EP2986885B1 - Tight and thermally insulating vessel - Google Patents

Description

Technical area.

The invention relates to the field of sealed and thermally insulating tanks arranged in a bearing structure for containing a cold fluid, in particular to membrane tanks for containing liquefied gases. The storage of liquefied gases is carried out at very low temperatures, approximately -160 ° C. This storage is exposed to an evaporation phenomenon depending on the level of thermal insulation of the tank. The reduction of this evaporation involves improving the thermal insulation of the tanks.

Technological background.

Sealed and thermally insulating tanks are known arranged in the hull of a ship for the transport of a liquefied natural gas (LNG) with a high methane content. Such a tank is disclosed for example in FR-A-2798902 . In this known tank, a primary insulating barrier and a secondary insulating barrier are formed in a modular form using juxtaposed wooden parallelepiped boxes.

FR-A-2877638 discloses another LNG tank arranged in the hull of a ship in which a secondary insulating barrier has insulating blocks arranged in a repeating pattern. The insulating block comprises a generally parallelepipedic block of low density polymer foam sandwiched between a bottom panel and a cover panel. The insulating block comprises pillars disposed between the bottom panel and the cover panel. The pillars are distributed in the insulating block to take the compression efforts that can not support the low density foam.

Summary.

An idea underlying the invention is to provide insulating blocks suitable for producing an insulation barrier of a sealed and thermally insulating tank in a relatively simple manner with high insulating power.

• une paroi porteuse,
• une barrière d'isolation thermique retenue sur la paroi porteuse, la barrière d'isolation thermique étant constituée d'une pluralité d'éléments calorifuges juxtaposés de manière à former une surface de support, et
• une barrière d'étanchéité en appui sur la surface de support,
• un élément calorifuge, présentant une forme globale prismatique aplatie, et comportant :
  • un isolant thermique,
  • une pluralité d'éléments porteurs traversant l'isolant thermique selon une direction d'épaisseur perpendiculaire à la paroi de cuve et
  • un panneau de couvercle et un panneau de fond parallèles à la paroi de cuve agencés à une première extrémité respectivement une seconde extrémité des éléments porteurs de l'élément calorifuge de manière à former des parois extérieures de l'élément calorifuge, les premières extrémités des éléments porteurs étant fixées au panneau de couvercle et les secondes extrémités des éléments porteurs étant fixés au panneau de fond et,
• un plateau anti-flambement parallèle au panneau de couvercle et au panneau de fond, pris en sandwich entre une première et une deuxième tranches d'épaisseur dudit isolant thermique, le plateau anti-flambement étant traversé par la pluralité d'éléments porteurs dans une pluralité d'ouvertures, du plateau anti-flambement, les ouvertures étant distantes les unes des autres de manières à garantir une distance entre deux éléments porteurs voisins, dans un plan défini par le plateau anti-flambement.

According to one embodiment, the invention provides a sealed and thermally insulating vessel integrated in a support structure for containing a fluid, in which a vessel wall comprises from the outside of the vessel towards the inside of the vessel:

• a load-bearing wall,
• a thermal insulation barrier retained on the carrier wall, the thermal insulation barrier consisting of a plurality of heat insulating elements juxtaposed so as to form a support surface, and
• a sealing barrier resting on the support surface,
• a heat insulating element, having a flattened overall prismatic shape, and comprising:
  • thermal insulation,
  • a plurality of carrier elements passing through the thermal insulation in a thickness direction perpendicular to the vessel wall and
  • a cover panel and a bottom panel parallel to the vessel wall arranged at a first end or a second end of the supporting elements of the heat insulating element so as to form outer walls of the heat insulating element, the first ends of the elements carriers being attached to the cover panel and the second ends of the carrier members being attached to the bottom panel and,
• an anti-buckling plate parallel to the cover panel and the bottom panel, sandwiched between a first and a second thickness of said thermal insulation, the anti-buckling plate being traversed by the plurality of carrier elements in a plurality of openings, the anti-buckling tray, the openings being spaced apart from each other so as to ensure a distance between two adjacent carrier members, in a plane defined by the anti-buckling plate.

Thanks to these characteristics, a bearing element undergoing significant stress is maintained by a force which opposes the buckling transmitted by the anti-buckling plate.

According to embodiments, such a tank may comprise one or more of the following characteristics.

According to one embodiment, an opening of the anti-buckling plate has dimensions greater than the dimensions of a cross section of the carrier member engaged in the opening so as to leave a mounting set.

Thanks to these characteristics, the manufacture is facilitated.

