Leak detection bell for sealing membrane

Abstract

The invention relates to a leak detection bell for detecting a leak on a test area (62) of a sealing membrane of a watertight and thermally insulating tank comprising a main body (100), a sealing gasket (60) connected to the main body (100) and configured, in its service state, to define a detection chamber between the main body (100) and the test area (62), the sealing gasket (60) having a peripheral sealing lip (64) having a closed contour to surround the test area, the leak detection bell (55) being characterized in that it comprises a first retaining element (73), said first retaining element (73) being disposed on the sealing gasket (60) and forming a surface contact with a portion of the sealing gasket (60) placed around the main body (100). Figure to be published: 2

Description

Description Title of the invention: Leak detection bell for membrane sealing Technical field

[0001] = The invention relates to a leak detection bell making it possible to detect leaks from a waterproofing membrane, in particular from a waterproofing membrane corrugated, for example in a sealed tank. These sealed tanks can for example be watertight and thermally insulating tanks for storage and / or transport of a fluid, such as a cryogenic fluid. Technological background

[0002] Document KR1020100050128 discloses a method for testing the tightness of a membrane of a sealed and thermally insulating natural gas storage tank liquefied natural gas (LNG). The tank has a multi-layer structure and has successively- sively, from the outside to the inside, a thermally insulating barrier se- secondary, a secondary waterproofing membrane, a thermally insulating barrier primary and a primary sealing membrane intended to be in contact with the LNG contained in the tank. The process aims more specifically to detect leaks in the through welding beads which allow the sheets to be connected in a watertight manner metal of the primary waterproofing membrane. The process involves injecting a tracer gas, such as helium, into the primary thermally insulating barrier and then to move detection equipment equipped with a tracer gas analyzer, to inside the tank, along the weld seams of the waterproofing membrane primary. Thus, if the detection equipment detects the presence of the tracer gas, it can be concluded to a defect in the sealing of the primary sealing membrane.

[0003] — Also known is document WO2019224479, filed in the name of the de- manderesse, which describes a leak detection device, using a tracer gas, having an elongated shape intended to follow the welding line of which said device aims to test the watertightness.

[0004] — Such a leak detection device should preferably be able to be manipulated by a single operator, while reducing the testing time of the numerous welding lines, also referred to hereinafter as “weld beads” or more simply "cords", it being understood that its first characteristic must reside in the most precise and accurate detection possible of a possible leak.

