Device for perforating a liquid natural gas tank

Abstract

The invention mainly relates to a perforating device (32) for sealing a thermally insulated tank (2) designed to contain a fluid, characterized in that the perforating device (32) comprises actuating means (34) and a member (36) for perforating the tank (2), the actuating means (34) being designed to generate a movement of the perforating member (36).

Description

Technical Field

[0001] This invention relates to the field of tanks for liquefied natural gas used in maritime transport. More specifically, this invention relates to a device used before repairing a tank in the event of a leak of liquefied natural gas from such a tank. Background Technology

[0002] Liquid natural gas (LNG), or liquid natural gas, is transported by sea in sealed and insulated tanks mounted on transport ships. To increase the amount of LNG transported in the tanks, the natural gas is kept in a liquid state; one liter of LNG has a much smaller volume than one liter of gaseous natural gas. These tanks maintain the LNG at very low temperatures, more precisely, below -163°C, the temperature at which natural gas is liquid under atmospheric pressure.

[0003] These liquefied natural gas tanks can also be used as fuel tanks on some ships. In other words, the ship loads and stores liquefied natural gas in the tanks, and then uses the liquefied natural gas as fuel for the ship's (multiple) engines.

[0004] In addition, these tanks can be used for onshore storage of liquefied natural gas, so as to recover liquefied natural gas at the dock, for example, during the unloading of liquefied natural gas transported by tanks arranged on ships.

[0005] Liquid natural gas tanks typically have a parallelepiped shape, and their walls mainly consist of a primary region and a secondary region. Each of these regions includes an insulation layer that ensures the liquid natural gas is maintained at -163°C, and a sealing layer that ensures the liquid natural gas remains within the tank.

[0006] However, liquefied natural gas (LNG) leaks can occur at the primary zone's sealing layer, for example, due to wear or improper assembly of the primary zone's sealing layer. The LNG contained in the tank then seeps into the primary zone and penetrates the primary zone's insulation. The LNG then spreads throughout the primary zone's insulation.

[0007] To approach and repair leaks in the sealing layer, the tank containing liquefied natural gas (LNG) must be emptied. LNG is thus drained from the tank, for example, through known devices designed to drain LNG from damaged tanks. At the end of this emptying step, a significant amount of LNG remains in the insulation layer of the primary region. Since the tank's internal space is empty, there is no longer a pressure balance between the insulation layer and the internal space. The weight of the LNG in the insulation layer pushes the sealing layer towards the tank's internal space, potentially damaging it. Furthermore, nitrogen gas, injected into the tank at a temperature higher than the LNG initially contained within, fills the internal space, raising its temperature. The hotter nitrogen increases the temperature of the tank walls. The temperature of the LNG permeating the tank walls subsequently rises, causing a change in the gas's state, from liquid to gas. This vaporization of the gas then increases the pressure on the tank walls by exerting a force that deforms the insulation layer of the primary region towards the tank's internal space. Depending on the amount of natural gas that seeps into the tank wall, the vaporization of the natural gas at least partially damages the tank wall, particularly by tearing the sealing layer that forms the tank wall. Summary of the Invention

[0008] In this context, the present invention proposes a perforation device that enables the formation of holes of sufficient diameter in the sealing layer of the primary region to allow natural gas that has permeated into the insulation layer to return very quickly to the interior space of the tank, thereby avoiding increased pressure on one or more walls of the tank. Therefore, the object of the present invention is to facilitate the discharge of liquefied natural gas that has permeated into the insulation layer of the primary region.

[0009] Therefore, the present invention relates primarily to a perforation device for sealing an insulated tank, the tank being designed to contain fluid, characterized in that the perforation device includes an actuating device and a component for perforating the tank, the actuating device being designed to generate movement of the perforating component.

[0010] The perforating member is designed to perforate the can, and the actuating device is designed to allow or prevent movement of the perforating member. The actuating device includes at least one fixed part and a movable part. The fixed part of the actuating device allows the perforating device to be held in place in space by, for example, fixing it to another object. The movable part participates in moving the perforating member, which performs the action of perforating the can.

[0011] The tank is designed to hold fluids at a temperature of approximately -163°C at atmospheric pressure, preferably liquefied natural gas (LNG). Therefore, the tank is insulated, as maintaining the cryogenic temperature is essential to keep the fluid in a liquid state. Furthermore, the tank is sealed to prevent leakage and / or loss of the fluid contained within.

[0012] The tank is spatially defined by multiple walls. The overall shape of these walls is cuboid. The perforation device allows for partial perforation of at least one of the tank's walls, advantageously the bottom wall, thereby creating a hole with a sufficiently large cross-section to allow natural gas that has permeated into the wall to return towards the interior of the tank.

[0013] According to an optional feature of the invention, the actuation device includes at least one frame, a roller, and a cable connecting a perforated member to the roller, the roller being designed to rotate about a rotation axis and to cause the cable to be wound or unwound around the roller.

[0014] The frame houses the rollers and at least a portion of the cable. The frame is a component of the fixed part of the actuator, while the rollers and cable are components of the movable part of the actuator.

[0015] Advantageously, the roller is cylindrical and can rotate about its axis of rotation. The device for actuating the perforated component also includes a crank that allows the roller to be rotated manually.

[0016] The cable comprises a first end rigidly connected to the roller and a second end rigidly connected to the perforating member. As a result, rotation of the roller in one or the opposite direction causes the cable to wind around or unwind from the roller. Because the cable is rigidly connected to the perforating member, the perforating member is suspended from the end of the cable. The rotation of the roller drives the movement of the perforating member, either to raise the perforating member, or to allow the perforating member to fall under gravity to perforate the sealing layer, or to lower the perforating member and apply a reference to the bottom wall of the tank.

[0017] The cable is made of metal or synthetic materials. It is also conceivable that the cable is partly made of synthetic materials and partly of metal.

[0018] According to another optional feature of the invention, the perforated member includes at least one perforated head and a body, each of the perforated head and the body extending longitudinally in succession.

[0019] The perforation component comprises a first part consisting of a body and a second part consisting of a perforation head. The perforation component is rigidly connected to the cable via the first part, and the perforation head is designed to perform the perforation action.

[0020] In this configuration, the body is the component that ensures the connection between the cable and the perforation head; the body does not directly participate in perforating the tank wall. Due to its mass, the body exerts inertia, which allows the perforation component to perform its function of breaking through the tank's primary seal.

