METHOD FOR MANUFACTURING A WALL OF A SEALED AND THERMALLY INSULATING TANK HAVING INTER-PANEL INSULATING INSERTS

Abstract

The invention relates to a method for manufacturing a sealed and thermally insulating tank wall comprising: providing a thermally insulating barrier comprising two insulating panels delimiting an inter-panel space, providing an insulating insert comprising a wrapper completely covering an insulating core, inserting a suction nozzle of a suction system into the insulating insert through an orifice in the wrapper, applying a vacuum pressure in the insulating insert so as to reduce the thickness of the insulating insert through vacuum pressure, inserting the insulating insert into the inter-panel space while maintaining the suction of the suction system, when the insulating insert has been inserted into the inter-panel space, removing the suction nozzle from the insulating insert.

Claims

1. A method for manufacturing a tank wall, said method comprising the steps of: providing a sealed and thermally insulating tank wall thermally insulating barrier, said thermally insulating barrier comprising a plurality of insulating panels juxtaposed in a regular pattern, the mutually facing lateral faces of two adjacent insulating panels delimiting an inter-panel space separating said two adjacent insulating panels, providing a parallelepipedal insulating insert comprising an insulating core, said insulating insert comprising a wrapper completely covering the insulating core, inserting a suction nozzle of a suction system into the insulating insert through an orifice in the wrapper, applying a vacuum pressure in the insulating insert so as to reduce the thickness of said insulating insert through vacuum pressure, inserting the insulating insert into the inter-panel space while maintaining the suction of the suction system in order to maintain the vacuum pressure during the step of inserting said insulating insert into the inter-panel space, when the insulating insert has been inserted into the inter-panel space, removing the suction nozzle from the insulating insert so that the interior space of the wrapper is in communication with ambient pressure via the orifice in the wrapper.

2. The method as claimed in claim 1, wherein the reduction in thickness of the insulating insert is such that the insulating insert exhibits a thickness smaller than the width of the inter-panel space.

3. The method as claimed in claim 1, wherein the suction nozzle of the suction system is configured to puncture the wrapper of the insulating insert, the step of inserting the suction nozzle into the insulating insert comprising a step of puncturing the wrapper using said suction nozzle of the suction system.

4. The method as claimed in claim 1, wherein the suction nozzle comprises a flange, the step of inserting the suction nozzle of the suction system into the insulating insert comprising the step of bringing the flange to bear against the wrapper.

5. The method as claimed in claim 1, wherein the insulating core of the insulating insert comprises at least a central portion of layered glass wool, said central portion of layered glass wool comprising a plurality of laps of fibers superposed in a direction of layering, and wherein the suction nozzle is inserted into the insulating insert at an edge face of the insulating insert.

6. The method as claimed in claim 5, wherein the insulating core comprises separators arranged parallel to the direction of layering of the central portion, the insulating insert being inserted into the inter-panel space in such a way as to arrange said separators parallel to the support surface formed by the thermally insulating barrier.

7. The method as claimed in claim 5, wherein a lengthwise direction of the insulating core extends in a lengthwise direction of the inter-panel space and said insulating core comprises, at least at one of the longitudinal ends of the central portion, at least an end portion comprising layered glass wool, said end portion comprising laps of fibers superposed in a direction of layering parallel to the lengthwise direction of the insulating insert.

8. The method as claimed in claim 5, wherein a lengthwise direction of the insulating insert extends in a lengthwise direction of the inter-panel space and said insulating insert comprises, at least at one of the longitudinal ends, at least one end piece comprising layered glass wool comprising laps of fibers superposed in a direction of layering parallel to the lengthwise direction of the insulating insert, said end piece being separated from the insulating core by the wrapper.

9. The method as claimed in claim 1, wherein the wrapper comprises a plurality of wrapper portions bonded to one another and/or bonded to the insulating core.

10. The method as claimed in claim 1, wherein at least a portion of the wrapper comprises a material selected from sheets of polymer, composite sheets including mineral fibers and a polymer matrix, composite sheets including mineral fibers bonded to a sheet of paper or of polymer, and combinations thereof.

11. The method as claimed in claim 10, wherein said sheet of polymer or said composite sheet is bonded to the insulating core by a coat of adhesive located between said sheet of polymer or said composite sheet and the insulating core.

12. The method as claimed in claim 1, wherein the wrapper comprises planar wrapper portions extending perpendicular to the widthwise direction of the inter-panel space on each side of the insulating core.

13. The method as claimed in claim 12, wherein at least one of the planar wrapper portions comprises a composite sheet including mineral fibers and a polymer matrix.

