Liquefied gas storage tank and vessel comprising same

Abstract

The present invention relates to a liquefied gas storage tank and a ship including the same, and the liquefied gas storage tank of the present invention is a liquefied gas storage tank storing a cryogenic substance, characterized by comprising: a primary protection wall forming a storage space storing the cryogenic substance, made of a metal material; a primary insulation wall in which a primary plywood and a primary insulation material are sequentially disposed outside the primary protection wall; a secondary protection wall disposed outside the primary insulation wall; and a secondary insulation wall in which a secondary insulation material and a secondary plywood are sequentially stacked and disposed outside the secondary protection wall, the secondary protection wall being composed of a main protection wall provided at an upper portion of each of the secondary insulation walls constituting unit elements and an auxiliary protection wall connecting the adjacent main protection walls to each other, the secondary protection wall being made of a mixed material of a metal and a non-metal, the primary insulation wall having a thickness of 66% to 166% of the secondary insulation wall to reduce a low-temperature burden.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquefied gas storage tank and a ship including the same. BACKGROUND

[0002] In recent years, with the development of technology, liquefied natural gas (LNG), liquefied petroleum gas (LPG), and the like are widely used instead of gasoline or diesel.

[0003] In addition, in a LNG carrier, a LNG RV (Regasification Vessel), a LNG FPSO (Floating, Production, Storage and Offloading), a LNG FSRU (Floating Storage and Regasification Unit), and the like, which transport or store LNG and the like on the sea, a storage tank (referred to as a so-called "cargo hold") for storing LNG in a super-cold liquid state is provided.

[0004] In addition, a liquefied gas storage tank can generate boil-off gas (BOG) due to heat intrusion from the outside, and reducing the boil-off rate (BOR) as a gasification rate of the boil-off gas through a thermal insulation design is a core technology of the liquefied gas storage tank design. In addition, since the liquefied gas storage tank is exposed to various loads such as sloshing, it is also essential to secure the mechanical strength of the thermal insulation panel.

[0005] In this regard, the thickness range of the primary insulation wall and the secondary insulation wall can be related to the mechanical strength of the liquefied gas storage tank. Thus, research is actively being conducted to eliminate the low-temperature burden of the secondary protection wall and also to maintain the mechanical strength of the secondary insulation wall.

[0006] Meanwhile, since the primary protection wall is directly exposed to a super-cold substance, in order to minimize the thermal stress caused by the super-cold and the pressure stress caused by sloshing, research is actively being conducted to optimize the cross-sectional shape of the curved portion. SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can minimize 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.

[0009] 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 protective wall at a predetermined level and reduce the low temperature burden and the sloshing burden of the secondary protective wall by making the thickness of the primary protective wall the same as or similar to that of the secondary protective wall in the total thickness of the thermal insulation 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 reduce the low temperature burden and the sloshing burden of the secondary protective wall within a range in which brittle failure of the ship body does not occur.

[0011] In addition, an object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can improve the thermal insulation performance by improving the constitution of the secondary protective wall.

[0012] In addition, an object of the present invention is to provide a liquefied gas storage tank and a ship including the same, which can improve the thermal insulation performance and reduce the number of man-hours by improving the constitution of the fixing member for fixing the secondary protective wall to the ship body.

[0013] Technical solution to solve the problem

[0014] The liquefied gas storage tank according to one embodiment of the present invention is a liquefied gas storage tank for storing a cryogenic substance, and is characterized by including: a primary protective wall formed to define a storage space for storing the cryogenic substance, made of a metal material; a primary thermal insulation wall in which a primary plywood and a primary thermal insulation material are sequentially disposed outside the primary protective wall; a secondary protective wall disposed outside the primary thermal insulation wall; and a secondary thermal insulation wall in which a secondary thermal insulation material and a secondary plywood are sequentially laminated outside the secondary protective wall, the secondary protective wall being constituted by a main protective wall provided at an upper portion of each of the secondary thermal insulation walls constituting unit elements and an auxiliary protective wall for connecting the adjacent main protective walls to each other, the secondary protective wall being made of a mixed material of a metal and a non-metal, the primary thermal insulation wall having a thickness of 66% to 166% of that of the secondary thermal insulation wall to reduce a low temperature burden.

[0015] Specifically, the primary insulation wall can include a connecting insulation wall disposed in a space portion between adjacent fixed insulation walls in a state where unit elements composed of the secondary insulation wall, the secondary protection wall, and the fixed insulation wall as a part of the primary insulation wall are arranged adjacent to each other.

[0016] Specifically, the connecting insulation wall can have a thickness of 67% to 167% of the secondary insulation wall.

[0017] Specifically, the secondary protection wall can be disposed in a central region corresponding to a range of 40% to 60% of the total thickness in the thickness direction in the liquefied gas storage tank.

[0018] Specifically, the primary insulation material can have a thickness of 90% to 110% of the secondary insulation material.

[0019] Specifically, the primary protection wall is composed of a flat portion in contact with a top surface of the primary insulation wall, a curved portion having a first radius of curvature, and a boundary portion formed in a corrugated shape having a second radius of curvature between the flat portion and the curved portion, and the first radius of curvature and the second radius of curvature can be different.

[0020] Specifically, horizontal and vertical corrugation sizes of the corrugated shape can be the same.

[0021] Specifically, the secondary protection wall is formed of a material of a structure in which a first member / aluminum foil / second member are laminated, and at least one of the first member and the second member can be a glass fabric, a glass-aramid fabric, a basalt fabric, or a glass fabric / aluminum foil / glass fabric.

[0022] Specifically, the primary insulation material can be formed of reinforced polyurethane foam using CO2 as a blowing agent, and the secondary insulation material can be formed of reinforced polyurethane foam using HFC-245fa as a blowing agent.

[0023] Specifically, a right-angle corner structure is further included, and a radius of curvature of the secondary protection wall formed at the right-angle corner structure can be 25% to 50% of a thickness of the primary insulation wall.

[0024] Specifically, an obtuse-angle corner structure is further included, and a radius of curvature of the secondary protection wall formed at the obtuse-angle corner structure can be 15% to 35% of a thickness of the primary insulation wall.

[0025] The liquefied gas storage tank according to another aspect of the present application is a liquefied gas storage tank that stores an extremely low temperature substance, characterized by comprising: a primary protection wall that forms a storage space that stores the extremely low temperature substance and is made of a metal material; a primary thermal insulation wall that is provided outside the primary protection wall in order; a secondary protection wall that is provided outside the primary thermal insulation wall; and a secondary thermal insulation wall that is provided outside the secondary protection wall in order of a secondary thermal insulation material and a secondary plywood, the secondary protection wall being composed of a main protection wall that is provided at an upper portion of each of the secondary thermal insulation walls that constitute unit elements, and an auxiliary protection wall that connects adjacent main protection walls to each other, the auxiliary protection wall having a non-adhered portion, and an upper limit value of a low temperature stress of the auxiliary protection wall caused by the extremely low temperature substance being 50 MPa or less.

[0026] The liquefied gas storage tank according to still another aspect of the present application is composed of a primary protection wall that forms a storage space that stores an extremely low temperature substance and is made of a metal material, a primary thermal insulation wall that is provided outside the primary protection wall, a secondary protection wall that is provided outside the primary thermal insulation wall and is composed of a main protection wall and an auxiliary protection wall, and a secondary thermal insulation wall that is provided outside the secondary protection wall, characterized in that the primary protection wall is composed of a plurality of flat portions that are fixed to a top surface of the primary thermal insulation wall, and a curved portion that is formed between the plurality of flat portions toward the storage space side and includes a lateral curved portion and a longitudinal curved portion, the curved portion including: a pair of first curved portions that are connected to adjacent flat portions, respectively, and have a first radius of curvature r1; a second curved portion that forms an upper portion of the curved portion and has at least a second radius of curvature r2 that is larger than the first radius of curvature r1; and a pair of third curved portions that are connected to the pair of first curved portions and the second curved portion, respectively, and have at least a third radius of curvature r3 that is larger than the second radius of curvature r2, a first center of curvature of any one of the pair of third curved portions and a second center of curvature of the other third curved portion being located at positions that are offset in a horizontal direction on an inner side of the curved portion.

[0027] Specifically, the lateral curved portion and the longitudinal curved portion can be formed to intersect, and the height and the width of the lateral curved portion and the longitudinal curved portion can be the same.

[0028] Specifically, the third radius of curvature can be larger than a value obtained by adding the second radius of curvature and the first radius of curvature.

[0029] Specifically, a ratio W / H of the width W to the height H of the curved portion can be in a range of 2.0 to 3.0 (2.0 ≤ W / H ≤ 3.0), and can be determined based on thermal stress and pressure stress at low temperature of the primary containment wall.

[0030] Specifically, the pair of the first curved portions each have a curved shape having the first radius of curvature between a first connection point connected to the flat portion and a second connection point connected to the pair of the third curved portions, respectively, the first connection point has the same position as a point at which a curve of a first circle having the first radius of curvature from a center of curvature on the accommodation space side intersects a longitudinal center line of the first circle, and the second connection point can be located within a 30-degree angle downward from a point at which the curve of the first circle intersects a transverse center line of the first circle.

[0031] Specifically, the primary containment wall can further include a protruding structure protruding toward the accommodation space side from the flat portion within a predetermined distance from an intersection portion at which the transverse curved portion and the longitudinal curved portion intersect.

[0032] Specifically, the protruding structure can have a size smaller than the transverse curved portion and the longitudinal curved portion, and can be formed in a convex circular shape or an arc shape.

[0033] Specifically, the first and second centers of curvature of the pair of the third curved portions can be located at an upper portion than an imaginary plane formed by the flat portion.

[0034] A ship according to still another aspect of the present application includes the liquefied gas storage tank described above.

[0035] Effects of the Invention

[0036] The liquefied gas storage tank and the ship including the same according to the present application can minimize thermal stress caused by low temperature and pressure stress caused by sloshing by optimizing a cross-sectional shape of a curved portion of a primary containment wall.

[0037] In addition, the liquefied gas storage tank and the ship including the same according to the present application can configure a thickness of a primary insulation wall to be the same as or similar to a secondary insulation wall in a total thickness including the primary insulation wall and the secondary insulation wall, thereby not only maintaining a mechanical strength of the secondary insulation wall at a predetermined level but also reducing a low temperature burden and a sloshing burden of the secondary containment wall, so that damage to the secondary containment wall can be prevented.

[0038] Further, the liquefied gas storage tank and the ship including the same according to the present application can prevent the brittle failure of the ship body and reduce the low-temperature burden and the sway burden of the secondary protection wall by configuring the thickness of the primary insulation wall to be 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 connected by the connecting insulation wall.

[0039] Further, the liquefied gas storage tank and the ship including the same according to the present application can further improve the insulation performance at the connecting portion of the adjacent secondary insulation walls of the unit element by providing the auxiliary insulation plate at the bottom surface of the connecting insulation wall provided in the space between the adjacent primary insulation walls of the unit element.

[0040] Further, the liquefied gas storage tank and the ship including the same according to the present application can improve the insulation performance by improving the configuration of the secondary protection wall.

