KR20120058485A - Floating structure having storage tanks arranged in plural rows - Google Patents

Abstract

PURPOSE: A floating structure having storage tanks arranged in multiple rows is provided to increase storage capacity of liquefied gas, and to reduce influence due to sloshing by arranging tanks having short length at a stem and a stern part where the sloshing is highly applied. CONSTITUTION: A floating structure comprises LNG tanks(3,5,7) longitudinally arranging in at least two rows. An upper facility is installed in the upper part of the floating structure. Copper dams are installed between the LNG tanks in longitudinal directions. The LNG tanks are separated to individual storage tanks by the longitudinal copper dams, and support and disperse the upper load of the upper facility.

Description

FLOATING STRUCTURE HAVING STORAGE TANKS ARRANGED IN PLURAL ROWS}

The present invention relates to a floating structure having a storage tank capable of storing liquefied gas, and more particularly, to the liquefied gas storage tanks are arranged in multiple rows within the hull of the floating structure at the same time the storage tank located at the bow and stern It relates to a floating structure whose length is shorter than the length of the storage tank located at the center of the hull in the longitudinal direction.

Natural gas is transported in a gaseous state through onshore or offshore gas piping, or transported to a distant consumer while stored in a transport in the form of liquefied gas, such as LNG or LPG. Liquefied natural gas is obtained by cooling natural gas at cryogenic temperatures (approximately -163 ° C), and its volume is reduced to approximately 1/600 of that of natural gas, making it well suited for long-distance transport through the 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 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. In addition, the structure of the MOSS type independent storage tank is described in Korean Patent No. 10-15063, etc., and the structure of the SPB type independent storage tank is described in Korean Patent No. 10-305513.

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 leakage of the primary sealing wall occurs, the secondary sealing wall can support the cargo safely for a considerable period of time. . 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 (that is, 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 contained in a storage tank, that is, liquefied gas such as LNG, flows when a vessel moves in various sea conditions. 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 sufficient strength to withstand the impact force due to the sloshing.

A method of forming the upper and lower chamfers inclined at approximately 45 degree angles on the upper and lower sides of the storage tank to reduce the sloshing impact force of liquid cargo, such as LNG or LPG, especially in the left and right directions. Is being used.

In the case of a conventional storage tank having a chamfer, the problem caused by the sloshing phenomenon can be solved to some extent by forming a chamfer on the upper and lower portions of the storage tank, but as the ship is gradually enlarged, the size of the storage tank becomes larger and slower. The impact force caused by the sawing has also been 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, in recent years, as the demand for offshore plants such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Units (FSRUs), that is, floating structures, has increased, In addition, it was required to solve the sloshing problem and the load problem of the superstructure.

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

In the case of a floating structure in which various facilities are installed in the upper portion, such as LNG FPSO or LNG FSRU, there are problems in that the arrangement of the upper structure has many restrictions in consideration of the structure and strength of the storage tank installed in the hull.

In addition, since the storage tanks were arranged in one row in the prior art, the size of the driven fluctuations was smaller than the horizontal fluctuations of the hull, so the impact of sloshing caused by the driven fluctuations was small. As the research on the multi-row arrangement structure arranged above progresses, the width of the hull is widened, and the need to consider the sloshing caused by the driven fluctuation.

Thus, sloshing due to driven fluctuations can be reduced, and the floating structure can appropriately support the load of the upper structure, while increasing the storage capacity of the liquefied gas and the space for the arrangement of the upper structure. Research needs to continue.

The present invention for solving the above problems, the liquefied gas storage tank is arranged in two or more rows inside the hull, the length of the storage tank located at the center of the hull in the longitudinal direction of the storage tank located at the fore and aft By making it shorter, to provide a floating structure that can cope with sloshing caused by driven fluctuations, can adequately support the load of the upper structure, and increase the storage capacity of the liquefied gas and the space for the arrangement of the upper structure. It is.

According to an aspect of the present invention for achieving the above object, a storage tank for storing liquefied gas is disposed in the hull and used floating while floating at sea, a plurality of the storage tank in the hull It is arranged in a row in the width direction, the length of the longitudinal direction of the storage tank is provided with a floating structure characterized in that it gradually decreases toward the bow and stern side from the center.

A cofferdam is installed between the storage tanks, and each storage tank is preferably capable of securing a separate storage space sealed by a sealing structure.

It is preferable that a reinforcing structure is installed inside the cofferdam to support the load of the upper structure.

A partition wall is installed between the storage tanks, and each storage tank is preferably able to secure a separate storage space sealed by a sealing structure.

The storage tank is preferably a membrane type or a standalone tank.

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

The ratio of the width and the length of the storage tank is 1: 1 to 2, it is preferable that the ratio of the width and length gradually decreases toward the bow and stern side from the center.

