Sealed tank

Abstract

The invention relates to a tank comprising a wall comprising a fastening wall having an inner end and a membrane (6) comprising metal sheets welded at overlapping regions, an overlapping region comprising a portion of a first metal sheet covered with a portion of a second metal sheet, the membrane comprising an outer face which is fastened against the inner end of the fastening wall by an anchoring member, the fastening wall comprising a retaining housing and a fastening wall-side locking part located in the retaining housing and a membrane-side locking part welded against the outer face of the membrane and projecting from the outer face of the membrane in the thickness direction of the wall at a distance from the overlapping region, the fastening wall-side locking part and the membrane-side locking part being fastened by locking.

Description

Watertight tank

[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, leak-proof tanks for the storage of liquefied gas are known. Such a leak-proof tank comprises, for example, a tank wall having a multilayer structure which includes successively, from the inside of the tank, a primary leak-proof membrane intended to be in contact with a liquefied gas contained in the tank, a primary insulating barrier, a secondary leak-proof membrane and a secondary insulating barrier intended to be fixed to a supporting structure.

[0003] The inventors observed that when storing a liquefied gas other than liquefied natural gas (LNG) in tanks originally designed for LNG storage, if the primary sealed membrane is damaged or has an imperfection that allows liquid gas to pass into the inter-membrane space, the tanks designed for LNG storage would not always allow the tank to remain in safe operation. This is because the components located beneath the primary membrane of tanks designed for LNG storage 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 below 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 exert greater stress on the primary waterproof membrane and could therefore cause damage to a primary waterproof membrane.

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

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

[0008] Another idea underlying the invention is to create a sealed tank capable of 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 behind the invention is to create an improved, watertight tank.

[0010] According to one embodiment, the invention provides a sealed tank for the storage of a liquefied gas, the sealed tank comprising a tank wall, the tank wall comprising along a thickness direction of the tank wall: - a fixing wall having an internal end;- and a metallic watertight membrane, wherein the watertight membrane comprises at least one external face, at least a portion of which is fixed against the internal end of the fixing wall by an anchoring member, wherein the fixing wall has a retaining housing, wherein the anchoring member has a locking piece on the fixing wall side located in the retaining housing and a locking piece on the membrane side welded against at least a portion of the external face of the watertight membrane and projecting from at least a portion of the external face of the watertight membrane in the thickness direction of the tank wall, the locking piece on the fixing wall side and the locking piece on the membrane side being fixed by interlocking.

[0011] Thanks to these features, the sealing membrane is effectively attached to the mounting wall. Furthermore, the locking piece protruding from the sealing membrane simplifies the manufacturing of the tank wall and thus the tank itself.

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

[0013] In one embodiment, the metallic waterproof membrane comprises metal sheets welded together at overlapping zones, each overlapping zone having an edge portion of a first metal sheet covered by an edge portion of a second metal sheet adjacent to the first. In another embodiment, the locking piece on the membrane side is welded to the outer face of the waterproof membrane at a distance from the overlapping zone.

[0014] Thanks to these characteristics, the locking piece on the membrane side is not at risk of being damaged or deformed by the application of heat during the welding of the edge portions of the metal sheets.

[0015] The fixing wall can be made in many ways. The fixing wall can be made for example by spacer blocks, by modular blocks of an insulating barrier, such as insulating panels or insulating boxes, by a load-bearing wall, for example made of concrete or steel, or by any combination of these elements.

[0016] According to one embodiment, the metallic sealing membrane is an internal sealing membrane intended to be in contact with the liquefied gas contained in the tank, the fixing wall comprising an external metallic sealing membrane and a modular block, the external metallic sealing membrane being located opposite the internal sealing membrane, the modular block having an external end, a flat internal face parallel to the external end, the modular block having the retaining housing located between the internal face and the external end of the modular block, the external end of the modular block being positioned against the external sealing membrane, the internal sealing membrane is spaced from the external sealing membrane by the modular block and comprises at least one external face of which at least a portion is fixed against the internal face of the modular block by the anchoring member, the internal end of the fixing wall comprising the internal face of the modular block.

[0017] Thanks to these features, the internal sealing membrane is effectively attached to the modular block. Furthermore, the locking piece protruding from the internal sealing membrane simplifies the construction of the tank wall and thus the overall tank manufacturing process.

[0018] In the presence of a modular block, the locking piece on the fixing wall side can also be called the locking piece on the modular block side because it will then be located in the retaining housing of the modular block.

[0019] According to one embodiment, each metal sheet of the waterproof membrane has corrugations spaced apart from each other by flat areas, at least a portion of the external face of the waterproof membrane being a portion of the external face of said first flat area.

[0020] According to one embodiment, each metal sheet of the waterproof membrane has parallel corrugations spaced apart from each other by flat areas, each flat area being delimited by two adjacent parallel corrugations of said metal sheet.

[0021] According to one embodiment, the corrugations of the waterproof membrane comprise a first corrugation and a second corrugation perpendicular to the first corrugation, a flat area being located between the first and second corrugations.

[0022] According to one embodiment, the locking is achieved by a rectilinear translational movement of one of the locking piece on the fixing wall side and the locking piece on the membrane side relative to the other of the locking piece on the fixing wall side and the locking piece on the membrane side.

[0023] According to one embodiment, the rectilinear translation movement is carried out by the wall-side locking piece in a second direction perpendicular to the thickness direction of the tank wall, between an unlocked position in which the membrane-side locking piece can be inserted and removed from the retaining housing in the thickness direction of the tank wall, and a locked position in which the membrane-side locking piece is locked to the wall-side locking piece.According to a preferred embodiment, the locking is performed by a rectilinear translational movement of the locking piece on the fixing wall side relative to the locking piece on the membrane side and relative to said fixing wall, along a second direction perpendicular to the thickness direction of the tank wall, between an unlocked position in which the locking piece on the membrane side can be inserted and removed from the retaining housing in the thickness direction of the tank wall, and a locking position in which the locking piece on the membrane side is locked to the locking piece on the fixing wall side.

[0024] According to one embodiment, in the locking position, a portion of the stop of the locking piece on the fixing wall side is abutted against a portion of the stop of the locking piece on the membrane side along the thickness direction of the tank wall.

