WO2003097446A1

WO2003097446A1 - Remotely operable tool systems

Info

Publication number: WO2003097446A1
Application number: PCT/GB2003/002147
Authority: WO
Inventors: Olav Aaserod; Ove Johan Nicolaus
Original assignee: Stolt Offshore As; Stolt Offshore Limited
Priority date: 2002-05-20
Filing date: 2003-05-19
Publication date: 2003-11-27
Also published as: BR0304870A; AU2003227958A1; GB0211495D0; NO20040251L

Abstract

Apparatus and associated methods for the transporting of tools to an ROV (300) at an underwater location, said apparatus comprising a tool carrier receptacle (100) having a hydraulic fluid source (224) and means for connection (140, 142, 144) of a hydraulically operated tool (134, 136, 138) to said hydraulic fluid source such that said tool is prepressurised prior to use by the ROV. The invention also relates to an ROV for use with such apparatus, the ROV incorporating a hydraulic circuit (500) which includes a source of hydraulic power (502, 504) for operating said equipment, said hydraulic circuit incorporating a filter means (600) functioning to separate water from hydraulic fluid.

Description

Remotely Operable Tool Systems

This invention relates to remotely operable tool systems, and relates more particularly but not exclusively to hydraulically powered tool systems that are remotely operable in a hyperbaric environment.

For the discovery and exploitation of hydrocarbon reservoirs located beneath the seabed there is a need for various items of underwater equipment to be assembled, installed, operated, inspected, maintained, repaired, and ultimately decommissioned. Where the water depth is not excessive, human divers can be used for underwater operations, but the cost and personal danger are considerable. If machinery can reliably substitute for human divers, the divers are no longer in personal peril, nor are operations restrained by lack of trained divers. Remotely operated underwater vehicles ('ROVs') fitted with suitable powered tools or manipulators and in communication with above-surface operators have a favourable combination of human control and underwater operational capability. ROVs have underwater operational durations exceeding human limits, and can operate at depths where the water pressure exceeds that which can be withstood by humans. Some known forms of ROV are connected to a ship or other surface installation by means of an umbilical, while other known forms of ROV, particularly those intended for wide-ranging operation and/or for operation at great depth, are self-contained vehicles not coupled to the surface installation by an umbilical or the like. (The latter form of ROV may be termed an "AOV" or "Autonomously Operating Vehicle").

However, known ROVs of both forms require to be returned to the surface every time a tool currently fitted to the ROV is to be substituted by a different tool, or if hydraulic fluid depleted by leakage from the ROV is to be replenished. The time wasted by the ROV having to make return trips between the underwater operating location and the surface can cause considerable extra expense, especially where the operating depth is great. The present invention proposes a remotely operable tool system that obviates or mitigates the disadvantages of the prior art.

In a first aspect of the invention there is a method of connecting a hydraulically operated tool to a remotely operated vehicle (ROV) while the ROV is at an underwater location, the tool not being initially carried to the underwater location by the ROV, the method comprising the steps of transporting the tool to the underwater location on a tool carrier receptacle independent of the ROV, transferring the tool from the tool carrier receptacle to the ROV, and connecting the transferred tool hydraulically to the ROV in an operational configuration, wherein said tool caπier receptacle incorporates a hydraulic fluid source and said tool is pre-pressurised by said tool carrier receptacle prior to connection to the ROV.

In an embodiment said tool is pre-pressurised to ambient fluid pressure by action of the surrounding seawater on hydraulic fluid.

The hydraulic fluid of the ROV may be replenished from a source of hydraulic fluid carried on said tool carrier receptacle. Said replenishing step may include mechanically driving a pump on the tool carrier receptacle using an actuator of the ROV.

Said tool carrier receptacle may be suspended from a ship or platform and comprise an auxiliary underwater vehicle. Said auxiliary underwater vehicle may be suspended by means of a winch or crane, said winch or crane being the only means of recovery/deployment, said vehicle having no propulsion means and requiring no external power or control to operate.

The method may be performed in reverse to allow substitution of various tools without returning to the surface.

The invention further provides apparatus for the transportation of tools to an underwater location, said apparatus comprising a tool carrier receptacle having a hydraulic fluid source and means for connection of a hydraulically operated tool to said hydraulic fluid source such that said tool is pre-pressurised prior to use.

Said apparatus is preferably a passive auxiliary underwater vehicle adapted for suspension from a ship or platform

Said apparatus may also have hydraulic fluid transfer means selectively operable when said apparatus is hydraulically coupled to an ROV, to enable transfer of hydraulic fluid from said apparatus to the hydraulic circuit of the ROV.

Further particular features of these methods and apparatus invention are defined in the dependent claims, and illustrated in the detailed description of embodiments which follows.

