GB2473165A

GB2473165A - Oil spill recovery vessel having an oil transfer bollard and oil spill recovery method

Info

Publication number: GB2473165A
Application number: GB1021012A
Authority: GB
Inventors: Paul F Jauncey
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-07-09
Filing date: 2010-12-13
Publication date: 2011-03-02
Anticipated expiration: 2030-12-13
Also published as: GB2473165B; GB201011645D0; GB201021012D0

Abstract

An oil spill recovery vessel 10 equipped with a skimmer unit 11 moves forward through an oil spill at a normal skimming speed with its skimming unit operating to recover oil, and simultaneously transfer recovered oil through an oil transfer hose 17 to a bladder 19 being towed by the vessel using a towing cable 14. The oil transfer hose 17 and towing cable 14 attach to an oil transfer bollard 15 of the vessel. The bollard 15 is situated substantially on the fore-aft centreline of the vessel, at least one third of the vessel's length from the stern or more forwardly. The bollard 15 comprise a towing post for attaching the towing cable for the towed storage, and an oil transfer pipe with a hose coupling for connecting to the oil transfer hose. Later embodiments relate to an oil transfer bollard and an oil spill recovery method.

Description

Oil Spill Recovery Method, Vessel and Apparatus

BACKGROUND

[0001] Oil spills at sea, in lakes, rivers, harbours, marinas or coastal areas are a serious environmental hazard. Wild life, marine life and coastal welfare, including commercial businesses, are at risk with each and every incident.

[0002] In responding to an oil spill, critical factors are speed of response and operational efficiency. These factors tend to favour the use of small skimmer-equipped vessels that can be rapidly transported to the area of an oil spill, can work multiple environments (lakes, rivers harbours and at least inshore), and with the use of the latest drum skimmer technology, are reasonably efficient in recovering oil. In contrast, large oil spill recovery vessels generally take longer to respond as they must make their own way by sea to the area of the oil spill, and are operationally limited to deep water. Larger vessels do, however, typically have the capability to sustain their oil recovery operations over longer periods not least because they have much larger storage tanks for recovered oil than can be installed on smaller vessels.

[0003] The limited oil storage capacity of many of the current types of small oil spill recovery vessels requires them to periodically cease operation while they transfer recovered oil either to another ship or to a land-based facility. Increasing the size of onboard oil storage tanks has the disadvantage of increasing fuel costs and limiting operational range; furthermore, the use of deck-carried oil storage bladders or tanks has an adverse effect on stability which can be a serious issue at sea. Using a floating oil storage bladder directly coupled to the oil recovery vessel, is also not a good solution as it severely restricts manoeuvrability.

[0004] It is an object of the present invention to provide an oil spill recovery vessel that has improved operational efficiency.

SUMMARY OF THE INVENTION

[0005] According to one aspect of the present invention, there is provided an oil transfer bollard unit for mounting on an oil spill recovery vessel for use in transferring recovered oil from the vessel to towed storage while the vessel is in motion, the oil transfer bollard comprising: a towing post for attaching a towing cable for the towed storage, and an oil transfer pipe having an outlet portion with a hose coupling by which an oil transfer hose can be coupled to the transfer pipe to transfer oil from the vessel.

[0006] According to another aspect of the present invention, there is provided an oil spill recovery vessel including an oil transfer bollard for use in transferring recovered oil from the vessel to towed storage while the vessel is in motion; the oil transfer bollard being disposed substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stern or more forwardly; the oil transfer bollard comprising: a towing post for attaching a towing cable for the towed storage, and an oil transfer pipe having an outlet portion with a hose coupling by which an oil transfer hose can be coupled to the transfer pipe to transfer oil from the vessel.

[0007] According to a further aspect of the present invention, there is provided an oil spill recovery method in which a vessel equipped with a skimmer unit moves forward through an oil spill at a normal skimming speed with its skimming unit operating to recover oil, and simultaneously transfers recovered oil through an oil transfer hose to a bladder being towed by the vessel using a towing cable; the oil transfer hose and the towing cable attaching to the vessel in the same general location situated substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stern or more forwardly.

BRIEF DESCRIPTION OF THE DRAWINGS

100081 Embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a diagram illustrating operation of an oil spill recovery vessel embodying the invention, with oil recovered by a skimmer sub-system of the vessel being transferred to a towed bladder; Figure 2 is a side elevation of the Figure 1 oil spill recovery vessel; Figure 3 is a plan view of the Figure 1 oil spill recovery vessel; Figure 4 is a plan view, similar to Figure 3, showing the internal layout of the Figure 1 oil spill recovery vessel; Figure 5 is a side elevation, similar to Figure 2, but with the nearside hull removed to show the internal layout of the Figure 1 oil spill recovery vessel; Figure 6 is a side elevation of an oil transfer bollard used on the Figure 1 oil spill recovery vessel; Figure 7 is an elevational view of the Figure 6 oil transfer bollard taken in a direction looking forward relative to the installed orientation of the bollard on the Figure 1 oil spill recovery vessel; Figure 8 is a plan view of the Figure 6 oil transfer bollard; Figure 9 is a side elevation of the Figure 6 oil transfer bollard illustrating operational use of the bollard; Figure 10 is a side elevation of first and second variants of the Figure 6 oil transfer bollard; Figure 11 is a side elevation of third and fourth variants of the Figure 6 oil transfer bollard; and Figure 12 is a side elevation of a fifth variant of the Figure 6 oil transfer bollard.

