[DESCRIPTION]

[invention Title]

LNG STORAGE TANK INSULATION SYSTEM HAVING WELDED SECONDARY BARRIER AND CONSTRUCTION METHOD THEREOF

[Technical Field]

The present invention relates to a Liquefied Natural Gas (LNG) storage/transportation tank insulation system having the welded secondary barrier and a construction method thereof and, more particularly, to an LNG storage/transportation tank insulation system having the welded secondary barrier, in which secondary insulation panels are fixed to a hull using coupling means, a secondary barrier is integrally formed by welding strakes, each of which is formed by processing a thin metal sheet, which is made of either Invar alloy, stainless steel, aluminum alloy or the like, primary insulation panels and secondary insulation panels are alternately stacked such that the edges of the primary insulation panels and the edges of the secondary insulation panels are staggered, and the primary insulation panels are bonded to the secondary barrier using adhesive agent, thus remarkably improving thermal insulation, tightness against LNG, and workability, and a construction method thereof.

[Background Art]

A low-temperature liquefaction method is chiefly used to store and transport materials such as hydrogen, oxygen and natural gas in large quantities. Accordingly, an insulated container for storing very low-temperature liquefied gas is important. When designing such an insulated container, an insulation technology of preventing liquefied gas from boiling due to the transmission of heat from the outside and a technology of preventing the liquefied gas from leaking are the key things.

Insulation methods currently used are classified as internal insulation methods and external insulation methods . The internal insulation method is advantageous in that there is no limitation as to the use of material, such as low-temperature material, because the temperature of a container enclosure can be maintained at a temperature similar to ambient temperature.

[Disclosure] [Technical Problem] FIG. 31 shows the insulated structure of a conventional LNG carrier cargo containment. The insulation system includes upper primary insulation panels 510 and lower secondary insulation panels 520, and has a dual barrier structure of a membrane-type primary barrier 550, which is made of stainless steel, and a secondary barrier

530, which is made of triplex. These insulation panels have respective thicknesses of 100 mm and 170 mm. Furthermore, in the above-described insulation system, when the insulation panels are mounted on the inner wall of an insulated container, in order to ensure tightness against LNG in the joint portion of the secondary barrier, two steps of work for bonding and sealing the joint portion between the secondary insulation panels in using secondary barrier material 531, which is called "flexible triplex," and mounting a connection plate 540, which is made of the same material as the primary insulation panels, on the sealed bonding portion is performed. Accordingly, many problems occur in that it takes a lot of time to conduct the work, and in that, when the system is constructed, great attention must also be paid in order to ensure tightness against LNG in the gap between the secondary barriers .

Furthermore, the conventional insulation system, described above, is configured such that the primary insulation panels are preliminarily coupled to the respective center portions of the upper surfaces of the secondary insulation panels, respective coupling holes are formed in two side portions of each secondary insulation panel to avoid interference with the primary insulation panels when the secondary insulation panels are fastened to a hull, and the secondary insulation panels are fastened to the hull through the coupling holes.

However, in the conventional insulation system as described above, the flatness in the longitudinal direction thereof can be controlled using tools because the respective coupling holes are arranged in two side portions of each secondary insulation board, but it is impossible to control the flatness of the center portions of the secondary insulation panels in the transverse direction thereof because the primary insulation panels are coupled first and also because the coupling holes in the secondary insulation panels are located in the ends thereof. Accordingly, a problem occurs in that a plurality of coupling holes must be formed in two side portions of each secondary insulation panels in order to mitigate this disadvantage. In particular, when a plurality of coupling holes is formed as described above, various problems occur in that the insulation system may be negatively affected, and in that it takes a lot of time for an assembly process and, thus, the work is delayed. The present invention has been proposed to solve the above-described problems, and an object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, which enable a secondary barrier to be integrally formed by welding strakes, each of which is formed by processing a thin metal sheet, and enable primary

insulation panels to be integrally bonded to the secondary barrier, thus reducing the number of work processes and the working time and improving the stability of insulation layers . Another object of the present invention is to provide an LNG storage tank insulation system and a construction method thereof, which enable secondary insulation panels to be easily and securely supported to a hull using coupling means, thus improving ease of assembly and overall constructability.

Another object of the present invention is to reduce the number of work processes and the working period by forming the metallic secondary barrier using resistance welding, thus improving productivity. Another object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, which enable the insulation system to be integrally formed using welding and adhesive agent, thus improving the constructability and realizing ease of assembly and excellent insulation, tightness against LNG and workability.

Another object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, which enable tongue to be mounted on the secondary insulation

panels, thus protecting the secondary insulation panels when the strakes, each of which is formed by processing a thin metal sheet, are welded, and improving the tightness against LNG of the secondary barrier by welding the tongue and the strakes.

Another object of the present invention is to provide an integrated secondary barrier, which can realize excellent tightness against LNG because a tongue is mounted in the secondary insulation panels and the tongue and the strakes, each of which is formed by processing a thin metal sheet, are welded.

Another object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, in which uniform bolt coupling pressure in the longitudinal and transverse directions of the secondary insulation panels is achieved by arranging coupling holes in the inside of each secondary insulation board, thus controlling the flatness in the longitudinal and transverse directions and improving the degree of coupling.

Another object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, which not only can improve ease of assembly and workability by reducing the number of coupling holes, but also can securely fasten the secondary insulation panels to the

hull .

Another object of the present invention is to provide an LNG storage tank insulation system having a welded secondary barrier and a construction method thereof, which enable the primary insulation panels to be bonded to and mounted on the secondary insulation panels so that the primary insulation panels are staggered with the secondary insulation panels without requiring holes to be formed in a connection plate, thus improving the thermal insulation performance of the insulation system.

[Technical Solution]

The present invention is configured such that a plurality of secondary insulation panels, which is continuously mounted to be connected to a hull, is connected to the hull using coupling means, a secondary barrier is integrally formed on the secondary insulation panels by welding strakes, each of which is formed by processing a thin metal sheet, primary insulation panels are bonded to and mounted on the secondary insulation panels using adhesive layers so that the primary insulation panels are staggered with the secondary insulation panels, after the adhesive layers are formed on the secondary barrier, and a primary barrier is mounted on the primary insulation panels, which are bonded and mounted. Furthermore, the present invention is configured such

that coupling holes are arranged along the inside of each secondary insulation board, the secondary insulation panels is fastened to the hull using the coupling holes and the coupling means, closing is made by inserting foam plugs into the coupling holes, and then primary insulation panels are mounted such that the edges of the secondary insulation panels and the edges of the primary insulation panels are staggered.

As described above, in the present invention, the secondary barrier is integrally formed, and the primary insulation panels are connected with the secondary barrier by bonding, so that the primary insulation panels can be securely fastened without the use of separate coupling means, excellent tightness against LNG can be ensured, and heat insulation performance between the primary and secondary insulation panels can be improved.

