BRPI0921272B1 - flotation device - Google Patents

Abstract

flotation device a flotation device (100) is provided, comprising a buoyancy chamber (110), a cryogen reservoir (210); and a heating tube (310) providing switchable fluid communication between the cryogen reservoir (210) and the buoyancy chamber (110). A method of raising an item from the seabed is provided, the method comprising the steps of: lowering a flotation device to the seabed; attach a flotation device to the item to be lifted; creating a supercritical fluid within a portion of the flotation device; and allowing the flotation device and item to rise to the surface using supercritical fluid buoyancy to lift the item to the surface.

Description

"FLOATING DEVICE" [001] The invention refers to flotation devices and in particular flotation devices for handling devices in an underwater environment and lifting items from the seabed.

[002] Vessels that cross the seas, such as ships and submarines, often carry valuable cargo, and are generally very valuable in their own right. If such ships are damaged while at sea and subsequently sink to the seabed, it is highly desirable to be able to recover the cargo, or even the ship itself. The recovery of items such as this requires a method of lifting items to the surface from the seabed. Other cases that require items to be raised and lowered to and from the seabed include exploration on the seabed, and the construction or deactivation of oil and gas platforms and old equipment.

[003] An example of a flotation device is exposed in

GB2435856. The flotation device comprises a container containing a liquefied gas, a gas chamber and a remotely operable device, the remotely operable device being switchable between a closed state in which fluid communication between the container and the gas chamber is prevented, and a open state in which fluid communication between the container and the gas chamber is permitted, and vaporization of the liquefied gas, in use, charges the gas chamber with gas.

[004] GB2435856 discloses a method of lifting an item from the seabed and lowering an item to the seabed using the device described above. The method comprises the steps of: attaching a flotation device as described above to the item and switching the remotely operable device from its closed state to its open state, so that the gas chamber is charged with gas resulting from vaporization of the liquefied gas .

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2/23 [005] When an object to be recovered is located in extreme conditions, gas cannot be created to flow into the gas chamber described in GB2438856 above. When conditions are sufficiently extreme, liquid nitrogen cannot evaporate to the gas phase in the context of extreme conditions comprising depths in excess of 300 m, that is, pressures in excess of 32 Bars and / or temperatures close to or below 0 ° C.

[006] An improved flotation device has now been indicated which overcomes or substantially mitigates the above mentioned disadvantages associated with the prior art.

[007] According to the present invention, a flotation device is provided comprising: a buoyancy chamber; a cryogen reservoir; a heating tube that provides switchable fluid communication between the cryogen reservoir and the buoyancy chamber. The provision of a cryogen reservoir that can, in use, contain a fluid that presents a transition to a supercritical fluid that allows the flotation device to operate at extreme depths in the region of 2000 m. The buoyancy chamber, cryogen reservoir and heating tube can be partially or completely contained within a housing.

[008] The housing can be provided with a reinforced portion adjacent to the cryogen reservoir. The reinforcement ensures that the cryogen reservoir is sufficiently robust to operate at depths in the region of 20000 m where the pressure will be in the region of 200 Bars.

[009] The device further comprises a microprocessor and a plurality of sensors (410, 412, 414, 418, 420). The sensors (410, 412, 414, 418, 420) are used to detect temperature and pressure at various key locations within the device. Drift sensors (410, 412, 414, 418, 420) are also provided to monitor the stability of the device. All of the

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3/23 sensors (410, 412, 414, 418, 420) transfer data to the microprocessor. The microprocessor can contain a unique identifier for the device.

[0010] The housing may incorporate a blowing portion that can be extended if a pressure imbalance between the device and the surrounding sea exerts a predetermined limit. An imbalance could result in an uncontrolled rapid rise to the surface, which could result in the rapid expansion of the supercritical fluid which could transition to a gas phase and damage the housing.

[0011] The buoyancy chamber can be subdivided into a plurality of compartments, each of which can be provided with a diaphragm. Providing a number of smaller diaphragms introduces an increasing degree of redundancy into the system because, if one of the diaphragms fails, the rest of the device can continue to function.

[0012] The buoyancy chamber, or each compartment of the buoyancy chamber, can be provided with at least one orifice to allow sea water to move in and out of the buoyancy chamber. The orifice (s) can be covered by a grid to prevent the entry of living marine animals.

[0013] The buoyancy chamber, or each compartment of the buoyancy chamber, can be provided with at least one one-way valve to allow supercritical cryogen fluid or gas to exit the device. The outward blowing portion can be provided by one-way valves that allow fluid to flow out, if the pressure differential between the interior of the device and the surrounding area becomes too high.

