Assembly method and storage tank facility for liquefied gas

Abstract

The invention relates to a storage facility for liquefied gas, comprising a support structure and a sealed and thermally insulating tank (71) arranged in the support structure, in which so-called contiguous membranes (13, 13') of the sealing membrane of the cofferdam wall of the main structure of the tank (71) protrude at least partially into the liquid dome (2), said so-called contiguous membranes being secured directly and sealingly to the so-called contiguous membranes of the liquid dome (2).

Description

[0001] The invention relates to the field of storage installations for liquefied gas comprising a sealed and thermally insulating membrane tank. In particular, the invention relates to the field of sealed and thermally insulating tanks for the storage and / or transport of liquefied gas at low temperature, such as tanks for the transport of Liquefied Petroleum Gas (also called LPG) having for example a temperature between -50°C and 0°C, or for the transport of Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be intended for the transport of liquefied gas or for receiving liquefied gas used as fuel for the propulsion of the floating structure.

[0002] Document FR2991430 describes a storage facility for liquefied gas comprising a sealed and thermally insulating tank integrated into a supporting structure consisting of the double hull of a ship. Each wall of the tank comprises a secondary thermally insulating barrier, a secondary sealing membrane, a primary thermally insulating barrier and a primary sealing membrane made of metal or metal alloy. Document WO2019 / 239071 also describes a storage facility for liquefied gas comprising a supporting structure and a sealed and thermally insulating tank arranged in the supporting structure according to the prior art.

[0003] The primary waterproofing membrane conventionally comprises waves intended to allow thermal contractions, without rupture of the membrane, these waves conventionally forming a network of small and large waves extending parallel to each other respectively so as to constitute a grid delimited by node zones, i.e. the generally perpendicular intersections of the small and large waves.

[0004] In an area located at the top of the tank, the tank has a projecting portion in the form of a chimney. In this area, the supporting structure is interrupted locally so as to delimit a loading / unloading opening intended to be crossed by fluid loading / unloading pipes. This loading / unloading opening and this chimney-shaped pipe, called a Liquid Dome, comprise a thermally insulating insulation or barrier as well as an element forming a primary sealing membrane.

[0005] As can be seen on the figures 1 et 2 annexed, this liquid dome is classically located at a longitudinal end of the tank so that one of the vertical walls of the liquid dome continues or extends, in the same plane, by a vertical wall of the main structure of the tank (containing a cold fluid). When the tanks are present in a vessel transporting cold fluid such as LNG or LPG, i.e. an LNGC ("Liquid Natural Gas Carrier"), this vertical wall common to the liquid dome and the main structure of the tank is called a cofferdam wall.

[0006] The tank is installed in a structure subject to very high mechanical stresses, such as a ship, which bends and twists depending on the conditions of its environment. Since the supporting structure is interrupted at the level of the liquid dome, these mechanical stresses are all the greater.

[0007] The walls of the main structure of the tank are mounted and assembled / fixed on the one hand while the walls of the liquid dome are mounted and assembled / fixed on the other hand, these two parts of the storage installation then being connected to each other in a watertight manner.

[0008] However, taking into account in particular the dimensions of the primary insulation membranes, the connection of the membranes and the continuity of the waves are ensured by a connecting sheet, generally of small size, fixed by welding to the adjoining membranes of the liquid dome and the main structure of the tank.

[0009] This connecting plate is not a satisfactory solution.

[0010] First of all, in order to ensure the continuity of the vertical waves between the liquid dome and the main structure of the tank, the operators are obliged to deform in situ, using striking tools, this connecting sheet metal because the waves of the two parts - liquid dome on one side and main structure on the other - are not aligned. This operation is tedious for operators and typically requires several hours of work.

[0011] Then, the shaping of this connecting sheet at the level of its vertical waves leads to its weakening. As mentioned previously, this area of ​​a ship is subject to high mechanical stresses. This is why it is not acceptable for a portion of the primary waterproofing membrane to fail and compromise the watertightness of the storage facility.

[0012] After various experiments and tests, the applicant found that it is possible to do without this connecting part, or portion of sheet metal, by proposing a simpler and faster assembly solution, while making it possible to make this connection zone between the primary membranes of the main structure of the tank and those of the liquid dome more reliable from the point of view of mechanical strength and sealing.

