Manufacturing method for producing a sealing membrane for a sealed and thermally insulating tank for storing liquefied gas

Abstract

The invention relates to a manufacturing method for producing a sealing membrane for a sealed and thermally insulating tank for storing liquefied gas, the method comprising: a step of positioning a first metal sheet (44) and a second metal sheet (44), wherein the second metal sheet (44) covers the first metal sheet (44) in a region of overlap (ZR), and positioning an inerting device (200, 300) comprising an inflatable balloon (220, 320); a step of inflating the inflatable balloon (220, 320) so as to close an inerting space (235, 335) around a central portion (225, 325) of the inflatable balloon (220, 320), wherein the inerting space (235, 335) is located in line with at least part of the region of overlap (ZR); a step of forming, once the inerting space (235, 335), in its closed state, has been placed under an inert atmosphere, a continuous weld between the second metal sheet (44) and the first metal sheet (44) along the region of overlap (ZR), wherein the continuous weld runs directly over the inerting space (235, 335).

Description

Manufacturing method for manufacturing a sealing membrane for a sealed and thermally insulating tank for storing liquefied gas

[0001] The invention relates to the field of sealed and thermally insulating membrane tanks. In particular, the invention relates to the field of sealed and thermally insulating tanks for the storage and / or transport of liquefied gas, such as liquid hydrogen which is at approximately -253°C at atmospheric pressure. Technological background

[0002] In the state of the art, sealed and thermally insulating tanks are known for storing liquefied gas, such as liquefied natural gas (LNG) or liquid hydrogen.

[0003] Document WO 2023 / 198637 A1 discloses a tank in which the walls have a multi-layer structure, i.e. successively have, in the direction of thickness of the wall, from the outside to the inside, a secondary thermally insulating barrier retained on the supporting structure, a secondary sealing membrane resting against the secondary thermally insulating barrier, a primary thermally insulating barrier resting against the secondary sealing membrane and a primary sealing membrane intended to be in contact with the liquefied gas contained in the tank.

[0004] The primary thermally insulating barrier comprises rows of load-bearing elements, each of the load-bearing elements being attached to an outer tray and an inner tray, the outer trays being attached to the secondary thermally insulating barrier and pressing the secondary waterproofing membrane against the secondary thermally insulating barrier, the inner trays forming a support surface for the primary waterproofing membrane.

[0005] The primary waterproofing membrane comprises a plurality of corrugated metal sheets, the edges of which are welded to the internal trays, and which are lap welded along their edges to ensure the waterproofing of the primary waterproofing membrane.

[0006] Such a tank is suitable for storing liquid hydrogen at -253°C at atmospheric pressure.

[0007] However, when filling the tank with liquid hydrogen at -253°C at atmospheric pressure, the primary sealing membrane is subjected to very high thermal stresses. It is therefore important to ensure the mechanical strength of the primary sealing membrane.

[0008] On the other hand, to give the primary thermally insulating barrier the required thermally insulating properties, the primary thermally insulating barrier has a gas phase which is placed at a very low absolute pressure. It is important that this vacuum is not degraded by the primary sealing membrane. Summary

[0009] Among the factors that affect the mechanical strength of the primary waterproofing membrane and the impact of the primary waterproofing membrane on the vacuumization of the primary thermally insulating barrier, there is the presence of residual porosity in the welds between the corrugated metal sheets of the primary waterproofing membrane. If the welding operation causes excessive melting of the metal alloy of the corrugated metal sheets, the welds between the corrugated metal sheets may have high residual porosity. This risk is greater when the welding operation is not carried out under an inert atmosphere, because then the metal alloy is likely to undergo hot oxidation due to the high temperature and the presence of oxygen in the atmosphere.The higher the residual porosity of the welds between the corrugated metal sheets, the more they present a surface irregularity likely to generate crack initiations which are detrimental to the mechanical strength of the primary waterproofing membrane, and the more they are likely to degrade the vacuum performance of the primary thermally insulating barrier.

[0010] One idea behind the invention is to propose a method for manufacturing a waterproofing membrane which tends to limit the residual porosity in the welds between the corrugated metal sheets.

[0011] According to one embodiment, the invention provides a manufacturing method for manufacturing a sealing membrane for a sealed and thermally insulating tank for storing a liquefied gas, the manufacturing method comprising the following steps: - arranging an inerting device, a first metal sheet and a second metal sheet on a flat support surface, the first metal sheet and the second metal sheet each comprising two flat portions resting on the flat support surface and a corrugation portion formed between the two flat portions, the corrugation portion projecting relative to the two flat portions, the corrugation portion of the first metal sheet and the corrugation portion of the second metal sheet being aligned,the second metal sheet covering the first metal sheet in an overlapping area defined between an edge of the first metal sheet and an edge of the second metal sheet parallel to the edge of the first metal sheet, the corrugation portion of the first metal sheet extending to said edge of the first metal sheet and the corrugation portion of the second metal sheet extending to said edge of the second metal sheet, one end of the corrugation portion of the second metal sheet covering one end of the corrugation portion of the first metal sheet in the overlapping area and the two flat portions of the second metal sheet covering the two flat portions of the first metal sheet in the overlapping area, the first metal sheet being located between the second metal sheet and the support surface in the overlapping area,the inerting device comprising a gas supply pipe and an inflatable balloon, the inflatable balloon comprising a central portion and two flanges on either side of the central portion, the gas supply pipe being configured to convey gas into an inerting space located between the two flanges and around the central portion;- inflating the inflatable balloon until the two flanges are compressed against the inner contour of the corrugation portion of the first metal sheet, so as to close the inerting space, the inerting space being located at least in line with a portion of the overlap zone;- placing the inerting space thus closed under an inert atmosphere by conveying an inert gas via the supply pipe;- making a continuous weld between the second metal sheet and the first metal sheet along the overlap zone while the inerting space is under an inert atmosphere,the continuous weld passing right through the inerting space.,

