System and method for transparent welding of a sealing plate onto an anchor plate

Abstract

System and method for welding a sealing plate to an anchor plate by transparency. The present invention relates to a welding system (S1) for a sealing plate (15) of a tank intended to contain liquefied gas, to an anchor plate (23). The welding system (S1) comprises: - a transparent welding tool (52), - means for clamping the sealing plate (15) onto the anchor plate (23), and - means for monitoring a force exerted by the clamping means (48) on the sealing plate (15), capable of detecting contact between the anchor plate (23) and the sealing plate (15). (Figure 3)

Description

Title of the invention: System and method for transparent welding of a sealing plate onto an anchor plate

[0001] The present invention relates to the field of tanks for gases in a liquid state, for example liquefied natural gas (LNG), particularly for maritime or river transport or for an onshore reservoir. More specifically, the invention relates to a welding system for a sealing membrane adapted for such a tank, and an associated welding process.

[0002] Liquefied gas tanks have a capacity of several thousand cubic meters of liquid gas each, or even several tens of thousands of cubic meters. Liquefied gas transport vessels have holds specifically designed to contain these tanks, their holds often being divided into several tanks. Such a tank can also be constructed outside a ship for onshore storage of liquefied natural gas.

[0003] The gas is kept inside the tank in a liquid state, for example at -163°C (degrees Celsius) for LNG, at atmospheric pressure. Therefore, the tank must be leak-proof and thermally insulated. Consequently, the internal surface of such a tank is covered with a sealing membrane, generally made of an assembly of metal sealing plates (typically stainless steel plates) welded together, each sealing plate forming part of the tank's sealing membrane.

[0004] The walls of the tank further comprise, successively under the sealing membrane intended to be in contact with the liquefied gas, this sealing membrane being called the primary sealing membrane:

[0005] - a primary insulation layer, for example made with wooden boxes filled with reinforced polyurethane foam,

[0006] - another sealing membrane, called a secondary sealing membrane, by example made of thin sheet metal

[0007] - a secondary insulation layer, for example also made with wooden crates filled with reinforced polyurethane foam.

[0008] The primary waterproofing membrane is fixed to the primary insulation layer by welding the waterproofing sheets to anchoring plates, which are integral with the primary insulation layer and which can, in particular, be riveted to the wooden frames of the primary insulation layer. These anchoring plates form a grid pattern across all the frames but do not completely cover them.

[0009] Since this welding is carried out by transparency, it is necessary, in order for the weld to be When properly executed, the distance between the sealing plate and the anchor plate must be less than 0.3 mm. In through-welding, a point of contact is ensured between the two plates, which are welded on only one side of each plate, near this point. Given the height differences of the various sections of the primary insulation layer, due to permitted assembly and manufacturing tolerances, it is not possible to guarantee proper contact between the sealing plate and the anchor plate without applying a default clamping force of 60 kg. This force is necessary to ensure contact between the sealing plate and the anchor plate when the height difference between these two plates corresponds to the maximum permissible height difference.

[0010] This welding process is however very long and can cause poor quality welds when the default applied force causes a lever effect lifting the sealing plate at the weld area.

[0011] The present invention aims to remedy at least in part the aforementioned drawbacks by providing in particular a welding system and a welding process which make it possible to guarantee good weld quality, and which allow automation of the welding process.

[0012] To this end, the invention proposes a welding system for a sealing plate of a tank intended to contain liquefied gas, to an anchoring plate, the sealing plate and the anchoring plate being metallic, the welding system comprising a welding device including: - a transparent welding tool intended to perform at least one weld in a weld zone, - means of attaching the sealing plate to the anchoring plate, and - means of controlling a force exerted by the clamping means on the sealing plate, capable of detecting a contact between the anchoring plate and the sealing plate.

[0013] The welding tool is, for example, a plasma welding torch or a laser welding device. When the welding system is used to weld the sealing plate to the anchor plate, the welding tool is positioned above the anchor plate, and more precisely above a weld area of ​​the sealing plate on this anchor plate. Such weld areas are located, for example, along an edge of the sealing plate situated above the anchor plate. For example, the sealing plate has between 3 and 21 weld areas along the edge, and preferably 15 weld areas along the edge when the sealing plate is 3 meters long. These weld areas are located on "weld areas," which are flat areas of the sealing plate, spaced, for example, about 30 centimeters apart when the sealing plate is The surface is crisscrossed with waves. Each weld zone is not located above rivets used to attach the anchor plate to the sub-layers of the primary insulation. It is understood that a weld zone, where a weld is performed, cannot be larger than the anchor plate. For example, a weld zone forms a rectangle 10 cm long and 5 cm wide, and the anchor plate is, for example, 100 mm by 70 mm. The sealing elements are applied to or adjacent to the weld zone so that the distance between the sealing plate and the anchor plate is less than 0.3 mm across the entire weld zone. These figures are, of course, indicative and must be adapted to the different types of tank walls and the methods of attaching the sealing plates to these tank walls.

[0014] Thanks to the invention, contact is detected between the anchor plate and the sealing plate to adapt the force exerted by the clamping means and ensure a high-quality weld between the anchor plate and the sealing plate, regardless of the initial distance between the sealing plate and the anchor plate, which depends on the height differences between the various boxes on which the sealing plate is placed. It should be noted that the anchor plate is fixed to a box so as to slightly protrude above the height of the box. The intended protrusion is, for example, 0.2 mm. Therefore, once the welds are made between the sealing plate and the underlying anchor plate(s), the sealing plate is in contact with the boxes.

[0015] The invention also allows for the automation of a welding process using the welding system according to the invention.

[0016] According to an optional feature of the invention, the clamping means comprise, for example, a pusher having a bearing surface defining a plane intended to extend parallel to the weld zone, and a cylinder whose head is fixed to the pusher. The cylinder is, for example, a hydraulic or electric cylinder. The head of the cylinder is, for example, an attachment zone disposed at the end of an extension rod of the cylinder. The extension rod of the cylinder is preferably disposed orthogonally to the plane defined by the bearing surface. However, it may also be inclined with respect to this plane.

[0017] As explained previously, the weld zone is a portion of a weld area (surrounded by corrugations when the sealing plate has them), the support surface being abutted against a surface of the weld area or bearing on the surface of the weld area. The support surface defines a plane that is parallel to the weld area; in fact, the plane coincides with the surface of the weld area.

[0018] According to an optional feature of the invention, the welding tool is secured using a clamping mechanism. This allows for setting a first distance between the welding tool head and the push stick, parallel to the plane, and a second distance between the welding tool head and the plane, perpendicular to it. The first distance is, for example, between 2 mm and 20 mm, and is 5 mm. The second distance is, for example, between 1 mm and 5 mm, and is 2 mm.

[0019] The first distance is measured between the edge-to-edge projections of the welding tool head on one side and between the pusher on the other, these projections being on a plane parallel to the plane of the bearing surface.

[0020] The purpose of setting the initial distance is to ensure proper contact between the sealing plate and the anchoring plate just below the welding tool, and to thermally protect the plunger from the welding tool's heat radiation. The "flexibility" of the sealing plate means that this initial distance will vary depending on the contact method used. It will be smaller when the contact means use a roller than when they use a wedge. This initial distance is also related to the presence or absence of thermal protection for the contact means.

[0021] The advantage of fixing the second distance is to ensure a good voltage of the electric arc to perform the weld, without using a distance sensor on the welding tool.

