HK1215011B - A submergible cleaning system - Google Patents

Description

Submersible cleaning system

Technical Field

The present invention relates to a submersible cleaning system for cleaning the underwater hull surface of a vessel while the vessel is floating or as an offshore installation. The invention also relates to a vessel or work vessel comprising such a submersible cleaning system and to the use of such a submersible cleaning system.

Background

A smooth underwater hull surface is essential to ensure optimal performance of the vessel and even a thin layer of rapidly growing slime can create additional friction. Given the high cost of fuel and the high utilization of the ship, even marginal additional friction has a significant negative impact on the overall fuel cost.

Current anti-fouling paint systems do not prevent the formation of slime and other fouling in the usual docking intervals; thus, there is a need for underwater hull cleaning between docks to minimize the formation of slime, dirt and other friction-enhancing objects on the underwater hull.

Clean underwater hulls are known in the art. However, with these known techniques, several drawbacks have been found, namely:

a) the anti-fouling layer (i.e. paint) on the underwater hull may occasionally be damaged, or even in some cases completely removed, whereby the underwater hull is exposed to the marine environment and there is therefore a great risk that the growth rate of slime on the underwater hull is getting faster and faster. This is often the case when mechanical cleaning, i.e. with brushes and similar devices, is used.

b) The cleaning of underwater hulls often pollutes the environment by residues of the anti-fouling layer in the slime. Slime itself can also be harmful to the environment as it may contain foreign species.

c) The cleaning operation is time consuming and in many cases may exceed the usual time of stay of the ship in port, which has serious consequences for the ship owner, since the ship owner is thus unable to comply with the schedule.

d) The cleaning operation is usually performed manually by divers and the underwater environment provides working conditions that are unfavorable for divers. Due to unfavorable working conditions for divers, divers often urgently want to complete cleaning operations quickly, which in some cases may cause unsatisfactory cleaning quality.

A submersible cleaning system is known from WO 2012/074408 a 2.

Disclosure of Invention

It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide a systematic, environmentally friendly, fast and cost-effective submersible cleaning system.

Furthermore, it is an object of the present invention to provide a submersible cleaning system in which the submerging forces are minimized.

It is a further object of the present invention to provide a submersible cleaning system that can clean underwater hulls and thereby remove slime and other dirt in a gentle manner without substantially damaging the anti-fouling paint on the hull.

It is another object of the present invention to provide a submersible cleaning system that minimizes environmental contamination.

It is a further object of the present invention to provide a submersible cleaning system that can be monitored and controlled relative to the surface of an underwater hull.

Another object is to provide a submersible cleaning system with low energy consumption and high cleaning efficiency.

Furthermore, it is an object to provide a submersible cleaning system that is easy to use by a minimum of crew by combining manual control and autonomous modes of operation.

The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a submersible cleaning system for cleaning an underwater hull surface of a vessel while the vessel is floating or as an offshore unit, according to aspects of the present invention, comprising:

-a housing comprising a top surface, a side surface with an edge and an open bottom surface, the edge and the bottom surface being arranged opposite the hull surface, and the housing further comprising:

a rotating disc having a plurality of nozzles arranged around the periphery of the rotating disc, the nozzles facing the hull surface,

-rolling spacer means for providing a predetermined first clearance between the rotating disc and the hull surface,

-a suction device in fluid connection with an outlet provided in the housing for providing a negative pressure within the housing,

-a pressurizing device in fluid connection with the nozzle for providing high pressure fluid to the nozzle, whereby the nozzle is adapted to discharge high pressure fluid against the hull surface for cleaning,

wherein the housing further comprises a shroud disposed at least partially between the rotatable disc and the housing, whereby a chamber is disposed between the housing and the shroud, the chamber being in fluid communication with the suction device.

In one embodiment, the shroud may include a shroud top surface, a shroud side surface having a shroud edge, and an open shroud bottom surface, the shroud edge and the shroud bottom surface being disposed opposite the hull surface.

Further, the shroud may be disposed within the housing with a predetermined second gap between a side of the shroud and a side of the housing.

The predetermined second gap may be less than 0.03m, preferably less than 0.025m, more preferably less than 0.015 m.

The edges of the sides of the housing may be disposed at a first distance from the hull surface.

Further, the first distance may be less than a second distance between the shroud edge and the hull surface.

In addition, by adjusting the first distance between the edge of the hull and the hull surface, the negative pressure in the hull can be controlled during operation.

Furthermore, the negative pressure may create a suction effect within the housing along the edges of the housing.

The suction within the housing may be provided along an edge of the housing.

Furthermore, the suction effect within the housing can be distributed over a larger area.