According to a separate aspect of the invention there is provided a remotely operable vehicle (ROV) for use underwater, the ROV mounting hydraulically powered equipment and incorporating a hydraulic circuit, said hydraulic circuit incorporating a filter means being operable to separate water from hydraulic fluid while the ROV remains at an underwater location

Said filter means obviates the effects of ingress of the surrounding water to the hydraulic fluid employed in the RON and in tools hydraulically coupled thereto. The use of such a water-separating filter can delay the moment at which the intake of water necessitates the RON being taken out of service, and is a useful adjunct to the hydraulic fluid topping-up function of the hydraulic fluid source on the auxiliary vehicle or other form of tool carrier means in terms of increasing the duration of in-service periods of the ROV.

Said ROV preferably incorporates manipulator means capable of being operated mechanically and hydraulically to disconnect a selected tool initially supported by the tool carrier receptacle, to enable transfer of the selected tool from the tool carrier receptacle to the ROV and vice versa. The hydraulic fluid transfer means may comprise hydraulic pump means that is preferably mounted on the auxiliary vehicle or other form of tool earner means and hydraulically coupled between the source of hydraulic fluid and the said respective hydraulic coupling part mounted on the auxiliary vehicle or other form of tool carrier means. The hydraulic pump means may be operable by use of the ROV-mounted manipulator.

Other features of any of the above aspects of the invention are as claimed in the appending claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings wherein:

Fig. 1 is a perspective view from above and to one side, of a partly assembled basket comprised in a first form of auxiliary vehicle in accordance with the present invention, with inset detail A;

Fig. 2 is an overhead view of the Fig. 1 basket, fully assembled and fitted with a hydraulic fluid source to constitute the first form of auxiliary vehicle, being lowered into the sea while carrying remotely operable underwater tools;

Fig. 3 is a perspective view from above and to one side, of a basket comprised in a second form of auxiliary vehicle in accordance with the present invention;

Figs. 4 and 5 are fragmentary details, to an enlarged scale, of alternative forms of side door forming part of the basket of Fig. 3; Fig. 6 is a perspective view from above and to the front, of the basket of Fig. 3 fitted with hydraulic equipment that converts the basket to a second form of auxiliary vehicle;

Fig. 7 is a perspective view of the basket of Fig. 3 during underwater deployment (and with its tether omitted for clarity), in proximity to an approaching ROV for which the basket constitutes part of the second form of auxiliary vehicle;

Fig. 8 is a perspective view of a manipulator of the Fig. 7 ROV reaching into the Fig. 7 auxiliary vehicle;

Fig. 9 follows on from Fig. 8 and shows the ROV manipulator about to disconnect a tool-coupled part of a two-part hydraulic coupling installed in the basket of Fig. 6;

Fig. 10 shows part of Fig. 9 from a different angle and to a relatively enlarged scale;

Fig. 11 follows on from Figs. 9 & 10, and shows the tool-coupled part of the hydraulic coupling from Figs. 9 & 10 re-connected to a hydraulic coupling permanently mounted on the ROV and coupled to the hydraulic circuit of the ROV;

Fig. 12 follows on from Fig. 1 1, and shows a tool previously carried by the auxiliary vehicle having been picked up by the ROV manipulator;

Fig. 13 is a schematic diagram of part of the hydraulic circuit of the auxiliary vehicle of Figs. 6-12;

Fig. 14 is a schematic diagram of part of the hydraulic circuit of the ROV of Figs. 7-12; Fig. 15 is a schematic diagram of a filter system for use with the hydraulic circuit of Fig. 15;

Fig. 16 is a schematic diagram of part of an alternative hydraulic circuit that can replace the hydraulic circuit of Fig. 13; and

Fig. 17 is a schematic diagram of part of an alternative hydraulic circuit that can replace the hydraulic circuit of Fig. 14.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring first to Fig. 1, this is a perspective view from above and to one side of the front of a basket 100 constituting part of a first form of auxiliary vehicle in accordance with the present invention. The basket 100 has a generally octagonal base 102 and vertical sides 104, the edges of the base and sides being constituted by steel structural members (angle-iron and I-girders) mutually joined by welds to form a panelled framework 106. The panels defined by the framework 106 are filled in with respective sheets 108 of expanded sheet metal (integral one-piece grilles), only some of which are shown emplaced in Fig. 1.

The interior of the basket 100 is symmetrically subdivided into two hemi-octagonal compartments 110 by a transverse vertical partition 112. Extending upwardly from the sides of the partition 112 is a bail or A-frame 114 that passes over the centre of the basket 100 to form a basket 'handle' or basket lifting means. The central (uppermost) part of the A-frame 114 is fitted with a fixed shackle 116 that allows the attachment of a tether 118 (Fig. 2) by which the basket 100 can be lifted and suspended, either above or in the sea.

The two hemi-compartments 1 10 into which the interior of the basket 100 is subdivided each have a respective lid formed with a steel frame 120 attached to the basket framework 106 by means of a respective pair of spaced- apart hinges 122. One of these hinges 122 is shown to an enlarged scale in Fig. 1A. Each of the compartment lids is completed by a panel of expanded sheet metal (not shown) secured within the lid frames 120.