[0022] According to an optional feature of the invention, the pusher comprises at least one roller. The pusher may, for example, consist of a single roller fixed to the cylinder head, or the pusher may comprise a housing carrying several rollers, i.e., several wheels, the housing being fixed to the cylinder head. Such an embodiment of the pusher allows the welding tool to be moved to perform a weld by transparency over several centimeters of the weld area. Furthermore, such a pusher allows pressure to be applied to the sealing plate without damaging it. In order to avoid damaging the roller or the weld, the welding tool is moved downstream of the movement of said at least one roller during a weld over several centimeters.When the pusher has a housing supporting several wheels, at least one roller forms a front wheel of the housing, the other wheels associated with the housing being rear wheels capable of passing on either side of the weld during the movement of the head of the welding tool, which is integral with the pusher.

[0023] According to an optional feature of the invention, the welding system includes means for thermally protecting the plunger. These protective means are, for example, a ceramic shield or a cooling jacket. They are particularly useful when the plunger includes a roller. They protect the roller from the thermal radiation of the welding tool and thus prevent the de The roller's shape is reinforced, thus extending its lifespan. The heat shield is at least partially interposed between the pusher and the welding tool.

[0024] According to an optional feature of the invention, the pusher comprises at least one shim on which the welding tool is able to slide parallel to the surface. In this alternative, the cylinder is attached to a sleeve mounted on a guide such as a rail or slide fixed to the shim. Thus, the clamping force exerted by the cylinder presses the shim against the sealing plate via the clamping force exerted by the cylinder on the sleeve, while the welding tool, attached to the clamping means and therefore to the cylinder, is able to slide along the guide, which makes it possible to perform a weld through several centimeters, by controlling the trajectory of the welding tool. Indeed, since the initial distance between the head of the welding tool and the shim is fixed, the welding tool, sliding along the guide, will follow the shape of an edge of the shim, parallel to the guide. It should be noted that the shim can comprise several guides.For example, it can form a U-shape between the arms of which the welding tool can move. The pusher can also have several shims between which the welding tool can move. More than controlling the trajectory of the welding tool, which can be done differently (for example, using a rail on which the welding device is mounted), the advantage of using a shim rather than a roller is to obtain better plate quality, as the shim deforms the sealing plate less than a roller, thanks to its larger contact surface with the sealing plate.

[0025] According to an optional feature of the invention, the control means of the welding system according to the invention comprise means for stopping the plating means coupled to means for detecting that a speed of the cylinder is less than a low speed threshold, or to means for detecting that a variation of a force exerted on the pusher is greater than a high force variation threshold, or even to means for detecting a variation of a metallic thickness measurement.

[0026] The force exerted on the pusher corresponds to the reaction force exerted by the support on which the pusher is pressed, also called the "normal reaction". The speed of the cylinder is, for example, measured orthogonally to the plane defined by the bearing surface of the pusher, or along the axis of the cylinder's extension rod.

[0027] The control means include, for example:

[0028] - a position detection means such as a linear potentiometer coupled to the actuator and allowing for precise measurement of its extension, which makes it possible to detect when the cylinder speed is below the low speed threshold,

[0029] - or a force sensor, such as a strain gauge force sensor, which allows detection when the variation in force exerted on the pusher is at the high threshold of force variation.

[0030] - or a means of measuring thickness using, for example, a sensor Ultrasound is used to detect changes in a metal thickness measurement. In this case, the change in metal thickness corresponds to the contact between the sealing plate and the anchoring plate. The thickness measuring device measures the metal thickness at the point of contact with the pusher. For example, the measuring device detects a first change in thickness when the pusher makes contact with the sealing plate, and a second change in thickness when the sealing plate makes contact with the anchoring plate. Therefore, the detection of the contact between the anchoring plate and the sealing plate corresponds to this second change in thickness, when the measuring device is activated before the pusher makes contact with the sealing plate.

[0031] The position detection means, force sensor, or thickness measurement means is mechanically coupled to the plating means and electrically coupled to a processing unit for at least one electrical output signal of the means in question. This processing unit may be located remotely from the welding system. The control means preferably comprise a human-machine interface coupled to a device including at least one processor, for example, a computer, which is itself coupled to the processing unit. The human-machine interface and the device may also be located remotely from the welding system.

[0032] In the case where the welding system includes a position detection means, the computer determines the speed of movement of the cylinder using the positions provided by the position detection means, which allows it to detect a contact between the sealing plate and the anchoring plate, by reaching a near-zero speed of movement of the cylinder, for example a speed less than 1mm per second.

[0033] In the case where the welding system includes a force sensor, the computer determines the variations in the force measurements provided by the force sensor, for example, every second. This allows it to detect contact between the sealing plate and the anchoring plate when a variation thus determined exceeds a high threshold set, for example, at 500 N (Newtons). Indeed, when this contact is obtained, the normal reaction applied by the anchoring plate to the sealing plate suddenly increases the force measured by the force sensor.

[0034] In the case where the welding system includes a thickness measurement means, the computer detects contact between the sealing plate and the anchor plate as soon as the output signal of the thickness measurement means varies, the metallic thickness in contact with the pusher then being increased by the thickness of the anchor plate.

[0035] According to an optional feature of the welding system according to the invention, this- This system comprises a frame with at least one rail and a sliding carriage mounted on the rail, with the welding device attached to the carriage. Such a frame facilitates the positioning of the clamping means and the welding tool along the weld areas of a sealing plate. Thanks to the carriage sliding on the rail, several weld areas can be processed consecutively and automatically. The carriage is, for example, motorized and includes a sliding element such as a rib adapted to slide in a guide of the rail, or a guide adapted to slide on the rail, depending on the rail configuration. The carriage is, for example, programmable to activate the welding tool and clamping means only on the weld areas, as it progresses along the rail. Means for controlling the force exerted by the clamping means on the sealing plate are preferably also mounted on the carriage.

[0036] According to an optional feature of the invention, the sealing plate having corrugations, the frame includes removable fastening means on corrugations delimiting welding zones between them, the frame forming a frame on which the rail is arranged and whose inner periphery is adapted to allow the welding tool access to the welding zones. The corrugations on the sealing plate correspond to ribs forming a grid on the sealing plate, allowing the absorption of deformations of the tank due to its thermal variations. In this embodiment of the invention, the removable fastening means are, for example, corrugation node clamps. Such a clamp slides on a first corrugation on either side of a second corrugation intersecting the first corrugation, in order to clamp the second corrugation.

[0037] According to another optional feature of the invention, with first weld zones aligned along a first axis between a first end of the sealing plate and a second end of the sealing plate, and second weld zones aligned along a second axis between a third end of the sealing plate and a fourth end of the sealing plate, the rail is configured to allow the welding tool to process all the first weld zones when aligned along the first axis. The frame includes removable fastening means for fixing at least a portion of the frame to a support external to the sealing plate. The first and second axes are distinct; for example, they are orthogonal to each other.

[0038] The rail extends, for example, from the first end of the sealing plate to the second end of the sealing plate when positioned along the first axis. The fastening means are, for example, hydraulic suction cups fixed on either side of the rail to another sealing plate already anchored to the primary insulation layer, or to the boxes of the primary insulation layer. As As an example, the sealing plate forms a rectangle measuring three meters by one meter of sheet metal. The rail allows for the processing of all welding areas along the three-meter length or the one-meter width of the sealing plate. The welding system, primarily consisting of the rail, the trolley, the rail fastening means, the clamping means, the welding tool, and the control means, remains easy to handle and therefore to move along the welding areas as the sealing plates of the primary tank sealing membrane are welded to the anchor plates of the primary insulation layer.

[0039] According to an optional feature of the invention, the welding system comprises two welding devices fixed to the carriage on either side of the rail. Thus, the welding system makes it possible to process two welding areas simultaneously, located on either side of the rail.