Furthermore, the edge of the shell may comprise a skirt made of a flexible material, so that the shell can be moved over a (mono-) and/or bi-curved hull surface.

The skirt may be water permeable.

In one embodiment, a plurality of rotating disks may be disposed within the housing.

Further, a shroud may be disposed between the plurality of disks and the housing.

Additionally, a shroud may be provided around each rotating disk.

Furthermore, two adjacent rotating discs may have opposite rotational directions to reduce friction therebetween.

Also, a shroud may be disposed between the plurality of disks and the housing.

Furthermore, a shroud may be provided around each rotating disc, and a chamber may be provided around the shroud, the chamber being in fluid communication with the suction device.

The rotating discs may be driven by one or more motors.

Also, each rotating disk may include a rotation axis, and the nozzles may be supplied with high-pressure fluid through a hollow main shaft disposed concentrically with the rotation axis.

Furthermore, the suction device may be a pump.

Furthermore, the pressurizing means may be a pump.

In one embodiment, the pressure of the fluid exiting the nozzle may be between 30 bar and 150 bar, preferably between 50 bar and 125 bar.

Furthermore, the rolling spacer may be adjustable to adjust a first clearance between the rotating disc and the hull surface.

By adjusting the rolling spacer by means of the pressure controller, the size of the first gap can be automatically adjusted during cleaning.

The rolling spacing means may be a roller.

Additionally, the rotation of the rotating disk may be adjustable.

In one embodiment, the rotation of the rotating disk may be in the range of 250rpm to 550rpm, preferably in the range of 350rpm to 450 rpm.

Furthermore, the pressure supplied to the nozzles may be adjusted in relation to the rotational speed of the rotating disc such that, when the rotational speed of the disc decreases, the pressure supplied to the nozzles decreases accordingly, and vice versa.

Also, the nozzle may be a cavitation type nozzle adapted to induce a cavitation effect (cavitation) in front of the nozzle to provide high and localized stresses on the hull surface due to cavitation collapse. Thereby an enhanced erosive power for cleaning the hull surface is obtained and at the same time the pumping power requirements are reduced.

Further, the rotating disc may comprise a disc surface arranged opposite the hull surface, the nozzles being arranged below the disc surface.

The nozzles may be arranged flush with the disc surface.

The nozzle may be adapted to be adjusted such that the impact angle of the high pressure fluid may be changed in consideration of the rotation direction of the rotating disc.

In addition, the nozzle may interlock with a pressure switch in the housing so that cleaning is only provided when the housing has a negative pressure.

In one embodiment, a residue and debris recovery device may be provided in relation to the outlet in the housing for collecting waste water resulting from the cleaning of the hull surface.

The recovery device may comprise a filtration unit adapted to filter residues and/or debris from the waste water.

The filter unit can be completely submerged so that the suction pump does not have to lift the waste water above sea level.

The filtered wastewater may be discharged into seawater after filtration.

Further, the filter unit may include a long filter sock (filter sock).

The submersible cleaning system as described above may also include a Remotely Operated Vehicle (ROV).

Further, the ROV may comprise a propulsion device.

In addition, the rotational speed of the rotating discs may be adjusted in relation to the speed of the ROV such that, when the speed of the ROV increases, the rotational speed of the discs will increase accordingly, and vice versa.

In one embodiment, the control unit may be arranged to control 4-to 6-dimensional movement of the ROV when submerged.

A propeller, camera, sonar, compass and/or light may be provided in conjunction with the ROV.

Such propellers may be electrically driven.

Furthermore, the ROV may be equipped with navigation and orientation means, which are connected to the control unit.

Further, the power supply to the cleaning system may be provided from an external source or from a boat.

The invention also relates to a vessel or work vessel comprising a submersible cleaning system as described above.

In one embodiment the vessel or work vessel may comprise lifting means (horisting means) arranged to lift the ROV onto the deck of the vessel and to lower the ROV from the vessel into the water.

Further, a control unit may be provided on the vessel, enabling the operator to control the submersible cleaning system and the ROV.

Furthermore, a storage unit may be provided on the vessel for storing data relating to the cleaning of the underwater hull surface.

Finally, the invention relates to the use of a submersible cleaning system as described above for cleaning the underwater hull surface of a vessel while the vessel is floating or as an offshore installation, such as an offshore unit, a drilling platform or an offshore wind turbine.