[0041] Further, the liquefied gas storage tank and the ship including the same according to the present application can adjust the level of the deformation portion of the ship body and improve the insulation performance of the tank by using the unattached elastic insulation material as the leveling member of the secondary insulation wall between the secondary insulation wall and the ship body, even without using the existing adhesive and leveling wedge.

[0042] Further, the liquefied gas storage tank and the ship including the same according to the present application can reduce the number of works by fixing the unit panel of the adjacent secondary insulation walls using the cleat structure in which the protrusion provided to protrude outward from the lower portion of the unit panel side surface of the secondary insulation wall and the double-headed bolt fixed to the ship body. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 FIG. 1 is a partial cross-sectional view of a liquefied gas storage tank for explaining a first embodiment of the present application.

[0044] Figure 2 FIG. 2 is a partial perspective view of the liquefied gas storage tank for explaining the first embodiment of the present application.

[0045] Figure 3 FIG. 3 is a view of a primary protection wall of the liquefied gas storage tank for explaining the first embodiment of the present application.

[0046] Figure 4 (a) and (b) of FIG. 4 are graphs showing the tension of the secondary protection wall according to the thickness variation of the primary insulation wall and the secondary insulation wall.

[0047] Figures 5 to 8 FIG. 5 is a graph showing the results of the structural analysis for deriving the thickness of the primary insulation wall and the secondary insulation wall of the liquefied gas storage tank by changing the thickness of the primary insulation wall and the secondary insulation wall of the first shell according to the first embodiment of the present application.

[0048] Figures 9 to 12 FIGS. 1 to 4 are graphs showing results of structural analysis for deriving thicknesses of a primary insulation wall and a secondary insulation wall of a liquefied gas storage tank according to a first embodiment of the present application, by changing thicknesses of the primary insulation wall and the secondary insulation wall of a second shell.

[0049] Figures 13 to 16 FIGS. 5 to 8 are graphs showing results of structural analysis for deriving thicknesses of a primary insulation wall and a secondary insulation wall of a liquefied gas storage tank according to the first embodiment of the present application, by changing thicknesses of the primary insulation wall and the secondary insulation wall of a third shell.

[0050] Figures 17 to 20 FIGS. 9 to 12 are graphs showing results of structural analysis for deriving thicknesses of a primary insulation wall and a secondary insulation wall of a liquefied gas storage tank according to the first embodiment of the present application, by changing thicknesses of the primary insulation wall and the secondary insulation wall of a fourth shell.

[0051] Figure 21 FIG. 13 is a graph showing low temperature stress of a secondary protection wall and brittle failure probability of a ship hull according to thicknesses of a primary insulation wall and a secondary insulation wall.

[0052] Figure 22 , Figure 23 and Figure 24 are graphs for explaining various configurations of a secondary protection wall of a liquefied gas storage tank according to the first embodiment of the present application.

[0053] Figure 25 is a partial sectional view for explaining a right angle corner structure of a liquefied gas storage tank according to the first embodiment of the present application.

[0054] Figure 26 is a partial sectional view for explaining an obtuse angle corner structure of a liquefied gas storage tank according to the first embodiment of the present application.

[0055] Figure 27 is a graph showing thermal conductivities of used materials of a primary insulation material and a secondary insulation material of a liquefied gas storage tank according to the present application.

[0056] Figure 28 is a partial sectional view for explaining a liquefied gas storage tank according to a second embodiment of the present application.

[0057] Figure 29 is a partial perspective view for explaining a liquefied gas storage tank according to the second embodiment of the present application.

[0058] Figure 30 is a partial sectional view for explaining a liquefied gas storage tank according to a third embodiment of the present application.

[0059] Figure 31 is an enlarged view of a main portion of a liquefied gas storage tank of the third embodiment of the present application.

[0060] Figure 32 is a view for explaining another embodiment of a primary protection wall of a liquefied gas storage tank of the first, second, and third embodiments of the present application.

[0061] Figure 33 is a view for explaining a shape of a primary protection wall.

[0062] Figure 34 are (a) and (b) are views for explaining a protruding structure provided to a primary protection wall.

[0063] Figure 35 is a perspective view for explaining a unit protection wall of a primary protection wall.

[0064] Figure 36 is a view showing a distribution of a normal equivalent stress value (thermal stress and compressive stress) according to a ratio W / H of a curved portion width to a curved portion height of a primary protection wall.

[0065] Figure 37 is a view showing a range of a curvature radius 'r3-r2-r1' value according to a ratio W / H of a curved portion width to a curved portion height of a primary protection wall by cross-sectional shape optimization simulation of the primary protection wall.

[0066] Figure 38 are (a), (b), and (c) are views showing a result of structural analysis on a sloshing pressure value when a fluid flows into a lateral curved portion and a longitudinal curved portion of a primary protection wall of the present application and a primary protection wall of a comparative object.

[0067] Figure 39 are (a) and (b) are views for explaining deformation when an equal distribution load is applied to a primary protection wall of the present application and a primary protection wall of a comparative object.

[0068] Figure 40 is a graph showing a stress change value of a secondary protection wall according to a change in a length of a portion where the secondary protection wall and a secondary insulation wall are not attached in an obtuse corner structure. DETAILED DESCRIPTION

[0069] The objects, specific advantages, and new features of the present application will become clearer by the following detailed description of the preferred embodiments with reference made to the accompanying drawings. In this specification, when a reference numeral is added to a constituent element of each drawing, it should be noted that the same reference numeral is given to the same constituent element as much as possible even if it is shown in different drawings. Also, in explaining the present application, if it is judged that a detailed description of related known technology can unnecessarily obscure the gist of the present application, a detailed description thereof will be omitted.

[0070] In addition, the drawings are for the purpose of facilitating an understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited to the drawings, and it should be understood that all modifications, equivalents, and alternatives within the idea and technical scope of the present application are included.

[0071] In addition, the terms including the first, second, and the like including ordinal numbers can be used to describe various constituent elements, but these constituent elements are not limited by these terms. These terms are used only to distinguish one constituent element from another.

[0072] Hereinafter, in the present specification, a liquefied gas can be used as a meaning encompassing all gas fuels that are usually stored in a liquid state, such as LNG or LPG, ethylene, ammonia, and the like, and cases where the liquefied gas is heated or pressurized without being in a liquid state, and the like, for the sake of convenience, can also be expressed as a liquefied gas. The same also applies to a boil-off gas. In addition, for the sake of convenience, LNG can be used as a meaning encompassing all NG (Natural Gas) in a liquid state, and LNG in a supercritical state, and the like, and a boil-off gas can be used as a meaning encompassing not only a boil-off gas in a gaseous state, but also a liquefied boil-off gas.

[0073] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0074] Figure 1 is a partial cross-sectional view for explaining a liquefied gas storage tank of a first embodiment of the present application, Figure 2 is a partial perspective view for explaining the liquefied gas storage tank of the first embodiment of the present application. Figure 3 is a view for explaining a primary containment wall of the liquefied gas storage tank of the first embodiment of the present application.

[0075] As Figures 1 to 2 shown, the liquefied gas storage tank 1 of the first embodiment of the present application can be provided in a ship, and stores a liquefied gas such as LNG, which is an extremely low temperature (about -160°C to -170°C) substance.

[0076] Although not shown, it should be appreciated that the ship provided with the liquefied gas storage tank 1 described below is a concept including an offshore structure that performs a specific work at a predetermined point floating on the sea, in addition to a merchant ship that transports cargo from a departure place to a destination. In addition, it should be made clear that the liquefied gas storage tank 1 in the present application includes any form of tank for storing a liquefied gas.

[0077] The liquefied gas storage tank 1 can include a primary protection wall 2 in contact with the liquefied gas, a primary insulation wall 3 provided outside the primary protection wall 2, a secondary protection wall 4 provided outside the primary insulation wall 3, and a secondary insulation wall 5 disposed outside the secondary protection wall 4. The liquefied gas storage tank 1 can be supported to a ship body 7 by an adhesive 6 provided between the secondary insulation wall 5 and the ship body 7.

[0078] The liquefied gas storage tank 1 can require optimization of thicknesses of the primary insulation wall 3 and the secondary insulation wall 5 to optimize thermal insulation performance and storage capacity. For example, in the case where polyurethane foam is used as a main material of the primary insulation wall 3 and the secondary insulation wall 5, the total thickness of the sum of the thickness of the primary insulation wall 3 and the thickness of the secondary insulation wall 5 can be in the range of 250 mm to 500 mm. This will be described in Figures 4 to 20 .

[0079] The above-described liquefied gas storage tank 1 can include a flat structure and a corner structure. For example, a transverse wall in a front-rear direction of the liquefied gas storage tank 1, a floor surface between the transverse walls, a vertical wall, and a ceiling can correspond to the flat structure. Also, for example, a structure in which the transverse wall, the floor surface, the vertical wall, and the ceiling of the liquefied gas storage tank 1 meet each other can correspond to the corner structure. Here, the corner structure can 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 varies, a change in the obtuse corner structure or the right angle corner structure can be accompanied, and this will be described in Figures 25 to 26 .

[0080] Referring to Figure 1 and Figure 2 , the primary protection wall 2 can form a containing space containing the liquefied gas as a cryogenic substance, and can be made of a metal material. For example, the metal material can be a stainless steel material, and is not limited thereto. The primary protection wall 2 can prevent the liquefied gas from leaking to the outside together with the secondary protection wall 4.

[0081] The primary protection wall 2 can be provided to be directly in contact with the liquefied gas as a cryogenic substance stored in the liquefied gas storage tank 1 by being fixedly coupled to an upper portion of the primary insulation wall 3 through an anchor (not shown).

[0082] Referring to Figure 3 , the primary protection wall 2 can be divided into a flat portion 21 in contact with a top surface of the primary insulation wall 3, a curved portion 22 for relieving a shrinkage or expansion stress due to temperature, and a boundary portion 23 between the flat portion 21 and the curved portion 22. For example, the primary protection wall 2 can be formed of a corrugation membrane sheet made of a stainless steel material having a thickness of 1.0 to 1.5 mm, and preferably a thickness of 1.0 to 1.2 mm. That is, the primary protection wall 2 can be formed in a corrugated shape.

[0083] The primary protection wall 2 can be formed so that the corrugated shape thereof has a first radius of curvature R1 and a second radius of curvature R2. That is, the primary protection wall 2 of the present embodiment can be formed to have two types of radius of curvature R1, R2, the first radius of curvature R1 being formed at the boundary portion 23 between the flat portion 21 and the curved portion 22, and the second radius of curvature R2 being formed at the curved portion 22. For example, the first radius of curvature R1 can be formed to be smaller than the second radius of curvature R2. In the primary protection wall 2 having the radii of curvature R1, R2, the upper portion forms a gentle curve, so that it is easy to perform a welding inspection, and in addition, fluid that hits from the side directly flows away, so that it is also possible to flexibly cope with sloshing. In this regard, the following will be described in more detail. Figures 32 to 39

[0084] In addition, the horizontal and vertical corrugation sizes in the entire region of the primary protection wall 2 of the present embodiment can be formed to be the same, without distinguishing between large corrugation and small corrugation. That is, since the horizontal and vertical corrugation sizes of the entire primary protection wall 2 are the same, it is possible to easily manufacture the primary protection wall.

