AU2014276717A1

AU2014276717A1 - Self-supporting case for thermally insulating a fluid storage tank and method for producing such a case

Info

Publication number: AU2014276717A1
Application number: AU2014276717A
Authority: AU
Inventors: Benoit Capitaine; Sebastien Delanoe; Bruno Deletre; Florent OUVRARD; Olivier Perrot; Nicolas WALKER
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2013-06-07
Filing date: 2014-05-23
Publication date: 2015-12-24
Anticipated expiration: 2034-05-23
Also published as: CN105393043A; JP2016524678A; KR20160017056A; AU2014276717B2; FR3006662A1; WO2014195602A3; EP3004718A2; EP3004718B1; FR3006662B1; CN105393043B; KR102276637B1; JP6333363B2; WO2014195602A2

Abstract

The invention relates to a method of manufacturing a self-supporting case (3, 7) intended to provide thermal insulation for a tank, with a fluid tight membrane, for storing a fluid, said method involving: a step of supplying a bottom panel (10) and a cover panel (11); a step of manufacturing a plurality of bearing walls (14), said step of manufacturing involving, for each bearing wall (14): o arranging in a mould a composite material comprising a fibre reinforced thermoplastic matrix; o inserting fixings inside the mould; o forming the composite material (14), during which forming the fixings are set in the mass of said bearing wall (14), interposing the bearing walls (14) between the bottom panel (10) and the cover panel (11) in such a way that the bottom panel (10) and the cover panel (11) are spaced apart in a thickness direction of the case (3, 7) and that the bearing walls (14) extend in the thickness direction, and fixing the bearing walls (14) to the bottom panel (10) and/or to the cover panel (14) using said fixings, lining the plurality of compartments (15) formed between the bearing walls (14) with an insulating lining. The invention also relates to a case thus manufactured and to a sealed and thermally insulating tank comprising a thermal insulation barrier comprising a plurality of cases as mentioned hereinabove.

Description

1 Self-supporting case for thermally insulating a fluid storage tank, and method for producing such a case Technical field The invention relates to field of fluid-tight, thermally insulated tanks with 5 membranes, for storage and/or transport of fluid such as a cryogenic fluid. Fluid-tight, thermally insulated tanks with membranes are used in particular for the storage of liquefied natural gas (LNG) which is stored at around -1620C at atmospheric pressure. These tanks may be installed on land or on a floating installation. In the case of a floating installation, the tank may be intended for the 10 transport of liquefied natural gas or to receive liquefied natural gas serving as fuel for propulsion of the floating installation. Technological background Document FR 2 877 639 describes a fluid-tight, thermally insulated tank which comprises a tank wall, is fixed to the supporting structure of a floating 15 installation and presents successively, in the thickness direction from the inside to the outside of the tank, a primary fluid-tight barrier intended to be in contact with the liquefied natural gas, a primary insulating barrier, a secondary fluid-tight barrier and a secondary insulating barrier anchored to the supporting structure. The insulating barriers comprise a plurality of adjacent, parallelepipedic, 20 heat-insulating cases. The parallelepipedic cases comprise a plywood base panel, a plywood cover panel and a plurality of bearing webs interposed between the base panel and the cover panel. The bearing webs are undulating and made from composite material so as to ensure good resistance to compressive forces in the direction perpendicular to the base and cover panels, and thus resist the hydrostatic 25 pressure exerted by the liquid contained in the tank. The cases are also filled with heat-insulating linings extending inside the compartments arranged between the bearing webs. The bearing webs are joined to said base and cover panels by gluing, stapling or encasing. However, none of the methods for joining the bearing webs to 2 the base and cover panels is fully satisfactory in terms of reliability and/or simplicity of assembly. In particular, the stapling systems which are normally used for this type of assembly are undesirable in view of the composite nature of the bearing web material. In fact, the fixing of the composite material walls to the base and cover 5 panels with staples tends to reduce the strength of the webs. Summary A concept on which the invention is based is to propose a method for production of a self-supporting case for thermally insulating a fluid-storage tank, wherein the fixing of the bearing webs to the base and/or cover panel is achieved in 10 a simple and reliable manner. According to one embodiment, the invention provides a method for producing a self-supporting case intended to provide thermal insulation for a fluid storage tank with a fluid-tight membrane, said method comprising: - a step of supplying a base panel and a cover panel; 15 - a step of producing a plurality of bearing webs, said production step comprising, for each bearing web: o arrangement of a composite material in a mold, said material comprising a fiber-reinforced plastic matrix; o insertion of fixing elements intended for fixing the bearing web to 20 the base panel and/or to the cover panel, inside the mold; o forming of the composite material, during which step the fixing elements are set in the mass of said bearing web; - interposing the bearing webs between the base panel and the cover panel such that the base panel and the cover panel are spaced apart in a 25 thickness direction of the case and the bearing webs extend in the thickness direction, and fixing the bearing webs to the base panel and/or to the cover panel by means of said fixing elements; - lining the plurality of compartments arranged between the bearing webs with a heat-insulating lining. 30 Thus the bearing webs may be joined to the base panel and/or cover panel in a reliable manner since the fixing elements do not degrade the structural integrity of the bearing webs, such that their strength is not reduced by the fixing to the base panel and/or cover panel.