Drawings

The invention and its many advantages are described in more detail below with reference to the accompanying schematic drawings, which show, for purposes of illustration, some non-limiting embodiments, and in which

Figure 1 shows the submersible cleaning system in a schematic side view,

figure 2 shows another embodiment of the submersible cleaning system in partial side view,

figure 3 shows the cleaning system of figure 2 in a bottom view,

figure 4 shows the cleaning system of figure 2 in an end view,

figure 5 shows the ROV of the shrouded cleaning system in a top view,

figure 6 shows the ROV of figure 5 in bottom view,

figure 7 shows the ROV of figure 5 with the bonnet removed,

figure 8 shows the ROV of figure 5 with the cover removed in bottom view,

FIG. 9 shows a work vessel, an

Fig. 10 shows equipment arranged on the deck of a work vessel.

All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary for the elucidation of the invention, other parts being omitted or mentioned only.

Detailed Description

In fig. 1, a submersible cleaning system 1 for cleaning an underwater hull surface 3 of a vessel while the vessel is floating is shown. The cleaning system 1 comprises a housing 2, which housing 2 comprises a top surface 3, a side surface 4 with an edge 5 and an open bottom surface, the edge and the bottom surface being arranged opposite the hull surface 3 in the cleaning position. The housing 2 further comprises a rotating disc 6 having a plurality of nozzles 7 arranged around the periphery of the rotating disc 6, the nozzles 7 facing the hull surface 3. The housing 2 further comprises rolling distance means 8 for providing a predetermined first clearance 9 between the rotating disc 6 and the hull surface 3. A suction device 10, for example a pump, is in fluid connection with an outlet 11 provided in the housing 2 for providing a negative pressure P inside the housing 2.

Furthermore, the cleaning system 1 comprises a pressurizing device 12 in fluid connection with the nozzle 7 for providing high pressure fluid to the nozzle 7, whereby the nozzle 7 is adapted to discharge high pressure fluid against the hull surface 3 for cleaning.

The housing 2 further comprises a shroud 13 at least partially disposed between the rotatable disk 6 and the housing 2. The shroud 13 is arranged at a distance from the housing such that a chamber 14 is provided between the shroud 13 and the housing, which chamber 14 is in fluid communication with the suction device 10. This achieves that the suction effect is exerted only in the chamber 14, so that the sinking forces on the system are significantly reduced. Furthermore, by providing a negative pressure in the chamber, a constant inflow of water from outside the housing is ensured preventing any objects escaping from the cleaning system to contaminate the environment. Furthermore, since the cleaning system 1 according to the present invention has the shroud 13 disposed inside the housing, the necessary water intake rate is reduced. Yet another advantage is that the chamber 14 provides a path for the suction device to suck up debris resulting from the cleaning operation.

The rotating disc 6 comprises nozzles 7. The nozzles 7 are adapted to direct a high pressure water jet through the open face to impinge on the hull surface 3 and thereby clean and/or remove slime, dirt and/or algae from the hull surface 3.

The rotating disc 6 comprises a rotation axis 70 and the nozzles 7 are supplied with high-pressure fluid via a hollow spindle 71 arranged concentrically with the rotation axis 70.

Furthermore, the nozzle 7 may be interlocked with the pressure switch 15 so that cleaning of the hull surface does not occur unless the housing 2 has a negative pressure P.

The negative pressure P in the hull 2 and thus the rate of the incoming water flow F can be controlled by adjusting the size of the gap between the hull 2 and the hull surface 3. In one embodiment, the size of the gap may be automatically adjusted during cleaning by adjusting the roller 8 by means of the pressure controller 16.

Furthermore, the housing 2 may be provided with a skirt or curtain (not shown) made of a flexible material, which allows the cleaning system 1 to operate on both (mono) and bi-curved surfaces of the hull surface 3 without compromising the recovery of debris. Furthermore, the skirt may be water permeable.

Furthermore, the shroud 13 may comprise a shroud top surface 17, a shroud side surface 18 with a shroud edge 19, and an open shroud bottom surface, the shroud edge 19 and the shroud bottom surface being arranged opposite the hull surface 3. As described above, the shroud 13 is disposed within the housing 2 with the predetermined second gap 20 between the shroud side 18 and the side 4 of the housing 2. The predetermined second gap 20 may be less than 0.03m, preferably less than 0.025m, and more preferably less than 0.015 m.

Furthermore, the edge 5 of the side 4 of the hull 2 is arranged at a first distance 21 from the hull surface 3. The first distance 21 is smaller than the second distance 22 between the shroud edge 18 and the hull surface 3.

Fig. 2 shows another embodiment of the cleaning system 1. In this embodiment, the cleaning system 1 comprises four rotating discs 6 arranged one after the other inside the shroud 13. Thus, the cleaning system 1 can clean a larger area of the hull surface. Other (not shown) embodiments may include a different number of rotating disks. Further, the disks in this embodiment are shown arranged in a row. In other (not shown) embodiments, the rotating discs may be arranged in two or more rows, each row having a plurality of rotating discs.