[0005] = This is why it is desirable to have a leak detection device of elongated shape to best follow a long welding line, while being the most light as possible. However, after multiple tests, it was noted by the applicant that the leak detection device may have certain deficiencies or a reduction in its leak detection capacity, due to this very search for lightening the device associated with a very elongated shape of the device and therefore of its detection chamber. Such deficiencies or inaccuracies of the leak detection device appear in particular when the membranes on which the said device rests have a poor surface condition (poor flatness), when the weld line is locally thicker or wider than usual or because the vacuum pump is not very efficient. In fact, the leak detection device's analysis equipment operates correctly when a minimum vacuum level is reached, uniformly, over the entire length of the detection chamber. To achieve this, it is essential to ensure perfect sealing of the detection chamber. Summary of the invention An idea behind the invention is to propose a detection bell and a leak detection device for testing the tightness of a waterproof membrane of a tank which is reliable and easy to use in the tank. More particularly, the present invention aims to propose a leak detection device that operates perfectly regardless of all these equipment and sizing constraints as well as the multiple environmental hazards. It should be noted here that a conventional sealed and thermally insulating tank, for example that equipping an LNGC (for "Liquid Natural GAS Carrier"), comprises more than a thousand membranes welded together, the equivalent of several kilometers of weld lines, or beads, the sealing of which must be checked. The applicant intends to remedy the shortcomings of the current detection process and equipment by proposing a membrane leak testing device that is perfectly reliable, simple and quick to implement. After various experiments and tests, the applicant has thus developed a leak detection bell for detecting a leak in a test area of ​​a sealing membrane of a sealed and thermally insulating tank, the leak detection bell being configured to evolve between an initial state and a service state, the leak detection bell comprising: - a main body, extending along a longitudinal axis L and rising along a vertical axis V, perpendicular to the longitudinal axis L, intended to be placed on the test area: - a seal connected to the main body and configured, in its service condition, to define a detection chamber between the main body and the test area, the seal having a peripheral sealing lip having a closed contour to surround the test area; the leak detection bell being characterized in that it comprises a first holding element, said first holding element being arranged on the seal and forming a surface contact with a portion of the seal placed around the main body. According to the invention, the terms "longitudinal", "transverse" and "vertical" refer to the orientation of the detection bell. A longitudinal axis L, of a reference L, V, T, corresponds to a main axis of elongation of the detection bell. A transverse axis T of the reference L, V, T corresponds to an axis perpendicular to the longitudinal axis L. Finally, a vertical axis V of the reference L, V, T corresponds to an axis perpendicular to the longitudinal axis L and the transverse axis T. According to one embodiment of the invention, the leak detection bell comprises at least one second holding element, each of the at least one second holding element being located on one end of the seal along the longitudinal axis E Preferably, the detection bell comprises two second holding elements, said two second holding elements each being located at a separate end of the detection bell. Advantageously, the seal comprises notches spaced apart along the longitudinal axis L, and the leak detection bell comprises at least one third holding element, each of the at least one third holding element being arranged on a portion of the seal placed around the main body on one of said notches and forming a surface contact with said portion of the seal placed around the main body on one of said notches. According to a characteristic of the invention, the leak detection bell comprises at least one of a first, a second and a third support element configured to translate along an axis parallel to the vertical axis V when the detection bell moves between the initial state and the service state, so as to come into abutment against the sealing lip in the service state. Advantageously, the first support element comprises two blades located on either side of the main body, between the first holding element and the sealing lip. According to one characteristic, the leak detection bell comprises at least a second support element fixed to the second holding element, and located at one end of the sealing joint along the longitudinal axis L. According to a preferred embodiment, the detection bell according to the invention comprises two second support elements each located at a separate end of the leak detection bell. According to another embodiment, the at least one second support element is formed of a block fixed to the end of the detection bell and extending all around the rounded portion of the main body and of a fixing portion directly fixed to the second holding element. According to one characteristic, the leak detection bell comprises at least a third support element and the third support element comprises a first set of two fingers located on the one hand of the third holding element and a second set of two fingers located on the other hand of the third holding element relative to a transverse axis T perpendicular to the longitudinal axis L and the vertical axis V, and for each set of two fingers, the two fingers are arranged on either side of the third holding element along the longitudinal axis L. According to another embodiment, the first set and the second set of two fingers are integral with the third holding element. According to another embodiment, each finger comprises an upper part and a lower part, the upper part being movable in rotation relative to the third holding element around a first axis I parallel to a transverse axis T, and the lower part being movable in rotation relative to the upper part around a second axis II parallel to the transverse axis T and distinct from the first axis I. Advantageously, each finger comprises at least one compression element connecting the upper part to the lower part. Advantageously, the leak detection bell in which the sealing gasket is made of an elastomer material having a hardness of between 20 and 50 shore A. Advantageously, the leak detection bell in which the main body comprises a rigid core, and in which the seal comprises an envelope applied hermetically against a peripheral wall of the rigid core. Advantageously, the leak detection bell in which the rigid core has a recess on a lower surface intended to be turned towards the test area. Advantageously, the detection bell [suite in which the rigid core comprises a channel extending from the recess and opening onto an opening in an upper surface of the rigid core, the opening being intended to connect at least one vacuum pump. The invention also relates to a leak detection device for detecting a leak on a test area of ​​a sealing membrane of a sealed and