Method and bench for manufacturing a metal strip

Abstract

The invention relates to a method for manufacturing a metal strip (10), comprising the steps of: - placing an end portion (13) of a first metal strip element (11) and an end portion (14) of a second metal strip element (12) on a flat support (21), juxtaposed in a longitudinal direction, each of the first and second elements having two opposing principal faces (11A, 12A) connected by two longitudinal lateral faces (11B, 12B), the end portion of the first element and the end portion of the second element each being terminated by a transverse end face (11C, 12C), - aligning the longitudinal lateral faces of the first and second elements so that they extend in line with each other, - welding the first and second metal strip elements end-to-end, forming a continuous weld bead extending along the transverse end faces (11C, 12C),across the entire width of the elements. Figure for the abbreviation: 1,

Description

Title of the invention: Method and bench for manufacturing a metal strip technical field

[0001] The invention relates to the field of manufacturing metal strips for the construction of a waterproof membrane, in particular for a waterproof and thermally insulating tank.

[0002] In particular, the invention relates to the field of membranes for leak-proof and thermally insulating tanks for the storage and / or transport of low-temperature liquids, such as tanks for transporting Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure, Liquid Hydrogen (LH2) at -253°C at atmospheric pressure, Ammonia (NH3) at -30°C at atmospheric pressure, or Liquefied Petroleum Gas (also known as LPG) with a temperature, for example, between -50°C and 0°C. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be used for transporting liquefied gas or for receiving liquefied gas to serve as fuel for the propulsion of the floating structure. In the case of an inland tank or port storage structure, it may rest on the ground or the seabed and may be partially or completely buried. Technological background

[0003] Methods for manufacturing metal strips measuring between 30 and 40 meters in length along a longitudinal direction are known for the construction of a sealed and thermally insulating tank membrane.

[0004] The manufacture of such metal strips is described for example in document FR2148366. For the manufacture of a sealed and thermally insulating tank membrane, the precision required for the straightness of the metal strips is very high.

[0005] The metal strip is stored wound around an axis perpendicular to the longitudinal direction. It is unwound and stretched using a straightening bench to avoid a "saber-like" deformation, then placed on a shearing bench and rectified by cutting the longitudinal edges of the metal strip.

[0006] The length of each of the straightening and shearing benches is adapted to accommodate a metal strip with a length of approximately 30 to 40 meters. Summary of the invention

[0007] One idea underlying the invention is to provide a manufacturing process enabling the production of very long metal strips, for example between 50 and 80 meters in length, in a small space.

[0008] This includes manufacturing very long metal strips using a manufacturing bench shorter than the total length of the metal strip being manufactured, for example a manufacturing bench less than 40 meters long.

[0009] According to one embodiment, the invention provides a method for manufacturing a metal strip, comprising the steps of: - to place an end portion of a first metal strip element and an end portion of a second metal strip element on a flat support, the end portion of the first metal strip element and the end portion of the second metal strip element being juxtaposed in a longitudinal direction, each of the first and second metal strip elements having two opposing principal faces connected by two longitudinal lateral faces, the first and second metal strip elements having the same width, the end portion of the first metal strip element and the end portion of the second metal strip element each being terminated by a respective transverse end face, such that a principal face of each of the first and second metal strip elements rests at least partially on the flat support, and that the transverse end face of the end portion of the first metal strip element extends close to the transverse end face of the end portion of the second metal strip element, - align the longitudinal lateral faces of the first and second metal strip elements so that they extend in line with each other, - weld the first and second metal strip elements end-to-end, forming a continuous weld bead extending along the end transverse faces, over the entire width of the metal strip elements.

[0010] Thanks to these characteristics, it is possible to manufacture very long metal strips by welding several metal strip elements together. Furthermore, the process allows the use of fabrication benches of a length adapted to receive a single metal strip element in its entirety. Thus, it is not necessary to have a straightening and / or shearing bench adapted to receive the metal strip with the final length obtained at the end of the manufacturing process.

[0011] According to embodiments, such a process may include one or more of the following characteristics.

[0012] According to one embodiment, the end portions are arranged such that the transverse face of the end portion of the first metal strip element extends to a distance from the transverse end face of the end portion of the second metal strip element which is less than or equal to half the thickness of one of the metal strip elements.

[0013] According to another embodiment, the end portions are arranged so that the transverse face of the end portion of the second metal strip element covers the end portion of the first metal strip element over a distance less than or equal to three times the thickness of one of the metal strip elements.

[0014] Thus, in practice, the end portions of the first and second metal strip elements are either arranged so that their end transverse faces extend opposite each other, separated from each other by a space whose dimension along the longitudinal direction of the metal strip elements is less than or equal to half the thickness of one of the metal strip elements, for example less than or equal to half the thickness of the metal strip element with the greatest thickness of the two metal strip elements, or arranged so that the end portion of the second metal strip element overlaps the end portion of the first metal strip element over a distance, measured along the longitudinal direction of the metal strip elements, less than or equal to three times the thickness of one of the metal strip elements,for example, less than or equal to three times the thickness of the thicker of the two metal strip elements.

[0015] According to one embodiment, the method further comprises: - unwind a roll carrying the first element of metal strip.

[0016] According to one embodiment, the method further comprises: - partially cut the first metal strip element along its longitudinal lateral faces using two cutting tools arranged on a feed path from the end portion of the first metal strip element, to a cutting stop point located at a distance from the end transverse face of the first metal strip element intended to be placed near the second metal strip element.

[0017] Thus, the longitudinal edges of the first metal strip element can be partially cut before welding it to the second metal strip element. This partial cutting allows for improved mechanical strength of the welded metal strip by cutting the beginning and end of the weld zones along its longitudinal lateral faces after welding, thereby eliminating welding defects.

[0018] According to one embodiment, the two cutting tools are positioned opposite each other and are not movable. The metal strip element is driven and moved according to the longitudinal direction. The flat support then includes a device for moving the metal strip element, for example a conveyor which can be equipped with a suction system to obtain a suction effect holding the metal strip element or with an attachment system fixed on an end portion of the metal strip element.

