Design method for liquefied hydrogen tanks

Abstract

To provide a structure and a design method which can prevent leakage of hydrogen of liquid or gas regardless of the size of a liquefied hydrogen tank which is mounted on a vessel so as to achieve mass transportation of liquified hydrogen at cryogenic temperature.SOLUTION: A liquified hydrogen tank mounted on a vessel includes an inner tank for storing liquified hydrogen, and an outer tank surrounding the inner tank. At least one of the inner tank and the outer tank is a leakage prevention tank. The leakage prevention tank has such wall thickness as to prevent propagation of an initial defect exceeding half of the wall thickness during a tank life.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to the structure of a liquefied hydrogen tank mounted on a ship that transports liquefied hydrogen in bulk (hereinafter referred to as a liquefied hydrogen carrier) and a design method for the liquefied hydrogen tank. [Background technology]

[0002] A known cargo tank for a liquefied hydrogen carrier includes an inner tank for storing liquefied hydrogen, an outer tank surrounding the inner tank, and a heat insulating layer between the inner and outer tanks. Patent Document 1 discloses an example of a cargo tank for a liquefied hydrogen carrier.

[0003] The design and manufacture of ships that transport liquefied gases are required to comply with the international regulations, the IGC Code (Non-Patent Document 1). The current IGC Code is intended for ships that transport liquefied gases such as LPG and LNG, but does not apply to liquefied hydrogen carriers, and the IGC Code does not specify requirements for the transportation of liquefied hydrogen.

[0004] It is known that the main cause of crack propagation in cargo tanks on ships is dynamic stress caused by repeated loads acting on the cargo tank due to the ship's motion. According to the design method for Type C tanks in accordance with the IGC Code, the design vapor pressure Po is set sufficiently high to allow for a safety factor, which results in a high minimum design pressure. The tank's wall thickness is designed to be sufficiently thick to provide the strength required to withstand this minimum design pressure. As a result, the tank's dynamic fluctuating stress is sufficiently small, and the propagation of any anticipated initial defects is also sufficiently small relative to the wall thickness. Therefore, leakage of liquid cargo is not anticipated, and the installation of a secondary barrier is not required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2014 / 174820 [Non-patent literature]

[0006] [Non-Patent Document 1] International Maritime Organization, “THE INTERNATIONAL CODE FOR THE CONSTRUCTION AND EQUIPMENT OF SHIPS CARRYING LIQUEFIED GASES IN BULK (IGC CODE)” CHAPTER 4 CARGO CONTAINMENT, adopted on 22 May 2014 Summary of the Invention [Problem to be solved by the invention]

[0007] Volume is 20,000m 3 For large independent cargo tanks for transporting liquefied gases exceeding 20,000m3, design methods other than Type C tanks (i.e., Type A tanks or Type B tanks) specified in the IGC Code have been applied. The design method for Type C tanks in accordance with the IGC Code is mainly for tanks with a capacity of 20,000m3 or more. 3 The reason is that if the design method for Type C tanks in accordance with the IGC Code is applied to large tanks, the wall thickness of the tank corresponding to the minimum design pressure will exceed the practical range.

[0008] The present disclosure has been made in consideration of the above circumstances, and its purpose is to propose a structure and design method that can prevent leakage of liquid or gaseous hydrogen from liquefied hydrogen tanks installed on ships, regardless of the size of the liquefied hydrogen tank, in order to realize the mass transportation of cryogenic liquefied hydrogen. [Means for solving the problem]