[0025] Thanks to these features, the stop portions increase friction, making the locking mechanism more robust by preventing slippage and thus improving the resistance to separation between the locking piece on the wall side and the locking piece on the membrane side. This assembly therefore increases the tank's lifespan.

[0026] In one embodiment, the membrane-side locking piece has a rod projecting from the internal sealing membrane. In another embodiment, the rod has a fastening head. In another embodiment, the fastening head forms the stop portion designed to be positioned, in the locked position, against the stop portion of the locking piece on the wall side, in order to lock the membrane-side fastening piece to the locking piece on the wall side.

[0027] In one embodiment, the fastening head has a conical shape. The conical shape facilitates, in particular, the insertion of the fastening head into the through hole of the locking piece on the wall side.

[0028] According to one embodiment, the rod has a protrusion intended to position itself, in the locking position, against the stop portion of the locking piece on the fixing wall side.

[0029] According to one embodiment, the rod has a notch intended to be positioned, in the locking position, against the stop portion of the locking piece on the fixing wall side.

[0030] According to one embodiment, the locking piece on the fixing wall side has a through orifice along the thickness direction of the tank wall, the through orifice having a first zone and a second zone of smaller width than the first zone and spaced from the first zone in said second direction, and in which the locking piece on the membrane side passes through the first zone in the unlocked position and the second zone in the locked position.

[0031] Thus, the first zone has dimensions allowing reversible or mobile insertion of the locking piece on the membrane side and the second zone has dimensions allowing the locking of the locking piece on the membrane side by preventing its release under normal conditions of use of the tank.

[0032] According to one embodiment, the wall-mounted locking piece includes a locking bar extending in said second direction and passing through the modular block retaining housing in said second direction.

[0033] According to one embodiment, the membrane-side locking piece is a first membrane-side locking piece and the modular block is a first modular block, wherein a second modular block is disposed on the external waterproof membrane and fixed against the external waterproof membrane in a position adjacent to the first modular block, the second modular block having an external end, a flat internal face parallel to the external end, the external end being positioned against the external waterproof membrane, wherein the second modular block has a retaining housing located between the internal face and the external end of the second modular block, the portion of the external face of the internal waterproof membrane being a first portion,wherein the internal sealing membrane is separated from the external sealing membrane by the second modular block and comprises at least a second portion of the external face of said second flat zone which is fixed against the internal face of the second modular block by the anchoring member, wherein the locking bar passes through the retaining housing of the second modular block in said direction perpendicular to the thickness direction of the tank wall, the anchoring member comprising a second locking piece on the membrane side welded against said second flat zone and projecting from at least a second portion of the external face of the internal sealing membrane in the thickness direction of the tank wall, the second locking piece on the membrane side being fixed to the locking bar by interlocking.

[0034] Thanks to these features, the modular block-side locking mechanism allows, with a single translational movement, the locking or unlocking of at least two flat portions of the internal watertight membrane to at least two aligned modular blocks. This configuration facilitates and accelerates tank assembly while ensuring robust locking. Depending on the length of the locking bar, this arrangement can be repeated more than twice, for example, between three and ten times, to lock or unlock multiple membrane-side locking components in a single operation.

[0035] In one embodiment, the retaining housing of the first modular block has a through opening perpendicular to the wall thickness direction, allowing the locking bar to pass through. In another embodiment, the retaining housing of the second modular block has a through opening perpendicular to the wall thickness direction, allowing the locking bar to pass from the retaining housing of the first modular block to the retaining housing of the second modular block.

[0036] In one embodiment, the locking bar is an elongated flat piece. This facilitates the insertion of the locking bar into a retaining housing.

[0037] In one embodiment, the locking bar is rigid; for example, the locking bar is made of metal or thermoplastic. Thanks to these characteristics, the tank has a robust fixing that securely attaches the flat portion of the internal sealing membrane to the inner face of the modular block.

[0038] According to one embodiment, the external waterproof membrane comprises parallel corrugations spaced apart from each other by flat areas.

[0039] In one embodiment, a first flat area of ​​the external waterproof membrane and a second flat area of ​​the external waterproof membrane are separated from each other by a corrugation. In another embodiment, the first modular block and the second modular block have a height greater than the height of the corrugation. In another embodiment, the locking piece passes over said corrugation.

[0040] Thus, the same locking piece can lock several modular blocks under the conditions of an external sealed membrane with undulations between the modular blocks.

[0041] According to one embodiment, the external end of the modular block is located on a flat area of ​​the external waterproof membrane, for example only located on a flat area of ​​the external waterproof membrane.

[0042] According to one embodiment, the external end of the modular block is located on several flat areas of the external waterproof membrane, for example on two adjacent flat areas separated from each other by a corrugation.

[0043] According to one embodiment, the internal housing of the first modular block and the internal housing of the second modular block are located above the height of the corrugation.

[0044] Thus, the locking piece, for example the locking bar, can be positioned so as to pass over the corrugations, without touching said corrugations.

[0045] According to one embodiment, the internal housing of the first modular block and the internal housing of the second modular block are located opposite each other.

[0046] Thus, the insertion of the locking piece, and in particular the locking bar, into the internal housing of the first modular block and the internal housing of the second modular block is facilitated.

[0047] In one embodiment, one of the membrane-side locking piece and the fixing wall-side locking piece is elastically deformable and able to be locked by snapping to the other of the membrane-side locking piece and the fixing wall-side locking piece.

[0048] Thus, locking the membrane-side locking piece to the fixing wall-side locking piece is facilitated.

[0049] According to one embodiment, the snap-in is performed by a rectilinear translational movement of the locking piece on the membrane side, along the thickness direction of the wall.

[0050] This simplifies the installation of the metallic waterproof membrane, particularly during the installation of the metal sheets before they are welded together. This snap-fit ​​system allows for the easy installation of the metal sheets, including, for example, the first and second sets of corrugations, by overlapping them before welding.

[0051] According to one embodiment, one of the locking piece on the fixing wall side and the locking piece on the membrane side, which is elastically deformable, clamps the other of the locking piece on the fixing wall side and the locking piece on the membrane side.

