KR20100122556A - Membrane type lng storage tank having a structure in two rows - Google Patents

Abstract

PURPOSE: Membrane type LNG storage tanks of a two-row structure are provided to save the manufacturing cost of an LNG storage tank by a fluid passage in a cofferdam. CONSTITUTION: Membrane type LNG storage tanks comprise a longitudinal cofferdam(35) and are arranged in two rows in a floating marine structure. The longitudinal cofferdam longitudinally divides the inner space of the LNG storage tank to decrease the effect of the sloshing and to support the load of an upper structure. A chamfer is not formed on at least one of the upper and lower ends of the cofferdam. A lower fluid passage is formed on the lower part of the cofferdam and LNG flows between two rows of the LNG storage tanks through the lower fluid passage. The lower fluid passage is insulated and prevents the heat transfer from the outside to the LNG storage tank.

Description

Membrane type LNG storage tank with two-row arrangement structure MEMBRANE TYPE LNG STORAGE TANK HAVING A STRUCTURE IN TWO ROWS

The present invention relates to an LNG storage tank capable of storing liquefied natural gas (Liquefied Natural Gas), and more particularly to a longitudinal copper dam installed to support a load of an upper structure while suppressing sloshing. It relates to a membrane type LNG storage tank in which the LNG storage tank is arranged in two rows.

Natural gas is transported in a gaseous state through onshore or offshore gas piping, or to a distant consumer while stored in an LNG carrier in the form of liquefied liquefied natural gas (LNG). Liquefied natural gas is obtained by cooling natural gas to cryogenic temperature (approximately -163 ℃), and its volume is reduced to about 1/600 than natural gas in gas state, so it is very suitable for long distance transportation through sea.

LNG carriers for loading LNG into the sea and loading and unloading LNG to land requirements include LNG storage tanks (commonly referred to as cargo holds) that can withstand the cryogenic temperatures of liquefied natural gas. LNG storage tanks installed inside LNG carriers can be classified into independent type and membrane type, depending on whether the load of cargo directly affects the insulation.

Independent tank type storage tanks are either SPB type or Moss type storage tanks. These types of storage tanks use a large amount of non-ferrous metal as the main material, which greatly increases the manufacturing cost of the storage tanks. Currently, LNG storage tanks are the most frequently used membrane storage tanks. Membrane storage tanks are relatively inexpensive and have been proven in LNG storage tanks for a long time without causing any safety problems. .

Membrane type storage tanks are further divided into GTT NO 96 type and Mark III type, which are described in US Pat. Nos. 5,269,247, 5,501,359, and the like.

The GTT NO 96 type storage tank includes a primary sealing wall and a secondary sealing wall made of Invar steel (36% Ni) having a thickness of 0.5 to 0.7 mm, a plywood box and a perlite. The primary heat insulation wall and the secondary heat insulation wall which consist of) are alternately laminated on the inner surface of a ship body.

In the case of the GTT NO 96 type, the primary sealing wall and the secondary sealing wall have almost the same degree of liquid tightness and strength, so that when the primary sealing wall 10 is leaked, the cargo is secured only by the secondary sealing wall for a considerable period of time. It can support. Also, the sealing wall of GTT NO 96 type is easy to weld than the Mark III type membrane because the membrane is straight type, so the automation rate is high, but the overall welding length is longer than Mark III type. In addition, in the case of GTT NO 96, a double couple is used to support an insulation box (ie, an insulation wall).

Meanwhile, the Mark III type storage tank includes a primary sealing wall made of a 1.2 mm thick stainless steel membrane, a secondary sealing wall made of a triplex, a polyurethane foam, and the like. The primary heat insulating wall and the secondary heat insulating wall formed are alternately provided on the inner surface of the hull.

In the case of Mark III type, the sealing wall has corrugated wrinkles, and shrinkage by the cryogenic LNG is absorbed by the corrugated wrinkles so that a large stress is not generated in the membrane. Mark Ⅲ type heat dissipation system is not easy to reinforce due to its internal structure, and its feature of preventing LNG leakage is weaker than that of GTT NO 96 type secondary sealing wall due to the characteristics of secondary sealing wall.

The liquefied natural gas storage tank of the membrane type described above is more vulnerable to sloshing problems because of its weak rigidity. Sloshing refers to a phenomenon in which a liquid substance, ie, LNG, flows in a storage tank when a vessel moves in various sea conditions, and the wall surface of the storage tank is severely impacted by sloshing.

