Patent Description:
Marine support structures typically suffer from ageing and degradation, particularly in the 'splash zone', which is the part of the structure that is periodically covered and uncovered by water, for example as a result of tidal range, wave action and/or splashing. Ageing may include corrosion and physical damage caused by wave action and impacts. Degradation may include accumulation of marine growth, such as weed, barnacles etc..

Marine support structures therefore need to be serviced, for example by cleaning, inspection, and coating or painting, to ensure continued performance and to extend their life. Conventionally, servicing is carried out by divers but this can be extremely difficult and hazardous, particularly in the splash zone, and is often not fully effective.

<CIT> discloses apparatus for servicing a structure, comprises cage or frame that carries drive wheels or rollers from driving the frame along the structure and/or tools for servicing the structure. The frame comprises at least two parts connected together by a hinge, so that the frame can be opened to fit around the structure to be serviced, and closed to secure the frame or cage around the structure. A plurality of such frames or cages may be connected together in series around the structure.

Structures may include obstacles to the passage of a servicing apparatus along the structure. For example, marine support structures may have clamps attached thereto for fitting structural parts such as cross-braces.

Various solutions have been proposed to this problem. For example, <CIT> discloses an apparatus in the form of an open ring that rotates around the structure so that the obstacle passes through the opening in the ring. <CIT> discloses a similar approach; additionally, the apparatus has drive rollers that can be lifted away from the structure in order to 'step over' small obstacles. The 'open ring' solution requires rotation of the whole apparatus around the structure, which can cause tangling of hydraulic hoses or cables connected to the apparatus.

In another example, <CIT> discloses an apparatus comprising collar segments that can be separated so as to pass over a flange on a pipe. This arrangement is not suitable for passing over obstacles such as cross-braces that extend away from a pipe.

There is a need for a simpler and more effective approach to passing large obstacles when servicing structures, including not only marine and offshore structures, but also land-based structures such as wind turbine towers. <CIT> relates to a piping examination apparatus for the maintenance and inspection of a number of closely clustered pipes. More particularly, the disclosure relates to a swing-type automatic examination apparatus for automatically examining piping while "walking" across the narrow spaces between pipes. <CIT> relates to the crawling device applied to a rod-shaped article, and more particularly to a crawling robot and a climbing structure thereof. <CIT> relates to remotely-operated subsea tools and to methods for moving such tools along elongate members of offshore structures.

Aspects of the invention are defined by the accompanying claims.

According to one embodiment, there is provided a bypass module for connection in series between first and second drive and/or servicing modules, each of which may be selectively closed around an elongate structure to be serviced, or opened to move away from the structure to be serviced, wherein the bypass module is actuable to move the first and second modules relative to each other in a direction perpendicular to the elongate structure, so that one of the modules is moved away from the structure while the other is closed around the structure. In this way, by arranging a train of drive and servicing modules with bypass modules therebetween, the train may bypass an obstacle on the structure by moving one or more modules in turn away from the structure, driving the one or more modules past the structure, then moving the one or more modules back towards the structure and closing them around the structure.

The or each drive and/or servicing module may be selectively opened and closed by a drive, such as a hydraulic ram or electric motor, mounted on the structure of the drive/servicing module. In this way, a drive which is used to attach the drive/servicing module to the structure may be actuated to allow the drive/servicing module to pass an obstacle on the structure, and no additional drive to open and close is required in the bypass module. The bypass module may include movable or pivotable mounting parts to allow the first and/or second drive/servicing modules to open and close.

The or each drive module is configured to drive along the structure, for example by means of drive wheels or rollers in contact with the structure. The or each servicing module may comprise one or more tools for servicing the structure. A combined drive and servicing module may combine the functions of the drive module and the servicing module.

The drive/servicing modules may each comprise a cage or frame comprising two or more segments or sections movably or pivotably connected together, for example by one or more hinges, so that cage or frame may be closed around the structure and opened to allow removal from the structure.

The cage or frame may comprise upper and lower supports connected together by axial struts. The upper and/or lower supports may have connecting parts for connecting to corresponding connecting parts on the bypass module. Drive and/or servicing parts may be mounted between the upper and lower supports, so as not to project beyond the upper and lower supports and interfere with the bypass module. There may be an intermediate support between the upper and lower supports, for mounting the drive and/or servicing parts.

Specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which:.

In the description below, the orientation of the apparatus will be described as assembled around a vertically elongate support structure <NUM>. 'Circumferential' and 'tangential' refers to a circumference around a notional central vertical axis, and 'radial' to a direction perpendicular to that axis.

Where dimensions are shown in the drawings, these are given in millimetres. The dimensions are not limiting on the size of specific embodiments and are provided purely by way of example.

For clarity, not all instances of a particular part are indicated by reference numerals in the drawings. It will be understood by inspection of the drawings as a whole which parts are referred to. Similar parts between different embodiments are indicated by the same reference numeral.

An embodiment of the invention is designed for use with apparatus for servicing a structure as disclosed in <CIT>, examples of which are described below. However, the present invention is not limited to use with those examples.

A first example is described below with reference to <FIG>. A cage or frame <NUM> comprises cage or frame segments or sections 1a, 1b, 1c which are removably connected together at frame connection points 2a, 2b, 2c, for example using removable pins. In use, the frame segments 1a, 1b, 1c are assembled around the support structure <NUM> to be serviced. The frame segments 1a, 1b, 1c include lifting points <NUM> for attachment of cables or the like, for lifting the frame segments 1a, 1b, 1c into position and/or for retrieving them after use. Preferably, each frame segment 1a, 1b, 1c is light enough to be manually lifted into position.

The frame <NUM> comprises an upper support <NUM> and a lower support <NUM>, interconnected by struts <NUM>. In this example, the upper and lower supports <NUM>, <NUM> are circular in shape, and coaxial. The struts <NUM> extend generally vertically between the upper and lower supports <NUM>, <NUM>. The upper support <NUM>, lower support <NUM> and struts <NUM> are preferably substantially rigid and are connected together so that the frame <NUM>, when assembled, is substantially rigid.

A plurality of (in this case <NUM>) pairs of upper and lower arms <NUM>, <NUM> are connected to the upper support <NUM> at different circumferential positions, preferably evenly circumferentially spaced around the upper support <NUM>, for example by <NUM>° in this example.

Each arm <NUM>, <NUM> is pivotally connected to the upper support <NUM> about a tangential, horizontal pivot axis, for example by means of a respective axle or spindle. In this example, the arms <NUM>, <NUM> are pivotable about respective axes on the upper and lower sides of the upper support <NUM>, but may alternatively be pivotable about the same axis. The upper and lower arms <NUM>, <NUM> are pivotable in opposite directions relative to each other so that they can both simultaneously move towards the support structure <NUM> or away from the support structure <NUM>. The upper and lower arms <NUM>, <NUM> may be pivotable independently of each other, so that the angle between the upper and lower arms <NUM>, <NUM> may vary.

Each arm <NUM>, <NUM> carries a respective wheel, roller or other rotating member <NUM>, <NUM> arranged to contact the support structure <NUM>. The wheels <NUM>, <NUM> may have contact surfaces arranged to enhance traction against the support structure <NUM> and/or to reduce wear to the wheels <NUM>, <NUM>. Each pair of wheels <NUM>, <NUM>, carried by a corresponding pair of arms <NUM>, <NUM>, may be mutually independently rotatable.

At least one of the pairs of arms <NUM>, <NUM> are reciprocally driveable to pivot towards and away from the support structure <NUM> so that the corresponding wheels <NUM>, <NUM> respectively clamp and release the support structure <NUM>. Preferably, this pair of arms <NUM>, <NUM> is driven by respective hydraulic cylinders <NUM>, <NUM>. The control of the hydraulic cylinders <NUM>, <NUM> may be interconnected so that the pair of arms is driven in synchronism. The hydraulic cylinders <NUM>, <NUM> may be supplied by respective hydraulic hoses (not shown), secured by a hose clamp <NUM>.

Others of the pairs of arms <NUM>, <NUM> may be adjustably held in a pivotal position, for example by adjustable length bars or bottle screws <NUM>, <NUM>, according to the diameter of the support structure <NUM> to be serviced.

The lower arms <NUM> are arranged to pass between the struts <NUM> to enable the corresponding wheels <NUM> to contact the support structure <NUM>.

