TITLE: SYSTEM FOR THE RECOVERY OF OBJECTS RESTING ON A SEABED

TECHNICAL FIELD OF THE INVENTION

[0001 ]The invention relates to a system for the recovery of at least one object resting on a seabed.

PRIOR ART

[0002]There are many objects on the seabed, both natural and man-made. These objects resting on the seabed include bombs and other shells and wastes submerged in seas throughout the world, shipwrecks which are to be raised, whatever their mass or their depth. More particularly, there are also minerals resting on the ocean floor in the form of polymetallic nodules at depths of 6000 m and more, but also other minerals of very great interest at varying depths.

[0003]There are currently devices allowing the recovery of polymetallic nodules such as that described in document WO2015/178854. The device comprises a first assembly pulled by a surface vessel making it possible to rake the seabed over a width so as to form a windrow of nodules behind it. Secondly, a second assembly makes it possible to recover the nodules from the windrow thus formed and to bring them up to a second, storage vessel. A drawback of this system is that the first assembly, in particular, very significantly disturbs the surrounding ecological environment, and this over hundreds of metres, or even kilometres, around the intervention area. In addition, such a system presupposes that the seabed is an abyssal plain, which is not the case at depths of 6000 m and more.

DESCRIPTION OF THE INVENTION

[0004]An object of the invention is therefore to provide a system for the recovery of at least one object, whatever it may be, resting on a seabed, whatever its mass, volume and the depth at which it is located, which system disturbs as little as possible the ecological environment of the seabed where said at least one object rests. [0005]To that end there is provided, according to the invention, a system for the recovery of at least one object resting on a seabed comprising a floating support device and at least one underwater vehicle connected to the support device by means forming an umbilical, the underwater vehicle further comprising a receiving container arranged to receive the recovered object, handling means arranged so as to transfer the object from the seabed into the container, a chassis, means of displacement on the seabed, the displacement means further comprising propulsion means arranged so as to allow movement of the underwater vehicle relative to the seabed and passive support means that are independent of the propulsion means and are arranged so as to bear on the seabed.

[0006]Thus, the fact of having passive support means that are independent of the propulsion means, these means together forming the means of displacement of the underwater vehicle, makes it possible to minimize the disturbance to the ecological environment of the seabed where the underwater vehicle is positioned and therefore where the object to be recovered lies.

[0007]Advantageously, but optionally, the recovery system according to the invention has at least one of the following technical features:

- the passive support means are of the multipod pedestrian type;

- the passive support means comprise at least three support pads, in particular made of rubber and non-inflatable;

- the passive support means comprise caterpillar tracks;

- the propulsion means are positioned at the stern of the underwater vehicle;

- the propulsion means comprise propeller or turbine thrusters;

- the thrusters are azimuthal;

- the underwater vehicle comprises ballasting means;

- the receiving container is removably mounted on the chassis of the underwater vehicle; - the floating support device comprises means for generating hydraulic power and/or electric power that are transmitted to the underwater vehicle via the means forming an umbilical;

- the floating support device comprises means for controlling and piloting the underwater vehicle via the means forming an umbilical;

- the handling means comprise at least one crane and/or one loading bucket;

- the underwater vehicle comprises means for cutting and/or assembling, in particular by welding, the object to be recovered;

- the recovery system further comprises a device for raising the object, once the latter has been recovered by the underwater vehicle;

- the raising device comprises an inflatable balloon; and

- the raising device comprises a noria of inflatable balloons.

BRIEF DESCRIPTION OF THE FIGURES

[0008]0ther features and advantages of the invention will emerge on reading the following description of an embodiment of the invention. In the appended drawings:

[Fig.1 ] is a schematic view of an embodiment of a recovery system according to the invention;

[Fig. 2] is a three-dimensional view of an embodiment of an underwater vehicle of the recovery system according to the invention;

[Fig. 3] is a side view of the underwater vehicle of Figure 2;

[Fig. 4] is a side view of a second embodiment of an underwater vehicle of the recovery system according to the invention;

[Fig. 5] is a schematic three-dimensional view of an embodiment of a floating support device of the recovery system according to the invention; [Fig. 6] is a schematic side view of a variant embodiment of the underwater vehicle of Figure 2;

[Fig. 7] is a schematic view of an embodiment of a raising device of the recovery system according to the invention; and

[Fig. 8] is a schematic view of another embodiment of a raising device of the recovery system according to the invention.

[0009]For greater clarity, identical or similar elements are identified with identical reference signs across all the figures.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0010]lt is initially stated that, throughout the description and in the context of the invention, the term "object" 2 is to be understood as any item that is tangible and perceptible by sight or touch and/or any manufactured solid item considered as a whole, which item can be resting on a seabed. For example, and without this being limiting, it can be a wreck, a shell, a bomb, various and varied waste, a pebble, nodules, a rock, sediment(s), rare earths and other minerals of very great interest, etc.