Furthermore, in the present invention, the primary insulation panels are integrally mounted to the secondary insulation panels using adhesive agent, so that more excellent assembly and constructability than those achieved when the primary insulation panels are fastened using conventional coupling means, can be realized.

Furthermore, in the present invention, tongues are mounted in the secondary insulation panels and the primary insulation panels, so that, when the secondary barrier is formed by welding, damage to the insulation panels,

attributable to such welding, can be prevented from occurring.

Furthermore, in the present invention, tongues, which are mounted in the secondary insulation panels, and the strakes, each of which is formed by processing a thin metal sheet, are welded, so that the tightness against LNG of the secondary barrier can be further improved.

Furthermore, when compared with an existing method of manufacturing the secondary barrier through triplex bonding, the present invention can reduce the manufacturing period, about fifty days, by half, about twenty days, thus improving working performance and the efficiency of production.

Furthermore, the edges of the primary insulation panels and the edges of the secondary insulation panels are staggered with each other, and an insulation material is inserted into the gap, in which a coupling means is mounted, so that the gap can be dually sealed, with the result that tightness against LNG can be improved and the reliability and heat insulation performance of the secondary barrier can be improved.

Furthermore, the width of the gap between neighboring primary insulation panels can be maintained 3 - 5 mm, preferably, 4 mm. Furthermore, in the present invention, all of neighboring secondary insulation panels are fastened and

supported using coupling means, so that the secondary insulation panels can be easily constructed and the working time can be reduced.

Furthermore, in the present invention, the secondary insulation panels are fastened and supported using coupling means, so that a worker can easily conduct the work, with the result that working performance can be improved.

Furthermore, in the present invention, coupling holes for fastening the secondary insulation panels are arranged along the central portion of each secondary insulation board, so that uniform bolt coupling pressure is applied in the longitudinal and transverse directions of the secondary insulation panels, with the result that the flatness of the secondary insulation panels in the longitudinal and transverse directions can be improved and the degree of deformation of the secondary insulation panels can be minimized.

Furthermore, the present invention can securely fasten the secondary insulation panels using a small number of coupling holes, with the result that ease of assembly and workability can be increased.

Furthermore, in the present invention, the edges of the primary insulation panels and the edges of the secondary insulation panels are staggered with each other, so that heat insulation performance is prevented from being lowered due to the fastening parts of the primary

insulation panels and the fastening parts of the secondary insulation panels.

[Description of Drawings]

FIG. 1 is a sectional illustrative view showing the schematic construction of the present invention;

FIG. 2 is an enlarged view of portion A of FIG. 1; FIG. 3 is a sectional illustrative view showing a first modification according to the present invention;

FIG. 4 is a sectional illustrative view showing a second modification according to the present invention;

FIG. 5 is a sectional illustrative view showing welding in the second modification of the present invention;

FIG. 6 is an enlarged view of portion B of FIG. 1; FIG. 7 is an illustrative view showing the construction of a coupling means according to the present invention;

FIG. 8 is an illustrative view showing a first modification of the coupling means according to the present invention;

FIG. 9 is an illustrative view showing a second modification of the coupling means according to the present invention;

FIG. 10 is an illustrative view showing a third modification of the coupling means according to the present

invention;

FIG. 11 is an illustrative view showing a fourth modification of the coupling means according to the present invention; FIG. 12 is an illustrative view showing a fifth modification of the coupling means according to the present invention;

FIG. 13 is an illustrative view showing a sixth modification of the coupling means according to the present invention;

FIG. 14 is an illustrative view showing a seventh modification of the coupling means according to the present invention;

FIG. 15 is an illustrative view showing the construction of a secondary barrier, which is formed of a thin metal sheet, according to the present invention;

FIG. 16 a flowchart illustrating an installation process according to the present invention;

FIG. 17 is an illustrative view showing the installation process according to the present invention;

FIG. 18 is a partially cut away illustrative view showing an installation according to the present invention;

FIG. 19 is an exploded perspective view showing the installation according to the present invention; FIG. 20 is an illustrative view showing the installation according to the present invention;

FIG. 21 is an illustrative view showing the assembly structure of secondary insulation panels using coupling holes;

FIG. 22 is an illustrative view showing the arrangement of coupling holes according to the present invention;

FIG. 23 is an illustrative view showing the flatness and the degree of deformation of the secondary insulation panels, which are assembled using the coupling holes; FIG. 24 is an illustrative view showing the positional relationship between the secondary insulation panels and the primary insulation panels, which are assembled using the coupling holes;

FIG. 25 is an illustrative view showing the degree of distortion according to an embodiment of the present invention;

FIG. 26 is an illustrative view showing a first modified arrangement of coupling holes according to the present invention; FIG. 27 is an illustrative view showing a second modified arrangement of coupling holes according to the present invention;

FIG. 28 is an illustrative view showing a third modified arrangement of coupling holes according to the present invention;

FIG. 29 is an illustrative view showing the

arrangement of conventional coupling holes;

FIG. 30 is an illustrative view showing the degree of distortion attributable to the arrangement of the conventional coupling holes; and FIG. 31 is an illustrative view showing the insulated structure of a conventional LNG carrier cargo containment. ^Description of characters of principal elements (10) : primary insulation panels (11) : upper plates (12) : weldment

(13) : heat insulating material (14) : gap

(20) : secondary insulation panels (21) : upper plates (22) : lower plates (23) : heat insulating material (24) : tongue insertion slots (25) : tongues

(26) : insertion heat insulating material (27) : gap (28) : insertion grooves (29): holes (29'): connection hole

(20a) : coupling holes (20b) : coupling holes

(conventional insulation system) (20c) : insertion heat insulating material (40) : primary barrier (42) : corrugations

(50, 50a, 50b) : secondary barriers (54, 54a, 54b) : thin metal sheet strakes (55,55b): welding parts (56, 56a, 56b) : welding portions (51a, 51b): metal inserts

(60) : adhesive layers (61) : space

(70) : hull

(80) : hull/insulation board connection parts

(81) : level wedges (82) : mastic (90) : coupling means

(90a): coupling means, showing a first modification (90b) : coupling means, showing a second modification (90c) : coupling means, showing a third modification (9Od) : coupling means, showing a fourth modification (9Oe) : coupling means, showing a fifth modification (9Of): coupling means, showing a sixth modification (9Og) : coupling means, showing a seventh modification (91, 91a, 91b, 91c, 91d, 91e, 91f, 9Ig) : fastening bolts (92, 92a, 92b, 92c, 92e, 92f) : supports (93,93a,93b,93c,93d,93e,93f,93g) : fastening nuts (94, 94a, 94b, 94c, 94e, 94f) : holes (95b) : connection portions

(92d) : first support (94d) : coupling hole

(95d) : thread (96d) : support plate (97d) : insertion hole (98d) : second support

