Method for generating a profile of a waterproofing membrane suitable for a tank and corresponding device

Abstract

Method for generating a profile of a sealing membrane suitable for a tank and corresponding device The present invention relates to a method for generating a profile of a sealing membrane (2) suitable for a tank intended to contain gas in the liquid state, using a mobile support (11) provided with a position sensor (12), the method comprising a step of passing the position sensor above the sealing membrane (2), the passing step comprising iterations of sub-steps of: - determining a distance (d) between a reference point of the position sensor and a point of the sealing membrane (2), - recording the determined distance (d), - moving the mobile support (11), the passing step being followed by a step of generating a profile of the sealing membrane (2) as a function of the distances (d) recorded during the recording sub-steps. (figure 1)

Description

Title of the invention: Method for generating a profile of a sealing membrane suitable for a tank and corresponding device

[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 method for generating a profile of a sealing membrane suitable for such a tank, a method for treating this sealing membrane and a method for controlling the sealing membrane.

[0002] These transport tanks have a capacity of several thousand cubic meters of gas in the liquid state each, or even several tens of thousands of cubic meters of gas in the liquid state. 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 gas in the liquid state. The gas is kept in the liquid state, for example at -163°C (degrees Celsius) for LNG, at atmospheric pressure. It must therefore be leaktight 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) welded to each other, each sealing plate being a part of the tank's sealing membrane.

[0003] To weld these metal plates to each other, a welding machine is used in which an operator must follow the edges of these sealing plates, arranged two by two adjacent to each other partially on top of each other (lap joint), using a guide rail. The operator starts a program on the machine and the latter, equipped with a welding torch, welds the edges of the sealing plates as it travels along these edges, while adjusting at all times the distance between the torch and the part to be welded using a positioning sensor mounted on the machine.

[0004] This operation is then followed by stripping the weld bead, the welding operation having produced metal oxides on the edges of the sealing plates, which can ultimately harm the integrity of the membrane (corrosion). The stripping operation uses a machine equipped with a position sensor and a laser stripping head, which gradually strips the weld bead produced by the welding machine, using the same guide rail. The position sensor allows the laser stripping head to be positioned as the machine advances along the rail.

[0005] These welding and stripping operations take a long time to perform. Since the relief of the waterproofing membrane must be taken into account, the machines move slowly along the edges of the waterproofing plates to be welded or stripped. Correct positioning of the welding torch or laser stripping head takes time and slows down the welding or stripping operation.

[0006] There is therefore a need to improve the execution time of welding and / or stripping operations of a sealing membrane of a gas transport tank in the liquid state.

[0007] The present invention at least partially overcomes the drawbacks of the prior art by providing a method for generating a profile of at least a portion of a sealing membrane, a method for treating the sealing membrane, a method for controlling the sealing membrane and a device for generating a profile, which make it possible to facilitate the treatments carried out on sealing membranes of gas tanks in the liquid state.

[0008] To this end, the invention proposes a method for generating a profile of at least one part of a sealing membrane suitable for a tank intended to contain gas in the liquid state, using a mobile support provided with a position sensor, the generation method comprising a step of passing the position sensor above the sealing membrane, the passing step comprising iterations of the sub-steps of:

[0009] - determining a distance between a reference point of the position sensor and at least one point of the waterproofing membrane part,

[0010] - recording of the determined distance,

[0011] - movement of the mobile support,

[0012] the passage step being followed by a step of generating a profile of the part of the sealing membrane as a function of the distances recorded during the recording sub-steps.

[0013] In particular if the position sensor is an optical sensor, the sub-step of determining a distance comprises sub-steps of:

[0014] - sending an initial optical signal to a point on a surface of the membrane sealing, - receiving a return optical signal corresponding to the initial optical signal, and - determination of a distance between the reference point of the position sensor and the point on the surface of the sealing membrane based on the initial optical signal and the return optical signal.

[0015] The generated profile is for example a two-dimensional profile of the part of waterproofing membrane, in a plane orthogonal to a main extension plane of the waterproofing membrane part.

[0016] By means of the invention, a profile of the waterproofing membrane portion is generated and available for a subsequent processing step of the waterproofing membrane portion, the execution of which will be accelerated by the prior knowledge of the membrane profile. By means of the invention, the subsequent processing step does not use a position sensor to determine the distance between a processing tool and the waterproofing membrane and the positioning of the processing tool relative to the membrane, even if the processing step possibly uses other sensors, for example to confirm a position of the processing tool along a predetermined path.

[0017] In one embodiment of the generation method according to the invention, the sealing membrane portion is an edge of a first sealing plate, an edge of a second sealing plate being arranged below the edge of the first sealing plate, and the sub-steps of the passing step also determine distances between points of the edge of the second sealing plate and the reference point of the position sensor, the generation step producing a profile of the edge of the first sealing plate, and of the edge of the second sealing plate. By edge of the second sealing plate, it is necessary to understand a peripheral zone of the second sealing plate. More precisely, an edge of one sealing plate is arranged on a portion of the other sealing plate (in the following, although not necessarily at the periphery of the plate, this portion can also be called edge of the plate).

[0018] In this embodiment of the invention, the mobile support is for example mounted on a rail secured to the sealing membrane, along the edges of the first sealing plate and the second sealing plate. When the sealing membrane comprises waves to assist in the deformation of the tank, these waves forming a grid on the sealing membrane, the rail is for example secured to at least two nodes of the grid, the distance between the edges of the sealing plates of the sealing membrane and the rail being substantially constant, that is to say constant to within + / - 3 mm.

