Method for controlling the thickness of adhesive between two composite sheets of a liquefied gas tank wall and associated device

Abstract

Method for controlling the thickness of glue between two sheets of a liquefied gas tank wall and associated device The invention relates to a method for controlling the thickness of glue in a study area extending between an upper composite sheet (133) and a lower composite sheet (231) arranged on at least one wall (8, 7) of the tank, the control method comprising the steps of: positioning one end (66) of an electromagnetic field emitter (65) on the upper composite sheet (133) at the right of a current portion (Pi) of the study area, the end of the emitter conforming to the shape of the upper composite sheet of the current portion; generating a variable magnetic field by the electromagnetic field emitter, so as to create induced currents circulating in the current portion (Pi);reception of a signal (69) having a magnetic phase shift characteristic of a distance (60) between the upper composite sheet and the lower composite sheet; determination of the glue thickness in the current portion from the magnetic phase shift. (Figure 5);

Description

Title of the invention: Method for controlling the thickness of adhesive between two composite sheets of a liquefied gas tank wall and associated device

[0001] The present invention relates to the field of liquid gas tanks, for example liquefied natural gas (LNG) tanks, especially for maritime or river transport or for a land storage tank. More precisely, the invention concerns a device and a method for controlling the thickness of adhesive between two composite sheets of a wall of a tank intended to receive liquefied gas.

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

[0003] The gas is kept in these transport or storage tanks in a liquid state, for example at -163°C (degrees Celsius) for LNG, at atmospheric pressure. It is therefore necessary that the tank be leak-proof and thermally insulated.

[0004] Figure 1 schematically represents a cross-sectional view of the wall of a state-of-the-art tank intended for the transport and / or storage of liquefied gas. The tank comprises a load-bearing structure 50, and such a wall is generally made up of two successive sealing membranes: the primary membrane 10 is intended to be in contact with the product contained in the tank, and the secondary membrane 30 is positioned between the primary membrane 10 and the load-bearing structure 50, for example, an internal bulkhead of the ship. Each of these membranes is associated with a thermally insulating barrier. The primary insulation thus comprises the primary membrane 10, which rests on the primary thermally insulating barrier 20, itself positioned on the secondary membrane 30, which rests on the secondary thermally insulating barrier 40 attached to the load-bearing structure 50.The primary membrane 10 is typically made of stainless steel and includes corrugations extending over one surface of the primary membrane. These corrugations are designed to give the primary membrane flexibility to accommodate the thermal contraction of the steel during the cooling of the tank. The insulation blocks forming the thermally insulating barriers 20, 40 are preferably made of reinforced polyurethane foam.

[0005] The secondary membrane 30 comprises at least one thin, continuous composite sheet, for example made of aluminum, sandwiched between two glass fiber fabrics, a binder This thin composite sheet, which ensures cohesion between the glass fabrics and the aluminum, is also called a rigid secondary barrier (RSB). It covers each of the insulation blocks of the thermally insulating barrier 40, for example, blocks 31 and 32 of wall 8 and blocks 33 and 34 of wall 7. In [Fig. 1], although not directly visible, block 32 is indicated to show its position on the tank wall. Block 32 is visible in [Fig. 2]. It should be noted that an insulator 41, for example glass wool, is placed between two thermal insulation blocks 31, 32 and between two insulation blocks 33, 34 of the thermally insulating secondary barrier 40, but also between the insulation blocks 31, 33 and 32, 34, to fill the gaps present between the thermal insulation blocks 31, 32, 33, 34.The insulation 41 forms a thermally insulating joint between the load-bearing structure 50 and the secondary waterproofing membrane 30.

[0006] A thin, continuous composite sheet 130 is bonded at the junction between two sets of insulation blocks to ensure the continuity of the barrier. This thin composite sheet 130 consists of an aluminum sheet sandwiched between two layers of fiberglass fabric and exhibits a degree of flexibility. The sheet 130 is also called a flexible secondary barrier or FSB. This sheet will be referred to as the flexible sheet. The overlapping of the rigid sheet (RSB) and flexible sheet (FSB) layers has been described here on a flat portion of the wall. The details of the assembly at a corner area between two walls 7, 8 will be described with reference to [Fig. 2].

[0007] It should be noted that the arrangement of the insulation element(s) and membranes described above is by way of illustration and is in no way limiting. The invention relates more specifically to the bonding area of ​​the flexible sheets.

[0008] Figure 2 schematically illustrates a prior art tank corner area during assembly, at the intersection of two tank walls 7, 8. These two walls 7, 8 form an angle A between them, for example of 90° or 135° (here angle A is 135°).

