Liquefied gas storage tank and ship comprising same

Abstract

The present invention relates to a liquefied gas storage tank for storing an extremely low temperature substance, and a ship comprising the same, the liquefied gas storage tank comprising: a primary protective wall which forms an accommodation space for accommodating the extremely low temperature substance and is made of a metal material; a primary heat-insulating wall formed by sequentially arranging a primary plywood and a primary heat-insulating material on the outer side of the primary protective wall; the secondary protection wall is arranged on the outer side of the primary heat insulation wall; and a secondary insulating wall formed by laminating a secondary insulating material and a secondary plywood in this order on the outer side of the secondary protective wall, the secondary protective wall comprising main protective walls provided on the upper portions of the secondary insulating walls constituting the unit elements, and auxiliary protective walls connecting the adjacent main protective walls to each other, the secondary protective wall is made of a mixed material of metal and nonmetal, and the thickness of the primary heat insulation wall is 66%-166% of that of the secondary heat insulation wall, so that the low-temperature burden is reduced.

Description

[0001] This invention is a divisional application of the following patent application: Application number: 202180039027.X, filing date: July 1, 2021, invention title: Liquefied gas storage tank and ship including the same Technical Field

[0002] The present invention relates to a liquefied gas storage tank and a ship comprising the same. Background Art

[0003] In recent years, as technology has developed, liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG) have been widely used instead of gasoline and diesel.

[0004] In addition, storage tanks (called "cargo tanks") for storing LNG in an extremely low-temperature liquid state are installed in ships such as LNG carriers, LNG RVs (Regasification Vessels), LNG FPSOs (Floating, Production, Storage and Offloading), and LNG FSRUs (Floating Storage and Regasification Units) that transport or store liquefied gases such as LNG at sea.

[0005] Furthermore, liquefied gas storage tanks can generate boil-off gas (BOG) due to external heat intrusion. Reducing the natural vaporization rate (BOR), which is the rate at which boil-off gas evaporates, through thermal insulation is a core technology in liquefied gas storage tank design. Furthermore, since liquefied gas storage tanks are exposed to various loads such as sloshing, ensuring the mechanical strength of the insulation panels is essential.

[0006] Taking this into consideration, the thickness range of the primary and secondary insulation walls can be related to the mechanical strength of the liquefied gas storage tank. Therefore, research is actively being conducted to eliminate the low-temperature burden of the secondary protective wall while also maintaining the mechanical strength of the secondary insulation wall.

[0007] At the same time, since the primary protective wall is directly exposed to extremely low-temperature materials, in order to minimize the burden of thermal stress caused by extremely low temperatures and pressure stress caused by shaking, research is being actively carried out to optimize the cross-sectional shape of the curved surface. Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The present invention is proposed to solve the problems of the prior art as described above. The purpose of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can minimize the burden of thermal stress caused by low temperature and pressure stress caused by sloshing by optimizing the cross-sectional shape of the curved portion of the primary protective wall.

[0010] In addition, an object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can maintain the mechanical strength of the secondary insulation wall at a predetermined level and reduce the low-temperature burden and sway burden of the secondary protective wall by making the thickness of the primary insulation wall the same as or similar to that of the secondary insulation wall in the total thickness of the insulation wall.

[0011] In addition, the object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can reduce the low temperature burden and sway burden of the secondary protective wall within a range where brittle failure of the hull does not occur by making the thickness of the primary insulation wall the same or similar to that of the secondary insulation wall in the total thickness of the insulation wall.

[0012] Another object of the present invention is to provide a liquefied gas storage tank and a ship including the same, in which the thermal insulation performance can be enhanced by improving the structure of the secondary protective wall.

[0013] Another object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can improve the insulation performance and reduce the number of steps by improving the structure of the fixing member for fixing the secondary thermal insulation wall to the ship hull.

[0014] Technical solutions to the problem

[0015] A liquefied gas storage tank according to one embodiment of the present invention is a liquefied gas storage tank for storing extremely low-temperature substances, and is characterized in that it includes: a primary protective wall, which forms a storage space for storing extremely low-temperature substances and is made of a metal material; a primary thermal insulation wall, on the outside of which a primary plywood and a primary thermal insulation material are sequentially arranged; a secondary protective wall, which is arranged on the outside of the primary thermal insulation wall; and a secondary thermal insulation wall, on the outside of which a secondary thermal insulation material and a secondary plywood are stacked in sequence, the secondary protective wall being composed of a main protective wall arranged on the upper part of each of the secondary thermal insulation walls constituting a unit element and an auxiliary protective wall connecting adjacent main protective walls to each other, the secondary protective wall being made of a mixed material of metal and non-metal, and the primary thermal insulation wall having a thickness of 66% to 166% of the secondary thermal insulation wall to reduce thermal stress.

[0016] Specifically, the primary insulation wall may include a connecting insulation wall, which is arranged in a space portion between adjacent fixed insulation walls when the unit elements composed of the secondary insulation wall, the secondary protective wall, and the fixed insulation wall which is part of the primary insulation wall are stacked adjacent to each other.

[0017] Specifically, the connecting insulation wall may have a thickness of 67% to 167% of the secondary insulation wall.

[0018] Specifically, in the liquefied gas storage tank, based on the thickness direction, the secondary protective wall may be disposed in a central region corresponding to a range of 40% to 60% of the total thickness.

[0019] Specifically, the primary thermal insulation material may have a thickness of 90% to 110% of the secondary thermal insulation material.

[0020] Specifically, the primary protective wall is composed of a planar portion in contact with the top surface of the primary insulation wall, a curved portion having a first curvature radius, and a boundary portion formed between the planar portion and the curved portion in a wrinkle shape having a second curvature radius, and the first curvature radius and the second curvature radius may be different.

[0021] Specifically, the horizontal and vertical pleats of the pleat shape may have the same size.

[0022] Specifically, the secondary protective wall is formed of a material having a laminated structure of first member / aluminum foil / second member, and at least one of the first member and the second member may be glass fabric, glass-aramid fabric, basalt fabric or glass fabric / aluminum foil / glass fabric.

[0023] Specifically, the primary heat insulating material may be formed of reinforced polyurethane foam using CO 2 as a foaming agent, and the secondary heat insulating material may be formed of reinforced polyurethane foam using HFC-245fa as a foaming agent.

[0024] Specifically, it further includes a right-angle corner structure, and the curvature radius of the secondary protective wall formed at the right-angle corner structure can be 25% to 50% of the thickness of the primary heat insulation wall.

[0025] Specifically, an obtuse corner structure is further included, and the curvature radius of the secondary protective wall formed at the obtuse corner structure may be 15% to 35% of the thickness of the primary heat insulation wall.

[0026] A liquefied gas storage tank according to another embodiment of the present invention is a liquefied gas storage tank for storing extremely low-temperature substances, and is characterized in that it includes: a primary protective wall, which forms a storage space for accommodating extremely low-temperature substances and is made of metal material; a primary thermal insulation wall, on the outside of which a primary plywood and a primary thermal insulation material are sequentially arranged; a secondary protective wall, which is arranged on the outside of the primary thermal insulation wall; and a secondary thermal insulation wall, on the outside of which a secondary thermal insulation material and a secondary plywood are sequentially arranged, the secondary protective wall being composed of a main protective wall arranged on the upper part of each of the secondary thermal insulation walls constituting a unit element and an auxiliary protective wall connecting adjacent main protective walls to each other, the auxiliary protective wall having an unbonded portion, and the upper limit value of the low-temperature stress of the auxiliary protective wall caused by the extremely low-temperature substance is less than 50 MPa.

[0027] According to another embodiment of the present invention, a liquefied gas storage tank is composed of a primary protective wall, a primary insulation wall, a secondary protective wall and a secondary insulation wall. The primary protective wall forms a storage space for accommodating extremely low temperature substances and is made of a metal material. The primary insulation wall is arranged on the outside of the primary protective wall. The secondary insulation wall is arranged on the outside of the primary insulation wall and is composed of a main protective wall and an auxiliary protective wall. The secondary insulation wall is arranged on the outside of the secondary protective wall. It is characterized in that the primary protective wall is composed of a plurality of planar portions fixed on the top surface of the primary insulation wall, and a curved surface is formed between the plurality of planar portions toward the storage space side and includes a transverse curved surface. The face portion is composed of a curved surface portion of a face portion and a longitudinal curved surface portion, and the curved surface portion includes: a pair of first curved surface portions, respectively connected to the adjacent planar portions, and having a first curvature radius r1; a second curved surface portion, forming the upper part of the curved surface portion, and having at least a second curvature radius r2 greater than the first curvature radius r1; and a pair of third curved surface portions, respectively connecting a pair of the first curved surface portions and the second curved surface portion, and having at least a third curvature radius r3 greater than the second curvature radius r2, and the first curvature center of any one of the third curved surface portions in the pair of the third curved surface portions and the second curvature center of the other third curved surface portion are located at positions staggered in the horizontal direction on the inner side of the curved surface portion.

[0028] Specifically, the transverse curved surface portion and the longitudinal curved surface portion may be formed to intersect each other, and the transverse curved surface portion and the longitudinal curved surface portion may have the same height and width.

[0029] Specifically, the third radius of curvature may be larger than a sum of the second radius of curvature and the first radius of curvature.

[0030] Specifically, a ratio W / H of a width W to a height H of the curved portion may be within a range of 2.0 to 3.0 (2.0≤W / H≤3.0), and may be determined based on thermal stress and compressive stress of the primary protective wall at low temperatures.

[0031] Specifically, a pair of the first curved surface portions are curved surface shapes having the first curvature radius between a first connection point connected to the planar portion and a second connection point connected to a pair of the third curved surface portions respectively, the position of the first connection point is the same as the position of the point where the curve of the first circle having the first curvature radius from the center of curvature of the accommodating space side intersects the longitudinal center line of the first circle, and the second connection point can be located on the curved portion of the first circle within an angle of 30 degrees downward from the point where the curve of the first circle intersects the transverse center line of the first circle.

[0032] Specifically, the primary protective wall may further include a protruding structure, which is located within a predetermined distance from an intersection of the transverse curved surface portion and the longitudinal curved surface portion and is formed on the planar portion to protrude toward the accommodating space.

[0033] Specifically, the size of the protruding structure may be smaller than the transverse curved surface portion and the longitudinal curved surface portion, and may be formed in a convex circular shape or an arc shape.

[0034] Specifically, the first and second centers of curvature of the pair of third curved surface portions may be located above a virtual plane formed by the planar portion.

[0035] A ship according to still another aspect of the present invention is characterized by including the above-described liquefied gas storage tank.

[0036] Effects of the Invention

[0037] The liquefied gas storage tank and the ship including the same according to the present invention can minimize the burden of thermal stress caused by low temperature and pressure stress caused by sloshing by optimizing the cross-sectional shape of the curved portion of the primary protective wall.

[0038] In addition, the liquefied gas storage tank of the present invention and the ship including the same, in the total thickness of the primary insulation wall and the secondary insulation wall including the connecting insulation wall, the thickness of the primary insulation wall is constructed to be the same as or similar to that of the secondary insulation wall, thereby not only maintaining the mechanical strength of the secondary insulation wall at a predetermined level, but also reducing the low temperature burden and shaking burden of the secondary protective wall, thereby preventing damage to the secondary protective wall.

[0039] In addition, the liquefied gas storage tank of the present invention and the ship including the same make the thickness of the primary insulation wall the same as or similar to that of the secondary insulation wall in the total thickness including the primary insulation wall and the secondary insulation wall connecting the insulation wall, thereby preventing brittle failure of the hull and reducing the low temperature burden and shaking burden of the secondary protective wall.