[0012] Since the continuous welding is carried out while the inerting space is under an inert atmosphere, hot oxidation of the metal alloy of the first metal sheet tends to be avoided, which tends to prevent the weld between the second metal sheet and the first metal sheet from having high residual porosity after recrystallization of the metal alloy. Thus, thanks to the inerting device, the sealing membrane has improved mechanical strength and degrades less the vacuuming of a thermally insulating barrier under the sealing membrane.

[0013] According to embodiments, such a manufacturing method may comprise one or more of the following features.

[0014] According to one embodiment, the inert gas is nitrogen or argon.

[0015] According to one embodiment, the gas supply line is configured to convey the inert gas into the inflatable balloon, at least a portion of an outer wall of the central portion being impermeable to the inert gas below an inflation pressure threshold and permeable to the inert gas above the inflation pressure threshold, and the inflatable balloon is inflated to at least the inflation pressure threshold by the inert gas, such that the inerting space is inerted by inert gas passing through said outer wall.

[0016] The inerting device, or at least the inflatable balloon, may optionally be left in place after performing the continuous weld. However, from an economic and industrial point of view, it is preferable to use the inerting device to successively perform several continuous welds between corrugated metal sheets. Thus, according to one embodiment, the manufacturing method further comprises a step of removing the inerting device, the step of removing the inerting device comprising deflating the inflatable balloon and then sliding the inflatable balloon into the corrugation portion of one of the first metal sheet and the second metal sheet, preferably the second metal sheet.

[0017] According to one embodiment, said one of the first metal sheet and the second metal sheet comprises first parallel corrugations, second corrugations perpendicular to the first corrugations, and a plurality of nodes at the intersections of said first corrugations and second corrugations, said corrugation portion of said one of the first metal sheet and the second metal sheet is a portion of a said first corrugation, said corrugation portion comprises between the edge and a said node a concave portion forming a narrowing of said first corrugation, and the step of removing the inerting device comprises tilting the inflatable balloon between the edge and the narrowing after deflating the inflatable balloon.

[0018] Tilting the inflatable ball allows the inflatable ball to easily pass through the constriction.

[0019] According to one embodiment, the second metal sheet comprises a groove along said edge of the second metal sheet.

[0020] According to one embodiment, the step of performing a continuous weld between the second metal sheet and the first metal sheet along the overlap area is performed by an automatic welding machine, the automatic welding machine moving parallel to said edges of the first metal sheet and the second metal sheet.

[0021] According to one embodiment, the support surface is an inner surface of a thermally insulating barrier.

[0022] According to one embodiment, the sealing membrane is a primary sealing membrane, the thermally insulating barrier is a primary thermally insulating barrier, and wherein the tank wall further comprises a secondary sealing membrane and a secondary thermally insulating barrier, the secondary thermally insulating barrier resting against a load-bearing wall, the secondary sealing membrane resting against the secondary thermally insulating barrier, and the primary thermally insulating barrier resting against the secondary sealing membrane.

[0023] According to one embodiment, the primary thermally insulating barrier comprises rows of supporting elements, each of the supporting elements being fixed to an outer plate and to an inner plate, the outer plates being fixed to the secondary thermally insulating barrier and pressing the secondary sealing membrane against the secondary thermally insulating barrier, the inner plates forming said support surface, and arranging the first metal sheet and the second metal sheet on the support surface comprises welding the first metal sheet and the second metal sheet to said inner plates.

[0024] According to one embodiment, arranging the inerting device on the support surface comprises routing the gas supply line through gaps provided between the internal plates.

[0025] According to another embodiment, the secondary thermally insulating barrier comprises a plurality of secondary insulating blocks juxtaposed on the load-bearing wall, the primary thermally insulating barrier comprises a plurality of primary insulating blocks juxtaposed on the secondary sealing membrane and anchored to the secondary thermally insulating barrier by anchoring members carried by the secondary insulating blocks, the primary insulating blocks comprising anchoring plates, and arranging the first metal sheet and the second metal sheet on the support surface comprises welding the first metal sheet and the second metal sheet to said anchoring plates.

[0026] According to one embodiment, the invention also provides a sealed and thermally insulating tank comprising a sealing membrane manufactured by the manufacturing method according to any one of the embodiments described above.

[0027] In one embodiment, the liquefied gas is liquid hydrogen.

[0028] Such a tank may be part of a land-based storage facility or installed in a floating, coastal, or deep-water structure, including a liquid hydrogen transport vessel, i.e., a hydrogen carrier, a floating storage and regasification unit (FSRU), a floating production and remote storage unit (FPSO), and others. Such a tank may also serve as a fuel tank in any type of vessel.

[0029] According to one embodiment, a ship for transporting a liquefied gas comprises a double hull and a aforementioned tank arranged in the double hull.

[0030] 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 tank installed in the hull of the vessel to a floating or land-based storage installation.

[0031] According to one embodiment, the transfer system also comprises a pump for driving a flow of liquefied gas through the insulated pipelines from or to the floating or land-based storage facility to or from the vessel tank.