A shroud 13 is provided between the rotating disc 6 and the housing 2. The rotating discs 6 are preferably driven by one motor, or in this embodiment by a plurality of motors 25, wherein each rotating disc 6 is driven by one motor. Furthermore, a transmission unit 26 may be provided with each rotating disc 6.

In one embodiment, two adjacent rotating discs 6 have opposite rotational directions to reduce friction between them, so that the energy consumption of the cleaning system 1 can be reduced.

The rotating disc 6 comprises a rotation axis (not shown) and the nozzles are supplied with high pressure fluid via a hollow spindle (not shown) arranged concentrically with the rotation axis. The pressure of the fluid leaving the nozzle is between 30 bar and 150 bar, preferably between 50 bar and 125 bar.

Furthermore, the rotational speed of the rotating disc may be adjustable. The rotational speed of the rotating disc may be in the range of 250rpm to 550rpm, preferably in the range of 350rpm to 400 rpm.

Furthermore, the pressure supplied to the nozzles may be adjusted in relation to the rotational speed of the rotating disc 6, so that when the rotational speed of the disc 6 decreases, the pressure supplied to the nozzles decreases accordingly, and vice versa. Hereby is achieved that the surface to be cleaned can be cleaned more smoothly, since the power of the nozzles is adjusted taking into account the rotational speed of the rotating disc.

Furthermore, a residue and debris recovery device 28 is provided in connection with an outlet (not shown) in the housing 2 for collecting waste water resulting from the cleaning of the hull surface. The recovery device 28 comprises a filtering unit 29 suitable for filtering residues and/or debris from the waste water. The filtered waste water may be discharged into the sea water during filtration. Furthermore, the pump 10 is adapted to provide a suction effect inside the housing 2.

In fig. 3, the cleaning system 1 of fig. 2 is shown in a bottom view. Four rotating discs 6 are shown within the shroud 13. In this embodiment, each disc 6 has three nozzles 7 arranged along the outer periphery 30. Advantageously, the nozzle 7 is a cavitation type nozzle adapted to induce cavitation effects in front of the nozzle to provide high and localized stresses on the hull surface due to cavitation bubble collapse. Thereby an enhanced erosion/erosion power for cleaning the hull surface is obtained and at the same time the pumping power requirements are reduced. Thus, by using the cavitation type nozzle 7, effective cleaning can be achieved at a lower fluid pressure than in the prior art. Furthermore, the rotating disc may comprise a disc surface arranged opposite the hull surface, the nozzles being arranged below the disc surface. Further, the nozzles may be adapted to be adjusted so that an angle of attack of the high-pressure fluid may be changed in consideration of the rotation direction of the rotating disk.

In fig. 4, the cleaning system 1 of fig. 2 is shown in an end view. The cleaning system 1 has two filter units 29 arranged on top of the housing 2.

On the surface, a work vessel or ship (described further below) may be used to control the following: guide wires to the ROV, a power source to power the ROV, winches for tethers and waste hoses, submergence and retrieval ROV and the lifting capability of external filters. In addition, a small RIB boat may be used for support during cleaning operations.

The cleaning system 1 further comprises a Remotely Operated Vehicle (ROV)35 as shown in fig. 5. ROV 35 is shown with a cover 36. In general, ROVs may be equipped as working grade ROVs, but are well suited for cleaning ship hulls in terms of propeller orientation, physical design, payload and sensors, so that ROVs may be adapted for 4-to 6-dimensional movement, preferably 6-dimensional movement, when submerged. The ROV may be powered from the surface via a neutral-buoyancy (neutral-buoyant) tether that also includes optical telemetry for communication.

In fig. 6, the ROV 35 is shown in a bottom view revealing the rotating disc 6. The different elements of the ROV will be described further below.

In fig. 7 and 8, ROV 35 is shown without a cover and includes a frame 37 constructed of welded stainless steel profiles. The frame 37 will serve as a base for all heavy equipment such as pumps, motors and propellers 38. The frame 37 is also connected to a lifting point for safe operation during submergence and recovery operations.

In this embodiment, ROV 35 is propelled by six propellers 38, each 4.5 kW. Three thrusters will press the ROV and thus the cleaning system 1 against the surface of the target vessel, while the other three thrusters will control the forward/backward and sideways movement of the ROV and control the heading of the ROV. Depending on the relative position of the thrusters, the thrusters and buoyant material configuration and the ROV control system make it possible to control the ROV in all six degrees of freedom (i.e. 6-dimensional movement), i.e. forward/backward, sideways, up/down, yaw/heading, pitch and roll. The reason for using six identical and rather powerful motors is to obtain a stable ROV that can be held in place and follow its trajectory in a turbulent, powerful water flow. ROVs will also be large in terms of volume and weight, requiring powerful propellers to obtain a submersible with good response. It is also advantageous from a spare part point of view to have only one type of motor.