[0040] In addition, the liquefied gas storage tank and the ship including the same of the present invention can further improve the insulation performance of the connection part of the adjacent secondary insulation walls constituting the unit element by arranging an auxiliary insulation board on the bottom surface of the connecting insulation wall arranged in the space between the adjacent primary insulation walls constituting the unit element.

[0041] In addition, the liquefied gas storage tank and the ship including the same according to the present invention can enhance the thermal insulation performance by improving the structure of the secondary protective wall.

[0042] In addition, the liquefied gas storage tank and the ship including the same of the present invention use unbonded elastic insulation material as a leveling member of the secondary insulation wall between the secondary insulation wall and the hull, thereby being able to adjust the level of the deformed part of the hull and improve the insulation performance of the tank even without using existing adhesives and leveling wedges.

[0043] In addition, the liquefied gas storage tank of the present invention and the ship including the same fix the adjacent unit panels of the secondary insulation wall by utilizing a clamping (cleat) structure of a protrusion protruding outward from the lower part of the side surface of the unit panel of the secondary insulation wall and stud bolts fixed to the hull, thereby reducing the number of labor compared to the method of drilling holes in the secondary insulation wall and fixing the unit panels with stud bolts. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a partial cross-sectional view of a liquefied gas storage tank for explaining the first embodiment of the present invention.

[0045] Figure 2 It is a partial perspective view of a liquefied gas storage tank for explaining the first embodiment of the present invention.

[0046] Figure 3 It is a diagram for explaining the primary protective wall of the liquefied gas storage tank according to the first embodiment of the present invention.

[0047] Figure 4 (a) and (b) are graphs showing the tensile force of the secondary protective wall according to the thickness changes of the primary insulation wall and the secondary insulation wall.

[0048] Figures 5 to 8 These are diagrams showing the results of structural analysis performed by varying the thicknesses of the primary and secondary insulation walls of the first shell in order to derive the thicknesses of the primary and secondary insulation walls of the liquefied gas storage tank according to the first embodiment of the present invention.

[0049] Figures 9 to 12 These are diagrams showing the results of structural analysis performed by varying the thicknesses of the primary and secondary insulation walls of the second shell in order to derive the thicknesses of the primary and secondary insulation walls of the liquefied gas storage tank according to the first embodiment of the present invention.

[0050] Figures 13 to 16 These are diagrams showing the results of structural analysis performed by varying the thicknesses of the primary and secondary insulation walls of the third shell in order to derive the thicknesses of the primary and secondary insulation walls of the liquefied gas storage tank according to the first embodiment of the present invention.

[0051] Figures 17 to 20 These are diagrams showing the results of structural analysis performed by varying the thicknesses of the primary and secondary insulation walls of the fourth shell in order to derive the thicknesses of the primary and secondary insulation walls of the liquefied gas storage tank according to the first embodiment of the present invention.

[0052] Figure 21 Graph showing the low-temperature stress of the secondary protective wall and the brittle failure probability of the hull according to the thickness changes of the primary insulation wall and the secondary insulation wall.

[0053] Figure 22 、 Figure 23 as well as Figure 24 These are diagrams for explaining various configurations of the secondary protective wall of the liquefied gas storage tank according to the first embodiment of the present invention.

[0054] Figure 25 It is a partial cross-sectional view for explaining the right-angled corner structure of the liquefied gas storage tank according to the first embodiment of the present invention.

[0055] Figure 26 It is a partial cross-sectional view for explaining the obtuse corner structure of the liquefied gas storage tank according to the first embodiment of the present invention.

[0056] Figure 27 This is a graph showing the thermal conductivity of materials used for the primary thermal insulation material and the secondary thermal insulation material of the liquefied gas storage tank according to the present invention.

[0057] Figure 28 It is a partial cross-sectional view of a liquefied gas storage tank for explaining a second embodiment of the present invention.

[0058] Figure 29 It is a partial perspective view of a liquefied gas storage tank for explaining a second embodiment of the present invention.

[0059] Figure 30 FIG. 1 is a partial cross-sectional view of a liquefied gas storage tank for explaining a third embodiment of the present invention.

[0060] Figure 31 It is an enlarged view of the main part of the liquefied gas storage tank according to the third embodiment of the present invention.

[0061] Figure 32 This is a diagram for explaining another embodiment of the primary protective wall of the liquefied gas storage tank according to the first, second, and third embodiments of the present invention.

[0062] Figure 33 It is a diagram for explaining the shape of the primary protective wall.

[0063] Figure 34 (a) and (b) are diagrams for explaining a protruding structure provided on a primary protective wall.

[0064] Figure 35 This is a perspective view of a unit protective wall for explaining a primary protective wall.

[0065] Figure 36 Graph showing the distribution of the paradigm equivalent stress value (thermal stress and compressive stress) according to the ratio W / H of the curved portion width to the curved portion height of the primary protective wall.

[0066] Figure 37 Graph showing the range of the curvature radius 'r3-r2-r1' value according to the ratio W / H of the curved portion width to the curved portion height of the primary protective wall obtained through the cross-sectional shape optimization simulation of the primary protective wall.

[0067] Figure 38 (a), (b) and (c) are diagrams showing the results of structural analysis of sloshing pressure values ​​when fluid flows into the transverse curved portion and the longitudinal curved portion of the primary protective wall of the present invention and the primary protective wall of the comparative object.

[0068] Figure 39 (a) and (b) are diagrams for explaining deformation when an equally distributed load is applied to the primary protective wall of the present invention and the primary protective wall of a comparative example.

[0069] Figure 40 This is a graph showing the stress change value of the secondary protective wall according to the change in the length of the portion where the secondary protective wall and the secondary heat-insulating wall are not attached in the obtuse corner structure. DETAILED DESCRIPTION

[0070] The objectives, specific advantages, and novel features of the present invention will become more apparent through the following detailed description and preferred embodiments in conjunction with the accompanying drawings. In this specification, when designating the components of the various drawings, it should be noted that, whenever possible, identical components, even if shown in different drawings, are designated with the same designations. Furthermore, when describing the present invention, if a detailed description of a related known technology is determined to unnecessarily obscure the main purpose of the present invention, the detailed description thereof will be omitted.

[0071] In addition, the drawings are only used to make the embodiments disclosed in this specification easier to understand, and the technical ideas disclosed in this specification are not limited by the drawings. They should be understood to include all changes, equivalents and substitutes within the ideas and technical scope of the present invention.

[0072] In addition, terms such as first, second, etc. including ordinal numbers may be used to describe various components, but these components are not limited by these terms. These terms are only used to distinguish one component from another.

[0073] Hereinafter, in this specification, the term "liquefied gas" will be used to encompass all gaseous fuels typically stored in a liquid state, such as LNG, LPG, ethylene, and ammonia. For convenience, even heated or pressurized gas that is not in a liquid state may be referred to as "liquefied gas." This also applies to boil-off gas. Furthermore, for convenience, the term "LNG" will be used to encompass all liquid NG (natural gas) and supercritical LNG, and boil-off gas will be used to encompass not only boil-off gas in a gaseous state but also boil-off gas in a liquefied state.

[0074] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0075] Figure 1 FIG. 1 is a partial cross-sectional view of a liquefied gas storage tank for explaining a first embodiment of the present invention. Figure 2 It is a partial perspective view of a liquefied gas storage tank for explaining the first embodiment of the present invention. Figure 3 It is a diagram for explaining the primary protective wall of the liquefied gas storage tank according to the first embodiment of the present invention.

[0076] like Figures 1 to 2 As shown, the liquefied gas storage tank 1 according to the first embodiment of the present invention can be installed on a ship to store liquefied gas such as LNG, which is a very low-temperature substance (approximately -160°C to -170°C).

[0077] Although not shown in the figure, it should be understood that the vessel equipped with the liquefied gas storage tank 1 described below encompasses not only merchant ships that transport cargo from a departure point to a destination, but also marine structures that float at a predetermined point on the sea to perform specific operations. Furthermore, it should be understood that the liquefied gas storage tank 1 herein encompasses any type of tank for storing liquefied gas.

[0078] The liquefied gas storage tank 1 may include a primary protective wall 2 in contact with the liquefied gas, a primary thermal insulation wall 3 disposed outside the primary protective wall 2, a secondary protective wall 4 disposed outside the primary thermal insulation wall 3, and a secondary thermal insulation wall 5 disposed outside the secondary protective wall 4. The liquefied gas storage tank 1 may be supported on the hull 7 by an adhesive 6 disposed between the secondary thermal insulation wall 5 and the hull 7.

[0079] The thickness of the primary insulation wall 3 and the secondary insulation wall 5 of the liquefied gas storage tank 1 may need to be optimized to optimize the insulation performance and storage capacity. For example, when polyurethane foam is used as the main material of the primary insulation wall 3 and the secondary insulation wall 5, the total thickness of the primary insulation wall 3 and the secondary insulation wall 5 can be in the range of 250 mm to 500 mm. Figures 4 to 20 is described in .

[0080] The above-mentioned liquefied gas storage tank 1 may include a plane and a corner structure. For example, the horizontal walls in the front-to-back direction of the liquefied gas storage tank 1, the bottom surface between the horizontal walls, the vertical walls, and the ceiling may be equivalent to a plane structure. In addition, for example, the structure where the horizontal walls, bottom surface, vertical walls, and ceiling of the liquefied gas storage tank 1 meet may be equivalent to a corner structure. Here, the corner structure may include an obtuse corner structure or a right-angle corner structure. In the case where the thickness of the primary insulation wall 3 or the secondary insulation wall 5 changes, it may be accompanied by a change in the obtuse corner structure or the right-angle corner structure, which will be discussed in detail. Figures 25 to 26 is described in .

[0081] Reference Figure 1 and Figure 2 The primary protective wall 2 forms a storage space for liquefied gas, a cryogenic substance, and can be made of a metal material. For example, the metal material can be stainless steel, but is not limited thereto. The primary protective wall 2 and the secondary protective wall 4 can prevent the liquefied gas from leaking to the outside.

[0082] The primary protective wall 2 may be fixedly coupled to the upper portion of the primary thermal insulation wall 3 by anchor rods (not shown) and in direct contact with the liquefied gas as a cryogenic substance stored in the liquefied gas storage tank 1 .

[0083] Reference Figure 3 The primary protective wall 2 can be divided into a flat surface portion 21 that contacts the top surface of the primary insulation wall 3, a curved surface portion 22 for relieving thermal contraction or expansion stress, and a boundary portion 23 between the flat surface portion 21 and the curved surface portion 22. For example, the primary protective wall can be formed from a corrugated membrane sheet made of stainless steel with a thickness of 1.0 to 1.5 mm, preferably 1.0 to 1.2 mm. In other words, the primary protective wall can be formed into a pleated shape.

[0084] The primary protective wall 2 can be formed so that its pleated shape has a first curvature radius R1 and a second curvature radius R2. That is, the primary protective wall 2 of the present embodiment can be formed to have two types of curvature radii R1 and R2, with the first curvature radius R1 being formed at the boundary portion 23 between the flat portion 21 and the curved portion 22, and the second curvature radius R2 being formed at the curved portion 22. For example, the first curvature radius R1 can be formed to be smaller than the second curvature radius R2. In the primary protective wall 2 with the curvature radii R1 and R2, a gentle curve is formed at the upper portion, so that welding inspection is easy. In addition, the fluid hit from the side flows away directly, so that shaking can also be handled flexibly. This will be addressed by Figures 32 to 39 Explain in more detail.

[0085] In addition, the primary protective wall 2 of this embodiment can be formed with the same horizontal and vertical corrugation sizes throughout the entire area, without distinguishing between large corrugations and small corrugations. That is, since the horizontal and vertical corrugation sizes of the entire primary protective wall 2 are the same, the primary protective wall can be easily manufactured.