[0032] According to one embodiment, the invention also provides a method of loading or unloading such a vessel, in which a liquefied gas is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the vessel's tank. Brief description of the figures

[0033] 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.

[0034] This is a partial perspective view of a tank wall of a sealed and thermally insulating tank.

[0035] This is a perspective view of an alternative embodiment of an inerting device.

[0036] This is a partial perspective view, showing the arrangement of the inerting device and a corrugated metal sheet on the primary thermally insulating barrier of the tank wall of the.

[0037] This is a perspective and partial sectional view of detail IV of the.

[0038] This is a perspective and partial sectional view, showing the arrangement of another corrugated metal sheet covering the corrugated metal sheet of the in an overlap area.

[0039] This is a sectional view along a plane cutting the overlap area visible on the.

[0040] This is a side view according to arrow D1 on the.

[0041] This is a sectional view along the same cutting plane as the, illustrating a step in removing the inerting device.

[0042] This is another side view according to arrow D1 on the, illustrating the step of removing the inerting device.

[0043] This is a perspective view similar to the, showing another variant embodiment of the inerting device.

[0044] This is a partial perspective view similar to the, showing the arrangement of the inerting device of the and of a corrugated metal sheet on the primary thermally insulating barrier of the tank wall of the.

[0045] This is a side view according to arrow D2 on the, illustrating the step of removing the inerting device.

[0046] This is a schematic cutaway representation of a ship's tank and a terminal for loading / unloading this tank.

[0047] By convention, the terms "external" and "internal" are used to define the relative position of one element to another, with reference to the inside and outside of the tank.

[0048] In the, a tank wall 11 of a sealed and thermally insulating tank for storing liquefied gas is partially shown in perspective. The wall 11 shown is produced according to the teaching of document WO 2023 / 198637 A1.

[0049] As described in WO 2023 / 198637 A1, the wall 11 is fixed against a load-bearing wall forming part of a load-bearing structure 1, for example polyhedral. The load-bearing structure 1 is, for example, formed by the double hull of a ship. The wall 11 has a multi-layer structure comprising, along the thickness direction of the wall 11, from the outside to the inside, a secondary thermally insulating barrier 12, a secondary sealing membrane 13, a primary thermally insulating barrier 14 and a primary sealing membrane 15 intended to be in contact with the liquefied gas contained in the tank.

[0050] The secondary thermally insulating barrier 12 comprises a plurality of insulating panels 16 anchored to the supporting structure 1. The insulating panels 16 each comprise a layer of insulating polymer foam 17 sandwiched between an inner plate 18 and an outer plate 19. The inner 18 and outer 19 plates are, for example, plywood plates glued to said layer of insulating polymer foam 17. According to a variant, the inner 18 and outer 19 plates are made from a polymer matrix reinforced by fibers, such as glass fibers. The insulating polymer foam may in particular be a polyurethane-based foam. The polymer foam is, advantageously, reinforced by fibers, such as glass fibers, contributing to reducing its thermal contraction.

[0051] The insulating panels 16 each comprise a layer of insulating polymer foam 17 sandwiched between an inner plate 18 and an outer plate 19. The inner 18 and outer 19 plates are, for example, plywood plates glued to said layer of insulating polymer foam 17. According to one variant, the inner 18 and outer 19 plates are made from a polymer matrix reinforced by fibers, such as glass fibers. The insulating polymer foam may in particular be a polyurethane-based foam. The polymer foam is advantageously reinforced by fibers, such as glass fibers, helping to reduce its thermal contraction.

[0052] Advantageously, portions of mastic 20 are interposed between the external plate 19 of the insulating panels 16 and the supporting structure 1. The portions of mastic 20 thus contribute to compensating for the surface irregularities of the supporting structure 1. According to an advantageous alternative embodiment, the portions of mastic 20 adhere to the external plate 19 of the insulating panels 16 and to the supporting structure 1. The portions of mastic 20 thus participate in anchoring the insulating panels 16 on the supporting structure 1. In such an alternative embodiment, the secondary anchoring devices are optional.

[0053] The insulating panels 16 have substantially the shape of a rectangular parallelepiped and are juxtaposed in parallel rows and separated from each other by gaps 21 ensuring functional assembly clearance. The gaps 21 are filled with a heat-insulating filling, not shown, such as glass wool, rock wool or flexible open-cell polymer foam, for example. The gaps can also be filled with insulating plugs, as described in applications WO2019155157 or WO2021028624, for example.

[0054] In the embodiment shown, the internal face of the insulating panels 16 has two series of grooves 22 perpendicular to each other and intended to receive corrugations 24, projecting towards the outside of the tank, formed on the corrugated metal sheets 25 of the secondary waterproofing membrane 13. Each of the series of grooves 22 is parallel to two opposite sides of the insulating panels 16. In the embodiment shown, the grooves 22 pass entirely through the thickness of the internal plate 10 as well as an internal portion of the layer of insulating polymer foam 17. Advantageously, the grooves 22 have a shape complementary to those of the corrugations that the secondary waterproofing membrane 13 comprises.

[0055] Furthermore, the insulating panels 16 have relaxation slots 27 which make it possible to reduce their stiffness so that the secondary thermally insulating barrier 12 deforms in the most homogeneous manner possible. This makes it possible to obtain the most uniform deformations possible of the corrugations of the secondary waterproofing membrane 13. Advantageously, the insulating panels 16 have relaxation slots 27 at least opposite each of the corrugations of the secondary waterproofing membrane 13. More details on the thermally insulating barrier 12 and the secondary waterproofing membrane 13 can be found in document WO 2023 / 198637 A1.

