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

Abstract

System and method for transparent welding of a sealing plate to an anchor plate The present invention relates to a welding system (S1) of a sealing plate (15) of a tank intended to contain liquefied gas, to an anchor plate (23), the welding system (S1) comprising:- a transparent welding tool (52),- means (48) for pressing the sealing plate (15) onto the anchor plate (23), and- means for controlling a force exerted by the pressing 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 transparently welding a sealing plate to an anchor plate

[0001] The present invention relates to the field of liquid gas tanks, for example liquefied natural gas (LNG), in particular for maritime or river transport or for a land tank. More specifically, the invention relates to a system for welding a sealing membrane suitable for such a tank, and an associated welding method.

[0002] Liquid gas tanks have a capacity of several thousand cubic meters of liquid gas each, or even several tens of thousands of cubic meters of liquid gas. Liquefied gas transport ships have holds specifically designed to contain these tanks, their holds often being partitioned into several tanks. Such a tank can also be made outside a ship for land-based storage of liquid natural gas.

[0003] The gas is kept inside the tank in the liquid state, for example at -163°C (degree Celsius) for LNG, at atmospheric pressure. The tank must therefore be sealed and thermally insulated. Therefore, 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 to each other, each sealing plate being a part of the tank's sealing membrane.

[0004] The walls of the tank also 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 waterproofing membrane, called a secondary waterproofing membrane, by example in thin sheet metal,

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

[0008] The primary waterproofing membrane is fixed to the primary insulation layer by welding the waterproofing plates to anchor plates, integral with the primary insulation layer, which may in particular be riveted to the wooden boxes of the primary insulation layer. These anchor plates form a grid pattern across all the boxes but do not cover them entirely.

[0009] This welding being carried out by transparency, it is necessary, for the weld to be properly carried out, that the distance between the sealing plate and the anchor plate is less than 0.3 mm. Indeed, in transparency welding, a point of plating of the two plates is ensured against each other, which is welded on one side of these two plates only, in the vicinity of the plating point. Given the differences in height of the different boxes of the primary insulation layer, due to the authorized assembly and manufacturing tolerances, it is not possible to be certain of a good plating between the sealing plate and the anchor plate without exerting a default plating force of 60 kg force, necessary to ensure contact between the sealing plate and the anchor plate when the difference in height between these two plates corresponds to a maximum authorized height difference.

[0010] This welding process is however very time consuming 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 method which make it possible to guarantee good welding quality, and which allow automation of the welding process.

[0012] To this end, the invention proposes a system for welding 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 comprising: - a transparency welding tool intended to carry out at least one weld in a welding zone, - means for pressing the sealing plate onto the anchor plate, and - means for controlling a force exerted by the pressing means on the sealing plate, capable of detecting contact between the anchor 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 welding zone of the sealing plate to this anchor plate. Such welding zones are located for example along an edge of the sealing plate located above the anchor plate. For example, the sealing plate has between 3 and 21 welding zones along the edge, and preferably 15 welding zones along the edge when the sealing plate is 3 meters long. These welding zones are located on “zones to be welded” which are flat areas of the sealing plate, spaced apart from each other for example by about thirty centimeters when the sealing plate is wave-shaped. Each weld zone is not located above rivets allowing the anchor plate to be fixed to boxes of an underlying primary insulation layer. It is understood that a weld zone, on which a weld is made, cannot be of dimensions larger than those of an anchor plate. For example, a weld zone forms a rectangle 10 cm (centimeters) long and 5 cm wide, and the anchor plate is, for example, 100 mm (millimeters) by 70 mm in dimensions. The plating means are plated on the weld zone or adjacent to this weld zone so that the distance between the sealing plate and the anchor plate is less than 0.3 mm over this entire weld zone. Of course, these numerical data are given for information purposes only and must be adapted to the different types of tank walls and fixing of the sealing plates of these tank walls.

[0014] Thanks to the invention, contact is detected between the anchoring plate and the sealing plate in order to adapt the force exerted by the plating means and to guarantee a quality weld between the anchoring plate and the sealing plate, independently of the initial distance between the sealing plate and the anchoring plate, which depends on the differences in height between the different boxes on which the sealing plate is arranged. It should be noted that the anchoring plate is fixed to a box so as to slightly exceed the height of the box. The expected excess is, for example, 0.2 mm. As a result, once the welds have been made between the sealing plate and the underlying anchoring plate(s), the sealing plate is in contact with the boxes.

[0015] The invention further makes it possible to automate a welding process using the welding system according to the invention.

[0016] According to an optional characteristic of the invention, the plating means comprise for example a pusher comprising a bearing surface defining a plane intended to extend parallel to the welding zone, and a jack whose head is secured to the pusher. The jack is for example a hydraulic or electric jack. The head of the jack is for example an attachment zone arranged at the end of an extension rod of the jack. The extension rod of the jack is preferably arranged orthogonally to the plane defined by the bearing surface. However, it can also be inclined relative to this plane.

[0017] As explained previously, the welding zone is a portion of an area to be welded (surrounded by waves when the sealing plate has them), the bearing surface coming against a surface of the area to be welded or bearing on the surface of the area to be welded. The bearing surface defines a plane which is parallel to the area to be welded, or the plane is the same as the surface of the area to be welded.

