Watertight tank

Abstract

The invention relates to a tank comprising a tank wall (1) including: - a fixing wall; - a spacer (5) disposed and fixed against the fixing wall by an anchor, the spacer having an external end, an internal face, and lateral ends, the external end being against the fixing wall; - and an internal membrane (6) spaced from the fixing wall by the spacer and comprising a flat portion fixed against the internal face of the spacer, the spacer having a retaining surface between the internal face and the external end, the anchor comprising a rigid element and an elastic fixing element, the rigid element having a retaining zone located between the external end and the internal end of the rigid element, the fixing element cooperating with the retaining zone and the retaining surface to fix the spacer to the fixing wall by elastic interlocking. Figure for the abstract: 1

Description

Title of the invention: Watertight tank technical field

[0001] The invention relates to the field of leak-proof tanks. In particular, the invention relates to the field of leak-proof tanks for the storage and / or transport of a liquefied gas. Technological background

[0002] In the prior art, sealed tanks for the storage of a liquefied gas are known. Such a sealed tank comprises, for example, a tank wall having a multilayer structure which includes successively, from the inside of the tank, a primary sealed membrane intended to be in contact with a liquefied gas contained in the tank, a primary insulating barrier, a secondary sealed membrane and a secondary insulating barrier intended to be fixed to a supporting structure. Summary of the invention

[0003] The inventors observed that, in the case of storing a liquefied gas other than liquefied natural gas (LNG) in tanks initially designed to store LNG, if the primary leak-proof membrane is damaged or has an imperfection that allows liquid gas to pass into the inter-membrane space, the tanks designed to store LNG would not always allow the tank to be kept in safe operation. This is because the components located below the primary membrane of tanks designed to store LNG are made of materials that deteriorate upon contact with certain liquefied gases.

[0004] For example, in the case of a tank suitable for use in storing LNG, the elements located under the primary membrane will not necessarily be suitable for contact with another liquefied gas, such as ammonia.

[0005] On the other hand, liquid ammonia, which is a denser liquid and therefore heavier than LNG for example, would have greater stresses transmitted to the primary sealing membrane and could therefore cause damage to a primary sealing membrane.

[0006] There is therefore a real need to design or improve tanks intended to receive liquefied gas, particularly for receiving liquefied gas that is incompatible with the underlying insulation elements, especially when the thermal insulation consists of polypropylene or polyurethane foam, or plywood. Indeed, contact between these elements and certain liquefied gases such as ammonia leads to a significant loss of mechanical strength of these elements.

[0007] One idea underlying the invention is to solve at least some of the aforementioned problems.

[0008] Another idea underlying the invention is to produce a sealed tank suitable for receiving a liquefied gas, in particular a gas incompatible with certain thermally insulating materials, for example liquefied ammonia which is at approximately -33°C at atmospheric pressure.

[0009] Another idea underlying the invention is to produce an improved sealed tank.

[0010] According to one embodiment, the invention provides a sealed tank for storing a liquefied gas, the sealed tank comprising a tank wall intended to be installed in a supporting structure, the tank wall comprising, along a thickness direction of the tank wall: - a fixing wall; - a spacer block placed on the fixing wall and fixed against the fixing wall by an anchoring device, the spacer block having an external end, a flat internal face parallel to the external end and lateral ends connecting the external end to the internal face, the external end being positioned against the fixing wall; - and an internal metallic sealing membrane intended to be in contact with the liquefied gas, wherein the internal sealing membrane is spaced from the fixing wall by the spacer block and includes at least one flat portion which is fixed against the inner face of the spacer block, wherein the spacer block has a retaining surface located between the inner face and the outer end, in which the anchoring member comprises a rigid element projecting from the fixing wall and an elastic fixing element, the rigid element having an external end fixed against the fixing wall and an opposite internal end located at a distance from the external end, the rigid element having a retention zone located between the external end and the internal end, the fixing element cooperating with the retention zone and the retention surface in order to fix the spacer block to the fixing wall by elastic interlocking of the fixing element in the retention zone.

[0011] Thanks to these features, the spacer block is effectively attached to the mounting wall. Furthermore, the elastic snap-fit ​​attachment facilitates the fixing of the spacer block to the mounting wall and thus simplifies the manufacturing of the tank.

[0012] According to embodiments, such a tank may include one or more of the following characteristics.

[0013] According to one embodiment, the fixing wall comprises an external waterproof membrane.

[0014] According to one embodiment, the rigid element is a rod protruding from the external waterproof membrane, the rod having an external end fixed against the external waterproof membrane, the fixing element cooperating with the retention area and the retention surface in order to fix the spacer block to the external waterproof membrane.

[0015] According to one embodiment, the inner end of the rod has a chamfer to facilitate the elastic fitting of the fastening element in the retention area.

[0016] According to one embodiment, the rigid element is a sheet metal part having cutouts and folds, welded for example by resistance to the external waterproof membrane.

[0017] In one embodiment, the external waterproof membrane comprises parallel corrugations spaced apart by flat areas, each flat area being delimited by two adjacent parallel corrugations. In one embodiment, the rigid element protrudes from said flat area, the outer end of the rigid element, preferably the outer end of the rod, being fixed against said flat area, and the outer end of the spacer block being positioned against said flat area.

[0018] According to one embodiment, the external waterproof membrane comprises a second series of corrugations perpendicular to the first series of corrugations.

[0019] According to one embodiment, said flat zone is defined between two undulations of the first series of undulations and two undulations of the second series of undulations.

[0020] According to one embodiment, the undulations of the external sealing membrane are salient with respect to the flat areas in the direction of the interior of the tank.