[0056] The primary thermally insulating barrier 14 comprises a plurality of load-bearing elements 30 which extend in the thickness direction of the wall 11. The load-bearing elements 30 make it possible to support the primary sealing membrane 15 and, consequently, to take up the forces due to the hydrostatic and dynamic pressures exerted on the primary sealing membrane 15 by the liquefied gas contained inside the tank. The load-bearing elements 30 are aligned in parallel rows.

[0057] Further details on the supporting elements 30 can be found in WO 2023 / 198637 A1. In particular, as described in this document, the supporting elements 30 are each attached to an external plate attached to the secondary thermally insulating barrier 12 and pressing the secondary sealing membrane 13 against the secondary thermally insulating barrier 12, and to an internal plate 42 (not shown in the but shown in the).

[0058] The primary waterproofing membrane 15 is obtained by assembling a plurality of corrugated metal sheets 44. The corrugated metal sheets 44 each have a substantially rectangular shape. The corrugated metal sheets 44 are, for example, made of Invar®: that is to say an alloy of iron and nickel whose coefficient of expansion is typically between 1.2.10 -6 and 2.10 -6 K -1 , or in an iron alloy with a high manganese content whose coefficient of expansion is typically of the order of 7.10 -6 K -1 Alternatively, the corrugated metal sheets 44 can also be made of stainless steel or aluminum.

[0059] The corrugated metal sheets 44 are overlap welded along their edges in order to ensure the sealing of the primary waterproofing membrane 15. The primary waterproofing membrane 15 comprises corrugations 45. More particularly, it comprises a first series of corrugations 45a extending parallel to a first direction and a second series of corrugations 45b extending parallel to a second direction. The directions of the series of corrugations 45a, 45b are perpendicular and are parallel or perpendicular to the rows of supporting elements 30. Each of the series of corrugations 45a, 45b is parallel to two opposite edges of the corrugated metal sheets 44. The corrugations 45 project towards the inside of the tank, that is to say in the opposite direction to the supporting structure 1. Each corrugated metal sheet 44 comprises between the corrugations 45, a plurality of flat zones 46.

[0060] The pitch of the corrugations of the secondary waterproofing membrane 13 is equal to the pitch of the corrugations 45 of the primary waterproofing membrane 15 or to an integer multiple thereof. In addition, each of the corrugations of the secondary waterproofing membrane 13 is arranged opposite, in the thickness direction of the wall 11, a corrugation 45 of the primary waterproofing membrane 15. Thus, each flat zone 46 of the primary waterproofing membrane 15 is located opposite, in the thickness direction of the wall 11, a flat zone of the secondary waterproofing membrane 13. Therefore, the axis of each supporting element 30 passes both through the center of a flat zone 46 of the primary waterproofing membrane 15 and through the center of a flat zone of the secondary waterproofing membrane 13.

[0061] The corrugated metal sheets 44 of the primary waterproofing membrane 15 are at least anchored, by welding, along their edges to the internal plates 42. To do this, the edges of the corrugated metal sheets 44 are welded to the internal plates 42, for example by spot welds. According to an advantageous embodiment, the corrugated metal sheets 44 are also anchored to internal plates 42 outside their edge areas. To do this, the corrugated metal sheets 44 can in particular be welded to the internal plates 42 by transparent welds. According to an advantageous embodiment, the corrugated metal sheets 44 are welded to each of the internal plates 42 which support them. Such an embodiment is particularly advantageous in that it makes it possible to distribute the stresses even more uniformly between the corrugations 45 of the primary waterproofing membrane 15.

[0062] More details on the primary thermally insulating barrier 14 can be found in document WO 2023 / 198637 A1. As described in this document, the wall 11 is suitable for producing a sealed and thermally insulating tank for storing liquid hydrogen. Liquid hydrogen is a liquefied gas which has the particularity of being stored at approximately -253°C at atmospheric pressure. When the tank is filled with liquid hydrogen at -253°C at atmospheric pressure, the primary sealing membrane 15 is subjected to very significant thermal stresses. It is therefore important to ensure the mechanical strength of the primary sealing membrane 15.

[0063] Furthermore, still as described in document WO 2023 / 198637 A1, in order to give the primary thermally insulating barrier 14 the required thermally insulating properties, the primary thermally insulating barrier 14 has a gas phase which is placed at an absolute pressure of less than 1 Pa, advantageously less than 10 -1 Pa, preferably less than 10 –2 Pa and for example of the order of 10 -3 Pa. This absolute pressure can be obtained by means of a vacuum pump and / or by means of a cryopumping phenomenon. It is therefore important that this vacuum is not degraded by the primary sealing membrane 15.