According to one embodiment, the mounting clearance is less than three millimeters.

Thanks to these characteristics, when buckling a pillar, the anti-buckling plate reflects the effort on the other pillars that oppose this effort.

According to one embodiment, the anti-buckling tray is positioned midway between the bottom panel and the cover panel.

Thanks to these characteristics, the pillar is maintained in three points constituting two equal pillar portions.

According to one embodiment, the thermal insulation comprises a second anti-buckling plate parallel to the bottom panel and the cover panel, sandwiched between the second and third thickness slots of said thermal insulation,
the second anti-buckling plate being traversed by the plurality of carrier elements in a plurality of openings, arranged in alignment with the openings of the first anti-buckling plate.

Thanks to these characteristics, it is possible to realize very thick insulation elements by adding as much anti buckling plate as necessary.

avec :

• E : module d'Young de l'élément porteur,
• S : surface en section de l'élément porteur,
• σ : est une contrainte limite en compression du matériau,

où les points de maintien sont la deuxième extrémité de l'élément porteur fixée au panneau de fond, la première extrémité de l'élément porteur fixée au panneau de couvercle et chaque portion de l'élément porteur engagée dans une ouverture des plateaux anti-flambement.According to one embodiment, a heat-insulating element comprises a plurality of anti-buckling plates, the anti-buckling plates being in a number greater than or equal to a theoretical number defined so that the distance between two successive holding points of an element carrier in the longitudinal orientation of the carrier member is less than a critical height, Hc predefined, said critical height being equal to: $$\mathit{hc}=\sqrt{\frac{{\mathit{<figure-callout\; id="2"\; label="\Pi "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\Pi </figure-callout>}}^2\mathit{ES}}{12\sigma }}$$

with:

• E: Young's modulus of the carrier element,
• S: sectional area of the carrier element,
• σ: is a limit stress in compression of the material,

where the holding points are the second end of the carrier member attached to the bottom panel, the first end of the carrier member attached to the cover panel and each portion of the carrier member engaged in an opening of the anti-buckling trays. .

Thanks to these characteristics, it is possible to determine the number of trays necessary for a defined thermal insulation element thickness.

According to one embodiment, the heat-insulating element comprises a plurality of anti-buckling plates positioned equidistantly in the thickness of the heat-insulating element.

Thanks to these characteristics, a force experienced by a carrier element is distributed identically on each of the sections of the carrier element defined by the position of the anti-buckling plates.

According to one embodiment, a heat-insulating element comprises positioning means able to position the anti-buckling plate in the thickness of the heat-insulating element.

Thanks to these characteristics, the anti-buckling plate does not crush non-structural insulation.

According to one embodiment, the positioning means are arranged on the carrier elements, to block the translation of the anti-buckling plate in a longitudinal direction of the plurality of carrier elements.

Thanks to these characteristics, the number of pieces is reduced.

According to one embodiment, the positioning means comprise a shoulder defined by a difference in cross-section between two adjacent longitudinal segments of a carrier element of the plurality.

According to one embodiment, for the shoulder capable of holding the anti-buckling plate,
the dimensions of the plurality of openings of the anti-buckling plate are between sectional dimensions of a first of the two segments and sectional dimensions of the second segment of the carrier element.

Thanks to these characteristics, the anti-buckling plate rests on the shoulder.

According to one embodiment, the positioning means comprise a spacer tube threaded onto a support member, the spacer tube having an outer diameter greater than the dimensions of the opening of the anti-buckling panel to provide an end of the spacer tube, a support at the anti-buckling panel, and at the other end of the spacer tube a support against the bottom panel of the heat insulating element or other anti-buckling plate.

Thanks to these characteristics, positioning is achieved more simply.

According to one embodiment, the positioning means is a clamped clip on the carrier member blocking the translation movement of the anti-buckling plate in a direction along the direction of the carrier elements. Alternatively, the anti-buckling plate is caught between two clips prohibiting any movement in the longitudinal direction of the carrier elements.

According to one embodiment, the positioning means comprise a longitudinal portion of a carrier member which is flared and in which the dimensions of an opening of the anti-buckling plate substantially correspond to the dimensions of the section of the longitudinal portion of the carrier element.

With these characteristics, it is possible with the same carrier element to create heat insulating elements, with trays at different heights by adapting the size of the opening on the tray.

According to one embodiment, the positioning means comprise support pillars orthogonal to the bottom panel, a first end of which is integral with the bottom panel and the other end serves as a fulcrum for said anti-buckling plate.