The bare basket 100 depicted in Fig. 1 is converted to a first form of auxiliary vehicle 150 (Fig. 2) in accordance with the invention by the addition of a reservoir holding hydraulic fluid. In the Fig. 2 view of the auxiliary vehicle 150, this hydraulic fluid reservoir is concealed behind a suction pump 124 and its connecting conduit 126. The reservoir has a rigid housing whose hollow interior is open to ambient. Hydraulic fluid is stored in a fluid-tight flexible bag (not shown) within the housing of the reservoir. A conduit (not shown) couples hydraulic fluid from the bag within the reservoir to a hydraulic circuit (detailed below) forming part of the auxiliary vehicle 150. Since the hydraulic fluid within the reservoir is stored in a flexible bag that is subjected to ambient fluid pressure, the hydraulic fluid on board the auxiliary vehicle 150 is at all times pressurised substantially to whatever is the depth-dependent pressure of surrounding water when the vehicle 150 is submerged. The reservoir can be constituted by a conventional hydraulic compensator or hydraulic accumulator (known per se) whose non-hydraulic side is open to ambient, or constituted by two or more such hydraulic compensators or hydraulic accumulators hydraulically connected in parallel. By way of example, of form of hydraulic compensator suitable for use in the present invention is the "WT-3-1001" hydraulic compensator of West Tech a/s (Norway).

Within the basket compartment 110 on the side of the basket 100 not supporting the reservoir are fixed a mesh box 128, clips 130, and brackets 132 by which respective hydraulic tools and/or hydraulic hose assemblies 134, 136, & 138 can be carried within the auxiliary vehicle 150. Each of the tools comprises a workpiece-engaging device and a hydraulic motor or other actuator (not shown) for driving the workpiece-engaging device, and each of the hose assemblies comprises twin or triple hydraulic hoses terminating in one part of a respective two-part connectable/disconnectable hydraulic coupling 140, 142, & 144 for coupling the tools into a hydraulic power circuit (as will be detailed below). By way of example, the illustrated tool 134 is a nine-inch rotary grinder, the illustrated tool 136 is a seventyfive-millimetre wire cutter, and 138 denotes an assembly of hydraulic hoses.

The hydraulic circuit on board the auxiliary vehicle 150 and to which the reservoir is connected includes the other part of each of the three two-part connectable/disconnectable hydraulic couplings 140, 142, and 144 which are mounted along the top edge of the internal partition 112 (see Fig. 2). A form of two-part connectable/disconnectable hydraulic coupling suitable for use with the invention is provided by Parker Fluid Connectors in their "2000 Series", with the assembly reference "4V 14X5X4" for the male connector part, and the assembly reference "4V54X5X4" for the female connector part.

The hydraulic couplings 140, 142, & 144 are each of the self-sealing type, i.e. two-part hydraulic couplings of the type which, when the coupling parts are physically separated, automatically close each hydraulic passage through both parts of the coupling. These hydraulic passages are automatically re-opened when two mutually compatible parts of a coupling are re-mated. The use of self-sealing two-part hydraulic couplings on the auxiliary vehicle 150 allows the rapid connection and disconnection of hydraulic tools and other hydraulic equipment without substantial ingress of seawater, and without loss of significant amounts of hydraulic fluid; internal hydraulic pressurisation of hydraulic tools and other hydraulic equipment immediately prior to disconnection is substantially maintained upon disconnection and until reconnection. (It would be possible to use two-part hydraulic couplings that are not self-sealing, if a respective shut-off hydraulic isolating valve were to be installed on both sides of the coupling and both isolating valves closed immediately prior to disconnection of the coupling parts; correspondingly, both isolating valves would be opened immediately after the coupling parts were united and mutually secured.)

The auxiliary vessel 150 and associated equipment (e.g. underwater tools) are transported by and deployed from a support ship (not shown). An ROV (not shown in

Figs. 1-2) will also be transported by and deployed from the same or another support ship. When the support ship carrying the auxiliary vessel 150 reaches an intended work location, the auxiliary vessel 150 is prepared and deployed as detailed below.

