Design method for insulation system of liquefied gas storage tank and ship

Abstract

The design method for an insulation system for an independent type B liquefied gas storage tank of the present invention is characterized by including a liquefied gas selection step for selecting the type of liquefied gas, a leakage standard setting step for setting a leakage standard value for the liquefied gas, a shape selection step for selecting the shape of the partial secondary barrier, a setting and evaluation step for setting a target evaporation rate of the liquefied gas and evaluating the leakage amount of the liquefied gas, a comparison step for comparing the target evaporation rate of the liquefied gas with the leakage amount of the liquefied gas, a step for designing the shape of the partial secondary barrier, and a step for installing the partial secondary barrier.

Description

[Technical Field]

[0001] The present invention relates to a design method for an insulation system for a stand-alone Type B liquefied gas storage tank and a ship equipped with an insulation system manufactured using the same. More specifically, the present invention relates to a design method for an insulation system for a stand-alone Type B liquefied gas storage tank, which completely vaporizes leaked liquefied gas, can be manufactured in various shapes, and can reflect changes in each step by applying a partial secondary barrier manufactured based on the type and physical properties of the liquefied gas leaked from the storage tank, and a ship equipped with an insulation system manufactured using the same. [Background technology]

[0002] Natural gas is usually transported in a gaseous state via onshore or offshore gas pipelines, or is stored in a liquefied natural gas (LNG) state on LNG carriers and transported to distant destinations.

[0003] Storage tanks for liquefied gases such as LNG (Liquefied Natural Gas) and LH2 (Liquefied Hydrogen), as well as transportation vehicles and structures that house such tanks, require various facilities and equipment to store and manage the liquefied gas within the storage tanks. Such facilities and equipment must meet all the conditions, such as temperature and pressure, required for storing and managing the liquefied gas, and must be designed with these conditions in mind.

[0004] Liquefied gas storage technologies are primarily classified into membrane tanks and independent tanks, based on classification standards such as the IGC code, which applies to liquefied gas carriers, and land-based tank technologies. Independent tanks are primarily classified into three types, type A, type B, and type C, based on the construction method of the secondary barrier. Of these, independent type B tanks have a partial secondary barrier, which is required to be watertight (also known as liquid tightness).

[0005] Independent type B tanks used on ships are designed and manufactured as spherical or prismatic tanks. At the bottom of these tanks, a drip tray is provided as a partial secondary barrier, connected to a passage through which leaked liquefied gas can be discharged.

[0006] Such drip trays are fixed to the bottom of the storage tank to collect the liquid (LNG) that flows downward due to gravity. The drip tray has an internal space and is installed at one or more locations on the bottom of the storage tank to collect the cryogenic liquid that flows downward.

[0007] While such drip trays provide temporary protection for the ship's hull (for 15 days), the size of the drip trays is too large to contain the leaked cryogenic fluid in liquid form during this period. Therefore, a practical alternative method that does not require gastightness is sought.

[0008] Additionally, if the bottom of the storage tank is relatively flat, multiple drip trays must be installed, which can complicate design and installation in a small space. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is intended to solve the problems of the prior art, and aims to provide an insulation system for a liquefied gas storage tank that meets the leakage design criteria by completely vaporizing liquefied gas leaked from the storage tank within a tubular partial secondary barrier, rather than recovering it using the conventional drip tray-type partial secondary barrier.

[0010] Another object of the present invention is to provide an insulation system for a liquefied gas storage tank that requires less space to install a partial secondary barrier and has fewer spatial constraints.

[0011] Another object of the present invention is to compare the target evaporation rate of the liquefied gas with the evaporation rate of the selected tubular partial secondary barrier, and to fabricate partial secondary barriers of various shapes. [Means for solving the problem]

[0012] The design method for an insulation system for an independent type B liquefied gas storage tank of the present invention is characterized by including a liquefied gas selection step for selecting the type of liquefied gas, a leakage standard setting step for setting a leakage standard value for the liquefied gas, a shape selection step for selecting the shape of the partial secondary barrier, a setting and evaluation step for setting a target evaporation rate of the liquefied gas and evaluating the leakage amount of the liquefied gas, a comparison step for comparing the target evaporation rate of the liquefied gas with the leakage amount of the liquefied gas, a step for designing the shape of the partial secondary barrier, and a step for installing the partial secondary barrier.

