EP0248721B1 - Thermally insulating wall structure of a fluid-tight container - Google Patents

Description

The present invention relates to a device forming a thermally insulating wall structure of an enclosure or containment vessel forming a sealed insulated tank for storing or conserving a very cold fluid such as in particular liquefied natural gas.

There are already known, in the prior art constituted by French patent No. 2,271,497 and its first Certificate of Addition No. 2,286,341 to the names of the applicant, reservoirs for the storage or transport of fluids liquids and / or gaseous having for the most part a liquid phase, such as for example cryogenic fluids such as in particular liquefied natural gases and in particular methane. These tanks have a self-supporting or rigid external wall, an impermeable internal wall or a substantially flexible or flexible primary barrier forming a membrane spaced from the external wall and a thermally insulating intermediate material, fixed to the external wall and serving as a support surface for the wall. internal, and essentially comprising a layer formed of adjacent panels separated from each other by gas-tight interlayer gasket liners.

The insert gasket is laterally bonded between two prefabricated insulating panels and is made of an elastic material such as flexible polyvinyl chloride foam.

However, this known wall structure has the drawback of causing a delay in the detection of leakage of the fluid through in particular the secondary impermeable barrier forming part of the structure and a portion of which is integrated by gluing to the intermediate gasket, delay due to the gas-tightness of the insulating foam used (cell insulation with closed cells made of polyurethane for example).

FR-A 2 329 933 describes a thermally insulating wall structure corresponding to the preamble of claim 1.

However, the lateral fiberglass seals fixed to the lining body rise up to the level of the primary barrier, as shown in FIG. 20 of this prior document, and therefore up to the coldest point of the structure: this is not is not at all efficient on the thermal level.

The present invention aims to overcome the aforementioned drawbacks by proposing a device forming a thermally insulating wall structure of a sealed fluid reservoir, as defined in claim 1.

According to a characteristic of the invention, the aforementioned sheet is made of Kraft paper or equivalent.

According to yet another characteristic of the invention, the device preferably comprises at least two superposed buffers.

Still according to another characteristic of the invention, the side seal is bonded to the packing body.

• - la figure unique représente une vue fragmentaire en coupe d'une portion de la structure de paroi thermiquement isolante conforme à l'invention.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawing given solely by way of example illustrating a mode of the invention and in which:

• - The single figure shows a fragmentary sectional view of a portion of the thermally insulating wall structure according to the invention.

• - une paroi externe autoportante ou rigide 1 notamment métallique et constituée par exemple par la double coque en acier d'un navire;
• - une couche extrême externe 2 comportant un quadrillage de bandes ou pastilles de mastic ou de matière équivalente suivant des lignes de pastillage espacées et assurant la liaison entre les éléments 1 et 8.
• - une couche intermédiaire 3 en une matière thermiquement isolante formée de panneaux sandwich adjacents séparés les uns des autres et fixés à la paroi externe 1 en des points discrets par des goujons 4 avantageusement soudés à la paroi externe 1, les intervalles entre panneaux adjacents étant remplis par des garnitures de joint intercalaires 5 constituées par exemple par une matière cellulaire isolante rigide telle que mousse de polyuréthane à cellules fermées et recouvertes intérieurement par des bandes de couvre-joint 6 ;
• - une barrière primaire étanche 7 supportée par la face interne de la couche intermédiaire 3 et constituée avantageusement par une tôle métallique mince ondulée, plissée, gaufrée ou nervurée par exemple en acier inoxydable, avec au moins une série d'ondes espacées, sensiblement parallèles et en saillie seulement du côté interne.

According to the embodiment shown in the figure and as applied to a tank integrated into the hull or bilge of a tanker for example for transporting liquefied natural gas, the heat-insulated wall structure of such a tank successively includes from outside to inside:

• - A self-supporting or rigid external wall 1, in particular metallic, constituted for example by the double steel hull of a ship;
• - an external extreme layer 2 comprising a grid of bands or pellets of mastic or equivalent material along spaced apart lines of pastillage and ensuring the connection between the elements 1 and 8.
• - An intermediate layer 3 of a thermally insulating material formed from adjacent sandwich panels separated from each other and fixed to the external wall 1 at discrete points by studs 4 advantageously welded to the external wall 1, the intervals between adjacent panels being filled by intermediate seal linings 5 constituted for example by a rigid insulating cellular material such as polyurethane foam with closed cells and covered internally by strips of joint cover 6;
• a sealed primary barrier 7 supported by the internal face of the intermediate layer 3 and advantageously constituted by a thin corrugated, pleated, embossed or ribbed metal sheet, for example made of stainless steel, with at least one series of spaced waves, substantially parallel and protruding only from the inner side.