In order to use the auxiliary vehicle 150, the vehicle's hydraulic circuit, including the flexible bag within its hydraulic fluid reservoir, is filled with hydraulic fluid, selected underwater hydraulic tools/hose assemblies 134, 136, and 138 are loaded into the box 128, the clips 130, and the brackets 132 respectively, and the respective parts of the hydraulic couplings 140, 142, and 144 are mutually connected to cause hydraulic fluid within each of these tools 134, 136, and 138 to become and remain about equal to the pressure of hydraulic fluid within the reservoir. (As previously explained, this hydraulic pressure is substantially the ambient fluid pressure around the auxiliary vehicle 150, whether above the sea or submerged in the sea.) The tether 118 is secured to the shackle 1 16, the auxiliary vehicle is hoisted from its preparation area on the support ship by running the tether 118 through a winch (not shown), swung overboard, and lowered into the sea as illustrated in Fig. 2. During hoisting and deployment of the vehicle 150, it is steadied against excessive or uncontrolled lateral movements by means of a steady line 146 linked to the shackle 116, and/or by deckhands holding a sturdily constructed circumferential hand-rail 148. The deployed vehicle 150 is lowered to the approximate working depth of the ROV, and held suspended at that depth. As previously detailed, the depth-dependent pressure of ambient seawater will be transmitted from the reservoir to the hydraulic fluid in the tools/hose assemblies 134, 136, and 138, thus causing the tools/hose assemblies to be internally pre-pressurised to the ambient water pressure to which the tools/hose assemblies will be exposed when transferred to the ROV. Such pre-pressurisation minimises malfunctions and ingress of water that would otherwise be more likely in the absence of pre-pressurisation. (Details of tool transfer from the auxiliary vehicle to an ROV (not shown in Figs. 1 -2) will subsequently be given in respect of Figs. 3-12.)

Referring now to Figs. 3-12, these depict a second form of auxiliary vehicle 250 for underwater use in conjunction with an ROV 300. Those parts of the second form of auxiliary vehicle 250 thai are identical or functionally analogous to parts of the first form of auxiliary vehicle 150 are given corresponding reference numerals (142=242 etc).

The auxiliary vehicle 250 is based on a basket 200 (Fig. 3) that has a generally rectangular base 202 and vertical sides 204. A central partition 212 divides the interior of the basket 200 into two rectangular compartments 210. The long sides (i.e. the sides 204 that are parallel to the central partition 212 and the plane of the A-frame 214) are formed as movable doors that may either be held in vertical slides 205 (Fig. 4) and be vertically removable for side access to the compartment 210, or the doors may be mounted along their bottom edges on hinges (not visible) that allow the doors to pivot downwards (Fig. 5).

As well as the couplings 240, 242, & 244 mounted on the upper edge of the transverse partition 212, a pump 414 is mounted alongside these couplings in the auxiliary vehicle 250. The input of the pump 414 is hydraulically coupled to the hydraulic fluid reservoir 224. By temporarily coupling the output of the pump 414 to the hydraulic system on the auxiliary vehicle 250, the ROV 300 can transfer to its hydraulic circuit as much hydraulic fluid as may be necessary to compensate for leakage from the ROV. Details of this 'top-up' leakage compensation sub-system will subsequently be given with particular reference to Fig. 13.

When the basket 200 (Fig. 3) is fitted out as a tool-carrying auxiliary vehicle 250 (Fig. 6), it is ready for underwater deployment into the vicinity of the ROV 300 (Fig. 7, from which the suspension tether for the auxiliary vehicle 250 is omitted for clarity). The ROV 300 is fitted with a manipulator 302, i.e. a power-driven articulated ami tipped with a grasping device 304, and capable of selected movements under the remote control of an operator (not shown) observing the scene by means of a video camera (not shown). Power for the manipulator 302 and for other ROV-mounted equipment comes either from on-board batteries if the ROV 300 is not coupled by an umbilical to a surface installation, or via an electric cable incorporated into an umbilical (not shown) by which the ROV 300 is suspended from a surface installation. The ROV 300 is a typically conventional ROV apart from those modifications and additions specific to the present invention, and as such, the ROV 300 has a second manipulator 306 (which does not play a direct part in the present invention).

In order for the ROV 300 to take on board a tool 236 initially carried by the auxiliary vehicle (Fig. 6), the ROV 300 is manoeuvred close to the auxiliary vehicle 250 (Fig. 8), and the ROV manipulator 302 is operated to bring the grasping device 304 into the vehicle compartment 210 occupied by the tool 236. Next, the ROV manipulator 302 and its grasping device 304 are operated to grip the tool-coupled part of the two-part hydraulic coupling 242 (Figs. 9 & 10), and thereupon to disconnect the tool-coupled part of the coupling 242 from the auxiliary vehicle 250. The grasping device 304 keeps hold of the tool-coupled coupling part, and the ROV manipulator 302 is operated to reconnect the tool-coupled coupling part to a corresponding hydraulic coupling part 308 permanently affixed to the ROV 300 (Fig. 11). The hydraulic coupling part 308 is permanently coupled to the ROVs hydraulic power supply (not shown in Figs. 7-12) as will subsequently be explained with reference to Fig. 14. Finally, the ROV manipulator 302 is operated to cause the grasping device 304 to grip the tool 236, and to lift the tool 236 into a position clear of the auxiliary vehicle 250 at which the ROV can effectively use the newly attached tool 236 (Fig. 12). (By way of example, the illustrated tool 236 is a hub-cleaning tool for rotary cleaning of the surfaces of hubs of pipe couplings.)

As with the hydraulic couplings 140, 142, & 144, the couplings 240, 242, 244, & 308 are each of the self-sealing type.