[0013] In the present invention, the leakage standard value set in the leakage standard setting step is characterized by being set based on the physical properties of the liquefied gas selected in the liquefied gas selection step and the leakage rate of the liquefied gas.

[0014] In the present invention, the shape selection step is characterized in that the material, diameter, thickness, length and volume of the partial secondary barrier are set based on the leakage reference value, and the length of the partial secondary barrier is set to be long.

[0015] In the present invention, the setting and evaluation step is characterized by setting a target evaporation rate and evaluating the amount of liquefied gas leakage based on the shape and arbitrary length reference volume of the partial secondary barrier adopted in the shape selection step.

[0016] In the present invention, the comparison step compares the target evaporation rate with the leakage amount of liquefied gas, and if the leakage amount of liquefied gas is equal to or less than the target evaporation rate, the process returns to the shape selection step.

[0017] In the present invention, the shape selection step is characterized by resetting the length of the partial secondary barrier so that the length of the partial secondary barrier increases.

[0018] The partial secondary barrier manufactured in the present invention is characterized in that it is formed in a tubular shape having an internal space and is formed in any one of a straight, curved, zigzag, spring, and radial shape to increase its length.

[0019] The ship of the present invention is also equipped with an insulation system connected to an independent type B liquefied gas storage tank and manufactured by the above design method. [Effects of the Invention]

[0020] According to the present invention, an insulation system for a liquefied gas storage tank that meets leakage design standards is provided by completely vaporizing liquefied gas leaking from the storage tank within a tubular partial secondary barrier, eliminating the need for a conventional drip tray.

[0021] Furthermore, the present invention provides an insulation system for a liquefied gas storage tank that requires less space to install a partial secondary barrier in an independent B-type tank and has fewer spatial constraints.

[0022] Furthermore, according to the present invention, by setting and evaluating the evaporation rate of the liquefied gas, partial secondary barriers of various shapes can be produced, taking into consideration conditions that vary depending on the type of liquefied gas and changes in each step and design process. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view of an installation portion of a tubular partial secondary barrier provided in a thermal insulation system of a liquefied gas storage tank according to a first embodiment of the present invention. [Figure 2] 4(a) to 4(f) are diagrams showing the shapes of the partial secondary barriers provided in the thermal insulation system of the liquefied gas storage tank according to the first embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing a connection structure of a heat insulation system for a liquefied gas storage tank according to a first embodiment of the present invention. [Figure 4] FIG. 5 is a schematic diagram showing a connection structure of a heat insulation system for a liquefied gas storage tank according to a second embodiment of the present invention. [Figure 5] 1 is a flowchart showing the steps of designing a partial secondary barrier for a stand-alone B-type liquefied gas storage tank using a design method according to an embodiment of the present invention. [Figure 6] 1 is a flowchart showing a method for designing an insulation system for a stand-alone type B liquefied gas storage tank, taking into consideration the optimal shape of the partial secondary barrier, according to a design method of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The objects, particular advantages, and novel features of the present invention will become more apparent from the following detailed description and embodiments taken in conjunction with the accompanying drawings. Furthermore, when referring to components in the drawings of this specification, please note that the same components are denoted by the same reference numerals whenever possible, even if they appear in different drawings. In describing the present invention, detailed descriptions of related publicly known technologies will be omitted if they are deemed to unnecessarily detract from the gist of the present invention.

[0025] Furthermore, it should be understood that the attached drawings are only intended to facilitate understanding of the embodiments described in the specification of this application, and that the attached drawings do not limit the technical ideas disclosed in the specification of this application, and that all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention are included.

[0026] Furthermore, although terms including ordinal numbers such as first, second, etc. are used to describe various components, these components are not limited by these terms and are used only to distinguish one component from another.

[0027] Hereinafter, in the specification of this application, the term "liquefied gas" is used to include all gaseous fuels that are generally stored in a liquid state, such as LNG, liquefied hydrogen, liquefied nitrogen, LPG, liquefied ethylene, and liquefied ammonia. For convenience of explanation, the term "liquefied gas" is also used to refer to gases that are no longer in a liquid state due to heating or pressurization. This definition also applies to evaporated gas. Furthermore, in the specification of this application, LNG is used to include not only a liquid state but also a supercritical state. Furthermore, evaporated gas is used to include not only a gaseous state but also a liquefied evaporated gas.

