EP0573327A1 - Prefabricated, fluid-tight and heat-insulating wall structure for vessels for cryogenic fluids - Google Patents

Abstract

The present invention relates to a prefabricated structure making it possible to produce fluid-tight and heat-insulating walls for a heat-insulated containment chamber (vessel) such as a fluid-tight tank for storing and/or transporting a cryogenic (very low temperature) fluid. This structure (1) which comprises an internal fluid-tight and flexible barrier (2), an insulation system (4), and an external skin (3) forming a support for the structure (1) is characterised in that distribution panels (53) secured to the external skin (3) are fixed to the latter particularly by screws or the like (35) located facing holes (435) formed in an external insulating layer (43) at a distance from joints (63) between plates (43a) forming this layer, whilst a fluid-tight connection (80) is located hermetically in each of these holes (435) and joints (63). The invention applies to the production of structures forming fluid-tight tanks, for example for ships for transporting cryogenic liquids such as methane tankers. <IMAGE>

Description

The present invention relates to a prefabricated structure making it possible to produce leaktight and thermally insulating walls for a thermally insulated confinement enclosure, such as a sealed reservoir for storing and / or transporting a fluid at very low temperature, such as by example a liquefied gas or a cryogenic liquid.

We have already described, in particular in document FR-A-2 599 468 in the name of the applicant, a structure constituted by prefabricated elements assembled so as to obtain a hermetic heat-insulated enclosure which may contain, for example, liquefied methane. This structure of the prior art can be mounted in the hold or double-hold of a merchant ship, whose rigid self-supporting partitions form an external support for the other elements of the structure. An internal or primary waterproof barrier, which defines a substantially deformable hermetic tank and designed to contain the fluid, is assembled from elements generally made of metal inside the space defined by the external partitions of the support. A thermal insulation system is interposed between the external partitions and the primary barrier. This insulation system comprises at least two layers of insulating and waterproof material such as plastic foam with closed cells, formed by juxtaposition of prefabricated plates. The two layers of insulation are sandwiched by two load distribution panels inside the structure, for example in plywood. A panel secured to the external partition is glued to a so-called "external" insulation layer, while the other panel which is secured to the internal barrier is glued to another so-called "internal" layer. To maintain the watertightness of the structure in the event of cracking of the primary barrier, buffers made of the same type of material as the insulation plates are placed in the joints between the juxtaposed plates of the outer layer and are respectively covered with a strip hermetically bonded to the outer layer and generally comprising a central sheet of waterproof aluminum as well as two layers of fiberglass fabric.

However, in the known structures at the joints, only the covering strip provides sealing between the layers of internal and external insulation. In fact, in the event of a leak through the primary barrier, the entire seal rests on this strip, which risks generating cooling if one of these covering strips is no longer hermetic.

In addition, since in known structures the load distribution panels are constituted by elements assembled using screws or the like opening into the joints of the outer insulation layer, the risks of loss of tightness.

Also, the present invention aims to overcome the above drawbacks, by proposing a simple and economical structure in which the insulation layers are continuous and therefore perfectly sealed.

To this end, the subject of the invention is a prefabricated structure for forming leaktight and thermally insulating walls for the production of a heat-insulated enclosure for confining a fluid at very low temperature such as a liquefied gas, and of the type comprising a substantially flexible internal or primary waterproof barrier to which an internal distribution panel is attached, a rigid external partition forming a support for the structure and to which another said external panel is attached as well as two intermediate layers of thermal insulation sandwiched between the distribution panels and respectively said internal and external, each layer which is produced by juxtaposition of insulating plates of waterproof material such as for example a closed cell plastic foam, defines joints between the plates respectively disposed opposite a plate of the other layer, each joint of the outer insulation layer being covered rte by a strip glued between the two layers of insulation, characterized in that the external distribution panels are fixed to the external partition in particular by screws or the like, arranged opposite holes formed in the external layer at a distance from the joints, and a sealed connection made of insulating material fills and adheres hermetically at each of these holes and joints, so that the external insulation layer is continuous and tight over the entire surface formed by the structure.