[0018] According to an optional characteristic of the invention, the welding tool is secured to the plating means. This makes it possible to fix a first distance between a head of the welding tool and the pusher, parallel to the plane, and a second distance between the head of the welding tool and the plane, orthogonal to it. The first distance is for example between 2 mm and 20 mm, and is for example 5 mm. The second distance is for example between 1 mm and 5 mm and is for example 2 mm.

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

[0020] The purpose of setting the first distance is to ensure good plating between the sealing plate and the anchor plate just below the welding tool, and to thermally protect the pusher from the thermal radiation of the welding tool. The “flexibility” of the sealing plate means that this first distance will not be the same depending on the plating method chosen. It will be smaller when the plating means use a roller than when the plating means use a shim. This first distance is also linked to the presence or absence of thermal protection for the plating means.

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

[0022] According to an optional characteristic of the invention, the pusher comprises at least one roller. The pusher is for example formed of a single roller fixed to the head of the cylinder, or the pusher comprises a casing carrying several rollers, i.e. several wheels, the casing being fixed to the head of the cylinder. Such an embodiment of the pusher makes it possible to move the welding tool to carry out a transparency weld over several centimeters of the weld zone. In addition, such a pusher makes it possible to exert pressure on the sealing plate without damaging it. In order not to damage 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 comprises a casing supporting several wheels, said at least one roller forms a front wheel of the casing, the other wheels associated with the casing being rear wheels capable of passing on either side of the weld when the head of the welding tool, integral with the pusher, is moved.

[0023] According to an optional feature of the invention, the welding system comprises means for thermal protection of the pusher. These protection means are for example a ceramic shield or a cooling jacket. They are particularly useful when the pusher comprises a roller. They make it possible to protect the roller from the thermal radiation of the welding tool and therefore to prevent the formation of the roller, thus extending its service life. The heat shield is at least partly interposed between the pusher and the welding tool.

[0024] According to an optional characteristic of the invention, the pusher comprises at least one wedge on which the welding tool is able to slide parallel to the plane. In this alternative, the jack is secured to a sleeve mounted on a guide such as a rail or a slide fixed to the wedge. Thus the pressing force exerted by the jack presses the wedge onto the sealing plate via the pressing force exerted by the jack on the sleeve, while the welding tool, secured to the pressing means and therefore to the jack, is able to slide along the guide, which makes it possible to carry out a transparency weld over several centimeters, while controlling the trajectory of the welding tool. Indeed, the first distance between the head of the welding tool and the wedge being fixed, the welding tool sliding along the guide will follow the shape of an edge of the wedge, parallel to the guide. It should be noted that the wedge may comprise several guides.For example, it can form a U-shape between the branches of which the welding tool can move. The pusher can also have several wedges 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 wedge rather than a roller is to have a better plating quality, the wedge deforming the sealing plate less than a roller, thanks to its contact surface with the sealing plate, which is larger than that of a roller.

[0025] According to an optional characteristic of the invention, the means for controlling the welding system according to the invention comprise means for stopping the plating means coupled to means for detecting that a speed of the jack is lower than a low speed threshold, or to means for detecting that a variation in a force exerted on the pusher is greater than a high force variation threshold, or even to means for detecting a variation in a metal 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 "normal reaction". The speed of the cylinder is for example measured orthogonally to the plane defined by the support surface of the pusher, or along the axis of the extension rod of the cylinder.

[0027] The control means include for example:

[0028] - a position detection means such as a linear potentiometer coupled to the cylinder and allowing the extension of the latter to be precisely measured, which makes it possible to detect that the speed of the cylinder is lower than the low speed threshold,

[0029] - or a force sensor, such as a strain gauge force sensor, which allows to detect that the variation of a force exerted on the pusher is at the high threshold of force variation,

[0030] - or a thickness measuring means using for example a sensor with ultrasound, which makes it possible to detect the variation of a metal thickness measurement. The variation of the metal thickness measurement corresponds here to the contact of the sealing plate with the anchor plate. The thickness measuring means measures a metal thickness in contact with the pusher. A first variation in thickness measurement is for example detected by the thickness measuring means when the pusher comes into contact with the sealing plate, then a second variation in thickness measurement is detected by the thickness measuring means when the sealing plate comes into contact with the anchor plate. The detection of the contact between the anchor plate and the sealing plate therefore corresponds to this second variation in thickness measurement, when the thickness measuring means is activated before the pusher is in contact with the sealing plate.

[0031] The position detection means, the force sensor or the thickness measuring means is mechanically coupled to the plating means and electrically to a processing member for at least one electrical output signal from the means in question, this processing member being able to be remote from the welding system. The control means preferably comprise a human-machine interface coupled to a device comprising at least one processor, for example a computer, itself coupled to the processing member. The human-machine interface and the device can also be remote from the welding system.

[0032] In the case where the welding system comprises a position detection means, the computer determines the speed of movement of the jack using the positions provided by the position detection means, which allows it to detect contact between the sealing plate and the anchoring plate, by reaching a quasi-zero speed of movement of the jack, for example a speed of less than 1 mm 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, which allows it to detect contact between the sealing plate and the anchor plate, when a variation thus determined is greater than a high threshold set, for example, at 500 N (Newton). Indeed, when this contact is obtained, the normal reaction applied by the anchor plate to the sealing plate suddenly increases the force measured by the force sensor.