(95c, 95f) : wing parts (96c, 96f): first wings (97c,97f): second wings (100) : primary insulation layer (200) : secondary insulation layer

[Best Mode]

The present invention is configured such that a plurality of secondary insulation panels 20, which is continuously mounted to be connected to a hull 70, is connected to the hull 70 using coupling means 90, a secondary barrier 50 is integrally formed on the secondary insulation panels 20 by welding strakes 54, each of which is formed by processing a thin metal sheet, adhesive layers 60 are formed on the secondary barrier 50, primary insulation panels 10 are bonded such that the primary insulation panels 10 are staggered with the secondary insulation panels 20 using the adhesive layers 60, and a primary barrier 40 is mounted on the primary insulation panels 10, which are bonded and mounted. That is, the present invention includes the plurality of secondary insulation panels 20, which is continuously mounted so as to be connected to the hull 70 using hull/insulation board connection parts 80, the coupling means 90, which are located between neighboring secondary insulation panels and are configured to fasten the

secondary insulation panels to the hull 70, the secondary barrier 50, which is located on the secondary insulation panels and is integrally formed by welding the strakes, each of which is formed by processing a thin metal sheet, the primary insulation panels 10, which are located on the secondary barrier and are arranged such that the edges thereof are staggered with the edges of the secondary insulation panels, the adhesive layers 60, which are located between the primary insulation panels 10 and the secondary barrier 50 and function to integrally bond the primary insulation panels 10 to the secondary barrier 50, and the primary barrier 40, which is welded to the upper surfaces of the primary insulation panels 10.

The primary barrier 40, which is mounted on the primary insulation panels, has a plurality of corrugations 42, which convexly rise upwards so that the primary barrier 40 can easily expand and contract according to variation in temperature, attributable to loaded cargo.

The secondary barrier is made of metal material, such as Invar alloy, stainless steel or aluminum alloy, is integrally formed by welding so as to maintain tightness against LNG, and is connected to the secondary insulation panels and securely fastened thereto.

The present invention is described in detail in conjunction with the accompanying drawings, that is, FIGS. 1 to 30, below.

FIG. 1 is a sectional illustrative view showing the schematic construction of the present invention, FIG. 2 is an enlarged view of portion A of FIG. 1, FIG. 3 is a sectional illustrative view showing a first modification according to the present invention, FIG. 4 is a sectional illustrative view showing a second modification according to the present invention, FIG. 5 is a sectional illustrative view showing welding of the second modification of the present invention, and FIG. 6 is an enlarged view of portion B of FIG. 1.

In the LNG storage tank insulation system having a welded secondary barrier, in which the plurality of secondary insulation panels 20 is continuously mounted to form a secondary insulation layer 200, the plurality of primary insulation panels 10 is continuously mounted on the secondary insulation panels 20 to form a primary insulation layer 100, the secondary barrier 50 is mounted to be located between the primary insulation layer 100 and the secondary insulation layer 200, and the primary barrier 40 is mounted on the primary insulation layer 100, the present invention is configured such that the secondary insulation panels are securely fastened and supported to the hull using the coupling means, the secondary barrier is integrally connected to the secondary insulation panels by welding the strakes, each of which is formed by processing a thin metal sheet, the primary insulation panels are

stacked such that the edges thereof are staggered with the edges of the secondary insulation panels using the adhesive layers, which are applied to the secondary barrier, and the primary barrier is formed on the primary insulation panels. The secondary barrier 50 is mounted to be located on the secondary insulation panels, and is integrally formed in such as way that the strakes 54 are inserted between tongues 25, which are mounted on neighboring secondary insulation panels, and the respective ends of each strake 54 are welded to the tongues 25, which come into contact with the strake 54, as shown in FIGS. 1 and 15.

That is, the secondary barrier 50, which is located on the secondary insulation panels 20, is formed by welding the strakes 54 to the tongues 25, which are inserted into the tongue insertion slots 24 of the secondary insulation panels .

The tongues 25 are used to connect the secondary barrier, which is formed by welding, to the secondary insulation panels and to support the secondary barrier. The tongues 25 are inserted and mounted in one direction of the secondary insulation panels. That is, the tongues 25 are mounted such that the respective lower portions thereof pass through the upper plates of the secondary insulation panels and are inserted into the secondary insulation panels, and the respective upper portions thereof protrude outside the upper plates of the secondary insulation

panels .

Each of the strakes 54, each of which is formed by processing a thin metal sheet, is provided with welding parts 55 on respective ends thereof, as shown in FIGS. 1 and 15. The welding parts 55 are integrally formed by bending two ends of each strake 54 so that they protrude upwards. That is, the strakes 54 are bent upwards such that the ends thereof have the same height, and parts of portions that are bent so as to protrude, as described above, correspond to welding portions 56, which are to be welded.

The welding parts 55 come into contact with the tongues 25, which are mounted such that they protrude through the central portion of each secondary insulation board 20 when the strakes 54 are mounted, and are integrated with the tongues 25 by welding, as shown in FIGS. 15.

That is, the welding parts 55, which are located in the respective ends of each strake 54, are mounted so as to be in contact with the tongues 25, which are mounted in the neighboring secondary insulation panels, and the welding parts 55 and the tongue 25, which come into contact with each other, are integrated with each other so that airtightness can be maintained by resistance welding. The secondary insulation panels 20 are made of heat insulating material 23, that is, polyurethane material, are

mounted to be located on the hull/insulation board connection parts, and are configured such that the upper plates 21, which are made of wood or synthetic resin, and lower panels 22, which are made of wood, synthetic resin or thin metal plates, are integrally formed on the upper and lower surfaces thereof.

Furthermore, the secondary insulation panels 20 are formed such that the lower panels 22 protrude more than the heat insulating material 23, that is, the polyurethane material, or such that the lower panels 22 and the heat insulating material 23 have the same length. Insertion grooves 28, having a predetermined depth, may be formed in the lower edges of the heat insulating material 23, which comes into contact with the upper surfaces of the lower panels 22.

That is, the insertion grooves 28 are formed in the inward direction of the heat insulating material, and the upper surfaces of the edges of the lower panels 22 are exposed due to the insertion grooves 28. Furthermore, the tongue insertion holes 24, having a "T" or "L" shape, into which the tongues 25 of the secondary barrier are inserted in one direction of the secondary insulation panels 20, are formed in the respective center portions of the upper plates 21 of the secondary insulation panels, as shown in FIGS. 1 and 2. That is, the tongues 25 of the secondary barrier are

inserted into the respective tongue insertion holes 24, which are formed in the central regions of the upper portions of the upper plates of the secondary insulation panels, and support the primary insulation panels, which are to be coupled with the secondary barrier.

