WO2018096214A1

WO2018096214A1 - Maintenance of underwater parts of a vessel

Info

Publication number: WO2018096214A1
Application number: PCT/FI2017/050812
Authority: WO
Inventors: Markku SANDELL
Original assignee: Quality Ocean Services Qos Oy Ltd
Priority date: 2016-11-23
Filing date: 2017-11-22
Publication date: 2018-05-31
Also published as: EP3544881A4; FI20165888A; FI20165888L; EP3544881A1

Abstract

An apparatus for underwater marine vessel maintenance may traverse along a ferrous surface (100). The apparatus has a continuous track (130)that clings to the ferrous surface (100)with electromagnets, while the apparatus executes maintenance tasks to the hull of the vessel. The apparatus may comprise arms that enable clinging to the ferrous surface (100)or clamping arms for attaching the apparatus to a propeller blade. On aspect discloses an apparatus for underwater marine vessel maintenance, wherein the vessel is equipped with a podded propulsion system (901).

Description

MAINTENANCE OF UNDERWATER PARTS OF A VESSEL

BACKGROUND The underwater portion of marine vessel's hull requires periodic maintenance and inspections. The hull gathers fouling, such as barnacles, seaweed or other debris, causing problems, such as increased fuel consumption, blocked water inlets or corrosion. Remotely controlled underwater vehicles, ROVs or diver- operated vehicles may be used to remove the fouling. The vehicle must cling to the hull during maintenance in an underwater environment, as the hull surface may be substantially vertical, or the vehicle may operate under the hull. Many mechanical means to remove the fouling, such as brushes or water jets, cause a force away from the hull surface.

When a ship is berthed in port, the schedule for maintenance or inspections is tight. A local service provider may not be available during the berthing window. At some locations, the de-fouling is not allowed due to environmental reasons, for example, the accumulation of the removed debris.

The propeller comprises curved surfaces that may be difficult for the ROV to attach to during the cleaning process. The propeller material may not provide magnetic properties; therefore, a further attachment method is required.

Podded propulsion systems may be serviced by detaching the pod from the hull under water and transporting the pod to the surface. One solution for

transporting the pod comprises cables for lowering the pod into service position and a crane for lifting the pod from the water. Transporting the pod from underneath the vessel to the surface using cabling and the crane is a complex process that may require additional distance between the seabed and the berth, and the vessel can cause risks of damaging the pod.

US2014023071 1 discloses an autonomous hull maintenance device to clean away fouling, wherein a chassis of the device clings to a ferrous surface with a magnet that moves towards or away from the surface to adjust the magnetic force. SUMMARY This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

An apparatus for underwater marine vessel maintenance is disclosed. One aspect discloses an apparatus for traversing a ferrous surface. The apparatus has a continuous track that clings to the ferrous surface with electromagnets, while the apparatus executes maintenance tasks to the hull of the vessel. The electromagnets may be activated only for the portion, wherein the continuous track is having contact on the ferrous surface. The force applied by the magnetic field to attach the apparatus may be adjusted with an electric current. Magnetic debris may release from the continuous track when it leaves contact with the ferrous surface, as the magnets may be shut off for that portion.

One aspect discloses an apparatus for underwater marine vessel maintenance. The apparatus comprises a pivoting arm that is configured to cling with an electromagnet to the ferrous surface, when the apparatus approaches the hull while floating on water. The pivoting arm is configured to turn the apparatus along the hull surface. The pivoting mechanism allows the wheels or continuous track of the apparatus to securely initiate contact to the hull surface.

Approaching the hull is easier as waves may interfere with the procedure. The pivoting arm may also ensure that the initial contact results in the apparatus being positioned correctly on the hull surface; the top side of the apparatus may be equipped with tools for maintenance that could be damaged if they accidentally collide with the hull. One aspect discloses an apparatus for underwater marine vessel maintenance, comprising at least two clamping arms configured to clamp onto the edges of the propeller, one clamping arm for the leading edge and one for the trailing edge. The apparatus is secured to the propeller blade and the propeller may be cleaned or inspected.