3 According to a particular embodiment, the method provides that during production of a bearing web: - a plurality of plates of composite material is arranged in the mold; and - the fixing elements are arranged between two adjacent plates of composite 5 material. According to one embodiment, the composite material is formed by thermoforming or thermocompression. According to one embodiment, the invention also provides a self-supporting case intended for thermal insulation of a fluid-storage tank with a fluid-tight 10 membrane, said case comprising: - a base panel and a cover panel, - a plurality of bearing webs interposed between said base panel and said cover panel and extending in the thickness direction so as to define a plurality of compartments, and 15 - a heat-insulating lining extending inside said compartments arranged between the bearing webs, wherein the bearing webs are produced by forming of a composite material comprising a fiber-reinforced thermoplastic matrix and having elements for fixing to the base panel and/or the cover panel, set into the mass of the bearing webs during 20 their forming. According to embodiments, such a case may comprise one or more of the following characteristics: - the fixing elements are pointed metal rods set into the mass of the bearing webs, each of the metal rods being embedded in the base panel or in the 25 cover panel. - the fixing elements are bushes comprising a threaded inner bore and each cooperating with a threaded element passing through the base panel or the cover panel. - the fixing elements are wooden slats set into the mass of the bearing webs, 30 each of the wooden slats being fixed against the base panel or the cover panel. - the wooden slats are fixed against the base panel or against the cover panel by staples.