[0086] Reference Figure 1 The primary insulation wall 3 can be designed to block heat intrusion from the outside and withstand impact from the outside or impact caused by internal liquefied gas shaking, and can be arranged between the primary protective wall 2 and the secondary protective wall 4.

[0087] The primary insulation wall 3 may have a structure in which a primary plywood 31 and a primary insulation material 32 are sequentially stacked on the outer side of the primary protective wall 2, and its thickness may correspond to the sum of the thickness of the primary plywood 31 and the thickness of the primary insulation material 32. The primary insulation wall 3 may be formed to a thickness of 160 mm to 250 mm.

[0088] The primary plywood 31 may be provided between the primary protective wall 2 and the primary heat insulating material 32 .

[0089] The primary plywood 31 may be formed to a thickness of 6.5 mm to 15 mm.

[0090] The primary heat insulating material 32 may be formed of a material having excellent heat insulating properties and excellent mechanical strength so as to be able to block heat intrusion from the outside and withstand external impact or impact caused by internal liquefied gas sloshing.

[0091] The primary insulation material 32 may be formed of polyurethane foam between the primary plywood 31 and the secondary protective wall 4 and may correspond to a thickness range of 150 mm to 240 mm.

[0092] Reference Figure 1 , a unit element can be formed by stacking a portion of the primary insulation wall 3, the secondary protective wall 4 and the secondary insulation wall 5. Here, the portion of the primary insulation wall 3 constituting the unit element can be defined as a fixed insulation wall 3b, the width of which can be smaller than the width of the secondary insulation wall 5 included in the unit element. In addition, the fixed insulation wall 3b, the secondary protective wall 4 and the secondary insulation wall 5 can be arranged in a pre-fixed state, but are not limited to this, and can also be separated and arranged in the liquefied gas storage tank 1. Therefore, a portion of the secondary protective wall 4 can be exposed to both sides of the primary insulation wall 3. The unit elements can be arranged adjacent to each other, and in this case, a connecting insulation wall 3a can be provided in the space portion between adjacent primary insulation walls 3, that is, the space portion where the secondary protective wall 4 is exposed.

[0093] The secondary protective wall 4 can be divided into a primary protective wall 41 and an auxiliary protective wall 42. The primary protective wall 41 is positioned above the secondary insulation wall 5 within the unit element, while the auxiliary protective wall 42 is positioned between the exposed primary protective wall 41 and the connecting insulation wall 3a. In this case, the auxiliary protective wall 42 is positioned so as to connect the primary protective walls 41 of adjacent unit elements. In other words, adjacent unit elements can be terminated by the auxiliary protective wall 42 and the connecting insulation wall 3a stacked on the primary protective wall 41.

[0094] The laminated structure of the portion connecting the heat insulating wall 3a is provided by Figure 2 The connecting heat-insulating wall 3a may be provided in a form similar to or identical to that described for the primary heat-insulating wall 3 constituting the unit element, with a connecting plywood 31a and a connecting heat-insulating material 32a being stacked. In this specification, it should be understood that the primary heat-insulating wall 3 may include the connecting heat-insulating wall 3a and the fixed heat-insulating wall 3b.

[0095] Figure 2 Shown Figure 1 In the cross-sectional structure of the A-A' plane, the connecting heat insulating wall 3a may have a structure in which the connecting plywood 31a and the connecting heat insulating material 32a are stacked. The thickness of the connecting heat insulating wall 3a may correspond to the sum of the thickness of the connecting plywood 31a and the thickness of the connecting heat insulating material 32a.

[0096] The connection plywood 31a may be formed to a thickness of 6.5 mm to 15 mm.

[0097] The connection insulation material 32a may be formed of polyurethane foam between the connection plywood 31a and the auxiliary protective wall 42 of the secondary protective wall 4, and may correspond to a thickness range of 150 mm to 240 mm.

[0098] As described above, the thickness of the primary insulation material 32 of the primary insulation wall 3 and the connecting insulation material 32a of the connecting insulation wall 3a can be the same. However, in the case of the connecting insulation material 32a of the connecting insulation wall 3a, the auxiliary protective wall 42 is stacked on its lower portion more than the main protective wall 41 of the secondary protective wall 4. Therefore, the connecting insulation material 32a of the connecting insulation wall 3a can have a thickness smaller than the thickness of the primary insulation material 32 of the primary insulation wall 3 by the thickness of the auxiliary protective wall 42.

[0099] The connecting heat insulating wall 3a is provided to seal the space generated between adjacent secondary heat insulating walls 5 together with the auxiliary protective wall 42 when adjacent unit elements are arranged, and to block heat intrusion from the outside.

[0100] However, because the connecting insulation wall 3a is interposed between adjacent fixed insulation walls 3b that constitute the unit element, the secondary protective wall 4 below the connecting insulation wall 3a is inherently vulnerable to extreme low temperatures. Consequently, the secondary protective wall 4 below the connecting insulation wall 3a, where the primary protective wall 41 and auxiliary protective wall 42 overlap, is likely to cause problems. This description will focus on the connecting insulation wall 3a.

[0101] The secondary protective wall 4 may be provided between the primary thermal insulation wall 3 including the thermal insulation wall 3 a and the secondary thermal insulation wall 5 , and may prevent the liquefied gas from leaking to the outside together with the primary protective wall 2 .

[0102] The secondary protective wall 4 at the lower end of the fixed insulation wall 3b can include a main protective wall 41 as a single protective wall, and the secondary protective wall 4 connecting the lower end of the insulation wall 3a can include a main protective wall 41 connecting unit elements to each other and an auxiliary protective wall 42 arranged on the secondary insulation wall 5 constituting the unit elements.

[0103] The main protective wall 41 can be provided on the secondary insulation wall 5 constituting the unit element and formed to a thickness of 0.6 mm to 1.0 mm. Adjacent main protective walls 41 can be made airtight by stacking auxiliary protective walls 42 .

[0104] The auxiliary protective wall 42 is a structure in which unit elements are connected to each other. It can be formed to a thickness of 0.6 mm to 1.0 mm and is stacked on the main protective wall 41.

[0105] On the other hand, refer to Figure 1 and Figure 2 The secondary insulation wall 5 can be designed to, together with the fixed insulation wall 3b and the connecting insulation wall 3a, block external heat intrusion and withstand external impacts or impacts caused by internal liquefied gas sloshing. Furthermore, the secondary insulation wall 5 can be positioned between the secondary protective wall 4 and the hull 7 and can include secondary insulation material 51 and secondary plywood 52.

[0106] The secondary insulation wall 5 can have a structure in which a secondary insulation material 51 and a secondary plywood 52 are stacked in sequence on the outside of the secondary protective wall 4, and the total thickness of the secondary insulation material 51 and the secondary plywood 52 can be formed to be 150mm to 240mm.

[0107] The secondary heat insulating material 51 may be formed of a material having excellent heat insulating properties and excellent mechanical strength so as to be able to block heat invasion from the outside and withstand external impact or impact caused by internal liquefied gas sloshing.

[0108] The secondary heat insulating material 51 may be formed of polyurethane foam between the secondary protective wall 4 and the secondary plywood 52 and may be formed to a thickness of 140 mm to 230 mm.

[0109] The secondary plywood 52 may be provided between the secondary heat insulating material 51 and the hull 7. For example, the secondary heat insulating material 51 may be provided so as to be in contact with the secondary plywood 52. The secondary plywood 52 may be formed to a thickness of 6.5 mm to 25 mm.

[0110] As described above, the liquefied gas storage tank 1 of this embodiment can be configured such that the thickness of the connecting insulating wall 3a is the same as or similar to that of the secondary insulating wall 5 by making the primary insulating wall 3 have a thickness of 66% to 166% of that of the secondary insulating wall 5, and the thickness of the connecting insulating wall 3a included in the primary insulating wall 3 is 67% to 167% of that of the secondary insulating wall 5. In connection with this configuration, the thickness of the connecting insulating material 32a of the connecting insulating wall 3a can be made the same as or similar to that of the secondary insulating material 51 by making the connecting insulating material 32a of the connecting insulating wall 3a have a thickness of 90% to 110% of that of the secondary insulating material 51. In this embodiment, it should be understood that even if the fixed insulating wall 3b portion of the unit element is not specifically mentioned, as long as the connecting insulating wall 3a is included, the fixed insulating wall 3b is the same as or similar to the connecting insulating wall 3a in relation to the secondary insulating wall 5.

[0111] When the connecting insulation wall 3a and the secondary insulation wall 5, or the connecting insulation material 32a and the secondary insulation material 51 of the connecting insulation wall 3a, are formed with this thickness ratio, the upper limit of the stress of the secondary protective wall 4 at low temperatures can be 50 MPa or less at the lower portion of the connecting insulation wall 3a. Specifically, the stress of the secondary protective wall 4 at low temperatures can be 40 MPa to 50 MPa at the lower portion of the connecting insulation wall 3a. This value is obtained based on the structural analysis described below.

[0112] In this embodiment, the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 or the thickness of the connecting insulation material 32a of the primary insulation wall 3 and the secondary insulation material 51 are the same or similar. Figures 4 to 20 Provide explanation.

[0113] Figure 4 (a) and (b) are diagrams showing the tension of the secondary protective wall 4 at the lower portion of the connecting insulation wall 3a according to the thickness change of the connecting insulation wall 3a and the secondary insulation wall 5 included in the primary insulation wall 3. Figure 4 In (a) and (b), the total thickness of the connected insulation wall 3a, the secondary protective wall 4, the secondary insulation wall 5, etc. is the same.

[0114] On the other hand, the secondary protective wall 4 and the secondary thermal insulation wall 5 differ in the amount of their own shrinkage depending on the temperature to which they are exposed. In the case of the secondary protective wall 4 and the secondary thermal insulation wall 5, the thinner the thickness of the connecting thermal insulation wall 3a, the more susceptible it is to the cold and hot effects of the extremely low temperature liquefied gas. In addition, in this case, the temperature itself decreases and the amount of shrinkage itself increases, thereby posing a problem of increasing the risk of damage to the secondary protective wall 4 due to increased stress at low temperatures. This problem is particularly common in the auxiliary protective wall 42 that connects the main protective walls 41 of the unit elements adjacent to each other at the lower part of the connecting thermal insulation wall 3a by adhesives or the like. This is because, at the lower part of the connecting thermal insulation wall 3a, the two ends of the auxiliary protective wall 42 are connected to the main protective walls 41 of each unit element, and as the secondary thermal insulation wall 5 of the unit element shrinks, the two ends of the auxiliary protective wall 42 may be deformed to move away from or closer to each other.

[0115] Reference Figure 4 (a) shows a case where the connecting insulation wall 3a is formed relatively thinner than the secondary insulation wall 5, and the height of the secondary protective wall 4 is located above the center of the total thickness in the thickness direction. In this case, in order to reduce the mechanical stress applied to the secondary protective wall 4 when the hull 7 deforms structurally due to the six-degree-of-freedom movement, the secondary insulation wall 5 can be made relatively thicker than the connecting insulation wall 3a by ensuring a larger thickness.

[0116] Reference Figure 4 (b) shows a case where the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 are similar, and the height of the secondary protective wall 4 is located in the center area of ​​the total thickness based on the thickness direction. Here, the center area can correspond to the range of 40% to 60% of the total thickness. In this case, Figure 4 Compared with (a), the shrinkage itself is reduced, thereby reducing the stress at low temperature. Figure 4 Compared with (a), the damage risk of the secondary protective wall is relatively reduced.

[0117] In the present invention, a liquefied gas storage tank 1 is derived that can maintain the mechanical strength of the secondary insulation wall 5 at a predetermined level and can reduce the low temperature burden and sloshing burden of the secondary protective wall 4. Figures 5 to 20 Explanation to understand.