[0040] According to an optional feature of the invention, the welding system comprises two circular arc guide members, on each of which a separate end of the rail is slidably mounted. The guide members are adapted to move the rail from a first configuration in which the welding system is able to process all the first weld zones, to a second configuration in which the welding system is able to process the second weld zones. In this case, the rail allows the welding tool to process the first zones and then the second zones without moving the chassis mounting means.

[0041] Furthermore, the welding system may include an external station to the chassis, the station being connected by electrical and possibly hydraulic connections to the chassis fixing means, the trolley, the welding tool and the cylinder, the external station comprising an electric generator, and possibly an air compressor as well as liquid for the cylinder, if it is hydraulic, or for cooling a roller of the welding system, if this roller is thermally protected by a cooling jacket.

[0042] The invention also relates to a method for welding a sealing plate of a tank intended to contain liquefied gas to an anchor plate, using the welding system according to the invention, and comprising the steps of: - positioning of the fastening devices above the sealing plate and the anchoring plate, - activation of the restraining devices, - control of the force exerted by the clamping means on the sealing plate, - locking of the clamping means as soon as contact between the anchoring plate and the sealing plate is detected, to maintain contact between the anchoring plate and the sealing plate, and - Transparency welding of the sealing plate to the anchoring plate.

[0043] The invention further relates to a method for welding a sealing plate of a tank intended to contain liquefied gas to an anchor plate, using the welding system according to the invention, wherein the clamping means comprise a pusher having a bearing surface defining a plane intended to come parallel to a weld zone, and a cylinder whose head is fixed to the pusher, and wherein the control means comprise means for stopping the clamping means coupled to means for detecting that a cylinder speed is below a low speed threshold, the welding process comprising steps of: - positioning of the support surface above the sealing plate and the anchoring plate, - actuation of the cylinder, - control of the cylinder's travel speed, - the cylinder locks as soon as the travel speed drops below the low speed threshold, to maintain contact between the anchor plate and the sealing plate, and - Transparency welding of the sealing plate to the anchoring plate.

[0044] The locking of the cylinder corresponds to a stop of the extension of its extension rod, the latter being held fixed relative to the hollow tube in which it has slid.

[0045] The invention further relates to a method for welding a sealing plate of a tank intended to contain liquefied gas to an anchor plate, using the welding system according to the invention, wherein the clamping means comprise a pusher having a bearing surface defining a plane intended to come parallel to a weld zone, and a jack whose head is fixed to the pusher, and wherein the control means comprise means for stopping the clamping means coupled to means for detecting that a variation in a force exerted on the pusher exceeds a high threshold for force variation, the welding system comprising a force sensor, the welding process comprising steps of: - positioning of the support surface above the sealing plate and the anchoring plate, - actuation of the cylinder, - control of an output signal from the force sensor, - the cylinder locks as soon as a variation in the output signal exceeds the upper threshold for force variation, to maintain contact between the anchor plate and the sealing plate, and - Transparency welding of the sealing plate to the anchoring plate.

[0046] The invention also relates to a method for welding a sealing plate of a tank intended to contain liquefied gas to an anchor plate, using the A welding system according to the invention, wherein the clamping means comprise a pusher having a bearing surface defining a plane intended to come parallel to a weld zone, and a cylinder whose head is fixed to the pusher, and wherein the control means comprise means for stopping the clamping means coupled to means for detecting a variation in a metal thickness measurement, the welding system comprising a means for measuring a metal thickness in contact with the pusher, the welding process comprising steps of: - Positioning of the support surface above the sealing plate and the anchoring plate, - Actuation of the cylinder, - control of an output signal from the measuring device, - locking of the cylinder as soon as a variation in the output signal is detected, to maintain contact between the anchor plate and the sealing plate, and - transparent welding of the sealing plate to the anchor plate.

[0047] A variation in the output signal is detected when this variation clearly stands out from the variations related to measurement noise.

[0048] When the pusher includes at least one roller, or a shim on which the welding tool is able to slide parallel to the plane, the welding step of the processes according to the invention preferably includes a step of moving the roller on the sealing plate, or a step of sliding the welding tool on the shim.

[0049] Furthermore, in each of the welding processes according to the invention, when the welding system comprises a frame having at least one rail and a sliding carriage mounted on the rail, with the welding device attached to the carriage, the positioning step is, for example, preceded by a step of fixing the frame to the sealing plate and then by a step of programming the carriage capable of moving it successively over several welding zones, and of activating the subsequent steps of the welding process as soon as one of the welding zones is reached. Of course, between each repetition of the steps of one of the welding processes according to the invention, these include a step of deactivating the clamping means, for example, the cylinder, which allows the welding device to be moved to the next welding zone without deforming the sealing plate.

[0050] The program resulting from the programming step includes instructions which, when executed on a processor, activate actuators of the welding system according to the invention, in particular the cylinder, a motor enabling the movement of the carriage, and / or commands of these actuators such as a locking or deactivation command of the cylinder.

[0051] The welding processes according to the invention have advantages similar to those of the welding system according to the invention.

[0052] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0053] [Fig-1] represents, viewed from above, a portion of a wall of a tank intended for containing liquefied gas, this portion being under construction and comprising a sealing plate on which welds are visible allowing its attachment to anchoring plates underlying the sealing plate,

[0054] [Fig.2] represents, according to a first embodiment of the invention, a system welding according to the invention, comprising in particular plating means equipped with a roller, and a welding tool,

[0055] [Fig.3] represents in perspective the welding system of the [Fig.2] operating on a sealing plate shown in transparency above boxes of a primary insulation layer of the tank wall mentioned in relation to [Fig.1],

[0056] [Fig.4] represents in perspective a pusher in an alternative mode to the roller of the [Fig.2], suitable for use by the welding system of [Fig.2],

[0057] [Fig.5] represents in perspective, according to a second embodiment of the invention, a welding system according to the invention, in which clamping means comprise a wedge, along which a welding tool of the welding system is able to slide,

[0058] [Fig.6] represents in perspective, according to a third embodiment of the invention, a welding system according to the invention, in which clamping means comprise a U-shaped wedge, between the arms of which a welding tool of the welding system is able to slide,

[0059] [Fig.7] represents, top view, the wedge of the clamping means of [Fig.6],

[0060] [Fig.8] represents different states as a function of time of the welding system of the [Fig. 5] or [Fig. 6], during the welding of a sealing plate onto an anchor plate, in an embodiment of a welding process according to the invention,

[0061] [Fig. 9] represents in perspective, according to a fourth embodiment of the invention, a welding system according to the invention, comprising a frame-shaped chassis, equipped with a rail on which the welding system of [Fig.2] is able to move, the chassis being shown fixed on a rectangle of waves of the sealing plate of [Fig.1],

[0062] [Fig. 10] represents, viewed from above, according to a fifth embodiment of the invention, a welding system according to the invention, comprising a rail on which a trolley is able to travel, two welding systems conforming to the first embodiment of the invention being fixed on the trolley on either side of the rail,

[0063] [Fig. 11] shows two views of a hydraulic suction cup that can be used as a means of fixing the rail of the [Fig. 10],

[0064] [Fig. 12] represents, viewed from above, according to a sixth embodiment of the invention, a welding system according to the invention, comprising a frame equipped with a removable rail on which the welding system of [Fig. 2] is able to move.

[0065] [Fig. 13] represents welding process steps according to the invention, in several embodiments of the invention.