[0052] Thus, during locking, the elastic locking piece designed to grip the other temporarily moves apart under the force exerted during insertion. This deformation allows the elastic locking piece to adjust and open sufficiently to permit the passage or engagement of the other locking piece. Once in the locked position, the locking piece tends to return to its initial shape, gripping the other locking piece. This configuration ensures a stable and secure connection between the two pieces.

[0053] According to one embodiment, one of the locking piece on the fixing wall side and the locking piece on the membrane side which is elastically deformable is housed in the other of the locking piece on the fixing wall side and the locking piece on the membrane side.

[0054] Thus, during locking, one of the locking pieces—either the locking piece on the fixing wall side or the locking piece on the membrane side—is elastic and deforms by compressing upon itself as it is inserted into the other piece. Once inserted, the elastic locking piece returns to its original shape, exerting outward pressure against the inner wall of the other piece, thereby ensuring a secure lock between the two locking pieces.

[0055] According to one embodiment, the locking piece on the fixing wall side comprises a rod projecting from the fixing wall, optionally from the external sealing membrane, the locking piece on the membrane side being snapped onto the rod.

[0056] According to one embodiment, one of the locking piece on the fixing wall side and the locking piece on the membrane side has a return for snapping.

[0057] According to one embodiment, the locking piece on the fixing wall side and the locking piece on the membrane side have a return for snapping.

[0058] According to one embodiment, the return is a protrusion projecting outwards or inwards from the locking piece on the modular block side and / or from the locking piece on the membrane side.

[0059] In one embodiment, the locking piece on the fixing wall side and / or the locking piece on the membrane side has rotational symmetry. For example, the locking piece on the fixing wall side and / or the locking piece on the membrane side has the shape of a right circular cylinder or a right circular cone.

[0060] In one embodiment, the external waterproof membrane comprises parallel corrugations spaced apart. In another embodiment, the modular block comprises lateral ends connecting the external end to the internal face; the lateral ends of the modular block comprise a first lateral end extending parallel to one of said corrugations of the external waterproof membrane and facing said corrugation; the internal face comprises a first end portion partially overhanging said corrugation.

[0061] Thanks to these characteristics, the modular block can be positioned partially above a corrugation in the external waterproofing membrane. Consequently, the transmission of hydrostatic pressure forces to the underlying elements is optimal and the load-bearing capacity of the internal waterproofing membrane is satisfactory.

[0062] According to one embodiment, the modular block is fixed against the external waterproof membrane via a screw-nut system.

[0063] In one embodiment, the modular block includes a retaining surface that cooperates with the screw-nut system to fix the modular block against the external waterproof membrane. In another embodiment, the retaining surface is located between the retaining housing and the outer end of the modular block, preferably at the center of the modular block.

[0064] According to one embodiment, the modular block comprises support ribs located under the inner face between the lateral ends and hollow cells located between the support ribs.

[0065] Thus, the modular block is reinforced by the support ribs. In addition, the hollow cells allow for the inerting of the internal space of the modular block, permitting the passage of gas molecules between the hollow cells located inside the modular block and the inter-membrane space located between the inner and outer airtight membranes.

[0066] According to one embodiment, the modular block is made of a material compatible with the liquefied gas intended to be contained in the tank.

[0067] According to one embodiment, the modular block is a spacer block comprising aluminum or a thermoplastic material.

[0068] In one embodiment, the spacer block comprises an aluminum alloy, for example, aluminum alloy 6082. In another embodiment, the spacer block comprises more than 50% aluminum by mass. In another embodiment, the spacer block consists of aluminum.

[0069] Thanks to these characteristics, the modular block is compatible with ammonia; that is, the modular block is not damaged by contact with liquid or gaseous ammonia. In other words, the physical properties of the modular block, which primarily support the internal membrane, are not altered by contact with ammonia. Consequently, thanks to these characteristics, if the internal airtight membrane is damaged and allows liquid or gaseous ammonia to pass into the inter-membrane space, the tank containing the damaged internal membrane can continue to operate without having to empty the tank.

[0070] The modular block is considered compatible if it can be in contact with liquid or gaseous ammonia for at least 8 days without its carrying capacity being altered.

[0071] According to one embodiment, the spacer block comprises aluminum and is obtained by extrusion.

[0072] According to one embodiment, the thermoplastic material is chosen from: high-density polyethylene, polypropylene and high-impact polystyrene.

[0073] According to one embodiment, the thermoplastic spacer block comprises fibers, for example long fibers.

[0074] According to one embodiment, the composite spacer block is obtained by thermoforming or by injection.

[0075] According to one embodiment, the spacer block does not contain thermally insulating materials.

[0076] According to one embodiment, the modular block includes a thermally insulating material.

[0077] According to one embodiment, the modular block is a thermally insulating panel.

[0078] According to one embodiment, the thermally insulating panel comprises polyurethane foam sandwiched between two rigid plates, for example plywood.

[0079] In one embodiment, the modular block is a thermally insulated box containing thermally insulating material. In one embodiment, the thermally insulating material is, for example, perlite or mineral wool. The thermally insulated box is, for example, made of plywood.

[0080] According to one embodiment, the load-bearing structure forms the fixing wall, the fixing wall optionally being a concrete wall, the load-bearing structure comprising the retaining housing, the internal waterproof membrane being fixed against the internal end of the load-bearing structure by the anchoring device.

[0081] According to one embodiment, a metal sheet of the internal waterproof membrane or of the external waterproof membrane has a general rectangular shape.

[0082] According to one embodiment, the parallel corrugations of each metal sheet of the internal or external waterproof membrane constitute a first series of corrugations, each metal sheet also presents a second series of corrugations parallel to each other and perpendicular to the first series of corrugations, thus forming flat areas each located between two adjacent corrugations of the first series of corrugations and two adjacent corrugations of the second series of corrugations.

[0083] According to one embodiment, the first series of undulations is a series of small undulations. In this case, the second series of undulations can be a series of large undulations.

[0084] According to another embodiment, the first series of undulations is a series of large undulations. In this case, the second series of undulations can be a series of small undulations.

[0085] In yet another embodiment, the first and second sets of undulations have the same height. In another embodiment, the first and second sets of undulations have different heights.

[0086] According to one embodiment, the corrugations protrude towards the inside of the tank.