[0085] Referring to Figure 1 The primary insulation wall 3 can be designed to be able to block the intrusion of heat from the outside, and to be able to withstand an impact from the outside or an impact caused by sloshing of the liquefied gas inside, and can be provided between the primary protection wall 2 and the secondary protection wall 4.

[0086] The primary insulation wall 3 can have a structure in which a primary plywood 31 and a primary insulation material 32 are sequentially stacked on the outside of the primary protection wall 2, and the thickness thereof can 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 can be formed to have a thickness of 160 mm to 250 mm.

[0087] The primary plywood 31 can be provided between the primary protection wall 2 and the primary insulation material 32.

[0088] The primary plywood 31 can be formed to have a thickness of 6.5 mm to 15 mm.

[0089] The primary insulation material 32 can be formed of a material having excellent heat insulation performance and excellent mechanical strength, so as to be able to block the intrusion of heat from the outside, and to be able to withstand an impact from the outside or an impact caused by sloshing of the liquefied gas inside.

[0090] The primary insulation material 32 can be formed of polyurethane foam between the primary plywood 31 and the secondary protection wall 4, and can correspond to a thickness range of 150 mm to 240 mm.

[0091] Referring to​Figure 1 A unit element can be configured by stacking a portion of the primary insulation wall 3, the secondary protection 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, and the width thereof 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 protection wall 4, and the secondary insulation wall 5 can be disposed in a state fixed in advance, but are not limited thereto, and can be separately disposed in the liquefied gas storage tank 1, respectively. Accordingly, a portion of the secondary protection wall 4 can be exposed to both sides of the primary insulation wall 3. The unit elements can be disposed adjacent to each other, and at this time, a space portion between the adjacent primary insulation walls 3, i.e., a space portion in which the secondary protection wall 4 is exposed, can be provided with a connection insulation wall 3a.

[0092] The secondary protection wall 4 can be divided into a main protection wall 41 and an auxiliary protection wall 42, the main protection wall 41 being disposed at an upper portion of the secondary insulation wall 5 in the unit element, and the auxiliary protection wall 42 being disposed between the exposed main protection wall 41 and the connection insulation wall 3a. At this time, the auxiliary protection wall 42 is disposed so as to connect the main protection walls 41 disposed in the unit elements adjacent to each other to each other. That is, the unit elements disposed adjacent to each other can be closed by the auxiliary protection wall 42 stacked on the main protection wall 41 and the connection insulation wall 3a.

[0093] The stacked structure of the portion in which the connection insulation wall 3a is disposed will be described below. Figure 2 The connection insulation wall 3a can be disposed in a form in which the connection plywood 31a and the connection insulation material 32a are stacked, as described above in the primary insulation wall 3 constituting the unit element, and in the present specification, it should be understood that the primary insulation wall 3 can include the connection insulation wall 3a and the fixed insulation wall 3b.

[0094] Figure 2 A cross-sectional structure of an A-A' surface of the liquefied gas storage tank 1 is shown in FIG. 4, and the connection insulation wall 3a can have a structure in which the connection plywood 31a and the connection insulation material 32a are stacked. Figure 1 The connection insulation wall 3a can have a thickness corresponding to the sum of the thickness of the connection plywood 31a and the thickness of the connection insulation material 32a.

[0095] The connection plywood 31a can be formed to have a thickness of 6.5 mm to 15 mm.

[0096] The connection insulation material 32a can be formed of polyurethane foam between the connection plywood 31a and the auxiliary protection wall 42 of the secondary protection wall 4, and can correspond to a thickness range of 150 mm to 240 mm.

[0097] As described above, the thickness of the primary thermal insulation material 32 of the primary thermal insulation wall 3 and the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a can be the same. However, in the case of the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a, the lower portion thereof is stacked with the auxiliary protection wall 42 in addition to the main protection wall 41 of the secondary protection wall 4, and thus the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a can have a thickness smaller than the thickness of the primary thermal insulation material 32 of the primary thermal insulation wall 3 by a thickness corresponding to the thickness of the auxiliary protection wall 42.

[0098] The connecting thermal insulation wall 3a described above is configured to seal a portion of a space between adjacent secondary thermal insulation walls 5 together with the auxiliary protection wall 42 when adjacent unit elements are arranged adjacent to each other, and to perform a role of blocking the intrusion of heat from the outside.

[0099] However, since the connecting thermal insulation wall 3a has a structure of being inserted between the adjacent fixed thermal insulation walls 3b constituting unit elements, it is inevitably weak in protecting the secondary protection wall 4 of the lower portion of the connecting thermal insulation wall 3a from the extremely low temperature. Thus, there is a high possibility that the secondary protection wall 4 of the lower portion of the connecting thermal insulation wall 3a in which the main protection wall 41 and the auxiliary protection wall 42 are stacked can be problematic. This will be described with the connecting thermal insulation wall 3a as the center.

[0100] The secondary protection wall 4 can be provided between the primary thermal insulation wall 3 including the connecting thermal insulation wall 3a and the secondary thermal insulation wall 5, and can prevent the leakage of the liquefied gas to the outside together with the primary protection wall 2.

[0101] The secondary protection wall 4 of the lower end of the fixed thermal insulation wall 3b can include the main protection wall 41 as a single protection wall, and the secondary protection wall 4 of the lower end of the connecting thermal insulation wall 3a can include the main protection wall 41 connecting unit elements to each other and the auxiliary protection wall 42 provided on the secondary thermal insulation wall 5 constituting unit elements.

[0102] The main protection wall 41 can be provided on the secondary thermal insulation wall 5 constituting unit elements, and can be formed in a thickness of 0.6 mm to 1.0 mm, and the main protection walls 41 adjacent to each other can be made airtight by stacking the auxiliary protection wall 42.

[0103] The auxiliary protection wall 42 is a structure for connecting unit elements to each other, and can be formed in a thickness of 0.6 mm to 1.0 mm and stacked on the main protection wall 41.

[0104] On the other hand, with reference to Figure 1 and Figure 2 , the secondary thermal insulation wall 5 can be designed to be able to block the intrusion of heat from the outside together with the fixed thermal insulation wall 3b and the connecting thermal insulation wall 3a, and to be able to withstand an impact from the outside or an impact caused by the sloshing of the liquefied gas inside. In addition, the secondary thermal insulation wall 5 can be provided between the secondary protection wall 4 and the ship body 7, and can include a secondary thermal insulation material 51 and a secondary plywood 52.

[0105] The secondary thermal insulation wall 5 can have a structure in which the secondary thermal insulation material 51 and the secondary plywood 52 are sequentially stacked on the outside of the secondary protection wall 4, and the total thickness of the thickness of the secondary thermal insulation material 51 and the thickness of the secondary plywood 52 can be formed to be 150 mm to 240 mm.

[0106] The secondary thermal insulation material 51 can be formed of a material having excellent thermal insulation performance and excellent mechanical strength to be able to block the invasion of heat from the outside and to be able to withstand an impact from the outside or an impact caused by the sloshing of the liquefied gas inside.

[0107] The secondary thermal insulation material 51 can be formed of polyurethane foam between the secondary protection wall 4 and the secondary plywood 52, and can be formed to a thickness of 140 mm to 230 mm.

[0108] The secondary plywood 52 can be provided between the secondary thermal insulation material 51 and the ship body 7. For example, the secondary thermal insulation material 51 can be provided in contact with the secondary plywood 52. The secondary plywood 52 can be formed to a thickness of 6.5 mm to 25 mm.

[0109] As described above, the liquefied gas storage tank 1 of the present embodiment can be configured such that the connection thermal insulation wall 3a included in the primary thermal insulation wall 3 has a thickness of 67% to 167% of the secondary thermal insulation wall 5 by making the primary thermal insulation wall 3 have a thickness of 66% to 166% of the secondary thermal insulation wall 5. In relation to this configuration, the thickness of the connection thermal insulation material 32a of the connection thermal insulation wall 3a can be made the same as or similar to the secondary thermal insulation material 51 by making the connection thermal insulation material 32a of the connection thermal insulation wall 3a have a thickness of 90% to 110% of the secondary thermal insulation material 51. In the present embodiment, it is necessary to make clear that even if the fixed thermal insulation wall 3b portion configuring the unitary element is not mentioned in detail as long as the connection thermal insulation wall 3a is included, but in relation to the secondary thermal insulation wall 5, the fixed thermal insulation wall 3b is the same as or similar to the connection thermal insulation wall 3a.

[0110] When the connection thermal insulation wall 3a and the secondary thermal insulation wall 5 or the connection thermal insulation material 32a of the connection thermal insulation wall 3a and the secondary thermal insulation material 51 are formed in this thickness ratio, the upper limit value of the stress at low temperature of the secondary protection wall 4 can correspond to 50 MPa or less at the lower portion of the connection thermal insulation wall 3a. In addition, specifically, the stress value at low temperature of the secondary protection wall 4 can be 40 MPa to 50 MPa at the lower portion of the connection thermal insulation wall 3a. This value is obtained from the structure according to the structural analysis described later.

[0111] 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 and the secondary insulation material 51 of the primary insulation wall 3, are configured to be the same or similar. This will be achieved through... Figures 4 to 20 Please provide an explanation.

[0112] Figure 4 (a) and (b) are diagrams illustrating the tension of the secondary protective wall 4 at the lower part of the connecting insulation wall 3a, which is included in the primary insulation wall 3, according to the thickness variation of the connecting insulation wall 3a and the secondary insulation wall 5. Assuming... Figure 4 In (a) and (b), the total thickness of the connecting insulation wall 3a, secondary protective wall 4, secondary insulation wall 5, etc. is the same.

[0113] On the other hand, the secondary protective wall 4 and the secondary insulation wall 5 differ in their shrinkage amount depending on the exposed temperature. In the case of the secondary protective wall 4 and the secondary insulation wall 5, the thinner the connecting insulation wall 3a, the more susceptible it is to the effects of the extremely low temperature liquefied gas. Furthermore, in this case, as the temperature decreases, the shrinkage amount increases, thus increasing the risk of damage to the secondary protective wall 4 due to increased stress at low temperatures. This problem is particularly prevalent in the auxiliary protective wall 42, which connects the main protective walls 41 of adjacent unit elements to each other using adhesives or the like, at the lower part of the connecting insulation wall 3a. This is because, at the lower part of the connecting insulation wall 3a, the two ends of the auxiliary protective wall 42 are connected to the main protective walls 41 of each unit element. As the secondary insulation wall 5 of the unit element shrinks, the two ends of the auxiliary protective wall 42 may deform, moving away from or closer to each other.

[0114] Reference Figure 4 (a) shows a case where the connecting heat insulation wall 3a is formed to be relatively thinner than the secondary heat insulation wall 5, and the height of the secondary protective wall 4 is located above the center of the total thickness with respect to the thickness direction. In this case, in order to reduce the mechanical stress exerted on the secondary protective wall 4 when the hull deforms structurally due to the six degrees of freedom motion of the hull 7, the thickness of the secondary heat insulation wall 5 can be made relatively thicker than that of the connecting heat insulation wall 3a by ensuring a larger thickness.

[0115] Reference Figure 4 (b) illustrates a case where the thicknesses 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 central region of the total thickness, with reference to the thickness direction. Here, the central region can correspond to a range of 40% to 60% of the total thickness. In this case, compared to... Figure 4 Compared to (a), the shrinkage itself is reduced, thereby reducing stress at low temperatures. Additionally, compared to... Figure 4 Compared to (a), the risk of damage to the secondary protective wall is relatively reduced.