thermal tank. mitically insulating. According to the invention, the leak detection device comprises: - such a leak detection bell; - at least one vacuum pump connected to the detection chamber configured to generate a vacuum in the detection chamber when the detection bell is in the operating state and the at least one vacuum pump is activated; - analysis equipment connected to the detection chamber configured to analyze a gas present in the detection chamber. Preferably, the detected gas present in the detection chamber is a tracer gas, different from one of the significant components of atmospheric air. The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings. Brief description of the drawings The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings. [Fig.1] is a schematic view of a leak detection device according to a first embodiment. [Fig.2] is a cross-sectional view along plane II-II of the detection bell of the leak detection device of [Fig.1]. [Fig.3] is a perspective view of a gasket of a leak detection bell of the leak detection device. [Fig.4] is a perspective view of a leak detection bell of the leak detection device. [Fig.5] is an exploded view of the detection bell of the leak detection device of [Fig.1]. [Fig.6] is a schematic view of a third holding element according to a first embodiment. [Fig.7] is a schematic view of a third holding element according to a second embodiment. [Fig.8] is a functional schematic view of a leak detection device employing the leak detection bell of |Fig.1] according to a second embodiment. [Fig.9] is a schematic illustration of a multi-layer structure of a membrane tank wall. [Fig.10] is a partial schematic view of a sealed and thermally insulating tank illustrating tracer gas injection devices positioned through a membrane in the bottom wall of the tank. Description of the embodiments The features, variants and different embodiments of the invention may be combined with each other in various combinations, 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 below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art. In the figures, elements common to several figures retain the same reference. A leak detection device will be described below that can be used to detect leaks in various sealed assemblies, for example, a welded assembly. In the examples below, the welded assembly is a sealing membrane for a fluid tank. During the leak test step for verifying the leaktightness of the weld seams of a membrane 5, 8, a leak detection device 54 is used, as shown in [Fig.1] and [Fig.2] in cross-section along plane II-II of the detection bell of the leak detection device of [Fig.1]. The leak detection device 54 comprises a detection bell 55 which is intended to be placed against the internal face of the membrane 5, 8 opposite a portion of the weld bead to be tested. The detection bell 55 has an elongated shape and generally has a length of between 0.5 and 4 m, for example of the order of 1 m. The length of the detection bell 55 is advantageously as long as possible so as to check the sealing of a larger area during a single test. Nevertheless, the length of the bell may be adapted as a function, on the one hand, of the dimensions of the membrane 5, 8 to be tested and, on the other hand, with a view to its maneuverability by a minimum of operator(s), preferably by a single operator. An elongated shape is particularly suitable for testing an assembly of rectangular metal sheets, in which the weld beads essentially follow the straight edges of the sheets. Advantageously, and due to its length, the detection bell 55 includes notches 65 so as to adapt to the waves present on the membrane 5, 8. These notches 65 are spaced from each other by a distance ranging from 15 to 50 em. The detection bell 55 according to the invention is configured to detect a leak on a test zone 62 of a sealing membrane of a sealed and thermally insulating tank. It is configured to evolve between an initial state and a service state. It comprises: - a main body 100, extending along a longitudinal axis L and rising along a vertical axis V, perpendicular to the longitudinal axis L, intended to be placed on the test zone 62: - a seal 60 connected to the main body 100 and configured, in its operating state, to define a detection chamber between the main body 100 and the test area 62, the seal 60 comprising a peripheral sealing lip 64 having a closed contour to surround the test area 62. The leak detection bell 55 comprises a first holding element 73, said first holding element 73 being disposed on the seal 60 and forming a surface contact with a portion of the seal 60 placed around the main body 100. The invention also relates to a leak detection device for detecting a leak on a test zone 62 of a sealing membrane of a sealed and thermally insulating tank. This device is illustrated schematically in [Fig. 1]. The leak detection device comprises a leak detection bell, the various embodiments of which will be described below, at least one vacuum pump connected to the detection chamber configured to generate a depression in the detection chamber when the detection bell is in the operating state and the at least one vacuum pump is activated, and analysis equipment connected to the detection chamber configured to analyze a gas present in the detection chamber. The vacuum pump 57 is associated with the analysis equipment 56. The vacuum pump 57 is connected, on the one hand, to the detection chamber of the detection bell 55 so as to allow the detection chamber to be depressurized and, on the other hand, to the analysis equipment 56 so as to conduct the gas contained in the detection chamber 61 towards the analysis equipment 56. The vacuum pump 57 is connected to the detection bell 55 via a pipe 58 which is preferably flexible. The pipe 58 is connected to a channel which is provided in the main body 100 and opens into the detection chamber 61. As shown in [Fig. 1], the analysis equipment 56 is connected to the leak detection bell 55 and is capable of detecting a predefined gas, for example a tracer gas or an ambient air gas present on the other side of the welded assembly to be tested. As soon as the analysis equipment 56 detects the predefined gas in a su- above a threshold, it can be concluded that there is a sealing defect in the portion of the weld bead 62 tested. According to one embodiment, the analysis equipment 56 is a mass spectrometer. [Fig. 2] is a cross-sectional view along plane II-II of the detection bell. As shown in [Fig. 2], the rigid main body 100, the flexible seal 60 and a first holding element 73 of the detection bell 55 are fixed to each other and are arranged to define with the membrane 5, 8 to be tested a sealed detection chamber 61, arranged opposite the portion of the weld bead 62 to be tested. These elements are fixed together by a fixing means 77, for example a screw, as shown in [Fig. 4]. As shown in Figures 2 and 3, the main body 100 advantageously comprises a rigid core 59 and the seal 60 comprises an envelope 63 applied hermetically against a peripheral wall of the rigid core 59. The seal 60 comprises an envelope 63 matching the shape of the rigid core 59 and a peripheral sealing lip 64 which extends the envelope 63 in the lower part of the bell along the vertical axis V, and extends along the transverse axis T on each side of the bell. The casing has a bottom 63 which covers the