At least one of the wheels <NUM>, <NUM> is driveable reciprocally in either one of opposite directions (e.g. forward and backward) so as to move the apparatus respectively up and down the support structure <NUM>. Preferably, the driveable wheel(s) <NUM>, <NUM> are provided on the reciprocally driveable arms <NUM>, <NUM>. Others of the wheels <NUM>, <NUM> may not be driven, but may freely rotate, preferably independently of each other, so as to act as guides for movement of the apparatus up and down the support structure <NUM>.

The lower support <NUM> supports a guide rail <NUM> for guiding a carriage <NUM> circumferentially around the lower part of the frame <NUM>. The carriage <NUM> has a drive gear <NUM> that engages a gear track <NUM> arranged circumferentially and horizontally around the lower part of the frame <NUM>. The drive gear <NUM> is driven so that the carriage <NUM> moves circumferentially around the guide rail <NUM>. The carriage <NUM> may be driveable circumferentially through approximately <NUM>°, but preferably the movement of the carriage <NUM> is limited to one complete rotation by a carriage stop <NUM> provided adjacent the guide rail <NUM>, as shown in <FIG>.

The carriage <NUM> preferably does not contact the support structure <NUM>, as accumulation on the support structure <NUM> could impede the progress of the carriage <NUM>. Instead, the carriage <NUM> is supported by a pair of inner rollers <NUM> that contact an inner side of the guide rail <NUM>, and a pair of outer rollers <NUM> that contact an outer side of the guide rail <NUM>. The inner rollers <NUM> are mounted on respective carriage arms <NUM> that extend horizontally to either side of the carriage <NUM>, for improved stability.

In an alternative example, the functions of the guide rail <NUM> and the gear track <NUM> may be combined. For example, the gear track <NUM> and drive gear <NUM> could be omitted and one or more of the inner or outer rollers <NUM>, <NUM> may be driven so as the drive the carriage <NUM> around the guide rail <NUM>. Alternatively, the guide rail <NUM> may be omitted and the gear track <NUM> modified so as to provide a guiding function. Instead of a gear/gear track or rack and pinion arrangement, an alternative linear drive arrangement may be used, such as a roller pinion or friction drive.

The carriage <NUM> is arranged to carry one or more tools <NUM> for servicing the support structure <NUM>. By moving the frame <NUM> up and down the support structure <NUM> using the driveable wheel(s) <NUM>, <NUM>, and moving the carriage <NUM> circumferentially around the support structure <NUM>, the tool(s) <NUM> may reach substantially any part of the external surface of the support structure <NUM>, at least within the splash zone and subject to any restrictions due to hydraulic lines and the like.

The tool(s) <NUM> may be moveably mounted on the carriage <NUM>, to allow movement of the tool(s) <NUM> relative to the carriage <NUM>. For example, the tool(s) <NUM> may be reciprocally driveable towards and away from the support structure <NUM>, for example in a radial direction.

Examples of the tool(s) that may be mounted either singly or together on the carriage <NUM>, and which may be interchangeable, include:.

In the second example, the carriage <NUM> carries a camera <NUM>, such as a video camera, in addition to a cleaning tool <NUM>.

The apparatus may include one or more distance sensors, to determine the distance travelled along the support structure <NUM>. The distance sensor(s) may for example determine the number of rotations of the wheel(s) <NUM>, <NUM>, for example by using one or more optical or magnetic angular position sensors.

The carriage <NUM> may include one or more rotational position sensors (e.g. optical or magnetic sensors) able to detect an absolute or relative circumferential position of the carriage <NUM> relative to the frame <NUM>, for example by detecting reference position markings on the guide rail <NUM> or the gear track <NUM>.

The distance sensor(s) and/or rotational position sensors (s) may be used to determine the position of the tool <NUM>, carriage <NUM> or another part of the apparatus on the support structure <NUM>. This may allow the apparatus to travel to a predetermined absolute position or to return to a previously visited position, for example where an anomaly or discrepancy has been detected.