[0021] The piercing head is a cylindrical body with one end angled to form a piercing point. The piercing head is a component of the piercing assembly that performs the action of piercing a hole in the wall of the container.

[0022] The perforated head is the longitudinal extension of the main body of the perforated component. It can be envisioned that the main body adopts the integral shape of a column, and the perforated head is the axial extension of the column forming the main body at one of its ends.

[0023] According to another optional feature of the invention, the body has a first longitudinal end rigidly connected to the perforation head and a second longitudinal end rigidly connected to the cable.

[0024] The body extends between a first longitudinal end and a second longitudinal end, with the body rigidly connected to the perforation head at its first longitudinal end and rigidly connected to the cable at its second longitudinal end. In other words, the body is rigidly connected to the cable on one side and rigidly connected to the perforation head on the other side, such that the perforation head is located at the end of the body opposite to the cable.

[0025] According to another optional feature of the invention, the body includes a plurality of wings and a shaft, the plurality of wings extending radially from the shaft.

[0026] The axis of the main body takes the overall shape of a column defined by the first and second longitudinal ends, and the plurality of wings extend radially from this axis. It should be understood that each wing appears in a plane containing an axis that passes through the center of the column and through the two longitudinal ends of the main body.

[0027] A wing is a generally rectangular planar wing. The body comprises at least three wings distributed at regular angles around the body axis. Regardless of whether the plurality of wings includes three or more wings, the angular sector separating two adjacent wings (that is, two wings separated by space excluding the wings) is constant and independent of the number of wings.

[0028] The plurality of wings extend in a star shape in a plane perpendicular to the main extension axis of the perforated member, the center of the star being represented by the axis of the body, and each branch of the star being formed by each of the plurality of wings.

[0029] According to another optional feature of the invention, at least one of the plurality of wings includes a free end that at least partially defines the periphery of the body and includes a cover that facilitates sliding of the body.

[0030] Each of the plurality of wings has three free ends, the first and second free ends extending outward from the perforated member from the axis of the body, and the third free end extending parallel to the axis of the body between the two other ends.

[0031] The third end of each of the plurality of wings participates in defining the periphery of the body, and the third end is the element that protrudes furthest outward from the body radially.

[0032] Each of the third ends of the plurality of fins includes a cover that helps reduce the frictional forces exerted between the third end of the plurality of fins and an external element, such as a metal tube constituting the can. More specifically, according to a non-limiting example, the cover may be made of a synthetic material, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), also known as Teflon. For example, this type of cover can reduce the frictional forces between the third end of the plurality of fins and the metal element.

[0033] According to another optional feature of the invention, the body has a support disc at its second longitudinal end.

[0034] Therefore, the disc is rigidly connected to the body at the second longitudinal end of the body.

[0035] The disk extends primarily in a plane perpendicular to the longitudinal axis of the shaft, which also passes through the center of the disk.

[0036] The function of the reel is to hold the cable above the perforated member, especially when the perforated member is installed in a pipe. This prevents the cable from entering between the perforated member and the pipe.

[0037] According to another optional feature of the invention, the disc includes at least one through opening.

[0038] A through opening is understood to be an opening on either side of a disk, allowing fluid to flow through it. The through opening can be closed around its perimeter, forming a through hole. Alternatively, the through opening can also be an opening on the outer periphery of the disk, thus forming a through channel.

[0039] The disc may include multiple through openings. The size of these through openings or multiple through openings is specifically designed so as not to slow down the descent of the perforated component. In practice, the tube may contain fluid, and the holes in the disc allow fluid to flow through the disc without slowing down the descent of the perforated component.

[0040] The disk includes at least one through-channel that allows cables to pass through.

[0041] The through-channel extends from the periphery of the disc towards its center. Once the perforated member is connected to the cable that connects the body to the roller, this through-channel allows the disc to be mounted onto the perforated member. In practice, when mounting the disc onto the perforated member, the disc is mounted onto the body by inserting the cable from the periphery of the disc to its center through the through-channel. The through-channel of the disc makes mounting the disc onto the body easier because the cable may already be pre-attached to the body.

[0042] According to another optional feature of the invention, the disc is at least partially made of a material that facilitates disc sliding.

[0043] The disc is at least partially made of a synthetic material, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), also known as Teflon. It should be understood that the disc may have contact with a surface around its perimeter, on which a material facilitating the disc's sliding motion is applied.

[0044] At least the periphery of the disc is made of a material that facilitates disc sliding, but the entire disc can also be made of a material that facilitates disc sliding without departing from the scope of the invention. Furthermore, according to another embodiment, the disc can also be made of a metallic material and at least its periphery is covered with a synthetic material, such as those described above.

[0045] According to another optional feature of the invention, the diameter of the disk is less than or equal to the diameter of the free ends of the plurality of wings.

[0046] According to another optional feature of the invention, the actuating device includes means for preventing the roller from rotating, the means being designed to release the perforated member and cause it to fall.

[0047] The roller has at least one opening designed to accommodate a device for preventing the roller from rotating. The device for preventing the roller from rotating includes at least one rod having a straight portion that is at least partially surrounded by a sleeve made of a material that facilitates the withdrawal of the preventing device from the opening of the roller, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), also known as Teflon.

[0048] When the rod is received in the opening of the roller, the roller cannot rotate, thus fixing the perforated component in place. Removing the rod from the roller allows the roller to rotate, thereby allowing the perforated component to fall.

[0049] The present invention also relates to a sealed, insulated tank designed to contain fluid, the tank comprising a plurality of walls, characterized in that the tank includes a tube passing through at least one of the walls of the tank and extending between a first end disposed inside the tank and a second end disposed outside the tank, the tank including a perforation device according to any one of the foregoing features.

[0050] The tank is capable of storing fluid, and its multiple walls are sealed and insulated. The tank also includes a perforation device comprising at least one of the aforementioned features. It should be understood that the tank and the perforation device are two distinct objects that can be coupled together.

[0051] Therefore, the can is spatially defined by multiple walls, which advantageously take the shape of a parallelepiped.

[0052] The tube passes through one of the plurality of walls of the tank, advantageously through the top plate, and has a first end leading into the interior of the tank and a second end leading into the exterior of the tank. The open end inside the tank is near the bottom wall of the tank.

