Equipment for servicing structures

Abstract

An apparatus for servicing a structure comprises a series of buoyancy chambers and a gas supply connected to a first of the buoyancy chambers, the buoyancy chambers being interconnected such that gas is supplied to a first of the buoyancy chambers and when that chamber fills with gas, the gas begins to escape into the next one of the series of buoyancy chambers until that next one is filled with gas, and so on until the series of buoyancy chambers are filled with gas. The gas supply is controllable to achieve a desired buoyancy level. Gas can be supplied from an external gas source or from a cylinder carried by the apparatus.

Description

[Technical field]

[0001] The present invention relates to an apparatus for servicing structures such as support structures, including but not limited to marine support structures such as risers, conductors, caisson piles, piers for marine platforms, piers or wharves, or pipes, and onshore or offshore structures such as wind turbine towers. [Background technology]

[0002] Marine support structures typically age and deteriorate, particularly in the "splash zone," which is the portion of the structure that is periodically exposed or touched by water, for example as a result of tides, wave action and / or splash. Aging can include corrosion and physical damage caused by wave action and impact. Deterioration can include buildup of algae, crustaceans, etc.

[0003] Therefore, marine support structures need to be serviced, for example by cleaning, inspecting, painting, etc., to make them last longer and extend their lifespan. Traditionally, servicing such as inspection and maintenance is performed by divers, which is very difficult, dangerous, especially in splash zones, and sometimes not effective enough.

[0004] WO-A-2020 / 096529 discloses an apparatus for servicing a structure, the apparatus having a cage or frame supporting drive wheels or rollers for driving the frame and / or a tool for servicing the structure along the structure. The frame includes at least two hinged parts so that it can be opened to fit around the structure to be serviced and closed to securely mount the frame or cage around the structure. A number of such frames or cages can be connected in series around the structure.

[0005] Although the frame or cage disclosed in WO-A-2020 / 096529 is relatively light in weight, there is a need to further reduce the weight of this and similar devices. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO-A-2020 / 096529 Description of the invention

[0007] Aspects of the invention are defined by the appended claims.

[0008] According to one aspect of the present invention, There is provided an apparatus for servicing a structure as described above having a variable buoyancy device comprising a series of buoyancy chambers and a gas supply connected to a first of the buoyancy chambers, the buoyancy chambers being interconnected such that gas is supplied to a first of the buoyancy chambers and when that chamber fills with gas it begins to escape into the next one of the series until that next one is filled with gas, and so on until the series of buoyancy chambers are filled with gas. The supply of gas can be controlled to achieve a desired buoyancy level. Gas can be supplied from an external gas source or from a cylinder carried by the apparatus.

[0009] The servicing apparatus comprises a series of modules connected together in series, each module configured to service and / or drive the module along the structure, and each module having at least one of the buoyancy chambers. Each module has its own buoyancy chamber, and there can be multiple buoyancy chambers on a module. The buoyancy chambers can be of a calculated volume to provide a desired level of buoyancy (e.g. intermediate buoyancy) for the interconnected modules.

[0010] The rows of modules may be connected together using gas lines removably connected to ports in the buoyancy chambers, and the connections may be sealed, for example with O-rings, to prevent gas leakage.

[0011] The buoyancy chamber may be open at or near one end so that as the module descends, gas can escape from the buoyancy chamber, eliminating the need for active venting controls. When multiple modules are arranged to service a substantially vertical structure, gas leakage from the buoyancy chambers is reduced or minimized so that a required buoyancy level can be achieved with a much smaller volume of gas.

[0012] The above-described apparatus provides a simple method of controlling the buoyancy of a module in water and is particularly effective for servicing substantially vertical underwater structures. [Brief description of the drawings]