• une barrière d'isolation thermique primaire en appuie et retenue sur la barrière d'étanchéité, la barrière d'isolation thermique primaire étant constituée d'une pluralité d'éléments calorifuges primaires juxtaposés de manière à former une surface de support primaire,
• une barrière d'étanchéité primaire en appui sur la surface de support primaire, un élément calorifuge primaire présentant les mêmes caractéristiques que l'élément calorifuge indiqué secondaire.

According to one embodiment, the invention also provides a sealed and insulating tank arranged in a supporting structure, the tank comprising from outside the tank towards the inside of the tank:

• a primary thermal insulation barrier is supported and retained on the sealing barrier, the primary thermal insulation barrier consisting of a plurality of primary heat insulating elements juxtaposed to form a primary support surface,
• a primary sealing barrier resting on the primary support surface, a primary heat-insulating element having the same characteristics as the secondary indicated heat-insulating element.

Such a tank can be part of a land storage facility, for example to store LNG or be installed in a floating structure, coastal or deep water, including a LNG tank, a floating storage and regasification unit (FSRU) , a floating production and remote storage unit (FPSO) and others.

According to one embodiment, a vessel for the transport of a cold liquid product comprises a double hull and a aforementioned tank disposed in the double hull.

According to one embodiment, the invention also provides a method of loading or unloading such a vessel, in which a cold liquid product is conveyed through isolated pipes from or to a floating or land storage facility to or from the vessel vessel.

According to one embodiment, the invention also provides a transfer system for a cold liquid product, the system comprising the abovementioned vessel, insulated pipes arranged to connect the vessel installed in the hull of the vessel to a floating storage facility. or terrestrial and a pump for driving a flow of cold liquid product through the insulated pipelines from or to the floating or land storage facility to or from the vessel vessel.

Some aspects of the invention start from the idea of increasing the insulation power of an insulating block. Some aspects of the invention start from the idea of increasing the thickness of the insulating block, increasing the length of the support elements. Some aspects of the invention start from the idea of reinforcing the insulating block. Certain aspects of the invention start from the idea of opposing the effects of buckling of the support elements.

Brief description of the figures.

• La figure 1 est une vue partielle en perspective écorchée d'une paroi de cuve étanche et thermiquement isolante utilisant des caissons calorifuges.
• La figure 2 est une représentation schématique de côté d'un élément calorifuge qui peut être utilisé dans la paroi de cuve de la figure 1 illustrant des contraintes et déformations auxquelles il est soumis.
• La figure 3 est une vue en perspective partiellement en transparence d'un élément calorifuge présentant un panneau de couvercle renforcé.
• La figure 4 est une vue schématique illustrant les effets du flambage d'un pilier soumis à une force supérieure à l'effort maximal admissible par ce pilier.
• La figure 5 est une vue partielle en perspective écorchée d'un caisson isolant comprenant un plateau anti-flambement placé entre deux couches d'isolant thermique.
• La figure 6 est une vue en perspective d'un pilier comportant un épaulement permettant le positionnement d'un plateau selon la figure 5.
• Les figures 7a à 7g sont des vues de dessus d'un pilier pouvant être utilisé dans pour un caisson selon la figure 5.
• La figure 8 est une représentation schématique écorchée d'une cuve de navire méthanier comportant une barrière isolante composée de caissons selon la figure 5 et d'un terminal de chargement/déchargement de cette cuve.

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the accompanying drawings.

• The figure 1 is a partial cutaway perspective view of a sealed and thermally insulating tank wall using heat insulated caissons.
• The figure 2 is a schematic side view of a heat insulating element that can be used in the tank wall of the figure 1 illustrating constraints and deformations to which it is subjected.
• The figure 3 is a partially transparent perspective view of a heat insulating element having a reinforced cover panel.
• The figure 4 is a schematic view illustrating the effects of buckling of a pillar subjected to a force greater than the maximum force allowed by this pillar.
• The figure 5 is a partial perspective cutaway view of an insulating box comprising an anti-buckling plate placed between two layers of thermal insulation.
• The figure 6 is a perspective view of a pillar having a shoulder for positioning a tray according to the figure 5 .
• The Figures 7a to 7g are top views of a pillar that can be used in for a box according to the figure 5 .
• The figure 8 is a cutaway schematic representation of a tank of a LNG carrier with an insulating barrier composed of caissons according to the figure 5 and a loading / unloading terminal of this vessel.

Detailed description of embodiments.

In this description, we call above, above or on, what is towards the inside of the tank, and below, below or below, which is towards the outside of the tank, independently of the gravity field. .