[0013] Thus, the present invention relates to a storage installation for liquefied gas comprising a supporting structure and a sealed and thermally insulating tank arranged in the supporting structure, the sealed and thermally insulating tank comprising a main structure formed by a plurality of tank walls connected to each other and fixed to the supporting structure, the main structure defining an internal storage space, the main structure comprising at least one sealing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane and the supporting structure;the sealing membrane, the thermally insulating barrier of the main structure and a so-called upper load-bearing wall being interrupted locally so as to delimit a pipe forming a load-bearing wall of a chimney extending along a vertical axis to an upper end consisting of a loading / unloading opening intended to be crossed by liquefied gas loading / unloading pipes, said pipe up to said opening defining a liquid dome of the tank comprising, like the main structure of the tank, at least one sealing membrane and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane and the load-bearing wall;the liquid dome being located at one of the axial ends of the tank, a vertical wall of the main structure of the tank, called the cofferdam wall, extends from said main structure to form, along the same plane, a wall of the liquid dome conduit; the sealing membrane of the main structure and of the liquid dome are composed of a plurality of flat metal membranes, fixed together in a sealed manner, each having at least two perpendicular corrugation lines, the shape and dimensions of these two corrugation lines being respectively identical for all the membranes so that the juxtaposed membranes have a repeated pattern. ;

[0014] The invention is characterized in that so-called contiguous membranes of the sealing membrane of the cofferdam wall of the main structure of the tank are at least partly protruding into the liquid dome, said so-called contiguous membranes being directly fixed, in a sealed manner, to so-called contiguous membranes of the liquid dome.

[0015] Thus, the applicant has found after multiple tests and analyses that it is possible to firmly and perfectly seal the main structure of the tank with the liquid dome, while optimizing the assembly or mounting time of the respective membranes of these two parts of a liquefied gas storage installation, without using a connecting sheet.

[0016] In doing so, the invention allows substantial savings in the production of the liquid dome while ensuring or maintaining perfect sealing against liquefied gas and excellent mechanical resilience of the latter to all constraints that this area is typically subjected to.

[0017] The expression "watertight" in relation to fixings, in particular between membranes, means that the fixing is carried out by welding, possibly supplemented by chemical fixing, by gluing, and / or mechanically, for example using a sealing joint.

[0018] The term "metallic" in relation to membranes in particular means that it is a metal or a metal-based alloy, more often a metal-based alloy such as steel.

[0019] The term "membrane" systematically refers to the fact that it is a waterproof membrane, impermeable to the fluid, whether the term is accompanied by the term "waterproof" or not. A membrane is qualified as such in the context of the present invention if it has, on the cofferdam wall, at least one vertical wave line, preferably a plurality of vertical waves, and at least one horizontal wave line. In the embodiment chosen to illustrate the invention, the vertical waves of / on the cofferdam wall are small waves while the horizontal waves are large waves.

[0020] The term "wave" or "corrugation", with or without the plural, refers to the same element present on a membrane to allow its deformation, by contraction and / or stretching, under the effect of thermal expansion linked to the presence or absence of a liquefied gas, cold or even very cold, in the tank. The two lines of waves or corrugations perpendicular to each other, defining a membrane in the context of the present invention, may be of identical or different shape. In the following, these two lines of waves or corrugations are advantageously different, with a horizontal line of large wave or corrugation and a vertical line of small wave or corrugation.

[0021] The term "contiguous" in relation mainly to the membranes, those of the liquid dome and those of the main structure of the tank, refers to the fact that these membranes are those closest to the other part of the tank, namely sometimes to the main structure for the membranes located in the liquid dome and to the liquid dome for the membranes located in the main structure.

[0022] The term "conduit" means that it forms the external wall of the liquid dome, more precisely the wall of the chimney opening into the tank containing the liquefied gas, the term "chimney" referring to the general shape of the liquid dome which extends vertically.

[0023] Other advantageous characteristics of the invention are presented briefly below:

[0024] Preferably, the metal planar membranes forming the sealing membrane of the main structure and the liquid dome have a rectangular shape with two large sides and two small sides.

[0025] Preferably, the metal planar membranes have a raised portion extending along two adjoining sides for covering the adjoining side of another membrane.