One aspect discloses an apparatus for underwater marine vessel maintenance, wherein the vessel is equipped with a podded propulsion system. The apparatus comprises a submersible flotation structure having at least three flotation tanks. The flotation tanks form a modular, in one example, a toroidal structure, wherein a load-bearing space is formed between the flotation tanks. The size of the structure is configurable according to the number of

interconnected flotation tanks. The structure is submersible and transferable under water to be in contact with the podded propulsion system. The podded propulsion system comprises cables or a similar supporting arrangement that may be used to lower the pod for servicing. The pod is positioned to the load- bearing space formed by the flotation tanks by moving the flotation structure. A cable attachment is configured to attach to the cable or the supporting arrangement of the pod, enabling the submersible flotation structure to move the pod to the water surface. The solution provides improved safety to transporting a heavy object under water. Further, the modular structure enables storing and transporting the submersible flotation structure effectively or adjusting the capacity to different sizes of podded propulsion systems. The modular structure may be transported to a location without means for servicing the podded propulsion system. Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings. The embodiments described below are not limited to implementations which solve any or all the

disadvantages of known ROVs or vessel maintenance apparatuses. BRIEF DESCRIPTION OF THE DRAWINGS

The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein

FIG. 1 illustrates schematically one example of an apparatus for traversing a ferrous surface;

FIG. 2a illustrates schematically one example of an inductive coupling between a chassis and a continuous track;

FIG. 2b illustrates schematically one example of an inductive coupling between a chassis and a continuous track; FIG. 3a is a schematical illustration of one exemplary embodiment of a brush configuration;

FIG. 3b is a schematical illustration of one exemplary embodiment of a brush unit;

FIG. 3c is a schematical illustration of one embodiment of the brush unit; FIG. 3d is a schematical illustration of one embodiment of the brush unit;

FIG. 3e is a schematical illustration of one embodiment of the brush unit;

FIG. 3f is a schematical illustration of one embodiment of the brush unit;

FIG. 3g is a schematical illustration of one embodiment of the brush unit;

FIG. 4a illustrates schematically one example of clamping arms; FIG. 4b illustrates schematically one example of an embodiment wherein the apparatus comprises a UV light and multiple flotation tanks;

FIG. 5a illustrates schematically one example of clamping arms;

FIG. 5b illustrates schematically one example of clamping arms;

FIG. 6a illustrates schematically one example of the apparatus attached to a propeller;

FIG. 6b illustrates schematically the apparatus attached to a propeller from another angle; FIG. 6c illustrates schematically one example of the apparatus attached to a propeller;

FIG. 7a illustrates schematically one example of a submersible flotation structure; FIG. 7b illustrates one example, wherein the elements are apart;

FIG. 8 illustrates schematically the modular structure of the submersible flotation structure;

FIG. 9 illustrates schematically the submersible flotation structure positioned under the ship's hull; FIG. 10a illustrates schematically a top view of transporting the submersible flotation structure to the podded propulsion unit from the water surface;

FIG. 10b illustrates schematically a side view of transporting the submersible flotation structure to the podded propulsion unit from the water surface;

FIG. 1 1 illustrates schematically a sequential view of one example of a cable attachment;

FIG. 12 illustrates schematically examples of one connector part with the latch member in different positions; and

FIG. 13 illustrates schematically examples of one connector part with a sleeve configuration for securing the connection. Like reference numerals are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. However, the same or equivalent functions and sequences may be accomplished by different examples.

Although the present examples are described and illustrated herein as being implemented in a remotely controlled underwater vehicle, ROV, the apparatus described is provided as an example and not a limitation. As those skilled in the art will appreciate, the present examples are suitable for application in a variety of different types of remotely controlled underwater vehicles. Some examples are suitable for maintenance or inspection tasks on various ferrous surfaces, such as the insides of tanks. The ROV may be used for selection of underwater tasks for marine vessels, such as ship hull cleaning or inspection. The ROV may carry various devices to suit various purposes, such as cameras, suction heads, brushes, lights, UV lights, sonars or devices for underwater analysis or surveillance. The ROV may comprise an umbilical cord linked to the host, for example, on the deck of the ship that carries information or consumables, such as electric power between the ROV and the host. The umbilical cord may deliver the debris or fouling detached from the hull or propeller to the host for further waste management. The debris may be filtered and collected, thus enabling usage in ports or places with environmental limits. The various devices that may be attached to the ROV may be stored in a reasonably small storage compartment, allowing the ship to carry a dedicated apparatus for quick maintenance tasks even during a short stopover.

