first ring portion 25, and an outer bottom cold insulation layer 26 are interposed. 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. A lightweight aerated concrete plate, for example, can be laid on top of the outer bottom cold insulation layer 26.

[0014] 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.

[0015] Between the intermediate tank bottom plate 31 and the inner tank bottom plate 41, there are interposed a second-level concrete layer 34, a second ring portion 35, and an inner bottom cold insulation layer 36. 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 top of 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, may be laid on top of the inner bottom cold insulation layer 36.

[0016] 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 is equivalent to the liquid hydrogen LH stored in the inner tank 4. The second space between the tanks 12 is filled with, for example, nitrogen gas.

[0017] [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, for example, allowing scaffolding and cranes to be shared for the construction of multiple tanks, thereby contributing to a shortened construction period. In this case, construction entrances must be opened in the outer tank side plate 22, intermediate tank side plate 32, and inner tank side plate 42 to allow for the transport of construction materials and equipment and for workers to enter and exit.

[0018] First Embodiment FIG. 2 shows a first embodiment of the opening of a construction port. FIG. 2(A) is a vertical cross-sectional view of the construction port opening location, and FIG. 2(B) is a horizontal cross-sectional view. During construction of the triple-shell tank 1, the first opening OP1 (first construction port) is opened when the outer tank side plate 22 is constructed, the second opening OP2 (second construction port) is opened when the inner tank side plate 42 is constructed, and the third opening OP3 (third construction port) is opened when the intermediate tank side plate 32 is constructed. These openings OP1, OP2, and OP3 are temporarily opened for construction purposes, and are sealed from the inside out after their use is completed. That is, the second opening OP2 is sealed after work inside the inner tank 4 is completed, the third opening OP3 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. Construction of the triple-shell tank 1 includes the processes of opening and sealing the construction ports described above.

[0019] The manner in which these construction openings are opened will now be explained. It is desirable that the work traffic line that passes through the three side panels 22, 32, and 42 of the triple-shell tank 1 and heads radially inward or outward be linear, considering the ease of workers entering and exiting and the ease of material delivery. Therefore, to ensure the linearity of the work traffic line, the first opening OP1, the second opening OP2, and the third opening OP3 are opened at positions where they at least partially overlap each other in the circumferential and vertical directions of the triple-shell tank 1. In other words, when viewed from the radial center of the cylindrical triple-shell tank 1, the first opening OP1, the second opening OP2, and the third opening OP3 are opened so that they at least partially overlap each other on a straight line LC that extends radially.

[0020] The first opening OP1 is opened at a predetermined opening height H1 and a circumferential opening width W1 in the lowest region of the outer tank side plate 22. The outer tank side plate 22 is erected near the outer peripheral edge of the outer tank bottom plate 21. The first opening OP1 is a rectangular opening whose lower edge is on the upper surface of the outer tank bottom plate 21 and whose upper edge is located above the opening height H1.

[0021] The second opening OP2 is opened in the lowest region of the inner tank side plate 42, with a predetermined opening height H2 and a circumferential opening width W2. The inner tank side plate 42 is erected on the inner tank annulus 411. The second opening OP2 is a rectangular opening whose lower edge is on the upper surface of the inner tank annulus 411 and whose upper edge is located above the opening height H2. Similarly, the third opening OP3 is opened in the lowest region of the intermediate tank side plate 32, with a predetermined opening height H3 and a circumferential opening width W3. The intermediate tank side plate 32 is erected on the intermediate tank annulus 311. The third opening OP3 is a rectangular opening whose lower edge is on the upper surface of the intermediate tank annulus 311 and whose upper edge is located above the opening height H3.

[0022] The triple-shell tank 1 has a shell structure in which the intermediate tank 3 is provided to completely cover the inner tank 4, and the outer tank 2 is provided to completely cover the intermediate tank 3. Therefore, the lowest positions of the side panels are the outer tank side panel 22, the intermediate tank side panel 32, and the inner tank side panel, resulting in a difference in height. On the other hand, considering workability, the construction openings for each side panel must be located near the lowest area of ​​each side panel 22, 32, 42, which is closest to the ground, as shown in Figure 2(A). However, in order to meet this requirement, the above-mentioned differences in height create differences in height between the lower edges of the first opening OP1 and the second opening OP2, between the lower edges of the first opening OP1 and the third opening OP3, and between the lower edges of the third opening OP3 and the second opening OP2. These differences in height at the construction openings can hinder smooth work flow and cause problems during work.

[0023] In consideration of this, as shown in FIG. 2(A), the relationship between the opening heights H1, H2, and H3 of the first opening OP1, second opening OP2, and third opening OP3 is set to satisfy the following formula (1). H1>H3>H2 (1) More specifically, the upper edges of the openings OP1, OP2, and OP3 are aligned at approximately the same height, while the lower edges are set at the lowest positions of the side plates 22, 32, and 42. As a result, the openings OP1, OP2, and OP3 are formed so as to satisfy the relationship of the above formula (1).

[0024] 2(B), the first opening OP1, the second opening OP2, and the third opening OP3 are arranged in the circumferential direction of the triple-shell tank 1 so as to align on a straight line LC directed toward the radial center of the triple-shell tank 1. It is desirable that the circumferential centers of the openings OP1, OP2, and OP3 align on the straight line LC. The openings OP1, OP2, and OP3 are set so that the relationship between their circumferential opening widths W1, W2, and W3 satisfies the following formula (2). W1>W3>W2 (2)

[0025] The opening areas AR1, AR2, and AR3 of the openings OP1, OP2, and OP3 can be calculated by multiplying the opening height and the opening width, ignoring the curvature of the side plates 22, 32, and 42. From the relationship between the above equations (1) and (2), the opening areas AR1, AR2, and AR3 satisfy the following equation (3). AR1>AR3>AR2 (3)

[0026] According to the first embodiment, the first opening OP1, the second opening OP2, and the third opening OP3 have a common horizontal opening width within the range of the opening height H2 of the innermost second opening OP2 in the height direction of the triple-shell tank 1. Furthermore, in the circumferential direction of the triple-shell tank 1, the three openings OP1, OP2, and OP3 have opening widths that overlap each other on a straight line LC extending toward the radial center. As a result, the openings OP1, OP2, and OP3 have opening areas AR1, AR2, and AR3 that satisfy the above formula (3). Therefore, even if there is a step at the lowest position of the three side panels 22, 32, and 42, a horizontal and linear work flow line extending radially inward or outward through these side panels can be ensured. This facilitates the entry and exit of workers and the delivery of materials through the openings OP1, OP2, and OP3.