[0118] Figures 5 to 20 In order to derive the thickness of the primary insulation wall 3 and the secondary insulation wall 5 including the connecting insulation wall 3a in the liquefied gas storage tank 1 of the present embodiment, the thickness of the primary insulation wall 3 and the secondary insulation wall 5 are calculated by pressing the first shell ( Figures 5 to 8 )、Second Shell ( Figures 9 to 12 )、Third Shell( Figures 13 to 16 )、The fourth shell ( Figures 17 to 20 ) shows the results of structural analysis by varying the thickness of the connecting insulation wall 3a and the secondary insulation wall 5. In this embodiment, although the thickness of the connecting insulation wall 3a is primarily used for the description, it should be understood that the thickness of the primary insulation wall 3 is also the same as or similar to that of the connecting insulation wall 3a.

[0119] When performing structural analysis on each shell, the analysis conditions are as follows.

[0120] First, the total thickness of the connecting insulation wall 3a and the secondary insulation wall 5 of the first to fourth shells used as the analysis model is the same as 400 mm.

[0121] Second, by changing the thickness of the connecting insulation wall 3a and the secondary insulation wall 5, only the position of the secondary protective wall 4 is changed.

[0122] Third, considering the same linear temperature distribution conditions, the temperature at the primary protective wall 2 is set to -163°C, which is the temperature of the liquefied gas, and the temperature at the hull 7 is set to 20°C, which is the normal temperature.

[0123] Fourth, the thickness ratio is the ratio of the thickness of the connecting insulation wall 3a to the total thickness (400 mm).

[0124] Under the above-described analysis conditions, the structures of the first to fourth shells as analysis models were analyzed.

[0125] Figures 5 to 8 They are diagrams showing the results of structural analysis performed by changing the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 of the first shell in order to derive the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 included in the primary insulation wall 3 in the liquefied gas storage tank of the first embodiment of the present invention.

[0126] like Figure 5As shown, the first shell has a connecting insulation wall 3a having a thickness of 100 mm and a secondary insulation wall 5 having a thickness of 300 mm. That is, in the first shell, the ratio of the thickness of the connecting insulation wall 3a to the total thickness (400 mm) of the connecting insulation wall 3a and the secondary insulation wall 5 is 0.25, and the secondary protective wall 4 is located closer to the upper primary protective wall 2 side from the center of the total thickness of the connecting insulation wall 3a and the secondary insulation wall 5.

[0127] In the case of this first shell, as Figures 6 to 8 As shown in FIG. 1 , the structural analysis results show that, when the unit elements are arranged adjacent to each other, the stress value of the secondary protective wall 4 corresponding to the adjacent secondary insulation walls 5 is calculated to be 70.12 MPa.

[0128] In the case of the first shell, by Figure 4 The reason why stress is generated in the secondary protective wall 4 is known to be that, as the thickness of the connecting heat-insulating wall 3a decreases, the secondary protective wall 4 is more affected by the heat and cold of the liquefied gas.

[0129] Figures 9 to 12 They are diagrams showing the results of structural analysis performed by changing the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 of the second shell in order to derive the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 included in the primary insulation wall 3 in the liquefied gas storage tank of the first embodiment of the present invention.

[0130] like Figure 9 As shown, the second shell has a connecting insulating wall 3a having a thickness of 160 mm and a secondary insulating wall 5 having a thickness of 240 mm. That is, in the second shell, the thickness of the connecting insulating wall 3a accounts for 0.4 of the total thickness (400 mm) of the connecting insulating wall 3a and the secondary insulating wall 5, and the secondary protective wall 4 is located slightly toward the primary protective wall 2 from the center of the total thickness of the connecting insulating wall 3a and the secondary insulating wall 5.

[0131] In the case of this second shell, as Figures 10 to 12 As shown in the structural analysis results, when the unit elements are arranged adjacent to each other, the stress value of the secondary protective wall 4 corresponding to the adjacent secondary insulation walls 5 is calculated to be 55.09 MPa.

[0132] Figures 13 to 16 They are diagrams showing the results of structural analysis performed by changing the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 of the third shell in order to derive the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 included in the primary insulation wall 3 in the liquefied gas storage tank of the first embodiment of the present invention.

[0133] like Figure 13As shown, the third shell is a shell in which the thickness of the connecting insulation wall 3a is formed to be the same or similar to the thickness of the secondary insulation wall 5. That is, in the third shell, the ratio of the thickness of the connecting insulation wall 3a to the total thickness (400 mm) of the connecting insulation wall 3a and the secondary insulation wall 5 is approximately 0.5, and the secondary protective wall 4 is located adjacent to the center of the total thickness of the connecting insulation wall 3a and the secondary insulation wall 5.

[0134] In the case of this third shell, as Figures 14 to 16 As shown in FIG. 1 , the structural analysis results show that, when the unit elements are arranged adjacent to each other, the stress value of the secondary protective wall 4 corresponding to the adjacent secondary insulation walls 5 is calculated to be 47.63 MPa.

[0135] Figures 17 to 20 They are diagrams showing the results of structural analysis performed by changing the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 of the fourth shell in order to derive the thickness of the connecting insulation wall 3a and the secondary insulation wall 5 included in the primary insulation wall 3 in the liquefied gas storage tank of the first embodiment of the present invention.

[0136] like Figure 17 As shown, the fourth shell has a connecting insulation wall 3a with a thickness of 240 mm and a secondary insulation wall 5 with a thickness of 160 mm. That is, in the fourth shell, the thickness of the connecting insulation wall 3a accounts for 0.6 of the total thickness (400 mm) of the connecting insulation wall 3a and the secondary insulation wall 5, and the secondary protective wall 4 is located below the center of the total thickness of the connecting insulation wall 3a and the secondary insulation wall 5.

[0137] In the case of this fourth shell, as Figures 18 to 20 As shown in FIG. 1 , the structural analysis results show that, when the unit elements are arranged adjacent to each other, the stress value of the secondary protective wall 4 corresponding to the adjacent secondary insulation walls 5 is calculated to be 41.21 MPa.

[0138] As described above, the structural analysis results of each of the first to fourth shells show that the secondary protective wall 4 connected to the lower part of the heat insulating wall 3a tends to reduce the low-temperature stress caused by thermal contraction as it moves away from the primary protective wall 2. Figure 21 Provide explanation.

[0139] Figure 21 This is a diagram showing the relationship between the low-temperature stress of the secondary protective wall and the brittle fracture probability of the ship body according to the thickness changes of the primary insulation wall and the secondary insulation wall.

[0140] like Figure 21From the graph shown in , it can be predicted that the stress value caused by thermal contraction at low temperature of the first shell to the fourth shell and the secondary protective wall 4 connected to the lower part of the heat insulating wall 3a decreases as they move away from the primary protective wall 2. That is, it can be seen that the temperature of the secondary protective wall 4 connected to the lower part of the heat insulating wall 3a increases relatively as it moves away from the primary protective wall 2, so the contraction becomes smaller and the stress decreases. In this embodiment, the secondary protective wall 4 connected to the lower part of the heat insulating wall 3a is mainly explained, but it is obvious that the stress of the secondary protective wall 4 at the lower part of the fixed heat insulating wall 3b constituting the unit element also decreases as it moves away from the primary protective wall 2. The secondary protective wall 4 connected to the lower part of the heat insulating wall 3a is a state in which the main protective wall 41 and the auxiliary protective wall 42 are stacked, and the secondary protective wall 4 at the lower part of the primary heat insulating wall 3 is composed only of the main protective wall 41.

[0141] As described above, in the liquefied gas storage tank 1 of this embodiment, the thickness of the connecting insulation wall 3a is increased within the total thickness of the connecting insulation wall 3a and the secondary insulation wall 5, thereby increasing the temperature experienced by the secondary protective wall 4 (reducing the influence of heat and cold from the cryogenic liquid gas). This reduces the shrinkage of the secondary protective wall 4 itself caused by heat and cold, and reduces the stress caused by heat and cold, thereby preventing damage to the secondary protective wall 4 caused by heat and cold. This principle also applies to the secondary protective wall 4, which is defined as the lower portion of the primary insulation wall 3, including the connecting insulation wall 3a.

[0142] Furthermore, as the thickness of the connecting insulation wall 3a and the fixed insulation wall 3b increases (while the thickness of the secondary insulation wall 5 decreases), the secondary protective wall 4 reduces the sway load and fluid dynamic load transmitted to the secondary protective wall 4, thereby reducing the stress caused by sway, thereby preventing damage caused by sway. Furthermore, as the thickness of the secondary insulation wall 5 decreases (while the thickness of the primary insulation wall 3 increases), the flatness of the secondary protective wall 4 can be easily adjusted.

[0143] In addition, as the thickness of the connecting insulation wall 3a and the fixed insulation wall 3b increases, the thickness of the secondary insulation wall 5 decreases relatively, and it is relatively far away from the primary protective wall 2. Therefore, the shrinkage force of the secondary insulation wall 5 caused by cold and heat also decreases, and as the shrinkage force of the secondary insulation wall 5 decreases, the tensile force of the secondary protective wall 4 decreases, thereby preventing the secondary protective wall 4 from being damaged by the shrinkage force of the secondary insulation wall 5.

[0144] Taking into account the low-temperature stress of the secondary protective wall 4, the present invention can be configured so that the connecting insulation wall 3a corresponds to at least 40% of the thickness of the combined thickness of the connecting insulation wall 3a and the secondary insulation wall 5. Preferably, the liquefied gas storage tank 1 of the present invention can be configured in the range of the second shell to the fourth shell, i.e., the connecting insulation wall 3a corresponds to 40% to 60% of the thickness of the combined thickness of the connecting insulation wall 3a and the secondary insulation wall 5. More preferably, the liquefied gas storage tank 1 of the present invention can be configured in the range of the third shell, i.e., the connecting insulation wall 3a corresponds to 47% to 53% of the thickness of the combined thickness of the connecting insulation wall 3a and the secondary insulation wall 5.

[0145] However, if the thickness of the connecting insulation wall 3a and the primary insulation wall 3 is increased, the thickness of the secondary insulation wall 5 is relatively reduced. Therefore, the secondary insulation wall 5 is inevitably vulnerable to the mechanical stress applied when the hull 7 is structurally deformed due to the six-degree-of-freedom movement of the hull 7. Therefore, the degree of mechanical stress transmitted to the secondary protective wall 4 through the secondary insulation wall 5 will inevitably increase.

[0146] In addition, when loaded with liquefied gas, an emergency condition such as a rupture of the primary protective wall 2 may occur. In this case, the primary protective wall 2 can no longer prevent the leakage of liquefied gas, so the liquefied gas may come into contact with the secondary protective wall 4. In addition, if the secondary protective wall 4 comes into contact with extremely low-temperature liquefied gas, the temperature of the hull decreases, and the probability of brittle failure may increase. In addition, as the temperature becomes lower, brittle problems may occur compared to the increase in material strength of the hull, so the probability of brittle failure may increase. Here, brittle failure (brittle fracture) can correspond to sudden failure with almost no plastic deformation, and can also be understood as a brittle crack (brittle crack).

[0147] In this regard, refer to Figure 21 In an emergency, as the secondary protective wall 4 that is in contact with the extremely low temperature liquefied gas gradually approaches the hull from the first shell to the fourth shell, the probability of brittle failure increases. Figure 21 The brittle failure probability of the hull increases from the first hull to the fourth hull, that is, as the thickness of the connecting insulation wall increases compared to the thickness of the secondary insulation wall 5. Furthermore, if the thickness of the connecting insulation wall 3a increases further beyond the fourth hull, the brittle failure probability approaches 1, and the hull may crack or split.