DETAILED DESCRIPTION

100091 Figure 1 depicts an oil spill recovery vessel (OSRV) 10 embodying the invention in a preferred operational mode in which a skimmer unit 11, carried between twin hulls of a catamaran bow section 12 of the OSRV 10, recovers oil from an oil spill 6 on a body of water 5 as the OSRV moves through the oil spill, the recovered oil then being transferred to a towed bladder 19 without interruption of the skimming operation; in this mode of operation, the recovered oil is not stored on the OSRV 10 though it may undergo some processing aboard, for example, to separate out water which the skimmer unit may output along with the recovered oil. The bladder 19 is towed by a towing cable 14 attached to a towing post of an oil transfer bollard 15 (described in detail hereinafter) mounted on an aft towing deck 16 of the OSRV. Recovered oil is transferred to the bladder 19 through a flexible oil transfer hose 17 that is attached at one end to a oil transfer pipe forming part of the oil transfer bollard 15, and at its other end to a hose coupling integral with the bladder 19; along its length the hose 17 is suspended from the towing cable 14 by slip rings.

[0010] The general form of the OSRV 10 is illustrated in Figures 2 and 3. Aft of the catamaran bow section 12 with the skimmer unit 11, the OSRV comprises a trimaran main section 13 in which a central hull 20 is interposed between the aft continuations of the twin hulls 21, 22 of the catamaran bow section 12. The triple hulls 20, 21, 22 of the trimaran main section 13 have conjoined upper portions with the depth of this conjoining increasing aftwards whereby to define two flow channels 24, 25 of decreasing cross-sectional area between the hulls.

[00111 When in the process of oil recovery using the skimmer unit 11, the OSRV 10 operates at slow speed (1-3 knots) and the hulls 21, 22 of the catamaran bow section 12 serve to channel the oil to be recovered to the skimmer unit 11; at the same time, the channels 24, 25 formed between the central hull 20 and the outer hulls 21 and 22 of the trimaran main section 12 help the flow through of water passing under or around the skimmer unit thereby minimizing pile up of the water in front of the skimmer unit 11.

[0012] When oil is not being recovered, the skimmer unit 11 can be raised clear of the water 5 enabling the OSRV to proceed at a fast speed (for example, 18-20 knots) and thereby minimize transit time to and from an oil spill. When the OSRV 10 is operating at its fast speed, the trimaran section of the vessel will cause it to plane partially lifting the bow section hulls 21, 22 and keeping the wetted areas to a minimum thereby reducing drag.

[0013] Regarding the general above-water arrangement of the OSRV 10, the catamaran bow section 12 and the front part of the trimaran main section 13 provide a raised fore deck 26. Most of the deck area of the main section 13 serves as the towing deck 16 on which the oil transfer bollard 15 is located; the towing deck 16 is at a lower level than the fore deck 26. A wheelhouse structure 27 is located on the front part of the trimaran main section 13 and provides the upper part of a wheelhouse; the wheelhouse extends down into the main section 13 such that the floor of the wheelhouse is substantially at the level of the towing deck 16.

[0014] The aft end of the towing deck 16 merges with a scooped transom 29 that slopes downwards towards the stern. An aft deck rail 30 is arranged to fold down from an upright position shown in Figure 2 to a towing-operation position shown in Figure 3 in which it lies against the scooped transom 29. The aft deck rail 30 is moved between its upright and towing-operation positions by hydraulic cylinders 31. The rail 30 is, for example, made from 38mm alloy tube and has a height of approximately im when in its upright position. The rail is slightly curved in the middle to match the curvature of the scooped transom.

[0015] The hull and wheelhouse structure are, for example, made of FRP (fibre reinforced plastic) though other materials, such as aluminum can alternatively be used. Where FRP is used, the bow and main sections 12 and 13 are treated as one and formed as two moldings, that is, a deck molding (including an uppermost portion of the hull), and a middle-and-lower hull molding; these moldings are arranged to fit closely together and a rub strake is used to cover the join.

[0016] Typical dimensions for an OSRY 10 of the above described form are: LOA 8.85m Beam 2.55m Draft (nominal) O.45m Freeboard at foredeck 1.52m Freeboard at towing deck 0.96m Height from keel to wheelhouse top 3.25m A vessel of such dimensions appropriately fabricated from FRP and fully fitted out would typically have: Weight when lifted (trailer weight) 3.00 Tonnes Displacement laden 3.50 Tonnes and be Llyods Register / American Bureau of Shipping (ABS) certifiable to 60 nautical miles from shore or from a mothership (daylight operation), that is, capable of handling 2m waves; as used herein "offshore seaworthiness" means seaworthiness to this level of Llyods/ABS certification.