The apparatus may be aligned with one or more reference marks on the support structure <NUM>, to allow the apparatus to return to a previously visited position relative to the reference marks. In one example, a horizontal and/or vertical visible mark is made on the support structure <NUM> corresponding to an initial position of one or more parts of the apparatus, such as the vertical position of the upper support <NUM> and the circumferential position of a predetermined one of the struts <NUM>, identified for example by a marking such as a distinguishing paint marking. The distance sensor(s) is set to zero. The carriage <NUM> is to its maximum circumferential position (either clockwise or anti-clockwise), and the rotational position sensor(s) is set to zero. As the apparatus moves along the support structure <NUM>, the distance sensor(s) and rotational position sensor(s) measure the distance travelled in an axial and circumferential direction relate to the initial position. This enables the position of any anomaly or discrepancy on the support structure to be mapped and returned to, if required.

The first example is designed to service support structures <NUM> with a diameter in the range <NUM> - <NUM> inches (<NUM>-<NUM> metres). Alternative examples of different sizes and/or numbers of frame segments 1a, 1b, 1c may be provided to service support structures of other diameters. For example, <FIG> show a second example which is similar in construction to the first example but has a frame <NUM> of smaller diameter designed to service a support structure <NUM> with a diameter in the range 9⅝ - <NUM> inches (<NUM> - <NUM> metres). The frame <NUM> comprises two frame segments 1a, 1b, which are semi-cylindrical and are assembled together to form a cylindrical frame <NUM>.

The second example has three pairs of upper and lower arms <NUM>, <NUM> as in the first example, evenly spaced around the upper support <NUM>. In other examples, particularly those designed for servicing support structures of larger diameter, there may be more than three pairs of arms <NUM>, <NUM>.

The arms <NUM>, <NUM>, together with the wheels <NUM>, <NUM>, hydraulic cylinders <NUM>, <NUM> and adjustable length bars <NUM>, <NUM>, may be removably attached to the frame segments 1a, 1b, 1c. These components may then be interchangeably used with the frame segments 1a, 1b, 1c of the first example and the frame segments 1a, 1b of the second example. Different carriages <NUM> may be required for the first and second examples, due to the different radius of curvature. Alternatively, a single adjustable carriage <NUM> may be interchangeably used between the first and second examples, for example with adjustable carriage arms <NUM>.

<FIG> show an apparatus in a third example, which differs from the first and second examples in that the cage or frame <NUM> includes a middle support <NUM> to which two pairs of upper and lower arms <NUM>, <NUM>, carrying corresponding wheels <NUM>, <NUM>, are connected. Hence, the cage <NUM> comprises three annular horizontal pieces (lower support <NUM>, middle support <NUM> and upper support <NUM>) connected together by vertically extending struts <NUM> to form a generally cylindrical structure. Hence, the third example can be thought of as a development of the first and second examples in which the middle support <NUM> performs a similar function to the upper support <NUM> of the first and second examples, and the upper support <NUM> of the third example is an additional structural part that extends beyond the upper arms <NUM>.

The cage <NUM> comprises two semi-cylindrical sections 1a, 1b hingedly connected together at connection points 2a, 2b, and lockable together, similarly to the second example. The cage in this example may designed in a larger version for fitting around structures <NUM> with a diameter of between <NUM> and <NUM> inches (<NUM> - <NUM>), or in a smaller version for structures <NUM> with a diameter of between <NUM> and <NUM> inches (<NUM>-<NUM>).

One pair of arms <NUM>, <NUM> has a corresponding pair of actuating cylinders <NUM>, <NUM>, while the other pair of arms has a corresponding pair of adjustable length bars <NUM>, <NUM>. The wheels <NUM>, <NUM> of at least one pair of arms <NUM>, <NUM> are reciprocally drivable to as to move the apparatus up and down the structure <NUM>.

In this example, the apparatus has no guide rail <NUM> or carriage <NUM> for carrying tools <NUM>. Hence, the centre of gravity (COG) is close to the geometric centre of the cage <NUM>, as shown in <FIG> and <FIG>. As shown in <FIG> and <FIG>, the apparatus is configured as a traction module for connection in series along and around the structure <NUM> to one or more servicing modules <NUM>, such as a cleaning module, NDT (non-destructive testing) module and/or cutting module. Each additional module comprises a cage or frame of similar construction to that of the traction module, and may comprise two or more pairs of arms <NUM>, <NUM> with corresponding wheels <NUM>, <NUM> similar to that of the traction module, except that none of the wheels <NUM>, <NUM> of the additional module are driveable; instead the servicing modules <NUM> are driven along the structure <NUM> by the traction module. Alternatively, the one or more servicing modules may be moved along the structure <NUM> by some other means, such as one or more winches attached to the structure <NUM> or to a platform.