In the different variants shown in the drawings, the components that play the same role have been designated by the same reference numerals even if their implementation has been somewhat modified.

The figure 1 represents a sealed and insulating wall of a tank integrated in a carrying structure of a ship.

The bearing structure of the tank is constituted by the inner hull of a double-hulled vessel, whose wall is represented by the number 1.

On the wall 1 of the supporting structure, a corresponding wall of the tank is made by superposition of, successively, a secondary insulation layer 2, a secondary sealed barrier 3, a primary insulation layer 4 and a primary sealed barrier 5 .

The primary insulation layer 4 and the secondary insulation layer 2 consist of heat-insulating elements and more particularly heat-insulated parallelepipedic boxes 6 and 7 juxtaposed in a regular pattern. The primary caissons 7 and the secondary caissons 6 thus form a substantially flat surface which carries respectively the primary watertight barrier 5 and the secondary watertight barrier 3.

The primary watertight barrier 5 and the secondary watertight barrier 3 consist of parallel Invar® 8 strakes with raised edges, which are alternately arranged with elongated welding supports (not shown), also in Invar®. More specifically, the welding supports extend perpendicularly to the wall and are retained each time at the underlying insulation layer 2 or 4, for example by being housed in inverted T-shaped grooves 10 formed in the lids panels 11 of the boxes 6 and 7. The raised edges of the strakes 8 are welded along the weld supports.

The primary insulating boxes 7 and the secondary insulating boxes 6 are held on the supporting structure by means of anchoring members 12. In particular, the anchoring members 12 of the secondary insulating layer 2 are fixed to the wall tank 1 through studs 13 welded perpendicularly to the wall 1. FR-A-2973097 describes such a tank, in particular the anchoring members 12 serving to fix the primary insulating boxes 7 and the secondary insulating boxes 8.

The figure 2 illustrates the structure of a box 15 which can be implemented in such a tank wall.

The box 15 has a bottom panel 16 on which are placed ladders 17 consisting of rows of pillars 18 extending perpendicularly to the bottom panel 16, a batten 19 and a beam 20. Each row of pillar 18 s presses the bottom panel 16 through the batten 19 and carries the beam 20 which supports the cover panel 11 and is attached thereto. The assembly of the ladders 17 and their attachment to the panels is carried out using fastening elements, for example by stapling. A heat-insulating lining 21 is disposed between the bottom panel 16 and the lid panel 11 and surrounds the pillars 18.

The beams 20 make it possible to stiffen the cover panel 11 and to distribute the load when the panel is subjected to the stresses which are for example exerted by the fluid present inside the tank and which are schematized here by the arrows 22, by for example, these stresses may be due to the sloshing of the fluid in the tank.

However, when the heat-insulating element is subjected to these constraints, the cover panel 11 tends to deform and warp between two scales 17, under the effect of pressure, along the curves schematized by the curves 24. This deformation tends to cause rotation of the lateral beams located on each side of the median plane of the caisson 15. This rotation is illustrated by the lines 23. This deformation and this rotation causes the bending of the lateral pillars 18 located on the scales on each side of the median plane of the heat insulating element 15 towards the outside of the box, as illustrated by the curve 25. The pillar is thus weakened by this deflection 25, which adds to the stresses of compression exerted on the pillars 18.

The fasteners between the beams and the various elements of the box 15 are thus strongly stressed, which can cause their separation. In addition, this deformation causes a poor distribution of the load through the pillars 18. Indeed, as represented by the arrows 26 and 27, the load 26 exerted by the pillars in the center of the box 15 is much larger than the load 27 exerted by the lateral pillars 20.

To overcome these drawbacks, the box 15 can be replaced by a reinforced box 30 as shown in FIG. figure 3 . Such a box 30 comprises a bottom panel 31 on which are attached slats 32. A row of pillars 33 is positioned and fixed each time above a batten 32 corresponding. A reinforced cover panel 34 is attached to the pillars 33. The pillars 33 allow in particular the transmission of the stresses exerted on the cover panel 34 to the wall 1 and therefore have a compressive strength function. A heat-insulating lining, not shown, fills the space between the pillars and may for example be made of an insulating foam cast between the pillars 33 or a block of foam machined to fit the pillars 33.

The rows of successive pillars 33 are shifted relative to each other. Indeed, the pillars 33 of the two successive rows 29 and 39 comprise pillars 33 spaced at the same regular spacing, however, the two rows of pillars 33 are offset in the direction of their length by half a spacing. Such an arrangement allows a good compromise between the number of pillars 33 in the box 30 and the good distribution of the load.