[0019] According to an advantageous characteristic of the generation method according to the invention, the position sensor is a scanning laser sensor, the sub-step of determining a distance corresponding to a sub-step of determining several distances for the same position of the mobile support, and the generation step producing a three-dimensional profile of the sealing membrane portion. In the case where the sealing membrane portion comprises two edges of sealing plates arranged against each other, this three-dimensional profile therefore includes a profile of each sealing plate edge of this part of the waterproofing membrane.

[0020] The invention also relates to a method for treating a sealing membrane suitable for a tank intended to contain gas in the liquid state, using a device for treating the sealing membrane, the treatment device comprising a mobile device and at least one treatment tool mounted on the mobile device, the treatment method comprising a step of treating the sealing membrane by the treatment tool along a predetermined path of the mobile device, the treatment method being characterized in that it comprises a prior step of generating a profile of at least a portion of the sealing membrane on the predetermined path, using the method for generating a profile according to the invention. The predetermined path is optionally derived from a step of analyzing the profile generated according to the invention.

[0021] The mobile device is preferably also the mobile support and therefore comprises both the position sensor and the processing tool, although the position sensor is not used during the processing step. The processing device possibly comprises a rail on which the mobile device moves, and / or a remote server.

[0022] According to an advantageous characteristic of the treatment method according to the invention, the treatment step comprises at least one sub-step of modifying the configuration of the mobile device and / or the treatment tool, and the treatment step is preceded by a step of cutting, as a function of the profile generated during the generation step, the predetermined path into treatment zones of the sealing membrane, between which said at least one sub-step of modifying the configuration of the mobile device and / or the treatment tool is necessary.Prior knowledge of the profile of the waterproofing membrane portion therefore allows for sequential processing of the treatment, each treatment sequence corresponding to a treatment area for which no configuration modification of the mobile device and / or the treatment tool is necessary, such configuration modification sub-steps being implemented only between each treatment sequence.

[0023] The treatment zones are preferably ordered by the treatment device in a treatment order making it possible to minimize the treatment time of the waterproofing membrane by the treatment device. This order may correspond to a discontinuous treatment of the waterproofing membrane during a first pass of the mobile device over the waterproofing membrane, several passes then being necessary to treat the entire waterproofing membrane on the predetermined path.

[0024] In one embodiment of the treatment method according to the invention, the treatment corresponds to an operation of stripping a weld bead at two edges of sealing plates of the sealing membrane, the sealing membrane portion being an edge of a first sealing plate, an edge of a second sealing plate being disposed against the edge of the first sealing plate.

[0025] In one embodiment of the processing method according to the invention, the configuration modification sub-step generates a movement of the mobile device and / or the processing tool, the processing being interrupted during said configuration modification sub-step. In other words, the configuration modification sub-steps correspond to “empty” movements, i.e. without processing, of the mobile device and / or the processing tool.

[0026] In one embodiment of the treatment method according to the invention, the sealing membrane comprises waves, these waves forming a grid on the sealing membrane, and the treatment tool is a laser stripping head positioned on the predetermined path to strip a weld bead, a configuration modification sub-step being triggered to position a point of impact of a laser beam projected by the laser stripping head, on an area located at the foot of a wave of the sealing membrane. The configuration modification sub-step therefore makes it possible to position the treatment tool in such a way that it can entirely treat a treatment area, here the laser stripping head being positioned in such a way that the point of impact of the laser beam can scan the entire area located at the foot of the wave of the sealing membrane.

[0027] In another embodiment of the processing method according to the invention, the processing step comprises at least one sub-step of modifying the configuration of the mobile device and / or the processing tool, and the processing step comprises a sub-step of reading the profile generated during the generation step, determining a triggering of said at least one sub-step of modifying the configuration of the mobile device and / or the processing tool. In this other embodiment of the invention, the sub-step of reading the profile takes place entirely before the processing step, or is carried out as the processing step is implemented. Reading the profile determines the times, during the implementation of the processing step, for which it is necessary to modify the configuration of the mobile device and / or the processing tool.

[0028] In this other embodiment of the treatment method according to the invention, the treatment corresponds for example to a welding operation at two edges of sealing plates of the sealing membrane, the part of the sealing membrane being an edge of a first sealing plate, an edge of a second sealing plate being arranged against the edge of the first sealing plate.

[0029] For example, in this other embodiment of the treatment method according to the invention, the sealing membrane comprises waves, these waves forming a grid on the sealing membrane, and the treatment tool is a welding tool, the modification sub-step corresponding to a change in speed of the mobile device when the latter arrives on a wave of the sealing membrane. In this example, the reading sub-step therefore makes it possible to detect the wave feet of the part of the sealing membrane to be welded, which makes it possible to adapt the speed of the mobile device.

[0030] The treatment step is optionally followed by a new step of generating a profile of the part of the waterproofing membrane that has just been treated. The invention also relates to a method for controlling a waterproofing membrane, comprising steps of:

[0031] - generation of a profile of at least a portion of the waterproofing membrane using the method for generating a profile according to the invention,

[0032] - comparison between a distance obtained using the previously generated profile, and a corresponding distance from a pre-recorded template of the waterproofing membrane part.

