Watertight tank

Abstract

The invention relates to a sealed tank comprising a tank wall (1) comprising: an outer sealed membrane (4) comprising a first series of parallel corrugations (14) and flat areas (15); a spacer block (5) arranged on a flat area and fixed to the outer sealed membrane, the spacer block having an outer end, a flat inner face and lateral ends connecting the outer end to the inner face, the outer end being positioned against said flat area, the lateral ends comprising a first lateral end extending parallel to the first series of corrugations and facing a first corrugation of the first series of corrugations, the inner face comprising an end portion partially overhanging the first corrugation; an inner sealed membrane (6) spaced from the outer sealed membrane by the spacer block and comprising a flat portion which is fixed against the inner face of the spacer block.Figure for abstract: 1.

Description

Title of the invention: Watertight tank Technical field

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

[0002] In the state of the art, sealed tanks are known for storing a liquefied gas. Such a sealed tank comprises, for example, a tank wall having a multi-layer structure which successively comprises a primary sealed membrane intended to be in contact with a product contained in the tank, a primary insulating barrier, a secondary sealed membrane and a secondary insulating barrier. Summary of the invention

[0003] The inventors have found that in the case of storing a liquefied gas, if the primary sealed membrane is damaged or has an imperfection which allows the liquid gas to pass into the inter-membrane space, the known tanks would not always allow the tank to be kept in operation safely. Indeed, the elements located under the primary membrane of the known tanks are made of materials which deteriorate on contact with certain liquefied gases.

[0004] Furthermore, in the case of an existing tank, for example in the case of a tank capable of being used to store liquefied natural gas (LNG), the elements located under the primary membrane will not necessarily be capable of being in 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, the forces transmitted to the primary waterproof membrane would be greater and could therefore cause damage to a primary waterproof membrane.

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

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

[0008] Another idea underlying the invention is to produce 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 underlying the invention is to produce a method for adapting a sealed and thermally insulating tank initially intended for the storage of LNG in order to store another liquefied gas such as ammonia.

[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, in a thickness direction of the tank wall: - an external metallic waterproof membrane comprising a first series of parallel undulations and flat areas; - a spacer block arranged on at least one said flat area of ​​the external waterproof membrane and fixed to the external waterproof membrane, the spacer block having an outer end, a flat inner face parallel to the outer end and lateral ends connecting the outer end to the inner face, the outer end being positioned against said at least one flat area, the lateral ends comprising a first lateral end extending parallel to the first series of undulations and facing a first undulation of the first series of undulations, the inner face comprising a first end portion partially overhanging the first undulation; - and an internal metallic sealed membrane intended to be in contact with the liquefied gas, in which the internal sealed membrane is spaced from the external sealed membrane by the spacer block and comprises at least one flat portion which is fixed against the internal face of the spacer block.

[0011] Thanks to these characteristics, the spacer block can be positioned above a corrugation of the external waterproof membrane. As a result, the transmission of hydrostatic pressure forces to the underlying elements is optimal and the support of the internal waterproof membrane is satisfactory.

[0012] 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 spacer block on at least one flat area of ​​an external waterproof membrane, in which the external waterproof membrane is a primary membrane belonging to a sealed tank wall for the storage of the first liquefied gas, the external waterproof membrane being metallic and comprising a first series of parallel corrugations; the spacer block having an external end, a flat internal face parallel to the outer end and lateral ends connecting the outer end to the inner face, the outer end being positioned against said at least one flat area, the lateral ends comprising a first lateral end extending parallel to the first series of undulations and facing a first undulation of the first series of undulations, the inner face comprising a first end portion partially overhanging the first undulation; and securing at least one planar area of ​​a metallic inner waterproof membrane against the inner face of the spacer block, such that the inner waterproof membrane is spaced from the outer waterproof membrane by the spacer block.

[0013] The use of this method makes it possible in particular to anchor the spacer block directly on a primary membrane belonging to a sealed and thermally insulating tank wall for the storage of LNG, without needing to install thermal protections between the flat zone of the external sealed membrane and the thermally insulating barrier.

[0014] According to embodiments, such a tank or such a method may comprise one or more of the following characteristics.

[0015] According to one embodiment, the first lateral end develops between the external end and the internal face of the spacer block towards the first corrugation.

[0016] According to one embodiment, the flat area of ​​the external waterproof membrane is located between two undulations of the first series of undulations.

[0017] According to one embodiment, the first lateral end has a concave shape so as to overhang the first corrugation.

[0018] Thanks to these characteristics, the first lateral end remotely matches the shape of the first corrugation in order to obtain good support of the internal surface of the spacer block without interacting with the corrugation of the external waterproof membrane, thus making it possible to obtain good support of the internal waterproof membrane.

[0019] According to one embodiment, the first lateral end is not in contact with the first corrugation. Thus, the first corrugation is free to open and close without its movement being hindered by contact of the spacer block against the first corrugation. According to one embodiment, the lateral ends are not in contact with the corrugations of the external waterproof membrane.

[0020] According to one embodiment, the spacer block is not in contact with the undulations of the external waterproof membrane.

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

[0022] According to one embodiment, the spacer block has a thickness greater than a height of the first series of undulations in the thickness direction of the tank wall.

[0023] According to one embodiment, the thickness of the spacer block is between 20 and 150 mm.

[0024] According to one embodiment, the external waterproof membrane comprises a second series of undulations perpendicular to the first series of undulations.

[0025] According to one embodiment, the lateral ends of the spacer block comprise a second lateral end extending parallel to the second series of undulations and facing respectively towards a first undulation of the second series of undulations, the internal face comprising a second end portion partially overhanging the first undulation of the second series of undulations.

[0026] According to one embodiment, the second lateral end develops between the external end and the internal face of the spacer block towards the first corrugation of the second series of corrugations.

[0027] According to one embodiment, the flat area is defined between two undulations of the first series of undulations and two undulations of the second series of undulations.

[0028] According to one embodiment, the undulations of the external waterproof membrane are protruding relative to the flat areas towards the interior of the tank.

[0029] According to one embodiment, a height of the first series of corrugations is less than a height of the second series of corrugations in the thickness direction of the tank wall. According to one embodiment, the spacer block has a thickness between the height of the second series of corrugations and the height of the first series of corrugations.

[0030] According to one embodiment, the spacer block comprises support ribs located under the internal face between the lateral ends and hollow cells located between the support ribs.

[0031] Thus, the spacer block is reinforced by the support ribs. In addition, the hollow cells make it possible to inert 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 internal sealed membrane and the external sealed membrane.