[0116] In the present application, a liquefied gas storage tank 1 capable of maintaining the mechanical strength of the secondary insulation wall 5 at a predetermined level and reducing the low-temperature burden and the sloshing burden of the secondary protection wall 4 is derived, as will be understood below by referring to the description. Figures 5 to 20

[0117] Figures 5 to 20 are graphs of the results of the structural analysis performed by changing the thicknesses of the connecting insulation wall 3a and the secondary insulation wall 5 of the first shell (A), the second shell (B), the third shell (C), and the fourth shell (D) in order to derive the thicknesses 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 1 of the above-described first embodiment. In the present embodiment, although the thickness of the connecting insulation wall 3a is mainly described, it should be understood that the thickness of the primary insulation wall 3 is the same as or similar to that of the connecting insulation wall 3a. Figures 5 to 8 Figures 9 to 12 Figures 13 to 16 Figures 17 to 20

[0118] When the structure of each shell was analyzed, the analysis conditions were as follows.

[0119] First, the total thicknesses of the connecting insulation wall 3a and the secondary insulation wall 5 of the first shell to the fourth shell as the analysis model were applied to be the same at 400 mm.

[0120] Second, the positions of the secondary protection wall 4 were changed only by changing the thicknesses of the connecting insulation wall 3a and the secondary insulation wall 5.

[0121] Third, the temperature at the position of the primary protection wall 2 was set to be -163°C, which is the temperature of the liquefied gas, and the temperature at the position of the ship body 7 was set to be 20°C, which is the normal temperature, in consideration of the same linear temperature distribution condition.

[0122] Fourth, the thickness ratio is the ratio of the thickness of the connecting insulation wall 3a to the total thickness (400 mm).

[0123] The structure of the first shell to the fourth shell as the analysis model was analyzed with the above-described analysis conditions.

[0124] Figures 5 to 8 are graphs of the results of the structural analysis performed by changing the thicknesses of the connecting insulation wall 3a and the secondary insulation wall 5 of the first shell (A), the second shell (B), the third shell (C), and the fourth shell (D) in order to derive the thicknesses 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 1 of the above-described first embodiment. In the present embodiment, although the thickness of the connecting insulation wall 3a is mainly described, it should be understood that the thickness of the primary insulation wall 3 is the same as or similar to that of the connecting insulation wall 3a.

[0125] As Figure 5 ​​​​​As shown, the first housing is a housing with a thickness of 100 mm for the connecting heat insulation wall 3a and a thickness of 300 mm for the secondary heat insulation wall 5. That is, in the first housing, the thickness of the connecting heat insulation wall 3a accounts for 0.25 of the total thickness (400 mm) of the connecting heat insulation wall 3a and the secondary heat insulation wall 5, and the secondary protective wall 4 is located near the upper end of the primary protective wall 2 from the center of the total thickness of the sum of the thicknesses of the connecting heat insulation wall 3a and the secondary heat insulation wall 5.

[0126] In the case of this first shell, such as Figures 6 to 8 As shown in the structural analysis results, under the condition of adjacent configuration of unit elements, the stress value of the corresponding secondary protective wall 4 between adjacent secondary insulation walls 5 is calculated to be 70.12 MPa.

[0127] In the case of the first housing, by Figure 4 It can be seen that the stress is generated in the secondary protective wall 4. That is, as the thickness of the connecting insulation wall 3a decreases, the secondary protective wall 4 is more affected by the temperature of the liquefied gas.

[0128] Figures 9 to 12 These are figures showing the results of structural analysis performed on the liquefied gas storage tank according to the first embodiment of the present invention, in order to derive the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 included in the primary heat insulation wall 3, by changing the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 of the second shell.

[0129] like Figure 9 As shown, the second shell is a shell with a thickness of 160 mm for the connecting heat insulation wall 3a and a thickness of 240 mm for the secondary heat insulation wall 5. That is, in the second shell, the thickness of the connecting heat insulation wall 3a accounts for 0.4 of the total thickness (400 mm) of the connecting heat insulation wall 3a and the secondary heat insulation wall 5, and the secondary protective wall 4 is located slightly off-center from the center of the total thickness of the sum of the thicknesses of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 towards the primary protective wall 2.

[0130] In the case of this second shell, such as Figures 10 to 12 As shown in the structural analysis results, under the condition of adjacent configuration of unit elements, the stress value of the corresponding secondary protective wall 4 between adjacent secondary insulation walls 5 is calculated to be 55.09 MPa.

[0131] Figures 13 to 16 These are figures showing the results of structural analysis performed on the liquefied gas storage tank according to the first embodiment of the present invention, in order to derive the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 included in the primary heat insulation wall 3, by changing the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 of the third shell.

[0132] like Figure 13As shown, the third shell is formed with the same or similar thickness of the connecting insulation wall 3a and the secondary insulation wall 5. That is, in the third shell, the thickness of the connecting insulation wall 3a accounts for approximately 0.5 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 adjacent to the center of the total thickness of the sum of the thicknesses of the connecting insulation wall 3a and the secondary insulation wall 5.

[0133] In the case of this third shell, such as Figures 14 to 16 As shown in the structural analysis results, under the condition of adjacent configuration of unit elements, the stress value of the corresponding secondary protective wall 4 between adjacent secondary insulation walls 5 is calculated to be 47.63 MPa.

[0134] Figures 17 to 20 These are figures showing the results of structural analysis performed on the liquefied gas storage tank according to the first embodiment of the present invention by changing the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 of the fourth shell in order to derive the thickness of the connecting heat insulation wall 3a and the secondary heat insulation wall 5 included in the primary heat insulation wall 3.

[0135] like Figure 17 As shown, the fourth shell is a shell with a thickness of 240 mm for the connecting heat insulation wall 3a and a thickness of 160 mm for the secondary heat insulation wall 5. That is, in the fourth shell, the thickness of the connecting heat insulation wall 3a accounts for 0.6 of the total thickness (400 mm) of the connecting heat insulation wall 3a and the secondary heat insulation wall 5, and the secondary protective wall 4 is located below the center of the total thickness of the sum of the thicknesses of the connecting heat insulation wall 3a and the secondary heat insulation wall 5.

[0136] In the case of this fourth shell, such as Figures 18 to 20 As shown in the structural analysis results, under the condition of adjacent configuration of unit elements, the stress value of the corresponding secondary protective wall 4 between adjacent secondary insulation walls 5 is calculated to be 41.21 MPa.

[0137] As described above, the structural analysis results of the first to fourth shells show that the secondary protective wall 4, which connects to the lower part of the heat insulation wall 3a, tends to exhibit a decrease in low-temperature stress caused by thermal contraction as it moves away from the primary protective wall 2. (Refer to...) Figure 21 Please provide an explanation.

[0138] Figure 21 This is a graph showing the relationship between the low-temperature stress of the secondary protective wall and the probability of brittle failure of the hull, depending on the thickness variations of the primary and secondary protective walls.

[0139] like Figure 21As shown in the graph, it is predicted that the stress values of the first to fourth casings and the secondary protective wall 4 connected to the lower portion of the thermal insulation wall 3a caused by thermal contraction at low temperatures decrease as the secondary protective wall 4 is distanced from the primary protective wall 2. That is, it is known that the temperature of the secondary protective wall 4 connected to the lower portion of the thermal insulation wall 3a relatively increases as it is distanced from the primary protective wall 2, and thus the contraction decreases and the stress decreases. In the present embodiment, the secondary protective wall 4 connected to the lower portion of the thermal insulation wall 3a is mainly described, but it is obvious that the secondary protective wall 4 of the lower portion of the fixed thermal insulation wall 3b constituting the unit element also decreases in stress as it is distanced from the primary protective wall 2. The secondary protective wall 4 of the lower portion of the connecting thermal insulation wall 3a is in a state in which the primary protective wall 41 and the auxiliary protective wall 42 are stacked, and the secondary protective wall 4 of the lower portion of the primary thermal insulation wall 3 is composed of only the primary protective wall 41.

[0140] The liquefied gas storage tank 1 of the present embodiment derived as described above decreases the temperature increase of the secondary protective wall 4 (reduces the influence of the cold and heat of the extremely low-temperature liquid gas) by increasing the thickness of the connecting thermal insulation wall 3a in the total thickness of the sum of the thicknesses of the connecting thermal insulation wall 3a and the secondary thermal insulation wall 5. Thereby, the contraction of the secondary protective wall 4 itself caused by the cold and heat is reduced, and the stress caused by the cold and heat is reduced, and thus it is possible to prevent the damage of the secondary protective wall 4 caused by the cold and heat. This principle is of course also applicable to the secondary protective wall 4 of the lower portion of the primary thermal insulation wall 3 defined to include the connecting thermal insulation wall 3a.

[0141] In addition, the secondary protective wall 4 decreases the sway load and the fluid dynamic load transmitted to the secondary protective wall 4 as the thicknesses of the connecting thermal insulation wall 3a and the fixed thermal insulation wall 3b increase (the thickness of the secondary thermal insulation wall 5 relatively decreases), and reduces the stress caused by the sway, and thus it is possible to prevent the damage caused by the sway. In addition, as the thickness of the secondary thermal insulation wall 5 becomes thin (the thickness of the primary thermal insulation wall 3 relatively becomes thick), it is possible to easily adjust the flatness of the secondary protective wall 4.

[0142] In addition, as the thicknesses of the connecting thermal insulation wall 3a and the fixed thermal insulation wall 3b increase, the thickness of the secondary thermal insulation wall 5 relatively decreases, and the secondary thermal insulation wall 5 is relatively distanced from the primary protective wall 2, and thus the contraction force of the secondary thermal insulation wall 5 caused by the cold and heat also decreases, and the tension of the secondary protective wall 4 decreases as the contraction force of the secondary thermal insulation wall 5 decreases, and thus it is possible to prevent the secondary protective wall 4 from being damaged by the contraction force of the secondary thermal insulation wall 5.

[0143] In consideration of the low temperature stress of the secondary protection wall 4, in the present application, the connecting insulation wall 3a can be configured to be 40% or more of the thickness corresponding to the sum of the connecting insulation wall 3a and the secondary insulation wall 5. Preferably, the liquefied gas storage tank 1 of the present application can be configured in the range of the second to fourth shells, i.e., the connecting insulation wall 3a is 40% to 60% of the thickness corresponding to the sum of the connecting insulation wall 3a and the secondary insulation wall 5. More preferably, the liquefied gas storage tank 1 of the present application can be configured in the range of the third shell, i.e., the connecting insulation wall 3a is 47% to 53% of the thickness corresponding to the sum of the connecting insulation wall 3a and the secondary insulation wall 5.

[0144] 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, and thus the secondary insulation wall 5 is inevitably weak against mechanical stress applied when the hull 7 is structurally deformed due to the six-degree-of-freedom motion of the hull 7, and thus the degree of mechanical stress transmitted to the secondary protection wall 4 through the secondary insulation wall 5 necessarily increases.