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

[0035] According to an optional characteristic of the welding system according to the invention, the This comprises a frame comprising at least one rail and a sliding carriage mounted on the rail, the welding device being fixed to the carriage. Such a frame makes it easier to position the plating means and the welding tool along welding zones of a sealing plate. Thanks to the carriage sliding on the rail, several welding zones can be processed consecutively and in an automated manner. The carriage is for example motorized and comprises a sliding member such as a rib capable of sliding in a slide of the rail, or a slide capable of sliding on the rail, depending on the configuration of the latter. The carriage is for example programmable to activate the welding tool and the plating means only on the welding zones, as it progresses on the rail. The means for controlling the force exerted by the plating means on the sealing plate are preferably also mounted on the carriage.

[0036] According to an optional characteristic of the invention, the sealing plate comprising waves, the frame comprises removable fixing means on waves delimiting between them welding zones, the frame forming a frame on which the rail is arranged and of which an internal periphery is capable of allowing the welding tool to access the welding zones. The waves on the sealing plate correspond to ribs forming a grid on the sealing plate, making it possible to absorb the deformations of the tank due to the thermal variations thereof. In this embodiment of the invention, the removable fixing means are for example wave node clamps. Such a clamp slides on a first wave on either side of a second wave intersecting the first wave, to clamp the second wave.

[0037] According to another optional characteristic of the invention, first welding zones being aligned along a first axis, between a first end of the sealing plate and a second end of the sealing plate, and second welding zones being 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 welding zones when it is aligned along the first axis, the frame comprising removable fixing means capable of fixing at least a portion of the frame on a support external to the sealing plate. The first axis and the second axis are distinct, they are for example 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 fixing means are for example hydraulic suction cups fixed on either side of the rail on another sealing plate already anchored to the primary insulation layer, or on boxes of the primary insulation layer. As For example, the sealing plate forms a rectangle of three meters on one meter of metal sheet. The rail allows all welding areas to be treated over the three-meter length or one-meter width of the sealing plate. The welding system, which mainly comprises the rail, the trolley, the rail fixing means, the plating 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 waterproofing membrane of the tank 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 treat two welding zones simultaneously, located on either side of the rail.

[0040] According to an optional characteristic of the invention, the welding system comprises two circular arc guide members, on each of which is slidably mounted a separate end of the rail, the guide members being capable of moving the rail from a first configuration in which the welding system is capable of treating all the first welding zones, to a second configuration in which the welding system is capable of treating second welding zones. In this case, the rail can allow the welding tool to treat the first zones and then the second zones without moving the chassis fixing means.

[0041] Furthermore, the welding system possibly comprises a station external to the chassis, the station being connected by electrical and possibly hydraulic connections to the means for fixing the chassis, to the carriage, to the welding tool and to the jack, the external station comprising an electric generator, and possibly an air compressor as well as liquid for the jack, if the latter 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 of welding a sealing plate of a tank intended to contain liquefied gas, to an anchoring plate, using the welding system according to the invention, and comprising steps of: - positioning of the plating means above the sealing plate and the anchor plate, - actuation of the plating means, - control of a force exerted by the plating means on the sealing plate, - locking of the plating means as soon as contact between the anchor plate and the sealing plate is detected, to maintain contact between the anchor plate and the sealing plate, and - transparent welding of the sealing plate to the anchor plate.

[0043] The invention further relates to a method for welding a sealing plate of a tank intended to contain liquefied gas, to an anchoring plate, using the welding system according to the invention, in which the plating means comprise a pusher comprising a bearing surface defining a plane intended to come parallel against a welding zone, and a jack, a head of which is secured to the pusher, and in which the control means comprise means for stopping the plating means coupled to means for detecting that a speed of the jack is lower than a low speed threshold, the welding method comprising steps of: - positioning of the support surface above the sealing plate and the anchor plate, - actuation of the cylinder, - control of the cylinder movement speed, - locking of the cylinder as soon as the movement speed falls below the low speed threshold, to maintain contact between the anchor plate and the sealing plate, and - transparent welding of the sealing plate to the anchor plate.

[0044] Locking the jack corresponds to stopping the extension of its extension rod, the latter being kept fixed relative to the hollow tube in which it has slid.

[0045] The invention also relates to a method for welding a sealing plate of a tank intended to contain liquefied gas, to an anchoring plate, using the welding system according to the invention, in which the plating means comprise a pusher comprising a bearing surface defining a plane intended to come parallel against a welding zone, and a jack of which a head is secured to the pusher, and in which the control means comprise means for stopping the plating means coupled to means for detecting that a variation in a force exerted on the pusher is greater than a high threshold of force variation, the welding system comprising a force sensor, the welding method comprising steps of: - positioning of the support surface above the sealing plate and the anchor plate, - actuation of the cylinder, - control of an output signal from the force sensor, - locking of the cylinder as soon as a variation in the output signal is greater than the high force variation threshold, to maintain contact between the anchor plate and the sealing plate, and - transparent welding of the sealing plate to the anchor plate.

[0046] The invention also relates to a method of welding a sealing plate of a tank intended to contain liquefied gas, to an anchoring plate, using the welding system according to the invention, in which the plating means comprise a pusher comprising a bearing surface defining a plane intended to come parallel against a welding zone, and a jack of which a head is secured to the pusher, and in which the control means comprise means for stopping the plating 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 method comprising steps of: - positioning of the support surface above the sealing plate and the anchor plate, - actuation of the cylinder, - control of an output signal from the measuring means, - 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 is of course distinguished from variations linked to measurement noise.

