JP7364440B2 - Liquefied gas tanks, ships, and floating structures - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies October 3, 2020 Published on the website (https://www.hanketsu.jiii.or.jp/giho/Menu01.jsp)

The present invention relates to a liquefied gas tank without a reinforcing member provided on the inner surface of the tank, a ship equipped with the liquefied gas tank, and a floating structure equipped with the liquefied gas tank.

Ships that transport liquefied gas, such as LNG (liquefied natural gas) ships and LPG (liquefied petroleum gas) ships, are equipped with liquefied gas tanks as cargo tanks. Further, a liquefied gas fueled ship that uses liquefied gas as fuel is equipped with a liquefied gas tank as a fuel tank.

Liquefied gas tanks for small ships are generally cylindrical tanks (Patent Documents 1 and 2). On the other hand, as described in paragraph 0006 of Patent Document 1, there is a problem in that it is difficult to increase the size of a cylindrical tank (cylinder tank type). In particular, when forming a cylinder-type liquefied gas tank with a tank capacity exceeding 10,000 ^m3 using a cylindrical tank, the outer shell alone cannot ensure the strength to store the liquefied gas, so reinforcing members such as columns and bulkheads must be installed inside the tank. There is a need. However, installing the reinforcing member increases the weight of the tank, and there is a risk that the tank weight may exceed the hull weight of the ship, so it may not be possible to install it on a large ship.

For this reason, liquefied gas tanks installed on large ships are either independent spherical tanks, such as the MOSS type, which can ensure strength without the need for reinforcing members inside the tank, or membrane-type tanks, in which the tank is supported by the ship itself. The structure is common.
Among them, MOSS type liquefied gas tanks are spherical, making it difficult for stress to concentrate in a specific location, minimizing the surface area, and minimizing heat input, so they are widely used in LNG carriers in particular.

On the other hand, since the MOSS type liquefied gas tank is spherical, there is a gap between it and the bottom and wall of the hold. Therefore, there was a problem in that the space utilization efficiency within the hold was lower than that of the membrane type.
Therefore, in the MOSS type liquefied gas tank, the spherical shell is divided into two at the equator, a ring (cylinder) is inserted into the dividing plane, and each divided hemisphere (upper and lower spherical shell) is connected to the ring (cylinder). A structure is known (Patent Document 3).

The structure of Patent Document 3 is useful in that the tank capacity can be increased by a volume corresponding to the volume inside the ring while retaining the advantage that the tank is spherical. On the other hand, in the structure of Patent Document 3, the ring is inserted in the height direction of the tank, so when the tank capacity is increased, the height of the ring becomes higher and the center of gravity of the tank also becomes higher, which affects the stability of the ship. Furthermore, as the height of the ring increases, the strength of the tank decreases, so there is a limit to how large the tank capacity can be.

Japanese Patent Application Publication No. 08-2478 JP2014-151922A JP 2019-15377 Publication

An object of the present invention is to provide a liquefied gas tank that does not require a reinforcing member on the inner surface of the tank, which can increase the tank capacity without impairing the stability of the ship carrying the tank or the strength of the tank.

In order to solve the above problems, a liquefied gas tank that is one aspect of the present invention is a liquefied gas tank that does not provide a reinforcing member on the inner surface of the tank, has an open lower end, and has an upwardly convex hemispherical upper sphere. a shell, a hemispherical lower spherical shell having an open upper end and convex downward, and a shell having an annular equatorial ring portion connecting the lower end of the upper spherical shell and the upper end of the lower spherical shell. The shell structure has a shape in which the upper spherical shell, the lower spherical shell, and the equatorial ring portion are divided into two by a plane parallel to the vertical direction, and further connects the divided planes. The meridian ring part also includes a pair of semicircular ring parts that connect the dividing surfaces of the upper spherical shell and the dividing surfaces of the lower spherical shell, respectively. , comprising a flat plate-like connecting portion that connects the dividing surfaces of the equatorial ring portion and the dividing surfaces of the pair of semicircular ring portions, and the thickness of the plate-like connecting portion is equal to the thickness of the plate-like connecting portion. It is thicker than the radial plate thickness of at least one of the equatorial ring part, the semicircular ring part, the upper spherical shell, and the lower spherical shell, and a step caused by the difference in plate thickness is inside the shell structure. It is characterized by being formed .