[0145] In addition, in a state where the liquefied gas is loaded, an emergency condition such as rupture of the primary protection wall 2 can occur. In this case, the primary protection wall 2 cannot prevent the leakage of the liquefied gas any more, and thus the liquefied gas can come into contact with the secondary protection wall 4. In addition, if the secondary protection wall 4 comes into contact with the liquefied gas at an extremely low temperature, the temperature of the hull decreases, and the probability of brittle fracture can increase. In addition, as the temperature becomes low, the brittle problem can occur compared to the increase in the material strength of the hull, and thus the probability of brittle fracture can increase. Here, the brittle fracture can correspond to sudden fracture in which almost no plastic deformation occurs, and can be understood as a brittle crack.

[0146] In relation to this, referring to Figure 21 In the emergency condition, as the secondary protection wall 4 contacted by the liquefied gas at an extremely low temperature gradually approaches the hull from the first shell to the fourth shell, the probability of brittle fracture increases. That is, in the Figure 21 In the present application, the probability of brittle fracture of the hull increases as the thickness of the connecting insulation wall increases compared to the thickness of the secondary insulation wall 5 from the first shell to the fourth shell. In addition, in the case where the thickness of the connecting insulation wall 3a further increases beyond the fourth shell, the probability of brittle fracture approaches 1, and the hull can crack or split.

[0147] Therefore, the insulation system of the liquefied gas storage tank 1 needs to consider not only the low temperature stress as described above but also the risk of cracking or damage of the hull to configure. In the present application, when both the low temperature stress and the hull cracking are taken into account, the second to fourth shells in which the secondary protective wall 4 is located in the central region of the total thickness of the sum of the thicknesses of the insulation wall 3a and the secondary insulation wall 5 can be suitable. Preferably, in terms of the mechanical aspects of the low temperature stress and the hull cracking, the third shell can be considered suitable.

[0148] Therefore, in the present application, by ensuring the thickness of the insulation wall 3a and the primary insulation wall 3 to reduce the low temperature stress of the secondary protective wall 4, and by appropriately setting the thickness of the secondary insulation wall 4 to ensure the spacing between the hull 7 and the secondary protective wall 4, the second to fourth shells in which the burden of the structural stress transmitted from the hull 7 to the secondary protective wall 4 can be reduced can be suitable embodiments. In addition, when both the low temperature stress and the mechanical strength are taken into account, the third shell therein can correspond to a preferred embodiment.

[0149] In the following [Table 1], the stress variation of the lower part of the connecting insulation wall 3a according to the thickness variation of the primary insulation wall 3 and the secondary insulation wall 5 is shown under the same or similar structural analysis conditions as the first to fourth shells described above. Here, as described above, the connecting insulation wall 3a can be an insulation wall included in the primary insulation wall 3, and therefore, in the following [Table 1], the thickness of the primary insulation wall 3 can be the thickness of the connecting insulation wall 3a. In addition, the stress variation of the lower part of the connecting insulation wall 3a can be the stress variation of the secondary protective wall 4 as the lower layer of the connecting insulation wall 3a.

[0150] In the following, it is necessary to clarify that the Examples 1 to 5 and Comparative Examples 1 to 3 explained with reference to [Table 1] do not necessarily refer to the same examples even if the same numerical values as the aforementioned examples (first to fourth shells) are used.

[0151] [Table 1]

[0152] Primary insulation wall Secondary insulation wall Stress value (MPa) of secondary protection wall 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

[0153] 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 formed to be 240 mm. In the case of this Example 1, the structural analysis result calculates the stress value of the secondary protective wall 4 as the lower layer of the connecting insulation wall 3a to be 55.09 MPa.

[0154] In Example 2, the thickness of the primary insulation wall 3 was 180 mm and the thickness of the secondary insulation wall 5 was formed to be 220 mm. In this Example 2, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 51.08 MPa.

[0155] In Example 3, the thickness of the primary insulation wall 3 was 200 mm and the thickness of the secondary insulation wall 5 was formed to be 200 mm. In this Example 3, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 47.63 MPa.

[0156] In Example 4, the thickness of the primary insulation wall 3 was 220 mm and the thickness of the secondary insulation wall 5 was formed to be 180 mm. In this Example 4, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 44.13 MPa.

[0157] In Example 5, the thickness of the primary insulation wall 3 was 240 mm and the thickness of the secondary insulation wall 5 was formed to be 160 mm. In this Example 5, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 41.21 MPa.

[0158] In Comparative Example 1, the thickness of the primary insulation wall 3 was 100 mm and the thickness of the secondary insulation wall 5 was formed to be 300 mm. In this Comparative Example 1, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 70.12 MPa.

[0159] In Comparative Example 2, the thickness of the primary insulation wall 3 was 300 mm and the thickness of the secondary insulation wall 5 was formed to be 100 mm. In this Comparative Example 2, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 34.29 MPa.

[0160] In Comparative Example 3, the thickness of the primary insulation wall 3 was 140 mm and the thickness of the secondary insulation wall 5 was formed to be 260 mm. In this Comparative Example 3, the structural analysis resulted in a stress value of the secondary protection wall 4, which is the lower layer connected to the insulation wall 3a, of 59.52 MPa.

[0161] In the above-described Embodiment 1 to Embodiment 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 relatively decreased from 240 mm to 160 mm, and as a result of the structural analysis, the stress value of the secondary protective wall 4 as the lower layer of the connecting insulation wall 3a is changed from 55.09 MPa to 41.21 MPa, and in the thickness range and stress value, it is appropriate when both the low temperature stress of the liquefied gas storage tank 1 and the crack of the hull 7 are taken into account.

[0162] However, in the case of Comparative Example 1 to Comparative Example 3, the thickness of the primary insulation wall 3 and the secondary insulation wall 5 is biased to one side, and thus it is not preferable to apply as an insulation system of the liquefied gas storage tank 1 when both the low temperature stress of the liquefied gas storage tank 1 and the crack of the hull 7 are taken into account.

[0163] On the other hand, the material of the secondary protective wall 4 can be variously constituted, and for this, it will be described in Figures 22 to 24 .

[0164] Figure 22 , Figure 23 and Figure 24 are drawings for explaining various constitutions of the secondary protective wall of the liquefied gas storage tank of the first embodiment of the present application, respectively.

[0165] As shown in Figure 22 , the secondary protective wall 4 can be formed of a first material of a three-layer structure of glass cloth (GC) / aluminum foil (AF) / glass aramid cloth (GAC) laminated.

[0166] The glass aramid cloth (GAC) uses aramid material in glass cloth (Glass Cloth), and can be manufactured by mixing one aramid for every two glass fibers (Glass fiber).

[0167] Such a first material can be applied to the auxiliary protective wall 42 of the secondary protective wall 4, and is not limited thereto, and of course, can be applied to the main protective wall 41 of the secondary protective wall 4.

[0168] As shown in Figure 23 , the secondary protective wall 4 can be formed of a second material of a five-layer structure of glass cloth (GC) / aluminum foil (AF) / glass cloth (GC) / aluminum foil (AF) / glass cloth (GC) laminated.

[0169] Such a second material can be applied to the main protective wall 41 of the secondary protective wall 4, and is not limited thereto, and of course, can be applied to the auxiliary protective wall 42 of the secondary protective wall 4.

[0170] As shown in Figure 24As shown, the secondary protection wall 4 uses an inorganic basalt fabric extracted from basalt, and can be formed of a third material of a three-layer structure of a basalt fabric (BC) / aluminum foil (AF) / basalt fabric (BC) stacked.

[0171] This third material can be applied to the main protection wall 41 of the secondary protection wall 4, and is not limited thereto, and of course can also be applied to the auxiliary protection wall 42 of the secondary protection wall 4.

[0172] As Figures 22 to 24 described in the foregoing, the secondary protection wall 4 of the present embodiment can be formed of various materials of a multi-layer structure of a first member / aluminum foil (AF) / second member stacked. At this time, at least one of the first member and the second member can be a glass fabric (GC), a glass-aramid fabric (GAC), a basalt fabric (BC), or a glass fabric (GC) / aluminum foil (AF) / glass fabric (GC).

[0173] In addition, the various materials applied to the secondary protection wall 4 can of course also be applied to the main protection wall 41 and the auxiliary protection wall 42 of the secondary protection wall 4 in various combinations.

[0174] Figure 25 is a partial cross-sectional view for illustrating a right-angle corner structure of a liquefied gas storage tank of a first embodiment of the present invention, Figure 26 is a partial cross-sectional view for illustrating an obtuse-angle corner structure of a liquefied gas storage tank of a first embodiment of the present invention.

[0175] In the foregoing Figures 5 to 20 , it is confirmed that in the case where 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, similar range, a more stable insulation system is obtained. For example, the same, similar range can mean a case where the position of the secondary protection wall 4 is located at 40% to 60% of the total thickness of the sum of the thickness of the connecting insulation wall 3a or the primary insulation wall 3 and the secondary insulation wall 5. The configuration as described above can also be similarly applied to Figure 25 the right-angle corner structure of the liquefied gas storage tank 1 shown in Figure 26 the obtuse-angle corner structure of the liquefied gas storage tank 1 shown in.

[0176] However, in the right-angle corner structure and the obtuse-angle corner structure of the liquefied gas storage tank 1, the secondary protection wall 4 can only be formed as a curve, and in the case of being formed as a curve, the load on the surrounding environment is weak compared to the straight portion, and the present embodiment can alleviate the stress caused by such a load. In addition, the present embodiment can easily absorb the deformation of the ship body.

[0177] Referring to Figure 25In the right-angle corner structure, the secondary protective wall 4 becomes thicker than the first and second shells as the primary insulation wall 3 becomes thicker, and the radius of curvature accounts for more than 25% of the thickness of the primary insulation wall 3, for example, 25% to 50%.

[0178] Furthermore, in the right-angle corner structure, the secondary protective wall 4 becomes thicker than both the first and second shells due to the thickness of the primary insulation wall 3, and moves towards the hull 7 compared to the existing thinner primary insulation wall. In this case, the radius of curvature increases, and with the increase in the radius of curvature, the length L1 of the un-glued portion (secondary barrier scab part not glued) of the secondary protective wall 4 also increases. This in the right-angle corner structure refers to increased flexibility of the secondary protective wall 4, thereby making it easier for the secondary protective wall 4 in the right-angle corner structure to absorb deformations of the surrounding area, such as hull deformation, and reducing low-temperature stress. For example, the length L1 of the un-glued portion can be 100mm to 200mm.

[0179] Reference Figure 26 In the obtuse angle corner structure, the secondary protective wall 4 becomes thicker than the first and second shells as the thickness of the primary insulation wall 3 increases, and the radius of curvature accounts for more than 15% of the thickness of the primary insulation wall 3, for example, 15% to 35%.

[0180] Furthermore, in the obtuse-angle corner structure, the secondary protective wall 4 becomes thicker than the first and second shells due to the thickness of the primary insulation wall 3, and moves towards the hull 7 and increases its 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 of the secondary protective wall 4 not glued to the secondary insulation wall 5 also increases. This means that the flexibility of the secondary protective wall 4 is increased in the obtuse-angle corner structure, thereby making it easier for the secondary protective wall 4 in the obtuse-angle corner structure to absorb deformation of the surrounding parts, such as hull deformation, and reducing low-temperature stress. For example, in this embodiment, the length L2 of the portion of the secondary protective wall 4 not glued to the secondary insulation wall 5 can be 50 mm to 100 mm, preferably more than 50 mm and less than 100 mm.