[0033] The difference between these distances in absolute value is for example compared to a predetermined threshold, an anomaly being detected if this difference is greater than this predetermined threshold.

[0034] The invention finally relates to a device for generating a profile of at least one part of a sealing membrane suitable for a tank intended to contain gas in the liquid state, comprising a mobile support provided with a position sensor, the generation device also comprising:

[0035] - means for determining a distance between a reference point of the sensor position and at least one point of the waterproofing membrane part,

[0036] - means for recording the distance determined by the determining means mination,

[0037] - means for moving the mobile support on a predetermined path above of the waterproofing membrane,

[0038] and means for generating a profile of the sealing membrane portion as a function of distances recorded by the recording means along the predetermined path.

[0039] The generation device according to the invention possibly comprises a rail on which the mobile support moves, and / or a remote server.

[0040] The generation device according to the invention has advantages similar to those of the generation method according to the invention.

[0041] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and of several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0042] [Fig.l] represents a device for generating a profile of at least one part of the sealing membrane according to the invention, in one embodiment of the invention, during a step of passing a position sensor above the sealing membrane,

[0043] [Fig.2] represents steps of a method for generating a profile of at least one part of the waterproofing membrane according to the invention, in one embodiment of the invention,

[0044] [Fig.3] represents a device for welding a waterproofing membrane according to the invention, implementing a step of welding a sealing plate with an adjacent sealing plate, in one embodiment of the invention,

[0045] [Fig.4] represents steps of a method of welding a waterproofing membrane according to the invention, in one embodiment of the invention,

[0046] [Fig.5] represents a device for stripping a waterproofing membrane according to the invention, implementing a step of stripping the waterproofing membrane, in one embodiment of the invention,

[0047] [Fig.6] represents an impact zone of a laser beam of the stripping device of [Fig.5],

[0048] [Fig.7] represents a stripping head for this laser beam, comprising a module of reflection,

[0049] [Fig.8] represents steps of a method of stripping a waterproofing membrane according to the invention, in one embodiment of the invention,

[0050] [Fig.9] represents the stripping of a wave of a waterproofing membrane, put in work during a stripping step of the stripping process of [Fig.8], and

[0051] [Fig. 10] represents steps of a method for controlling a waterproofing membrane according to the invention, in one embodiment of the invention.

[0052] According to an embodiment of the invention shown in [Fig. 1], a profile of a part of a sealing membrane 2 adapted for a tank intended to contain gas in the liquid state is generated using a profile generation device 1. This sealing membrane 2 is, in this embodiment of the invention, made from metal plates 1.2 millimeters thick, welded together or to be welded together.

[0053] The tank is typically delimited by an internal hull of a transport vessel and has a capacity of several thousand cubic meters of gas in the liquid state, or even several tens of thousands of cubic meters of liquid gas. The sealing membrane 2 covers the entire internal surface of the tank of such a transport vessel. transport. In order to compensate for deformations of the tank due in particular to variations in temperature or navigation conditions, the sealing membrane 2 comprises ribs or waves 24 crisscrossing the surface of the sealing membrane 2. Viewed in profile in a plane parallel to a longitudinal direction L and to a transverse direction T orthogonal to the longitudinal direction L, the sealing membrane therefore comprises flat areas 22 and waves 24.

[0054] The profile generation device 1 comprises a mobile support 11 provided with a position sensor 12 which measures the distance which separates a reference point of the device from a point of impact on the membrane. The position sensor 12 is here a class 2 laser distance sensor, with a measurement frequency of 300 to 600 Hz (Hertz). Alternatively, the position sensor 12 may be an LVDT (Linear Variable Differential Transformer) type sensor.

[0055] In this embodiment of the invention, the mobile support 11 is mounted on a rail 3 arranged about ten centimeters above the surface of the sealing membrane 2, against an edge of a sealing plate 2-1 of the sealing membrane 2. Indeed, in this embodiment of the invention, the profile of an edge of the sealing plate 2-1 of the sealing membrane 2 is generated.

[0056] The rail 3 follows this edge of the sealing plate 2-1, arranged in the longitudinal direction L, the distance between the edge of the sealing plate 2-1 and the rail 3 being constant to within a few centimeters, the rail being able to be several tens of meters, for example thirty meters, and possibly being made in several pieces. The rail 3 is held by clamps 4, fixed for example on nodes of the grid formed by the waves of the sealing membrane 2.

[0057] A method for generating the profile of the edge of the sealing plate 2-1 is implemented in software and / or hardware by the generation device 1, and is shown in [Fig.2].

[0058] A first step 100 of the profile generation method is the passage of the position sensor 12 above the edge of the sealing plate 2-1.

[0059] Step 100 of passing the position sensor comprises a first sub-step 102 of determining the distance d between a reference point of the position sensor 12 and a point on the surface of the sealing plate 2-1. The point on the surface of the sealing plate 2-1 is vertical to the position sensor 12. Indeed, in this embodiment of the invention, the position sensor 12 takes measurements in a vertical direction V relative to the position sensor 12, the vertical direction V being orthogonal to the longitudinal L and transverse T directions. In this sub-step 102 of determination, the generation device 1 reads a measurement sent back by the position sensor 12. The generation device 1 indeed comprises a software module interfaced with the inputs and outputs of the position sensor 12. The sub-step 102 therefore itself comprises, in this embodiment of the invention, sub-steps implemented by the position sensor 12, which are sub-steps of:

[0060] - sending 1022 of an initial optical signal to a point on the surface of the edge of the plate sealing 2-1, this initial optical signal being for example a laser pulse, - reception 1024 of a return optical signal corresponding to the initial optical signal, this return optical signal being for example a reflection of the laser pulse initially sent onto the surface of the sealing plate 2-1, and - measures 1026 a distance d between the reference point of the position sensor 12 and the point on the surface of the edge of the sealing plate 2-1 as a function of the initial optical signal and the return optical signal; this measurement typically uses the time between sending the laser pulse and receiving the reflected laser pulse.