We already understand that thanks to the external layer of continuous insulation, the tightness of the structure specific to the invention can be checked very easily and quickly compared to the structures of the prior art, for example by measuring pressure differentials .

According to another characteristic of the invention, the covering strip is formed by a continuous reinforcing sheet of glass fiber or the like, which extends over a surface substantially greater than that of the plate juxtaposed with the internal insulation layer. , opposite the joint to be covered and preferably over the entire surface of the corresponding wall formed by the structure.

According to yet another characteristic, at least one of the aforementioned connections is an insert of shape corresponding to that of the joint or of the hole to be filled, of which at least the external peripheral surface is coated with an adhesive material, preferably foaming.

It will also be specified here that at least one of the aforementioned connections is constituted by two elements which are substantially symmetrical with respect to a median plane of assembly, and whose internal surfaces of assembly facing each other are coated with adhesive material.

The invention is also characterized in that at least one of the aforementioned connections is formed in situ by pressure injection of the aforementioned waterproof insulation plastic material inside the hole or the joint to be filled.

Furthermore, the material forming the aforementioned fittings is injected by means of a tool bearing against the surface of the external layer of insulation opposite the external partition, and fixed to the latter facing the opening of the hole. or the join to be completed.

In addition, the stresses generated inside or between the plates juxtaposed with the outer insulation layer by the aforementioned fittings in the final position, have a negligible value.

According to another characteristic, a pad made of waterproof material to which the aforementioned connection of a joint adheres hermetically is interposed between the reinforcement panel and the external partition.

It will also be noted here that a flexible connector is interposed between the plates of insulating material which constitute the internal layer of insulation and adhere to them.

• la figure 1 est une vue en coupe transversale et en éclaté d'une structure préfabriquée conforme à l'invention;
• la figure 2 est une vue schématique en perspective d'un panneau plat préfabriqué pour une structure conforme à l'invention;
• la figure 3 est une vue schématique en perspective d'un panneau d'angle préfabriqué pour une structure conforme à l'invention;
• la figure 4 est une vue partielle en coupe transversale d'une jointure dans le système d'isolation d'une structure avec un raccord étanche injecté, suivant un mode de réalisation de l'invention;
• la figure 5 est une vue similaire à la figure 4, avec des raccords étanches rapportés et collés suivant un autre mode de réalisation de l'invention.

However, other characteristics and advantages of the invention will emerge more clearly from the detailed description of embodiments given solely by way of example, which follows and refers to the appended drawings, in which:

• Figure 1 is a cross-sectional and exploded view of a prefabricated structure according to the invention;
• Figure 2 is a schematic perspective view of a prefabricated flat panel for a structure according to the invention;
• Figure 3 is a schematic perspective view of a prefabricated corner panel for a structure according to the invention;
• FIG. 4 is a partial view in cross section of a joint in the insulation system of a structure with an injected tight connection, according to an embodiment of the invention;
• Figure 5 is a view similar to Figure 4, with waterproof fittings reported and glued according to another embodiment of the invention.

Referring in particular to FIG. 1, we see a prefabricated structure 1 which makes it possible to form leaktight and thermally insulating walls for the production of a confinement enclosure or reservoir, for example for storing and / or transporting a very low fluid. temperature. Here, and this only by way of example, the structure 1 is a reservoir constituted by an assembly of sealed and heat-insulated walls, in which a cryogenic liquid such as a very cold liquefied gas, such as in particular methane, can be stored.

The structure 1 comprises a sealed internal envelope capable of containing the fluid to be stored, which is composed by assembling prefabricated elements forming jointly for each wall of the structure 1, an internal or primary waterproof barrier 2. In FIG. 1, the barrier Primary 2 is formed by thin metal elements such as stainless steel or aluminum sheet. The reference numeral 2a designates ribs projecting parallel to the connections 2b between the different elements of the barrier 2, which allow the envelope formed by this barrier to be substantially flexible, in order to be able to deform under the effect of the stresses, notably thermal generated by the fluid stored therein.