[0181] The stress variation values ​​of the secondary protective wall 4, which vary according to the length L2 of the unattached portion of the secondary protective wall 4 as the thickness of the primary insulation wall 3 increases, are shown in Table 2 below. Figure 40 .

[0182] [Table 2]

[0183] Length (L2) of non-fitted portion 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

[0184] As shown in [Table 2] and Figure 40 As shown in [Table 2] and

[0185] As described above, the secondary protection wall 4 in the right angle corner structure and the obtuse angle corner structure of the present application can reduce the stress applied to the existing secondary protection wall at low temperature, compared to the right angle corner structure and the obtuse angle corner structure of the primary thermal insulation wall formed by a relatively thin thickness. In addition, since the unattached portion is increased, the hull deformation absorption is also easy.

[0186] Figure 27 is a graph showing the thermal conductivity of the material used according to the primary thermal insulation material and the secondary thermal insulation material of the liquefied gas storage tank.

[0187] In the liquefied gas storage tank 1 of the above-described embodiment of the present application, it is described that the primary thermal insulation material 32, 32a connecting the thermal insulation wall 3a and the primary thermal insulation wall 3 and the secondary thermal insulation material 51 of the secondary thermal insulation wall 5 are each formed of polyurethane foam of the same material, but polyurethane foam of different materials can be selectively used according to circumstances.

[0188] Specifically, the reinforced polyurethane foam (RPUF) is manufactured by mixing polyol, isocyanate, blowing agent, and HFC-245fa or CO2 can be used as the blowing agent. Compared to CO2, HFC-245fa can be relatively expensive.

[0189] In the case of the present embodiment, the primary thermal insulation material 32, 32a is formed of reinforced polyurethane foam using CO2 as the blowing agent, and the secondary thermal insulation material 51 is formed of reinforced polyurethane foam using HFC-245fa as the blowing agent.

[0190] Referring to the graph of Figure 27 The thermal conduction characteristics of the blowing agent HFC-245fa and the blowing agent CO2 are observed, and the thermal conduction value of the blowing agent HFC-245fa at normal temperature is low compared to the blowing agent CO2, but the more to the extremely low temperature, the more the same or similar value is shown.

[0191] 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 and show a lower value of the blowing agent HFC-245fa than the blowing agent CO2 at temperatures above -80°C.

[0192] Thus, in the present embodiment, the relatively expensive blowing agent HFC-245fa is not used for both the primary thermal insulation material 32, 32a and the secondary thermal insulation material 51, and in consideration of the economic aspect, the primary thermal insulation material 32, 32a which is relatively close to the extremely low temperature can be formed of the reinforced polyurethane foam using CO2 as the blowing agent, and the secondary thermal insulation material 51 can be formed of the reinforced polyurethane foam using HFC-245fa as the blowing agent.

[0193] Figure 28 is a partial cross-sectional view of a liquefied gas storage tank for explaining the second embodiment of the present application, Figure 29 is a partial perspective view of a liquefied gas storage tank for explaining the second embodiment of the present application.

[0194] As Figures 28 to 29 shown, the liquefied gas storage tank 1 of the second embodiment of the present application can include a primary protection wall 2 which is in contact with a liquefied gas inside, a primary thermal insulation wall 3 which is provided outside the primary protection wall 2, a connecting thermal insulation wall 3a which is connected to the thermal insulation wall 3, a secondary protection wall 4 which is provided outside the primary thermal insulation wall 3 and the connecting thermal insulation wall 3a, and a secondary thermal insulation wall 5 which is disposed outside the secondary protection wall 4 and fixed to a ship body 7, and compared with the above-described first embodiment, the connecting thermal insulation wall 3a is different in constitution, and the other constitutions are the same or similar, and thus only the different part will be described below to avoid repeated description.

[0195] In the present embodiment, compared with the above-described first embodiment, the connecting thermal insulation wall 3a can be different in constitution.

[0196] Specifically, compared with the above-described first embodiment, the connecting thermal insulation wall 3a can further include an auxiliary thermal insulation plate 33.

[0197] That is, the connecting thermal insulation wall 3a can be formed in a structure in which the connecting plywood 31a, the connecting thermal insulation material 32a, and the auxiliary thermal insulation plate 33 are laminated.

[0198] The auxiliary thermal insulation plate 33 can have a thickness of 5 to 10 mm, be made of plywood or high-density polyurethane foam (HDPUF), FRP (Fiber Reinforced Plastic), or the like, and thus can obtain the load dispersion effect of the secondary protection wall 4. Alternatively, the auxiliary thermal insulation plate 33 can be composed of VIP (Vacuum Insulation Panel), LDPUF, or the like, which has excellent thermal insulation properties, and thus can compensate for the thermal insulation weakness of the portion in which the connecting thermal insulation wall 3a is formed.

[0199] The thickness of the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a and the primary thermal insulation material 32 of the fixed thermal insulation wall 3b constituting the unit element can be the same. However, in the case of the connecting thermal insulation wall 3a, the lower portion thereof is stacked with the auxiliary protection wall 42 in addition to the main protection wall 41 of the secondary protection wall 4, and further includes the auxiliary thermal insulation plate 33, and thus the thickness of the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a can be 5 to 10 mm, which is smaller than the thickness of the primary thermal insulation material 32 of the primary thermal insulation wall 3, by the thickness of the auxiliary protection wall 42 and the thickness of the auxiliary thermal insulation plate 33.

[0200] Of course, the above-described auxiliary thermal insulation plate 33 can be provided not only in the lower portion of the connecting thermal insulation material 32a of the connecting thermal insulation wall 3a but also in the lower portion of the primary thermal insulation material 32 of the primary thermal insulation wall 3 constituting the unit element.

[0201] Figure 30 is a partial cross-sectional view of a liquefied gas storage tank for explaining a third embodiment of the present application, Figure 31 is an enlarged view of a main portion of the liquefied gas storage tank of the third embodiment of the present application.

[0202] As Figures 30 to 31 shown, the liquefied gas storage tank 1 of the third embodiment of the present application can include a primary protection wall 2 which is in contact with a liquefied gas inside, a primary thermal insulation wall 3 and a connecting thermal insulation wall 3a which are provided outside the primary protection wall 2, a secondary protection wall 4 which is provided outside the primary thermal insulation wall 3 and the connecting thermal insulation wall 3a, a secondary thermal insulation wall 5 which is disposed outside the secondary protection wall 4 and is fixed to a ship body 7, a leveling member 8 which is provided between the secondary thermal insulation wall 5 and the ship body 7, and a fixing member 9 which fixes the secondary thermal insulation wall 5 to the ship body 7, and compared with the above-described first embodiment, the leveling member 8 and the fixing member 9 are different, and the other constitutions are the same or similar, and thus hereinafter only the leveling member 8 and the fixing member 9 which are the constitution elements different from the first embodiment and the portions changed thereby will be described to avoid redundant description.

[0203] The leveling member 8 can be provided between the secondary thermal insulation wall 5 and the ship body 7.

[0204] The leveling member 8 can adjust the level of the deformed portion of the hull 7, can improve the heat insulation performance of the tank by supporting the secondary insulation wall 5 without attaching the elastic insulation material, and can be EPS (Expanded Polystyrene) or the like.

[0205] In this leveling member 8, the top surface of the secondary insulation wall 5 can be flat due to the elastic force, and the bottom surface of the hull 7 can have a curved surface corresponding to the deformation of the hull 7. For example, the deformation of the hull 7 can occur when the hull 7 is welded between blocks.

[0206] That is, the leveling member 8 can adjust the level of the deformed portion of the hull even without using the existing adhesive and leveling wedge. Here, the leveling wedge can be optionally used, of course.

[0207] In the present embodiment, by applying the leveling member 8 as described above, unlike the case where the adhesive is applied in various forms according to the size of the existing gap, it can be applied in a single size, and the adhesive hardening time is not required, so that the work time can be shortened, and the heat insulation capacity can be improved by applying the insulation material.

[0208] The fixing member 9 can be configured of a cleat structure including a protrusion 91 and a stud bolt 92 to fix the secondary insulation wall 5 to the hull 7.

[0209] The protrusion 91 can be provided to protrude outward from the both side surfaces of the unit panel of the secondary insulation wall 5, and can be formed as a plywood.

[0210] One side surface of the protrusion 91 can be fixedly provided to be overlapped with the side surface of the secondary plywood 52 of the secondary insulation wall 5 and a portion of the side surface of the secondary insulation material 51 from the secondary plywood 52 to a predetermined height, and the bottom surface thereof can be formed to be the same level as the bottom surface of the secondary plywood 52.

[0211] The width of the protrusion 91 can be such that the stud bolt 92 can be inserted between the protrusions 91 opposite to each other when a plurality of unit panels configuring the secondary insulation wall 5 are arranged.

[0212] The stud bolt 92 can be fixed to the hull 7.

[0213] The stud bolt 92 can be fixedly provided to the hull 7 in a manner corresponding to the space between the unit panels of the secondary insulation wall 5 adjacent to each other when a plurality of unit panels configuring the secondary insulation wall 5 are arranged.

[0214] The stud bolt 92 can fix the secondary insulation wall 5 to the hull 7 by tightening the bolt in a state of being located between the two protrusions 91 provided to the side surfaces of the unit panels of the secondary insulation wall 5 adjacent to each other and opposite to each other.

[0215] As described above, in the present embodiment, by making the thickness of the primary thermal insulation wall 3, 3a the same as or similar to that of the secondary thermal insulation wall 5 in the total thickness including the primary thermal insulation wall 3 and the secondary thermal insulation wall 5 connected by the connecting thermal insulation wall 3a, not only the mechanical strength of the secondary thermal insulation wall 5 can be maintained at a predetermined level, but also the low-temperature burden and the sway burden of the secondary protection wall 4 can be reduced, so that the damage of the secondary protection wall 4 can be prevented.

[0216] In addition, in the present embodiment, by providing the auxiliary thermal insulation plate 33 to the bottom surface of the connecting thermal insulation wall 3a provided in the space between the adjacent primary thermal insulation walls 3 constituting the unit element, the thermal insulation performance of the connecting portion of the adjacent secondary thermal insulation walls 5 constituting the unit element can be further improved.

[0217] In addition, the present embodiment can improve the thermal insulation performance by improving the constitution of the secondary protection wall 4.

[0218] In addition, in the present embodiment, by using the unattached elastic thermal insulation material as the leveling member 8 of the secondary thermal insulation wall 5 between the secondary thermal insulation wall 5 and the ship body 7, the level of the deformation portion of the ship body 7 can be adjusted even without using the existing adhesive and leveling wedge, and the thermal insulation performance of the tank can be improved.

[0219] In addition, in the present embodiment, by fixing the unit panel of the adjacent secondary thermal insulation walls 5 by the cleat structure using the protrusion 91 protruding outward at the lower portion of the unit panel side surface of the secondary thermal insulation wall 5 and the stud 92 fixed to the ship body 7, the number of man-hours can be reduced compared to the method of fixing the unit panel by drilling the secondary thermal insulation wall 5 and fixing the unit panel by the stud.