[0032] According to one embodiment, the support ribs are parallel. According to one embodiment, the support ribs are connected to each other.

[0033] According to one embodiment, the hollow cells have, in sectional view, a rectangular or triangular shape.

[0034] According to one embodiment, the outer end of the spacer block is formed by edges of the lateral ends and / or end edges of the support ribs, the hollow cells being open at the outer end of the spacer block.

[0035] Thus, the hollow cells make it possible to inert the internal space of the spacer block, allowing the passage of gaseous molecules between the hollow cells located inside the spacer block and the inter-membrane space located between the internal sealed membrane and the external sealed membrane.

[0036] According to one embodiment, one lateral end of the lateral ends is formed by lateral edges of the support ribs. According to one embodiment, the first lateral end is formed by lateral edges of the support ribs. According to one embodiment, the lateral ends are formed by end edges of the support ribs.

[0037] According to one embodiment, the outer end and the lateral ends are formed by end edges of the support ribs.

[0038] According to one embodiment, the external end of the spacer block is formed by a flat external face parallel to the internal face.

[0039] Thanks to these characteristics, the carrying of the internal waterproof membrane by the spacer block is improved.

[0040] According to one embodiment, at least one lateral end of the lateral ends comprises a side wall crossed by a through passage. According to one embodiment, the first lateral end comprises a side wall crossed by a through passage

[0041] According to one embodiment, at least one lateral end of the lateral ends comprises a plurality of through passages.

[0042] According to one embodiment, a lateral end comprises a plurality of support elements spaced from each other by through passages, the support elements preferably being spacers connecting the external end and the internal face of the spacer block.

[0043] According to one embodiment, the tank further comprises a fixing piece fixed to the flat area of ​​the external waterproof membrane and projecting towards the internal waterproof membrane, the spacer block being fixed to the fixing piece. According to one embodiment, the fixing piece is chosen from a metal cylinder or a metal strip. According to a preferred embodiment, the fixing piece is a metal rod, for example a metal stud.

[0044] According to one embodiment, the fixing part is fixed to the external waterproof membrane by welding on an internal face of the flat area of ​​the external waterproof membrane. According to one embodiment, the fixing part is fixed via the capacitor discharge welding method.

[0045] Thus, the fixing part such as a fixing rod can be fixed directly to the external membrane, without passing through said external sealed membrane. This embodiment is particularly advantageous when it comes to adapting a sealed and thermally insulating tank initially intended for the storage of LNG, in order to store liquid ammonia. Indeed, the capacitor discharge welding process also makes it possible not to degrade the underlying insulation by heat, without the need to add additional thermal protection.

[0046] According to one embodiment, the spacer block comprises a temporary through-hole intended for the passage and fixing of the fixing rod. According to one embodiment, the spacer block comprises a metal cover closing the temporary fixing hole.

[0047] According to one embodiment, the spacer block comprises a retaining surface cooperating with a nut or a clip mounted on the fixing part.

[0048] 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.

[0049] According to one embodiment, the spacer block comprises aluminum or a thermoplastic material.

[0050] According to one embodiment, the spacer block has a composition similar to the thermally insulating barrier. The spacer block comprises, for example, thermally insulating materials, such as polyurethane foam or glass wool. Advantageously, the spacer block comprises at least one rigid plate.

[0051] According to one embodiment, the spacer comprises an aluminum alloy, for example aluminum alloy 6082. According to one embodiment, the spacer block comprises more than 50% aluminum by mass of the spacer. According to one embodiment, the spacer block consists of aluminum.

[0052] Thanks to these characteristics, the spacer block is compatible with ammonia, that is to say that the spacer block is not damaged by contact with liquid or gaseous ammonia, that is to say that the physical properties of the spacer block mainly allowing the carrying of the internal membrane are not altered by contact with ammonia. Consequently, thanks to these characteristics, if the internal sealed membrane is damaged and allows liquid or gaseous ammonia to pass into the inter-membrane space, said tank comprising the damaged internal membrane will be able to continue to operate, without having to empty said tank.

[0053] The spacer block is notably considered compatible if it can be in contact with liquid or gaseous ammonia for at least 8 days without its carrying capacity being altered.

[0054] According to one embodiment, the spacer block comprises aluminum obtained by extrusion.

[0055] According to one embodiment, the thermoplastic material is chosen from: high density polyethylene, polypropylene and impact polystyrene.

[0056] According to one embodiment, the spacer block made of thermoplastic material comprises fibers, for example long fibers.

[0057] According to one embodiment, the composite spacer block is obtained by thermoforming or by injection.

[0058] According to one embodiment, the spacer block does not comprise thermally insulating materials.

[0059] According to one embodiment, the at least one flat zone comprises a first flat zone, 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 arranged on at least a second flat zone of the external waterproof membrane, the spacer block extending over at least one other corrugation of the first series of corrugations located between said first flat zone and said second flat zone.

[0060] According to one embodiment, the spacer block has a thickness greater than a height of the second series of corrugations in the thickness direction of the tank wall and the external end of the spacer block is arranged on at least one other flat zone of the external waterproof membrane, the spacer block extending over another corrugation of the second series of corrugations located between said first flat zone and said other flat zone.

[0061] Preferably in this case, the height of the first series of undulations is less than the height of the second series of undulations in the thickness direction of the tank wall.

[0062] According to one embodiment, the outer end of the spacer block is arranged on at least one second flat area of ​​the outer waterproof 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 and the outer end of the spacer block is further arranged on at least one other flat area of ​​the outer waterproof membrane, the spacer block extending over another corrugation of the second series of corrugations located between said first flat area and said other flat area.

[0063] According to one embodiment, the external end of the spacer block is arranged on n flat zones of the external waterproof membrane, n being a number chosen between 2 and 20, and preferably chosen between 2 and 9.

[0064] According to one embodiment, the spacer block extends over a number between 2 and 9 undulations of the first series of undulations.

[0065] According to one embodiment, the spacer block extends over a number between 2 and 9 undulations of the second series of undulations.

[0066] According to one embodiment, the spacer block extends over two corrugations of the first series of corrugations and over two corrugations of the second series of corrugations. According to one embodiment, the spacer block extends over two corrugations of the first series of corrugations and over three corrugations of the second series of corrugations. According to one embodiment, the spacer block extends over three corrugations of the first series of corrugations and over two corrugations of the second series of corrugations. According to one embodiment, the spacer block extends over three corrugations of the first series of corrugations and over three corrugations of the second series of corrugations.