[0028] Furthermore, the terms "primary" and "secondary" are used in this specification to distinguish between the function of primarily sealing or insulating LNG and the function of secondarily sealing or insulating LNG, based on the LNG stored in the storage tank.

[0029] Additionally, the terms "top" or "above" as applied to elements of a storage tank refer to the direction toward the inside of the storage tank, regardless of the direction of gravity, and similarly, the terms "bottom" or "below" refer to the direction toward the outside of the storage tank, regardless of the direction of gravity.

[0030] The present invention will now be described in detail by way of example with reference to the accompanying drawings, in which like reference numerals refer to like elements throughout the various drawings.

[0031] Furthermore, the vessels equipped with liquefied gas storage tanks described below include not only merchant ships that transport cargo from a departure point to a destination, but also marine structures that float at a specified point on the sea and perform specified operations. Furthermore, in the specification of this application, liquefied gas storage tanks include tanks of all types that store liquefied gas.

[0032] Structure of insulation system for liquefied gas storage tank The present invention can be applied to an independent type B liquefied gas storage tank in which the secondary barrier is formed of a partial secondary barrier and watertightness is required.

[0033] Fig. 1 is a cross-sectional view of an installation portion of a tubular partial secondary barrier provided in the thermal insulation system of a liquefied gas storage tank according to a first embodiment of the present invention. Fig. 2 (a) to (f) are diagrams showing the shapes of the partial secondary barriers provided in the thermal insulation system of a liquefied gas storage tank according to the first embodiment of the present invention. Fig. 3 is a schematic diagram showing a connection structure of the thermal insulation system of a liquefied gas storage tank according to the first embodiment of the present invention. Fig. 4 is a schematic diagram showing a connection structure of the thermal insulation system of a liquefied gas storage tank according to a second embodiment of the present invention.

[0034] The following description will be given with reference to Figure 1. The insulation system for a liquefied gas storage tank according to the first embodiment of the present invention comprises a primary barrier 100 in contact with liquefied gas, an insulating layer 200 provided on the outside of the primary barrier 100, a leakage movement passage 300 located between the primary barrier 100 and the insulating layer 200 and through which liquefied gas leaked from the primary barrier 100 (hereinafter also referred to as "leaked liquefied gas") moves, a leakage movement through-passage 400 inserted into the insulating layer 200 and connected to the leakage movement passage 300 and through which the leaked liquefied gas passes, and a tubular partial secondary barrier 500 communicating with the leakage movement through-passage 400. In addition, if leakage of liquefied gas occurs from the primary barrier 100, the entire amount of the leaked liquefied gas will vaporize as it passes through the tubular partial secondary barrier 500.

[0035] Specifically, the primary barrier 100 of the insulation system of the liquefied gas storage tank of this embodiment is configured to come into direct contact with the liquefied gas to seal it, and is formed of a metal material such as aluminum, nickel alloy steel, high manganese steel, stainless steel, and nickel depending on the characteristics of the liquefied gas to be stored.

[0036] The leakage migration passage 300 of the insulation system for the liquefied gas storage tank of this embodiment is provided between the primary barrier 100 and the insulation layer 200, and is a passage through which liquefied gas leaked from the primary barrier 100 moves. Specifically, the leakage migration passage 300 is a space for discharging leaked liquefied gas when damage to the primary barrier 100 causes leakage of the liquefied gas stored in the storage tank.

[0037] In addition, the leakage movement passage 300 is formed with an outlet 310 on the side of the heat insulating layer 200 so that the leaking liquefied gas can be easily discharged from the leakage movement through passage 400 described later.

[0038] The leakage movement through passage 400 of the insulation system for a liquefied gas storage tank of this embodiment is configured as a small-diameter pipe that penetrates and is inserted into the insulation layer 200, communicates with the outlet 310 of the leakage movement passage 300, and allows leaked liquefied gas to pass through. Specifically, the leakage movement through passage 400 is a passage that penetrates the insulation layer 200 and allows leaked liquefied gas to flow out of the storage tank, and is made of a material suitable for the characteristics of the liquefied gas. When the liquefied gas is LNG, it is preferably made of aluminum steel, stainless steel, or the like.

[0039] In addition, the leakage movement passage 400 of the insulation system of the liquefied gas storage tank in this embodiment has leakage movement passages 400 inserted into the insulation layer 200 at different positions in the insulation layer 200 so that liquefied gas leaking from the primary barrier 100 covering the storage tank can be completely discharged.