4 - the fixing elements are L-shaped fixing tabs each with a wing embedded in the mass of the bearing web and a wing extending against the base panel or the cover panel and provided with an opening allowing passage of a screw fixed to the base panel or the cover panel. 5 - the bearing webs have load distribution plates extending along the two edges of said bearing webs arranged facing the base panel and the cover panel respectively, and the fixing elements for the base panel and/or the cover panel are set into the mass of the bearing webs at the load distribution plates. 10 - the bearing webs have a plurality of undulations, the axis of which extends perpendicular to the base panel and cover panel. According to one embodiment, the invention also provides a fluid-tight, thermally insulated fluid-storage tank comprising a thermal insulation barrier comprising a plurality of the above-mentioned cases arranged next to each other, 15 and a sealing membrane resting against the thermal insulation barrier. Such a tank may form part of a land-based storage installation, for example for storing LNG, or be installed in a floating structure in coastal waters or off-shore, in particular an LNG tanker, a floating storage and regasification unit (FSRU), a floating production, storage and offloading unit (FPSO), and others. 20 According to one embodiment, a ship for transporting a fluid comprises a double hull and a tank as described above arranged in the double hull. According to one embodiment, the invention also provides a method for loading or unloading such a ship, wherein a fluid is conducted through insulated pipelines from or to a floating or land-based storage installation to or from the ship's 25 tank. According to one embodiment, the invention also provides a system for transferring a fluid, the system comprising said ship, insulated pipelines arranged so as to connect the tank installed in the ship's hull to a floating or land-based storage installation, and a pump for driving a fluid through insulated pipelines from or to the 30 floating or land-based storage installation to or from the ship's tank. Brief description of the figures 5 The invention will be better understood and further aims, details, characteristics and advantages thereof will appear more clearly from the following description of several particular embodiments of the invention, given merely for illustration and without limitation, with reference to the attached drawings. 5 0 Figure 1 is a simplified perspective view of a tank wall according to one embodiment. * Figure 2 is a simplified top view of an insulating case of the tank wall from figure 1. * Figure 3 is a side view of a bearing web. 10 0 Figure 4 is a cross-section view along plane IV-IV of figure 3. * Figures 5 and 6 illustrate the steps of production of a bearing web. * Figure 7 is a cross-section view illustrating the assembly of a bearing web to a base panel, according to a first embodiment. * Figure 8 is a cross-section view illustrating the assembly of a 15 bearing web to a base panel, according to a second embodiment. * Figure 9 is a cross-section view illustrating the assembly of a bearing web to a base panel, according to a third embodiment. * Figure 10 is a cross-section view illustrating the assembly of a bearing web to a base panel, according to a fourth embodiment. 20 0 Figure 11 is a perspective view illustrating the assembly of figure 10. * Figure 12 is a diagrammatic cross-section view illustrating the assembly of a bearing web to a cover panel, according to a fifth embodiment. 25 0 Figure 13 is a cross-section view illustrating the assembly of a bearing web to a cover panel, according to a sixth embodiment. * Figure 14 is a perspective view of the assembly of figure 13. * Figure 15 is a cross-section view of an insulating case illustrating the assembly of a bearing web to a cover panel and to a base 30 panel, according to a seventh embodiment.

6 * Figure 16 is a cross-section view illustrating a variant of the seventh embodiment of figure 15. * Figure 17 is a perspective view of the assembly of a web to a base panel, according to an eighth embodiment, the bearing web being 5 shown transparently. * Figure 18 is a diagrammatic cross-section view illustrating a variant of the assembly in figure 17. * Figure 19 is a view from above of the assembly of a bearing web to a base panel, according to a ninth embodiment. 10 0 Figure 20 is a view from above of the assembly of figure 19. * Figure 21 is a view from above of the assembly of a bearing web to a base panel, according to a tenth embodiment. * Figure 22 is a side view of the assembly of figure 21. * Figure 23 is a cross-section view of the assembly of figure 21. 15 0 Figure 24 is a perspective view illustrating an assembly of a bearing web to a base panel, according to an eleventh embodiment. * Figure 25 is a view from above of the assembly of figure 24. * Figure 26 is a side view of the assembly of figure 24. * Figure 27 is a cross-section view of the assembly of figure 24. 20 0 Figure 28 is an simplified diagrammatic depiction of a tank of an LNG tanker, and of a terminal for loading and unloading this tank. Detailed description of embodiments Figure 1 shows a wall of a fluid-tight, thermally insulated tank. The general structure of such a tank is well-known and has a polyhedral form. Therefore only 25 one zone of the tank wall will be described, given that all walls of the tank may have a similar general structure. The wall of the tank, from the outside to the inside of the tank, comprises a supporting structure 1, a secondary thermal insulation barrier 2 which is formed from heat-insulating cases 3 arranged adjacent to each other on the supporting structure 7 1 and anchored thereto by secondary retention elements 4, a secondary sealing membrane 5 carried by the cases 3, a primary thermal insulation barrier 6 formed by heat-insulating cases 7 arranged next to each other and anchored to the secondary sealing membrane 5 by primary retention elements 8, and a primary sealing 5 membrane 9 carried by the cases 7 and intended to be in contact with the cryogenic fluid contained in the tank. The supporting structure 1 may in particular be a self-supporting metal plate, or more generally any type of rigid partition with suitable mechanical properties. The supporting structure may in particular be formed by the hull or 10 double hull of a ship. The supporting structure comprises a plurality of walls defining the general shape of the tank. The primary 9 and secondary 5 sealing membranes are for example formed from a continuous strip of metal strakes with raised edges, said strakes being welded by their raised edges to parallel weld supports fixed to the cover of the cases 15 3, 7. The metal strakes are for example made of Invar@: i.e. an alloy of iron and nickel, the coefficient of expansion of which is typically between 1.2 . 10-6 and 2 . 10-6 K- 1 . The cases 3 of the secondary thermal insulation barrier 2 and the cases 7 of the primary thermal insulation barrier 6 may have identical or different structures 20 and the same or different dimensions. With reference to figure 2, we will now describe the general structure of a case 3, 7 of the secondary thermal insulation barrier 2 and/or the primary thermal insulation barrier 6. The case 3, 7 has substantially the form of a parallelepipedic rectangle. The case 3, 7 comprises a base panel 10 and a cover panel 11 which are 25 parallel to each other. The base panel 10 and cover panel 11 are for example made of plywood. On its inner face, the cover panel 11 has grooves 12 for housing the weld supports of the metal strakes of the sealing membrane. A plurality of spacer elements is interposed between the base panel 10 and the cover panel 11, perpendicular thereto. The plurality of spacer elements 30 comprises firstly two opposing side walls 12, 13, and secondly a plurality of bearing webs 14. The bearing webs 14 are arranged parallel to each other between the two side walls 12, 13 in a direction perpendicular to said side walls 12, 13.