By utilising the auxiliary vehicle 250 to carry extra tools for the ROV 300 and to allow tools to be interchanged underwater without the need for a time-consuming return trip to and from the surface, the ROV 300 is freed of the need to accommodate more than one or two tools at any one time, but has the ability to select and fit in minimal time whatever further tool is required. Automatic pre-pressurisation of tools carried on the auxiliary vehicle (as previously detailed) ensures that each tool newly fitted to the ROV is ready for immediate use, and is largely free of malfunctions and leakage otherwise arising from lack of pre-pressurisation. By temporarily coupling to the output of the pump 414 on the auxiliary vehicle 250, the ROV 300 can transfer to its hydraulic circuit as much hydraulic fluid as may be necessary to compensate for leakage, but without requiring to make a return trip to the surface.

Referring now to Fig. 13, this is a schematic diagram of the hydraulic circuit 400 on the auxiliary vehicle 250. The reservoir 224 comprises a pair of compensators or accumulators 402 each having a rigid casing 404 holding a flexible container 406. Each casing 404 has an aperture 408 that admits seawater surrounding the reservoir 224 when the auxiliary vehicle 250 is submerged. The seawater admitted through the apertures 408 into the interiors of the casings 404 contacts the outside of the flexible containers 406 and thereby pressurises the interiors of the flexible containers 406 which are filled with hydraulic fluid, and which are hydraulically coupled to the remainder of the hydraulic circuit 400 by way of conduit system 410. Thus the hydraulic fluid in the conduit system 410 is maintained substantially at the depth-dependent pressure of the surrounding seawater when the auxiliary vehicle 250 is submerged.

The hydraulic circuit 400 includes four female hydraulic coupling parts 412 that are permanently mounted on a suitable part of the framework 206, e.g. the upper edge of the transverse partition 212. The coupling parts 412 are each permanently hydraulically coupled to the hydraulic conduit system 410. The coupling parts 412 serve as 'parking slots' that function as mechanical holders for up to four complementary tool-connected male coupling parts (not shown in Fig. 13) while the respective tools (not shown in Fig. 13) are being carried by the auxiliary vehicle 250. (Such 'parking' use of one of the coupling parts 412 is depicted in Fig. 6, wherein the combination of the two connected parts is denoted with the reference numeral '242'; an equivalent 'parking' use of three coupling parts is depicted in Fig. 1 wherein the complementary pairs of connected parts are denoted '140', '142', & '144'). Since each tool that is so coupled is also hydraulically coupled to the remainder of the hydraulic circuit 400 by way of the conduit system 410, each tool that is 'parked' on the auxiliary vehicle 250 with its respective hydraulic coupling part connected to one of the coupling parts 412 will be constantly exposed to the pressure of hydraulic fluid in the reservoir 224, and consequently continuously be pressurised substantially to the depth-dependent pressure of surrounding seawater. This pre-pressurises each tool ready for use immediately on being connected to the hydraulic circuit of the ROV 300. (Four female hydraulic coupling parts 412 were shown in Fig. 13 by way of example; different pluralities of couplings can be provided and used as may be necessary or desirable.)

The pump 414 previously referred to is mounted adjacent the row of coupling parts 412. The pump inlet 416 is permanently coupled to the conduit system 410 through a non-return flow control valve 418 that permits flow from the conduit system 410 to the pump inlet 416 while preventing the return of hydraulic fluid from the pump inlet 416 back into the conduit system 410. The pump 414 can be mechanically operated (i.e. rotated or reciprocated, according to pump type) by movement of a handle 420 as will subsequently be detailed. The pump outlet 422 is hydraulically coupled by way of a conduit 424 and a hose 426 to a male hydraulic coupling part 428. A further female coupling part 430 is mounted on the auxiliary vehicle alongside the row of coupling parts 412. The coupling parts 428 and 430 are mutually complementary, and the part 430 serves as a 'parking slot' for the coupling part 428 in the same manner as the coupling parts 412 serve for the tool-coupled coupling parts. A handle 432 on the male coupling part 428 allows the coupling part 428 to be manipulated for disconnection from the female coupling part 430 on the auxiliary vehicle 250 followed by reconnection of the coupling part 428 to the complementary female coupling part 308 on the ROV 300.