[0009] The corner zone consists of two pre-assembled blocks 70, 80 and an insulating layer 41 placed between the blocks 70, 80 to ensure thermal sealing between said two pre-assembled blocks 70, 80. Each pre-assembled block comprises two thermal insulation blocks (31, 33 for the pre-assembled block 80 and 32, 34 for the pre-assembled block 70), each placed on one of the walls 7 or 8 so as to form the aforementioned corner. For each pre-assembled block, an insulating layer, for example glass wool, is generally inserted between the two thermal insulation blocks.

[0010] In this corner area, for each of the pre-assembled blocks, for example block 80, a rigid sheet (RSB) 131 is glued onto each of the thermal insulation blocks 31, 33 of the two walls 7, 8 of the tank. Similarly for block 70, a second rigid sheet (RSB) 132 is glued onto each of the two thermal insulation blocks 32, 34 of the two walls 7, 8 of the tank.

[0011] For the pre-assembled block 80, a flexible sheet (FSB), referred to as the lower composite sheet 231, is bonded at the intersection of the two tank walls 7, 8. The flexible sheet covers the junction of the two walls and extends from the junction on either side of each of the insulation blocks 31, 33. The flexible sheet thus partially covers the rigid sheets 131 in the corner area. Two distal portions 2311 of the flexible sheet are each bonded to a portion of the rigid sheet 131, while a central portion 2312 of the flexible sheet may not be bonded.

[0012] What has just been described for the pre-assembled block 80 is similarly applicable to the pre-assembled block 70 with a flexible sheet, being a lower composite sheet 232.

[0013] In the remainder of this description, the term "composite sheet" may refer to either an FSB sheet or an RSB sheet. As a reminder, a composite sheet, within the scope of the invention described in this document, consists of an aluminum sheet sandwiched between two layers of glass fiber fabric. In other words, a composite sheet comprises a metal sheet, and this composite sheet may be an FSB sheet or an RSB sheet.

[0014] The pre-assembled blocks 70, 80 are prefabricated. This pre-assembly is delivered to the site for installation in the tank. The two pre-assembled blocks 70, 80 are positioned and secured in the tank. The insulation 41 is inserted between the two pre-assembled blocks. At this stage, in superposition from the load-bearing structure towards the interior of the tank, the pre-assembled blocks thus comprise a succession of layers: the insulating blocks (31, 33 and 32, 34), a rigid sheet (131 and 132), and a flexible sheet (lower composite sheets 231 and 232).

[0015] To ensure the continuity of the secondary barrier, an additional flexible sheet, referred to as the upper composite sheet 133, is bonded across the two adjacent flexible sheets (lower composite sheets 231, 232). It should be noted that the lower sheet positioned beneath the additional flexible sheet can be a rigid sheet (RSB). The additional flexible sheet seals the secondary sealing membrane between the adjacent thermal insulation blocks 31, 32, 33, 34 in the corner area. This bonding step is performed on the pre-assembly shown above. This step is carried out on-site, within the tank. The bonding of the additional flexible sheet is generally performed manually, which can lead to variations in the thickness of the adhesive between the two layers of flexible sheets.It is important to understand here that the glue thickness considered is the thickness between, on the one hand, the level of the flexible sheets of the pre-assembled blocks. 70 and 80, and on the other hand, the level of the additional flexible sheet. Furthermore, once applied, the adhesive on wall 7 tends to slide towards the intersection 9 of the tank walls 7 and 8 due to the effect of gravity. This results in an excess of adhesive localized at the intersection 9 of the walls and an adhesive defect in the upper part of the additional flexible sheet.

[0016] The corner area is subject to particular stress due to its position between two tank walls. This corner area must be both flexible and resistant to the thermomechanical stresses it undergoes. The adhesive thickness between the flexible sheets and the additional flexible sheet is crucial for ensuring the corner area is watertight. The adhesive thickness between these two flexible sheets must be between two threshold values, for example, between 0.2 and 1.2 mm (millimeters). If the adhesive thickness does not meet this requirement, there is a risk of cracking in the additional flexible sheet, leading to a leak in the sealing membrane in the corner area.

[0017] An existing solution for checking the glue thickness between the flexible sheets and the additional flexible sheet involves using a measuring gauge, for example, a ruler. An operator places the measuring gauge on an edge 1331, or 1332, of the additional flexible sheet 133 to measure the distance between the flexible sheet of the pre-assembled block 80, or the pre-assembled block 70, and the additional flexible sheet, in a direction locally perpendicular to the flexible sheets. The measured distance between the flexible sheet and the additional flexible sheet allows the glue thickness between these two flexible sheets to be deduced. Although generally satisfactory, this manual check has a reading bias related to the positioning of the measuring gauge and the operator's position during the reading.Furthermore, this measurement only provides information on the adhesive thickness at the periphery of the additional flexible sheet. Using such a measuring shim does not provide information on the adhesive thickness across the entire surface of the additional sheet, i.e., between the two edges 1331, 1332 of the additional sheet.