14. The method as claimed in claim 13, wherein the composite sheet is covered with a sheet of polymer.

15. The method as claimed in claim 13, wherein the composite sheet is covered with a sheet of paper.

16. The method as claimed in claim 12, wherein at least one of the planar wrapper portions comprises kraft paper.

17. The method as claimed in claim 12, wherein the wrapper comprises an edge-face wrapper portion extending in the widthwise direction of the inter-panel space between the planar wrapper portions situated on each side of the insulating core, said edge-face wrapper portion being located along all or part of the perimeter of the insulating core.

18. The method as claimed in claim 17, wherein the edge-face portion comprises kraft paper.

19. The method as claimed in claim 17, wherein the edge-face portion comprises a sheet of polymer.

20. The method as claimed in claim 1, wherein the insulating insert is inserted into the inter-panel space with a face through which the suction nozzle of the suction system passes facing toward the inside of the tank.

21. The method as claimed in claim 1, wherein the wrapper exhibits a leakage flow rate less than the pumping flow rate of the suction system.

22. The method as claimed in claim 1, wherein, in the insertion step, the insulating insert is guided into the inter-panel space by means of a rigid guide in the form of plates.

23. The method as claimed in claim 1, further comprising the step of cutting at least one of the lateral faces of the wrapper after the insulating insert has been inserted into the inter-panel space.

24. The method as claimed in claim 1, wherein the suction system is a vacuum pump or a vacuum generator using a Venturi system.

25. The method as claimed in claim 24, wherein the suction system exhibits a pumping flow rate of between 8 m.sup.3/h and 30 m.sup.3/h, preferably 15 m.sup.3/h.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0109] The invention will be better understood and further objects, details, features and advantages thereof will become more clearly apparent during the course of the following description of a number of particular embodiments of the invention, which are given purely by way of nonlimiting illustration and with reference to the attached drawings.

[0110] FIG. 1 is an exploded schematic perspective view of an insulating insert intended to be inserted between two insulating panels of a thermally insulating barrier of a sealed and thermally insulating tank;

[0111] FIG. 2 is a schematic perspective view of the insulating insert of FIG. 1, in the assembled state;

[0112] FIG. 3 is a schematic view in section of the insulating insert of FIG. 1;

[0113] FIG. 4 is a schematic perspective view of a facility for manufacturing layered glass wool;

[0114] FIG. 5 is a schematic perspective view of a vacuum pump nozzle as it is being inserted into an insulating insert of FIG. 1;

[0115] FIG. 6 is a schematic perspective view of the insulating insert of FIG. 2 associated with a vacuum pump, in which view the end of the vacuum pump nozzle is inserted in said insulating insert;

[0116] FIG. 7 is a schematic perspective view of the insulating insert of FIG. 5 as it is being inserted into the inter-panel space separating two adjacent panels of a thermally insulating barrier of a sealed and thermally insulating tank;

[0117] FIG. 8 is an exploded schematic perspective view of an insulating insert according to an embodiment variant;

[0118] FIG. 9 is a view in section through an insulating insert according to another embodiment variant;

[0119] FIG. 10 is a schematic depiction with cutaway of a tank of a methane carrier ship and of a terminal for loading/offloading from this tank;

[0120] FIG. 11 is a schematic depiction of an insulating insert during the process of being inserted into an inter-panel space by means of a rigid guide;

[0121] FIG. 12 is a partial detailed view of FIG. 11;

[0122] FIG. 13 is an exploded perspective view of one embodiment of the insulating insert, in which the core comprises a central portion and an end portion of layered glass wool;

[0123] FIG. 14 is a view in section of an insulating insert according to an embodiment variant;

[0124] FIG. 15 is a schematic perspective view of the insulating insert comprising a core covered by a wrapper and an end portion of layered glass wool;

[0125] FIG. 16 is a view similar to FIG. 3 showing another embodiment of the wrapper.

DETAILED DESCRIPTION OF EMBODIMENTS

[0126] A sealed and thermally insulating tank for storing and transporting a cryogenic fluid, for example liquefied natural gas (LNG) comprises a plurality of tank walls each having a multilayer structure.

[0127] Such sealed and thermally insulating tank walls exhibit, from the outside to the inside of the tank, a secondary thermally insulating barrier resting against a bearing structure, a secondary sealing membrane resting against the secondary thermally insulating barrier, a primary thermally insulating barrier resting against the secondary sealing membrane and a primary sealing membrane intended to be in contact with the liquefied gas contained in the tank.

[0128] The bearing structure may notably be a self-supporting metal sheet or, more generally, any type of rigid partition exhibiting suitable mechanical properties. The bearing structure may notably be formed by the hull or the double hull of a ship. The bearing structure comprises a plurality of walls defining the overall shape of the tank, usually a polyhedral shape.