[0053] The perforation device is installed at the end of the pipe leading to the outside of the tank, allowing the perforation member to move between the first and second ends of the pipe, and even down to the bottom wall of the tank.

[0054] According to another optional feature of the invention, the perforated member is arranged in the tube, and the cable is wound around the roller to raise the perforated member.

[0055] Understandably, the perforating component can move partially within the tube due to the rotation of the roller, the direction of which causes the cable to wind around or unwind from the roller, resulting in the perforating component being closer to or further away from the bottom wall of the tank.

[0056] According to another optional feature of the invention, the perforated member and the tube are designed such that the perforated member slides within the tube.

[0057] Therefore, the cross-section of the perforated component is smaller than that of the pipe to prevent the perforated component from becoming stuck in the pipe.

[0058] It should be understood that in order for the perforated member to move within the tube, the circumference of the free ends of the plurality of wings, at least partially inscribed therein, must be smaller than the inner cross-section of the tube.

[0059] According to another optional feature of the invention, each of the plurality of walls successively includes, in the thickness direction from the outside to the inside of the tank, a secondary thermal barrier, a secondary sealing membrane, a primary thermal barrier, and a primary sealing membrane, the primary sealing membrane being intended to contact the fluid contained in the tank, the primary sealing membrane having a perforated area arranged opposite to the end of a pipe leading to the inside of the tank.

[0060] The secondary insulation barrier and secondary sealing membrane form the secondary region of the tank, while the primary insulation barrier and primary sealing membrane form the primary region of the tank.

[0061] It should also be understood that the secondary sealing membrane is supported by the secondary thermal barrier and is in contact with the primary thermal barrier.

[0062] Thermal barriers help maintain the temperature of the fluid stored in the tank by limiting heat exchange between the tank's external environment and its interior. Sealing membranes prevent any leakage of fluid to the outside of the tank.

[0063] The perforated area is characterized by a thinning of the primary sealing membrane, which facilitates the perforation of the membrane by the perforating component. The tube is positioned such that the end with the opening inside the can is opposite the perforated area.

[0064] According to another optional feature of the invention, the primary sealing film forms a protrusion that includes at least one flat area at the level of the perforated area.

[0065] This protrusion allows the perforated area to be closer to the open end inside the tank, thereby reducing the risk of the perforating member penetrating the secondary seal after having already penetrated the primary seal. The perforating member perforates in a flat area of ​​the protrusion, which advantageously faces the end of the tube leading into the tank.

[0066] According to another optional feature of the invention, the length of the perforating head in the direction of perforator movement is less than the thickness of the primary insulation barrier or the thickness corresponding to the sum of the thickness of the primary insulation barrier and the height of the protrusion. This advantageously allows puncture of the secondary membrane to be avoided by creating a stop at the level of the plurality of wings via the primary membrane.

[0067] The present invention also relates to a ship comprising a tank according to any of the foregoing features.

[0068] The vessel includes a tank capable of storing fluids, the multiple walls of which are sealed and insulated. The vessel also includes a perforation device comprising at least one of the aforementioned features.

[0069] The present invention also relates to a method for perforating a tank mounted on a ship according to any of the foregoing features, characterized in that the first step includes installing a perforation device at the second end.

[0070] The first step involves positioning the device for actuating the perforation device at the horizontal position of the second end of the tube, and the perforation member is also installed in the tube at the horizontal position of the second end of the tube.

[0071] According to another feature of the invention, the second step includes sliding the perforated member in the tube to move it downwards to the bottom wall of the can.

[0072] Understandably, the second step involves moving the perforating member, i.e., lowering it in a controlled manner within the tube to the bottom wall of the tank. For this purpose, the perforating member slides within the tube.

[0073] According to another feature of the invention, the third step includes positioning the perforating member at the drop height in the tube, and then, once the perforating member is positioned at the drop height, blocking the roller constituting the perforating device.

[0074] The user positions the perforated component at a specific height, such as three meters, and then stops the rotation of the roller to fix the perforated component at that height. To ensure that the measurement of the perforated component's drop height is accurate, the perforated component is positioned on the bottom wall of the tank as a reference. This position is then referred to as the measurement starting point and serves as the initial reference for the drop height.

[0075] According to another feature of the invention, the fourth step is to place the perforated member.

[0076] The user can rotate the roller to release the perforating component and allow it to impact the bottom wall of the container. Driven by its weight toward the perforation zone, the perforating component accumulates kinetic energy, which is converted into mechanical energy when it impacts the perforation zone. The height is set so that the perforating component can accumulate enough kinetic energy to perforate the primary sealing membrane.

[0077] According to an optional feature of the invention, steps two, three and four are repeated until the primary sealing membrane is perforated.

[0078] According to an optional feature of the invention, the fourth step includes lifting the perforated member into the tube. Attached Figure Description

[0079] Other features and advantages of the invention will become apparent from the following description and several exemplary embodiments, which are given for illustrative purposes and are not limited to the accompanying schematic diagrams, in which:

[0080] [ Figure 1 [ ] is a cross-sectional view of a can equipped with the perforation device according to the present invention;

[0081] [ Figure 2 ] is used for actuation based on Figure 1 A cross-sectional view of the perforation device;

[0082] [ Figure 3 [This is based on] Figure 1 A perspective view of the perforated component of the perforation device;

[0083] [ Figure 4 [This is a perspective view of the blocking device that constitutes the actuation perforation device.] Detailed Implementation

[0084] The various features, variations, and different embodiments of the present invention can be combined with each other in various combinations, as long as they are not incompatible or mutually exclusive. In particular, variations of the present invention may be contemplated that include only a selection of the features described below, without the other features described, if the selection of features is sufficient to give the present invention a technical advantage or to distinguish the present invention from the prior art.

[0085] Figure 1 A sealed, insulated tank 2, spatially defined by multiple walls 4, is shown. The tank 2 is generally rectangular in shape; only four walls are shown here. The tank 2 is designed to contain and / or store fluids, more specifically cryogenic liquids, such as liquefied natural gas or liquefied petroleum gas. By way of non-limiting example, this type of tank 2 is used in maritime transport as a tank for transporting liquefied natural gas, or even as a fuel tank for ships. Furthermore, the tank 2 can also be used for onshore storage of liquefied natural gas.

[0086] Liquid natural gas is denser than gaseous natural gas, therefore its storage capacity is larger. Natural gas is liquid at atmospheric pressure and a temperature of -163°C.