The tongue insertion holes 24 are formed by mechanically processing the portions at which the secondary insulation panels 20 come into contact with the upper plates 21, and the upper plates 21, and are configured such that depressions having a depth of 1 to 5 mm are formed to such an extent that the tongues 25 are inserted into the respective center regions of the upper portions of the secondary insulation panels 20, and the tongue insertion holes 24 are formed in one direction of the secondary insulation panels 20 by bonding the upper plates 21, which results from cutting and division into two or more parts, to the upper portions of the depressions, as shown in FIG. 2.

The tongue insertion holes 24, which are constructed as described above, facilitate manufacture and inspection for defects more than a conventional structure, in which a connection depression is provided in a reinforcing board, which is made of wood, and provides many advantages when manufacturing the secondary insulation layer 200, in which the tongue insertion holes 24 are provided.

The above-described secondary barrier of the present

invention is integrally formed in such a way that the tongues are inserted into respective tongue insertion holes, which are formed in the central regions of the upper portions of the secondary insulation panels 20 in one direction of the secondary insulation panels 20, and the welding parts 55, which are formed in the respective ends of each strake 54, are welded to portions of the tongues 25, which protrude in the upward direction of the secondary insulation panels. The welding parts 55 of each strake 54 are welded to the tongues 25, and the bent portions of the welded tongues 25 are supported by the tongue insertion holes 24, which are formed in the upper plates 21 of the secondary insulation panels 20, and are fastened thereto. In this case, in order to increase the coupling strength between the secondary barrier 50 and the secondary insulation panels 20, the lower portions of the strakes, which constitute the secondary barrier, and portions of the upper plates 21 of the secondary insulation panels 20, which come into contact with the strakes 54, may be bonded and fastened using adhesive agent.

Furthermore, in order to hermetically seal the continuously mounted secondary insulation panels, the tongues 25 and the strakes 54, which form the secondary barrier 50, are sufficiently long to cover the plurality of secondary insulation panels.

Furthermore, as shown in FIGS. 3 to 5, the welded secondary barrier may be formed by inserting a welded metal insert into the upper plate of each secondary insulation board and welding two or more neighboring strakes on the welded metal insert, or by welding the welded metal insert, which is mounted in the upper plate of each secondary insulation board, and strakes, which come into contact with the mounted welded metal insert, and welding the ends of neighboring strakes. That is, FIG. 3 is a sectional illustrative view showing a first modification of the secondary barrier according to the present invention. The secondary barrier 50b is integrally formed in such a way that a welded metal insert 51b is mounted to the upper plate of each secondary insulation board, the welded metal insert 51b is welded to the ends of the strakes 54b, which are in contact with the welded metal insert 51b, and the edges of neighboring strakes 54b are in contact with and welded to each other. In this case, the welding parts 55b, which are used for welding, are formed in the respective ends of the strakes 54b.

That is, the present invention is configured such that at least one welded metal insert 51b is mounted in the upper plate of each secondary insulation board, the welded metal insert and portions of the strakes 54b, which come into contact with the welded metal insert, are welded to

each other, and the welding parts of the neighboring strakes are welded to each other in a contact manner, thus forming the integrated secondary barrier 50b.

As shown in FIG. 3, metal inserts 51b are mounted in the respective edge portions of the upper plate of each secondary insulation board, or one or more metal inserts 51b are mounted at arbitrary locations in each upper plate, and parts of strakes 54b, which come into contact with the metal inserts 51b, are welded and coupled on welding portions 56b.

Furthermore, FIG. 4 is a sectional illustrative view showing a second modification of the secondary barrier according to the present invention. The secondary barrier 50a is integrally formed in such a way that a welded metal insert 51a is mounted in the upper plate of each secondary insulation board, and two or more neighboring strakes 54a and the welded metal insert 51a are welded to each other. That is, the secondary barrier 50a is integrally formed on the welded metal insert 51a by welding the welded metal insert and the two or more neighboring strakes 54a.

In this case, the strakes 54a, as shown in FIG. 5, are integrated with each other using fillet welding, butt welding, lap welding or the like.

The above-described secondary barriers 50a, 50b and 50 of the present invention are integrally formed in such a way that the metal inserts 51a and 51b or the tongues 25

are inserted into the secondary insulation panels, and the strakes 54a, 54b and 54, each of which is formed by processing a thin metal sheet, are welded to the metal inserts 51a and 51b or the tongues 25. The above-described welded secondary barrier of the present invention is not limited to the above-described modifications, and may include any welded secondary barrier, which is integrally formed by welding.

Furthermore, the adhesive layers 60 are formed by applying the adhesive agent to the upper portion of the secondary barrier 50, 50a or 50b according to the present invention, which is constructed as described above, or according to the modifications of the present invention, that is, to the upper portion of the strake 54a, 54b or 54, at predetermined intervals, and the primary insulation panels 10 are bonded to the formed adhesive layers 60, thus integrating them.

The lower plates 22 are made of wood, synthetic resin or thin metal plates, are mounted to be located on the hull/insulation board connection parts 80, and are supported and fastened in such a way that the edge portions thereof are in direct contact with the coupling means 90 and the coupling means press the edge portions. That is, all of the secondary insulation panels 20 are fastened by the fastening and supporting of the above-described lower plates 22.

Each of the hull/insulation board connection parts 80 includes level wedges 81, which are configured to have a predetermined bearing capacity when the secondary insulation panels are mounted using the coupling means, and mastic 82, which is an agent for fastening the secondary insulation panels to the hull.

The coupling means 90 are used to securely support the secondary insulation panels to the hull, and enable the secondary insulation panels 20 to be fastened to the hull 70 by coupling between fastening bolts and fastening nuts.

That is, each of the coupling means includes the fastening bolts, which are fastened and supported to the hull, a support, which is provided with holes, through which the fastening bolts pass, are pressed to the lower panels of the secondary insulation panels, and the fastening nuts, which are coupled to the ends of the fastening bolts, which pass through the holes of the supports, to thus fasten the support. In the secondary insulation panels, which are formed such that the lower plates protrude more than the heat insulating material, that is, the polyurethane material, the coupling means of the present invention may directly support the lower panels of the secondary insulation panels using the fastening bolts and the fastening nuts, without the use of any support.

Furthermore, in order to realize coupling between the

bolts and the nuts, washers having elasticity may be mounted under the fastening nuts 93.