[0013] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view of the device in the first embodiment as seen from above. FIG. 2 is a first side elevational view of the first example device. FIG. 3 is a second side elevation of the first example device, perpendicular to the first side elevation. FIG. 4 is a cross-sectional view of plane AA of FIG. 2, showing the location of the support structure; FIG. 5 is a top view of the first example device. FIG. 6 is a perspective view of the second example device as seen from above. FIG. 7 is a perspective view of the second example device as seen from below. FIG. 8 is a first side elevational view of the second example device. FIG. 9 is a second side elevation of the second example device, perpendicular to the first side elevation. FIG. 10 is a cross-sectional view of plane AA of FIG. FIG. 11 is a cross-sectional view taken along plane BB of FIG. FIG. 12 is a top view of the second example device. FIG. 13 is a diagram of a kit of parts for assembly to form a device according to the first or second embodiment. FIG. 14 is a diagram of the operation of the device in this example. FIG. 15 is a partial diagram of the hydraulic system of the device in this example. FIG. 16 is a diagram illustrating a remote control system for operating the device in this example. FIG. 17 is a first side elevational view of the device in the third embodiment. FIG. 18 is a second side elevation of the device in the third embodiment, perpendicular to the first side elevation. FIG. 19 is a perspective view of the third embodiment of the device as seen from above. FIG. 20 is a bottom view of the device of the third embodiment. FIG. 21 shows the top of the third example device. FIG. 22 is a partial cross-sectional view taken along plane AA of FIG. FIG. 23 is a diagram showing different configurations of the third example traction module with additional modules. FIG. 24 is a detailed view of the inter-module connection system in the configuration of FIG. FIG. 25 is a side elevational view of the device in the fourth embodiment. FIG. 26 is a schematic diagram of the first embodiment of the present invention. FIG. 27 is a schematic diagram of the second embodiment of the present invention. Detailed Description of the Embodiments

[0014] In the following description, the apparatus is described as being assembled around a vertically extending support structure 30. "Circumferential" and "tangential" refer to the circumference about an imaginary central vertical axis, and "radial" refers to the direction perpendicular to that axis.

[0015] Where dimensions are given in the drawings, they are in millimeters (mm); however, these dimensions are not limiting as to the size of a particular embodiment, but are purely exemplary.

[0016] For clarity, certain parts are labeled with reference numbers in the drawings, although not in all cases. A view of the drawings will allow one to understand which parts are being referred to as a whole. Similar parts between different embodiments are labeled with the same reference numbers.

[0017] An embodiment of the present invention is for servicing structures such as those disclosed in the first patent document WO-A-2020 / 096529, examples of which are described below, but which are not intended to limit the invention.

[0018] A first embodiment of the invention will now be described with reference to Figures 1 to 5. A cage or frame 1 includes cage or frame segments or sections 1a, 1b, 1c which are releasably connected at frame connection points 2a, 2b, 2c, for example by means of removable pins. In use, the frame segments 1a, 1b, 1c are assembled around a support structure 30 to be serviced. The frame segments 1a, 1b, 1c include lifting points 23 for attachment of cables or the like for lifting the frame segments 1a, 1b, 1c to a desired position and / or retrieving them after use. Preferably, each of the frame segments 1a, 1b, 1c is light enough to be lifted manually to a desired position.

[0019] Frame 1 includes an upper support 3 and a lower support 4 connected by a number of struts 5. In this example, the upper and lower supports 3, 4 are circular and coaxial. The struts 5 extend generally vertically between the upper and lower supports 3, 4. The upper support 3, lower support 4 and struts 5 are preferably substantially rigid and are coupled together such that, when assembled, frame 1 is substantially rigid.

[0020] Multiple pairs (three pairs in this example) of upper and lower arms 6, 7 are connected to the upper support 3 at different circumferential positions, preferably at equal circumferential intervals around the upper support 3, for example, 120° apart in this embodiment.

[0021] Each arm 6, 7 is pivotally supported on the upper support 3 about a tangential, horizontal pivot axis, e.g., by a respective shaft or spindle. In this example, the arms 6, 7 are pivotable about their respective axes above and below the upper support 3, but may alternatively be pivotable about the same axis. The upper and lower arms 6, 7 are pivotable in opposite directions so that they can move simultaneously towards or away from the support structure 30. The upper and lower arms 6, 7 can be pivoted independently of each other so that the angle between the upper and lower arms 6, 7 can be changed.

[0022] Each arm 6,7 includes a respective wheel, roller, or other rotating member 8,9 arranged to contact the support structure 30. The wheels 8,9 may have contact surfaces arranged to enhance traction and / or reduce wear on the wheels 8,9 relative to the support structure 30. Each pair of wheels 8,9 may be supported by a corresponding pair of arms 6,7 and may be rotatable independently of each other.