When it is desired to replace hydraulic fluid that has leaked from the ROV 300, the ROV is manoeuvred up to the auxiliary vehicle 250 (as depicted in Figs. 7 & 8), the ROV manipulator 302 is operated to bring the grasping device 304 up to the handle 432 (similar to the procedure depicted in Figs. 9 & 10) for removal of the coupling part 428 from the complementary 'parking' part 430 and reconnection of the coupling part 428 into the complementary coupling part 308 on the ROV 300 (similar to the procedure depicted in Fig. 11). The grasping device 304 is then freed from the coupling handle 432, the ROV manipulator is operated to attach the grasping device 304 to the pump handle 420 on the auxiliary vehicle 250, and the ROV manipulator 302 is operated to rotate or reciprocate the pump handle 420 (as appropriate) and thereby actuate the pump 414 to transfer hydraulic fluid from the hydraulic circuit 400 on the auxiliary vehicle 250 into the hydraulic circuit of the ROV 300. When the hydraulic fluid in the hydraulic circuit of the ROV 300 is replenished, the above procedure is reversed to disconnect the coupling part 428 from the ROV coupling part 308 and re-park the coupling part 428 in the 'parking' part 430 on the auxiliary vehicle 250. The ROV 300 can then pick up a tool from the auxiliary vehicle 250 (as depicted in Fig. 12) and reliably operate the tool without having to make a time-consuming return journey to the surface and back again solely for the^' purpose of replacing hydraulic fluid lost by leakage from the ROV.

Refeiring now to Fig. 14, this is a schematic diagram of the hydraulic circuit 500 on the ROV 300. The hydraulic power supply of the ROV 300 is a closed hydraulic circuit including a hydraulic pump 502 driven by an electric motor 504 powered by on-board batteries (where the ROV is untethered and free-ranging) or by electricity delivered to the ROV through an umbilical (where the ROV is tethered). (The pump 502 and motor 504 may be dispensed with if the ROV is directly fed with pressurised hydraulic fluid through an umbilical). The pump inlet 506 is fed from an on-board hydraulic fluid tank 508, to which the fluid leaving in-use tools is returned along low-pressure collection conduit 510. The high-pressure hydraulic fluid delivered from the pump outlet 512 along high-pressure conduit 514 is controlled by two closed-centre change-over valves 516 within a first valve block 518. The valves 516 selectively pressurise either 'A' or 'B' conduits in the hydraulic coupling part 308, while depressurising the alternate one of these conduit pairs, according to control signals applied to the valves 516 by the ROVs human operator. Thus it is possible to provide remote control of two distinct hydraulically powered functions in a tool (not shown in Fig. 14) connected to the coupling part 306 (e.g. as in Fig. 12).

When the valves 516 are both in their central closed configurations (as depicted in Fig. 14), both 'A' and 'B' conduits are depressurised through respective ones of a bank 520 of four normally open bleed valves 522, by way of a low-pressure collection conduit 524 leading to the reservoir tank 508. Prior to either of the valves 516 being controlled to either of their off-centre pressure-transmitting configurations, a further control valve 526 in a second valve block 528 is operated to transmit hydraulic pressure from the high-pressure conduit 514 along bleed valve control line 530 to force each of the normally-open bleed valves 522 to a closed position, and hence to cease bleeding off all pressure in the 'A' and 'B' conduits leading to the coupling part 308. Thereupon, either or both of the valves 516 can be switched to cause pressurisation of selected conduits in the coupling part 308, and hence cause remotely controlled operation of whichever tool is currently connected to the coupling part 308.

For the purpose of allowing replenishment of hydraulic fluid in the ROV reservoir 508 (e.g. in the event of leakage), the coupling part 306 has an additional conduit denoted 'C in Fig. 14 that is connected by linlc conduit 532 to the low-pressure collection conduit 524 leading to the reservoir tank 508. For replenishment, the coupling part 428 is unplugged from the coupling part 430 on the auxiliary vehicle 250 (Fig. 13) by suitable operation of the ROV-mounted manipulator 302 acting on the handle 432, and the coupling part 428 is then plugged into the 'C conduit in the coupling part 308 (Figs. 11 & 14). Upon completion of replenishment, the coupling part 428 is unplugged from the coupling part 308 and returned to its parking position in the coupling part 430. The conduits 524 and 528 can also be used to drain the hydraulic circuit 500 when required. The ability to make good losses due to leakage, but without having to return the ROV to the surface, allows a valuable increase in the duration of ROV duty cycles in comparison to ROVs not provided with means for replacing lost hydraulic fluid.