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

[0049] Furthermore, in each of the welding methods according to the invention, when the welding system comprises a frame comprising at least one rail and a sliding carriage mounted on the rail, the welding device being fixed to the carriage, the positioning step is for example preceded by a step of fixing the frame relative 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 following steps of the welding method as soon as one of the welding zones is reached. Of course, between each repetition of the steps of one of the welding methods according to the invention, these include a step of deactivating the plating means, therefore for example the jack, which makes it possible to move the welding device to the next welding zone without deforming the sealing plate.

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

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

[0052] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0053] [Fig-1] represents, seen from above, a portion of a wall of a tank intended for contain liquefied gas, this portion being assembled and comprising a sealing plate on which welds appear allowing its attachment to anchor 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 provided with a roller, and a welding tool,

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

[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 plating 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 plating means comprise a U-shaped wedge, between the branches of which a welding tool of the welding system is able to slide,

[0059] [Fig.7] represents, seen from above, the wedge of the plating 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], when welding a sealing plate to an anchor plate, in one embodiment of a welding method according to the invention,

[0061] [Fig.9] shows in perspective, according to a fourth embodiment of the invention, a welding system according to the invention, comprising a frame-shaped chassis, provided with a rail on which the welding system of [Fig.2] is capable of circulating, the chassis being shown fixed on a rectangle of waves of the sealing plate of [Fig.l],

[0062] [Fig. 10] represents seen from above, according to a fifth embodiment of the invention, a welding system according to the invention, comprising a rail on which a carriage is able to circulate, two welding systems in accordance with the first embodiment of the invention being fixed to the carriage on either side of the rail,

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

[0064] [Fig. 12] represents, seen from above, according to a sixth embodiment of the invention, a welding system according to the invention, comprising a chassis provided with a removable rail on which the welding system of [Fig.2] is able to circulate, and

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

[0066] In [Fig. 1] is illustrated a portion of a tank wall intended to contain liquefied gas, that is to say a cryogenic liquid such as liquid natural gas or liquid dihydrogen, at very low temperature, for example at -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.l] includes in particular:

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

[0069] - a secondary waterproofing membrane, formed from corrugated iron sheets,

[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 crisscross 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 transparent welding on the anchor plates 21, 22. Other anchor plates (for example the anchor plate 24 [Fig. 3]) are smaller and can be arranged diagonally on certain boxes.

[0073] The tank portion shown in [Fig.l] extends mainly along a first axis A1 and a second axis A2 orthogonal to the first axis A1, and in thickness along a third axis A3 orthogonal to the first and second axes A1, A2. The tank portion may 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 welded to each other at their edges. They also include waves forming a grid on the primary sealing membrane.

[0075] In particular, they comprise large waves 12 extending in the direction of the first axis A1, and small waves 14 extending in 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 them. These waves 12, 14 draw wave rectangles of which two adjacent sides comprise a small wave 14 and a portion of large wave 12.

[0076] One of the sealing plates 1, shown entirely in [Fig.l], extends in the direction of the first axis A1 from a first 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 anchoring plates 21 oriented along the first axis Al, of length 100 mm and width 70 mm, 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 wave rectangles of the sealing plate 1 covering second anchor plates 22 oriented along the second axis A2, of length 100 mm and width 70 mm, in this example of use of the invention. These second anchor plates 22 are arranged under the sealing plate 1 every three wave rectangles. The sealing plate 1 is thus welded along the second axis A2 on second anchor plates 22 distributed regularly along the first axis AL

[0079] The second anchoring plates 22 partially cover the first anchoring plates 21 under three wave rectangles in which the sealing plate 1 comprises four third weld lines 34 oblique with respect to the directions of the first and second axes A1, A2. It should be noted that these oblique weld lines 34 can be produced with a welding system presented later in relation to [Fig. 9], but that when the weld lines 31, 32 are produced with other welding systems presented later in relation to FIGS. 10 and 12, the weld lines produced at the intersections of the anchoring plates 21 and 22 are L-shaped corresponding to a half-weld line 31 adjacent to a half-weld line 32 (as visible in FIGS. 10 and 12).

[0080] The first, second and third welding lines 31, 32, 34 correspond to weldings of the sealing plate 1 carried out by transparency on a first or second anchoring plate 21, 22. These welding lines 31, 32, 34 are carried out on predetermined welding zones, corresponding in particular to portions of anchoring plates 21, 22 devoid of rivets.

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

[0082] [Fig.2] shows a welding system SI in a first embodiment of the invention, making it possible to carry out the welding lines 31, 32, 34 of the sealing plate 1 on the anchor plates 21, 22 by transparency.

[0083] The welding system SI comprises a transparency welding tool 5 which is here a plasma welding torch. It allows, by being positioned on the sealing plate 1, to weld the latter on one of the anchor plates 21, 22. For example, the sealing plate has a thickness of approximately 1.2 mm, and the anchor plates have a thickness of approximately 2 mm. The welding tool 5 is fixed by a fixing flange 47 to an extension rod of a jack 45 arranged parallel to the welding tool 5. The jack 45 comprises an electric motor 44 connected to an outer tube 46 of the jack in which the extension rod of the jack is mounted. A linear potentiometer 6 integrated in the jack makes it possible to measure the displacement of the extension rod relative to the outer tube 46.