[0027] Second Embodiment 3A and 3B show a second embodiment of the construction entrance opening, with FIG. 3A being a longitudinal cross-sectional view of the construction entrance opening location and FIG. 3B being a horizontal cross-sectional view. The second embodiment shows an example in which the opening heights H1, H2, and H3 and the circumferential opening widths W1, W2, and W3 of the first opening OP1, second opening OP2, and third opening OP3 are the same. That is, the opening heights H1, H2, and H3 and the circumferential opening widths W1, W2, and W3 are set to satisfy the following formulas (11) and (21). As a result, the opening areas AR1, AR2, and AR3 satisfy the relationship of the following formula (31). H1=H3=H2 (11) W1=W3=W2 (21) AR1=AR3=AR2 (31)

[0028] As shown in Fig. 3(A), the upper and lower edges of the three openings OP1, OP2, and OP3 are located at approximately the same height. That is, the three openings OP1, OP2, and OP3 are opened at the same height in each of the side plates 22, 32, and 42. Furthermore, as shown in Fig. 3(B), the three openings OP1, OP2, and OP3 are opened at the same circumferential position in each of the side plates 22, 32, and 42 of the triple-shell tank 1. This construction opening mode of the second embodiment also ensures a horizontal and linear work flow line that passes through the three side plates 22, 32, and 42 and faces radially inward or outward.

[0029] The opening heights H1, H2, H3, opening widths W1, W2, W3, and opening areas AR1, AR2, AR3 of the first opening OP1, second opening OP2, and third opening OP3 can be set appropriately within ranges that do not significantly deviate from the ranges of the above-mentioned equations (1) to (11), (2) to (21), and (3) to (31), respectively.

[0030] For example, when focusing on the first opening OP1 and the second opening OP2, the opening heights H1, H2, opening widths W1, W2, and opening areas AR1, AR2 can be set as follows: H1>H2 or H1≧H2 (41) W1>W2 or W1≧W2 (42) AR1>AR2 or AR1≧AR2 (43) By satisfying the above formulas (41) to (43), even if there is a difference in height between the lowest position of the outer tank side plate 22 and the lowest position of the inner tank side plate 42, the difference in height can be eliminated, and it becomes easy to form a construction opening that can ensure a work flow line that extends horizontally and linearly in the radial direction. In this case, the third opening OP3 may be set to an opening with an opening height H3, opening width W3, and opening area AR3 of appropriate sizes that do not obstruct the work flow line.

[0031] The second opening OP2 and the third opening OP3 may be set to have the same opening height, the same circumferential opening width, and the same opening area. That is, the three openings OP1, OP2, and OP3 may be formed so as to satisfy the following equations (12), (22), and (32). H1>H3=H2 (12) W1>W3=W2 (22) AR1>AR3=AR2 (32)

[0032] In summary, the opening heights H1, H2, H3, opening widths W1, W2, W3, and opening areas AR1, AR2, AR3 of the first opening OP1, second opening OP2, and third opening OP3 should be set within ranges that satisfy the following equations (13), (23), and (33). H1 ≥ H3 ≥ H2 (13) W1 ≥ W3 ≥ W2 (23) AR1 ≥ AR3 ≥ AR2 (33)

[0033] Third Embodiment Next, an example of opening a construction port by removing a side panel piece will be described as a third embodiment. Fig. 4 shows the third embodiment of opening a construction port, with Fig. 4(A) being a vertical cross-sectional view of the construction port opening location and Fig. 4(B) being a horizontal cross-sectional view. Fig. 5 is a view showing the construction port opening mode of the third embodiment, exploded into the inner tank side panel 42, the intermediate tank side panel 32, and the outer tank side panel 22.

[0034] The outer tank side plate 22, inner tank side plate 42, and intermediate tank side plate 32 of the triple-shell tank 1 shown in Figure 1 are generally assembled by stacking multiple annular steps, each formed by arranging multiple side plate pieces in an annular shape. Figures 4 and 5 show an example of stacking the annular steps. The outer tank side plate 22 is assembled using multiple outer tank side plate pieces 22P, each made of a rectangular plate that is gently curved in an arc. More specifically, multiple outer tank side plate pieces 22P are arranged in an annular shape, and adjacent side plate pieces 22P are welded together to form one annular step. The outer tank side plate 22 is constructed by stacking multiple such annular steps.

[0035] The outer tank side plate piece 22P1 shown in Figures 4 and 5 is a side plate piece that constitutes the lowest annular tier of the outer tank side plate 22, erected directly above the outer tank bottom plate 21. The outer tank side plate piece 22P2 is a side plate piece that constitutes the second annular tier stacked on top of the lowest tier. The outer tank side plate pieces 22P3, 22P4, etc. form the third, fourth, etc. annular tiers of the outer tank side plate 22. The outer tank side plate pieces 22P1 to 22P4 are of the same or similar size. Since the hydraulic pressure decreases toward the top of the side plate, the outer tank side plate pieces 22P of the upper tiers may be thinner and larger than the lower tiers. Furthermore, side plate pieces for height adjustment and for filling in the remaining space after equal division may be of a different size than the regular size.

[0036] The inner tank side plate 42 and the intermediate tank side plate 32 are also assembled by stacking multiple annular steps formed by arranging multiple side plate pieces in an annular shape. The inner tank side plate 42 has the lowest annular step formed by arranging the inner tank side plate piece 42P1 in an annular shape on the inner tank annulus 411. This lowest annular step is located at approximately the same height as the second annular step of the outer tank side plate 22. Subsequently, the second, third, and other annular steps of the inner tank side plate 42 formed by the inner tank side plate pieces 42P2, 42P3, ... are stacked.

[0037] The intermediate tank side plate 32 has a lowest annular step formed by arranging intermediate tank side plate pieces 32P1 in an annular shape on the intermediate tank annulus 311. This lowest annular step is also a side plate piece that matches the height of the second annular step of the intermediate tank side plate 32, constructed with the intermediate tank side plate piece 32P2, and the lowest annular step of the inner tank side plate 42 described above. The second, third, and other annular steps of the intermediate tank side plate 32, formed by the intermediate tank side plate pieces 32P2, 32P3, etc., are stacked on top of the lowest annular step. The second annular step (side plate piece 32P2) of the intermediate tank side plate 32 is at the same height as the lowest annular step (side plate piece 42P1) of the inner tank side plate 42 and is also at approximately the same height as the second annular step (side plate piece 22P2) of the outer tank side plate 22.

[0038] 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.

[0039] The first opening OP1, the second opening OP2, and the third opening OP3 are formed by removing one or more of the side plate pieces 22P, 32P, and 42P constituting the annular stages of each side plate 22, 32, and 42. In FIGS. 4 and 5, the first opening OP1 is formed by removing the outer tank side plate pieces 22P1 and 22P2 from the lowest and second annular stages of the annular stages constituting the outer tank side plate 22, respectively. The second opening OP2 is formed by removing the inner tank side plate piece 42P1 from the lowest annular stage of the annular stages constituting the inner tank side plate 42. The third opening OP3 is formed by removing the intermediate tank side plate piece 32P from the second annular stage above the lowest level-adjusting annular stage of the annular stages constituting the intermediate tank side plate 32.

