GB2135571A

GB2135571A - Cleaning underwater surfaces

Info

Publication number: GB2135571A
Application number: GB08403162A
Authority: GB
Inventors: David Fitzherbert Jones; Bernard Harry Ford
Original assignee: UNDERWATER MAINTENANCE Co
Current assignee: UNDERWATER MAINTENANCE Co
Priority date: 1983-02-11
Filing date: 1984-02-07
Publication date: 1984-09-05
Also published as: GB8403162D0

Abstract

Fouled underwater surfaces e.g. the hulls of ships are cleaned by means of rotatable, non-bristled, surface treatment members 14, 15. The members may be polishing, abrasive, or industrial scouring pads. The treatment members may be rotated by means of hydraulic motors 9, (10), mounted on a chassis (2) provided with wheels 3, (4), 5, the latter being associated with a steering and driving assembly 6, which may be operated by a frogman or diver. Conventional hull cleaning brushes may be utilised with the equipment. <IMAGE>

Description

SPECIFICATION Treating an underwater surface This invention relates to a method of, and apparatus for, treating a fouled and/or rough underwater surface, e.g. a hull or a propeller of a ship or the underwater parts of an oil rig.

Surface irregularities on the underwater parts of a ship's hull increase the frictional resistance of the hull to passage through the water, leading to increased fuel consumption and/or reduction in the speed of the ship. Such surface irregularities may be caused by the repeated application of layers of paint which result in the hull surface becoming comparatively rough and contoured compared with the original comparatively smooth and flat hull surface, although perhaps the main cause of surface irregularities on a hull is the growth thereon of marine organisms.

Even the use of self-polishing marine paints typically containing anti-fouling agents is not completely effective in preventing the growth of marine organisms on a ship's hull since such paint is only effective when in contact with moving sea water. Hence the performance of self-polishing marine paints varies with changes in operational requirements, such as slow steaming, or periods of inactivity. Accordingly it is necessary, even when self-polishing marine paints are used, mechanically to clean the hull from time to time.

One commonly used hull cleaning apparatus uses brushes, with bristles, as mechanical treating members, the rotation of the brushes, in use of the apparatus, serving to cause the brushes to be sucked against the hull thereby holding the apparatus against the hull and also serving to scrub the hull. Up until now the use of bristles in the brushes has been considered essential for the necessary suction forces to be generated, the gaps between the bristles or tufts of bristles providing flow channels for water from the centre of each brush to the brush exterior. However, brushes are not ideal for certain uses.For instance, in cleaning a hull having slime over a top coat of a self-polishing paint, the vigorous scrubbing and brushing action of the conventional hull cleaning brushes, e.g. stiff brushes typically having wire bristles, generally inflicts unacceptable damage on the self-polishing marine paint.

The present invention seeks to provide for the treatment of a fouled and/or rough underwater surface (e.g. a ship's hull, by rotating a nonbristled treating member against the surface to remove marine growth from, and/or to smooth, the surface and to retain the treating member against the surface.

According to one aspect of the present invention a method of treating a fouled and/or rough underwater surface comprising rotating at least one treating member against the underwater surface to hold the at least one treating member against the underwater surface and to remove marine growth from and/or to smooth, the underwater surface, is characterised in that the or each treating member has a non-bristled treating surface.

The present invention is thus based on the realisation that it is not essential for treating members to be provided with bristles for the treating members to be sucked against the underwater surface to be treated. Indeed it has been found that completely flat treating members are sucked strongly towards an underwater surface when the treating members are rotated underwater against such a surface.

The purpose of the treatment of the underwater surface, e.g. a ship's hull, depends on the condition of the surface being treated. For example in the case of a hull having a layer of slime over a coating of a self-polishing marine paint, the purpose of the treatment is primarily to provide a gentle wiping action which is sufficient to remove the surface slime without damaging the coating of self-polishing marine paint. Such a gentle wiping action may be achieved if the or each treating member comprises a polishing pad.

A typical polishing pad may comprise a fine grade abrasive pad or even, for example, a lambswool pad.