[0084] The end of the extension rod is connected to a pusher. More particularly, the end of the extension rod is here connected to a roller, being provided with a U-shaped attachment 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 surrounding the extension rod just above the attachment zone, so as to cool the roller 48 when the welding tool 5 is in operation. The extension rod and the attachment being 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 elements mentioned in the jack if they have sufficient mechanical and thermal resistance to carry out the invention.Furthermore, the cooling device may take a form other than a cooling jacket cylindrically surrounding the extension rod of the jack 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 jack 45 makes it possible to fix a first distance dl between the head 52 of the welding tool 5 and the roller 48, measured parallel to a plane P coplanar with the surface of a welding 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 jack 45 being orthogonal to the plane P.

[0086] Similarly, the fixing flange 47 of the welding tool 5 to the jack 45 makes it possible to fix a second distance d2 between the end of the head 52 of the welding tool and the plane P, for example at 2 mm, which makes it possible to guarantee good quality welding by transparency. Of course this value must be adapted according to the welding tool used and the plates to be welded.

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

[0088] The sensor associated with the cylinder, here the potentiometer 6, is in a different variant and measures other data also making it possible to observe the increase in the force feedback exerted on the rod of the cylinder 45. The sensor is in a variant a force sensor, such as a strain gauge force sensor, or a thickness measuring means using for example ultrasound, the position of the sensor on the cylinder or more generally in the welding system depending of course on the type of sensor used. In particular, the ultrasonic thickness measuring means is not necessarily physically linked to the cylinder, it is sufficient that it is arranged near the pusher.

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

[0090] It is understood that thanks to the fixing of the welding tool 5 to the extension rod of the jack 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 onto the associated anchoring plate, the welding tool 5 is positioned at the correct distance from the sealing plate 1 to carry out a transparency weld, when the jack presses the sealing plate 1 onto a welding zone.

[0091] The roller 48 and the jack 45 form means 4 for pressing the sealing plate onto the anchoring plate 21 or 22.

[0092] [Fig. 3] illustrates the transparent welding of the sealing plate 1 on an anchor plate 23 fixed on a corner of a box 72, by the SL welding system. In order to visualize the differences in height between the boxes 72 under the sealing plate 1, the latter is made transparent in [Fig. 3] while being represented by a few relief lines 15. The roller 48 allows easy access to this corner of the sealing plate 1 and to make a weld line 33 by transparency on the anchor plate 23, between the rivets fixing the latter 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 makes it possible to place the roller 48 as close as possible to the weld 33 to be made.

[0093] It can be clearly seen in this [Fig. 3] that the sealing plate 1 must be deformed more to press it against the anchoring plate 23, to make the weld line 33, than if it were necessary to make this on an anchoring plate 24 of a box 72 located higher than that on which the anchoring plate 23 is fixed. This means that the force F exerted by the jack 45 must be greater. For information, the manufacturing standards of the tank are set such that this force F must not exceed 60 kg, that is to say that a maximum threshold of difference in height between the boxes 72 is established.

[0094] [Fig.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 alternative pusher 48b comprises a roller fixed for example by its axle to the attachment of the extension rod of the cylinder. This roller forms a front wheel 482 of the alternative pusher 48b, its axle also passing through ends of flanks 480 parallel to each other and extending orthogonally to the axis X of the extension rod of the cylinder. The opposite ends of the flanks 480 each comprise 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 welding zone without rolling over the weld line being formed, when using the welding system SL. For this purpose, the head 52 of the welding tool 5 is for example positioned on the upper walls of the flanks 480, in a central zone 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 jack 45 and the potentiometer 6.

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

[0098] - an elongated 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 forming projection of the elongated plate on either side of the welding tool 5 fixed to the jack 45,

[0100] - a ball socket slidably mounted on the guide 432,

[0101] - a fixing lug 430, a first part of which is secured to the socket at balls and a second part of which, orthogonal to the first part, is fixed at the end of the extension rod of the jack, here by a through screw, and

[0102] - a return spring 434, capable of being compressed between the fixing lug 430 and a wall of one of the supports, as represented in an initial state S2(t0) of the welding system S2, represented [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 for the fact that the pusher fixed to the jack 45 is a wedge 43b, as in the second embodiment of the invention, but comprising two guides 432b of circular sections.

[0104] More precisely, the wedge 43b of the welding system S3, 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 of circular sections, each fixed to two supports projecting from each branch of the U-shaped plate, on either side of the welding tool 5 fixed to the jack 45, the welding tool 5 being arranged between the two branches of the U-shaped plate,

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

[0108] - a fixing lug 430b, a first part of which is secured to the sockets at balls and a second part of which, orthogonal to the first part, is fixed at the end of the extension rod of the jack, here by a through screw, and

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

[0110] As visible in Figures 5, 6 and 8, the welding systems S2 and S3 with wedge allow a radiation zone 54 created by the head 52 of the welding tool 5 to run along the elongated or U-shaped plate of the welding system S2 or respectively S3, when producing a weld line 31, 32, 33 or 34 on the sealing plate 1. The pusher remains fixed for the duration of the movement of the welding head, which makes it possible to ensure uniform pressing of the sealing plate on the anchor plate for the entire duration of the production of the weld line.

