GB2492554A - Apparatus for the in-situ cleaning of a floating boom - Google Patents

Abstract

Apparatus 10 is provided for the in-situ cleaning of a floating boom 1 that comprises a floatation portion 3 and a curtain portion 4. The apparatus comprises two pivotally connected frames 11, 14 each supporting a cleaning subsystem 21, 31 with abrasive elements that are arranged to be driven in repeating closed-loop movement. The pivotal interconnection of the two frames 11, 14 is such the cleaning subsystems 21, 31 lie opposite each other and can be closed towards each other by pivoting of the frames 11, 14. As a result, with the apparatus 10 straddling the boom 1, the cleaning subsystems 21, 31 can be closed towards each other into a cleaning position in which they embrace the boom 1 and enable cleaning of respective sides of the boom 1 by the closed-loop movement of the abrasive elements of the cleaning subsystems 21, 31. The cleaning subsystems 21, 31 are adapted to accommodate variation in boom thickness between its curtain and floatation portions 3, 4.

Description

APPARATUS FOR THE IN-SITU CLEANING OF A FLOATING BOOM.

BACKGROUND lO

[0001] The present invention relates to apparatus for the in-situ cleaning of a floating boom such as, but not limited to, an oil containment boom.

[0002] As is illustrated in Figure 1 of the accompanying drawings, a floating boom l,such as oil containment boom, generally comprises a floatation portion 3 formed by either a continuous buoyant element or a string of individual buoyant elements, and a non-buoyant continuous underwater curtain portion 4 depending from the floatation portion. Floating booms are manufactured in manageable lengths, and can be joined together to form a continuous barrier of any desired length.

100031 When clean, a floating boom I will float with its floatation portion 3 riding relatively high in a body of water 2 as is depicted in Figure 1 by the relative water level represented by dashed line 5. However, as marine growth builds up on the boom 1,the extra weight causes the boom to sink down, this being depicted in Figure 1 by the relative waler level represented by solid line 6.

10004] In the context of oil containment the ffinction ofthe flotation portion 3 is not only to support the weight of the curtain portion 4, but also to prevent overspill of surface oil to the water beyond the boom; the function of the curtain portion 4 is to prevent the passage of oil under the floatation portion 3 in abnormal or rough conditions, and also to prevent or slow the drift of the boom due to current or wind. The optimal size (height/width) of the flotation portion 3, and depth of the curtain portion 4 will depend on the location of, and type of, oil containment for which the boom is intended.

100051 Oil containment booms are the first line of defence to prevent the spread of oil, accidentally or deliberately spilled on the surface of water whcthcr in thc ocean, inshore, in harbour or in another body of water. Thus, in the event of an oil spill, the first response is generally to place a boom around the affected area to contain the contamination, prevent it spreading to a wider area, and to facilitate a satisfactory response and clean-up.

[0006] Additionally, oil containment booms are used in dockyards and similar repair facilities, both military and commercial, to surround a vessel when at anchor, or partially surround it when docked alongsidc in order to prevent spreading ofoils discharged from the vessel during the repair or maintenance period.

10007] Oil containment booms are also used around vessels (military or commercial) that have been temporarily or permanently withdrawn from service and moth-balled either awaiting re-commissioning into service or scrapping. Such vessels normally have skeleton crews for general maintenance and safety purposes, and thus oil containment booms are needed as a precaution to prevent oil leakage and other contamination from spreading to surrounding waters.

[0008] Moth-balled vessels and those undergoing major or extensive repairs/alteration/upgrades can be anchored or docked for extended periods of time.

During this time marine growth, namely barnacles, weed and similar, attach to the floatation and curtain portions of the oil containment booms placed around the vessels. As already indicated, build up of marine growth on a boom causes the boom to sink down under the weight, thus increasing the risk of oil and other contaminants overflowing the boom to escape to the surrounding waters.

[0009] It is an object of the present invention, to provide in-situ cleaning of floating booms, eliminating the need for lifting or removal from the water.

SUMMARY OF TilE INVENTION

100101 According to one aspect of the present invention, there is provided apparatus for the in-situ cleaning of a floating boom that comprises a floatation portion and a curtain portion depending from the floatation portion, the apparatus comprising: two frames, and a respective cleaning subsystem supported by each frame and each comprising abrasive elements and a drive arrangement for driving repeating closed-loop movement of the abrasive elements; the frames being pivotally connected to each other such that the cleaning subsystems lie opposite each other and can be closed towards each other by pivoting of the frames whereby, with the apparatus straddling the boom, the cleaning subsystems can be closed towards each other into a cleaning position in which they embrace the boom and enable cleaning of respective sides of the boom by the closed-loop movement of the abrasive elements of the cleaning subsystems, the cleaning subsystems being adapted to accommodate variation in boom thickness between its curtain and floatation portions.

