KR20110051855A - Floating structure having roll motion reduction structure - Google Patents

Abstract

PURPOSE: An offshore structure having a roll reduction device is provided to reduce sloshing at a storage tank since the roll reduction device is attached to the side of the hull. CONSTITUTION: An offshore structure comprises a roll reduction device(10). The roll reduction device is attached to the outer sides of port and starboard of the hull(1) of the offshore structure. Heavy loads are filled in the roll reduction device. The roll reduction device is divided into an upper space(12) and a lower space by a diaphragm(11). The heavy loads are filled in the upper space. To enable the free flow of seawater to the lower space, an opening is formed on the lower part of the roll reduction device. The diaphragm is formed at the same height as the sea surface.

Description

FLOATING STRUCTURE HAVING ROLL MOTION REDUCTION STRUCTURE}

The present invention relates to an offshore structure that can be used while floating in the sea, and more particularly to an offshore structure having a lateral shake reduction device attached to the side of the hull so as to suppress the lateral shake of the offshore structure.

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 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 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 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 a sufficient strength to withstand the impact force due to the sloshing. On the other hand, as transport ships gradually increased in size, the size of the storage tanks increased and the impact force due to sloshing increased greatly.

In particular, as the demand for offshore plants such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Unit (FSRU), ie, offshore structures, has been increasing, It was required to solve the sloshing problem.

LNG FPSO is a marine structure used for producing and liquefying natural gas directly from the sea, storing it in a storage tank and, if necessary, transferring LNG stored in the storage tank to an LNG carrier. In addition, LNG FSRU is an offshore structure that stores LNG unloaded from LNG carriers in storage tanks far from the land, and then vaporizes LNG as needed to supply land demand.

As LNG-related offshore structures such as LNG FPSO and LNG FSRU under development in recent years, it is proposed that the hull form has a barge form or a ship form. In addition, offloading operations to move cargo from these offshore structures are carried out in the form of side-by-side offloading of LNG carriers, or the LNG carriers and offshore structures are tandem with each other. offloading).

By the way, the sloshing occurrence in the storage tank due to the movement of the wave structure can be suppressed by using a two-row tank arrangement or a stand-alone tank in which the membrane-type tanks are arranged in two rows, but still due to the low draft of the marine structure There is a problem that the lateral fluctuation is large, the efficiency of the offloading operation.

On the other hand, when the lateral fluctuation of the offshore structure is not properly suppressed, there is a problem in that the mooring line in the side mooring state cannot maintain the mooring state because the strength cannot be ensured at a height of approximately 2.0 m to 3.0 m or more.

Although various apparatuses for suppressing hull fluctuations are disclosed in Korean Patent Nos. 10-0466646 and 10-0852375, etc., it is possible to reduce sloshing due to fluctuations at sea and to efficiently perform offloading operations. There is a need to continue research on offshore structures with capable of lateral disturbance reduction.

The present invention for solving the above problems, by attaching a lateral sway reducing device to the side of the hull to suppress the lateral fluctuations while suppressing the sloshing phenomenon in the storage tank and at the same time performing the offloading operation efficiently To provide a maritime structure that can be.

According to an aspect of the present invention for achieving the above object, as a marine structure to be used floating in the sea, attached to the outer side of the hull side port of the offshore structure, the lateral fluctuation reduction device that can be filled with heavy material therein There is provided an offshore structure comprising:

The lateral fluctuation reducing device is partitioned into an upper space and a lower space by a diaphragm, and the weight is preferably filled in the upper space.

It is preferable that an opening is formed in the lower portion of the lateral fluctuation reducing device to enable free flow of seawater into the lower space.

The diaphragm is preferably formed at the same height as the sea level.

It is preferable that the lateral fluctuation reducing device is provided over the entire length of the hull.

It is preferable that the lateral fluctuation reducing device is installed two or more spaced apart from each other on the left and right strings of the hull.

The lateral fluctuation reducing device is preferably installed so as to be symmetrical with respect to the longitudinal centerline of the hull on the left and right sides of the hull.

The offshore structure is preferably LNG FPSO or LNG FSRU, having a storage tank for storing liquid cargo loaded at a cryogenic state and used in a floating state at sea where flow occurs.

The height of the lateral shake reduction device is determined to be the same height as the upper deck of the LNG carrier mooring the upper end, it is preferable that the mooring device or off-loading device is installed on the upper surface of the lateral shake reduction device.

Preferably, the first bilge kill extending along the longitudinal direction of the hull is installed at the lower edge of the hull structure.