[0064] As mentioned above, the corrugated metal sheets 44 are lap welded along their edges to seal the primary waterproofing membrane 15. During the welding operation, the metal alloy constituting the corrugated metal sheets 44 undergoes melting followed by recrystallization. If the welding operation causes excessive melting of the metal alloy, the welds between the corrugated metal sheets 44 may have high residual porosity after recrystallization of the metal alloy. This risk is greater when the welding operation is not carried out under an inert atmosphere, because then the metal alloy is likely to undergo hot oxidation due to the high temperature and the presence of oxygen in the atmosphere.The higher the residual porosity of the welds between the corrugated metal sheets 44, the more they present a surface irregularity likely to generate crack initiations which are detrimental to the mechanical strength of the primary sealing membrane 15, and the more they are likely to degrade the vacuum performance of the primary thermally insulating barrier 14. The residual porosity will mainly increase the specific surface area of ​​the metal surfaces, thereby increasing the theoretical degassing rate calculated from an underestimated nominal surface area. The vacuum performance can also be degraded by the creation of almost closed spaces, the seat of a volume of gas which will be all the more difficult to evacuate by pumping as the resistance to flow at the outlet of these spaces is great.Therefore, it is particularly desirable to limit residual porosity due to the welding operation in the welds between the corrugated metal sheets 44.

[0065] Embodiments of a method for manufacturing the primary waterproofing membrane 15 which tend to limit this residual porosity are described below. This manufacturing method uses an inerting device, an alternative embodiment of which has been shown in perspective in the.

[0066] With reference to the, the inerting device 200 comprises an inflatable balloon 220 and a gas supply pipe 290. The inflatable balloon 220 carries two flanges 230. The flanges 230 are parallel and on either side of a central portion 225 of the inflatable balloon 220. In other words, the central portion 225 is positioned between the two flanges 230. The flanges 230 are deformable as will be detailed below.

[0067] In a first step of the manufacturing process, two corrugated metal sheets 44 (hereinafter “sheets 44”) and inerting devices 200 are provided. This step is illustrated by Figures 3 to 6.

[0068] In the, a sheet 44 has been shown partially and in perspective. As mentioned above, the sheet 44 comprises flat portions 86 intended to rest on the internal plates 42. The sheet 44 comprises corrugation portions 85a, 85b projecting relative to the flat portions 86. Each corrugation portion 85a, 85b is formed between two flat portions 86. The corrugation portions 85a, 85b are intended to respectively constitute a part of a corrugation 45a, 45b (cf.) of the primary waterproofing membrane 15. The reference signs 56a each designate a junction between a flat portion 86 and a corrugation portion 85a. The reference signs 56b each designate a junction between a flat portion 86 and a corrugation portion 85b. Nodes 55 are formed at the intersections between the corrugation portions 85a, 85b. The nodes 55 have been omitted from the drawing so as not to clutter the drawing.

[0069] The sheet 44 has a generally rectangular outer contour which is delimited by four straight edges 68 orthogonal to each other. Two of the four edges 68 are visible on the. As shown, the corrugation portions 85a, 85b extend to the edges 68.

[0070] In the first step of the manufacturing process, a first sheet 44 is placed on internal plates 42, as shown in the.

[0071] Furthermore, an inerting device 200 is arranged in a corrugation portion 85a extending to a given edge 68. More specifically, the inflatable balloon 220 is arranged in the corrugation portion 85a, close to the edge 68 as best seen in the. As shown in the and the, the gas supply line 290 runs to the inflatable balloon 220, preferably through gaps between adjacent internal plates 42.

[0072] Returning to the, the sheet 44 is joggled along at least one other of the edges 68, so that the sheet 44 has a job bend 67 along said edge 68.

[0073] It can also be seen that the internal plates 42 are provided with fixing elements 43. The fixing elements 43 are distributed around the axis of the carrier element 30 to fix a support collar 40 (cf.) of the carrier element 30 to the internal plates 42 as described in document WO 2023 / 198637 A1.

[0074] Referring now to the and to the, the first sheet 44 and the inerting device 200 having been thus positioned, a second sheet 44 is positioned (on the right and shown in partial section on the) whose groove 67 covers the first sheet 44 in an overlap zone ZR. With reference to the, the overlap zone ZR is defined between the edge 68 of the first sheet 44 (on the left on the) and the parallel edge 68 of the second sheet 44 (on the right on the). The dotted lines on the indicate the position of the overlap zone ZR.As shown in Figures 5 and 6, the corrugation portions 85a of the first sheet 44 and the second sheet 44 are aligned; one end of the corrugation portion 85a of the second sheet 44 covers the end of the corrugation portion 85a of the first sheet 44 in the overlapping area ZR; and the flat portions 86 of the second sheet 44 on either side of the corrugation portion 85a cover the flat portions 86 of the first sheet 44 on either side of the corrugation portion 85a in the overlapping area ZR.

[0075] It will be understood that when the first sheet 44 and the second sheet 44 are thus positioned, their flat portions 86 rest on internal plates 42 (cf., and). These internal plates 42 form a support surface for the first sheet 44 and the second sheet 44, and consequently a support surface for the primary waterproofing membrane 15. Before proceeding to the second step, the first sheet 44 and the second sheet 44 are anchored by welding, along their edges 68, on the internal plates 42 as mentioned above. For example, the first sheet 44 is welded to the internal plates 42 before positioning the second sheet 44 to cover the first sheet 44 in the overlap zone ZR.

[0076] In a second step of the manufacturing method, the inflatable balloon 220 is inflated. The inflatable balloon 220 is shown in its uninflated state in the, and in its inflated state in the and the. The flanges 230 being carried by the inflatable balloon 220 and being made of a deformable material, the inflation of the inflatable balloon 220 deforms the flanges 230 until the flanges 230 are compressed against the inner contour of the corrugation portion 85a of the first sheet 44. For this, the outer contour of the flanges 230 corresponds substantially to the inner contour of the corrugation portion 85a.