[0067] According to one embodiment, the outer end of the spacer block comprises a portion having a shape complementary to a corrugation of the first series of corrugations and / or a shape complementary to a corrugation of the second series of corrugations so as to pass over and at a distance from the corrugation of the first series of corrugations and / or over the second series of corrugations. According to one embodiment, the complementary shape is formed by embossing the outer end of the spacer block.

[0068] According to one embodiment, the lateral ends comprise a third lateral end located opposite the first lateral end extending parallel to the first series of undulations, the internal face comprising a third end portion partially overhanging said second undulation of the first series of undulations.

[0069] According to one embodiment, the third lateral end develops between the external end and the internal face of the spacer block towards the second corrugation of the first series of corrugations.

[0070] According to one embodiment, the internal face has a larger dimension than the external end in a direction transverse to the first series of undulations.

[0071] According to one embodiment, the lateral ends comprise a fourth lateral end located opposite the second lateral end, the fourth lateral end developing between the external end and the internal face of the spacer block towards a second corrugation of the second series of corrugations, so that the internal face comprises a fourth end portion partially overhanging said second corrugation.

[0072] According to one embodiment, the internal waterproof membrane comprises a first series of undulations parallel to the first series of undulations of the external waterproof membrane and flat areas.

[0073] According to one embodiment, at least one corrugation of the first series of corrugations of the internal waterproof membrane is opposite the first corrugation of the first series of corrugations of the external waterproof membrane in the thickness direction of the tank wall.

[0074] Thus, this makes it possible in particular to obtain a tank in which the thickness of the spacer block is less than the height of the first undulations of the external membrane.

[0075] According to one embodiment, at least one corrugation of the first series of corrugations of the internal waterproof membrane is offset from the first corrugation of the first series of corrugations of the external waterproof membrane in the thickness direction of the tank wall.

[0076] According to one embodiment, the two feet of the corrugation of the first series of corrugations are positioned against the internal face of the spacer block.

[0077] According to one embodiment, the pitch of the undulations of the first series of undulations of the external waterproof membrane is identical to the pitch of the undulations of the first series of undulations of the internal waterproof membrane.

[0078] According to one embodiment, the pitch of the undulations of the first series of undulations of the external waterproof membrane is different from the pitch of the undulations of the first series of undulations of the internal waterproof membrane.

[0079] According to one embodiment, the first series of undulations is a series of small undulations. In this case, the second series of undulations may be a series of large undulations.

[0080] According to another embodiment, the first series of undulations is a series of large undulations. In this case, the second series of undulations may be a series of small undulations.

[0081] According to yet another embodiment, the first series of undulations and the second series of undulations have the same height.

[0082] According to one embodiment, the undulations of the internal waterproof membrane are protruding relative to the flat areas towards the interior of the tank.

[0083] According to one embodiment, the internal sealed membrane of the sealed tank is intended to be in contact with a liquefied gas chosen from: ammonia, dihydrogen, butane, propane or ethane, and preferably ammonia.

[0084] According to one embodiment, an internal space of the tank delimited by the internal sealed membrane contains a liquefied gas chosen from: ammonia, dihydrogen, butane, propane or ethane, and preferably with ammonia.

[0085] According to one embodiment, the tank wall comprises a metal insert which is fixed on the internal face of the spacer block and the internal waterproof membrane is welded to the metal insert. Further details on the geometry or the fixing of the metal insert are illustrated in particular in document EP0064886A1, mainly with figures 7 to 10 in which it is appropriate to replace the insulating barrier with the spacer block. According to one embodiment, the internal waterproof membrane and the external waterproof membrane are made of stainless steel.

[0086] According to one embodiment, the sealed tank is thermally insulating and the tank wall comprises at least one thermally insulating barrier arranged between the external sealed membrane and the supporting structure. For example, the thermally insulating barrier may comprise insulating elements made of various materials, in particular materials incompatible with ammonia such as polyurethane foam or glass wool.

[0087] Thus, when the external waterproof membrane is fixed against the thermally insulating barrier, the spacer block makes it possible in particular to transmit the hydrostatic pressure forces to said thermally insulating barrier. In addition, the spacer block makes it possible to better distribute the loads on the underlying thermally insulating barrier. Indeed, when the internal waterproof membrane undergoes a concentrated stress form on a smaller surface than the surface of the spacer block, the insulating block will make it possible to distribute the stress over a larger surface of the underlying thermally insulating barrier.

[0088] Furthermore, thanks to these characteristics, it is possible to achieve inerting of the inter-membrane space located between the internal sealed membrane and the external sealed membrane. Consequently, in the event of gas leakage from the internal sealed membrane to the inter-membrane space, it will be possible to evacuate the unwanted gas from said inter-membrane space without damaging the underlying thermally insulating barrier.

[0089] According to one embodiment, the tank wall comprises an additional waterproof membrane arranged between the external waterproof membrane and the supporting structure. According to one embodiment, a primary thermally insulating barrier is arranged between the additional waterproof membrane and the external waterproof membrane and a secondary thermally insulating barrier is arranged between the additional waterproof membrane and the supporting structure. According to one embodiment, the primary thermally insulating barrier and / or the secondary thermally insulating barrier comprises polyurethane foam or glass wool.

[0090] According to one embodiment, the tank wall comprises a plurality of spacer blocks which are each located on a respective flat area of ​​the plurality of flat areas of the external waterproof membrane.

[0091] According to one embodiment, a spacer block is located on each flat zone of the external waterproof membrane.

[0092] According to one embodiment, each flat zone of the external waterproof membrane is covered by an external end of a spacer block which is arranged thereon.

[0093] An external end of the same spacer block may rest on several flat areas and / or an external end of a spacer block may rest on a single flat area.

[0094] According to one embodiment, the internal space of the tank has a storage capacity of more than 70,000 m3.

[0095] According to one embodiment, the aforementioned tank wall is a bottom wall of the tank when the tank is in a position of use.

[0096] According to one embodiment, the aforementioned tank wall is a side wall of the tank when the tank is in a position of use.

[0097] According to one embodiment, the tank comprises a plurality of aforementioned walls.

[0098] According to one embodiment, the invention also provides a storage facility of a liquefied gas comprising a supporting structure and a aforementioned sealed tank, the sealed tank being positioned and fixed against the supporting structure.

[0099] According to one embodiment of the method, the first liquefied gas is LNG.

[0100] According to one embodiment of the method, the internal waterproof membrane is intended to be in contact with ammonia, dihydrogen, butane, propane or ethane, preferably with ammonia.