[0010] Book The disclosed method for designing a liquefied hydrogen tank includes an inner tank for storing liquefied hydrogen and an outer tank surrounding the inner tank, and is a method for designing a liquefied hydrogen tank to be installed on a ship, comprising: At least one of the inner tank and the outer tank is a leakage prevention tank, a first processor acquires the tank life of the leakage prevention tank, the size of the initial defect in the leakage prevention tank, the temperature of the leakage prevention tank, the stress intensity factor of the leakage prevention tank, and the stress generated in the leakage prevention tank, and determines the amount of crack growth in the initial defect due to the stress for the number of cycles corresponding to the tank life through fatigue crack growth analysis; a second processor acquires the determined crack growth amount and the design wall thickness of the leakage prevention tank, and determines the design wall thickness as appropriate when the crack growth amount does not grow beyond half of the design wall thickness, and determines the design wall thickness as inappropriate when the crack growth amount grows beyond half of the design wall thickness; The wall thickness of the leakage prevention tank is determined so as to be equal to or greater than the design wall thickness determined to be appropriate. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to propose a structure and design method for a liquefied hydrogen tank installed on a ship that can prevent leakage of liquid or gaseous hydrogen regardless of the size of the liquefied hydrogen tank. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a ship equipped with a liquefied hydrogen tank according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of a liquefied hydrogen carrier. [Figure 3] FIG. 3 is a diagram showing the configuration of a leak prevention tank design device. [Figure 4] FIG. 4 is a functional block diagram of a leak-proof tank design device. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, an embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a schematic configuration diagram of a ship 1 equipped with liquefied hydrogen tanks 3 according to one embodiment of the present disclosure. The ship 1 shown in FIG. 1 comprises a hull 2 ​​and four liquefied hydrogen tanks 3 mounted on the hull 2. The liquefied hydrogen tanks 3 according to this embodiment are cargo tanks for transporting liquefied hydrogen, and the ship 1 is a liquefied hydrogen carrier. In this embodiment, the liquefied hydrogen tanks 3 are aligned along the length of the ship, but may also be aligned along the width of the ship if the ship is wide. Furthermore, the number of liquefied hydrogen tanks 3 mounted on the hull 2 ​​may be one, or two or more.

[0015] In this embodiment, the four liquefied hydrogen tanks 3 have substantially the same structure. In this embodiment, the liquefied hydrogen tanks 3 are configured as multi-layer tanks. However, if the ship 1 is equipped with multiple liquefied hydrogen tanks 3, the multiple liquefied hydrogen tanks 3 may each have a different structure.

[0016] Fig. 2 is a cross-sectional view of the ship 1. As shown in Figs. 1 and 2, the liquefied hydrogen tank 3 comprises an inner tank 4 that stores liquefied hydrogen and an outer tank 5 that surrounds the inner tank 4. The capacity of the inner tank 4 is 20,000 m 3 Over 50,000m 3 The liquefied hydrogen tank 3 is classified as a relatively large tank.

[0017] The inner tank 4 includes a substantially spherical inner tank body 41. The inner tank 4 may be provided with an inner tank dome that protrudes upward from the inner tank body 41. The outer tank 5 includes a substantially spherical outer tank body 51. The outer tank 5 may be provided with an outer tank dome that protrudes upward from the outer tank body 51. However, the inner tank body 41 and the outer tank body 51 do not necessarily have to be spherical, and may be cylindrical in shape that is elongated in the horizontal direction or cylindrical in shape that is elongated in the vertical direction. Alternatively, the inner tank body 41 and the outer tank body 51 may be cubic or rectangular.

[0018] The inner tank 4 and the outer tank 5 are spaced apart in the thickness direction of the tanks. The space between the inner tank 4 and the outer tank 5 is referred to as the "first region 31." A first insulating layer is formed in the first region 31. The first insulating layer is composed of a first gas filled in the first region 31 and an insulating material.

[0019] The first region 31 filled with the first gas is substantially at atmospheric pressure or in a low vacuum state. The first gas is hydrogen gas or helium gas. Atmospheric pressure is approximately 10 5 However, since the pressure in the first region 31 may fluctuate due to temperature and the motion of the hull 2, the "substantially atmospheric pressure" in this specification and claims is defined as approximately 10 5 Pa and approximately 10 5 The low vacuum state may include a pressure lower than atmospheric pressure, and may be 10 Pa or higher within the pressure fluctuation range. 5 Pa to 10 2 This indicates the atmospheric pressure ranging from 0 to 10 Pa. When the first gas is hydrogen gas, the gas phase of the inner tank 4 may be connected to the first region 31 so that the vaporized gas generated in the inner tank 4 flows into the first region 31. As described above, the liquefied hydrogen tank 3 according to this embodiment is not a vacuum insulated tank, but a vacuum insulation layer may be provided between the inner tank 4 and the outer tank 5 by arranging an insulation layer in the first region 31 and evacuating the first region 31.

[0020] The hull 2 ​​has multiple holds 21 that open upward. The multiple holds 21 are lined up in the longitudinal direction of the ship and are separated from one another by walls 22. The lower parts of the inner tub 4 and outer tub 5 are housed inside each hold 21. The upper part of the outer tub 5 is covered by a tank cover 6. The outer tub 5 is surrounded by the walls 22 and tank cover 6, which are components of the hull 2 ​​that form the hold 21. The area between the outer tub 5, the tank cover 6, and the walls 22 of the holds 21 is referred to as the "second area 32." A second insulating layer is formed in the second area 32. The second insulating layer is composed of insulating material arranged around the outer wall of the outer tub 5 and a second gas filled in the second area 32.