A rigid external partition 3 of the structure 1 acts as a support for the latter. According to the example illustrated, this partition 3 is a self-supporting metal sheet of hold or of double hold of a merchant ship, such as an LNG carrier. Obviously, other types of rigid partitions whose mechanical properties are appropriate, such as in particular a concrete wall in a firm ground construction, could be used as external partition supporting the structure 1.

Furthermore, a thermal insulation system generally designated at 4 is provided between the primary barrier 2 and the external partition 3. The insulation or insulation system 4 of the structure 1 notably includes an internal insulation layer 42 to which is linked primary barrier 2, as well as an external insulation layer 43 secured to the external support partition 3.

The outer and inner layers 42, 43 are made from a waterproof thermal insulation material. Advantageously, use a plastic or synthetic foam with closed cells. A closed cell foam based on polyurethane or polyvinyl chloride in particular may be perfectly suitable for the production of these insulation layers 42,43.

In FIG. 1, it can be seen that the two insulation layers 42, 43 are sandwiched or sandwiched between two force distribution panels 52 and 53. These panels 52, 53 respectively internal and external, are for example made from of assembled pieces of plywood or laminate. The internal and external panels 52 and 53 make it possible to distribute almost uniformly in the structure and in particular the insulation system 4, the forces for example linked to deformations of the external partition 3 and of the envelope defined by the internal barrier 2 To do this, the panel 52 is supported, and preferably glued to the upper surface (that is to say the one closest to the barrier 2) of the insulation layer 42, while the outer panel 53 is in abutment, and preferably glued to the lower surface (namely facing with the partition 3) of the insulation layer 43.

Since the structure 1 is prefabricated, each insulation layer 42, 43 is formed by juxtaposition of insulating plates made of waterproof material, designated at 42a or 43a, respectively, and whose shape is generally prismatic rectangular. It goes without saying that in the corner or edge parts of the structure 1, the insulating plates 42a or 43a may be bevelled at an angle appropriate to that formed by the structure 1 at this edge, in order to form the largest possible joins. In addition, the plates 42a, 43a will be prefabricated with standard dimensions, which obviously can be modified by cutting according to the shape of the structure to be produced.

The insulating plates 42a, 43a are arranged end-to-end so as to define in each layer 42, 43 generally linear joints 62, 63 respectively. These joints 62, 63 generally extend along a direction plane perpendicular to the median plane of the panels 52, 53, over at least the entire thickness of the corresponding insulation layer 42, 43. Each of the joints 63 formed in the layer outer is covered by a strip 70 which is interposed and glued between the two layers of insulating foam 42 and 43 and comes in line with a plate 42a of the inner layer 42.

According to the invention, the distribution panels 53 are fixed to the external partition 3, in particular by screws or the like 35, visible in FIG. 5. These screws 35 shown in the other figures only by their longitudinal axis, are arranged in hole look 435, themselves formed in the outer insulation layer 43, at a distance from the joints 63 between the different juxtaposed plates 43a constituting this layer. Furthermore, each of the joints 63 and all the holes 435 in question are filled by a fitting 80 made of thermally insulating and waterproof material. These insulating and leaktight connections 80 may in particular be made of the same material or of a material similar to that of the insulation layers 42 and 43, for example ethyl vinyl acetate. In addition, all the fittings 80 arranged in the joints 63 and in the holes 435 of the layer 43 are bonded to adhere tightly to the walls of the hole 435 or of the corresponding joint 63, in order to make the outer layer 43 continuous and tight over all the area defined by structure 1.