[0101] According to one embodiment of the method, the sealed and thermally insulating tank wall for storing the first liquefied gas has a multi-layer structure which successively comprises, from the outside of the tank, a secondary insulating barrier, a secondary sealed membrane, a primary insulating barrier and a primary sealed membrane.

[0102] According to one embodiment, the spacer block is fixed to the flat area of ​​an external waterproof membrane via a fixing piece welded to an internal face of the flat area of ​​the external waterproof membrane and projecting from the external waterproof membrane, the spacer block being fixed to the fixing piece, the welding being able to be carried out via a short cycle welding method, for example by capacitor discharge. According to one embodiment, the fixing piece is chosen from a metal cylinder or a metal strip. According to a preferred embodiment, the fixing piece is a metal rod, for example a metal stud.

[0103] According to one embodiment, the spacer block comprises at least one metal insert forming at least in part the internal face of the spacer block and the at least one flat portion of the internal waterproof membrane is fixed at least in part to the metal insert.

[0104] Thus, the internal waterproof membrane can be welded to an element of the spacer block to ensure mechanical strength. The assembly formed by the internal waterproof membrane and the spacer block makes it possible to hold the welded elements in place. In addition, since the spacer block is attached to the external waterproof membrane, the welded internal waterproof membrane is attached to the structure.

[0105] According to one embodiment, the spacer block comprises a housing receiving the metal insert, the housing being capable of blocking a translation of the metal insert in the thickness direction.

[0106] Thus, the metal insert cannot be removed by a simple translation.

[0107] According to one embodiment, the internal face of a spacer block comprises an opening delimited by internal edges of the spacer block.

[0108] According to one embodiment, the metal insert comprises at least: a flat central surface extending in a first plane at a first height; two ends parallel to the flat central surface extending in a second plane at a second height; two joining portions making it possible to join the flat central surface to the two ends; such that the flat central surface of the metal insert is flat with the internal face of the spacer block through the opening,

[0109] According to one embodiment, the inner edges of the opening have a shape complementary to the ends of the metal insert.

[0110] Thus, it is possible to insert the metal insert after installing the spacer block on the external waterproof membrane,

[0111] Such a tank may be part of a land-based storage facility or installed in a floating, coastal, or deep-water structure, including a liquefied gas transport vessel, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO), and the like. Such a tank may also serve as a fuel tank in any type of vessel.

[0112] According to one embodiment, the supporting structure rests on the ground, on a seabed or is part of a ship.

[0113] According to one embodiment, a land-based installation comprises a supporting structure and a aforementioned tank arranged in the supporting structure.

[0114] According to one embodiment, a ship for transporting a liquefied gas comprises a double hull and a aforementioned tank arranged in the double hull.

[0115] According to one embodiment, the invention also provides a transfer system for a liquefied gas, the system comprising the aforementioned vessel and insulated pipes arranged so as to connect the vessel's tank to a floating or land-based storage facility.

[0116] According to one embodiment, the transfer system also comprises a pump for driving 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 ship, in which a liquefied gas is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the tank of the ship. Brief description of the figures

[0118] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the appended drawings.

[0119] [Fig. 1] represents a partial schematic sectional view of a wall of a sealed tank.

[0120] [Fig.2] is an enlarged, sectional view of zone I of [Fig.l], representing a tank wall according to a first embodiment.

[0121] [Fig.3] represents a bottom view of a spacer block according to the first embodiment.

[0122] [Fig.4] represents a partial, exploded perspective view of a tank wall according to the first embodiment.

[0123] [Fig.5] represents a partial view, in section, representing a tank wall according to a second embodiment.

[0124] [Fig.6] represents a sectional view of a tank wall according to a third embodiment.

[0125] [Fig.7] represents a top view of a tank wall according to a fourth embodiment.

[0126] [Fig.8] represents a partial view, in section, of a corner zone of a tank comprising a spacer block according to a fifth embodiment.

[0127] [Fig.9] represents a partial view of a spacer block comprising a metal insert according to a sixth embodiment.

[0128] [Fig. 10] represents a sectional view of a spacer block according to the sixth embodiment.

[0129] [Fig. 11] represents a partial view of a spacer block comprising a toothed metal insert according to a seventh embodiment.

[0130] [Fig. 12] represents a top view of a spacer block according to the seventh embodiment.

[0131] [Fig. 13] represents a schematic cutaway representation of a tank of a ship and a terminal for loading and unloading this tank. Description of the embodiments

[0132] By convention, the terms "external" and "internal" are used to define the relative position of one element with respect to another, with reference to the inside and outside of the tank.

[0133] In connection with [Fig.l], a sealed tank wall 1 according to embodiments is generally described below. Such a wall structure may be used to form substantially all the walls of a polyhedral tank. In this regard, the terms 'on', 'overhanging', 'above', 'upper' and 'high' generally refer to a position located towards the inside 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 outside of the tank and therefore do not necessarily coincide with the notion of low in the Earth's gravitational field.

[0134] The wall 1 has a multi-layer structure comprising, along the thickness direction E of the wall 1, from the outside to the inside of the tank: a supporting structure 3, an auxiliary barrier 2, an external sealed membrane 4, a plurality of spacer blocks 5 and an internal sealed membrane 6 intended to be in contact with the liquefied gas such as liquid ammonia.

[0135] The supporting structure 3 may in particular be formed from self-supporting metal sheets or, more generally, from any type of rigid partition having appropriate mechanical properties, such as a concrete partition or a partition formed by the double hull of a ship.

[0136] The auxiliary barrier 2 is thermally insulating and is fixed to the supporting structure 3 and comprises, for example, a plurality of thermally insulating panels (not shown) anchored to the supporting structure 3.

[0137] The auxiliary barrier 2 may further comprise a secondary flexible membrane made of composite material (not shown) glued against the thermally insulating panels.

[0138] The auxiliary barrier 2 may further comprise a second layer of thermally insulating panels glued against the secondary flexible membrane.

[0139] The external waterproof membrane 4 is metallic, preferably made of stainless steel. The external waterproof membrane 4 comprises 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.

[0140] Similarly, the internal waterproof membrane 6 is metallic, preferably made of stainless steel. The internal waterproof membrane 6 comprises parallel corrugations 16 and flat areas 17 defined between the corrugations 16. The corrugations 16 protrude from the flat areas 17 towards the interior of the tank.

[0141] 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.

[0142] Tank walls according to several embodiments will be described in more detail below.

[0143] In Figures 2 to 4, elements identical or similar to those of [Fig.l] bear the same reference numbers incremented by 100.