[0026] Advantageously, the thermally insulating barrier of the main structure and the liquid dome of the tank comprise metal plates onto which the sealing membrane of the main structure and the liquid dome are welded discontinuously.

[0027] Advantageously, the so-called contiguous membranes of the liquid dome comprise a raised portion extending along the large lower side while the so-called directly contiguous membranes of the main structure of the tank comprise a raised portion extending along one of the two short sides of the membrane. According to a particular example, the so-called directly contiguous membranes of the main structure of the tank comprise only a single raised portion extending along one of the two short sides of the membrane.

[0028] According to a particular embodiment, when these so-called contiguous membranes are mounted and assembled after the other membranes of the liquid dome, which is a preferred embodiment of the invention, the so-called contiguous membranes of the liquid dome comprise a raised portion extending along the two opposite large sides while the so-called directly contiguous membranes of the main structure of the tank comprise only a single raised portion extending along one of the two small sides of the membrane, respectively.

[0029] According to a feature of the invention, preferably, the protruding part of the so-called contiguous membranes of the sealing membrane of the cofferdam wall (B) of the main structure of the tank protrude by at least 30 millimeters into the liquid dome, preferably 55 millimeters.

[0030] Storage facility according to any one of the preceding claims, in which the protruding part of the so-called contiguous membranes of the sealing membrane of the cofferdam wall (B) of the main structure of the tank protrude by at most 60 millimeters into the liquid dome.

[0031] It can be noted here that the expression "of the cofferdam wall", that is the wall referenced B or B' on the figure 2 , in particular in connection with the main structure of the tank is superfluous because the only membranes which are of interest to the present invention in the embodiment chosen to illustrate it are the membranes of the cofferdam wall because this wall is the only one which is extended vertically, in other words without breaking an angle, in the liquid dome.

[0032] Of course, the invention would also find application if, for example, the liquid dome is located in a corner of the main structure, so that in addition to the cofferdam wall, a side wall - wall F on the figure 2 , in the case where there are no chamfers E - would be extended vertically in the liquid dome. This scenario is covered by the present invention although such an arrangement of the liquid dome, in a corner of the tank, is a priori unattractive and practical.

[0033] Advantageously, the so-called contiguous membranes of the liquid dome have a length of between 500 millimeters and 3300 millimeters and a width of between 200 millimeters and 800 millimeters.

[0034] Advantageously, the so-called contiguous membranes of the sealing membrane of the cofferdam wall of the main structure of the tank have a length of between 500 millimeters and 3300 millimeters and a width of between 200 millimeters and 800 millimeters.

[0035] According to yet another advantageous aspect of the invention, the so-called contiguous membranes of the sealing membrane of the cofferdam wall of the main structure of the tank are presented in two rows of parallel membranes, one row of membranes having a width of between 200 and 400 millimeters and the other row of membranes having a width of between 700 and 800 millimeters.

[0036] The invention also relates to a method of mounting a storage installation as described above, in which it comprises: a first step of mounting and fixing, in a sealed manner, the entire sealing membrane of the cofferdam wall of the main structure of the tank; a second step of mounting and fixing, in a sealed manner, the entire sealing membrane of the liquid dome with the exception of the contiguous membranes of said liquid dome; the first and second steps being carried out in any order or simultaneously; a final step of mounting and fixing, in a sealed manner, the so-called contiguous membranes of said liquid dome so that the entire cofferdam wall, the main structure and the liquid dome are sealed.

[0037] The invention relates to a ship for transporting a cold liquid product, the ship comprising a double hull and a storage facility as described above arranged in the double hull.

[0038] The invention also relates to a transfer system for a cold liquid product, the system comprising a vessel as described above, insulated pipes arranged to connect the tank installed in the hull of the vessel to an external floating or land-based storage facility and a pump for driving a flow of cold liquid product through the insulated pipes from or to the external floating or land-based storage facility to or from the vessel's tank.

[0039] Finally, the present invention relates to a method of loading or unloading a ship as described above, in which a cold liquid product is conveyed through insulated pipes from or to an external floating or land-based storage facility to or from the ship's tank.

