Liquefied gas tank

Abstract

This liquefied gas tank comprises: a tank shell that has a top opening; a tank dome that is disposed above the top opening of the tank shell and has a body section with a smaller diameter than the opening diameter of the top opening of the tank shell; and a flare member that has a lower end section joined to the opening edge of the top opening of the tank shell, an upper end section joined to the lower end of the body section of the tank dome, and a flared section increasing in diameter from the upper end section toward the lower end section.

Description

Liquefied gas tank

[0001] The present disclosure relates to the structure of a liquefied gas tank having a tank dome protruding from a tank shell.

[0002] Some liquefied gas tanks mounted on a hull include a tank dome for connecting the piping inside the tank and the piping on the hull side. Patent Document 1 discloses this type of liquefied gas tank. The liquefied gas tank disclosed in Patent Document 1 is a cargo tank mounted on a hull, and a dome top, that is, a tank dome is provided at the top of the tank shell.

[0003] The tank shell and the dome top base are connected by welding. Generally, the tank shell and the tank dome base are welded in a state where the end face of the tank shell abuts against the surface of the wall plate of the tank dome base, and the tank shell and the tank dome base are combined at substantially a right angle to form a T-shaped joint.

[0004] Japanese Unexamined Patent Application Publication No. 2019 - 14438

[0005] When low-temperature liquefied gas is stored in the liquefied gas tank, both the liquefied gas tank and the hull on which the liquefied gas tank is installed thermally contract, but the degree of thermal contraction of the liquefied gas tank is greater than that of the hull. Therefore, for outfitting components such as piping passed through the tank dome of the liquefied gas tank, the part penetrating the tank dome from inside the tank is supported by the tank dome, and the tip thereof is supported by the hull. Due to the load of the outfitting components supported by the tank dome, locally high stress is generated at the T-shaped joint portion between the tank shell and the tank dome base.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to suppress the occurrence of local stress concentration at the connection portion between the tank shell and the tank dome base in a liquefied gas tank having a tank dome protruding from the tank shell.

[0007] To solve the above problems, a liquefied gas tank according to one aspect of the present disclosure comprises: a tank shell having a top opening; a tank dome having a body portion with a smaller diameter than the opening diameter of the top opening of the tank shell and positioned above the top opening of the tank shell; and a flared member having a lower end joined to the opening edge of the top opening of the tank shell, an upper end joined to the lower end of the body portion of the tank dome, and a flared portion that expands in diameter from the upper end to the lower end.

[0008] According to this disclosure, in a liquefied gas tank having a tank dome protruding from the tank shell, it is possible to suppress the occurrence of localized stress concentration at the connection between the tank shell and the base of the tank dome.

[0009] Figure 1 is a schematic cross-sectional view of a vessel equipped with a liquefied gas tank according to one embodiment of the present disclosure. Figure 2 is an enlarged cross-sectional view of the connection between the tank shell and the tank dome of the liquefied gas tank. Figure 3 is a schematic cross-sectional view of a liquefied gas tank according to Modification 1. Figure 4 is an enlarged cross-sectional view of the connection between the tank shell and the tank dome of the liquefied gas tank according to Modification 1.

[0010] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0011] 《Outline Configuration of Liquefied Gas Tank 10》 Figure 1 is a cross-sectional view of a ship 1 equipped with a liquefied gas tank 10 according to one embodiment of the present disclosure. The ship 1 shown in Figure 1 comprises a hull 11 and at least one liquefied gas tank 10 mounted on the hull 11. The liquefied gas is not particularly limited, but examples of liquefied gases include LNG, liquefied nitrogen, liquefied hydrogen, and liquefied helium. Furthermore, although the liquefied gas tank 10 according to this embodiment is a cargo tank mounted on a liquefied gas carrier, the liquefied gas tank 10 is not limited to a cargo tank and may be a fuel tank mounted on a liquefied gas-fueled ship that uses liquefied gas as propulsion fuel.

[0012] The liquefied gas tank 10 comprises a tank casing 2 for containing liquefied gas and a tank dome 3 protruding upward from the tank casing 2. The liquefied gas tank 10 is surrounded by a tank cover 12 covering the top and retaining walls 14 covering the sides and bottom. The top of the liquefied gas tank 10 may be covered by a part of the hull 11 instead of the tank cover 12. The space enclosed by the liquefied gas tank 10, the tank cover 12, and the retaining walls 14 is filled with, for example, a non-flammable or flame-retardant gas such as nitrogen gas or inert gas, or dry air.