FIG. 1 illustrates schematically one example of an apparatus for traversing a ferrous surface 100. The ferrous surface 100 is, in one example, an underwater portion of ship's hull. In one example, the ferrous surface comprises an inner portion of a tank or a container that is substantially large to accommodate the apparatus. The apparatus comprises a chassis 1 10. The chassis 1 10 is configured to house components of the apparatus, such as control electronics 1 1 1 that may comprise at least one processor 1 12 and a memory 1 13 storing instructions that, when executed, control at least part of the operation of the apparatus. The apparatus comprises at least two wheels 120 and a continuous track 130 configured to be driven by the two wheels 120. The apparatus may comprise more than two wheels 120 or guide rollers configured to guide or support the continuous track 130. The structure having wheels 120 and a continuous track 130 form a vehicle propulsion system suitable for moving the apparatus over various surfaces. The apparatus may have only one propulsion system with a continuous track 130, wherein the balance of the apparatus may be maintained with an additional wheel on the opposite side of the chassis 1 10. In the present example, the apparatus comprises two propulsion systems on the opposite sides of the chassis 1 10. The movement of the apparatus may be autonomous following the processor 1 12 executing program stored in the memory 1 13. In one example, the apparatus comprises a camera configured to transmit a live view to the host via the umbilical cord 180, wherein the operator may control the movements. In an example, the apparatus comprises a magnet 140 having poles aligned to attract the apparatus to the ferrous surface 100. In an example, the magnet is connected to the continuous track 130, being configured to provide connection between the apparatus and the ferrous surface 100. The continuous track 130 may comprise multiple magnets, wherein at least one magnet is in connection with the ferrous surface 100, providing a connection as the apparatus traverses along the ferrous surface 100.

The magnetic field is configurable, as the magnet 140 comprises a first electromagnetic element 141 , wherein an electric current flowing through the first electromagnetic element 141 causes the magnetic field to be generated. The magnet 140 may be an electromagnet. The first electromagnetic element 141 is attached to the continuous track 130 and configured to move along the continuous track 130.

In an example, the apparatus comprises means 150 for driving the electric current to the first electromagnetic element 141 when a portion of the

continuous track 130 is in contact with the ferrous surface 100. Examples of the means 150 for driving the electric current comprise the control electronics 1 1 1 , a conductor 153 for providing the current to the continuous track 130, a conductor 154 for providing the current to the first electromagnetic element 141 and a first connector 151 for providing the electrical energy between the conductors 153 and 154. The first connector 151 may provide the electric current to the first electromagnetic element 141 for the period when the first electromagnetic element 141 is in contact with the ferrous surface 100, when the apparatus is traversing the ferrous surface 100. In another arrangement, the current is driven to the first electromagnetic element 141 only during a portion of the contact period. Alternatively, the current may be driven to the first

electromagnetic element 141 before it is in contact with the ferrous surface 100, for example, when the continuous track 130 is in contact with the wheel 120.

In an example, the apparatus comprises means 152 for disconnecting the electric current from the first electromagnetic element 141 when the portion of the continuous track 130 is disconnected from the ferrous surface 100. A second connector 152 may be configured to detect when the first

electromagnetic element 141 travels past a predetermined position on the continuous track 130. In one embodiment, the first connector 151 and the second connector 152 are switching elements configured to control the electric current provided to the first electromagnetic element 141 . In one example, the control electronics 1 1 1 provide the current to the first electromagnetic element 141 according to its position when rotatably moving along the continuous track 130.

In one example, the electric current from the chassis 1 10 to the continuous track and further to the first electromagnetic element is provided by induction. FIG. 2a illustrates schematically one example, wherein a primary inductive element 161 is coupled to the chassis 1 10. A primary electric current is led to the primary inductive element 161 causing a magnetic field. The magnetic field induces a secondary electric current to the secondary inductive element 162 and a secondary electric circuit leading to the first electromagnetic element 141 . The electric current is, in this example, alternating current. There is no galvanic connection between the electric source 1 1 1 on the chassis 1 10 and the first electromagnetic element 141 on the continuous track 130. A primary electric current in the primary inductive element 161 causes a secondary electric current in the secondary inductive element 162 and on the first electromagnetic element 141 as they are both in the same secondary electric circuit.