[0087] Tank 2 is designed to maintain liquefied natural gas at a temperature of up to -163°C. To this end, each of the plurality of walls 4 of tank 2 includes, in the thickness direction from the outside to the inside of tank 2, a sealed and independent secondary region 16 and a primary region 14.

[0088] The secondary region includes a secondary insulation barrier 6 and a secondary sealing membrane 8 supported by the secondary insulation barrier 6. The primary region includes a primary insulation barrier 10 resting on the secondary sealing membrane 8 and a primary sealing membrane 12 supported by the primary insulation barrier 10. The primary sealing membrane 12 is intended to contact the fluid contained in the tank 2.

[0089] The secondary insulation barrier 6 is in contact with the external environment of the tank 2, particularly with the supporting structure. In the case where the tank is mounted on a ship, the secondary insulation barrier 6 may be in contact with, for example, the ship's inner hull. Therefore, the secondary insulation barrier 6 has an outer surface 18 facing the external environment of the tank 2. The secondary sealing membrane 8 is in contact with the secondary insulation barrier 6 on one side and with the primary insulation barrier 10 supporting the primary sealing membrane 12 on the other side. The insulation barriers 6 and 10 help maintain the internal temperature of the tank 2, while the sealing membranes 8 and 12 form a layer impermeable to any fluids that the tank 2 may contain.

[0090] According to the present invention, the can 2 includes a perforation device 32, which includes at least one actuation device 34 and a member 36 for perforating the can 2. The actuation device 34 is designed to move the perforation member 36. Thus, the actuation device 34 can raise the perforation member 36 or allow it to lower.

[0091] The perforation device 32 is designed to pierce the primary sealing membrane 12 and form a hole connecting the internal space of the primary insulation barrier 10 to the internal space 15 of the tank 2, so as to quickly drain the fluid that has penetrated into the primary region 14 of the plurality of walls 4 during the unloading of the fluid contained in the tank 2, without damaging the plurality of walls 4 of the tank 2.

[0092] The perforation device 32 and the method for perforating the can 2 will be described below after the description of the tube 38 of the can 2, which guides the perforation member 36 of the perforation device 32.

[0093] The tank 2 includes at least one pipe 38 passing through at least one of the walls of the tank 2, which is also referred to in the remainder of the specification as the "tank top plate 40". The pipe 38 extends longitudinally between a first end 42 leading to the interior space 15 of the tank 2 and a second end 44 leading to the exterior of the tank 2, and the pipe 38 extends substantially along a vertical axis A between the two ends. In the remainder of the specification, the term "inner end 42" will also be used to refer to the first end 42 of the pipe 38 extending into the interior of the tank 2; both expressions refer to the same object. Similarly, the term "outer end 44" will be used to refer to the second end 44 of the pipe 38 disposed outside the tank 2; therefore, both expressions refer to the same object.

[0094] Therefore, the tube 38 comprises two parts: an outer portion 46 extending between the outer end 44 of the tube 38 and the top plate 40 of the tank, and an inner portion 48 extending between the inner end 42 of the tube 38 and the top plate 40 of the tank. Advantageously, the inner end 42 of the tube 38 is close to the wall opposite the top plate 40 to the interior of the tank 2, which is referred to as the "bottom 50 of the tank" in the remainder of the specification. Thus, the inner portion 48 of the tube 38 extends from the top of the tank 40 through the tube 38 to the bottom of the tank 50, but does not contact the bottom.

[0095] The tube 38 may include an inlet 52 at the level of the outer portion 46 for measuring the fluid level contained in the tank 2, the measuring device not shown in the figure. Therefore, in addition to performing the function of the perforation device 32 according to the invention, the tube 38 may also perform the function of measuring the fluid level in the tank.

[0096] Here, the inlet 52 is separate from the outer end 44 of the tube 38. However, as described above, the tube 38 has an inlet 52 for measuring devices located at the outer end 44 of the tube 38, which does not depart from the scope of the invention.

[0097] The tube 38 is hollow between its outer end 44 and inner end 42. In other words, the tube 38 has a cavity 54 defined by its inner surface 33, which extends between its ends 42 and 44, and terminates at an outer nozzle 56 at the outer end 44 and an inner nozzle 58 at the inner end 42. When the perforating device 32 is mounted on the tube 38, the perforating member 36 slides within the cavity 54 of the tube 38 between each end 42 and 44 of the tube 38.

[0098] Furthermore, when the tank 2 contains fluid, the tube 38 is at least partially immersed in the fluid, which at least partially fills the cavity 54 of the inner portion 48 of the tube 38. In this way, the measuring device can be positioned at the level of the outer portion 46 of the tube 38 within the tube 38 and reach the interior of the tank 2 to measure the level of the fluid present in the tube 38, which is equal to the amount of fluid contained in the tank 2.

[0099] The inner nozzle 58 of tube 38 is opposite to at least a portion of the bottom 50 of the can. More specifically, the inner nozzle 58 is opposite to the perforated area 60 of the primary sealing film 12 located at the bottom 50 of the can. The perforated area 60 is defined in this area because the thickness of the primary sealing film 12 is less than or equal to the thickness of the rest of the bottom 50 of the can, the thickness of which is measured in a direction perpendicular to the main extension plane of the primary sealing film 12. Therefore, the primary sealing film 12 can be more easily perforated by the perforation device 32.

[0100] However, the perforation of the primary sealing membrane 12 must not affect the secondary region 16, therefore the perforated member 36 must not reach the secondary sealing membrane 8.

[0101] For this purpose, the perforated area 60 takes the form of a protrusion 62, which protrudes from the primary sealing membrane 12 and includes a flat area 64. The protrusion 62 extends toward the interior space 15 of the tank 2, such that the flat area 64 is opposite to the inner nozzle 58 of the tube 38. In this configuration, the perforating member 36 perforates the primary sealing membrane 12 at the flat area 64 without reaching the secondary sealing membrane 8.

[0102] Furthermore, the tube includes a device 55 for preventing the perforating member 36 from descending at the inner opening 58 of the tube. This stop device may take the form, for example, a welded disc that extends primarily in a plane perpendicular to the vertical axis A. The disc includes an advantageous circular aperture designed to allow a portion of the perforating member to reach the primary sealing membrane 12, but without completely disengaging the perforating member 36 from the tube 38.