[0013] The tank hull 2 ​​is generally spherical in shape. However, the tank hull 2 ​​may also be rectangular, a spherical shape stretched vertically or in the length direction, or an elliptical shape. Insulation material is placed on the outer surface of the tank hull 2.

[0014] The tank dome 3 is positioned on top of the tank shell 2 and protrudes upward from the tank shell 2. The top of the tank dome 3 protrudes into the exposed space above the tank cover 12. The tank dome 3 has a cylindrical body portion 31 that extends vertically and a ceiling portion 32 that closes the top of the body portion 31. The tank dome 3 is provided with a penetration portion 33 for passing through fittings such as pipes and wiring. The penetration portion 33 is positioned above the flare member 6, which will be described later.

[0015] Below the tank dome 3, a pipe tower 4 is positioned. The pipe tower 4 is a cylindrical body that extends vertically from the top to the bottom of the tank hull 2. The tank dome 3 and the pipe tower 4 are positioned in overlapping locations in a plan view, and the interiors of the tank dome 3 and the pipe tower 4 are in communication. A pump for pumping up liquefied gas is installed at the bottom of the pipe tower 4. Pipes such as liquid supply pipes and electrical pipes are connected to the pump. These pipes pass through the inside of the pipe tower 4, extend to the outside through the penetration 33 of the tank dome 3, and connect to the piping on the hull side. However, the pump located at the bottom of the pipe tower 4 may be omitted.

[0016] 《Connection Structure Between Tank Shell 2 and Tank Dome 3》 Here, the connection structure between the tank shell 2 and the tank dome 3 of the liquefied gas tank 10 will be explained in detail. Figure 2 is a longitudinal cross-sectional view of the connection between the tank shell 2 and the tank dome 3 of the liquefied gas tank 10.

[0017] As shown in Figure 2, a top opening 21 is provided at the top of the tank shell 2. The top opening 21 is an opening that penetrates the wall of the tank shell 2 in the vertical direction. The diameter of the top opening 21 of the tank shell 2 is larger than the outer diameter of the lower end of the body portion 31 of the tank dome 3. The lower end of the body portion 31 of the tank dome 3 is positioned slightly above the top opening 21 of the tank shell 2. The opening edge of the top opening 21 of the tank shell 2 and the lower end of the body portion 31 of the tank dome 3 are connected via a flare member 6.

[0018] The minimum plate thickness of the flare member 6 is greater than or equal to the minimum plate thickness of the body portion 31 of the tank dome 3, and greater than the minimum plate thickness of the tank shell 2. Since the tank shell 2, tank dome 3, and flare member 6 are made of the same material, the flare member 6 has wall strength equal to or greater than that of the body portion of the tank dome 3, and greater than that of the tank shell 2. There is no particular upper limit set for the minimum plate thickness of the flare member 6, but it is preferable that the minimum plate thickness of the flare member 6 be 2.5 times or less the minimum plate thickness of the body portion of the tank dome 3, so that the joint between the tank dome 3 and the tank shell 2 has a smooth surface.

[0019] The flared member 6 is a cylindrical or ring-shaped member with a flared shape that widens downwards. The flared member 6 has an upper end portion 61 that is approximately the same diameter as the lower end of the body portion 31 of the tank dome 3, a lower end portion 62 that is approximately the same diameter as the opening diameter of the top opening 21 of the tank shell 2, and a flared portion 63 between the upper end portion 61 and the lower end portion 62. The maximum diameter of the flared member 6, i.e., the outer diameter of the lower end portion 62, is larger than the maximum diameter of the tank dome 3.

[0020] In the profile of the flared member 6, i.e., the vertical cross-sectional shape, the tangential direction of the outline of the upper end portion 61 is approximately vertical, and the tangential direction of the outline of the lower end portion 62 is approximately perpendicular to the vertical direction. The tangential direction of the outline of the lower end portion 62 is approximately parallel to the tangential direction of the opening edge of the top opening 21 of the tank shell 2. The flared portion 63 expands in diameter from the upper end portion 61 to the lower end portion 62 in a trumpet or bell mouth shape, and the peripheral wall of the flared portion 63 is formed as a curved surface. In the profile of the flared member 6, i.e., the vertical cross-sectional shape, the outline of the flared portion 63 is represented by an arc or a curved line, and the tangential direction of the outline of the flared portion 63 gradually changes from approximately vertical to approximately perpendicular to the vertical direction between the upper end portion 61 and the lower end portion 62. From the viewpoint of avoiding stress concentration, the radius of curvature of the outline of the flared portion 63 is preferably 5% to 20% of the maximum diameter of the tank dome 3, and more preferably 5% to 40%.