upper surface of the rigid core 59 and a peripheral wall 68 which matches the periphery of the rigid core 59. The bottom 63 has at least one hole, not shown, to which the pipe 58 connected to the at least one vacuum pump 57 can be connected in a sealed manner. The rigid core 59 has on its lower surface 80 a recess 79 over the entire length of the rigid core 59.The recess 79 makes it possible, when the detection chamber 61 is under vacuum, to ensure, despite a lowering of the rigid core 59 towards the membrane 5, 8 due to a deformation of the sealing lip 64, that the test zone 62 is always in fluid contact with the detection chamber 62. In addition, the rigid core 59 also comprises a channel 82, not shown in [Fig. 2] because it is present only in a plane passing at the level of the pipe 58, making it possible to connect the recess 79 to an upper surface 81 of the rigid core 59. The channel 82 makes it possible to put the detection chamber 61 in communication with the at least one vacuum pump 57 and the analysis equipment 56 via the pipe 58. The peripheral sealing lip 64 is curved towards the outside of the detection bell 55 and is thus configured to flex and press against the membrane 5, 8 when the sealed chamber 61 is under vacuum. In other words, the peripheral sealing lip 64 has a section having a general L shape. The outwardly curved portion of the peripheral sealing lip 64 typically has a width of the order of 15 to 40 mm. The peripheral sealing lip 64 is shaped to adapt to the geometry of the membrane 5, 8 along the weld bead to be tested. Also, in [Fig. 3], the peripheral sealing lip 64 includes notches 65 having a shape corresponding to that of the undulations of the membrane 5, 8 which the detection bell 55 is intended to span when it is in position against the portion of the weld bead 62 to be tested. The sealing gasket 60 is advantageously made of an elastomer material having a hardness of between 20 and 50 Shore A. The sealing gasket is for example made of elastomer polyurethane, EPDM rubber, silicone, nitrile or Viton ®. [Fig. 4] is a perspective view of a leak detection bell of the leak detection device. In this embodiment, the first holding elements 73 are positioned on either side of each notch 65, along the detection bell along the longitudinal axis L to hold the seal 60 against the main body 100 and thus ensure the sealing of the detection bell 55 of the detection device 54. As indicated in [Fig. 2], the first holding elements 73 each comprise an upper face 92 which applies mechanical pressure to an upper part of the casing 63 of the seal 60, as well as two lateral faces 91 located on either side of the main body 100 relative to the longitudinal axis L and applying mechanical pressure to the seal along the peripheral wall 68 along the vertical axis V, coming into abutment against the sealing lip 64 so as to exert pressure on the membrane 5, 8. Such mechanical pressure applied by these first holding elements 73 makes it possible to avoid deformation of the seal 60, and thus guarantee better sealing of the detection bell 55. According to one embodiment, the detection bell 55 comprises at least one of a first, a second and a third support element 90, 87, 85 configured to translate along an axis parallel to the vertical axis V when the detection bell 55 moves between the initial state and the service state, so as to come into abutment against the sealing lip 64 in the service state. In one embodiment, the first holding elements 73 of the detection bell of the leak detection device comprise a first support element 90. The first support element 90 comprises two blades 93 located on either side of the main body 100, between the first holding element 73 and the sealing lip 64. According to an embodiment visible in [Fig.2], the two blades 93 come into contact with the sealing lip 64 in order to ensure that this sealing lip 64 is pressed against the membrane 5, 8. The blades 93 may, for example, have an L shape. According to one embodiment, as shown [Fig.2], the two blades 93 are mounted independently of the first holding elements 73, allowing a rectilinear translational movement along the vertical axis V. Preferably, the blades 93 are arranged on the internal face of the lateral faces 91 of the first holding elements 73 According to another variant of this embodiment, the two blades 93 are mounted independently and can be fixed to the lateral faces 91 of the first holding elements 73, for example by means of screws or by gluing. According to another variant of this embodiment, as shown in [Fig.4], the two blades 93 are the extension of the first holding elements 73. As shown in Figures 4, and according to another embodiment, the bell 55 comprises at least one second holding element 74, each of the at least one second holding element 74 being located on one end of the seal 60 along the longitudinal axis L. Preferably, two second holding elements 74 are located respectively at the two ends of the leak detection bell 55, given that the latter has a generally longitudinal shape. The second holding elements 74 make it possible to apply mechanical pressure against the seal along the vertical axis V in order to press and hold the seal 60 against the main body 100. This makes it possible to avoid deformation of the seal 60 and thus to guarantee better sealing of the detection bell 55. In another embodiment, and as shown in [Fig. 5], the bell 55 comprises at least one second support element 87 fixed to the second holding element 74, and located at one end of the seal 60 along the longitudinal axis L. Preferably, two second support elements 87 are located respectively at the two ends of the leak detection bell 55, given that the latter has a generally longitudinal shape. The second support elements 87 can be designed according to a plurality of distinct variants, in shapes and materials, which may or may not be combined on the same leak detection bell 55. According to one embodiment, the at least one second support element 87 is formed of a block 99 fixed to the end of the detection bell and extending all around the rounded portion of the main body 100 and a fixing portion 98 directly fixed to the second holding element 74. The block 99 may be of a rounded shape and has a lower face bearing against the sealing lip 64 and an upper face coming into contact with the fixing portion 98. The block 99 has the advantage of being a lightweight structure lightening the structure of the detection bell. In addition, the block 99 here has a spring element function. Indeed, when the operator presses on the handling handles 51, 52, the block 99 deforms elastically and applies a uniform elastic return force over its entire surface. lower part which is in contact with the sealing lip 64 in order to ensure that this sealing lip 64 is pressed against the area to be tested. The block 99 is advantageously made of an elastomer material having a hardness of between 35 and 50 Shore A, such as polyurethane. According to one embodiment, handles 51, 52 are mounted on the second holding elements 74 in order to facilitate gripping of the bell. As shown in [Fig.4] and [Fig.5], the bell 55 may comprise at least one third element 72 for holding the seal located at a notch 65 of the detection bell 55, each being arranged on a portion of the seal placed around the main body 100 on one of said notches 65 and forming a surface contact with said portion