[0023] At least one of the pairs of arms 6,7 is reciprocally drivable to pivot towards and away from the support structure 30 so that a corresponding wheel 8,9 can clamp and release the support structure 30, respectively. Preferably, the pairs of arms 6,7 are driven by respective hydraulic cylinders 10,11. The controls of the hydraulic cylinders 10,11 can be interconnected so that the arm pairs are driven synchronously. The hydraulic cylinders 10,11 are driven by respective hydraulic hoses (not shown) which are attached to hose clamps 24.

[0024] The other pair of arms 6,7 are adjustably held in a pivoted position, for example by length-adjustable rods or bottle screws 12,13, depending on the diameter of the support structure 30 to be serviced.

[0025] The lower arm 7 passes between the columns 5 so that the corresponding wheel 9 can contact the support structure 30 .

[0026] At least one of the wheels 8,9 is reciprocally drivable in either opposite direction (i.e. forward and backward) to move the apparatus respectively up and down the support structure 30. Preferably, the drivable wheels 8,9 are mounted on reciprocally drivable arms 6,7. The other wheels 8,9 are not driven and are free to rotate, preferably independently of each other, to act as guides for movement of the apparatus up and down the support structure 30.

[0027] The lower support 4 supports a guide rail 14 for guiding a carriage 15 circumferentially around the lower portion of the frame 1. The carriage 15 has a drive gear 16 which engages a gear track 17 disposed circumferentially and horizontally around the lower portion of the frame 1. The drive gear 16 is driven to move the carriage 15 circumferentially around the guide rail 14. The carriage 15 can be driven circumferentially through approximately 360 degrees, although movement of the carriage 15 is preferably limited to one complete revolution by a carriage stopper 18 provided adjacent the guide rail 14, as shown in FIG.

[0028] Carriage 15 preferably does not contact support structure 30 because buildup on support structure 30 could impede the progress of carriage 15. Instead, carriage 15 is supported by a pair of inner rollers 19 that contact the inside of guide rail 14 and a pair of outer rollers 20 that contact the outside of guide rail 14. The inner rollers 19 are mounted on horizontally extending carriage arms 21 on either side of carriage 15 to improve stability.

[0029] In alternative embodiments, the functions of the guide rail 14 and gear track 17 can be combined. For example, the gear track 17 and drive gear 16 can be omitted and one or more of the internal or external rollers 19, 20 can be driven to drive the carriage 15 around the guide rail 14. Alternatively, the guide rail 14 can be omitted and the gear track 17 modified to provide the guiding function. A linear drive arrangement, such as a roller pinion or friction drive, can be substituted for the gear / gear track or rack and pinion arrangement.

[0030] The carriage 15 is configured to support and carry one or more tools 22 for servicing the support structure 30. By moving the frame 1 up and down the support structure 30 using drivable wheels 8, 9, and by moving the carriage 15 circumferentially around the support structure 30, the tools 22 can reach virtually any portion of the exterior surface of the support structure 30, at least within the splash zone and subject to any restrictions such as hydraulic lines.

[0031] The tool 22 is movably mounted to the carriage 15 such that the tool 22 can be moved relative to the carriage 15. For example, the tool(s) 22 can be reciprocally drivable toward and away from the support structure 30, e.g., radially.

[0032] One or more tools can be mounted on the carriage 15, but they are interchangeable. - high pressure water nozzles for cleaning the surface of the support structure 30; a wall thickness measuring probe for measuring the wall thickness of the support structure 30, for example by means of ultrasound, - 27 video cameras for service site inspections, - a clearance sensor for detecting the clearance from the surface of the supporting structure; - painting tools, such as paint rollers or brushes, for painting the surface of the support structure 30; - a wrapping tool for applying a protective wrapping to the support structure 30; Examples include a cutting tool for cutting off a portion of the support structure 30 using, for example, a high pressure abrasive cut.

[0033] In a second example, the carriage 15 supports and carries, in addition to the cleaning tool 22, a camera 27, such as a video camera.

[0034] The device may have one or more distance sensors to measure the distance traveled along the support structure 30. The distance sensors may for example be arranged to determine the number of rotations of the wheels 8, 9, for example using one or more optical or magnetic angular position sensors.

[0035] The carriage 15 may have one or more rotational position sensors (e.g. optical or magnetic sensors) to determine the absolute or relative circumferential position of the carriage 15 with respect to the frame 1, for example by detecting reference position marks on the guide rail 14 or gear track 17.