[0018] The present invention aims to remedy at least in part the aforementioned drawbacks by providing a device and a method for controlling the thickness of glue between two flexible composite sheets of a tank wall, allowing for rapid, precise and easy-to-implement control of the glue thickness.

[0019] To this end, the invention proposes a method for controlling the thickness of adhesive in a study area extending between an upper composite sheet and a lower composite sheet arranged on at least one tank wall, the control method comprising: - A placement step (also called the first step) of one end of an electromagnetic field emitter on the upper composite sheet at the right of a current portion of the study area, the end of the emitter conforming to the shape of the upper composite sheet of the current portion; - A generation stage (also called the second stage) of a variable magnetic field by the electromagnetic field emitter, so as to create induced currents circulating in the current portion; - A reception stage (also called the third stage) of a signal exhibiting a magnetic phase shift characteristic of a distance between the upper composite sheet and the lower composite sheet; - A determination step (also called the fourth step) of the glue thickness in the current portion from the magnetic phase shift.

[0020] Thanks to these characteristics, the control method relies on the creation of induced currents in the two composite sheets separated by a layer of adhesive. A reaction magnetic field is generated in each of the composite sheets. The control method uses the magnetic phase shift resulting from the spacing of the two composite sheets to determine the distance between the two magnetic sheets. This distance corresponds to the adhesive thickness that the method aims to control.

[0021] In other words, the use of a magnetic field makes it possible to determine, in a non-invasive manner, the thickness of the adhesive separating the two sheets of FSB. This determination is quick and precise, and can be carried out on any area of ​​the tank wall.

[0022] According to an optional feature of the invention, the control method includes a step of moving the end of the electromagnetic field emitter on the upper composite sheet to the right of a portion adjacent to the current portion, and carrying out the generation, reception and determination steps for the adjacent portion, so as to determine the thickness of glue in said adjacent portion.

[0023] This step allows the adhesive thickness to be determined successively for a study area. In particular, thanks to the method of the invention, it is possible to determine the adhesive thickness between the two composite sheets, under the entire surface of the upper composite sheet, and not only at its periphery as is the case in existing solutions.

[0024] According to an optional feature of the invention, the generation, reception, and determination steps are performed continuously. This means that the generation, reception, and determination steps are also performed while the end of the electromagnetic field emitter is moving along the sheet. Superior composite. This refers to a linear embodiment in which the glue thickness measurement is also performed during the movement step.

[0025] According to an optional feature of the invention, the upper composite sheet and the lower composite sheet are arranged on two intersecting tank walls along an axis of intersection and forming a tank angle between them, the end of the electromagnetic field emitter being arranged on the axis of intersection during the arrangement step (first step).

[0026] It is thus possible to determine the glue thickness at the corner of the tank, that is, in a very localized area where there is likely to be excess glue between the two sheets. Indeed, as explained above, the angle between two walls causes the glue to slide by gravity during the bonding step of the FSB sheets. Since this area between the two FSB sheets in the corner zone is inaccessible, it is traditionally impossible to verify the glue thickness. Thanks to the method of the invention, the use of a magnetic field and the recovery of the resulting magnetic phase shift from the two FSB sheets makes it possible to access this information and to verify whether the glue thickness is within the required range.

[0027] In one embodiment of the invention, the step of moving the end of the electromagnetic field emitter is carried out along the axis of intersection. By moving the emitter along the axis of intersection, a plurality of adhesive thicknesses are obtained. This makes it possible to control the adhesive thickness over a large area of ​​the study zone.

[0028] According to an optional feature of the invention, the control method includes a preliminary calibration step for calibrating the magnetic phase shift as a function of predetermined adhesive thicknesses. The predetermined adhesive thicknesses form part of, or constitute a database.

[0029] The calibration step consists of taking a single measurement of the adhesive thickness as discussed previously. In other words, in a given configuration, and for a plurality of known adhesive thicknesses, the emitter is placed on the upper surface of a test area that corresponds exactly to the area to be evaluated. For each adhesive thickness, an electromagnetic field is generated by the emitter, creating induced currents. This results in two reaction magnetic fields exhibiting a magnetic phase shift. Each collected magnetic phase shift is associated with the known adhesive thickness of the configuration under test. A lookup table is thus obtained between the measured magnetic phase shift and the adhesive thickness.Thus, during the execution of the control process, an operator is able to determine the glue thickness from the measured magnetic phase shift using the lookup table.

[0030] According to an optional feature of the invention, the control method includes a step of comparing the glue thickness determined in the determination step with a range of reference values. This comparison makes it possible to identify whether the determined glue thickness meets the criteria required for the area under study.