[0019] According to one embodiment, the two cutting tools are positioned opposite each other and are movable along the longitudinal direction. The cutting tools are, for example, mounted movably on guide rails parallel to the longitudinal axis of the manufacturing bench.

[0020] According to one embodiment, the method further comprises: - wrap the end portion of the first cut metal strip element around a winding axis perpendicular to the longitudinal direction.

[0021] This step allows the flat support to be at least partially freed so as to allow it to receive the second metal strip element.

[0022] According to one embodiment, before the welding step, a portion of the second metal strip element is also cut along its longitudinal lateral faces, a cut portion of the second metal strip element extending from an end transverse face of this second metal strip element to a cutting stop point located at a distance from the end transverse face of the second metal strip element intended to be positioned near the first metal strip element.

[0023] According to one embodiment, the flat support comprising a metal plate, the transverse end faces of the first and second metal strip element arranged close to each other extend opposite the metal plate during the welding step.

[0024] According to one embodiment, the process comprises a step of: - press the end portions of the first and second metal strip elements against the flat support, by pressing on the main faces opposite the flat support, on either side of the transverse end faces arranged close to each other.

[0025] According to one embodiment, the step of clamping the end portions of the first and second metal strip elements against the flat support is carried out with a clamping device comprising a metal support portion bearing on the main faces of the metal strip elements on either side of the transverse end faces of the metal strip elements arranged close to each other.

[0026] According to one embodiment, the method further comprises: - perform a tack weld before applying the continuous weld bead.

[0027] According to one embodiment, the continuous weld bead is produced by a process selected from: TIG arc welding, plasma or micro-plasma welding, roller crushing welding, friction stir welding.

[0028] According to one embodiment, the longitudinal edges of the metal strip obtained are cut at least along a region extending from a place located on one side of the weld bead to a place located on the other side of the weld bead, along the longitudinal direction of the metal strip.

[0029] Thus, the longitudinal edges of the portion of the metal strip containing the weld bead are cut after the weld has been made. This has the advantage of eliminating an initial and a final zone of the weld that could potentially contain welding defects.

[0030] According to one embodiment, each metal strip element has a length greater than 25 meters.

[0031] According to one embodiment, each element of the metal strip has a constant thickness.

[0032] According to one embodiment, the first and second metal strip elements have the same thickness.

[0033] According to one embodiment, the stopping point of the cutting is located at a distance of between 1 and 3 meters from the transverse end face of the first or second cut metal strip element.

[0034] According to one embodiment, metal strip elements made of an iron and nickel alloy with a coefficient of expansion typically between 1.106 and 2.106 K1 or of an iron and manganese alloy with a coefficient of expansion between 7.106 K1 and 9.106 K1 are used.

[0035] According to one embodiment, each metal strip element has a thickness between 0.5 and 1 mm.

[0036] According to one embodiment, the manufacturing process further comprises a step of folding the longitudinal edges of the metal strip.

[0037] According to one embodiment, the invention also provides a bench for manufacturing a metal strip comprising: - a flat support adapted to receive an end portion of a first metal strip element and an end portion of a second metal strip element, the end portion of the first metal strip element and the end portion of the second metal strip element being juxtaposed in a longitudinal direction, each of the first and second metal strip elements having two opposing principal faces connected by two longitudinal lateral faces, the end portion of the first metal strip element and the end portions of the second metal strip element each terminated by a respective end transverse face, an end transverse face of the first metal strip element extending close to an end transverse face of the second metal strip element, - an alignment device to adjust the relative position of the longitudinal lateral faces of the first and second metal strip elements so that they extend in line with each other, - a welding gantry for butt-welding the two metal strip elements, using a continuous weld bead extending along the end transverse faces, over the entire width of the metal strip elements.

[0038] According to one embodiment, the flat support includes a groove adapted to receive the end portions of the metal strip elements.

[0039] According to one embodiment, said alignment device comprises, on the one hand, a fixed main part having a bottom wall and a first longitudinal side wall delimiting said groove and, on the other hand, a movable side part having a second side wall facing the first side wall, the movable side part of the alignment device being adapted to laterally clamp the end portions of the metal strip elements placed in the groove in a transverse direction perpendicular to the longitudinal direction.

[0040] According to one embodiment, the movable side part of the alignment device is adapted to slide in the main part of the alignment device in the transverse direction, between an open position in which the second side wall is disposed at a distance from the first side wall strictly greater than the width of the metal strip elements and a clamping position in which the second side wall is disposed at a distance from the first side wall less than or equal to the width of the metal strip elements.

[0041] According to one embodiment, the manufacturing bench includes a clamping device adapted to press the two metal strip elements against the flat support, by pressing on their main faces opposite the flat support, on either side of the transverse end faces arranged close to each other.

[0042] According to one embodiment, the clamping device is in the form of a first metal plate having a through slot intended to extend transversely, opposite the transverse end faces arranged close to each other of the metal strip elements received on the flat support.

[0043] According to one embodiment, the manufacturing bench includes a second plate forming part of the flat support and intended to be arranged opposite the end transverse faces arranged near the metal strip elements.

[0044] According to one embodiment, the second plate is made of ceramic or metal, more particularly copper and its alloys or stainless steel.

[0045] According to one embodiment, the welding gantry comprises a welding head and a guide rail, the welding head being adapted to slide along the rail, such that the welding head moves in the slot of said first metal plate.

[0046] According to one embodiment, the invention also provides a metal strip adapted for the production of a watertight membrane for a watertight and thermally insulating tank, comprising a metal strip obtained by the process described above, from two metal strip elements each having a constant thickness over their entire length, the metal strip having, according to its width, a flat central portion and two lateral edges folded substantially perpendicular to the flat central portion, the two lateral edges having a small width compared to the flat central portion.

[0047] According to one embodiment, the invention also provides a watertight membrane for a watertight and thermally insulating tank, comprising a repeated structure comprising alternately a metal strake as described above and an elongated weld wing connected to a support surface of the watertight membrane and projecting relative to it, the weld wing extending parallel to the metal strake over at least part of the length of the metal strake, the flat central portion of the metal strake being placed on the support surface and the lateral edges of the metal strake being disposed against the adjacent weld wings and welded watertight to the weld wings.