The propeller is preferably electrically driven to obtain accurate and vibration-free operation.

High pressure pump 12 may include a self-cleaning filter for incoming water to the high pressure pump. The self-cleaning mechanism is driven by a motor that is driven by water pressure.

The high pressure is provided by two fixed displacement axial piston pump units 12 driven by a 3000V/60Hz dual shaft motor. These pumps 12 together provide a fixed flow of 340 l/min. 20l/min from these pumps will be used for self-cleaning, while 1l/min is used for hydraulic motor drive of the filter. Each pump unit is connected to two rotating discs 6. This means that only two rotating discs can be run as required.

In order to be able to reduce the flow to the nozzles when necessary, a proportional control valve 39 can be provided after the two high-pressure pumps. These valves 39 also serve to open and shut off flow to the nozzles in conjunction with a pressure relief valve as described below.

A pressure relief valve may be provided after the other two pumps to be able to open and shut off the flow to the nozzle. To reduce the back pressure (pump/motor load) at pump start-up, the flow will also be cut off (relief valve venting to the surrounding sea).

The suction pump 10 is located on the ROV because the pump must be close to the source (suction). The pump is an environmentally friendly particulate centrifugal pump having a capacity of about 620L/min at rated pressure drop. This pressure drop has been calculated by considering the diameter and length of the waste hose plus other factors such as different joints and external filters. The power required to operate the suction pump is in the range of 10 kW.

The concept of an external filter is a large "sock" that floats just below the water surface. The filter is connected to a buoy located at the surface of the water so that it can be seen where it is located and so that it can be more easily retrieved. A counterweight is provided at the bottom of the filter to hold it in place. The debris inlet is also arranged in the bottom part of the filter bag. During the cleaning operation, the external filter is located beside the target vessel. The filter follows the ROV as it moves along the target vessel, because the debris hose has a fixed length and is connected to both the bag and the ROV. If necessary, the position of the filter can be adjusted using support lines that can be attached alongside the target vessel and controlled from the platform/cleaning support vessel. Small RIB boats are also used to monitor the location and status of the filters.

When the filter bag is lifted from the water using a crane, the remaining water will be drained leaving only the debris. The basic concept is to use a disposable filter.

The tether 40 from the work vessel 50 consists internally of cables suitable for 3000 vac, 500 vdc and optionally they will be spliced into an oil-filled junction box on the end of the ROV. The first part is 3000 vac to the pump in two different cables and the second part is 500 vdc to the ROV main pressure housing. The third section is an optical fiber leading to the ROV main pressure housing. To remove the tether 40 from the ROV, connectors suitable for 3000 vac, 500 vdc, and optical fibers need to be disconnected. The tether inlet to the ROV is located on the same side as the hose connection 41 and the guide wire 42.

When changing filter bags, it is necessary to easily handle the waste hose 41 connected to the external filter from the RIB ship 52.

A guide wire 42 is attached to the ROV on the same side as the waste hose and tether. The idea is to make it easily accessible from the RIB ship 52 so that it can be disconnected when cleaning components close to the ship's propulsion.

The ROV may be equipped with two sonars 43. A profiling sonar can be used to monitor the environment, distance from the sea floor and dock etc. Another sonar may be a forward looking high resolution sonar used to avoid obstacles and the like.

Preliminary experiments have shown that the boundary between a cleaned surface and an uncleaned surface on the target hull can be detected so that the sonar can assist navigation control.

A lamp and a camera may be mounted on each of the two pan and tilt units 44. The angular viewing range of these units 44 will be limited by the surrounding ROV components and cables for the lights and cameras. Pan and tilt unit 44 will be positioned to achieve a maximum viewing angle in all directions, which is particularly useful for identifying obstacles in conjunction with data from the obstacle avoidance sonar.

The angular position of pan and tilt unit 44 is programmable: multiple set points can be defined and the previously programmed camera viewing heading can be restored/reset by pressing a button. This feature may be used to quickly reconfigure the ROV during operation, for example to ensure that the camera is pointed in the direction of travel of the ROV.

Six color cameras 45 may be mounted on the ROV. Two of them are movable via the pan and tilt unit and four are arranged in fixed positions. The camera 45 serves as both an observation camera and a navigation camera.

The housing 2 with the flexible skirt or curtain portion reducing the first distance from the hull surface in combination with the suction pump flow will prevent any debris from escaping during cleaning.