In this configuration, in a structure in which the spherical shell is extended in the height direction at the equatorial ring part, the spherical shell is also extended in the horizontal direction at the meridian ring part, so that the volume equivalent to the internal volume of the meridian ring part is Even if the tank capacity increases, the height of the tank remains the same, and the center of gravity does not rise. Therefore, the tank capacity can be increased without impairing the stability of a ship equipped with this shell structure.

In addition, in this configuration, the tank capacity is increased in two annular sections, the equatorial annular section and the meridian annular section, so compared to a structure in which the tank capacity is increased only in one annular section, each annular section is The tank capacity can be increased without increasing the axial width of the tank. Therefore, the tank capacity can be increased without compromising the strength of the tank.

Furthermore, in this configuration, since the equatorial ring part and the meridian ring part are ring-shaped and the plate-like connecting part is plate-like, none of the equatorial ring part, the meridian ring part, and the plate-like connecting part are connected. The cross section of the connected portion is rectangular, and the connection can be made without any processing to match the cross-sectional shape of the connection surface.
Therefore, the tank capacity can be increased without compromising the strength of the tank.

A ship according to another aspect of the present invention is characterized in that the liquefied gas tank according to any one of the above is arranged as a cargo tank or a fuel tank in a hold so that the axial direction of the meridian ring portion is along the ship's ship direction. shall be.
In a floating structure according to still another aspect of the present invention, the liquefied gas tank according to any one of the above is arranged as a cargo tank or a fuel tank in a hold so that the axial direction of the meridian ring portion is along the ship's ship direction. It is characterized by

In this configuration, the ship or floating structure is equipped with a tank with a larger capacity in two ring parts, the equatorial ring part and the meridian ring part. The tank capacity that can be installed can be increased.
In addition, in this configuration, the liquefied gas tank is arranged in the hold so that the axial direction of the meridian ring part is along the ship's ship direction, so the length in the ship width direction is the same as that of a liquefied gas tank that does not have a meridian ring part.
Generally, a plurality of liquefied gas tanks are provided in the ship's longitudinal direction, but only one is provided in the ship's width direction. Therefore, as the length of the tank increases in the transverse direction, it is necessary to increase the length in the transverse direction of the ship on which the tank is mounted, but such design changes are difficult due to restrictions such as canals. Therefore, by installing the liquefied gas tank of the present invention that can increase the tank capacity without changing the length in the transverse direction of the ship, the capacity of the tank to be loaded can be increased without increasing the length in the transverse direction of the ship.

According to the present invention, it is possible to provide a liquefied gas tank that does not include a reinforcing member on the inner surface of the tank and can increase the tank capacity without impairing the stability of the ship carrying the tank or the strength of the tank.

It is a side view showing a ship concerning this embodiment. It is a top view showing a ship concerning this embodiment. FIG. 3 is an exploded perspective view of one shell structure of the liquefied gas tank of FIG. 2; 3 is a sectional view taken along line AA of one of the liquefied gas tanks of FIG. 2. FIG. FIG. 3 is a BB sectional view of one of the liquefied gas tanks in FIG. 2, with the skirt omitted.

Hereinafter, the configuration of a ship 2 equipped with a liquefied gas tank 1 according to a preferred embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5.
Here, as the ship 2, a liquefied gas carrier ship that stores and transports liquefied gas in a liquefied gas tank 1 is illustrated.

As shown in FIGS. 1 and 2, the ship 2 includes a hull 3 and a liquefied gas tank 1.
The hull 3 is a structure serving as the hull of the ship 2, and is configured to surround the inside of the ship with a bottom 5a, a side wall 5b, and an exposed deck 5c.
In FIG. 1, in the hull 3, an engine compartment 6, a cargo compartment 7, and a bow compartment 11 are arranged in this order toward the bow side in the longitudinal direction, and adjacent compartments are separated by a transverse bulkhead.

The engine compartment 6 is a compartment in which a main engine that propels the ship 2 and auxiliary equipment such as a boiler and a pump required for navigation of the ship 2 are arranged. In a liquefied gas carrier such as the ship 2, the engine compartment 6 is arranged closer to the stern than the cargo compartment 7, as shown in FIG.
The cargo compartment 7 is a compartment in which a liquefied gas tank 1 for storing liquefied gas as cargo is arranged. In FIG. 1, the cargo compartment 7 is arranged near the center in the longitudinal direction. When the upper end of the liquefied gas tank 1 is located at a higher position than the exposure deck 5c as shown in FIG. . In FIG. 1, four liquefied gas tanks 1 are arranged in series in the cargo compartment 7 in the longitudinal direction.
The bow compartment 11 is a compartment at the bow end in the ship's ship direction, and is provided with drainage equipment, equipment for storing an anchor, and the like.
The lengths of the engine compartment 6, the cargo compartment 7, and the bow compartment 11 in the longitudinal direction may be appropriately set according to the equipment necessary for navigation of the vessel 2 and the dimensions of the liquefied gas tank 1 to be mounted.