[0220] The present application is not limited to the above-described embodiments, and as a further embodiment, a combination of the above-described embodiments or a combination of at least any one of the above-described embodiments and a known technology can be included. For example, Figures 28 to 29 the embodiment of Figures 4 to 27 may be combined with the embodiment of Figures 30 to 31 the embodiment of Figure 1 and Figure 2 the thermal insulation system of Figure 28 and Figure 29 the thermal insulation system.

[0221] Hereinafter, the primary protection wall shape of the liquefied gas storage tank described above will be described in detail by Figures 32 to 39

[0222] Figure 32 is a view for explaining another embodiment of the primary protection wall of the liquefied gas storage tank of the first, second, and third embodiments of the present application, Figure 33 is a view for explaining the shape of the primary protection wall.​

[0223] like Figures 32 to 33 As shown, compared with the reference Figure 3 Compared to the primary protective wall 2 with two types of radii of curvature R1 and R2 described above, the cross-sectional shapes of the primary protective wall 2 of the liquefied gas storage tank 1 in the first, second, and third embodiments of the present invention are different, and will be described in detail below.

[0224] Reference Figure 32 The primary protective wall 2 may be composed of a plurality of planar portions 21 that are in contact with the top surface of the primary heat insulation wall 3, and a plurality of curved portions 22 for relieving the contraction or expansion stress caused by temperature.

[0225] The curved surface 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 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.

[0226] At this time, the width W of the curved surface 22 can be 50mm to 105mm, preferably 65mm to 93mm, more preferably 70mm to 80mm, and the height H of the curved surface 22 can be 30mm to 50mm, preferably 30mm to 45mm, more preferably 33mm to 40mm.

[0227] These multiple curved surfaces 22 can be formed to intersect in the transverse and longitudinal directions, and the transverse curved surfaces 22 and the longitudinal curved surfaces 22 can be the same size. That is, the transverse and longitudinal curved surfaces 22 in the entire primary protective wall 2 are the same size, so the primary protective wall can be easily manufactured.

[0228] Furthermore, the spacing between adjacent curved surfaces 22 in the plurality of curved surfaces 22 can be wider than in the prior art (here, the prior art may be used as the term "comparison object" hereinafter), for example, a spacing of 350 mm to 400 mm. Here, the spacing between the curved surfaces 22 can correspond to the spacing between the uppermost endpoints of the curved surfaces 22. Additionally, 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 a ratio greater than 3:1 of the prior art. For example, they can be formed to have a length of 3,150 mm to 3,600 mm and a width of 1,050 mm to 1,200 mm.

[0229] As described above, in the primary protective wall 2 of this embodiment, increasing the spacing between the curved sections 22 and increasing the size of the unit protective wall 2a can be achieved by using a cross-sectional shape of the curved section 22 in which the ratio W / H of the width W between adjacent planar sections 21 to the height H from the planar section 21 to the upper end of the curved section 22 is in the range of 2.0 to 3.0 (2.0 ≤ W / H ≤ 3.0). This can be achieved by referring to... Figures 36 to 39 Further explanation will follow in the following sections.

[0230] On the other hand, such as Figure 2 As shown, the horizontal curved surface and the vertical curved surface can be formed to intersect. In this case, the horizontal curved surface and the vertical curved surface can be formed to have the same height and width.

[0231] In addition, the curved surface 22 can be formed into a cross-sectional shape having a first curved surface 22a, a second curved surface 22b, and a third curved surface 22c with different radii of curvature.

[0232] The first curved portion 22a is connected to the adjacent flat portion 21 to form a pair, and has a first radius of curvature r1. The first radius of curvature r1 can be 4 mm to 12 mm.

[0233] Each of the first curved surfaces 22a can be a curved surface shape having a first radius of curvature r1 between a first connection point P1 connected to the planar portion 21 and a second connection point P2 connected to a pair of third curved surfaces 22c.

[0234] Here, the first connection point P1 may be the same location as the point where the lowest curved portion of the first circle A1 with a first radius of curvature r1 from the first curvature center C1 on the receiving space side intersects with the longitudinal center line of the first circle A1. The first curvature center C1 of the first curved surface 22a may be located higher than the imaginary plane formed by the planar portion 21.

[0235] The second connection point P2 can be located within a 30-degree downward angle of the curved portion of the first circle A1, from the point where the curve of the first circle A1 intersects with the transverse centerline of the first circle A1.

[0236] The second curved surface 22b forms the upper part of the curved surface 22, and has at least a second radius of curvature r2 that is larger than the first radius of curvature r1. Here, the second radius of curvature r2 can be 7 mm to 15 mm.

[0237] The second curved surface 22b can be a surface shape having a second radius of curvature r2 between a third connection point P3 connected to any one of the pair of third curved surfaces 22c and a fourth connection point P4 connected to the other third curved surface 22c.

[0238] Here, the third connection point P3 and the fourth connection point P4 can be located, respectively, at a predetermined angle, for example, between 3 degrees and 10 degrees, to both sides of a longitudinal center line of the second circle A2 having the second radius of curvature r2 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 more upward than an imaginary plane formed by the flat surface portion 21.

[0239] The third curved surface portion 22c is formed to connect the pair of first curved surface portions 22a to the pair of second curved surface portions 22b, respectively, and has at least a third radius of curvature r3 larger than the second radius of curvature r2. Here, the third radius of curvature r3 can be 25 mm to 45 mm.

[0240] That is, the sizes of the first radius of curvature r1, the second radius of curvature r2, and the third radius of curvature r3 of the first curved surface portion 22a, the second curved surface portion 22b, and the third curved surface portion 22c, respectively, can be "the first radius of curvature r1 < the second radius of curvature r2 < the third radius of curvature r3". At this time, in the present embodiment, the size of the third radius of curvature r3 can be larger than the sum of the size of the second radius of curvature r2 and the size of the first radius of curvature r1.

[0241] Any one of the pair of third curved surface portions 22c can be a curved surface shape having the third radius of curvature r3 between the second connection point P2 connected to any one of the pair of first curved surface portions 22a and the third connection point P3 connected to one side of the second curved surface portion 22b.

[0242] Any one of the third curved surface portions 22c can be provided at a curved portion of a third circle A3 having the third radius of curvature r3 from a third center of curvature C3 on the opposite side of the accommodation space.

[0243] In addition, the other of the pair of third curved surface portions 22c can be a curved surface shape having the third radius of curvature r3 between the second connection point P2 connected to the other 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.

[0244] The other of the third curved surface portions 22c can be provided at a curved portion of a fourth circle A4 having the third radius of curvature r3 from a fourth center of curvature C4 on the opposite side of the accommodation space.

[0245] In the above, when observing the positions of the second connection point P2, the third connection point P3, and the fourth connection point P4 with a pair of third curved surfaces 22c as a reference, the second connection point P2 can be the point where the curve of the first circle A1 of any one of the first curved surfaces 22a intersects with the curve of the third circle, or the point where the curve of the first circle A1 of the other first curved surface 22a intersects with the curve of the fourth circle A4.

[0246] Additionally, the third connection point P3 can be the point where the curves of the second circle A2 and the third circle A3 intersect. The third connection point P3 can also be the same location as the point where the uppermost curved portion of the third circle A3 intersects with the longitudinal centerline of the third circle A3.

[0247] The fourth connection point P4 can be the point where the curves of the second circle A2 and the fourth circle A4 intersect. The fourth connection point P4 can also be the same location as the point where the uppermost curved portion of the fourth circle A4 intersects with the longitudinal centerline of the fourth circle A4.

[0248] The aforementioned pair of third curved surfaces 22c can have the same third radius of curvature r3, and the third curvature center C3 of any one third curved surface 22c and the fourth curvature center C4 of the other third curved surface 22c can be located at opposite positions in the horizontal direction. Furthermore, in this embodiment, the third curvature center C3 and the fourth curvature center C4 are located inside the curved surface 22. Therefore, when adjacent planar portions 21 are connected by imaginary lines, the third curvature center C3 and the fourth curvature center C4 are located inside the curved surface 22 above the imaginary lines. That is, the third curvature center C3 and the fourth curvature center C4 of the third curved surface 22c can be located higher than the imaginary plane formed by the planar portions 21.

[0249] As described above, all curvature centers C1, C2, C3, and C4 of the curved surface 22 in this embodiment can be located higher than the imaginary plane formed by the flat surface 21.

[0250] Figure 34 (a) and (b) are diagrams used to illustrate the protruding structures provided on the primary protective wall.

[0251] like Figure 34 As shown in (a) and (b), the primary protective wall 2 of this embodiment may also provide a protruding structure 24 on the peripheral plane 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. In addition, the predetermined distance may correspond to one-third of the distance between intersections located on the same line, and is not limited thereto.

[0252] 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 The convex circle shown in (a) or as Figure 34 (b) shows various shapes such as arcs.

[0253] This protruding structure 24 can further minimize the pressure stress caused by swaying at the intersection of the transverse curved section 22 and the longitudinal curved section 22.

[0254] Figure 35 It is a three-dimensional diagram used to illustrate a unit protective wall of a primary protective wall.

[0255] In this embodiment, the primary protective wall 2 can achieve a spacing of 350mm to 400mm wider between adjacent curved surfaces 22 than in the prior art. Therefore, as... Figure 35 As shown, the dimensions of each of the plurality of unit protective walls 2a constituting the primary protective wall 2 can be formed to a ratio greater than the 3:1 ratio of known technologies. For example, they can be formed to have a length of 3,150 mm to 3,600 mm and a width of 1,050 mm to 1,200 mm. In this embodiment, by increasing the size of the unit protective wall 2a, the number of unit protective walls 2a installed is reduced compared to the prior art, thereby reducing the number of installation tasks for the primary protective wall 2.

[0256] In addition, Figure 35 In the unit protective wall 2a shown, the width between the uppermost ends of the curved sections 22 can correspond to 350mm to 400mm. Here, the uppermost ends of the curved sections 22 can correspond to... Figure 32 The uppermost point of the second curved surface 22b. Compared to the unit protective wall of the comparison object (a known unit protective wall), this increases the width between the uppermost ends of the curved surfaces, thus making it easier to manufacture and install compared to the unit protective wall of the comparison object. In addition, the width and height of the transverse curved surface 22 and the longitudinal curved surface 22 of the unit protective wall 2a of the embodiment of the present invention are the same, thereby reducing manufacturing costs compared to the unit protective wall of the comparison object.

[0257] Figure 36 This is a graph showing the distribution of equivalent stress values ​​(thermal stress and compressive stress) based on the ratio of the curved surface width to the curved surface height W / H of a primary protective wall. Figure 37 This is a graph showing the range of values ​​for the radius of curvature 'r3-r2-r1' of the ratio W / H of the curved surface width to the curved surface height of the primary protective wall, simulated through cross-sectional shape optimization of the primary protective wall.

[0258] In the primary protective wall 2 of this embodiment, as described above, the cross-sectional shape of the curved surface 22 is formed such that 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 22 is in the range of 2.0 to 3.0 (2.0 ≤ W / H ≤ 3.0). Based on this, the first curvature radius r1, the second curvature radius r2, and the third curvature radius r3 of the first curved surface 22a, the second curved surface 22b, and the third curved surface 22c are different, and the size of the third curvature radius r3 is greater than the sum of the size of the second curvature radius r2 and the size of the first curvature radius r1, so as to minimize the thermal stress caused by low temperature and the pressure stress caused by shaking. This cross-sectional shape of the curved surface 22 is achieved through the following... Figures 36 to 39 The experimental data shown were obtained, and based on this, a known primary protective barrier was used as a comparison object.