of the seal 60. The third holding elements 72 are U-shaped, adapting to the notch 65, making it possible to apply mechanical pressure to the seal 60 in order to press and hold the casing 63 of the seal 60 against the main body 100. This mechanical pressure makes it possible to avoid deformation of the seal 60 and thus guarantee better sealing of the detection bell 55. The first, second and third holding elements 72, 73, 74 may be made of a material having a hardness greater than 50 Shore D. The first, second and third holding elements 72, 73, 74 are, for example, made of polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), acrylonitrile-butabiene-styrene (ABS), polyamide 6 (PA6) plastic. The first, second and third holding elements 72, 73, 74 may, for example, also be made of carbon fiber or aluminum. As shown [Fig.4], the detection bell 55 may comprise at least a third support element 85 with a notch 65. Figures 6 and 7 show two different embodiments of a third support element 85. The third support element 85 comprises a first set of two fingers 851 located on the one hand of the third holding element 72 and a second set of two fingers 851 located on the other hand of the third holding element 72 relative to a transverse axis T perpendicular to the longitudinal axis L and the vertical axis V. And for each set of two fingers 851, the two fingers 851 are arranged on either side of the third holding element 72 along the longitudinal axis L. The two sets of two fingers 851 are in contact with the sealing lip 64 in order to ensure that this sealing lip 64 is pressed against the base of the corrugation of the membrane 5, 8. According to one embodiment, shown [Fig.6], the third holding element 72 is integral with the third support element 85 forming a single piece. According to another embodiment, the third support element 85 is located on a lower part of the third holding element 72. Advantageously, the third support element 85 is configured to clamp the peripheral sealing lip 64 against the sealing membrane, near the base of the corrugation, by means of the two sets of two fingers 851. According to another embodiment, shown [Fig.7], each finger 851 comprises: - an upper part 85a and a lower part 85b; - the upper part 85a being movable in rotation relative to the third holding element 72 around a first axis I parallel to the transverse axis T; - the lower part 85b being movable in rotation with respect to the upper part 85a around a second axis II parallel to the transverse axis T and distinct from the first axis I. The third support element 85 can be rigidly fixed to the third holding element 72, or it can be connected to the third holding element 72. In this case, the upper part 85a is not integral with the third holding element 72, and connected to said third holding element 72 by means of a first fixing element 86, for example a screw, located on the upper part 85a. According to one embodiment, the upper part 85a is connected to an upper zone of the third holding element 72 along the vertical axis V. According to one embodiment, the upper part 85a and the lower part 85b are not integral with each other and are fixed by means of at least one second fixing element 88, for example a screw. According to one embodiment, the upper portion 85a and the lower portion 85b are configured to fit together. According to one embodiment, the bell 55 comprises at least one compression element. The upper part 8Sa and the lower part 85b are connected to each other by means of a compression element 852, for example a spring, then allowing each set of two fingers 851 to perform a pinching movement. Thus the third support element 85 is configured to apply a pinching force on the peripheral sealing lip 64 against the membrane 5, 8. Advantageously, the two sets of two fingers 851 are configured to clamp the peripheral sealing lip 64 against the sealing membrane, near the base of the corrugation. The third holding element 72 advantageously comprises an opening 831, located on the upper zone of the pressure element 83 along the vertical axis V. The opening 831 allows the passage of a tapping point 78 located on the notch of the leak detection bell 55 in order to connect the pipe 58. As shown in [Fig.8], the leak detection device 54 comprises the detection bell 55, the analysis equipment 56 with its associated vacuum pump 57, possibly a second vacuum pump 37 of higher power and / or a third vacuum pump 53, and a suction circuit connecting the detection chamber 61 to the analysis equipment 56, to the second vacuum pump 37 of higher power as well as to the third vacuum pump 53 via at least one solenoid valve 48. The suction circuit preferably comprises a flexible pipe 58 of sufficient length to promote the mobility of the detection bell 55 over a relatively large working area around the analysis equipment 56. This flexible pipe 58 is for example connected by connectors 39, on the one hand to an outlet of the detection chamber 61 and on the other hand to the analysis equipment 56. When a second and / or a third vacuum pump(s) 37, 53 is used, branch connections 38 may be provided to connect the analysis equipment 56, the vacuum pump(s) 37, 53 in derivation from each other. Concerning the solenoid valves 48, different positioning configurations in the circuit according to the invention can be envisaged, namely in particular one solenoid valve 48 per vacuum pump, or only for the detection bell 55. A control unit 36 ​​is also provided to control the solenoid valve 48, and possibly other elements such as the analysis equipment 56, in response to actions of an operator on one or more control members of the detection bell 55, for example arranged on one or more handling handles 51, 52 of the detection bell 55. For example, the two handling handles 51, 52 may each be provided with a thumb-actuated push button 761 configured respectively as an activation button and a deactivation button. Control members having a form other than a push button may be considered alternatively, for example a capacitive touch button, a rocking lever, or any other manually actuable member. In a preferred mode of operation, the vacuum pump(s) 37, 53 or other source of vacuum are pre-activated and permanently generate a vacuum in the suction circuit. The solenoid valves 48 have a closed state by default, so that the detection chamber 61 is not initially subjected to the vacuum, which allows the detection bell 55 to be moved freely on the membrane 5, 8. The solenoid valve 48 can be positioned on the gas outlet of the detection bell 55. It can also be positioned at another location in the suction circuit. The control signals between the control unit 36, the solenoid valves 48 and the activation and deactivation buttons are transported by wired or wireless communication links 35, for example produced in the form of a flexible electrical cable or a braid of flexible cables to promote the mobility of the detection bell 55. In one embodiment, the control unit 36 ​​is configured to also control the analysis equipment 56. For this, a wired or wireless communication link 35 is also provided between the control unit 36 ​​and the analysis equipment 56. In addition, a pressure sensor 49 also connected to the control unit 36 ​​is provided on the detection bell 55 to measure the pressure in the detection chamber 61. The depression source being previously activated, the operator grasps