KR101167915B1 - Floating offshore structure - Google Patents

Abstract

The present invention relates to a floating offshore structure, wherein a line width reduction portion is formed in the hull near the waterline. Accordingly, the present invention increases the resonant cycle of the hull by reducing the GMT by reducing the KMT (height from keel to transverse metacenter) due to the area second moment by reducing the water-rectangular cross-sectional area, the ballast tank up and down By increasing the inertia radius, it contributes to the increase of the roll resonant period.As the roll resonant period is far from the periodic region of the ocean wave, the roll motion becomes smaller and the horizontal lateral acceleration is reduced. Highly distributed topside parts are less exposed to lateral acceleration than conventional offshore structures, allowing more room for structural strength design and reducing sloshing inside the tank. It has the effect of preventing damage to the cargo containment system.

Hull, roll motion, line width, reinforcement, waterline

Description

Floating Offshore Structures {FLOATING OFFSHORE STRUCTURE}

The present invention increases the resonant period of the hull by reducing the GMT (height from the center of gravity to the transverse metacenter) by reducing the water cross-sectional area, and the roll motion is moved away from the periodic region of the general ocean wave. It relates to a floating offshore structure which is smaller and which reduces horizontal lateral acceleration.

Generally, floating offshore structures include Floating, Production, Storage and Offloading (FPSO), LNG-FPSO, Floating Storage Offloading Unit (FSO), Floating Storage and Regasification Unit (FSRU), and the like. Among these, FPSO and FSO start from the existing tanker modification and include some new constructions. LNG-FPSO and LNG-FSRU currently have no track record and will be built with new construction.

Since these tankers operate at speed, very little consideration is given to stationary kinetic performance.

However, as described above, the floating offshore structures such as FPSO can be said to have a decisive role in the overall performance due to the characteristic of performing work in a stationary work area. Therefore, the conventional floating offshore structure has a characteristic that the roll movement is particularly weak compared to the general ship in Hangzhou when the work is performed while stationary in a certain work area.

This is because the roll speed of Hangzhou ship with forward speed is 3-4 times larger than that of stationary ship, so the roll motion is relatively small and the lateral acceleration (Ay, The relatively small m / s ² ) is not a big problem in the structural design of Hangzhou ships if it is designed according to the existing classification rules. Topside equipment is exposed to greater lateral acceleration because topsides are installed in a highly distributed manner, such as an oil refinery on the upper deck of a ship. Therefore, the design considering the kinetic performance must be made in the structural design of the top side (force = acceleration x mass).

In addition, floating offshore structures such as FPSO have problems of structural design due to such lateral acceleration, as well as sloshing, which is a liquid flow in the tank by lateral motion, ie, rolls and sway. The liquid flow in the tank is mutually coupled to the kinetic performance of the roll and sway of the hull to change the kinetic performance itself of the hull and at the same time induces a sloshing impact pressure on the inner wall of the tank due to liquid flow.

In particular, GTT's MK III and No.96 membrane type tanks have so far consisted of single tanks, which are subject to significant impact pressures when the LNG is partially filled, causing significant damage to the cargo containment system (CCS). do.

Therefore, in the case of floating offshore structures, such as LNG-FPSO and LNG-FSRU, it must be designed so as not to apply a device and a method for suppressing the lateral motion or to cause the lateral motion itself.

The present invention has been made to solve the above problems, by reducing the horizontal lateral acceleration by increasing the roll resonant period of the hull, minimizing the exposure of the lateral acceleration even if the height of the top side is distributed, thereby raising the height direction The topside, which is highly distributed, is less exposed to lateral acceleration than the existing offshore structures, so that the topside can have much more room for structural strength design, and by reducing sloshing in the tank, CCS Prevent damage to the cargo containment system.

The floating marine structure according to the present invention is characterized in that, in the floating marine structure, a line width reduction portion is formed in which the line width is narrowed near the waterline in the hull.

The present invention increases the roll resonance period of the hull by reducing the GMT by reducing the KMT (height from the keel to the transverse metacenter) due to the area second moment to reduce the water section area, and the ballast tank is divided up and down By increasing the inertia radius, it contributes to the increase of the roll resonant period, and the roll resonant period is far from the periodic region of normal ocean waves, resulting in smaller roll motion and lower horizontal and lateral acceleration, resulting in higher distribution in the height direction. Part of the topside is less exposed to lateral acceleration than existing offshore structures, so that the topside can have a large margin in the design of structural strength, and by reducing sloshing in the tank, CCS ( Prevent damage to the cargo containment system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is a cross-sectional view showing a floating offshore structure according to an embodiment of the present invention, Figure 2 is a cross-sectional view taken along the line AA 'of FIG. As shown, the floating offshore structure 100 according to an embodiment of the present invention may be formed with a line width reduction portion 120 in the hull (110).