Since the sloshing phenomenon inevitably occurs during the operation of the ship, it is necessary to design the storage tank structure to have a sufficient strength to withstand the impact force due to the sloshing.

In Fig. 1, the upper and lower chamfers 11 inclined at approximately 45 degree angles to the upper and lower sides of the LNG storage tank 10 to reduce the sloshing impact force of the LNG, particularly the sloshing impact force in the left and right directions. , An example of an LNG storage tank 10 having a 12 is shown.

In the case of the conventional storage tank 10 having the chamfer (11, 12), by forming the chamfer (11, 12) in the upper and lower portions of the storage tank, the problem due to the sloshing phenomenon can be solved to some extent, LNG As the size of the transport ship gradually increased, the size of the storage tank 10 also increased and the impact force due to the sloshing was greatly increased.

In addition to the problem that the impact force due to sloshing increases as the volume of the storage tank increases, the storage tank needs to be reinforced to support the load of the upper structure as the load of various devices installed on the upper portion of the storage tank increases. This has risen.

In particular, as the demand for floating offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Unit (FSRU) has been increasing recently, LNG storage tanks installed in such floating offshore structures In addition, it was required to solve the sloshing problem and the load of the superstructure.

The LNG FPSO is a floating offshore structure used to directly liquefy the produced natural gas at sea and store it in an LNG storage tank, and, if necessary, to transfer LNG stored in the LNG storage tank to an LNG carrier. In addition, the LNG FSRU is a floating offshore structure that stores LNG unloaded from LNG carriers in an LNG storage tank at sea far from the land, and then vaporizes LNG as needed to supply land demand.

Therefore, instead of increasing the size of the storage tank, a partition-like structure is installed inside the storage tank to divide a storage tank into several storage spaces, which is as effective as installing several storage tanks of small capacity. A method for solving the sloshing problem has been proposed.

In FIG. 2, in order to reduce the effect of sloshing, an example in which a partition-shaped structure is installed in the LNG storage tank 20 and the internal space of one LNG storage tank 20 is divided into two spaces is illustrated. It is.

By the way, in the past, the upper chamfer 21 and the lower chamfer 22 were formed in the divided spaces even when the internal space of the LNG storage tank 20 was divided into two rows by the partition wall. Therefore, there is a problem that the storage space is significantly reduced compared to the LNG storage tank of a single row arrangement structure.

In the case of LNG storage tanks, the stability to withstand sea conditions (particularly to sloshing) and storage capacity are very important. In particular, membrane type storage tanks have many advantages in terms of price and other advantages over other types of storage tanks. However, in order to prevent damage due to sloshing, chamfers should be installed at upper and lower corners, and accordingly The storage capacity was reduced as much as the space in which the fur is formed.

Since the loss of storage space reduces the amount of LNG transported, it is an important factor in determining the performance of LNG carriers in the market related to LNG transport. The space efficiency problem is very important to determine whether or not a vessel is traded, and the storage capacity not only directly affects LNG transportation volume but also affects the size of floating offshore structures such as LNG carriers. In other words, when the storage capacity is lowered, the size of the storage tank must be increased to secure the same storage space, which leads to an increase in the size of the floating offshore structure in which the storage tank is installed.

In order to increase the size of the storage tank, the demand for expensive steel is increased, and the demand for the reinforcing member is also increased to reinforce the structural strength, thereby increasing the manufacturing cost of the floating offshore structure, thereby reducing the price competitiveness.

In addition, in the case of floating offshore structures, such as LNG FSRU, various facilities are installed, in consideration of the structure and strength of the storage tank installed in the hull, there is a problem that the arrangement of the upper structure has a lot of restrictions.

In addition, when the partition 25 is installed inside the LNG storage tank 20, since the internal space of the LNG storage tank is divided into a separate space, a pump for discharging the LNG loaded in the LNG storage tank to the outside or Since equipment and piping such as a pump tower should be separately installed in each space, there is a problem that not only increases the manufacturing cost of the LNG storage tank but also complicated operation and management of the LNG storage tank.

The present invention for solving these problems, even if the LNG storage tanks are arranged in two rows by installing a longitudinal copper dam to suppress the sloshing phenomenon and to support the load of the upper structure, the upper or lower portion of the copper dam Another object of the present invention is to provide a membrane type LNG storage tank having a two-row arrangement structure in which a storage space can be increased by not forming a chamfer on the upper and lower sides.