The distance travelled along the structure <NUM> may be measured by a measuring wheel <NUM> that is supported by the frame <NUM>, for example by middle support <NUM>, and is pivotable into contact with the structure <NUM>. The measuring wheel may be an encoding wheel from which the distance travelled may be detected optically and/or electronically.

As shown in <FIG>, adjacent first and second modules may be connected together by one or more first docking parts on a first module that docks with a corresponding one or more second docking parts of the second module; for example, the first docking part(s) may comprise one or more male docking probes <NUM> and the second docking part(s) may comprise one or more receptacle(s) <NUM> into which the corresponding male docking probe(s) <NUM> fit. The connection may be secured by a locking system such as a quick release bolt <NUM> that passes through apertures in the male docking probe and the receptacle. Alternative docking and/or securing mechanisms may be used.

The traction module may have a plurality of feet <NUM> attached to the lower support <NUM>. Preferably, the feet <NUM> are removable to allow connection of an additional module below the traction module.

The traction module includes a master controller <NUM> that is removably connectible by leads <NUM> to one or more corresponding slave controllers <NUM> on the one or more additional modules. The master controller <NUM> is controlled from the surface by the remote control unit <NUM>, and passes communication signals and/or electrical power to the slave controllers <NUM>.

The components of any of the examples may be provided as a kit of parts. For example, <FIG> shows a kit of parts that may be provided to allow apparatus of either the first or second example to be assembled, comprising at least the frame segments 1a, 1b, 1c of the first example, the frame segments 1a, 1b of the second example, the arms <NUM>, <NUM>, together with the wheels <NUM>, <NUM>, hydraulic cylinders <NUM>, <NUM> and adjustable length bars <NUM>, <NUM> (shown here attached to the frame segments 1a, 1b of the second example), carriages <NUM> for the first and second examples, a set of hydraulic hoses <NUM>, and a hydraulic power supply <NUM>. In this example, the kit of parts is provided in a transportable container <NUM> including a workbench <NUM>, to facilitate partial assembly of the apparatus before assembly around the support structure <NUM>.

In examples designed for support structures <NUM> of only one diameter, or a small range of diameters, some of the non-driven pairs of arms <NUM>, <NUM> and wheels <NUM>, <NUM> may be replaced by other types of guides, such as rollers or wheels of fixed radial position.

<FIG> shows examples of driveable functions of the apparatus such as the examples as described above:.

The driveable functions may be each be powered and/or controlled by hydraulic or electric power, for example by hydraulic hoses and/or electrical cables connected to the apparatus. Hydraulic power is preferable for at least some applications, for example in order to reduce the weight of the apparatus and/or to avoid the use of electricity in a marine environment. A hydraulic power unit may be mounted on a platform and connected to the apparatus by flexible hydraulic hoses.

An example of a hydraulic drive system for the apparatus is shown in <FIG>, in which the pivoting of one of the pairs of arms <NUM>, <NUM>, the rotation of the corresponding wheels <NUM>, <NUM>, and in the case of the first and second examples, the rotation of the drive gear <NUM>, and the reciprocal driving of the tool <NUM> are driven by separate hydraulic lines, connected to a hydraulic power unit (not shown).

The apparatus is preferably controlled by a remote control unit <NUM>, as shown for example in <FIG>, which allows control of some or all of the functions described above, preferably by means of corresponding user actuable controls. The remote control unit <NUM> may be connected by a wired or wireless connection to a controller <NUM> of the functions described above. Power for driving the functions may be provided by a power supply <NUM>, under the control of the controller <NUM>.

Preferably, the drive speeds of the wheels <NUM>, <NUM> and of the drive gear <NUM> are controllable independently to adjust for the servicing required. Alternatively or additionally, the remote control unit <NUM> or controller <NUM> may be programmable or programmed to carry out a particular service by coordinated control of the different functions, optionally in response to the distance travelled as detected by the distance sensor(s), and/or the circumferential position of the carriage <NUM> as detected by the circumferential position sensor(s). This may enable a predetermined section of the support structure <NUM> to be serviced.

The pivot angle of the arms <NUM>, <NUM> may be varied during use, for example to allow the apparatus to be driven up or down a sloping or curved support member.