8 Compartments 15 for receiving a heat-insulating lining are provided between the bearing webs 14. The heat-insulating lining may be made of any material with suitable thermal insulation properties. For example, the heat-insulating lining is selected from 5 materials such as perlite, glass wool, polyurethane foam, polyethylene foam, polyvinyl chloride foam, aerogels or other. The bearing webs 14 are undulating with protrusions to either side of their general longitudinal direction. Each undulation thus extends along an axis perpendicular to the base panel 10 and cover panel 11. In the embodiment shown, 10 the undulations are substantially sinusoidal. However, other forms of undulation are also possible. For example, the undulations may in particular take the form of triangular teeth or rectangular notches. Thanks to their shape, such undulating bearing webs 14 have a high buckling resistance without needing a great thickness. Although undulations with a periodic structure allow good uniformity of compressive 15 strength, it is also possible to provide non-periodic undulations in order to meet to certain localized mechanical requirements. Figure 3 and 4 illustrate a bearing web 14. Along its edges extending along the base panel 10 and cover panel 11, the bearing web 14 comprises load distribution plates 16a, 16b. The upper plate 16a has a flat surface intended to rest 20 against the cover panel 11, while the lower plate 16b has a flat surface intended to rest against the base panel 10. The plates 16a, 16b have a width which is greater than the thickness of the wall of the bearing web 14 in its principal part extending between the two plates 16a, 16b. Thus the load distribution plates 16a, 16b prevent a concentration of stress on a particular zone, by offering a larger support surface 25 between the bearing web 14 and the base panel 10 and cover panel 11. The load distribution plates may have a parallelepipedic form as shown on figures 3 or 4. In this case, the width of the plates 16a, 16b may be equal to the amplitude of the undulations. In other embodiments as shown on figures 17, 20 or 24, the load distribution plates 16a, 16b may themselves have undulations. 30 The bearing webs are made of composite material with a glass-fiber reinforced thermoplastic matrix. A method for production of the bearing webs 14 is described in relation to figures 5 and 6.