According to an aspect of the present invention for achieving the above object, as a membrane type LNG storage tank that can be installed in the floating offshore structure to store LNG, can reduce the effects of the sloshing phenomenon and at the same time can support the load of the upper structure. Including two longitudinal copper dams to vertically divide the internal space of the LNG storage tank so as to be arranged in two rows in the floating offshore structure, the chamfer is not formed on at least one of the top and bottom of the longitudinal copper dam Provided is a membrane type LNG storage tank, characterized in that.

The membrane type LNG storage tank preferably includes a lower fluid passage formed through the lower portion of the longitudinal copper dam to allow the movement of LNG between the LNG storage tanks arranged in two rows.

The lower fluid passage is preferably insulated to prevent heat transfer from the outside of the LNG storage tank.

The membrane type LNG storage tank preferably further includes an upper fluid passage formed through the upper portion of the longitudinal copper dam so as to allow the movement of the BOG between the LNG storage tanks arranged in two rows.

The floating offshore structure is any one selected from among LNG FPSO, LNG FSRU, LNG transport ship, and LNG RV, which is used in a floating state at sea where a flow occurs while having a storage tank for storing liquid cargo loaded at a cryogenic state. It is preferable.

In addition, according to another aspect of the present invention, a floating offshore structure having an LNG storage tank for storing LNG is installed therein, to reduce the effects of the sloshing phenomenon and at the same time to support the load of the upper structure A reinforcement structure arranged to divide the hull inner space of the floating offshore structure in the longitudinal and transverse directions, and the LNG storage tank disposed in each space formed by the reinforcement structure, the interior of the reinforcement structure There is a void space (void space) is formed, the LNG storage tank is arranged in a plurality of rows along the longitudinal direction of the floating offshore structure, characterized in that the chamfer is not formed on at least one of the top and bottom of the reinforcement structure. A floating offshore structure is provided.

According to the present invention as described above, even if the LNG storage tanks are arranged in two rows by installing a vertical copper dam to support the load of the upper structure while suppressing the sloshing phenomenon, the upper, lower, or upper and lower portions of the copper dam A membrane type LNG storage tank having a two-row arrangement structure can be provided, which can increase the storage space by not forming a chamfer in the.

Further, according to the present invention, even if the LNG storage tank is divided into a plurality of copper dams, the fluid dam is formed in the copper dam so as not to increase the number of installations for discharging the LNG loaded in the LNG storage tank. In addition, the manufacturing cost of the LNG storage tank can be reduced, as well as the operation and management of the LNG storage tank can be facilitated.

Hereinafter, an LNG storage tank for storing LNG in a floating offshore structure according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

In the present specification, the floating offshore structure is a concept including both a structure and a vessel used while floating on the sea where a flow occurs while having a storage tank for storing a liquid cargo loaded at a cryogenic state such as LNG. For example, LNG includes both LNG carriers and LNG Regasification Vessels (RVs) as well as offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Units (FSRUs).

Fig. 3 is a cross sectional view showing the LNG storage tank of the floating offshore structure laterally cut according to the first embodiment of the present invention, and Fig. 4 illustrates the internal structure of the LNG storage tank of the first embodiment. The perspective view which cut out a part for illustration is shown.

As shown in Figs. 3 and 4, the LNG storage tank 30 according to the first embodiment of the present invention is suspended in order to support the load of the upper structure while reducing the influence due to the sloshing phenomenon of the received LNG. It includes a longitudinal copper dam (35) which is installed to partition the inner space of the nautical structure along the longitudinal direction.

In the present invention, the copper dam is a grid-shaped structure in which a void space is provided therein, and allows a membrane-type storage tank to be installed in each compartment by vertically and horizontally partitioning the internal space of the floating marine structure. to be. Such copper dams have been used to partition between a plurality of storage tanks along the length of a conventional floating offshore structure.

According to the present invention, the copper dam can be largely divided into a longitudinal copper dam 35 and a transverse copper dam. The lateral copper dam is a structure that partitions the inner space of the floating offshore structure horizontally so that the membrane type LNG storage tank can be arranged along the longitudinal direction, and the longitudinal copper dam 35 is the hull of the floating offshore structure. The structure allows the membrane type LNG storage tank to be disposed along the width direction by vertically dividing the internal space. The lateral copper dam may form the front wall portion and the rear wall portion of the LNG storage tank, and the longitudinal copper dam 35 may form the left or right wall portion of the LNG storage tank.