In the case where marine fouling of a ship's hull is more severe than merely a layer of slime on the hull, the mechanical rubbing action has to be more severe than a gentle wiping action. In particular the treating member is chosen to provide an abrading action which both removes the maring fouling, e.g. weeds, from the hull and smooths the hull surface (whether the hull is coated with a self-polishing marine paint or a more conventional marine paint). Conveniently this abrading action is achieved with the use of a medium grade abrasive pad.

Finally the treatment may be employed to smooth hulls or other underwater surfaces which have a rough or contoured finish caused, for example, by repeated applications of coats of paint. In this case the treating member may comprise a coarse grade abrasive pad to provide a sandpapering effect to smooth the hull surface.

A particularly convenient type of abrasive pad, which can be produced in various grades of coarseness, is made from adhesively bonded nylon fibres or similar materials arranged in a nonwoven open skeletal structure.

According to another aspect of the present invention a method of treating a hull of a ship which is afloat, which hull has a layer of marine growth over a self-polishing marine paint comprising rotating a treating member against the hull to hold the treating member against the hull and to remove the marine growth and expose the said coating to the surrounding water, is characterised in that said treating member has a non-bristled treating surface.

According to a still further aspect of the present invention, apparatus for treating a fouled and/or rough underwater surface comprising at least one detachable, rotatably mounted, surface treating member, and drive means for rotating the or each treating member against the underwater surface to be treated for holding by suction the apparatus against the underwater surface and for effecting removal of marine growth front, and/or smoothing of, the underwater surface, is characterised in that the or each treating member has a substantially flat non-bristled treating surface.

In the case where the apparatus is used to treat a ship's hull, the apparatus includes a wheeled chassis which is held against the ship's hull in use by the suction generated by rotation of the or each treating member. Typically the chassis has at least three wheels, at least one of which may be adjustably mounted relative to the frame to enable adjustment of the working height of the or each treating member.

To provide good suction in use, the or each treating member should provide a dimensionally stable, substantially flat treating surface when rotated underwater. In practice the treating surface will not be smooth, but will be roughened to provide an abrading action (e.g. by the use of abrasive pads) or a polishing action (e.g. by the use of polishing pads) in use.

Effective treating members are achieved with the use of substantially flat pads of treating material affixed to a backing member.

Alternatively, however, a long strip of treating material may be employed, the strip of treating material being tightly wound in a tortuous path (e.g. a helical path or a zig-zag or sinuous path) to provide a pad having a treating surface provided by a long edge of the treating material. A pad so formed may be affixed to a suitable backing member.

Suitably the or each treating member comprises an annular treating pad (formed from a flat pad, or a tightly wound strip, of treating material) and a backing member having perforations formed in a central region thereof.

The provision of the perforations prevents too low a pressure being generated between the surface to be treated and the treating member in use of the apparatus. The generation of too low a pressure is undesirable since it leads to the treating pads being sucked too strongly against the underwater surface causing increased wear of the treating pads and difficulties in movement and control of the apparatus. Other ways of controlling the suction generated by the or each rotating treating member include varying the speed of rotation of the treating member and resiliently mounting the treating member.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic plan of apparatus according to the invention for treating a fouled and/or rough underwater surface of a hull of a ship which is afloat, the apparatus being shown with its casing and steering equipment removed, Figure 2 is a partly sectioned schematic side view of the apparatus shown in Figure 1 but showing the casing and steering equipment thereof, Figure 3 is a schematic sectional view taken on the line Ill-Ill of Figure 1 and showing the casing but not the steering equipment of the apparatus, Figure 4 is a plan of the steering equipment of the apparatus shown in Figures 1 to 3, Figure 5 is a view from below of a treating member of the apparatus shown in Figures 1 to 4, Figure 6 is a sectional view taken on the line VI--VI of Figure 5, and Figure 7 is a schematic plan of another type of treating member for use with the apparatus shown in Figures 1 to 4.

Figures 1 to 3 show an apparatus according to the invention generally designated by the reference numeral 1, for treating a fouled and/or rough-surfaced hull of a ship which is afloat. The apparatus shown in the Figures is specifically intended for removing marine growth, particularly slime, from the hull which is coated with a selfpolishing marine paint.