The number of wheels <NUM>, <NUM> that are powered may be varied according to the load to be carried by the apparatus or the operating conditions of the apparatus. The pivoting of more than one of the pairs of arms <NUM>, <NUM> may be powered, depending on the adjustability or clamping force required.

Examples may be used for servicing tapering support structures, by varying the degree of pivoting of the arms <NUM>, <NUM> to adjust for varying diameter as the apparatus moves up and down the support structure.

In an alternative example, the arms <NUM>, <NUM> may be mounted on the lower support <NUM> and the guide rail <NUM> may be mounted on the upper support <NUM>.

Preferably, the frame segments 1a, 1b, 1c are constructed of aluminium tube so as to be lightweight. For example, the mass of the apparatus, excluding hydraulic or electrical lines, may be in the range <NUM>-<NUM>.

For larger examples, the method of closure by removable pins may be replaced by a hydraulic closure method, in which two or more of the cage or frame segments 1a, 1b, 1c are connected together with hinged connections, actuated for example by hydraulic rams or cylinders <NUM>, as shown for example in <FIG>. The segments 1a, 1b, 1c may be connected together on a suitable surface such as a floating pontoon or barge, supported for example by the feet <NUM>. The hinged connections may be opened such that the cage or frame <NUM> fits around the support structure <NUM> to be serviced, then closed so as to secure the frame <NUM> around the structure <NUM>. The segments 1a, 1b, 1c may be secured together by one or more locking mechanisms, such as locking cylinders <NUM>, which may be hydraulically actuated.

The above examples are designed for servicing a circular cylindrical support structure <NUM> such as a pile, and therefore the frame <NUM> is approximately circular cylindrical, having an inner diameter slightly larger than the diameter of the support structure <NUM>. Alternative examples may have alternative shapes and sizes to match the type of support structure <NUM> which they are designed to service. For example, a square or rectangular cylindrical frame <NUM>, preferably with a pair of arms <NUM>, <NUM> on each of the four sides, may be used in an example designed for servicing a square or rectangular cylindrical support structure <NUM>.

The above examples may be used in a marine or aquatic splash zone, or at a shallow depth below the surface, such as <NUM> metres. The examples may be modified for operation below <NUM> metres in depth, for example by the use of suitable hydraulic seals. The examples may be used for servicing pipes, to the extent that they are not impeded by the support of the pipes.

Alternative examples may be used for servicing non-marine or on-shore support structures, such as wind turbines or radio masts. For these applications, the frame segments 1a, 1b, 1c may be provided with one or more detachable or permanently attached wheels for or other transport members, allowing the frame segments to be moved into position around the support structure, along the ground. For example, each frame segment 1a, 1b, 1c may have one or more wheels attached at each side and an additional removable wheel on a truss at the apex of a triangle formed by two wheels on the frame <NUM> and on the outside of the frame. The segments 1a, 1b, 1c may then be assembled or closed around the support structure <NUM>, for example by means of removable pins or by the hydraulic rams as described above.

<FIG> shows apparatus in a fourth example. This example has a frame <NUM> with upper and lower supports <NUM>, <NUM> and a middle support <NUM> on which upper and lower arms <NUM>, <NUM> carrying respective wheels <NUM>, <NUM> as in the third example. The upper and lower arms <NUM>, <NUM> are positioned between adjacent struts <NUM> and pass between the struts <NUM> so that the wheels <NUM>, <NUM> can contact the structure.

As in the third example, the mounting of the upper and lower arms <NUM>, <NUM> on the middle support leaves the upper and lower supports <NUM>, <NUM> clear. This enables a guide rail <NUM> and gear track <NUM> carrying a tool carriage <NUM>, similar to those of the first and second examples, to be mounted on each of the upper and lower supports <NUM>, <NUM>. This arrangement increases the capacity of the apparatus to carry tools on a single module.

The apparatus of the fourth example is particularly suitable for servicing the towers of wind turbines. The positions of the upper and lower arms <NUM>, <NUM> may be controlled independently to accommodate a tapered tower.