In the present invention, since the LNG storage tank is a membrane type storage tank, the above-mentioned copper dam is used as a structure for dividing the internal space. In the case of a stand-alone storage tank, a simple bulkhead can be used as a structure that divides the internal space. However, in a stand-alone storage tank, the bulkhead does not have the strength sufficient to support the load of the upper structure, and supports the load of the upper structure. In order to have the strength to be possible, the thickness of the bulkhead must be quite thick. However, since the price of the material used in the stand-alone storage tank is expensive, it is unrealistic in terms of price competitiveness because the manufacturing cost of the storage tank is inevitably increased to make such a thick bulkhead.

Tank arrays with two or more batch structures are known in the fields of oil tankers and bulk carriers, but these tanks are made without consideration of problems such as sloshing or thermal deformation. It's just one or more installed.

However, in the field of LNG storage tanks for storing and transporting LNG which is a cryogenic liquid cargo, the shape of the storage tank must be completely redesigned to achieve a two-row arrangement structure.

In the membrane type storage tank, the membrane structure cannot form a partition by itself, and when non-ferrous metal partitions are installed in the existing membrane type storage tank, the use of expensive nonferrous metal causes a price increase. In addition, when non-ferrous metal bulkheads are installed inside the membrane-type storage tank, special design considering the installation of bulkheads should be made. In addition, the inside of the storage tank may not be composed of a single membrane structure, and there is a potential risk of damage to the partition wall due to a discontinuity between the membrane structure and the partition wall.

The inventors of the present invention, in forming the two-row arrangement structure by the membrane-type storage tank, as shown in Figures 3 and 4, the longitudinal copper dam (35) extending longitudinally inside the hull of the floating offshore structure (35). ) And a transverse copper dam extending in the transverse direction, suggesting a structure in which two LNG storage tanks are arranged in two rows along the longitudinal direction substantially in the width direction of the floating offshore structure.

A longitudinal copper dam 35, that is, a void space, is formed between the storage tanks arranged in two rows, and the storage tanks formed to be arranged in two rows on both sides with the space portion therebetween are each formed by a membrane structure. You can have a separate storage space that is completely sealed.

As described above, according to the present invention, the membrane-type storage tank, the copper dam, and another membrane-type storage tank are arranged in succession when viewed in the lateral direction of the floating offshore structure, thereby verifying the existing membrane-type storage tank. The manufacturing technique (lateral copper dam) can be applied to form a two-row arrangement structure, the intermediate longitudinal copper dam 35 is to support the load of the upper structure at the same time.

The present invention can be applied to SPB type storage tanks as well as membrane type storage tanks. When the present invention is applied to the SPB type storage tank, instead of simply installing a partition inside the SPB type storage tank, it may be configured to install a copper dam inside the SPB type storage tank as shown in FIG. .

By arranging the storage tanks 30 in two rows, the impact force due to sloshing applied to the storage tanks can be drastically reduced. Considering the numerical results, it can be understood that the sloshing impact force is greatly reduced for two reasons. First, the amount of cargo stored, ie LNG, is reduced, thereby reducing the impact force due to sloshing. Second, as the width of the storage tank is reduced by more than half, the movement of the liquid cargo, that is, the LNG inherent movement away from the natural cycle of the floating offshore structure, reduces the size of the movement of the liquid cargo.

In addition, the offshore structure such as LNG FPSO is required for a storage tank that can withstand such heavy loads because the weight of the upper structure increases, in the case of the storage tank 30 of the two-row arrangement structure such as the present invention simply by a thin partition Rather than dividing the tank in half, the longitudinal copper dam 35 may be installed between the membrane-type storage tanks 30 so that the copper dam 35 may support and distribute the upper load.

The design of supporting the upper load by installing the copper dam 35 in the center is a concept not applicable to the existing membrane type tank, Mohs type tank, SPB type tank, and the like. As described above, in the case of the SPB, the central bulkhead may exist, but the bulkhead needs to be significantly thicker in order to support the upper load, and in this case, the price of the central bulkhead is increased. Using to support is impractical.

According to the present invention, as shown in FIGS. 3 and 4, the chamfer is not formed on the lower side of the copper dam 35 so as to secure the storage capacity while arranging the storage tanks 30 in two rows. Even if the chamfer is not formed in the lower part of the copper dam 35 side according to the numerical analysis result mentioned above, the storage tank 30 which has a 2-row arrangement structure can support a sloshing impact force.