[0017] It will be appreciated that the hull forms can be varied from those illustrated.

100181 Figures 4 and 5 show the general disposition within the OSRV 10 of its propulsion system and central service equipment (hydraulic and electrical power).

[0019] A marine diesel engine 50 (for example, 250HP (184kw) 4200rpm supercharged marine diesel) serves both to provide propulsive power and power for the central services.

Fuel is supplied to the engine 50 from a fuel tank 51 located between fireproof bulkheads 40, 41. The compartment defined by the bulkheads 40, 41 also houses two oil separators and tanks for hydraulic fluid.

[0020] The propulsion system comprises a water jet drive unit 53 (such as the Ultra-Jet 251 jet drive) powered from the engine 50 via a transmission (such as an Aquadrive transmission from Mack Boring & Parts Co, NJ, USA) comprising a shaft with a constant velocity joint fitted to each end. One of these joints couples to the jet drive unit 53, and the other to a reversible hydraulic marine gearbox 52 (such as the PRM 750 from PRM Marine Ltd, UK). The water intake for the jet drive unit 53 is directly below it and is protected by a screen 58. The water jet outlet is a large central duct through the stem of the vessel just on the water line. Steering is effected by a hydraulically operated steering cylinder which moves a deflector plate 59 to direct the water jet produced by the unit 53 to port or starboard. The jet drive outlet and steering deflector are protected by the transom overhang during the launch and recovery of towed bladders. All controls for the engine 50 and water jet unit 53 are located in the wheelhouse.

[0021] The water jet from the jet drive unit 53, as well as providing propulsion, also serves to entrain the oillwater mix that by-passes the skimmer 11 and passes beneath the OSRV (principally via channels 24, 25); this entrainment helps to prevent a "pile up" of oillwater at the front of the OSRV.

[0022] As the transmission from the engine 50 to the water jet unit 53 is reversible, the flow of water through the unit 53 can be reversed to enable "back-flushing" of the jet drive intake screen 58 in the event of blockage by debris; this eliminates the need to dive under the boat to clear debris which can be hazardous in certain environments (for example, swamplands where alligators may be present or at sea in shark infested waters).

[0023] The propulsion system is selected to give a speed of the order of 18-20 knots for transit to/from an oil spill site and a slow seed of 1-3 knots for use when skimming to recover oil. Typical range is of the order of 180 nautical miles.

[0024] Regarding the central services, dual pressure hydraulic power is provided by two tandem mounted hydraulic pumps 55 driven by a transmission mounted power take off unit 54 (alternatively, this power take off may be integral with the gearbox 52). The hydraulic pump 55 supplies a central pressurised ring main (not shown, but typically stainless steel tube or similar) that distributes hydraulic pressure around the vessel; the pressurised ring main is matched by a corresponding return ring main. Drip-less quick release pressure/return connectors are strategically installed around the pressurised ring main for powering standard-supply or optional equipment. One use of this hydraulic power is to drive a hydraulically powered electric alternator unit 56 providing 110 volt ac supply as a central service; advantageously, the alternator is a synchronous spark free alternator.

Another use of the power provided by the central hydraulic service is to power the skimmer unit 11 and an associated lifting arrangement. Other equipment that can conveniently be powered from the central hydraulic service includes pressure washing equipment, power capstans, fire fighting pumps and/or other ancillary equipment/controls, by simply "plugging in".

Oil Recovery System [0025] The oil recovery system of OSRV 10 comprises the skimmer unit 11, the on-board oil handling and processing system (including the oil separators 100), and the oil transfer bollard 15. Before describing the oil transfer bollard in detail, a general description of the oil recovery system will first be given with reference to Figures 4 and 5 (certain external features of the OSRV, such as the aft deck rail 30, have been omitted from these Figures so as not to obscure internal layout details).

[0026] As already noted, the skimmer unit 11 can be raised out of the water when not needed (the position of the unit 11 when raised is shown in dashed outline in Figure 5), and subsequently lowered back into its operating position (shown in full lines in Figure 5).

Raising and lowering of the skimming unit is effected by a lift arrangement 80 powered from the central hydraulic service. The skimmer unit 11 is, for example, a floating drum oil skimmer such as the Elastec TDS 11 8G model available from Elastec / American Marine, L, USA; this model has a maximum collection rate of 78 US gallons per minute (16 tonnes per hour).When in its operational position, the skimmer unit is free-floating but constrained in position by a cat's cradle' of wires. Other types of skimmer and installation arrangement can alternatively be used.

[0027] Oil recovered by the skimmer unit 11 is pumped away from the unit through flexible hose 60 and then through fixed pipe-work 60 to a directional manifold valve 62 that permits the recovered oil, still with a small amount of water (e.g. 3%), to be selectively fed either direct to the oil transfer bollard 15 for transfer to a towed storage bladder 19 (as depicted in Figure 1), or first to the separators 100 for removal of most of the remaining water and from there, via pumps 63 and valves 64 (only referenced in Figure 5 in respect of one of the separators 100) to the oil transfer bollard 15. Preferably, the valves of the directional manifold valve 62 and the valves 64 operate on an interlocked basis to ensure only permitted flows are possible.