[0014] The heating pipe is guided through the housing so that at least a portion of the heating pipe is adjacent to an external surface of the housing. This allows the cryogenic fluid to be heated by extracting heat from the surrounding seawater. This reduces or eliminates the need for a heat source within the device. O

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The device may further comprise a plurality of heat conductors configured to introduce heat into the cryogen reservoir. The heat conductors also allow heat from the surrounding seawater to be introduced into the device, in this case directly into the cryogen reservoir. The heat introduced into the cryogen reservoir by the heat conductors helps to initiate the transition from the cryogenic fluid to a supercritical fluid and the subsequent movement of this fluid through the heating tube. The heating tube can be switchable using a valve.

[0015] In addition, according to the present invention, there is provided a method of raising an item from the seabed, the method comprising the steps of: lowering a flotation device to the seabed; attach a flotation device to the item to be lifted; creating a supercritical fluid within a portion of the flotation device; and allowing the flotation device and item to rise to the surface using the supercritical fluid fluctuation to lift the item to the surface. The supercritical fluid can be supercritical nitrogen, carbon dioxide, helium or hydrogen.

[0016] The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

figures 1A and 1B are seen in schematic cross section through a photofill chamber that forms part of a flotation device according to the invention;

figures 2A and 2B are seen in schematic cross section through a cryogen reservoir that is part of the device according to the present invention;

figures 3A and 3B are schematic side and cross-sectional views of a heating system for use with the flotation device according to the present invention;

figures 4A and 4B are seen in cross section

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5/23 schematic of the device according to the present invention in the configuration adopted when the device descends to the seabed;

figures 5A and 5b are seen in schematic cross section of the device shown in figures 4A and 4B in the configuration adopted when the buoyancy chamber is ready to be filled with a low density fluid;

figures 6A and 6B are schematic cross-sectional views of the device shown in figures 4A and 4B in the configuration adopted when the buoyancy chamber is being filled with a low density fluid;

figures 7A and 7B are seen in schematic cross section of the device shown in figures 4A and 4B in the configuration adopted when the device ascends;

figure 8 is a schematic overview of another example of a flotation device according to the present invention;

Figure 9 is a schematic cross-sectional view of yet another example of a flotation device according to the present invention.

[0017] The attached figures are schematic and the various constituent parts are not illustrated to scale. Features from the examples can be combined with the same reference numbers that are used throughout the description when the same components are employed. For clarity, not all components present are shown in the figures.

[0018] The flotation device 100 has a buoyancy chamber 110; a 210 cryogenic reservoir; a heating system 302 and a control system 400. The buoyancy chamber 110 is configured to retain a fluid that is less dense than water and thus facilitate the lifting of the device 100 and a load to be raised. O

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6/23 cryogen reservoir 210 is configured to contain cryogenic fluid that is typically in a liquid phase at atmospheric pressure. The heating system 302 is configured to heat the liquid cryogen so that it becomes a supercritical fluid that can then move the buoyancy chamber 110. A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. Near the critical point, small changes in pressure or temperature result in large variations in density. The flotation device 100 can extend between 1 m and 20 m in length and a device, or a number of devices 100 that cooperate together may be able to lift loads weighing between 1 ton and 2000 tons.

[0019] In the example shown in the figures with a suffix A, these integers are all contained within a closed housing 112. As a result of the provision of a closed housing 112, although device 100 is illustrated with the buoyancy chamber 110 positioned vertically above the cryogen reservoir 210, the device could also be developed with the buoyancy chamber 100 extending horizontally.

[0020] Housing 112 has an elongated central portion 114 of circular cross section, disposed between two hemispherical end portions 115, 116. Housing 112 surrounds buoyancy chamber 110; the 210 cryogenic reservoir; some parts of the heating system 302 and the control system 400. Housing 112 provides protection and prevents unwanted interactions between the various elements that could occur if they were not contained in a single unit.

[0021] Housing 112 may be formed as a single piece or may be partially defined by the outer surfaces of the buoyancy chamber 110 and the cryogen reservoir 210. For example, in figure 4A, the housing is formed by the hemispherical end portion 115 and

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7/23 elongated central portion 114 of the buoyancy chamber 110 and part of the cryogen reservoir 210. In addition, a ring of housing material is provided to join the above mentioned together. Housing 112 may be manufactured from glass fiber reinforced plastic (GRP), aluminum or a carbon composite. If aluminum is used, then housing 112 can be formed into several parts which are subsequently fixed together using age-impermeable joints. The housing 112 must be able to withstand the differential pressure of 2 to 3 Bars between the interior of the housing 112 and the surrounding environment. If the pressure differential between the interior and exterior of the device exceeds about 3 Bars, changes will be triggered, which equalize the pressure before damage is caused. For example, valves can be opened to equalize the pressure differential between the inside and outside of the device 100.