[0087] According to one embodiment, a metal sheet covers a series of n modular blocks mentioned above arranged on x flat areas, n and / or x being between 2 and 20, preferably between 10 and 16. For example, a rectangular metal sheet can cover two longitudinal and parallel lines each comprising 5 to 8 spacer blocks arranged on 5 to 8 flat areas.

[0088] According to one embodiment, the tank comprises a modular block for each flat area present on a metal sheet.

[0089] According to one embodiment, the adjacent modular blocks are spaced by an undulation of the external waterproof membrane.

[0090] In one embodiment, the locking bar passes through the retaining slots of the series of n modular blocks aligned along the length of the metal sheet. For example, the locking bar passes through 5 to 8 modular blocks.

[0091] According to one embodiment, the locking bar passes through the retaining housings of the series of n modular blocks aligned in the width of the metal sheet.

[0092] According to one embodiment, the locking bar passes through the retaining housings of n aligned modular blocks, the locking bar being positioned under one or more metal sheets, for example positioned under one or two metal sheets.

[0093] According to one embodiment, the retaining housings are located at a height greater than the height of the corrugations separating the retaining housings, the locking bar passing over said corrugations.

[0094] According to one embodiment, a metal sheet of the metallic waterproof membrane, for example the first metal sheet or the second metal sheet, comprising for example the first series of corrugations and the second series of corrugations, is fixed against the fixing wall by several locking pieces on the fixing wall side that are identical to each other.

[0095] According to one embodiment, metal sheets adjacent to the metallic sealing membrane, and located at a distance from the edges of the tank, have locking pieces on the wall side that are identical to each other and / or locking pieces on the membrane side that are identical to each other.

[0096] Thus, the manufacture of the metallic waterproof membrane is simplified, particularly during the installation of the metal sheets before their mutual welding.

[0097] According to one embodiment, the wall-side locking parts for fixing a metal sheet of the waterproof membrane consist of locking bars.

[0098] According to one embodiment, all locking parts on the wall side of fixing a metal sheet or all locking parts on the membrane side of a metal sheet are elastically deformable and able to be locked by snapping along the thickness direction of the wall.

[0099] This facilitates the installation of the metal sheets of the waterproof membrane using a snap-fit ​​system, particularly for sheets with the first and second sets of corrugations. Snap-fitting the sheets along the wall thickness direction reduces the risk of unwanted movement of the metal sheet and the risk of unwanted deformation of the corrugations during installation.

[0100] According to one embodiment, the fixing wall comprises an auxiliary barrier on which the external waterproof 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 waterproof membrane resting against the secondary thermally insulating layer and an intermediate thermally insulating layer located against the secondary waterproof membrane, the external waterproof membrane being positioned against the intermediate thermally insulating layer.

[0101] 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.

[0102] According to one embodiment, the auxiliary barrier comprises a modular block fixed to the load-bearing 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.

[0103] According to one embodiment, the auxiliary waterproof membrane is a flexible membrane made of composite material bonded to the secondary thermally insulating layer.

[0104] 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®.

[0105] According to one embodiment, the aforementioned tank wall is a bottom wall of the tank when the tank is in a position of use.

[0106] According to one embodiment, the aforementioned tank wall is a side wall of the tank when the tank is in a position of use.

[0107] According to one embodiment, the tank comprises a plurality of the aforementioned walls.

[0108] According to one embodiment, the internal waterproof membrane is intended to be in contact with ammonia, butane, propane or ethane, preferably with ammonia.

[0109] According to one embodiment, the tank contains liquefied gas.

[0110] According to one embodiment, the invention also provides a method for adapting a sealed tank initially intended for the storage of a first liquefied gas, the method comprising: - fixing a aforementioned modular block 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 fixing at least one flat area of ​​an internal metallic sealed membrane against the inner face of the modular block via a aforementioned anchoring device.

[0111] The use of this process makes it possible in particular to anchor the modular block directly onto a primary membrane belonging to a sealed and thermally insulating tank wall for LNG storage in order to make the tank compatible with ammonia.

[0112] Such tanks can be part of an onshore storage facility, for example, for storing ammonia, or installed in a floating structure, whether coastal or deep-water, including a ship, a floating storage and regasification unit (FSRU), a floating production and storage unit (FPSO), and others. Such tanks can also serve as fuel tanks on any type of ship.

[0113] According to one embodiment, the load-bearing structure rests on the ground, on a seabed, or is part of a ship.

[0114] According to one embodiment, an onshore installation comprises a supporting structure and the aforementioned tank disposed in the supporting structure.

[0115] 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.

[0116] 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.

[0117] 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

[0118] 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.

[0119] The diagram represents a partial schematic cross-sectional view of a wall of a sealed tank.

[0120] This is an enlarged, partial top view of zone I of the, representing a tank wall according to a first embodiment, in which the internal sealing membrane has been intentionally omitted.

[0121] This is an enlarged view, according to a first cross-section, of zone I of the, representing a tank wall according to the first embodiment.

[0122] This is an enlarged view, according to a second cross-section, of zone I of the, representing a tank wall according to the first embodiment.

[0123] This is an enlarged, top-down, partial view of the locking bar, according to the first embodiment.

[0124] This is an enlarged, partial, perspective view of zone I of the, according to the first embodiment, in an unlocked position.

[0125] Laest is an enlarged, partial, perspective view of zone I of the, according to the first embodiment, in a locked position.

[0126] This is an enlarged, cross-sectional view of zone I of the, representing a tank wall according to a second embodiment.

[0127] This is an enlarged, cross-sectional view of zone I of the, representing a tank wall according to a third embodiment.

[0128] This is an enlarged, partial, cross-sectional view of zone I of the, representing a tank wall according to a fourth embodiment.

[0129] This is a schematic cutaway representation of a ship's tank and a loading / unloading terminal for that tank.

[0130] This is a partial cross-sectional view of a tank wall according to a fifth embodiment.

[0131] Laest is a partial, exploded perspective view of a tank wall according to a sixth embodiment.

[0132] This is a partial cross-sectional view of the tank wall according to the sixth embodiment.

[0133] 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.