[0036] Distance and / or rotational position sensors can be used to determine the position of the tool 22, carriage 15 or other parts of the apparatus on the support structure 30. This makes it possible to move the apparatus to a predefined absolute position or to return to a previously visited position, for example if an anomaly or discrepancy is detected.

[0037] The device can be aligned with one or more of the reference marks on the support structure 30 and returned to a previously passed position relative to the reference marks. As an example, a horizontal and / or vertical visible mark can be made on the support structure 30 corresponding to an initial position of a part or parts of the device, such as the vertical position of the upper support 3 and a predetermined circumferential position of the support column 5, identified by markings, such as prominent paint markings. The distance sensor is set to zero. The carriage 15 is placed in its maximum circumferential position (either clockwise or counterclockwise) and the rotational position sensor is set to zero. As the device moves along the support structure 30, the distance sensor and the rotational position sensor measure the distance traveled axially and circumferentially relative to the initial position. In this way, a map of abnormal or inconsistent positions on the support structure 30 can be made and returned to if necessary.

[0038] The first example is designed to service support structures 30 having diameters ranging from 22 to 36 inches (0.56 to 0.91 meters). Other examples with different sizes and / or numbers of frame segments 1a, 1b, 1c can be adapted to service support structures of other diameters. For example, FIGS. 6-12 show a second example, which is similar in construction to the first example, but has a smaller diameter frame 1 designed to service support structures 30 having diameters ranging from 95 / 8 to 22 inches (0.24 to 0.56 meters). The frame 1 is comprised of two frame segments 1a, 1b, which are semi-cylindrical bodies that are assembled to form a cylindrical frame 1.

[0039] The second example, like the first example, has three pairs of upper and lower arms 6, 7 spaced equally around the upper support 3. Other examples, particularly for servicing support structures with larger diameters, may have more than three pairs of arms 6, 7.

[0040] The arms 6,7 can be removably attached to the frame segments 1a,1b,1c together with the wheels 8,9, hydraulic cylinders 10,11 and length adjustable bars 12,13. These elements can be used interchangeably with the frame segments 1a,1b,1c of the first embodiment and the frame segments 1a,1b of the second embodiment. Different carriages 15 may be required for the first and second embodiments due to the different radii of curvature. Alternatively, a single adjustable carriage 15 can be used interchangeably between the first and second embodiments, for example with an adjustable carriage arm 21.

[0041] 17 to 22 show the device in the third example, which is different from the first and second examples in that the cage or frame 1 has an intermediate support 33 to which two pairs of upper and lower arms 6, 7 having corresponding wheels 8, 9 are connected. Thus, the cage 1 has three annular horizontal pieces (the lower support 3, the intermediate support 33 and the upper support 4) which are connected by a number of vertically extending struts 5 to form a generally cylindrical structure. Thus, the third example can be considered as an advanced form of the first and second examples in which the intermediate support 33 performs a similar function to the upper support 4 in the first and second examples, and the upper support 4 in the third example is an additional structural part extending beyond the upper arm 6.

[0042] Cage 1 includes two semi-cylindrical sections 1a, 1b that are hinged together at connection points 2a, 2b and can be locked together as in Example 2. In this example, the cage may be designed in a larger version for fitting around a structure 30 having a diameter in the range of 22 to 36 inches (0.56 to 0.91 meters) or in a smaller version for structures 30 having a diameter in the range of 8 to 22 inches (0.20 to 0.56 meters).

[0043] One pair of arms 6,7 has a corresponding pair of drive cylinders 10,11, while the other pair of arms has a corresponding pair of length-adjustable bars 12,13. The wheels 8,9 of at least one pair of arms 6,7 are reciprocatably drivable to move the apparatus up and down on a structure 30.

[0044] In this example, the device does not have guide rails 14 or carriages 15 to support and carry the tool 22. The center of gravity (COG) is therefore close to the geometric center of the cage 1, as shown in Figs. 17 and 18. As shown in Figs. 23 and 24, the device is configured as a traction module and is connected to one or more service modules 34, such as a cleaning module, an NDT module and / or a cutting module, in a line along and around the structure 30. Each of the additional modules has a cage or frame of similar construction to that of the traction module, with two or more pairs of arms 6, 7 and corresponding wheels 8, 9, except that the wheels 8, 9 of the additional modules are not driven. The service module 34 is driven along the structure 30 by the towing or traction module. Alternatively, one or more service modules may be moved along the structure 30 by other means, such as one or more winches attached to the structure 30 or to a platform.