[0031] According to an optional feature of the invention, the control method includes a step of emitting an alert signal if the glue thickness determined in the determination step is outside the range of reference values.

[0032] The invention also relates to a device for controlling the thickness of glue in a study area extending between an upper composite sheet and a lower composite sheet arranged on at least one tank wall, the device comprising: - An electromagnetic field emitter having an end conforming to the shape of the upper composite sheet at the right of a current portion of the study area; - An electric current generator intended to power the electromagnetic field emitter so as to generate a variable magnetic field creating induced currents flowing in the current portion, - A means for processing a signal exhibiting a magnetic phase shift characteristic of the glue thickness, said means being configured to determine the glue thickness in the current portion from the magnetic phase shift.

[0033] According to an optional feature of the invention, the upper composite sheet and the lower composite sheet being arranged on two intersecting tank walls along an axis of intersection and forming a tank angle between them, the end of the electromagnetic field emitter is of a shape complementary to the tank angle.

[0034] The complementary shape between the emitter tip and the tank angle ensures complete contact between the emitter and the study area. This prevents measurement biases that could be caused by air trapped between the emitter and the study area.

[0035] Furthermore, the electromagnetic field emitter may include a shoe forming the emitter's end. The shoe allows the shape of the emitter's end to be adapted to the shape of the study area to ensure that the shape of the emitter's end is complementary to that of the study area. The shoe can be interchangeable depending on the study area. Thus, there is no need to change the electromagnetic field emitter for different shapes of study area.

[0036] According to an optional feature of the invention, the electromagnetic field emitter comprises a laterally extending positioning device and intended to bear against the upper composite sheet of the current portion on either side of the electromagnetic field emitter.

[0037] The positioning device allows the transmitter to be correctly positioned both against the area of ​​study and relative to the tank walls. The positioning device, combined with the complementary shape of the transmitter's tip, ensures that no measurement bias is introduced by the operator. Indeed, the transmitter is placed in a stable reference position. This feature contributes to high measurement accuracy and speed.

[0038] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0039] [Fig. 1] schematically represents a cross-sectional view of a wall of a tank intended for the transport and / or storage of liquefied gas known from the prior art,

[0040] [Fig.2] schematically illustrates a prior art tank corner area in progress assembly, at the intersection of two tank walls,

[0041] [Fig.3] represents a flowchart of the steps in the process of controlling a glue thickness according to the invention,

[0042] [Fig.4] schematically represents the principle of induced current creation used in the method of controlling the invention,

[0043] [Fig.5] schematically represents an embodiment of the field emitter magnetic device for controlling the thickness of glue according to the invention,

[0044] [Fig.6] schematically represents an example of implementation of the process of controlling the thickness of the adhesive between two sheets of FSB,

[0045] [Fig.7] schematically represents another example of implementation of the process for controlling the thickness of the adhesive between two sheets of FSB.

[0046] The features, variants, and different embodiments of the invention, as described or as they will be presented in the detailed description that follows, can be combined in various ways, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0047] For the sake of clarity, the same elements are designated by the same references in the different figures.

[0048] Figure 1 schematically represents a cross-sectional view of a wall of a tank intended for the transport and / or storage of liquefied gas, known from the prior art. Figure 2 schematically illustrates a corner area of ​​a prior art tank during assembly, at the intersection of two tank walls. These figures were described in the introduction to present the context in which the method for controlling the thickness of the adhesive between two sheets of FSB is applied.

[0049] Figure 3 shows a flowchart of the steps in the method for checking the thickness of an adhesive according to the invention. Although not shown in Figure 3, the reader may refer to Figures 4 to 7 for the references mentioned. The method for checking the thickness of an adhesive 60 is carried out in a study area extending between an upper composite sheet 133 and a lower composite sheet 231 arranged on at least one wall 7, 8 of a tank. The method for checking the thickness of the invention aims to determine the thickness of the adhesive 60 between the two composite sheets 231, 133. The upper and lower composite sheets are two sheets of FSB presented in the introduction.

[0050] According to the invention, the control method comprises a step 100 of arranging one end 66 of an electromagnetic field emitter 65 on the upper composite sheet 133 opposite a current portion Pi of the study area. The study area can be, for example, a width of the upper composite sheet 133 (between the edge 1331 and the edge 1332 shown in [Fig. 2]). Opposite the current portion Pi means that the emitter 65 is arranged opposite a portion of the study area determined to be the current portion Pi. Thus, the study area can be formed from a succession of current portions (which we will call Pi-1, Pi, Pi+1).

[0051] The end 66 of the transmitter 65 conforms to the shape of the upper composite sheet 133 of the current portion. This allows the transmitter to adapt to the angle of the tank for control carried out at the junction of two walls.