It is already understood that with such a structure 1, the secondary seal is obtained by making the plates 43a and fittings 80 hermetically integral, so that the prefabricated layer of external insulation 43 forms, after its assembly and bonding, a barrier secondary continuous and therefore perfectly waterproof.

In addition, the joints 62 between the plates 42a of the internal insulation layer will preferably also be hermetically sealed by flexible joints (possibly glued) in liquid mastic polymerized by example. In this case, the secondary barrier is formed by the entire insulation system 4.

However, since it is in particular the outer insulation layer 43 which guarantees good confinement of the fluid inside the structure 1 in the event of a crack or the like in for example the primary barrier 2, it is not necessary that the strips 70 covering the joints 63 and the fittings 80 are sealed and hermetically fixed between the two insulating layers 42 and 43. Consequently, these cover strips 70 will have the main role of keeping the plates 42a and 43a of the layers together. corresponding insulation of the system 4. For this purpose, it will be advantageous to use a reinforcing sheet such as a fiberglass fabric or the like, which will be bonded at least at the joints 63 and holes 435, between the two corresponding insulation layers 42 and 43. With one of its faces adhering to at least two insulation plates 42a, and its other face adhering to at least two plates 43a, each covering strip 70 will effectively reinforce the cohesion between the joint fittings 80 and the plates of insulation 42a, 43a.

In order to obtain the best possible reinforcement, each covering strip 70 must extend widely beyond the surface of the external layer 43 where the holes 435 and the joint 63 to be covered are formed.

It can be seen in FIG. 1 that the prefabricated insulation plates 42a and 43a are disposed within the structure 1 in an offset manner, so that the joints 63 and the holes 435 of two external plates 43a are located in line with a plate internal 42a. With such an arrangement, the surface of each reinforcing strip 70 will be chosen so that it is substantially equal to that of the corresponding external plate 42a. It is advantageous if the imperatives of assembly of the prefabricated elements of the structure 1 allow it, to completely cover the external layer of insulation 43 with a reinforcing fabric on which the reinforcing strips 70 may be glued.

It will also be noted here that, by providing the holes 435 at a distance from the joints 63, these open out opposite a solid surface of the corresponding distribution panels 53, so that it is easier to obtain a seal. between the layer 43 and the corresponding panel 53, in particular thanks to the bonding of these two prefabricated elements.

Referring now to FIG. 5 which represents a first embodiment of the invention, it can be seen that the fittings 80 provided for filling the holes 435 as well as the joints 63 illustrated, are constituted by inserts of shape corresponding to that orifices (63, 435) to be filled in the layer 43. More specifically, the connection intended to be housed in the direction of the arrow F1 in the joint 63 and designated at 83, is a tight flat seal. This joint in the form of a flat joint 83 has a length in the direction of the arrow F1 which is substantially equal to the thickness of the assembly formed by the layer 43 and the panels 53.

On the other hand, it can be seen that a pad 33 preferably made of a waterproof flexible plastic foam is interposed between the panels 53 arranged on either side of the joint 63, and the external partition 3. This pad 33, the section along a transverse plane perpendicular to the median plane P of the joint 63 is trapezoidal, rests by one of its parallel faces whose surface is the smallest, against the internal face of the partition 3. Furthermore, the longitudinal edges of its most important parallel face are respectively in abutment against the external face opposite the partition 3 of one of the panels 53 contiguous to the joint 63. Thanks to the tightening of the screws 35 for fixing the panels 53 to the external partition 3, the longitudinal edges of the pad 33 are clamped between these panels 53 and the partition 3, like the support pads 34 visible in Figures 1 and 4. This tightening of the pads 33 provides a sealed contact between them and p rings 53. The tightness of this contact could be further improved by applying a hermetic adhesive between the lateral edges of each pad 33 and the corresponding panels 53. These pads 34 are glued on the one hand to the external partition 3 and on the other hand to one of the panels 53.