[0134] In relation to this, a watertight tank wall is described below in general terms according to various embodiments. Such a wall structure can be used to construct virtually all the walls of a tank, for example, a polyhedral one. In this respect, the terms 'on', 'overhanging', 'above', 'superior', and 'high' generally refer to a position located towards the interior of the tank and therefore do not necessarily coincide with the notion of 'high' in the Earth's gravitational field. Similarly, the terms 'under', 'below', 'lower', and 'low' generally refer to a position located towards the exterior of the tank and therefore do not necessarily coincide with the notion of 'low' in the Earth's gravitational field.

[0135] 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 load-bearing structure 3, an auxiliary barrier 2, an external sealing membrane 4 and a plurality of modular blocks 5 forming a fixing wall 8 and an internal sealing membrane 6 fixed to the fixing wall and intended to be in contact with the liquefied gas such as liquid ammonia.

[0136] The load-bearing structure 3 may in particular be formed of self-supporting metal sheets or, more generally, of any type of rigid partition with appropriate mechanical properties, such as a concrete partition or wall or a partition formed by the double hull of a ship.

[0137] 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.

[0138] The auxiliary barrier 2 may also include a secondary flexible membrane made of composite material (not shown) bonded against the thermally insulating panels.

[0139] The auxiliary barrier 2 may also include a second layer of thermally insulating panels bonded against the secondary flexible membrane.

[0140] 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 protrude from the flat areas 15 towards the interior of the tank.

[0141] 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.

[0142] 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.

[0143] The term "plane area" of the internal or external waterproof membrane should be understood in the context of the invention as being flat on the side of the internal face and on the side of the external face.

[0144] Tank walls will be described in more detail below according to several embodiments.

[0145] In figures 2 to 7, the elements identical or similar to those of the carrier have the same reference numbers incremented by 100.

[0146] In relation to figures 2 to 7, a first variant of a sealed tank wall 101 for the storage of liquefied gas such as ammonia is described below.

[0147] The tank wall 101 comprises an external watertight membrane 104 having a series of small parallel corrugations 118 and also having a series of large corrugations 114 perpendicular to the small corrugations 118. The large corrugations 114 and the small corrugations 118 project towards the interior of the tank. The large corrugations 114 have a height greater than the height of the small corrugations 118.

[0148] Flat areas 115 of the external waterproof membrane 104 are defined between the small undulations 118 and between the large undulations 114.

[0149] Similar to the external sealing membrane, the internal sealing membrane 106 comprises a series of small parallel corrugations 119 and, in addition, a series of large corrugations 116 perpendicular to the small corrugations 119. Both the large corrugations 116 and the small corrugations 119 project towards the interior of the tank. The large corrugations 116 have a greater height than the small corrugations 119.

[0150] The illustration shows two adjacent spacer blocks 105 positioned on two adjacent flat areas 115. The two spacer blocks have the same characteristics, so the same reference numbers were used.

[0151] Each of the spacer blocks 105 is located on a flat area 115 of the external waterproof membrane 104, as can be seen for example in figures 2 to 4.

[0152] The thickness of the spacer block 105 is here between the height of the small undulations 118 and the height of the large undulations 114.

[0153] The spacer block 105 has an external end 130 positioned against the flat area 115, a flat internal face 131 parallel to the external end 130 positioned against the flat area 117 of the internal sealing membrane 106 and four lateral ends connecting the external end 130 to the internal face 131.

[0154] The contour of the outer end 130 corresponds approximately to the contour of the flat area 115 and does not touch the toes of the small corrugations 118 and the large corrugations 114. A toe of a corrugation can be defined as the area in which the sealing membrane deflects towards the internal space of the tank. This deflection zone is located between the corrugation and the flat area of ​​the sealing membrane.

[0155] The four lateral ends develop between the outer end 130 and the inner face 131 of the spacer block 105 and comprise: two first lateral ends 132 facing each other and extending parallel to the small undulations 118, that is to say in the longitudinal direction of the small undulations 118, and two second lateral ends 133 facing each other and extending parallel to the large undulations 114, that is to say in the longitudinal direction of the large undulations 114. The lateral ends do not touch said undulations.

[0156] In the illustrated embodiment, the first two lateral ends 132 are turned respectively towards two small corrugations 118 without touching the two small corrugations 118. The first two lateral ends 132 extend outwards from the spacer block 105 such that the inner face 131 has a larger dimension than the outer end 130 in a direction transverse to the small corrugations 118, i.e., in a direction parallel to the large corrugations 114, so that two opposite end portions of the inner face 131 each partially overhang the adjacent small corrugation 118 and support a foot of a corrugation 119 of the internal sealing membrane 106. The first two lateral ends 132 have a concave shape that remotely follows the shape of a portion of the small corrugation 118.Similar to the first two lateral ends 132, the second two lateral ends 133 are turned respectively towards two large corrugations 114 without touching the two large corrugations 114. The two second lateral ends 133 extend outwards from the spacer block 105 such that the inner face 131 has a larger dimension than the outer end 130 in a direction transverse to the large corrugations 114, i.e., in a direction parallel to the small corrugations 118, so that two opposite end portions of the inner face 131 each partially overhang the adjacent large corrugation 114 and support a foot of a corrugation 116 of the internal sealing membrane 106. The two second lateral ends 133 have a concave shape that remotely follows the shape of a portion of the large corrugation 114.

[0157] According to an alternative embodiment (not illustrated) of figures 2 to 7, the lateral ends do not overhang the large undulations 114 or the small undulations 118. In this case, the spacer block has a general shape of a rectangular parallelepiped.

[0158] The spacer block 105 further comprises a plurality of support ribs 134 which form hollow cells 135, a retaining housing 136 and a retaining surface 137.

[0159] The hollow cells 135 have the shape of a plurality of compartments. The plurality of supporting ribs 134 allows the spacer block 105 to support the internal waterproof membrane 106 and to resist the hydrostatic pressure forces exerted against the spacer block 105.

[0160] The retaining surface 137 is located between the retaining housing 136 and the flat area 115. The spacer block 105 is fixed against said flat area 115 via the retaining surface 137 and a screw-nut system, visible for example in the diagram, which is described below. Other fastening systems may also be used.

[0161] The retaining housing 136 is located above the retaining surface 137 and is delimited by a portion of two parallel grooves 134 spaced apart, a portion of the flat inner face 131 and a groove 134 located opposite the flat inner face 131.

[0162] The retaining housing 136 further includes a retaining groove 138 in which is housed a locking piece on the spacer side 109 having a locking bar 191.