[0103] According to the present invention, the tube 38 is supported by a perforation device 32 arranged at the outer end 44 of the tube 38.

[0104] The perforation device 32 includes an actuation device 34 and a member 36 for perforating the can 2. The actuation device 34 is designed to generate movement of the perforation member 36. Therefore, the actuation device 34 can move or fix the perforation member 36. In other words, the movement of the perforation member 36 depends on the actuation device 34.

[0105] The actuation device 34 includes at least one frame 66, a roller 68, and a cable 70 connecting the perforated member 36 to the roller 68. In all figures, the roller 68 is designed to rotate about an axis of rotation B. Rotation of the roller 68 about the axis of rotation B causes the cable 70 to wind around or unwind around the roller 68. In this case, the roller 68 is rotated manually, specifically by a crank 72.

[0106] like Figure 2As shown in more detail, the means 34 for actuating the perforating member 36 includes a manual system for rotating the roller 68, the manual system including at least a crank 72. The means 34 for actuating the perforating device 32 may alternatively be motorized or even automated without departing from the scope of the invention.

[0107] Crank 72 extends along a transverse axis C perpendicular to the vertical axis A between the handle 74 and the inner end 76 of crank 72. The handle 74 of crank 72 allows the user to set the movement of the device 34 for actuating the perforated device 32, specifically by rotating crank 72 about the transverse axis C. The inner end 76 of crank 72 includes a gear 78 of roller 68 and is held in place by a first rotary bearing 80 of frame 66. In addition to the first rotary bearing 80, crank 72 is also supported by a second rotary bearing 82 of frame 66, which contacts crank 72 between handle 74 and the inner end 76 of crank 72. These bearings for rotating crank 72 on frame 66 ensure that crank 72 continues to rotate about the transverse axis C.

[0108] The roller 68 of the actuating device 34 includes a driven element 84, such as a pinion, that is rotated by a gear 78 of a crank 72. The driven element 84 is designed to rotate about the axis of rotation B of the roller 68. Thus, when the user rotates the crank 72 about the transverse axis C, the gear 78 of the crank 72 causes the driven element 84 of the roller 68 to rotate, and also causes the roller 68 to rotate about the axis of rotation B. The direction of rotation of the crank 72 about the transverse axis C affects the direction of rotation of the roller 68.

[0109] In addition to the driven element 84, the roller 68 includes a shaft 86 extending between a first side disc 85 and a second side disc 87, the diameters of which are larger than the diameter of the shaft 86. Because the side discs 85 and 87 are symmetrical about each other with respect to the shaft 86, a feature of one side disc 85 or 87 can be applied to the other side disc 85 or 87. The center of the roller 68, the center of the shaft 86, the centers of the side discs 85 and 87, and the axis of rotation B coincide. The shaft 86 of the roller 68 allows the roller 68 to be secured to the frame 66 while allowing the roller 68 to rotate about the axis of rotation B.

[0110] Cable 70 is wound around the shaft 86 of roller 68 between side discs 85 and 87. The side discs guide cable 70 as it is wound or unwound on the roller. Like the second side disc 87, the first side disc 85 has at least one positioning hole 88. In this case, the positioning hole 88 is located between the center of the first side disc 85 and its peripheral edge 90, and the positioning hole 88 is generally elliptical, with its maximum dimension extending in the radial direction of the roller. Figure 2As shown, the first side plate 85 includes a plurality of positioning holes 88, each of which is formed through the first side plate 85 of the roller 68 and is angularly distributed around the rotation axis B of the roller 68.

[0111] The roller 68 includes at least one advantageously colored notch 160 on one of the peripheral edges 90 of one of the side discs 85, 87, the notch 160 being designed to be at least partially visible to the user of the perforated device 32. Alternatively, the roller 68 includes a notch 160 on each of the side discs 85, 87 of the roller 68, allowing the user to track or count the number of revolutions of the roller from either side of the roller.

[0112] The actuating device 34 also includes a means 92 for preventing rotation of the roller 68. The means 92 is designed to prevent or allow movement of the perforated member 36. More specifically, the means 92 engages with the positioning hole 88 to prevent rotation of the roller 68 about the axis of rotation B. For example, the means 92 extends at least partially into the positioning hole 88.

[0113] like Figure 4 As shown, the stopping device 92 includes an advantageous rectangular handle 94 and a rod 96, the rod 96 extending from the handle 94 toward an end 98 for inserting the stopping device 92 into a positioning hole 88 of the roller 68. The handle 94 is a zone through which the user grips the stopping device 92, and the rod 96 is received in the positioning hole 88. In effect, a portion of the rod 96 extending from the insertion end 98 toward the handle 94 is received in the positioning hole 88 of the roller 68, thereby preventing the roller 68 from rotating about the axis of rotation B.

[0114] To allow the roller 68 to rotate, thus allowing the perforated member to fall, the blocking device 92 is manually pulled out of the roller 68. To facilitate removal of the blocking device from the roller 68, the blocking device 92 includes a sleeve 100 extending from the insertion end 98 towards the handle 94, thereby facilitating the sliding of the rod 96 in the positioning hole 88. The sleeve 100 is at least partially constructed of a synthetic material, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), also known as Teflon. This material has the property of reducing friction between the blocking device 92 and the roller 68. The presence of the sleeve 100 surrounding the rod 96 at the insertion end 98 makes it easier to remove the blocking device 92 from the positioning hole 88 of the roller 68. Given the significant weight of the perforated member, which is necessary for it to perform its function in a liquid environment, this type of sleeve 100 reduces the effort required to pull the blocking device 92 out of the positioning hole 88.

[0115] As previously described, the roller 68 is rigidly connected to the cable 70, and the roller 68 causes the cable 70 to wind or unwind around the roller 68 as it rotates about the axis of rotation B. When the blocking device 92 is received in the positioning hole 88, the cable 70 cannot wind or unwind.

[0116] like Figure 2 As shown, the cable 70 of the actuation device 34 includes a first end 102 rigidly connected to the roller 68 and a second end 104 rigidly connected to the perforated member 36. The first end 102 of the cable 70 is rigidly connected to the roller 68 at the shaft 86 of the roller 68.

[0117] The actuation device 34 may optionally include an element 112 for guiding the cable 70, thereby optimizing the winding or unwinding of the cable 70 around the roller 68.

[0118] The actuation device 34 may optionally include a guide pulley 114, which is advantageously an axis around which the cable 70 can slide.