[0022] In the example shown in figure 4A, the housing 112 is provided with a reinforced section 118, adjacent to the cryogen reservoir 210. The reinforced section 118 allows the device 100 to withstand operating pressures in extreme conditions at depths in the region of 2000 m and therefore pressures of 200 bar. The reinforced section 118 can be formed from the same material or a different material as the housing 112.

[0023] The housing 112 is provided with at least one fixation 130 that facilitates the attachment of the device 100 to an object to be raised from the seabed. The illustrated fixture 130 includes two sets of parallel projections that can be attached to the item to be lifted. The fixture 130 can be attached via an intermediate piece, such as a length of steel cable passed through an eyelet provided in the fixture 130.

[0024] The configuration of the fixings 130 dictates the orientation in which the device 100 will operate. In the example shown in figures IA to 7A, two

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8/23 sets of fixings 130 on the exterior of housing 112 are provided. If the fixings are attached to the item to be lifted in a horizontally spaced configuration, then the major axis of the device 100 will be substantially in the horizontal plane when the device 100 is attached to an item to be lifted. Conversely, if the fixings are affixed to the item in a vertically spaced configuration, then the device will operate in the vertical configuration illustrated in figures IA to 7A.

[0025] The housing 112 is also provided with at least one lifting eye 140 which allows the device 100 to remain attached to a vessel on the water surface for the entire ascension and descent cycle. Alternatively, the lifting eye 140 can be used only to help lift the device 100 into the water before use and / or to remove the device from the water after use, in which case the device 100 is in unattached use. . If only one lifting eye 140 is provided then it is located at the apex of the hemispherical portion 116 of housing 112. In the illustrated example, the lifting eye shown is out of symmetry. If a lifting eye is out of symmetry, it is typically used in cooperation with at least one other eye (not shown).

[0026] In the example shown in the figures with a suffix B, the filling chamber takes the form of an open base cofferdam 122, that is, a bell-shaped enclosure that is at least partially open at the base. The cofferdam base is indicated by the dashed line 124. Since the cofferdam is open to the surroundings, the material from which it is manufactured is not required to be ideal for large pressure differentials. Therefore, it could be formed from a partially flexible material. Depending on the required material and size of the cofferdam 122, the cofferdam may not be bell-shaped, but may instead be spherical or otherwise shaped. The cofferdam 122 is provided with fixings 130 and a lifting eye 140 similar to that described above with

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9/23 reference to figures IA to 7A.

[0027] At the base of the cofferdam 122, a lip 145 can be additionally provided in order to increase the stability of the cofferdam 122. The lip 145 prevents supercritical fluid from flowing out of the cofferdam 122, if the cofferdam 122 is close to being fully loaded and it’s not entirely vertical.

[0028] Although not illustrated in these examples, housing 112 or the cryogen reservoir 210 can be provided with a stand that includes a base that rests on any suitable support surface, including a ship's deck or the seabed, and four inclined beams that extend from the upper surface of the base and are fixed to the external surface of the housing 112 or cryogen reservoir 210 at one end, thus supporting the device 100 in a vertical orientation.

[0029] In the alternative example, housing 112 or cryogen reservoir 210 is provided with means, by which device 100 can interface with a cradle. In the example shown in Figure IA, the interface means could be the portions of the heating coil that coils around the exterior of the housing 112 or the cryogen reservoir 210. Alternatively, a plurality of fins can be provided to allow the housing 112 or the cryogen reservoir 210 rest in a cradle.

[0030] In another alternative example, the housing is provided with additional fixings that facilitate the attachment of a supplementary cryogen tank to the exterior of housing 112. The supplementary tank could be used when a number of descents and partial ascents is planned. The cryogen reservoir 210 could then be refilled from the supplementary tank without requiring the device 100 to return to the surface.

[0031] The buoyancy chamber 110 is shown in detail in figures IA and 1B. in the example shown in figure IA, it has a rigid hull

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10/23

150 formed of plastic material reinforced with glass fibers (CRP). The inner volume of hull 150 has a central cylindrical portion 152 and hemispherical end portions 154, 156. The inner volume of hull 150 is divided by a diaphragm 160 in a first chamber 162 and a second chamber 164. Diaphragm 160 is fixed in its periphery to the inner surface of the hull 150 in a plane that bisects the internal volume of the hull 150 along its longitudinal axis.