The reinforced cover panel 34 has an upper panel 35 and a lower panel 36 each having a thickness of 15mm and spaced apart by a series of parallel solid beams 37. In particular, the beams 37 extend parallel to the longitudinal sides of the box 30. A beam 37 is each time positioned along and above a row of pillars 33. The beams 37 have a rectangular section and a thickness of 15mm. However, these beams may also have a trapezoidal section. The beams 37 and the panels 35 and 36 are rigidly connected, thus when the upper panel 35 is subjected to the stresses exerted by the fluid and tends to warp, the lower panel 36 works in tension, which prevents the rotation of the beams 37. Moreover , the beams 37 being immobilized by the lower panel 36, the deformation of the upper panel 35 is attenuated.

avec:

• E : module d'Young de l'élément porteur ;
• S : surface en section de l'élément porteur ;
• σ : est une contrainte limite en compression du matériau de l'élément porteur.

As described, the mechanical characteristics of a box 6 or a box 7 are related to those of the cover panel 11 or 34, but also the pillars 33 undergoing the compressive force. To be able to increase the insulating power of a box 6 or 7, one uses a material having a superior insulating power, or one increases the thickness of the box. In this second case, this results in increasing the length of the pillars 33. Beyond a certain length, the pillar 33 is exposed to a risk of buckling or rupture. The case of the rupture corresponds to a stress on the pillar 33 much higher than that which one must exercise to cause a buckling. For a pillar 33 made of plywood, the break is more like a delamination between the different layers. In the event of a force lower than the breaking point of the pillar 33, but greater than that of buckling, the box 6 or 7 is likely to locally deform. It is therefore necessary to determine the critical buckling height of a pillar made of a given material. This critical height Hc this calculation with the following formula: $$\mathit{hc}=\sqrt{\frac{{\mathit{<figure-callout\; id="2"\; label="\Pi "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\Pi </figure-callout>}}^2\mathit{ES}}{12\sigma }}$$

with:

• E: Young's modulus of the carrier element;
• S: sectional area of the carrier element;
• σ: is a limiting stress in compression of the material of the carrier element.

For example, the evaluation of the critical height Hc, as a function of the surface of the carrier element is determined using the data of Table 1. It is found that the critical height is dependent on the temperature of use of the material . <i> Table 1: characteristics of materials for examples of load-bearing elements. </ i> Plywood Composite material, fiberglass polypropylene resin 23 ° C -70 ° C -160 ° C 23 ° C -170 ° C E in GPa 6.7 9 10 7 9 σ in MPa 30 60 80 95 300

Thus, it is possible to determine whether for a box thickness 6 or 7 chosen as a function of its thermal insulation power, the pillars 33 have a length greater than the critical height.

The figure 4 illustrates the effects of a variable load 45 at different locations on the surface of a box 30. This load 45 is not evenly distributed over the surface of the cover panel 34 of the box 30. The load 45 is lower with a 45a force outside the surface of the box in the alignment of the pillar 33a and increases to the maximum force 45c. This effort 45c located at right pillar 33c flambers the pillar 33c. As shown in figure 4 , the effects of buckling on the pillar 33c are the highest at half the distance between two attachment points of the pillar 33c. In this schematic illustration the fixing points are the fixing with the lid panel 34 and the fixing with the bottom panel 31 which is not shown here.

Containing the buckling therefore amounts to blocking the lateral movement undergone by the pillar 33c under the effect of the force 45c. By interposing between the pillars 33 a plate 40, it is possible to limit the lateral movements. Each pillar 33 passes through this plate 40 into openings 41. The plate 40 secures the pillars 33 between them to avoid displacements in the plane. The force exerted by a pillar 33c on the plate 40 under a force 45c is taken up by all the other pillars 33a.

This plate 40 is preferably placed at mid-distance between the two anchoring points of the pillar 33. Thus, the plate 40 is placed at the point of maximum observed deformation, of the pillar 33 in the buckling mode 1.

Alternatively, it is possible to arrange the plate at other locations in the longitudinal direction of a pillar 33. However, to improve its efficiency, it is necessary to prevent the length of one of the segments of the pillar 33 between the plate and the bottom panels or covers, is greater than the critical height Hc of buckling of this pillar 33.