[0129] Furthermore, the thermally insulating barriers may be produced in numerous ways, from numerous materials. Such thermally insulating barriers each comprise a plurality of insulating panels of parallelepipedal shape juxtaposed in a regular pattern. The insulating panels of these thermally insulating barriers jointly form planar support surfaces for the sealing membranes. Such insulating panels are, for example, made from blocks of polyurethane foam. Such insulating panels made of blocks of polyurethane foam may further comprise a top sheet and/or a bottom sheet, for example made of plywood.

[0130] By way of example, such tanks are described in patent applications WO14057221 or FR2691520.

[0131] The juxtaposition of the insulating panels to form a thermally insulating barrier generates the presence of inter-panel spaces between two adjacent insulating panels 3. In other words, an inter-panel space 2 separates the mutually facing lateral faces of two adjacent insulating panels 3 (see FIG. 7). To ensure the continuity of the insulation in the thermally insulating barrier, an insulating insert 1 is inserted into the inter-panel space 2 separating the two mutually facing lateral faces of the two adjacent insulating panels 3. FIGS. 1 to 3 illustrate such an insulating insert 1.

[0132] The insulating insert 1 comprises an insulating core 4 covered by a wrapper 5. This insulating insert 1 exhibits a parallelepipedal shape corresponding to the parallelepipedal shape of the inter-panel space 2 and defining the shape of the insulating insert 1. Thus, this insulating insert 1 comprises two planar large faces 6 which are parallel. These two planar large faces 6 define a lengthwise direction 7 of the insulating insert 1 and a widthwise direction 8 of the insulating insert 1. Edge faces 9 which extend in a thickness direction 10 of the insulating insert 1 connect the sides of the large faces 6.

[0133] The insulating core 4 has a central portion 11 made of glass wool. The glass wool employed is a layered glass wool, which is to say that the production method results in a mat of glass wool which is made up of multiple interlaid parallel laps visible to the naked eye which are superposed in a direction of layering 12. In other words, the fibers are very predominantly oriented in planes perpendicular to the direction of layering 12.

[0134] Such a layered glass wool can be obtained for example by a manufacturing method using a horizontal conveyor belt 13, illustrated schematically in FIG. 4. In such a manufacturing method, sand and crushed glass are melted in a furnace 14 the temperature of which is for example from 1300 to 1500° C. The molten sand and crushed glass are then converted into fibers by spinning using rapid rotation. A binder is added to these fibers and the entity thus obtained is received on the horizontal conveyor belt 13 to pass through a polymerization oven 15 intended to polymerize the binder. In that case, the fibers are essentially parallel to the conveyor belt 13. The direction of layering corresponds to the vertical direction in the production tool because the layering is the result of the effect of gravity. Other production methods for producing a layered glass wool are conceivable.

[0135] In the embodiment illustrated in FIGS. 1 to 3, the glass wool of the core 4 exhibits a density of 22 or 35 or 40 kg/m.sup.3.

[0136] In this embodiment, the core 4 is made up entirely of its central portion 11 of glass wool layered in the direction 12. The core 4 comprises glass wool sections 16 separated by separators 17. Such separators 17 extend perpendicular to the widthwise direction 8 of the insulating insert 1. These separators 17 extend over the entire length 7 and through the entire thickness 10 of the insulating insert 1. The separators 17 are advantageously bonded to the glass wool sections 16 separated by said separators 17.

[0137] FIG. 1 thus illustrates a core 4 comprising four glass wool sections 16 separated in the widthwise direction 8 of the insulating insert 1 by three separators 17. FIG. 1 constitutes a preferred solution regarding the number of separators, namely the minimum number of separators in order not to have convection when the temperature gradient is higher than 100° C. FIG. 3 illustrates an embodiment variant in which the core 4 comprises three sections 16 separated in the widthwise direction 8 of the insulating insert 1 by two separators 17.

[0138] The glass wool is arranged in the core 4 in such a way as to exhibit a direction of layering 12 perpendicular to the width 8 of the insulating insert 1. In other words, the laps of fibers that make up the glass wool are arranged substantially parallel to the widthwise direction 8 of the insulating insert 1.

[0139] As a preference, the glass wool is arranged in the core 4 with a direction of layering 12 parallel to the thickness direction 10 of the insulating insert 1, which is to say that the laps of fibers of the glass wool are substantially parallel to the large faces 6 of the insulating insert 1. In other words, the laps of fibers that make up the glass wool are arranged substantially parallel to the widthwise direction 8 and to the lengthwise direction 7 of the insulating insert 1. In an alternative embodiment shown in FIG. 13, the insulating core comprises, at least at one of the longitudinal ends of the central portion 11, an end portion 50 made of layered glass wool. This end portion, manufactured using the same method as the glass wool of the central portion 11, is also made up of superposed laps of fibers, but its direction of layering differs from that of the glass wool of the central portion 11: it is parallel to the lengthwise direction 7 of the insulating insert 1. Such an end portion gives the insulating core better longitudinal compressibility so that several insulating inserts 1 arranged end to end between two insulating panels 3 can be mounted perfectly contiguously. The end portion 50 may for example exhibit a dimension of 1 cm in the direction of its direction of layering, namely along the length of the insulating insert 1. This dimension may be reduced to 5 mm when the end portion 50 is evacuated, thanks to the compressibility its structure confers upon it in the lengthwise direction of the insulating insert 1.