The liquefied gas tank 1 is a pressure vessel that stores liquefied gas by keeping it cool, pressurizing it, or both. Liquefied gas herein means a substance that is a gas at normal temperature and pressure and is liquefied by cooling or pressurizing. Specific examples of liquefied gases include liquefied combustible gases such as LNG and LPG.

The liquefied gas tank 1 is a pressure vessel having a structure independent from the hull 3. The independent structure here means a structure in which the liquefied gas tank 1 itself maintains the pressure that confines the liquefied gas inside and maintains the weight of the liquefied gas. Therefore, a structure in which a part of the hull 3 is used as a pressure vessel, such as a membrane structure, is not included.

Furthermore, the liquefied gas tank 1 has a structure in which no reinforcing member is provided on the inner surface of the tank. The inner surface of the tank here refers to the surface of the shell structure 15, which is a hollow container that stores liquefied gas, that is in contact with the space that stores liquefied gas.
The reinforcing member herein refers to a structure other than the shell structure 15 that is provided on the inner surface of the shell structure 15 in order to ensure the strength to store the liquefied gas. Specific examples of reinforcing members include partition walls and struts.
The reason why the liquefied gas tank 1 of this embodiment does not provide a reinforcing member on the inner surface of the tank is that if the reinforcing member is provided, the weight will increase and it may not be possible to mount it on the ship 2. Further, when a reinforcing member is provided, it is not necessary to adopt the tank shape of this embodiment shown in FIGS. 3 to 5 because strength can be ensured even with a conventional cylindrical shape.

As shown in FIGS. 3 to 5, the liquefied gas tank 1 includes a shell structure 15 and a skirt 31. As shown in FIGS.
The shell structure 15 is a hollow container for storing liquefied gas, and includes an upper spherical shell 21, a lower spherical shell 23, an equatorial ring part 25, and a meridian ring part 27, as shown in FIG.

The upper spherical shell 21 is an upwardly convex hemispherical member. The upper spherical shell 21 in FIG. 3 is a hemisphere with an open equatorial plane at the lower end. The upper spherical shell 21 in FIG. 3 has a shape divided into two by a plane including the meridian (a plane parallel to the vertical direction). In the following description, among the divided parts, the part on the bow side (the front indicated by arrow C) will be referred to as the bow side upper spherical shell 21a, and the stern side part will be referred to as the stern side upper spherical shell 21b. In FIG. 3, the dividing plane of the upper spherical shell 21 and the plane formed by the equator are perpendicular to each other.

Note that in the following description, "divided" means having a shape in which the appearance is divided. This does not mean that it is necessary to manufacture the bow side upper spherical shell 21a and the stern side upper spherical shell 21b by dividing the hemisphere along a plane including the meridian. All members constituting the shell structure 15 can be manufactured using known materials and methods.

In FIG. 3, the upper spherical shell 21 has the same shape as a hemisphere obtained by dividing a sphere into two along the equatorial plane. Therefore, the radius _R1 , which is the distance from the center _O1 of the equatorial plane of the upper spherical shell 21 to the inner surface, has the same value regardless of the position of the inner surface. However, the radius R ₁ may vary depending on the position of the inner surface. Further, it is preferable that the lower end be at the equator because the internal volume increases, but it may be a surface located higher than the equator as long as it is parallel to the equator.
Further, in FIG. 3, the bow-side upper spherical shell 21a and the stern-side upper spherical shell 21b have the same shape except that their directions in the ship length direction are opposite, but they may have different shapes. Note that if the shapes are the same, workability during manufacturing will be improved. In FIG. 3, the dividing plane between the bow side upper spherical shell 21a and the stern side upper spherical shell 21b is a plane that passes through the apex of the hemisphere, but it may be a plane that does not pass through the apex as long as it is perpendicular to the equator. Note that if the dividing plane between the bow side upper spherical shell 21a and the stern side upper spherical shell 21b is a plane passing through the apex of the hemisphere, the bow side upper spherical shell 21a and the stern side upper spherical shell 21b have the same shape. This improves workability during manufacturing.