Each sandwich panel 3 advantageously consists, from the outside towards the inside: of an external plywood plate 8; an intermediate plate of insulating material 9 made of polyurethane foam, for example with superimposed layers of a thickness much greater than that of the external plate 8; an internal plate 10 which, together with the joint covers 6, serve as a sealed secondary barrier; an internal extreme heat-insulating layer 11, forming a separating layer between the two spaced sealing barriers respectively secondary 6, 10 and primary 7, and constituted by aligned elements 11 juxtaposed not contiguously forming pavers with opposite sides or edges respectively parallel to the respective directions of waves 7a of the primary barrier 7, the blocks 11 being spaced apart from each other and of such dimension that each separation gap 12 between two neighboring blocks is situated substantially at the right of a wave 7a of the primary barrier and extends along it; a relatively rigid distribution layer 13 constituted by plates, for example of plywood or of suitable synthetic material and interposed between the separating layer 11 and the primary barrier 7.

The fractionation by division of the inner extreme layer 11 allows the latter to more easily follow the thermal expansions and contractions not only of itself but also of the primary barrier 7 thereby reducing residual internal stresses of thermal origin. This inner inner layer 11 is made of a cellular synthetic material, in particular expanded or foam, such as, for example, polyurethane which is relatively flexible, especially compared to the relatively more rigid distribution layer 13, advantageously discontinuous, being interrupted respectively at each interval 12 between the blocks. 11, so as not to hinder, by their relative stiffness, the aforementioned thermal deformations while allowing them to follow. The distribution layer 13 is assembled respectively to the various elements making up the inner end layer 11, in particular by bonding at the time of the prefabrication of these elements separately.

Each panel stud 4 retains the corresponding sandwich panel 3 by its clamping nut 14 applying against the internal face of the external plywood plate 8 by means of a plate 15 also of plywood and while being screwed to the bottom of a recess in the corresponding packing body 5. The stud 4 encloses the plate 15 and part of the plate 8 between the nut 14 and a metal support 4a screwed to the stud under the plate 8.

The various plates and layers constituting the sandwich panels 3 are all glued against one another at the time of prefabrication, the external plywood plate 8 then being glued against the strips of mastic 2 after fixing the sandwich panels 3 to the outer wall 1.

The internal plate 10 and the joint covers 6 are constituted by a laminated material with three contiguous layers described in detail in particular in French patent No. 2,302,982 in the name of the applicant. The secondary barrier comprising the external plate 10 is embedded in the sandwich panel 3 so as to be spaced from the bearing face of the primary barrier 7.

Each sandwich panel 3 comprises, along each edge adjacent to a neighboring sandwich panel, a rebate 16 creating a shoulder 17 leaving uncovered a corresponding marginal strip of the secondary barrier 10. The joint cover barrier strip 6 overlaps the shoulders 17 opposite the two neighboring sandwich panels 3 and is fixed in a sealed manner, for example by gluing against the shoulders, covering the gasket lining 5 to establish the continuity of the secondary barrier. The block 11, located above the corresponding seal gasket 5, fills the cavity defined by the corresponding rebates 16 with two neighboring sandwich panels 3 (as shown in phantom in the figure) in order to restore the continuity of the face d 'support of the primary barrier 7. In order to better understand certain features of the device of the invention, this block 11 is shown in the figure partially set back from its housing cavity, it being understood that this block is actually fully housed in this cavity to ensure the aforementioned continuity of the bearing face of the primary barrier.

According to the invention, each intermediate seal gasket 5 is mounted in the gap between two adjacent intermediate layers 9 and is bonded, once mounted by its opposite end faces, respectively upper and lower to the plate 15 and to the joint cover strip. 6 but no adherent lateral connection of the lining to the longitudinal edges of the intermediate layers 9 is provided. It should be noted that the bonding by bonding of the lower face of the lining body 5 is carried out using a thick adhesive of the charged resin type to thus allow during the prefabrication to glue the body against the bottom of its housing between two adjacent panels 9, while the upper end face of this body, when the latter is definitively mounted, is flush with the internal planar faces of the intermediate layers 9.