In addition, according to another aspect of the invention, the storage tank is installed in the floating structure to store the liquefied gas, to reduce the effects of the sloshing phenomenon and at the same time to support the load of the upper structure of the floating structure Partitioned by a longitudinal cofferdam and a width cofferdam installed in the hull and arranged in a widthwise multi-row, wherein the distance between the width cofferdam at the center of the hull is the distance between the width cofferdam at the bow or the stern There is provided a storage tank having a multi-row arrangement, characterized in that it is longer.

According to the present invention as described above, the liquefied gas storage tanks are arranged in two or more rows inside the hull, but the length of the storage tank located at the fore and aft is shorter than the length of the storage tank located at the center of the hull in the longitudinal direction. Floating structures are provided.

According to the floating structure of the present invention, while the storage capacity of the liquefied gas can be increased, a short length tank is arranged on the bow and the stern where the sloshing caused by the driven fluctuation is large, so that the effect of the sloshing can be reduced. do.

In addition, according to the floating structure of the present invention, it is possible to properly support the load of the upper structure by the cofferdam partition wall or reinforcing structure provided between the storage tank adjacent in the width direction,

According to the present invention as described above, the liquefied gas storage tanks are arranged in two or more rows inside the hull, but the length of the storage tank located at the fore and aft is shorter than the length of the storage tank located at the center of the hull in the longitudinal direction. Floating structures are provided.
According to the floating structure of the present invention, while the storage capacity of the liquefied gas can be increased, a short length tank is arranged on the bow and the stern where the sloshing caused by the driven fluctuation is large, so that the effect of the sloshing can be reduced. do.
In addition, according to the floating structure of the present invention, it is possible to properly support the load of the upper structure by the cofferdam partition or reinforcing structure installed between the adjacent storage tanks in the width direction, sufficient space for the arrangement of the upper structure Can be secured.

Hereinafter, a floating structure having a storage tank of a multi-row arrangement structure according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

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

Figure 1 is a plan view of a floating structure having a storage tank arranged in two rows in accordance with the present invention, Figure 2 is a view for explaining the displacement of the fluid according to the distance from the center of the hull when the driven of the hull It is. 3 shows a cross-sectional view of a floating structure having storage tanks arranged in three rows in accordance with the present invention.

As shown in FIG. 1, the floating structure according to the present invention has storage tanks 3 and 5 arranged in two rows in the width direction for storing liquefied gas inside the hull 1.

At this time, among the storage tanks arranged in two rows, the central storage tank (3) disposed in the middle in the longitudinal direction, the fore-side storage tank (5) disposed on the bow and stern side of the central storage tank (3) and It is preferable that the width is longer than that of the stern side storage tank 7.

The length of the bow storage tank 5 and the stern storage tank 7 may be the same, or may be designed differently from each other in consideration of the distance from the centerline of the hull.

As shown in Fig. 2, the sloshing caused by the driven fluctuations is aggravated away from the centerline of the hull, i.e., toward the bow or stern side. The further away from it, the worse it gets.

Therefore, the sloshing impact force in the bow side storage tank 5 and the stern side storage tank 7 becomes larger than the central storage tank 3 close to the centerline of the hull 1.

On the other hand, as the capacity of the storage tank is shorter and the length is shorter, the sloshing phenomenon due to the fluctuation is less likely to occur. As shown in FIG. 1, the length of the bow storage tank 5 and the stern storage tank 7 is centered. When the size of the bow side storage tank 5 and the stern side storage tank 7 is reduced by making it shorter than the length of the storage tank 3, the sludge in the bow side storage tank 5 and the stern side storage tank 7 is reduced. The phenomenon can be suppressed.

As shown in FIG. 1, when the length of the storage tank is A and the width is B, it is preferable that B: A is in a range of about 1: 1 to 2. In the case of the central storage tank (3), B: A1 is designed to be close to 1: 2, and for the foreside storage tank (5) and stern side storage tank (7), B: A2 is designed to be close to 1: 1. do.

On the other hand, according to the present invention, each of the storage tanks (3, 5, 7) may be a membrane tank, or may be a stand-alone tank.

In addition, according to the present invention, by installing only one pump tower each in two or more storage tanks adjacent in the width direction or longitudinal direction, the total cost of the pump tower installed in the floating structure to reduce the cost required for manufacturing Save time and time.

At this time, it is preferable that two or more adjacent storage tanks have a lower passage through which liquefied gas can move. In addition, the upper portion of the storage tank is preferably provided with an additional upper passage through which the boil-off gas can move. These lower passages and upper passages may be replaced by pipes.

In addition, in order to withstand the impact force due to sloshing, chamfers may be formed at upper and lower side edges of each storage tank, that is, the central storage tank 3, the bow side storage tank 5, and the stern side storage tank 7, respectively. Can be.