[0119] The frame 66 of the actuator 34 includes multiple sides, wherein the first side 115 is located on... Figure 2 As is particularly visible in the frame 66, the mounting flange 118 is included. The mounting flange 118 of the frame 66 extends primarily in a plane substantially perpendicular to the vertical axis A. The multiple sides of the frame 66 and the mounting flange 118 thus define a space 116 in which the roller 68 and the cable 70 are at least partially accommodated. The space 116 in the frame 66 communicates with the external environment of the frame 66 at the mounting flange 118, allowing at least a portion of the cable 70 to be outside the frame 66. Specifically, the first end 102 of the cable 70, connected to the roller 68, is located inside the frame 66 in the space 116, and the second end 104 of the cable 70 is located outside the frame 66, passing through a portion of the space 116 in the frame 66. The second end 104 of the cable 70 is rigidly connected to the perforated member 36.

[0120] The mounting flange 118 of the frame 66 is intended to contact the outer end 44 of the tube 38. For this purpose, the mounting flange 118 of the frame 66 is positioned opposite the mounting flange of the outer opening 56 of the tube 38. The mounting flange 118 of the frame 66 and the mounting flange 120 of the tube 38 are designed to mate with each other to rigidly connect the frame 66 to the tube 38. This assembly secures the perforation device 32 to the tube 38. The assembly also provides a seal between the mounting flange 118 of the frame 66 and the mounting flange 120 of the tube 38.

[0121] Once the frame 66 has been mounted on the tube 38 at the outer end 44, at least a portion of the cable 70 and the perforated member 36 are positioned within the hollow portion 54 of the tube 38, with said portion of the cable 70 and the perforated member 36 substantially aligned along a vertical axis A. The pivot element 114 ensures that the perforated member 36 is positioned along this axis. Figure 2As shown. Positioned in this way, the perforated member 36 located in the tube 38 remains suspended from the second end 104 of the cable 70. The rotation of the roller 68 causes the cable 70 to wrap around or unwrap from the roller 68, and also causes the perforated member 36 to move toward or away from the outer end 44 and / or the inner end 42 of the tube 38.

[0122] according to Figure 3 In the example shown, the perforated member 36 includes at least one perforated head 122 and a body 124, which extend one after the other. More precisely, the body 124 of the perforated member 36 extends longitudinally between a first longitudinal end 126 rigidly connected to the perforated head 122 and a second longitudinal end 129 rigidly connected to a second end 104 of the cable 70. It can be understood that the cable 70 is therefore located at the end of the body 124 of the perforated member 36 opposite to the perforated head 122.

[0123] The body 124 includes a shaft 128 longitudinally defined by a first longitudinal end 126 and a second longitudinal end 129, extending along a vertical axis A. In this configuration, the shaft 128 is generally cylindrical, with its center coinciding with the vertical axis A. Furthermore, more specifically, the shaft 128 of the body 124 is rigidly connected at each end to the cable 70 and the through-hole head 122.

[0124] The shaft 128 includes a slot 130 that extends from the periphery of the shaft 128 to the center of the column at the second longitudinal end 129 of the body 124. The slot 130 facilitates the mounting of the cable 70 onto the shaft 128 of the body 124.

[0125] According to another embodiment, the shaft 128 of the perforated member 36 may include a retaining ring, more specifically located at the second longitudinal end 129, and the cable 70 may be secured to the retaining ring.

[0126] The body 124 also supports a plurality of wings 132, each of which extends radially from the axis 128 of the body 124. Each of the plurality of wings 132 extends longitudinally between a first longitudinal end 126 and a second longitudinal end 129 of the body 124 and extends perpendicularly to the axis 128 away from the perforated member 36. In other words, each of the plurality of wings 132 extends primarily from the axis 128 of the body 124 away from the perforated member 36 in the plane containing the vertical axis A.

[0127] Each of the plurality of wings 132 forms a flat rectangular side with three free edges. First and second free edges 134, 136 participate in defining each wing at a first longitudinal end 126 and a second longitudinal end 129 of the body 124. Thus, the first and second free edges 134, 136 of each wing extend substantially perpendicular to the vertical axis A. Each of the plurality of wings 132 includes a third free edge 138, which is advantageously parallel to the vertical axis A and extends at least partially between the first edge 134 and the second edge 136 of each of the plurality of wings 132.

[0128] exist Figure 3 In the example shown, the plurality of wings 132 have six wings, which are distributed such that the angular sectors between each wing of the plurality of wings 132 are the same. Therefore, it can be understood that the distance separating the third free edge 138 from any two adjacent wings of the plurality of wings 132 is equal, and regardless of which adjacent wing of the plurality of wings 132 is selected to perform the measurement, this distance is measured perpendicular to the vertical axis A. According to another embodiment, the plurality of wings 132 includes at least three wings. If the body 124 has three wings, they are distributed around the axis 128 of the body 124, thereby forming an angle of approximately 120 degrees.

[0129] The third free edge 138 of each of the plurality of wings 132 at least partially defines the periphery of the body 124, the third free edge being inscribed in a circle representing the periphery.

[0130] The third free edge 138 of each of the plurality of wings 132 supports a cover 140 that facilitates the sliding of the body 124 within the tube 38. The cover 140 advantageously extends from the first edge 134 of each wing to the second edge 136, thereby covering the entire third free edge 138 of each wing. The cover 140 is made of a synthetic material, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), also known as Teflon, to reduce friction between the third free edge 138 of each of the plurality of wings 132 of the perforated member 36 and the inner surface of the tube 38. In addition to the cover 140, the perforated member 36 is advantageously made of stainless steel, such that its weight is sufficient to allow the primary sealing membrane 12 to be perforated in the perforation area 60.

[0131] At its second longitudinal end 129, the body 124 supports a disc 142, which prevents the cable 70 from entering the area of ​​the plurality of wings 132 when the perforated member 36 is in the cavity 54 of the tube 38. In fact, when the perforated member 36 is stopped at the end of its descent, the roller 68 continues to rotate due to the weight of the cable 70. A portion of the cable 70 is gathered on the disc 142, which prevents the cable 70 from passing between the plurality of wings 132 and the inner surface 33 of the tube 38. The disc 142 extends primarily in a plane perpendicular to the vertical axis A, which coincides with the center of the disc 142.