[0066] Figure 1 illustrates a portion of a tank wall intended to contain liquefied gas, i.e., a cryogenic liquid such as liquid natural gas or liquid hydrogen, at very low temperatures, for example -163°C (degrees Celsius) for liquid natural gas. Such a tank is intended to contain at least several thousand cubic meters of liquefied gas. Its walls are sealed and insulated.

[0067] The portion of the tank wall shown [Fig. 1] includes, in particular:

[0068] - a secondary insulation layer, formed for example of filled wooden boxes insulating foam,

[0069] - a secondary sealing membrane, formed of corrugated sheet metal plates,

[0070] - a primary insulation layer, formed of wooden boxes 72 filled for example reinforced polyurethane foam, and

[0071] - a primary sealing membrane, formed of welded sealing plates 1 between them so as to line the inside of the tank.

[0072] Anchor plates 21, 22 are arranged in a grid pattern across the surface of the primary insulation layer and are fixed to the boxes 72 by rivets. These anchor plates 21, 22 allow the sealing plates 1 to be fixed by through-welding to the anchor plates 21, 22. Other anchor plates (for example, anchor plate 24 [Fig. 3]) are smaller and can be arranged diagonally on some of the boxes.

[0073] The portion of the tank shown in [Fig.1] extends mainly along a first axis Al and a second axis A2 orthogonal to the first axis Al, and in thickness along a third axis A3 orthogonal to the first and second axes Al, A2. The portion of the tank can be horizontal and form part of a lower or upper wall of the tank, or be vertical and form part of a side wall of the tank.

[0074] The sealing plates 1 are, for example, each approximately three meters long and one meter wide, and are lap-welded to each other along their edges. They also have corrugations forming a grid on the primary sealing membrane.

[0075] In particular, they comprise large waves 12 extending along the direction of the first axis A1, and small waves 14 extending along the direction of the second axis A2. The large waves 12 are wider than the small waves 14 which connect the large waves 12 between each other. These waves 12, 14 draw wave rectangles of which two adjacent sides contain a small wave 14 and a portion of a large wave 12.

[0076] One of the sealing plates 1, shown in full in [Fig. 1], extends in the direction of the first axis A1 from one of its ends 17 to a second of its ends 19, these ends 17, 19 being edges of the sealing plate 1 parallel to the second axis A2. This sealing plate 1 further extends in the direction of the second axis A2 from a third of its ends 16 to a fourth of its ends 18, these ends 16, 18 being edges of the sealing plate 1 parallel to the first axis A1.

[0077] The sealing plate 1 is welded along the direction of the first axis Al by first weld lines 31 formed in wave rectangles on a peripheral portion of the sealing plate 1, these wave rectangles covering first anchor plates 21 oriented along the first axis Al, of length 100mm and width 70mm, in this example of use of the invention.

[0078] The sealing plate 1 is welded along the direction of the second axis A2 by second weld lines 32 formed in the corrugations of the sealing plate 1 covering second anchoring plates 22 oriented along the second axis A2, 100 mm long and 70 mm wide, in this example of use of the invention. These second anchoring plates 22 are arranged under the sealing plate 1 every three corrugations. The sealing plate 1 is thus welded along the second axis A2 onto second anchoring plates 22 regularly distributed along the first axis AL

[0079] The second anchor plates 22 partially cover the first anchor plates 21 under three wave rectangles in which the sealing plate 1 has four third weld lines 34 oblique to the directions of the first and second axes A1, A2. It should be noted that these oblique weld lines 34 are feasible with a welding system presented later in relation to [Fig. 9], but that when the weld lines 31, 32 are made with other welding systems presented later in relation to Figures 10 and 12, the weld lines made at the crossings of the anchor plates 21 and 22 are in the shape of an L corresponding to a half weld line 31 adjacent to a half weld line 32 (as seen in Figures 10 and 12).

[0080] The first, second and third weld lines 31, 32, 34 correspond to welds of the sealing plate 1 made by transparency on a first or second anchor plate 21, 22. These weld lines 31, 32, 34 are made on predetermined weld areas, corresponding in particular to portions of anchor plates 21, 22 without rivets.

[0081] Of course, the invention is not limited to this particular wall composition of tank, the invention being applicable to different shapes and sizes of sealing plates, which may not contain corrugations. Furthermore, the invention is applicable to fixing the sealing plates by spot welds and not only by weld lines. The locations of the weld areas are of course not limited to those in the example in [Fig. 1].

[0082] Fig. 2 shows a SI welding system in a first embodiment of the invention, allowing the weld lines 31, 32, 34 of the sealing plate 1 to be made on the anchor plates 21, 22 by transparency.

[0083] The welding system SI includes a transparent welding tool 5, which is in this case a plasma welding torch. When positioned on the sealing plate 1, it allows the sealing plate to be welded to one of the anchoring plates 21, 22. For example, the sealing plate has a thickness of approximately 1.2 mm, and the anchoring plates have a thickness of approximately 2 mm. The welding tool 5 is fixed by a mounting flange 47 to an extension rod of a cylinder 45 arranged parallel to the welding tool 5. The cylinder 45 has an electric motor 44 connected to an outer tube 46 of the cylinder in which the cylinder's extension rod is mounted. A linear potentiometer 6 integrated into the cylinder allows the displacement of the extension rod relative to the outer tube 46 to be measured.

[0084] The end of the extension rod is connected to a pusher. More specifically, the end of the extension rod is connected to a roller, by means of a U-shaped bracket in which the axle of the steel roller 48 is rotatably mounted. Finally, a cooling device 42 is formed in the vicinity of the pusher, here by surrounding the extension rod just above the attachment area, so as to cool the roller 48 when the welding tool 5 is in operation. Since the extension rod and the bracket are themselves made of steel, they are capable of conducting the cold produced by the cooling device 42 to the roller 48. Of course, materials other than steel can be used for the roller and / or the aforementioned components of the cylinder if they have sufficient mechanical and thermal resistance to implement the invention.Furthermore, the cooling device may take a different form than a cooling jacket cylindrically surrounding the extension rod of the cylinder and, for example, include a tab forming a thermal barrier and intended to be interposed between the roller 48 and the welding tool 5.

[0085] The fixing flange 47 of the welding tool 5 to the cylinder 45 allows a first distance dl to be fixed between the head 52 of the welding tool 5 and the roller 48, measured parallel to a plane P coplanar to the surface of a weld zone on the sealing plate P, the roller 48 being positioned on this surface which defines a bearing surface of the roller 48, and the axis X of the extension rod of the cylinder 45 being orthogonal to the plane P.

[0086] Similarly, the mounting flange 47 of the welding tool 5 to the cylinder 45 allows a second distance d2 to be set between the end of the head 52 of the welding tool and the plane P, for example at 2 mm, which ensures good weld quality through transparency. Of course, this value must be adjusted according to the welding tool used and the plates to be welded.

[0087] When the pusher, here the roller 48, is positioned on the weld area just before welding the sealing plate 1, and the cylinder 45 is orthogonal to the surface to be welded, the cylinder 45 is able to exert a force F on the weld area which increases until the sealing plate 1 makes contact with the underlying anchor plate 21 or 22, detected by the potentiometer 6 which measures a sudden decrease in the extension of the extension rod of the cylinder 45. Once the contact is detected, the welding tool 5 is activated and the welding system SI is moved on the sealing plate 1 by means of the roller 48 so as to form a weld bead 31, 32 or 34.

[0088] The sensor associated with the cylinder, here the potentiometer 6, is alternatively different and measures other data, which also allow for the observation of the increase in the return force exerted on the cylinder rod 45. The sensor is alternatively a force sensor, such as a strain gauge force sensor, or a thickness measurement device using, for example, ultrasound. The position of the sensor on the cylinder, or more generally within the welding system, depends, of course, on the type of sensor used. In particular, the ultrasonic thickness measurement device is not necessarily physically linked to the cylinder; it is sufficient that it be positioned near the plunger.