[0048] According to one embodiment, the invention also provides a sealed and thermally insulating tank integrated into a load-bearing structure, the load-bearing structure comprising a plurality of load-bearing walls, the tank comprising a plurality of tank walls fixed each time on a respective load-bearing wall, a tank wall comprising: a thermally insulating barrier retained on the load-bearing wall, the thermally insulating barrier having a flat support surface parallel to the respective load-bearing wall, and a sealed membrane as described above.

[0049] According to one embodiment, the invention also provides a vessel for the transport of a fluid, the vessel comprising a double hull and a tank disposed in the double hull.

[0050] According to one embodiment, the invention also provides a transfer system for a fluid, the system comprising a vessel, insulated pipes arranged to connect the vessel's tank to a floating or land-based storage facility and a pump to drive a fluid through the insulated pipes from or to the floating or land-based storage facility to or from the vessel's tank.

[0051] According to one embodiment, the invention also provides a method for loading or unloading a ship, in which a fluid is conveyed through insulated pipes from or to a floating or land-based storage facility to or from the ship's tank. Brief description of the figures

[0052] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0053] Fig. 1 represents a schematic perspective view of part of a metal strip manufacturing bench.

[0054] Fig. 2 represents a schematic view of the manufacturing bench for a metal strip of Fig. 1, in section along plane AA.

[0055] [Fig.3] represents an enlarged schematic view of detail B of [Fig.2].

[0056] Figure 4 shows a schematic top view of part of the bench manufacturing of the [Fig.1].

[0057] Fig. 5 schematically represents 4 steps of a process for manufacturing the metal strip.

[0058] Fig. 6 schematically represents a profile view of the configuration of the end portions of the metal strip elements during a crushing roller weld and a cross-section of the metal strip obtained after such a weld.

[0059] Fig. 7 is a schematic cutaway representation of a tank of a methane tanker and a loading / unloading terminal for this tank. Description of the implementation methods

[0060] The accompanying figures show part of a metal strip manufacturing bench and various stages of its manufacture. Identical or corresponding elements shown in these figures will be referenced by identical symbols and will not be described each time.

[0061] Figures 1, 2 and 3 show a partial view of an embodiment of a manufacturing bench 20 for a metal strip 10.

[0062] This manufacturing bench 20 allows the implementation of a manufacturing process for a very long metal strip 10, for example of a length greater than or equal to 50 meters.

[0063] According to the metal strip manufacturing process described herein, the metal strip 10 is manufactured from a plurality of metal strip elements 11, 12, for example at least two metal strip elements.

[0064] The case where the metal strip 10 is made from a first 11 and a second 12 metal strip elements will be described below.

[0065] Each metal strip element 11, 12 is in the form of an elongated strip along a longitudinal direction D1, D2 and has a straight profile along a direction perpendicular to the longitudinal direction.

[0066] It has two main faces 11 A, 12A opposite connected by two longitudinal lateral faces 11B, 12B and two transverse end faces 11C, 12C (figures 1 and 6).

[0067] Each metal strip element 11,12 typically has a length of approximately 25 to 40 meters, for example 35 meters, along the longitudinal direction D1, D2, and a width slightly greater than 540 millimeters in a direction perpendicular to the longitudinal direction and extending parallel to the main faces 1 IA, 12A of the metal strip 11, 12. The width of the metal strip element is for example between 540 mm and 560 mm.

[0068] The reference thickness of the metal strip element 11,12 is on the order of 0.7 mm, for example between 0.5 and 1 mm.

[0069] Each metal strip element has a uniform and constant thickness along its entire length. This thickness is equal to its reference thickness with a tolerance strictly less than 5%, i.e., 0.035 mm for a reference thickness of 0.7 mm. Each metal strip element thus has a thickness whose local variations are less than 5% of the reference thickness of the metal strip element. Preferably, each metal strip element has a thickness whose local variations are less than 4%, 3%, 2%, or 1% of its reference thickness.

[0070] The first and second metal strip elements preferably have identical widths and thicknesses. They may have identical or different lengths.

[0071] Each of the first and second metal strip elements is made of metal, for example, an iron-nickel alloy with a coefficient of thermal expansion typically less than 2 x 10⁶ K⁻¹, for example, between 1 x 10⁶ and 2 x 10⁶ K⁻¹. For example, the alloy known as "Invar®". According to another embodiment, each metal strip element is made of an iron-manganese alloy with a coefficient of thermal expansion between 7 x 10⁶ K⁻¹ and 9 x 10⁶ K⁻¹. This alloy generally reduces costs.

[0072] The manufacturing process for the metal strip 10 comprises the following steps: - to place an end portion 13 of the first metal strip element 11 and an end portion 14 of the second metal strip element 12 on a flat support 21, - align the longitudinal lateral faces 11B, 12B of the first and second metal strip elements 11, 12 so that they extend in line with each other, - weld end-to-end the first and second metal strip elements 11, 12, forming a continuous weld bead extending along the end transverse faces 1 IC, 12C over the entire width of the first and second metal strip elements.

[0073] In practice, each metal strip element 11,12 is initially stored in the form of a roll in which the metal strip element is wound around itself, around an axis extending according to the width of the metal strip element.

[0074] The process thus includes a preliminary step in which the roll carrying the first metal strip element 11 is unwound.

[0075] The metal strip element 11 may exhibit, immediately after unwinding, a so-called "saber-like" deformation, with both longitudinal edges of the metal strip element being curved in the same direction. Using such a metal strip element without correcting this deformation would not result in a metal strip exhibiting straightness and dimensioning accuracy compatible with the level of precision required for manufacturing watertight membranes.

[0076] Indeed, the required precision is on the order of 0.5 mm per meter, non-cumulative. This means that, along the entire length of the metal strip, the longitudinal edge of the metal strip must not deviate by more than 0.5 mm from a theoretical ideal straight-line location extending between the longitudinal ends of this longitudinal edge.

[0077] In order to correct this deformation, the manufacturing process of the metal strip includes a step of drawing the first metal strip element 11.