[0021] According to one embodiment, a height of the first series of undulations is less than a height of the second series of undulations in the thickness direction of the tank wall.

[0022] According to one embodiment, the fastening element is able to be elastically fitted by a rectilinear translation movement.

[0023] According to one embodiment, the rectilinear translation movement is carried out along the thickness direction of the tank wall and / or along the direction perpendicular to the thickness direction of the tank wall.

[0024] According to one embodiment, the fixing element is constrained by compression along the thickness direction of the tank wall.

[0025] Thus, the elastic fixing element is in a constrained state and will tend to regain its shape from the unconstrained state, improving the fixing of the spacer block to the external sealing membrane.

[0026] According to one embodiment, the fastening element comprises a first portion in contact with the retention surface and a second portion in contact with the retention zone.

[0027] According to one embodiment, the first portion of the fastening element is fixed on the retaining surface.

[0028] According to one embodiment, the first portion is connected to the second portion, the first and second portions being able to be brought together elastically. In other words, said first and second portions are configured to be brought together under the effect of an external force and to return to their initial position when no force is applied, thus giving the element an elastic springback property.

[0029] According to one embodiment, the first portion is an external portion and the second portion is an internal portion, the internal portion being closer to the inside of the tank than the external portion.

[0030] According to one embodiment, the inner portion and the outer portion are formed by a single bent rod.

[0031] According to one embodiment, the fixing element has a plane of symmetry along the thickness direction of the tank wall.

[0032] According to one embodiment, the fastening element comprises an elastic locking chamber receiving the retention zone and fixing the fastening element to the retention zone.

[0033] According to one embodiment, the locking chamber has locking claws configured to lock the rod retention area in the locking chamber.

[0034] According to one embodiment, the locking chamber includes a release sleeve configured to allow the release of the retention area by exerting an action on the release sleeve, the action being for example pushing the sleeve or pulling the sleeve.

[0035] In one embodiment, the fastening element includes a compression stop intended to limit the elastic travel of the fastening element. In another embodiment, the retention area includes a recess cooperating with the fastening element.

[0036] According to one embodiment, the retention area includes a protrusion cooperating with the fastening element.

[0037] According to one embodiment, the retaining surface has a groove, the fixing element being housed in said groove.

[0038] Thus, the groove allows the fixing element to be guided to facilitate its positioning and / or allows compression to be applied in the direction perpendicular to the thickness direction of the wall.

[0039] According to one embodiment, the groove extends on both sides of the retaining surface.

[0040] In one embodiment, the groove is formed by a protrusion projecting from an inner face of the retaining surface. In one embodiment, the protrusion is located at a distance from the inner face of the spacer block. In one embodiment, the protrusion is located at a distance from the external sealing membrane.

[0041] According to one embodiment, the groove is formed by a protrusion projecting from an external face of the retaining surface. According to another embodiment, the groove is formed by two protrusions projecting from an external face of the retaining surface, the two protrusions being located at a distance and opposite each other.

[0042] According to one embodiment, the external portion is housed in the groove of the retaining surface.

[0043] According to one embodiment, the fastening element is located between the inner end of the rigid element, preferably the inner end of the rod, and the retaining surface.

[0044] According to one embodiment, the first portion of the fastening element is in contact with an internal face of the retaining surface.

[0045] According to one embodiment, the fastening element has two longitudinal branches extending on either side of the rigid element, preferably the rod, in a direction transverse to the direction of the tank wall thickness, the two longitudinal branches clamping the rod at the retention zone. According to another embodiment, the fastening element has two longitudinal branches extending on either side of the rigid element, preferably the rod, in a direction perpendicular to the direction of the wall thickness.

[0046] According to one embodiment, the fastening element comprises a through hole along the thickness direction of the tank wall, the through hole having a first zone, and a second zone of smaller width than the first zone and spaced from the first zone in the direction perpendicular to the thickness direction of the tank wall, and in which the rod passes through the first zone in an unlocked position in which the rod can be inserted and removed from the hole in the thickness direction of the tank wall and the second zone in a fastening position.

[0047] Thus, the first stage has dimensions allowing the reversible or movable insertion of the rod and the second stage has dimensions allowing the locking the rod by preventing its release under normal conditions of use of the tank.

[0048] According to one embodiment, the contour of the second stage of the through orifice is in a butt position against the retention zone.

[0049] According to one embodiment, the fastening element is located between the retaining surface and the external metallic sealing membrane.

[0050] According to one embodiment, the fixing element has an arched shape comprising a top and two bases, the top being located near the inner face of the spacer block and the two bases being located against the retaining surface.

[0051] In one embodiment, the first of the two bases forms a first lateral end of the fastening element and the second of the two bases forms a second lateral end of the fastening element. In another embodiment, the apex is located equidistant from the two bases.

[0052] According to one embodiment, the arched shape is slightly curved. According to one embodiment, a segment is delimited by the first and second lateral ends of the fixing element, and a height is delimited by the distance between the apex and the midpoint of the segment, in which the height is less than the length of the segment, for example the ratio height to length of the segment is less than 2.

[0053] According to one embodiment, the compression stop of the fastening element comprises a portion projecting from the top of the inner portion, in the wall thickness direction, towards the outside of the tank. According to another embodiment, the portion projects while remaining at a distance from the retaining surface.

[0054] According to one embodiment, the fastening element is a thin piece, for example less than 20 mm.

[0055] According to one embodiment, the fastening element is mounted in a removable manner.