[0052] The control method includes a step 200 of generating a variable magnetic field by the electromagnetic field emitter 65, so as to create induced currents flowing in the current portion Pi. These induced currents will generate a reaction magnetic field which will serve as the basis for determining the glue thickness. This aspect will be detailed below.

[0053] The control method then includes a step 300 of receiving a signal 69 having a magnetic phase shift 61 characteristic of a distance 60 between the upper composite sheet 133 and the lower composite sheet 231.

[0054] The control method further includes a step 400 of determining the thickness of glue 60 in the current portion Pi from the magnetic phase shift 61.

[0055] The invention is based on the creation, in an electrically conductive material, of currents induced by an external current. The control method according to the invention takes advantage of the presence of the two FSB sheets 133, 231, each containing a metallic layer, in particular aluminum. Thus, by supplying the electromagnetic field emitter 65 with a sinusoidal voltage, an electromagnetic field is generated by the emitter 65. Induced currents are formed and flow in the current portion Pi, in each of the metallic layers of the FSB sheets 133, 231. A reaction magnetic field is generated for each metallic layer. A difference between the reaction magnetic fields results from the two layers (namely the metallic layer of the FSB sheet 231 and the metallic layer of the FSB sheet 133). This difference, or magnetic phase shift, depends on the distance between the two FSB sheets 231, 133.In other words, thanks to the magnetic phase shift received in step 300, it is possible to determine the distance between the two FSB 133, 231 sheets, i.e., the 60 thickness of adhesive between the two FSB sheets. This determination is carried out using a database compiling the correspondence between magnetic phase shifts and the distances between two composite sheets.

[0056] The phenomena involved in the control method of the invention will be detailed below.

[0057] Figure 4 schematically represents the principle of induced current creation on which the invention is based to determine the thickness of the adhesive between the two sheets of FSB 231, 133. The circulation of induced currents in an electrically conductive material is a non-destructive testing technique. This technique consists of using an electromagnetic field emitter 65, for example a coil or a magnetic bar, which is supplied, via a voltage generator 67, with a sinusoidal voltage U.

[0058] In the vicinity of a part to be controlled, the electromagnetic field emitter emits a magnetic field Bi. Eddy currents are then induced in the conductive material and a reaction magnetic field is created in the material.

[0059] In the context of the invention, the study area comprises two sheets of FSB 133, 231, one above the other and spaced apart by a distance to be determined. In other words, two layers of conductive material are superimposed at a certain distance 60 from each other. The emission by the emitter 65 of a magnetic field Bi will induce eddy currents in the two sheets of FSB 133, 231. For each of the sheets of FSB 133, 231, a reaction magnetic field is created (Brl for the upper sheet of FSB 133 and Br2 for the lower sheet of FSB 231). A processing means 68 recovers a signal 69 from the two magnetic fields Brl, Br2. This signal 69 has a magnetic phase shift characteristic of the thickness of glue 60. In a variant, the electromagnetic field emitter can act as an electromagnetic field sensor by measuring the magnetic field.

[0060] Indeed, it is known that the distribution of induced currents depends on many parameters such as the frequency of the sinusoidal supply voltage of the electromagnetic emitter, the geometry of the part, the characteristics of the electromagnetic emitter (for example its geometry, and its number of turns) and the value of the amplitude of the supply voltage, as well as the distance between the emitter and the part to be controlled.

[0061] During the testing procedure of the invention, all these parameters are kept constant. The only difference is the distance between the electromagnetic emitter and the FSB sheets: the electromagnetic field emitter 65 is in contact with the upper sheet of FSB 133, and the electromagnetic field emitter 65 is located at a certain distance from the lower sheet of FSB 231, a distance corresponding to the thickness of the adhesive 60 that is to be tested. Due to this distance between the two FSB sheets, a magnetic phase shift is observed. This magnetic phase shift is directly correlated to the distance between the two FSB sheets 231 and 133.

[0062] The invention thus makes it possible to determine the distance between two composite sheets by reading a magnetic phase shift.

[0063] Advantageously, the control method of the invention includes a prior calibration step 90 intended to calibrate the magnetic phase shift according to predetermined glue thicknesses.

[0064] During this calibration step, steps 100, 200, and 300 are performed on a test tank wall. All operating conditions are identical to the actual case in which the control process will subsequently be implemented. The FSB sheets of the test tank are identical to sheets 133 and 231, and the same adhesive is used between the two FSB sheets as that which will be placed between sheets 133 and 231 under actual conditions in the tank. With all parameters identical, a series of measurements is performed for different known adhesive thicknesses between the two FSB sheets 133 and 231. The reference range for the adhesive thickness is preferably between 0.2 and 1.2 mm. The resulting magnetic phase shift is recorded for each adhesive thickness.Thus, calibration step 90 allows for a tabulation of the magnetic phase shift obtained as a function of the glue thickness between the two FSB sheets. This calibration step is performed only once, in order to associate a glue thickness separating the two FSB sheets 231, 133 with a measured magnetic phase shift.