FIG. 2b illustrates two examples with cross-sectional views for providing the electric current to the electromagnetic element 141 of the continuous track 130. In one example, the primary electric current is provided to the primary inductive element 163 configured on a rail supporting the continuous track 130, wherein the secondary inductive element 164 is configured to the continuous track 130, when it is in contact with the ferrous surface 100. In one example, the primary inductive element 165 is configured to surround an extrusion 166 having the secondary inductive element.

The apparatus may comprise various instruments, sensors or modules for performing the maintenance. In the example of FIG. 1 , a brush unit 170 is connected to the chassis 1 10. The brush unit 170 is configured to brush the surface 100 and remove debris and fouling. FIG. 3a further illustrates the brush configuration of this example. Two brushes 171 , 172 are configured to rotate in opposite directions, causing a vortex leading under the chassis 1 10. A third brush 173 is positioned to the vortex, brushing the surface area that the two brushes 171 ,172 have left untouched. A suction pipe 174 is positioned to the middle of the brushes 171 , 172, 173, removing the fouling that may be led to the surface via the umbilical cord 180. The host unit on the ship deck may provide the suction to the underwater apparatus.

FIGs. 3b to 3d illustrate schematically examples of the brush unit 170. The suction pipe 174 is positioned to the middle of the brush unit 170. A brush motor 175 rotates the brush 176. In one embodiment the brush 176 is shaped to form a vortex to the middle portion, to the suction pipe 174. In one embodiment the brush motor 175 causes the water from the suction pipe 174 to flow in high velocity to the centrifugal portion 177 of the suction pipe 174, acting as a pump and causing the water to exit towards the umbilical cord 180. The brush motor 175 may be arranged to various positions - for example to the top portion of the brush unit as in FIG. 3b. FIG. 3c illustrates the motor 175 between the centrifugal portion 177 and the brush 176. In FIG. 3d the motor 175 is

connected to the brush 176 and/or to the pump of the centrifugal portion 176 via a chain or a belt. Various alternatives may provide different benefits in waterproof housing or serviceability.

FIG. 3e illustrates schematically one example of a brush unit 170, wherein the motor 175 provides rotation to pump blades 178, causing the flow of the water to accelerate towards the centrifugal portion 177. The brush unit 170 may function as a pump causing the water and debris to flow towards the umbilical cord 180. In this example the brush 176 may comprise pump blades having sharp lower edge, effectively cutting growth such as seaweed. Long seaweed may be cut to shorter length before it enters the apparatus and further into the umbilical cord 180, thereby reducing the clogging effect.

FIG. 3f and FIG. 3g illustrate schematically one example of a brush unit 170 having expandable bellows 179. The bellows 179 surround at least partially the lower edge of the brush unit 170. The bellows 179 comprise a water inlet for receiving pressurized water. The pressurized water may be provided via the umbilical cord 180. The pressurized water causes the bellows 179 to expand and the lowest portion of the bellows 179 to be in contact with the ferrous surface 100. In the expanded mode, as illustrated in FIG. 3f, the bellows 179 comprise openings that act as water outlets, wherein the pressurized water flows through the openings towards the brush 176. In the retracted mode, as illustrated in FIG. 3g, the bellows 179 raise allowing sea water to flow to the brush 176. The two modes of the bellows 179 allow different operations on the ferrous surface 100. For example, cargo ships' displacement may vary according to the cargo on board. The apparatus may operate over or under the water surface. Over the water surface the bellows 179 may be used in the expanded mode, wherein the pressurized water rinses the ferrous surface 100. Below the water surface additional rinsing may not be required and the retracted mode of the bellows 179 may be used.

In one example, the apparatus or ROV is provided with ultraviolet light (UV) 198. A powerful UV light 198 may kill a portion of the living substance within the fouling. The UV light 198 may be used as additional cleaning or maintenance feature configurable to the ROV as it traverses along the ferrous surface 100. The UV light 198 may be under the chassis 1 10 or in a position near the ferrous surface 100. The UV light 198 may be focused onto the ferrous surface 100 to reduce possible harmful effects to other living substance near the ROV. One example of the UV light 198 is illustrated in FIG. 4b.