The coupling means according to the present invention is described in detail in conjunction with the accompanying drawings below. Furthermore, the coupling means according to the present invention may be modified and constructed in various ways according to the construction of the secondary insulation panels and the construction of the supports, as shown in FIG. 6 to 14. FIGS. 6 to 11 show coupling means for the secondary insulation panels, which are formed such that the lower plates of the secondary insulation panels protrude more than the polyurethane heat insulating material, FIS. 12 and 13 show coupling means for the secondary insulation panels, which are configured such that the insertion grooves are formed in the edge portions of the lower portions of the heat insulating material, which comes into contact with the lower panels, and FIG. 14 shows a coupling means for fastening the secondary insulation panels, which are formed such that the edge portions of the lower plates of the secondary insulation panels are formed so as to protrude more than the polyurethane heat insulating material, using the fastening bolts and the fastening nuts, without requiring any support. FIG. 6 is an enlarged view of portion B of FIG. 1, and FIG. 7 is an illustrative view showing the construction

of a coupling means according to the present invention. The coupling means 90 according to the present invention includes fastening bolts 91, which are fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92, which is configured such that holes 94, into which the fastening bolts are inserted, are formed therein at regular intervals, and such that two lower side surfaces thereof come into contact with the upper surfaces of the edge portions of the lower plates of the secondary insulation panels 20, and fastening nuts 93, which are coupled to respective ends of the fastening bolts 91, which pass through the holes 94 of the support and protrude therethrough.

The coupling means 90, which is constructed as described above, fastens the secondary insulation panels 20 in such a way that two lower side surfaces of the support 92 are in contact with and are supported by the upper surfaces of the protruding lower plates 22 of the secondary insulation panels. Accordingly, when coupling between the fastening nuts 93 and the fastening bolts 91 is made, the support 92 presses and supports all of the lower plates 22 of the neighboring secondary insulation panels.

That is, the coupling means 90 of the present invention, shown in FIGS. 6 and 7, is configured such that all of the edge portions of the neighboring secondary insulation panels 20 are supported by the single support

92, into which a plurality of fastening bolts 91 is inserted.

FIG. 8 is an illustrative view showing a first modification of the coupling means according to the present invention. The first modified coupling means 90a includes a fastening bolt 91a, which is fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92a, which is provided with a hole 94a, into which the fastening bolt is inserted, and which is configured such that two lower side surfaces thereof are in contact with the upper surfaces of the edge portions of the lower plates of the secondary insulation panels, and a fastening nut 93a, which is coupled to the end of the fastening bolt 91a, which passes through the hole 94a of the support and protrudes therethrough.

That is, the first modified coupling means 90a, which is shown in FIG. 8, is obtained by modifying the construction of the support of the coupling means shown in FIGS. 6 and 7. The support 92 of the coupling means 90, shown in FIGS. 6 and 7, has the shape of a long plate, in which the plurality of holes 94, into which fastening bolts are inserted, are formed at regular intervals. In contrast, the support 92a of the coupling means 90a, which is shown in FIG. 8, has the shape of a short plate, in which only a single hole 94a, into which a fastening bolt is inserted, is formed.

As described above, the coupling means shown in FIGS. 6 and 7 can support the neighboring secondary insulation panels using a single support, whereas the first modification, which is shown in FIG. 8, can support the neighboring secondary insulation panels using a plurality of supports. Accordingly, the above-described coupling means have different respective advantages in assembly and in realizing secure fastening.

Furthermore, FIG. 9 is an illustrative view showing a second modification of the coupling means according to the present invention. The second modified coupling means 90b includes a fastening bolt 91b, which is fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92b, which is configured such that a hole 94b, into which the fastening bolt is inserted, is formed therein and such that connection portions 95b, which protrude from respective ends thereof in the downward direction thereof, are inserted into respective connection holes 29' , which are formed in the edge portions of the lower plates of the secondary insulation panels, and a fastening nut 93b, which is coupled to the end of the fastening bolt 91b, which passes through the hole 94b of the support and protrudes therethrough.

That is, the connection portions 95b are formed to protrude from the respective ends of the support 92b in the downward direction thereof, and the connection holes 29'

are formed in the protruding lower plates 22 of the secondary insulation panels, and thus the support 92b of the second modified coupling means 90b supports the secondary insulation panels in such a way that the connection portions are inserted into the connection holes, which are formed in the respective lower plates of the secondary insulation panels, and the fastening nut is coupled to the end of the fastening bolt, which passes through the hole of the support. The coupling means 90b, which is constructed as described above, enables the connection portions of the support to be inserted into the respective connection holes, which are formed in the lower plates of the secondary insulation panels, thus more securely fastening the secondary insulation panels.

Furthermore, FIG. 10 is an illustrative view showing a third modification of the coupling means according to the present invention. The coupling means 90c includes fastening bolts 91c, which are fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92, which is configured such that holes 94c, into which the fastening bolts are inserted, are formed therein at regular intervals, and such that wing parts 95c, which protrude from respective ends thereof in the upward direction thereof, come into contact with the upper surfaces of the lower plates of the secondary

insulation panels, and fastening nuts 93c, which are coupled to the ends of the fastening bolts, which pass through the respective holes of the support and protrude therethrough. That is, the support of the third modified coupling means is formed such that the wing parts 95c protrude from the respective ends thereof in the upward direction thereof. Each of the wing parts 95c include a first wing 96c, which is formed to protrude in the upward direction of the support, and a second wing 97c, which protrudes from the upper end of the first wing in the outward direction, perpendicular to the first wing.

The third modified coupling means 90c of the present invention, which is constructed as described above, supports the secondary insulation panels in such a way that, when the fastening bolts 91c and the fastening nuts 93c are coupled, the side surfaces of the first wings 96c of the support 92c come into contact with the respective side surfaces of the lower plates of the secondary insulation panels, and the lower surfaces of the second wings 97c come into contact with the respective upper surfaces of the edge portions of the lower plates of the secondary insulation panels.

Furthermore, FIG. 11 is an illustrative view showing a fourth modification of the coupling means according to the present invention. The coupling means 9Od includes a

fastening bolt 91d, which is fastened to the hull so as to be located between neighboring secondary insulation panels, a first support 92, which is provided with a coupling hole 94d, which is threadedly coupled with the fastening bolt 91d, is provided in the outer surface of a thread 95d, and is provided with a support plate 96d, which comes into contact with the lower surfaces of the lower plates, in the lower portion thereof, a second support 98d, which is provided with an insertion hole 97d, into which the first support 92d having the thread 95d is inserted, and is mounted such that the lower surface thereof come into contact with the upper surfaces of the lower plates, and a fastening nut 93d, which is coupled to the thread 95d of the first support, which passes through the insertion hole 97d of the second support and protrudes therethrough.

That is, the fourth modified coupling means 9Od securely fastens the secondary insulation panels using the first and second supports 92d and 98d in such a way as to couple the first support 92d to the fastening bolt 91d, continuously locate the secondary insulation panels, mount the second support 98d to the first support 92d such that the second support 98d comes into contact with the upper surfaces of the lower plates of the secondary insulation panels, and couple the fastening nut 93d to the thread 95d of the first support, which passes through the insertion hole 97d of the second support and protrudes therethrough.