[0040] The partial secondary barrier 500 of the insulation system for a liquefied gas storage tank of this embodiment is formed as a pipe communicating with the leakage movement through-path 400. Specifically, the partial secondary barrier 500 is configured such that one end is connected to the leakage movement through-path 400 and the other end is formed with a gas release port 510, so that leaked liquefied gas that flows from the leakage movement through-path 400 into the partial secondary barrier 500 is vaporized in its entirety as it flows toward the gas release port 510. Specifically, the partial secondary barrier 500 is connected to the leakage movement through-path 400 by welding, screwing, or bolting so as to prevent the leaked liquefied gas from leaking to the outside (i.e., watertight). The leakage movement through-path 400 is made of a small-diameter pipe, and the partial secondary barrier 500 is also made of a small-diameter pipe.

[0041] The partial secondary barrier 500 is fabricated as a long pipe so that the entire amount of leaked liquefied gas discharged from the leakage movement through-passage 400 is vaporized. That is, by forming the length of the pipe through which the leaked liquefied gas flows long, the area for heat release (in other words, the heat transfer area) increases. Various shapes such as those shown in FIG. 2 can be adopted as the shape of such a partial secondary barrier 500.

[0042] Furthermore, the dimensions of the partial secondary barrier 500, such as the length, diameter, and surface area of ​​the internal space, are determined based on the diameter of the leakage transfer passage 400, the size of the storage tank, the loading capacity of the liquefied gas, and the like.

[0043] In addition, the partial secondary barrier 500 of the insulation system of the liquefied gas storage tank of this embodiment is formed of a metallic barrier material that is suited to the characteristics of the liquefied gas, and is preferably formed of a material that has good heat transfer properties due to the metallic properties.

[0044] 1, the partial secondary barrier 500 of the thermal insulation system for the liquefied gas storage tank of this embodiment may have a bent portion such as an "L" shape in part thereof. Such a shape enables a structure in which the partial secondary barrier 500 is stably fixed and supported to the leakage movement passage 400. However, the position and shape of the partial secondary barrier 500 are not particularly limited, and can be modified or changed as appropriate depending on the structural characteristics of the ship.

[0045] As shown in Figures 2(a) to 2(f), the partial secondary barrier 500 may be formed in a linear shape (Figure 2(a)), a circular spiral coil shape (Figure 2(b)), a fin tube shape (Figure 2(c)), a square spiral coil shape (Figure 2(d)), a zigzag shape (Figure 2(e)), or a concentric coil shape (Figure 2(f)). However, other shapes may be used as long as they facilitate heat transfer. The partial secondary barrier 500 may be formed in a circular spiral coil shape, a square spiral coil shape, or a concentric coil shape, and these may be arranged in series or parallel. However, other shapes may be used as long as they are arranged in a shape that facilitates heat transfer as described above.

[0046] As described above, by configuring the partial secondary barrier 500 in a tubular shape, a drip tray installed to collect leaked liquefied gas is no longer necessary, which solves various problems that arise when installing a drip tray (for example, problems such as occupying space inside the ship).

[0047] Furthermore, partial secondary barrier 500 is formed in a tubular shape, which is a much simpler structure than existing drip trays, making it possible to realize a thermal insulation system with fewer spatial constraints. Specifically, existing drip trays require the installation of thermal insulation means or the like in a limited space to prevent the wall surface of the space near the drip tray from cooling. In contrast, tubular partial secondary barrier 500 has a structure in which tubular partial secondary barrier 500 is stably fixed and supported to leak movement passageway 400, requiring less space for installation and making it possible to build a thermal insulation system with fewer spatial constraints.

[0048] As described above, the partial secondary barrier 500 of the insulation system for a liquefied gas storage tank of this embodiment is configured so that the entire amount of liquefied gas that has flowed into the partial secondary barrier 500 is vaporized and discharged to the outside as it flows into the gas release port 510 formed at the other end of the partial secondary barrier 500. Here, the amount of vaporization of the liquefied gas can be estimated by calculating the amount of heat that penetrates into the liquefied gas that has flowed into the partial secondary barrier 500 using the following formula (Equation 1) for calculating the evaporation rate of the liquefied gas.