BRIEF DESCRIPTION OF THE DRAWINGS

[00111 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 cross-section through one known form of oil containment boom; Figure 2 is a side view of a first form of boom cleaning apparatus embodying the invention; Figure 3 is a perspective view of the Figure 2 apparatus; Figure 4 is a side view of a known form of jet-powered oil spill recovery vessel (OSRV); Figure 5 is a plan view of the Figure 4 OSRV; Figure 6 is a stern view of the Figure 4 OSRV; Figure 7A is a stern view of the Figure 4 OSRV showing the mounting of the Figure 2 boom cleaning apparatus on a frame attached to a rear rail of the OSRV, the rail and boom cleaning apparatus being shown in a raised position; Figure 7B is a plan view of a rear portLon of the Figure 4 OSRV showing the Figure 2 boom cleaning apparatus mounted on a frame attached to a rear rail of the OSRV, the rail and boom cleaning apparatus being shown in a raised positiom Figure 7C is a side view of a rear portion of the Figure 4 OSRY showing the Figure 2 boom cleaning apparatus mounted on a frame attached to a rear rail of the OSRV, the rail and boom cleaning apparatus being shown in a raised position; Figure 8A is a stem view corresponding to Figure 7A but showing the rail and boom cleaning apparatus in a lowered position; Figure SB is a plan view corresponding to Figure 7B but showing the rail and boom cleaning apparatus in a lowered position; Figure 8C is a side view corresponding to Figure 7C but showing the rail and boom cleaning apparatus in a lowered position; Figure 9 is a side view of a second form of boom cleaning apparatus embodying the invention; and Figure 10 is a perspective view of part of a third form of boom cleaning apparatus embodying the invention.

DETAILED DESCRIPTION

10012] Figures 2 and 3 depict a first form of boom cleaning apparatus 10 embodying the invention. As can be best seen in Figure 3, this apparatus 10 comprises two generally rectangulartubular alloy frames 11, 14 which in side view (as shown in Figure 2) are shaped like respective halves of a pair of scissors. The two frames 11, 14 arc pivotally connected in a scissor form arrangement with the axis of pivoting 9 of the frames relative to each other lying intermediate the top and bottom of the frames (relative to the orientation of the apparatus shown in Figure 2). In the apparatus 10, each frame 11, 14 can thus be considered to comprise an upper portion 1 2, 15 respectively positioned above the axis of pivoting 9 of the frames, and a lower portion 13, 16 respectively positioned below the axis of pivoting 9.

S

[0013] The lower portion 13, 16 of each frame 11, 14 carries a respective cleaning subsystem 21, 31, these cleaning subsystems being mounted to lie opposite each other such that thcy can be closed towards each other (and, conversely, moved apart) by pivoting of the frames about the axis 9.

10014] A double-acting hydraulic actuator 17 is disposed between the upper portions 12, of each frame II, 14 and is selectively operable to move apart (arrow 18) or close together the frame upper portions 1 2, 1 5 thereby respectively to move the cleaning system towards each other (arrows 19) or move them apart. Hydraulic power is supplied to the actuator through feed and return hose lines (not shown) from an attending vessel (also not shown in Figures 2 and 3). Other forms of actuator 17 can alternatively be used, such as a pneumatic or electric actuator it is also possible to use a single-acting actuator arranged to move apart the frame upper portions 12, 15 (and thereby move the cleaning subsystems towards each other), the reverse movement for moving the cleaning subsystems apart being effected manually. Indeed, moving the frame upper portions 1 2 and 1 5 apart to move the cleaning subsystems towards each other can also be effected manually thereby obviating the need for actuator 17.

[0015] When the apparatus 10 is positioned straddling a boom 1 to be cleaned, that is, with the lower portions 13, 16 of the two frames 11, 14 on respective sides of the boom 1 (see Figure 2), the cleaning subsystems 21, 31 can be closed towards each other bypivoting of the two frames 11, 14 relative to each other (by operation of the actuator 17 or manually) thereby to bring the cleaning subsystems 21, 31 into a cleaning position (the position illustrated in Figure 2) in which they embrace the boom 1 and are positioned to clean respective sides of the boom.