Furthermore, FIG. 12 is an illustrative view showing a fifth modification of the coupling means according to the present invention. The coupling means 9Oe includes a fastening bolt 91e, which is fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92e, which is provided with a hole 94e, into which the fastening bolt is inserted, and is configured such that respective ends thereof are inserted into the insertion grooves 28, which are formed in the heat insulating material of the secondary insulation panels, and the lower surfaces of the inserted ends come into contact with the upper surfaces of the edges portions of the lower plates of the secondary insulation panels, and a fastening nut 93e, which is coupled to the end of the fastening bolt 91e, which passes through the hole 94e of the support and protrudes therethrough.

That is, the support of the fifth modified coupling means is used to fasten the secondary insulation panels, in which the insertion grooves 28 are formed, and supports the secondary insulation panels in such a way as to mount the fastening bolts 91e to the hull, mount the support such that the fastening bolt passes through the hole of the support, insert the respective ends of the support into the insertion grooves, which are formed in the insulating material of the secondary insulation panels, bring the lower surfaces of the ends of the support into contact with

the upper surfaces of the lower plates of the secondary insulation panels, and couple the fastening nut to the fastening bolt, which passes through the holes in the support . The coupling means 9Oe, which is constructed as described above, enables the lower plates of the mounted secondary insulation panels not to protrude from the heat insulating material and to have the same length as the heat insulating material, thus not only achieving excellent heat insulation performance but also securely fastening the secondary insulation panels.

Furthermore, FIG. 13 is an illustrative view showing a sixth modification of the coupling means according to the present invention. The coupling means 9Of includes a fastening bolt 91f, which is fastened to the hull so as to be located between neighboring secondary insulation panels, a support 92f, which is provided with a hole 94f, into which the fastening bolt is inserted, and is configured such that wing parts 95f, which protrude from respective ends thereof in the upper direction thereof, come into contact with the upper surfaces of the lower plates of the secondary insulation panels, and a fastening nut 93f, which is coupled to the end of the fastening bolt 91f, which passes through the hole 94f of the support and protrudes therethrough.

That is, the support of the sixth modified coupling

means is formed such that the wing parts 95f protrude from the respective ends thereof in the upward direction thereof. Each of the wing parts 95f includes a first wing 96f, which is formed to protrude in the upward direction of the support, and a second wing 97f, which protrudes from the upper end of the first wing 96f in the outward direction, perpendicular to the first wing.

The sixth modified coupling means of the present invention, which is constructed as described above, supports the secondary insulation panels in such a way that, which the fastening bolt and the fastening nuts are coupled to each other, the side surfaces of the first wings of the support come into contact with the respective side surfaces of the lower plates of the secondary insulation panels, and the lower surfaces of the second wings come into contact with the respective upper surfaces of the edge portions of the lower plates of the secondary insulation panels .

The support of the sixth modified coupling means, which is constructed as described above, is formed to have only a single hole, into which the fastening bolt is inserted. In contrast, the support of the third modified coupling means, shown in FIG. 10, is formed to have a plurality of holes, into which the fastening bolts are inserted, at regular intervals.

That is, the sixth modification, shown in FIG. 13,

can support the neighboring secondary insulation panels using a plurality of supports, whereas the third modification, shown in FIG. 10, can support both of the neighboring secondary insulation panels using a single support, and enables the wing parts of the support to be inserted into the insertion grooves, which are formed in the heat insulating material of the secondary insulation panels, thus not only achieving excellent heat insulation performance but also securely fastening the secondary insulation panels.

FIG. 14 is an illustrative view showing a seventh modification of the coupling means according to the present invention. The seventh modified coupling means 9Og, shown in FIG. 14, enables the secondary insulation panels to be fastened using only fastening bolts and fastening nuts, without requiring that any support be mounted. That is, the secondary insulation panels may be directly fastened in such a way that fastening bolts 91g are mounted to the hull 70, holes 29, which are configured such that the fastening bolts 91g are inserted thereinto and protrude therethrough, are formed in the edge portions of the lower plates, which are formed to protrude more than the polyurethane heat insulating material, and fastening nuts 93g are coupled to the respective ends of the fastening bolts 91g, which pass through the holes 29 and protrude upwards.

The coupling means, which are mounted as described

above, enable the direct fastening of the lower plates, which are formed to protrude more than the insulating material of the secondary insulation panels, thus achieving excellent ease of assembly and secure bearing capacity. As described above, in the present invention, the secondary insulation panels are continuously and securely fastened to the hull using the coupling means, which are constructed as shown in FIGS. 6 to 14.

Furthermore, in the secondary insulation layer, which is formed of the secondary insulation panels, which are continuously mounted as described above, gaps 27, in which coupling means are mounted, are formed between the neighboring secondary insulation panels, and heat insulating material 26 is inserted into the gaps 27. In this case, the heat insulating material 26 is the same as the heat insulating material for the primary and secondary insulation panels 10 and 20, or is some other well-known high-performance heat insulating material.

The adhesive layers 60 are formed on the secondary barrier 50, which is integrally formed by welding, and are spaced part from each other by a predetermined distance so that the respective ends of the adhesive layers 60 do not reach the welding parts 55 of each strake, that is, so that a space 61 is formed between the welding parts 55 and the ends of the adhesive layers 60. In this case, it is preferred that the adhesive layers 60 be formed using

polyurethane adhesive agent.

Furthermore, it is preferred that the width of each of the formed adhesive layers 60 fall within a range of about 60%, preferably about 70%, to 99% of the width between the ends of each strake. That is, in the case where each of the adhesive layers 60 is formed such that the width thereof is smaller than 60%, the fastening force of the primary insulation panels is lowered, so that it is preferred that the primary insulation panels be bonded to the secondary barrier such that the adhesive layers are applied to have a width that is equal to or greater than 60%.

The primary insulation panels 10 are mounted using the adhesive layers, which are formed on the secondary barrier, and are configured such that the upper plates 11, which are made of wood or synthetic resin, are integrally formed on the upper surface of the polyurethane heat insulating material 13.

Furthermore, a weldment 12 is mounted in the upper plates 11 so that, when the primary barrier 40 is coupled to the primary insulation panels 10 by welding, the primary insulation panels 10 are protected and are easily welded.

Furthermore, the polyurethane heat insulating material 13 of the primary insulation panels 10 and the upper plates 11 are bonded to each other, and the polyurethane heat insulating material 23 of the secondary insulation panels 20, the upper plates 21, and the lower

plates 21 are also bonded to each other.

Furthermore, the gaps 14, in which the tongues and the welding parts of the strakes are located, are formed between the neighboring primary insulation panels. The gaps are formed to have a width of about 3 - 5 mm, preferably, a width of 4 mm.

That is, the primary insulation panels are integrally bonded to the secondary barrier using the adhesive layers, so that the primary insulation panels are closely mounted such that the distance between the neighboring primary insulation panels is sufficiently small within the range of 3 - 5 mm, thus improving heat insulation performance.