[0021] The second region 32 filled with the second gas is substantially at atmospheric pressure. Although not particularly limited, the second region 32 may be at a higher pressure than the first region 31. The second gas includes at least one of an inert gas such as nitrogen and dry air. For example, the second region 32 may be filled with dry air, and an inert gas may be held in the second insulating layer.

[0022] A pair of skirts 25 spaced apart in the longitudinal direction of the ship are provided inside each hold 21. The skirts 25 support the outer tub 5. In addition, a pair of support members 35 supporting the inner tub body 41 are provided between the inner tub 4 and the outer tub 5. In this embodiment, the skirts 25 are arranged on the extension of the support members 35, but the arrangement of the support members 35 and the skirts 25 is not limited to this embodiment.

[0023] [Tank type of liquefied hydrogen tank 3] Here, the tank type of the liquefied hydrogen tank 3 will be described in detail.

[0024] The outer tank 5 is configured as an independent tank that is separate from the hull 2, and the liquefied hydrogen tank 3 as a whole is an independent tank. An independent tank is a self-supporting tank that does not form part of the hull structure and is not essential to the strength of the hull.

[0025] At least one of the inner vessel 4 and the outer vessel 5 is a leak-proof tank. A leak-proof tank has a wall thickness that prevents an initial defect from propagating beyond half the wall thickness during the tank's lifespan. In such a leak-proof tank, the propagation of a possible initial defect is sufficiently small compared to the wall thickness (wall thickness), so leakage of the liquid or gas contained in the leak-proof tank is not expected. A leak-proof tank defined in this way corresponds to a Type C tank defined in the IGC Code in that leakage of the liquid or gas contained therein is not expected.

[0026] In this embodiment, both the inner tank 4 and the outer tank 5 are leak-proof tanks. In the liquefied hydrogen tank 3 according to this embodiment, liquefied hydrogen is stored in the inner tank 4, and the first region 31 between the inner tank 4 and the outer tank 5 is filled with hydrogen gas. Therefore, it is difficult to distinguish whether the hydrogen gas in the first region 31 is due to a leak from the inner tank 4 or hydrogen gas that was previously filled in the first region 31. Because it is difficult to detect a leak of liquefied hydrogen from the inner tank 4, the inner tank 4 is particularly required to be configured to prevent leakage of liquefied hydrogen. Therefore, it is desirable that at least the inner tank 4 be a leak-proof tank. If the inner tank 4 is a leak-proof tank and the outer tank 5 is not, the required level of fracture strength for the outer tank 5 is lowered, allowing the outer tank 5 to have a thinner plate, which leads to a reduction in material costs. Furthermore, in this embodiment, it is desirable that the outer tank 5 be a leak-proof tank to prevent flammable hydrogen gas in the first region 31 from leaking from the outer tank 5. Furthermore, if the outer tank 5 is a leak-proof tank and the first region 31 is filled with a first gas other than hydrogen gas or the first region 31 is in a vacuum, the inner tank 4 does not have to be a leak-proof tank.

[0027] [Design method for leak prevention tank of liquefied hydrogen tank 3] Here, a method for designing the leakage prevention tank out of the inner tank 4 and outer tank 5 that make up the liquefied hydrogen tank 3 will be described in detail.

[0028] FIG. 3 is a schematic diagram of a design device 8 for leak-proof tanks. The design method for leak-proof tanks is implemented using the design device 8. The design device 8 is composed of at least one computer 80. Each computer 80 includes a processor 81 and a memory 82 storing programs, information, and the like to be executed by the processor 81. The functions of the design device 8 disclosed herein can be implemented using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor includes transistors and other circuits, and therefore is considered a processing circuit or circuit. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the enumerated functions. When the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0029] 4 is a functional block diagram of the design device 8. The design device 8 includes the following functional units: a stress analysis unit 84, a fatigue crack growth analysis unit 85 that calculates the amount of crack growth, a stress intensity factor analysis unit 86 that calculates the stress intensity factor, a judgment unit 87, and a wall thickness determination unit 88. A plurality of functional units may be configured in a single computer 80, or a plurality of functional units may be distributed across a plurality of computers 80.