[0056] According to one embodiment, the fastening element is chosen from: a spring with blade, a formed wire spring and a locking chamber.

[0057] In one embodiment, the lateral ends of the spacer block comprise a first lateral end extending parallel to the first series of corrugations. In another embodiment, the first lateral end is oriented towards a first corrugation of the first series of corrugations. In another embodiment, the inner face comprises a first end portion partially overhanging the first corrugation of the first series of corrugations.

[0058] According to one embodiment, the lateral ends of the spacer block comprise a second lateral end extending parallel to the second series of corrugations. According to another embodiment, the second lateral end is oriented respectively towards a first corrugation of the second series of corrugations. According one embodiment, the inner face comprising a second end portion partially overhanging the first undulation of the second series of undulations.

[0059] In one embodiment, the lateral ends comprise a third lateral end located opposite the first lateral end and extending parallel to the first series of corrugations. In another embodiment, the third lateral end is oriented towards a second corrugation of the first series of corrugations. In another embodiment, the inner face comprises a third end portion partially overhanging said second corrugation of the first series of corrugations.

[0060] In one embodiment, the lateral ends comprise a fourth lateral end located opposite the second lateral end, extending parallel to the second series of corrugations. In another embodiment, the fourth lateral end extends between the outer end and the inner face of the spacer block towards a second corrugation of the second series of corrugations. In another embodiment, the inner face comprises a fourth end portion partially overhanging said second corrugation of the second series of corrugations.

[0061] According to one embodiment, the spacer block comprises support ribs located under the inner face between the lateral ends and hollow cells located between the support ribs. Thus, the spacer block is reinforced by the support ribs. In addition, the hollow cells provide inerting of the internal space of the spacer block, allowing the passage of gas molecules between the hollow cells located inside the spacer block and the inter-membrane space located between the inner and outer airtight membranes.

[0062] According to one embodiment, the external end of the spacer block is formed by a flat external face parallel to the internal face.

[0063] Thanks to these characteristics, the support of the internal waterproof membrane by the spacer block is improved.

[0064] According to one embodiment, at least one of the lateral ends comprises a side wall through which a through passage passes. Thus, the installation of the fastening element is facilitated.

[0065] According to one embodiment, the first lateral end comprises a lateral wall through which a through passage passes.

[0066] According to one embodiment, at least one lateral end of the lateral ends comprises a plurality of through passages.

[0067] According to one embodiment, the spacer block is made of a material compatible with the liquefied gas which is intended to be contained in the tank.

[0068] According to one embodiment, the spacer block comprises aluminum or a thermoplastic material.

[0069] In one embodiment, the spacer comprises an aluminum alloy, for example, aluminum alloy 6082. In another embodiment, the spacer block comprises more than 50% aluminum by mass of the spacer. In another embodiment, the spacer block consists of aluminum.

[0070] Thanks to these characteristics, the spacer block is compatible with ammonia; that is, the spacer block is not damaged by contact with liquid or gaseous ammonia. In other words, the physical properties of the spacer block, which primarily support the internal sealing membrane, are not altered by contact with ammonia. Consequently, thanks to these characteristics, if the internal sealing membrane is damaged and allows liquid or gaseous ammonia to pass into the inter-membrane space, the tank containing the damaged internal sealing membrane can continue to operate without having to empty the tank.

[0071] The spacer block is in particular considered compatible if it can be in contact with liquid or gaseous ammonia for at least 8 days without its carrying capacity being altered.

[0072] According to one embodiment, the spacer block comprises aluminum and is obtained by extrusion.

[0073] According to one embodiment, the thermoplastic material is chosen from: high-density polyethylene, polypropylene and high-impact polystyrene.

[0074] According to one embodiment, the thermoplastic spacer block comprises fibers, for example long fibers.

[0075] According to one embodiment, the composite spacer block is obtained by thermoforming or by injection.

[0076] According to one embodiment, the spacer block does not include thermally insulating materials.

[0077] According to one embodiment, the thickness of the spacer block is between 20 and 150 mm.

[0078] According to one embodiment, the spacer block has a thickness greater than a height of the first series of corrugations in the thickness direction of the tank wall and the external end of the spacer block is disposed on a second flat area of ​​said flat areas of the external sealing membrane, the spacer block extending over at least one other corrugation of the first series of corrugations located between said first flat area and said second flat area.

[0079] According to one embodiment, the spacer block has a thickness greater than a height of the second series of undulations in the thickness direction of the tank wall and the outer end of the spacer block is disposed on another flat area of ​​the outer sealing membrane, the spacer block extending over another corrugation of the second series of corrugations situated between said first flat area and said other flat area.

[0080] According to one embodiment, the spacer block is a first spacer block, the flat area is a first flat area and the anchoring member is a first anchoring member comprising a first rigid element and a first elastic fixing element, the tank wall further comprises a second spacer block and a second anchoring member, and the second spacer block is fixed to a second flat area of ​​the external sealing membrane by the second anchoring member.

[0081] According to one embodiment, the second anchoring member comprises a second rigid element projecting from the second flat area and a second elastic fixing element, the second rigid element having an external end fixed against the external metallic waterproof membrane and an opposite internal end located at a distance from the external end, the second rigid element having a retention area located between the external end and the internal end, the second fixing element cooperating with the retention area and the retention surface in order to fix the second spacer block to the external waterproof membrane by elastic interlocking of the second fixing element in the retention area.

[0082] According to some embodiments, the second anchoring member has the same technical characteristics as the aforementioned first anchoring member. According to other embodiments, the second anchoring member has different characteristics from the aforementioned first anchoring member.