[0111] [Fig.8] illustrates the production of a weld line with the welding system S2 of the second embodiment, this embodiment being transposable to the production of a weld line with the welding system S3 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 a contact between the sealing plate 1 and an anchoring plate 22, and stop the deployment of the extension rod of the jack 45, thus fixing the value of the pressing 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 a first of the supports of the guide 432 and the sleeve which allows the jack 45 and the welding tool 5 to slide along the wedge 43.

[0113] Then a weld line is made by activating the welding tool 5 and sliding the jack 45 and the welding tool 5 along the wedge 43 by means of the ball slide, in a direction D, parallel to the guide 432, the pressing force F being kept constant. The movement of the jack 45 and the welding tool 5 is for example ensured by a carriage on which the jack 45 and the welding tool 5 are mounted. The ball bushing ends its travel along the guide 432 at a time 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 jack 45 is unlocked and its extension rod retracted, so as to cancel the plating force F. At the corresponding state S2(t2) of the welding system S2, the shim 43 is detached from the sealing plate 1, and the welding system S2 is ready to be reused on another welding zone.

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

[0116] We will now describe in relation to [Fig.9], in a fourth embodiment of the invention, a welding system S4 integrating the elements of the welding system SI of the first embodiment of the invention.

[0117] The welding system S4 comprises a frame-shaped chassis 8, which is fixed to nodes of a rectangle of waves of the sealing plate 1. For this, it comprises at each of the corners of its lower face (i.e. facing towards the sealing plate 1), clamps 84 each comprising 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 further comprises a locking member 840 making it possible to keep it clamped on the node of the rectangle of waves 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 frame 8 make it possible to easily transport the welding system S4.

[0119] The frame 8 comprises on its upper face (i.e. opposite the sealing plate 1) a rail 86 delimiting its inner periphery, and a carriage 9 mounted to slide on the rail 86. The rail 86 draws a frame parallel to the plane P coplanar or substantially coplanar with the welding zones in the rectangle of waves. The rail 86 is in fact arranged as parallel as possible to the welding zones, in a manner substantially coplanar with the main 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 jack 45 is orthogonal to the plane P. The position of the arm 92 is adjustable so as to be able to advance the plating means 4 and the welding tool 5 more or less 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 jack 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 anchoring plate, the welding tool 5 comes to position itself at the correct distance from the sealing plate 1 to carry out a transparency weld, when the jack comes to press the sealing plate 1 on a welding zone. In addition, the movement of the welding tool 5 parallel to the plane P to carry out a welding line is carried out by setting the carriage 9 in motion along the rail 86, this movement being followed by the roller 48 over the distance necessary to carry out this welding line.

[0122] Finally, as visible in [Fig.8], when the carriage 9 travels around the perimeter of the rail 86, it makes it possible to form with the welding tool 5 weld lines 31 or 32 when it is positioned on a median zone 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 suitable for targeted repairs on scattered wave rectangles of the tank's sealing membrane.

[0124] Of course, in an alternative embodiment of this fourth embodiment, the roller 48 is replaced by the wedge 43 or 43b. In this case, the movement of the welding tool 5 parallel to the plane P to make a weld line is carried out by setting the carriage 9 in motion along the rail 86, this movement being followed by the socket(s) of the wedge 43, 43b pressed against the sealing plate 1, over the distance necessary to make this weld line. Once the weld line has been made, the rise of the extension rod relative to the plane P detaches the wedge 43, 43b which causes the socket(s) to return to their initial position on the wedge 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 comprises a rail 86b on which a carriage 9b is slidably mounted, this rail 86b being rectilinear 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 A1 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 capable of being fixed to a box 72, beyond the edge 19 of the sealing plate 1 and outside the latter, by a foot 83 screwed to the box 72.

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

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

[0130] Two template tabs 80 sliding together on the rail 86b are spaced apart from each other 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 make it possible to arrange the rail 86b optimally above the sealing plate 1 to make welding lines 31 parallel to the first axis Al.

[0131] For this, two welding systems SI, in accordance with the first embodiment of the invention, are fixed on either side of the carriage 9b, so that the axis X of the extension rod of the jack 45 is orthogonal to the plane P of the welding zones on the sealing plate 1.

[0132] The production of the weld lines 31 is carried out in a similar manner to that of the weld lines 31 with the welding system S4 of the fourth embodiment of the invention. The carriage 9b is nevertheless controlled, in this fifth embodiment of the invention, by programming means 90 fixed to the carriage 9b and comprising a human-machine interface. These programming means 90 comprise a computer and are capable of programming the movement of the carriage 9b to carry out several weld lines 31 on either side of the rail 86b over the length of the sealing plate 1. The instructions of the corresponding program therefore comprise means for activating a motorization of the carriage 9b, means for activating and stopping the jack 45, coupled to means for detecting a contact between the sealing plate 1 and the first underlying anchoring plate 21, and means for activating and stopping the welding tool 5.The instructions also possibly include means for adapting the speed of the carriage 9b depending on the activated or switched 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 treat the welding zones along the same axis A1 or A2 on different sealing plates 1.

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

[0135] In another example of 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 example of use, the welding system S5 is used to carry out the welding lines 32 of the sealing plate 1 on these second anchor plates 22, in a similar manner to the execution of the welding lines 31 on the first anchor plates 21.