The apparatus is configured to traverse the surface with the propulsion from one or two continuous tracks 130. Turning with the continuous tracks 130 may cause traces to the hull surface 100. In one embodiment, sharp turns may be executed with a suction cup 190. The suction cup 190 is positioned under the chassis 1 10 facing the surface 100. The suction cup 190 is configured to attach the apparatus to the surface 100, having a rotation axis transverse to the ferrous surface. An actuator 191 is configured to move the suction cup 190 towards the surface 100, wherein the suction cup 190 may be in contact with the surface 100. The umbilical cord 180 may provide suction from the ship deck to the suction cup 190. The suction cup 190 is with the actuator 191 configured to lift the continuous track 130 from the surface 100. The axis on the suction cup 190 is configured to rotate the apparatus along the rotation axis, causing a pivoting turn along the surface 100. The apparatus may proceed to the edge of the surface area and turn, for example, 90 degrees, covering the whole area effectively. The movement may be autonomous following the processor executing program stored in the memory 1 13. In one example, the apparatus comprises a camera configured to transmit live view to the host via the umbilical cord 180, wherein the operator may control the movements of the suction cup 190 or the apparatus.

In one example, the ROV is brought to the ferrous surface 100 by approaching the hull while floating on water. The ROV may not have propulsion for moving effectively underwater without contact to the ferrous surface 100. While floating, the ROV may be guided with ropes or the umbilical cord 180. While floating, the ROV may cause propulsion to the water with the continuous track 130. The splash zone has many risks for damaging the ROV. A pivoting arm 193 comprises a second electromagnetic element 194 on the end of the pivoting arm 193. The second electromagnetic element 194 is configured to receive electric current from the host unit via the umbilical cord 180. The electric current causes a magnetic field having poles aligned to attract the ferrous surface 100. When the ROV approaches floatingly the hull and the ferrous surface 100, the pivoting arm provides first contact to the ferrous surface 100. The second electromagnetic element 194 is configured to connect to the ferrous surface 100 as a response to the electric current, securing the ROV to the ship's hull. The pivoting arm 193 is configured to move the ROV to the ferrous surface 100 by pivoting and turning the ROV in a predetermined direction along the ferrous surface 100. In one example, the pivoting arm 193 turns the ROV to the ferrous surface 100 along the water surface, in another example, the ROV is turned to the underwater portion of the ferrous surface 100 or the ship's hull.

One example of the ROV comprises a flotation tank 199 configured to control the buoyancy of the apparatus underwater. The flotation tank 199 may assist the pivoting arm 193 to turn the apparatus underwater. The pivoting arm may comprise several pivots or hinges having actuators or motors configured to move the apparatus. The movement may be autonomous following the processor executing program stored in the memory 1 13. In one example, the apparatus comprises a camera configured to transmit live view to the host via the umbilical cord 180, wherein the operator may control the pivoting arm' s movements.

In one embodiment the ROV comprises multiple flotation tanks 199 in different positions, as illustrated in FIG 4b. The flotation tanks 199 may be used to control the angle of the ROV. In one example the ROV comprises four flotation tanks positioned at four different sides. When the ROV is operating on a vertical portion of the ferrous surface 100, only the flotation tank 199 being closest to the water surface is empty while the others may be filled with water. The flotation tanks 199 may be used to keep the ROV in vertical or horizontal position, or balance the position according to the ferrous surface 100.

One aspect discloses an apparatus for cleaning a propeller surface. The apparatus may comprise the features discussed previously or disclosed with FIGs 1 to 3. In one embodiment, the apparatus is dedicated to cleaning the propeller surface. FIG. 4a illustrates a side view of one example, wherein the apparatus comprises two clamping arms 401 , 402 and a pivoting tool arm 403.