[0132] The disc 142 has an upper surface 144 and a lower surface (not visible in the figure) facing each other, with the lower surface facing the plurality of wings 132 of the shaft 128 and the body 124. Furthermore, the diameter of the disc 142 is less than or equal to the diameter of the mating third free edges 138 of the plurality of wings 132. However, the diameter of the disc 142 must be large enough to prevent the cable 70 from passing through the space between the peripheral edge 148 of the disc 142 and the inner surface of the tube 38.

[0133] The disk 142 includes at least one through opening 146, and advantageously includes multiple through openings 146, which allow fluid to flow through the disk 142 as the disk falls through the tube 38. The prefix "through" is understood to mean that the opening is open on both the lower and upper surfaces 144 of the disk 142, thereby connecting the two surfaces of the disk 142. Figure 3 The disk 142 shown includes a plurality of through openings 146 arranged near the radial outer periphery of the disk 142. The openings in the plurality of through openings 146 may be closed at their periphery, thus forming through holes, or they may be open on the outer periphery of the disk, in which case forming through channels. In practice, the disk 142 has a peripheral edge 148 extending between the upper and lower surfaces of the disk 142, and the plurality of through openings 146 are formed near this peripheral edge 148, however, in this case do not contact it.

[0134] The peripheral edge 148 has a chamfered shape between the upper surface 144 and the lower surface of the disk 142. It should be understood that the peripheral edge 148 advantageously has three surfaces: a first surface extending in a plane perpendicular to the extending planes of the upper surface 144 and the lower surface of the disk 142; a second surface providing a connection between the upper surface 144 and the first surface of the peripheral edge 148; and a third surface providing a connection between the lower surface of the disk 142 and the first surface of the peripheral edge 148.

[0135] The reel 142 includes a channel 150 extending from its peripheral edge 148 to its center. The channel 150 is formed to align with a slot 130 of the shaft 128, allowing the cable 70 to be mounted on the perforated member 36 in a manner similar to the slot 130 of the shaft 128. Therefore, after attaching the reel 142 to the cable 70, the reel 142 can be mounted on the perforated member 36.

[0136] According to another embodiment, the disk 142 includes a closed through hole instead of a channel 150 through which the cable 70 passes.

[0137] The disc 142 has at least one mounting hole 152, and advantageously has multiple mounting holes 152, so that the disc 142 can be rigidly connected to the shaft 128 of the body 124. For this purpose, the mounting holes 152 engage with fastening devices (not shown) such as screws to secure the disc 142 to the shaft 128 of the body 124.

[0138] The perforated member 36 includes a perforated head 122, which takes the general shape of a column 121 extending between a connecting edge 154 and a perforated cone 156. The column 121 has at least one groove 123 extending from the perforated cone 156 toward the connecting edge 154.

[0139] The perforating head 122 is rigidly connected to the body 124 at the connecting edge 154, so that the connecting edge contacts the first longitudinal end 126 of the body 124. The perforating cone 156 of the perforating head 122 tapers to the perforating tip 158.

[0140] A method for perforating a can 2 will now be described, wherein the perforating member 36 is configured to move in order to perforate one of the plurality of walls 4 of the can 2.

[0141] Once a leak of fluid contained in tank 2 through the primary sealing membrane 12 has been identified, the user places the piercing device 32 at the inlet of tube 38 of tank 2, thus constituting the first step of the piercing method. The piercing device 32 is positioned at the outer opening of tube 38 such that the space 116 in frame 66 contacts the outer opening 56 of tube 38, and a portion of cable 70 and the piercing member 36 are arranged horizontally at the outer end 44 of tube 38 within the cavity 54 of tube 38. The cable 70 is then wound around roller 68 to hold the piercing member 36 horizontally at the outer end 44 of tube 38.

[0142] The second step involves positioning the perforated member 36 at the level of the inner end 42 of the tube 38. For this purpose, the user rotates the crank 72, causing the roller 68 to unwind the cable 70, thereby allowing the perforated member 36 to descend through the tube 38 toward the bottom wall of the can 2. The descent of the perforated member 36 is thus controlled by the user rotating the crank 72. To prevent premature release of the perforated member 36 during its descent through the tube 38, the roller 69 includes a braking system that limits the rotational speed of the roller 68, thereby preventing the perforated member 36 from falling and penetrating one of the multiple walls 4 of the can 2. The braking system is reversible, so it can be removed when the user wishes to release the perforated member 36. The controlled descent of the perforated member 36 is performed until the perforated tip 158 of the perforated member 36 contacts the flat area 64 of the protrusion 62 on the bottom 50 of the can.

[0143] The third step of the perforation method involves raising the perforating member 36 to the drop height within the tube 38, and then stopping the roller 68 once the perforating member 36 is at said height. In this way, the user raises the perforating member 36 to a predetermined height, which depends on factors such as the thickness of the primary sealing film or the presence of fluid in the tube 38. For example, this height is three meters, measured along the vertical axis A.

[0144] Because of the notch 160, when the perforated member 36 is raised before falling, the user can calculate the number of rotations of the roller 68. In the example shown here, the size of the roller 68 is such that the circumference of the roller 60 is approximately one meter, such that one rotation of the roller 60 results in the cable 70 being wrapped or unwound by one meter.

[0145] To raise the perforated member 36 to three meters above the inner nozzle 58 of the tube 38, the user uses the crank 72 to rotate the roller 68 and relies on the notch 160 to count the number of rotations of the roller 68 until it has rotated three times. When the perforated member 36 has reached this height, the user places the stopping device 92 in the roller 68 to stop the rotation of the roller 68.

[0146] The fourth step of the method involves lowering the perforated member 36. Thus, the user releases the roller 68 from the locking device 92, and the perforated member 36 is pushed by its weight into the flat area 64 of the protrusion 62 on the bottom of the can.

[0147] The weight of the perforated member 36 pushes the perforated tip 158 of the perforated member 158 towards the flat area 64 of the protrusion 62 on the bottom 50 of the can with sufficient speed, thereby generating kinetic energy. When the perforated tip 158 contacts the flat area 64, the kinetic energy is converted into mechanical energy, causing the perforated tip 158 to perforate the primary sealing membrane 12 at the flat area 64 of the protrusion 62. Once the primary sealing membrane 12 is perforated, the perforated member 36 is lifted by the user to the outer end 44 of the tube 38.