[0061] Alternatively, other types of sensor can be used, for example an infrared optical sensor, or a capacitive sensor.

[0062] A following sub-step 104 of the first step 100 of passage of the position sensor 12 is the recording of the distance d determined in the sub-step 102, in a memory of the generation device 1.

[0063] Finally, a last sub-step 106 of the first step 100 of passage of the position sensor 12, is the displacement of the mobile support 11. The generation device 1 comprises for this a software module interfaced with actuators of the mobile support 11. The combination of the speed of displacement of the mobile support 11 and the pulse frequency of the laser beam results in a displacement step, for example a step of one tenth of a millimeter, the speed of displacement of the mobile support 11 being, in this embodiment of the invention, between 100 and 200 mm / s (millimeters per second).

[0064] The sub-steps 102 to 106 of the first step 100 of passing the position sensor 12 are repeated until the movable support 11 reaches the end of the rail 3 or any stop instruction or command.

[0065] When the end of the rail is reached, which is detected by the generation device 1, for example by the detection of a stop on the rail 3, or by the detection of the reaching of a travel distance on the rail 3 predetermined and programmed in the generation device 1, the generation device 1 implements a step 200 of generating the profile of the edge of the sealing plate 2-1, as a function of the distances recorded during the recording sub-steps 104. The generation step 200 is carried out in a software module of the generation device 1, which may include a remote server.

[0066] During this generation step 200, in this embodiment of the invention, the generation device 1 generates a profile of the edge of the sealing plate 2-1, in the form of points in a reference frame located in a plane orthogonal to the main extension plane of the sealing membrane 2, that is to say in a plane parallel to the di vertical V and longitudinal L sections. The generated profile is therefore a profile with at least two dimensions, one of the dimensions corresponding to a position reached by the mobile support 11 on the rail 3 since the start of step 100, and the other of the dimensions corresponding to the distance d determined during sub-step 102 by the generation device 1 when the mobile support 11 is at this position reached on the rail 3.

[0067] Depending on the use of the generated profile, the generation device 1 filters the distances d recorded during the sub-step 104, and the generated profile then only includes certain points corresponding for example to the distances d recorded at the limits of the flat zones 22 and at the peaks of the waves 24 of the sealing membrane 2.

[0068] In an alternative embodiment of the invention, the position sensor 12 is a scanning laser sensor, which for the same position of the position sensor 12 on the rail 3, measures distances between a reference point of the position sensor 12 and different points on the surface of the sealing membrane 2, located on a segment parallel to the transverse direction T, these distances being measured in a vertical plane parallel to the transverse T and vertical V directions, passing through the position sensor 12. In this alternative embodiment, the generation device 1 determines at each sub-step 102, a distance vector for the same position of the mobile support 11, this vector being recorded during the sub-step 104. In this alternative embodiment, the profile generated in step 200 is therefore a three-dimensional profile of the edge of the sealing plate 2-1.

[0069] In the case where the edge of the sealing plate 2-1 is arranged on an edge of another sealing plate 2-2 (shown [Fig.6] as being welded to the sealing plate 2-1), for example welded to this other edge, the three-dimensional profile generated in this other variant embodiment is for example a profile of the edge of a first sealing plate 2-1 and of the edge of a second sealing plate 2-2.

[0070] In another alternative embodiment of the invention, the mobile support 11 is not arranged on a rail 3 and travels at least part of the sealing membrane 2 by moving directly on the surface of the sealing membrane 2, along a predetermined or adaptive path depending on the obstacles encountered by the mobile support 11 on its path.

[0071] An example of a method for treating the sealing membrane 2 using the method for generating a profile according to the invention is now described. In this example of use shown in [Fig. 3], the treatment method is a method of welding an edge of the sealing plate 2-1 with an edge of the sealing plate 2-2, implemented in hardware and / or software by a welding device 7.

[0072] The welding device 7 comprises the rail 3 which follows the edge of the sealing plate 2-1, and a movable device 70 on which a welding torch 72 is mounted. The welding device 7 possibly also comprises a remote server. Alternatively, the welding device 7 comprises a mobile device which is constituted by the mobile support 11 of the generation device 1, the mobile support 11 in this case being equipped with a welding torch in addition to the position sensor 12, and possibly with a laser stripping head 52 used for a subsequent stripping operation (illustrated [Fig.5]).

[0073] The welding method implemented by the welding device 7, shown [Fig.4], comprises first steps 100 and 200 of passing the position sensor 12 and generating a profile of the edge of the sealing plate 2-1, implementing the method of generating a profile previously described in relation to FIGS. 1 and 2.