[0089] The potentiometer 6 is therefore part of the control means of the welding system SI, these means comprising a signal processing element for the output of the potentiometer, which can be located on the cylinder or at a distance from it.

[0090] It is understood that thanks to the attachment of the welding tool 5 to the extension rod of the cylinder 45, and thanks to the implementation of the control means which make it possible to ensure that adequate pressure is exerted for the pressing of the sealing plate on the associated anchor plate, the welding tool 5 comes to position itself at the correct distance from the sealing plate 1 to perform a transparent weld, when the cylinder presses the sealing plate 1 onto a welding area.

[0091] The roller 48 and the jack 45 form means of clamping 4 of the sealing plate on the anchoring plate 21 or 22.

[0092] Figure 3 illustrates the transparent welding of the sealing plate 1 onto an anchor plate 23 fixed to a corner of a box 72, using the SL welding system. In order to visualize the height differences between the boxes 72 under the sealing plate 1, the latter is made transparent in Figure 3 while being represented by a few raised lines 15. The roller 48 allows easy access to this corner of the sealing plate 1 and to make a weld bead 33 by transparency on the anchor plate 23, between the rivets fixing it to the box 72. It should be noted that by using a welding tool which is a laser welding device, the optics can be offset which allows the roller 48 to be pressed as close as possible to the weld 33 to be made.

[0093] It is clear from [Fig. 3] that the sealing plate 1 must be deformed more to fit it onto the anchor plate 23, in order to make the weld bead 33, than if this bead were to be made on an anchor plate 24 of a caisson 72 located higher than the one to which the anchor plate 23 is fixed. This means that the force F exerted by the jack 45 must be greater. As a guide, the manufacturing standards for the tank are set so that this force F must not exceed 60 kg, that is to say, a maximum threshold for the difference in height between the caissons 72 is established.

[0094] Figure 4 shows an alternative pusher 48b to the roller 48 for the welding system SI, which can be fixed to the attachment of the extension rod of the cylinder 45. This reciprocating plunger 48b includes a roller fixed, for example, by its axle to the attachment of the cylinder extension rod. This roller forms a front wheel 482 of the reciprocating plunger 48b, its axle also passing through the ends of parallel flanks 480 and extending orthogonally to the X-axis of the cylinder extension rod. The opposite ends of the flanks 480 each have a rear wheel 484 on the side opposite the front wheel 482 with respect to the corresponding flank 480.

[0095] The front wheels 482 and rear wheels 484 are intended to roll over a weld area without rolling over the weld bead being formed, when using the SL welding system. For this purpose, the head 52 of the welding tool 5 is, for example, positioned on the upper walls of the sides 480, in a median area 488 located between the rear wheels 484 and the front wheel 482.

[0096] According to a second embodiment of the invention shown [Fig.5], a welding system S2 according to the invention comprises elements similar to those of the welding system SI of the first embodiment and referenced in the same way, in particular the welding tool 5, the elements of the cylinder 45 and the potentiometer 6.

[0097] Unlike the SI welding system of the first embodiment, the pusher of the clamping means of the S2 welding system of the second embodiment is formed of a wedge 43, comprising:

[0098] - a long, thin plate intended to come into contact with the sealing plate 1,

[0099] - a guide 432 in the form of a circular section rail fixed to two supports making projection of the long plate on either side of the welding tool 5 fixed to the cylinder 45,

[0100] - a ball bushing mounted sliding on the guide 432,

[0101] - a fixing bracket 430, a first part of which is fixed to the socket balls, and a second part of which, orthogonal to the first part, is fixed to the end of the cylinder's extension rod, here by a through screw, and

[0102] - a return spring 434, capable of being compressed between the mounting tab 430 and a wall of one of the supports, as represented in an initial state S2(t0) of the welding system S2, shown [Fig.8].

[0103] According to a third embodiment of the invention shown [Fig.6], a welding system S3 according to the invention is also similar to the welding system SI of the first embodiment except that the pusher fixed to the cylinder 45 is a wedge 43b, as in the second embodiment of the invention, but comprising two guides 432b of circular sections.

[0104] More specifically, the 43b wedge of the S3 welding system, also shown [Fig.7], comprises:

[0105] - a U-shaped plate intended to come into contact with the sealing plate 1,

[0106] - the two guides 432b in the form of rails with circular cross-sections, each fixed to two supports projecting from each arm of the U-shaped plate, on either side of the welding tool 5 fixed to the cylinder 45, the welding tool 5 being positioned between the two arms of the U-shaped plate,

[0107] - two ball bushings, each mounted to slide on one of the 432b guides,

[0108] - a 430b mounting bracket, a first part of which is fixed to the sockets balls, and a second part of which, orthogonal to the first part, is fixed to the end of the cylinder's extension rod, here by a through screw, and

[0109] - two return springs 434b, capable of being compressed between the mounting tab 430b and the supports, in an initial state of the S2 welding system.

[0110] As seen in Figures 5, 6 and 8, the S2 and S3 welding systems with wedge allow a radiation zone 54 created by the head 52 of the welding tool 5 to follow the long or U-shaped plate of the S2 or S3 welding system respectively, when a weld bead 31, 32, 33 or 34 is made on the sealing plate 1. The pusher remains fixed during the movement of the welding head, which ensures uniform plating of the sealing plate on the anchor plate throughout the entire duration of the weld bead making.

[0111] Fig. 8 illustrates the production of a weld bead with the S2 welding system of the second embodiment, this production being transposable to the production of a weld bead with the S3 welding system of the third embodiment.

[0112] During the initial state S2(t0) of the welding system S2, at a time t0, the control means of the welding system S2 detect contact between the sealing plate 1 and an anchoring plate 22, and stop the deployment of the extension rod of the cylinder 45, thus fixing the value of the clamping force F between the sealing plate 1 and an anchoring plate 22. During this initial state S2(t0), the return spring 434 is compressed between one of the guide 432 supports and the sleeve which allows the cylinder 45 and the welding tool 5 to slide along the wedge 43.

[0113] Then a weld bead is made by activating the welding tool 5 and sliding the cylinder 45 and the welding tool 5 along the block 43 by means of the ball bearing slide, in a direction D, parallel to the guide 432, the clamping force F being kept constant. The movement of the cylinder 45 and the welding tool 5 is, for example, ensured by a carriage on which the cylinder 45 and the welding tool 5 are mounted. The ball bearing sleeve completes its travel along the guide 432 at an instant t1, the return spring 434 being stretched towards a second of the supports, and the welding system S2 being in a state S2(t1).

[0114] Finally, at a time t2 following time t1, at the end of the welding operation, the cylinder 45 is unlocked and its extension rod retracted, so as to cancel the clamping force F. At the corresponding state S2(t2) of the welding system S2, the wedge 43 is detached from the sealing plate 1, and the welding system S2 is ready to be reused on another weld area.

[0115] As previously mentioned, the use of a shim 43, 43b rather than a roller ensures homogeneous plating along the weld line, and less deterioration of the surface of the sealing plate 1.

[0116] In relation to [Fig.9], a fourth embodiment of the invention is now described a welding system S4 incorporating the elements of the welding system SI of the first embodiment of the invention.