[0032] Diaphragm 160 is enlarged in relation to the corresponding cross-sectional area of hull 150 so that diaphragm 160 can be displaced so as to be elongated on an internal surface of hull 150. In this way, displacement of diaphragm 160 it varies in relation to the relative sizes of the first and second chambers 162, 164. The diaphragm 160 may be formed of an elastic material so that it is under tension when it is elongated on the inner surface of the hull. Alternatively, diaphragm 160 can be formed of a flexible material and can be sized to be located along the side of an inner surface of hull 150.

[0033] The hull 150 further comprises a set of holes 180 that allow the passage of sea water into and out of the first chamber 162. Six holes 180 are illustrated in figure IA. However, the number of holes and the size of the holes can be changed. Holes 180 may be provided with a grid and coarse mesh to prevent large marine living beings from entering device 100.

[0034] In both of the examples shown, a set of one-way valves 170 is provided, which can be opened to allow fluid contained in the buoyancy chamber 110 to escape from device 100. One-way valves 170 have a Mecca pressure release valve, whereby fluid is allowed to leave the buoyancy chamber 110 when the pressure inside the buoyancy chamber 110 exceeds the pressure of seawater

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11/23 surrounding by a predetermined limit value, such as 1 Bar. Six one-way valves 170 are shown in figure IA and two are shown in figure 1B at the apex of the bell-shaped cofferdam 122. However, the number of valves and the size of the valves can be changed. Because the cofferdam 122 is open at its base, it must be operated in the orientation shown in figure 1B. One-way valves 170 are therefore provided at the top of the cofferdam 122 in order to release fluid from within the cofferdam 122 without destabilizing the device 100.

[0035] The cryogenic reservoir 210 is shown in detail in figures 2A and 2B. The cryogen reservoir 210 has an inner wall 212 that defines an enclosure 214 suitable for containing cryogenic fluid 216, and an outer wall 218 fully comprising inner wall 212. Enclosure 214, in both illustrated examples, has a hemispherical portion 222 and a thinned portion 224. Hemispherical portion 222 is configured to conform to the shape of housing 112. Therefore, if end portion 116 of housing 112 adjacent to cryogen reservoir 210 is not hemispheric, the shape of enclosure 214 will differ from example shown, so that the shape of the enclosure 214 conforms to the shape of the end portion of the housing 112.

[0036] The inner wall 212 of the cryogen reservoir 210 may be formed of austenitic steel, but it could be of some other material, for example 9% nickel steel or cryogenic aluminum. The outer wall 218 can be formed of GR, but it could be of some other material, for example, carbon composite. The outer wall 218 is separated from the inner wall 212 by a hermetically sealed cavity 226. During manufacture, a vacuum is formed within this cavity between the inner and outer walls 212, 216, thus providing heat insulation for the enclosure 214.

[0037] At the end of the slimmed portion 224, a tube of

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12/23 filling 230 and a ventilation tube 232 extend through the inner and outer walls 212, 218 of the cryogen reservoir 210.

[0038] The filling tube 230 extends substantially along the length of the enclosure 214 to a position close to the lowest point of the hemispheric portion 222. The ventilation tube 232 terminates on the inner surface of the outer wall.

[0039] In the vicinity of the lowest point of hemispheric portion 222 of enclosure 214, the inner wall 212 includes at least one opening 234. A cooling coil 236 extends from the vicinity of opening 234, and is wound around the outer surface of the inner wall 212. The cooling coil 236 includes a pressure release valve at its upper end, which allows fluid to flow from the cooling coil 236 into the buoyancy chamber 110 when the pressures within the cooling coil 236 are approximately 100 millibars higher than the pressure inside the buoyancy chamber 110. The cooling coil 236 is formed predominantly of metal. However, the portion 238 of the cooling coil 236 that extends between the cryogen reservoir 210 and the buoyancy chamber 110 is formed of a plastic material that has a low coefficient of thermal conductivity.

[0040] As shown in figure 2B, the cryogen reservoir 210 is enclosed in a reinforced spherical enclosure 240. Enclosure 240 must be thick-coated and can be made of a carbon compound. Enclosure 240 must be able to withstand pressure differentials from 1 Bar to 203 Bars so that it can operate at depths of 2000 m. In addition to the thick liner of enclosure 240, additional reinforcement can be provided by rib formations either internal or external to enclosure 240. Spherical enclosure 240 can be provided with pressure-resistant, waterproof inspection covers (not shown) ) in order to allow access within spherical enclosure 240 for maintenance or other purposes. In addition, you can

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13/23 an additional tube (not shown) is provided that allows the recirculation of cryogenic fluid back to the cryogen reservoir 210 to occupy the space above the liquid cryogen.