The openings 41 have a dimension slightly greater than that of the pillars 33, creating a game 42. This game 42 is intended to facilitate the mounting of the plate 10 on the pillars 33. The presence of this game 42, leaves a degree of freedom of the plaque. Under the effect of a force exerted by the pillar 33c at the point of contact 47, the plate is translated in the direction of the buckling 46 undergone by the pillar 33c. The openings 41 of the plate 40 are then in abutment with the pillars 33a in contact zones 47. The set of pillars 33a then oppose the buckling force by an opposing force 48.

For a good operation the game 42 must be weak. For example, the clearance is less than 3 millimeters, and preferably greater than 1 millimeter.

Alternatively, the holes are fitted on the pillars 33. In the absence of mounting clearance, there is no floating of the plate 40.

Such an anti-buckling plate 40 can be arranged in a box 15 shown in dotted line on the figure 2 .

The figure 5 illustrates a box 30 in which an anti-buckling plate 40 is inserted between two layers 21a and 21b of the heat-insulating packing 21.

The heat-insulating lining 21 can be made using various insulators, such as polyurethane foam, or mineral wools. In the case of the use of a very little structural insulation, such as perlite, the insulation collapses under the weight of the plate 40. In this case, it is necessary to provide positioning means which make it possible to prevent the plate 40 to slide on the pillars 33. Thus, this prevents the plate 40 from crushing the heat insulating pad 21 or in the case of a powdery insulator to produce transfer effects between the compartments of the box 30 delimited by the plate 40.

As illustrated by figure 6 This function is then performed using a positioning pillar 60 comprising a shoulder 61 separating two portions 62 and 63 of the positioning pillar 60. The two portions 62 and 63 are of different square section. The opening 41 corresponding to the positioning pillar 60 has dimensions between the dimensions of the two sections of the positioning pillar 60. Thus, the plate can slide during assembly to come to a stop at the level of the section change defined by the shoulder 61.

The shoulder 61 can be obtained in the mass of the positioning pillar 60, over all or part of its periphery. It can also be obtained using a patch held on the pillar by any known means. For example, the patch is glued. Alternatively, the insert is assembled by a tapped anchor with a glued screw.

To maintain the plate 40, simply install three positioning pillars 60 to stabilize the plate. For this, it is preferable to choose to place the positioning pillars 60 to define a triangle whose surface inscribed in the surface of the box 15 or 30 is the largest.

With the small set of mounting relative to the size of a box 15 or 30, two positioning pillars 60 diagonally are also suitable. It is also possible to support the plate 40 by all the pillars installed in the box 15 or 30. In a preferred embodiment, the positioning pillars 60 are placed at the corners of the box. In the case of caissons 15 or 30 particularly stressed, the center of the plate 40 is also supported.

On a ceiling wall, the shoulder 61 is turned towards the bottom panel 16 or 31, namely upwards in the direction of the gravity field. For a box 15 or 30 disposed on a wall wall, the box 15 or 30 will for example be equipped with two sets of pillars. The shoulders of the first series will be turned towards the bottom panel 16 or 31 and the pillars 60 fixed on the cover panel 11 or 34. In contrast, the pillars 60 of the second series will be fixed on the bottom panel 16 or 31, with the shoulders facing the cover panel 11 or 34.

As an alternative to the shoulder 61, the support is obtained using a spacer tube. This tube is threaded around the pillars 33 disposed at the support positions, such as the corners and the center. This spacer then acts as a reported shoulder. The shoulder 61 or reported spacer prohibit the displacement along the longitudinal axis of the pillars 33 of the plate 40 in one direction. In some cases, it may be useful to block the plate 40 in both directions. It then suffices, after having installed the plate 40 in abutment, to thread a second spacer tube corresponding to the remaining pillar length 33 to immobilize the plate 40 in both directions.

In a variant, the plate 40 is integral with at least three pillars 33. can move more in the direction of the thickness to crush the heat-insulating lining 21. Such a plate 40 is made for example by molding.

The pillars section of the figure 6 is square, but with reference to Figures 7a to 7g all circular, polygonal, solid or hollow H-shaped cross pillars are adapted and can be held by an anti-buckling plate. The anti-buckling function of the plate 40 is ensured by adapting the shape of the opening 41 to the shape of the pillar.

As an alternative to the figure 5 in the case of very thick box 30, it is possible to add as many plates 40 as necessary. It is then preferable that the distance between a plate 40 and a bottom panel 16 or cover panel 34, or between two consecutive plates 40, is less than the critical buckling height of the pillar 33.