[0144] In relation to Figures 2 to 4, a first variant of a sealed tank wall 101 for storing liquefied gas such as ammonia is described below.

[0145] The tank wall 101 comprises an external waterproof membrane 104 comprising a series of small parallel corrugations 114 and further comprising a series of large corrugations 118 perpendicular to the small corrugations 114. The large corrugations 118 and the small corrugations 114 project towards the interior of the tank. The large corrugations 118 have a height greater than the height of the small corrugations 114.

[0146] Flat areas 115 are defined between the small undulations 114 and between the large undulations 118.

[0147] Advantageously, the internal waterproof membrane 106 is composed of a plurality of metal sheets. The metal sheets are welded together in a waterproof manner.

[0148] Each metal sheet of the internal waterproof membrane 106 has edges and also corners at the junction between two edges of the internal waterproof membrane 106.

[0149] A spacer block 105 is located on the flat area 115 of the external waterproof membrane 104, as visible for example in FIGS. 2 and 4. The thickness of the spacer block 105 is here between the height of the small undulations 114 and the height of the large undulations 118.

[0150] 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 waterproof membrane 106 and four lateral ends connecting the external end 130 to the internal face 131.

[0151] The contour of the outer end 130 corresponds substantially to the contour of the flat area 115 and does not touch the feet of the small undulations 114 and the large undulations 118. A foot of a undulation can be defined as being the area in which the waterproof membrane deflects towards the internal space of the tank. This deflection zone is located between the corrugation and the flat area of ​​the waterproof membrane.

[0152] The four lateral ends develop between the external end 130 and the internal face 131 of the spacer block 105 and comprise: first and third lateral ends 132, facing each other and extending parallel to the small undulations 114, that is to say in the longitudinal direction of the small undulations 114, and second and fourth lateral ends 133, facing each other and extending parallel to the large undulations 118, that is to say in the longitudinal direction of the large undulations 118. The lateral ends do not touch said undulations.

[0153] The first and third lateral ends 132 are turned respectively towards two small corrugations 114 without touching the two small corrugations 114. The first and third lateral ends 132 develop towards the outside of the spacer block 105 so that the internal face 131 has a larger dimension than the external end 130 in a direction transverse to the small corrugations 114, that is to say in a direction parallel to the large corrugations 118, so that two opposite end portions of the internal face 13 1 each partially overhang the adjacent small corrugation 114 and support a foot of a corrugation 116 of the internal waterproof membrane 106. The first and third lateral ends 132 have a concave shape which remotely matches the shape of a portion of the small corrugation 114.

[0154] The spacer block 105 further comprises a plurality of support ribs 134 which form hollow cells 135. The hollow cells 135 have the shape of a plurality of aligned rectangular compartments. The plurality of support ribs 134 notably 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.

[0155] The spacer block 105 comprises a temporary orifice 121 which passes through the thickness of the spacer block 105, and in the middle of the spacer block 105, in order to allow the spacer block 105 to be fixed against the flat area 115.

[0156] The spacer block 105 is fixed against said flat area 115 via a screw-nut system, visible in [Fig.4]. Other fixing systems can also be used.

[0157] In order to fix the spacer block 105, a threaded rod 120 is welded to the flat area 115 of the external waterproof membrane 104, for example via the capacitor discharge welding method, so that the threaded rod 120 projects upwards, i.e., projects towards the inside of the tank. The spacer block 105 is then positioned on the flat area 115 by inserting the threaded rod 120 into the temporary orifice 121. The spacer block 105 is then fixed via a retaining surface cooperating with a nut 122.

[0158] After fixing the spacer block 105 against the flat area 115, the temporary orifice 121 is closed by a metal cover 123 so that the internal face 131 is flat in order to best support the internal waterproof membrane 106. The metal cover is for example made of aluminum or stainless steel.

[0159] The flat area 117 of the internal waterproof membrane 106 rests against the flat internal face 131 and is fixed to the spacer block 105. The fixing is for example carried out by welding on a metal insert positioned at the level of the internal face 131. The metal insert is for example the metal cover 123 which is fixed against a fixing portion 119 on the flat internal face 131. It should be noted that the metal insert can also be positioned at another position on the internal face 131.

[0160] [Fig. 5] illustrates an alternative embodiment of the spacer block. In [Fig. 5], elements identical or similar to those of Figures 2 to 4 bear the same reference numbers incremented by 100.

[0161] The spacer block 205 differs from the spacer block of Figures 2 to 4 in that the first and third lateral ends 232 facing each other have a greater curvature. In addition, the through hole 221 has a different shape and includes a retaining surface 224 cooperating with a threaded rod 220 and a nut 222 mounted on the threaded rod 220. The spacer block 205 includes a smaller number of support ribs 234 and therefore hollow cells 235.

[0162] The spacer blocks described above cover a single flat area of ​​the external waterproof membrane. However, a spacer block may have larger dimensions, and in particular so as to cover several flat areas.

[0163] Figures 6 and 7 illustrate two alternative embodiments of the spacer block covering several flat areas. In Figures 6 and 7, elements identical or similar to those of Figures 2 to 4 bear the same reference numbers incremented by 200.

[0164] The spacer block 305 of [Fig. 6] differs from the spacer block of FIGS. 2 to 4 in that the spacer block 305 is positioned on two adjacent flat areas 315 of the outer waterproof membrane 304 separated by a small undulation 314. Each flat area is delimited by two adjacent large undulations 318 and two adjacent small undulations 314. The outer end 330 of the spacer block 305 comprises two flat portions each positioned on a flat area 315. The outer end 330 of the spacer block 305 further comprises a connecting portion 340 which connects the two flat portions. The connecting portion 340 extends over the small corrugation 314. In other words, the connecting portion 340 forms a tunnel crossed by the small corrugation 114, over the entire dimension of the spacer block 305.

[0165] The spacer block 305 of [Fig. 7] has a thickness greater than the height of the large undulations 118. The outer end 330 of the spacer block 305 comprises four flat portions each positioned on a flat area 315. The outer end 330 of the spacer block 305 further comprises connecting portions which connect the four portions of the outer end 330. The connecting portions extend over a small undulation 314 or a large undulation 318. In other words, a first connecting portion 340 of the spacer block 305 forms a tunnel crossed by the large undulation 118, over the entire length of the spacer block 305. A second connecting portion 341 forms a tunnel crossed by the small undulation 314, over the entire width of the spacer block 305. The inner face 331 of the spacer block has a larger dimension than the outer end 330. Each of the four edges of the inner face 331 partially overhangs a corrugation.