The lower spherical shell 23 is a downwardly convex hemispherical member. The lower spherical shell 23 in FIG. 3 is a hemisphere with an open equatorial plane at the upper end. The lower spherical shell 23 in FIG. 3 has a shape divided into two parts by a plane including the meridian (a plane parallel to the vertical direction). In the following description, among the divided parts, the bow side portion will be referred to as the bow side lower spherical shell body 23a, and the stern side portion will be referred to as the stern side lower spherical shell body 23b. In FIG. 3, the dividing plane of the lower spherical shell 23 and the plane formed by the equator are perpendicular to each other.

In FIG. 3, the lower spherical shell 23 has the same shape as a hemisphere obtained by dividing a sphere into two along the equatorial plane. Therefore, the radius _R2 , which is the distance from the center _O2 of the equatorial plane of the lower spherical shell 23 to the inner surface, is the same regardless of the position of the inner surface. However, the radius R ₂ may vary depending on the position of the inner surface. Further, it is preferable that the dividing plane be at the equator because the internal volume will be large, but it may be a plane located at a position lower than the equator as long as it is parallel to the equator.
In FIG. 3, the radius R ₂ of the lower spherical shell 23 is the same as the radius R ₁ of the upper spherical shell 21, but they may be different. Note that if the radius R ₂ is the same as the radius R ₁ , the upper spherical shell 21 and the lower spherical shell 23 have the same shape, which improves workability during manufacturing.
Further, in FIG. 3, the lower spherical shell 23a on the bow side and the lower spherical shell 23b on the stern side have the same shape except that their directions in the ship length direction are opposite, but they may have different shapes. Note that if the shapes are the same, workability during manufacturing will be improved.
In FIG. 3, the dividing plane between the bow side lower spherical shell 23a and the stern side lower spherical shell 23b is a plane that passes through the apex (bottom point) of the hemisphere, but if it is a plane perpendicular to the equator, it will not pass through the apex. It can also be a face.
In addition, if the dividing plane of the bow side lower spherical shell 23a and the stern side lower spherical shell 23b is a plane passing through the apex of the hemisphere, the bow side lower spherical shell 23a and the stern side lower spherical shell 23b have the same shape. This improves workability during manufacturing.

In FIG. 3, the upper spherical shell 21 and the lower spherical shell 23 are simply opposite in their vertical directions, and are both hemispheres having the same radius divided at the equatorial plane. However, the shapes of the upper spherical shell 21 and the lower spherical shell 23 may be different. Examples of such a shape include a structure in which the radius R ₁ of the upper spherical shell 21 becomes smaller as it approaches the apex, such as a so-called apple-shaped MOSS spherical tank.

The equatorial ring part 25 is a ring-shaped member that connects the lower end of the upper spherical shell 21 and the upper end of the lower spherical shell 23. The equatorial ring portion 25 in FIG. 3 has a shape divided into two by a dividing plane parallel to the vertical direction. Among the divided portions, the bow side portion is referred to as the bow side equatorial ring portion 25a, and the stern side portion is referred to as the stern side equatorial ring portion 25b.

By providing the equatorial annular portion 25, the capacity of the shell structure 15 can be increased by an amount corresponding to the internal volume V ₁ of the equatorial annular portion 25 while the shell structure 15 maintains its spherical shape to some extent. Specifically, if the radius of the inner periphery of the equatorial ring portion 25 is R ₃ and the width in the axial direction is H ₁ , then V ₁ =πR ₃ ² ×H ₁ .

In FIG. 3, the radius R ₃ of the equatorial ring portion 25 is constant regardless of the axial position, but if the sizes of the upper spherical shell 21 and the lower spherical shell 23 are different, the radius R ₃ It may differ in direction.
In FIG. 3, the dividing plane of the equatorial annular portion 25 is a plane passing through the center of the equatorial annular portion 25, but it may be a plane that does not pass through the center as long as it is perpendicular to the equator. However, the dividing plane of the equatorial ring portion 25, the dividing plane of the upper spherical shell 21, and the dividing plane of the lower spherical shell 23 need to be at the same position in the horizontal direction.

The meridian ring part 27 is a ring-shaped member that connects the dividing planes parallel to the vertical direction in the upper spherical shell 21, the lower spherical shell 23, and the equatorial ring part 25, and includes the upper semicircular ring part 27a, the lower part It includes a semicircular ring portion 27b and plate-like connecting portions 29a and 29b.