9 In a first phase shown on figure 5, an intermediate product is produced in the form of composite material plates. To do this, a double-belt press 17 is supplied with glass fibers 18 and thermoplastic resin 19. The thermoplastic resin 19 may be loaded into the double-belt press 17 in the form of extruded films or powder. The 5 glass fibers 18 are provided in the form of glass fiber coils cut to the desired length. The thermoplastic resin 19 and the glass fibers 18 are laminated together in the double-belt press 17. At the outlet from the double-belt press 17, a cutting device allows a plurality of plates to be obtained. In one embodiment, the thermoplastic resin is based on polypropylene. 10 Such plates have a composite structure comprising a thermoplastic matrix and a glass-fiber felt or mat. Such composite structures are designated GMT, for glass-fiber mat reinforced thermoplastics. Then the composite material plates are formed as shown on figure 5. To do this, the composite material plates are heated in an oven 20 then arranged in a mold 15 21 in which they will be formed by application of pressure. The bearing webs thus formed are then cooled. The bearing webs 14 are thus formed by thermocompression, by heating the composite material plates then by deep-drawing them under pressure. In another embodiment, the bearing webs may also be produced by thermoforming i.e. by flux of the composite material plates under 20 conditions of temperature and vacuum. In the embodiments shown in figures 7 to 11, the elements for fixing the bearing webs 14 to the base panel 10 and/or the cover panel 11 are inserted in the mold 21 during forming. Thus the bearing webs 14 are molded over the fixing elements. In other words, the fixing elements are set into the mass of the bearing 25 webs 14 during their forming. In one embodiment, the bearing webs 14 are made from a stack of several composite material plates, and the fixing elements are arranged in the mold 21 sandwiched between two adjacent composite material plates. Thus the fixing elements are suitably set into the mass 5 of the bearing webs 14. 30 In the embodiment shown on figure 7, the bearing webs are pointed metal rods 22 of the staple or nail type, set into the mass of the bearing web 14 during its forming. The metal rods 22 are embedded in the base panel 10 and thus ensure the fixing of the bearing web 14 to the base panel 10. Similarly, the bearing web 14 also 10 has such metal rods 22 along its edge against the cover panel 11, set into the mass of the bearing web 14 and fixed to the cover panel 11. In the embodiment shown on figure 8, the fixing elements set into the mass of the bearing webs 14 are L-shaped fixing tabs 23 arranged laterally on either side 5 of said webs 14. The L-shaped fixing webs 23 each comprise a first wing 24 embedded in the mass of the bearing web 14, and a second wing 25 protruding laterally towards the outside of said bearing web 14. The second wing 25 rests against the base panel 10 and is provided with an opening. Screws 26 pass through said openings and are fixed to the base panel 10 in order to ensure the fixing of the 10 bearing webs 14. Similarly, the edge of the bearing web 14 cooperating with the cover panel 11 may also be fitted with such L-shaped fixing tabs 23. In the embodiment shown on figure 9, the fixing elements set into the mass are bushes 27 with a threaded inner bore. The bushes 27 cooperate with threaded elements, such as screws 28, passing through an opening formed in the base panel 15 10 and opening opposite the bushes 27. Similarly, the other edge of the bearing web 14 may also be provided with such bushes 27. In the embodiment shown on figures 10 and 11, wooden slats 29 extend longitudinally over the entire length of said bearing webs 14 along their load distribution plates 16a, 16b, and are set into the mass of said bearing webs 14. The 20 wooden slats 29 have a rectangular cross-section and comprise a flat surface intended to rest against the cover panel 11 or the base panel 10. In one embodiment, the wooden slats 29 are fixed to the cover panel 11 or base panel 10 by stapling. Thus the staples are not introduced directly into the composite material. In the embodiment in figure 12, the bearing webs 14 are fixed to the base 25 panel 10 and the cover panel 11 by means of nail plates 30 inserted between the cover panel 11 and base panel 10 and the plates 16a, 16b of the bearing web 14. Such a nail plate 30 comprises a carrier plate, a first series 31 of nails installed in the cover panel 10 or the base panel 11, and a second series 32 of nails installed in the plate 16a, 16b of the bearing web 14. 30 In the embodiment in figures 13 and 14, a bearing web 14 is fixed to the base panel 10 and cover panel 11 by rails 33 fixed against the base panel 10 and cover panel 11. The rails are arranged to receive a plate 16a, 16b of the bearing web 14. A rail 33 is formed by two lateral wooden strips 34 allowing lateral guidance 11 of a plate 16a, 16b. Two retaining strips 35 resting against the lateral strips 34 allow the load distribution plate to be retained in a direction perpendicular to the base panel 10 and cover panel 11. In order to allow such an assembly, the bearing webs 14 are firstly interposed between the base panel 10 and cover panel 11 by sliding 5 their plates 16a, 16b into the rails 33, then secondly, when the set of bearing webs 14 has been positioned, the lateral edges 12, 13 of the case 3, 7 may be installed. The embodiment of figure 15 differs from the embodiment of figures 13 and 14 in that the rails 36 are formed by grooves provided directly in the base panel 10 and cover panel 11. 10 In the embodiment of figure 16, the rails 37 formed in the base panel 10 and cover panel 11 take the form of a dovetail. In the embodiment of figures 17 and 18, the bearing webs 14 are fixed by hooks 38, one curved end of which cooperates with the plates of the bearing webs in order to retain the bearing webs against the base panel 10 and cover panel 11. In 15 an embodiment not shown, the hooks 38 are elastic hooks allowing an elastic fitting by "clipping". In the embodiment shown on figure 17, the hooks 38 are rigid and are immobilized in a position for retaining the bearing web 14 by means of wooden wedges 39 which may be introduced through the base panel 10 or cover panel 11. Figure 18 shows an embodiment in which the retaining hooks 38 each 20 comprise two jaws 39, 40 placed on either side, in the thickness direction of the tank, of a tongue 41 protruding laterally from the bearing web 14. In the embodiment of figures 19 and 20, the bearing web 14 is fixed to the base panel 10 or cover panel 11 by a fixing element 42 comprising a cylindrical rod, bearing at its two ends heads with a diameter larger than that of the cylindrical rod. 25 The bearing web 14 bears a metallic part provided with an oblong hole 43 having a short dimension greater than the diameter of the cylindrical rod and smaller than the diameter of the heads, said oblong hole 43 being extended by a circular opening 44 with a diameter greater than that of the head of the fixing element 42. Similarly, the base panel 10 or cover panel 11 opposite has an oblong hole 45 extended by a 30 circular opening 46. The association of the oblong hole 45 and circular opening 46 of the panel 10, 11 is arranged head-to-tail relative to the association of the oblong hole 43 and circular opening 44 provided in the bearing web 14. To ensure assembly, the circular openings 44, 46, carried by the bearing web 14 and base 12 panel 10 or cover panel 11 respectively, are aligned in order to allow passage of a head of the fixing element through the panel 10, 11 and the metal part. Then the bearing web 14 slides relative to the panel 10, 11 in order to capture the cylindrical rod at the ends of the oblong holes 45, 43. 5 In the embodiment of figures 21 to 23, the bearing webs 14 have openings through which pins 47 are inserted. The pins 47 have two ends which are arranged on either side of said bearing web 14 and have grooves cooperating with the staples 48 fixed in the base panel 10 or cover panel 11, in order to ensure the fixing of the pins 47. 10 In the embodiment of figures 24 to 27, wooden wedges 49 are arranged on either side of the bearing web 14 and fixed to the base panel 10 or cover panel 11 in order to wedge the bearing web 14 laterally. In the embodiment shown, the plates 16a, 16b have undulations. Thus the wedges 49 have an undulating form complementary to the undulations of the plates 16a, 16b, so as to immobilize the 15 movement of the bearing web 14 in its longitudinal direction. Finally, in order to block the movement of the bearing web 14 in a direction perpendicular to the base panel 10 and cover panel 11, the wedges 49 may have a protruding portion 50 cooperating with a cavity of complementary form arranged in the bearing web 14. On the embodiment shown, the protruding part has the form of a dovetail. In another 20 embodiment, the protruding portion may also protrude above the lower plate 16b or below the upper plate 16a, so as to hold the upper plate 16a or lower plate 16b respectively against the base panel 10 or cover panel 11. The heat-insulating lining may be positioned in the compartments 15 provided between the bearing webs 14 after the bearing webs 14 have been fixed to 25 the cover panel 11 and base panel 10. However, the order in which this step is performed is irrelevant. In particular, it is also possible to pre-assemble the heat insulating lining and the bearing webs 14, and then fix the bearing webs 14 to the base panel 10 and cover panel 11. According to another embodiment, it is also possible to fix the bearing webs 14 to one of the base panel 10 or cover panel 11, 30 then line the compartments 15 provided between the bearing webs 14, for example by projection of foam, then close the self-supporting case by fixing the other of the base panel 10 or cover panel 11 to the bearing webs 14.