1001 6J Each cleaning subsystem 2 I, 31 comprises abrasive elements and a drive arrangement for driving repeating closed-loop movement of the abrasive elements whereby with the cleaning subsystems in their cleaning position embracing a boom to be cleaned, the driven closed-loop movement of the abrasive elements is effective to clean the adjacent areas of the boom. In the present form of apparatus 10, each cleaning subsystem 21, 31 comprises two differently-sized cleaning heads here constituted by drums 22, 23 for the cleaning subsystem 21 and by drums 32, 33 for the cleaning subsystem 21. The different sizes (diameters) of the two drums 22 and 23 and of the two drums 32 and 33 accommodates the variation in boom thickness between its floatation and curtain portions 3, 4, the smaller-diameter drums 22, 32 being arranged to engage with opposite faces of the thicker floatation portion 3 of the boom while the larger-diameter drums 23,33 engage with opposite faces of the thinner curtain portion 4 of the boom.

[0017] The drums 22, 23 of the cleaning subsystem 21 are coaxially secured to a shaft 24 which is rotatably mounted via bushes 25 (only one visible in Figure 3) on transverse elements of the lower portion 13 ofthe frame 11 thereby to enable rotation ofthe drums 22, 23 about their longitudinal axis 29 (this axis is substantially vertical when the cleaning subsystems are in their cleaning position closed about a boom to be cleaned). The shaft 24 is arranged to be rotatably driven by a suitable drive arrangement, for example, a hydraulic motor 26 powered through feed and return hose lines (not shown) from an attending vessel.

[0018] In a similar manner, the drums 32, 33 of the cleaning subsystem 31 are coaxially secured to a shafi 34 which is rotatably mounted via bushes 35 (only one visible in Figure 3) on transverse elements of the lower portion 16 ofthe frame 14 thereby to enable rotation of the drums 32, 33 about their longitudinal axis 39 (this axis is substantially vertical when the cleaning subsystems are in their cleaning position closed about a boom to be cleaned). The shaft 34 is arranged to be rotatably driven by a suitable drive arrangement, for example, a hydraulic motor 36.

[0019] When powered up to drive the drums 22, 23, 32, 33, for cleaning a boom, the motors 26, 36 are arranged to rotate in opposite senses (clockwise, anti-clockwise) but at substantially the same angular velocity whereby to drive drum 22, 23 in one sense and the drums 32, 33 in the opposite sense.

[0020] The cylindrical face of each of the drums 22, 23, 32, 33 is provided with abrasive elements which in the present embodiment comprise helical beater bars 40 alternating with helical bristle runs 41, the bars 40 serving to dislodge crustaceans and the bristles 41 to remove weed and debris. Different types and arrangements of abrasive elements are, of course, possible.

10021] It may be noted that when the cleaning subsystems 21, 31 are in their cleaning position embracing a boom to be cleaned, the weight of the subsystems and the fact that they lie below thc pivot axis 9 of the frames 11, 14, means that a certain closing pressure will be present pushing the cleaning drums 22, 23 and 32, 33 up against the boom to be cleaned. This closing pressure is, however, normally augmented by use of the hydraulic actuator 17 to urge the cleaning subsystems 21, 31 towards each other; regulation of the pressure exerted through use of the actuator 17 enables the pressure with which the drums 22,23 and 32, 33 engage the the boom to be optimized.

[0022] Preferably, but not necessarily, to allow for the cleaning drums 22, 23, 32, 33, to be changed, provision is made for removal of the shafts 24. 36 from the frames 1], 14; this allows damaged or woni drums to be replaced or for drums with different types of abrasive elements to be tried. It also permits the cleaning subsystems 21, 31 to be adapted to different boom profiles, that is, to different transverse thicknesses and depths (vertical) of the floatation and curtain portions 3, 4 of a boom to be cleaned; furthermore, should the boom be constructed with more (or less) than tile two different transverse thicknesses of the Figure 1 example boom, then the number of differently-sized cleaning heads (drums in the present embodiment) can be varied accordingly.

[0023] To provide the boom cleaning apparatus 10 with a degree of buoyancy. each of the frames 11, 14 is provided with a lateral extension 42,43 respectively, beneath which is installed a float 44, 45 respectively. Preferably, the floats 44. 45 provide sufficient buoyancy for the apparatus to float freely in water (though this is not necessary where the weight of the apparatus is at least partially supported by an attending vessel).