[0040] The invention will be better understood, and other objects, 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 accompanying drawings. [ fig.1 ] There figure 1 is a schematic sectional and perspective view of a liquefied gas carrier of the LNGC type. fig.2 ] There figure 2 is a sectional and cutaway view of a tank of the ship shown on the figure 1 . [ fig.3 ] There figure 3 is a schematic view illustrating a waterproofing membrane with three parallel rows of large corrugation or wave and nine parallel rows of small corrugation or wave, the two types of row being perpendicular to each other. fig.4 ] There figure 4 is a schematic view illustrating the arrangement of the membranes at the liquid dome area and the main structure of the tank, with an indication of the overlap of each membrane relative to its neighbor. fig.5 ] There figure 5 is an enlarged view of a portion P of the figure 4 . [ fig.6 ] There figure 6 is a detailed and dimensioned view of a contiguous membrane, called the lateral membrane, of the main structure of the tank. fig.7 ] There figure 7 is a view, identical to the view of the figure 4 , illustrating thermal insulation blocks present under the membranes, with in particular the metal plates allowing the membranes to be fixed by welding to these thermal insulation blocks. fig.8 ] There figure 8 is a schematic cutaway representation of an LNG tanker storage facility and a loading / unloading terminal for this tank.

[0041] The term "vertical" here means extending in the direction of the Earth's gravitational field. The term "horizontal" here means extending in a direction perpendicular to the vertical direction.

[0042] When the storage facility is positioned on a vessel 70 such as an LNG carrier, the supporting structure, not visible in the attached figures, is formed by the double hull of the vessel. The external upper load-bearing wall is called the external deck of the vessel.

[0043] In the following, the present invention is illustrated with a vessel 70 transporting liquefied gas of a conventional type, namely an LNGC for "Liquid Natural Gas Carrier", but it is understood that the invention can be applied to other types of tanks provided that such a tank comprises a sealing membrane, called primary due to its direct contact with a fluid contained in the tank and the possible presence of a second sealing membrane, and a liquid dome 2 or the like, that is to say a chimney and an opening for loading / unloading said fluid, having at least one wall section continuous with a wall of the main structure of the tank 71, 71'. These two characteristics being verified, the present invention finds application to such an installation for storing a fluid.

[0044] So, as it is visible on the figure 1 , we can see the distribution of the four LNG tanks 71, 71' conventionally present in a LNG carrier ship 70 of the LNGC type. Thus, as we have seen previously, three of the four tanks 71 have the same dimensions while the last one, that 71' located at the front of the ship 70, has smaller dimensions so in particular that the ballasts, arranged laterally and under the tank 71', have dimensions much larger than the other ballasts, located around the other three tanks 71, in order to more easily rebalance the trim of the ship 70, taking into account the fact that the majority of the weight of the ship 70 is located at the rear of the latter when the tanks 71 are empty.

[0045] At the rear of the ship 70 are typically the machines or engine room, not visible in the attached figure, intended to manage the entire ship 70, from the propulsion to all the generation and power supply circuits for the various equipment of the ship 70. Furthermore, above the machines is the castle 31 which typically consists of a tower or similar where the crew accommodation and the ship's command post are located.

[0046] A tank 71 comprises a main structure formed by a front wall D, a rear wall B, a ceiling wall A, a bottom wall C and two side walls F, both of which are not visible on the figure 2 attached (one side of the tank not being visible in this figure), connecting the bottom wall C to the ceiling wall A, and finally two to four chamfer walls E, G connecting the side walls F to the bottom wall C or to the ceiling wall A. The walls of the tank 71 are thus connected to each other so as to form a polyhedral structure and to delimit an internal storage space. The tank 71' is presented in a manner substantially identical to a tank 71.

[0047] In order to load and unload the tank 71 with liquefied gas, the storage installation comprises a loading / unloading opening locally interrupting the external upper load-bearing wall, the internal upper load-bearing wall and the ceiling wall of the tank 71 so as to allow in particular loading / unloading pipes, not shown in the attached figures, to reach the bottom of the tank 71 by passing through this opening.

[0048] The storage facility also includes a loading / unloading tower, not visible in the attached figures, located to the right of the opening of the liquid dome 2 and inside the tank 71 forming a support structure for the loading / unloading pipes over the entire height of the tank 71 as well as for the pumps (not shown).