A first embodiment of the present invention will now be described with reference to <FIG>. This embodiment is designed to be used with the hinged modules described above, in which each module comprises two or more of cage or frame segments 1a, 1b, 1c connected together with hinged connections, which may be opened such that the cage or frame <NUM> fits around the support structure <NUM> to be serviced and closed so as to secure the frame <NUM> around the structure <NUM>, using a drive such as a hydraulic cylinder or an electric motor to open and close the cage or frame <NUM>.

The first embodiment is also designed to be used with the examples described above with reference to <FIG> and <FIG>, in which multiple modules can be connected together in series along the structure, each module comprising a drive and/or servicing module.

<FIG> show a bypass module <NUM> for connection in series between adjacent modules <NUM> so as to allow the drive and/or servicing modules <NUM>, <NUM> to pass an obstacle on the structure to be serviced, including obstacles such as cross-braces that extend away from the structure. The module <NUM> comprises upper and lower pairs of slotted plates <NUM>, <NUM> carrying respectively upward and downwardly projecting module attachment pins <NUM> for removable attachment to corresponding attachment parts (e.g. receptacles <NUM>) of the drive and/or servicing modules respectively above and below the bypass module <NUM>.

Between the upper and lower slotted plates <NUM>, <NUM> are provided a pair of linear telescopic rails <NUM>, arranged such that the upper slotted plates <NUM> can move linearly relative to the lower slotted plates <NUM>. This linear movement is driven by a hydraulic ram <NUM> connected to a mounting block <NUM> connected to one end of the respective telescopic rail <NUM>, although other drive means such as an electric or hydraulic motor with a linear drive connection may be used instead. The end of the rail <NUM> is protected by a bumper <NUM>.

Each of the pairs of upper and lower slotted plates <NUM>, <NUM> are pivotally mounted on a structure comprising stabiliser bars <NUM> and stabiliser plates <NUM>, by means of load-bearing blocks <NUM> moveable within movement slots <NUM>. There may be provided an anti-friction coating on the contact surfaces of the blocks <NUM> and slots <NUM>.

As shown in <FIG>, each pair of upper and lower slotted plates <NUM>, <NUM> are able to pivot towards and away from each other in the manner of a pair of jaws or pincers. This pivoting movement follows the opening and closing movement of the module <NUM> to which the upper/lower plates <NUM>, <NUM> are attached. In the example shown, each pair can open by up to approximately <NUM>°. As shown in <FIG>, this allows the bypass module <NUM> to fit around a pipe or riser <NUM>.

Modules <NUM> may be connected together via the bypass module <NUM> to form a train of modules <NUM>. For example, the train may comprise in series:.

A method of operation of the train so as to pass an obstacle such as a cross-brace is shown in flow chart of <FIG>, in which steps S1 - S11 correspond respectively to <FIG>. Each of the drive modules 1a, 1b and the tool module <NUM> can be opened and closed independently of each other, driven by their respective drive means such as a hydraulic ram or electric motor. Each of the top and bottom bypass modules 50a, 50b are able to move their connected drive and/or servicing modules linearly relative to one another by extending or retracting the telescopic rails <NUM>, driven by the respective hydraulic ram <NUM>. The opening, closing, driving, extending and retracting steps may be controlled manually, automatically or semi-automatically, for example by means of remote control unit <NUM> and/or controller <NUM> with the position and state of the modules being detected by one or more sensors and/or by visual inspection.

At step S1, the train is located on a riser <NUM> just above a clamp <NUM> to which a cross-brace <NUM> is attached. In this state, both the drive modules 1a, 1b and tool module <NUM> are closed around the pipe <NUM>. At step S2, the bottom traction module 1b and the tool module <NUM> are opened. At step S3, the top bypass module <NUM> is extended so that the tool module <NUM> and bottom drive module 1b are moved linearly away from the riser <NUM> and the clamp <NUM>.

At step S4, the top drive module 1a drives the train down the pipe <NUM>, so that the bottom drive module 1b is past the clamp <NUM>. At step S5, the bottom bypass module 50b extends so that the bottom drive module 1b is positioned around the riser <NUM>. At step S6, the bottom drive module 1b closes around the riser <NUM>.