[0041] In addition, spherical enclosure 240 may be provided with supplementary fixings (not shown) to allow an additional cryogen tank (not shown) to be attached to enclosure 240. This allows device 100 to make a number of elevations and partial guided descents without having to rise to the surface to be recharged with cryogen. In addition, the supplementary cryogen tank can be connected to the cryogen reservoir 210 so that the cryogenic fluid 216 can flow from the supplementary tank, into the cryogen reservoir 210, the cryogen can then be subjected to heating and transition to a supercritical state and enters cofferdam 122. This configuration allows the cryogenic fluid 216 used to exceed the maximum capacity of the cryogen reservoir 210.

[0042] The heating system 302 is shown, primarily in figures 3A and 3B, although some characteristics are shown in figures 2A and 2B. The heating system 302 includes a heating tube 310 which extends from the opening 234 in the inner wall 212 of the enclosure 214; a heating chamber 336 and a pair of electrical heating elements 346. The heating tube 310 is tortuous and a portion that passes through the housing 112 and coils around the outer surface of the housing 112. The portion of the heating pipe 310 which is external to the housing 112 is reinforced to withstand the pressures exerted as a result of operation of the device 100 under extreme conditions.

[0043] A protective grid (not shown) is provided to protect heating tube 310 when it is outside housing 112. The provision of a grid or grid reduces the risk of damage to heating tube 310 that occurs as a result contact between the

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14/23 heating 310 and the item to be raised, or the seabed or any other hazards.

[0044] The heating system 302 also includes a valve 338 to control the flow of fluid through the heating tube 310 and thus into the buoyancy chamber 130. The valve 338 is positioned adjacent to the inner surface of the outer wall 218 .

[0045] The heating system 302 also includes a heat shield 330 which is provided between the cryogen reservoir 210 and the buoyancy chamber 110. In the example shown in figure 3A, heat shield 330 includes a first portion 332 which is adjacent to the buoyancy chamber and a second portion 334 which is adjacent to the cryogen reservoir 210. The two portions 332, 334 of the heat shield 330 define the annular heating chamber 336. The heating chamber 336 is thermally insulated from both the buoyancy chamber 110 and the cryogen reservoir 210.

[0046] A plurality of remotely operable heat conductors 340 are attached to the inner surface of the outer wall 218 around the hemispheric portion 222 of the enclosure 214. The heat conductors 340 each comprise a copper rod 342 which is pivotally mounted on the inner surface of the outer wall 218 of the cryogen reservoir 210. The copper rods 342 are pivotable between an active position in which the rods extend substantially perpendicular to the surface of the outer wall 218 and a deactivated position in which the rods are located substantially parallel to the surface of the outer wall 124. The length of the rods 342 is selected to closely match the distance between the inner wall 212 and the outer wall 218, so that when the rods are activated, they provide a path for thermal conduction to inside the enclosure 214. In the example shown in the attached drawings, the inner and outer walls of the enclosure o are substantially parallel

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15/23 and, therefore, all of the stems 342 are substantially the same length. The number of shanks 342 shown in the figures are illustrative only. They can be provided in the region of 30. If the heat introduced into the cryogen reservoir 210 by the heat conductors 340 is insufficient, then this can be amplified by electric heating from the electric heating elements 346. Although a pair of heating elements electric is provided in the illustrated example, the number and size of the heating elements can be varied according to the size of the device 100 and / or the intended field of use. For example, more heating elements may be required for a device used in the polar regions.

[0047] Figures 4a and 4B show a complete device, as described above, including the fuitable chamber 110, the cryogenic reservoir 210, the heating system 302 and the control system 400.

[0048] Although in the example shown in figure 4B the width of the cofferdam 122 is substantially equal to the diameter of the spherical enclosure 240, the cofferdam 122 could be wider or less wide than the spherical enclosure 240.

[0049] Spherical enclosure 240 is connected to the cofferdam using at least one cylindrical rim 242. The cylindrical rim 242 can extend partially or completely around the circumference of the spherical enclosure. Alternatively, a plurality of hoops can be used. In the latter case, each ring can be lengthened, that is, its length greatly exceeds its width. The rims can be rigid or flexible.

[0050] In an alternative example, not shown in the accompanying drawings, a universal coupling could be used in place of the rim (s) in order to connect the cofferdam 122 to the spherical enclosure 240.