[0040] As a result, the opening heights H1, H2, H3, opening widths W1, W2, W3 and opening areas AR1, AR2, AR3 of the first opening OP1, second opening OP2 and third opening OP3 have the following relationships. H1>H3=H2 (14) W1=W3=W2 (24) AR1 ≥ AR3 = AR2 (34) The opening width W1 may be slightly different from W2 and W3. Even in this case, the first opening OP1 is opened by removing the side plate pieces 22P1 and 22P2 that straddle the two annular steps of the outer tank side plate 22, so the relationship of the above formula (34) remains unchanged.

[0041] According to the third embodiment, the first opening OP1, the second opening OP2, and the third opening OP3 can be opened by the simple method of removing the side plate pieces 22P1, 22P2, 32P2, and 42P1. Furthermore, the sealing work of these openings OP1, OP2, and OP3 can be performed by the simple method of fitting the previously removed side plate pieces 22P1, 22P2, 32P2, and 42P1 into the respective openings and fixing them by welding or the like. The first opening OP1 is opened by removing the two lowest side plate pieces 22P1 and 22P2 of the outer tank side plate 22, the second opening OP2 by removing the lowest side plate piece 42P1 of the inner tank side plate 42, and the third opening OP3 by removing the second side plate piece 32P2 above the height-matching annular step. Therefore, a construction entrance can be opened in each side panel according to the step at the lowest position of the three side panels 22, 32, 42, making it easy to ensure a work route that extends horizontally and linearly in the radial direction.

[0042] 4 and 5 show an example in which the first opening OP1 is opened by removing two stages of side plate pieces from the outer tank side plate 22. However, it may be opened by removing three or more stages of side plate pieces. On the other hand, the second opening OP2 and the third opening OP3 can be opened by removing one stage fewer side plate pieces than the number of stages of the outer tank side plate 22 to be removed. That is, the first opening OP1 is opened by removing N adjacent side plate pieces 22P from the annular stages that constitute the outer tank side plate 22. On the other hand, the second opening OP2 and the third opening OP3 are opened by removing (N-1) stages of side plate pieces 42P, 32P from the annular stages that constitute the inner tank side plate 42 and the intermediate tank side plate 32, respectively. This allows the first opening OP1, whose opening area is larger than those of the second opening OP2 and the third opening OP3, to be easily opened by adjusting the number of stages of side plate pieces to be removed.

[0043] Fig. 6 is a cross-sectional view showing a modified example of the third embodiment. The difference from the example shown in Fig. 4(A) is that the intermediate tank anchor straps 81 and the inner tank anchor straps 82 extending from the tank foundation 10 are connected to the intermediate tank side plate 32 and the inner tank side plate 42, respectively. This improves the strength and earthquake resistance of the intermediate tank side plate 32 and the inner tank side plate 42. The lower end 811 of the intermediate tank anchor strap 81 is fixed to a first anchor box 83 embedded in the tank foundation 10. Meanwhile, the upper end 812 of the intermediate tank anchor strap 81 is connected to the intermediate tank side plate piece 32P1 that forms the lowest annular stage of the intermediate tank side plate 32.

[0044] Because the intermediate tank anchor strap 81 is connected, it may be difficult to remove the lowest intermediate tank side plate piece 32P1 to open the third opening OP3. However, because the third opening OP3 is opened by removing the second intermediate tank side plate piece 32P2, it is not necessary to remove the lowest intermediate tank side plate piece 32P1.

[0045] The lower end 821 of the inner tank anchor strap 82 is fixed to a second anchor box 84 embedded in the tank foundation 10. On the other hand, the upper end 822 of the inner tank anchor strap 82 is connected to the inner tank side plate piece 42P1 that forms the lowest annular stage of the inner tank side plate 42. The inner tank side plate piece 42P1 to which the inner tank anchor strap 82 is connected is a piece other than the inner tank side plate piece 42P1 that is removed to open the second opening OP2.

[0046] [Construction method for triple-shell tanks] Next, a method for constructing the triple-shell tank 1 shown in Fig. 1 will be described. Fig. 7 is a process chart showing one embodiment of the method for constructing the triple-shell tank 1, including the steps of opening and sealing the first opening OP1, second opening OP2, and third opening OP3. Here, an example is shown in which the triple-shell tank 1 is constructed by stacking side panel pieces, linked to the third embodiment shown in Figs. 4 and 5.

[0047] Figure 7 shows the relationship between steps S1 through S14 performed during the construction phase of the triple-shell tank 1 and the construction timing of each part of the triple-shell tank 1. Specifically, for the bottom plates 21, 31, and 41, roofs 23, 33, and 43, and side plates 22, 32, and 42 of the outer tank 2, intermediate tank 3, and inner tank 4, the construction period during which the main construction work actually takes place is indicated by solid arrows, and the period after construction is indicated by dotted lines. For the side plates 22, 32, and 42, the opening timing of the first opening OP1, second opening OP2, and third opening OP3, which serve as construction entrances and exits, is indicated as "open," and the closing timing of these openings is indicated as "closed." Note that steps S1 through S14 are not necessarily divided into units that represent a section of the tank construction procedure; in some cases, the "steps" simply represent the progress of construction work.

[0048] In the construction method of this embodiment, a roof assembly consisting of the intermediate tank roof 33 and the inner tank roof 43 temporarily fixed to the outer tank roof 23 is formed on the ground (step S6), and the roof assembly is then raised by air lasing (step S8). Figures 8 to 21 are schematic diagrams showing the construction state of the triple-shell tank 1 in steps S1 to S14 shown in Figure 7. Figures 8 to 21 show cross sections of a portion corresponding to half of the triple-shell tank 1 from the radial center RC. Each of steps S1 to S14 will be explained below with reference to Figures 3 to 16.

[0049] <Process S1> FIG. 8 shows the construction status of step S1. In step S1, a portion of the outer tank 2 is installed on the tank foundation 10. Specifically, an outer tank annulus 211, which constitutes a portion of the outer tank bottom plate 21, and an outer tank side plate piece 22P1, which constitutes a portion of the outer tank side plate 22, are installed near the peripheral edge of the tank foundation 10. The outer tank annulus 211 constitutes an annular portion near the outer periphery of the disc-shaped outer tank bottom plate 21, and is the portion located below the first ring portion 25. The outer tank annulus 211 has a thickness greater than that of other portions of the outer tank bottom plate 21 to improve load-bearing capacity. FIG. 8 shows the outer tank side plate piece 22P1, which constitutes the lowest annular section of the outer tank side plate 22.