[0028] Various forms of oillwater separator are known and all generally rely on the fact that, as the specific gravity of oil is around 0.9, oil will float on water enabling it to be separated. The separators 100 may be of any form and may operate either in a continuous mode in which is drawn off continuously (that is, the suction pumps 63 are operated all the time), or in an intermittent, cyclic, mode in which oil is drawn off on an intermiftent basis.

More particularly regarding intermittent mode operation, each separator 100 is, for example, provided with upper and lower oil-level sensors respectively arranged to detect the oil level in the separator rising to an upper level, and falling to a lower level; oil is sucked out of the separator (by activation of the corresponding pump 63) commencing when the oil level reaches the upper level detected by the upper oil-level sensor, and subsequently terminating when the oil level falls to the lower level detected by the lower oil-level sensor.

Oil Transfer bollard [0029] Oil recovered by the skimmer unit 11 is pumped either directly, or via the separators 100, to the oil transfer bollard 15. As depicted in Figure 1, the bollard 15 is fixed in position on the towing deck 16 of the OSRV 10 substantially on the fore-aft centreline of the latter and halfway between front of the centre hull 20 and the transom. The oil transfer bollard 15 provides the means to transfer recovered oil, via a transfer hose 17, to a floating 19 bladder, and simultaneously to tow the bladder 19, without impairing steerage, using a towing cable 14. With the towing cable 14 appropriately shorter in length than the transfer hose 17, the cable will take the frill load of the towed bladder 19 thereby avoiding strain on the hose 17. Both hose 17 and cable 14 flex/pivot at substantially the same point, namely, the bollard 15 whereby ease of steerage is maintained as the OSRV 10 can effectively swivel around the bollard 15. Use of the oil transfer bollard 15 means that operation of the OSRV 10 is not compromised by only being able to store recovered oil to onboard storage tanks or bladders; instead, oil can be transferred off the OSRV continually while skimming (apart from occasional pauses to change bladders when the currently-towed bladder becomes full).

[0030] The construction, installation and usage of the oil transfer bollard 15 is further described below in respect of an embodiment where the bollard takes the form of a stand-alone unit that can be mounted on a vessel as and where desired (as opposed to an oil transfer bollard constructed in situ).

[0031] Referring to Figures 6 to 8, the unit-form oil transfer bollard 15 (hereinafter "bollard unit 15") comprises a base plate 150 provided with bolt holes 151 to enable the bollard unit 15 to be bolted to any sturdy deck area.

100321 A rigid, curved, oil transfer pipe 152 extends upwards through a central hole in the base plate 150 and is welded (or otherwise secured to) the base plate, The upper end portion of the pipe 152 curves round from the vertical to the horizontal. The lower end of the oil transfer pipe is provided with an oil entry coupling 154 and the upper end is provided with an oil outlet coupling 153 -preferably, standard universal quick release hose connections are used for the couplings 153, 154. When the bollard unit 150 is installed on a deck, the oil inlet coupling will be located below the deck for connection to a pipe or hose that serves to supply recovered oil to the bollard unit 15.

[00331 A towing post 156 is welded (or otherwise securely fixed) to the upper part of oil transfer pipe 152 coaxially with the latter. The towing post 156 is rigidly supported by front and rear vertical gussets 157 that serve to substantially eliminate tow loading on the oil transfer pipe 152 when the bollard unit 15 is being used to tow a bladder. The towing post 156 has a pair of vertically spaced orthogonal cross bars 158 to locate the towing cable.

[00341 The bollard unit 15 can be manufactured from a range of materials. Rather than fabricating the bollard unit, it can be cast using bronze, stainless steel or other suitable material. The height of the bollard unit 15 is chosen to provide adequate cable clearance when under load above the aft deck structure of the vessel for which the bollard unit is intended; a typical height from deck to the lower cross bar 158 is 0.5m.

100351 The bollard unit 15 is installed by securing it to any sturdy, flat deck area or to a cambered deck area by use of pre-formed solid packing. At least on small vessels, the bollard unit 15 is optimally mounted on the fore-aft centreline of the vessel, approximately centrally (that is, centre of gravity � 10% of the vessel's length) or more forwardly. The position of the bollard can be moved more towards the stem but this progressively increases the difficulty of steering when towing a bladder; the bollard should be at least one third of the vessel's length from the stem for adequate steering performance. In the present embodiment, securing the bollard unit to the deck of a vessel simply involves bolting the unit in position (with the oil outlet coupling 153 of the oil transfer pipe 152 facing aft) using bolts passed through the holes 151 of the base plate 150 and corresponding holes in the deck. Additional bolt holes can be drilled as required. With the bollard unit 15 secured in position, the oil inlet coupling 154 can be connected up to the pipe or hose that will provide the recovered oil directly or indirectly from the skimmer unit.