[0148] Therefore, the thermal insulation system of the liquefied gas storage tank 1 must be configured not only to account for the aforementioned low-temperature stresses, but also for the risk of cracks or damage to the hull. In the present invention, when considering both low-temperature stresses and hull cracks, the second to fourth hulls, with the secondary protective wall 4 located at the center of the total thickness of the combined insulation wall 3a and the secondary insulation wall 5, are suitable. Preferably, from a mechanical perspective of low-temperature stresses and hull cracks, the third hull is considered suitable.

[0149] Therefore, in the present invention, the second to fourth hulls can be suitable embodiments, as they reduce the low-temperature stress on the secondary protective wall 4 by ensuring the thickness of the connecting insulation wall 3a and the primary insulation wall 3, and ensure the spacing between the hull 7 and the secondary protective wall 4 by appropriately setting the thickness of the secondary insulation wall 4. This can reduce the burden of structural stress transmitted from the hull 7 on the secondary protective wall 4. Furthermore, when considering both low-temperature stress and mechanical strength, the third hull can be considered a preferred embodiment.

[0150] Table 1 below shows stress changes in the lower portion of the connecting insulation wall 3a, based on changes in the thickness of the primary insulation wall 3 and the secondary insulation wall 5, under structural analysis conditions similar to or identical to those described above for the first to fourth shells. As described above, the connecting insulation wall 3a may be an insulation wall included in the primary insulation wall 3. Therefore, in Table 1 below, the thickness of the primary insulation wall 3 may refer to the thickness of the connecting insulation wall 3a. Furthermore, the stress changes in the lower portion of the connecting insulation wall 3a may refer to the stress changes in the secondary protective wall 4, which serves as a lower layer of the connecting insulation wall 3a.

[0151] In the following, it should be understood that Examples 1 to 5 and Comparative Examples 1 to 3 described with reference to [Table 1] do not necessarily refer to the same examples even if they use the same numerical values ​​as those of the aforementioned examples (first to fourth housings).

[0152] [Table 1]

[0153] Primary insulation wall Secondary insulation wall Secondary protective wall stress value (MPa) Example 1 160 240 55.09 Example 2 180 220 51.08 Example 3 200 200 47.63 Example 4 220 180 44.13 Example 5 240 160 41.21 Comparative Example 1 100 300 70.12 Comparative Example 2 300 100 34.29 Comparative Example 3 140 260 59.52

[0154] As shown in [Table 1], in Example 1, the thickness of the primary insulation wall 3 is 160 mm, and the thickness of the secondary insulation wall 5 is 240 mm. In this case of Example 1, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 55.09 MPa.

[0155] In Example 2, the thickness of the primary insulation wall 3 is 180 mm, and the thickness of the secondary insulation wall 5 is 220 mm. In this case of Example 2, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 51.08 MPa.

[0156] In Example 3, the thickness of the primary insulation wall 3 is 200 mm, and the thickness of the secondary insulation wall 5 is 200 mm. In this case of Example 3, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 47.63 MPa.

[0157] In Example 4, the thickness of the primary insulation wall 3 is 220 mm, and the thickness of the secondary insulation wall 5 is 180 mm. In this case of Example 4, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 44.13 MPa.

[0158] In Example 5, the thickness of the primary insulation wall 3 is 240 mm, and the thickness of the secondary insulation wall 5 is 160 mm. In this case of Example 5, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 41.21 MPa.

[0159] In Comparative Example 1, the thickness of the primary insulation wall 3 is 100 mm, and the thickness of the secondary insulation wall 5 is 300 mm. In the case of this Comparative Example 1, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 70.12 MPa.

[0160] In Comparative Example 2, the thickness of the primary insulation wall 3 is 300 mm, and the thickness of the secondary insulation wall 5 is 100 mm. In the case of this Comparative Example 2, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 34.29 MPa.

[0161] In Comparative Example 3, the thickness of the primary insulation wall 3 is 140 mm, and the thickness of the secondary insulation wall 5 is 260 mm. In the case of this Comparative Example 3, the structural analysis results calculated that the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, is 59.52 MPa.

[0162] In the above-mentioned Examples 1 to 5, the thickness of the primary insulation wall 3 is increased from 160 mm to 240 mm, and the thickness of the secondary insulation wall 5 is correspondingly reduced from 240 mm to 160 mm. As a result of the structural analysis, the stress value of the secondary protective wall 4, which is the lower layer connecting the insulation wall 3a, changes from 55.09 MPa to 41.21 MPa. When the low-temperature stress of the liquefied gas storage tank 1 and the cracks in the hull 7 are taken into account, this thickness range and stress value are suitable.

[0163] However, in the cases of Comparative Examples 1 to 3, the thickness of the primary insulation wall 3 and the secondary insulation wall 5 are biased toward one side, and therefore, when taking into account the low-temperature stress of the liquefied gas storage tank 1 and the cracks in the hull 7, it is not preferred to be applied as an insulation system for the liquefied gas storage tank 1.

[0164] On the other hand, the material of the secondary protective wall 4 can be variously constituted, which will be described in detail in the following sections. Figures 22 to 24 is described in .

[0165] Figure 22 、 Figure 23 as well as Figure 24 These are diagrams for explaining various configurations of the secondary protective wall of the liquefied gas storage tank according to the first embodiment of the present invention.

[0166] like Figure 22 As shown, the secondary protective wall 4 may be formed of a first material having a three-layer structure of glass fabric (GC) / aluminum foil (AF) / glass-aramid fabric (GAC).

[0167] Glass-aramid fabric (GAC) uses aramid material in glass fabric and can be manufactured by mixing one aramid fiber with every two glass fibers.

[0168] This first material can be applied to the auxiliary protective wall 42 of the secondary protective wall 4 , but is not limited thereto, and can also be applied to the main protective wall 41 of the secondary protective wall 4 .

[0169] like Figure 23 As shown, the secondary protective wall 4 may be formed of a second material having a five-layer structure of glass fabric (GC) / aluminum foil (AF) / glass fabric (GC) / aluminum foil (AF) / glass fabric (GC).

[0170] This second material can be applied to the main protective wall 41 of the secondary protective wall 4 , but is not limited thereto, and can also be applied to the auxiliary protective wall 42 of the secondary protective wall 4 .

[0171] like Figure 24As shown, the secondary protective wall 4 uses inorganic basalt fabric extracted from basalt, and can be formed of a third material with a three-layer structure of basalt fabric (BC) / aluminum foil (AF) / basalt fabric (BC).

[0172] This third material can be applied to the main protective wall 41 of the secondary protective wall 4 , and is not limited thereto, and can also be applied to the auxiliary protective wall 42 of the secondary protective wall 4 .

[0173] like Figures 22 to 24 As described in , the secondary protective wall 4 of this embodiment can be formed of various materials of a multilayer structure of a first member / aluminum foil (AF) / second member. In this case, at least one of the first member and the second member can be glass fabric (GC), glass-aramid fabric (GAC), basalt fabric (BC), or glass fabric (GC) / aluminum foil (AF) / glass fabric (GC).

[0174] In addition, various materials used for the secondary protective wall 4 can of course also be used in various combinations for the main protective wall 41 and the auxiliary protective wall 42 of the secondary protective wall 4 .

[0175] Figure 25 FIG. 1 is a partial cross-sectional view illustrating a right-angled corner structure of a liquefied gas storage tank according to a first embodiment of the present invention. Figure 26 It is a partial cross-sectional view for explaining the obtuse corner structure of the liquefied gas storage tank according to the first embodiment of the present invention.

[0176] In the above Figures 5 to 20 In the present invention, it is confirmed that when the thickness of the connecting insulation wall 3a or the primary insulation wall 3 and the thickness of the secondary insulation wall 5 are formed in the same or similar range, a more stable insulation system is obtained. For example, the same or similar range can mean that the position of the secondary protective wall 4 is 40% to 60% of the total thickness of the sum of the thicknesses of the connecting insulation wall 3a or the primary insulation wall 3 and the secondary insulation wall 5. The above-mentioned structure can also be applied to Figure 25 The right-angled corner structure of the liquefied gas storage tank 1 is shown Figure 26 The obtuse corner structure of the liquefied gas storage tank 1 is shown.

[0177] However, in the right-angle and obtuse-angle corner structures of the liquefied gas storage tank 1, the secondary protective wall 4 can only be formed into a curved shape. Curved shapes are more vulnerable to the loads of the surrounding environment than straight sections. This embodiment can alleviate the stress caused by such loads. Furthermore, this embodiment can facilitate the absorption of hull deformation.

[0178] Reference Figure 25The secondary protective wall 4 in the right-angle corner structure becomes thicker than the first shell and the second shell as the thickness of the primary insulation wall 3 becomes thicker, and the curvature radius accounts for more than 25% of the thickness of the primary insulation wall 3, for example, 25% to 50%.

[0179] In addition, the secondary protective wall 4 in the right-angle corner structure becomes thicker than the first shell and the second shell as the thickness of the primary insulation wall 3 becomes thicker, and moves toward the side of the hull 7 compared to the existing thinner primary insulation wall. In this case, the radius of curvature increases, and as the radius of curvature increases, the length L1 of the portion where the secondary protective wall 4 and the secondary insulation wall 5 are not glued (secondaryBarrier scab part not glued) also increases. This means that the flexibility of the secondary protective wall 4 in the right-angle corner structure increases, whereby the secondary protective wall 4 in the right-angle corner structure easily absorbs deformation of the peripheral portion, such as deformation of the hull, and low-temperature stress is also reduced. For example, the length L1 of the unbonded portion can be 100 mm to 200 mm.

[0180] Reference Figure 26 The secondary protective wall 4 in the obtuse corner structure becomes thicker than the first shell and the second shell as the thickness of the primary insulation wall 3 becomes thicker, and the curvature radius accounts for more than 15% of the thickness of the primary insulation wall 3, for example, 15% to 35%.

[0181] In addition, the secondary protective wall 4 in the obtuse corner structure becomes thicker than the first shell and the second shell as the thickness of the primary insulation wall 3 becomes thicker, and moves toward the side of the hull 7 and increases the radius of curvature compared to the existing thinner primary insulation wall. In this case, as the radius of curvature of the secondary protective wall 4 increases, the length L2 of the portion where the secondary protective wall 4 and the secondary insulation wall 5 are not glued (secondary Barrier scab part not glued) also increases. In the obtuse corner structure, this means that the flexibility of the secondary protective wall 4 increases, whereby the secondary protective wall 4 in the obtuse corner structure easily absorbs deformation of the peripheral portion, such as deformation of the hull, and low-temperature stress is also reduced. For example, in the present embodiment, the length L2 of the portion where the secondary protective wall 4 and the secondary insulation wall 5 are not glued can be 50 mm to 100 mm, preferably more than 50 mm and less than 100 mm.

[0182] The stress change values ​​of the secondary protective wall 4 according to the change in the length L2 of the non-bonded portion of the secondary protective wall 4 which increases as the thickness of the primary heat insulating wall 3 increases are shown in the following [Table 2] and Figure 40 .

[0183] [Table 2]

[0184] Length of unbonded portion (L2) Stress value (MPa) Comparative Example 4 50 34.47 Example 6 60 25.56 Example 7 70 19.71 Example 8 80 15.63 Example 9 90 12.84 Example 10 97.3 11.17

[0185] As shown in [Table 2] and Figure 40 As shown, it can be seen that as the length L2 of the non-bonded portion increases, the stress change value of the secondary protective wall 4 decreases. This means that as the length L2 of the non-bonded portion increases, the flexibility of the secondary protective wall 4 in the obtuse corner structure increases. In the case of the present invention, by forming the thickness of the primary insulation wall 3 to be the same as or similar to the thickness of the secondary insulation wall 5, a secondary protective wall 4 with a longer non-bonded portion length L2 can be formed, such as in Comparative Example 4 and Examples 6 to 10.