[0074] The next step 600 of the welding method is a step of lap welding the edges of the sealing plates 2-1 and 2-2, with the welding torch 72. During this welding step, the sealing plates 2-1 and 2-2 are welded by melting material from the edge of the sealing plate 2-1 to the edge of the sealing plate 2-2, this melting being carried out as the mobile device 70 advances along the rail 3.

[0075] The first sub-step 602 is the reading of the profile of the edge of the sealing plate 2-1, generated during the profile generation step 200. The generated profile is here a two-dimensional profile in a plane parallel to the longitudinal L and vertical V directions, and comprises at least indications making it possible to detect a wave base or a wave peak on the sealing membrane 2. These indications are for example distance measurements each associated with a position of the mobile device 70 on the rail 3, or values ​​of a parameter giving for each position of the mobile device 70 on the rail 3, an indication on the nature of the zone vertical to the welding torch 72 for example a value of 0 is associated with a flat zone 22, and a value of 1 with a wave 24. Optionally, the generated profile only comprises the positions of the wave peaks 24 along the edges of the sealing plates 2-1 and 2-2, the shape of the waves 24 being able to be pre-recorded.

[0076] The reading sub-step 602 is carried out continuously at the same time as the mobile device 70 travels along the rail 3, or prior to the passage of the mobile device 70 over the rail 3. Indeed, the reading sub-step 602 makes it possible to detect the positions of the mobile device 70 for which the speed of the mobile device 70 must be modified during the welding of the sealing plates 2-1 and 2-2 of the sealing membrane 2. These positions can therefore be determined in advance.

[0077] In this embodiment of the welding method according to the invention, the reading sub-step 602 is carried out as the mobile device 70 advances on the rail 3. As long as the nature of the zone vertical to the welding torch 72 detected during this reading sub-step 602 does not vary, the speed of the device mobile device 70 remains constant. When the nature of the area vertical to the welding torch 72 detected during this reading sub-step 602 changes, the reading sub-step 602 triggers a sub-step 604 of changing the speed of the mobile device 70. In particular during this sub-step 604:

[0078] - when the reading sub-step 602 has detected a passage from a flat area 22 to a foot of a wave 24, the speed of the mobile device 70 is reduced and the orientation of the welding torch is modified with adaptation of the parameters;

[0079] - when the reading sub-step 602 has detected a passage of a foot of a wave 24 to a flat area 22, the speed of the mobile device 70 is increased again and the orientation of the welding torch is modified with adaptation of the parameters.

[0080] Based on a three-dimensional profile generated as explained previously, it is possible, during the reading sub-step 602, to detect a possible shift in the position of the membrane and to make a transverse correction for the correct positioning of the welding torch.

[0081] Another example of a method for treating the sealing membrane 2 using the method for generating a profile according to the invention is now described. In this other example of use shown in [Fig. 5], the treatment method is a method for stripping a weld bead 26 between an edge of the first sealing plate 2-1 and an edge of the second sealing plate 2-2, implemented in hardware and / or software by a stripping device 5.

[0082] The stripping device 5 comprises the rail 3 which follows the edge of the sealing plate 2-1 and a mobile device constituted by the mobile support 11 of the generation device 1, which comprises both the position sensor 12 and the laser stripping head 52. The stripping device 5 possibly also comprises a remote server. Advantageously, the stripping device 5 may further comprise a suction nozzle (not shown), making it possible to suck up the oxide dust or fumes created during the stripping of the sealing membrane 2. It is understood here that the stripping device 5 implements stripping via a laser beam projected onto the area to be stripped.

[0083] The laser stripping head 52 is tiltable on the movable support 11, so that it projects a laser beam 6 at an angle of incidence 27, of the order of a few degrees relative to a normal 25 to the surface of the sealing membrane 2. This makes it possible to prevent the reflection of a laser beam 6 projected by the laser stripping head 52 from damaging the latter by return of an incident beam. Indeed, the laser stripping head 52 projects a class 4 laser beam 6 (according to the IEC60825-1 standard), with a power preferably between 20W and 200W, emitting pulses at a frequency preferably between 100kHz and 200kHz and producing a beam with a wavelength of 1064nm. Such characteristics of the laser beam 6 allow stripping a layer of impurities or oxidation 28 formed on the weld bead 26.

[0084] The mobile support 11 comprises an electric motor 53 capable of rotating a rotation shaft 51 secured to the laser stripping head 52. Thus, the laser stripping head 52 is mobile in rotation relative to the mobile support 11, which makes it possible to modify the angle of incidence 27 of the laser beam 6 relative to the normal 25 to the surface of the sealing membrane 2. The stripping device 5 therefore comprises a means for modifying the inclination of the laser stripping head 52 relative to the normal 25 to the surface of the sealing membrane 2.

[0085] The stripping device 5 also comprises a means (not shown) for modifying a height h of the rotation shaft 51 on the movable support 11, and therefore the height of the laser stripping head 52 in the vertical direction V.

[0086] These means for modifying the inclination and height of the head 52 are means for modifying the configuration of the laser stripping head 52 on the mobile support 11. As a variant, the stripping device 5 comprises means for modifying the height of the mobile support 11 relative to the rail 3.

[0087] The stripping device 5 also comprises means for moving the mobile support 11 on the rail 3, which are identical to those used for moving the device 1 for generating a profile, namely software interfaced with at least one actuator of the mobile support 11.