[0049] The tank 71 thus comprises a chimney, or conduit, located on or above the main structure and allowing the tank walls to extend continuously from the internal deck to the external deck at the level where these are interrupted by the loading / unloading opening. For tanks 71, 71' for storing liquefied gas, such a chimney, or conduit, provided with a cover closing said loading / unloading opening, is called: the liquid dome 2.

[0050] The loading / unloading opening and the chimney typically have a rectangular or square outline or action. The chimney thus comprises four walls, one B' being the extension of the rear wall B, also referred to as the "cofferdam wall" of the main structure of the tank 71, 71', as seen in the figure 2 , while the other three are connected to the ceiling wall A forming a 90° angle with it.

[0051] The present invention is concerned only with the wall B, B', or with the two walls in a different embodiment, continuous or extending without breaking the angle between the main structure of the tank 71, 71' and the liquid dome 2, more precisely at the level of the sealing membrane and its junction between the main structure of the tank 71, 71' and the liquid dome 2.

[0052] There figure 3 represents such a conventional waterproofing membrane 3. A waterproofing membrane is defined, in the context of the present invention, as a metal or metal alloy sheet comprising at least one first wave or corrugation line 4 and at least one second wave or corrugation line 5, the first and second wave or corrugation lines 4, 5 extending perpendicular to each other.

[0053] According to one embodiment, the main structure of the tank 71, 71' is produced using Mark Ill ® technology which is described in particular in document FR-A-2691520.

[0054] In such a main structure, the secondary thermally insulating barrier, the primary thermally insulating barrier and the secondary waterproofing membrane are essentially made up of panels juxtaposed on the load-bearing structure, which may be the internal load-bearing structure or the structure connecting the internal upper load-bearing wall to the external upper load-bearing wall at the opening. The secondary waterproofing membrane is formed from a composite material comprising an aluminum sheet sandwiched between two sheets of fiberglass fabric. The primary waterproofing membrane is obtained by assembling a plurality of metal plates, welded to each other along their edges, and comprising corrugations extending in two perpendicular directions. The metal plates are, for example, made of stainless steel or aluminum, shaped by folding or stamping.

[0055] More specifically to illustrate an embodiment of the invention, the sealing membrane is a so-called primary sealing membrane (because it is in direct contact with the fluid stored in the tank 71, 71') and is obtained by assembling a plurality of corrugated metal sheets conforming to the membrane shown in the figure 3 . Each corrugated metal membrane 3 comprises a first series of parallel corrugations 5, called high or large, extending in a first direction and a second series of parallel corrugations 4, called low or small, extending in a second direction perpendicular to the first series. The node zones 6 are the crossing zones of these two types of corrugations 4, 5. The corrugations 4, 5 protrude towards the inside of the tank 71, 71'. As mentioned previously, these corrugated metal membranes 3 are, for example, made of stainless steel or aluminum.

[0056] The corrugated metal membranes 3 are fixed to insulating panels 21 by means of metal plates 20 extending in two perpendicular directions, vertically and horizontally on the cofferdam wall B, B', these plates 20 being fixed to the internal face (facing the internal space of the tank) of the insulating panels 21. Thus, each insulating panel 21 has an internal face equipped with metal plates 20 on which the corrugated metal membranes 3 forming the primary waterproofing membrane are welded. These insulating panels 21 on which the waterproofing membranes 3 are fixed are visible, with the aforementioned metal plates 20, on the figure 7 attached.

[0057] The metal plates 20 extend in two perpendicular directions which are each parallel to two opposite edges of the insulating panels 21. The metal plates 20 are fixed in recesses provided in the internal face of the insulating panel 21 and fixed to the latter, by screws, rivets or staples for example.

[0058] The attached figures 4 to 7 illustrate the actual arrangement of the sealing membrane 3, or primary sealing membrane, at the level of the wall B of the main structure of the tank 71, 71' and of the wall B' continuous with the wall B in the liquid dome 2.

[0059] The first characteristic of such an arrangement lies in the fact that only sealing membranes 3, 13, 13', 33 - comprising at least two perpendicular corrugation or wave lines 4, 5 between them - are used to achieve the continuity of the sealing of these two walls, the cofferdam wall B of the main structure of the tank 71, 71' and the continuous wall B' of the liquid dome 2. Thus, no intermediate element is present in this area, it being understood that an "intermediate element", such as a sheet, is not a sealing membrane 3, 13, 13', 33 according to the present invention, that is to say the definition of a membrane given previously.