Floating offshore structure 100 according to the present invention is a general vessel as well as structures such as Floating, Production, Storage and Offloading (FPSO), LNG-FPSO, Floating Storage Offloading Unit (FSO), Floating Storage and Regasification Unit (FSRU) Applicable to

The line width reduction part 120 is formed by narrowing the line width in the hull 110 near the draft line. That is, the line width reduction part 120 is formed to have a line width D2 smaller than the original line width D1 of the hull 110. Accordingly, the hull 110 narrows the line width D2 with respect to the area near the waterline where the line width reduction unit 120 is located, and the area other than the waterline, that is, the water surface lower region 111 and the water surface upper region 112. Widen the line width (D1).

The line width reduction part 120 is inclined such that the lower part and the upper part are connected to the lower surface area 111 and the upper surface area 112, respectively, and the slope may be formed in a straight line or a curved line. It may be made of a combination, it may be formed in the hull 110 so that the water line (L1) when the full load of the hull 110 and the water line (L2) when the ballast loading (ballast loading) is located respectively. Furthermore, it can be formed at the location where all the waterlines in full load and ballast loading conditions are present.

The line reduction unit 120 may have a height of 1 to 5 m in consideration of a draft difference between full load and ballast loading due to the characteristics of the floating offshore structure 100.

When the line width reduction unit 120 applies a survival loading condition, which is a draft in a survival environmental condition, for example, the height corresponding to the degree of digging of the survival environmental condition is added up and down in the survival draft. It may be formed in the hull 110 to reduce the line width only up to a portion.

On the other hand, the hull 110 has no need for reinforcement when there is no or insufficient structural influence or vibration by the flow around the line reduction unit 120, in contrast, when reinforcement is required due to the structural or vibration A reinforcement part 113 for structural reinforcement may be provided outside the line reduction part 120.

The reinforcement part 113 may be provided to protrude a plurality along the direction in which the line reduction part 120 is formed as in the present embodiment, and have a structure that protrudes to form a triangle on a plane, or alternatively, has a truss structure It may have a plate shape installed perpendicular to the outside of the line-width reduction unit 120.

The hull 110 may be provided with a storage tank 114 for storing a storage medium such as LNG that needs to be stored due to the characteristics of the floating offshore structure 100, and the ballast tanks on both sides of the storage tank 114. 115 may be provided. At this time, the partition wall 116 for dividing the upper and lower portions of the ballast tank 115 up and down may be installed, thereby the ballast tank 115 is divided up and down by the partition wall 116. Meanwhile, the partition wall 116 may be installed at a height at which the line width reduction part 120 is positioned in the ballast tank 115. In addition, the bottom ballast tank 117 may be located below the storage tank 114.

Referring to the operation of the floating offshore structure according to the present invention having such a configuration as an example.

The line width reduction portion 120 is formed due to the reduced line width near the waterline in the hull 110 so that the water cross-sectional area is reduced so that the cross-sectional metacenter in the KMT due to the area second moment, that is, the keel. Height decreases, thereby causing a decrease in GMT, the distance from the center of gravity G of the hull 110 to the transverse metacenter, increasing the roll resonant period of the hull 110.

In addition, the ballast tank 115 located on both sides of the hull 110 is divided up and down by the partition wall 116 to increase the inertia radius, thereby contributing to the increase in the roll resonance period of the hull 110. .

As described above, the floating offshore structure 100 according to the present invention increases roll resonant period and moves away from the periodic region of the ocean wave, thereby reducing roll motion and reducing horizontal lateral acceleration. Part of the topside is less exposed to lateral acceleration than conventional offshore structures, allowing more room for structural strength design of the topside, and by reducing sloshing inside the storage tank 114, the CCS Prevent damage to the cargo containment system.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. And will be included in the described technical idea.

1 is a cross-sectional view showing a floating offshore structure according to an embodiment of the present invention,

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1.

<Explanation of symbols for the main parts of the drawings>

110: hull 111: water surface area

112: upper surface of the water 113: reinforcement

114: storage tank 115: ballast tank

116: bulkhead 117: bottom ballast tank

120: line width reduction part

Claims (6)

In floating offshore structures, The line narrowing part is formed in the hull near the waterline, so that the line width is narrowed. Floating offshore structure provided with a reinforcement for structural reinforcement on the outside of the line shrinkage. The method of claim 1, The line width reduction unit, Floating offshore structure is formed so that the water line is located when the full load and ballast loading of the hull. 3. The method according to claim 1 or 2, The line width reduction unit, Floating offshore structures 1 to 5m in height. delete The method of claim 1, The reinforcement part, Floating offshore structure is provided so as to protrude a plurality along the direction of the line-reduction portion. 3. The method according to claim 1 or 2, The hull, A storage tank is provided in the center, a ballast tank is provided on both sides of the storage tank, and the floating offshore structure is provided with a partition wall that divides the upper and lower parts of the ballast tank up and down.

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