[0051] Because the cofferdam 122 and the cryogen reservoir 210 are not fully formed, the heating tube 310 ends in a

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16/23 cryogen feed vent 244 protruding from spherical enclosure 240 and into the cofferdam 122. The cryogen feed vent 244 is provided with a one-way valve 245 to prevent seawater from entering 300 from the cofferdam 122 into the heating tube 310.

A control system 400 includes a microprocessor 402 mounted within the housing 112 of the device 100 and a remote control device (not shown) that is typically positioned on the vessel, from which the device 100 is launched and controlled. The microprocessor 402 communicates with the control device on board the ship via a data link 404. The data link 404 can be provided by an optical fiber link or a copper cable that is enclosed in a protective sheath. The data link 404 can be detachable from the device 100.

[0053] The microprocessor 402 mounted inside the housing 112 is configured to collect data from sensors (410, 412, 414, 418, 420) mounted inside the device 100 and to transmit this information to the remote control device. In addition, each device 100 has a unique identifier, which is stored in microprocessor 402 and transmitted, along with position data, via data link 404. This allows two or more devices 100 to be controlled to cooperate and thus raise an item which is either too large or of such a format that a single device 100 would be insufficient. The data can be sent directly to the remote control device or can be shared directly between cooperating devices 100.

[0054] There are a number of different sensors (410, 412, 414, 418, 420) mounted in different locations inside and on the outer surface of the device 100. The illustrated positions of the sensors (410, 412, 414, 418, 420) 410, 412, 414, 418, 420 within the device are merely

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Exemplary 17/23. The sensors (410, 412, 414, 418, 420) can be provided in other locations, or a number of sensors (410, 412, 414, 418, 420) described below can be provided in any of the locations illustrated in the attached drawings . The sensors (410, 412, 414,418, 420) are configured to monitor process conditions and to feed information back to the 402 microprocessor.

[0055] Some sensors (410, 412, 414, 418, 420), for example, sensor 410, can be a temperature or pressure sensor. The provision of a number of pressure sensors (410, 412, 414, 418, 420) allows pressure differentials between different parts of device 100 to be calculated either by means of microprocessor 402 or by the remote control device. In addition, the external pressure to the device 100 correlates strongly with the depth of the device 100.

[0056] Some sensors (410, 412, 414, 418, 420), for example, sensor 412, can be configured to contribute to resource management within the device. In this example, sensor 412 can indicate how much cryogen remains inside reservoir 210.

[0057] Sensors (410, 412, 414, 418, 420), such as sensor 414, can be provided to ensure the integrity of sensitive parts of device 100. Sensor 414 is mounted in the vicinity of microprocessor 402 which is isolated from the device 100 by means of a heat shield 350. This sensor 414 will monitor the conditions to which the microprocessor 402 is subjected.

[0058] In addition to the positioning sensors (410, 412, 414, 418, 420) that identify the position of the device 100 as a whole, and the pressure sensors (410, 412, 414, 418, 420) that provide information about the depth of the device, the orientation of the device 100 can be monitored by a drift sensor 418. The drift sensor 418 provides an indication of the stability of the device 100 and identifies problems that

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18/23 develop when countless devices are working together to recover an object that is either irregular in shape or partially submerged in the seabed. Drift sensor information 418 can be used to identify whether one part of the item is free, while another remains stuck in the seabed. Once this information has been fed through microprocessor 402 and up through data link 404 to the surface vessel, device 100 positioned as close to the part of the item that is attached can be instructed to produce more supercritical fluid at in order to provide greater positive fluctuation to release the stuck part of the item.

[0059] The data link 404 can be incorporated in a lifting cable that connects the lifting eye 140 to the surface vessel, alternatively, the data link 404 can be separated from the lifting cable. If the cable connection 404 and the lifting cable are combined, then the combined cable will be reinforced to ensure that the integrity of the data connection 404 is maintained as well as to provide sufficient strength to lift the device 100 from the ship to inside the sea.

[0060] The example shown in figure 8 differs from the examples shown in figures 1 to 7 in that the buoyancy chamber 110 is subdivided into a plurality of compartments 190, each including a diaphragm 166. Each of the compartments 190 is provided with at least one one-way valve 170 and at least one orifice 180. Providing a number of different compartments introduces a level of redundancy in the device, because if a diaphragm 166 has failed, the device would still be operable, although the weight maximum that could be raised was reduced. In addition, if an irregular load is to be high, or a number of devices are to be used together to lift an item, certain compartments could be filled before others in order to optimize the performance of the device 100.