[0083] According to one embodiment, the tank wall comprises a plurality of spacer blocks including said spacer block and comprises a plurality of anchoring members including said anchoring member, in which the plurality of spacer blocks are respectively fixed to one of the flat areas of the external sealing membrane by an anchoring member of the plurality of anchoring members.

[0084] According to one embodiment, the spacer blocks are as described above. According to one embodiment, the spacer blocks have the same technical characteristics. According to one embodiment, the spacer blocks may have different characteristics.

[0085] According to one embodiment, the anchoring elements are anchoring elements as described above. According to one embodiment, the anchoring elements have the same technical characteristics. According to one embodiment, the anchoring elements may have different characteristics.

[0086] According to one embodiment, a spacer block is located on each flat area of ​​the external waterproof membrane and fixed to said flat area via an anchoring device.

[0087] According to one embodiment, each flat area of ​​the external waterproof membrane is covered by an external end of a spacer block which is disposed on it.

[0088] According to one embodiment, each flat area of ​​the external waterproof membrane includes a rod of the anchoring element as mentioned above.

[0089] In one embodiment, the outer end of the spacer block rests on several flat areas. In another embodiment, the anchoring member comprises rods projecting from each flat area where the outer end of the spacer block rests and includes an elastic fastening element for each rod to fix the spacer block to the external waterproof membrane.

[0090] According to one embodiment, the outer end of the spacer block rests on a single flat area.

[0091] In one embodiment, the internal sealing membrane comprises parallel corrugations spaced apart by flat areas, each flat area being delimited by two adjacent parallel corrugations. In one embodiment, the internal sealing membrane comprises a second series of corrugations perpendicular to the first series of corrugations. In one embodiment, at least one of the flat areas is defined between two corrugations of the first series of corrugations and two corrugations of the second series of corrugations. In one embodiment, the corrugations of the external sealing membrane are projecting from the flat areas towards the interior of the tank. In one embodiment, a height of the first series of corrugations is less than a height of the second series of corrugations in the direction of the tank wall thickness.

[0092] According to one embodiment, the internal sealing membrane is intended to be in contact with ammonia, butane, propane or ethane, preferably with ammonia.

[0093] According to one embodiment, the internal sealing membrane and the external sealing membrane are made of stainless steel.

[0094] According to one embodiment, the fixing wall comprises a concrete wall or a ship's hull.

[0095] According to one embodiment, the fixing wall includes an auxiliary barrier on which the external sealing membrane is positioned, and the auxiliary barrier comprises, from the outside to the inside of the tank: a secondary thermally insulating layer intended to be fixed to a load-bearing structure, an auxiliary sealing membrane resting against the secondary thermally insulating layer and an intermediate insulating layer located against the secondary sealing membrane, the external sealing membrane being positioned against the intermediate thermally insulating layer.

[0096] For example, the secondary and / or intermediate thermally insulating layer may include insulating elements made of various materials, including materials incompatible with ammonia such as polyurethane foam or glass wool.

[0097] According to one embodiment, the auxiliary barrier comprises a modular block fixed to the supporting structure, the modular block comprising successively, along a thickness direction of the modular block, a secondary thermally insulating layer, a waterproof membrane made of composite material which rests against the secondary thermally insulating layer, an intermediate thermally insulating layer covering the waterproof membrane made of composite material.

[0098] According to one embodiment, the auxiliary waterproof membrane is a flexible membrane made of composite material bonded to the secondary thermally insulating layer.

[0099] According to one embodiment, the waterproof membrane made of composite material comprises a metallic sheet sandwiched between two layers of unresined glass fibers, also known as Triplex®.

[0100] According to one embodiment, the tank contains liquefied gas, for example ammonia, butane, propane or ethane, and preferably ammonia.

[0101] According to one embodiment, the aforementioned tank wall is a bottom wall of the tank when the tank is in a position of use.

[0102] According to one embodiment, the aforementioned tank wall is a side wall of the tank when the tank is in a position of use.

[0103] According to one embodiment, the tank comprises a plurality of the aforementioned walls.

[0104] According to one embodiment, the invention also provides a method for adapting a a sealed tank initially intended for the storage of a first liquefied gas, the process comprising: - fix a spacer block as described above on the inside of the tank on at least one flat area of ​​a sealed membrane, in which the sealed membrane is a primary membrane belonging to a sealed tank wall for the storage of the first liquefied gas such as LNG, the sealed membrane being metallic and comprising a first series of parallel corrugations, - and fix at least one flat area of ​​an internal metallic waterproof membrane against the inner face of the spacer block via a primary anchoring device mentioned above.

[0105] The use of this process makes it possible in particular to anchor the spacer block directly onto a primary membrane belonging to a sealed and thermally insulating tank wall for the storage of LNG in order to make the tank compatible with ammonia.

[0106] Such a tank may be part of an onshore storage facility, for example for storing LNG, or be installed in a floating structure, coastal or deep water, in particular an LNG carrier, a floating storage unit and regasification units (FSRUs), floating production and storage units (FPSOs), and others. Such a tank can also serve as a fuel tank in any type of vessel.

[0107] According to one embodiment, the supporting structure rests on the ground, on a seabed or is part of a ship.

[0108] According to one embodiment, a ship for the transport of a liquefied gas comprises a double hull and the aforementioned tank disposed in the double hull.

[0109] According to one embodiment, the invention also provides a transfer system for a liquefied gas, the system comprising the aforementioned vessel, insulated pipes arranged to connect the tank installed in the hull of the vessel to a floating or land-based storage facility and a pump to drive a flow of liquefied gas through the insulated pipes from or to the floating or land-based storage facility to or from the vessel's tank.