[0140] In another alternative embodiment, depicted in FIG. 15, the insulating insert 1 comprises an insulating core consisting only of a central portion 11 of layered glass wool like that described in the first embodiment, and covered by a wrapper 5, and the insulating core also comprises, at least at one of its longitudinal ends, an end piece 51 situated outside the wrapper 5. This end piece 51 is made of layered glass wool and exhibits the same technical features as the end portion 51 described hereinabove. Further, the glass wool of the end piece 50 exhibits a density of 20 or 35 or 40 kg/m.sup.3.

[0141] As illustrated in FIG. 1, the wrapper 5 comprises a plurality of wrapper portions. More particularly, the wrapper 5 comprises planar wrapper portions 18, rectilinear edge-face wrapper portions 19 and corner edge-face wrapper portions 20. These wrapper portions 18, 19, 20 are fixed to the core 4, for example by bonding.

[0142] The planar wrapper portions 18 cover the core 4 and form the large faces 6 of the insulating insert 1. These planar wrapper portions 18 are of rectangular shape and have dimensions substantially identical to the dimensions of the core 4 on its large faces.

[0143] The rectilinear edge-face wrapper portions 19 comprise a central section of rectangular shape covering a corresponding edge face of the core 4. The central section forms a corresponding edge face 9 of the insulating insert 1. The rectilinear edge-face wrapper portions 19 also comprise, on each side of the central section, a return 21. These returns 21 extend from longitudinal sides of the central portion. These returns 21 extend parallel to a respective planar wrapper portion 18 so as to overlap an edge margin of said planar wrapper portion 18. These returns 21 are bonded to said edge margins of planar wrapper portions 18. In other words, the rectilinear edge-face wrapper portions 19 form an edge face 9 of the insulating insert 1 and also overlap the core 4 at the edge corners 22 that connect said edge face 9 and the large faces 6.

[0144] The corner edge-face wrapper portions 20 overlap the rectilinear edge-face wrapper portions 19 that form two adjacent edge faces 9 of the insulating insert 1. In other words, these corner edge-face wrapper portions 20 overlap the edges of the core 4 at the junction where two edge faces 9 of the insulating insert 1 meet. In a similar way to the returns 21 of the edge-face wrapper portions 19, the corner edge-face wrapper portions 20 have corner returns 23 extending parallel to and overlapping the ends of the returns 21 of the corresponding edge-face wrapper portions 19. The corner edge-face wrapper portions 20 are bonded to the edge-face wrapper portions 19 that they overlap.

[0145] Thus, the various wrapper portions 18, 19, 20 are bonded together and to the glass wool to form a continuous wrapper 5 completely surrounding the core 4. In an embodiment which has not been illustrated, the portions 18 and 19 placed on the bottom and the top may be produced as a single piece of kraft. In another embodiment, the wrapper 5 completely surrounds the core 4 without being bonded thereto.

[0146] In a first embodiment, the wrapper 5 is made of kraft paper. Such a kraft paper offers a low coefficient of friction, thus allowing the insulating insert 1 to slide into the inter-panel space 2 as it is being inserted into said inter-panel space 2. Furthermore, such a kraft paper has a coefficient of thermal contraction of the order of 5 to 20×10.sup.−6/K. Thus, such a kraft paper exhibits a coefficient of thermal contraction similar to that of the insulating core 4 placed in the inter-panel space. Thus, the insulating insert 1 exhibits uniform behavior towards cold. Specifically, the insulating core 4 has no risk of deforming under the effect of compression associated with the thermal contraction of the wrapper 5. In particular, there is no risk of the insulating core 4 deforming to adopt a wavy shape under the effect of this compression, such a wavy shape generating within the inter-panel space 2 voids that encourage convection and are therefore detrimental to the insulating properties of the thermally insulating barrier.

[0147] The kraft paper of the wrapper 5 exhibits a grammage higher than 60 g/m.sup.2 in order to avoid risks of the wrapper 5 tearing when the insulating insert 1 is being inserted into the inter-panel space. Further, this kraft paper exhibits a grammage lower than 150 g/m.sup.2 so that the wrapper 5 retains enough flexibility to allow the insulating insert 1 to deform in compression, and preferably of between 70 and 100 g/m.sup.2.