The rotational speed of the rotatable disc 6 can be controlled independently of the water flow to the rotatable disc. The rotational speed needs to be changed according to the forward speed of the ROV. The reference point was 400rpm at a forward speed of 0.5 m/s. The control system will provide the function to ensure that the rotating discs slow down proportionally in the event that the ROV slows down.

The motor 25 for rotating the disc may be a three-phase delta-connected 400V ac motor with a maximum power of 1.5kW per motor. The motor will be powered by a 500V dc mains supply via a separate motor drive.

The main surface platform for the cleaning system 1 is a vessel or work vessel 50 as shown in fig. 9, which is moored at the quay and in front of or behind the target vessel during operation. The filter bag for debris will follow the ROV next to the target vessel. A small RIB boat 52 is also required to assist in handling the filter bags and may be used for other support issues.

ROV control sensors include depth sensors, gyroscopes, accelerometers, and Doppler Velocity Log (DVL) (optional). They are used to control ROV in all degrees of freedom.

Other sensors such as fixed length data from a guidewire winch, roller data, DVL (optional) would be used in conjunction with the ROV control sensor to determine the position of the ROV. An accurate GPS will be installed on the work vessel to return to the starting point and be able to take its place again in case of a task being aborted and to continue the task later.

A typical cleaning solution is for the ROV to travel forward in 1.6m steps, forming an orthogonal trajectory that can be seen from the heading. The trajectory is determined by the length of the guide wire. The ROV control system will always use two horizontal thrusters to extend the guide wire. It also commands three vertical thrusters to push the vehicle against the hull. If the ROV is too far from the hull to affect the cleaning effect, the rollers and DVL (optional) will indicate on the MMI and give a warning.

Several help functions can be introduced depending on the rotational speed of the drive and the water pressure is regulated by the steering system of the ship. The water pressure and the rotational speed may be automatically changed, for example, according to the forward speed of the ROV.

All trajectories, including sensor data from the ROV, such as heading, pitch, roll, depth, line length, wheel data, and DVL (optional), are used to determine if the hull has been completely cleaned and presented to the pilot in real time during operation.

All position data and camera images are recorded and can be seen in the software on the playback HMI after operation. The playback function may also be installed on a standard computer. This recorded data is stored in a separate hard disk drive for quality control.

Work vessel 50 may have a crane 54 to operate the load.

The tether 40 will be in a positive buoyancy position (posively buoyant) and if desired a marked buoy may be attached to make it more readily visible at the surface. The tether 40 will be attached to the external filter buoy and, after the tension is released, to a waste hose connected down to the ROV.

To enable maneuvering of the ROV, a guide wire is attached to the ROV. The guide wire may be a 3mm type Dyneema (Dyneema) wire which passes through the tether protection system 57(TPS) to a layer of winch which controls the length of the wire. The tension from the winch 56 is fixed and not adjustable until such a degree that the winch will begin sending out the line to avoid line breakage. A sensor on the winch will measure the tension in the guide wire so that the position of the TPS counterweight can be calculated and the track for the ROV maintained.

The concept of TPS 57 depends on the appearance of the platform for the device. Existing TPS's include those with winches and TPS submersibles (launch vehicles).

The work vessel 50 as shown in fig. 10 must be equipped with a crane 54 with load, lift height and expansion capability to handle all the components to be submerged and recovered, such as ROV 35 and filter bag 55.

The vessel 50 needs to have available space on deck 51 for the system winches, framed TPS, ROV 35 in the cradle and space for handling the filter bags. The operator needs an easily accessible area inside the work vessel 50 in order to operate the system.

The preferred option is that the work vessel has hovering capability to avoid anchoring or lashing on the dock or on the vessel to be cleaned. This will also minimize movement that would adversely affect the cleaning effect.

Under normal conditions, the cleaning of the ship may comprise the following steps:

-attaching support lines for the filter bags beside the target vessel if the circumstances require.

-positioning the ROV platform in front of the target vessel.

Launch the ROV, lower the TPS, send out the guide wire, send out the tether and send out the ROV waste hose.

After 80m, begin attaching floats to the tether every 20 m.

-launching the filter bag and attaching it to the support line if necessary. The ROV waste hose is attached to the outer filter bag and ensures that the other end is firmly attached to the ROV.

Positioning the ROV and starting cleaning the target vessel. If necessary, the position of the filter bag is adjusted and the tether is fed out.

When the operator encounters various obstacles along the intended cleaning track, such as bilge keels or the like, the ROV will need to navigate between the surface and the bilge keels until these obstacles no longer obstruct access to the hull along the intended cleaning track. Cleaning is then resumed from the next available safe hull landing position.