It is preferable that a second bilge kill having a larger size than the first bilge kill is provided below the lateral fluctuation reducing device.

Preferably, the second bilge kill has the same length as that of the lateral fluctuation reducing device.

The horizontal bilge keel extending along the longitudinal direction of the hull and protruding in the horizontal direction is installed at the lower edge of the hull structure, and the horizontal bilge keel does not protrude more than the transverse shaking reduction device when viewed from the cross section of the hull. desirable.

In addition, according to another aspect of the present invention, having a storage tank for storing liquefied gas and is used floating in the sea, by the widthwise cofferdam and the longitudinal cofferdam in the hull of the offshore structure The storage tank is divided into two rows; A ballast tank installed outside the storage tank; A transverse fluctuation reducing device installed outside the ballast tank and having a space for filling a heavy object on the inner upper portion thereof; There is provided a marine structure comprising a.

It is preferable that the marine structure further includes a bilge kill installed on an oblique lower surface of the transverse shake reduction device.

The weight is preferably a material having a specific gravity greater than or equal to water.

According to the present invention as described above, there is provided a marine structure in which a lateral fluctuation reducing device is attached to the side of the hull to suppress lateral fluctuations.

According to the offshore structure of the present invention, the sloshing phenomenon in the storage tank can be suppressed and the offloading operation can be efficiently performed.

Hereinafter, with reference to the accompanying drawings will be described in detail the offshore structure having a lateral fluctuation reduction device according to a preferred embodiment of the present invention.

In the present specification, the offshore structure is a concept including both an offshore plant and a ship which are used while floating in the sea where a flow occurs while having a storage tank for storing a liquid cargo loaded at a cryogenic state, such as LNG. This 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).

1 shows a plan view of a marine structure with a roll-over reduction apparatus, and FIG. 2 shows a side view of a marine structure with a roll-over reduction apparatus. 3 shows a cross-sectional view of an offshore structure with a transverse disturbance reduction device.

In order to solve the sloshing problem, as shown in FIGS. 1 and 3, instead of increasing the size of the storage tank, a plurality of storage tanks are installed by installing a structure such as a cofferdam or a partition wall in the longitudinal direction in the inner space of the marine structure. By arranging the two rows, it has been proposed to achieve the same effect as installing several small storage tanks.

Inside the hull 1 of the offshore structure, longitudinal bulkhead structures (ie, longitudinal cofferdams 3, etc.) and widthwise bulkhead structures (ie, widthwise) are installed along the longitudinal direction and the widthwise direction so as to distinguish this internal space. Directional copper dam 4).

The partition structure may be formed of a copper dam, a bulkhead, or the like, and the storage tank 2 is installed in each space divided by the partition structure. Since the partition structure reduces the inner space of each storage tank 2, in particular the widthwise length of the storage tank, the effect of the sloshing phenomenon of the received liquefied gas can be reduced and the load of the upper structure can be supported.

In the present invention, the cofferdam is a lattice-shaped structure in which a void space is provided inside the cofferdam partition wall (that is, the bulkhead), and divides the internal space of the floating offshore structure vertically and horizontally into each compartment. It is a structure to install the membrane type storage tank. Such a cofferdam has been used to partition between a plurality of storage tanks along a longitudinal direction in a conventional LNG carrier.

The cofferdam can be largely divided into a longitudinal cofferdam 3 and a width cofferdam 4. The widthwise cofferdam 4 is a structure that partitions the inner space of the offshore structure horizontally so that a membrane-type storage tank can be disposed along the longitudinal direction, and the longitudinal cofferdam 3 is an inner space of the hull structure. The structure is partitioned vertically so that the membrane-type storage tank can be disposed along the width direction. The cofferdam bulkhead (ie, bulkhead) of the widthwise cofferdam (4) may form the front and back walls of the storage tank, and the cofferdam bulkhead (ie the bulkhead) of the longitudinal cofferdam (3) The left or right wall of the storage tank can be formed.

In the drawings, the present invention is shown to be applied to a marine structure having a storage tank arranged in two rows as described above, but this is only an example and the present invention is also applicable to a marine structure in which the storage tank is arranged in one or three rows or more. Of course this can be applied.

1 and 2, the offshore structure according to the preferred embodiment of the present invention, one or more roll motion reduction device (10) respectively installed on the outer side of the side of the hull (1) Have

Rolling reduction device 10 is preferably installed on the left and right strings of the hull 1 so as to be symmetrical with respect to the center axis of the hull.