[0148] In an alternative embodiment, all or certain parts of the wrapper 5, for example the planar wrapper portions 18, are sheets of composite material made up of a fabric or mat of mineral fibers, for example glass and basalt fibers, and of a polymer matrix. If appropriate, other parts of the wrapper 5, for example the edge-face portions 19, 20, may be made of a kraft paper with the same characteristics as the paper used for the wrapper described in the first embodiment. The kraft paper used for the edge-face portions 19, 20 may be adhesive.

[0149] Such a composite material possesses better dimensional stability than kraft paper as it is less sensitive to moisture. In addition, the use of a fabric or mat of mineral fibers in addition to the polymer matrix makes it possible to obtain a coefficient of thermal contraction similar to that of the glass wool, so that the behavior of the insulating insert 1 towards cold is uniform. Specifically, if the wrapper is made only of polymer material, there is a risk that it will have far greater dimensional variations than the glass wool during the temperature variations to which the wall of the tank is subjected, especially when this temperature gradient may reach high values in excess of 100° C. Now, it is possible to choose a fabric or mat of glass fibers that is such that the difference between its coefficient of thermal contraction and that of the glass wool is less than 5×10.sup.−6 K.sup.−1. Thus, in this embodiment, the mineral fiber fabric used to make the composite material of which the planar wrapper portions 18 are made may for example exhibit a coefficient of thermal contraction of the order of 10.sup.−5 K.sup.−1 in the lengthwise direction whereas that of the glass wool of the central portion 11 of the insulating core is between 5×10.sup.−6 K.sup.−1 and 8×10.sup.−6 K.sup.−1 in the direction in which it is measured.

[0150] The polymer matrix may be incorporated into the composite sheet according to the following two examples. In the first example, the fabric of glass or basalt fibers is impregnated or coated with polymer matrix, the latter being selected from among solvated adhesives, polyurethane, silicone, rubber, epoxides or the like. As a preference, the surface density of the composite sheet is between 50 and 400 g/m.sup.2 and its thickness is between 25 and 500 μm.

[0151] In a second example, the fabric of glass or basalt fibers is covered with a sheet of polymer bonded, for example, using a spot bonding or fusion bonding method. This sheet of polymer may be a plastic resin selected from polyethylene, polypropylene, polyethylene terephthalate and polyvinyl chloride. The density of polymer matrix after drying is for example between 0.8 and 1.4. The thickness of the sheet of polymer may be between 25 and 50 μm, which corresponds to a surface density of, for example, between 20 and 40 g/m.sup.2.

[0152] In another embodiment, all or certain parts of the wrapper, for example the planar wrapper portions 18, are sheets of composite material made up of a fabric or mat of mineral fibers, for example glass and basalt fibers, bonded to a sheet of paper.

[0153] In another embodiment illustrated in FIG. 16, the planar wrapper portions 18 are sheets of composite material comprising a fabric or mat of mineral fibers, for example glass and basalt fibers, and a polymer matrix. These composite sheets are covered with a sheet of paper 52 on their exterior face, namely the face oriented toward the insulating panel. In this embodiment, the sheet of paper 52 covering the composite sheet is bonded to the composite sheet that constitutes the planar wrapper portion 18, and the internal face of the return 21 is also bonded to the sheet of paper 52.

[0154] Relative fluid-tightness is enough for the method described hereinbelow to be able to be employed for inserting the insulating insert 1 into the inter-panel space. The composite sheet as described, where appropriate covered with a sheet of polymer or of paper in addition, allows this relative fluid-tightness to be obtained.

[0155] In another alternative embodiment, the planar wrapper portions 18 are made of composite material and the edge-face wrapper portions 19, 20 are made of adhesive tape. This allows the dimensional stability toward moisture, and the fluid-tightness of the wrapper, to be improved still further.

[0156] The method for inserting the insulating insert 1 into the inter-panel space is described hereinafter with reference to FIGS. 5 to 7.

[0157] First of all, an insulating insert 1 exhibiting the structure as described hereinabove with reference to FIGS. 1 to 3 is provided. This insulating insert 1 exhibits a shape that complements that of the inter-panel space 2, typically a parallelepipedal shape as described hereinabove.

[0158] This insertion method employs a suction system. Such a suction system is, in the remainder of the description and by way of example, a vacuum pump 24 as illustrated in FIGS. 6 and 7. In an embodiment which has not been illustrated, such a suction system is a vacuum generator using a Venturi system. Such a vacuum pump 24 is connected to a suction nozzle 25 via a pumping hose 26. This suction nozzle 25 exhibits a flange 27 of planar circular shape. The suction nozzle 25 exhibits a frustoconical shape so that it has an opposite end to the pumping hose 26 that is capable of puncturing the wrapper 5. Thus, the suction nozzle 25 and, more particularly, its puncturing end, is inserted into the insulating insert 1, puncturing the wrapper 5. This puncturing of the wrapper 5 generates a suction orifice 28 in the insulating insert 1.