the detection bell 55 by the two handles 51, 52 and positions the detection bell 55 on the chosen test zone, if necessary using, for example, aiming devices 762. Then the operator presses the activation button. The operator only has to press the deactivation button to position the detection bell 55 on another test area. The detection bell 55 can therefore be used without the operator having to interact with the vacuum pump 37, the control unit 36 ​​or the analysis equipment 56, throughout a working area defined by the length of the fluidic and electrical connections of the detection bell 55 with these elements. To promote the mobility of the leak detection device 54 on a larger scale, the vacuum pump 37, the control unit 36 ​​and the analysis equipment 56 can be mounted on a rolling cart, not shown. The detection bell, the leak detection device 54 and the method of using the device described above are more particularly intended to test the tightness of a membrane of a sealed and thermally insulating membrane tank. By way of example, such membrane tanks are described in particular in patent applications WO14057221, FR2691520. The membrane tanks have a plurality of walls which have a multi-layer structure, as shown in [Fig. 9]. Each wall 1 comprises, from the outside to the inside of the tank, a secondary thermally insulating barrier 2 comprising secondary insulating panels 3 anchored to a supporting structure 4, a secondary membrane 5 resting against the secondary thermally insulating barrier 2, a primary thermally insulating barrier 6 comprising primary insulating panels 7 resting against the secondary membrane 2 and anchored to the supporting structure A or to the secondary insulating panels 3 and a primary membrane 8 which rests against the primary thermally insulating barrier 6 and which is intended to be in contact with the liquefied gas contained in the tank. The tank has a generally polyhedral shape. In the embodiment illustrated in [Fig. 10], the tank has a front wall 9 and a rear wall, not shown, which are here octagonal in shape. The tank also comprises a ceiling wall 10, a bottom wall 11 and side walls 11, 12, 13, 14, 15, 16, 17 which extend in a longitudinal direction L of the tank between the front wall 9 and the back wall. The secondary thermally insulating barriers 2 of the tank walls communicate with each other so as to form, between the supporting structure 4 and the secondary membrane 5, a secondary, sealed thermally insulating space. Similarly, the primary thermally insulating barriers 6 of the tank walls communicate with each other so as to form, between the secondary membrane 5 and the primary membrane 8, a primary, sealed thermally insulating space. At least one of the primary 8 and secondary 5 membranes comprises a plurality of metal sheets which are welded to each other. The leak testing method which will be described later aims more particularly to test the leaktightness of the welds used to connect the metal sheets to each other. According to one embodiment, the membrane to be tested has corrugations which allow it to deform under the effect of the thermal and mechanical stresses generated by the fluid stored in the tank. To do this, as shown for example in [Fig.7], each metal sheet comprises two series of corrugations perpendicular to each other. In one embodiment, the leak testing method comprises three steps, namely: - the diffusion of a tracer gas in a thermally insulating space covered by the membrane 5, 8 whose tightness is to be tested; - control of the diffusion of the tracer gas in the thermally insulating space; and - checking the tightness of the membrane welds 5, 8. In another embodiment, the leak testing method only comprises checking the leaktightness of the welds of the membrane 5, 8 without the aid of tracer gas. The step of diffusing a tracer gas consists of injecting a tracer gas into the thermally insulating space which is covered by the membrane 5, 8 whose tightness is to be checked. When the tightness of the secondary membrane 5 is to be checked, the tracer gas is injected into the secondary thermally insulating space. In this case, the tightness test method is implemented before the primary thermally insulating barrier 7 and the primary membrane 8 are installed. When the tightness of the primary membrane 8 is to be checked, the tracer gas is injected into the primary thermally insulating space. [Fig.10] schematically illustrates a sealed and thermally insulating tank and a system for injecting tracer gas into a thermally insulating space. The injection system comprises a plurality of conduits 18 which are, on the one hand, connected to a source of tracer gas, not illustrated, and, on the other hand, connected to tracer gas injection devices 19 providing a passage for injecting the tracer gas into the through the membrane 5, 8 whose tightness is to be tested. More particularly, the tracer gas injection devices 19 provide tracer gas passages through the membrane of the bottom wall 11. Such an arrangement is particularly advantageous because the tracer gas has a lower vapor density than that of air so that it tends to rise in the thermally insulating space. Therefore, the injection of the tracer gas from below, through the membrane 5, 8 to be tested of the bottom wall 11, makes it possible to ensure rapid and homogeneous diffusion of the tracer gas in the thermally insulating space. In the embodiment shown in [Fig. 10], the bottom wall 11 is equipped with at least four tracer gas injection devices 19 which are regularly distributed over the surface of the bottom wall 11. The bottom wall 11 has a rectangular shape and can thus be divided into four zones of equal surface area by its two axes of symmetry x and y. Each of the four tracer gas injection devices 19 is arranged in one of the four aforementioned zones. In the particular embodiment illustrated, each tracer gas injection device 19 is arranged near the center of its respective zone. In a particular embodiment, each of the four tracer gas injection devices is arranged at a distance 44 L from the adjacent longitudinal edge and at a distance !4 B from the adjacent transverse edge with L: the longitudinal dimension of the bottom wall 11 and B: the transverse dimension of the bottom wall 11. The tracer gas diffusion control step consists of, when the tracer gas has diffused through the thermally insulating space, controlling the diffusion of the tracer gas in the thermally insulating space. To do this, the gas contained in the thermally insulating space into which the tracer gas has been injected is sampled by means of a plurality of gas sampling devices arranged through the membrane covering said thermally insulating space. Each sampling device is connected to analysis equipment, such as a mass spectrometer, which makes it possible to verify the presence and concentration of the tracer gas in the corresponding area of ​​the thermally insulating space. The weld verification step consists of using the leak detection device 54, previously described, on one of the membranes 5, 8 of the sealed and thermally insulating tank. Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention. The use of the verb “comporter”, “comprendre” or “include” and its forms conjugated does not exclude the presence of other elements or other steps than those set out in a claim. In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Claims