[0117] The S4 welding system comprises a frame-shaped chassis 8, which is fixed to nodes of a wave rectangle of the sealing plate 1. For this purpose, it has at each of the corners of its lower face (i.e. facing the sealing plate 1), clamps 84 each having two jaws sliding on small waves 14 located on either side of a large wave 12, and clamping this large wave 12. Each clamp 84 also has a locking member 840 allowing it to be held clamped on the node of the wave rectangle corresponding to the intersection of the large wave 12 and the small waves 14 on which it is installed.

[0118] Handles 82, each installed on two opposite sides of the chassis 8, allow the S4 welding system to be easily transported.

[0119] The frame 8 has on its upper face (i.e., opposite the sealing plate 1) a rail 86 defining its inner perimeter, and a carriage 9 mounted to slide on the rail 86. The rail 86 forms a frame parallel to the plane P, coplanar or substantially coplanar with the weld areas in the wave rectangle. The rail 86 is in fact positioned as parallel as possible to the weld areas, in a manner substantially coplanar with the principal elongation plane of the sealing plate 1, i.e., coplanar to within 10 degrees.

[0120] The plating means 4, equipped with its sensor 6 forming part of the control means, and the welding tool 5, fixed to the plating means 4, are fixed to an arm 92 of the carriage 9, extending towards the inside of the chassis 8, so that the axis X of the extension rod of the cylinder 45 is orthogonal to the plane P. The position of the arm 92 is adjustable so as to be able to advance more or less the plating means 4 and the welding tool 5 towards the center of the wave rectangle.

[0121] It is understood that, thanks to the attachment of the welding tool 5 to the extension rod of the cylinder 45, and thanks to the implementation of the control means which ensure that adequate pressure is exerted for the sealing plate to be pressed against the associated anchor plate, the welding tool 5 is positioned at the correct distance from the sealing plate 1 to perform a through weld when the cylinder presses the sealing plate 1 against a weld area. Furthermore, the movement of the welding tool 5 parallel to plane P to perform a weld bead is achieved by moving the carriage 9 along the rail 86, this movement being followed by the roller 48 over the distance necessary to perform this weld bead.

[0122] Finally, as can be seen in [Fig.8], when the carriage 9 travels around the perimeter of the rail 86, it allows the welding tool 5 to form weld lines 31 or 32 when it is positioned on a median area on one side of the rail 86, or weld lines 34 when it is positioned on oblique corners 862 of the rail 86.

[0123] This fourth embodiment of the invention is particularly suited to targeted repairs on scattered wave rectangles of the tank sealing membrane.

[0124] As an alternative embodiment of this fourth configuration, the roller 48 is replaced by the shim 43 or 43b. In this case, the movement of the welding tool 5 parallel to plane P to perform a weld bead is achieved by moving the carriage 9 along the rail 86. This movement is followed by the bushing(s) of the shim 43, 43b, which is pressed against the sealing plate 1, over the distance necessary to perform this weld bead. Once the weld bead is completed, the upward movement of the extension rod relative to plane P disengages the shim 43, 43b, which returns the bushing(s) to their initial position on the shim 43, 43b by the effect of the return spring(s) 434, 434b.

[0125] According to a fifth embodiment of the invention shown [Fig.10], a welding system S5 according to the invention also includes a rail 86b on which a sliding carriage 9b is mounted, this rail 86b being straight and of greater length than the main dimension of the sealing plate 1.

[0126] In the example of use of the invention shown [Fig. 10], the rail 86b is arranged parallel to the first axis Al on a line of wave rectangles of the plate sealing 1 located above first anchor plates 21.

[0127] A first end of the rail 86b is suitable for being fixed on a box 72, beyond the edge 19 of the sealing plate 1 and outside of it, by a foot 83 screwed to the box 72.

[0128] A second end of the rail 86b is suitable for being fixed beyond the edge 17 of the sealing plate 1 and outside of it, on another sealing plate by means of a suction cup fixing 84b, described later in relation to [Fig.1 1].

[0129] The assembly formed by the foot 83 and the suction cup fixing 84b forms a chassis 8b on which the rail 86b is mounted.

[0130] Two template tabs 80 sliding together on the rail 86b are spaced apart by the length of the sealing plate 1 in the direction of the axis Al. They are therefore adapted to the template of the sealing plate 1. They allow the rail 86b to be positioned optimally above the sealing plate 1 to make weld lines 31 parallel to the first axis Al.

[0131] For this purpose, two SI welding systems, conforming to the first embodiment of the invention, are fixed on either side of the carriage 9b, such that the axis X of the extension rod of the cylinder 45 is orthogonal to the plane P of the welding areas on the sealing plate 1.

[0132] The production of the weld seams 31 is carried out in a similar manner to that of the weld seams 31 with the S4 welding system of the fourth embodiment of the invention. However, in this fifth embodiment of the invention, the carriage 9b is controlled by programming means 90 attached to the carriage 9b and comprising a human-machine interface. These programming means 90 include a computer and are capable of programming the movement of the carriage 9b to perform several weld seams 31 on either side of the rail 86b along the length of the sealing plate 1. The instructions of the corresponding program therefore include means for activating a motor for the carriage 9b, means for activating and stopping the cylinder 45, coupled with means for detecting contact between the sealing plate 1 and the first underlying anchor plate 21, and means for activating and stopping the welding tool 5.The instructions may also include means of adapting the speed of the carriage 9b according to the activated or off state of the welding tool 5.

[0133] It should be noted that in an alternative embodiment of the invention, the template legs 80 are fixed, which makes it possible not to modify the programming of the carriage 9b to process the welding areas along the same axis Al or A2 on different sealing plates 1.

[0134] Furthermore, several chassis 8b with their rails 86b can be arranged one after the other so as to allow the carriage 9b to perform welds on two adjacent sealing plates without having to move the entire S5 welding system.

[0135] In another use of the invention not shown, the rail 86b is arranged parallel to the second axis A2 on a line of wave rectangles of the sealing plate 1 located above second anchor plates 22. In this other use, the welding system S5 is used to perform the weld seams 32 of the sealing plate 1 on these second anchor plates 22, in a manner similar to the execution of the weld seams 31 on the first anchor plates 21.

[0136] It should be noted that in this fifth embodiment of the invention, the oblique weld lines 34 are each replaced by a half weld line 31 extended by a half weld line 32 so as to follow a corner of the wave rectangle covering an intersection of anchor plates 21 and 22. Thus the welding system S5 is sufficient to treat all the weld areas of the sealing plate 1.

[0137] Figure 11 shows in more detail a suction cup mounting 84b of the chassis 8b. This mounting includes a suction cup 846 and a vacuum pump 841 having a compressed air inlet 844 for activating and deactivating the suction cup 846. The vacuum pump 841 creates a pressure differential enabling the suction cup 846 to hold a heavy load such as the welding system S5. A ball joint 848 allows the rail 86b to rotate around the suction cup mounting 84b as long as the foot 83 is not screwed in.

[0138] The vacuum pump 841 and the ball joint 848, fixed movably in rotation to the suction cup 846, clamp by an elastic connection the edges of a slot arranged in a bracket 843 and in which they can slide in a direction substantially parallel to the gripping surface of the suction cup 846. The bracket 843 is fixed by a hinge 845 to a support 847 of the rail 86b, the hinge 845 making a pivot connection with an axis orthogonal to the main extension axis of the slot (according to its length) and substantially parallel to the gripping surface of the suction cup 846.

[0139] Gas springs 842 coupled with compressed air inlets 849 to block the movement of their pistons, allow the support 847 to be rotated relative to the bracket 843 around the hinge 845. For this purpose, each of the gas springs 842 has at one of its ends, fixed on its body, an eye mounted movably in rotation in a rod fixed to one end of the bracket 843, distal to the support 847, and at the other of its ends, fixed to the piston of the gas spring 842, an eye mounted movably in rotation in a rod fixed on the support 847.