[0021] The upper end portion 61 of the flare member 6 is joined to the lower end of the body portion 31 of the tank dome 3. Specifically, the lower end surface of the body portion 31 of the tank dome 3 and the upper end surface of the flare member 6 are butt-welded, forming a smooth continuous surface between the body portion 31 of the tank dome 3 and the upper end portion 61 of the flare member 6. The lower end portion 62 of the flare member 6 is joined to the opening edge of the top opening 21 of the tank shell 2. Specifically, the lower end surface of the flare member 6 and the opening edge of the top opening 21 of the tank shell 2 are butt-welded, forming a smooth continuous surface between the lower end portion 62 of the flare member 6 and the tank shell 2.

[0022] The outer diameter of the upper end of the pipe tower 4 is larger than the opening diameter of the top opening 21 of the tank shell 2. The upper end of the pipe tower 4 is joined to the outer circumference of the opening edge of the top opening 21 of the tank shell 2. More specifically, the upper end surface of the pipe tower 4 is butted against the surrounding wall surface of the top opening 21 of the tank shell 2 and joined by welding.

[0023] In the liquefied gas tank 10 with the above configuration, a flare member 6 is interposed between the tank shell 2 and the tank dome 3, and the connection between the tank shell 2 and the tank dome 3 is a smoothly continuous curved surface due to the flare member 6. The load of the tank dome 3 itself and the load of the fittings supported by the penetration portion 33 of the tank dome 3 are applied to the connection between the tank dome 3 and the tank shell 2, but because the connection is made of a flare member 6, the generation of locally high stress at the connection between the tank shell 2 and the tank dome 3 is suppressed.

[0024] [Modified Examples] Next, modified examples of the above embodiment will be described. Figure 3 is a schematic longitudinal cross-sectional view of the liquefied gas tank 10A according to Modified Example 1. In this description of modified examples, the same or similar components as in the above embodiment are denoted by the same reference numerals in the drawings, and detailed descriptions are omitted.

[0025] As shown in Figure 3, the liquefied gas tank 10A according to Modification 1 comprises an inner tank 8 in which liquefied gas is contained, and an outer tank 7 surrounding the inner tank 8. In other words, the liquefied gas tank 10A is a multi-shell tank comprising an inner tank 8 and an outer tank 7 spaced apart in the thickness direction of the tank shells 2,81.

[0026] The outer tank 7 has substantially the same configuration as the liquefied gas tank 10 according to the above embodiment. That is, the outer tank 7 comprises a tank shell 2, a tank dome 3 projecting upward from the top of the tank shell 2, and a flare member 6 positioned at the connection between the tank shell 2 and the tank dome 3. Fittings such as piping and wiring pass through a penetration 33 provided in the tank dome 3 and are supported by the penetration 33. A detailed description of the outer tank 7 is omitted by reference to the description of the liquefied gas tank 10 of the above embodiment.

[0027] Figure 4 is an enlarged cross-sectional view of the connection between the tank shell 2 and the tank dome 3 of the liquefied gas tank 10A according to Modification 1. As shown in Figure 4, the inner tank 8 has an inner tank shell 81 housed in the tank shell 2 and an inner tank dome 82 protruding upward from the top of the inner tank shell 81. The inner tank dome 82 has a cylindrical body portion 82a extending in the vertical direction and a ceiling portion 82b covering the upper part of the body portion 82a. In the liquefied gas tank 10A according to this modification, the ceiling portion 82b of the inner tank dome 82 and the ceiling portion 32 of the tank dome 3 are shared.

[0028] The inner tank shell 81 has an insertion opening 84 at its top. The opening diameter of the insertion opening 84 is larger than the outer diameter of the lower end of the inner tank dome 82. The opening edge of the insertion opening 84 of the inner tank shell 81 and the lower end of the inner tank dome 82 are connected via an inner flare member 83. A detailed description of the inner flare member 83 is omitted by referring to the description of the flare member 6 in the above embodiment. The lower end surface of the inner tank dome 82 and the upper end surface of the inner flare member 83 are butt-welded, and the opening edge of the insertion opening 84 of the inner tank shell 81 and the lower end surface of the inner flare member 83 are butt-welded. With the inner flare member 83 interposed between the inner tank shell 81 and the inner tank dome 82 in this way, the connection between the inner tank shell 81 and the inner tank dome 82 is a smoothly continuous curved surface.