F0024J To enable the boom cleaning apparatus 10 to be transported around, and physically supported during boom cleaning, by an attending vessel, one of the frames 11, 14, here the frame 11, is provided with two apertured mounting brackets 46, 47 to which respective arms 81, 82 (indicated in dashed lines in Figure 3) of an attachment frame can be pivotally connected. The attachment frame is secured to the attending vessel (an example of attachment frame is described more filly below). The pivotal connection of the cleaning apparatus to the arms 81, 82 of the attachment vessel enables the apparatus when in use in the water during boom cleaning, to tilt relative to the attachment frame thereby to accommodate differing movements of the vessel and apparatus. Fixed anti-roll stops (not shown) can be provided on the frame 11 and/or on the attachment frame arms 81, 82 to limit the degree of relative movement between the cleaning apparatus 10 and the attachment frame (in particular, to eliminate the possibility of the apparatus capsizing when being lowered over a boom to be cleaned.

100251 It may be noted that when the boom cleaning apparatus 10 is being used supported by an attending vessel (its supported' operational mode rather than its free-floating' operational mode) the buoyancy provided by the floats 44, 45 serves to relieve weight on the attachment frame and facilitates self-levelling during operation.

100261 The supporting of the boom cleaning apparatus 10 from a specific, example, attending vessel will now be described; first, however, a brief description is given of the example attending vessel, in this case an oil spill recovery vessel OSRY 50 of the general form shown in Figures 4 to 6 (further details can be found in published application GB 2473 165(A), herein incorporated by reference).

[0027] As illustrated in Figures 4 to 6, OSRV 50 comprises a catamaran bow section 51 with twin hulls 61 & 62, and a trimaran main section 52 in which a central hull 60 is interposed between the aft continuations of the twin hulls 61, 62 of the catamaran bow section 51. The triple hulls 60, 61, 62 of the trimaran main section 52 have conjoined upper portions that together provide a large rear towing deck 56.

100281 A skimmer unit 53 is carried between twin hulls 61 & 62 of the catamaran bow section 51 of the OSRV 50 and can be moved between a raised position (shown in dashed lines in Figure 4) in which it is clear of the water, and a lowered position (shown in chain-dashed outline in Figure 4) in which it sits in the water. When the skimmer unit 53 is in its lowered position, it is arranged to recover oil from an oil spill as the OSRY moves at low speed through the spill; the recovered oil is transferred via pipework 59 (shown in dotted lines in Figure 4) to an oil transfer bollard 55 from where it is passed through a transfer hose to a towed bladder attached to the bollard 55 by a towing cable (for simplicity, the transfer hose, towing cable and bladder are not shown in the drawings but arow 57 in Figure 4 depicts the direction of oil flow out of the bollard 55 along the hose.) 100291 When oil is not being recovered, the skimmer unit 53 is lifted into its raised position clear of the water thereby enabling the OSRV 50 to proceed at a fast speed. In the present example, the OSRV propulsion system comprises a water jet drive unit the outlet 58 of which is centrally positioned in the stem of the OSRV 50 (see Figure 6). The use ofajet drive for a boom-cleaning attending vessel is advantageous as reduces the risk of accidental damagc to the boom that might occur from an external propeller.

100301 At its end the towing deck 16 merges with a scooped transom 69 that slopes downwards towards the stern. An aft deck rail structure 70 is arranged to fold down from a near upright position shown in Figures 4 and 6, to a bladder-towing opcrational position shown in Figure 5 in which it lies against the scooped transom 69. The aft deck rail structure 70 is moved between its near upright and bladder-towing operational positions by hydraulic cylinders 71. The rail structure 70 is, for example, made from alloy tube and has a height of approximately 1 m when in its near upright position.

[00311 In the present example casc ofthe boom cleaning apparatus 10 being supported by the OSRV 50, the attachment frame 80 (see Figure 7A) used to support the apparatus from the OSRV 50 is releasably secured the aft rail structure 70 and comprises the two arms 81, 82 that connect to the support brackets 46, 47 of the boom cleaning apparatus, and two cross-members 83, 84 that rigidly interconnect the arms 81, 82. The attachment frame 80 is secured to the aft rail structure 70, for example, by clamping the arms 81, 82 to intermediate and lower rails of the structure 70 using clamps and bolts (not shown).