[0049]

number

[0050] In the above equation (Equation 1), Q is the amount of heat entering the partial secondary barrier 500, d is the density of the leaked liquefied gas, V is the volume of the leaked liquefied gas, and L is the latent heat of the leaked liquefied gas. This equation makes it possible to calculate the amount of heat entering required to vaporize all of the liquefied gas that has flowed into the partial secondary barrier 500. Furthermore, by estimating the amount of liquefied gas that will be completely vaporized based on the calculated amount of heat entering, it is possible to determine the diameter or length of the partial secondary barrier 500 that will allow the liquefied gas to pass through.

[0051] Next, a pressure relief valve is provided at the other end of the partial secondary barrier 500 of the thermal insulation system of the liquefied gas storage tank of this embodiment to block or control the flow of liquefied gas passing through the partial secondary barrier 500. The opening degree of this pressure relief valve can be adjusted according to the above formula, and the pressure relief valve is controlled based on the amount of liquefied gas that has flowed into the partial secondary barrier 500.

[0052] In addition, the insulation system for a liquefied gas storage tank of this embodiment further includes a connecting pipe for recovering the entire amount of liquefied gas that leaks from the primary barrier 100.

[0053] Specifically, the description will be made with reference to FIG. 3. The leakage movement through passages 400 and the partial secondary barrier 500 of the insulation system for a liquefied gas storage tank of this embodiment are provided at the bottom of the storage tank. In particular, the leakage movement through passages 400 are provided at multiple locations at the bottom of the storage tank in order to recover all of the liquefied gas leaking from the storage tank. Furthermore, the insulation system for a liquefied gas storage tank of this embodiment may be provided with two or more leakage movement through passages 400, and two adjacent leakage movement through passages 400 may be connected by one or more connecting pipes 610. The connecting pipe 610 connects the multiple leakage movement through passages 400 in series, and is configured to supply liquefied gas to the partial secondary barrier 500 located downstream thereof. In addition, as the leaked liquefied gas discharged from the leakage movement passage 400 passes through the connecting pipe 610 connected to the adjacent leakage movement passage 400, part of the leaked liquefied gas is vaporized, and as the leaked liquefied gas passes through the partial secondary barrier 500 connected to the most downstream leakage movement passage 400 among the multiple leakage movement passages 400, the entire amount of the leaked liquefied gas is finally vaporized and discharged to the outside.

[0054] 4 is a schematic diagram showing a connection structure of a thermal insulation system for a liquefied gas storage tank according to a second embodiment of the present invention. In the embodiments described below, the same or similar reference symbols are used for components that are the same as or similar to those in the first embodiment, and the description thereof is the same as that of the first embodiment.

[0055] The leakage movement through-passages 400 of the insulation system for a liquefied gas storage tank according to the second embodiment of the present invention are each connected to a connecting pipe 620. Specifically, the insulation system for a liquefied gas storage tank according to the second embodiment of the present invention is provided with one or more leakage movement through-passages 400, and one or more connecting pipes 620 are each connected to the leakage movement through-passages 400. Furthermore, the connecting pipes 620 connected to the leakage movement through-passages 400 may be integrated into a single line and connected to the partial secondary barrier 500. Alternatively, leaked liquefied gas discharged from a plurality of leakage movement through-passages 400 may be collected in a separate leaked liquid collection device 630 and then sent to the partial secondary barrier 500.

[0056] Therefore, in the second embodiment, a portion of the leaked liquefied gas discharged from the leakage movement passage 400 is vaporized as it is sent to the partial secondary barrier 500 via the connecting pipe 620, and the entire amount is vaporized by heat exchange as it passes through the partial secondary barrier 500, and is finally discharged outside the hull through the gas release port 510.

[0057] Design method for insulation systems for liquefied gas storage tanks Fig. 5 is a flowchart showing the steps of designing a partial secondary barrier for a stand-alone type B liquefied gas storage tank using a design method according to an embodiment of the present invention. Fig. 6 is a flowchart showing a method of designing a thermal insulation system for a stand-alone type B liquefied gas storage tank taking into consideration the optimal shape of the partial secondary barrier using a design method according to an embodiment of the present invention.