[0050] <Process S2> FIG. 9 shows the construction status of step S2. In step S2, the outer tank bottom plate 21 and the outer tank side plate 22 are constructed. For the outer tank bottom plate 21, the radially inner portion of the outer tank annulus 211 is laid. This inner portion is located directly below the outer bottom cold insulation layer 26. Although not shown in FIG. 9, the first level concrete layer 24 shown in FIG. 1 is poured on the outer tank bottom plate 21 after laying. First, a portion of the first level concrete layer 24 is poured on the outer tank annulus 211. Then, the inner tank roof 43 and the intermediate tank roof 33 are constructed to eliminate the risk of rainwater infiltration, and then the remaining portion of the first level concrete layer 24 is poured on the inner portion of the outer tank annulus 211.

[0051] For the outer tank side plate 22, the outer tank side plate piece 22P2 constituting the second annular step is installed on top of the outer tank side plate piece 22P1 constituting the lowest annular step. After the second annular step is constructed, the lower half of the first opening OP1 (first construction opening) is opened in the lowest annular step. As described above, the first opening OP1 is opened by removing the outer tank side plate piece 22P1. Specifically, after multiple outer tank side plate pieces 22P1 are arranged in a ring shape to form an annular step, only the outer tank side plate piece 22P1 corresponding to the position of the first opening OP1 is removed from the annular step without being welded to adjacent pieces.

[0052] A central roof frame 51 is installed near the radial center RC of the outer tank bottom plate 21. The central roof frame 51 is a frame that enables the dome-shaped inner tank roof 43 to be constructed on the ground side before air lasing.

[0053] <Process S3> 10 shows the construction status of step S3. In step S3, construction of the outer tank side plate 22 continues, and construction of the inner tank roof 43 begins. For the outer tank side plate 22, the outer tank side plate piece 22P3 constituting the third annular step is installed on top of the outer tank side plate piece 22P2 constituting the second annular step. As described above, after the third annular step is constructed, the outer tank side plate piece 22P2 of the second annular step is removed to open the upper half of the first opening OP1. The outer tank side plate piece 22P2 to be removed is the piece located directly above the outer tank side plate piece 22P1 in the lowest annular step that was removed to open the first opening OP1.

[0054] For the inner tank roof 43, an inner tank roof piece 43P, which constitutes the radial center of the inner tank roof 43, is installed on top of the central roof frame 51 installed in the previous step S2. Meanwhile, an outer periphery roof frame 52 is installed on the upper surface of the outer tank bottom plate 21 near the radial outer periphery. The outer periphery roof frame 52 is a frame that temporarily supports the outer periphery lower edges of the inner tank roof 43 and intermediate tank roof 33. An inner tank knuckle plate 44 is installed on the upper surface of the outer periphery roof frame 52. The inner tank knuckle plate 44 is a plate that connects the upper end of the inner tank side plate 42 and the outer periphery lower edge of the inner tank roof 43.

[0055] <Process S4> FIG. 11 shows the construction status of step S4. In step S4, construction of the inner tank roof 43 continues, and construction of the intermediate tank roof 33 begins. The inner tank roof 43 is finally formed in a dome shape by connecting the radially central inner tank roof piece 43P installed in step S3 and the inner tank knuckle plate 44 with an inner tank roof block pre-assembled on the ground. The inner tank roof block consists of a roof frame that serves as a support frame and multiple roof plates attached to this roof frame. The outer peripheral edge 43E of the inner tank roof 43 is fixed to the upper end of the inner tank knuckle plate 44. At this point, the inner tank roof 43 is supported by the outer peripheral roof frame 52 and is in a self-supporting state, so the central roof frame 51 is removed.

[0056] For the intermediate tank roof 33, an intermediate tank roof piece 33P that forms the radial center of the intermediate tank roof 33 is installed on the radial center of the inner tank roof 43 completed in step S3. An intermediate tank roof support 61 is used for this installation. The intermediate tank roof support 61 is interposed between the inner tank roof 43 and the intermediate tank roof 33, and temporarily fixes them at a predetermined distance. A rigid member such as an H-beam can be used as the intermediate tank roof support 61. The temporary fixation can be performed, for example, by welding the lower end of the H-beam to the inner tank roof 43 via a predetermined backing plate, and then placing and fixing the intermediate tank roof piece 33P on the upper end of the H-beam.

[0057] Construction of the outer tank side plate 22 also continues as appropriate. Figure 11 shows the state in which the outer tank side plate piece 22P4 constituting the fourth annular stage has been installed. In addition, an intermediate tank knuckle plate 37 is installed on the upper surface of the outer peripheral roof frame 52. The intermediate tank knuckle plate 37 is a plate that connects the upper end of the intermediate tank side plate 32 to the lower outer peripheral edge of the intermediate tank roof 33. Furthermore, blocks that constitute the first ring portion 25 are laid on the upper surface of the outer tank bottom plate 21 near the radial outer periphery.

[0058] <Process S5> FIG. 12 shows the construction status of step S5. In step S5, construction of the intermediate tank roof 33 continues, and construction of the outer tank roof 23 begins. Construction of the intermediate tank bottom plate 31 and the intermediate tank side plate 32 also begins. The dome-shaped intermediate tank roof 33 is finally formed by connecting the radially central intermediate tank roof piece 33P installed in step S4 and the intermediate tank knuckle plate 37 with an intermediate tank roof block pre-assembled on the ground. Like the inner tank roof block described above, the intermediate tank roof block consists of a roof frame and multiple roof plates. When installing this intermediate tank roof block, an intermediate tank roof support 61 is disposed in an appropriate position between the intermediate tank roof 33 and the inner tank roof 43, and the two are temporarily fixed together. The outer peripheral edge 33E of the intermediate tank roof 33 is fixed to the upper end of the intermediate tank knuckle plate 37.

[0059] For the outer tank roof 23, an outer tank roof piece 23P, which forms the radial center of the outer tank roof 23, is installed on the radial center of the intermediate tank roof 33 completed in step S4. For this installation, an outer tank roof center support 62 is used. The outer tank roof center support 62 is interposed between the intermediate tank roof 33 and the radially center outer tank roof piece 23P, and temporarily fixes the two at a predetermined distance. The outer tank roof center support 62 can be made of H-beams or a frame made of steel materials assembled into a truss structure. The temporary fixation can be performed by welding and fixing the lower end of the H-beam or the like to the intermediate tank roof 33 via a predetermined backing plate, and then placing and fixing the outer tank roof piece 23P on the upper end of the H-beam or the like.

[0060] On the first ring portion 25 installed in the previous step S4, an intermediate tank annulus 311, which constitutes part of the intermediate tank bottom plate 31, and an intermediate tank side plate piece 32P1, which constitutes the lowest annular step of the intermediate tank side plate 32, are installed. The intermediate tank annulus 311 is an annular portion near the outer periphery of the disk-shaped intermediate tank bottom plate 31, and has a thickness greater than that of other parts of the intermediate tank bottom plate 31. The intermediate tank side plate piece 32P1 is erected vertically upward from the radially outer peripheral edge of the intermediate tank annulus 311. As described above, the intermediate tank side plate piece 32P1 is also a side plate piece that aligns the height of the second annular step of the intermediate tank side plate 32 and the lowest annular step of the inner tank side plate 42.