[0159] The suction nozzle 25 is inserted into the insulating insert 1 through the wrapper 5 at an edge face 9 that is intended to face toward the inside of the sealed and thermally insulating tank.

[0160] As a preference, the suction nozzle 25 is inserted into the insulating insert 1 on an edge face 9 perpendicular to the direction of layering 12 of the glass wool of the central portion 11.

[0161] Furthermore, the suction nozzle 25 is inserted into the insulating insert 1 until the flange 27 is brought into contact with the wrapper 5.

[0162] Once the suction nozzle 25 has been inserted into the insulating insert 1 and correctly positioned, which is to say once the flange 27 is in contact with the wrapper 5, the vacuum pump 24 is actuated in order to generate a vacuum pressure in the insulating insert 1.

[0163] Advantageously, the wrapper 5 exhibits sufficient fluid-tightness for this, despite the porosity of the materials of which it may be made, such as, for example, kraft paper or a composite material made up of a fabric or mat of mineral fibers and a polymer matrix, and the bonded joints between the various wrapper portions 18, 19, 20. Thanks to this relative fluid-tightness, the pumping flow rate of the vacuum pump 24 is enough to create a vacuum pressure in the wrapper 5. Further, the pressing of the flange 27 against the wrapper 5 limits the leakage flow rate from the wrapper 5 at the orifice 28 through which the suction nozzle 25 passes. Thus, the wrapper 5 exhibits a leakage flow rate that is lower than the pumping flow rate of the vacuum pump 24 so that the suction produced by the vacuum pump 24 generates a vacuum pressure in the insulating insert 1. In other words, the head losses of the wrapper which are due to the porosity of the materials, possible imperfect bonding at the joins between the wrapper portions 18, 19, 20 and any leaking that may occur at the orifice 28 made in the wrapper for the insertion of the suction nozzle 25 are lower than the head losses created by the vacuum pump 25 and its suction nozzle 24, thereby allowing a vacuum pressure to be generated in the insulating insert 1.

[0164] The suction generated by the vacuum pump 24 has a suction flow rate of between 8 and 30 m3/h. As a preference, the pumping flow rate is 15 m.sup.3/h and such a pumping flow rate of the vacuum pump 24 allows a vacuum pressure to be generated in the insulating insert 1 without the risk of the kraft paper wrapper 5 being damaged by too great a suction flow rate.

[0165] As a preference, the vacuum pump 24 comprises a filter to filter any glass wool fibers and dust from the central portion 11 that might be drawn up by the vacuum pump 24.

[0166] Furthermore, the suction produced by the vacuum pump is advantageously facilitated by inserting the suction nozzle 25 on a face situated on the edge face 9 of the insulating insert 1 parallel to the direction of layering 12 of the glass wool of the central portion 11. Specifically, inserting the suction nozzle 25 via such a face situated on the edge face 9 of the insulating insert 1 allows suction without head loss associated with the layering of the various laps of fibers that constitute the glass wool of the central portion 11.

[0167] Furthermore, an arrangement whereby the glass wool of the central portion 11 has a direction of layering 12 parallel to the thickness direction 10 of the insulating insert 1 allows the insulating insert 1 to be compressed by vacuum pressure in said thickness direction 10 more easily. In a preferred embodiment, the longitudinal compression of the insulating insert 1 is also made easier by the end portion or portions 50 of glass wool layered in the lengthwise direction of the insulating insert 1.

[0168] The presence of separators 17 in the core 4 makes the insulating insert 1 more rigid so that the compression of said insulating insert 1 becomes uniform.

[0169] The vacuum pressure in the insulating insert 1 produces a compression of the glass wool and therefore of the insulating insert 1. This compression of the glass wool 1 allows a reduction in thickness of the insulating insert 1. Typically, the insulating insert 1 is dimensioned to exhibit, in the unconstrained state, i.e. when not compressed, a thickness greater than or equal to the width of the inter-panel space 2 and, in the compressed state, a thickness smaller than said width of the inter-panel space 2. For example, in the context of an inter-panel space 2 of between 33 mm and 27 mm, the insulating insert 1 is dimensioned to exhibit an initial thickness, which is to say a thickness in the unconstrained state, of 35 mm and, in a compressed state, a thickness of 25 mm.

[0170] The insulating insert 1 is then inserted into the inter-panel space 2 between two adjacent insulating panels 3 of the thermally insulating barrier. As illustrated in FIG. 7 by the arrows 29, the insulating insert 1 is inserted into the inter-panel space 2 with its large faces 6 parallel to the lateral faces of the adjacent insulating panels 3 delimiting the inter-panel space 2. During this insertion, the suction nozzle 25 is kept in the insulating insert 1 and the vacuum pump 27 continuously generates a vacuum pressure in said insulating insert 1 in order to keep the insulating insert 1 in its compressed state. Keeping the insulating insert 1 in its compressed state makes it easier to insert it into the inter-panel space 2 because the insulating insert 1 then has a thickness smaller than the width of the inter-panel space 2.