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

[0137] [Fig. 11] shows in more detail a suction cup attachment 84b of the frame 8b. This attachment comprises a suction cup 846 and a vacuum pump 841 comprising an inlet 844 of compressed air to activate and deactivate the suction cup 846. The vacuum pump 841 creates a pressure difference allowing the suction cup 846 to hold a heavy load such as the welding system S5. A ball joint 848 allows the rail 86b to be moved in rotation around the suction cup attachment 84b as long as the foot 83 is not screwed.

[0138] The vacuum pump 841 and the ball joint 848, fixed in rotation to the suction cup 846, enclose by an elastic connection the edges of a buttonhole arranged in a bracket 843 and in which they can slide in a direction substantially parallel to the attachment 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 providing a pivot connection with an axis orthogonal to the main extension axis of the buttonhole (along its length) and substantially parallel to the attachment surface of the suction cup 846.

[0139] Gas cylinders 842 coupled to compressed air inlets 849 to block the movement of their pistons, make it possible to turn the support 847 relative to the bracket 843 around the hinge 845. For this, each of the gas cylinders 842 has at one of its ends, fixed to its body, an eyelet mounted to rotate 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 cylinder 842, an eyelet mounted to rotate in a rod fixed to the support 847.

[0140] It is understood that this suction cup attachment 84b makes it possible to fix the distance of the rail 86b relative to the position of the suction cup 846 thanks to the slot arranged in the bracket 843. In addition, the system of jacks 842 coupled to the bracket 843 and to 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 attachment surface of the suction cup 846 by relative to a welding zone, and to maintain the rail 86b parallel to the plane P of the welding zone and at the same height therefrom, even when the sealing plate 1 is pressed against 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 provided with a removable rail 86c on which is slidably mounted a carriage 9b identical to that of the fifth embodiment of the invention and referenced in the same way. As in the fifth embodiment of the invention, two welding systems SI in accordance with 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 jack 45 is orthogonal to the plane P of the welding zones on the sealing plate 1. Programming means 90 of 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 fasteners 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 on two opposite bars of the frame for the maneuverability of the chassis 8c.

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

[0143] For this, a first guide rail 85 in an arc of a circle is fixed to the frame by joining two opposite corners thereof. One end of the removable rail 86c comprises a slide capable of sliding on this first guide rail 85 in an arc of a circle and whose center of curvature is close to a corner of the frame near which is fixed a second guide rail in an arc of a circle 87, less extended than the first guide rail 85. The second guide rail in an arc of a circle 87 is more precisely fixed on the chassis 8c outside the frame. The other end of the removable rail 86c comprises a slide capable of sliding on this second guide rail 87 in an arc of a circle. In other words, the guide rails 85, 87 in an arc of a circle 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 A1, which allows the welding system S6 to carry out all the welding lines 31 on the welding zones aligned along this first axis and included in the frame, to a position aligned along the second axis A2, which allows the welding system S6 to carry out all the welding lines 32 on the welding zones aligned along this second axis and included in the frame.

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

[0146] The welding system S6 therefore makes it possible to treat all the welding zones of a sealing plate 1 with three steps of positioning the frame 8c on three distinct portions of the sealing plate 1, where four steps of positioning the frame 8b are necessary with the welding system S5 of the fifth embodiment of the invention.

[0147] Template legs are optionally fixed to the frame 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 method 100a of welding the sealing plate 1 to one of the anchor plates 21, 22 or 23 is now described in relation to [Fig. 13]. This welding method 100a uses one of the welding systems S4, S5 or S6.

[0149] A first step 102 of the welding method 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 welding zone to be treated, that is to say parallel to the plane P, and parallel to at least one direction of one of the axes A1, A2 on at least one 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 box 72, as well as possibly template 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 method 100a is possibly the programming of the carriage 9b, by giving it instructions capable of successively moving it over several welding zones, and of activating the following steps of the welding method 100a as soon as one of the welding zones is reached. This second step 104 can take place before the first positioning step 102 if template legs are used.

[0151] A third step 106 of the welding method 100a is the positioning of the bearing surface of the pusher, and in particular of the roller 48, above a welding zone. During this step, the welding tool 5 and the jack 45 are arranged, thanks to the carriage 9, 9b, above the welding zone so as to then allow the formation of a weld line on the welding zone. 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 method 100a, after the positioning step 106, is the actuation of the jack 45, so as to press the sealing plate 1 at the welding zone progressively against the underlying anchoring plate 21, 22 or 23.

[0153] The next step 110a is the control of the displacement speed V of the jack, using the output signal of the potentiometer 6, processed for example by an analog-digital conversion circuit, connected to an input of the computer, whether the latter is on board the welding system or arranged remotely and connected by a wired or wireless link to the conversion circuit. The computer deduces from the output signal processed by the conversion circuit, the displacement speed V of the jack.

[0154] The movement of the cylinder, i.e. the bringing together of the sealing plate towards the anchor plate, continues as long as the movement speed remains substantially the same, which reflects that the sealing plate is not pressed against the anchor plate. As soon as this movement speed V is lower than a low speed threshold Sb, set for example at 1 mm / s, it is estimated that the sealing plate is sufficiently pressed against the anchor plate to be able to carry out the transparency welding operation, and we move on (branch Y) to the next step 114a of locking the cylinder 45. Otherwise, (branch N) we continue the deployment of the extension rod of the cylinder 45.