[0061] <Process S6> Figure 13 shows the construction status of step S6. In step S6, construction of the outer tank roof 23 continues, and finally, a roof connection body 20 is formed in which the three roofs are integrated. In addition, the outer tank side panels 22 are installed to a predetermined height. The outer tank roof 23 is finally formed in a dome shape by connecting the outer tank roof blocks pre-assembled by ground work to the radially central outer tank roof piece 23P installed in step S5. During this extension, an outer tank roof peripheral support 63 made of H-beam or the like is arranged in an appropriate position between the intermediate tank roof 33 and the outer tank roof 23, and the two are temporarily fixed together.

[0062] Once the construction of the outer tank roof 23 is complete, the formation of the roof connecting body 20 is complete. That is, the roof connecting body 20 is formed by temporarily fixing the intermediate tank roof 33 onto the inner tank roof 43 with the intermediate tank roof support 61, and temporarily fixing the outer tank roof 23 onto the intermediate tank roof 33 with the outer tank roof central support 62 and the outer tank roof peripheral support 63. By forming the roof connecting body 20 in this manner, it becomes possible to air-lathe the three roofs together. The above-mentioned supports 61, 62, and 63 serve as support members for the upper roof until air-lazing is complete, but after air-lazing they become suspension members for the lower roof.

[0063] In addition, when the roof connector 20 is formed, the gaps between the inner tank roof 43 and the intermediate tank roof 33, and between the intermediate tank roof 33 and the outer tank roof 23 are set slightly narrower than the gaps between them in the completed triple-shell tank 1. This is to facilitate the work of fixing the inner tank roof 43 to the inner tank side plate 42 and the work of fixing the intermediate tank roof 33 to the intermediate tank side plate 32, which are performed after air lasing.

[0064] The construction of the outer tank side panels 22 is completed by stacking the required number of annular steps formed by the side panel pieces. This completes the construction of the outer tank side panels 22 to a specified height around the roof connector 20, making it ready for air lasing. An outer periphery walkway 27 is installed on the top 22T of the outer tank side panels 22. Furthermore, a portion of the second level concrete layer 34 (not shown here) is poured on top of the intermediate tank annulus 311, and then blocks that will form the second ring portion 35 are laid.

[0065] <Process S7> Figure 14 shows the construction status of step S7. In step S7, preparation work for air lasing is primarily performed. To form a sealed space, a sealing process is performed by attaching a sealant 28 to the outer peripheral edge 23E of the outer tank roof 23. The sealant 28 seals the gap between the outer peripheral edge 23E and the inner surface of the outer tank side plate 22. A blower 7 is prepared on the outside of the outer tank side plate 22 to supply air for air lasing. An air duct is connected to the air outlet of the blower 7, and this air duct is drawn into the inside of the outer tank side plate 22 through the first opening OP1. The first opening OP1 is also sealed to seal the periphery of the air duct. Since the outer tank bottom plate 21 is already completed before step S7, sealing of the bottom portion is not particularly necessary. Therefore, at this point, the space surrounded by the outer tank bottom plate 21, outer tank side plate 22, and outer tank roof 23 is sealed.

[0066] In parallel with the above air lasing preparation work, the inner tank annulus 411 is installed on the upper surface of the second ring portion 35. The inner tank annulus 411 is an annular portion near the outer periphery of the inner tank bottom plate 41, which has a disk shape.

[0067] <Process S8> Figure 15 shows the state after air lasing in step S8. When air lasing is performed, the blower 7 shown in Figure 14 is operated to supply air into the sealed space surrounded by the outer tank bottom plate 21, outer tank side plates 22, and outer tank roof 23. The air supply increases the air pressure in the sealed space, and this pressure causes the roof connector 20 to float. At this time, the outer tank side plates 22 act as a guide for the roof connector 20 as it floats.

[0068] It is the outer tank roof 23 that is directly lifted by air lasing. However, the inner tank roof 43 and intermediate tank roof 33 are previously integrated with the outer tank roof 23 using temporary supports 61, 62, and 63. Therefore, the inner tank roof 43 and intermediate tank roof 33 are also lifted integrally while suspended from the outer tank roof 23. In other words, because the roof connecting body 20 is formed in advance, the three roofs 23, 33, and 43 that form the triple-shell structure can be lifted all at once with a single air lasing. During air lasing, the lifting position of the roof connecting body 20 is controlled using a balance wire.

[0069] After air lasing, the outer peripheral edge 23E of the outer tank roof 23 is fixed to the upper end of the outer tank side plate 22. At this point, the temporary fastening of the roof connecting body 20 is not released, and the inner tank roof 43 and intermediate tank roof 33 remain suspended from the outer tank roof 23. The air lasing equipment is removed. That is, the sealing material 28 attached near the outer peripheral edge 23E of the outer tank roof 23 is removed, and the blower 7 and air duct are removed.

[0070] <Process S9> Fig. 16 shows the construction status of step S9. In step S9, construction of the inner tank side plate 42 begins. An inner tank side plate piece 42P1, which constitutes the lowest annular stage of the inner tank side plate 42, is installed on top of the inner tank annulus 411. The inner tank side plate piece 42P1 stands vertically upward from the radially outer peripheral edge of the inner tank annulus 411. Fig. 16 shows a state in which an inner tank side plate piece 42P2, which constitutes the second annular stage, is installed on top of the lowest inner tank side plate piece 42P1.

[0071] When constructing the inner tank side plate 42, a second opening OP2 (second construction opening) is provided as a construction opening. The second opening OP2 is opened by removing one or more of the inner tank side plate pieces 42P1 that constitute the lowest annular stage. As explained with reference to Figures 4 and 5, the opening position of the second opening OP2 is a position that overlaps with the first opening OP1 opened in the outer tank side plate 22 in the circumferential direction and the height direction.

[0072] <Process S10> 17 shows the construction status of step S10. In step S10, the inner tank side plate 42 and the intermediate tank side plate 32 are constructed. For the inner tank side plate 42, an inner tank side plate piece 42P3 constituting the third annular step is installed on top of an inner tank side plate piece 42P2 constituting the second annular step. An inner tank side plate piece 42P4 constituting the fourth step is installed on top of that, and so on, gradually increasing the height of the side plates.