[0065] In [Fig. 4], the principle on which the invention is based is applied to a flat wall. However, as explained in the introduction, the particularly important area to be controlled is a corner area between two walls forming The two walls 7 and 8 intersect at an angle A, which can be either 90° or 135°. At the intersection, the two walls 7 and 8 intersect along an axis of intersection 9 (visible in [Fig. 5]) and form the tank angle A. Each FSB sheet has a fold in this intersection, which elicits a different response in terms of magnetic resonance field than flat FSB sheets. Therefore, calibration step 90 must also be performed at the tank angle A for which the adhesive thickness will be checked. Thus, if the adhesive thickness between two FSB sheets on a flat wall is to be checked in a tank angle area between two walls, for example, at 90°, calibration step 90 must first be performed once on a flat wall and once at a 90° tank angle.For each wall configuration (flat or forming an angle between two walls), calibration step 90 provides a series of magnetic phase shift values, each corresponding to a distance between the two FSB sheets (i.e., the glue thickness between these two FSB sheets).

[0066] Figure 5 schematically represents an embodiment of the magnetic field emitter 65 of the control device 1000 for a glue thickness 60 according to the invention. In this illustration, the tank angle, i.e., the angle formed by the two walls 7, 8 at their intersection, is 135°. The area of ​​study is located at the intersection 9 of the two walls 7, 8. The aim is therefore to control the glue thickness between the two sheets of FSB 231, 133 at the intersection 9. Two standard portions are shown (Pi-1 and Pi). As can be seen, the end 66 of the emitter 65 conforms to the shape of the upper composite sheet 133 of the standard portion. This means that the end 66 of the emitter 65 forms an angle of 135° to conform to the tank angle between the walls 7, 8.This complementary shape between the end 66 of the emitter 65 and the upper surface of the study area allows the end 66 to be in complete contact with the upper surface of the study area. This prevents measurement drifts that could be caused by air gaps that might be interposed between the end 66 of the emitter 65 and the upper surface of the area to be monitored.

[0067] According to an optional feature of the invention, the electromagnetic field emitter 65 comprises a shoe 661 forming the end 66 of the emitter 65. The shoe 661 has two ends. A first end of the shoe 661 is connected to a lower end of the emitter 65. A second end of the shoe 661 is complementary in shape to the upper surface of the area under study. To control the adhesive thickness between two sheets of FSB on a flat wall, the second end of the shoe 661 is flat. To control the adhesive thickness between two sheets of FSB in an area at an angle A, the second end of the shoe 661 is complementary in shape to angle A. The second end of the shoe 661 is thus well wedged in the corner of the tank. The second end of the shoe 661 is coplanar with the two planes formed by the two walls 7,8.

[0068] In addition to ensuring accurate measurement, the complementary shape of the end 66 of the transmitter 65 helps to facilitate the movement of the transmitter 65 along the study area.

[0069] The shoe 661 can be made of plastic, for example polytetrafluoroethylene (better known by its abbreviation PTFE), steel or any other alloy or composite material.

[0070] It should be noted that calibration step 90 must be carried out in the intended measurement configuration. This means that in order to check the thickness of the adhesive between two sheets of FSB at a tank angle A with a transmitter including a PTFE shoe, the calibration step must first be carried out in this same configuration (same tank angle A and same PTFE shoe).

[0071] According to an optional feature of the invention, the electromagnetic field emitter 65 comprises a laterally extending positioning device 662 designed to bear against the upper composite sheet 133 of the current portion Pi, on either side of the electromagnetic field emitter 65. The positioning device 662 may be a pair of strips extending from a central body 663 of the emitter, on either side of the central body 663, advantageously symmetrically with respect to the central body 663, and whose ends bear against the upper surface of the area under study. It is thus understood that the length of the strips depends on the angle A of the tank. Depending on the shape of the emitter 65, it may comprise several pairs of strips distributed on either side of the central body 663 of the emitter 65.

[0072] The positioning device 662 facilitates positioning the transmitter 65 relative to the walls 7, 8 and maintains this position during measurement. It thus defines a stable reference position for the transmitter 65. Furthermore, the positioning device 662 prevents any risk of the transmitter 65 tipping over during handling. It guides the transmitter 65 along the study area. Combined with the complementary shape of the end 66 of the transmitter 65, the positioning device 662 allows the transmitter 65 to be secured against the study area and in the same orientation relative to the walls. The complementary shape of the end 66 of the transmitter 65 and the positioning device 662 eliminate the impact of the operator, since the transmitter 65 is thus always positioned in its stable reference position.In addition to the speed of execution of the movement and positioning of transmitter 65, this results in high measurement accuracy.