[0186] As described above, the secondary protective wall 4 of the present invention with right-angled and obtuse-angled corners can reduce the stress applied to existing secondary protective walls at low temperatures, compared to the right-angled and obtuse-angled corner structures of relatively thin primary insulation walls. Furthermore, since the unattached portion is larger, it is easier to absorb hull deformation.

[0187] Figure 27 This is a graph showing the thermal conductivity of the primary insulation material and the secondary insulation material of the liquefied gas storage tank according to the materials used.

[0188] In the liquefied gas storage tank 1 of the above-mentioned embodiment of the present invention, it is described that the primary insulation materials 32, 32a connecting the insulation wall 3a and the primary insulation wall 3 and the secondary insulation material 51 of the secondary insulation wall 5 are respectively formed of polyurethane foams of the same material, but polyurethane foams of different materials can be selectively used according to the situation.

[0189] Specifically, reinforced polyurethane foam (RPUF) is manufactured by mixing polyol, isocyanate, and a blowing agent, and HFC-245fa or CO2 can be used as the blowing agent. Compared with CO2, HFC-245fa may be relatively expensive.

[0190] In the present embodiment, the primary heat insulating materials 32, 32a are formed by reinforced polyurethane foam using CO2 as a foaming agent, and the secondary heat insulating material 51 is formed by reinforced polyurethane foam using HFC-245fa as a foaming agent.

[0191] Reference Figure 27 The thermal conductivity characteristics of the blowing agent HFC-245fa and the blowing agent CO2 are observed in the curve graph. Compared with the blowing agent CO2, the thermal conductivity value of the blowing agent HFC-245fa is lower at room temperature, but the thermal conductivity value becomes the same or similar as the temperature drops to extremely low temperatures.

[0192] That is, the thermal conductivity values ​​of the blowing agent HFC-245fa and the blowing agent CO2 show the same or similar values ​​at temperatures below -80°C, while the thermal conductivity values ​​of the blowing agent HFC-245fa are lower than those of the blowing agent CO2 at temperatures above -80°C.

[0193] Therefore, in this embodiment, the relatively expensive foaming agent HFC-245fa is not used in both the primary thermal insulation material 32, 32a and the secondary thermal insulation material 51, and considering the economic aspect, the primary thermal insulation material 32, 32a relatively close to the extremely low temperature can be formed by reinforced polyurethane foam using CO2 as a foaming agent, and the secondary thermal insulation material 51 can be formed by reinforced polyurethane foam using HFC-245fa as a foaming agent.

[0194] Figure 28 FIG. 1 is a partial cross-sectional view of a liquefied gas storage tank according to a second embodiment of the present invention. Figure 29 It is a partial perspective view of a liquefied gas storage tank for explaining a second embodiment of the present invention.

[0195] like Figures 28 to 29 As shown, the liquefied gas storage tank 1 of the second embodiment of the present invention may include a primary protective wall 2 in contact with the liquefied gas inside, a primary insulation wall 3 and a connecting insulation wall 3a arranged on the outside of the primary protective wall 2, a secondary protective wall 4 arranged on the outside of the primary insulation wall 3 and the connecting insulation wall 3a, and a secondary insulation wall 5 arranged on the outside of the secondary protective wall 4 and fixed to the hull 7. Compared with the above-mentioned first embodiment, the structure of the connecting insulation wall 3a is different, and the other structures are the same or similar. Therefore, only the different parts will be described below to avoid repeated description.

[0196] In this embodiment, the structure of the connecting heat-insulating wall 3a may be different from that of the first embodiment.

[0197] Specifically, compared with the first embodiment, the connecting heat insulating wall 3 a may further include an auxiliary heat insulating board 33 .

[0198] That is, the connection heat-insulating wall 3 a may be formed into a structure in which the connection plywood 31 a , the connection heat-insulating material 32 a , and the auxiliary heat-insulating board 33 are stacked.

[0199] The auxiliary insulation board 33 can be 5 mm to 10 mm thick and made of plywood, high-density polyurethane foam (HDPUF), fiber reinforced plastic (FRP), or the like, thereby achieving the load distribution effect of the secondary protective wall 4. Alternatively, the auxiliary insulation board 33 can be composed of VIP (Vacuum Insulation Panel) or LDPUF, which have excellent thermal insulation properties, thereby compensating for the thermal insulation fragility of the portion connected to the thermal insulation wall 3a.

[0200] The thickness of the connecting insulation material 32a of the connecting insulation wall 3a and the primary insulation material 32 of the fixed insulation wall 3b constituting the unit element can be the same. However, in the case of the connecting insulation wall 3a, in addition to the main protective wall 41 of the secondary protective wall 4, the auxiliary protective wall 42 is stacked below it, and the auxiliary insulation board 33 is also included. Therefore, the thickness of the connecting insulation material 32a of the connecting insulation wall 3a can be 5 mm to 10 mm less than the primary insulation material 32 of the primary insulation wall 3, corresponding to the thickness of the auxiliary protective wall 42 and the thickness of the auxiliary insulation board 33.

[0201] Of course, the auxiliary insulation board 33 can be provided not only at the bottom of the connection insulation material 32a of the connection insulation wall 3a, but also at the bottom of the primary insulation material 32 of the primary insulation wall 3 constituting the unit element.

[0202] Figure 30 FIG. 1 is a partial cross-sectional view of a liquefied gas storage tank according to a third embodiment of the present invention. Figure 31 It is an enlarged view of the main part of the liquefied gas storage tank according to the third embodiment of the present invention.

[0203] like Figures 30 to 31 As shown, the liquefied gas storage tank 1 of the third embodiment of the present invention may include a primary protective wall 2 in contact with the liquefied gas inside, a primary insulation wall 3 and a connecting insulation wall 3a arranged on the outside of the primary protective wall 2, a secondary protective wall 4 arranged on the outside of the primary insulation wall 3 and the connecting insulation wall 3a, a secondary insulation wall 5 arranged on the outside of the secondary protective wall 4 and fixed to the hull 7, a leveling member 8 arranged between the secondary insulation wall 5 and the hull 7, and a fixing member 9 for fixing the secondary insulation wall 5 to the hull 7. Compared with the above-mentioned first embodiment, the leveling member 8 and the fixing member 9 are different, and the other structures are the same or similar. Therefore, the following will only describe the leveling member 8 and the fixing member 9 as components different from the first embodiment and the parts changed thereby to avoid repeated description.

[0204] A leveling member 8 may be provided between the secondary insulation wall 5 and the hull 7 .

[0205] The leveling member 8 can adjust the level of the deformed portion of the hull 7 and is a non-laminated elastic insulation material that can improve the thermal insulation performance of the tank and support the secondary insulation wall 5, and can be EPS (Expanded Polystyrene) or the like.

[0206] In this leveling member 8, the top surface close to the secondary insulation wall 5 due to elastic force is flat, and the bottom surface close to the hull 7 can have a curved surface corresponding to the deformation of the hull 7. For example, the deformation of the hull 7 may occur when welding between the blocks of the hull 7.

[0207] That is, even if leveling member 8 does not use existing adhesive and leveling wedge, also can adjust the level of the deformation position of hull. Here, certainly can selectively use leveling wedge.

[0208] In this embodiment, by applying the leveling member 8 as described above, instead of applying adhesive in various forms according to the size of the existing gap, construction can be carried out in a single size, and no adhesive curing time is required, thereby shortening the working time and improving the thermal insulation capacity by applying thermal insulation materials.

[0209] The fixing member 9 may be composed of a cleat structure including a protrusion 91 and a stud bolt 92 to enable fixing the secondary insulation wall 5 to the hull 7 .

[0210] The protrusions 91 may be provided to protrude outward from lower portions of both side surfaces of the unit panels of the secondary insulation wall 5 and may be formed of plywood.

[0211] One side of the protrusion 91 can be fixedly placed on the side of the secondary plywood 52 of the secondary insulation wall 5 and a part of the side of the secondary insulation material 51 from the secondary plywood 52 to a predetermined height, and its bottom surface is at the same level as the bottom surface of the secondary plywood 52.

[0212] The width of the protrusion 91 may be such that the stud bolts 92 can be inserted between the protrusions 91 facing each other when a plurality of unit panels constituting the secondary heat-insulating wall 5 are arranged.

[0213] The stud bolts 92 may be fixed to the hull 7 .

[0214] The stud bolts 92 may be fixed to the hull 7 so as to correspond to spaces between adjacent unit panels of the secondary insulation wall 5 when a plurality of unit panels constituting the secondary insulation wall 5 are arranged.

[0215] The stud bolts 92 can be located between two opposing protrusions 91 provided on the side surfaces of adjacent unit panels of the secondary insulation wall 5 , and the secondary insulation wall 5 can be fixed to the hull 7 by tightening the stud bolts 92 .

[0216] As described above, in this embodiment, in the total thickness of the primary insulation wall 3 including the connecting insulation wall 3a and the secondary insulation wall 5, by making the thickness of the primary insulation wall 3, 3a the same as or similar to that of the secondary insulation wall 5, not only can the mechanical strength of the secondary insulation wall 5 be maintained at a predetermined level, but also the low temperature burden and shaking burden of the secondary protective wall 4 can be reduced, thereby preventing damage to the secondary protective wall 4.

[0217] In addition, in this embodiment, by providing an auxiliary insulation board 33 on the bottom surface of the connecting insulation wall 3a provided in the space between adjacent primary insulation walls 3 constituting the unit element, the insulation performance of the connecting portion of the adjacent secondary insulation walls 5 constituting the unit element can be further improved.

[0218] In addition, this embodiment can improve the thermal insulation performance by improving the structure of the secondary protective wall 4.

[0219] In addition, in this embodiment, by using unbonded elastic insulation material as the leveling member 8 of the secondary insulation wall 5 between the secondary insulation wall 5 and the hull 7, the level of the deformed portion of the hull 7 can be adjusted even without using existing adhesives and leveling wedges, and the insulation performance of the tank can be improved.

[0220] In addition, in this embodiment, adjacent unit panels of the secondary insulation wall 5 are fixed by utilizing a clamping (cleat) structure method of a protrusion 91 protruding outward from the lower part of the side surface of the unit panel of the secondary insulation wall 5 and a stud bolt 92 fixed to the hull 7. This can reduce the number of labors compared to a method of drilling holes in the secondary insulation wall 5 and fixing the unit panels with stud bolts.

[0221] The present invention is not limited to the above-described embodiments, and another embodiment may include a combination of the above-described embodiments or a combination of at least one of the above-described embodiments and a known technique. For example, Figures 28 to 29 The embodiment can be used with Figures 4 to 27 In addition, for example, Figures 30 to 31 The embodiment can be used with Figure 1 and Figure 2 Thermal insulation system or Figure 28 and Figure 29 Thermal insulation system combination.

[0222] The following will be Figures 32 to 39 The shape of the primary protective wall of the liquefied gas storage tank described above will be described in detail.

[0223] Figure 32 FIG. 1 is a diagram for explaining another embodiment of the primary protective wall of the liquefied gas storage tank according to the first, second, and third embodiments of the present invention. Figure 33 It is a diagram for explaining the shape of the primary protective wall.

[0224] like Figures 32 to 33 As shown, with reference Figure 3 Compared with the primary protective wall 2 having two types of curvature radii R1 and R2 described above, the cross-sectional shapes of the primary protective wall 2 of the liquefied gas storage tank 1 of the first, second and third embodiments of the present invention are different, which will be described in detail below.

[0225] Reference Figure 32 The primary protective wall 2 may be composed of a plurality of flat surfaces 21 in contact with the top surface of the primary heat-insulating wall 3 and a plurality of curved surfaces 22 for alleviating shrinkage or expansion stress caused by temperature.