[0166] [Fig.8] illustrates an alternative embodiment of the spacer block. In [Fig.8], elements identical or similar to those of Figures 2 to 4 bear the same reference numbers incremented by 300.

[0167] The two spacer blocks 405 of [Fig. 8] differ from the spacer block of Figures 2 to 4 in that they are located at a corner of the tank. The flat areas 415 of the outer waterproof membrane 4 0 4 are located between a corrugation 414 and the corner of the tank.

[0168] The spacer blocks 405 are each positioned on a flat area 415, at the angle and each have a beveled lateral end 432b located opposite the lateral end 432. The beveled lateral ends 432b of the spacer blocks 405 are positioned in abutment against each other. Illustrated in [Fig.8] is a 90° tank angle with the beveled lateral ends 432b at 45° but such an arrangement can be adapted to be positioned at another tank angle, such as an angle of 135° for example. In addition, the two beveled lateral ends 432b can have a different bevel angle from each other, as long as their meeting forms an angle corresponding to the angle of the tank

[0169] According to one embodiment, the tank wall described above can be obtained from a pre-existing sealed and thermally insulating tank wall for LNG storage, in which the spacer blocks 5, 105 or 205 and the internal sealed membrane 6, 106, 206 have been installed. Many structures exist in the state of the art for the sealed and thermally insulating tank wall for LNG storage. According to one embodiment, the sealed and thermally insulating tank wall for LNG storage complies with publications FR2739675 or WO2022200539. Thus, further details regarding the auxiliary barrier 2 and the external sealed membrane 4, 104, 204 can be found in these publications.

[0170] Figures 9 and 110 illustrate an alternative embodiment of the spacer block. In Figures 9 and 10, elements identical or similar to those of Figures 2 to 4 bear the same reference numbers incremented by 400,

[0171] The spacer block 505 of [Fig. 9] differs from the spacer block of FIGS. 2 to 4 in that the spacer block 505 has a metal insert 550 forming at least in part the internal face of the spacer block and the at least one flat portion of the internal waterproof membrane is fixed at least in part to the metal insert.

[0172] Advantageously, this makes it possible to weld the internal waterproof membrane 6, 106, 206, 306 to the spacer block 505. More precisely, a metal sheet of the internal waterproof membrane 6, 106, 206, 306 has at least one edge or corner, this edge or corner is welded to the metal insert 550 of the spacer block 505. Advantageously, the metal insert 550 has at least one face extending along a plane parallel to the internal face 531 of the spacer block 505.

[0173] Advantageously, the metal insert 550 has a linear shape.

[0174] In another variant of the sixth embodiment, the spacer block 505 comprises two coplanar metal inserts 550. Advantageously, the two metal inserts 550 are co-directional.

[0175] In an embodiment not shown, the shape of the metal insert 550 coincides with one of the corners of a metal sheet of the internal waterproof membrane 6, 106, 206, 306, allowing welding in a junction zone having several metal sheets of the internal waterproof membrane 6, 106, 206, 306. Advantageously, the spacer block 505 comprises two metal inserts which form an angle coinciding with one of the corners of a metal sheet. Advantageously, the two metal inserts are of complementary shape relative to each other to form the angle,

[0176] In a variant of this embodiment, the metal inserts 550 of the spacer block 505 form a cross. Advantageously, the spacer block 505 comprises three or four metal inserts 550.

[0177] In one embodiment, the spacer block comprises a single cross-shaped metal insert 550.

[0178] In another variation of this embodiment, the metal inserts 550 of the spacer block 505 form a “T”. The spacer block 505 comprises two or three metal inserts 550.

[0179] In one embodiment, the spacer block comprises a single “T” shaped metal insert 550,

[0180] Figures 9 and 10 illustrate that the spacer block 505 comprises a housing 551 receiving the metal insert 550. The housing 551 holds the metal insert 550 such that once in place, the metal insert 550 has no freedom of movement depending on the height of the spacer block 505.

[0181] The housing is capable of blocking a translation of the metal insert in the thickness direction E.

[0182] The spacer block 505 has on its internal face _ 531 an opening 552 in the transverse direction and / or the longitudinal direction. Advantageously, the opening 552 passes through the spacer block 505 over the entire length of the internal face 531 in the transverse direction and / or the longitudinal direction. The opening 552 is delimited by at least two internal edges 553. The internal edges 553 coincide with the shape of the metal inserts 550. For example, if the metal insert 550 is of linear shape, the opening 552 is delimited by two parallel internal edges 553.

[0183] The spacer block 505 also comprises two planar protrusions 554 parallel to the two inner edges 553. A first planar protrusion 554 is located opposite the first inner edge 553 and the second planar protrusion 554 is located opposite the second inner edge 553, such that the space between the first planar protrusion 554 and the first inner edge 553 forms a first groove 555 and the space between the second planar protrusion 554 and the second inner edge 553 forms a second groove 555.

[0184] The housing 551 of the spacer block 505 comprises the two grooves 555.

[0185] In this embodiment, the two grooves 555 extend in parallel and at least partly border the opening 552, here two sides of the opening 552 located opposite each other,

[0186] Thus, when assembling the metal insert 550 in the opening 552, the metal insert 550 is first inserted at the edge and opposite the two grooves 555 before sliding inside the spacer block 505 and, here in the two grooves 555, so that the metal insert 550 is fully inserted into the housing 551 of the spacer block 505.

[0187] [Fig. 10] also illustrates a possible shape of the metal insert 550. The metal insert 550 here comprises: a flat central surface 560 evolving in a first plane at a first height; two ends 561 parallel to the flat central surface 560 evolving in a second plane at a second height; two joining portions 562 making it possible to join the flat central surface 560 to the two ends 561. The two joining portions 562 can be flat or curved.

[0188] In other words, in this embodiment, the metal insert 550 has an omega shape in cross-sectional view.

[0189] The two parallel ends 561 of the metal insert 550 slide in the two grooves 555 of the spacer block 505, such that the flat central surface 560 will be brought into contact with the internal waterproof membrane 6, 106, 206, 306. Advantageously, the difference between the first height and the second height allows the flat central surface 560 of the metal insert 550 to be flat with the internal face 531 of the spacer block 505.

[0190] In other words, once assembled, the metal insert 550 forms a cover for the opening 552,

[0191] Advantageously, the metal insert 550 can be placed in a spacer block 505 already installed and attached to the external waterproof membrane 4, 104, 204, 304, 404.