[0073] Figure 6 schematically illustrates an example of implementing the method for checking the adhesive thickness between two sheets of FSB. At this stage of the checking process, calibration step 90 has been previously performed once on a test area with the same tank angle (here 135°), using the same emitter 65 and under operating conditions identical to the actual checking situation. The operator thus has a lookup table linking the magnetic phase shifts observed during the calibration step to the corresponding adhesive thicknesses between two sheets of FSB.

[0074] The end 66 of the emitter 65 is positioned on the upper FSB sheet 133 at the edge of a current portion Pi of the study area. The current portion Pi is located at the intersection 9 between the two walls 7, 8. The end 66 of the emitter 65 conforms to the shape of the upper composite sheet 133 of the current portion. It is understood that in the example of [Fig. 6], the emitter 65 has a beveled end 66 with an angle of 135°.

[0075] Figure 7 schematically represents another example of implementation of the Method for controlling the glue thickness between two sheets of FSB. In this example, the transmitter 65 has a U-shape with two portions in contact with the upper surface of the FSB sheet 133. In fact, these two portions form an end of the transmitter that conforms to the shape of the FSB sheet 133.

[0076] It should be noted that this is a non-limiting example. The invention applies to any form of electromagnetic emitter one end of which has a shape complementary to the area of ​​study that one wishes to control.

[0077] The control device 1000 of the invention further comprises an electric current generator 67 for powering the electromagnetic field emitter 65. After the emitter 65 is powered, a variable magnetic field is created, and induced currents flow in the current portion Pi.

[0078] At the transmitter 65, two sheets of FSB 133, 231 are arranged one above the other and separated by a layer of adhesive. Since each FSB sheet comprises a thin metallic layer, induced currents flow at the Pi portion in each of the two FSB sheets. For each FSB sheet 133, 231, a reaction magnetic field is created. Sheet 231 is farther from the transmitter 65 than sheet 133. Compared to sheet 133, it experiences the magnetic field generated by the transmitter 65 with a phase shift. This results in a phase shift between the two magnetic fields created, which is the basis for determining the distance between the two sheets 133, 231.

[0079] The control device 1000 of the invention comprises a processing means 68 for a signal 69 having the magnetic phase shift 61 characteristic of the glue thickness 60. The processing means 68 can determine the glue thickness 60 in the current portion Pi from the measured magnetic phase shift 61. As an example, the processing means 68 may include an oscilloscope that directly displays the measured magnetic phase shift corresponding to a glue thickness between the two FSB sheets. Alternatively, the processing means 68 may include a display screen that shows the glue thickness value after reading the table of correspondence between glue thicknesses and magnetic phase shifts established in calibration step 90.

[0080] After steps 100, 200, 300, and 400, i.e., after determining the adhesive thickness for portion Pi, the inspection method of the invention may include a step 500 of moving the end 66 of the electromagnetic field emitter 65 along the upper composite sheet 133 to a portion Pi+1 adjacent to the current portion Pi. Thanks to the specific shape of the emitter end 66 and, where applicable, the holding device 662, it is easy to translate the emitter 65 along the area under study to evaluate the adhesive thickness in a portion adjacent to the portion that has just been evaluated.

[0081] It should be noted that in [Fig. 7], portion Pi+1 is offset from portion Pi. Indeed, the portion adjacent to portion Pi (the one located between portion Pi and Pi+1 in the figure) does not have two sheets of FSB. Under sheet 133 is the insulating block 41. There is no adhesive thickness to measure for this portion.

[0082] Once the emitter 65 is positioned on the new current portion Pi+1, the second 200, third 300, and fourth 400 steps—that is, the positioning, generation, reception, and determination steps—are performed for this portion Pi+1, so as to determine the thickness of the adhesive 60 for this portion Pi+1. By proceeding in this manner step by step, the thickness of the adhesive between the two sheets of FSB 133, 231 along the study area can be determined. In the preceding text, the study area represented a width of the sheet 133. However, the same principle of the invention can be applied to a length of the sheet 133, in which case the emitter 65 is positioned on a flat surface (it is understood that in this configuration, the end 66 of the emitter 65 is flat).

[0083] According to an optional feature of the invention, the generation 200, reception 300, and determination 400 steps are performed continuously regardless of the positioning of the emitter 65 on the sheet. This means that steps 200, 300, and 400 are also performed during the movement 500 step. Steps 200, 300, and 400 are carried out continuously during the movement of the emitter 65. This allows for linear determination of the adhesive thickness.