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19/23 [0061] Although the heat conductors 340 are illustrated in all of the figures, they are not essential for the operation of the device 100 and the cryogen reservoir 210 could achieve the heat transfer required by alternative means.

[0062] Figure 9 shows another alternative configuration with an open cofferdam 122. The cofferdam 122 in the example shown in figure 9 differs from the cofferdam 122 shown in figures 1B to 7B in that the cofferdam 122 of figure 9 is only partially open . The cofferdam 122 is also elongated in the horizontal plane, instead of the vertical plane. In addition, the cryogen reservoir 210 is positioned inside the cofferdam 122. This configuration allows the very convenient attachment of the device 100 to an item to be lifted using the fixings 130. To improve the stability of the device 100, two lifting eyes 140 are provided.

[0063] The method by which device 100 is operated will now be described.

[0064] In order to prepare the device 100 ready for use, the enclosure 214 is charged with a cryogenic fluid 216. This can be liquid nitrogen, carbon dioxide, helium or hydrogen. The choice of fluid depends on the depth at which the device will be operated. Nitrogen can be used at depths in the region of 1000 m. Helium and hydrogen can be used at depths of and in excess of 1000 m, including 2000 m.

[0065] The process of preparing or loading the device 100 is usually carried out while the flotation device is on board a ship or similar. A supply of cryogenic fluid 216 is introduced into device 100 through a pressure-proof hatch 350 and attached to filler tube 230. Cryogenic fluid 216 passes through filler tube 230 and enters enclosure 214 near its base. Since the interior of room 214 is at a temperature comparatively

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20/23 elevated in relation to the cryogenic fluid, some of the fluid will evaporate in contact with the interior of the filling tube 230 and the enclosure 214 and the gas resulting from the evaporation of the cryogenic fluid will leave the enclosure 214 through the cryogenic vent tube 232 .

[0066] This process is continued until the interior of the enclosure 214 is at a sufficiently low temperature for the cryogenic fluid 216 to remain in a liquid state. Once the enclosure 214 has been fully charged with cryogenic fluid 216 in the liquid phase, the supply is decoupled from the filling tube 230 and the pressure-proof hatches 350, 352 are closed.

[0067] The device 100 is then carefully lowered into the sea and allowed to descend towards the load to be lifted (not shown in the figures) on the seabed.

[0068] When device 100 is first placed in water, seawater 300 enters the first chamber 162 through holes 180, as shown in figure 4A. In the example shown in figure 4B, seawater 300 enters the cofferdam 122 through the openings at the base of the cofferdam 122, as indicated by the arrows in figure 4B. sea water 300 displaces air from the buoyancy chamber 110 and causes diaphragm 160 to decrease the size of the second chamber 164 in relation to the size of the first chamber 162. Once the first chamber 162 occupies substantially the entire volume of the buoyancy chamber 110 and the first chamber 162 is filled with water, the device 100 as a whole is negatively buoyant and descends towards the bottom of the sea.

[0069] If the device 100 is not sufficiently negatively buoyant to descend towards the bottom of the sea, weights can be attached to the fixture 130 or to the bottom of the external surface of the housing to help a stable descent. Device 100 can be positively buoyant as a result of the presence of air pockets in the heating chamber

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336 or as a result of the density of cryogenic fluid 216. For example, liquid nitrogen has a density in the region of 80% that of water. While the device is descending towards the charge, a small amount of cryogenic fluid 216 will evaporate to form gas. Due to the construction of the device 100, the fluid in the cooling coil 236 will tend to vaporize, rather than the cryogenic fluid 216 inside the enclosure 214. Vaporization cools the cooling coil 236 and therefore helps to maintain the fluid cryogenic within the cold room 214. The gas forming in the cooling coil 236 will move through the cooling coil 236 and into the second chamber 164 of the buoyancy chamber 110. In order to prevent diaphragm 160 from allowing the second chamber 164 to expand and displace some of the seawater 300, one-way valves 170 can be maintained in an open state. Alternatively, one-way valves 170 can be kept closed to prevent cryogen from boiling and moving into the sea. This is specifically applicable when device 100 is kept on the seabed for some time before being activated to lift a load.

[0070] When the flotation device 100 reaches the seabed and the load to be raised, the load is retained in the anchorages 130 in an appropriate manner. The action of affixing the flotation device to the load is typically performed by a robot (not shown in the figures) that is controlled by a user on the surface.