In the example of FIG. 5a, illustrating a side view of the apparatus, a first clamping arm 401 is configured to clamp onto a leading edge of a propeller blade and a second clamping arm 402 is configured to clamp onto a trailing edge of the propeller blade. The first clamping arm 401 and the second clamping arm 402 are coupled to the chassis 1 10. The clamping arms 401 , 402 may be movable with pivots 406, hinges 407 or actuators 408 configured to cause the movement as a response to the control electronics 1 1 1 . When at least one clamping arm, for example, the first clamping arm 401 is connected to the propeller blade, the second clamping arm 402 may be used to guide the apparatus to the correct position on the propeller blade.

The first clamping arm 401 and the second clamping arm 402 may be used to secure the grip on the propeller blade while the apparatus may be equipped with additional cleaning tools on a tool arm 403. FIG. 5b illustrates a top view of the apparatus, wherein the tool arm 403 is equipped with an instrument 405 having a cable leading to the umbilical cord 180. The instrument 405 may be a sensor, a camera or an inspection device configured to detect structural failures. In one example, the apparatus comprises the first clamping arm 401 and the second clamping arm 402, and the tool arm 403 is a manipulator arm used for operating a cleaning device 405. The tool arm 403 may be arranged off the centreline, enabling the apparatus chassis 1 10 to rotate along the axis A defined by the stem of the first clamping arm 401 and the second clamping arm 402. The apparatus may pivot along the axis A, allowing an improved operating range to the tool arm 403. The instrument 405 may be a manipulator configured to clean the propeller surface. FIG. 6a and FIG. 6b illustrate schematically one example of the apparatus being attached to the propeller 600 with the clamping arms. FIG. 6c illustrates schematically one example of an embodiment, wherein the first clamping arm 401 and the second clamping arm 402 are equipped with cleaning devices 405, enabling cleaning both sides of the propeller blade 600 simultaneously. The apparatus comprises a clamp 601 configured to grip onto the edge of the propeller 600. The cleaning time may be reduced, as both sides of the propeller blade 600 may be cleaned simultaneously.

In one example, the apparatus or ROV is provided with an ultrasonic cleaning device. The ultrasonic cleaning device may be used as additional cleaning or maintenance feature configurable to the ROV for example as the cleaning device 405, as the ROV traverses along the ferrous surface 100. Ultrasonic cleaning uses cavitation bubbles induced by high frequency pressure waves to agitate the sea water. Ultrasonic cleaning penetrates blind holes, cracks, and recesses. The ultrasonic cleaning device 405 may be connected to tool arm 403, wherein the ultrasonic energy may be focused onto difficult areas. The ROV mode allows the use of ultrasonic cleaning device, as it may be harmful to humans nearby.

One aspect discloses a submersible flotation structure for lifting podded propulsion systems from the underwater portion of the ship's hull. One example of the podded propulsion system comprises an electric motor being mounted inside a pod unit and the propeller being connected directly to the motor shaft and to the electric motor. In one example, the motor is mounted inside the ship's hull. A mechanical transmission connects the motor inside the ship to the outboard unit by gearing. Examples of such gearing are L-drive and Z-drive.

The podded propulsion unit may sometimes be serviced while the ship stays afloat. For some podded propulsion types, the propulsion unit is positioned under the hull, wherein removal of the podded propulsion unit would require space below the ship, rendering dry docking unpractical. For some podded propulsion systems, wherein dry docking is optional, dry dock may not be available or the podded propulsion system may require urgent repairs. The submersible flotation structure is configured to attach to the podded propulsion unit, which may be lowered to the support of the submersible flotation structure. The podded propulsion unit may be detached from the ship and transported to the water surface. The submersible flotation structure operates underwater and enables lifting the podded propulsion unit to the water surface. A shore crane or a ship crane may continue lifting the podded propulsion unit from a suitable location. The submersible flotation structure may be lifted along with the podded propulsion unit. FIG. 7a illustrates schematically one example of the submersible flotation structure from above. FIG. 7b illustrates one example, wherein the elements are apart. The submersible flotation structure comprises at least three flotation tanks 701 , 702, 703 arranged toroidally, forming a shape resembling a donut. The flotation tanks comprise coupling elements on opposite sides, a first coupling element 71 1 on a first side of the flotation tank and a second coupling element 712 on the second side of the flotation tank. The coupling elements may be fixed or allow hinged movement. Interconnected flotation tanks 701 , 702, 703 form a load-bearing space 720 between the flotation tanks. The load- bearing space 720 is configured for the pod, wherein the submersible flotation structure may be moved underwater positioning the space 720 below the pod and float up the structure, causing the flotation tanks to surround the pod. The submersible flotation structure may also be opened on one side and thus floated under the hull to the pod and, when in position, by a hinged movement be closed and secured around the pod. The flotation tanks 701 , 702, 703 comprise means for controlling the buoyancy with the amount of water contained in the flotation tank, for example, ballast tanks, pumps and valves. The buoyancy may be controlled between positive, neutral or negative conditions. The controlled buoyancy between flotation tanks may differ.