[0045] The distance traveled along the structure 30 is measured by a measuring wheel 43 supported on the frame 1, for example by an intermediate support 33, and pivotable into contact with the structure 30. The measuring wheel may be an encoder wheel capable of measuring the distance traveled optically and / or electrically.

[0046] As shown in Figure 24, adjacent first and second modules may be coupled together by one or more first mating components on the first module with one or more corresponding mating components on the second module, for example the first mating component may have one or more male mating probes 35 and the second mating component may have one or more receptacles 36 for mating with the corresponding male mating probes 35. This coupling may be secured by a locking means such as a quick release bolt 37 that passes through the male mating probe and the receptacle, although other mating and / or locking mechanisms may be used.

[0047] The traction module may have a number of feet 42 attached to the lower support 4. The feet 42 are preferably removable to allow additional modules to be joined below the traction module.

[0048] The traction module has a master controller 38 that is removably connectable by leads 40 to one or more corresponding slave controllers 39 on one or more additional modules. The master controller 38 is controlled from the surface by a remote control unit 25, which passes communication signals and / or power to the slave controllers 39.

[0049] The components for these examples may be provided as a kit of parts. 13 shows a kit of parts provided to enable either the first or second embodiment of the apparatus to be assembled, including at least the frame segments 1a, 1b, 1c of the first embodiment, the frame segments 1a, 1b of the second embodiment, the arms 6, 7, together with the wheels 8, 9, hydraulic cylinders 10, 11, length adjustable bars 12, 13 (shown here attached to the frame segments 1a, 1b of the second embodiment), the carriage 15 for the first and second embodiments, a set of fluid hoses 29, and a fluid power supply 28. In this embodiment, the kit of parts is provided in the form of a transportable container 32 including a work platform 31 to facilitate partial assembly of the apparatus prior to assembly around the support structure 30.

[0050] In examples designed for a single diameter or multiple diameter support structure 30 with a small range of diameters, some pairs of arms 6, 7 and wheels 8, 9 that are not driven can be replaced by other types of guides, such as rollers or wheels at fixed radius positions.

[0051] FIG. 14 shows examples of drivable functions of a device, such as the example above: i driving the pivotable upper and lower arms 6, 7 to pivot radially outward / inward respectively to open and close the clamping; ii. contacting the surface of the support structure 30 to drive the drivable wheels 8, 9 in forward / reverse directions respectively to move up and down; iii) driving the drive gear 16 forward / reversely to rotate the carriage clockwise / counterclockwise; iv. Drive the tool 22 in the radial forward / backward directions relative to the carriage 15 to adjust the tool in the forward / backward directions.

[0052] The drivable functions may be powered and / or controlled by a hydraulic or electrical source, respectively, via hydraulic hoses and / or electrical cables connected to the device. Hydraulic power may be preferred for at least some applications, e.g., to reduce the weight of the device and / or to avoid the use of electricity in a marine environment. The hydraulic power unit may be mounted on a platform and connected to the device by flexible hydraulic hoses.

[0053] An example of a hydraulic drive system for the apparatus is shown in FIG. 15 in which the pivoting of one of the pair of arms 6, 7, the rotation of the corresponding wheels 8, 9, and in the first and second examples the rotation of the drive gear 16 and the reciprocating drive of the tool 22 are driven by separate hydraulic lines connected to a hydraulic power source unit (not shown).

[0054] As shown, for example, in Figure 16, the apparatus is preferably controlled by a remote control unit 25 in which control of some or all of the functions described above can be effected, preferably by corresponding user actuatable controls. The remote control unit 25 can be connected by wire or wirelessly to a controller 26 for the functions described above. Power for operating the functions can be provided by a power source 28 under the control of the controller 26.

[0055] Preferably, the drive speeds of the wheels 8, 9 and the drive gear 16 are independently controllable for the required servicing operations. Alternatively or additionally, the remote control unit 25 or controller 26 is programmable or can be programmed to perform certain operations by unifying the control of different functions, optionally in response to the travel distance detected by the distance sensor and / or the circumferential position of the carriage 15 detected by the circumferential position sensor, thus allowing servicing operations to be performed at predetermined positions on the support structure 30.

[0056] The pivot angle of the arms 6,7 can be varied during use, for example so that the apparatus can be driven up and down a sloped or curved support member.