[0030] When carrying out the design method for a leakage prevention tank, a design wall thickness is set in the design device 8. The design wall thickness may be any value, but is set within a range of values ​​that can be used as the wall plate of a leakage prevention tank. For example, if the wall plate of the leakage prevention tank is made of steel plate, the design wall thickness may be set in a range of 60 mm or less, and if the wall plate of the leakage prevention tank is made of non-ferrous steel plate, the design wall thickness may be set in a range of 80 mm or less.

[0031] The design method for a leakage prevention tank includes (1) a stress analysis step, (2) a stress intensity factor analysis step, (3) a crack growth analysis step, (4) a judgment step, and (5) a wall thickness determination step. However, the wall thickness determination step may be performed by a designer instead of the wall thickness determination unit 88.

[0032] (1) Stress analysis step As the ship 1 navigates through ocean waves, fluctuating pressure due to the waves acts on the surface of the hull 2. This fluctuating pressure causes the hull 2 ​​to pitch and roll, and the acceleration of the pitch causes a fluctuating load caused by the inertial force of the cargo, liquid hydrogen, to act on the leak prevention tank. This fluctuating load generates fluctuating stress, i.e., dynamic stress, in the leak prevention tank. The stress analysis unit 84 calculates the stress generated in the leak prevention tank, particularly in the welds of the leak prevention tank, due to the pitch of the hull 2 ​​in this way.

[0033] The method of stress analysis by the stress analysis unit 84 is not particularly limited, and examples include numerical analysis methods such as the finite element method, as well as simulation. For example, the stress analysis unit 84 acquires fluctuating loads caused by the motion of the hull 2 ​​due to waves while in service and the waves that the hull 2 ​​receives, and applies these fluctuating loads to a numerical analysis model of the entire ship 1, including the hull structure, the leakage prevention tank structure, and the tank support structure, to perform numerical analysis to determine the estimated generated stress (the generated stress distribution in the leakage prevention tank). The leakage prevention tank structure incorporates a set wall thickness as a parameter. The fluctuating loads and the numerical analysis model may be provided to the stress analysis unit 84 in advance. The fluctuating loads can be determined by simulation based on the conditions of the ship 1's route, or experimentally.

[0034] (2) Stress intensity factor analysis step The stress intensity factor analysis unit 86 determines the stress intensity factor of the crack (stress intensity factor distribution of the leakage prevention tank). Various methods for analyzing stress intensity factors are known. The method for analyzing the stress intensity factor by the stress intensity factor analysis unit 86 is not particularly limited, but examples include numerical analysis methods such as the finite element method. The stress intensity factor analysis unit 86 determines the stress intensity factor of the crack by elastic stress analysis using the finite element method, for example, using a numerical analysis model including the generated stress determined by the stress analysis unit 84, the leakage prevention tank structure including the weld shape, the size of the initial defect in the leakage prevention tank, and the crack shape. The stress intensity factor analysis unit 86 may change the analysis method depending on the analysis portion of the leakage prevention tank.

[0035] (3) Crack propagation analysis step The fatigue crack propagation analysis unit 85 determines the crack propagation amount of an initial defect in the leakage prevention tank through fatigue crack propagation analysis. The method of fatigue crack propagation analysis by the fatigue crack propagation analysis unit 85 is not particularly limited, and examples include numerical analysis methods such as the finite element method and simulation. For example, the fatigue crack propagation analysis unit 85 acquires the tank life of the leakage prevention tank, the fracture toughness of the leakage prevention tank material, the stress intensity factor of the analysis area, and the stress generated at the analysis area, and loads these data into a fatigue crack propagation analysis model to perform numerical analysis, thereby determining the crack propagation amount of the initial defect over the tank life. Information regarding the tank structure, such as the tank life, the size of the initial defect, the temperature of the leakage prevention tank, and the fracture toughness of the leakage prevention tank material, is provided to the fatigue crack propagation analysis unit 85 in advance. The size of the initial defect may be any value corresponding to the size of an initial defect that may actually exist. The tank life may be any value corresponding to the life of the ship 1. The number of cycles of stress generated during the tank life can be estimated based on the tank life. The temperature of the leakage prevention tank is the temperature of the leakage prevention tank when liquefied hydrogen is stored in the inner tank 4. The fracture toughness may be the fracture toughness of the material at the temperature of the leakage prevention tank when liquefied hydrogen is stored in the inner tank 4. The stress intensity factor of the analyzed portion may be calculated by the stress intensity factor analysis unit 86. The stress generated in the analyzed portion may be calculated by the stress analysis unit 84.