[0110] According to one embodiment, the invention also provides a method for loading or unloading such a vessel, in which a liquefied gas is conveyed through insulated pipelines from or to a floating or land-based storage facility to or from the vessel's tank. Brief description of the figures

[0111] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0112] Fig. 1 represents a partial schematic cross-sectional view of a wall of a sealed tank.

[0113] [Fig.2] illustrates a cross-sectional view of a spacer block that can be used in area I of [Fig.1], according to one embodiment.

[0114] Fig. 3 illustrates a partial cross-sectional view of a tank wall according to a first embodiment that can be used in zone I of Fig. 1.

[0115] Fig. 4 illustrates a partial cross-sectional view of a tank wall according to the first embodiment as shown by arrow IV in Fig. 3.

[0116] Fig. 5 illustrates a partial view of the top of a tank wall according to the first embodiment along arrow V of Fig. 4, in which the internal sealing membrane of the spacer block has been intentionally omitted.

[0117] [Fig.6] illustrates a partial, perspective view of a tank wall according to a second embodiment that can be used in zone I of [Fig.1], in which the rod of the anchoring member has been deliberately omitted.

[0118] Fig. 7 illustrates a cross-sectional, perspective view of a tank wall according to the second embodiment.

[0119] Fig. 8 illustrates a top view of the fastening element according to the second embodiment.

[0120] Fig. 9 illustrates a partial cross-sectional view of a tank wall according to a third embodiment that can be used in zone I of Fig. 1, in which the rod of the anchoring member has been intentionally omitted.

[0121] Fig. 10 illustrates a perspective, cross-sectional view of the fastening element according to the third embodiment.

[0122] Figure 11 is a schematic cutaway representation of a tank of an LNG carrier and a loading / unloading terminal for this tank. Description of embodiments

[0123] By convention, the terms "external" and "internal" are used to define the relative position of one element with respect to another, by reference to the inside and outside of the tank.

[0124] In relation to [Fig. 1], a watertight tank wall is described in general terms according to various embodiments below. Such a wall structure can be used to construct substantially all the walls of a tank, for example, a polyhedral one.

[0125] In this respect, the terms 'on', 'overhanging', 'above' and 'superior' indicated in the figures generally refer to a position located towards the inside of the tank and therefore do not necessarily coincide with the notion of 'up' in the Earth's gravitational field. Similarly, the terms 'under' and 'below' generally refer to a position located towards the outside of the tank and therefore do not necessarily coincide with the notion of 'down' in the Earth's gravitational field.

[0126] The tank wall 1 has a multilayer structure comprising, along the thickness direction E of the tank wall 1, from the outside to the inside of the tank: a fixing wall comprising an auxiliary barrier 2 and an external sealing membrane 4. The auxiliary barrier 2 is fixed to a supporting structure 3 and the external sealing membrane 4 is located against the auxiliary barrier 2. The tank further comprises: spacer blocks 5 located on the external sealing membrane and an internal sealing membrane 6 positioned on the spacer blocks 5 and intended to be in contact with the liquefied gas such as liquid ammonia.

[0127] The load-bearing structure 3 may in particular be formed of self-supporting metal sheets or, more generally, of any type of rigid partition having appropriate mechanical properties, such as a concrete partition or wall or a partition formed by the double hull of a ship.

[0128] The auxiliary barrier 2 is thermally insulating and is fixed to the load-bearing structure 3 and comprises, for example, a plurality of thermally insulating panels (not shown) anchored to the load-bearing structure 3.

[0129] The auxiliary barrier 2 may further comprise a secondary waterproof membrane made of composite material (not shown) bonded against the thermally insulating panels.

[0130] The auxiliary barrier 2 may further comprise a second layer of thermally insulating panels bonded against the secondary waterproof membrane.

[0131] The external sealing membrane 4 is metallic, preferably stainless steel. The external sealing membrane 4 has parallel corrugations 14 and flat areas 15 defined between the corrugations 14. The corrugations 14 project from the flat areas 15 towards the interior of the tank.

[0132] Similar to the external sealing membrane 4, the internal sealing membrane 6 is metallic, preferably made of stainless steel. The internal sealing membrane 6 has parallel corrugations 16 and flat areas 17 defined between the corrugations 16. The corrugations 16 project from the flat areas 17 towards the interior of the tank.

[0133] The undulations 16 and the undulations 14 as well as the flat areas 17 and the flat areas 15 are respectively located opposite each other but could according to embodiments be offset.

[0134] The term "plane area" of the internal or external waterproof membrane should be understood in the context of the invention as being planar on the inner face side and on the outer face side.

[0135] An embodiment of a spacer block that can be used in zone I shown in [Fig.1] is illustrated in [Fig.2].

[0136] The spacer block 105 has an external end 130 positioned against the flat area 15, a flat internal face 131 parallel to the external end 130 positioned against the flat area 17 of the internal sealing membrane 6 and two lateral ends 132 connecting the external end 130 to the internal face 131.

[0137] The contour of the outer end 130 corresponds generally to the contour of the flat area 15 and does not touch the feet of the corrugations 14. A foot of a corrugation can be defined as the area in which the sealing membrane deflects towards the internal space of the tank. This deflection area is located between the corrugation and the flat area of ​​the sealing membrane.

