KR20170085735A - Plywood for insulation system of lng cargo and plywood membrer - Google Patents

Abstract

The present invention relates to a member for reinforcing the vertical rigidity of a panel-shaped heat insulating wall provided for insulation of a cargo hold storing cryogenic liquid cargo such as LNG, and includes a plywood in which a plurality of veneers are stacked The flywood member for a cargo hold insulation system according to the present invention is characterized in that the water content of the plywood is adjusted to be not more than 3% by dryness. According to the plywood member of the present invention, the heat transfer through the plywood in the cargo hold insulation system Can be reduced.

Description

[0001] PLYWOOD FOR INSULATION SYSTEM OF LNG CARGO AND PLYWOOD MEMBRER [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plywood to be applied to an insulation system of a cargo hold for storing a cryogenic fluid such as LNG in a hull and a plywood member including the plywood.

Natural gas is a fossil fuel containing methane as a main component and a small amount of ethane, propane, and the like, and has recently been regarded as a low-pollution energy source in various technical fields.

Natural gas is transported in a gaseous state through land or sea gas pipelines, or is transported to a remote location where it is stored in an LNG carrier in the form of liquefied natural gas (LNG). 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.

The liquefied natural gas carrier is equipped with a cargo (also referred to as a storage tank) capable of storing and storing liquefied natural gas that has been liquefied by cooling the natural gas. Since the boiling point of liquefied natural gas is about -163 ° C at atmospheric pressure, the liquefied natural gas hold is made of materials that can withstand extremely low temperatures such as aluminum steel, stainless steel and 35% nickel steel to safely store and store liquefied natural gas And is designed to be resistant to thermal stress and heat shrinkage, and to prevent heat penetration.

LNG RV (Regasification Vessel), which transports LNG carriers and LNG for unloading LNG to land customers by landing LNG and landing on land, reclaiming stored LNG after arriving at land demand and unloading it into natural gas, Floating marine structures such as LNG FPSO (Floating, Production, Storage and Offloading) and LNG FSRU (FSRU) also include storage tanks installed in LNG carriers or LNG RVs.

In this way, a storage tank installed in a marine structure such as an LNG transporting line, LNG RV, LNG FPSO, and LNG FSRU for transporting or storing a liquid cargo such as LNG is required to have an insulation system for storing LNG in a cryogenic condition, The stored LNG is vaporized immediately when the temperature rises above -163 ° C, and when the vaporization amount of LNG in the storage tank is increased, there is a risk of explosion, so the insulation performance of the cargo hold is very important.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a heat insulating structure of a general membrane-type cargo hold. In general, the heat insulating system is insulated by the heat insulating wall 4 filled with inert gas and heat insulating material such as pearlite or polyurethane foam in the inner space of the heat insulating box 1 and 2 made of plywood, The flywheel vertical members 3 are arranged in order to maintain the rigidity to withstand the load that the laminated insulating walls are subjected to in the vertical direction.

The flywheel, which must be provided in such an adiabatic system, has to be manufactured with sufficient strength to withstand the load caused by the loading of the liquid cargo, which has hindered the insulation performance of the adiabatic system.

In other words, the insulation performance of the insulation system is as important as the stiffness, and the heat transfer through the plywood box or vertical member is 50%.

However, conventionally, there has been a concern about the structural problem of the adiabatic system with regard to the adiabatic performance of the adiabatic system, and the heat transfer through such a plywood is not paid much attention.

This is due to the fact that there was not much interest in Boolean-Off Rate (BOR) in the past.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plywood and a plywood member including the plywood which can reduce the heat transfer through the plywood used in the insulation system of the cargo hold.

The plywood member for the insulation system of a cargo hold according to the present invention is a member for reinforcing the vertical rigidity of a panel-shaped insulation wall provided for insulation of a cargo hold for storing cryogenic liquid cargo such as LNG, ), And the plywood is dried by adjusting the water content of the plywood to 3% or less.

More specifically, the water content of the plywood is 2 to 3%.

It is preferable that the above-described flywheel be dried and manufactured in a vacuum state.

Further, it may further include a water-repellent coating layer formed on both sides of the plywood.

The water-repellent coating layer is applied with latex wax or polyurethane foam.