The primary barrier 40 is mounted to be located on the primary insulation panels 10, and is formed by continuously mounting stainless steel metal panels having corrugations 42 on the primary insulation panels 10. In this case, two or more stainless steel metal panels are welded on the weldment 12 of the neighboring primary insulation panels by welding, and thus the stainless steel metal panels, having the corrugations, form the primary barrier 40.

Furthermore, in the present invention, the corrugations 42 of the primary barrier is formed to be located in two ends of each primary insulation panel and in the central portion of each primary insulation panel, and are thus located more widely than the corrugations of an

existing primary barrier.

FIG. 16 is a flowchart illustrating an installation process according to the present invention, FIG. 17 is an illustrative view showing the installation process according to the present invention, FIG. 18 is a partially cut away illustrative view showing an installation according to the present invention, FIG. 19 is an exploded perspective view showing the installation according to the present invention, and FIG. 20 is an illustrative view showing the installation according to the present invention. The present invention includes a primary mounting step of mounting the hull/insulation panel connection parts 80, and the coupling means, that is, the fastening bolts, to the hull; a secondary insulation panel mounting step of continuously mounting the secondary insulation panels 20 to the hull/insulation panel connection part; a coupling step of fastening all of the neighboring secondary insulation panels 20, which are continuously mounted, using the coupling means; a secondary barrier forming step of integrally forming the secondary barrier on the fastened secondary insulation panels 20 by welding the plurality of strakes, each of which is formed by processing a thin metal sheet; an adhesive layer forming step of forming the adhesive layers 60 by applying adhesive agent to the formed secondary barrier 50; a primary insulation panel mounting step of bonding and mounting the

primary insulation panels 10 using the applied adhesive layers 60; and a primary barrier forming step of forming the primary barrier 10 such that corrugations 42 are located in two ends of each primary insulation panel and in the center portion of each primary insulation panel by welding the stainless steel metal sheets, which are provided with the corrugations 42 on the fastened primary insulation panels 10.

The primary mounting step is a step of the hull/insulation panel connection parts 80 and the coupling means, that is, the fastening bolts, to the hull. At this step, the plurality of fastening bolts are mounted to the hull at regular intervals so that the insulation system of an LNG cargo containment can be fastened to the hull, the plurality of hull/insulation panel connection parts 80 for supporting the insulation system and fastening the insulation system to the hull are mounted between the fastening bolts, the level wedges 81 are mounted at locations that are close to the fastening bolts, and the mastic 82 is applied to be located between the level wedges.

At the secondary insulation panel mounting step, the plurality of secondary insulation panels are continuously mounted such that the secondary insulation panels 20 are located on the level wedges and the mastic, which is located between the level wedges.

The coupling step may be performed in such a way that the fastening bolts, which are fastened to the hull, are inserted into the holes formed in each support, and the fastening nuts are coupled to the respective ends of the fastening bolts, which pass through the holes, thus fastening and supporting the lower plates of the neighboring secondary insulation panels using a single support, or may be performed in such a way that the fastening bolts, which are fastened to the hull, are mounted so as to pass through the lower panels of the secondary insulation panels and fastening nuts are coupled to the fastening bolts, which pass though the edges of the lower plates, thus fastening and supporting the secondary insulation panels. The secondary barrier forming step includes a tongue mounting step of inserting the tongues 25 into the respective upper portions of the secondary insulation panels 20, and a welding step of inserting the strakes 54 between the inserted tongues 25 and welding the respective ends of the strakes 54 to the tongues.

Furthermore, the secondary barrier forming step may be performed in such a way that two or more strakes and a metal insert may be welded to each other on the metal insert, which is integrated with the upper plate of each secondary insulation panel, or may be performed in such a way that the metal insert, which is mounted in the upper

plate of each secondary insulation board, and strakes, which come into contact with the metal insert, are welded to each other, and the ends of neighboring strakes are welded to each other. Furthermore, in order to increase coupling strength between the secondary barrier 50 and the secondary insulation panels 20, the lower portions of the strakes 54, which constitute the secondary barrier, and portions of the upper plates 21 of the secondary insulation panels 20, which come into contact with the strakes 54, are may be bonded and fastened using adhesive agent.

At the adhesive layer forming step, adhesive agent is applied to the secondary barrier such that the space 61, in which no adhesive layer is formed, is formed between the welding parts 55 and the ends of the adhesive layers 60.

At the primary insulation panel mounting step, the primary insulation panels and the secondary barrier are integrated with each other using the adhesive layers, and the lower portions of the primary insulation panels are bonded to the secondary barrier using the adhesive layers 60, which are formed between the secondary barrier 50 and the primary insulation panels 10.

At the primary barrier forming step, two or more neighboring stainless steel metal sheets are welded on the weldment 12, which is mounted on the primary insulation panels 10, using welding, thus forming an integrated

primary barrier.

In this case, the primary barrier is formed such that the protruding corrugations 42 are located in two ends of each primary insulation panel and in the central portion of each primary insulation panel.

The present invention, which is constructed as described, has a structure in which the secondary insulation panels 20 are securely fastened and supported to the hull using the coupling means, the primary insulation panels 10 and the secondary insulation panels 20 are alternately stacked such that the edges of the primary insulation panels 10 and the edges of the secondary insulation panels 20 are staggered, the integrated secondary barrier 50 is formed between the primary insulation panels 10 and the secondary insulation panels 20 by welding the strakes 54, each of which is formed by processing a thin metal sheet, and the primary insulation panels 10 is integrally bonded to the secondary barrier 50 using the adhesive agent, thus increasing excellent ease of assembly, assuring airtightness, and greatly reducing the time taken for the process of bonding the conventional secondary barrier and the inspection of tightness against LNG.

Furthermore, the present invention may realize the coupling between the secondary insulation panels and the hull in such a way that coupling holes are arranged along

the inside of each secondary insulation panel, the secondary insulation panels is fastened to the hull using the coupling holes and the coupling means, closing is made by inserting foam plugs into the coupling holes, and then primary insulation panels are mounted such that the edges of the secondary insulation panels and the edges of the primary insulation panels are staggered, as shown in FIGS. 21 to 30. In addition, parts that are not mentioned in detail in the description of the construction, described below, are mounted using the technology described in FIGS. 1 to 20.

The above-described construction is described in detail in conjunction with FIGS. 21 to 30 below.