[0163] The locking bar 191 is an elongated component extending along a direction X perpendicular to the thickness direction E of the tank wall. As illustrated in the figure, the same locking bar 191 passes through several retaining slots 136 of several aligned spacer blocks 105, passing over the small corrugations 118. The locking bar 191 is a separate component from the retaining slot 136 and the internal sealing membrane 106.

[0164] Indeed, the height of the retaining housing 136 and the height of the groove 138 are located above the small undulations 118, allowing the locking bar 191 to pass over the small undulations 118, without touching the small undulations 118.

[0165] A flat area 117 of the internal waterproof membrane 106 rests against the flat inner face 131 and is fixed to the spacer block 105 by locking a membrane-side locking piece 110 to the spacer-side locking piece 109. In this embodiment, there are as many membrane-side locking pieces 110 as there are spacer blocks 105. For example, the illustration shows two spacer blocks 105, and each of them has a membrane-side locking piece 110 located opposite one of the two spacer blocks 105.

[0166] The membrane-side locking piece 110 has a cylindrical rod 111 projecting from the flat area 117 of the internal sealing membrane 106. The cylindrical rod 111 has a circumference narrowing area 112 and a conical fixing head 113 located at one end of the rod.

[0167] In order to allow the fixing of the internal sealing membrane 106 to the spacer blocks 105, the internal face 131 of the spacer block 105 has a through hole 140 opening into the retaining housing 136 and the locking bar 191 has a through hole with two zones, a first zone 192 and a second zone 193 of smaller width, in particular visible in figures 5 to 7. The through hole 140 and the through hole with two zones being located opposite each other.

[0168] The internal sealing membrane 106 is secured to the spacer blocks 105 by attaching the membrane-side locking piece 110 to the spacer-side locking piece 109. To achieve this, the rod 111 is inserted both into the through-hole 140 and into the first zone 192 of the through-hole in the locking bar. The fastening head 113 is located below the locking bar 191. At this stage, the membrane-side locking piece 110 is not yet locked to the spacer-side locking piece 109, as can be seen in the figure.

[0169] In order to lock the membrane-side locking piece 110 to the spacer-side locking piece 109, a rectilinear translational movement of the locking bar 191 is made relative to the membrane-side locking piece 110 and relative to the spacer block 105, along the direction X perpendicular to the thickness direction E of the wall and towards the second zone 193. This movement places the fixing head 113 under the second zone 193 of the through orifice and moves the circumferential narrowing zone 112 which receives the thickness of the locking bar 191, to the level of the second zone 193, as particularly visible on the.

[0170] The fixing head 113 has a diameter greater than the width of the second zone 193. Thus, in a locked position, the membrane-side locking piece 110 is locked to the spacer-side locking piece 109; more precisely, the junction between the circumferential narrowing zone 112 and the fixing head forms a stop portion that is in contact with a stop portion of the locking bar 191. Consequently, the internal sealing membrane 106 is pressed and locked against the spacer block 105.

[0171] In the present embodiment, the head is conical in shape to facilitate insertion into the first zone 192 of the orifice.

[0172] Laillustrate un seconde mode de mise en œuvre de la mur de cuve.

[0173] In this, elements identical or similar to those in figures 2 to 7 bear the same reference numbers incremented by 100.

[0174] As previously stated, the spacer block 205 is fixed against the flat area 215 via the retaining surface 237 and a screw-nut system in which the spacer block 205 is fixed against the external sealing membrane 204. To achieve this, a threaded rod 220 is fixed to the flat area 215 of the external sealing membrane 204 such that the threaded rod 220 protrudes upwards, i.e., towards the inside of the tank. The spacer block 205 is then positioned on the flat area 215. The spacer block 205 is then fixed via a retaining surface 237 cooperating with a nut 222 and optionally a washer 223 interposed between the nut and the retaining surface.

[0175] The tank wall 201 differs from the tank wall 101 illustrated with figures 2 to 7 in that it does not have a locking bar and in that the locking piece 210 on the membrane side has an elastically deformable attachment 281 projecting from the internal sealing membrane 206 around a rod 228 also projecting from the internal sealing membrane 206.

[0176] The locking piece on the spacer side 209 of the tank wall 201 has a symmetry of revolution and includes a hook piece 291 projecting into the interior of the tank from a bottom wall 239 of the retaining housing 236.

[0177] The elastically deformable fastener 281 and the hook piece 291 each have a return 221, 294. The return 221 and the return 294 are configured to match each other to allow snap-fit ​​fastening.

[0178] To lock the membrane-side locking piece 210 to the spacer-side locking piece 209, the elastically deformable fastener 281 is moved linearly relative to the hook piece 291, along the wall thickness direction E. This linear movement deforms the elastically deformable fastener 281 by compressing it towards the stem to seat the return 221 in the hook piece 291 at the return 294. Once seated in the hook piece 291, the elastically deformable fastener 281 returns to its original shape, exerting pressure towards its lateral ends against the inner wall of the hook piece 291, thus ensuring a lock between the two locking pieces and pressing the internal sealing membrane 206 against the spacer 205.

[0179] Laillustrate un troisième mode de mise en œuvre de la mur de cuve.

[0180] In the, the elements identical or similar to those of the carry the same reference numbers incremented by 100.

[0181] The tank wall 301 differs from the tank wall 201 illustrated with laen in that the threaded rod 320 used for fixing the spacer block to the external sealing membrane extends into the retaining housing 336 by passing through the retaining surface 337 and the bottom wall 339 of the retaining housing.

[0182] The locking piece on the spacer side 309 has a protrusion 391 having a rotational symmetry formed on the portion of the threaded rod located in the retaining housing 336.

[0183] The locking piece 310 on the membrane side has an elastically deformable fastener 381 projecting from the internal sealing membrane 306. The return 321 of the elastically deformable fastener 391 projects inwards from the elastically deformable fastener 381, in the direction of the protrusion 391.