The upper semicircular ring part 27a and the lower semicircular ring part 27b are a pair of semicircular ring parts that connect the upper spherical shell bodies 21 and the lower spherical shell bodies 23, respectively.
Specifically, the upper semicircular ring portion 27a connects the dividing surfaces of the bow side upper spherical shell 21a and the stern side upper spherical shell 21b. Further, the lower semicircular ring portion 27b connects the divided surfaces of the bow-side lower spherical shell 23a and the stern-side lower spherical shell 23b.
The plate-like connecting parts 29a and 29b are substantially rectangular plate-like members that connect the divided surfaces of the equatorial ring part 25. The plate-like connecting parts 29a and 29b are also members that connect the upper semicircular ring part 27a and the lower semicircular ring part 27b.

In FIG. 3, the radius _R4 of the meridian annular portion 27 is constant regardless of the axial position, but if the sizes of the bow side upper spherical shell 21a and the stern side upper spherical shell 21b are different, etc. R ₄ may be different in the axial direction. The same applies when the bow side lower spherical shell body 23a and the stern side lower spherical shell body 23b are different in size.
In FIG. 3, the dividing plane of the meridian ring part 27 is a plane passing through the center of the meridian ring part 27, but it may be a plane that does not pass through the center as long as it is a horizontal plane.

In this way, in the shell structure 15, in a structure in which the spherical shell is extended in the height direction by inserting the equatorial ring part 25 in the height direction, the spherical shell is extended in the height direction by inserting the meridian ring part 27 in the horizontal direction. It also extends in the horizontal direction (direction of the ship). Therefore, although the tank capacity of the shell structure 15 increases by a volume V ₂ corresponding to the internal volume of the meridian ring portion 27, the height of the tank remains unchanged and the center of gravity does not become high. Therefore, the tank capacity can be increased without impairing the stability of the ship 2 on which the tank of the shell structure 15 is mounted.

Note that the volume V ₂ of the meridian ring portion 27 is the volume V _2-1 of the upper semicircular ring portion 27a and the lower semicircular ring portion 27b, and the angle formed by providing the plate-shaped connecting portions 29a and 29b. This is the sum of the volumes V _2-2 of columnar regions D (see FIG. 3).
If the radius of the inner circumference of the meridian ring portion 27 is R ₄ and the width in the axial direction is L ₁ , then V _2-1 = πR ₄ ² ×L ₁ , and V _2-2 = H ₁ ×L _1. ×2R becomes ₄ . Therefore, the volume V ₂ =πR ₄ ² ×L ₁ +H ₁ ×L ₁ ×2R ₄ .

Further, in this configuration, the capacity of the tank is increased by two annular parts, the equatorial annular part 25 and the meridian annular part 27. Therefore, compared to the conventional structure in which the capacity of the tank is increased only with the equatorial ring part 25, the axial width of each ring part (the equatorial ring part 25 and the meridian ring part 27) does not have to be made very long. The tank capacity can also be increased. Therefore, the tank capacity of the liquefied gas tank 1 can be increased without losing strength.

Furthermore, in this configuration, the plate-like connecting portions 29a and 29b are substantially rectangular flat plates. Therefore, when the equatorial annular portion 25 and the meridian annular portion 27 are annular with a constant radius, all of the equatorial annular portion 25, the meridian annular portion 27, and the plate-like connecting portions 29a and 29b are connected to each other. The cross section is rectangular, and the connection can be made without processing to match the cross-sectional shape of the connection surface.
Therefore, the tank capacity of the liquefied gas tank 1 can be increased without losing strength.

The planar dimensions H ₁ ′ and L ₁ ′ of the plate-like connecting portions 29 a and 29 b are determined by the shape of the meridian ring portion 27 . Specifically, the length H ₁ ′ of the surface connected to the equatorial ring portion 25 is the same as the width H ₁ of the equatorial ring portion 25 in the axial direction.
Further, the length L ₁ ' of the surface connected to the upper semicircular ring part 27a and the lower semicircular ring part 27b (meridian ring part 27) is the axial direction of the upper semicircular ring part 27a and the lower semicircular ring part 27b. is the same as the width _L1 .