[0192] Advantageously, in the sixth embodiment, the spacer block 505 is metallic, for example made of aluminum.

[0193] Figures 11-12 illustrate an alternative embodiment of the spacer block. In Figures 11 and 12, elements identical or similar to those of Figures 2 to 4 bear the same reference numbers incremented by 500.

[0194] The spacer block 605 of figures 11 and 12 differs from the spacer block of figures 2 to 4 in that the spacer block 605 has a metal insert 650 for welding the internal waterproof membrane 6, 106, 206, 306 to the spacer block 605. More precisely, the internal waterproof membrane 6, 106, 206, 306 has at least one flat zone 17, 117, 317 for example located at an edge of the internal waterproof membrane 6, 106, 206, 306, this flat zone 17, 117, 317 is welded to the metal insert 650 of the spacer block 605. Advantageously, the spacer block 605 comprises between 1 and 4 metal inserts 650.

[0195] Advantageously, the number of metal inserts _ 650 _ is adapted according to the number of internal waterproof membranes 6, 106, 206, 306 present in the junction zone to be welded.

[0196] Figures 11 and 12 illustrate that the spacer block 605 has at least one housing 651 accommodating a metal insert 650. The housing 651 holds the metal insert 650 such that once in place, the metal insert 650 has no freedom of movement depending on the height of the spacer block 605.

[0197] The spacer block 605 has on its internal face _ 631 an opening 652 in the transverse direction and the longitudinal direction. Advantageously, the opening 652 passes through the spacer block 605 over the entire length of the internal face 631 in the transverse direction and the longitudinal direction. The opening 652 is here delimited by eight internal edges 653. In this embodiment, the opening 652 has a substantially cross shape.

[0198] Figures 11 and 12 also illustrate a possible shape of the metal insert 650. The metal insert 650 comprises: a flat central surface 660 evolving in a first plane at a first height; two ends 661 parallel to the flat central surface 660 evolving in a second plane at a second height; two joining portions 662 making it possible to join the flat central surface 660 to the two ends 661. The two joining portions 662 can be flat or curved.

[0199] In other words, in this embodiment, the metal insert 6 50 has an omega shape in cross-sectional view.

[0200] Advantageously, the difference between the first height and the second height allows the flat central surface 660 of the metal insert 650 to be flat with the internal face 631 of the spacer block 605.

[0201] In other words, once assembled, the metal insert 650 forms a cover for the opening 652,

[0202] In this embodiment, the metal inserts 650 are toothed, more precisely each of the two ends 661 of the metal insert 650 has at least one notch 663. Advantageously, the ends 661 have a plurality of notches 663. repeating, for example, a similar shape. More advantageously, the notches 663 are rectangular in shape.

[0203] In this embodiment, the inner edges 653 of the spacer block 605 are also toothed. More precisely, the inner edges 653 have a shape complementary to the ends 661 of the metal inserts 650. making it possible to insert the metal inserts 650 from the thickness direction E when the spacer blocks 605 are already installed and attached to the external waterproof membrane 4, 104, 204, 304, 404.

[0204] Advantageously, once the metal inserts 650 are inserted into the spacer block 605, a translational movement towards the center of the spacer block 605 makes it possible to block the movement of the metal inserts 650 according to the height.

[0205] In an embodiment not shown, filling pieces are placed in housing portions 651 of the spacer block 605 not comprising a metal insert 650.

[0206] Advantageously, in the seventh embodiment, the spacer block 605 is made of thermoplastic material.

[0207] Advantageously, the metal inserts 550, 650 of the sixth and seventh embodiments have a tab, allowing the insertion of the metal inserts 550, 650 and allowing the translational movement of the metal insert 550 and 560 to be carried out in the opening 552, 652.

[0208] Advantageously, the spacer blocks 605 of the seventh embodiment have a metal cover 623.

[0209] This metal cover 623 is placed, for example, in the center of the internal face 631 of the spacer block 605 and makes it possible to block the translation of the metal inserts 650. The metal cover 623 can also allow the spacer block 650 to be fixed to the external waterproof membrane 4, 104, 204, 304, 404,

[0210] Advantageously, the spacer blocks 505 of the sixth embodiment comprise a metal cover as described previously,

[0211] Advantageously, the spacer blocks 505, 605 of the sixth and seventh mode embodiments have an internal notch for each metal insert 550, 650 making it possible to block the translation of the metal inserts 550, 650.

[0212] Advantageously, the spacer block 505, 605 of the sixth and seventh embodiments has a fixing means for each metal insert 550, 650 making it possible to fix the metal inserts 550, 650 inside the spacer block 505, 605.

[0213] With reference to [Fig. 13], a cutaway view of a ship 70 shows a sealed and thermally insulating tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. 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 ship, 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.

[0214] In a manner known per se, loading / unloading pipes 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a maritime or port terminal to transfer a cargo of liquefied gas from or to the tank 71.

[0215] [Fig. 13] also shows an example of a maritime terminal comprising a loading and unloading station 75, an underwater pipeline 76 and an onshore installation 77. The loading and unloading station 75 is a fixed offshore installation comprising a mobile arm 74 and a tower 78 which supports the mobile arm 74. The mobile arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading / unloading pipelines 73. The orientable mobile arm 74 adapts to all vessel sizes. A connecting pipe, not shown, extends inside the tower 78. The loading and unloading station 75 allows the loading and unloading of the ship 70 from or to the onshore installation 77. The latter comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading or unloading station 75.The underwater pipeline 76 allows the transfer of liquefied gas between the loading or unloading station 75 and the onshore installation. 77 over a long distance, for example 5 km, which allows the vessel 70 to be kept at a great distance from the coast during loading and unloading operations.

[0216] To generate the pressure necessary for the transfer of the liquefied gas, one can either implement pumps on board the vessel 70 and / or pumps equipping the onshore installation 77 and / or pumps equipping the loading and unloading station 75 or allow a rise in pressure in the interior space of the tank under the effect of the evaporation of the liquefied gas stored in the tank.