1. Leak detection bell (55) for detecting a leak on a zone of test (62) of a waterproof membrane of a watertight and thermal tank mitically insulating, the leak detection bell (55) being configured to evolve between an initial state and a service state, the bell of leak detection (55) comprising: - a main body (100), extending along a longitudinal axis (L) and rising along a vertical axis (V), perpendicular to the longitudinal axis (L), intended to be placed on the test area (62); - a seal (60) connected to the main body (100) and configured, in its service state, to define a detection chamber between the main body (100) and test area (62), seal (60) comprising a peripheral sealing lip (64) having a closed contour to surround the test area (62); the leak detection bell (55) being characterized in that it comprises a first holding element (73), said first element retaining member (73) being arranged on the seal (60) and forming a surface contact with a portion of the seal (60) placed around the main body (100).

2. A leak detection bell (55) according to claim 1, comprising at least one second holding element (74), each of the at least a second holding element (74) being located on one end of the seal (60) along the longitudinal axis (L).

3. A leak detection bell (55) according to claim 1 or 2, in which the seal (60) comprises notches (65) spaced apart along the longitudinal axis (L), the bell of leak detection comprising at least a third element of holding (72), each of the at least one third holding element (72) being disposed on a portion of the seal placed around the main body (100) on one of said notches (65) and forming a surface contact with said portion of the seal (60).