At step S7, the top drive module 1a opens. At step S8, the top bypass module 50a retracts so that the top drive module 1a moves away from the riser <NUM>. At step S9, the bottom drive module 1b drives the train down the riser <NUM> so that the top bypass module 50a and tool module <NUM> move past the clamp <NUM>. At step S10, the bottom bypass module 50b retracts so as to move the top drive module 1a and tool module <NUM> back onto the riser <NUM>. Finally, at step S11 the top drive module 1a and tool module <NUM> close onto the riser <NUM>. The train can then be driven further down the riser <NUM>.

Hence, by the addition of the top and bottom bypass modules 50a, 5b, the drive modules 1a, 1b and tool module <NUM> are able to bypass obstructions such as clamp <NUM>.

Alternative train configurations may be used, with a similar method of operation. For example, one or more additional tool modules or drive modules may be added, and combined tool and driving modules may be used. One or more dolly wheel modules may be added at one or both ends of the train, with non-driven wheels that are arranged to contact the support <NUM>; this provides greater stability against moments exerted by the bypass module(s) <NUM>.

In some embodiments, for example where the bypass module <NUM> has a greater length along the structure than the obstacle, the train may comprise first and second drive modules 1a, 1b, at least one of which is also configured as a tool module, connected together in series by a single bypass module <NUM>. In this case, the first drive module 1a is opened, moved away from the structure by the bypass module <NUM>, and driven past the obstacle by the second drive module 1b. The first drive module 1b is then moved towards the structure by the bypass module <NUM> and closes around the structure. The second drive module 1b is then opened, moved away from the structure by the bypass module <NUM>, and driven past the obstacle by the first drive module 1b. The second drive module 1b is then moved towards the structure by the bypass module <NUM> and closes around the structure.

The first embodiment provides a bypass module <NUM> for use with existing drive and/or servicing modules <NUM>, <NUM> such as in the examples above. However, in alternative embodiments some of the components or functions of the bypass module <NUM> may be integrated into the drive and/or servicing modules <NUM>, <NUM>. For example, <FIG> and <FIG> show a section of an upper half of a drive module <NUM> in a second embodiment in which at least one of the slotted plate(s) <NUM>, <NUM> form the upper and/or lower supports <NUM>, <NUM>. This reduces the weight of the train since there is no need to provide separate slotted plates <NUM>, <NUM> and upper/lower supports <NUM>, <NUM>, or pins <NUM>. Additionally, the connection between modules may be made stronger.

In the second embodiment, the bypass module <NUM> consists only of the telescopic rails <NUM>, hydraulic ram <NUM> and stabiliser plates <NUM> and bars <NUM>, together with pins or blocks <NUM> that fit within slots <NUM> within the slotted plates <NUM>, <NUM> of the drive and/or servicing module <NUM>, <NUM> above or below and are secured within the slots <NUM> by removable caps, as shown for example in <FIG> and <FIG> in which the pin or block <NUM> comprises a nut and bolt type fixing with nylon bushes to reduce friction against the corresponding slot <NUM>.

The parts of the pin or block <NUM> are labelled in <FIG> as follows:.

A combination of modules <NUM>, <NUM> according to the first and second embodiments may be used together in the same train, by using a bypass module <NUM> having a slotted plate <NUM>, <NUM> and pins <NUM> on one side for connection to the upper/lower supports <NUM>, <NUM> of a drive and/or servicing module <NUM>, <NUM>, and with telescopic rails <NUM> on the other side connected or connectable directly to a drive and/or servicing module <NUM>, <NUM> having an integrated slotted plate <NUM>, <NUM> on that side. Hence, there may be provided a hybrid bypass module <NUM> having one side as in the first embodiment and another side according to the second embodiment.

Claim 1:
Apparatus for servicing an elongate structure (<NUM>), comprising a bypass module (<NUM>) connected in series along the structure (<NUM>) between a first drive (1a) module and a second drive (1b) and/or servicing module (<NUM>), each of which may be selectively closed around the structure (<NUM>) or opened to enable removal from the structure (<NUM>), wherein the bypass module (<NUM>) is actuable to move the first (1a) and second (1b) modules relative to each other in a perpendicular direction to the elongate structure (<NUM>) towards or away from the elongate structure (<NUM>), so that the second module (1b) is moved in the perpendicular direction away from the structure (<NUM>) while the first module (1a) is closed around the structure (<NUM>) and the first module (1a) is drivable along the elongate structure (<NUM>) so as to drive the second module (1b) past an obstruction on the elongate structure (<NUM>).