Lifting device for a fixed offshore structure, system and method for installing a fixed offshore structure with such a lifting device

Abstract

A lifting device for a fixed structure in an aquatic environment comprising a platform (3) and at least one leg (4) movable in translation relative to the platform (3) for raising or lowering the leg (4) relative to the platform (3). The removable lifting device (5) is adapted to be easily assembled and disassembled for reuse to install other fixed structures having similar legs (4). (Figure 2)

Description

Title of the invention: Lifting device for a fixed offshore structure, system and method for installing a fixed offshore structure with such a lifting device

[0001] The present invention relates to a lifting device for fixed structures, as opposed to floating structures, at sea or in other aquatic environments, such as for example lakes, ponds, rivers, lagoons, etc.

[0002] It further relates to a system for installing fixed structures in an aquatic environment using a lifting device mentioned above, as well as an installation method corresponding, but not exclusively, to the implementation of the installation system.

[0003] The invention applies in particular to the installation of so-called offshore structures linked to the exploitation of hydrocarbons, but it can also be applied to all types of fixed installations intended for the exploitation of underwater resources, such as the pumping of water or other liquid or gaseous effluents, or the exploitation of offshore energy such as for example wind energy.

[0004] The installation of structures at sea, or in other aquatic environments, generally requires the intervention of specialized means such as cranes or gantries mounted on floating devices or on self-elevating platforms. These lifting means are expensive and relatively rare, which makes their mobilization long and expensive. Most often, these structures installed by the conventional means indicated above are composed of several parts assembled on site.

[0005] Alternatively, there are many concepts of self-installing platforms or structures. These are most often mobile. This is particularly the case for drilling platforms which, once drilling is completed, are towed to another site. However, they can also be permanently installed at a given location.

[0006] These self-installing structures are in fact self-elevating structures ("jack-up" in English) composed of a floating part (hereinafter called a platform) and legs that can translate vertically relative to the platform, thanks to a lifting device remaining in position on the platform. The lifting device allows the legs to be lowered to the seabed and then the platform to be raised above the surface of the water by continuing to "lower" the legs. This lifting device conversely allows the legs to be raised to lower the platform again in order to put it back into a floatation state when the structure must be uninstalled.

[0007] Different systems exist to enable this controlled vertical translation of the legs across the platform. Either the lifting device comprises motorized pinions meshing with racks secured to the legs, or it comprises jacks acting between the platform and the legs. In this case, the jacks are coupled to a device for locking the platform on the legs once it has reached the desired height. This locking device can cooperate with racks mechanically connected to the legs, or it can consist of a system of flanges closing or opening on smooth legs.

[0008] The aim of the present invention is to propose a system for installing structures which is quick to implement and inexpensive.

[0009] To this end, there is proposed, according to a first aspect of the invention, a lifting device for a fixed structure in an aquatic environment comprising a platform and at least one leg movable in translation relative to the platform, said lifting device being characterized in that it comprises: - a first fixing device comprising: - a fastening means configured to secure said first fastening device to said platform; and - a first locking means configured to temporarily secure said first fixing device to said at least one leg of the fixed structure; - a second fixing device comprising: - a second locking means configured to temporarily secure said second fixing device to said at least one leg of the fixed structure; and - a translational movement means to move said first fixing device away from and / or towards said second fixing device.

[0010] Thus, such a lifting device used to raise a platform above sea level, as for a conventional self-elevating structure, has a relatively simple design which does not require modifying or adding additional elements to the structure. The lifting device according to the invention can be dismantled once the fixed structure has been installed and the platform raised to the desired height in order to be reused to install another fixed structure, whereas in known systems, the means for lifting or lowering the legs are designed to remain in place and therefore cannot be reused.

[0011] By using this set of fastening devices to move the leg(s) of the structure, for example vertically, a movable mechanical assembly is formed which can be easily mounted and dismounted from one fixed structure to another having a leg of substantially similar geometry.

[0012] The first fixing device and the second fixing device can each form a compact one-piece assembly which is easily disassembled and which can be used to temporarily lock the position of the platform on the jamb.

[0013] Preferably, the first and second locking means are operable between a first position in which the first and second locking means are respectively configured to secure the first and second fixing devices to said at least one leg and a second position in which the first and second locking means are respectively configured to detach the first and second fixing devices from said at least one leg.