The apparatus 1 includes a wheeled main chassis 2 mounting rear castor wheels 3 and 4 and a front wheel 5, having a tyre on its rim, of a steering and driving assembly, generally designated 6. The chassis 2 also carries a GRP fairing 3a (see Figures 2 and 3), apertured at the front to permit part of the steering and driving assembly 6 to project therethrough, support means 7 and 8 for mounting hydraulic motors 9 and 10, respectively, and a plate 11 on which is mounted hydraulic control valves 12 and 13 (not shown in Figure 2) for controlling operation- of the motors 9 and 10, respectively.Surface finishing or treating assemblies 14 and 1 5 (see Figures 5 and 6), each comprising an annular polishing pad 1 4a (1 Sa) fixed to a rigid backing plate 1 6 having through holes 1 7 formed in a central region thereof, are detachably connected to the motors 9 and 10, respectively.

The steering and driving assembly 6 (see Figure 2) comprises the front wheel 5, which is mounted on a mounting bracket 1 8 carrying a hydraulic motor 19 (see Figures 1 and 4) for driving the wheel 5, and a steering wheel assembly, generally designated 20, which is connected to the bracket 1 8 by means of a short tubular extension 21 which passes through an aperture 22 in a mounting plate 23. The front end of the mounting plate 23 is attached to a nut 24 received on a feed screw member 25 which is turnably mounted on a part 40 of the chassis 2 and is provided with a turning handle 26. The rear end of the plate is pivoted at pivot 27 to the chassis 2 about a pivot axis parallel to the axis of rotation of the wheel 5. Manual turning of the handle 26 causes the nut 24 to move along the member 25 and the member 23 to pivot about pivot 27 thereby enabling the height of the wheel 5 to be adjusted.

The steering wheel assembly 20 (see Figure 4) comprises a circular plate 28, fixed to the tubular extension 21, and a steering wheel 29 rigidly connected to the plate 28 by means of spokes 30.

An isolating valve 31 and a throttle valve 32 for controlling the operation of the hydraulic motor 1 9 are mounted on the plate 28. A flexible hydraulic supply pipe 50 connects the valve 31 to a surface hydraulic supply means (not shown) and a flexible hydraulic return pipe (not shown) is connectible to a return port 51 on the motor 19 for returning hydraulic fluid to the hydraulic supply means. Steering of the apparatus 1 is effected by turning the steering wheel 29 which causes the entire assembly 6 to be turned relative to plate 28, in directions A or B (see Figure 1) about an axis 41 containing the axis of the tubular extension 21.

The apparatus 1 is intended to be operated underwater by a frogman or diver and for ease of handling during operation the apparatus includes a side hand rail 33, a rear hand rail 34 and a telescopically adjustable foot rest 35. The apparatus 1 further includes a rubber front fender 37 and rubber rear corner fenders 38 and 39.

Hydraulic supply and return couplings 52 and 53, respectively, are provided for enabling flexible hydraulic supply and return pipes (not shown) to be connected between the surface hydraulic supply means (not shown) and the apparatus 1 for operating the hydraulic motors 9 and 10. In underwater operation, hydraulic fluid is supplied to the motors 9 and 10 via an isolating valve 36 and the control valves 12 and 1 3 before being returned to the hydraulic supply means.

In use the apparatus 1 is positioned underwater by a frogman or diver against the side of a ship's hull (not shown) to be cleaned or treated. Actuation of the motors 9 and 10 causes the surface finishing assemblies 14 and 1 5 to rotate so that the substantially flat annular polishing surfaces of the pads 1 4a and 1 spa are rotated against the side of the ship's hull. This rotation of the polishing pads 1 4a and 1 5a against the ship's hull causes a low pressure to be generated between each surface-finishing assembly and the hull so that the apparatus 1 is sucked against the hull. The holes 17 in the backing plates 1 6 of the surface finishing assemblies relieve, to a certain extent, the suction forces generated between each surface finishing assembly and the ship's hull.Further control of the suction forces is achieved by adjusting the height of the front wheel 5 so that the surface finishing assemblies 14 and 1 5 are either moved closer towards, or further away from, the surface of the ship's hull. The suction forces are therefore controlled so that they are sufficient to hold the apparatus in an operating position against the hull but not too great as to adversely affect manoeuvrability of the apparatus 1 or to cause excessive wear of the polishing pads.