[0140] It is understood that this suction cup fixing 84b allows the distance of the rail 86b relative to the position of the suction cup 846 to be fixed by means of the slot arranged in the bracket 843. In addition, the system of jacks 842 coupled to the bracket 843 and the support 847, which are fixed to each other by the hinge 845, allows the rail 86b to adapt to the angular and height differences between the gripping surface of the suction cup 846 by in relation to a welding zone, and to maintain the rail 86b parallel to the plane P of the welding zone and at the same height as it, even when the sealing plate 1 is pressed onto an anchor plate 21, 22 or 23 by the jack 45. According to a sixth embodiment of the invention shown [Fig. 12], a welding system S6 according to the invention comprises a frame 8c equipped with a removable rail 86c on which a carriage 9b, identical to that of the fifth embodiment of the invention and referenced in the same way, is slidably mounted. As in the fifth embodiment of the invention, two welding systems SI conforming to the first embodiment of the invention are fixed on either side of the carriage 9b, such that the axis X of the extension rod of the cylinder 45 is orthogonal to the plane P of the weld areas on the sealing plate 1. Programming means 90 for the carriage 9b, identical to those of the fifth embodiment of the invention, are fixed to the carriage 9b.

[0141] Unlike the fifth embodiment, however, the chassis 8c comprises a frame. Suction cup fixings 84b are fixed to the underside of the frame so as to allow the chassis 8c to be fixed on either side of the sealing plate 1, on boxes 72 or on other sealing plates 1. In addition, handles 82c are fixed to two opposite bars of the frame for handling the chassis 8c.

[0142] The frame is approximately one meter by one meter, so as to encompass one-third of the welding areas of the sealing plate 1. In the example of use of [Fig. 12], the frame of the chassis 8c encompasses 8 welding areas aligned along the first axis A1 and 8 welding areas aligned along the second axis A2. These sixteen welding areas are suitable for processing by the welding system S6 without moving the chassis 8c, thanks to the removable rail 86c.

[0143] To this end, a first circular guide rail 85 is fixed to the frame by joining two opposite corners thereof. One end of the removable rail 86c has a slide adapted to slide on this first circular guide rail 85, the center of curvature of which is close to a corner of the frame near which a second circular guide rail 87, shorter than the first guide rail 85, is fixed. The second circular guide rail 87 is more precisely fixed to the chassis 8c on the outside of the frame. The other end of the removable rail 86c has a slide adapted to slide on this second circular guide rail 87. In other words, the circular arc guide rails 85, 87 are arranged relative to each other in such a way that the distance between the two ends of the removable rail 86c is constant during the travel of the rail 86c from one end to the other of each guide rail 85, 87.

[0144] Thus the removable rail 86c is able to move from a position aligned along the first axis Al, which allows the welding system S6 to perform all the weld lines 31 on the weld areas aligned along this first axis and encompassed within the frame, to a position aligned along the second axis A2, which allows the S6 welding system to perform all weld lines 32 on the weld areas aligned along this second axis and encompassed within the frame.

[0145] It should be noted that, as in the fifth embodiment of the invention, the oblique weld lines 34 are each replaced by a half weld line 31 extended by a half weld line 32 so as to follow a corner of the wave rectangle covering an intersection of anchor plates 21 and 22. Thus the S6 welding system is sufficient to treat all the weld areas of the sealing plate 1.

[0146] The S6 welding system therefore makes it possible to treat all the welding areas of a sealing plate 1 with three positioning steps of the chassis 8c on three separate portions of the sealing plate 1, whereas four positioning steps of the chassis 8b are required with the S5 welding system of the fifth embodiment of the invention.

[0147] Template legs are optionally attached to the chassis 8c so as not to have to modify the programming of the carriage 9b from one portion of sealing plate 1 to be treated to another.

[0148] A welding process 100a of the sealing plate 1 onto one of the anchor plates 21, 22 or 23 is now described in relation to [Fig. 13]. This welding process 100a uses one of the welding systems S4, S5 or S6.

[0149] A first step 102 of the welding process 100a is the fixing of the frame 8, 8b or 8c so as to position the rail 86, 86b or 86c parallel to at least one weld area to be treated, i.e. parallel to plane P, and parallel to at least one direction of one of the axes A1, A2 on at least a portion of the rail 86, 86b, 86c. This fixing step 102 uses the clamps 84, or one or more suction cups 84b and / or a foot 83 which is screwed into a housing 72, as well as possibly jig tabs when the frame 8b, 8c is equipped with them, depending on the welding system S4, S5 or S6 used.

[0150] A second step 104 of the welding process 100a is optionally the programming of the carriage 9b, by giving it instructions capable of moving it successively over several welding areas, and of activating the subsequent steps of the welding process 100a as soon as one of the welding areas is reached. This second step 104 can take place before the first positioning step 102 if jig legs are used.

[0151] A third step 106 of the welding process 100a is the positioning of the pusher bearing surface, and in particular of the roller 48, above a weld area. During this step, the welding tool 5 and the cylinder 45 are positioned, using the carriage 9, 9b, above the weld area so as to subsequently allow the formation of a weld bead on the weld area. This positioning step 106 is possibly common to step 102 of fixing the chassis 8, 8b, 8c.

[0152] A fourth step 108 of the welding process 100a, after the positioning step 106, is the actuation of the cylinder 45, so as to press the sealing plate 1 at the level of the weld area progressively against the underlying anchor plate 21, 22 or 23.

[0153] The next step 110a is the control of the cylinder's travel speed V, using the output signal from potentiometer 6, processed, for example, by an analog-to-digital converter circuit connected to a computer input, whether the computer is mounted on the welding system or remotely connected to the converter circuit via a wired or wireless link. The computer deduces the cylinder's travel speed V from the output signal processed by the converter circuit.

[0154] The movement of the cylinder, i.e., the bringing of the sealing plate towards the anchoring plate, continues as long as the movement speed remains substantially the same, reflecting that the sealing plate is not yet pressed against the anchoring plate. As soon as this movement speed V falls below a low speed threshold Sb, set for example at 1 mm / s, it is assumed that the sealing plate is sufficiently pressed against the anchoring plate to allow the through-welding operation to be carried out, and the process proceeds (branch Y) to the next step 114a of locking the cylinder 45. Otherwise, (branch N) the extension rod of the cylinder 45 continues to be deployed.

[0155] Step 114a of locking the cylinder 45 corresponds to stopping the deployment of the extension rod of the cylinder 45. When the cylinder 45 is locked, it is thus ensured that the sealing plate 1 is in contact with the anchor plate 21, 22 or 23 at the weld area, since adjusting the clamping force to obtain this contact, without it being necessary to apply too much force, makes it possible to avoid a lever effect which would tend to move the two plates away from each other as one moves away from the bearing surface.

[0156] The next step 116a is then the transparent welding of the sealing plate 1 to the anchoring plate 21, 22 or 23. This step 116a can consist of making a single spot weld, or a weld bead 31, 32, 33 or 34, by moving the carriage 9, 9b, causing the roller 48 to move upstream of the welding tool 5.

[0157] We now describe, still in relation to [Fig. 13], a welding process 100b of the sealing plate 1 on one of the anchor plates 21, 22 or 23. This welding process 100b uses a variant of one of the welding systems S4, S5 or S6, in which, instead of being equipped with a potentiometer 6, the welding system S4, S5 or S6 is equipped with a force sensor, disposed for example at the axle of the roller 48.