FIG. 21 is an illustrative view showing the assembly structure of a secondary insulation panels using coupling holes, FIG. 22 is an illustrative view showing an arrangement of coupling holes according to the present invention, FIG. 23 is a illustrative view showing the flatness and the degree of deformation of the secondary insulation panels, which is assembled using the coupling holes, and FIG. 24 is an illustrative view showing the positional relationship between the secondary insulation panels and the primary insulation panels, which are assembled using the coupling holes. The coupling means 90 is coupled to the secondary insulation panels 20 though the plurality of coupling holes 20a, which are arranged along

the inside of each secondary insulation panel 20, and thus the secondary insulation panels 20 are securely fastened and supported to the hull 70. The secondary barrier 50 is integrally connected to the secondary insulation panels 20 by welding members, which are formed by processing thin metal sheets. The primary insulation panels 10 are bonded to and stacked on the secondary insulation panels 20 so that the edges of the primary insulation panels 10 are staggered with the edges of the secondary insulation panels 20.

That is, the plurality of coupling holes 20a is formed in the inside of each secondary insulation panel 20, which are continuously mounted to be connected to the hull 70, the secondary insulation panels 20 is connected to the hull 70 and is fastened thereto by inserting the coupling means 90 into the coupling holes 20a and coupling them, the closing is made by inserting the foam plugs, which are made of heat insulating material, in the coupling holes, the secondary barrier 50 is formed by integrally forming the members, which are formed by processing thin metal sheets, on the secondary insulation panels 20 by welding, and then the primary insulation panels are bonded to and mounted on the secondary barrier 50 such that they are staggered.

The coupling holes 20a are used to fasten the secondary insulation panels 20 to the hull 70 through insertion of the coupling means 90, such as bolts and nuts,

insertion, and are formed in the secondary insulation panels 20 so as to pass through the upper plates 21 of the secondary insulation panels, as shown in FIGS. 21 to 28.

It is preferred that, when viewed in the longitudinal direction of the secondary insulation panels 20, each of the coupling holes 20a be located within a range of 15% ~ 85% of two ends of each secondary insulation panel.

Furthermore, the coupling holes 20a are symmetrically formed, at the left and right sides or the upper and lower sides of each secondary insulation panel, around the central portion of each secondary insulation panel so that uniform bolt coupling pressure is applied to all of the secondary insulation panels, thus improving the flatness of the secondary insulation panels and minimizing the deformation thereof.

When viewed in the transverse direction of the secondary insulation panels 20, the above-described coupling holes are formed such that six coupling holes, which are located between both ends of each secondary insulation panel and the central portion thereof, are symmetrically arranged at the upper and lower sides of each secondary insulation panel in threes, as shown in FIG. 22. That is, in the conventional insulation system, coupling holes, which are used to fasten the secondary insulation panels to the hull, are formed to be located at both ends of each secondary insulation board in order to eliminate

interference between the primary insulation panels. However, when viewed in the transverse direction of the secondary insulation panels 20, the coupling holes according to the present invention are formed to be located within a range of 15 % ~ 85% of the edges of each secondary insulation panel, rather than being formed in the edges of each secondary insulation panel.

Furthermore, the lower plates 22 of the secondary insulation panels have the same length as the heat insulating material 23.

In the present invention, which is constructed as described above, when the primary insulation panels are stacked on the secondary insulation panels, the primary insulation panels are stacked on the secondary insulation panels so that the edges of the secondary insulation panels and the edges of the primary insulation panels are staggered with each other, as shown in FIG. 24.

FIG. 26 is an illustrative view showing a first modified arrangement of coupling holes according to the present invention. Respective coupling holes are formed in four corner portions of each secondary insulation panel, and three coupling holes are formed in the central portion of each secondary insulation panel at regular intervals in the longitudinal direction of the secondary insulation panels, thus applying uniform bolt coupling pressure.

FIG. 27 is an illustrative view showing a second

modified arrangement of coupling holes according to the present invention. Coupling holes are formed in each secondary insulation panel and are symmetrically arranged at the upper and lower sides of each secondary insulation panel to have a diamond shape.

That is, in the present invention, a coupling hole is formed at the center of gravity of each secondary insulation panel, and two coupling hole groups, including the formed coupling hole, are arranged to form a diamond shape, so that bolt coupling pressure is uniformly applied.

FIG. 28 is an illustrative view showing a third modified arrangement of coupling holes according to the present invention. Coupling holes are formed in the edge portions of each secondary insulation panel at regular intervals, and respective coupling holes are formed at locations at which division lines intersect in the longitudinal and transverse directions of the coupling holes of the edge portions.

That is, coupling holes are formed at the left and right sides of each secondary insulation panel so as to be located the same distance from the coupling holes formed in the central portion of each secondary insulation panel, thus applying uniform bolt coupling pressure.

The present invention, which is constructed to improve the coupling between the secondary insulation panels and the hull, is described in detail with reference

to the following embodiment. Embodiment

Six coupling holes having a diameter of 45 inni are formed in each secondary insulation panel, having a length of 3030 mm, a width of 990 mm and a thickness of 170 mm, at locations 25% and 75% of the way along a transverse axis of the secondary insulation panels, are symmetrically arranged in such a way that three coupling holes are formed in the left side of each secondary insulation panel and three coupling holes are formed in the right side of each secondary insulation panel. In this case, the coupling holes are formed such that the distance between coupling holes in the transverse direction is 495 mm, and the distance between the coupling holes in the longitudinal direction is 1010 mm. Subsequently, the amount of distortion that occurs when bolts and nuts are coupled through the above-described coupling holes, was evaluated

(in this case, the thickness of the upper plates and lower plates was 9 mm) . FIG. 25 is an illustrative view showing the degree of distortion according to an embodiment of the present invention. It can be seen that the maximum amount of distortion is 0.048 mm in the longitudinal direction (Y- direction) , and that the distortion occurs in the end of each secondary insulation panel. Comparison Example

Ten coupling holes having a diameter of 45 mm are formed in each secondary insulation board, having a length of 3030 mm, a width of 990 mm and a thickness of 170 mm, and are symmetrically arranged in such a way that five coupling holes are formed in the left end of each secondary insulation panel and five coupling holes are formed in the right end of each secondary insulation panel, in the same manner as the method of forming coupling holes in the secondary insulation panels of the conventional insulation system. In this case, the coupling holes are formed such that the distance between the coupling holes in the transverse direction is 880 mm, and the distance between coupling holes in the longitudinal direction is 730 mm. Subsequently, the amount of distortion that occurs when bolts and nuts are coupled through the above-described coupling holes, was evaluated when the above-described coupling holes were used (in this case, the thickness of the lower plates was 9 mm) .

FIG. 30 is an illustrative view showing the degree of distortion based on the comparison example of the present invention. It can be seen that the maximum amount of warping is 0.050 mm in the longitudinal direction (Y- direction) , and that the distortion occurs in the longitudinal direction. The present invention is not limited to the above- described specific preferred embodiments. Furthermore, a

person having ordinary knowledge in the technical field to which the invention pertains will appreciate that various modifications and implementations are possible without departing from the gist of the present invention, which is claimed in the claims, and that such modifications are all included in the scope of the claims.