100321 The attachment frame 80 is so shaped that with the aft rail structure 79 in its raised position the boom cleaning apparatus 10 is positioned clear of the water with the axes 29, 39 of the cleaning drums 22, 23, 32, 33 substantially horizontal, this being the position illustrated in the stern, plan and side views shown in Figures 7A, 7B, 7C. When the aft rail structure 70 is lowered to its position normally used for towing operations, the boom cleaning apparatus 10 is turned through 90 degrees such that the axes 29, 39 of the cleaning drums 22, 23, 32, 33 are substantially horizontal; at the same time the apparatus 10 is brought down into the water due to the crank-shaped form of the attachment-frame arms 81, 82 (as is visible in Figure 7B). The position of the cleaning apparatus 10 with the aft nil structure 70 lowered is illustrated in the stem, plan and side views shown in Figures SA, 8B, 8C.

100331 In Figures 7A-7C and 8A-8C the elements of the attachment frame 80 have been shown in thick lines to enable their ready identification and to clearly show the shape of the two arms 81, 82.

[0034] The manner of use of the boom cleaning apparatus 10 when carried byOSRV 50 is generally as follow's. With the aft rail structure 70 raised, the apparatus 10 is clear of the water and the OSRV 50 can be rapidly driven to the vicinity of a boom to be cleaned. Once at the boom, the OSRV is manoeuvred alongside such that the apparatus 10 overlies the boom. The actuator 17 is then activated to open apart the cleaning subsystems 21, 31.

Thereafter, the aft rail structure 70 is moved to its lowered position causing the apparatus to swing down with its two cleaning subsystems 21, 31 descending into the water on respective sides ofthe boom 1. The actuator 17 is then activated again to close the cleaning subsystems 21, 31 towards each other thereby to embrace the boom, and to apply a desired closing pressure engaging the cleaning drums 22, 23 and 32, 33 against the boom (see Figure 8A). The hydraulic motors 26, 36 are then started to cause the cleaning drums to rotate imparting repeated cyclic movement to the abrasive elements 40, 41 carried by the drums. This movement ofthe abrasive elements is effective to dislodge crustaceans, weeds and debris from the boom, the dislodged material falling to the seabed. It is noted that current US legislation permits this whereas material removed more than 9" (225mm) above the water surface, such as when booms are lifted above this height for cleaning, must be collected and removed for deposit to landtill.

[0035] To clean the boom 1 along its length, the OSRY 50 is driven slowly forward parallel to the boom thereby advancing the cleaning apparatus 1 0 along the boom. The rotation of the cleaning drums 22, 23, 32, 33 and the closing pressure exerted on them serves to entrain the boom 1 between the drums thereby assisting in the advance of the cleaning apparatus along the boom; this effect can be increased or decreased as desired by controlling the closing pressure exerted via the actuator 17. In one implementation, the closing pressure is cyclically raised for a short period to firmly grip the boom between the drums and advance the apparatus along the boom; between the periods of high closing pressure, the abrasive elements of the drums clean the boom without the latter being entrained by the drums.

[0036] It may be noted that since the tangential speed of the smaller diameter drums 22, 32 will be less than that of the larger diameter drums 23, 33, the two different sizes of drum will tend to entrain the boom at different speeds. It may therefore be desirable, though not essential, to provide for the larger diameter drums to rotationally slip relative to the smaller diameter drums when the torque applied to the larger diameter drums via the driven shafts reaches a predetermined level.

[0037] The pivotal connection of the cleaning apparatus 10 to the attachment frame 80 and the buoyancy provided by the floats results in the apparatus 10 being self-levelling in its working position, independently of rocking of the OSR'V 50.

100381 Once cleaning of the boom I has been completed, the hydraulic motors 26, 36 are stopped, the cleaning subsystems 21, 31 moved apart by operation of the actuator 17, and the apparatus 10 swung up out of the water and clear of the boom by raising the aft rail structure 70 to its near vertical position.

10039] As already indicated, the number and size of cleaning drums 22, 23, 32, 33 of the apparatus can be changed to accommodate different types of boom to be cleaned. The drums may also be changed to change the type of abrasive elements effecting the cleaning action.

[0040] It is to be understood that the form of the attending vessel and of the attachment frame, as well as the equipment used by the attending vessel to raise and lower the boom cleaning apparatus 10, may differ from that described above in connection with OSRV 50 and attachment frame 80.

10041] The cleaning apparatus 10 can be disconnected from the attachment frame 80 and used in its free-floating mode (assuming the floats 44, 45 provide adequate buoyancy) in which the attending vessel provides hydraulic power to the apparatus but does not physically support it. In this case, the apparatus moves (or crawls') along a boom to be cleaned entirely as a result of the entrainment of the boom between the opposcd pairs of S cleaning drums 22, 23 and 32, 33.