[0029] The body portion 82a of the inner tank dome 82 of the inner tank 8 penetrates the top opening 21 of the tank shell 2 of the outer tank 7 and is positioned inside the tank dome 3. The upper end of the body portion 82a of the inner tank dome 82 is joined to the inner wall of the tank dome 3 above the joint between the tank dome 3 and the flare member 6.

[0030] In the outer tank 7 of the liquefied gas tank 10A with the above configuration, a flare member 6 is interposed between the tank shell 2 and the tank dome 3, and the connection portion of the tank shell 2 to the tank dome 3 is a smoothly continuous curved surface due to the flare member 6. The load of the fittings supported by the penetration portion 33 of the tank dome 3 is applied to the connection portion between the tank dome 3 and the tank shell 2, but because this connection portion is made of a flare member 6, the generation of locally high stress at the connection portion between the tank dome 3 and the tank shell 2 is suppressed. In addition, in the inner tank 8, an inner flare member 83 is interposed between the inner tank dome 82 and the inner tank shell 81, and the connection portion of the inner tank dome 82 and the inner tank shell 81 is a smoothly continuous curved surface due to the inner flare member 83. In the inner tank 8 containing the liquefied gas, there is a difference in the degree of thermal contraction between the inner tank shell 81 and the inner tank dome 82, resulting in relative displacement between the inner tank dome 82 and the inner tank shell 81. This relative displacement causes stress concentration at the connection point between the inner tank shell 81 and the inner tank dome 82, which is mitigated by the inner flare member 83.

[0031] [Summary] The liquefied gas tanks 10 and 10A according to the first item of this disclosure include: a tank shell 2 having a top opening 21; a tank dome 3 having a body portion 31 with a smaller diameter than the opening diameter of the top opening 21 of the tank shell 2 and positioned above the top opening 21 of the tank shell 2; and a flared member 6 having a lower end portion 62 joined to the opening edge of the top opening 21 of the tank shell 2, an upper end portion 61 joined to the lower end of the body portion 31 of the tank dome 3, and a flared portion 63 that expands in diameter from the upper end portion 61 to the lower end portion 62. The flared shape expands in diameter in a trumpet shape or bell mouth shape, and the tangential direction of the outline changes in the profile of the flared portion 63.

[0032] In the liquefied gas tanks 10 and 10A with the above configuration, the connection between the tank shell 2 and the tank dome 3 is formed as a smoothly continuous curved surface by interposing a flare member 6. The load of the tank dome 3 and the fittings supported by the tank dome 3 is applied to the connection between the tank shell 2 and the tank dome 3, but because the connection is made of a flare member 6, it is possible to suppress the occurrence of localized stress concentration at the connection between the tank shell 2 and the tank dome 3.

[0033] The liquefied gas tanks 10 and 10A relating to the second item of this disclosure are the same as the liquefied gas tanks 10 and 10A relating to the first item, wherein the tank dome 3 has a penetration 33 through which piping or wiring is passed, which is located above the joint with the flare member 6.

[0034] In the liquefied gas tanks 10 and 10A with the above configuration, the load of fittings such as pipes and wiring passed through the penetration 33 of the tank dome 3 is applied to the connection between the tank shell 2 and the tank dome 3. However, the flare member 6 can alleviate the localized concentration of stress at the connection between the tank shell 2 and the tank dome 3.

[0035] In the liquefied gas tanks 10, 10A relating to the third item of this disclosure, the maximum diameter of the flare member 6 is larger than the maximum diameter of the tank dome 3, as in the liquefied gas tanks 10, 10A relating to the first or second item.

[0036] This allows the flared member 6 to stably support the mass of the tank dome 3.

[0037] In the liquefied gas tanks 10 and 10A relating to the fourth item of this disclosure, in the 10 and 10A relating to any of the first to third items, the radius of curvature of the flared portion 63 of the flared member 6 is 5% or more and 40% or less of the maximum diameter of the tank dome 3.

[0038] This effectively avoids localized stress concentration at the connection point between the tank shell 2 and the tank dome 3.

[0039] The liquefied gas tanks 10, 10A relating to item 5 of this disclosure are those relating to any of items 1 to 4, wherein the minimum plate thickness of the flare member 6 is greater than or equal to the minimum plate thickness of the body portion 31 of the tank dome 3 and greater than the minimum plate thickness of the tank shell 2.