[0077] The reference 235 designates an inerting space located between the two flanges 230 and around the central portion 225 of the inflatable balloon 220. As can be seen in the figure, the inerting space 235 is located at least in line with a portion of the overlap zone ZR, at least when the inflatable balloon 220 is in its inflated state.

[0078] Thus, the inflation of the inflatable balloon 220 and the resulting compression of the flanges 230 against the inner contour of the corrugation portion 85a of the first sheet 44 close the inerting space 235, which is located at least in line with a portion of the overlap zone ZR.

[0079] In a third step of the manufacturing process, the inerting space 235 thus closed is placed under an inert atmosphere by supplying an inert gas via the gas supply line 290. For this, the gas supply line 290 is connected to a gas source 990 (shown schematically in the) which sends a flow of inert gas FG (cf.) into the gas supply line 290. The inert gas can be nitrogen (N2) or argon (Ar) for example.

[0080] It should be noted that the positioning of the gas supply line 290 relative to the inerting space 235 and the inflatable balloon 220 shown in the drawings is only an example. Various positions of the gas supply line 290 are conceivable.

[0081] According to a variant, the gas supply line 290 is connected to the inerting space 235, and the inflation of the inflatable balloon 220 is carried out by means of an inflation gas supply line separate from the gas supply line 290 and connected to the inflatable balloon 220. This makes it possible to inflate the inflatable balloon 220 with an inflation gas that is less expensive than the inert gas, for example with air, or even with nitrogen (N2) if the inert gas is argon (Ar).

[0082] According to another more preferred variant, the inert gas used to place the inert space 235 under an inert atmosphere is also used for inflating the inflatable balloon 220. For this, at least a part of the external wall of the central portion 225 which delimits the inert space 235 is impermeable to the inert gas below an inflation pressure threshold and permeable to the inert gas above the inflation pressure threshold. The inert gas is conveyed through the gas supply line 290 into the inflatable balloon 220. The inflatable balloon 220 is inflated to at least the inflation pressure threshold, then the inert gas passes through the outer wall of the central portion 225 which has become permeable to the inert gas and fills the inerting space 235. In this way, the risk of contamination of the inerting space 235 by an unwanted gas is reduced.

[0083] In a fourth step of the manufacturing method, a continuous weld is made between the first sheet 44 and the second sheet 44 along the overlap zone ZR while the inerting space 235 is under an inert atmosphere, the continuous weld passing in line with the inerting space 235. The continuous weld is made according to known welding techniques by a welding torch. For example, the welding torch is mounted on an automatic welding machine moving parallel to the edges 68 defining the overlap zone ZR. The arrow W on the figure indicates the direction of advance of the automatic welding machine. The automatic welding machine can for example be constructed as described in the document EP 0 611 217 A1. At the end of the fourth step, the second sheet 44 is therefore overlap welded to the first sheet 44 along the overlap zone ZR.

[0084] Various materials are conceivable for making the flanges 230 and the inflatable balloon 220, as long as the inflation of the inflatable balloon 220 deforms the flanges 230 until the flanges 230 are compressed against the inner contour of the corrugation portion 85a of the first sheet 44. The flanges 230 and the inflatable balloon 220 should have sufficient resistance to the heat generated by the welding torch. For example, the flanges 230 may be made of a polymer such as PTFE, PPSU or PEEK. For example, the inflatable balloon 220 may be made of a polymer such as high-performance rubber or in the form of a multi-layer structure comprising at least one polymer layer combined with a woven flexible composite skin.

[0085] Since the continuous welding is carried out while the inerting space 235 is under an inert atmosphere, there is a tendency to avoid hot oxidation of the metal alloy of the first sheet 44, which tends to prevent the weld between the second sheet 44 and the first sheet 44 from having high residual porosity after recrystallization of the metal alloy. Thus, thanks to the inerting device 200, the primary sealing membrane 15 has improved mechanical strength and degrades the vacuuming of the primary thermally insulating barrier 14 less.

[0086] The inerting device 200, or at least the inflatable balloon 220, may optionally be left in place after the continuous weld has been carried out. However, from an economic and industrial point of view, it is preferable to use the inerting device 200 to successively carry out several continuous welds between sheets 44.

[0087] For this, in a fifth step of the manufacturing process, the supply of inert gas to the inerting space 235 is stopped, and the inflatable balloon 220 is removed from the covering zone ZR.

[0088] Figures 7 to 9 illustrate one possible way of removing the inflatable balloon 220.

[0089] With reference in particular to Figures 5, 7, 8 and 9, on either side of the apex 55T of a node 55, narrowings 55R of the corrugation portions 85a are each formed by a concave portion of a corrugation portion 85a. The narrowing 55R defines a minimum section of the corrugation portion 85a. With reference to the, which is a side view along the arrow D1 on the and shows the inflatable balloon 220 in its inflated state, due to the narrowing 55R, it may be difficult to remove the inflatable balloon 220 if it remains in its inflated state.

[0090] In order to remove the inflatable balloon 220, the inflatable balloon 220 is first deflated, i.e. the inflatable balloon 220 is returned to its uninflated state shown in 1 and 1a. The deflation of the inflatable balloon 220 can be caused or assisted in various ways, for example by means of springs or other return elements internal to the inflatable balloon 220 and / or by connecting the inflatable balloon 220 to a vacuum pump.