100421 The above-described boom cleaning apparatus exhibits a numberof advantages. In particular, the in-situ removal of growths from a boom eliminates the need (in the USA) for debris deposit to landfill. The described form of apparatus 10 is adaptable to different forms of boom as it permits thc number, size and abrasive characteristics of the cleaning drums to be changed. The apparatus 10 can be used in a free-floating mode or in a supported mode carried by an attending vessel; in the latter case, the attachment frame 0 used to connect the apparatus to the vessel can be adapted for seeural to different types of vessel. The described apparatus 10 is low maintenance, easy and economic to operate, and operationally efficient.

[0043] Many variants are, of course, possible to the above described form of boom cleaning apparatus. For example, and as already indicated, the opening and closing of the frames 11, 14 to allow the cleaning subsystems 21, 23 to embrace a boom to be cleaned, can be effected manually rather than by means of actuator 17.

10044] The frames 111, 14 can be pivotally inter-connected in an arrangement other than scissor-form, as is illustrate in Figure 9. In the Figure 9 form of boom-cleaning apparatus 90, two pivotally inter-connected frames 91, 92 (corresponding generally to the frames 11 and 14 of the previously-described apparatus 101) carry respective cleaning subsystems 21, 31 of substantially the same form as the cleaning subsystems of the apparatus 10.

Considered relative to the orientation of the frames 91, 92 when the cleaning subsystems are in their cleaning position (as shown in Figure 9), the cleaning subsystems 21, 31 are carried by the lower parts of thc frames 91, 92 and the frames 91, 92 are pivotally inter-connected at their top ends (in Figure 9, the axis 93 of pivoting of the frames 91,92 extends substantially perpendicular to the plane of the drawing sheet). In the apparatus 90, the opening and closing together of the two frames 91, 92 is effected by an actuator 97 (for example, a hydraulic actuator) positioned intermediate the cleaning subsystems 21, 31 and where the frames are pivotally connected to each other, whereby selective operation of the actuator arrangement to close the frames 91, 92 towards each other (arrows 98) also serves to close thc cleaning subsystems 21, 3 1 together (arrows 99); conversely, the opening apart of the frames 91, 92 by selective operation of the actuator 97 serves to open apart the cleaning subsystems 21, 31.

[0045] The cleaning heads of the cleaning subsystems may take forms other than of the cleaning drums of the apparatus' 10 and 90. One such alternative form of cleaning head is depicted in Figurc 10 which shows the lower portion 101 of one frame of cleaning apparatus 100 that comprises two frames pivotally inter-connected in a scissor-form arrangement similar to the apparatus 10. The frame portion 101 carries a cleaning subsystem 1 21 with two cleaning heads each of which comprises a closed-loop cleaning belt 103, 106 respectively canying abrasive elements (not shown) on its outer face and mounted on thc frame portion 102 for circulation by a drive arrangement comprising a hydraulic motor 113, such that, with the cleaning subsystems of the apparatus 100 in their cleaning position embracing a boom to be cleaned, the outer face of each cleaning belt 103, 106 is arranged to move parallel to the longitudinal direction of the boom sweeping the abrasive elements of the belt across the surface of the boom. More particularly, in the illustrated form of the cleaning apparatus 100, the cleaning belt 103 passes around rollers 104 and 105 and the cleaning belt 106 passes around rollers 107 and 108. Rollers 104 and 107 are mounted on a common shaft 109 rotatablymountedin frameportion 101; similarly,rollers and 108 are mounted on a common shaft 110 also rotatably mounted in frame portion 101, the shaft 110 being arranged to be rotatably driven by the motor 113. The diameter of the rollers 104, 105 is such that the cleaning head comprising the rollers 104, 105 and cleaning belt 103 is adapted to engage the curtain portion 3 of a boom ofthe Figure 1 form, whereas the diameter of the rollers 107, 108 is such that the cleaning head comprising the rollers 107, 108 and cleaning belt 106 is adapted to engage the floatation portion 3 of a boom of the Figure 1 form.

100461 In another embodiment of the cleaning apparatus, each cleaning head of the cleaning subsystem comprises a flail mounted on the frame supporting the cleaning subsystem concerned and arranged to be rotatably driven by the drive arrangement. In the present specification, a "flail" means an arrangement of multiple abrasive elements each comprising a flexible stem fixed at one end to a common rotatably-drivable member and carrying at its free end a head of significant mass (for example, spherical in form). When the common member is rotated at speed, the heads of the elements pick up enough momentum to be effective to dislodge growths from a boom when the heads collide with such growths.