13 The technique described above for production of a self-supporting case may be used in various types of tank, for example to produce the primary thermal insulation barrier and/or the secondary thermal insulation barrier of an LNG tank in a land-based installation or in a floating structure, such as an LNG tanker or similar. 5 With reference to figure 28, a simplified view of an LNG tanker 70 shows a fluid-tight and insulated tank 71 of generally prismatic form, mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary fluid-tight barrier intended to come into contact with the LNG contained in the tank, a secondary fluid tight barrier arranged between the first fluid-tight barrier and the double hull 72 of the 10 ship, and two thermal insulation barriers arranged respectively between the primary fluid-tight barrier and the secondary fluid-tight barrier, and between the secondary fluid-tight barrier and the double hull 72. In a manner known in itself, loading/unloading pipelines 73 arranged on the upper deck of the ship may be connected by means of suitable connectors to a 15 floating or port-based terminal, in order to transfer a cargo of LNG from or to the tank 71. Figure 28 shows an example of a floating terminal comprising a loading and unloading station 75, an underwater pipeline 76, and a land-based installation 77. The loading and unloading station 75 is a fixed offshore installation comprising a 20 mobile arm 74 and a tower 78 which supports the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible hoses 79 which can connect to the loading/unloading pipelines 73. The orientable mobile arm 74 can be adapted to all sizes of tanker. A connecting pipe (not shown) extends inside the tower 78. The loading and unloading station 75 allows the tanker 70 to be loaded or unloaded from 25 or to a land-based installation 77. This comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipeline 76 to the loading or unloading station 75. The underwater pipeline 76 allows the transfer of liquefied gas between the loading or unloading station 75 and the land-based installation 77 over a great distance, for example 5 km, which allows the LNG tanker 70 to remain at a 30 great distance from the coast during the loading and unloading operations. To create the pressure necessary for the transfer of liquefied gas, on-board pumps in the ship 70 are used, and/or pumps installed in the land-based installation 77, and/or pumps fitted to the loading and unloading station 75.