Next, the plywood for a thermal insulation system of a cargo hold according to the present invention is prepared by laminating a plurality of veneers, and is dried and manufactured to have a moisture content of 3% or less, whereby the insulation of a cargo hold that stores cryogenic liquid cargo such as LNG System.

According to the plywood for the insulation system of the present invention and the plywood member including the same, the water content through the plywood is drastically reduced by minimizing the water content of the existing plywood, thereby minimizing the heat transfer through the plywood .

Accordingly, the heat insulating performance of the adiabatic system to which the plywood of the present invention is applied is prevented from being hindered by the plywood.

By minimizing the heat transfer through the flywood, the heat insulating performance of the cargo holds is improved, and the BOR in the storage tank can be reduced, thereby enhancing the safety of the storage tank and the hull.

Further, as the water content of the plywood is lowered, its rigidity is further reinforced, its thickness can be reduced for the same rigidity, and ultimately the weight of the adiabatic system and the ship can be lightened and the manufacturing cost can be reduced.

As a result of the reduction of the thickness, it is possible to supplement the heat insulating material so that the heat insulating performance can be further improved.

1 schematically shows a heat insulation structure of a general membrane type cargo hold.
2 schematically shows a plywood member for a heat insulation system of a cargo hold according to the present invention.
Fig. 3 relates to a plywood member in which a latex wax is water-repellent coated on a fabricated plywood.
Fig. 4 relates to a ply wood member in which a polyurethane foam is water-repellent coated on the produced ply wood.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

2 schematically shows a plywood member for a heat insulation system of a cargo hold according to the present invention. Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The ply wood member for the insulation system of the cargo hold according to the present invention is arranged as a vertical member arranged in a plywood box or heat insulating wall for a heat insulating wall structure so as to maintain the vertical rigidity of the heat insulating wall, And to reinforce the rigidity so as to withstand.

The plywood disposed in such an insulating wall is important not only for its own strength for maintaining rigidity but also for maintaining the heat insulating performance of the heat insulating wall.

Because storage tanks for storing LNG are important in terms of the nature of the cargoes, and when the stored LNG temperature rises and the BOR (boil-off rate) increases, the LNG is vaporized due to the vaporized LNG, And the safety risk of the hull. In the past, the management of the BOR of the storage tank has not been noticed, and the increase of the BOR has not been correlated with the plywood.

In the past, the heat input into the storage tank through the flywheel for the insulation system has reached 50% of the total heat input. Eventually, the degree of heat input through the plywood is related to the thermal conductivity of the flywood, The thermal conductivity of wood is related to the moisture content of the plywood.

The relationship between the flywood moisture content and the thermal conductivity is illustrated in the following graph.

[Figure 1]

Moisture content refers to the ratio of the moisture weight to the dry weight of the wood. The title of the tree, which has been blanched and processed, has a constant moisture content, and the indoor humidity It can be kept constant and therefore it is produced by drying in a usual range.

In other words, when cutting wood in natural state (water content 30 ~ 200%), it has a certain moisture content (MC), and my title after processing in the natural state is that if processed water is not exposed for a long time, do.

Conventionally, the moisture content of the flywood used in the cargo hold insulation system is about 7 ~ 10%, which means that the flywood has a certain degree of heat transfer.

In addition, when the humidity control is not strictly carried out through the process of making, installing, transporting, and stacking the plywood, the water content increases.

Furthermore, when the manufactured plywood is applied to an adiabatic system, the water content of the plywood can be gradually increased because the environment in which it is applied is continuously used in a cryogenic condition.

The present invention is based on the relationship between the heat transfer coefficient and the heat transfer coefficient depending on the water content of the flywood, and the water content of the flywood is made to be 3% or less to achieve the object of the present invention, more preferably 2 to 3% .

The plywood can be manufactured by drying the veneer before the plywood is manufactured, or by drying the plywood after the plywood is manufactured. The drying can be done by natural drying in a constant temperature and humidity chamber, It is also possible to adjust the water content by performing quick drying in the environment.

In a vacuum environment, the boiling point of water is lowered to room temperature or lower, so that the drying process can be shortened.