[0014] Thus, the first and second locking means can make it possible to lock or unlock the position of the platform on the jamb.

[0015] Indeed, when the first locking means is moved into the first position, the first fixing device blocks the position of the at least one leg relative to the platform since the first fixing device is secured to the platform by means of the fixing means. If the second locking means is moved into the second position, the second fixing device can move relative to the leg by means of the translational movement means.

[0016] Conversely, when the first locking means is moved into the second position and the second locking means is moved into the first position, the leg is fixed relative to the second fixing device. Thus, the leg can be moved relative to the platform by moving the first fixing device closer to or further away from the second fixing device with the translational movement means.

[0017] Advantageously, the lifting device comprises control means for controlling said translational movement means so as to bring the first and second fixing devices together or apart and for actuating said first and second locking means between said first position and said second position.

[0018] In this configuration, the first and second locking means can be easily actuated automatically and remotely.

[0019] The control means may be configured to automatically and / or remotely control the raising or lowering of the at least one leg relative to the platform.

[0020] Preferably, the translational displacement means and / or the first and second locking means are actuated hydraulically or pneumatically by said control means.

[0021] The use of hydraulic or pneumatic energy to operate the various components of the removable lifting device allows automatic control of these components. Hydraulic power is generally available at the installation sites of such structures.

[0022] The translational displacement means and / or the first and second locking means can alternately be actuated pneumatically by said control means.

[0023] Advantageously, the first and second locking means comprise inflatable elements which are operable between a first position in which the inflatable elements are pressurized to secure the first and second fixing devices to said at least one leg and a second position in which the inflatable elements are depressurized to detach the first and second fixing devices from said at least one leg.

[0024] Such inflatable elements are relatively simple to implement and are easily controllable or actuable, in particular for movement between the first and second position.

[0025] Further, the inflatable members are configured and sized to exert sufficient force, without requiring significant sizing, to secure one or the other of the first and second attachment devices to the at least one leg.

[0026] Preferably, the inflatable members are configured to exert pressure on an outer surface of the leg when pressurized, each inflatable member comprising at least two half-moon shaped inflatable chambers.

[0027] Thus, it is possible to not use any additional element in the lifting device to secure the first or second fixing device to the at least one leg.

[0028] The at least two half-moon inflatable chambers are particularly suitable for legs of substantially circular section. When these chambers are independent of each other, they can move apart or closer together in order to adapt to legs of more or less large sections.

[0029] Furthermore, thanks to their deformable nature, the inflatable elements can adapt to legs whose section is not circular.

[0030] Preferably, the first and second fixing devices each form a mechanical assembly comprising two sub-assemblies, said two sub-assemblies being configured to be assembled respectively between them around said at least one leg by removable fixing means.

[0031] This arrangement makes it possible to mount the at least one removable lifting device around the at least one leg, without it being necessary to thread it through the top of the latter.

[0032] Once the first and second fixing devices are mounted around the at least one leg by assembling each of the two sub-assemblies, the means of translational displacement means may in turn be assembled. Alternatively, the translational displacement means may be assembled prior to mounting the first and second fixing devices around the at least one leg.

[0033] Advantageously, the translational displacement means comprises a jack, said jack being connected by a first end to said first fixing device and by a second end to said second fixing device.

[0034] The use of a jack makes it possible to do without elements mechanically connected to the leg, for example a rack, and interacting with the lifting means. Thus, it is possible to avoid leaving the rack in place once the fixed structure has been installed. This arrangement thus allows the jack to move the first and second fixing devices away from or towards each other.

[0035] According to a second aspect of the invention, there is proposed a system for installing a fixed structure in an aquatic environment comprising a platform and at least one leg movable in translation relative to the platform, characterized in that it comprises: - at least one lifting device according to the first aspect of the invention; and - immobilizing means for locking the position of the platform relative to said at least one leg when said at least one removable lifting device is dismantled and after the platform has reached its operational height.

[0036] Finally, according to a third aspect of the invention, there is proposed a method of installing in an aquatic environment a fixed structure comprising a platform and at least one leg movable in translation relative to the platform, with a lifting device comprising a first and a second fixing device, said method comprising the following steps: - mounting of the first and second fixing devices on the fixed structure, comprising the sub-steps of: - securing a means of fixing said first fixing device to the platform; - temporary securing of a first means for locking said first fixing device and / or of a second means for locking said second fixing device to said at least one leg; - bringing together and / or separating by a means of translational movement of the first fixing device relative to said second fixing device; - provision of immobilization means for locking the position of the platform relative to said at least one leg after the platform has reached its operational height; and - dismantling of the first and second fixing devices of the fixed structure.