[0138] In the illustrated embodiment, the two lateral ends 132 are turned respectively towards two large undulations 14 without touching the two large undulations 14. The two lateral ends 132 extend outwards from the spacer block 105 so that the inner face 131 has a larger dimension that the outer end 130 in a direction transverse to the large corrugations 14, so that two portions of opposite ends of the inner face 131 each partially overhang the adjacent large corrugation 14 and support a foot of a corrugation of the inner waterproof membrane 6. The two lateral ends 132 have a concave shape which remotely follows the shape of a portion of the large corrugation 14.

[0139] The spacer block 105 further comprises a plurality of support ribs 134 which form hollow cells 135. The hollow cells 135 may, for example, have the shape of a plurality of rectangular compartments. The plurality of support ribs 134 enables the spacer block 105 to support the internal sealing membrane 6 and to withstand hydrostatic pressure forces exerted against the spacer block 105. The hollow cells 135 may, for example, allow the passage of a gas for inerting.

[0140] The spacer block 105 further comprises a retaining surface 124 comprising a wall situated between the inner face 131 and the outer end 130 in the center of the spacer block 105 and between two adjacent support ribs 134.

[0141] More details will be described below of the tank walls detailing more precisely the fixing of the spacer block to the external sealing membrane by an anchoring device, according to several embodiments.

[0142] In relation to figures 3, 4 and 5, a tank wall is described below according to a first embodiment in which the spacer block 205 is for example as described in relation to [Fig.2].

[0143] Elements identical or similar to those in [Fig.2] bear the same reference numerals incremented by 100.

[0144] The tank wall includes an anchoring member comprising a rigid element which is a rod 220 and a fixing element 240. The rod 220 protrudes from the flat area 15 of the external metallic sealing membrane 4 and passes through a through orifice 225 of the retaining surface 224, in the thickness direction of the tank wall, towards the interior of the tank. The rod 220 has a general shape of a circular cylinder with a retention zone 222 formed by a circular section of reduced diameter compared to the rest of the rod 220, located between the retention surface 224 and the inner end 221 of the rod 220. The retention zone 222 has a recess 223 housing an internal portion 241 of the fastener 240 within the recess 223 of the rod 220. Optionally, the rod 220 has a chamfer, notably to facilitate the insertion of the rod 220 into the through hole 225 and to facilitate the elastic engagement of the fastener 240.

[0145] The fastening element 240 has an external portion 242 in contact with the retaining surface 224. The external portion 242 and the internal portion 241 of the element The 240 fixings are linked together and formed by the same metal wire bent to form a two-level structure, the first level forming the external portion 242 and the second level forming the internal portion 241.

[0146] The internal portion 241 comprises two longitudinal branches 261, 262 extending on either side of the rod 220 in a direction transverse to the direction of the wall thickness E. The two longitudinal branches 261, 262 are spaced apart and located opposite each other, and each comprises a straight portion 263, 264 interrupted by an angled portion 265, 266 having a general shape of an arc of a circle. The two angled portions 265, 266 are located at a distance from and opposite each other, and the two straight portions 263, 264 are located at a distance from and opposite each other.

[0147] The structure and elastic properties of the fastener 240 allow for easy installation of the fastener 240 as explained below.

[0148] The placement of the fastening element 240 is carried out as follows: - optionally use a compression tool to exert compression on the external portion 242 in order to open the fixing element 240, i.e., to increase the spacing between the two longitudinal branches 261, 262, thus increasing the spacing between the straight portions 263, 264 and the spacing between the angled portions 265, 266 as represented by the arrow on [Fig.4] representing the opening movement of the fixing element; - place the angled portions 265, 266 of the open fixing element 240 around the retaining area 222 of the rod 221 and stop applying compression in order to place the fixing element 240, by elastic return, in a locking position in which the angled portions 265, 266 clamp the rod 220 by conforming to the shape of the rod 220 at the retaining area 222.

[0149] In the locking position in which the fixing element 240 is installed, the internal portion 241 of the fixing element 240 exerts pressure, by elastic return of the two longitudinal branches 261, 262 of the fixing element 240, in a position against the wall of the recess 223 in order to fix the spacer block 205 against the external sealing membrane.

[0150] Optionally, the fixing element 240 includes a compression stop (not shown) in order to limit the elastic movement of the fixing element 240, for example to limit the opening movement of the fixing element 240.

[0151] Optionally, the retaining surface 224 has a groove 226 (visible in [Fig. 4]) projecting from the inner face of the retaining surface wall 224 located between the two adjacent support ribs 234. The outer portion 242 is housed in the groove 226. Such a groove 226 facilitates installation of the fixing element 240 because the groove 226 allows the external portion 242 to be guided to facilitate the installation of the fixing element 240.

[0152] Optionally, the inner face 231 of the spacer block has a through opening 236 for inserting the fixing element 240. The through opening 236 can be a temporary opening which will be closed by a cover before positioning the internal sealing membrane 6 on it in order to ensure a flat surface to receive the internal sealing membrane 6.

[0153] In relation to figures 6, 7 and 8, a tank wall according to a second embodiment is described below in which the spacer block 305 is for example as described in relation to [Fig.2].

[0154] Elements identical or similar to those in [Fig.2] bear the same reference numerals incremented by 200. In addition, elements identical or similar to the rod 220 or the fixing element 240 illustrated in [Fig.3] bear the same reference numerals incremented by 100.