However, the plate-like connecting parts 29a and 29b do not need to have the same thickness as the other members constituting the shell structure 15.
For example, the thickness of the plate-like connecting portion 29a may be greater than the thickness of at least one of the equatorial ring portion 25, the meridian ring portion 27, the upper spherical shell 21, and the lower spherical shell 23 in the radial direction. As an example, FIG. 4 shows a configuration in which the thickness T ₂ of the plate-like connecting portion 29a is thicker than the radial thickness T ₁ of the upper semicircular ring portion 27a and the lower semicircular ring portion 27b of the meridian ring portion 27. .
In this configuration, since the plate thickness T ₂ of the plate-like connecting portion 29a is thicker than the other members constituting the shell structure 15, sufficient strength can be ensured even when the plate-like connecting portion 29a has a shape that does not have a curved surface.

When the thickness of the plate-like connecting portion 29a is thicker than the other members constituting the shell structure 15, a step S caused by the difference in plate thickness is formed inside the shell structure 15, as shown in FIG. is preferable.
In this configuration, it is not necessary to form the step S on the outside of the shell structure 15, so even if the thickness of the plate-like connecting portion 29a is increased, the width in the thickness direction of the outer shape of the shell structure 15 does not increase. . Therefore, when the liquefied gas tank 1 is installed in the hold of the cargo compartment 7 of the ship 2, it is possible to prevent the liquefied gas tank 1 from interfering with the side walls of the hold.

The longer the axial width H ₁ of the equatorial ring portion 25 and the axial width L ₁ of the meridian ring portion 27, the greater the amount of liquefied gas stored in the shell structure 15. However, if it is too long, the shell structure 15 will have a nearly cylindrical shape, which will require a reinforcing structure inside the shell structure 15 to ensure the required strength, which may increase the weight and make it impossible to mount it on the ship 2. There is. Therefore, the axial width H ₁ of the equatorial ring portion 25 and the axial width L ₁ of the meridian ring portion 27 are set within a range in which the shell structure 15 can secure the necessary strength. If the necessary strength can be secured only with the shell structure 15, no internal reinforcing structure is necessary.

Further, it is preferable that the axial width L ₁ (L ₁ ') of the meridian annular portion 27 shown in FIG. 3 is equal to or less than the axial width H ₁ of the equatorial annular portion 25. The reason is as follows.
The equatorial ring part 25 receives the load of the upper spherical shell 21 in the axial direction, whereas the meridian ring part 27 receives the load of the upper spherical shell 21 in the radial direction. Stress is more likely to be concentrated in the equatorial ring portion 25 than in the equatorial ring portion 25.
Therefore, by setting the axial width L ₁ (L ₁ ′) of the meridian ring portion 27 to be equal to or less than the axial width H ₁ of the equatorial ring portion 25, the tank capacity can be increased without impairing the strength of the liquefied gas tank 1. You can make it bigger.

Specifically, when the maximum radius of the spherical shell of the shell structure 15 is 10 m or more and 25 m or less, the axial width H ₁ of the equatorial ring portion 25 is preferably 1 m or more and 5 m or less. It is preferable that the axial width L ₁ (L ₁ ′) of the meridian annular portion 27 is 1 m or more and 5 m or less, and the axial width H ₁ of the equatorial annular portion 25 is less than or equal to 1 m. Expressed as a percentage, the axial width H ₁ of the equatorial ring portion 25 is 4% or more and 20% or less of the maximum value of the radius of the spherical shell of the shell structure 15 (radius R ₁ and radius R ₂ in FIG. 3). It is preferable that The axial width L ₁ (L ₁ ') of the meridian ring portion 27 is 4% or more and 20% of the maximum value of the radius of the spherical shell of the shell structure 15 (radius R ₁ and radius R ₂ in FIG. 3). It is preferable that the width H in the axial direction of the equatorial ring portion 25 is equal to or less than H ₁ .

The skirt 31 is a support structure that allows the ship 2 to support the shell structure 15 with the lower spherical shell 23 floating above the bottom of the hold of the ship 2, and as shown in FIG. Be prepared.
The support column 33 is a member that receives the weight of the shell structure 15, and is a cylindrical structure that surrounds the lower spherical shell 23 and is erected on the bottom surface of the hold.
The connecting portion 35 is a member that connects the support column 33 and the shell structure 15, and is integrally connected to the equatorial ring portion 25 and the plate-like connecting portions 29a and 29b.