A further valuable increase in the underwater duration of the ROV can be achieved by fitting the hydraulic circuit 500 with a filter system 600 (Fig. 15) that separates water from hydraulic fluid. This filter system 600 (shown in Fig. 15 separately from the hydraulic circuit 500) allows the separation of seawater that has entered the hydraulic system 500 (e.g. due to leaks and/or due to trapping of water between hydraulic coupling parts during their connection), and delays (at least until the water capacity of the filter system is reached) return of the ROV 300 to the surface for de-watering or replacement of the stock of hydraulic fluid on board the ROV. The filter system 600 comprises a pressure-tight filter housing 602 holding a filter cartridge 604 through which possibly water-contaminated hydraulic fluid passes from an inlet 606 to an outlet 608. Fluid is delivered from a suitable point in the ROV hydraulic circuit 500 to the filter system 600 through a quarter-inch hose 610 and a manually operable isolating valve 612. In a pressure control and monitoring hydraulic sub-circuit 614 forming part of the filter system 600, newly delivered fluid first passes through a pressure- compensated flow control valve 616 and is then fed to the filter inlet 606 for passage through the filter cartridge 604, eventually being discharged from the filter outlet 608 to a return hose 618 leading via a check valve 620 back to the ROV hydraulic circuit 500. To cope with excessive back pressure in the filter housing 602 (e.g. due to choking of the filter cartridge 604), the sub-circuit contains a pressure relief valve 622 that shunts the filter input 606 directly to the filter output 608 when the filter back pressure exceeds a predeteπnined limit. Fluid losses associated with on-board de- watering of the hydraulic fluid can be compensated by replenishment of the ROVs stock of hydraulic fluid from the hydraulic fluid reservoir 224 on the auxiliary vessel 250. During use of the filter system 600, the remaining water-separation capacity of the filter system 600 can be monitored by using a video camera (not shown) to view an in-built manometer 624 coupled by way of a sample point 626 to the filter inlet 606 so as to measure pressure drop across the filter system 600 during its operation. During setting up of the filter system 600, air is bled from within the housing 602 through an air bleed valve 628 fitted in a lid 630 of the housing 602. The filter housing 602 and its filter cartridge 604 can be constituted by a suitably adapted form of the "Oscar H350-S" filter, and mounted on the ROV 300 by means of the U-shaped mounting bracket 632 of the "Oscar H350-S" filter.

Fig. 16 is a schematic diagram of part of a hydraulic circuit 700 that can be substituted for the auxiliary vehicle hydraulic circuit 400 shown in Fig. 13. As before those parts of the hydraulic circuit 700 that are identical or functionally analogous to parts of the hydraulic circuit 400 as described above with reference to Fig. 13 are given corresponding reference numerals.

Compared to the circuit 400 of Fig. 13, the circuit 700 of Fig. 16 has three coupling parts 712, the rotary pump 414 is replaced by a double-acting single-cylinder reciprocating piston pump 714, and the mechanical pump drive input 420 is replaced by a hydraulically-powered linear actuator 720. The actuator 720 is hydraulically operated to drive the pump 714 when the coupling part 728 is disconnected from the coupling part 730 and plugged into the ROV hydraulic circuit 500 by way of the coupling part 308. To allow for the pump 714 now being a double-acting reciprocating pump, the single check valve 418 is replaced by a flow-rectifying quadruple check valve bridge 718. The twin-accumulator reservoir 224 is replaced by a single spring-loaded compensator 724 that may be constituted by the West Tech "WT-3-1001" hydraulic compensator previously refeπed to. The internal hydraulic connections 710 of the hydraulic circuit 700 are mutually interconnected through a manifold 734 that does not have a direct counterpart in the hydraulic circuit 400.

Fig. 17 is a schematic diagram of part of a hydraulic circuit 800 that can be substituted for the auxiliary vehicle hydraulic circuit 500 shown in Fig. 14. As before, those parts of the hydraulic circuit 800 that are identical or functionally analogous to parts of the hydraulic circuit 500 as described above with reference to Fig. 14 are given corresponding reference numerals.

A principal difference in the part of the hydraulic circuit 800 shown in Fig. 17 compared to the circuit 500 shown in Fig. 14 is the substitution of the ROV hydraulic fluid tank 508 by a spring-loaded hydraulic compensator 808, with the consequence that the return connections of the circuit 800 are permanently pressurised (in the absence of significant leakage of hydraulic fluid). In the circuit 800, the connector 308 can comprise a plate-mounted aπay of five female coupling parts of the previously described "4V54X5X4" type from Parker Fluid Connectors.

As an alternative to the use of auxiliary vehicles in the forms of the baskets 100 and 200 augmented by hydraulic fluid sources capable of pre-pressurising underwater tools, other forms of tool carrier means may be employed in accordance with the invention. For example, tool carrier means can be constituted by the unaugmented baskets 100 & 200, or by simple tool clips on a support member hanging from the lower end of a cable or other suitable form of tether, preferably with provision for pre-pressurisation as previously described. While certain alternative forms of the invention have been described above, the invention is not restricted thereto, and (for example) the shape, dimensions, and geometry of the auxiliary vehicle can be modified as required. The number, function, and capacity of the various hydraulic lines can be varied from those described above, and selected to suit the requirements of tasks to which the invention is to be applied. The invention can be used for all types of submarine operations hitherto conducted by conventional ROVs, for example for assisting the on-seabed connection of submarine pipelines and/or other submarine equipment, e.g. by tie-in connections, pull-in connections, etc. The present invention can be used without depth limitation. Other modifications and variations of the invention can be adopted without departing from the scope of the invention as defined in the appended claims.

The method can be applied and apparatus used beneficially in oil & gas field discovery and development (sub-sea construction/operation/maintenance etc) in depths beyond 300m or where use of unmanned vehicles is desirable, particularly in light of the potential danger faced by any human divers.