14 Although the invention has been described in connection with several particular embodiments, it is evident that it is in no way limited thereto and comprises all technical equivalents of the means described and their combinations if these fall within the scope of the invention. 5 The use of the verb "comprise" or "contain" or "include" and its conjugated forms does not exclude the presence of elements or steps other than those stated in a claim. The use of the indefinite article "a" for an element of step does not, unless specified otherwise, exclude the presence of a plurality of such elements or steps. In the claims, any reference symbol in brackets should not be interpreted 10 as a limitation of the claim.

Claims

1. A method for producing a self-supporting case (3, 7) intended to provide thermal insulation for a fluid-storage tank with a fluid-tight membrane, said method comprising: 5 - a step of supplying a base panel (10) and a cover panel (11); - a step of producing a plurality of bearing webs (14), said production step comprising, for each bearing web (14): o arrangement of a composite material in a mold (21), said material comprising a fiber-reinforced plastic matrix; 10 o insertion of fixing elements (22, 23, 27, 29) intended for fixing the bearing web (14) to the base panel (10) and/or to the cover panel (11), inside the mold (21); o forming of the composite material, during which step the fixing elements (22, 23, 27, 29) are set in the mass of said bearing web (14); 15 - interposing the bearing webs (14) between the base panel (10) and the cover panel (11) such that the base panel (10) and the cover panel (11) are spaced apart in a thickness direction of the case (3, 7) and the bearing webs (14) extend in the thickness direction, and fixing the bearing webs (14) to the base panel (10) and/or to the cover panel (14) by means of said fixing elements (22, 23, 27, 29); 20 - lining the plurality of compartments (15) arranged between the bearing webs (14) with a heat-insulating lining.