When the cleaning mode has been completed, sailing the ROV to the platform and recovering the tether and the vehicle on board. Recovery may also be required when shifting the platform position from a forward position to a rearward position of the vessel. The filter bag is retrieved to deck and stored until it is retrieved onshore for pre-scheduled disposal/destruction.

-removing the support lines for the filter bags alongside the target vessel.

The operating procedure in extreme climatic conditions is the same as in normal conditions, the main difference being the time required to perform the operation. If visibility is limited and there is a strong current, the speed of the vehicle will decrease. In the case of strong winds with large waves, it is more difficult to position the platform, moor the platform, manipulate the filter bags, etc., and is therefore more time consuming.

By using the cleaning system according to the invention a gentle cleaning of the underwater hull is achieved. At the same time, the cleaning process is very environmentally friendly due to the residue and debris recovery means, and it does not substantially contaminate the environment. Furthermore, the ROV and the control unit ensure that the cleaning process can be planned according to the actual design of the underwater hull, and that during the actual cleaning process the underwater hull can be monitored in order to ensure that the entire underwater hull is cleaned as intended.

Although the invention has been described above in connection with preferred embodiments of the invention, it will be evident to a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the appended claims.

Claims (49)

1. A submersible cleaning system (1) for cleaning an underwater hull surface (3) of a vessel while the vessel is floating or as an offshore facility, the cleaning system (1) comprising:

-a housing (2) comprising a top face, a side face (4) with an edge (5) and an open bottom face, the edge (5) and bottom face being arranged opposite the hull surface (3), and the housing (2) further comprising:

-a rotating disc (6) having a plurality of nozzles (7) arranged around its outer circumference (30), said nozzles facing the hull surface (3),

-rolling spacer means (8) for providing a predetermined first gap (9) between the rotating disc (6) and the hull surface (3),

-a suction device (10) in fluid connection with an outlet (11) provided in the housing (2) for providing a negative pressure inside the housing (2),

-a pressurizing device (12) in fluid connection with the nozzle (7) for providing high pressure fluid to the nozzle (7), whereby the nozzle (7) is adapted to discharge high pressure fluid against the hull surface (3) for cleaning,

wherein the housing (2) further comprises a shroud (13) arranged at least partially between the rotating disc (6) and the housing (2), whereby a chamber (14) is arranged between the housing (2) and the shroud (13), the chamber (14) being in fluid communication with the suction device (10),

the mantle (13) has a mantle top surface with an opening for receiving the hollow spindle (71), wherein the mantle top surface is arranged at a distance from the top surface of the housing (2).

2. Submersible cleaning system (1) according to claim 1, wherein the shroud (13) comprises a shroud top face (17), a shroud side face (18) with a shroud edge (19) and an open shroud bottom face, the shroud edge (19) and shroud bottom face being arranged opposite the hull surface (3).

3. Submersible cleaning system (1) according to claim 2, wherein the shroud is arranged within the housing with a predetermined second gap (20) between the shroud side and the side of the housing.

4. Submersible cleaning system (1) according to claim 3, wherein the predetermined second gap (20) is less than 0.03 m.

5. Submersible cleaning system (1) according to any one of claims 1-4, wherein the edge of the side of the housing is provided at a first distance from the hull surface.

6. Submersible cleaning system (1) according to claim 5, wherein the first distance is smaller than a second distance between a shroud edge and the hull surface.

7. Submersible cleaning system (1) according to claim 5, wherein the negative pressure in the housing is controlled during operation by adjusting the first distance between the edge of the housing and the hull surface.

8. Submersible cleaning system (1) according to claim 1, wherein the negative pressure creates a suction effect within the housing along the edge of the housing.

9. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein an edge of the housing comprises a skirt, which is made of a flexible material.

10. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein a plurality of rotating discs (6) are provided within the housing (2).

11. Submersible cleaning system (1) according to claim 10, wherein two adjacent rotating discs have opposite rotational directions to reduce friction between them.

12. Submersible cleaning system (1) according to claim 10, wherein the shroud is arranged between the plurality of rotating discs and the housing.

13. Submersible cleaning system (1) according to claim 10, wherein a shroud is provided around each rotating disc and a chamber is provided around the shroud, which chamber is in fluid communication with the suction device.

14. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the rotating disc (6) is driven by one or more motors (25).

15. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein each rotating disc comprises a rotation axis and the nozzles are supplied with high pressure fluid via a hollow spindle arranged concentrically to the rotation axis.

16. Submersible cleaning system (1) according to claim 15, wherein the pressure energy of the fluid leaving the nozzle is between 30 and 150 bar.

17. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the rolling spacer device is adjustable for adjusting a first gap between the rotating disc and the hull surface.