[0184] To lock the membrane-side locking piece 310 to the spacer-side locking piece 309, a rectilinear translational movement of the elastically deformable fastener 381 is performed, along the thickness direction E of the tank wall 301, to insert the elastically deformable fastener 381 around the threaded rod 320 up to the protrusion 391. This rectilinear movement deforms the elastically deformable fastener 381 by moving it away in the opposite direction to the threaded rod 320 in order to open it sufficiently to allow the return 321 to pass under the protrusion 391. Then, the elastically deformable fastener 381 returns to its initial shape under the protrusion 391, allowing the elastically deformable fastener 381 to be secured to the threaded rod by snapping the return 321 onto the protrusion 391.Due to the effect of elasticity, the elastically deformable fastener 381 exerts pressure towards the threaded rod 320, allowing the return 321 to be pressed against the wall of the protrusion 391, thus ensuring a lock between the two locking pieces, allowing the internal sealing membrane 306 to be pressed against the spacer 305.

[0185] The return assembly 321 – protuberance 391 in the locking position prevents the locking piece on the membrane side 310 from being released to the locking piece on the spacer side 309 along the thickness direction E of the tank wall.

[0186] Laillustre un quatrième mode de embodiment de la mur de cuve.

[0187] In the, the elements identical or similar to those of the carry the same reference numbers incremented by 200.

[0188] The tank wall 401 differs from the tank wall 201 illustrated with laen in that the locking piece on the spacer side 409 includes the elastically deformable attachment 491.

[0189] The elastically deformable attachment 491 projects into the interior of the tank from a bottom wall 439 of the retaining housing 436 and includes a return 494.

[0190] The locking piece on the spacer side 410 comprises, similarly to the first embodiment illustrated with figures 2 to 7, a cylindrical rod 411 projecting from the flat area 417 of the internal sealing membrane 406. The cylindrical rod 411 comprises a circumference narrowing area 412 and a fixing head 413 located at one end of the rod 411, the fixing head 413 having a conical shape.

[0191] To lock the membrane-side locking piece 410 to the spacer-side locking piece 409, a rectilinear translational movement of the rod 411 is performed, along the thickness direction E of the tank wall 401, to insert the fastening head 413 into the elastically deformable fastener 491. This rectilinear movement deforms the elastically deformable fastener 491, and in particular the return 494, by moving it away in the opposite direction to the direction of the rod 411 in order to open it sufficiently to allow the passage of the fastening head 413 and to allow the return 491 to be positioned in the circumferential narrowing zone 412 by snapping it into place. Indeed, the return 494 of the elastically deformable fastener 491 is configured to be housed and locked in the circumferential narrowing zone 412, as illustrated in the figure.

[0192] Laillustre a variant of the construction of a wall of the tank 501, in which the fixing wall is a concrete wall 508 forming the load-bearing structure of the tank.

[0193] In the, the elements identical or similar to those of the carry the same reference numbers incremented by 400.

[0194] The concrete wall 508 has a plurality of retaining housings 536 opening at the level of the internal surface of the concrete wall 508.

[0195] The 536 containment housings are located at a distance from an overlap zone 560 formed by welding between a portion of the edge of a first metal sheet and a portion of the edge of a second metal sheet. The portion of the edge of the second metal sheet includes a raised edge 561 that overlaps the portion of the edge of the first metal sheet and is welded to the portion of the edge of the first metal sheet.

[0196] Each retainer housing 536 includes a locking piece 509 configured to cooperate with an inverted "L" shaped locking piece 510 protruding from a flat area 515 of the internal sealing membrane 506.

[0197] In order to lock the internal waterproof membrane 506 to the concrete wall 508, the locking pieces 510 are inserted through the opening of the retaining piece 536 and then slid towards the locking piece 509 on the concrete wall 508 side, i.e. in the X direction perpendicular to the thickness direction E of the wall.

[0198] Figures 13 and 14 illustrate an alternative embodiment of a tank wall 601 in which the fixing wall is a concrete wall 608 forming the load-bearing structure of the tank.

[0199] In figures 13 and 14, the elements identical or similar to those of the carrier have the same reference numbers incremented by 500.

[0200] This variant also differs from the embodiment of the latter in that the concrete wall 605 has a groove 655 opening at the level of the internal surface of the concrete wall 605.

[0201] The groove 655 includes a retaining element 656 conforming to the shape of the groove 655. The retaining element 656 has an internal space and has two protrusions 684 located opposite each other in the direction of the internal space in order to form a rail receiving an elongated piece 657 having the retaining housing 636 into which a locking bar 691 is inserted.

[0202] The elongated piece 657 has an opening 658 leading into the retaining housing 636 to allow the insertion and fixing of the locking piece 610 membrane side to the locking bar 691.

[0203] The inner face of the concrete wall 605, the inner face of the retaining element 656 and the inner face of the elongated piece 657 form a flat surface to receive the internal waterproof membrane 606.

[0204] With reference to the diagram, a cutaway view of a vessel 70 shows a sealed and thermally insulating tank 71 of generally prismatic shape mounted in the double hull 72 of the vessel. The wall of the tank 71 comprises a primary sealing membrane intended to be in contact with the liquefied gas contained in the tank, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 72 of the vessel, and two thermally insulating barriers arranged respectively between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double hull 72. The tank wall may be one of the aforementioned tank walls, for example, tank wall 1, 101, 201, 301, 501, 601.

[0205] As is 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 liquefied gas from or to the tank 71.

[0206] Figure 75 represents an example of a marine terminal comprising a loading and unloading berth 75, a subsea pipeline 76, and an onshore facility 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 hoses 79 that can be connected to the loading / unloading pipelines 73. The steerable movable arm 74 accommodates all vessel sizes. A connecting pipeline (not shown) extends inside the tower 78. The loading and unloading berth 75 allows the vessel 70 to be loaded and unloaded to or from the onshore facility 77. The onshore facility comprises 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 station 75 and the onshore facility 77 over a long distance, for example 5 km, which allows the ship 70 to be kept a long distance from the coast during loading and unloading operations.

[0207] 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.

[0208] 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.