1 and 2 show that the two lateral sway reducing devices 10 are spaced apart from each other and the two lateral sway reducing devices 10 are spaced apart from each other. It may be modified to have more than one sway reducing device installed. Alternatively, one transverse shake reduction device may be installed in the port and starboard so as to extend over the entire length of the hull.

Rolling reduction device 10 may be additionally attached to the hull of the completed production state, may be attached in consideration from the design.

Considering the case of mooring the LNG carrier in a side-by-side manner on the side of the offshore structure on which the hoist shaking device 10 is attached, the hopping shaking device is arranged so that the moistened LNG ship can be arranged in parallel with the offshore structure. The separation distance of 10 can be determined.

The width, length and height of the sideways reduction device 10 can be appropriately changed in consideration of various variables in the design, the installation position is also changeable. In addition, it is preferable that the height of the sway reduction device 10 is determined so that the upper end of the sway reduction device 10 can be approximately the same height as the upper deck of the mooring LNG carrier.

As shown in FIG. 3, the offshore structure according to a preferred embodiment of the present invention has storage tanks 2 arranged in two rows in a width direction for storing liquefied gas inside the hull 1, and the hull 1 And a ballast tank 5 is installed between the storage tank 2.

The roll shake reduction device 10 is disposed outside the ballast tank 5, so that the line width of the portion in which the roll shake reduction device 10 is installed is wider than the line width of the portion not installed. A fender 9 may be attached to the outside of the lateral attenuation reduction device 10, that is, the outside of the hull.

The inside of the roll member 10 may be divided into an upper space 12 and a lower space 13 by the diaphragm 11. The upper space 12 is filled with a heavy object having a specific gravity equal to or greater than water (for example, seawater, sand, concrete, etc.) and used as a fixed ballast, and the lower space 13 can freely inflow or outflow of seawater. Configure it to be. Seawater may be used to fill the upper space 12, but in this case, the effect of reducing lateral fluctuations may be relatively reduced.

The upper surface of the lateral fluctuation reducing device 10 is formed in a substantially horizontal plane, but the lower surface thereof is formed obliquely so that the entire linear becomes narrower downward. On the upper surface of the lateral attenuation reduction device 10, various devices for mooring an LNG carrier or various devices for offloading may be installed.

The diaphragm 11 is preferably installed at approximately the same height as the sea level, and one or more openings may be formed in the side and bottom surfaces of the lower space 13 for free flow of seawater into the lower space 13.

As described above, since the seawater can freely flow in and out of the lower space 13, the lower space 13 does not affect the buoyancy or weight of the offshore structure. Therefore, it is possible to further improve the exercise performance by controlling the GM due to the weight stuffed in the upper space 12.

GM is a value related to the stability of offshore structures and is the vertical distance from the center of gravity (G) to the metacenter (M). A large value of GM means that the center of the offshore structure is biased downward. As the GM value increases, the resilience increases, and the smaller the GM, the better the performance.

In addition, due to the lower space 13 of the lateral oscillation reducing device 10 capable of freely flowing in and out of seawater, lateral oscillation, that is, the rolling phenomenon of the ship is expected to decrease.

In addition to the first bilge keel 7 installed at the lower edge of the hull, a second bilge keel 15 larger than the first bilge keel 7 may be installed in the lower portion of the horizontal shaking reduction device 10. Can be. The first bilge keel 7, which was also installed in a conventional offshore structure, usually has a size of about 40 cm to 1.2 m (that is, a length protruding from the hull when viewed in cross section as shown in FIG. 3), but the second bilge keel 15 ) May have a size larger than this first bilge kill 7.

The second bilge kill 15 may be installed to have the same length as the length of the horizontal shaking reduction device 10. By the second bilge kill 15, the lateral fluctuation of the offshore structure can be further suppressed.

On the other hand, according to the present invention, instead of installing the second bilge kill outside the roll sway reducing device 10, a roll stabilizer (roll stabilizer) is installed, the lower space 13 of the roll sway reducing device 10 The control chamber which can control this roll stabilizer is installed in the inside, and it can change so that a lateral fluctuation can be suppressed. In the conventional offshore structure, the roll stabilizer and its control room could not be installed because the storage tank and the ballast tank made it difficult to secure the free space on the side of the hull, but in the offshore structure having the lateral fluctuation reducing device 10 of the present invention, The space 13 can be used to install these devices.

Referring to FIG. 4, where a variant of the invention is shown, instead of two bilge kills, namely the first bilge kill 7 and the second bilge kill 15 as in FIG. 3, the lower left and right sides of the hull 1 A horizontal bilge kill 17 protruding from the corner in the horizontal direction may be installed.