4. A leak detection bell (55) according to any one of the claims- indications 1 to 3, comprising at least one of a first, a second and a third support element (90, 87, 85) configured to translate along an axis parallel to the vertical axis (V) when the bell of detection (55) evolves between the initial state and the service state, so as to come into contact with the sealing lip (64) in the operating condition.

5. A leak detection bell (55) according to claim 4, wherein the first support element (90) comprises two blades (93) located on either side of the main body (100), between the first element of retaining (73) and the sealing lip (64).

6. A leak detection bell (55) according to claim 4 or 5 in com- combination with claim 2, comprising at least a second support element (87) fixed to the second holding element (74), and located at one end of the seal (60) along the longitudinal axis (L).

7. Leak detection bell (55) according to one of claims 4 to 6 in combination with claim 3, comprising at least a third support element (85), wherein the third support element (85) understand : a first set of two fingers (851) located on one side of the third holding element (72) and; a second set of two fingers (851) located on the other hand of the third holding element (72) relative to an axis transverse (T) perpendicular to the longitudinal axis and the axis vertical ; and for each set of two fingers (851), the two fingers (851) are arranged on either side of the third element of holding (72) along the longitudinal axis (L).

8. A leak detection bell (55) according to claim 7, wherein the first set and the second set of two fingers (851) are integral with the third holding element (72).

9. A leak detection bell (55) according to claim 7, wherein each finger (851) includes: - an upper part (85a) and a lower part (85b); - the upper part (85a) being movable in rotation relative to the third holding element (72) around a first parallel axis (I) to the transverse axis (T); - the lower part (85b) being movable in rotation relative to the part upper (85a) around a second axis (IT) parallel to the transverse axis (T) and distinct from the first axis (D).

10. A leak detection bell (55) according to claim 9, wherein each finger (851) comprises at least one compression element (852) connecting the upper part (85a) to the lower part (85b).

11. A leak detection bell (55) according to any one of the claims- indications 1 to 10, wherein the main body (100) comprises a rigid core (59), and in which the seal (60) comprises an envelope (63) applied hermetically against a peri- wall spherical of the rigid core (59).

12. A leak detection bell (55) according to claim 11, in which the rigid core (59) has a recess (79) on a lower surface (80) intended to be turned towards the test area (62).

13. A leak detection bell (55) according to claim 12, in which the rigid core (59) comprises a channel (82) extending from the recess (79) and opening onto an opening of a surface su- upper (81) of the rigid core (59), the opening being intended for connect at least one vacuum pump (37, 53, 57).

14. A leak detection device (54) for detecting a leak in an area testing of a waterproof membrane of a waterproof and thermal tank mitically insulating, the leak detection device (54) comprising: - a leak detection bell (55) according to any one of the re- indications 1 to 13; - at least one vacuum pump (37, 53, 57) connected to the chamber of detection (61) configured to generate a depression in the chamber detection (61) when the detection bell is in the service state and the at least one vacuum pump (37, 53, 57) is activated; - analysis equipment (56) connected to the detection chamber (61) configured to analyze a gas present in the detection chamber (61).