Although this is not visible in FIGS. 1 and 4 in particular, the external or peripheral faces of each connector 80 are coated with a layer of suitable glue, preferably a foaming glue. Thus, when the fitting 80 is introduced into the corresponding orifice (63) or (435), the latter adheres hermetically to the insulation plates 43a of the external layer, and to the pad 33 in order to form a single continuous piece. , without possible passage for the fluid to be stored in the structure 1.

To facilitate the production as well as the fitting of the fitting 83 (or of any other fitting 80 consisting of an insert), it is possible that this is obtained by assembling at least two elements glued to one another. Preferably, each element will be symmetrical to the other along a plane coincident with the (or one) of the median planes of the orifice 63 or 435 to be filled using this connection in several elements. For example, the fitting 83 could be formed by assembling two elements symmetrical with respect to the median plane P. The faces of these elements constituting the fitting 83 which extend along the plane P are coated with an appropriate adhesive, preferably foaming , and assembled just before mounting and gluing the fitting thus formed in the joint 63.

In view of Figure 1, we note that near an angle defined by two walls of the structure 1, there is provided between the connector 80 which is here constituted by an insert, and the external partition 3 a positioning stop insulation plates 43a of the outer layer 43. For this purpose, in place of the buffer 33 described above, there is on the side opposite to the plate 43a defining said angle, a bar 33 'clamped and glued between the corresponding panel 53 to the other plate 43a and the external partition 3. In addition, a series of shims 36 resting against this end bar 33 'resting against the end faces of a shoe 34, of the panel 53 and of the plate 43 located on the side of the angle formed by the structure 1. These shims will generally comprise from right to left in FIG. 1, for example a metal part, a joint in mastic and a shim in plywood or laminated wood. The base of fitting 80 corresponding is obviously glued tightly on this set of shims 36. Thus, it is possible to immobilize the prefabricated elements in question in a suitable position in the direction perpendicular to the edge of the angle formed by the structure 1 to this place.

Note also in Figure 1 that an empty space 56 is provided in the joint 63 between the insulation layer 43 and the metal shim 36 located on the side opposite the corner defined by the structure 1. A filling 86 for example in putty whose elongated shape corresponds to that of space 56, is provided in this space so that the fitting 80 can adhere to its entire base and seal the bottom of the joint 63 between the insulation plates 43a.

Similar to what has just been explained, fittings 85 shown in FIG. 5 and intended to fill the holes 435 are in the form of cylindrical studs or logs of shape corresponding to that of each hole. Their end faces coming opposite the corresponding panel 53 are hollowed out at their center, so that the screw 35 protruding into this hole 435 can be accommodated there. However, near the periphery of the log forming a connection 85, an annular end surface is provided which can be brought into contact with the panel 53 constituting the bottom of the hole 435, and be hermetically bonded to this panel around the screw 35 Likewise, the cylindrical walls of the connector 85 are coated with suitable adhesive, preferably foaming, so that the latter forms, after setting the adhesive, a single sealed part with the insulating plate 43a inside which it is housed.

Furthermore, like the joint forming a fitting 83, the cylindrical insert 85 can also be obtained by assembling and bonding two elements, for example made of closed-cell polyurethane foam.

In FIG. 4, the connection filling the joint 63 between the two juxtaposed insulation plates 43a is obtained in situ. More specifically, the bottom of the joint 63 is hermetically sealed by a buffer 33 generally identical to that which has been described above. An injection tool 100 is fixed to the insulation system 4, in order to close off the opening part of the joint 63. The injection tool 100 is composed of a plate 103 capable of coming to hermetically bear against the face top of the insulation layer 43 by covering the joint 63, and by at least two extension studs 135 provided for fixing on the screws 35. Thus, the plate 103 of the tool 100 can be pressed tightly against the outer insulation layer 43, so that the interior space defined by the joint 63 is hermetically sealed. In addition, the plate 103 of the tool 100 comprises an injection mouth 160 associated with at least one vent which makes it possible to put the interior of the joint 63 into communication with a source S of insulating and waterproof plastic material capable of expand, such as preferably closed cell polyurethane.