[0057] The number of powered wheels 8,9 can be varied depending on the load carried by the device or depending on the operating conditions of the device. Depending on the adjustability or clamping force required, multiple pairs of pivoting of arms 6,7 can be powered.

[0058] This example can be used to service tapered support structures by varying the degree of pivoting of the arms 6,7 to adjust the radius as the device raises or lowers the support structure.

[0059] In the alternative, the arms 6,7 may be mounted on the lower support 4 and the guide rail 14 may be mounted on the upper support 3.

[0060] The frame segments 1a, 1b, 1c are preferably made of aluminum tubing to reduce weight, for example the mass of the device may be in the range of 200-300 kg, excluding any hydraulic or electrical lines.

[0061] In larger instances, instead of a removable pin closure, a hydraulic closure may be used. In this case, two or more of the cage or frame segments 1a, 1b, 1c are connected by a hinge connection actuated by a hydraulic ram or cylinder 41, for example as shown in FIG. 17. The segments 1a, 1b, 1c may be connected on a suitable surface, such as a floating pontoon or barge, supported by feet 42, for example. The hinge connection may be opened to allow the cage or frame 1 to fit around the support structure 30 to be serviced, and then closed to secure the frame 1 around the structure 30. The segments 1a, 1b, 1c may be secured in place by one or more hydraulically actuated locking mechanisms, for example lock cylinders 44.

[0062] The above example is designed to service a cylindrical support structure 30 such as a pile, and therefore the frame 1 is generally cylindrical with an inside diameter slightly larger than the diameter of the support structure 30. In other examples, the frame 1 may have a different shape and size depending on the type of support structure 30 and be designed to suit the structure being serviced. For example, in an example designed to service a square or rectangular tubular support structure 30, a square or rectangular tubular frame 1 could be used, preferably with a pair of arms 5, 6 on each of the four sides.

[0063] The above examples are suitable for use in the sea or splash areas, or below the surface, at shallow depths of around 10 metres. For operation at depths greater than 10 metres, they can be modified, for example by using suitable hydraulic seals. The above examples can be used for servicing work such as servicing of pipe-like structures, provided that this is not hindered by the supports of the pipe-like structure.

[0064] As another example, the frame segments 1a, 1b, 1c can be used for non-marine, i.e. land-based support structures, such as wind turbines or radio masts. For these applications, the frame segments 1a, 1b, 1c can be provided with one or more wheels or transport members, either removable or permanently attached, to allow the frame segments to be moved along the ground and around the support structure. For example, each of the frame segments 1a, 1b, 1c can be provided with one or more wheels attached to each side, with additional removable wheels on the truss at the apex of the triangle formed by the two wheels on the frame 1 and on the outside of the frame. The segments 1a, 1b, 1c can then be assembled or closed around the support structure 30, for example by removable pins or hydraulic rams as described above.

[0065] Fig. 25 shows an apparatus in the fourth embodiment, which has a frame 1 equipped with upper and lower supports 3, 4 and an intermediate support 33, as in the third embodiment, and upper and lower arms 6, 7 on the intermediate support 33 support wheels 8, 9, respectively. The upper and lower arms 6, 7 are positioned between adjacent supports, and the wheels 8, 9 can come into contact with a structure by passing between the supports.

[0066] As in the third embodiment, mounting the upper and lower arms 6,7 to the intermediate support 33 leaves the upper and lower supports 3,4 free. This allows the guide rails 14 and gear tracks 15 which support and carry the tool carriage 15 to be mounted to each of the upper and lower supports 3,4 as in the first and second embodiments. This arrangement increases the ability to support and carry tools on a single module.

[0067] The fourth embodiment of the apparatus is particularly suitable for servicing the tower of a wind turbine: the positions of the upper and lower arms 6,7 can be independently controlled to accommodate tapered towers.

[0068] A first embodiment of the invention will now be described with reference to Fig. 26. Fig. 26 shows a schematic diagram of a module as described above, such as the traction module 1 or the service module 34, having a number of buoyancy chambers 52, 53, 54 disposed therein and arranged in series with one another. Each of the buoyancy chambers 52, 53, 54 is at least partially open at or near its lower end to allow water or gas to escape. The first, lowermost buoyancy chamber 52 is supplied with gas (e.g., air) via a hose or gas line 50 removably attached to an inlet port 52a. The gas can be supplied from a remote pump or from a cylinder or other form of gas tank supported and carried by the module 1, 34. The supply of gas can be controlled, for example, by a valve in the inlet port 52a.