[0036] To put the oil transfer bollard 15 to use, a towing cable 14 is looped over the towing post 156 of the bollard 15 and located between cross bars 158 to prevent it sliding up or down the post (see Figure 9). The other end of the cable 14 is connected to a bladder to be towed (the bladder itself will generally be provided with a towing harness to which the cable can easily be coupled). An oil transfer hose 17 is connected to the outlet coupling 153 of the oil transfer pipe 152 of the bollard 15 using a coupling 171 that is integral with the hose and of complementary form to the outlet coupling 153. The opposite end of the oil transfer hose 17 is directly connected to an input of the towed bladder. As already noted, the towing cable 14 must be of a lesser length than the oil transfer hose 17 to avoid strain on the hose. Preferably, the hose 17 is supported along its length (or at least over its portion above the towing deck 16) by rings, cable ties, or the like, generally referenced 172 in Figure 9, that pass around the hose 17 and cable 14, and allow relative slippage of the hose and cable.

[0037] When the OSRV 10 is operating to recover oil (moving slowly ahead with the skimmer unit ii in its lowered position and powered on), then assuming the oil flow control valves are appropriately set to supply recovered oil to the oil transfer bollard either directly from the skimmer unit 11 or indirectly via the separators 100, oil will be pumped through the oil transfer pipe 152, into the transfer hose, and across into the towed bladder 19 for storage.

[0038] As already mentioned, ease of steerage is maintained when towing a bladder as the OSRV can still rotate around its central point where the oil transfer bollard is positioned.

The towing cable 14 and the hose 17 move in unison, with the towing cable pivoting about the towing post 156 and the hose flexing in a zone adjacent the transfer pipe 152. The towing load is taken by the towing cable 14 alone without loading the hose 17; the towing load is transferred from the cable 14 to the towing post 156 and from there through the gussets 157 to the deck of the towing vessel without any undue load being placed on the oil transfer pipe 152.

100391 When a towed bladder 19 is full, the oil recovery process is temporarily suspended while the bladder is capped, identified and set free for later collection. The hose and cable are easily disconnected from the towed bladder either by reversing the OSRV to the bladder or by winching the bladder to the boat using the towing cable; either way, the use ofjet drive propulsion effectively eliminates any risk of the towing cable becoming entangled with the OSRV. Once a full bladder has been detached, another, empty, bladder can then be connected and the oil recovery process continued. At a convenient time, the filled bladders that have been set free can be collected -for example, connected as a "necklace" and towed to shore for pump out.

100401 It may be noted that when the OSRV 10 is recovering oil in shallow locations, use of a towed bladder may be impractical due to surf, debris, or vegetation making steerage with a towed bladder very difficult. In this event, a conveniently-sized bladder can be securely installed on the towing deck 16 of the OSRV and directly coupled to oil outlet connection 153 of the oil transfer bollard 15. When full, this deck-carried bladder can be pumped out at a dock or into a tanker as with a skimmer vessel fitted with integral storage tanks for recovered oil.

[0041] The above-described form of oil transfer bollard provides a number of advantages several of which have already been mentioned. These advantages include simplicity of form with no moving parts, unit construction allowing ready installation on new and existing vessels; and elimination of the need to cany an on-board storage facility for oil recovered from an oil spill (the space freed up by not having to provide oil storage tanks can be utilised for the stowage of spare/empty bladders). The described arrangement for towing a bladder that is being filled provides much improved steerage as compared to having the bladder directly attached to a skimmer vessel. The used of towed bladders that are set free when full eliminates the need for constant trips to a shore-based pump-out facility and enables a suitably equipped OSRV to operate 24/7 (assuming a mother ship is on station to provide vessel re-fuelling, crew changes and a constant supply of replacement bladders).

100421 Many variants are possible to the above described form of oil transfer bollard. Thus for example, the bollard could be constructed in situ rather than being provided as a separate unit than can be bolted (or otherwise secured) in place. Furthermore, the measures taken to ensure that the towing post is sufficiently strong to take the towing load are not limited to the provision of gussets 157; for example other forms of bracing can be used or the towing post and the lower part of the transfer pipe can be made from materials and of a thickness as to be sufficiently strong without additional bracing. The oil transfer pipe 152 need not be rigid provided it provides a suitable coupling for connection to the transfer hose and it capable of taking a degree of tension.

[0043] In the form of oil transfer bollard described with respect to Figures 6 to 9, the operative flexing zone of the hose 17 (the portion immediately adjacent the outlet coupling of the oil transfer pipe 152 where the majority of flexing occurs on turning of the OSRV) is close to, but offset from, the axis of the towing post 156 about which the towing cable 14 pivots. A limited offset of this nature is not a problem as it does not substantially interfere with the cable and hose operating in unison as the OSRV turns. Accordingly, and as illustrated in Figure 10, it is possible to arrange for the oil transfer pipe 152 to be repositioned so that its lower portion is no longer co-axial with the towing post 156. In a first variant of the oil transfer bollard (depicted by the non chain-dashed portions of Figure 10), the lower, vertical, portion of the oil transfer post 152A is displaced aftwards of the towing post 1 56B (relative to its installed orientation) and the towing post and transfer pipe are independently connected to the base plate. In a second variant of the oil transfer bollard (depicted in Figure 10 by the towing post 156B and the chain-dashed oil transfer pipe 1 52B), the oil transfer pipe 1 52B is displaced forward of the towing post 1 56B (relative to its installed orientation) and, again, the towing post and transfer pipe are independently connected to the base plate.