[0084] According to an optional feature of the invention, the control method may include a step 450 of comparing the glue thickness determined in the determination step 400 (or fourth step) with a range of values reference. For example, the reference range can be initialized between 0.2 and 1.2 mm. The operator checks whether the determined adhesive thickness is within this range. This value can be displayed by the processing unit 68, in which case the comparison of values ​​is performed directly by the operator. Alternatively, if the processing unit 68 indicates a magnetic phase shift value, the operator can compare this value to those indicated in the lookup table from the calibration step to determine whether the determined adhesive thickness falls within the desired range.

[0085] According to an optional feature of the invention, the control method may include a step 460 for emitting an alert signal if the glue thickness 60 determined in the determination step 400 is outside the range of reference values. The alert signal may be a visual or audible signal that alerts the operator to a defect or excess glue in the area under investigation.

[0086] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different embodiments of the invention can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

Demands

1. Method for controlling the thickness of glue (60) in a study area extending between an upper composite sheet (133) and a lower composite sheet (231) arranged on at least one wall (8, 7) of a tank, the control method comprising: - A step of placing (100) one end (66) of an electromagnetic field emitter (65) on the upper composite sheet (133) over a current portion (Pi) of the study area, the end (66) of the emitter (65) conforming to the shape of the upper composite sheet (133) of the current portion; - A step of generating (200) a variable magnetic field by the electromagnetic field emitter (65), so as to create induced currents circulating in the current portion (Pi);- A receiving step (300) of a signal (69) having a magnetic phase shift (61) characteristic of a distance (60) between the upper composite sheet (133) and the lower composite sheet (231); - A determining step (400) of the thickness of glue (60) in the current portion (Pi) from the magnetic phase shift (61).

2. A control method according to claim 1, comprising a step of moving (500) the end (66) of the electromagnetic field emitter (65) on the upper composite sheet (133) to a portion adjacent (Pi+1) to the current portion (Pi), and carrying out the steps of generation (200), reception (300) and determination (400) for the adjacent portion (Pi+1), so as to determine the thickness of glue (60) in said adjacent portion (Pi+1).

3. A control method according to claim 2, wherein the generation (200), reception (300) and determination (400) steps are carried out continuously.

4. A testing method according to any one of claims 1 to 3, wherein the upper composite sheet (133) and the lower composite sheet (231) are arranged on two intersecting tank walls (7, 8) along an axis of intersection (9) and forming between them an angle (A) of the tank, the end (66) of the electromagnetic field emitter (65) being disposed on the axis of intersection (9) during the disposition step (100).

5. Control method according to claim 4 in combination with claim 2 or 3, wherein the displacement step (500) of the end (66) of the electromagnetic field emitter (65) is carried out along the intersection axis (9).

6. A control method according to any one of claims 1 to 5, comprising prior to a calibration step (90) intended to calibrate the magnetic phase shift as a function of predetermined glue thicknesses.

7. A control method according to any one of claims 1 to 6, comprising a comparison step (450) of the glue thickness determined in the determination step (400) with a range of reference values.

8. A control method according to claim 7, comprising an emission step (460) of an alert signal if the glue thickness (60) determined in the determination step (400) is outside the range of reference values.

9. Control device (1000) of a glue thickness (60) in a study area extending between an upper composite sheet (133) and a lower composite sheet (231) arranged on at least one wall (7, 8) of a tank, the device comprising: - An electromagnetic field emitter (65) having an end (66) conforming to the shape of the upper composite sheet (133) at the right of a current portion (Pi) of the study area; - An electric current generator (67) intended to supply the electromagnetic field emitter (65) so as to generate a variable magnetic field creating induced currents circulating in the current portion (Pi), - A means for processing (68) a signal (69) having a magnetic phase shift (61) characteristic of the thickness of glue (60), said means (68) being configured to determine the thickness of glue (60) in the current portion (Pi) from the magnetic phase shift (61).

10. Control device (1000) according to claim 9, the upper composite sheet (133) and the lower composite sheet (231) being arranged on two intersecting tank walls (7, 8) along an axis of intersection (9) and forming between them a tank angle (A), in which the end (66) of the electromagnetic field emitter (65) is of complementary shape to the tank angle (A).

11. Control device (1000) according to claim 9 or 10, wherein the electromagnetic field emitter (65) comprises a shoe (661) forming the end (66) of the emitter (65).

12. Control device (1000) according to any one of claims 9 to 11, wherein the electromagnetic field emitter (65) comprises a laterally extending positioning device (662) intended to bear against the upper composite sheet (133) of the current portion (Pi) on either side of the electromagnetic field emitter (65).

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