[0226] The curved surface portion 22 of this embodiment has a cross-sectional shape in which the ratio W / H of the width W between adjacent planar portions 21 to the height H from the planar portion 21 to the upper end of the curved surface portion 22 is in the range of 2.0 to 3.0 (2.0≤W / H≤3.0), thereby minimizing the burden of thermal stress caused by low temperature and pressure stress caused by shaking.

[0227] At this time, the width W of the curved portion 22 can be 50mm to 105mm, preferably 65mm to 93mm, more preferably 70mm to 80mm, and the height H of the curved portion 22 can be 30mm to 50mm, preferably 30mm to 45mm, more preferably 33mm to 40mm.

[0228] Such multiple curved surface portions 22 can be formed to intersect in the horizontal and vertical directions, and the horizontal curved surface portions 22 and the vertical curved surface portions 22 can be the same size. That is, the horizontal and vertical curved surface portions 22 in the entire primary protective wall 2 are the same size, so the primary protective wall can be easily manufactured.

[0229] In addition, the intervals between adjacent curved surface portions 22 in the plurality of curved surface portions 22 may be wider than those in the prior art (hereinafter, the prior art may be used as the term "comparison object"), for example, an interval of 350 mm to 400 mm may be achieved. Here, the intervals between the curved surface portions 22 may correspond to the intervals between the uppermost end points of the curved surface portions 22. In addition, as Figure 35 As shown, the dimensions of the plurality of unit protective walls 2a constituting the primary protective wall 2 can be formed to be larger than the 3:1 ratio of the known technology, for example, the dimensions can be formed to be 3,150 mm to 3,600 mm in length and 1,050 mm to 1,200 mm in width.

[0230] As described above, in the primary protective wall 2 of the present embodiment, increasing the intervals between the curved surface portions 22 and increasing the size of the unit protective wall 2a can be achieved by making the cross-sectional shape of the curved surface portion 22 such that the ratio W / H of the width W between the adjacent flat surface portions 21 and the height H from the flat surface portion 21 to the upper end of the curved surface portion 22 is within the range of 2.0 to 3.0 (2.0≤W / H≤3.0). Figures 36 to 39 This will be explained later for further understanding.

[0231] On the other hand, Figure 2 As shown, the transverse curved portion and the longitudinal curved portion may be formed to intersect. In this case, the transverse curved portion and the longitudinal curved portion may be formed to have the same height and width.

[0232] In addition, the curved surface portion 22 may be formed into a cross-sectional shape having a first curved surface portion 22 a , a second curved surface portion 22 b , and a third curved surface portion 22 c having different curvature radii.

[0233] The first curved surface portions 22a are connected to the adjacent flat surface portions 21 to form a pair, and have a first curvature radius r1. The first curvature radius r1 may be 4 mm to 12 mm.

[0234] Each of the pair of first curved surface portions 22 a may have a curved surface shape having a first curvature radius r1 between a first connection point P1 connected to the planar portion 21 and a second connection point P2 connected to each of the pair of third curved surface portions 22 c.

[0235] Here, the first connection point P1 may be located at the same position as the point where the lowest curved portion of the first circle A1 having the first curvature radius r1 extending from the first curvature center C1 on the accommodating space side intersects the longitudinal centerline of the first circle A1. The first curvature center C1 of the first curved surface portion 22a may be located above the imaginary plane formed by the planar portion 21.

[0236] The second connection point P2 may be located on a curved portion of the first circle A1 within an angle of 30 degrees downward from a point where the curved portion of the first circle A1 intersects a transverse centerline of the first circle A1 .

[0237] The second curved surface portion 22b forms the upper portion of the curved surface portion 22 and has at least a second curvature radius r2 that is larger than the first curvature radius r1. Here, the second curvature radius r2 may be 7 mm to 15 mm.

[0238] The second curved surface portion 22b may have a curved surface shape having a second curvature radius r2 between a third connection point P3 connected to one of the pair of third curved surface portions 22c and a fourth connection point P4 connected to the other third curved surface portion 22c.

[0239] Here, the third connection point P3 and the fourth connection point P4 can each be located at a predetermined angle, for example, between 3 and 10 degrees, from the longitudinal centerline of the second circle A2 having the second radius of curvature r2 and extending from the second center of curvature C2 on the opposite side of the accommodation space. The second center of curvature C2 of the second curved surface portion 22b can be located above the imaginary plane formed by the planar portion 21.

[0240] The third curved surface portion 22c is formed as a pair connecting the pair of first curved surface portions 22a and the second curved surface portion 22b, and has at least a third curvature radius r3 larger than the second curvature radius r2. Here, the third curvature radius r3 may be 25 mm to 45 mm.

[0241] That is, the first, second, and third radii of curvature r1, r2, and r3 of the first, second, and third curved surfaces 22a, 22b, and 22c, respectively, may satisfy the following relationship: "first radius of curvature r1 ≤ second radius of curvature r2 < third radius of curvature r3." In this embodiment, the third radius of curvature r3 may be greater than the sum of the second radius of curvature r2 and the first radius of curvature r1.

[0242] Any one of the pair of third curved surface portions 22c may be a curved surface shape having a third curvature radius r3 between a second connection point P2 connected to any one of the pair of first curved surface portions 22a and a third connection point P3 connected to one side of the second curved surface portion 22b.

[0243] Any one of the third curved surface portions 22 c may be provided on a curved portion of a third circle A3 having a third curvature radius r3 from a third curvature center C3 on the opposite side to the accommodation space.

[0244] In addition, the other third curved surface portion 22c of the pair of third curved surface portions 22c can be a curved surface shape having a third curvature radius r3 between the second connection point P2 connected to the other first curved surface portion 22a of the pair of first curved surface portions 22a and the fourth connection point P4 connected to the other side of the second curved surface portion 22b.

[0245] Another third curved surface portion 22c may be provided on a curved portion of a fourth circle A4 having a third curvature radius r3 from a fourth curvature center C4 on the opposite side of the accommodation space.

[0246] In the above, when observing the respective positions of the second connection point P2, the third connection point P3, and the fourth connection point P4 with a pair of third curved surface portions 22c as a reference, the second connection point P2 can be a point where the curve of the first circle A1 of any one of the first curved surface portions 22a in a pair of first curved surface portions 22a intersects with the curve of the third circle, or a point where the curve of the first circle A1 of the other first curved surface portion 22a in a pair of first curved surface portions 22a intersects with the curve of the fourth circle A4.

[0247] In addition, the third connection point P3 may be a point where the curve of the second circle A2 intersects the curve of the third circle A3. The third connection point P3 may be the same position as the point where the uppermost curve portion of the third circle A3 intersects the longitudinal center line of the third circle A3.

[0248] The fourth connection point P4 may be a point where the curve of the second circle A2 intersects the curve of the fourth circle A4. The fourth connection point P4 may be the same position as a point where the uppermost curve portion of the fourth circle A4 intersects the longitudinal centerline of the fourth circle A4.

[0249] The pair of third curved surface portions 22c described above can have the same third radius of curvature r3, and the third center of curvature C3 of one third curved surface portion 22c and the fourth center of curvature C4 of the other third curved surface portion 22c can be located at offset positions in the horizontal direction. Furthermore, in this embodiment, the third and fourth centers of curvature C3 and C4 are located inside the curved surface portion 22. Therefore, when an imaginary line connects adjacent planar portions 21, the third and fourth centers of curvature C3 and C4 are located inside the curved surface portion 22 above the imaginary line. In other words, the third and fourth centers of curvature C3 and C4 of the third curved surface portion 22c can be located above the imaginary plane formed by the planar portions 21.

[0250] As described above, all the centers of curvature C1 , C2 , C3 , and C4 of the curved surface portion 22 of the present embodiment may be located above the virtual plane formed by the planar portion 21 .

[0251] Figure 34 (a) and (b) are diagrams for explaining a protruding structure provided on a primary protective wall.

[0252] like Figure 34 As shown in (a) and (b) of FIG. 2 , the primary protective wall 2 of this embodiment may further include a protruding structure 24 on the peripheral planar portion 21 of the intersection of the transverse curved portion 22 and the longitudinal curved portion 22. For example, the protruding structure 24 may be provided within a predetermined distance from the intersection. Furthermore, the predetermined distance may correspond to, but is not limited to, 1 / 3 of the distance between intersections located on the same line.

[0253] The size of the protruding structure 24 is smaller than the transverse curved portion 22 and the longitudinal curved portion 22, and can be formed as follows: Figure 34 (a) shown as a convex circle or as Figure 34 Various shapes such as the arc shown in (b).

[0254] Such a protruding structure 24 can further minimize the pressure stress burden caused by shaking at the intersection of the lateral curved surface portion 22 and the longitudinal curved surface portion 22 .

[0255] Figure 35 This is a perspective view of a unit protective wall for explaining a primary protective wall.

[0256] The primary protective wall 2 of this embodiment can make the interval between adjacent curved surface portions 22 reach 350mm to 400mm, which is wider than the interval in the prior art. Figure 35 As shown, the dimensions of the multiple unit protective walls 2a that comprise the primary protective wall 2 can each be formed to a larger ratio than the conventional 3:1 ratio. For example, the dimensions can be 3,150 mm to 3,600 mm in length and 1,050 mm to 1,200 mm in width. In this embodiment, by increasing the dimensions of the unit protective walls 2a, the number of unit protective walls 2a required is reduced compared to the conventional technology, thereby reducing the number of labor required to install the primary protective wall 2.

[0257] In addition, Figure 35 In the unit protective wall 2a shown, the width between the uppermost ends of the curved surface 22 may correspond to 350 mm to 400 mm. Figure 32 The uppermost end of the second curved surface portion 22b is located at the uppermost end of the curved surface portion. This increases the width between the uppermost ends of the curved surface portions compared to a comparative unit protective wall (known unit protective wall), making production and installation easier than with the comparative unit protective wall. Furthermore, the width and height of the transverse curved surface portion 22 and the longitudinal curved surface portion 22 of the unit protective wall 2a of the present embodiment are identical, thereby reducing manufacturing costs compared to the comparative unit protective wall.

[0258] Figure 36 Graph showing the distribution of the paradigm equivalent stress value (thermal stress and compressive stress) according to the ratio W / H of the curved portion width to the curved portion height of the primary protective wall. Figure 37 Graph showing the range of the curvature radius 'r3-r2-r1' value of the ratio W / H of the curved portion width to the curved portion height of the primary protective wall obtained through the cross-sectional shape optimization simulation of the primary protective wall.

[0259] In the primary protective wall 2 of the present embodiment, as described above, the cross-sectional shape of the curved surface portion 22 is formed so that the ratio W / H of the width W between adjacent flat surfaces 21 to the height H from the flat surface portion 21 to the upper end of the curved surface portion 22 is within the range of 2.0 to 3.0 (2.0≤W / H≤3.0), and based on this, the first curvature radius r1, the second curvature radius r2, and the third curvature radius r3 of each of the first curved surface portion 22a, the second curved surface portion 22b, and the third curved surface portion 22c are different, and the size of the third curvature radius r3 is larger than the sum of the sizes of the second curvature radius r2 and the first curvature radius r1, so as to minimize the burden of thermal stress caused by low temperature and pressure stress caused by shaking. The cross-sectional shape of the curved surface portion 22 is achieved by the following Figures 36 to 39 The experimental data shown were obtained, and based on this, a comparison was made with a known primary protection wall.

[0260] Here, unlike the primary protective wall 2 of the present invention, the primary protective wall of the comparative object has large corrugations (Large corrugation) and small corrugations (Small corrugation).