[0044] There is no well-defined limit as to what size of offset is acceptable between the operative flexing zone of the oil transfer hose 17 and the axis of pivoting of the towing cable 14 -it is simply the greater the offset, the more cumbersome the whole arrangement becomes. A practical limit of approximately 2.0 m is considered realistic for the offset (taken to the approximate middle of the operative flexing zone of the oil transfer hose 17); this leads to a maximum separation between the towing post and the outlet coupling of the oil transfer pipe of about 1.5m depending on the flexibility of the hose when fransferring oil.

100451 It is to be noted that with the second variant of the oil transfer bollard, the operative zone of flexing of the transfer hose 17 connected to the oil transfer pipe 152B is actually closer to the axis of the towing post 156B than is the case for the form of bollard described with respect to Figures 6 to 9. By appropriate forward displacement of the oil transfer pipe 152B relative to the towing post 156B, it is, in fact, possible to bring the operative zone of flexing of the transfer hose 17 to lie above the towing post giving effectively zero offset between the axis of flexing of the oil transfer hose l7and the axis of pivoting of the towing cable 14.

100461 Instead of relying on hose flexibility to allow the oil transfer hose to accommodate turning of the OSRV when towing a bladder, it is alternatively possible to provide a rotatable upper portion to the oil transfer pipe of the oil transfer bollard. Figure 11 show two such oil transfer bollard variants, these being based on the first and second variants shown in Figure 10 but now provided with rotatable upper portions to the oil transfer pipe.

More particularly, a third bollard variant, based on the first variant of Figure 10 (oil fransfer pipe 152C displaced aftwards of the towing post 156C), has an upper portion 191C of the oil transfer pipe 1 52C rotatable relative to the vertical lower portion 1 92C -this rotation is provided for by a sealed rotatable joint 195C a bottom part of which is fixed to the base plate 150 of the bollard while a top part (which is rotatable relative to the bottom part) is fixed to the upper part 191C of the oil transfer pipe 152C). Figure 11 also shows a fourth bollard variant, based on the second variant of Figure 18 (oil transfer pipe 152C displaced forwards of the towing post 15 6D); in this variant, an upper portion 191 D of the oil fransfer pipe 1 52D (shown in chain-dashed lines) is also made rotatable relative to the vertical lower portion 192D by means of a sealed rotatable joint 195D.

100471 Figure 12 shows a further, fifth, bollard variant in which an upper portion 191 E of the oil transfer pipe 1 52E is made rotatable relative to the vertical lower portion 1 92E of the pipe 152E by means of a sealed rotatable joint 195E. In this variant, the axis of rotation of the upper portion 191 E of the oil transfer pipe 1 52E is the same as the axis of the towing post 1 56E. This is achieved by arranging for the towing post to double as the lower portion 1 92E of the oil transfer pipe; to this end the towing post 1 56E is provided with a central oil channel 200 (shown in dashed lines) and the post is dimensioned to be sufficiently strong despite this central channel. A sealed rotatable joint 195E has one part secured to the top of the towing post 1 56E and another part (rotatable relative to the first-mentioned part) connected to the upper portion 191E of the oil transfer pipe 152E. It will be appreciated that in use of this bollard variant, before the oil transfer hose 17 is connected to the upper portion 191E of the oil transfer pipe 152E, the towing cable 14 must first be placed in position by passing it over the upper portion 191E of the oil transfer pipe 152E and then down around the towing post 1 56E.

[0048] A further possible variant (not illustrated) of the oil transfer bollard would be to combine the rotatable joint of the third to fifth variants with a hose coupling to produce a vertical oil transfer pipe topped by one half of this combined rotatable-joint / hose-coupling, and an oil transfer hose that connects at one end, via a short right-angled section of pipe, with the other half of the combined rotatable-joint / hose-coupling. Mating the two halves of the combined rotatable-joint / hose-coupling produces a rotatable joint between the oil transfer pipe and the hose, the latter extending away at right angles from the oil transfer pipe.

[0049] Additional cross bars can be provided up the bollard tow post (with adjacent cross bars orthogonal to each other) thereby to provide a range of positions height-wise for locating the towing cable; this is useful to accommodate different types of bladders and their attachment points.

[0050] It is to be understood that the described oil transfer bollard (including its variants) can be used on any type of vessel though it is particularly suited for use on small skimming vessels (regardless of the location or type of the skimmer unit); when used aboard a large vessel, the oil transfer bollard can be mounted in positions other than centrally amidships.