2. The production method as claimed in claim 1, wherein during production of a bearing web (14): - a plurality of plates of composite material is arranged in the mold (21); and 25 - the fixing elements (22, 23, 27, 29) are arranged between two adjacent plates of composite material.

3. A self-supporting case (3, 7) intended for thermal insulation of a fluid storage tank with a fluid-tight membrane, said case (3, 7) comprising: - a base panel (10) and a cover panel (11) spaced apart in a thickness 30 direction of the case (3, 7), - a plurality of bearing webs (14) interposed between said base panel (10) and said cover panel (11) and extending in the thickness direction so as to define a plurality of compartments (15), and 16 - a heat-insulating lining extending inside said compartments (15) arranged between the bearing webs (14), wherein the bearing webs (14) are produced by forming of a composite material, comprising a fiber-reinforced thermoplastic matrix and having elements (22, 23, 27, 5 29) for fixing to the base panel (10) and/or the cover panel (11), set into the mass of the bearing webs (14) during their forming.

4. The case (3, 7) as claimed in claim 3, wherein the fixing elements are pointed metal rods (22) set into the mass of the bearing webs (14), each of the metal rods (22) being embedded in the base panel (10) or in the cover panel (11). 10

5. The case (3, 7) as claimed in claim 3, wherein the fixing elements are bushes (27) comprising a threaded inner bore and each cooperating with a threaded element (28) passing through the base panel (10) or the cover panel (11).

6. The case (3, 7) as claimed in claim 3, wherein the fixing elements are wooden slats (29) set into the mass of the bearing webs (14), each of the wooden 15 slats being fixed against the base panel (10) or the cover panel (11).

7. The case (3, 7) as claimed in 6, wherein the wooden slats (29) are fixed against the base panel or against the cover panel by staples.

8. The case (3, 7) as claimed in 3, wherein the fixing elements are L-shaped fixing tabs (23) each with a wing (24) embedded in the mass of the bearing web (14) 20 and a wing (25) extending against the base panel (10) or the cover panel (11) and provided with an opening allowing passage of a screw (26) fixed to the base panel (10) or the cover panel (11).

9. The case (3, 7) as claimed in any of claims 3 to 8, wherein the bearing webs (14) have load distribution plates (16a, 16b) extending along the two edges of 25 said bearing webs (14) arranged facing the base panel (10) and the cover panel (10) respectively, and wherein the fixing elements (22, 23, 27, 29) for the base panel and/or the cover panel are set into the mass of the bearing webs (14) at the load distribution plates (16a, 16b).

10. The case (3, 7) as claimed in any of claims 3 to 9, wherein the bearing 30 webs (14) have a plurality of undulations, the axis of which extends perpendicular to the base panel (10) and cover panel (11). 17

11. A fluid-tight, thermally insulated fluid-storage tank comprising a thermal insulation barrier (2, 6) comprising a plurality of cases (3, 7) as claimed in any of claims 3 to 10 arranged next to each other, and a sealing membrane (5, 9) resting against the thermal insulation barrier. 5

12. A ship (70) for transporting a fluid, ship comprising a double hull (72) and a tank (71) as claimed in claim 11, arranged in the double hull.

13. A method for loading or unloading a ship (70) as claimed in claim 12, wherein a fluid is conducted through insulated pipelines (73, 79, 76, 81) from or to a floating or land-based storage installation (77) to or from the ship's tank (71). 10

14. A system for transferring a fluid, the system comprising a ship (70) as claimed in claim 12, insulated pipelines (73, 79, 76, 81) arranged so as to connect the tank (71) installed in the ship's hull to a floating or land-based storage installation (77), and a pump for driving a fluid through insulated pipelines from or to the floating or land-based storage installation to or from the ship's tank.