[0060] The second characteristic of such an arrangement according to the invention lies in the fact that the sealing membrane 13 of the main structure of the tank 71, 71' directly contiguous to the liquid dome 2 - i.e. the three membranes 14, 15, 16 visible on the figure 4 - protrudes into the liquid dome 2, that is to say into the space forming this liquid dome 2 from the opening present in the ceiling wall A, the insulation and sealing elements being considered here to define the location of this opening of the liquid dome 2.

[0061] As can be seen on the figure 6 , the protrusion 17 of the sealing membrane 13 in the liquid dome 2 is 55 millimeters in this example. Generally, this protrusion 17 is at least 30 millimeters and at most 60 millimeters. As can be clearly seen in the figure 6 , to produce this protuberance 17, either the contiguous membrane 13 is protruding over its entire width as is the case with the central membrane 15, or the contiguous membrane is protruding over only part of its length as is the case for the lateral membranes 14 and 16. For these so-called lateral membranes 14 and 16, a cut was made, for example by laser or using a saw, in a conventional membrane to extract the portion not contiguous to the liquid dome 2 and which is therefore not protruding in the latter 2.

[0062] Another particularity of the present invention lies in the dimensions of the contiguous membranes 13, 13', 33 of both the liquid dome 2 and the main structure of the tank 71, 71'. Indeed, these dimensions are not conventional and have been chosen to adjust perfectly, and as reliably as possible, the connection of the membranes 13, 13' of the main structure of the tank 71, 71' and those 33 of the liquid dome 2. Thus, a conventional membrane 3 of the main structure of the tank 71, 71' normally comprises three lines 5 of large wave or corrugation, but the contiguous membranes 13, 13' of the main structure of the tank 71, 71' only comprise two lines 5 of large wave or corrugation for the directly contiguous membrane 13, or even a single / unique line 5 of large wave for the contiguous membrane 13'.In the same way, a conventional membrane 3 of the liquid dome 2 normally comprises two lines 5 of large wave or corrugation, but the contiguous membranes 33 of the liquid dome 2 only comprise a single line 5 of large wave.

[0063] As a non-limiting example, the following are given on the figure 6 , the dimensions, expressed in millimeters, of the contiguous lateral membrane 14 of the main structure of the tank 71, 71', with in particular a protuberance 17 of 55 millimeters resulting from a prior cutting of the membrane 14. Given that the figures 4 And 5 present to scale the membranes 13, 13' and 33, a part of the main structure of the tank 71, 71' and the liquid dome 2, we can deduce the dimensions, or more exactly the domains or ranges of dimensions of each of the membranes 13, 13' and 33, knowing the dimensions precisely given for the contiguous lateral membrane 14 on the figure 6 . Of course, it is recalled here that the precise dimensions given on the figure 6 represent only one embodiment and that other embodiments of the invention may be provided, the dimensions given on the figure 6 which may vary, with the exception of the protruding portion 17, within a range or domain of + / - 30 millimeters (mm) preferably + / - 15 mm at most. For the protruding portion 17, it will be noted that it cannot be less than 30 millimeters and greater than 60 millimeters.

[0064] Another feature of the invention lies in the fact that the contiguous membranes 33 of the liquid dome 2 have, on their two lower / upper faces 34, 35 or even the two opposite large sides, a raised portion 7 extending along said two faces or sides 34, 35 so as to cover the two lower and upper membranes to which they are fixed respectively. It should be noted here that only the lower raised portion 7 is imperative in the context of the present invention where the contiguous membranes 33 of the liquid dome must be mounted and assembled after those of the main structure of the tank 71, 71'.

[0065] This particular characteristic of these contiguous membranes 33 is justified by the assembly method specific to the storage installation according to the invention in which these contiguous membranes 33 of the liquid dome 2 are advantageously mounted last, once the sealing membranes of the liquid dome 2 have been mounted and fixed and the sealing membranes of the main structure of the tank 71, 71' (or at least the membranes located near the liquid dome 2) are also mounted and fixed. In doing so, the directly contiguous membranes 13 of the main structure of the tank 71, 71' have only a single raised portion 7, more precisely on one of the small sides (width).