[0078] The first metal strip element 12 is thus preferably stretched in a tension straightening device. This straightening device is known to those skilled in the art and will not be described in detail here. It comprises, for example, two self-locking jaws, one fixed to a fixed frame of the straightening device and the other movable, as it belongs to a part that can slide on the frame. The end portions 13 of the first metal strip element 11 are placed in the self-locking jaws, and the movable self-locking jaw slides so as to exert a longitudinal tensile force on the first metal strip element 11. This longitudinal tensile force is calibrated to be slightly greater than the elastic deformation limit of the metal strip element.

[0079] Once straightened by stretching, the first metal strip element 11 is placed flat on the flat support 21 of the manufacturing bench 20 (see diagram a) of [Fig. 5]). The first metal strip element can optionally be rewound at the exit of the straightening device to be conveyed to the manufacturing bench 20 and unwound to be placed flat on the flat support 21 of the manufacturing bench 20.

[0080] The flat support 21 has a flat receiving surface which can accommodate the first or second fully unrolled metal strip element (diagram a) of [Fig.5]).

[0081] The flat support 21 extends along a longitudinal axis L. The metal strip element is placed on the flat support 21 so that the longitudinal direction Dl, D2 of the metal strip element 11,12 extends along the longitudinal axis L of the flat support.

[0082] The manufacturing process then preferably includes a step of partially cutting the first metal strip element 11 along its longitudinal lateral faces 1 IB, up to a stopping point AD of the cutting located at a distance from the transverse end face 1 IC of the first metal strip element 11 intended to be placed near the second metal strip element 12.

[0083] This cutting step is schematically represented in diagram b) of [Fig.5],

[0084] The cutting of the longitudinal edges of the first metal strip 11 is carried out using two cutting tools 22 arranged on a feed path of the end portion 13 of the first metal strip element 11.

[0085] In the example shown in [Fig. 5], the two cutting tools 22 are positioned opposite each other and are not movable. Each cutting tool 22 comprises, for example, a shear with two circular blades. The cutting tools 22 are located at one longitudinal end of the flat support 21 of the manufacturing bench.

[0086] The first metal strip element 11 is set in motion by a conveyor which may be equipped with a suction system to obtain a suction effect holding the metal strip element or with a fastening system fixed to an end portion of the metal strip element. It is thus moved longitudinally in translation along the longitudinal axis L of the flat support 21, parallel to the longitudinal direction Dl of the first metal strip element 11, until the cutting tools reach the cutting stop AD (diagram c) of [Fig. 5]).

[0087] The stopping point AD of the cutting is located for example at a distance of between 1 and 3 meters from the transverse end face 1 IC of the first metal strip element 11.

[0088] Alternatively, the two cutting tools can be placed opposite each other and movable along the longitudinal direction. The two cutting tools 22 are, for example, mounted on a frame that moves in translation along a rail extending along the flat support, along the longitudinal axis L of the flat support 21.

[0089] Preferably, as the longitudinal edges of the first metal strip element 11 are cut, the cut part of the first metal strip element is rewound around a winding axis perpendicular to the longitudinal direction DI of the first metal strip element 11. This is shown in diagram c) of [Fig.5].

[0090] Thus, at the end of this cutting step, the first metal strip element 11 comprises a re-cut portion and a portion of the first metal strip element 11 between the cutting stop AD and the nearest end transverse face 1 IC, whose longitudinal edges are uncut and which is arranged on the flat support 21. This latter portion constitutes the end portion 13 of the first metal strip element 11.

[0091] The space occupied by the first metal strip element 11 on the flat support 21 is limited to its end portion 13. It is then possible to place the second metal strip element 12 flat on the flat support 21 (diagram c) of [Fig. 5]).

[0092] The process preferably includes a preliminary step in which the roll formed by the second metal strip element 12 is unwound.

[0093] The manufacturing process for the metal strip preferably also includes a step of drawing the second metal strip element 12, in order to avoid any "saber-like" deformation of the latter.

[0094] The second metal strip element 12 is thus preferably stretched in a tension straightening device such as that described above.

[0095] Once straightened by stretching, the second metal strip element 12 is placed on the flat support 21 of the manufacturing bench 20 (see diagram c) of [Fig. 5]). The second metal strip element 12 can optionally be rewound at the exit of the straightening device to be conveyed to the manufacturing bench 20 and then unwound to be placed flat on the flat support 21.

[0096] The second metal strip element 12 is placed next to the first metal strip element, such that the end portion 13 of the first metal strip element 11 and the end portion 14 of the second metal strip element 12 are longitudinally aligned. The longitudinal direction DI of the first metal strip element 11 and the longitudinal direction D2 of the second metal strip element 12 are then parallel.

[0097] One of the main faces 1 IA, 12A of each of the first and second metal strip elements 11, 12 rests at least partially on the receiving surface of the manufacturing bench 20. Part of this main face 11 A, 12A belonging to the end portion of the first and second metal strip elements rests in particular on the flat support 21.

[0098] The transverse end face 1 IC of the end portion 13 of the first metal strip element 11 extends close to the transverse end face 12C of the end portion 14 of the second metal strip element 12.

[0099] More specifically, two configurations are envisaged in which the end transverse faces 1 IC, 12C of the first and second metal strip elements extend close to each other.

[0100] According to a first possible configuration, the transverse face 1 IC of the end portion of the first metal strip element extends to a distance from the transverse end face of the end portion of the second metal strip element that is less than or equal to half the thickness of each metal strip element.

[0101] More specifically, the transverse end face 1 IC of the first metal strip element 11 extends opposite the transverse end face 12C of the second metal strip element 12, either in contact with the transverse end face 12C of the second metal strip element 12, or separated from it by a distance less than or equal to half the thickness of each metal strip element. This first configuration is shown in [Fig. 3].

[0102] According to a second possible configuration, the end portion 14 of the second metal strip element 12 slightly overlaps the end portion 13 of the first metal strip element, over a distance less than or equal to three times the thickness of each metal strip element. This second configuration is shown in [Fig. 6]. In this second configuration, the end transverse faces 1IC, 12C of the first and second metal strip elements are separated by a distance, measured along the longitudinal direction of the metal strip elements, less than or equal to three times the thickness of one of the metal strip elements.