[0209] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0210] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

A leak-proof tank (71) for the storage of a liquefied gas, the leak-proof tank comprising a tank wall (1, 101, 201, 301, 401, 501, 601), the tank wall comprising, along a thickness direction (E) of the tank wall: - a fixing wall having an internal end; - and a metallic leak-proof membrane (6, 106, 206, 306, 406, 506, 606) comprising metal sheets welded together at overlapping areas, an overlapping area comprising an edge portion of a first metal sheet covered with an edge portion of a second metal sheet adjacent to the first metal sheet, in which the leak-proof membrane comprises at least one external face, at least a portion of which is fixed against the internal end of the fixing wall by an anchoring device, in which the fixing wall comprises a retaining recess (136, 236, 336, 436, 536, 636),in which the anchoring element comprises a wall-side locking piece (109, 209, 309, 409, 509) located in the retaining housing and a membrane-side locking piece (110, 210, 310, 410, 510, 610) welded against at least one portion of the outer face of the sealing membrane and projecting from at least one portion of the outer face of the sealing membrane in the thickness direction (E) of the tank wall at a distance from the overlap zone, the wall-side locking piece and the membrane-side locking piece being fixed by interlocking. Tank according to claim 1, wherein each metal sheet of the sealing membrane has corrugations (16, 116, 216) spaced from each other by flat areas (17, 117, 217, 317, 417), wherein at least a portion of the external face of the sealing membrane is a portion of the external face of said first flat area. A tank according to claim 1 or 2, wherein the metallic sealing membrane is an internal sealing membrane intended to be in contact with the liquefied gas contained in the tank, the fixing wall comprising an external metallic sealing membrane and a modular block, the external metallic sealing membrane being located opposite the internal sealing membrane, the modular block having an external end (130, 230, 330), an internal face (131, 231, 331, 431) flat parallel to the external end, the modular block having the retaining housing (136, 236, 336, 436, 536, 636) located between the internal face and the external end of the modular block, the external end of the modular block being positioned against the external sealing membrane, the internal sealing membrane is separated from the external sealing membrane by the modular block and comprises at least one external face of which at least a portion is fixed against the internal face of the modular block by the anchoring member,the inner end of the fixing wall comprising the inner face of the modular block. Tank according to any one of claims 1 to 3, wherein the locking is effected by a rectilinear translational movement of one of the locking piece on the wall fixing side and the locking piece on the membrane side relative to the other of the locking piece on the wall fixing side and the locking piece on the membrane side. Tank according to claim 4, wherein the rectilinear translational movement is carried out by the wall-side locking piece along a second direction (X) perpendicular to the thickness direction of the tank wall, between an unlocked position in which the membrane-side locking piece can be inserted and removed from the retaining housing in the thickness direction of the tank wall, and a locked position in which the membrane-side locking piece is locked to the wall-side locking piece. Tank according to claim 5, wherein, in the locked position, a portion of the stop of the locking piece on the fixing wall side is abutted against a portion of the stop of the locking piece on the membrane side along the thickness direction of the tank wall. Tank according to claim 5 or 6, wherein the locking piece on the fixing wall side has a through orifice along the thickness direction of the tank wall, the through orifice having a first zone (192) and a second zone (193) of smaller width than the first zone and spaced from the first zone in said second direction, and wherein the locking piece on the membrane side passes through the first zone in the unlocked position and the second zone in the locked position. Tank according to any one of claims 5 to 7, taken in combination with claim 3, wherein the wall-mounted locking piece comprises a locking bar (191) extending in said second direction and passing through the modular block retaining housing in said second direction. Tank according to claim 8, wherein the membrane-side locking piece is a first membrane-side locking piece and the modular block is a first modular block, and wherein a second modular block is disposed on the external sealing membrane and fixed against the external sealing membrane in a position adjacent to the first modular block, the second modular block having an external end, a flat internal face parallel to the external end, the external end being positioned against the external sealing membrane, wherein the second modular block has a retaining housing located between the internal face and the external end of the second modular block, wherein the portion of the external face of the internal sealing membrane is a first portion,wherein the internal sealing membrane is separated from the external sealing membrane by the second modular block and comprises at least a second portion of the external face of said second flat zone which is fixed against the internal face of the second modular block by the anchoring member, wherein the locking bar passes through the retaining housing of the second modular block in said direction perpendicular to the thickness direction of the tank wall, the anchoring member comprising a second locking piece on the membrane side welded against said second flat zone and projecting from at least a second portion of the external face of the internal sealing membrane in the thickness direction of the tank wall, the second locking piece on the membrane side being fixed to the locking bar by interlocking. Tank according to claim 9, wherein the external sealing membrane has parallel corrugations (118, 218) spaced apart from each other by flat areas, a first flat area of ​​the external sealing membrane and a second flat area of ​​the external sealing membrane being separated from each other by a corrugation, the first modular block and the second modular block having a height greater than the height of the corrugation, the locking piece passing over said corrugation. Tank according to any one of claims 1 to 4, wherein one of the membrane-side locking piece and the wall-side locking piece is elastically deformable and able to be locked by snapping to the other of the membrane-side locking piece and the wall-side locking piece. Tank according to claim 11, in which the snap-in is performed by a rectilinear translational movement of the locking piece on the membrane side, along the thickness direction of the wall. Tank according to any one of claims 11 to 12, wherein said one of the locking piece on the wall side of the fixing and the locking piece on the membrane side which is elastically deformable clamps the other of the locking piece on the wall side of the fixing and the locking piece on the membrane side. Tank according to any one of claims 11 to 13, wherein the locking piece on the fixing wall side comprises a rod (320) projecting from the fixing wall, the locking piece on the membrane side being snapped onto the rod. Tank according to any one of claims 3 to 13, wherein the external sealing membrane has parallel undulations spaced apart and wherein the modular block has lateral ends (132, 133, 232) connecting the external end to the internal face, the lateral ends (132, 232) of the modular block having a first lateral end extending parallel to one of said undulations of the external sealing membrane and turned towards said undulation, the internal face having a first end portion partially overhanging said undulation. Tank according to any one of claims 2 to 14, wherein the fixing wall further comprises an auxiliary barrier (2) on which the external sealing membrane is positioned, wherein 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 thermally insulating layer situated against the secondary sealing membrane, the external sealing membrane being positioned against the intermediate thermally insulating layer. 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 16 disposed in the double hull. Transfer system for a liquefied gas, the system comprising a vessel (70) according to claim 17, 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 to drive a flow of liquefied gas through the insulated pipelines from or to the floating or land-based storage facility to or from the vessel's tank. Method of loading or unloading a ship (70) according to claim 17, in which 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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