[0217] Although the invention has been described in connection with several particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0218] The use of the verb “comport” or “comprendre” and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0219] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Claims

1. Sealed tank for storing a liquefied gas, the sealed tank comprising a tank wall (1, 101, 201, 301, 401) intended to be installed in a supporting structure (3), the tank wall comprising, in a thickness direction (E) of the tank wall: - an external metallic sealed membrane (4, 104, 204, 304, 404) and comprising a first series of parallel corrugations (14, 114, 214, 314, 414) and flat areas (15, 115, 215, 315, 415);- a spacer block (5, 105, 205, 305, 405, 505, 605) arranged on at least one said flat area (15, 115, 215, 315, 415) of the outer waterproof membrane and fixed to the outer waterproof membrane, the spacer block having an outer end (130, 230, 330, 430), a flat inner face (131, 231, 331, 431, 531, 631) parallel to the outer end and lateral ends (132, 133, 232, 332, 432, 532, 533, 632, 633) connecting the outer end to the inner face, the outer end being positioned against said at least one flat area, the lateral ends comprising a first lateral end (132, 133, 232, 332, 432, 532, 533, 632, 633) and a second lateral end ... and a second lateral end (132, 133, 232, 332, 432, 532, 533, 632, 633) and a third lateral 232, 332, 432, 532, 632) extending parallel to the first series of undulations (14, 114, 214, 314, 414) and facing a first undulation of the first series of undulations, the internal face comprising a first end portion partially overhanging the first undulation;- and an internal metallic sealed membrane (6, 106, 206, 306) intended to be in contact with the liquefied gas, in which the internal sealed membrane is spaced from the external sealed membrane by the spacer block and comprises at least one flat portion (17, 117, 317) which is fixed against the internal face of the spacer block.;

2. A sealed tank according to claim 1, wherein said first lateral end has a concave shape so as to overhang the first corrugation.

3. A sealed tank according to claim 1 or 2, wherein the first lateral end is not in contact with the first corrugation.

4. A sealed tank according to one of claims 1 to 3, wherein said at least one flat area comprises a first flat area and wherein the spacer block has a thickness greater than a height of the first series of undulations in the thickness direction of the tank wall and wherein the outer end of the spacer block is arranged on at least one second flat area (15, 115, 215, 315, 415) of the external waterproof membrane, the spacer block extending over at least one other corrugation (14, 114, 214, 314, 414) of the first series of corrugations located between said first flat area and said second flat area.

5. Sealed tank according to one of claims 1 to 4, in which the external sealed membrane comprises a second series of undulations (118, 218, 318) perpendicular to the first series of undulations, in which the lateral ends comprise a second lateral end (133, 333, 533, 633) extending parallel to the second series of undulations and facing a first undulation of the second series of undulations, the internal face comprising a second end portion partially overhanging the first undulation of the second series of undulations.

6. A sealed tank according to claim 5, wherein a height of the first series of corrugations is less than a height of the second series of corrugations in the thickness direction (E) of the tank wall, wherein the spacer block has a thickness between the height of the second series of corrugations and the height of the first series of corrugations.

7. A sealed tank according to claim 5, wherein the spacer block has a thickness greater than a height of the second series of corrugations in the thickness direction of the tank wall and wherein the outer end of the spacer block is arranged on at least one other flat area (15, 115, 215, 315, 415) of the outer sealed membrane, the spacer block extending over another corrugation (118, 218, 318) of the second series of corrugations located between said first flat area and said other flat area.

8. A sealed tank according to one of claims 1 to 7, wherein the lateral ends comprise a third lateral end (132, 232, 332, 432, 532, 632) located opposite the first lateral end extending parallel to the first series of undulations, the internal face comprising a third end portion partially overhanging said second undulation of the first series of undulations, the internal face (131, 231) having a more larger than the outer end (130, 230) in a direction transverse to the first series of undulations.

9. Sealed tank according to one of claims 1 to 8, in which the spacer block comprises support ribs (134, 234) located under the internal face between the lateral ends and hollow cells (135, 235) located between the support ribs.

10. A sealed tank according to claim 9, wherein the outer end of the spacer block is formed by edges of the side ends and / or end edges of the support ribs, the hollow cells being open at the outer end of the spacer block.

11. A sealed tank according to claim 9 or 10, wherein the first lateral end is formed by lateral edges of the support ribs.

12. A sealed tank according to one of claims 1 to 11, further comprising a fixing piece (120, 220) fixed to the flat area of ​​the external sealed membrane and projecting towards the internal sealed membrane, the spacer block being fixed to the fixing piece.

13. Sealed tank according to one of claims 1 to 12, the spacer block comprises at least one metal insert (550, 650) forming at least in part the internal face of the spacer block and at least one flat portion of the internal sealed membrane is fixed at least in part to the metal insert.

14. Sealed tank according to claim 13, the spacer block comprises a housing (551, 651) receiving the metal insert, the housing being capable of blocking a translation of the metal insert in the thickness direction (E).

15. A sealed tank according to one of claims 1 to 14, wherein the internal sealed membrane comprises a first series of undulations (16, 116, 216, 316) parallel to the first series of undulations of the external sealed membrane and flat areas (17, 117), at least one undulation of the first series of undulations of the internal sealed membrane being opposite the first undulation of the first series of undulations of the external sealed membrane in the thickness direction of the tank wall.

16. Method for adapting a sealed tank initially intended for the storage of a first liquefied gas, the method comprising: fixing a spacer block (5, 105, 205, 305, 405, 505, 605) on at least one flat area (15, 115, 215, 315, 415) of a sealed membrane external (4, 104, 204, 304, 404), wherein the external sealed membrane is a primary membrane belonging to a sealed tank wall (1, 101, 201, 301, 401) for the storage of the first liquefied gas, the external sealed membrane being metallic and comprising a first series of parallel corrugations (14, 114, 214, 314, 414);the spacer block having an outer end (130, 230, 330, 430), a flat inner face (131, 231, 331, 431, 531, 631) parallel to the outer end and lateral ends (132, 133, 232, 332, 432, 532, 533, 632, 633) connecting the outer end to the inner face, the outer end being positioned against said at least one flat area, the lateral ends comprising a first lateral end (132, 232, 332, 432, 532, 632) extending parallel to the first series of undulations and facing a first undulation of the first series of undulations, the inner face comprising a first end portion partially overhanging the first undulation; and securing at least one flat area (17, 117, 317) of a metallic inner sealing membrane (6, 106, 206, 306) against the inner face of the spacer block, such that the inner sealing membrane is spaced from the outer sealing membrane by the spacer block.;

17. Land-based installation comprising a supporting structure and a tank according to one of claims 1 to 15 arranged in the supporting structure.

18. A vessel (70) for transporting a liquefied gas, the vessel comprising a double hull (72) and a tank (71) according to one of claims 1 to 15 arranged in the double hull.

19. A transfer system for a liquefied gas, the system comprising a vessel (70) according to claim 18 and insulated pipes (73, 79, 76, 81) arranged to connect the vessel's tank (71) to a floating or land-based storage facility (77).

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

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