[0051] Regarding the bladder towing cable, this is, for example, a 10mm diameter stainless steel cable. It will be appreciated that when loaded the towing cable could potentially chafe a significant groove into the OSRV deck. This is avoided in the present embodiment of the OSRV 10 by the following features: with respect to the transom 29, during towing operations the aft deck rail 30 is folded down against the transom 29 and serves as an anti chafe unit; the folded-down rail also guides the cable/hose combination "up and over" the bulwarks during a turning/manoeuvring situation; with respect to the bulwarks, these are capped with an alloy strip as protection from chafe.

Of course, proper choice of the length of towing cable used should ensure that when the cable is taut, it adequately clears the vessel. A typical suitable cable length would be such that the bladder is towed at a distance from the vessel of around 8m and generally no less than Sm (that is, at least approximately half the length of the OSRV 10). It should, however, be noted that no matter how large a clearance is theoretically provided for between the vessel and cable when towing, wave action on the vessel and bladder will always cause the cable to strike the vessel at times except in millpond conditions.

[0052] As already indicated, while it is intended that recovered oil will generally be transferred off the OSRV 10 to a towed bladder, the recovered oil may alternatively be transferred from the bollard 15 to a towing-deck-carried bladder, directly coupled to the oil transfer bollard, for storage or held temporarily in the separators 100.

[0053] Bladders are available from Elastec / American Marine, IL, USA in standard sizes ranging from 1.89 cubic metres (500 US gallons) to 13.3 cubic metres (3500 US gallons), the latter being 16.5 m in length. With the above-mentioned Elastec TDS 11 8G model skimmer unit, a bladder of 3500 US gallons capacity takes about 45 minutes to fill. Each bladder has a self sealing valve to prevent oil leakage once the transfer hose is removed. Tn general the smaller bladders are suitable for use as deck-carried storage bladders while the larger sizes are suited for use as towed bladders. Bladders intended to be used as towed bladders will generally be equipped with a towing bridle, be hydro-dynamic when towed, and be brightly coloured; they may also be fitted with light retaining strips along their full length and/or being provided with night lights.