On operation of the motor 19, the wheel 5 is driven and the apparatus moves over the surface of the ship's hull under the control of the frogman or diver. As can be seen in Figure 1 , the axes of the surface finishing assemblies 14 and 1 5 are slightly offset from each other in the longitudinal direction of the apparatus 1. This enables the surface finishing assemblies to be mounted so that there is an overlap between tracks made by the polishing pads 1 4a and 1 spa during forward movement of the apparatus.

The apparatus shown in the Figures is intended to be used to clean or treat the hull of a ship coated with a self-polishing marine paint typically containing anti-fouling material. Such paints are normally referred to as SPC (self-polishing copolymer) marine paints. The gentle rubbing action provided by moving the rotating polishing pads 1 4a and 1 spa over the hull surface cleans the latter by removing therefrom any slime, which is the prelude to more severe marine fouling, and/or any spent anti-fouling material which may be present on the marine paint surface in the form, for example, of a soapy film.

Although polishing pads 1 4a and 1 spa having little or no abrading action are effective in cleaning spent anti-fouling material and slime from a ship's hull coated with a self-polishing marine paint, the gentle wiping action provided by such pads is not effective for removing more severe fouling or for smoothing a rough or contoured painted hull surface. For these applications it is necessary to replace the surface finishing assemblies 14 and 15 with surface finishing assemblies having abrasive or more abrasive annular surface finishing pads. Thus in the case where a ship's hull (which may be coated with a self-polishing marine paint or a more conventional anti-fouling marine paint) is severely fouled with marine organisms, e.g. weed, it is necessary to scour or abrade the hull surface to remove the marine organisms and smooth the underlying paint surface.Surface finishing pads which have been found to be particularly suitable for providing such an abrading or scouring action to clean and smooth the hull surface are those made of adhesively bonded fibres of nylon or the like arranged in a non-woven skeletal structure-e.g.

industrial scouring pads. Industrial scouring pads are cleanable to enable them to be re-used and are available in various grades of coarseness. A medium grade pad has been found to be effective in removing weed-like marine growth from a ship's hull and in smoothing the finish of the underlying marine paint. In particular the texture of the marine paint is modified by smoothing any "short wave" roughness in the surface of the marine paint and reducing the drag of the hull. In fact if the marine paint is of the self-polishing kind, this smoothing action is similar to the selfpolishing action of a marine paint on a hull as the latter moves through sea water after being newly coated with the marine paint-i.e. all the highspots and over-sprayings are removed.

If it is desired to smooth the surface of a hull which is contoured and rough (e.g. as a result of being repeatediy painted), surface finishing assemblies may be provided which have abrasive pads which in use flatten and smooth the hull surface. This rubbing action is like a "sandpapering action" and may, for example, be achieved with coarse grade industrial scouring pads.

It will be appreciated that an apparatus according to the invention would normally be provided with a number of different, detachable surface finishing assemblies for enabling different surface treatments to be performed on a ship's hull. In fact the apparatus may also be designed to accept conventional hull cleaning brushes which are useful, at least as an initial treatment, for removing very severe marine foulings from a ship's hull.

Another type of surface treating member which may be used with advantage is shown in Figure 7 in which treating material 60 in the form of an elongate strip is folded tightly in a sinuous or zigzag manner backwards and forwards on itself and is arranged in a circle to define an annulus with a longitudinal edge of the strip providing a substantially flat treating surface (only part of the zig-zag arrangement is shown in Figure 7). A central cavity 61 is defined by the annulus and apertures 62 are provided in a backing plate 63 for relieving pressure in use of the treating member to limit the suction force of the treating member towards the underwater surface being treated. Mounting means, schematically shown at 64, are also provided for securing the treating member to the motor shaft.Instead of being wound in a zig-zag manner the elongate strip could be tightly wound helically or, if it is not required to provide an annular treating pad, in any other tortuous manner. The treating material 60 may be any desired grade of scouring or abrading material-e.g. adhesively bonded fibres of nylon or the like arranged in a non-woven skeletal structure.

Although the present invention has been described with particular reference to the surface treatment of a ship's hull, it should be realised that it may be applied to the treatment of other underwater surfaces, e.g. ship's propellers or stationary underwater structures such as oil rigs.