[0037] Preferably, once the fixed structure to be installed has arrived at the operating site, the at least one leg is lowered relative to the platform by the at least one lifting device.

[0038] Thus, the method further comprises a step of lowering the at least one leg relative to said platform comprising the following sub-steps: - in a first step, actuation of the first locking means in a first position in which the first fixing device is secured to said at least one leg and actuation of the second locking means in a second position in which the second fixing device is detached from said at least one leg, and separation of the first fixing device relative to the second fixing device by the translational movement means; - in a second step, actuation of the second locking means in the first position so that the second fixing device is secured to said at least one leg; - in a third step, actuation of the first locking means in the second position so that the first fixing device is detached from said at least one leg and bringing the first fixing device closer to the second fixing device by said translational movement means; - then repeat this sequence until the platform has reached its operational height.

[0039] Other characteristics and advantages of the invention are highlighted by the following description of non-limiting examples of embodiments of the different aspects of the invention.

[0040] The description refers to the appended figures which are also given as non-limiting examples of embodiments of the invention: - [Fig.l] represents a fixed structure schematized in a floating position; - [Fig.2] represents a fixed structure shown schematically in the installed position; - [Fig.3] represents a sectional side view of a removable lifting device according to one embodiment of the invention; - [Fig.4] illustrates a semi-transparent side view of a first and a second fixing device according to an embodiment of the invention; - [Fig.5] illustrates, in a top view, a first and a second fixing device according to an embodiment of the invention; - [Fig.6] illustrates a semi-transparent side view of a third fixing device according to an embodiment of the invention; and - [Fig.7] illustrates a top view of a third fixing device according to an embodiment of the invention.

[0041] A fixed structure 1 for operation at sea or in any other aquatic environment may be, as illustrated in [Fig.l], of the floating type. That is to say that before its installation on an operating site, the fixed structure 1 is towed in a floating configuration.

[0042] Once arrived at the operating site, it is anchored on the seabed 2, as illustrated in [Fig.2].

[0043] The fixed structure 1 comprises a platform 3 which acts as a hull in order to be able to float, legs 4 and a removable lifting device 5.

[0044] Before towing the fixed structure 1 to the operating site, the legs 4 are placed vertically in wells 32, visible in [Fig. 3], formed through the platform 3. The legs 4 are generally three or four in number, as in the example described here, in order to together form a stable base for the platform 3 on the seabed 2. However, it is possible for specific platforms, for example small ones, that there is only one leg 4. The legs 4 have a generally smooth cylindrical shape to allow them to slide in their respective well 32 and facilitate the interaction between each leg 4 and a removable lifting device 5.

[0045] A removable lifting device 5, described in relation to [Fig.2] below, is installed around each leg 4 and mechanically connected to the platform 3.

[0046] To enable the fixed structure 1 to be towed to the operating site, each leg 4 is held in a high position relative to the platform 3 by a simple temporary immobilization system (not shown). Such a simple immobilization system may act as a stop resting on a portion of the previously installed removable lifting device 5. It may also take the form of a mechanical lock at the lower level of the removable lifting device 5. Alternatively, the legs 4 may be held in a high position by the removable lifting device 5 itself, in particular for short towing journeys, for example between a site for mounting the fixed structure 1 and the operating site.

[0047] Once the fixed structure 1 has arrived in floating configuration above its installation location on the operating site, the temporary immobilization system, if there was one, is removed and each leg 4 is held in the high position by the associated removable lifting device 5, after its activation. Once unlocked, the legs 4 are lowered relative to the platform 3 by the removable lifting devices 5.

[0048] As illustrated in [Fig.2], once the legs 4 have been lowered until they rest on the seabed 2, the removable lifting devices 5 continue to lower them which in reaction has the effect of raising the platform 3 above the sea level 6 until it reaches a desired elevation.