Once the tool 100 and the source S are in place as illustrated in FIG. 4, the plastic material of the source S is injected under an appropriate pressure into the space defined by the joint 63, in order to fill it completely. . When the injected expandable material designated here at 84 is dried and it adheres hermetically to the walls of the joint 63 and of the pad 33, a connection 80 has been obtained. Once the tool 100 is disassembled, the material 84 of the connection 80 and the two plates of insulating material 43a juxtaposed to the corresponding connection 63 no longer form a single continuous part, and consequently cannot in any case allow a fluid to pass. It will be noted here that although this is not illustrated, the holes 435 provided for access to the assembly or fixing screws 35 can also be filled by injection of an expandable waterproof material such as that designated at 84.

Obviously, thanks to an injection tool such as that which has just been described, the material 84 can fill the joint 63 up to the flower of the outer layer of insulation 43, so that the plates 43a will be connected in a manner continues through the fitting 80 thus produced, and it will be easy to apply to a surface thus formed a reinforcing strip 70.

It will be specified here that the injection pressure of the material 84 as well as the force necessary to accommodate the fittings 80 constituted by attached parts such as those which are illustrated in FIG. 5, will be chosen so that in the final position of these fittings 80 and juxtaposed plates 43a, the stresses generated by these fittings 80 inside the outer layer 43 are of negligible value, in particular with respect to the cohesive force exerted by the adhesives (including by the injected material 84) as well only by the covering strips 70 which connect the fittings 80 and the plates 43a.

From Figures 1 and 3, we note that in the corners at 90 ° or with a different angle, the load distribution panel 52 is replaced by a metal angle. As best seen in Figure 3, the metal angle is made up of elements 52a of stainless metal such as treated steel or aluminum, which are juxtaposed and assembled using screws 45 (Figure 1) which are fixed in the material of the plates 42a constituting the internal insulation layer 42 of the system 4. A flexible joint 62a such as that described with reference to FIG. 1, can be interposed between the elements 42a so as to adhere to them .

Here too, when the bevelled plates 43a are assembled using a corner connector 80 such as that of FIG. 3, the whole of the layer 43 will be covered with a strip 70 preferably made of fiberglass. Then, the insulation plates 42a forming by juxtaposition the internal layer 42 will be assembled, with at the level of the corner defined by the structure 1, a corner connector 82 (FIG. 1) hermetically glued to the plates 42a which are contiguous to it.

Similar to the prefabricated structure 1 of FIG. 3 which forms a corner wall, FIG. 2 shows a planar structure 1 made up of prefabricated elements assembled in accordance with the invention.

In the prefabricated structure of FIG. 2, the panel 52 consists of elements fixed to the corresponding insulation plates 42a by collage. Metallic inserts 142 can be provided on such a panel 52 for fixing tools in particular. Strips of stainless metal 166 which extend transversely to each of the elements of the panel 52 are respectively crimped in suitable housings arranged in alignment and formed in the elements which constitute this panel by juxtaposition.

As shown schematically in Figure 2, it will also be possible with the prefabricated element visible in this figure to interpose between layer 43 and layer 42 a fiberglass fabric 70 which extends beyond holes 435 of this prefabricated element. Such sheets could be glued to each other by the covering strips so as to form only one single reinforcing envelope over the entire surface of the structure 1.

A structure 1 was therefore obtained in accordance with the invention which, in the event of a leakage through the primary barrier 2 makes it possible to ensure that the thermal gradient in the insulation system 4 is not affected.

It should also be specified here that since the layer 70 has only a mechanical function, it is no longer necessary to provide a sealed metal sheet sandwiched at the level of the strips and of the covering sheet. In fact, in addition to the cost reductions associated with obtaining the structure from prefabricated elements, the invention makes it possible to significantly reduce the costs of manufacturing tanks for cryogenic liquids in, for example, commercial ships, while guaranteeing a higher quality of insulation and sealing than could be obtained in the prior art. In particular, the displacement of the secondary sealing makes it possible to use a less expensive grade of steel for the external partition. of support.