[0088] The laser stripping head 52 comprises at least one focusing lens 54, with a focal length of between 80 mm and 360 mm, making it possible to focus the laser beam 6 on an impact zone 61 on the surface of the sealing membrane 2. The laser beam 6 scans this impact zone 61 at the rate of pulses, each creating an impact point 63 shown [Fig. 6], the impact points 63 overlapping to ensure that the weld bead 26 is completely stripped. The impact zone 61 has a width (along the transverse direction T) of approximately two centimeters, which makes it possible to completely strip the weld bead 26, the width of which is approximately one centimeter.

[0089] This scanning is made possible by the structure of the laser stripping head 52 shown [Fig.7]. The stripping device 5 comprises a laser beam generator 56, projecting the laser beam 6 onto a reflection module 57 at the free end of the laser stripping head 52. The laser stripping head 52 is shown in [Fig.7] in a very simplified manner in order to lighten its illustration. Indeed, the laser beam generator 56 is in fact external to the laser stripping head 52, and it is the fiber 9 which brings the generated beam into the laser stripping head 52. The reflection module 57 is for example a set of mirrors which deflects the trajectory of the laser beam 6 at the output of the beam generator in a direction DI included in a plane parallel to the longitudinal directions L and vertical V, or along a direction D2 included in a plane parallel to the transverse directions T and vertical V. As a variant, the reflection module is located on the mobile support 11 outside the laser stripping head 52. Thus the stripping device 5 comprises a means for modifying the orientation of the laser beam 6 independently of the orientation of the laser stripping head 52.

[0090] The method of stripping the weld bead 26 implemented by the stripping device 5 comprises first steps 100 of passing the position sensor 12 and 200 of generating a profile of the edge of the sealing plate 2-1, represented [Fig.8], and implementing the method of generating a profile previously described in relation to Figures 1 and 2.

[0091] The following step 400 is the cutting, as a function of the profile generated during step 200, of a predetermined path of the stripping device 5 along the rail 3, corresponding to a path along the part of the waterproofing membrane 2 to be treated, into treatment zones of the waterproofing membrane 2, here zones to be stripped, for which it is necessary to reconfigure the laser stripping head 52 or the mobile support 11 before stripping the zone to be stripped in question.

[0092] Indeed, in order to increase the stripping speed of the edges of the sealing plates 2-1 and 2-2, in mm / s, it is preferable to limit as much as possible the movements of the mobile support 11 and the laser stripping head 52. For this, the stripping method sequentially strips the areas to be stripped resulting from the cutting during step 400, these areas to be stripped being configured to allow on each of these areas to be stripped, stripping using only the laser scanning made possible by the reflection module 57, without additional movement of the mobile support 11 or the laser stripping head 52. For this, the size of a predefined area to be stripped makes it possible to keep an angle of incidence 27 small enough to allow effective stripping of the area to be stripped. In particular, this angle of incidence makes it possible to remain within the focal distance of the focusing lens 54 with an acceptable tolerance margin.For example, for a 54 focusing lens with a focal length of 330mm (millimeters), this tolerance margin is 3mm.

[0093] Thus in this step 400, the flat areas 22 are each cut into two halves, and the waves 24 are each cut into six areas to be stripped as illustrated in [Fig.9]. More precisely when the mobile support 11 moves in a direction 55 of the longitudinal direction L, it first strips a slope 241 of a wave 24. In order to effectively strip this slope 241, the laser beam at the output of the reflection module 57 has an almost zero angle of incidence 27 on the surface of the wave 24. For this, the laser stripping head 52 uses the rotation shaft 51, which allows the laser beam 6 to have an angle of 70° or 50° in the counterclockwise direction by relative to the vertical direction, at the output of the laser stripping head 52.

[0094] A first zone 243 to be stripped at the foot of the slope 241 is therefore defined to be attacked by the laser beam 6 with an angle of 70° relative to the vertical direction V, which makes it possible to stick to within a few degrees, to a radius of curvature of the foot of the wave 24.

[0095] A second zone 245 to be stripped in the middle of the slope 241 is also defined to be attacked by the laser beam 6 with an angle of 50° relative to the vertical direction V, which makes it possible to stick to within a few degrees, to a normal to the surface of the wave on a central zone of the slope 241.

[0096] Finally, a third zone 247 to be stripped at the top of the slope 241 is defined to be attacked by the laser beam 6 with an angle of 50° relative to the vertical direction V, which makes it possible to stick to within a few degrees, to a radius of curvature of the top of the wave 24.

[0097] Similarly, when the mobile support 11 moves in the other direction 59 of the longitudinal direction L, it strips the other slope 242 of the wave 24, in a similar manner to the stripping of the slope 241 of the wave 24. In particular, it begins to strip a fourth zone 244 at the foot of the slope 242, the laser beam 6 having an angle of 70° in the clockwise direction relative to the vertical direction V, then a fifth zone 246 in the middle of the slope 242, the laser beam 6 having an angle of 50° in the clockwise direction relative to the vertical direction V, and finally a sixth zone 248 at the top of the slope 242, the laser beam 6 having an angle of 50° in the clockwise direction relative to the vertical direction V.

[0098] The zones 243, 245, 247, 244, 246, 248 to be stripped overlap two by two partially on at least one of their transverse edges, so that the stripping is carried out without discontinuity over the entire weld bead 26 on the predetermined path.