18. Submersible cleaning system (1) according to claim 17, wherein the size of the first gap is automatically adjusted during cleaning by adjusting the rolling spacer by means of a pressure controller.

19. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the rotation of the rotating disc (6) is adjustable.

20. Submersible cleaning system (1) according to claim 19, wherein the rotation of the rotating disc is in the range of 250 to 550 rpm.

21. Submersible cleaning system (1) according to claim 19, wherein the pressure provided to the nozzles is adjusted in relation to the rotational speed of the rotating disc such that, when the rotational speed of the rotating disc decreases, the pressure provided to the nozzles decreases accordingly and vice versa.

22. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the nozzle (7) is a cavitation type nozzle adapted to induce cavitation effects in front of the nozzle (7) to provide higher and localized stresses on the hull surface (3) due to cavitation bubble collapse.

23. Submersible cleaning system (1) according to any one of claims 1-4, wherein the rotating disc comprises a disc surface arranged opposite the hull surface, the nozzle being arranged below the disc surface.

24. Submersible cleaning system (1) according to claim 23, wherein the nozzle is arranged flush with the disc surface.

25. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the nozzle is adaptable such that the impact angle of the high pressure fluid can be changed taking into account the direction of rotation of the rotating disc.

26. Submersible cleaning system (1) according to any one of claims 1 to 4, wherein the nozzle is interlocked with a pressure switch in the housing, such that cleaning is provided only when the housing has a negative pressure.

27. Submersible cleaning system (1) according to any one of claims 1-4, wherein a residue and debris recovery device (28) is provided in connection with the outlet (11) in the housing (2) for collecting waste water resulting from the cleaning of the hull surface (3).

28. Submersible cleaning system (1) according to claim 27, wherein the recovery device (28) comprises a filtering unit (29) adapted to filter residues and/or debris from the wastewater.

29. Submersible cleaning system (1) according to claim 28, wherein the filter unit (29) is fully submerged such that the suction device (10) does not have to lift the waste water above sea level.

30. Submersible cleaning system (1) according to claim 29, wherein the filtered waste water is discharged into the sea water after filtration.

31. Submersible cleaning system (1) according to claim 28, wherein the filter unit comprises a long filter bag.

32. Submersible cleaning system (1) according to any one of claims 1 to 4, further comprising a Remotely Operated Vehicle (ROV) (35).

33. Submersible cleaning system (1) according to claim 32, wherein the ROV comprises a propelling device.

34. Submersible cleaning system (1) according to claim 32, wherein the rotational speed of the rotating disc is adjusted in relation to the speed of the ROV such that, when the speed of the ROV increases, the rotational speed of the rotating disc increases accordingly and vice versa.

35. Submersible cleaning system (1) according to claim 32, wherein a control unit is provided for controlling the 4-to 6-dimensional movement of the ROV (35) when submerged.

36. Submersible cleaning system (1) according to claim 32, wherein a propeller (38), a camera (45), a sonar device (43), a compass and/or a light device are provided in connection with the ROV (35).

37. Submersible cleaning system (1) according to claim 36, wherein the propeller is electrically driven.

38. Submersible cleaning system (1) according to claim 35, wherein the ROV (35) is equipped with navigation and orientation means, which are connected with the control unit.

39. Submersible cleaning system (1) according to claim 4, wherein the predetermined second gap (20) is less than 0.025 m.

40. Submersible cleaning system (1) according to claim 39, wherein the predetermined second gap (20) is less than 0.015 m.

41. Submersible cleaning system (1) according to claim 16, wherein the pressure energy of the fluid leaving the nozzle is between 50 and 125 bar.

42. Submersible cleaning system (1) according to claim 20, wherein the rotation of the rotating disc is in the range of 350rpm to 450 rpm.

43. A vessel or work vessel (50) comprising a submersible cleaning system (1) according to any one of claims 1 to 42.

44. A vessel or work vessel (50) according to claim 43, wherein the vessel or work vessel comprises lifting means arranged to lift the ROV onto the deck of the vessel and to lower the ROV from the vessel into the water.

45. Vessel or work vessel (50) according to claim 43 or 44, wherein a control unit is arrangeable on the vessel, enabling an operator to control the submersible cleaning system and the ROV.

46. A vessel or work vessel (50) according to claim 43 or 44, wherein a storage unit is provided on the vessel for storing data relating to the cleaning of the underwater hull surface.

47. Use of a submersible cleaning system according to any one of claims 1-42 for cleaning an underwater hull surface (3) of a vessel while the vessel is floating or as an offshore installation.

48. Use according to claim 47, wherein the offshore facility is an offshore unit.

49. Use according to claim 48, wherein the offshore device is an oil drilling platform or an offshore wind turbine.