Claims

CLAIMS:

1. In a first aspect of the invention there is a method of connecting a hydraulically operated tool to a remotely operated vehicle (ROV) while the ROV is at an underwater location, the tool not being initially earned to the underwater location by the ROV, the method comprising the steps of transporting the tool to the underwater location on a tool caπier receptacle independent of the ROV, transferring the tool from the tool caπier receptacle to the ROV, and connecting the transfeπed tool hydraulically to the ROV in an operational configuration, wherein said tool caπier receptacle incorporates a hydraulic fluid source and said tool is pre-pressurised by said tool caπier receptacle prior to connection to the ROV.

2. A method as claimed in claim 1 wherein said tool is pre-pressurised when hydraulically coupled via coupling means to said tool carrier receptacle.

3. A method as claimed in claim 2 wherein said coupling means are of the self- sealing type.

4. A method as claimed in any of claims 1 to 3 wherein said tool is pre-pressurised to ambient fluid pressure by action of the suπounding seawater on hydraulic fluid.

5. A method as claimed in any of claims 1 to 4 further comprising a step of replenishing hydraulic fluid of the ROV from a source of hydraulic fluid caπied on said tool carrier receptacle.

6. A method as claimed in claim 5 wherein said replenishing step includes mechanically driving a pump on the tool caπier receptacle using an actuator of the ROV.

7. A method as claimed in any preceding claim wherein the tool caπier receptacle is suspended from a ship or platfoπn and comprises an auxiliary underwater vehicle.

8. A method as claimed in claim 7 wherein said auxiliary underwater vehicle is suspended by means of a winch or crane, said winch or crane being the only means of recovery/deployment, said vehicle having no propulsion means and requiring no external power or control to operate.

9. A method as claimed in claim 8 wherein said underwater vehicle takes the form of a basket.

10. A method as claimed in any preceding claim, wherein a further tool is already connected to the ROV, the method comprising the preliminary steps of disconnecting the further tool from the ROV, transferring the further tool to a tool-supporting location on the tool earner receptacle.

11. A method as claimed in claim 10 wherein said further tool is connected to a hydraulic fluid source on the tool carrier receptacle to maintain pressurisation ready for re-use.

12. A method as claimed in any of claims 1-11 further comprising filtering hydraulic fluid of the ROV to counteract ingress of water, without returning the ROV to the surface.

13. A method as claimed in claim 12 wherein said filtering step uses a filter incorporated in said ROV.

14. Apparatus for the transportation of tools to an underwater location, said apparatus comprising a tool carrier receptacle having a hydraulic fluid source and means for connection of a hydraulically operated tool to said hydraulic fluid source such that said tool is pre-pressurised prior to transfer of said tool to an operational hydraulic supply.

15. Apparatus as claimed in claim 14 wherein said tool caπier receptacle comprises an auxiliary underwater vehicle adapted for suspension from a ship or platform.

16. Apparatus as claimed in claim 15 wherein said vehicle is passive, having no propulsion means and requiring no external power or control to operate.

17. Apparatus as claimed in claim 15 or 16 wherein said vehicle takes the form of a basket.

18. Apparatus as claimed in claim 17 wherein said basket incorporates a transverse vertical partition means subdividing the interior of the basket into two or more horizontally adjacent compartments.

19. Apparatus as claimed in claim 16 or 17 wherein said basket includes at least one movable lid means for temporarily enclosing the interior of the basket or a compartment thereof.

20. Apparatus as claimed in claims 17 to 19 wherein said basket has hinged sides for selective opening or closing of the basket sides.

21. Apparatus as claimed in claim 14 to 20 wherein said tool pre-pressurisation is to ambient fluid pressure by action of the surrounding seawater on the hydraulic fluid.

22. Apparatus as claimed in claims 14 to 21 wherein there is further provided hydraulic fluid transfer means selectively operable when said apparatus is hydraulically coupled to an ROV, to enable transfer of hydraulic fluid from said apparatus to the hydraulic circuit of the ROV.

23. Apparatus as claimed in claim 22 wherein the hydraulic fluid transfer means comprises hydraulic pump means.

24. Apparatus as claimed in claim 22 or 23 wherein the hydraulic pump means is operable by use of a manipulator mounted to the ROV.

25. A remotely operable vehicle (ROV) for use underwater, the ROV mounting hydraulically powered equipment and incorporating a hydraulic circuit, said hydraulic circuit incorporating a filter means being operable to separate water from hydraulic fluid while the ROV remains at an underwater location.

26. An ROV as claimed in claim 25 wherein said hydraulic circuit further includes a source of hydraulic power for operating said equipment.

27. An ROV as claimed in claim 25 wherein said hydraulic circuit obtains hydraulic power for operating said equipment from a surface vessel or platfoπri via an umbilical.

28. An ROV as claimed in claims 25 to 27 wherein said ROV incorporates manipulator means capable of being operated mechanically and hydraulically to disconnect a selected tool initially supported by the tool caπier receptacle, to enable transfer of the selected tool from the tool caπier receptacle to the ROV and vice versa.