[0099] At the end of step 400, the stripping device 5 stores in a ROM (Read Only Memory) or RAM (Random Access Memory) memory, the division thus carried out of the predetermined path into zones to be stripped, each zone to be stripped being associated with a single configuration of the mobile support 11 and / or the laser stripping head 52. Indeed, during the stripping of a zone to be stripped resulting from step 400, the mobile support 11 and the laser stripping head 52 remain stationary. The zones to be stripped are also ordered by the stripping device 5 in a list according to a processing order making it possible to minimize the stripping time of the waterproofing membrane 2 by the stripping device 5. As will be seen below, this ordering does not correspond to continuous stripping on the predetermined path.

[0100] It should be noted that as a variant, the cutting step 400 is carried out at least in part, in parallel with the profile generation step 200.

[0101] The following step is a step of treating the waterproofing membrane 2 by the treatment device, here a stripping step 500 implemented by the stripping device 5, along the predetermined path. This treatment step comprises at least one sub-step of modifying the configuration of the mobile device and / or a treatment tool of the treatment device, here a sub-step 502 of modifying the configuration of the mobile support 11 and / or the laser stripping head 52. In particular, sub-step 502 corresponds to a modification of a height of the laser stripping head 52, and / or of the position of the mobile support 11 on the rail, and / or of an angle of the laser stripping head 52 relative to an axis orthogonal to a main plane of extension of the waterproofing membrane 2.

[0102] Unlike the prior art, the stripping step 500 does not use a position sensor relative to the sealing membrane 2.

[0103] More precisely, at the start of the stripping step 500, the stripping device 5 places the mobile support 11 longitudinally on the rail 3 and orients the laser stripping head 52 so as to be able to strip the first zone to be stripped in the list of zones to be stripped resulting from the cutting step 400, without subsequent movement of the mobile support 11 and the laser stripping head 52. This modification of the configuration of the mobile support 11 and / or the laser stripping head 52 corresponds to a first sub-step 502 of configuration modification on a current zone to be stripped, which is at the start of step 500, this first zone to be stripped.

[0104] A second sub-step 504 of the stripping step 500 is the stripping of the current area to be stripped, using scanning by the laser beam 6 of the current area to be stripped. For information, the stripping speed in this exemplary embodiment is 7cm2 / s (square centimeter per second).

[0105] Finally, a third sub-step 506 of the stripping step 500 is the change of current zone to be stripped, if the list of zones to be stripped has not been fully traversed, otherwise the end of the stripping step 500. If the list of zones to be stripped has not been fully traversed, the current zone to be stripped is replaced by the zone to be stripped immediately following the current zone to be stripped in the list of zones to be stripped, and the following sub-step of the stripping step 500 is a new sub-step 502 of configuration modification taking into account the new zone to be stripped.

[0106] Sub-steps 502 to 506 are therefore iterated until the weld bead 26 is completely stripped.

[0107] The configuration modification sub-steps 502 correspond, in this example of use of the invention, to:

[0108] - a longitudinal displacement of the mobile support 11, and / or

[0109] - a change in orientation of the laser stripping head 52, and / or

[0110] - a change in height of the laser stripping head 52 relative to the waterproofing membrane 2.

[0111] These configuration modification sub-steps are carried out without projection of the laser beam 6, therefore “empty”. The stripping time is reduced compared to the prior art.

[0112] In other examples of use of the invention, such a configuration modification sub-step 502 may comprise other types of movement, for example a transverse movement of the mobile device and / or of a processing tool.

[0113] The stripping method therefore takes place sequentially, the configuration modification steps 502 being carried out empty between each stripping sequence on an area to be stripped. The stripping sequences which follow one another do not necessarily correspond to adjacent areas of the waterproofing membrane 2.

[0114] For example, the mobile support 11 performs, during step 100, a continuous passage along the predetermined path on the rail 3 at the edge of the sealing plate 2-1 in the direction 55 of the longitudinal direction L. This continuous passage is carried out empty. The cutting step 400 is then carried out by the generating device 1 without movement of the stripping device 5. In step 500, the stripping device 5 then performs a first path in the direction 59, during which it strips all the slopes 242 of the waves 24 that it encounters, as well as the first halves 221 (referenced [Fig.5]) of the flat areas 22 that it encounters. Then the stripping device 5 makes a second journey in the direction 55, during which it strips all the slopes 241 of the waves 24 that it encounters, as well as the second halves 222 of the flat areas 22 that it encounters.

[0115] The fact that the stripping device 5 first performs a first path during which it strips the slopes 241 of waves 24, which are rising slopes in the direction 59 of this first path, then performs a second path during which it strips the slopes 242 of waves 24, which are rising slopes in the direction 55 of this second path, makes it possible to gain in speed of execution of the stripping method, in particular in rotation time of the laser stripping head 52. Indeed, if the stripping device 5 stripped each wave 24 in a single unidirectional path along the rail 3, the laser stripping head 52 would be required to perform several rotations of 140°, which is not the case in this example of the stripping method according to the invention. The stripping process according to this example is optimized in terms of longitudinal movements and in terms of rotations of the laser stripping head 52, for the same division of the predetermined path into areas to be stripped.

[0116] Of course, other variants of the stripping method according to the invention are possible, in particular as a variant, the waves 24 of the waterproofing membrane 2 are cut into four zones to be stripped only, each slope 241, 242 being then divided into two areas to be stripped, one covering the foot of a slope 241, 242 and the other covering the top of a slope 241, 242. In this case the areas to be stripped corresponding to wave feet are stripped with a laser beam angle of 70° relative to the vertical direction V, and the areas to be stripped corresponding to wave tops are stripped with a laser beam angle of 50° relative to the vertical direction V.