[0103] Preferably, the end transverse faces 11C, 12C of the two metal strip elements are straight, i.e. perpendicular to the principal faces of the metal strip elements, as shown in Figures 3 and 6. In addition, in both configurations envisaged, the end transverse faces 11C, 12C of the first and second metal strip elements 11,12 are separated by a distance, measured along the longitudinal direction of the metal strip elements, less than or equal to three times the thickness of one of the metal strip elements.

[0104] Preferably, the end transverse faces 11C, 12C of the two metal strip elements are arranged in contact with each other.

[0105] This configuration is used for example with TIG, plasma or friction stir welding.

[0106] The flat support 21 further includes a groove 24 adapted to receive the end portions 13, 14 of the metal strip elements 11, 12.

[0107] In order to precisely position the end portions of the first and second metal strip elements 11,12 in line with each other, the method includes a step of aligning the longitudinal lateral faces 11B, 12B of the first and second metal strip elements so that they extend in line with each other.

[0108] For this purpose, the manufacturing device 20 includes an alignment device 30 to adjust the relative position of the longitudinal lateral faces 11B, 12B of the first and second metal strip elements 11, 12 so that they extend in line with each other.

[0109] A portion of the flat support 21, intended to extend under the end portions 13, 14 of the first and second metal strip elements 11, 12, is shown in [Fig. 4]. This portion of the flat support comprises two complementary parts 31, 32 which together form the alignment device 30.

[0110] More specifically, the alignment device 30 here comprises, on the one hand, a fixed main part 31 having a first side wall 31A and a bottom wall 31B, of which a first external side face 33 and a central external face 34 delimit said groove 24 and, on the other hand, a movable side part 32 having a second side wall 32A, of which a second external face 35 faces the first external side face 33 of the first side wall 31A to delimit said groove 24.

[0111] The movable side part 32 of the alignment device 30 is adapted to laterally clamp the end portions 13, 14 of the metal strip elements 11, 12 placed in the groove 24 in a transverse direction perpendicular to the longitudinal direction L of the manufacturing bench.

[0112] The movable side piece 32 of the alignment device 30 is here adapted to slide within the fixed main piece 31 of the alignment device 30 in the transverse direction. The movable side piece 32 has for this purpose a series of pins 36 projecting from the second side wall 32A towards the fixed main piece 31, and the fixed main piece has, in its bottom wall 31B, recesses 37 which open towards the pins 36 and are adapted to receive the sliding pins 36.

[0113] The movable side piece 32 is thus adapted to slide between an open position in which the second side wall is disposed at a distance from the first side wall strictly greater than the width of the metal strip elements and a clamping position in which the second side wall is disposed at a distance from the first side wall equal to the width of the metal strip elements.

[0114] To align the end portions of the first and second metal strip elements, the movable part 32 of the alignment device 30 is slid to clamp the longitudinal lateral faces 11B, 12B of the two metal strip elements between the external lateral faces 33, 35 of the first lateral wall 31A of the main fixed part 31 and of the second lateral wall 32A of the movable part 32 of the alignment device 30. This ensures that the longitudinal lateral faces 11B, 12B of the two metal strip elements extend in line with each other and that the end portions 13, 14 of the two metal strip elements are perfectly aligned.

[0115] The butt welding step of the first and second metal strip elements 11, 12 can be carried out in different ways. This step is shown schematically by the arrow W in diagram c) of [Fig. 5].

[0116] The continuous weld bead is for example produced by a process chosen from: TIG (Tungsten Inert Gas) arc welding, plasma or micro-plasma welding, roller crushing welding, friction stir welding.

[0117] In the example shown in figures 1 to 3, the welding is carried out by TIG arc welding or by plasma process.

[0118] In order to ensure precise welding of the two metal strip elements, the process includes a step in which the end portions 13, 14 of the first and second metal strip elements 11, 12 are pressed against the flat support 21, by pressing on the main faces 1 IA, 12A opposite the flat support 21, on either side of the transverse end faces 11C, 12C arranged close to each other.

[0119] This step ensures correct positioning of the end portions of the metal strip elements during welding, avoiding defects related to thermal deformations of the metal strip elements during welding, due to heating of the materials during welding.

[0120] In practice, the step of clamping the end portions of the first and second metal strip elements against the flat support is carried out with a clamping device 40 comprising a metal support portion 41 bearing against the main faces of the metal strip elements 11, 12 on either side of the faces end cross members of metal strip elements arranged close to each other.

[0121] An example of such a clamping device 40 is shown schematically in Figures 1 and 3. The metallic support part is formed by a first plate having a median slot 42.

[0122] The first plate has a length greater than the width of the metal strip elements 11, 12 measured along the transverse direction.

[0123] The ends of the first plate of the clamping device 40 rest on the first and second side walls 31 A, 32 A of the alignment device 30 and are pressed against them by a jack system not shown, integral with the alignment device 30 or the welding gantry 50. The depth of the groove 24 formed by the alignment device 30 is preferably greater than or equal to the thickness of each metal strip element.

[0124] Thus, when the first plate of the clamping device 40 is pressed onto the alignment device, after the alignment step, the first plate clamps the end portions 13, 14 of the metal strip elements 11, 12 against the bottom of the groove 24.

[0125] The slot 42 of the first plate extends beyond the outer faces of the first and second lateral walls 31A, 32A of the alignment device 30, and therefore beyond the longitudinal lateral faces 11B, 12B of the metal strip elements 11, 12, thus leaving completely unobstructed access to the transverse end faces 11C, 12C of the metal strip elements 11, 12. The slot 42 preferably has beveled lateral edges flaring outwards from the support plane.

[0126] The first plate is a metal plate, preferably made of a metal with high thermal conductivity, such as copper and its alloys. This limits the heating of the end portions of the metal strip elements by promoting heat dissipation.

[0127] The welding is carried out using a welding gantry 50. The welding gantry 50 includes a welding head 53 and a guide rail 51.