[0066] It should indeed be noted that a conventional membrane 3, like that shown in the figure 3 , has two elevations 7 extending along two contiguous sides of the membrane 3, namely one of the short sides defining the width of the membrane 3 and one of the long sides of the membrane 3. As can be noted on the figures 4 à 6 , the black isosceles triangles indicate, thanks to the orientation of the point of said triangle, the position of the elevation 7 so that the membrane on which the black isosceles triangle is located covers, at the level of this portion of elevation 7, the adjacent membrane at the level of the small or large side considered. Thus, the figure 4 in particular is very explicit on the relative assembly or mounting of the different membranes, whether they are those 3, 13, 13' of the liquid dome 2 or those 3, 33 of the main structure of the tank 71, 71'.

[0067] There figure 7 illustrates the thermal insulation blocks 21 which equip a storage installation for liquefied gas. In the context of the present invention, these thermal insulation blocks 21 are not modified compared to the state of the art and details of such thermal insulation blocks 21 are described in particular in FR-A-2861060. Nevertheless, a particularity of this invention lies in the metal plates 20, described previously, located on these thermal insulation blocks 21, opposite the membranes 3, 13, 13', 33, so as to fix by welding or soldering the latter 3, 13, 14', 33 to the thermal insulation block 21 by means of these metal plates 21. These metal plates 20, also called "Anchoring Strip" (AS), are here arranged in a manner adapted to the contiguous membranes 13, 13', 33, both those 13, 13' of the main structure of the tank 71, 71' and those 33 of the liquid dome 2.

[0068] Thus, the contiguous membranes 33 of the liquid dome 2 are located in close proximity to metal plates 20, so that they have a discontinuous weld line extending over more than 70% of their length, while these membranes 33 are not wide because they have only one long wave line 5 or corrugation. By comparison, the other membranes 3 of the liquid dome 2 have two long wave lines 5 or corrugation and have only one discontinuous weld line on plates 20, representing more than 70% of their length. The small contiguous membranes 13' of the main structure of the tank 71, 71' are also provided with such a discontinuous weld line while they also have only one long wave line 5, like the membranes 33.

[0069] In reference to the figure 8 , a cutaway view of an LNG carrier 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealing membrane intended to be in contact with the LNG contained in the tank, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 72 of the ship, and two 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.

[0070] In a manner known per se, loading / unloading pipelines 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 LNG from or to the tank 71.

[0071] There figure 8represents 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 sizes of LNG carriers. A connecting pipe, not shown, extends inside the tower 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 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 subsea 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 makes it possible to keep the LNG carrier 70 at a great distance from the coast during loading and unloading operations.

[0072] To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the onshore installation 77 and / or pumps equipping the loading and unloading station 75 are used.

[0073] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto 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.

[0074] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim. The use of the indefinite article "un" or "une" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

[0075] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

1. Liquefied gas storage installation comprising a load-bearing structure and a sealed and thermally insulating tank (71) arranged in the load-bearing structure, the sealed and thermally insulating tank (71) including a main structure made up of a plurality of tank walls connected to each other and fastened to the load-bearing structure, the main structure defining an internal storage space, the main structure comprising at least one sealing membrane (3, 13, 13') and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 13, 13') and the load-bearing structure; the sealing membrane (3, 13, 13'), the thermally insulating barrier of the main structure and a so-called upper load-bearing wall being locally interrupted so as to define a duct forming a load-bearing wall of a chimney extending along a vertical axis to an upper end consisting of a loading / unloading opening through which liquefied gas loading / unloading pipes can pass, said duct leading to said opening defining a liquid dome (2) of the tank (71) including, like the main structure of the tank (71, 71'), at least one sealing membrane (3, 33) and at least one thermally insulating barrier, the thermally insulating barrier being placed between the sealing membrane (3, 33) and the load-bearing wall; the liquid dome (2) being situated at one axial end of the tank (71), a vertical wall of the main structure of the tank (71), referred to as the cofferdam wall (B), extends from said main structure to form, along the same plane, a wall (B') of the duct of the liquid dome (2); the sealing membrane (3, 13, 13', 33) of the main structure and the sealing membrane of the liquid dome (2) are made up of a plurality of flat metal membranes, sealably fastened together, each having at least two perpendicular rows of corrugations (4, 5), the shape and dimensions of these two rows of corrugations (4, 5) being respectively identical for all of the membranes so that these juxtaposed membranes display a repeating pattern; characterized in that so-called adjacent membranes (13, 13') of the sealing membrane of the cofferdam wall (B) of the main structure of the tank (71) protrude at least partially into the liquid dome (2), said so-called adjacent membranes being directly sealably fastened to so-called adjacent membranes of the liquid dome (2).