[0117] A method for controlling a sealing membrane 2 is now described in relation to [Fig. 10]. This control method comprises first steps 100 of passing the position sensor 12 and 200 of generating a profile of at least a portion of the sealing membrane 2, implementing the method for generating a profile previously described in relation to FIGS. 1 and 2.

[0118] The following step 700 of the control method is the comparison between a distance obtained using the profile generated during the generation step 200, and a corresponding distance of a pre-recorded template of the waterproofing membrane part 2. These distances correspond for example to:

[0119] - a distance measured on the sealing membrane 2 and a corresponding distance laying taken on the pre-recorded template,

[0120] - or a distance measured along the vertical direction V between a point on an axis of reference (e.g. rail 3) and the waterproofing membrane and, and a corresponding distance from the pre-recorded template.

[0121] During this comparison, the difference between the distance obtained using the generated profile and the corresponding distance of the pre-recorded template is calculated. Then the difference calculated during step 700 is compared with a predetermined threshold. This predetermined threshold is for example one or two millimeters and makes it possible to detect poor positioning of a wave 24 on the sealing membrane 2, or deformation of a wave 24 on the sealing membrane 2.

[0122] In the following step 800, if the distance calculated during step 700 is lower in absolute value than the predetermined threshold, then steps 700 and 800 are iterated over other distances of the profile generated in step 200 and of the pre-recorded template, until the generated profile is completely covered or an anomaly is detected in step 800.

[0123] If, on the contrary, the distance calculated during step 700 is greater in absolute value than the predetermined threshold, then an anomaly of the sealing membrane 2 is detected, which triggers, for example, in step 800, a step of recording the anomaly, and / or of raising an alert on a user interface.

[0124] Of course, the invention is 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.

Claims

Claims

1. A method of treating a sealing membrane (2) suitable for a tank intended to contain gas in the liquid state, using a treatment device (5, 7) for the sealing membrane (2), the treatment device (5, 7) comprising a mobile device (70, 11) and at least one treatment tool (72, 52) mounted on the mobile device (70, 11), the treatment method comprising a step of treating (600, 500) the sealing membrane (2) by the treatment tool (72, 52) along a predetermined path of the mobile device (70, 11), the treatment method comprising: - a prior step of generating (200) a profile of at least a part of the sealing membrane (2) on the predetermined path, using a mobile support (11) provided with a position sensor (12) and a passage (100) of the position sensor above the sealing membrane (2), during which the sub-steps of: - determination (102) of a distance (d) between a reference point of the position sensor and at least one point of the sealing membrane part (2), - recording (104) of the determined distance (d), - moving (106) of the mobile support (11), the generation (200) of the profile of the part of the waterproofing membrane (2) being a function of the distances (d) recorded during the recording sub-steps (104), the processing method being characterized in that it further comprises: - a step of cutting (400), as a function of the profile generated during the generation step (200), the predetermined path into processing zones (243,244,245,246,247,248) of the waterproofing membrane (2), between which at least one sub-step of modification (502) of the configuration of the mobile device (11) and / or of the processing tool (52) is necessary, and - at least one sub-step of modification (502) of the configuration of the mobile device (11) and / or of the processing tool (52), between two of said processing zones.

2. A treatment method according to claim 1, wherein the sealing membrane (2) comprises first and second sealing plates arranged against each other, the sealing membrane (2) portion being an edge of the first sealing plate (2-1), the edge of the first sealing plate (2-1) being arranged above an edge of a second sealing plate (2-2), and wherein the passage (100) of the position sensor (12) is also adapted to determine distances (d) between points of the edge of the second sealing plate (2-2) and the reference point of the position sensor, the generating step (200) producing a profile of the edge of the first sealing plate (2-1), and of the edge of the second sealing plate (2-2).

3. A treatment method according to claim 1 or 2, wherein the position sensor (12) is a scanning laser sensor, the sub-step of determining (102) a distance (d) corresponding to a sub-step of determining (102) several distances (d) for the same position of the movable support (11), and the generation step (200) producing a three-dimensional profile of the sealing membrane portion (2).

4. A treatment method according to any one of claims 1 to 3, wherein the treatment corresponds to an operation of stripping a weld bead (26) at two edges of sealing plates (2-1, 2-2) of the sealing membrane (2), the sealing membrane portion (2) being an edge of a first sealing plate (2-1), an edge of a second sealing plate (2-2) being arranged against the edge of the first sealing plate (2-1).

5. Method for treating a sealing membrane (2) suitable for a tank intended to contain gas in the liquid state according to any one of claims 1 to 4, in which the configuration modification sub-step (502) generates a movement of the mobile device (11) and / or of the treatment tool (52), the treatment being interrupted during said configuration modification sub-step (502).

6. A treatment method according to any one of claims 1 to 5, wherein the sealing membrane (2) comprises waves (24), these waves (24) forming a grid on said sealing membrane (2), and wherein the treatment tool (52) is a laser stripping head positioned on the predetermined path for stripping a weld bead (26), a configuration modification sub-step (502) being triggered to position an impact point (63) of a laser beam (6) projected by the laser stripping head, on an area (243, 244) located at the foot of a wave (24) of the sealing membrane (2).

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