[0058] A design method of an embodiment of the present invention for designing a partial secondary barrier for a stand-alone type B liquefied gas storage tank includes a liquefied gas selection step S100 for selecting the type of liquefied gas, a leakage standard setting step S200 for setting a leakage standard value for the selected liquefied gas, a shape selection step S300 for selecting the shape of the partial secondary barrier, a setting and evaluation step S400 for setting a target evaporation rate of the liquefied gas and evaluating the leakage amount of the liquefied gas, a comparison step S500 for comparing the target evaporation rate of the liquefied gas with the leakage amount of the liquefied gas, a shape design step S600 for designing the shape of the partial secondary barrier, and an installation step S700 for installing the partial secondary barrier.

[0059] In the design method of this embodiment, the type of natural gas to be transported to a distant consumer is selected in liquefied gas selection step S100. The liquefied gas selected in liquefied gas selection step S100 is, for example, atmospheric pressure LNG.

[0060] In the leakage standard setting step S200 of the design method of this embodiment, a leakage standard value of the liquefied gas is set based on the physical properties of the liquefied gas and the leakage rate of the liquefied gas. For example, the leakage standard value of the liquefied gas at atmospheric pressure discharged from the leakage movement through-passage 400 is set to 200 L per hour.

[0061] In addition, in the liquefied gas selection step S100 and the leakage standard setting step S200, all conditions for measuring the evaporation rate of the liquefied gas are set in addition to the type of liquefied gas and the leakage standard value. For example, the external temperature of the storage tank is set to -10°C, and it is set that no external insulation material is installed other than the partial secondary barrier. In addition, in order to accurately evaluate the evaporation rate of the liquefied gas, all conditions other than the shape of the piping are kept constant.

[0062] In the shape selection step S300 of the design method of this embodiment, the material, diameter, thickness, length, and volume of the partial secondary barrier 500 are set based on the type of liquefied gas selected in the liquefied gas selection step S100 and the leakage standard value of the liquefied gas set in the leakage standard setting step S200. For example, in order to increase the length of the partial secondary barrier 500, the shape of the partial secondary barrier 500 may be any of a straight shape, a coil shape, a fin tube shape, and a zigzag shape.

[0063] In the setting and evaluation step S400 of the design method of this embodiment, a target evaporation rate of the liquefied gas is set, and the leakage amount of the liquefied gas for the partial secondary barrier 500 selected in the shape selection step S300 is evaluated.

[0064] Specifically, the target evaporation rate set in the setting and evaluation step S400 means the evaporation rate at which the entire amount of leaked liquefied gas is evaporated. The target evaporation rate may be set based on design standards established by a classification society or the like, or may be evaluated by analyzing the degree of damage to the primary barrier of the storage tank.

[0065] In the setting and evaluation step S400 of the design method of this embodiment, the material, diameter, thickness, length, and volume of any partial secondary barrier selected in the shape selection step S300 are set, and a target evaporation rate of the evaporating liquefied gas is calculated. For example, if the leakage rate of liquefied gas passing through the partial secondary barrier is less than the target evaporation rate, the partial secondary barrier is fabricated so that its length is increased. Note that, in this embodiment, an example has been described in which the evaporation rate of liquefied gas is adjusted by increasing the length of the partial secondary barrier 500, but the present invention is not limited to this. The evaporation rate of liquefied gas may also be adjusted by changing the material or diameter of the partial secondary barrier.

[0066] The length of the partial secondary barrier can be set to any length. For example, in the case of a tubular partial secondary barrier made to the dimensions of 50A#40s, in order to vaporize all of the leaked liquefied gas within the partial secondary barrier, it is desirable that the length of the partial secondary barrier be 105 m. Based on these design criteria, the partial secondary barrier is configured as a coil with a diameter of 200 mm and approximately 167 turns.

[0067] In the comparison step S500 of the design method of this embodiment, the target evaporation rate of the liquefied gas is compared with the leakage rate of the liquefied gas. If the leakage rate of the liquefied gas compared in the comparison step S500 is smaller than the target evaporation rate, the design process returns to the shape selection step S300.

[0068] In the shape design step S600 of the design method of this embodiment, an optimal shape of the partial secondary barrier is determined to achieve an evaporation rate close to the target evaporation rate, thereby completing the design process of the partial secondary barrier. Specifically, in the shape design step S600, a method for increasing the length of the partial secondary barrier is identified based on the material, diameter, thickness, length, and volume of the partial secondary barrier, as well as the evaporation rate at which the entire amount of liquefied gas flowing into the internal space of the partial secondary barrier is evaporated.

[0069] In the installation step S700 of the design method of this embodiment, the partial secondary barrier, whose dimensions such as length and shape have been determined, is actually installed.