[0259] Here, unlike the primary protective wall 2 of the present invention, the primary protective wall of the comparative object has large corrugation and small corrugation.

[0260] like Figure 36 As shown, when both thermal and compressive stresses are taken into account in the equivalent stress (Von Mises Stress) based on the ratio W / H of the width W to the height H of the curved surface 22 of the primary protective wall 2, the ratio W / H of the primary protective wall 2 of the present invention is in the range of 2.0 to 3.0, resulting in concentrated thermal and compressive stresses. In contrast, in the case of the primary protective wall of the comparative object, the ratio W / H of the width to height of the large or small corrugations is approximately 1.5 or less, resulting in a significant difference in thermal and compressive stresses. That is, it can be seen that, compared with the comparative object whose ratio W / H is 1.5 or less, the present invention, with a ratio W / H in the range of 2.0 to 3.0, exhibits good thermal and compressive stresses.

[0261] Specifically, in this invention, the thermal stress increases proportionally to the ratio W / H of the width to height of the primary protective wall 2, while the compressive stress decreases inversely proportionally to the ratio W / H of the width to height of the primary protective wall 2. When the ratio W / H of the width to height is in the range of 2.0 to 3.0, the distribution of thermal stress and compressive stress is concentrated. At this time, it can be seen that the thermal stress and compressive stress of the primary protective wall 2 of this invention are between 110MPa and 210MPa.

[0262] Conversely, in the comparison, the maximum thermal stress of large corrugations with a width-to-height ratio (W / H) of approximately 1.5 or less in the primary protective wall is approximately 73 MPa, and the maximum compressive stress is approximately 310 MPa. The maximum thermal stress and maximum compressive stress of small corrugations with a width-to-height ratio (W / H) of approximately 1.5 or less in the primary protective wall are approximately 150 MPa.

[0263] In addition, such as Figure 37 As shown, in this invention, the ratio of the width to the height of the primary protective wall 2, W / H, is in the range of 2.0 to 3.0, and the radius of curvature 'r3-r2-r1' is in the range of 10 mm to 30 mm, preferably in the range of 15 mm to 27 mm, thus obtaining the optimized cross-sectional shape of the primary protective wall 2.

[0264] Conversely, in the comparison object, when the ratio of the width to the height (W / H) of the large and small corrugations of the primary protective wall is about 1.5 or less, the radius of curvature 'r3-r2-r1' of the large corrugation is about 48 mm, and the radius of curvature 'r3-r2-r1' of the small corrugation is about 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.

[0265] 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 Celsius. Since it is manufactured at room temperature, it needs to be in the range of 170 MPa to 180 MPa.

[0266] Therefore, the primary protective wall 2 in this embodiment preferably has a width-to-height ratio (W / H) in the range of 2.0 to 3.0, and a shape that satisfies the requirement of 'r3-r2-r1' values ​​in the range of 15 mm to 27 mm below 170 MPa, thereby reducing thermal stress (y = 72.446e). 0.3522x ) or compressive stress (y=255.95e) -0.233x (Not exceeding approximately 170 MPa and distinct from the comparison object.)

[0267] The following [Table 3] uses charts to illustrate... Figure 36 The distribution of thermal and compressive stresses in the equivalent stress (Von Mises Stress) is shown based on the ratio W / H of the width W of the curved surface 22 of the primary protective wall 2 to the height H of the curved surface 22.

[0268] [Table 3]

[0269]

[0270]

[0271] Figure 38Fig. 2 (a), (b) and (c) are graphs showing the results of structural analysis of sloshing pressure values when fluid flows into the transverse and longitudinal curved portions of the primary containment wall of the present application and the primary containment wall of the comparative object, at this time, the velocity of the fluid flowing into the transverse and longitudinal curved portions is 5 m / s. Figure 38 Fig. 2 (a) is a structural analysis of sloshing pressure values when fluid flows into the transverse or longitudinal curved portion 22 of the primary containment wall 2 of the present application, the maximum sloshing pressure value 305.29 Pa is obtained at the first point Pl of the curved portion 22. In addition, Figure 38 Fig. 2 (b) is a structural analysis of sloshing pressure values when fluid flows into the transverse curved portion (large corrugation) of the primary containment wall of the comparative object, the maximum sloshing pressure value 10,515 Pa is obtained at the second point P2 of the transverse curved portion (large corrugation), Figure 38 Fig. 2 (c) is a structural analysis of sloshing pressure values when fluid flows into the longitudinal curved portion (small corrugation) of the primary containment wall of the comparative object, the maximum sloshing pressure value 3577.6 Pa is obtained at the third point P3 of the longitudinal curved portion (small corrugation).

[0272] Here, as described above, the primary containment wall 2 of the present application has the same size and height of the cross-sectional shape of the transverse and longitudinal curved portions 22, but the primary containment wall of the comparative object is crossed by a large transverse curved portion (large corrugation) having a conventional curved portion cross-sectional shape of a large size and a small longitudinal curved portion (small corrugation) of a small size, so it can be seen that the sloshing pressure value of the primary containment wall 2 of the present application is excellent in the transverse curved portion and very excellent in the longitudinal curved portion compared to the primary containment wall of the comparative object.

[0273] Figure 39 Fig. 3 (a) and (b) show the deformation when the same distribution load is applied to the primary containment wall of the present application and the primary containment wall of the comparative object (showing the results of structural analysis according to the sloshing impact pressure), at this time, the plastic-elastic structural analysis is performed by applying an impact pressure of 10 bar to the entire primary containment wall. This is to grasp the dynamic behavior and plastic deformation amount in the cross-sectional shape of the primary containment wall. Figure 39 The cross-sectional shape of the curved portion 22 of the primary containment wall 2 of the present application shown in Fig. 3 (a) is inclined more than Figure 39 The cross-sectional shape of the curved portion (large corrugation) of the primary containment wall of the comparative object shown in Fig. 3 (b) is gentle, so it can be seen that there is almost no deformation in the primary containment wall 2 of the present application, but there is a lot of deformation in the primary containment wall of the comparative object. As described above, in the case of the primary containment wall of the comparative object, additional work such as filling a wedge or a shape-retaining object such as wood or metal at the lower end of the curved portion is required to prevent deformation.

[0274] The above has been described in detail through specific embodiments, but this is only for specifically illustrating the present application, and the present application is not limited thereto, and it is obvious for those skilled in the art to make modifications or improvements within the technical idea of the present application.

[0275] Simple modifications or changes of the present application all belong to the field of the present application, and the specific protection scope of the present application can be explicitly defined by the scope of the appended claims.

[0276] Reference signs

[0277] 1: liquefied gas storage tank 2: primary protection wall

[0278] 2a: unit protection wall 21: flat portion

[0279] 22: curved portion 22a: first curved portion

[0280] 22b: second curved portion 22c: third curved portion

[0281] 23: boundary portion 24: protruding structure

[0282] 3: primary insulation wall 3b: fixed insulation wall

[0283] 31: primary plywood 32: primary insulation material

[0284] 3a: connecting insulation wall 31a: connecting plywood

[0285] 32a: connecting insulation material 33: auxiliary insulation board

[0286] 4: secondary protection wall 41: main protection wall

[0287] 42: auxiliary protection wall GAC: glass-aramid fabric

[0288] AF: aluminum foil GC: glass fabric

[0289] BC: basalt fabric 5: secondary insulation wall

[0290] 51: secondary insulation material 52: secondary plywood

[0291] 6: adhesive 7: ship body

[0292] 8: leveling member 9: fixing member

[0293] 91: protruding portion 92: stud bolt

[0294] A1: first circle A2: second circle

[0295] A3: third circle A4: fourth circle

[0296] C1: first center of curvature C2: second center of curvature

[0297] C3: third center of curvature C4: fourth center of curvature

[0298] P1: first connection point P2: second connection point

[0299] P3: third connection point P4: fourth connection point

[0300] r1: first radius of curvature r2: second radius of curvature

[0301] r3: third radius of curvature

Claims

1. A liquefied gas storage tank, comprising a primary protective wall, a primary insulation wall, a secondary protective wall, and a secondary insulation wall, wherein the primary protective wall forms a containment space for cryogenic substances and is made of a metallic material; the primary insulation wall is disposed outside the primary protective wall; the secondary protective wall is disposed outside the primary insulation wall and is composed of a main protective wall and an auxiliary protective wall; the secondary insulation wall is disposed outside the secondary protective wall, characterized in that... The primary protective wall is composed of a plurality of planar portions fixed to the top surface of the primary insulation wall, and curved portions formed between the plurality of planar portions toward the receiving space side, including transverse curved portions and longitudinal curved portions. The curved surface includes: A pair of first curved surfaces, each connected to an adjacent planar portion, have a first radius of curvature r1; The second curved surface, forming the upper part of the curved surface, has at least a second radius of curvature r2 that is greater than the first radius of curvature r1; and A pair of third curved surfaces, respectively connecting a pair of first curved surfaces and a pair of second curved surfaces, each having a third curvature radius r3 greater than the second curvature radius r2. The first curvature center of one of the three third curved surfaces and the second curvature center of the other third curved surface are located horizontally offset on the inner side of the curved surface.

2. The liquefied gas storage tank according to claim 1, characterized in that, The horizontal curved surface and the vertical curved surface intersect, and the horizontal curved surface and the vertical curved surface have the same height and width.

3. The liquefied gas storage tank according to claim 1, characterized in that, The third radius of curvature is greater than the sum of the second radius of curvature and the first radius of curvature.

4. The liquefied gas storage tank according to claim 1, characterized in that, The ratio of the width W to the height H of the curved surface, W / H, is in the range of 2.0 to 3.0, i.e., 2.0 ≤ W / H ≤ 3.0, and is determined based on the thermal stress and compressive stress of the primary protective wall at low temperature.

5. The liquefied gas storage tank according to claim 1, characterized in that, Each of the first curved surfaces is a surface shape having the first radius of curvature between a first connection point connected to the planar portion and a second connection point connected to the pair of third curved surfaces. The location of the first connection point is the same as the location of the point where the curve of the first circle with the first radius of curvature from the center of curvature on the receiving space side intersects the longitudinal centerline of the first circle. The second connection point is located within a 30-degree downward angle of the curved portion of the first circle from the point where the curve of the first circle intersects with the transverse center line of the first circle.

6. The liquefied gas storage tank according to claim 1, characterized in that, The primary protective wall also includes a protruding structure located within a predetermined distance from the intersection of the transverse curved surface and the longitudinal curved surface, protruding into the planar portion toward the receiving space.

7. The liquefied gas storage tank according to claim 6, characterized in that, The protruding structure is smaller than the transverse curved surface and the longitudinal curved surface, and is formed in a convex circle or arc shape.

8. The liquefied gas storage tank according to claim 1, characterized in that, The first curvature center and the second curvature center of the pair of third curved surfaces are located on the upper part than the imaginary plane formed by the planar portion.

9. A ship, characterized in that, Includes the liquefied gas storage tank according to any one of claims 1 to 8.

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