At this time, the length of the horizontal bilge kill 17 protruding (that is, the length protruding from the hull when viewed in cross section as shown in FIG. 4) has a smaller value than the transverse shaking reduction device 10 installed on the left and right sides of the hull 1. In view of the cross section, it is preferable to have a value in the range which does not protrude from the lateral fluctuation reducing device 10.

The horizontal bilge kill 17 extends along the longitudinal direction of the hull 1, and may be installed longer than the transverse shaking reduction device 10 and shorter than the total length of the hull 1.

As described above, according to the offshore structure having the lateral shake reduction device of the present invention, it is possible to install the fixed ballast on the left and right strings, especially the upper surface of the free surface can reduce the GM, thereby reducing the lateral fluctuation of the hull Offloading efficiency can be increased.

Further, by suppressing the flow of the liquefied gas stored in the storage tank can reduce the impact force due to the sloshing, it is possible to maintain the LNG vessel in a stable mooring state. In addition, the area of the upper deck can be increased, thereby facilitating the arrangement of various devices installed on the upper deck, including mooring equipment and offloading equipment.

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

1 is a plan view of the offshore structure having a lateral fluctuation reducing device according to the present invention,

Figure 2 is a side view of the offshore structure having a transverse shaking reduction apparatus according to the present invention,

3 is a cross-sectional view of the offshore structure having a transverse shaking reduction apparatus according to the present invention, and

Figure 4 is a cross-sectional view of the offshore structure having a transverse shaking reduction device according to a modification of the present invention.

Description of the Related Art

1: hull 2: storage tank

3: longitudinal cofferdam 4: widthwise cofferdam

5: ballast tank 7: first bilge kill

9: Fender 10: Rolling Reduction Device

11: plate 12: upper space

13: lower space 15: the second bilge kill

17: horizontal bilge kill

Claims (16)

It is a marine structure that is used floating in the sea, The offshore structure is attached to the outer side of the hull sideboard of the offshore structure, characterized in that it comprises a transverse shake reduction device that can be filled with a heavy material therein. The method according to claim 1, The transverse shaking reduction device is partitioned into an upper space and a lower space by a diaphragm, and the heavy material is filled in the upper space. The method according to claim 2, An offshore structure, characterized in that an opening is formed in the lower portion of the transverse shake reduction device to enable free flow of seawater into the lower space. The method according to claim 2, The diaphragm is formed at the same height as the sea surface. The method according to claim 1, The lateral fluctuation reducing device is installed over the entire length of the hull structure. The method according to claim 1, Said sideways reduction device is a marine structure, characterized in that two or more are installed on each side of the hull spaced apart from each other. The method according to claim 1, The lateral fluctuation reducing device is a marine structure, characterized in that installed on the left and right sides of the hull symmetrical with respect to the longitudinal centerline of the hull. The method according to claim 1, The offshore structure is an offshore structure, characterized in that the LNG FPSO or LNG FSRU, having a storage tank for storing the liquid cargo loaded in the cryogenic state used in the floating state at the flow occurs. The method according to claim 8, The height of the lateral shake reduction device is determined to be the same height as the upper deck of the LNG carrier mooring the upper end, the marine structure, characterized in that the mooring device or off-loading device is installed on the upper surface of the lateral shake reduction device. The method according to claim 1, Offshore structure of the offshore structure, characterized in that the first bilge kill extending along the longitudinal direction of the hull is installed. The method according to claim 10, A marine structure, characterized in that the second bilge kill is larger than the first bilge kill is installed in the lower portion of the lateral fluctuation reducing device. The method of claim 11, The second bilge kill is an offshore structure, characterized in that it has the same length as the length of the transverse shaking reduction device. The method according to claim 1, The horizontal bilge keel extending along the longitudinal direction of the hull and protruding in the horizontal direction is installed at the lower edge of the hull structure, the horizontal bilge keel does not protrude more than the transverse shaking reduction device when viewed from the cross section of the hull Offshore structure characterized in that. An offshore structure having a storage tank for storing liquefied gas and used floating at sea, The storage tank is divided into two rows in the hull of the offshore structure by a cofferdam in the width direction and a longitudinal cofferdam; A ballast tank installed outside the storage tank; A transverse fluctuation reducing device installed outside the ballast tank and having a space for filling a heavy object on the inner upper portion thereof; Offshore structure comprising a. The method according to claim 14, Maritime structure further comprises a bilge kill is installed on the oblique lower surface of the transverse shaking reduction device. The method according to claim 14, The heavy material is an offshore structure, characterized in that the material is greater than or equal to the specific gravity.

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