In the treatment of propellers, hand-held apparatus is employed typically having a single rotatable treating member which in use is sucked against the propeller surface to improve the surface finish of the propeller. In particular this may be achieved by removing fouling material from the propeller, modifying by abrasion the surface of the propeller and/or polishing the propeller.

In the treatment of the hull of a ship with apparatus according to the invention having annular treating pads (14a, 1 5a, 60), each treating pad typically has an outer diameter of approximately 45 cm and an inner diameter of approximately 25 cm to define an endless, annular non-bristled treating surface. The through holes (17, 62) typically have a diameter of approximately 12.5 mm.

Although the present invention is not limited to the use of abrasive treating members, it will be appreciated that low-density abrasive pads-e.g.

formed by crimped staple fibres which have been formed into a mat and impregnated with adhesive and abrasive-provide excellent results. Such low-density abrasive pads are available in a variety of types, some which are only mildly abrasive which can be used as polishing pads and others which are extremely abrasive which can be used for sanding or removing severe fouling from an underwater surface.

Claims

1. A method of treating a fouled and/or rough underwater surface comprising rotating at least one treating member against the underwater surface to hold the at least one treating member against the underwater surface and to remove marine growth from, and/or to smooth, the underwater surface, characterised in that the or each treating member has a non-bristled treating surface.

2. A method according to claim 1, wherein the said underwater surface comprises a ship's hull.

3. A method according to claim 1, wherein the ship's hull has a coating of a self-polishing marine paint applied thereon.

4. A method according to any of the preceding claims, wherein the underwater surface to be treated is abraded by the treating member(s).

5. A method according to any of claims 1 to 4, wherein the underwater surface to be treated is polished by the treating member(s).

6. A method of treating a hull of a ship which is afloat and has a layer of marine growth over a self-polishing marine paint comprising rotating a treating member against the hull to hold the treating member against the hull and to remove the marine growth and expose the said coating to the surrounding water, characterised in that said treating member has a non-bristled treating surface.

7. Apparatus for treating a fouled and/or rough underwater surface comprising at least one detachable rotatably mounted, surface treating member, and drive means for rotating the or each treating member against the underwater surface to be treated for holding by suction the apparatus against the underwater surface and for effecting removal of marine growth from, and/or smoothing of, the underwater surface, is characterised in that the or each treating member has a substantially flat, non-bristled treating surface.

8. Apparatus according to claim 7, wherein the or each treating member comprises an abrasive pad.

9. Apparatus according to claim 8, wherein the or each abrasive pad comprises adhesively bonded fibrous material (e.g. nylon fibres) arranged in a non-woven open skeletal structure.

10. Apparatus according to claim 7, wherein the or each treating member comprises a polishing pad.

11. Apparatus according to any of claims 7 to 10, wherein the or each treating member comprises an annular pad of treating material affixed to a backing member.

12. Apparatus according to claim 11, wherein a central portion of the or each backing member not covered by said annular pad has through hole means formed therein for controlling the pressure at the centre of the treating member during use of the apparatus.

13. Apparatus according to claim 11 or 12, wherein the annular pad is formed by tightly winding an elongate strip of material in a tortuous path so that a longitudinal edge of the wound strip provides a treating surface.

1 4. Apparatus according to claim 13, wherein the strip of material is wound in a helical path to provide the annular pad.

1 5. Apparatus according to claim 13, wherein the strip of material is wound in a zig-zag or sinuous manner arranged in a circle to provide the annular pad.

1 6. Apparatus according to any of claims 7 to 10, wherein the or each treating member comprises a treating pad formed of an elongate strip of treating material tightly wound in a tortuous path.

1 7. A method of treating a fouled and/or rough underwater surface substantially as herein described with reference to Figures 1-6 or Figures 1-4 and Figure 7.

1 8. Apparatus for treating a fouled and/or rough underwater surface substantially as herein described with reference to, and as illustrated in, Figures 1-6 or Figures 1--4 and Figure 7.

Amendments to the claims have been filed, and have the following effect:- New or textually amended claims have been filed as follows:-

1. A method of treating a fouled and/or rough underwater surface comprising rotating at least one treating member against the underwater surface to hold the at least one treating member against the underwater surface and to remove marine growth from, and/or to smooth, the underwater surface, characterised in that the or each treating member has a substantially flat, non-bristled treating surface.