[0049] When the platform 3 reaches a desired elevation, the legs 4 are locked in the platform 3 by immobilizing means (not shown). The immobilizing means can take different forms, such as for example a weld, a clamping device, wedges inserted between the legs 4 and the well 32 in which they are mounted, or even pins-axes placed transversely to the main axis of the legs 4.

[0050] [Fig. 3] schematically shows a lifting device 5 installed around a leg 4. In the exemplary implementation of the invention described here, the lifting device comprises one or more jacks 7 arranged around the leg 4 and associated with fixing devices, described below and interacting with a smooth cylindrical outer surface 8 of a leg 4. This particular configuration makes it possible to maximize the economic interest of the invention as explained below. Nevertheless, the invention can be transposed to a system of jacks coupled with a rack locking in order to extend the field of use of the invention to fixed structures comprising legs having other achievable geometric shapes, for example in the form of a lattice.

[0051] Each lifting device 5 comprises jacks 7 which, due to their extension or contraction, are configured to raise or lower the leg 4 along its respective well 32 formed through the platform 3. These jacks can be energized either electrically or pneumatically or hydraulically.

[0052] Due to their ease of implementation, hydraulic jacks will most often be used.

[0053] As described below, several design elements of the removable lifting device 5 give it a removable character which allows its reuse for the installation of different fixed structures 1 having legs of similar design to those described here.

[0054] The removable lifting device 5 comprises a first fixing device 40 installed around the leg 4.

[0055] The first fixing device 40 comprises a fixing means 9 and a first locking means 12 which is mechanically secured to the fixing means 9.

[0056] The fixing means 9 is configured to secure the fixing device to the platform 3.

[0057] The well 32 has a collar 11 fixed to a free end of the well 32, opposite the platform 3.

[0058] The fixing means 9 comprises an annular mechanical part forming a groove 10 capable of mechanically cooperating with the collar 11 of the well 32. This design of the mechanical interface between the platform 3 and the removable lifting device 5 allows simple translational locking which makes it possible to accommodate the tolerances of geometrical construction of the legs 4 and the platform 3, and the relative movements of the legs 4 and the platform 3 in a plane perpendicular to the main longitudinal axis of the legs 4.

[0059] The first locking means 12 is configured to temporarily secure the first fixing device 40 to the leg 4.

[0060] The first locking means 12 is here mounted around the leg 4.

[0061] The first locking means 12 comprises a first mechanical element 13, a first inflatable element 14 and a first skate 16.

[0062] The first mechanical element 13 defines a first annular housing 15 configured to receive the first inflatable element 14.

[0063] The first inflatable element is formed by two half-moon inflatable chambers arranged around the leg 4. These half-moon inflatable chambers are here received in the first housing 15.

[0064] The first pad 16 is interposed between the first inflatable element 14 and the outer surface 8 of the leg 4. The first pad 16 is here housed partly in the first housing 15 and is intended to slide in the first housing.

[0065] When the first inflatable member 14 is pressurized, the first inflatable member 14 inflates, to press the first pad 16 against the outer surface 8 of the leg 4 and press against upper and lower surfaces of the first annular housing 15.

[0066] When the first inflatable element 14 is depressurized, the first fixing device 40 and the platform 3 are able to slide around the leg 4.

[0067] Thus, the first inflatable element 14 is configured, when it is pressurized, to block the translation between the leg 4 and the platform 3, and when it is depressurized, to allow the translation between the leg 4 and the platform 3.

[0068] The fixing means 9 and the first locking means 12 are here formed from a single piece. Alternatively, they could be formed from two or more separate pieces mechanically connected to each other in a definitive or removable manner.

[0069] The removable lifting device 5 also comprises a second fixing device 50 arranged here around the leg 4.

[0070] The second fixing device 50 has a design substantially similar to that of the first fixing device 40.

[0071] The second fixing device 50 comprises a second locking means 18 mounted around the leg 4. The second fixing device 50 is configured to temporarily secure the second fixing device to the leg 4.

[0072] The second locking means 18 comprises a second mechanical element 19, a second inflatable element 20 and a second pad 22.

[0073] The second mechanical element 19 defines a second annular housing 21 configured to receive the second inflatable element 20.

[0074] The second inflatable element is formed by two half-moon inflatable chambers arranged around the leg 4. These half-moon inflatable chambers are here received in the second housing 21.