[0073] Similarly, for the intermediate tank side plate 32, the intermediate tank side plate pieces 32P2, 32P3, and 32P4 constituting the second, third, and fourth annular stages are sequentially stacked on top of the already installed lowest intermediate tank side plate piece 32P1. In this embodiment, the inner tank side plate piece 42Pn and the intermediate tank side plate piece 32Pn (excluding the side plate piece 32P1 for height adjustment) have the same height. Therefore, the inner tank side plate pieces 42P1, 42P2, and 43P3 and the intermediate tank side plate pieces 32P2, 32P3, and 32P4 shown in FIG. 17 are at the same height.

[0074] In step S10, the annular sections of either the inner tank side plate 42 or the intermediate tank side plate 32 may be stacked first, followed by the other annular section. However, it is preferable to stack the annular sections of the inner tank side plate 42 and the intermediate tank side plate 32 simultaneously. For example, the second inner tank side plate piece 42P2 of the inner tank side plate 42 is stacked, followed by the third intermediate tank side plate piece 32P3 of the intermediate tank side plate 32, and then the third inner tank side plate piece 42P3 of the inner tank side plate 42. By adopting such a construction method, it is possible to share scaffolding when constructing the inner tank side plate 42 and the intermediate tank side plate 32, thereby improving work efficiency. Furthermore, for the convenience of crane lifting and assembly of the side plate pieces, it is preferable to stack the inner tank side plate piece 42Pn located radially inward before stacking the intermediate tank side plate piece 32Pn.

[0075] When constructing the intermediate tank side plate 32, a third opening OP3 (third construction opening) is also provided as a construction opening. The third opening OP3 is opened by removing one or more of the intermediate tank side plate pieces 32P2 that form the second annular stage. As indicated by the "open" in the chart in FIG. 7, at the time of step S10, the second opening OP2 is opened in the inner tank side plate 42 and the third opening OP3 is opened in the intermediate tank side plate 32. This ensures a horizontal and linear work flow line that passes through the three side plates 22, 32, and 42 via the first opening OP1, the second opening OP2, and the third opening OP3, as shown by the arrows in FIG. 17.

[0076] In step S10, a first level concrete layer 24 (not shown in Fig. 17) and an outer bottom cold insulation layer 26 are laid in this order on the outer tank bottom plate 21. Since the portion of the first level concrete layer 24 above the outer tank annulus 211 has already been laid in step S2, the remaining portion is now laid. As mentioned above, the outer bottom cold insulation layer 26 is constructed by laying insulating blocks such as foam glass inside the first ring portion 25.

[0077] <Process S11> Figure 18 shows the construction status of step S11. In step S11, the construction of the inner tank side plates 42 and the intermediate tank side plates 32 continues, the inner tank side plates 42 are fixed to the inner tank roof 43, and the intermediate tank bottom plate 31 is laid. The inner tank side plates 42 and the intermediate tank side plates 32 are installed from the middle to the upper tier of each annular tier. Figure 18 shows the inner tank side plate 42 in a state where the inner tank side plate piece 42PT constituting the uppermost annular tier has been assembled, one tier ahead of the intermediate tank side plate 32.

[0078] After the installation of the uppermost inner tank side plate piece 42PT, work is carried out to fix the outer peripheral edge of the inner tank roof 43 to the upper end of the inner tank side plate 42. Prior to this fixing work, a re-hanging work is carried out in which the intermediate tank roof support 61 connecting the intermediate tank roof 33 and the inner tank roof 43 is replaced with a first jack 64. After air lasing, if the outer tank roof 23 is fixed to the outer tank side plate 22 without the temporary fixation of the roof connector 20 being released, the inner tank roof 43 is suspended from the intermediate tank roof 33 by the intermediate tank roof support 61 at a position higher than the normal height position. This is to ensure adjustment space when connecting the inner tank roof 43 to the inner tank side plate 42.

[0079] The first jack 64 is placed at an appropriate position between the intermediate tank roof 33 and the inner tank roof 43, and after the rehanging, it suspends and supports the inner tank roof 43 so that it can be raised and lowered. While jacking down the inner tank roof 43 with the first jack 64 by the amount of the adjustment space, the lower end of the inner tank knuckle plate 44 and the upper end of the uppermost inner tank side plate piece 42PT are aligned. After alignment, the two are fixed together, and the inner tank 4 is approximately completed.

[0080] Furthermore, in step S11, the remaining part of the intermediate tank bottom plate 31 is laid on the outer bottom cold insulation layer 26. Since the intermediate tank annulus 311 constituting the outer peripheral part has already been installed, only the inner part of the intermediate tank bottom plate 31 is laid.

[0081] <Process S12> 19 shows the construction status of step S12. In step S12, the intermediate tank side plate 32 and the intermediate tank roof 33 are fixed together, and the inner bottom cold insulation layer 36 is laid. As with the inner tank roof 43, the jacking method is also used to fix the intermediate tank roof 33. After the inner tank roof 43 is fixed to the inner tank side plate 42, the intermediate tank side plate piece 32PT, which forms the uppermost annular stage of the intermediate tank side plate 32, is installed. Meanwhile, a re-hanging operation is performed in which the outer tank roof center support 62 and the outer tank roof peripheral support 63, which connect the outer tank roof 23 and the intermediate tank roof 33, are replaced with second jacks 65. The intermediate tank roof 33 is also suspended from the outer tank roof 23 at a position higher than its normal height by the amount of the adjustment space.

[0082] The second jack 65 is placed at an appropriate position between the outer tank roof 23 and the intermediate tank roof 33, and after the re-hanging, it suspends and supports the intermediate tank roof 33 so that it can be raised and lowered. While jacking down the intermediate tank roof 33 with the second jack 65 by the amount of the adjustment space, the lower end of the intermediate tank knuckle plate 37 is aligned with the upper end of the uppermost intermediate tank roof piece 33PT. After alignment, the two are fixed together, and the intermediate tank 3 is approximately completed.

[0083] In step S12, an inner bottom cold insulation layer 36 is laid on the intermediate tank bottom plate 31 (second level concrete layer 34). The inner bottom cold insulation layer 36 is constructed by laying insulating blocks such as foam glass inside the second ring portion 35.

[0084] <Process S13> 20 shows the construction status of step S13. In step S13, the inner tank bottom plate 41 is laid, the second opening OP2 is sealed, and the deck is installed. The inner tank bottom plate 41 is laid on the inner bottom cold insulation layer 36. Since the inner tank annulus 411 that constitutes the outer periphery has already been installed, the inner tank bottom plate 41 for the inner part is laid.

[0085] After the work inside the inner tank 4 is completed and the scaffolding installed inside the inner tank 4 is removed, the second opening OP2 of the inner tank side plate 42 is sealed. This sealing work involves fitting the inner tank side plate piece 42P1 extracted from the lowest annular stage in step S9 into the second opening OP2 and welding the inner tank side plate piece 42P1 to the surrounding side plate pieces. Figure 20 shows the second opening OP2 in a sealed state.