[0171] The insulating insert 1 is inserted into the inter-panel space 2 in such a way that the edge face 9 through which the suction nozzle 25 passes faces toward the inside of the tank, thus making the assembly formed by the insulating insert 1 and the suction nozzle 25 easier to handle. Further, the insulating insert 1 is advantageously inserted into the inter-panel space 1 with a direction of stratification 12 parallel to the width of the inter-panel space 2. Moreover, the separators 17 are advantageously arranged in the insulating insert 1 in such a way as to be parallel to the support surface 30 formed by the insulating panels 3. In FIG. 7, such insulating panels 3 comprise a block of polyurethane foam 31 covered by a sheet of plywood 32 forming the support surface 30. Such an arrangement of the separators 17 limits convection through the glass wool of the central portion 11 in the tank wall.

[0172] Once the insulating insert 1 has been correctly positioned in the inter-panel space 2, the suction nozzle 25 is removed from the insulating insert 1. From that moment, the inside of the wrapper 5 is in communication with the external environment via the orifice 28. This communication allows the glass wool, because the vacuum pressure is no longer maintained in the insulating insert 1, to expand in the absence of a compressive constraint. The expansion of the glass wool increases the thickness of the insulating insert 1 so that the insulating insert 1 completely fills the inter-panel space 2, thus ensuring good continuity of the insulation of the thermally insulating barrier.

[0173] In an embodiment illustrated in FIGS. 11 and 12, a rigid guidance system may be used as a guide tool when inserting the insulating insert 1 into the inter-panel space 2.

[0174] Such a guidance system comprises a first rigid plate 33 and a second rigid plate 37. These two rigid plates 33, 37 are each of L-shaped cross section, the L being formed by a rectangular large face 38 and a return 39 extending perpendicular to the large face 38.

[0175] The large face 38 exhibits dimensions similar to the dimensions of the planar large faces 6 of the insulating insert 1.

[0176] An internal face of the return 39 of the first plate 33 has a handle 40. This handle is more or less centered in the longitudinal direction of said return 39.

[0177] The return 39 of the second plate 37 exhibits a cutout able to accept the handle 40 when the two plates 33, 37 are assembled as in FIG. 11. An internal face of the return 39 of the second plate 37 exhibits two handles 41. These handles 41 are arranged on each side of the cutout able to house the handle 40 of the first plate 33.

[0178] In order to insert the insulating insert 1 into the inter-panel space 2 using the rigid plates 33, 37, the insulating insert 1 is inserted between the two rigid plates 33, 37. More specifically, the large faces 6 of the insulating insert 1 are interposed and compressed between the large faces 38 of the rigid plates 33, 37. The returns 39 of the rigid plates are superposed in the thickness direction of the tank wall as illustrated in FIG. 12. This superposition is made possible by the handle 40 being housed in the cutout provided for that purpose in the return 39 of the second rigid plate 37.

[0179] The rigid plates 33, 37, between which the insulating insert 1 is held in its compressed state, may thus be inserted into the inter-panel space 2 with the insulating insert 1. Once the insulating insert 1 has been inserted into the inter-panel space 2, the rigid plates may be withdrawn using the handles 40, 41, thus releasing the insulating insert 1 from its compressed state and allowing it to expand to occupy the inter-panel space 2.

[0180] FIG. 8 exhibits a variant embodiment of the insulating insert 1. In this first variant, elements that are identical to or perform the same function as those described hereinabove with reference to FIGS. 1 to 3 bear the same references.

[0181] This first variant differs from the insulating insert 1 illustrated in FIGS. 1 to 3 in that the central portion 11 of the insulating core 4 comprises two insulating layers superposed in the thickness direction of the insulating insert 1.

[0182] A first insulating layer 34 exhibits a structure analogous to the structure of the core described hereinabove with reference to FIGS. 1 to 3, namely a structure comprising sections 16 of the central portion 11 of layered glass wool which are separated by separators 17 made of kraft paper. Said layered glass wool sections 16 exhibit a direction of layering of the glass wool parallel to the support surface 30 formed by the insulating panels 3, preferably parallel to the width of the inter-panel space 2, namely parallel to the thickness direction 10 of the insulating insert 1.

[0183] A second insulating layer 35 comprises a single layer of layered glass wool. The direction of layering of the layered glass wool that forms this second layer 35 is parallel to the support surface 30 formed by the insulating panels 3 and preferably parallel to the thickness direction 10 of the insulating insert 1.