Claims

CLAIMS1. An oil spill recovery vessel including an oil transfer bollard for use in transferring recovered oil from the vessel to towed storage while the vessel is in motion; the oil transfer bollard being disposed substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stem or more forwardly; the oil transfer bollard comprising: a towing post for attaching a towing cable for the towed storage, and an oil transfer pipe having an outlet portion with a hose coupling by which an oil transfer hose can be coupled to the transfer pipe to transfer oil from the vessel.
2. An oil spill recovery vessel according to claim 1, wherein the axis of the outlet portion of the transfer pipe is substantially horizontal in the region of the hose coupling, the towing post extending above the transfer pipe and being provided with abutment means for preventing a towing cable descending down the towing post to below the level of the transfer pipe.
3. An oil spill recovery vessel according to claim 1 or claim 2, wherein the oil transfer pipe, including its outlet portion, is rigid with the towing post, the hose coupling of the transfer pipe being positioned offset from the axis of the towing post by a distance no greater than 1.5m.
4. An oil spill recovery vessel according to claim 1 or claim 2, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially parallel with that of the towing post.
5. An oil spill recovery vessel according to claim 4, wherein the axis about which the said outlet portion of the oil transfer pipe is rotatable, is offset from the axis of the towing post by a distance no greater than 1.5m.
6. An oil spill recovery vessel according to claim 1, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially coaxial with that of the towing post.
7. An oil spill recovery vessel according to claim 1, wherein the vessel has an aft deck rail that can be lowered when the oil transfer bollard is being used for towing, the aft deck rail when in its lowered position providing protection for the stem of the vessel from chaffing by the towing cable.
8. An oil spill recovery vessel according to claim 1, wherein the oil transfer bollard is disposed, with respect to the fore-aft centreline of the vessel, at the centre of gravity� 10% of the vessel's length or more forwardly.
9. An oil transfer bollard unit for mounting on an oil spill recovery vessel for use in transferring recovered oil from the vessel to towed storage while the vessel is in motion, the oil transfer bollard comprising: a towing post for attaching a towing cable for the towed storage, and an oil transfer pipe having an outlet portion with a hose coupling by which an oil transfer hose can be coupled to the transfer pipe to transfer oil from the vessel.
10. An oil transfer bollard unit according to claim 8, wherein the axis of the outlet portion of the transfer pipe is substantially horizontal in the region of the hose coupling, the towing post extending above the transfer pipe and being provided with abutment means for preventing a towing cable descending down the towing post to below the level of the transfer pipe.
11. An oil transfer bollard unit according to claim 8 or claim 9, wherein the oil transfer pipe, including its outlet portion, is rigid with the towing post, the hose coupling of the transfer pipe is positioned offset from the axis of the towing post by a distance no greater than 1.5m.
12. An oil transfer bollard unit according to claim 8 to claim 9, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially parallel with that of the towing post.
13. An oil transfer bollard unit according to claim 11, wherein the axis about which the said outlet portion of the oil transfer pipe is rotatable, is offset from the axis of the towing post by a distance no greater than 1.5m.
14. An oil transfer bollard unit according to claim 12, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially coaxial with that of the towing post.
15. An oil spill recovery vessel including an oil transfer bollard unit according to any one of claims 9 to 14 mounted on a towing deck of the vessel.
16. An oil spill recovery vessel according to claim 15, wherein the oil transfer bollard is mounted substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stern or more forwardly.
17. An oil spill recovery vessel according to claim 16, wherein the oil transfer bollard is disposed, with respect to the fore-aft axis of the vessel, at the centre of gravity � 10% or more forwardly.
18. An oil spill recovery method in which a vessel equipped with a skimmer unit moves forward through an oil spill at a normal skimming speed with its skimming unit operating to recover oii, and simultaneously transfers recovered oil through an oil transfer hose to a bladder being towed by the vessel using a towing cable; the oil transfer hose and the towing cable attaching to the vessel in the same general location situated substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stern or more forwardly.
19. An oil spill recovery method according to claim 18, wherein the oil transfer hose and the towing cable attach to the vessel, with respect to the fore-aft centreline of the vessel, at the centre of gravity � 10% of the vessel's length or more forwardly.
20. A method according to claim 18, wherein the bladder is towed at a distance from the vessel of at least half the length of the vessel.
21. A method according to claim 18, wherein recovered oil output by the skimmer unit is passed through an oillwater separator before being transferred through the oil transfer hose to the towed bladder, the separator operating in one of a continuous mode in which it outputs oil for transfer substantially continuously, and an intermittent, cyclic mode, in which oil is output for transfer on an intermittent basis.Amendments to the claims have been filed as followsCLAIMS1. An oil spill recovery vessel including an oil transfer bollard for use in transferring recovered oil from the vessel to towed storage while the vessel is in motion; the oil transfer bollard being disposed substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stem or more forwardly; the oil transfer bollard comprising: a towing post for attaching a towing cable for the towed storage, and an oil transfer pipe having an outlet portion with a hose coupling by which an oil transfer hose can be coupled to the transfer pipe to transfer oil from the vessel.2. An oil spill recovery vessel according to claim 1, wherein the axis of the outlet portion of the transfer pipe is substantially horizontal in the region of the hose coupling, the towing post extending above the transfer pipe and being provided with abutment means for preventing a towing cable descending down the towing post to below the level of the Q transfer pipe. Co3. An oil spill recovery vessel according to claim 1 or claim 2, wherein the oil transfer pipe, including its outlet portion, is rigid with the towing post, the hose coupling of the transfer pipe being positioned offset from the axis of the towing post by a distance no greater than 1.5m.4. An oil spill recovery vessel according to claim 1 or claim 2, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially parallel with that of the towing post.5. An oil spill recovery vessel according to claim 4, wherein the axis about which the said outlet portion of the oil transfer pipe is rotatable, is offset from the axis of the towing post by a distance no greater than 1.5m.6. An oil spill recovery vessel according to claim 1, wherein at least the outlet portion of the oil transfer pipe is rotatable about an axis substantially coaxial with that of the towing post.7. An oil spill recovery vessel according to claim 1, wherein the vessel has an aft deck rail that can be lowered when the oil transfer bollard is being used for towing, the aft deck rail when in its lowered position providing protection for the stem of the vessel from chaffing by the towing cable.8. An oil spill recovery vessel according to claim 1, wherein the oil transfer bollard is disposed, with respect to the fore-aft centreline of the vessel, at the centre of gravity� 10% of the vessel's length or more forwardly.9. An oil spill recovery method in which a vessel equipped with a skimmer unit moves forward through an oil spill at a normal skimming speed with its skimming unit operating to recover oil, and simultaneously transfers recovered oil through an oil transfer hose to a Q bladder being towed by the vessel using a towing cable; the oil transfer hose and the towing CO cable attaching to the vessel in substantially the same location situated substantially on the fore-aft centreline of the vessel and at least one third of the vessel's length from the stem or more forwardly.10. An oil spill recovery method according to claim 9, wherein the oil transfer hose and the towing cable attach to the vessel, with respect to the fore-aft centreline of the vessel, at the centre of gravity � 10% of the vessel's length or more forwardly.11. A method according to claim 9, wherein the bladder is towed at a distance from the vessel of at least half the length of the vessel.12. A method according to claim 9, wherein recovered oil output by the skimmer unit is passed through an oil/water separator before being transferred through the oil transfer hose to the towed bladder, the separator operating in one of a continuous mode in which it outputs oil for transfer substantially continuously, and an intermittent, cyclic mode, in which oil is output for transfer on an intermittent basis.13. A method according to claim 9, wherein the oil transfer hose connects to a hose coupling of an oil transfer pipe of the vessel and the towing cable is attached to a towing post of the vessel, the hose coupling of the transfer pipe being positioned no greater than 1.5m from the axis of the towing post. Co