Each intermediate seal lining 5 comprises, at each of its sides opposite the longitudinal edges of the intermediate layers 9, at least one lateral seal 18 made of a flexible compressed or expandable insulating material housed in a corresponding recess 19 in the body of the lining seal 5. Each side seal 18 is bonded for example by gluing to the packing body at the time of prefabrication. In the mounting position, shown in the figure, of the seal lining 5 between the two adjacent intermediate layers 9, each side seal 18 is in free pressed contact against the adjacent intermediate layer.

Advantageously, each lateral seal 18 is constituted by a glass wool pad coated externally, except on its end face facing the secondary barrier 6, 10, with a sheet 20 of material impervious to cold liquid and permeable to gas and having good cryogenic properties. This sheet of waterproof material may for example be a sheet of Kraft paper, each pad thus being constituted by a strip of glass wool coated on its face with Kraft paper and folded transversely in a U. Each pad 18 acts as a retaining gutter for the fluid liquid through the secondary barrier but allows, thanks to the porous gas permeable, the balancing of gas pressures in the side seal, quick and easy detection of leaks as well as degassing of the structure, either by simple sweeping with an inert gas, either by performing alternating vacuum cycles followed by injection of inert gas. Preferably, at least two such buffers are provided on each side of the intermediate seal lining 5 in their corresponding recess 19.

The internal block 11 glued to the joint cover strip 6 is coated on its external face adjacent to the secondary barrier 6, 10 with a fiberglass fabric 21 glued to said external face to reinforce the mechanical resistance of the block which must achieve the continuity between the two adjacent sandwich panels 3. The block 11 is glued against the bottom of its housing cavity 16 formed by the shoulders 17 and the inner end face of the seal gasket. Avanta gouement, the joint cover block 11 is chamfered bilaterally along these two external longitudinal edges, as indicated by reference 22, to create a space for discharging the excess glue in order to avoid internal stresses which can cause a primer cracking.

Claims (8)

1. A device forming a heat insulating wall structure of a fluid-tight heat-insulated tank, of the kind comprising an outer self-supporting or rigid wall (1), a substantially flexible or yielding membrane-like impervious inner wall or primary barrier (7) spaced from the outer wall and a heat insulating intermediate material (3), and secured to the outer wall (1) and serving as a bearing surface for the inner wall (7) and essentially including a layer consisting of adjacent panels separated from each other by interposed gas-tight joint packings (5), each interposed joint packing (5) comprising on each of its sides at least one lateral joint (18) consisting of a glass-wool pad connected to the joint packing (5), the said joint (18), after said packing (5) having been mounted between two adjacent panels (9), being in free pressed bearing engagement with the neighbouring panel, characterized in that the glass-wool pad (18) is received in a corresponding recess (19) of the packing body (5) and is covered outwardly, except on its end face facing the primary barrier (7), with a sheet (20) of a material which is tight to the cold liquid, gas permeable and has good cryogenic behaviour properties, which sheet is transversally folded in the shape of a U.

2. A device according to claim 1, characterized in that said sheet (20) is made from Kraft paper or the like.

3. A device according to claim 1 or 2, characterized in that it comprises preferably at least two overlying pads (18).

4. A device according to one of the preceding claims, characterized in that said lateral joint (18) is connected through adhesive bonding to said interposed joint packing body (5).

5. A device according to one of the preceding claims, characterized in that said interposed joint packing (5) is made from a rigid insulating cellular material such as a polyurethane foam with closed cells.

6. A device according to one of the preceding claims, characterized in that said packing body (5) is stuck to the bottom of its housing recess between two panels (9).

7. A device according to claim 1, wherein each panel comprises a fluid-tight layer or secondary barrier embedded within said panel so as to be spaced from the bearing face of the primary barrier and a rabbet formed along each adjacent edge of a neighbouring panel and providing a shoulder leaving uncovered a corresponding marginal strip of said secondary barrier, a barrier butt-strip straddling the confronting shoulders of any two neighbouring panels and tightly secured as through adhesive bonding to said shoulders while covering the joint packing for providing the continuity of the secondary barrier and a block of heat insulating material filling up the cavity defined by the corresponding rabbets of any two neighbouring panels thereby restoring the continuity of the bearing face of the primary barrier, characterized in that said block (11) is lined on its end face adjacent to said butt-strip (6) with a glass fiber fabric (21) and is glued to the bottom wall of its housing recess (16).

8. A device according to claim 7, characterized in that said block (11) comprises two chamfers (22) for discharging the excess adhesive along its two longitudinal edge lines.

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