[0184] The first insulating layer 34 and the second insulating layer 35 are separated by a separation layer 36. This separation layer 36 is for example made of glass fabric or kraft paper. To improve the compressibility of the insulating insert 1 in its lengthwise and widthwise directions, this separation layer 36 is preferably shortened in these two dimensions, as partially depicted in FIG. 14.

[0185] The first insulating layer 34 exhibits a layered glass wool of density greater than the density of the layered glass wool of the second insulating layer 35. For example, the layered glass wool of the first insulating layer 34 exhibits a density of 35 to 40 kg/m.sup.3 and the layered glass wool of the second insulating layer 35 exhibits a density of 22 kg/m.sup.3.

[0186] FIG. 9 depicts a second variant embodiment of the insulating insert 1. In this second variant, the elements that are identical to or perform the same function as those described hereinabove with reference to FIGS. 1 to 3 bear the same references.

[0187] This second variant differs from the first variant illustrated in FIG. 8 in that the wrapper 5 does not completely cover the insulating core 4. Specifically, in this FIG. 9, the second insulating layer 35 is not covered on an edge face 9 of the insulating insert 1. In other words, one of the rectilinear edge-face wrapper portions 19 covers only the first insulating layer 34 and has just one return 21, said return 21 being bonded to the planar wrapper portion 18 that covers the first insulating layer 34.

[0188] An insulating insert 1 according to the variants illustrated in FIGS. 8 and 9 offers good capacity for compression and expansion thanks to the second insulating layer 35, but maintains enough rigidity to allow it to deform uniformly and limit the convection through the layered glass wool thanks to its first insulating layer 34. Thus, such an insulating insert 1 can easily be deformed by compression to facilitate its insertion into the inter-panel space 2 while at the same time completely filling said inter-panel space 2 when the compression is no longer maintained and thereby avoiding convection in the thermally insulating barrier. This compression may be achieved through the use of a suction system such as a vacuum pump 24 in the case of an insulating insert 1 like the one according to FIG. 8, in which the wrapper 5 completely covers the insulating core 4, thus offering enough fluid-tightness to compress under the effect of a vacuum pressure. This compression may, on the other hand, be achieved without a suction system in the case of an insulating insert as depicted in FIG. 9, in which the wrapper 5 does not completely cover the insulating core 4.

[0189] The above-described technique for creating a sealed and thermally insulating tank can be used in various types of reservoir, in order for example to constitute the secondary insulating barrier and/or the primary insulating barrier of an LNG reservoir in an on-shore facility or in a floating structure such as a methane carrier ship or the like.

[0190] With reference to FIG. 10, a cut away view of a methane carrier ship 70 shows a sealed and insulated tank 71 of prismatic overall shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealing barrier intended to be in contact with the LNG contained in the tank, a secondary sealing barrier arranged between the primary sealing barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary sealing barrier and the secondary sealing barrier, and between the secondary sealing barrier and the double hull 72.

[0191] In a way known per se, loading/offloading pipelines 73 located on the upper deck of the ship can be coupled, through appropriate connectors, to a maritime or harbor terminal for transferring a cargo of LNG from or to the tank 71.

[0192] FIG. 10 depicts an example of a maritime terminal comprising a loading and offloading station 75, an underwater pipe 76 and an on-shore facility 77. The loading and offloading station 75 is a fixed off-shore installation comprising a mobile arm 74 and a tower 78 supporting the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible hoses 79 which can be connected to the loading/offloading pipelines 73. The orientable mobile arm 74 is able to adapt to all sizes of methane carrier ship. A connecting pipe, not depicted, extends inside the tower 78. The loading and offloading station 75 allows the methane carrier ship 70 to be loaded and offloaded from or to the on-shore facility 77. The latter comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading or offloading station 75. The underwater pipe 76 allows liquefied gas to be transferred between the loading or offloading station 75 and the on-shore facility 77 over a long distance, for example 5 km, allowing the methane carrier ship 70 to be kept standing off the coast by a long distance during the loading and offloading operations.

[0193] In order to generate the pressure needed for transferring the liquefied gas, use is made of pumps carried on board the ship 70 and/or pumps with which the on-shore facility 77 is equipped and/or pumps with which the loading and offloading station 75 is equipped.

[0194] Although the invention has been described in connection with a number of particular embodiments, it is quite obvious that it is not in any way restricted thereto and that it comprises all technical equivalents of the means described and combinations thereof where these fall within the scope of the invention as defined by the claims.

[0195] The use of the verbs “to comprise” or “to include” and of the conjugated forms thereof does not exclude the presence of elements or steps other than those listed in a claim.

[0196] In the claims, any reference sign placed between parentheses must not be interpreted as a limitation of the claim.