The chamfer formed by tilting the corner wall surface of the storage tank to approximately 45 degrees can change its size according to the magnitude of the sloshing impact force applied. For example, the stern side of the chamfer and stern side storage tank 7 which is located farthest from the centerline of the hull 1 and is installed at the upper edge of the bow side storage tank 5 in which the sloshing impact force acts the most. The chamfer provided in the upper corner can be formed longer than the chamfer provided in the other position.

In addition, a chamfer is formed only at the upper edge of the bow side storage tank 5 and the stern side upper edge of the stern side storage tank 7 where the sloshing impact force acts the most, and the chamfer is not formed at the remaining edges. Instead, the storage tank may be formed such that the front wall or the rear wall and the floor or the ceiling are connected at a right angle.

A cofferdam extending in the width direction or the longitudinal direction of the hull 1 may be installed between each storage tank. Cofferdam is a grid-shaped structure in which a void space is provided therein, and a structure for installing a membrane-type storage tank in each compartment by vertically and horizontally dividing the internal space of the floating structure. Such a cofferdam is conventionally used as a cofferdam in a widthwise direction for partitioning between a plurality of storage tanks arranged in a row along the longitudinal direction of a floating structure.

The cofferdams installed between the storage tanks arranged in two rows according to the present invention may be divided into longitudinal cofferdams and width cofferdams. The widthwise cofferdam is a structure that allows the membrane-type storage tank to be arranged along the longitudinal direction by horizontally partitioning the inner space of the floating structure, and the longitudinal cofferdam vertically partitions the inner space of the floating structure. The structure is such that the membrane-type storage tank can be disposed along the width direction. The width cofferdam may form a front wall portion and a rear wall portion of the storage tank, and the longitudinal cofferdam may form a left or right wall portion of the storage tank.

In the present invention, a simple partition wall may be installed between each storage tank instead of the above-mentioned cofferdam. In addition, when the cofferdam is installed, a reinforcing structure such as a pillar for supporting the load of the upper structure may be installed inside the cofferdam.

As described above, according to the present invention, a structure in which a storage tank, a cofferdam (or a partition), another storage tank, a cofferdam (or a partition), and another storage tank are arranged in succession when viewed in the transverse direction of the floating structure is provided. In this way, a two-row arrangement structure can be formed by applying a proven manufacturing technique of a conventional storage tank (e.g., a width cofferdam), and a longitudinal cofferdam bulkhead or the like for installing an intermediate longitudinal cofferdam (necessary) A separate reinforcement structure may be installed inside the cofferdam) to simultaneously support the load of the upper structure.

In addition, a floating structure such as LNG FPSO is required to withstand such heavy loads because there are more upper facilities to be installed on the upper side than ships such as LNG carriers, the two-row arrangement structure of the storage tank as the present invention In the case of the thin partitions, rather than simply partitioning the tank by installing a longitudinal cofferdam or the like between the separate storage tanks, the cofferdam bulkhead and the like can serve to support and distribute the upper load.

On the other hand, according to the present invention as described above, the upper and lower chamfers may be partially omitted so as to secure the storage capacity while arranging the storage tanks in two rows. That is, the chamfer may be formed only at the upper and lower corners where the impact force due to the sloshing acts most strongly.

In this way, the storage capacity can be increased by arranging the storage tanks in two rows and forming only a chamfer.

In addition, the present invention can be applied in a three-row arrangement or three or more rows as shown in Figure 3, in addition to arranging the storage tanks in two rows in the width direction.

3 shows an example of a floating structure having storage tanks 3, 5, 7 arranged in three rows in the width direction for storing liquefied gas inside the hull 1 according to the invention.

At this time, among the storage tanks arranged in three rows, the central storage tank (3) disposed in the middle in the longitudinal direction, the fore side storage tanks (5) disposed on the bow and stern sides of the central storage tank (3) and It is preferable that the width is longer than that of the stern side storage tank 7.

The storage tank of the three-row arrangement structure of FIG. 3 differs only in that the storage tanks are arranged in three rows, compared to the storage tank of the two-row arrangement structure of FIG. 1.

Although the structure of the floating structure according to the present invention has been described with reference to the accompanying drawings as described above, the present invention is not limited to the embodiments and drawings described above, and the present invention belongs to the claims. Of course, various modifications and variations can be made by those skilled in the art.

1: hull 3: central storage tank
5: bow storage tank 7: stern storage tank

Claims (1)

The upper facility is installed on the upper part of the floating structure such as LNG FPSO,
The floating structure has two or more rows of LNG tank in the longitudinal direction,
Between the longitudinal direction of the LNG tank is installed a cofferdam,
The LNG tank is divided into separate storage tanks by a longitudinal cofferdam and at the same time to support and distribute the upper load of the upper installation.

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