[0155] The fastening element 340 is a thin, elastic, arched piece having an inner portion 341 and two outer portions 342 located against the inner face of the retaining surface 324. The inner portion 341 comprises the apex of the fastening element 340. The inner portion 341 has a through-hole along the thickness direction E of the tank wall. The through-hole has a first zone 343 and a second zone 344, narrower than the first zone 343 and spaced from the first zone 343 in a direction perpendicular to the thickness direction of the tank wall. The dimensions of the first zone 343 are chosen to allow the passage of the rod 320, i.e., a width greater than the largest diameter of the rod 320.Similar to the first embodiment illustrated with Figures 3, 4 and 5, the rod 320 protrudes from the flat area 15 of the external metallic sealing membrane 4 and passes through a through orifice 325 of the retaining surface 324, in the thickness direction of the tank wall, towards the interior of the tank.

[0156] The placement of the fastening element 340 can be carried out as shown below.

[0157] The fastening element 340 is, for example, inserted through a lateral opening (not represented) of the spacer block 305. The fastening element 340 is moved, for example, by sliding on the retaining surface 324 until it reaches the level of the rod 320. At this stage of installation, the rod is located below the inner portion 341 and, more specifically, below the first zone 343 of the through-hole. Next, a compression movement is applied along the wall thickness direction, for example, using a compression tool that elastically brings the apex of the inner portion 241 closer to the outer portions 342, so that the rod 320 initially passes through the first zone 343. In this configuration, the fastening element 340 can still be disengaged from rod 320, the anchoring member is in an unlocked position.

[0158] When the rod passes through the first zone 343 and in order to lock the spacer block 305 by elastic interlocking against the external sealing membrane 4, a rectilinear translational movement in the direction perpendicular to the thickness direction E of the wall is carried out in order to place the retaining zone 322 of the rod 320 in the second zone 344. The second zone 344 has a width greater than the reduced diameter of the rod 320 and less than the diameter of the rest of the rod 320 in order to place the fixing element 340 in an interlocked position in which the top of the internal portion 341 of the fixing element 340 exerts pressure, by elastic return of the fixing element 340, in a position against the internal wall of the recess 323 in order to fix the spacer block 305 against the external sealing membrane.

[0159] In the nested position, the inner end 321 of the rod 320 and the top of the fixing element 340 are located near the inner face 331 of the spacer block 305 without being in direct contact with the inner face 331.

[0160] Optionally, the fastening element 340 includes a compression stop (not shown) to limit the elastic travel in crushing, for example when the compression tool compresses the fastening element 340. The compression stop can be made in different ways, for example in the form of a portion projecting from the top of the inner portion 341, in the thickness direction of the wall, towards the outside of the tank, so as to allow the inner portion 341 to approach the outer portion 342 up to a certain threshold of distance determined between the inner portion 341 and the outer portion 342.

[0161] Optionally, the inner face of the spacer block has a through opening 336 for inserting the fixing element 340. The through opening 336 can be a temporary opening which will be closed by a cover before positioning the internal sealing membrane 6 on it in order to ensure a flat surface to receive the internal sealing membrane 6.

[0162] With reference to Figures 9 and 10, a tank wall according to a third embodiment is described below, in which the spacer block 405 is, for example, as described with reference to [Fig. 2]. Elements identical or similar to those in [Fig. 2] bear the same reference numerals incremented by 300.

[0163] The fixing element 440 is fixed to the retaining surface 424 to protrude towards the flat area 15 external sealing membrane 4.

[0164] The fastening element 440 includes a locking chamber 450 having, from the retaining surface 424, in the direction of the external sealing membrane 4: a a fixing portion 451, for example screwed into a threaded hole (not shown) present in the retaining surface 424; optionally an internal sealing gasket 452 or external gasket 453, optionally a support ring 454 for example made of polyoxymethylene (POM), elastic locking claws 455 and optionally a release sleeve 456 for releasing the rod retained by the locking claws 455.

[0165] The rod (not shown) is inserted into the locking chamber 450 up to the level of the fastening portion 451. The locking claws 455 elastically allow passage during the insertion of the rod and prevent its withdrawal when in a locked position. The elastic engagement of the fastening element 440 on the rod is therefore irreversible, i.e., an elastic snap-fit, unless the release sleeve 456 is actuated. Optionally, in an embodiment comprising the support ring 454 and the release sleeve 456, the support ring 454 has slightly deformable properties to facilitate the bending of the locking claws 455 while preventing the locking claws 455 from folding completely against an internal longitudinal wall of the locking chamber 450.

[0166] In order to remove the rod from the locking chamber, pressure must be applied to the release sleeve in the direction of the retaining surface 424 so that the release sleeve 456 is interposed between the locking claws 455 and the rod in order to release the rod from the locking claws 455 by elastic separation of the latter.

[0167] With reference to [Fig. 11], a cutaway view of a LNG carrier 70 shows a sealed and thermally insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the vessel. The tank 71 may be a tank as described previously. The tank 71 comprises, for example, an internal sealed membrane intended to be in contact with the liquefied gas contained in the tank, a secondary sealing membrane arranged between the internal sealed membrane and the double hull 72 of the vessel, and two thermally insulating barriers arranged respectively between the internal sealed membrane and the secondary sealing membrane and between the secondary sealing membrane and the double hull 72.

[0168] In a manner known per se, loading / unloading pipelines 73 arranged on the upper deck of the ship can be connected, by means of suitable connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

[0169] Fig. 11 represents an example of a marine terminal comprising a loading and unloading berth 75, a subsea pipeline 76, and an onshore installation 77. The loading and unloading berth 75 is a fixed offshore installation comprising a movable arm 74 and a tower 78 that supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can be connected to the loading / unloading pipes 73. The steerable movable arm 74 adapts to all ship sizes, for example to the sizes of LNG carriers. An unshown connecting pipeline extends inside the tower 78. The loading and unloading berth 75 allows the ship 70 to be loaded and unloaded from or to the onshore facility 77. This facility includes liquefied gas storage tanks 80 and connecting pipelines 81 linked by the subsea pipeline 76 to the loading or unloading berth 75. The subsea pipeline 76 allows the transfer of liquefied gas between the loading or unloading berth 75 and the onshore facility 77 over a long distance, for example 5 km, which makes it possible to keep the ship 70 a considerable distance from the coast during loading and unloading operations.