[0261] like Figure 36 As shown, when considering both thermal and compressive stresses in the paradigm equivalent stress (Von Mises Stress) based on the ratio W / H of the width W of the curved portion 22 of the primary protective wall 2 to its height H, the present invention's primary protective wall 2 has concentrated thermal and compressive stresses when its width-to-height ratio W / H is in the range of 2.0 to 3.0. In contrast, in the case of the comparative primary protective wall, where the width-to-height ratio W / H of each of the large and small corrugations is approximately 1.5 or less, the thermal and compressive stresses differ significantly. This shows that the present invention, with a width-to-height ratio W / H in the range of 2.0 to 3.0, exhibits improved thermal and compressive stresses compared to the comparative wall, which has a width-to-height ratio W / H of 1.5 or less.

[0262] Specifically, in the present invention, the thermal stress increases in direct proportion to the ratio W / H of the width to the height of the primary protective wall 2, and the compressive stress decreases in inverse proportion to the ratio W / H of the width to the height of the primary protective wall 2. When the ratio W / H of the width to the height is in the range of 2.0 to 3.0, the distribution of the thermal stress and the compressive stress is concentrated. At this time, it can be seen that the thermal stress and the compressive stress of the primary protective wall 2 of the present invention are between 110MPa and 210MPa.

[0263] In contrast, in the comparison objects, the maximum thermal stress of the large corrugation with a width to height ratio W / H of the primary protective wall of less than about 1.5 is about 73 MPa, and the maximum compressive stress is about 310 MPa, and the maximum thermal stress and maximum compressive stress of the small corrugation with a width to height ratio W / H of the primary protective wall of less than 1.5 are about 150 MPa.

[0264] In addition, if Figure 37 As shown, in the present invention, the ratio W / H of the width to the height of the primary protective wall 2 is in the range of 2.0 to 3.0, the curvature radius 'r3-r2-r1' value is in the range of 10mm to 30mm, and preferably in the range of 15mm to 27mm to obtain the optimized result of the cross-sectional shape of the primary protective wall 2.

[0265] On the contrary, in the comparison object, when the ratio W / H of the width to height of the large corrugations and small corrugations of the primary protective wall is approximately 1.5 or less, the curvature radius 'r3-r2-r1' of the large corrugations is approximately 48 mm, and the curvature radius 'r3-r2-r1' of the small corrugations is approximately 21 mm. It can be seen that the cross-sectional shape of the primary protective wall of the comparison object is different from that of the primary protective wall 2 of the present invention.

[0266] On the other hand, the yield stress of the primary protective wall 2 of the present invention is 170 MPa at room temperature and about 220 MPa at a low temperature of -170 degrees. Since it is manufactured at room temperature, it needs to be within the range of 170 MPa to 180 MPa.

[0267] Therefore, the primary protective wall 2 of this embodiment preferably has a width to height ratio W / H in the range of 2.0 to 3.0 and a shape satisfying a value of 'r3-r2-r1' of 170 MPa or less in the range of 15 mm to 27 mm, so that the thermal stress (y = 72.446e 0.3522x ) or compressive stress (y=255.95e -0.233x ) does not exceed about 170 MPa and is distinguishable from the comparative objects.

[0268] The following [Table 3] is a graph showing Figure 36 The distribution of thermal stress and compressive stress in the paradigm equivalent stress (Von Mises Stress) according to the ratio W / H of the width W of the curved portion 22 of the primary protective wall 2 to the height H of the curved portion 22 is shown.

[0269] [Table 3]

[0270]

[0271]

[0272] Figure 38(a), (b) and (c) are graphs showing the results of structural analysis of the sloshing pressure values ​​when the fluid flows into the transverse and longitudinal curved portions of the primary protective wall of the present invention and the primary protective wall of the comparison object. At this time, the velocity of the fluid flowing into the transverse and longitudinal curved portions is 5 m / s. Figure 38 (a) is a structural analysis of the sloshing pressure value when the fluid flows into the horizontal or vertical curved surface 22 of the primary protective wall 2 of the present invention. The maximum sloshing pressure value of 305.29 Pa was obtained at the first point P1 of the curved surface 22. In addition, Figure 38 (b) shows the structural analysis of the sloshing pressure when the fluid flows into the transverse curved portion (large ripples) of the primary protective wall of the comparison object. The maximum sloshing pressure of 10,515 Pa was obtained at the second point P2 of the transverse curved portion (large ripples). Figure 38 (c) is a structural analysis of the sloshing pressure value when the fluid flows into the longitudinal curved portion (small ripples) in the primary protective wall of the comparison object. The maximum sloshing pressure value of 3577.6 Pa was obtained at the third point P3 of the longitudinal curved portion (small ripples).

[0273] Here, as described above, the primary protective wall 2 of the present invention has a cross-sectional shape in which the transverse and longitudinal curved portions 22 have the same size and height, but the primary protective wall of the comparison object is crossed by a transverse curved portion (large corrugation) having a larger size and a longitudinal curved portion (small corrugation) having a conventional curved portion cross-sectional shape. Therefore, it can be seen that compared with the primary protective wall of the comparison object, the shaking pressure value of the primary protective wall 2 of the present invention is excellent in the transverse curved portion and very excellent in the longitudinal curved portion.

[0274] Figure 39 Figures (a) and (b) show the deformation of the primary protective wall of the present invention and the primary protective wall of the comparative example when a uniformly distributed load is applied (showing the structural analysis results based on the sloshing impact pressure). In this case, a plastic-elastic structural analysis was performed with an impact pressure of 10 bar applied to the entire primary protective wall. This was done to understand the dynamic behavior and plastic deformation of the primary protective wall's cross-sectional shape. Figure 39 The inclination ratio of the cross-sectional shape of the curved portion 22 of the primary protective wall 2 of the present invention shown in (a) is Figure 39 The curved portion (large corrugations) of the comparative primary protective wall shown in (b) has a gentle cross-sectional shape, indicating that the primary protective wall 2 of the present invention exhibits almost no deformation, while the comparative primary protective wall exhibits significant deformation. As described above, the comparative primary protective wall requires additional work such as filling the lower end of the curved portion with a retaining material such as a wooden wedge or metal to prevent deformation.

[0275] The present invention has been described in detail above through specific embodiments, but this is only for the purpose of illustrating the present invention in detail. The present invention is not limited thereto, and it is obvious that those skilled in the art can make modifications or improvements within the technical concept of the present invention.

[0276] Simple modifications or variations of the present invention all fall within the scope of the present invention, and the specific protection scope of the present invention can be clarified by the scope of the appended claims.

[0277] Reference numerals

[0278] 1: Liquefied gas storage tank 2: Primary protective wall

[0279] 2a: Unit protection wall 21: Flat surface

[0280] 22: curved surface portion 22a: first curved surface portion

[0281] 22b: Second curved portion 22c: Third curved portion

[0282] 23: Boundary 24: Protruding structure

[0283] 3: Primary insulation wall 3b: Fixed insulation wall

[0284] 31: Primary plywood 32: Primary insulation material

[0285] 3a: Connecting insulation wall 31a: Connecting plywood

[0286] 32a: Connecting insulation material 33: Auxiliary insulation board

[0287] 4: Secondary protective wall 41: Primary protective wall

[0288] 42: Auxiliary protective wall GAC: Glass-aramid fabric

[0289] AF: Aluminum foil GC: Glass fabric

[0290] BC: Basalt Fabric 5: Secondary Insulation Wall

[0291] 51: Secondary insulation material 52: Secondary plywood

[0292] 6: Adhesive 7: Hull

[0293] 8: Leveling component 9: Fixing component

[0294] 91: protrusion 92: stud bolt

[0295] A1: First circle A2: Second circle

[0296] A3: third circle A4: fourth circle

[0297] C1: First center of curvature C2: Second center of curvature

[0298] C3: Third center of curvature C4: Fourth center of curvature

[0299] P1: First connection point P2: Second connection point

[0300] P3: Third connection point P4: Fourth connection point

[0301] r1: first radius of curvature r2: second radius of curvature

[0302] r3: third radius of curvature

Claims

1. A liquefied gas storage tank for storing extremely low-temperature substances, characterized in that: include: The primary protective wall forms a holding space for extremely low-temperature substances and is made of metal material; A primary heat-insulating wall is formed by sequentially arranging primary plywood and primary heat-insulating material on the outer side of the primary protective wall; a secondary protective wall, arranged outside the primary insulation wall; and The secondary insulation wall is formed by sequentially stacking secondary insulation materials and secondary plywood on the outside of the secondary protective wall. The secondary protective wall is composed of a main protective wall provided on the upper portion of each secondary heat insulating wall constituting a unit element and an auxiliary protective wall connecting adjacent main protective walls to each other. The secondary protective wall is made of a mixed material of metal and non-metal. The primary insulation wall has a thickness of 66% to 166% of the secondary insulation wall to reduce a low temperature burden.

2. The liquefied gas storage tank according to claim 1, characterized in that: The primary insulation wall includes a connecting insulation wall, which is arranged in a space portion between adjacent fixed insulation walls when the unit elements composed of the secondary insulation wall, the secondary protective wall, and the fixed insulation wall which is part of the primary insulation wall are stacked adjacent to each other.

3. The liquefied gas storage tank according to claim 2, characterized in that: The connecting insulation wall has a thickness of 67% to 167% of the secondary insulation wall.

4. The liquefied gas storage tank according to claim 1, characterized in that: In the liquefied gas storage tank, the secondary protective wall is disposed in a central region corresponding to a range of 40% to 60% of the total thickness based on the thickness direction.

5. The liquefied gas storage tank according to claim 1, characterized in that: The primary heat-insulating material has a thickness of 90% to 110% of that of the secondary heat-insulating material.

6. The liquefied gas storage tank according to claim 1, characterized in that: The primary protective wall is composed of a flat surface portion in contact with the top surface of the primary heat insulating wall, a curved surface portion having a first curvature radius, and a boundary portion formed in a corrugated shape having a second curvature radius between the flat surface portion and the curved surface portion. The first radius of curvature and the second radius of curvature are different.

7. The liquefied gas storage tank according to claim 6, characterized in that: The horizontal and vertical pleats of the pleated shape are of equal size.

8. The liquefied gas storage tank according to claim 1, characterized in that: The secondary protective wall is formed of a material having a laminated structure of a first member / aluminum foil / a second member. At least one of the first member and the second member is glass fabric, glass-aramid fabric, basalt fabric, or glass fabric / aluminum foil / glass fabric.

9. The liquefied gas storage tank according to claim 1, characterized in that: The primary insulation material is formed of reinforced polyurethane foam using CO2 as a foaming agent, The secondary thermal insulation material is formed of reinforced polyurethane foam using HFC-245fa as a blowing agent.

10. The liquefied gas storage tank according to claim 1, characterized in that: Also includes right-angle corner structures, The curvature radius of the secondary protective wall formed at the right-angle corner structure is 25% to 50% of the thickness of the primary insulation wall.

11. The liquefied gas storage tank according to claim 1, characterized in that: Also includes obtuse corner structures, The curvature radius of the secondary protective wall formed at the obtuse corner structure is 15% to 35% of the thickness of the primary insulation wall.

12. A liquefied gas storage tank for storing extremely low temperature substances, characterized in that: include: The primary protective wall forms a holding space for extremely low-temperature substances and is made of metal material; A primary heat-insulating wall is formed by sequentially arranging primary plywood and primary heat-insulating material on the outer side of the primary protective wall; a secondary protective wall, arranged outside the primary insulation wall; and The secondary insulation wall is formed by sequentially arranging secondary insulation materials and secondary plywood on the outer side of the secondary protective wall. The secondary protective wall is composed of a main protective wall provided on the upper portion of each secondary heat-insulating wall constituting a unit element and an auxiliary protective wall connecting adjacent main protective walls to each other. The auxiliary protective wall has an unbonded portion, and an upper limit value of low-temperature stress of the auxiliary protective wall caused by the cryogenic substance is 50 MPa or less.

13. A ship, characterized in that: A liquefied gas storage tank comprising the liquefied gas storage tank according to any one of claims 1 to 12.

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