[0128] The guide rail 51 extends opposite the slot 42 of the first plate 41 of the clamping device 40. The guide rail 51 is, for example, supported by walls 54 extending from the first side wall 31A of the fixed main part 31 of the alignment device 30 and from the second side wall 32A of the movable side part 32. The welding head 53 includes, for example, an electrode 52 for a TIG or plasma torch used for welding. The welding head 53 and its electrode 52 are adapted to slide along the rail 51, such that the electrode 52 moves in the slot 42 of said first metal plate 41 ([Fig. 3]).

[0129] Before producing the continuous weld bead, the process may include a spot welding step. Preferably, a spot weld is made every 5 centimetres at most.

[0130] This step makes it possible to limit the deformations of the end portions 13, 14 of the metal strip elements 11, 12 during the final welding.

[0131] For welding the metal strip elements 11, 12, the flat support 21 of the manufacturing bench 20 preferably includes a second plate 60. The second plate 60 is for example part of the bottom wall 31B of the main fixed part 31 of the alignment device 30 ([Fig.3]).

[0132] The second plate 60 is housed in this bottom wall 31B and is flush with the central external face 34 of the groove 24. It is located opposite the slot 42 of the first plate 41 and the guide rail 51 of the welding gantry 50.

[0133] Thus, the transverse end faces of the first and second metal strip element 11,12 arranged close to each other extend in relation to the metal plate during the welding step.

[0134] The second plate is made of ceramic or metal, preferably a metal with high thermal conductivity, such as copper and its alloys. This limits heating of the end portions of the metal strip elements by promoting heat dissipation during welding. When using copper or a copper-based alloy, a groove (not shown) must be formed in the second plate at the location of the area to be welded.

[0135] The weld bead is formed by the fusion of a part of each metal strip element near their end transverse face, with or without the addition of external metal.

[0136] Once the two metal strip elements 11,12 are welded together to form the metal strip 10, the longitudinal edges of the resulting metal strip are cut at least along a region extending from a place on one side of the weld bead to a place on the other side of the weld bead, along the longitudinal direction of the metal strip 10. This step is schematically represented in diagram d) of [Fig.5].

[0137] This cutting of the longitudinal edge of the metal strip 10 at the weld bead, after the weld has been formed, has the advantage of eliminating any welding defects occurring at the beginning and end of the welding step, and therefore in the immediate vicinity of the longitudinal lateral faces 11B, 12B of the metal strip elements. The remaining longitudinal edges of the second metal strip element are then cut. This cutting is carried out using the cutting tools 22 described previously.

[0138] In the embodiment described here, the longitudinal edge of the metal strip is cut from the point where the cutting of the first metal strip element stopped until a point on the other side of the weld bead, for example until the free end of the metal strip 10.

[0139] Alternatively, before the welding step, the longitudinal edges of a portion of the second metal strip element are also cut along its longitudinal lateral faces. The cut portion of the second metal strip element extends from an end transverse face of this second metal strip element to a cutting stop located at a distance from the end transverse face of the second metal strip element intended to be positioned near the first metal strip element. The stopping stop is also preferably located at a distance of between 1 and 3 meters from the end transverse face of the second metal strip element intended to be positioned near the first metal strip element.

[0140] In this case, after welding the metal strip elements, the longitudinal edges of the metal strip obtained are cut between the cutting stop point of the first metal strip and the cutting stop point of the second metal strip.

[0141] The metal strip 10 obtained is for example wound around a transverse axis perpendicular to its longitudinal direction Dl, D2.

[0142] The thickness of the resulting metal strip 10 is uniform and constant along its entire length. Only the weld bead may introduce a slight local increase in thickness.

[0143] In a later step of the manufacturing process, a folding step can be carried out on the longitudinal edges of the metal strip. This step is performed directly in the tank. This makes it possible to form the folds that can be used to manufacture the watertight membrane of a tank as described in the introduction.

[0144] The manufacturing process described has the advantage of being simple and economical. In addition, mechanical strength tests on metal strips 40 mm wide and 0.7 mm thick obtained after butt welding as described above show a mechanical strength of 13 kN, which is 20 percent higher than the mechanical strength of a 40 mm wide metal strip obtained by lap welding of 1 mm / 0.7 mm.

[0145] Furthermore, plasma welding tests, with a high current of 50 A, a low current of 30 A, a low current time / high current time ratio of 70%, a speed of 35 cm / minute and a frequency of 4 Hz, give a good quality weld bead, with little excess thickness and no deformation at the welded junction between the first and second metal strip elements.

[0146] TIG welding tests, with a high current of 45 A, a low current of 20 A, a low current time / high current time ratio of 45%, a speed of 20 cm / minute and a frequency of 10 Hz also give a good quality weld bead, with little excess thickness and no deformation at the welded junction between the first and second metal strip elements.

[0147] According to another embodiment of the manufacturing process, the welding is a butt weld with crushing, for example, performed by crushing roller welding. Figure 6 schematically shows the end portions 13, 14 of the first and second metal strip elements, and two electrodes 70 in the form of wheels (copper discs or rollers) rotating in opposite directions. The two electrodes apply a crushing force to the longitudinal edges in addition to heating them by passing a high-frequency current, thus enabling continuous welds. The flat support then includes an opening for the electrode located under the metal strip elements.

[0148] Butt welding with crushing allows obtaining a metal strip 10 as shown in [Fig.6].

[0149] The metal strip 10 manufactured using this process is intended to be used for the construction of a watertight and thermally insulating tank membrane.

[0150] For this purpose, the metal strip obtained by the process described below is used to form a metal strip with raised edges, intended for the production of a watertight membrane in a tank.

[0151] The metal strip comprises the metal strip obtained by the process described above, from two metal strip elements each having a constant thickness over their entire length.

[0152] The metal strake has, depending on its width, a flat central portion and two lateral edges folded substantially perpendicular to the flat central portion, the two lateral edges having a small width compared to the flat central portion.

[0153] The raised edges of the metal strip can be obtained from the metal strip using a bending machine with three rollers on each side of the metal strip. The rollers exert pressure on the metal strip to deform it and generate the raised edges. The resulting waterproof membrane has a continuous sheet of metal strips with raised edges.

[0154] The metal strakes are welded by their raised edges onto parallel welding supports which are fixed in the underlying thermally insulating barrier.