At the same tirne, the flexible stems allow a degree of adaptation to variations in boom thickness, such as between the floatation and curtain portions (provided this difference is not too large and the stems of the abrasive elements are sufficiently long). As a result, a single size of flail cleaning head may be able to accommodate both the floatation and curtain portions of a boom.

100471 Other possible forms of cleaning head include reciprocating plates each canying abrasive elements on a face disposed opposite the boom, and rotatable brushes arranged to rotate about an axis perpendicular to the general plane of the boom.

100481 Whatever the formof the cleaning heads, each cleaning subsystemcan bepiovided with supplementary cleaning means comprising at least one of the following: -an arrangement for directing water jets at the boom; -an arrangement for directing underwater sonic or ultrasonic vibrations at the boom; and -an arrangement for causing cavitation at the boom.

100491 The possibility has already been described of causing or assisting movement of the cleaning apparatus along a boom being cleaned by sufficiently entraining the boom between the cleaning subsystems such that the apparatus at leastpartially pulls itself (or crawls') along theboom. In fact, it is also possible to provide the apparatus with a boom crawling alTangement operating in this general manner but which is separate from the cleaning subsystems. Such a boom crawling arrangement would typically comprise opposed rollers or closed-loop belts that arc arranged to embrace the boom under a closing pressure whereby to grip the boom; rotation of one or more of the roller(s) or circulation of one or more of the belt(s) entrains the boom and results in the cleaning apparatus crawling along the boom. Preferably, both the closing pressure and the speed of roller rotation / belt circulation are adjustable.

Claims (1)