[0086] A shoulder deck 231 and a top deck 232 are installed on the outer tank roof 23. The shoulder deck 231 is disposed on the radial outer periphery of the outer tank roof 23. The top deck 232 is disposed in the radial center of the outer tank roof 23. In addition, work such as filling the first tank space 11 and the second tank space 12 with insulating material and installing various pipes and accessories is also performed.

[0087] <Process S14> 21 shows the construction status of step S14. In step S14, the third opening OP3 and the first opening OP1 are sealed. The third opening OP3 of the intermediate tank side plate 32 is sealed after the work inside the intermediate tank 3 is completed and scaffolding and the like installed inside the intermediate tank 3 are removed. In this sealing work, the intermediate tank side plate piece 32P2 removed in step S10 is fitted into the third opening OP3, and the intermediate tank side plate piece 32P2 is welded to the surrounding side plate pieces.

[0088] Next, after the work inside the outer tank 2 is completed and the scaffolding installed inside the outer tank 2 is removed, the first opening OP1 of the outer tank side plate 22 is sealed. In this sealing work, the outer tank side plate pieces 22P1 and 22P2 removed in steps S2 and S3 are fitted to close the first opening OP1 and welded together. As described above, the construction openings are sealed sequentially as work inside each side plate is completed, starting with the inner second opening OP2, the middle third opening OP3, and the outer first opening OP1.

[0089] [Modified embodiment] Although the embodiment of the triple-shell tank construction method according to the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment. For example, the above-described triple-shell tank construction method can be modified as follows.

[0090] (1) Necessary buildings and facilities may be installed near the triple-shell tank 1 described above. For example, a liquid barrier may be erected around the triple-shell tank 1 to prevent the liquid inside the tank from spreading if it leaks during a disaster or other event. The liquid barrier may be constructed, for example, from prestressed concrete (PC). The liquid barrier may be constructed integrally with the metal outer tank 2. Specifically, the PC constituting the liquid barrier may be constructed in close contact with the outer peripheral surface of the outer tank side plate 22. In this case, the strength of the outer tank side plate 22, which serves as a guide when the roof connecting body 20 is aerated, can be increased.

[0091] (2) A communication pipe may be attached to the inner tank roof 43 to connect the interior space of the inner tank 4 with the space between the first tanks 11. According to this modification, hydrogen gas vaporized from the liquid hydrogen LH stored in the inner tank 4 can be circulated into the first tanks 11. In other words, the stored liquid hydrogen LH can be used to enhance the cooling effect.

[0092] (3) In the above embodiment, an example was given in which the roof assembly 20 connecting the three roofs, i.e., the inner tank roof 43, the intermediate tank roof 33, and the outer tank roof 23, was air-lazed using the outer tank side plate 22 as a guide (outer tank air-lazing). Alternatively, the roof assembly connecting the two roofs, i.e., the inner tank roof 43 and the intermediate tank roof 33, may be air-lazed using the intermediate tank side plate 32 as a guide (intermediate tank air-lazing), or may be air-lazed using the inner tank side plate 42 as a guide (inner tank air-lazing).

[0093] Summary of this disclosure The specific embodiments described above include disclosures having the following configurations.

[0094] The construction method for a triple-shell tank according to the present disclosure is a construction method for a triple-shell tank having an inner tank, an intermediate tank, and an outer tank, each having a roof and side panels, and includes the steps of opening a first construction port in the side panel of the outer tank when the outer tank side panel is constructed, a second construction port in the side panel of the inner tank when the inner tank side panel is constructed, and a third construction port in the side panel of the intermediate tank when the intermediate tank side panel is constructed, as construction entrances and exits, sealing the second construction port after work inside the inner tank is completed, then sealing the third construction port after work inside the intermediate tank is completed, and then sealing the first construction port after work inside the outer tank is completed, wherein the first construction port, the second construction port, and the third construction port are opened at positions where they at least partially overlap each other in the circumferential and vertical directions of the triple-shell tank, and when the opening area of ​​the first construction port is AR1 and the opening area of ​​the second construction port is AR2, AR1≧AR2 The first construction entrance and the second construction entrance are opened so as to satisfy the relationship.

[0095] According to this construction method, the first, second, and third access points are opened at positions where they at least partially overlap each other in the circumferential and vertical directions of the triple-shell tank. This ensures linearity of work traffic flowing radially inward or outward through the three side walls of the triple-shell tank, facilitating the entry and exit of workers and the delivery of materials. Furthermore, the first and second access points are opened so as to satisfy the relationship AR1 ≥ AR2. A triple-shell tank has a shell structure in which an intermediate tank is provided to entirely cover an inner tank, and an outer tank is provided to entirely cover the intermediate tank. Therefore, the lowest positions of the side plates are the lowest for the outer tank side plate and the highest for the inner tank side plate, which can result in a height difference between the lower edge of the first access point and the lower edge of the second access point. This difference in height at the access points can hinder work. However, by satisfying the relationship AR1 ≥ AR2, preferably AR1 > AR2, an access point can be formed that mitigates the impact of the difference in height.

[0096] In the above-mentioned triple-shell tank construction method, when the opening area of ​​the third construction port is AR3, AR1≧AR3≧AR2 It is desirable to open the first construction entrance, the second construction entrance and the third construction entrance so as to satisfy the relationship.

[0097] In terms of the relationship between the outer tank and the intermediate tank, the lowest position of the intermediate tank side plate is higher than the lowest position of the outer tank side plate, so a difference in height may occur between the lower edge of the first construction opening and the lower edge of the third construction opening. Therefore, by satisfying the relationship AR1 ≥ AR3 ≥ AR2, preferably AR1 > AR3 ≥ AR2 or AR1 > AR3 > AR2, the first construction opening, the second construction opening, and the third construction opening can be opened with the effect of the difference in height reduced.

[0098] In the above-mentioned triple-shell tank construction method, when the opening heights of the first construction opening and the second construction opening are H1 and H2, respectively, H1≧H2 It is desirable to open the first construction entrance and the second construction entrance so as to satisfy the relationship.

[0099] According to this construction method, the vertical opening width of the first access point is set equal to or wider than the vertical opening width of the second access point, so even if there is a height difference between the lowest position of the outer tank side plate and the lowest position of the inner tank side plate, it is easy to eliminate the difference and form an access point that ensures a work line that extends horizontally and linearly in the radial direction.

[0100] In the above-mentioned triple-shell tank construction method, when the opening height of the third construction opening is H3, more preferably, H1≧H3≧H2 The first construction entrance, the second construction entrance and the third construction entrance are opened so as to satisfy the relationship.

[0101] With this construction method, even if there is a height difference at the lowest position of the three side panels, it is easy to eliminate the difference and create a construction entrance that ensures a work route that extends horizontally and linearly in the radial direction of the three side panels.