[0070] The design method of an embodiment of the present invention for designing a partial secondary barrier of an insulation system for a stand-alone type B liquefied gas storage tank proceeds in the following steps.

[0071] Fig. 6 is a flowchart showing a method for designing a thermal insulation system for a stand-alone type B liquefied gas storage tank, taking into consideration the optimal shape of the partial secondary barrier, according to the design method of an embodiment of the present invention.

[0072] First, the type of liquefied gas leaking from the storage tank is selected, and a leakage reference value for that liquefied gas is set. Specifically, the leakage reference value for the liquefied gas is set based on all conditions for measuring the evaporation rate of the liquefied gas, the physical properties of the selected liquefied gas, and the average evaporation rate of the liquefied gas. Furthermore, the target evaporation rate is set based on the target evaporation rate of the liquefied gas set by a classification society or the like, or on an analysis of the degree of damage to the primary barrier of the storage tank. Note that the target evaporation rate may be set at any step.

[0073] Next, the material, diameter, thickness, length, and volume of the partial secondary barrier are selected based on the set leakage reference value. The amount of liquefied gas leakage is then compared with the target evaporation rate. If the amount of liquefied gas leakage exceeds the target evaporation rate, the selected shape is determined as the shape of the partial secondary barrier, and the partial secondary barrier is fabricated and installed. On the other hand, if the amount of liquefied gas leakage is equal to or less than the target evaporation rate, the process returns to the step of selecting the shape of the partial secondary barrier, and after at least one of the material, diameter, thickness, length, and volume of the partial secondary barrier is changed (e.g., after increasing the length of the partial secondary barrier), the evaporation rate of the liquefied gas is evaluated. This design method allows the fabrication of a partial secondary barrier capable of completely vaporizing leaked liquefied gas, and various shapes of partial secondary barriers are fabricated that reflect the conditions changed during the design process.

[0074] The present invention is not limited to the first and second embodiments, but includes all embodiments resulting from a combination of the first and second embodiments, or a combination of at least one of the first and second embodiments with known technology.

[0075] The present invention has been described in detail above using specific embodiments, but this is for the purpose of specifically explaining the present invention, and the present invention is not limited thereto. It is clear that modifications and improvements can be made by a person having ordinary knowledge in the relevant field within the technical spirit of the present invention.

[0076] Any mere variations or modifications of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be defined by the appended claims.

Claims

1. a liquefied gas selection step of selecting a type of liquefied gas; and a leakage standard setting step of setting a leakage standard value of the liquefied gas; a shape selection step of selecting a shape for the partial secondary barrier; and A setting and evaluation step of setting a target evaporation rate of the liquefied gas and evaluating the leakage amount of the liquefied gas; a comparison step of comparing a target evaporation rate of the liquefied gas with the leakage amount of the liquefied gas; designing the shape of the partial secondary barrier; and installing a partial secondary barrier; Design method for insulation system of stand-alone type B liquefied gas storage tank.

2. The leakage reference value set in the leakage reference setting step is The method is characterized in that it is set based on the physical properties of the liquefied gas selected in the liquefied gas selection step and the leakage rate of the liquefied gas. A method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 1.

3. The shape selection step is characterized in that the material, diameter, thickness, length and volume of the partial secondary barrier are set based on the leakage reference value, and the length of the partial secondary barrier is set to be long. A method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 1.

4. The setting and evaluation step sets the target evaporation rate, The leakage amount of the liquefied gas is evaluated based on the shape of the partial secondary barrier and the arbitrary length reference volume selected in the shape selection step. A method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 1.

5. The comparing step The target evaporation rate is compared with the leakage amount of the liquefied gas, and if the leakage amount of the liquefied gas is equal to or less than the target evaporation rate, the process returns to the shape selection step. A method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 1.

6. The shape selection step includes: resetting the length of the partial secondary barrier so that the length of the partial secondary barrier increases; The method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 5.

7. The partial secondary barrier is formed in a tubular shape having an internal space, and is formed in any one of a straight line, a curved line, a zigzag line, a spring line, and a radial line to increase the length. The method for designing an insulation system for a stand-alone B-type liquefied gas storage tank according to claim 3.

8. A ship equipped with an insulation system for a stand-alone type B liquefied gas storage tank manufactured by the design method according to any one of claims 1 to 7.

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