[0075] The second pad 22 is interposed between the second inflatable element 20 and the outer surface 8 of the leg 4. The second pad 22 is here housed partly in the second housing 21 and is intended to slide in the second housing.

[0076] When the second inflatable element 20 is pressurized, the second inflatable element 20 inflates, to press the second pad 22 against the outer surface 8 of the leg 4 and press against upper and lower surfaces of the second annular housing 21.

[0077] When the second inflatable element 14 is depressurized, the second fixing device 50 and the platform 3 are able to slide around the leg 4.

[0078] Thus, the second inflatable element 20 is configured, when it is pressurized, to block the translation between the leg 4 and the second fixing device 50, and when it is depressurized, to allow the translation between the leg 4 and the second fixing device 50.

[0079] The first inflatable element 14 and the second inflatable element 20 can be inflated hydraulically or pneumatically. The first and second inflatable elements 14 and 20 are thus configured to deform according to a variation in hydraulic or pneumatic pressure. In the exemplary implementation of the invention described, the first and second inflatable elements 14 and 20 are inflated by hydraulic pressure.

[0080] One or more jacks 7, here there are two, connect the first fixing device 40 to the second fixing device 50. The cylinders 7 are here double-acting hydraulic cylinders and comprise, in a known manner, a cylinder 24 having a closed end and a piston 23 having a free end, opposite the closed end of the cylinder.

[0081] In the example implementation of the invention described, the free end of the piston 23 of the jacks 7 is mechanically connected to the first mechanical element 13 of the first fixing device 40, while the closed end of the cylinder 24 of the jack 7 is mechanically connected to the second mechanical element 19 of the second fixing device 50. The jacks 7 could be mounted indifferently in the other direction if desired.

[0082] Thus when the jacks 7 are deployed, the first fixing device 40 and the second fixing device 50 are spaced apart from each other. When the jacks 7 are contracted the first fixing device 40 and the second fixing device 50 are brought closer to each other.

[0083] The first and second pads 16 and 22 as well as the first and second inflatable elements 14 and 20 are made of an elastically deformable material, such as for example rubber, which can if necessary be reinforced by a metal or synthetic fiber mesh.

[0084] The lifting device 5 is easily mounted and dismounted around the legs 4, which allows it to be used for the installation of several fixed structures 1 having legs 4 of similar section. This aspect of the invention makes it possible to greatly reduce the unit cost of installing fixed structures. It goes hand in hand with means for simple definitive locking of the platform 3 at operational height on the legs 4 once the removable lifting device 5 has been dismounted.

[0085] As indicated above, the immobilization means can be produced simply in different ways not described. After the fixed structure 1 has been installed on the operating site, only the immobilization means remain on the fixed structure. The cost of these immobilization means is however marginal compared to the cost of the lifting devices 5 used, which therefore does not in any way call into question the economic interest of the invention.

[0086] As illustrated in Figures 4 and 5, the first fixing device 40 is formed by two sub-assemblies 26 of semi-annular shape.

[0087] Each of the two semi-annular subassemblies 26 is configured to receive one of the half-moon inflatable chambers forming the first inflatable element 14. This design makes it possible to mount and dismount the first fixing device 40 around the leg 4 without it being necessary to thread it around the leg 4 by one of its ends.

[0088] The two subassemblies 26 of the first fixing device 40 are connected to each other so that they can be easily disassembled, for example by two axes 27 as shown here. Other connection systems are conceivable, such as for example bolted external flanges.

[0089] Once the two sub-assemblies 26 of the first fixing device 40 are mounted around the leg 4, the second fixing device 40 is assembled around the leg 4.

[0090] As shown in Figures 6 and 7, the second fixing device 50 is also formed by two sub-assemblies 28 of semi-annular shape.

[0091] Each of the two semi-annular sub-assemblies 28 is configured to receive one of the half-moon inflatable chambers forming the second inflatable element 20. The two sub-assemblies 28 of the second fixing device 50 are here connected to each other. by two axes 37 similar to the axes connecting the two sub-assemblies 26 of the first fixing device 40.

[0092] Each jack 7 is fixed by the closed end of its cylinder 24 to a subassembly 28 of the second fixing device 18 by means of assembly flanges 29 which are provided on the first mechanical element 13 of the first fixing device 40.

[0093] Each cylinder 7 is fixed by the free end of its piston 23 on a subassembly 26 of the second fixing device 40 by means of assembly flanges 30 which are provided on the second mechanical element 19 of the second fixing device 40.