[0069] The gas displaces the water in the first buoyancy chamber 52 until the buoyancy chamber 52 is substantially full of gas, at which point the gas escapes through outlet port 52b and gas line 55 to the inlet port 53a of the middle buoyancy chamber 53, from where it reaches outlet port 53b and displaces the water via gas line 56 to the third, uppermost buoyancy chamber 54.

[0070] The supply of gas through gas lines 55, 56 can be controlled by further valves, for example at one or more of ports 52b, 53, 53b, but this is not essential - for simplicity, only the entry of gas into inlet port 52a may be controlled.

[0071] In this manner, the buoyancy chambers 52, 53, 54 can be filled with gas to create a buoyancy level that substantially corresponds to the displacement of the combined volumes of the buoyancy chambers 52, 53, 54. As the module 1 is made deeper (e.g., by being lowered along a substantially vertical underwater structure), the gas in the buoyancy chambers 52, 53, 54 compresses and reduces in volume as the water pressure increases, and because the buoyancy chambers are open at or near their lower ends, the gas pressure equalizes with the water pressure. Conversely, more gas can be supplied through the gas line 50 without risk of overpressure, since the excess gas escapes from the open lower ends of the buoyancy chambers 52, 53, 54. As the module 1 is made shallower (e.g., by being raised along a substantially vertical underwater structure), the gas in the buoyancy chambers 52, 53, 54 reduces in pressure and increases in volume. The excess gas escapes from the lower ends of the buoyancy chambers 52, 53, 54.

[0072] The buoyancy chambers 52, 53, 54 may be substantially rigid and made, for example, from fiberglass, plastic or aluminium. They may be located within the modules 1, 34 in the available space between the struts 5 without interfering with the operation of the modules 1, 34.

[0073] In Fig. 27, a second embodiment is shown which is similar to the first embodiment, except that the buoyancy chambers 52, 53, 54 are provided on different modules 1, 34 which are connected in series along a substantially vertical structure 30, such as that shown in Figs. 23 and 24. Gas lines 55, 56 can be removably connected between the respective ports 52b, 53a and 53b, 53a, using removable connectors, such as those having O-ring seals. Each buoyancy chamber 52, 53, 54 can be calculated to move to bring the buoyancy of the module 1, 34 to the required level. In this way, a series of modules 1, 34 can be connected to the required buoyancy level as a whole.

[0074] Aspects of the first embodiment and the first embodiment may be combined, for example a plurality of buoyancy chambers as in the first embodiment may be provided in one or more of the modules 1, 34 in the second embodiment, in which case the uppermost buoyancy chamber of the lower module 1, 34 is connected by a gas line to the lowermost buoyancy chamber of the adjacent upper module 1, 34.

[0075] Alternative embodiments of the invention which will become apparent to those skilled in the art upon reading this specification are within the scope of the invention as defined in the claims.

Claims

1. 1. Apparatus for servicing an elongated underwater structure, comprising: at least one module disposed about the structure and configured to service the structure and / or for transport along the structure; The apparatus comprises a first buoyancy chamber having a gas inlet, the first buoyancy chamber being positioned such that gas from the gas inlet displaces water from the first buoyancy chamber.

2. 2. The device of claim 1, further comprising a second buoyancy chamber connected directly or indirectly in series with the first buoyancy chamber by a gas line, such that gas can pass from the first buoyancy chamber to the second buoyancy chamber, thereby displacing water from the second buoyancy chamber.

3. 3. The apparatus of claim 2, wherein the apparatus comprises at least first and second modules having first and second buoyancy chambers, respectively.

4. 4. The apparatus of claim 3, wherein the first and second modules are removably connectable together along the structure and the gas line is removably connectable between the first and second buoyancy chambers.

5. 5. An apparatus as claimed in any one of claims 2 to 4, wherein the second buoyancy chamber is located above the first buoyancy chamber.

6. 10. Apparatus according to any preceding claim, wherein the or each said buoyancy chamber is open at or near its lower end to allow water to be displaced by the gas.

7. 10. Apparatus according to any preceding claim, comprising a valve arranged to control the supply of gas through the gas inlet.

8. 10. An apparatus according to any one of the preceding claims, comprising a gas supply provided in at least one of the modules.

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