[0036] (4) Judgment step The determining unit 87 determines the design wall thickness as "suitable" if it satisfies the requirement that "a wall thickness at which an initial defect does not propagate beyond half the wall thickness during the tank's life," and determines the design wall thickness as "unsuitable" otherwise. Specifically, the determining unit 87 obtains the crack propagation amount of the initial defect over the tank's life calculated by the fatigue crack propagation analysis unit 85, and determines the design wall thickness as suitable if the crack propagation amount does not exceed half the design wall thickness (i.e., if the crack propagation amount is half or less of the design wall thickness), and determines the design wall thickness as unsuitable if the crack propagation amount exceeds half the design wall thickness.

[0037] (5) Wall thickness determination step The wall thickness determination unit 88 determines the wall thickness of the leakage prevention tank so that it is equal to or greater than the design wall thickness determined to be appropriate by the determination unit 87. A leakage prevention tank having the wall thickness determined in this manner is designed.

[0038] In the design method for a leakage prevention tank described above, the suitability of the design wall thickness is determined based on the amount of crack growth. However, the suitability of the design wall thickness may also be determined based on whether or not unstable fracture occurs. In this case, the stress intensity factor analysis unit 86 determines the stress intensity factor of a crack that has grown from an initial defect by the amount of crack growth determined by the fatigue crack growth analysis unit 85 (i.e., a crack during the tank's life) as a judgment index for unstable fracture. If this judgment index is equal to or greater than the fracture toughness value, unstable fracture is expected to occur during the tank's life. Therefore, the judgment unit 87 acquires the judgment index and the fracture toughness value of the material of the leakage prevention tank, and determines the design wall thickness as inappropriate if the judgment index is equal to or greater than the fracture toughness value, and determines the design wall thickness as appropriate if the judgment index is less than the fracture toughness value.

[0039] [Summary] A liquefied hydrogen tank 3 according to an embodiment of the present disclosure is a liquefied hydrogen tank 3 to be installed on a ship 1, and comprises an inner tank 4 in which liquefied hydrogen is stored and an outer tank 5 surrounding the inner tank 4, and at least one of the inner tank 4 and the outer tank 5 is a leak-proof tank, characterized in that the leak-proof tank has a wall thickness that prevents initial defects from propagating beyond half the wall thickness during the tank's lifespan.

[0040] In the liquefied hydrogen tank 3, both the inner vessel 4 and the outer vessel 5 may be leak-proof tanks.

[0041] In the liquefied hydrogen tank 3, hydrogen gas is filled between the inner tank 4 and the outer tank 5, and the inner tank 4 may be a leak-proof tank.

[0042] In the liquefied hydrogen tank 3, hydrogen gas is filled between the inner tank 4 and the outer tank 5, and the outer tank 5 may be a leak-proof tank.

[0043] With the liquefied hydrogen tank 3 configured as described above, even if an initial defect exists in the leak prevention tank provided in the liquefied hydrogen tank 3, the progression of the initial defect during the tank's life is sufficiently small relative to the wall thickness, so leakage of the liquid or gas contained in the leak prevention tank is not expected. This type of leak prevention tank corresponds to a Type C tank as defined in the IGC Code, in that leakage of the contained liquid or gas is not expected. Therefore, the leak prevention tank and the liquefied hydrogen tank 3 provided with it can omit a secondary barrier.

[0044] In the liquefied hydrogen tank 3, the capacity of the inner tank 4 is 20,000 m 3 Over 50,000m 3 It may be the following:

[0045] In this way, even if the liquefied hydrogen tank 3 is a relatively large tank as described above, it can have a wall thickness that is actually feasible to construct while still providing a predetermined leakage prevention function.