[0094] Once the lifting devices 5 are mounted around each leg 4 of the fixed structure 1 and the inflatable elements 14 and 20 are pressurized, the temporary immobilization system can be removed and the fixed structure 1 can be installed on the operating site.

[0095] The operations of lifting and lowering the legs 4 relative to the platform 3 which can be implemented during the installation of the fixed structure 1 on the operating site are described below in connection with [Fig.3].

[0096] Thus, to raise or lower a leg 4, the jacks are successively deployed or retracted according to the so-called “hand-to-hand” method explained below.

[0097] To lower a leg 4 relative to the platform 3, the first locking means 12 and the second locking means 18 are actuated in a first position in which the first fixing device 40 and the second fixing device are secured to the leg 4. The first fixing device 40 and the second fixing device 50 are here spaced apart from each other by the jacks 7, that is to say that the jacks 7 are not in a retracted position.

[0098] The first locking means 12 is then actuated into a second position in which the first fixing device 40 is detached from the leg 4.

[0099] Then the second fixing device 50 is brought closer to the first fixing device 40 by the jacks 7, which has the effect of lowering the leg 4 relative to the platform 3.

[0100] The first locking means 12 is again actuated in the first position in which the first fixing device 40 is secured to the leg 4, while the second locking means 18 is actuated in the second position and the second fixing device 50 is moved away from the first fixing device 40 by means of the jacks 7. Finally, the second locking means 18 is actuated in the first position in which the second fixing device 50 is secured to the leg 4 so that the steps described above can again be implemented until the platform has reached a desired height, for example.

[0101] In particular, the first inflatable element 14 of the first locking means 12 is put under pressure or pressurized to block the translation of the leg 4 in its respective well 32 on the platform 3. Then, the second inflatable element 20 of the second locking means 18 is depressurized to allow the sliding of the second fixing device 50 relative to the leg 4. Then, the jacks 7 are extended and move the second fixing device 50 away from the first fixing device 40, and therefore from the platform 3.

[0102] Once the jacks 7 are extended, the second inflatable element 20 of the second locking means 18 is pressurized to block the translation between the second fixing device 50 and the leg 4. Subsequently, the first inflatable element 14 of the first locking means 12 is depressurized to allow the leg 4 to slide relative to the platform 3, and the jacks 7 are retracted to lower the leg 4.

[0103] The first inflatable element 14 is then put back under pressure to block the translation of the leg 4 in its well 32 and so on until the platform 3 has reached a desired height, for example a predetermined height above sea level.

[0104] Conversely, to raise a leg 4 relative to the platform 3, the first inflatable element 14 of the first locking means 12 is pressurized to block the translation of the leg 4 relative to the platform 3.

[0105] Then, the second inflatable element 20 is depressurized to allow the second fixing device 50 to slide relative to the leg 4. Then the jacks 7 are retracted and bring the second fixing device 50 closer to the first fixing device 40, and therefore to the platform 3.

[0106] Once the jacks 7 are retracted, the second inflatable element 20 of the second locking means 18 is pressurized to block the sliding of the leg 4 relative to the second fixing device 50. Subsequently, the first inflatable element 14 of the first locking means 12 is depressurized to allow the sliding of the leg 4 relative to the platform 3 and the jacks 7 are extended to raise the leg 4.

[0107] The first inflatable element 14 is then put back under pressure to block the translation of the leg 4 in the well of the platform 3 and so on.

[0108] Once the leg(s) 4 have been lowered to the seabed 2 and the platform 3 has been lowered to the desired height, the leg(s) 4 are blocked in their well of the platform 3 by the immobilization means.

[0109] The lifting device 5 can then be removed as simply as it was put in place, by detaching the jacks 7 from the first and second fixing devices. 40 and 50, then by separating the two sub-assemblies 26 from the first fixing device 40 and the two sub-assemblies 28 from the second fixing device 50.

[0110] Once the fixed structure 1 is in place, there is therefore no longer any element of the lifting device 5, which can be completely dismantled and is thus directly reusable for the installation of another fixed structure 1 whose legs 4 are similar.