[0155] The continuous sheet thus presents a repeated structure comprising alternately a metallic strake as described above and an elongated weld wing forming the weld support.

[0156] A surface of the underlying thermally insulating barrier oriented towards the waterproof membrane forms a support surface for the waterproof membrane. Each weld flange is bonded to this support surface and protrudes from it.

[0157] The sealed and thermally insulating tank is integrated into a load-bearing structure comprising a plurality of load-bearing walls. The tank comprises a plurality of tank walls, each fixed to a respective load-bearing wall.

[0158] The load-bearing wall may, in particular, be formed by the hull or double hull of a ship. The load-bearing wall is typically part of a load-bearing structure comprising a plurality of walls defining the general shape of the tank, usually a polyhedral shape.

[0159] The sealed and thermally insulating tank is formed by the assembly of several tank walls. For LNG, the tank wall typically comprises successively, in the thickness direction, from the outside to the inside of the tank, a secondary thermally insulating barrier retained to a load-bearing wall, a secondary sealed membrane resting against the secondary thermally insulating barrier, a primary thermally insulating barrier resting against the secondary sealed membrane and a primary sealed membrane intended to be in contact with the liquefied natural gas contained in the tank.

[0160] When there are two sealing membranes, the primary sealing membrane can be made identically or differently from the secondary sealing membrane. Each of the two sealing membranes of the tank wall can be made as described above.

[0161] At the angle between the two tank walls, the secondary watertight membranes of the two tank walls and / or the primary watertight membranes of the two walls can be connected by a connecting ring in the form of a square tube. The connecting ring forms a structure that allows it to withstand the tensile forces resulting from thermal contraction, particularly of the metallic elements forming the watertight membranes, deformation of the hull at sea, and cargo movements. A possible structure of the connecting ring is described in more detail in FR-A-2549575.

[0162] The secondary thermally insulating barrier comprises a plurality of secondary insulating blocks and the primary thermally insulating barrier comprises a plurality of primary insulating blocks. These insulating blocks have, for example, a general parallelepiped shape and can be anchored to the load-bearing wall in various ways, for example by anchoring devices.

[0163] The support surface of the waterproof membrane of each thermally insulating barrier is flat and parallel to the respective load-bearing wall.

[0164] Such membrane tanks can be used for the storage and / or transport of a low-temperature liquid, such as Liquefied Natural Gas (LNG) at approximately -162°C at atmospheric pressure, Liquid Hydrogen (LH2) at -253°C at atmospheric pressure, Ammonia (NH3) at -30°C at atmospheric pressure, or Liquefied Petroleum Gas (also known as LPG), for example, at a temperature between -50°C and 0°C. These tanks can be installed on land or on a floating structure. In the case of a floating structure, the tank can be used for transporting liquefied gas or for receiving liquefied gas to serve as fuel for the propulsion of the floating structure. In the case of an onshore tank or a port storage structure, it can rest on the ground or the seabed and can be partially or completely buried.

[0165] The tank wall may comprise only one sealed membrane and one thermally insulating barrier, for example for storing LPG.

[0166] With reference to [Fig. 7], a cutaway view of a LNG carrier 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the vessel. The wall of the tank 71 comprises a primary watertight barrier intended to be in contact with the LNG contained in the tank, a secondary watertight barrier arranged between the primary watertight barrier and the double hull 72 of the vessel, and two thermally insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72.

[0167] In a manner known per se, loading / unloading pipelines 73 arranged on the upper deck of the ship can be connected, by means of suitable connectors, to a marine or port terminal or to an LNG bunker ship to transfer an LNG cargo to or from the tank 71.

[0168] Figure 7 shows an example of a marine terminal comprising a loading and unloading berth 75, a subsea pipeline 76 and an onshore facility 77. The loading and unloading berth 75 is a fixed offshore facility comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading / unloading pipelines 73. The steerable movable arm 74 is suitable for all LNG carrier sizes. An unshown connecting pipeline extends inside tower 78. The loading and unloading station 75 allows the loading and unloading of the LNG carrier 70 from or to the onshore facility 77. This facility includes liquefied gas storage tanks 80 and connecting pipelines 81 linked by the subsea pipeline 76 to the loading or unloading station 75.The subsea pipeline 76 allows the transfer of liquefied gas between the loading or unloading station 75 and the onshore installation 77 on a . a large distance, for example 5 km, which allows the LNG carrier 70 to be kept a considerable distance from the coast during loading and unloading operations.

[0169] To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the vessel 70 and / or pumps equipping the shore-based installation 77 and / or pumps equipping the loading and unloading station 75 are used.

[0170] The invention applies to ship tanks 71 and also to land-based reservoirs and port structures.

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

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

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

Claims

1. Demands A method for manufacturing a metal strip (10), comprising the steps of: - to arrange an end portion (13) of a first metal strip element (11) and an end portion (14) of a second metal strip element (12) on a flat support (21), the end portion (13) of the first metal strip element (11) and the end portion (14) of the second metal strip element (12) being juxtaposed in a longitudinal direction, each of the first and second metal strip elements (11, 12) having two opposite principal faces (11A, 12A) connected by two longitudinal lateral faces (11B, 12B), the first and second metal strip elements having the same width, the end portion (13) of the first metal strip element (11) and the end portion (14) of the second metal strip element (12) each being terminated by a respective transverse end face (11C, 12C), such that a principal face (1 IA, 12A) of each of the first and second metal strip elements (11, 12) rests at least partially on the flat support (21), and that the transverse end face (1 IC) of the end portion (13) of the first metal strip element (11) extends close to the transverse end face (12C) of the end portion (14) of the second metal strip element (12), - align the longitudinal lateral faces (11B, 12B) of the first and second metal strip elements (11, 12) so that they extend in line with each other, - weld the first and second metal strip elements (11, 12) end-to-end, forming a continuous weld bead extending along the transverse end faces (11C, 12C), over the entire width of the metal strip elements (11, 12) - cut longitudinal edges of the metal strip (10) obtained at least along a region extending from a place on one side of the weld bead to a place on the other side of the weld bead, along the longitudinal direction of the metal strip (10).