[0040] This allows the flared member 6 to stably support the mass of the tank dome 3.

[0041] The liquefied gas tank 10A according to the sixth item of the present disclosure is the liquefied gas tank 10A according to any one of the first to fifth items, further including an inner tank shell 81 having an insertion port 84 and an inner tank dome 82 connected to the opening edge of the insertion port 84 of the inner tank shell 81. The inner tank shell 81 is surrounded by the tank shell 2, the inner tank dome 82 is arranged in the tank dome 3 through the top opening 21 of the tank shell 2, and the upper end of the body portion 82a of the inner tank dome 82 is joined to the inner wall of the tank dome 3.

[0042] Although the liquefied gas tank 10A with the above configuration is a multi-shell tank, even in this case, since the connection portion between the tank shell 2 and the tank dome 3 is constituted by the flare member 6, the stress concentration generated at the connection portion between the tank shell 2 and the tank dome 3 due to the load of the tank dome 3 and the outfitting items supported by the tank dome 3 can be suppressed.

[0043] The liquefied gas tank 10A according to the seventh item of the present disclosure is the liquefied gas tank 10A according to the sixth item, in which the lower end of the inner tank dome 82 and the opening edge of the insertion port 84 of the inner tank shell 81 are connected via an inner flare member 83 having a flare shape that expands in diameter from the lower end of the inner tank dome 82 toward the opening edge of the insertion port 84 of the inner tank shell 81.

[0044] In the liquefied gas tank 10A with the above configuration, the connection portion between the inner tank shell 81 and the inner tank dome 82 is formed as a smoothly continuous curved surface due to the interposition of the inner flare member 83. In the inner tank 8 in which the liquefied gas is stored, there is a difference in the degree of thermal contraction between the inner tank shell 81 and the inner tank dome 82, resulting in relative displacement between the inner tank dome 82 and the inner tank shell 81. However, the stress concentration applied to the connection portion between the inner tank shell 81 and the inner tank dome 82 due to this relative displacement is alleviated by the inner flare member 83.

[0045] The embodiments described above are presented for illustrative and explanatory purposes only and are not intended to limit the disclosure to the forms disclosed herein. For example, in the detailed description above, various features of the disclosure are grouped into one embodiment for the purpose of streamlining the disclosure, but some of the features may be combined. Also, some of the features included in the disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above.

[0046] 2: Tank shell 3: Tank dome 6: Flare member 7: Outer tank 8: Inner tank 10, 10A: Liquefied gas tank 21: Top opening 31: Body 33: Through section 61: Upper end 62: Lower end 63: Flare-shaped section 81: Inner tank shell 82: Inner tank dome 83: Inner flare member 84: Through port

Claims

1. A liquefied gas tank comprising: a tank shell having a top opening; a tank dome having a body portion with a smaller diameter than the opening diameter of the top opening of the tank shell and positioned above the top opening of the tank shell; and a flared member having a lower end joined to the opening edge of the top opening of the tank shell, an upper end joined to the lower end of the body portion of the tank dome, and a flared portion that expands in diameter from the upper end to the lower end.

2. The liquefied gas tank according to claim 1, wherein the tank dome has a penetration through which piping or wiring passes, located above the joint with the flared member.

3. The liquefied gas tank according to claim 1, wherein the maximum diameter of the flared member is greater than the maximum diameter of the tank dome.

4. The liquefied gas tank according to claim 1, wherein the radius of curvature of the flared portion of the flared member is 5% or more and 40% or less of the maximum diameter of the tank dome.

5. The liquefied gas tank according to claim 1, wherein the minimum plate thickness of the flared member is greater than or equal to the minimum plate thickness of the body of the tank dome and greater than the minimum plate thickness of the tank shell.

6. A liquefied gas tank according to claim 1, further comprising an inner tank shell having an insertion port, and an inner tank dome connected to the opening edge of the insertion port of the inner tank shell, wherein the inner tank shell is surrounded by the tank shell, the inner tank dome is placed inside the tank dome through the top opening of the tank shell, and the upper end of the body portion of the inner tank dome is joined to the inner wall of the tank dome.

7. The liquefied gas tank according to claim 6, wherein the lower end of the inner tank dome and the opening edge of the insertion port of the inner tank shell are connected via an inner flared member having a flared shape that expands in diameter from the lower end of the inner tank dome toward the opening edge of the insertion port of the inner tank shell.

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