1. <claim-text>CLAIMS1. Apparatus for the in-situ cleaning of a floating boom that comprises a floatation portion and a curtain portion depending from the floatation portion, the apparatus comprising: two frames, and a respective cleaning subsystem supported by each frame and each comprising abrasive elements and a drive arrangement for driving repeating closed-loop movement of the abrasive elements; the frames being pivotally connected to each other such that the cleaning subsystems lie opposite each other and can be closed towards each other by pivoting of the frames whereby, with the apparatus straddling the boom, the cleaning subsystems can be closed towards each other into a cleaning position in which they embrace the boom and enable cleaning of respective sides of the boom by the closed-loop movement of the abrasive elements of the cleaning subsystems, the cleaning subsystems being adapted to accommodate variation in boom thickness between its curtain and floatation portions.</claim-text> <claim-text>2. Apparatus according to claim 1, wherein each cleaning subsystem comprises at least one cleaning head that carries multiple said abrasive elements and is arranged to bydriven by the drive arrangement of the cleaning subsystem whereby to impart said repeating closed-loop movement of the abrasive elements.</claim-text> <claim-text>3. Apparatus according to claim 2, wherein each cleaning head comprises at least one cleaning drum carrying abrasive elements on its cylindrical face and mounted on the frame supporting the cleaning subsystem concemed such that, with the cleaning subsystems in their cleaning position embracing the boom, the longitudinal axis of the drum is substantially vertical, and the drum being arranged to be rotatably driven about its longitudinal axis by the drive arrangement.</claim-text> <claim-text>4. Apparatus according to claim 3, wherein for each cleaning drum, the abrasive elements comprises at least one run ofbristles and at least one beater bar each helically disposed over the cylindrical face of the drum.5. Apparatus according to claim 2, wherein each cleaning head comprises a closed-loop cleaning belt canying abrasive elements on its outer face and mounted on the frame supporting the cleaning subsystem concerned for circulation by the drive arrangement such that, with the cleaning subsystems intheir cleaning position embracing the boom, the outer face of the cleaning belt is arranged to move parallel to the longitudinal direction of the boom.</claim-text> <claim-text>5. Apparatus according to claim 2, wherein each cleaning head comprises a flail mounted on the frame supporting the cleaning subsystem concerned and arranged to be rotatably driven by the drive arrangement.</claim-text> <claim-text>6. Apparatus according to claim 2, wherein accommodation to variations inboom thickness between its curtain and floatation portions is effected by providing each cleaning subsystem with at least one first cleaning head for cleaning the floatation portion of the boom and at least one second cleaning head for cleaning the curtain portion of the boom, the first and second cleaning heads being of different sizes.</claim-text> <claim-text>7. Apparatus according to claim 3, wherein accommodation to variations in boom thickness between its curtain and floatation portions is effected by providing each cleaning subsystem with at least one first cleaning drum for cleaning the floatation portion of the boom and at least one second cleaning drum for cleaning the curtain portion of the boom, the first and second cleaning drums being of different diameter.</claim-text> <claim-text>8. Apparatus according to claim 1, wherein accommodation to variations inboomthickness is effected by providing each cleaning subsystem in the form of one or more flails including the abrasive elements and adapted to be driven by the drive arrangement of the cleaning snbsystem.</claim-text> <claim-text>9. Apparatus according to any one ofthe preceding claims, wherein the drive arrangements of the cleaning subsystems are powered by hydraulic motors.</claim-text> <claim-text>10. Apparatus according to any one of the preceding claims, wherein each cleaning subsystem frirther comprises supplementary cleaning means comprising at least one of the following: an arrangement for directing water jets at the boom an arrangement for directing underwater sonic or ultrasonic vibrations at the boom; and an arrangement for causing cavitation at the boom.</claim-text> <claim-text>Ii. Apparatus according to claim 2, whercin the said at least one cleaning head of each cleaning subsystem can be changed to adapt the apparatus to different sizes of boom.</claim-text> <claim-text>12. Apparatus according to any one of the preceding claims, further comprising an actuator arrangement connected between the frames and selectively operable to pivot the frames relative to each other whereby to selectively close together and open apart the cleaning subsystems.</claim-text> <claim-text>13. Apparatus according to claim 12, wherein the two frames are arranged scissor-form with an axis of pivoting of the frames relative to each other lying intermediate the top and bottom of the pivoted frames considered with reference to thc orientation ofthe apparatus in its cleaning position, the cleaning subsystems being carried by the portions of the frames below the axis of pivoting and the actuator arrangement being positioned above the axis of pivoting to selectively open apart and close together the portions of the two frames above the axis of pivoting whereby to close together and open apart the cleaning subsystems.</claim-text> <claim-text>14. Apparatus according to claim 12, wherein the two frames are pivotally connected at their upper ends considered with reference to the orientation of the apparatus in its c'eaning position, the cleaning subsystems being carried by lower portions of the frames and the actuator arrangement being positioned intermediate the cleaning subsystems and where the frames are pivotally connected to each other whereby selective operation of the actuator arrangement to open apart and close together the two frames, opens apart and closes together the cleaning subsystems.</claim-text> <claim-text>15. Apparatus according to any one of the preceding claims, wherein each frame is provided with at least one float.</claim-text> <claim-text>16. Apparatus according to claim 15, wherein the floats arc arranged to provide sufficient buoyancy to enable the apparatus to be used free-floating without support from an attending vessel other than the supply of power.</claim-text> <claim-text>17. Apparatus according to any one of the preceding claims, further comprising a connection arrangement for pivotally connecting the apparatus to support bars extending laterally from an attending vessel for supporting the apparatus in the water astride the boom to be cleaned while permitting the angle of the support bars to the horizontal to vaiy as the vessel moves up and down in the water.</claim-text> <claim-text>18. Apparatus according to any one of the preceding claims, further comprising a boom crawling arrangement for engaging with the boom and advancing the apparatus in its dean ing position along the boom whereby to progressively clean the boom along its length.</claim-text> <claim-text>19. Apparatus according to claim 18, wherein the boom crawling arrangement is formed by the cleaning subsystems.</claim-text> <claim-text>20. Apparatus according to claim 19, further comprising means for applying a closing pressure to the two cleaning subsystems to press them towards each other when in their cleaning position, and means for adjusting the closing pressure applied to the two cleaning subsystems thereby to vary the effective grip of the cleaning subsystems on the boom and enable control of advance of the apparatus along the boom.</claim-text> <claim-text>21. Apparatus according to claimi, wherein the apparatus is adapted for use both in a free-floating mode in which the apparatus floats in the water astride the boom to be cleaned without support from an attending vessel other than the supply of power, and in a supported mode in which the apparatus is at least partially supported astride theboom to be cleaned by an attending vessel: the apparatus being adapted for use in its free floating mode by the provision of floats, and for use in its supported mode by provision of a connection arrangement for pivotally connecting the apparatus to support arms extending laterally from an attending vessel; and the apparatus further comprising a boom crawling arrangement for engaging with the boom and advancing the apparatus in its cleaning position along the boom whereby to progressively clean the boom along its length.</claim-text>