If support is required for a box 30 with several plates 40, in the case of a use of positioning pillar 60, it comprises a shoulder 61 plates 40. It then has three portions with three different sectional dimensions. In this case, each plate 40 has openings 41 whose dimensions depend on the section of the positioning pillar 60 at its destination height in the box 15 or 30. Alternatively, the box 15 or 30 has two types of positioning pillars 60 The first type of positioning pillars 60 has a shoulder height 61 different from the height of the shoulder 61 of the second type of positioning pillars 60. The box 15 or 30 is then equipped with two plates 40 which are distinguished by openings 41 whose size to the right of each pillar 33 of the box 15 or 30 is adapted according to the location of the plate 40 in the thickness of the box 15 or 30.

The placement of plates 40 in height relative to the pillar 33, or in the direction of the thickness of the caisson 15 or 30, is free and depends on the conditions of use of the caisson 15 or 30. Preferably, the distribution in the thickness will be homogeneous, regular. The plate or plates 40, the bottom panel 16 and the cover panel 11 or 34 are equidistant in pairs.

As an alternative to the pillars 33 of constant section, the pillar has a section that increases from the top to the base of the pillar, over all or part of its length. For example, it flares out from a square section towards the base to form a truncated pyramid. Alternatively the section of the pillar is a disc and the pillar in the shape of a truncated cone. This solution with increasing section has the additional advantage of making it possible to make a box 15 or 30 with several plates whose height is simply adjusted by the size of the openings 41 present on each plate 40.

The manufacture of the anti-buckling plate 40 can be made of any material, especially plywood with a thickness of less than 20 mm, composite or metallic materials. For a plywood top, the wood used may be birch or any other species.

The realization of the openings 41 may be pierced by any known means and in particular the waterjet cutting, laser cutting, cutting from a punch (or punch), the cutting with the milling cutter.

In the case of pillar 33 with rectangular section for example, the plate 40 may for example be metallic with stamped openings. The stamped portion forming a flange to increase the bearing area 47 of the plate 40 in contact with the pillar 33.

Alternatively, the plate 40 is made of a plastic material, by molding.

The assembly of a heat insulating element can be done in different ways. For example, the manufacturing begins with the realization of the assembly of the bottom panel 16 with the slats 19 serving soleplate on which are added the pillars 33. Then, the lower insulation layer 21a is inserted on the pillar structure 33 followed by the perforated plate 40. A second insulating layer 21b is inserted into the upper structure of the pillars 33. Finally, the cover panel 11 or 34 is fixed to the pillars 33.

Alternatively, the assembly begins with the attachment of the slats 19 to the bottom panel 16. Then the lower insulation slice 21a is added, followed by the perforated plate 40 and the upper insulation slice 21b. The pillars are then inserted using a template plate for positioning the pillars 33. Finally, the box 15 or 30 is finalized with the cover panel 34.

The technique described above for producing an insulating layer can be used in different types of tanks, for example to form the primary and / or secondary insulating membrane of an LNG tank in a land installation or in a floating structure such as a ship LNG carrier or others.

With reference to the figure 8 , a cutaway view of a LNG tanker 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary waterproof barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72.

In a manner known per se, loading / unloading lines 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG to or from the tank 71.

The figure 8 represents an example of a marine terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is an off-shore fixed installation comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges of LNG carriers. A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the shore installation 77 and / or pumps equipping the loading and unloading station 75 are used.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims (17)

1. A sealed, thermally insulated tank incorporated into a support structure for containing a fluid, in which a tank wall comprises, from the outside of the tank toward the inside of the tank:

   a load-bearing wall (1),

   a thermal insulation barrier (2, 4) retained on the load-bearing wall, the thermal insulation barrier being formed from a plurality of insulating elements (15, 30) juxtaposed to form a support surface, and

   a sealing barrier (3, 5) bearing on the support surface,

   an insulating element having a generally flattened prismatic shape, and comprising:

   a thermal insulating material (21),

   a plurality of load-bearing elements (33) passing through the thermal insulating material along a direction of thickness perpendicular to the tank wall, and

   a cover panel (11, 34) and a base panel (16, 31) parallel to the tank wall and arranged at the first ends and the second ends, respectively, of the load-bearing elements of the insulating element, so as form exterior walls of the insulating element, the first ends of the load-bearing elements being fastened to the cover panel and the second ends of the load-bearing elements being fastened to the base panel, and