As described above, in the present invention, the membrane-type storage tanks 30 are disposed in two rows with the copper dams 35 interposed therebetween, and the edges adjacent to the longitudinal copper dams 35 are conventional membrane-type storage tanks 20 (see FIG. 2). Unlike, the storage capacity can be increased by forming approximately at right angles. This breaks the existing concept that membrane storage tanks are not suitable for fabricating floating offshore structures supporting partial stacks and superstructures, and is an important change in the concept that enables market entry of membrane storage tanks.

FIG. 5 is a perspective view of a portion cut away to explain the internal structure of the LNG storage tank according to the second embodiment of the present invention. The LNG storage tank 30 of the second embodiment differs only in that the fluid passage 38 is formed below the copper dam 35 as compared to the LNG storage tank 30 of the first embodiment. That is, in the LNG storage tank 30 of the second embodiment, the upper chamfer 31 is formed at the upper end in the inner direction, that is, at the upper end and the outer end upper end of the copper dam 35 based on the transverse cross section of the floating offshore structure. The lower chamfer 32 is formed at an inner lower end, that is, at an outer lower end except for the lower end of the copper dam 35.

According to the second embodiment, one or more lower fluid passages 38 are formed in the lower portion of the copper dam 35. The lower fluid passage 38 is for communicating LNG between two rows of LNG storage tanks 30 arranged to allow LNG to move.

Due to the lower fluid passage 38, the liquid LNG may move between both LNG storage tanks 30, so that pumps (not shown) and piping (not shown) capable of discharging LNG stored in the LNG storage tank 30 to the outside are provided. Even if only one facility such as an omission) and a pump tower (not shown) is installed in the LNG storage tank 30, all LNG in the LNG storage tank 30 can be discharged. For this purpose, the lower fluid passage 38 is preferably formed at the lowermost part of the copper dam 35, ie adjacent to the bottom of the LNG storage tank 30.

In the formation of the lower fluid passage 38 in the copper dam 35 as described above, in accordance with the present invention is substantially perpendicular to the bottom surface of the storage tank without the chamfer formed at the bottom of the copper dam 35 Therefore, it is advantageous to form the lower fluid passage 38 as compared with the case where the chamfer is formed for the following reasons.

In order to manufacture a membrane type storage tank, a rectangular insulating box of a certain size must be stacked and assembled. Particularly, for a corner part, a box having a shape that matches the shape of the corner part is separately manufactured and then assembled into the corresponding part to manufacture a storage tank. do.

If the tank design applied to the conventional LNG storage tank 20 as shown in Figure 2 is used, the lower chamfer 22 is formed at the bottom of the copper dam 25, the lower portion of the copper dam 25 of this type In order to form the fluid passage, the fluid passage must be formed to penetrate the lower chamfer 22 portion.

Therefore, when the lower fluid passage is formed in the lower chamfer 22, it is necessary to manufacture a new type of thermal insulation box that did not exist in the conventional LNG storage tank 20. This new type of thermal insulation box is more difficult to manufacture than the flat insulation box and requires a lot of work time. That is, it is difficult to manufacture a large thermal insulation box by hand according to the shape of the fluid passage to be formed in the chamfer portion, and also to perform a complicated welding operation in the welding operation performed for the bonding of the thermal insulation boxes.

However, when the copper dam 35 is formed such that the chamfer is not formed at the lower end of the copper dam 35 and the connection portion with the bottom of the storage tank is substantially perpendicular as proposed in the present invention, Compared to the case in which the fur is formed, the shape is relatively simple and there is no inclined surface, so that the production method and work tool and technology of the existing insulation box can be used as it is, and the productivity can be improved.

On the other hand, although not shown, the pump and tubing is preferably disposed above the lower fluid passage 38. Installation number or shape of the lower fluid passage 38 is not limited to the present invention, and may be appropriately changed in consideration of the size of the LNG storage tank 30.

In addition, the lower fluid passage 38 is preferably insulated so as to prevent heat transfer from the outside of the LNG storage tank 30, the insulating method is a membrane type storage tank or independent storage (independent type) storage Any insulation technique applied to the tank may be utilized.

In addition to the lower fluid passage 38, an upper fluid passage may be formed at an upper end of the copper dam 35 to allow a boil-off gas (BOG) naturally occurring during transportation of LNG to move.