[0170] To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the land installation 77 and / or pumps equipping the loading and unloading station 75 are used.

[0171] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0172] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0173] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. A leak-proof tank (71) for the storage of a liquefied gas, the leak-proof tank comprising a tank wall intended to be installed in a supporting structure, the tank wall comprising, along a thickness direction of the tank wall: - a fixing wall; - a spacer block disposed on the fixing wall and fixed against the fixing wall by an anchoring member, the spacer block having an external end, a flat internal face parallel to the external end and lateral ends connecting the external end to the internal face, the external end being positioned against the fixing wall; - and an internal metallic leak-proof membrane intended to be in contact with the liquefied gas, wherein the internal leak-proof membrane is spaced from the fixing wall by the spacer block and comprises at least one flat portion which is fixed against the internal face of the spacer block,in which the spacer block has a retaining surface located between the inner face and the outer end, in which the anchoring member has a rigid element projecting from the fixing wall and an elastic fixing element, the rigid element having an outer end fixed against the fixing wall and an opposite inner end located at a distance from the outer end, the rigid element having a retaining zone located between the outer end and the inner end, the fixing element cooperating with the retaining zone and the retaining surface in order to fix the spacer block to the fixing wall by elastic interlocking of the fixing element in the retaining zone.

2. Tank according to claim 1, wherein the fixing wall comprises an external sealing membrane which has parallel corrugations spaced apart from each other by flat areas, each flat area being delimited by two adjacent parallel corrugations, wherein the rigid element protrudes from said flat area, wherein the external end of the rigid element is fixed against said flat area, and wherein the external end of the spacer block is positioned against said flat area.

3. Tank according to any one of claims 1 to 2, in which the fastening element is able to be elastically fitted by a rectilinear translational movement.

4. Tank according to claim 3, wherein the rectilinear translation movement is carried out along the thickness direction of the tank wall and / or along the direction perpendicular to the thickness direction of the tank wall.

5. Tank according to any one of claims 1 to 4, wherein the fixing element is constrained by compression along the thickness direction of the tank wall.

6. Tank according to any one of claims 1 to 5, wherein the fixing element comprises a first portion in contact with the retention surface and a second portion in contact with the retention zone.

7. Tank according to claim 6, wherein the first portion is fixed on the retaining surface.

8. Tank according to any one of claims 1 to 7 in which the fastening element comprises an elastic locking chamber receiving the retention zone and fixing the fastening element to the retention zone.

9. Tank according to any one of claims 1 to 8, wherein the retention area comprises a recess or protrusion cooperating with the fastening element.

10. Tank according to any one of claims 1 to 9, wherein the retaining surface has a groove, the fixing element being housed in said groove.

11. Tank according to any one of claims 1 to 10, wherein the fixing element is located between the inner end of the rigid element and the retaining surface.

12. Tank according to any one of claims 1 to 11, wherein the fixing element has two longitudinal branches extending on either side of the rigid element in a direction transverse to the direction of the thickness of the tank wall, the two longitudinal branches enclosing the rigid element at the retention area.

13. Tank according to any one of claims 1 to 11, wherein the fastening element comprises a through-hole along the thickness direction of the tank wall, the through-hole having a first zone and a second zone of smaller width than the first zone and spaced from the first zone in the direction perpendicular to the thickness direction of the tank wall, and in which the rigid element passes through the first zone in an unlocked position in which the rigid element can be inserted and removed from the orifice in the thickness direction of the tank wall and the second zone in a fixed position.

14. Tank according to any one of claims 2 to 13, wherein the fixing element is located between the retaining surface and the external metallic sealing membrane.

15. Tank according to claim 2, wherein said spacer block is a first spacer block, the flat area is a first flat area and said anchoring member is a first anchoring member comprising a first rigid element and a first elastic fastening element, wherein the tank wall further comprises a second spacer block and a second anchoring member, wherein the second spacer block is fixed to a second flat area of ​​the external sealing membrane by the second anchoring member, wherein the second anchoring member comprises a second rigid element projecting from the second flat area and a second elastic fastening element, the second rigid element comprising an external end fixed against the external metallic sealing membrane and an opposite internal end located at a distance from the external end,The second rigid element comprises a retention zone located between the outer end and the inner end; the second fixing element cooperates with the retention zone and the retention surface to fix the second spacer block to the external waterproof membrane by elastic interlocking of the second fixing element in the retention zone.

16. Vessel (70) for the transport of a liquefied gas, the vessel comprising a double hull (72) and a tank (71) according to any one of claims 1 to 15 disposed in the double hull.

17. A transfer system for a liquefied gas, the system comprising a vessel (70) according to claim 16, insulated pipelines (73, 79, 76, 81) arranged to connect the vessel's tank (71) to a floating or land-based storage facility (77), and a pump for driving a flow of liquefied gas through the insulated pipelines. 24 from or to the floating or land-based storage facility to or from the ship's tank.

18. A method of loading or unloading a ship (70) according to claim 16, wherein a liquefied gas is conveyed through insulated pipelines (73, 79, 76, 81) from or to a floating or land-based storage facility (77) to or from the tank (71) of the ship (70).

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