The tank capacity of the shell structure 15 of the liquefied gas tank 1 is appropriately set in consideration of the required storage amount of liquefied gas and the capacity of the hold of the ship 2 in which it is installed.
However, in this embodiment, the tank capacity is preferably 10,000 m ³ or more and 55,000 m ³ or less. The reason is as follows.
In general, it is difficult to ensure the strength of cylindrical liquefied gas tanks with a capacity of 10,000 m3 or ^more without providing reinforcement structures such as columns and bulkheads on the inner surface, but if reinforcement structures are provided, the weight increases and the ship 2 It may not be possible to install it. On the other hand, in the liquefied gas tank 1 of this embodiment, the tank capacity can be increased by providing two annular parts, the equatorial annular part 25 and the meridian annular part 27, in the shell structure 15. It has sufficient strength even without a reinforcing structure. Therefore, the liquefied gas tank 1 is particularly suitable when the tank capacity is 10,000 m ³ or more.
On the other hand, it is difficult to imagine that a liquefied gas tank with a tank capacity exceeding 55,000 m ³ will be manufactured industrially, so by having a tank capacity of 55,000 m ³ or less, the liquefied gas tank 1 has a sufficient tank capacity required for existing liquefied gas tanks. .

The liquefied gas tank 1 is a cargo tank or a fuel tank, and is arranged in a ship hold so that the axial direction (direction of arrow C) of the meridian ring portion 27 is along the longitudinal direction of the ship body 3, as shown in FIG.
As shown in FIG. 1, in a ship 2, a liquefied gas tank 1 is arranged in a hold of a cargo compartment 7 as a cargo tank.

In this way, in the ship 2, the liquefied gas tank 1 is arranged in the hold so that the axial direction (arrow C direction) of the meridian ring portion 27 is along the ship's ship direction. Therefore, the length of the liquefied gas tank 1 in the arranged state in the ship width direction is the same as that of an independent spherical tank without the meridian ring portion 27.

Not limited to the liquefied gas tank 1 of this embodiment, a plurality of MOSS type independent spherical tanks are generally provided in the longitudinal direction of the ship 2 as shown in FIG. 1, but only one is provided in the ship width direction as shown in FIG. provided. Therefore, the longer the length of the tank in the transverse direction, the longer the length in the transverse direction of the ship 2 on which the tank is mounted needs to be lengthened. It is difficult to change the length of Therefore, by installing the liquefied gas tank 1 that can increase the tank capacity without changing the length in the transverse direction of the ship, the capacity of the tank loaded by the ship 2 can be increased without increasing the length in the transverse direction of the ship 2. .

The liquefied gas tank 1 may be provided not on a ship but on a floating structure. The term "floating structure" as used herein means a structure that can float on the ocean and does not require self-propulsion capability. For example, a floating storage and regasification unit (FSRU) corresponds to a floating structure.
Also when the liquefied gas tank 1 is provided in a floating structure, the liquefied gas tank 1 is arranged in the hold so that the axial direction (arrow C direction) of the meridian ring portion 27 is along the ship's ship direction. The longitudinal direction of a floating structure means the longitudinal direction, and the hold means a cargo compartment or a fuel storage compartment within the floating structure. However, if the floating structure is a modified second-hand ship, the direction of the ship's length is the direction of the ship's length, and the hold of the source ship is the hold of the floating structure. .
The above is an explanation of the configurations of the ship 2 and the floating structure on which the liquefied gas tank 1 is mounted according to the present embodiment.

As described above, according to the present embodiment, the liquefied gas tank 1 includes an upper spherical shell 21, a lower spherical shell 23, an equatorial ring part 25, and a meridian ring part 27, and the equatorial ring part 25 raises the spherical shell. The shell structure 15 is formed by extending the spherical shell horizontally at the meridian ring portion 27.
Therefore, even if the tank capacity increases by a volume V ₂ corresponding to the internal volume of the meridian ring portion 27, the height of the liquefied gas tank 1 does not change, and the center of gravity does not become high. Therefore, the tank capacity can be increased without impairing the stability of the ship 2 on which the tank of the shell structure 15 is mounted.

Further, according to the present embodiment, the tank capacity is increased in two annular parts, the equatorial annular part 25 and the meridian annular part 27. Therefore, compared to the conventional structure in which the tank capacity is increased only with the equatorial ring part 25, the axial width of each ring part (equatorial ring part 25 and meridian ring part 27) does not have to be made very long. Tank capacity can be increased. Therefore, the tank capacity of the liquefied gas tank 1 can be increased without losing strength.