Obviously, the invention is in no way limited to the embodiments which have just been described, but includes all the equivalents and combinations of the technical means explained and illustrated, if these are carried out according to the spirit.

Thus, between two insulating plates of the external layer, provision may be made for certain sealed connections to be obtained by injection and others by bonding of added parts.

Claims (10)

Prefabricated structure for forming tight and thermally insulating walls for the production of a heat-insulated enclosure for confining a fluid at very low temperature such as a liquefied gas, and of the type comprising a substantially flexible internal or primary waterproof barrier (2) with which a so-called internal distribution panel (52) is attached, a rigid external partition (3) forming a support for the structure (1) and with which another said panel (53) is attached, as well as two intermediate layers of thermal insulation (42,43) sandwiched between the distribution panels (52,53) and respectively said internal (52) and external (53), each layer which is produced by juxtaposition of insulating plates (42a, 43a) of waterproof material such as for example a closed cell plastic foam, defines joints (62, 63) between the plates (42a, 43a), respectively disposed opposite a plate (43a, 42a) of the other layer (42,43), every e joint (63) of the outer insulation layer (43) being covered by a strip (70) bonded between two layers of insulation and closed by a connector (80) made of waterproof insulating material, characterized in that the panels of external distribution (53) are fixed to the external partition (43) in particular by screws or the like (35), arranged opposite holes (435) formed in the external layer (43) at a distance from the joints (63), and a sealed connection (80) made of insulating material fills and adheres hermetically to each of these holes (435) and joints (63), so that the external insulation layer (43) is continuous and sealed over the entire surface formed by the structure ( 1). Structure according to claim 1, characterized in that the covering strip (70) consists of a continuous reinforcing sheet of fiberglass or the like, which extends over a surface substantially greater than that of the juxtaposed plate (42a) of the internal insulation layer (42) opposite the joint (63) to be covered, and preferably over the entire surface of the corresponding wall formed by the structure (1). Structure according to claim 1 or 2, characterized in that at least one of the aforementioned connections (80) is an insert (83,85) of shape corresponding to that of the joint (63) or the hole (435) to fill, with at least the outer peripheral surface coated with an adhesive material, preferably foaming. Structure according to Claim 3, characterized in that at least one (83, 85) of the connections (80) consists of two elements which are substantially symmetrical with respect to a median plane (P) of assembly, and whose internal surfaces opposite assembly are coated with adhesive material. Structure according to one of claims 1 or 2, characterized in that at least one (84, 82) mentioned above is formed in situ by pressure injection of the plastic insulating seal inside the hole (435 ) or the joint (63) to be filled. Structure according to claim 5, characterized in that the material (84, 82) forming the connections (80) is injected by means of a tool (100) bearing against the surface of the external insulation layer (43 ) opposite the external partition (3), and fixed to the latter opposite the opening of the hole (435) or of the joint (63) to be filled. Structure according to one of claims 1 to 6, characterized in that the stresses generated inside or between the juxtaposed plates (43a) of the external insulation layer (43) by the aforementioned fittings (80) in final position , are of negligible value. Structure according to one of Claims 1 to 7, characterized in that a plug (33.33 ') of leaktight material on which the connection (80) of a joint (63) hermetically adheres is interposed between the reinforcement panel ( 53) and the external partition (3). Structure according to one of claims 1 to 8, characterized in that a flexible connection (62) is interposed between the material plates insulation (42a) which constitute the internal insulation layer (42) and adhere thereto. Structure according to one of claims 1 to 9, characterized in that a metal angle (52a) forming a distribution panel (52) is interposed between the primary barrier (2) and the internal insulation layer (42), and is attached to it.

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