[0111] As indicated in the preceding description, the different aspects of the invention can be implemented in different contexts and in variant configurations different from those described above. For example, the lifting devices can have jacks combined with fixing devices as described above, or a motor with a pinion interacting with a rack installed on the leg. In this case the legs can have other geometric shapes and be made of latticework.

Claims

1. Claims Lifting device for a fixed structure in an aquatic environment comprising a platform (3) and at least one leg (4) movable in translation relative to the platform (3), said lifting device (5) being characterized in that it comprises: - a first fixing device (40) comprising a first locking means (12) configured to temporarily secure said first fixing device (40) to said at least one leg (4) of the fixed structure (1); - a second fixing device (50) comprising a second locking means (18) configured to temporarily secure said second fixing device (50) to said at least one leg (4) of the fixed structure (1); and - a translational movement means (7) for moving said first fixing device (40) closer to and / or further apart from said second fixing device (50), the first and second locking means (12, 18) each comprising an inflatable element (14, 20) operable between a first position in which the inflatable element (14, 20) is pressurized to secure the fixing device (40, 50) to said at least one leg (4) and a second position in which the inflatable element (14, 20) is depressurized to detach the fixing device (40, 50) from said at least one leg (4), each inflatable element (14, 20) being configured to exert pressure on an outer surface (8) of the leg (4) when it is pressurized, characterized in that the first fixing device (40) further comprises a fixing means (9) configured to secure said first fixing device to said platform (3); in that the first and second fixing devices (40, 50) each form a mechanical assembly comprising two sub-assemblies (26, 28), said two sub-assemblies (26, 28) being configured to be assembled respectively between them around said at least one leg (4) by removable fixing means (27, 37); and in that each inflatable element (14, 20) comprises at least two half-moon inflatable chambers, each subassembly receiving one of the half-moon inflatable chambers.

2. Lifting device according to claim 1, characterized in that it comprises control means for controlling said translational movement means (7) so as to bring the first and second fixing devices (40, 50) closer or further apart and for actuating said first and second locking means (12, 18) between said first position and said second position.

3. Lifting device according to claim 2, wherein said translational displacement means (7) and / or the first and second locking means (12, 18) are actuated hydraulically or pneumatically by said control means.

4. Lifting device according to any one of claims 1 to 3, characterized in that said translational displacement means (7) comprises a jack, said jack being connected by a first end (23) to said first fixing device (40) and by a second end (24) to said second fixing device (50).

5. System for installing a fixed structure in an aquatic environment comprising a platform (3) and at least one leg (4) movable in translation relative to the platform (3), characterized in that it comprises: - at least one lifting device (5) according to any one of claims 1 to 4; and - immobilization means for locking the position of the platform (3) relative to said at least one leg (4) when said at least one removable lifting device (5) is dismantled and after the platform (3) has reached its operational height.

6. Method for installing in an aquatic environment a fixed structure comprising a platform (3) and at least one leg (4) movable in translation relative to the platform (3), with a lifting device (5) according to any one of claims 1 to 4, said method comprising the following steps: - mounting the first and second fixing devices (40, 50) on the fixed structure (1), comprising the sub-steps of: - securing the fixing means (9) on the platform (3); - temporarily securing the first locking means (12) and / or the second locking means (18) to said at least one leg (4);

7. - bringing together and / or separating by the translational movement means (7) of the first fixing device (40) relative to said second fixing device (50); - setting up immobilization means for locking the position of the platform (3) relative to said at least one leg (4) after the platform (3) has reached its operational height; and - dismantling the first and second fixing devices (40, 50) from the fixed structure (1). Method for installing a fixed structure according to claim 6, characterized in that it further comprises a step of lowering the at least one leg (4) relative to said platform (3) comprising the following sub-steps: - in a first step, actuation of the first locking means (12) in a first position in which the first fixing device (40) is secured to said at least one leg (4) and actuation of the second locking means (18) in a second position in which the second fixing device (50) is detached from said at least one leg (4), and separation of the first fixing device (40) relative to the second fixing device (50) by the translational movement means (7); - in a second step, actuation of the second locking means in the first position so that the second fixing device (50) is secured to said at least one leg (4); - in a third step, actuation of the first locking means in the second position so that the first fixing device (40) is detached from said at least one leg (4) and bringing the first fixing device (40) closer to the second fixing device (50) by said translational movement means (7); - then, repeat this sequence until the platform (3) has reached its operational height.

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