[0091] In a second step, the inflatable balloon 220 having been deflated, the inflatable balloon 220 is tilted towards the adjacent node 55 of the second sheet 44 (arrow M1 on the), then the inflatable balloon 220 is slid into the corrugation portion 85a of the second sheet 44 towards this node 55 (arrow M2 on the). With reference to la and la, tilting the inflatable balloon 220 allows the inflatable balloon 220 to easily pass through the constrictions 55R. The inflatable balloon 220 is then continued to slide in the corrugation portions 85a of the second sheet 44 (arrow M3 on la), until the inflatable balloon 220 is extracted from under the second sheet 44. The inflatable balloon 220 can then be reused to make another weld between sheets 44. The tilting and sliding of the inflatable balloon 220 can be caused by pulling on the gas supply pipe 290 and / or on a rope, one end of which is fixed to the inflatable balloon 220.

[0092] Alternatively, the just described tilting and sliding of the inflatable balloon 220 may take place in the corrugation portions 85a of the first sheet 44 and not of the second sheet 44 as shown in the. It is however preferable that the tilting and sliding of the inflatable balloon 220 take place in the corrugation portions 85a of the second sheet 44, because in this case the gas supply line 290 can run under the second sheet 44 in the direction of the first sheet 44 (cf.,), which is easier than running the gas supply line 290 under the first sheet 44.

[0093] The above-described steps of the manufacturing process are repeated as necessary until the manufacturing of the primary waterproofing membrane 15 is completed.

[0094] As shown in 1a and 1a, one inflatable balloon 220 is preferably used per corrugation portion 85a of the first sheet 44.

[0095] Inerting devices identical or similar to the inerting device 200 may be used for the corrugation portions 85b. In Figures 10 to 12, an alternative embodiment of an inerting device 300 suitable for the corrugation portions 85b is shown by way of example. The elements of the inerting device 300 similar to those of the inerting device 200 bear the same reference signs increased by 100. The operation of the inerting device 300 is identical to the operation of the inerting device 200, except that the dimensions of the inflatable balloon 320 and the outer contour of the flanges 330 are adapted to the inner contour of the corrugation portions 85b, so that inflating the inflatable balloon 320 closes the inerting space 325 in the corrugation portion 85b of the first sheet 44.

[0096] As shown in the, one inflatable balloon 320 is preferably used per corrugation portion 85b of the first sheet 44.

[0097] With reference to the, which is a side view according to arrow D2 on the and shows the inflatable balloon 320 in its uninflated state, the inflatable balloon 320 can be tilted towards the node 55 of the first sheet 44, or preferably of the second sheet 44, as described above for the inflatable balloon 220.

[0098] The dimensions of the inflatable balloons 220, 320 and the outer contour of the flanges 230, 330 are adapted respectively to the inner contour of the corrugation portions 85a, 85b. Alternatively, the same inerting device may be used for the corrugation portions 85a and the corrugation portions 85b.

[0099] Although not shown in the figures, the invention also applies in the case where an internal plate 42 is connected to another internal plate 42 which is adjacent to it by a connection which has a degree of freedom in translation in a direction perpendicular to the direction of thickness of the wall and a degree of connection in the direction of thickness of the wall. This allows the internal plates on which the flat portions 186 of the waterproofing membrane are fixed to perform relative movements in the direction perpendicular to the direction of thickness of the wall.

[0100] The manufacturing process has been described in the context of a sealed and thermally insulating tank for storing liquefied hydrogen. Alternatively, the sealed and thermally insulating tank can be used to store other liquefied gases, including liquefied natural gas (LNG), liquefied petroleum gas (LPG), ethane, or ammonia.

[0101] The manufacturing method has been described in the context of a tank wall produced according to the teaching of document WO 2023 / 198637 A1. The manufacturing method is however also applicable to any other tank wall in which a sealing membrane is produced by overlap welding corrugated metal sheets, in particular to a tank wall in which the secondary thermally insulating barrier comprises a plurality of secondary insulating blocks juxtaposed on the load-bearing wall, the primary thermally insulating barrier comprises a plurality of primary insulating blocks juxtaposed on the secondary sealing membrane and anchored to the secondary thermally insulating barrier by anchoring members carried by the secondary insulating blocks, the primary insulating blocks comprising anchoring plates.Such a tank wall can be produced according to the teaching of document FR 2 691 520 A1, document WO 2014 / 057221 A2 or document WO 2017 / 006044 A1 for example. The sheets 44 are anchored by their edges to the anchoring plates and not to the internal plates 42 described above.

[0102] With reference to the, 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, preferably liquid hydrogen, 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.

[0103] 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 liquefied gas from or to the tank 71.

[0104] It also represents 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 hydrogen carriers. A connecting pipe, not shown, extends inside the tower 78. The loading and unloading station 75 allows the hydrogen carrier 70 to be loaded and unloaded 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 hydrogen carrier vessel 70 at a great distance from the coast during loading and unloading operations.

[0105] To generate the pressure necessary for the transfer of the liquefied gas, it is possible either to use pumps on board the ship 70 and / or pumps fitted to the onshore installation 77 and / or pumps fitted to the loading and unloading station 75 or to 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.

[0106] 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.