As described above, according to the second embodiment of the present invention, the membrane-type LNG is provided with a longitudinal copper dam for suppressing sloshing and supporting the load of the upper structure so that the internal space of the floating offshore structure is divided. Even when the storage tanks are arranged in two rows, only one installation per two rows of LNG storage tanks, such as pumps, pipes, pump towers, and gas domes, to discharge the loaded LNG (or BOG) to the outside Even LNG storage tanks can be operated smoothly. As a result, the manufacturing cost of the LNG storage tank can be reduced, and the operation and management can be facilitated.

6 is a perspective view of a portion cut away to explain the internal structure of the LNG storage tank according to the third embodiment of the present invention. The LNG storage tank 40 of the third embodiment differs from the LNG storage tank 30 of the first embodiment only in that chamfers are not formed not only at the lower end but also at the upper end of the copper dam 35. That is, in the LNG storage tank 40 of 3rd Embodiment, the upper chamfer 41 and the lower chamfer 42 are formed only in the outer side upper end and the lower end based on the horizontal cross section of a floating offshore structure.

As such, the structure in which no chamfer is formed at the upper and lower ends of the copper dam is preferably adopted when the effect of sloshing is small in consideration of the sea condition.

Although not shown in the drawing, the LNG storage tank 40 according to the third embodiment may be provided with a fluid passage (not shown) passing through the copper dam.

In addition, fluid passages through the copper dams may be formed in the longitudinal copper dam as well as in the transverse copper dam as desired.

As described above, the storage tank structure of the floating offshore structure according to the present invention has been described with reference to the illustrated drawings, but the present invention is not limited to the embodiments and drawings described above, and the present invention within the claims. Of course, various modifications and variations can be made by those skilled in the art.

1 is a perspective view showing the appearance of the LNG storage tank according to the prior art,

Figure 2 is a cross-sectional view of the LNG storage tank transversely cut according to the prior art,

3 is a cross-sectional view of a state in which a LNG storage tank of a floating offshore structure is cut laterally according to a first preferred embodiment of the present invention;

4 is a perspective view cut out a part to explain the internal structure of the LNG storage tank of the floating offshore structure according to the first preferred embodiment of the present invention;

5 is a perspective view cut out a part to explain the internal structure of the LNG storage tank of the floating offshore structure according to the second embodiment of the present invention, and

Fig. 6 is a perspective view of a portion cut away to explain the internal structure of the LNG storage tank of the floating offshore structure according to the third embodiment of the present invention.

Description of the Related Art

30, 40: LNG storage tank 31, 41: upper chamfer

32, 42: lower chamfer 35: copper dam

38: lower fluid passage

Claims (6)

Membrane type LNG storage tank installed in the floating offshore structure to store LNG, Disposed in two rows within the floating offshore structure, including a longitudinal copper dam that longitudinally divides the internal space of the LNG storage tank to support the load of the upper structure while reducing the effects of sloshing, Membrane type LNG storage tank, characterized in that the chamfer is not formed on at least one of the top and bottom of the longitudinal copper dam. The method according to claim 1, Membrane type LNG storage tank comprising a lower fluid passage formed through the lower portion of the longitudinal copper dam to enable the movement of the LNG between the LNG storage tank arranged in two rows. The method according to claim 2, The lower fluid passage is LNG storage tank of the floating offshore structure, characterized in that the heat insulation to prevent heat transfer from the outside of the LNG storage tank. The method according to any one of claims 1 to 3, Membrane type LNG storage tank further comprises an upper fluid passage formed through the upper portion of the longitudinal copper dam to enable the movement of the BOG between the LNG storage tank arranged in two rows. The method according to any one of claims 1 to 3, The floating offshore structure is any one selected from among LNG FPSO, LNG FSRU, LNG transport ship and LNG RV, which are used in a floating state at sea where a flow occurs while having a storage tank for storing liquid cargo loaded at a cryogenic state. LNG storage tank of the floating offshore structure, characterized in that. As a floating offshore structure having an LNG storage tank installed therein for storing LNG, A reinforcement structure which is arranged to divide the hull inner space of the floating offshore structure in the longitudinal and transverse directions so as to reduce the influence of sloshing phenomenon and to support the load of the upper structure; It includes the LNG storage tank disposed in each space, A void space is formed inside the reinforcement structure, and the LNG storage tank is disposed in a plurality of rows along the longitudinal direction of the floating offshore structure, and at least one of the top and bottom of the reinforcement structure has a chamfer. Floating offshore structure, characterized in that not formed.

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