[0046] Further, the design method of the liquefied hydrogen tank 3 according to this embodiment is as follows: a first processor (fatigue crack propagation analysis unit 85) acquires the tank life of the leakage prevention tank, the size of the initial defect in the leakage prevention tank, the temperature of the leakage prevention tank, the stress intensity factor of the leakage prevention tank, and the stress occurring in the leakage prevention tank, and determines the amount of crack propagation of the initial defect due to the stress of the number of repetitions corresponding to the tank life through fatigue crack propagation analysis; A second processor (determination unit 87) acquires the calculated crack growth amount and the design wall thickness of the leakage prevention tank, and determines that the design wall thickness is appropriate if the crack growth amount does not grow beyond half the design wall thickness, and determines that the design wall thickness is inappropriate if the crack growth amount grows beyond half the design wall thickness; The wall thickness of the leakage prevention tank is determined so that it is equal to or greater than the design wall thickness that is judged to be appropriate.

[0047] According to the above-described method for designing the liquefied hydrogen tank 3, it is possible to design a tank that does not leak the gas or liquid contained therein, within a realistic range of wall thickness.

[0048] The design method of the liquefied hydrogen tank 3 is as follows: The method may further include a third processor (stress intensity factor analysis unit 86) determining, as a judgment index, the stress intensity factor of a crack that has grown from an initial defect during the tank's life, and a fourth processor (wall thickness determination unit 88) acquiring a fracture toughness value of the material of the leakage prevention tank, and determining, if the judgment index is equal to or greater than the fracture toughness value, that the design wall thickness is inappropriate because unstable fracture is expected to occur during the tank's life. Note that the calculation of the stress intensity factor may be performed for the final crack shape after the tank's life has elapsed, or may be performed sequentially for the crack shape that grows during the tank's life.

[0049] According to the above design method, the suitability of the designed wall thickness is further judged based on whether or not unstable fracture occurs, so that a tank can be designed that can more reliably prevent leakage.

[0050] In the above embodiment, the inner tank 4 is generally classified as a large tank, but the inner tank 4 is 20,000 m 3 The inner tank 4 may be a tank classified as small as follows, and the inner tank 4 may be a leak-proof tank. In other words, the structure and design method of the liquefied hydrogen tank 3 according to the present disclosure is not limited to the size of the tank, and may be applied to small tanks or tanks with a capacity of 50,000 m 3 This may be applied to large tanks exceeding 1000 m.

[0051] In the above embodiment, the liquefied hydrogen tank 3 is a cargo tank, but the structure and design method of the liquefied hydrogen tank 3 according to the present disclosure may be applied to a fuel tank mounted on a ship 1. In this case, the ship 1 is not limited to a liquefied hydrogen carrier.

[0052] The foregoing discussion of the present disclosure has been presented for purposes of illustration and description and is not intended to limit the present disclosure to the form disclosed herein. For example, in the foregoing Detailed Description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. However, multiple features included in the present disclosure can be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0053] 1: Ship 2: Hull 3: Liquefied hydrogen tank 4: Inner tank 5: Outer tank 8:Design equipment 22: Wall 25: Skirt 80: Computer 81: Processor 82: Memory 84: Stress analysis section 85: Fatigue crack propagation analysis section 86: Stress intensity factor analysis section 87: Judgment section 88:Wall thickness determination part

Claims

1. A design method for a liquefied hydrogen tank to be installed on a ship, the tank comprising an inner tank for accommodating liquefied hydrogen and an outer tank surrounding the inner tank, comprising: At least one of the inner tank and the outer tank is a leakage prevention tank, a first processor acquires the tank life of the leakage prevention tank, the size of the initial defect in the leakage prevention tank, the temperature of the leakage prevention tank, the stress intensity factor of the leakage prevention tank, and the stress occurring in the leakage prevention tank, and determines the amount of crack growth in the initial defect due to the stress for the number of cycles corresponding to the tank life through fatigue crack growth analysis; a second processor acquires the determined crack growth amount and the design wall thickness of the leakage prevention tank, and determines the design wall thickness as appropriate when the crack growth amount does not grow beyond half of the design wall thickness, and determines the design wall thickness as inappropriate when the crack growth amount grows beyond half of the design wall thickness; determining a wall thickness of the leakage prevention tank so that the wall thickness is equal to or greater than the design wall thickness determined to be appropriate; How to design a liquefied hydrogen tank.

2. a third processor determines a stress intensity factor of a crack that has grown from the initial defect during the tank's life as a judgment index; a fourth processor acquires a fracture toughness value of the material of the leakage prevention tank, and if the judgment index is equal to or greater than the fracture toughness value, determines that the design wall thickness is inappropriate because unstable fracture is expected to occur during the tank's lifespan; The design method for a liquefied hydrogen tank according to claim 1.

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