[0107] The use of the verb "comprise", "comprise" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0108] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

A manufacturing method for manufacturing a sealing membrane for a sealed and thermally insulating tank for storing a liquefied gas, the manufacturing method comprising the following steps: - arranging an inerting device (200, 300), a first metal sheet (44) and a second metal sheet (44) on a flat support surface, the first metal sheet (44) and the second metal sheet each comprising two flat portions (86) resting on the flat support surface and a corrugation portion (85a, 85b) formed between the two flat portions (86), the corrugation portion (85a, 85b) projecting relative to the two flat portions (86), the corrugation portion (85a, 85b) of the first metal sheet (44) and the corrugation portion (85a, 85b) of the second metal sheet (44) being aligned,the second metal sheet (44) covering the first metal sheet (44) in an overlap zone (ZR) defined between an edge (68) of the first metal sheet (44) and an edge (68) of the second metal sheet (44) parallel to the edge (68) of the first metal sheet (44), the corrugation portion (85a, 85b) of the first metal sheet (44) extending to said edge (68) of the first metal sheet (44) and the corrugation portion (85a, 85b) of the second metal sheet (44) extending to said edge (68) of the second metal sheet (44), one end of the corrugation portion (85a, 85b) of the second metal sheet (44) covering one end of the corrugation portion (85a, 85b) of the first metal sheet (44) in the overlap zone (ZR) and the two flat portions (86) of the second metal sheet (44) covering the two flat portions (86) of the first metal sheet (44) in the overlap zone (ZR),the first metal sheet (44) being located between the second metal sheet (44) and the support surface in the overlap zone (ZR),the inerting device (200, 300) comprising a gas supply line (290, 390) and an inflatable balloon (220, 320), the inflatable balloon (220, 320) comprising a central portion (225, 325) and two flanges (230, 330) on either side of the central portion (225, 325), the gas supply line (290, 390) being configured to convey gas into an inerting space (235, 335) located between the two flanges (230, 330) and around the central portion (225, 325);- inflating the inflatable balloon (220, 320) until compress the two flanges (230, 330) against the inner contour of the corrugation portion (85a, 85b) of the first metal sheet (44), so as to close the inerting space (235, 335), the inerting space (235,335) being located in line with at least part of the overlap zone (ZR);- placing the inerting space (235, 335) thus closed under an inert atmosphere by supplying an inert gas via the supply line (290, 390);- carrying out a continuous weld between the second metal sheet (44) and the first metal sheet (44) along the overlap zone (ZR) while the inerting space (235, 335) is under an inert atmosphere, the continuous weld passing in line with the inerting space (235, 335)., The manufacturing method of claim 1, wherein the gas supply line (290, 390) is configured to convey the inert gas into the inflatable balloon (220, 320), at least a portion of an outer wall of the central portion (225, 325) being impermeable to the inert gas below an inflation pressure threshold and permeable to the inert gas above the inflation pressure threshold, and wherein the inflatable balloon (220, 320) is inflated to at least the inflation pressure threshold by the inert gas, such that the inerting space (235, 335) is inerted by inert gas passing through said outer wall. A manufacturing method according to any one of claims 1 to 2, wherein the manufacturing method further comprises a step of removing the inerting device (200, 300), the step of removing the inerting device (200, 300) comprising deflating the inflatable balloon (220, 320) and then sliding the inflatable balloon into the corrugation portion (85a, 85b) of the second metal sheet (44). The manufacturing method of claim 3, wherein the second metal sheet (44) comprises first parallel corrugations, second corrugations perpendicular to the first corrugations, and a plurality of nodes (55) at the intersections of said first corrugations and second corrugations, said corrugation portion (85a) of the second metal sheet is a portion of a said first corrugation, said corrugation portion (85a) comprises between the edge (68) and a said node (55) a concave portion forming a narrowing (55R) of said first corrugation, and wherein the step of removing the inerting device (200) comprises tilting the inflatable balloon (220) between the edge (68) and the narrowing (55R) after deflating the inflatable balloon (220). A manufacturing method according to any one of claims 1 to 4, wherein the second metal sheet (44) comprises a groove (67) along said edge (68) of the second metal sheet (44). A manufacturing method according to any one of claims 1 to 5, wherein the step of performing a continuous weld between the second metal sheet (44) and the first metal sheet (44) along the overlap zone (ZR) is performed by an automatic welding machine, the automatic welding machine moving parallel to said edges (68) of the first metal sheet (44) and the second metal sheet (44). A manufacturing method according to any one of claims 1 to 6, wherein the support surface is an inner surface of a thermally insulating barrier. A manufacturing method according to any one of claims 1 to 7, wherein the sealing membrane is a primary sealing membrane (15), the thermally insulating barrier is a primary thermally insulating barrier (14), and wherein the tank wall further comprises a secondary sealing membrane (13) and a secondary thermally insulating barrier (12), the secondary thermally insulating barrier resting against a load-bearing wall, the secondary sealing membrane (13) resting against the secondary thermally insulating barrier (12), and the primary thermally insulating barrier (14) resting against the secondary sealing membrane (13), wherein the primary thermally insulating barrier (14) comprises rows of load-bearing elements (30), each of the load-bearing elements being fixed to an outer platen and to an inner platen (42),the outer plates being fixed to the secondary thermally insulating barrier (12) and pressing the secondary sealing membrane (13) against the secondary thermally insulating barrier (12), the inner plates (42) forming said support surface, and wherein arranging the first metal sheet (44) and the second metal sheet (44) on the support surface comprises welding the first metal sheet (44) and the second metal sheet (44) to said inner plates (42)., A manufacturing method according to claim 8, wherein arranging the inerting device (200, 300) on the support surface comprises routing the gas supply line (290, 390) in gaps provided between the internal plates (42).

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