[0011]With reference to Figure 1 , there follows a description of a recovery system 1 according to the invention. The recovery system 1 according to the invention is shown here schematically in situ: it comprises a floating support device 20 located at a surface M of a body of water such as a sea or an ocean, for example. The floating support device 20 is for example a support vessel or a floating platform or else a buoy according to the embodiment chosen for the recovery system 1 according to the invention. On the other hand, the recovery system 1 according to the invention furthermore comprises an underwater vehicle 10 intended, when the recovery system 1 according to the invention is in use, to come to rest on a seabed F, preferably in the vicinity of an object 2 that is to be recovered and is resting on said seabed F. The underwater vehicle 10 is connected to the floating support device 20 using means forming an umbilical 40. The means forming an umbilical 40 make it possible to transfer electrical and/or hydraulic power, generated at the floating support device 20, to the underwater vehicle 10. On the other hand, the means forming an umbilical 40 make it possible to pilot and control the underwater vehicle 10 from the floating support device 20 which comprises to that end piloting and control means provided for this purpose. In addition, the recovery system 1 according to the invention comprises a raising device 30 connected to the floating support device 20 via connecting means 32. The raising device 30 cooperates with means 31 for raising the object 2, once the latter has been recovered, from the underwater vehicle 10. In order to be able to recover the object 2, the underwater vehicle 10 comprises handling means 11 provided for this purpose.

[0012]With reference to Figures 2 to 4, there follows a more detailed description of the underwater vehicle 10, 1 10 of the recovery system 1 according to the invention.

[0013]ln general terms, the underwater vehicle 10, 1 10 comprises a chassis 14 on which there is mounted a set of elements forming the underwater vehicle 10, 1 10. In particular, the underwater vehicle 10, 1 10 comprises ballasting means 13 fixed to the chassis 14 and supplied and controlled via the means forming an umbilical 40. Here, the ballasting means 13 are formed of two tanks fixed to the chassis 14 and on either side thereof.

[0014]According to a first embodiment, the underwater vehicle 10 is intended to operate on the seabed F at a depth referred to as the operating depth, extending from immediately under the surface M to maximum depths of 300 m. At these depths, the recovery system 1 according to the invention allows recovery and/or maintenance missions of any kind within these depths. The handling means 1 1 comprise a crane as well as multipurpose tools depending on the uses and requirements of the operations to be carried out by the recovery system 1 according to the invention: raising of wrecks of all kinds, various objects such as shells and bombs, etc.

[0015]The means for producing electrical and/or hydraulic power comprise hydraulic, ballast and pressurized water pumps on the floating support device 20. These means also include a generator set, the hydraulic and electrical power being transmitted to the underwater vehicle 10, 110 via the means forming an umbilical 40.

[0016]A skip or container 12 is provided removably or non-removably mounted on the chassis 14 of the underwater vehicle 10, 1 10. This container 12 is intended to receive the object 2, once the latter has been recovered by the handling means 1 1. For a container 12 fixedly mounted on the chassis 14 of the underwater vehicle 10, unloading of the latter is carried out either by bucket, or by opening the bottom doors of the container 12 into a buffer container placed below and resting on the seabed F. In the case of a removably mounted container 12, the latter is raised/lowered using the raising device 30 of the recovery system 1 according to the invention.

[0017]On the other hand, the underwater vehicle 10, 1 10 comprises propulsion means 16, preferably mounted at the stern of the underwater vehicle 10, 1 10 on the chassis 14. For example, the propulsion means 16 comprise propeller or turbine thrusters, in this case two such thrusters. The thrusters can be of the azimuthal type, such as the Rolls-Royce® PM type thrusters. These propulsion means 16 make it possible to move the underwater vehicle 10, 1 10 relative to the seabed F and to the object 2 to be recovered. Their structure and their positioning make it possible to minimize any interaction between these propulsion means 16 and the seabed F, with the aim of reducing disturbance to the ecological environment around the underwater vehicle 10, 1 10. In an alternative embodiment, the propulsion means 16 can be mounted preferably at the stern of the underwater vehicle 10 on the container 12 when the latter is mounted fixedly on the chassis 14 (Figures 2 and 3).

[0018]On the other hand, the underwater vehicle 10, 1 10 comprises passive support means 15, which are independent of the propulsion means 16. Here, the passive support means 15 are of the multipod pedestrian type, in this case quadripod as illustrated in Figures 2 to 4. The number of feet is at least three. Thus, the underwater vehicle 10, 1 10 lands on the seabed F on, for example, non-inflatable rubber pads 151 , without this being limiting. Again, this makes it possible to reduce disturbance to the ecological environment around the underwater vehicle 10, 1 10.

[0019]Descent and ascent of the underwater vehicle 10, 110 is effected by action of the ballast-forming means 13.

[0020]ln an alternative embodiment illustrated in Figure 4, the underwater vehicle 1 10 includes handling means, in this case comprising two cranes 1 14 and 1 12 and a loading bucket 1 1 1. The underwater vehicle 1 10 further comprises tools 1 13 such as tools for cutting or for assembling (by welding, for example), or for drilling the object 2 to be recovered.