[0148] The fifth step of the perforation method involves lifting the perforating member 36 into the tube 38. If the perforating member 36 does not sufficiently perforate the primary sealing membrane 12 after the first attempt, the user restarts the perforation process by positioning the perforating member 36 at a predetermined height from the inner nozzle 58 of the tube 38 and lowering the perforating member 36 back onto the primary sealing membrane 12, thus constituting the fifth step of the perforation method.

[0149] Therefore, the user can restart the perforation process, more specifically, steps two, three, and four, until the primary sealing membrane 12 has been perforated. In other words, the user repeats these three steps as long as the holes in the primary sealing membrane 12 do not have sufficient area for the fluid to leave the primary insulation barrier very quickly and return to the internal space 15 of the tank 2.

[0150] Once the sealing membrane is perforated, the fluid contained in tank 2 can be drained without damaging the walls of tank 2. In effect, the liquefied natural gas that has permeated into at least one wall 4 returns to the interior space 15 of tank 2 via a perforation created by the perforation member 36 in the primary sealing membrane 12. Furthermore, fluid that has permeated into the first insulation barrier 10 can thus be recovered, thereby avoiding any risk of overpressure inside the walls of the tank that have already permeated. Once all the liquefied natural gas has been drained, the leak and perforation can be repaired so that the tank can be resealed.

[0151] However, the invention is not limited to the devices and constructions described and shown herein, but extends to any equivalent devices or constructions described and shown herein, and to any combination of techniques using such devices. In particular, without departing from the scope of the invention, the means 34 for actuating the perforated member can be at least partially motorized or even fully automated.

Claims

1. A perforation device (32) for a sealed and insulated tank (2) designed to contain fluid, characterized in that, The perforating device (32) includes an actuating device (34) and a perforating member (36) for perforating the can (2). The actuating device (34) is designed to generate movement of the perforating member (36). The actuating device (34) includes at least one frame (66), a roller (68), and a cable (70) connecting the perforating member (36) to the roller (68). The roller (68) is designed to rotate about a rotation axis (B) and cause the cable (70) to wind or unwind around the roller (68).

2. The perforation device (32) according to claim 1, wherein, The perforated member (36) includes at least one perforated head (122) and a body (124), the perforated head and the body extending longitudinally one after the other.

3. The perforation device (32) according to claim 2, wherein, The body (124) has a first longitudinal end (126) rigidly connected to the perforated head (122) and a second longitudinal end (129) rigidly connected to the cable (70).

4. The perforation device (32) according to claim 2 or 3, wherein, The main body (124) includes a plurality of wings (132) and a shaft (128), the plurality of wings (132) extending radially from the shaft.

5. The perforation device (32) according to claim 4, wherein, At least one of the plurality of wings (132) includes a free end (138) that at least partially defines the periphery of the body (124) and includes a cover (140) that facilitates sliding of the body (124).

6. The perforation device (32) according to claim 3, characterized in that, The main body (124) supports the disk (142) at the second longitudinal end (129).

7. The perforating device (32) according to claim 6, characterized in that, The disk (142) includes at least one through opening (146).

8. The perforation device (32) according to claim 6 or 7, wherein, The disk (142) is at least partially made of a material that facilitates the sliding of the disk.

9. The perforation device (32) according to claim 6 or 7, wherein, The main body (124) includes a plurality of wings (132) and a shaft (128), the plurality of wings (132) extending radially from the shaft, and the diameter of the disk (142) is less than or equal to the diameter of the free ends (138) of the plurality of wings (132).

10. The perforating device (32) according to any one of claims 1-3 and 6-7, wherein, The actuation device (34) includes a stop device (92) for preventing the roller (68) from rotating, the stop device (92) being designed to cause the perforated member (36) to fall.

11. A sealed and insulated tank (2) designed to contain fluid, the tank (2) comprising a plurality of walls (4), characterized in that, The can (2) includes a tube (38) that passes through at least one of the walls of the can (2) and extends between a first end (42) disposed inside the can (2) and a second end (44) disposed outside the can (2), the can (2) including a perforation device (32) according to any of the preceding claims.

12. The tank (2) according to claim 11, wherein, The perforated member (36) is arranged in the tube (38), and the roller (68) winds the cable (70) to raise the perforated member (36).

13. The tank (2) according to claim 11 or 12, wherein, The perforated member (36) includes at least one perforated head (122) and a body (124) extending longitudinally one after the other. The body (124) includes a plurality of wings (132) and a shaft (128). The plurality of wings (132) extend radially from the shaft. At least one of the plurality of wings (132) includes a free end (138) that at least partially defines the periphery of the body (124) and includes a cover (140) that facilitates sliding of the body (124). The perforated member (36) and the tube (38) are designed such that the perforated member (36) slides within the tube (38).

14. The tank (2) according to claim 11 or 12, characterized in that, Each of the plurality of walls (4) comprises, from the outside to the inside, a secondary heat insulation barrier (6), a secondary sealing membrane (8), a primary heat insulation barrier (10), and a primary sealing membrane (12) for contact with the fluid contained in the tank (2), the primary sealing membrane (12) having a perforated area (60) arranged opposite to the open end of the tube (38) inside the tank (2).

15. A ship comprising at least one tank (2) according to any one of claims 11 to 14.

16. A method for perforating a tank (2) installed on a ship according to any one of claims 11 to 14, characterized in that, The first step includes installing a perforation device (32) at the second end (44) of the tube (38).

17. The method for perforating a can (2) according to claim 16, characterized in that, The second step involves sliding the perforated member (36) in the tube (38) to move the perforated member downward to the bottom wall (50) of the tank (2).

18. The method for perforating a can (2) according to claim 17, characterized in that, The third step involves lifting the perforating member (36) into the tube (38) to the falling height, and then, once the perforating member (36) is positioned at the height, blocking the roller (68) that constitutes the perforating device (32).

19. The method for perforating a can (2) according to claim 16 or 18, characterized in that, The fourth step includes dropping the perforated component (36).

20. The method for perforating a can (2) according to claim 19, wherein the can comprises, in a thickness direction from the outside to the inside of the can (2), a secondary heat insulation barrier (6), a secondary sealing membrane (8), a primary heat insulation barrier (10), and a primary sealing membrane (12) for contacting a fluid contained in the can (2), wherein the second, third, and fourth steps are repeated until the primary sealing membrane (12) is perforated.

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