   characterized in that the insulating element further comprises an anti-buckling plate (40), parallel to the cover panel (11, 34) and to the base panel, sandwiched between a first (21 a) and a second (21 b) portion of the thickness of said thermal insulating material (21), the anti-buckling plate having a plurality of load-bearing elements (33) passing through it in a plurality of openings (41) in the anti-buckling plate, the openings being spaced apart from one another so as to provide a distance between two neighboring load-bearing elements, in a plane defined by the anti-buckling plate.
2. The tank as claimed in claim 1, wherein an opening (41) in the anti-buckling plate has dimensions greater than the dimensions of a cross section of the load-bearing element engaged in the opening, so as to leave an assembly clearance (42).
3. The tank as claimed in claim 2, wherein the assembly clearance (42) is less than three millimeters.
4. The tank as claimed in any of claims 1 to 3, wherein the anti-buckling plate (40) is positioned halfway between the base panel and the cover panel.
5. The tank as claimed in any of claims 1 to 4, wherein the thermal insulating material comprises a second anti-buckling plate parallel to the base panel and the cover panel, sandwiched between the second and a third portion of the thickness of said thermal insulating material,
   the second anti-buckling plate having the plurality of load-bearing elements passing through it in a plurality of openings positioned in alignment with the openings in the first anti-buckling plate.
6. The tank as claimed in any of claims 1 to 5, wherein a said insulating element comprises a plurality of anti-buckling plates (40), the number of anti-buckling plates being greater than or equal to a theoretical number defined in such a way that the distance between two successive support points (47) of a load-bearing element according to the longitudinal orientation of the load-bearing element is less than a predetermined critical height Hc, said critical height being equal to: $$\mathit{Hc}=\sqrt{\frac{{\mathit{\Pi }}^2\mathit{ES}}{12\sigma }}$$

   

   where:

   E: Young's modulus of the load-bearing element,

   S: cross-sectional surface area of the load-bearing element,

   σ is an ultimate compressive stress of the material

   where the support points are the second end of the load-bearing element fastened to the base panel, the first end of the load-bearing element fastened to the cover panel, and each portion of the load-bearing element engaged in an opening of the anti-buckling plates.
7. The tank as claimed in any of claims 1 to 6, wherein the insulating element comprises a plurality of anti-buckling plates (40) positioned in an equidistant way in the thickness of the insulating element.
8. The tank as claimed in any of claims 1 to 7, wherein an insulating element comprises positioning means capable of positioning the anti-buckling plate in the thickness of the insulating element.
9. The tank as claimed in claim 8, wherein the positioning means are arranged on the load-bearing elements, to prevent the translation of the anti-buckling plate in a longitudinal direction of the plurality of load-bearing elements.
10. The tank as claimed in claim 9, wherein the positioning means comprise a shoulder (61) formed by a difference in cross section between two adjacent longitudinal segments of one load-bearing element of the plurality of load-bearing elements.
11. The tank as claimed in claim 10, wherein, for the shoulder (61) capable of supporting the anti-buckling plate,
    the dimensions of the plurality of openings in the anti-buckling plate lie between cross-sectional dimensions of a first of the two segments and cross-sectional dimensions of the second segment of the load-bearing element.
12. The tank as claimed in claim 9, wherein the positioning means comprise a spacer tube fitted onto a load-bearing element, the spacer tube having an outside diameter greater than the dimensions of the opening in the anti-buckling panel so as to provide, at one end of the spacer tube, a bearing point for the anti-buckling panel, and, at the other end of the spacer tube, a bearing point for the base panel of the insulating element or another anti-buckling plate.
13. The tank as claimed in claim 9, wherein the positioning means comprise a longitudinal portion of a load-bearing element which is flared from the first end of the load-bearing element toward the second end of the load-bearing element, and wherein the dimensions of an opening in the anti-buckling plate substantially correspond to the cross-sectional dimensions of the longitudinal portion of the load-bearing element.
14. The tank as claimed in claim 8, wherein the positioning means comprise supporting pillars orthogonal to the base panel, a first end of each pillar being fastened to the base panel, while the other end serves as a bearing point for said anti-buckling plate.
15. A ship (70) for transporting a refrigerated liquid product, the ship comprising a double hull (72) and a tank (71) as claimed in any of claims 1 to 14 positioned in the double hull.
16. A method for loading or unloading a ship (70) as claimed in claim 15, wherein a refrigerated liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or land-based storage installation (77) to or from the tank of the ship (71).
17. A transfer system for a refrigerated liquid product, the system comprising a ship (70) as claimed in claim 15, insulated pipes (73, 79, 76, 81) arranged so as to connect the tank (71) installed in the ship's hull to a floating or land-based storage installation (77), and a pump for propelling a flow of refrigerated liquid product through the insulated pipes from or to the floating or land-based storage installation to or from the ship's tank.

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