Furthermore, according to this embodiment, the plate-like connecting parts 29a and 29b are substantially rectangular flat plates. Therefore, when the equatorial annular portion 25 and the meridian annular portion 27 are annular with a constant radius, all of the equatorial annular portion 25, the meridian annular portion 27, and the plate-like connecting portions 29a and 29b are connected to each other. The cross section is rectangular, and the connection can be made without processing to match the cross-sectional shape of the connection surface.
Therefore, the tank capacity of the liquefied gas tank 1 can be increased without losing strength.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the configuration of the embodiments. It is natural for those skilled in the art to come up with various modifications and improvements within the scope of the technical idea of the present invention, and these are also included in the present invention.
For example, in the present embodiment, the present invention has been explained using a liquefied gas carrier that stores and transports liquefied gas in the liquefied gas tank 1, but the ship 2 of the present invention has a structure that can be equipped with an independent tank that stores liquefied gas. A liquefied gas fueled ship may also be used.

1: Liquefied gas tank 2: Ship 3: Hull 5a: Bottom 5b: Side wall 5c: Exposure deck 6: Engine compartment 7: Cargo compartment 11: Bow compartment 15: Shell structure 17: Superstructure 21: Upper spherical shell 21a: Bow side upper spherical shell 21b: Stern side upper spherical shell 23: Lower spherical shell 23a: Bow side lower spherical shell 23b: Stern side lower spherical shell 25: Equatorial ring part 25a: Bow side equatorial ring part 25b: Stern side equatorial ring part 27: Meridian ring part 27a: Upper semicircular ring part 27b: Lower semicircular ring parts 29a, 29b: Plate-like connecting part 31: Skirt 33: Support column 35: Connection part

Claims (5)

A liquefied gas tank that does not have a reinforcing member on the inner surface of the tank, which has a hemispherical upper spherical shell with an open lower end and a convex upward, and a lower spherical shell with an open upper end and a downward convex shape. and a shell structure having an annular equatorial ring portion connecting the lower end of the upper spherical shell and the upper end of the lower spherical shell,
The shell structure is
The upper spherical shell, the lower spherical shell, and the equatorial ring part have a shape divided into two by a plane parallel to the vertical direction, and further include an annular meridian ring part connecting the divided planes,
The meridian ring portion is
a pair of semicircular ring portions that connect the dividing surfaces of the upper spherical shell and the dividing surfaces of the lower spherical shell, respectively;
comprising a flat plate-like connecting portion that connects the dividing surfaces of the equatorial ring portion and the dividing surfaces of the pair of semicircular ring portions,
The thickness of the plate-like connecting portion is thicker than the thickness of at least one of the equatorial ring portion, the semicircular ring portion, the upper spherical shell, and the lower spherical shell in the radial direction, and A liquefied gas tank characterized in that a step caused by the difference is formed inside the shell structure . The liquefied gas tank according to claim 1 , wherein the axial width of the meridian annular portion is less than or equal to the axial width of the equatorial annular portion. A liquefied gas tank that does not have a reinforcing member on the inner surface of the tank, which has a hemispherical upper spherical shell with an open lower end and a convex upward, and a lower spherical shell with an open upper end and a downward convex shape. and a shell structure having an annular equatorial ring portion connecting the lower end of the upper spherical shell and the upper end of the lower spherical shell,
The shell structure is
The upper spherical shell, the lower spherical shell, and the equatorial ring part have a shape divided into two by a plane parallel to the vertical direction, and further include an annular meridian ring part connecting the divided planes,
The meridian ring portion is
a pair of semicircular ring portions that connect the dividing surfaces of the upper spherical shell and the dividing surfaces of the lower spherical shell, respectively;
comprising a flat plate-like connecting portion that connects the dividing surfaces of the equatorial ring portion and the dividing surfaces of the pair of semicircular ring portions,
A liquefied gas tank characterized in that an axial width of the meridian annular portion is less than or equal to an axial width of the equatorial annular portion. A ship, characterized in that the liquefied gas tank according to any one of claims 1 to 3 is arranged as a cargo tank or a fuel tank in a hold so that the axial direction of the meridian ring portion is along the ship's ship direction. A floating structure, characterized in that the liquefied gas tank according to any one of claims 1 to 3 is arranged as a cargo tank or a fuel tank in a hold so that the axial direction of the meridian annular portion is along the ship's ship direction. thing.

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