2. Storage installation according to Claim 1, in which the flat metal membranes (3, 13, 13', 33) forming the sealing membrane of the main structure and of the liquid dome (2) have a rectangular shape with two long sides and two short sides.

3. Storage installation according to Claim 1 or 2, in which the flat metal membranes include a raised (7) portion extending along two adjacent sides suitable for overlapping the adjacent side of another membrane.

4. Storage installation according to any one of the claims, in which the thermally insulating barrier of the main structure and the thermally insulating barrier of the liquid dome (2) of the tank (71) include metal plates to which the sealing membrane (3, 13, 13' 33) of the main structure and the sealing membrane of the liquid dome (2) are discontinuously welded.

5. Storage installation according to at least any one of Claims 2 to 4, in which the so-called adjacent membranes of the liquid dome (2) include a raised portion (7) extending along the lower long side while the so-called directly adjacent membranes of the main structure of the tank (71, 71') include a raised portion (7) extending along one of the two short sides of the membrane.

6. Storage installation according to any one of the preceding claims, in which the protruding part (17) of the so-called adjacent membranes (13) of the sealing membrane of the cofferdam wall (B) of the main structure of the tank (71) protrudes by at least 30 millimetres into the liquid dome (2), preferably by 55 millimetres.

7. Storage installation according to any one of the preceding claims, in which the protruding part (17) of the so-called adjacent membranes (13) of the sealing membrane of the cofferdam wall (B) of the main structure of the tank (71) protrudes by at most 60 millimetres into the liquid dome (2).

8. Storage installation according to one of the preceding claims, in which the so-called adjacent membranes of the liquid dome (2) have a length of between 500 millimetres and 3,300 millimetres and a width of between 200 millimetres and 800 millimetres.

9. Storage installation according to any one of the preceding claims, in which the so-called adjacent membranes (13, 13') of the sealing membrane of the cofferdam wall (B) of the main structure of the tank (71) have a length of between 500 millimetres and 3,300 millimetres and a width of between 200 millimetres and 800 millimetres.

10. Storage installation according to Claim 9, in which the so-called adjacent membranes (13, 13') of the sealing membrane of the cofferdam wall (B) of the main structure of the tank (71, 71') are in two rows of parallel membranes, one row of membranes (13') having a width of between 200 and 400 millimetres and the other row of membranes (13) having a width of between 700 and 800 millimetres.

11. Method for assembling a storage installation according to any one of the preceding claims, in which it comprises; - a first step of sealably assembling and fastening the sealing membrane assembly (3, 13, 13') of the cofferdam wall (B) of the main structure of the tank; - a second step of sealably assembling and fastening the sealing membrane assembly (3) of the liquid dome (2), with the exception of the adjacent membranes of said liquid dome (2); the first and second steps being performed in any order or simultaneously; - a final step of sealably assembling and fastening the so-called adjacent membranes (33) of said liquid dome (2) so that the assembly of the cofferdam wall (B, B'), of the main structure and of the liquid dome (2), is sealed.

12. Vessel (70) for transporting a cold liquid product, the vessel including a double hull (72) and a storage installation (1) according to one of Claims 1 to 10 arranged in the double hull.

13. System for transferring a cold liquid product, the system including a vessel (70) according to Claim 12, insulated pipes (73, 79, 76, 81) arranged so that they connect the tank (71) installed in the hull of the vessel to a floating or onshore external storage installation (77) and a pump for conveying a stream of cold liquid product through the insulated pipes from or to the floating or onshore external storage installation to or from the tank of the vessel.

14. Method for loading or unloading a vessel (70) according to Claim 12, in which a cold liquid product is conveyed through insulated pipes (73, 79, 76, 81) from or to a floating or onshore external storage installation (77) to or from the tank (71) of the vessel.

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