[0071] The flotation device 100 is then actuated by transmitting signals close to the one-way valves 170 and to open valve 338, placing heating tube 310 in fluid communication with the cryogenic fluid 216 contained in enclosure 214. As a result of the extreme conditions surrounding the device, the cryogenic fluid 216 becomes supercritical as it passes through the heating tube 310. The supercritical fluid moves into the flotation unit 110 and forces the

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22/23 diaphragm 160 to move, increasing the size of the second chamber 164. As a result of the increase in size of the second chamber 164, the first chamber 162 reduces the size and pressure of the sea water in it exceeds the water pressure surrounding sea and therefore sea water 300 exits through holes 180, as shown in figure 6A. In the example shown in figure 6B, seawater 300 exits through the open area at the base 124 of the cofferdam 122.

[0072] Once when the fuitability chamber 110 is sufficiently charged with supercritical cryogenic fluid 216, as shown in figures 7A and 7B, the flotation device 100 and charge will begin to ascend. In the example shown in figure 7A, in order to control the rise of the float and load device, the one-way valve 170 can be opened to allow supercritical fluid to leave the buoyancy chamber 110, and sea water 300 to enter the first chamber 162, thereby reducing the upward buoyancy force. When the flotation device 100 and charge ascend towards the surface, the sea water pressure will decrease. The supercritical fluid 216 may transition to a gas phase and will exit through the valves of a pathway 170 or through the open area of the base 124 of the cofferdam 122 when the device 100 ascends.

[0073] In addition to the use of device 100 for lifting a load from the seabed to the surface, device 100 can be used to provide lift force for an item by reducing its effective weight and thus making it more easy to be manipulated under water. For example, if the device is attached to an item weighing 50 tons, and enough cryogen transitions to a supercritical state to reduce the effective weight of the object to just 5 tons, then the item will be easier to handle.

[0074] As mentioned above, more than one device 100 can be used to lift a particularly large or configured item

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23/23 irregularly. It is especially important, in this case, that the one-way valves 170 can be opened, on demand, in order to create temporary negative fluctuation during an elevation phase in one or more of the devices 100 being operated together. This contributes to the effective control of the orientation of the item being raised from, or guided to, the seabed.

[0075] When the uppermost part of the device 100 reaches the water surface, the load will remain submerged for a greater or lesser extent, depending on the configuration of the device. From this position on or near the water surface, the flotation device 100 and the charge are recovered and the flotation device 100 is detached from the charge. The flotation device 100 can be refilled with cryogenic fluid 216 and reused.

[0076] In another example, not illustrated in the accompanying drawings, housing 112 may be substantially spherical or may take the form of a regular or irregular polygon. The rhombus shape and the spherical shape are advantageous because they are formed only by curved shapes and therefore avoid the stresses associated with sharp corners and sharp edges.

Claims (9)

1. Flotation device (100), comprising: a buoyancy chamber (110); a cryogen reservoir (210); a heating tube (310) that provides switchable fluid communication between the cryogen reservoir (210) and the buoyancy chamber (110); and, characterized by the fact that it further comprises a microprocessor (402) and a plurality of sensors (410, 412, 414, 418, 420); wherein the microprocessor (402) contains a unique identifier for the device. 2. Device (100) according to claim 1, characterized in that the buoyancy chamber (110), the cryogen reservoir (210) and the heating tube (310) are at least partially contained in a housing (112). Device (100) according to claim 2, characterized by the fact that the housing (112) is provided with a reinforced portion adjacent to the cryogen reservoir (210). Device (100) according to any one of claims 1 to 3, characterized in that the buoyancy chamber (110) is subdivided into a plurality of compartments (190). Device (100) according to any one of claims 1 to 4, characterized in that the buoyancy chamber (110) or each compartment of the buoyancy chamber (110) is provided with at least one orifice (180) to allow sea water to move in and out of the buoyancy chamber (110). 6. Device (100) according to any one of claims 1 to 5, characterized by the fact that the buoyancy chamber Petition 870190091311, of 9/13/2019, p. 29/86 2/2 (110) or each buoyancy chamber compartment (110) is provided with at least one one-way valve (170) to allow supercritical cryogen fluid or gas to exit the device (100). Device (100) according to any one of claims 1 to 6, characterized in that the heating tube (310) is guided through the housing (112) so that at least a portion of the heating tube ( 310) is adjacent to an external surface of the housing (112). Device (100) according to any one of claims 1 to 7, characterized in that the heating tube (310) is interchangeable using a valve (338). Device (100) according to any one of claims 1 to 8, characterized in that it further comprises a plurality of heat conductors (340) configured to introduce heat into the cryogen reservoir (210).