[0102] In the above-mentioned triple-shell tank construction method, it is desirable that the outer tank side plate, the inner tank side plate, and the intermediate tank side plate are assembled by stacking multiple annular stages formed by arranging multiple side plate pieces in a ring shape, and that the first construction opening, the second construction opening, and the third construction opening are opened by removing one or more of the multiple side plate pieces that make up the annular stage.

[0103] According to this construction method, the first, second, and third construction entrances can be opened by simply removing the side panel pieces. The sealing of these entrances can also be achieved by simply fitting the previously removed side panel pieces into the respective entrances and securing them by welding or the like.

[0104] In the above-mentioned triple-shell tank construction method, it is desirable that the side plate pieces have rectangular shapes of the same or similar size, the first construction opening be opened by removing a plurality of adjacent side plate pieces corresponding to N stages among the annular stages that constitute the outer tank side plate, and the second construction opening and the third construction opening be opened by removing a plurality of side plate pieces corresponding to (N-1) stages among the annular stages that constitute the inner tank side plate and the intermediate tank side plate, respectively.

[0105] According to this construction method, the first access hole is opened by removing N levels of side plate pieces from the outer tank side plate. In contrast, the second and third access holes, which are opened in the inner tank side plate and the intermediate tank side plate, are opened by removing (N-1) levels of side plate pieces, which is one level less than the outer tank side plate. Therefore, the first access hole, which has an opening area larger than the second and third access holes, can be easily opened by removing the same number of levels of side plate pieces.

[0106] In the above-mentioned triple-shell tank construction method, it is desirable that the side plate pieces have rectangular shapes of the same or similar size, the first construction opening be opened by removing the side plate pieces of the lowest and second annular steps among the annular steps constituting the outer tank side plate, the second construction opening be opened by removing the side plate piece of the lowest annular step among the annular steps constituting the inner tank side plate, and the third construction opening be opened by removing the side plate piece of the second annular step above the lowest level-matching annular step among the annular steps constituting the intermediate tank side plate.

[0107] According to this construction method, the first access point is opened by removing the two lowest side panel pieces of the outer tank side panel. The second access point is opened by removing the lowest side panel piece of the inner tank side panel, and the third access point is opened by removing the second side panel piece above the height adjustment annular step. Therefore, access points can be opened in each side panel according to the difference in the lowest steps of the three side panels, making it easy to ensure a work line that extends horizontally and linearly in the radial direction.

[0108] In the above triple-hull tank construction method, it is desirable that the upper ends of anchor straps extending from the tank foundation are connected to the height-adjusting annular steps of the intermediate tank side plates, thereby connecting the tank foundation to the lowest annular step of the intermediate tank side plates with the anchor straps, thereby improving the strength of the intermediate tank side plates. [Explanation of symbols]

[0109] 1. Triple-shell tank 2 Outer tank 20 Roof connector 21 Outer tank bottom plate 22 Outer tank side plate 22P Outer tank side plate piece (side plate piece) 23 Outer tank roof 3 Intermediate tank 31 Intermediate tank bottom plate 32 Intermediate tank side plate 32P Intermediate tank side panel piece (side panel piece) 33 Intermediate tank roof 4 Inner tank 41 Inner tank bottom plate 42 Inner tank side plate 42P Inner tank side plate piece (side plate piece) 43 Inner tank roof 81 Intermediate tank anchor strap OP1 First opening (first construction entrance) OP2 Second opening (second construction entrance) OP3 Third opening (third construction entrance)

Claims

1. A construction method for a triple-shell tank having an inner tank, an intermediate tank, and an outer tank, each of which has a roof and side panels, comprising: As entrances and exits for construction work, a first construction entrance is opened in the outer tank side plate when the outer tank side plate is constructed, a second construction entrance is opened in the inner tank side plate when the inner tank side plate is constructed, and a third construction entrance is opened in the intermediate tank side plate when the intermediate tank side plate is constructed. The method includes a step of sealing the second access port after completing the work inside the inner tank, then sealing the third access port after completing the work inside the intermediate tank, and then sealing the first access port after completing the work inside the outer tank, The first construction port, the second construction port, and the third construction port are opened at positions where they at least partially overlap each other in the circumferential direction and the height direction of the triple-shell tank, When the opening area of ​​the first construction entrance is AR1 and the opening area of ​​the second construction entrance is AR2, AR1 ≧ AR2 A construction method for a triple-shell tank, in which the first construction opening and the second construction opening are opened so as to satisfy the relationship:

2. The method for constructing a triple-hull tank according to claim 1, When the opening area of ​​the third construction entrance is AR3, AR1 ≧ AR3 ≧ AR2 A construction method for a triple-shell tank, in which the first construction opening, the second construction opening, and the third construction opening are opened so as to satisfy the relationship.

3. The method for constructing a triple-hull tank according to claim 1 or 2, When the opening heights of the first construction entrance and the second construction entrance are H1 and H2, respectively, H1≧H2 A construction method for a triple-shell tank, in which the first construction opening and the second construction opening are opened so as to satisfy the relationship:

4. The method for constructing a triple-hull tank according to claim 3, When the opening height of the third construction entrance is H3, H1 ≧ H3 ≧ H2 A construction method for a triple-shell tank, in which the first construction opening, the second construction opening, and the third construction opening are opened so as to satisfy the relationship.

5. The construction method for a triple-hull tank according to any one of claims 1 to 4, the outer tank side plate, the inner tank side plate, and the intermediate tank side plate are assembled by stacking a plurality of annular stages formed by arranging a plurality of side plate pieces in an annular shape, A construction method for a triple-shell tank, wherein the first construction opening, the second construction opening, and the third construction opening are opened by removing one or more of the side panel pieces that make up the annular stage.

6. The method for constructing a triple-hull tank according to claim 5, The side panel pieces have rectangular shapes of the same or similar size, The first access hole is opened by removing a plurality of adjacent side plate pieces corresponding to N stages among the annular stages constituting the outer tank side plate, a construction method for a triple-shell tank, wherein the second access port and the third access port are opened by removing (N-1) of the side panel pieces from the annular stages that respectively constitute the inner tank side panel and the intermediate tank side panel.

7. The method for constructing a triple-hull tank according to claim 5, The side panel pieces have rectangular shapes of the same or similar size, The first access hole is opened by removing the side plate pieces of the lowermost annular step and the second annular step among the annular steps constituting the outer tank side plate, The second access port is opened by removing the side plate piece of the lowest annular stage among the annular stages constituting the inner tank side plate, a construction method for a triple-shell tank, wherein the third construction opening is opened by removing the side panel piece of the second annular step above the lowest annular step for adjusting height, among the annular steps constituting the intermediate tank side panel;

8. The method for constructing a triple-hull tank according to claim 7, A construction method for a triple-shell tank, wherein the upper ends of anchor straps extending from the tank foundation are connected to the height-adjusting annular steps of the intermediate tank side panels.

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