[0021 ]On the other hand, the underwater vehicle 10 or 1 10 includes viewfinding means such as cameras to allow steering and control of the vehicle.

[0022]ln another embodiment of the underwater vehicle 10 or 110, intended to operate at depths extending from immediately under the surface M to depths of 2000 m, the passive support means 15 comprise, instead of feet, caterpillar tracks, as illustrated schematically in Figure 6, or even wheels. In the context of caterpillar tracks, the latter are two sets 152, 153 of tracks: one set 152 at the stern and one set 153 at the prow of the underwater vehicle 10 or 1 10.

[0023]According to yet another embodiment of the recovery system 1 according to the invention, the latter is intended to operate at depths extending from immediately under the surface M to depths of 10 000 m and more.

[0024]ln this embodiment, the underwater vehicle 10 or 110 does not include ballastforming means.

[0025]With reference to Figure 7, the raising device 30 here comprises a hoist 310 remotely located above the container 12 and connected via a cable or a chain 31 1 to the removable container 12 or buffer container, connecting it (via a chain or a cable 312) to an inflatable balloon 301 held in an attachment lattice at a distance under the surface M, of the order of 200 to 300 m. Pressure within the inflatable balloon 301 is provided by inflation means 302 connecting it to the floating support device 20. This makes it possible to dispense with a very expensive and delicate swell compensation system on the floating support device 20. As an alternative embodiment, the hoist 310 makes it possible to raise the removable container 12 from the underwater vehicle 10 or 110 and then position it above the buffer container 120 to transfer the object 2 from the removable container 12 to the buffer container 120. The latter is then raised using the associated raising means 31.

[0026] In an alternative embodiment, the recovery system 1 according to the invention comprises one or more auxiliary vessels responsible for raising and storing the objects 2 recovered by the underwater vehicle 10 or 1 10, this being done in conjunction with the raising device 30.

[0027]ln a further embodiment of the recovery system 1 according to the invention, a schematic view of which is illustrated in Figure 8, the latter differs from the foregoing in that the raising device 30 includes a noria of balloons 315 which are deflated and reinflated at a maximum depth of 250 m (25 bar) which will allow the container 12 and/or the buffer container to be gradually raised by increments of approximately 220 m. Indeed, and purely by way of illustration, a captive balloon 315 with a radius of 10.6 m generates an upthrust of the order of 5000 1 (50 000 kN), and a captive balloon with a radius of 15 m generates an upthrust of the order of 14 000 1 (140 000 kN). By means of such a raising device 30, it is possible to raise any mass from any depth, even if it is by increments of 200 m, and 5 times 200 m brings us 1000 m closer to the surface M. In use, each of the balloons 315 is brought down in a deflated state to a depth of 250 m. Then it is hooked onto a link of the chain 312, then inflated via the associated inflation means 302. Once inflated, the balloon 315 rises towards the surface, pulling on the chain 312 and thus raising the object 2 connected to a lower end of the chain 312, via different attachment chains 313. Once raised to a depth of approximately 10/20 metres, the balloon 315 is deflated and unhooked from the link of the chain 312 to be brought back down, deflated. The cycle then resumes for this balloon 315 of the noria of balloons 315. The chain portion 312 above the balloon 315 is simultaneously stored on the floating support device 20.

[0028]lt should be noted that this embodiment of the recovery system 1 according to the invention is preferred to be able to raise wrecks of all sizes (steel and wood), and from all depths. In the context of raising a wreck 121 , the raising device 30 is attached directly to the latter 121 as explained below in the description (illustrated on the left side of Figure 8). Such a recovery system 1 according to the invention makes it possible to bring about Archimedean degravitation operating in the same way at the surface M of the sea as on the seabed F where the wrecks rest.

[0029]To that end, the recovery system 1 according to the invention and in particular the tooling of the underwater vehicle 10 or 1 10 will make it possible to weld plates onto a broadside/periphery of the wreck, then to lay suitable cables 313 engaged in rings provided on these plates over the entire length of the wreck, at least to port, starboard, prow and stern. Then, on each cable 313 secured to the wreck, a chain 312 is taken up towards the raising device 30 and its noria of balloons. [0030]The very high suction upon lift-off of the wreck will be addressed by the hydraulic power provided via the means forming an umbilical 40 to the underwater vehicle 10 or 1 10, or tilting will be necessary with asymmetrical traction on the chains 313.

[0031 ] With reference to Figure 5, the floating support device 20 is in this case a support vessel having the means for generating hydraulic and electrical power and the means for controlling and piloting the underwater vehicle 10 or 1 10. On the other hand, the floating support device 20 comprises a reel 21 for the means forming an umbilical 40.

[0032]0f course, it will be possible to modify the invention in numerous ways without departing from the scope thereof.