[0155] Step 114a of locking the jack 45 corresponds to stopping the deployment of the extension rod of the jack 45. When the jack 45 is locked, it is thus certain that the sealing plate 1 is in contact with the anchoring plate 21, 22 or 23 at the weld zone, since the adjustment of the pressing force to obtain this contact, without it being necessary to apply too great a 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 support surface.

[0156] The following step 116a is then the transparent welding of the sealing plate 1 to the anchoring plate 21, 22 or 23. This step 116a may consist of producing a single welding point, or a welding line 31, 32, 33 or 34, by moving the carriage 9, 9b, causing the roller 48 to move upstream of the welding tool 5.

[0157] A method 100b for welding the sealing plate 1 to one of the anchor plates 21, 22 or 23 is now described, still in relation to [Fig. 13]. This welding method 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, arranged for example at the axle of the roller 48.

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

[0159] Unlike the welding method 100a, in the welding method 100b, the step 108 of actuating the jack 45 is followed by a step 110b of controlling an output signal from the force sensor. This output signal is again processed for example by an analog-digital conversion circuit, connected to an input of the computer fixed 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, set 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 anchoring plate 21, 22 or 23 at the welding zone.

[0162] The following step 116b is then the transparent welding of the sealing plate 1 to the anchoring plate 21, 22 or 23. This step 116b may consist of producing a single welding point, or a welding line 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 a variant of these welding methods 100a, 100b, when the system S4, S5 or S6 uses an ultrasonic thickness measuring means to measure the metal thickness under the roller 48, a method of welding the sealing plate 1 to an underlying anchor plate 21, 22 or 23 comprises first steps of fixing the frame 8, 8b or 8c, of possible programming of the carriage 9b, of positioning the roller 48 above a welding zone and of actuation of the jack 45, identical to those of the methods 100a, 100b previously described. These first steps are followed, in this variant of the welding method, by a step of controlling an output signal from the ultrasonic thickness measuring means, processed by an analog-digital conversion circuit, connected to a computer fixed to the carriage 9b or remote from the carriage 9, 9b.

[0164] As soon as a variation in metal thickness under the roller 48 is detected, the jack 45 is locked, since this means that contact between the sealing plate 1 and the underlying anchoring plate 21, 22, 23, at the welding zone, has been obtained. Then, in this variant of the welding method, the transparency welding is carried out, in a similar manner to steps 116a, 116b already described.

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

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

[0167] The invention is of course not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of different variants or different embodiments of the invention can be combined to achieve the invention, insofar as these variants or embodiments are not incompatible with each other.

Claims

Claims

1. Welding system (SI, S2, S3, S4, S5, S6) of 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 comprising: - a transparency welding tool (5) intended to carry out at least one weld in a welding zone, - means (4) for pressing the sealing plate (1) onto the anchoring plate (21, 22, 23), and - means (6) for controlling a force (F) exerted by the pressing means (4) on the sealing plate (1), capable of detecting contact between the anchoring plate (21, 22, 23) and the sealing plate (1).

2. Welding system (S1, S2, S3, S4, S5, S6) according to claim 1, wherein the welding tool (5) is secured to the plating means (4).

3. Welding system (S1, S2, S3, S4, S5, S6) according to claim 1 or 2, in which the pressing means (4) comprise a pusher comprising a bearing surface defining a plane (P) intended to extend parallel to the welding zone, and a jack (45) one head of which is secured to the pusher.

4. Welding system (S1, S2, S3, S4, S5, S6) according to claim 3, comprising means for thermal protection of the pusher.

5. Welding system (S1, 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 wedge (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, in which the control means (6) comprise means for stopping the plating means (4) coupled to means for detecting that a speed (V) of the jack (45) is lower than a low speed threshold (Sb), or to means for detecting that a variation (AN) of a force exerted on the pusher is greater than a high force variation threshold (Sh), or to means for detecting a variation of a metal thickness measurement.

8. Welding system (S4, S5, S6) according to any one of the claims- indications 1 to 7, comprising a frame (8, 8b, 8c) comprising 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, in which the sealing plate (1) comprises waves (12, 14), the frame (8) comprises removable fixing means (84) on waves delimiting between them welding zones, the frame (8) forming a frame on which the rail (86) is arranged and an internal periphery of which is capable of allowing the welding tool (5) to access the welding zones.

10. Welding system (S5, S6) according to claim 8, wherein, first welding zones being 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 second welding zones being 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 welding zones when it is aligned along the first axis (A1, A2), the frame (8b, 8c) comprising removable fixing means (84b) capable of fixing at least a portion of the frame (8b, 8c) on a support external to the sealing plate (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 guide members (85, 87) in an arc of a circle, on each of which is slidably mounted a separate end of the rail (86c), the guide members (85, 87) being capable of moving the rail (86c) from a first configuration in which the welding system (S6) is capable of treating all the first welding zones, to a second configuration in which the welding system (S6) is capable of treating second welding zones.

13. Method for welding (100a) 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 one of claims 1 to 12, comprising steps of: - positioning (106) the plating means (4) above the sealing plate (1) and the anchoring plate (21, 22, 23) to be welded, - actuation (108) of the plating means (4), - control (110a) of a force (F) exerted by the pressing means (4) on the sealing plate (1), - locking (114a) of the plating means (4) as soon as contact between the anchoring plate (21, 22, 23) and the sealing plate (1) is detected to maintain contact between the anchoring 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).

Images