[0158] As shown [Fig. 13], the 100b welding process includes first steps 102 to 108 identical to those of the welding process 100a previously described.

[0159] Unlike welding process 100a, in welding process 100b, the actuation step 108 of the cylinder 45 is followed by a step 110b of checking an output signal from the force sensor. This output signal is again processed, for example, by an analog-to-digital conversion circuit connected to an input of the computer attached to the carriage 9b, or to a remote computer.

[0160] The computer deduces from this output signal processed by the conversion circuit, a variation AN of the reaction force exerted by the sealing plate 1 on the roller 48. As soon as this variation AN exceeds a high threshold Sh of force variation, fixed for example at 70 N / mm, then we move (branch Y) to the next step 114b of locking the cylinder 45, otherwise (branch N) we continue the deployment of the extension rod of the cylinder 45.

[0161] Step 114b of locking the cylinder 45 corresponds to stopping the deployment of the extension rod of the cylinder 45. When the cylinder 45 is locked, it is certain that the sealing plate 1 is in contact with the anchor plate 21, 22 or 23 at the weld area.

[0162] The next step 116b is then the transparent welding of the sealing plate 1 to the anchoring plate 21, 22 or 23. This step 116b can consist of making a single weld point, or a weld bead 31, 32, 33 or 34, by moving the carriage 9, 9b, causing the roller 48 to move upstream of the welding tool 5.

[0163] As an alternative to these welding processes 100a, 100b, when the system S4, S5, or S6 uses an ultrasonic thickness gauge to measure the metal thickness under the roller 48, a welding process for the sealing plate 1 to an underlying anchor plate 21, 22, or 23 includes initial steps of securing the frame 8, 8b, or 8c, optionally programming the carriage 9b, positioning the roller 48 above a weld area, and actuating the cylinder 45, identical to those of the processes 100a and 100b described above. In this alternative welding process, these initial steps are followed by a step of monitoring an output signal from the ultrasonic thickness gauge, processed by an analog-to-digital converter circuit, connected to a computer attached to the carriage 9b or located remotely from the carriage 9b.

[0164] As soon as a variation in metal thickness under the roller 48 is detected, the cylinder 45 is locked, since this means that contact between the sealing plate 1 and the underlying anchor plate 21, 22, 23, at the weld zone, has been achieved. Then, in this variant of the welding process, the through-weld is carried out, similarly to steps 116a, 116b already described.

[0165] Of course, the invention is usable without the chassis 8, 8b or 8c. A welding method corresponding according to the invention does not then include steps 102 of fixing the chassis and 104 of programming the trolley 9b, but includes the following steps, identical to those of the welding processes previously described depending on the control means used to detect contact between the sealing plate 1 and the underlying anchor plate 21, 22 or 23 at the level of the welding area.

[0166] Finally, the welding processes described are adaptable to the use of the S2 welding system, using a wedge 43 or 43b rather than a roller 48. Another variant consists of using a programmable carriage 9b with the chassis 8 of the fourth embodiment of the invention.

[0167] The invention is of course not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different variants or different embodiments of the invention can be combined to carry out the invention, provided that these variants or embodiments are not incompatible with each other.

Claims

Demands

1. A welding system (SI, S2, S3, S4, S5, S6) for a sealing plate (1) of a tank intended to contain liquefied gas, to an anchoring plate (21, 22, 23), the sealing plate (1) and the anchoring plate (21, 22, 23) being metallic, the welding system (SI, S2, S3, S4, S5, S6) comprising a welding device including: - a through-welding tool (5) for performing at least one weld in a weld zone, - means for clamping (4) the sealing plate (1) onto the anchoring plate (21, 22, 23), and - means for monitoring a force (F) exerted by the clamping means (4) on the sealing plate (1), capable of detecting contact between the anchoring plate (21, 22, 23, 23) and the sealing plate (1).

2. Welding system (SI, S2, S3, S4, S5, S6) according to claim 1, wherein the welding tool (5) is secured to the plating means (4).

3. Welding system (SI, S2, S3, S4, S5, S6) according to claim 1 or 2, wherein the clamping means (4) comprise a pusher having a bearing surface defining a plane (P) intended to extend parallel to the weld zone, and a cylinder (45) having a head attached to the pusher.

4. Welding system (SI, S2, S3, S4, S5, S6) according to claim 3, comprising means for thermal protection of the pusher.

5. Welding system (SI, S4, S5, S6) according to claim 3 or 4, wherein the pusher comprises at least one roller (48, 482).

6. Welding system (S2, S3) according to claim 3 or 4, wherein the pusher comprises at least one shim (43, 43b) on which the welding tool (5) is able to slide parallel to the plane (P).

7. Welding system (SI, S2, S3, S4, S5, S6) according to any one of claims 3 to 6, wherein the control means (6) comprise means for stopping the clamping means (4) coupled to means for detecting that a speed (V) of the cylinder (45) is less than a low threshold (Sb) of speed, or to means for detecting that a variation (AN) of a force exerted on the pusher is greater than a high threshold (Sh) of force variation, or to means for detecting a variation of a measurement of metallic thickness.

8. Welding system (S4, S5, S6) according to any one of the claims indications 1 to 7, comprising a chassis (8, 8b, 8c) having at least one rail (86, 86b, 86c), and a sliding carriage (9, 9b) mounted on the rail (86, 86b, 86c), the welding device being fixed to the carriage (9, 9b).

9. Welding system (S4) according to claim 8, wherein the sealing plate (1) has waves (12, 14), the frame (8) has removable fastening means (84) on waves delimiting between them welding zones, the frame (8) forming a frame on which the rail (86) is disposed and whose internal periphery is adapted to allow the welding tool (5) to access the welding zones.

10. A welding system (S5, S6) according to claim 8, wherein, with the first weld zones aligned along a first axis (A1, A2) between a first end (17, 16) of the sealing plate (1) and a second end (19, 18) of the sealing plate (1), and the second weld zones aligned along a second axis (A2, A1) between a third end (16, 17) of the sealing plate (1) and a fourth end (18, 19) of the sealing plate (1), the rail (86b, 86c) is configured to allow the welding tool to process all the first weld zones when aligned along the first axis (A1, A2), the frame (8b, 8c) having removable fastening means (84b) suitable for fixing at least a portion of the frame (8b, 8c) to a support external to the plate sealing (1).

11. Welding system (S5, S6) according to claim 10, comprising two welding devices fixed to the carriage (9b) on either side of the rail (86b, 86c).

12. Welding system (S6) according to claim 10 or 11, comprising two circular arc guide members (85, 87), on each of which a separate end of the rail (86c) is slidably mounted, the guide members (85, 87) being able to move the rail (86c) from a first configuration in which the welding system (S6) is able to process all the first weld zones, to a second configuration in which the welding system (S6) is able to process second weld zones.

13. A welding method (100a) of a sealing plate (1) of a tank intended to contain liquefied gas, to an anchoring plate (21, 22, 23), using the welding system (S1, S2, S3, S4, S5, S6) according to any one of claims 1 to 12, comprising steps of: - positioning (106) of the plating means (4) above the sealing plate (1) and the anchoring plate (21, 22, 23) to be welded, - actuation (108) of the clamping means (4), - control (110a) of a force (F) exerted by the clamping means (4) on the sealing plate (1), - locking (114a) of the clamping means (4) as soon as contact between the anchor plate (21, 22, 23) and the sealing plate (1) is detected to maintain contact between the anchor plate (21, 22, 23) and the sealing plate (1), and - welding (116a) by transparency of the sealing plate (1) to the anchoring plate (21, 22, 23).

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