By forming the water repellent coating layer 120 on the fabricated plywood 110 to manufacture the plywood member 100, even if the plywood member according to the present invention undergoes installation and transportation processes, So that the water content of the flywood 110, which has been adjusted and controlled even under the extreme application environment of the flywheel member, can be maintained.

That is, the water-repellent coating layer allows the moisture generated by the low temperature in the adiabatic system in the storage tank to diffuse and not be contained in the plywood, so that the water-repellent coating layer can be easily separated and absorbed by the heat insulating wall, It will be possible in extreme situations.

This water-repellent coating layer is formed after complete adjustment of the water content of the plywood as described above, which may be made of latex wax or polyurethane foam.

FIG. 3 shows the formation of a latex wax layer, and FIG. 4 shows the formation of a polyurethane foam layer, which can be prepared by spray application.

When the coating is carried out using a polyurethane foam, it is necessary to remove foreign matter such as moisture and oil dust on the surface of the polyurethane foam, and the coating can be carried out in the absence of an empty space or scratches. Such a coating layer can be coated with a polyurethane foam for 2 hours or more, and then coated with a waterproof coating.

In the case of coating with latex wax, a brush can be utilized.

By making the water content of the flywood according to the present invention 3% or less and maintaining it during use, it is possible to minimize the heat inflow through the flywheel, thereby helping to maintain the heat insulating performance of the heat insulating system and to reduce the BOR as much as possible Which can contribute to the safety of the storage tank and hull.

Further, as the water content of the plywood is lowered, its rigidity is further reinforced, its thickness can be reduced for the same rigidity, and ultimately the weight of the adiabatic system and the ship can be lightened and the manufacturing cost can be reduced.

As a result of the reduction of the thickness, it is possible to supplement the heat insulating material so that the heat insulating performance can be further improved.

The relationship between the strength of the plywood and the water content is shown in the graphs of Fig. 2 and Fig.

[Figure 2]

[Figure 3]

If the water content of the plywood is maintained at a level of 2 to 3% according to the preferred embodiment of the present invention, the thermal conductivity is reduced by about 7% compared to the conventional 7 to 10% level plywood, %, And BOR could be reduced by 3 ~ 5%.

The storage tank to which the flywood of the present invention is applied is a low-temperature liquefied gas such as LNG, LPG or the like. The flywheel of the present invention can be used in a cargo hold insulation structure of a ship or a special ship having a cargo hold to store such liquefied gas Can be applied. Such a vessel may be, for example, an LNG carrier (LNGC).

Particularly, since the LNG is at a cryogenic temperature of about -163 ° C., an insulation system is very important in order to block heat input and output to a cargo hold where LNG sensitive to heat input is stored. For this purpose, in the case of a membrane type storage tank, A double insulation box is provided so as to block the entrance and exit, and a membrane is provided between the insulation boxes for liquid tightness. The inside of the heat insulating box is provided with a vertical member for giving structural rigidity and increasing buckling strength. The plywood member of this embodiment can be applied to the outer wall and vertical member of such a heat insulating box.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. And will be apparent to those skilled in the art. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

100: Ply wood member
110: Plywood
120: Water repellent coating layer

Claims (6)

The present invention relates to a member for reinforcing the vertical rigidity of a panel-shaped heat insulating wall provided for insulation of a cargo hold for storing cryogenic liquid cargo such as LNG,
A plywood comprising a plurality of veneers stacked,
Characterized in that the water content of the plywood is adjusted to be not more than 3%
Plywood member for cargo hold insulation system. The method according to claim 1,
Characterized in that the water content of the plywood is 2 to 3%
Plywood member for cargo hold insulation system. The method of claim 2,
Characterized in that the plywood is manufactured by drying in a vacuum state,
Plywood member for cargo hold insulation system. The method of claim 2,
Further comprising a water repellent coating layer formed on both sides of the plywood,
Plywood member for cargo hold insulation system. The method of claim 4,
Characterized in that the water-repellent coating layer is applied with latex wax or polyurethane foam.
Plywood member for cargo hold insulation system. A plurality of veneers are stacked and provided,
By drying and setting the moisture content to 3% or less,
Plywood for insulation systems in cargo holds, which is applied for insulation systems in cargo holds that store cryogenic liquid cargoes such as LNG.

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