2. A method according to claim 1, wherein the end portions (13, 14) are arranged so that the cross face (1IC) of the end portion (13) of the first metal strip element (11) extends to a distance from the cross end face (12C) of the end portion (14) of the second metal strip element (12) that is less than or equal to half a thickness of one of the metal strip elements (11, 12).

3. A method according to claim 1, wherein the end portions (13, 14) are arranged so that the end portion (14) of the second metal strip element (12) covers the end portion (13) of the first metal strip element (11) over a distance less than or equal to three times the thickness of one of the metal strip elements (11, 12).

4. Method according to any one of claims 1 to 3, further comprising - unwinding a roll carrying the first metal strip element (H).

5. A method according to any one of claims 1 to 4, further comprising: - partially cutting the first metal strip element (11) along its longitudinal lateral faces (11B) using two cutting tools (22) arranged on a feed path of the end portion (13) of the first metal strip element (11), to a stopping point (AD) of the cutting located at a distance from the transverse end face (1 IC) of the first metal strip element (11) intended to be arranged near the second metal strip element (12).

6. Method according to claim 5, wherein the two cutting tools (22) are placed opposite each other and are not movable.

7. A method according to claim 5, wherein the two cutting tools are placed opposite each other and movable along the longitudinal direction.

8. A method according to any one of claims 5 to 7, further comprising: - winding a cut portion of the first metal strip element (11) around a winding axis perpendicular to the longitudinal direction.

9. A method according to any one of claims 1 to 8, wherein, before the welding step, a portion of the second metal strip element is also cut along its longitudinal lateral faces, a cut portion of the second strip element metallic extending from a transverse end face of this second metal strip element to a cutting stop point located at a distance from the transverse end face of the second metal strip element intended to be placed near the first metal strip element.

10. A method according to any one of claims 1 to 9, wherein the flat support (21) comprising a metal plate (60), the transverse end faces (1 IC, 12C) of the first and second metal strip element (11, 12) arranged close to each other extend opposite the metal plate (60) during the welding step.

11. A method according to any one of claims 1 to 10, comprising a step of: - pressing the end portions (13, 14) of the first and second metal strip elements (11, 12) against the flat support (21), by pressing on the main faces (11A, 12A) opposite the flat support, on either side of the transverse end faces (1IC, 12C) arranged close to each other.

12. A method according to claim 11, wherein the step of clamping the end portions of the first and second metal strip elements (11, 12) against the flat support (21) is carried out with a clamping device (40) comprising a metal support portion (41) bearing on the main faces (11A, 12A) of the metal strip elements (11; 12) on either side of the transverse end faces of the metal strip elements arranged close to each other.

13. A method according to any one of claims 1 to 12, further comprising: - performing tack welding before making the continuous weld bead.

14. A method according to any one of claims 1 to 13, wherein the continuous weld bead is produced by a method selected from: TIG arc welding, micro-plasma welding, roller crush welding, friction stir welding.

15. A method according to any one of claims 5 to 9, wherein the stopping point (AD) of the cutting is located at a distance of between 1 and 3 meters from the transverse end face (1 IC, 12C) of the first or second metal strip element (11, 12) cut.

16. A method according to any one of the preceding claims, wherein metal strip elements (11, 12) are used, made of an iron and nickel alloy having a coefficient of expansion typically between 1.106 and 2.106 K' or of an iron and manganese alloy having a coefficient of expansion between 7.106 K1 and 9.106 K1.

17. A method according to any one of the preceding claims, wherein each metal strip element (11, 12) has a thickness between 0.5 and 1 mm.

18. A method according to any one of the preceding claims, further comprising a step of folding the longitudinal edges of the metal strip (10).

19. A metal strip manufacturing bench comprising: - a flat support (21) adapted to receive an end portion (13) of a first metal strip element (11) and an end portion (14) of a second metal strip element (12), the end portion of the first metal strip element and the end portion of the second metal strip element being juxtaposed in a longitudinal direction, each of the first and second metal strip elements having two opposing principal faces (11A, 12A) connected by two longitudinal lateral faces (11B, 12B), the end portion of the first metal strip element and the end portion of the second metal strip element each being terminated by a respective transverse end face (11C, 12C),a transverse end face (1 IC) of the first metal strip element (11) extending close to a transverse end face (12C) of the second metal strip element (12), - an alignment device (30) for adjusting the relative position of the longitudinal lateral faces of the first and second metal strip elements so that they extend in line with each other, - a welding gantry (50) for butt-welding the two metal strip elements, by means of a continuous weld bead extending along the transverse end faces, over the entire width of the metal strip elements, - two cutting tools adapted to cut longitudinal edges of the metal strip (10) obtained at least along a region extending from a place on one side of the weld bead to a place on the other side of the weld bead, along the longitudinal direction of the metal strip (10).

20. A metal stile adapted for the production of a watertight membrane for a watertight and thermally insulating tank, comprising a metal strip (10) obtained by the process according to any one of claims 1 to 18, from two metal strip elements (11, 12) each having a constant thickness over their entire length, the metal stile having, according to its width, a flat central portion and two lateral edges folded substantially perpendicular to the flat central portion, the two lateral edges having a small width compared to the flat central portion.

21. A watertight membrane for a watertight and thermally insulating tank, comprising a repeating structure comprising alternately a metal strake according to claim 20 and an elongated weld wing connected to a support surface of the watertight membrane and projecting therefrom, the weld wing extending parallel to the metal strake over at least part of the length of the metal strake, the flat central portion of the metal strake being placed on the support surface and the lateral edges of the metal strake being disposed against the adjacent weld wings and welded watertight to the weld wings.

22. A watertight and thermally insulating tank integrated into a load-bearing structure, the load-bearing structure comprising a plurality of load-bearing walls, the tank comprising a plurality of tank walls fixed each time to a respective load-bearing wall, a tank wall comprising: a thermally insulating barrier retained on the load-bearing wall, the thermally insulating barrier having a flat support surface parallel to the respective load-bearing wall, and a watertight membrane according to claim 21.

23. Vessel (70) for the transport of a fluid, the vessel comprising a double hull (72) and a tank (71) according to claim 22 disposed in the double hull (72).

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