The submersible flotation structure comprises, in one embodiment, control electronics 730 that may comprise at least one processor 731 and a memory 732 storing instructions that, when executed, control at least part of the operation of the apparatus. In one example, the submersible flotation structure comprise sensors 740 for detecting the tilt angle, providing information for the processor 731 to control the buoyancy to keep the structure level during operation. The lateral position may be controlled by detecting the distance from the ship's hull, water surface or the seabed. The distance may be detected with a sensor, a sonar, a probe, a rope or a plummet.

In one example, the podded propulsion system is suspended from the ship on a cable, when it is lowered to the service position or to the transport position. In one example, the podded propulsion system is suspended on a rod configured to move laterally in the ship's support structure. In one example, the

submersible flotation structure comprises a cable attachment 750 connected to at least one flotation tank 701 , 702, 703 configured to be connected to a supporting cable of a podded propulsion system of a vessel at a lowered state. The cable attachment 750 is configured to suspend the podded propulsion system in the load-bearing space. The cable 902 may be connected to the submersible flotation structure 910 at a position above the centre of gravity of the podded propulsion system. The cable attachment 750 may be arranged into such position, ensuring the stability of the podded propulsion system's connection to the submersible flotation structure 910.

FIG. 8 illustrates schematically the modular structure of the submersible flotation structure. The structure may comprise multiple flotation tanks 801 , 802, 803, 804, for example, four flotation tanks. The modular structure enables modifying the size of the structure to fit various podded propulsion systems. A connecting element 810 may be connected between the two flotation tanks. The connecting element 810 may be a simple structure comprising supporting bars. The number of flotation tanks may be adjusted according to the required buoyancy, in one example, multiple flotation tanks are arranged vertically, on top of each other. The load may require additional buoyancy on other side as the podded propulsion systems may be unbalanced when disconnected from the ship.

FIG. 9 illustrates schematically the submersible flotation structure 910 under the ship's hull 900, wherein the hull 900 is illustrated partially. The podded propulsion system 901 is in the lowered position, suspended by the cables 902. A spacer element 920 is configured to limit the distance between the

submersible flotation structure 910 and the hull 900. The spacer element 920 may be configured to sense the pressure caused by the submersible flotation structure 910 to the hull 900. The pressure may be sensed by a sensor, wherein the information is transmitted to the processor 731 . The processor may control the buoyancy to limit the pressure applied to the spacer element 920. The submersible flotation structure is configured to carry the podded propulsion system 901 , the pod or the podded propulsion unit to the water surface 930.

FIG. 10a and FIG. 10b illustrate schematically a method for transporting the submersible flotation structure 910 to the podded propulsion unit from the water surface 930. FIG. 10a is a view from the top, whereas FIG. 10b is a side view of the same situation. A support arm 955 is configured to be coupled to the hull side 900. The support arm 955 comprises a pivoting L-shaped portion having an elbow near the bottom portion of the hull 900, wherein a transport arm 950 is configured to attach to the submersible flotation structure 910. The transport arm 950 may be telescopic to enable flexible positioning. The support arm 955 comprises two positions, a first position under the hull 900 and a second position near the water surface 930. Rotating the support arm 955, about 90 degrees in this example, pulls the submersible flotation structure 910 from under the hull 900 to near the water surface 930. In this example, at the second position, the reference numeral of the submersible flotation structure is 91 1 and the transport arm is 951 . The submersible flotation structure 910 may be further guided with ropes, such as spectra ropes or similar ropes having neutral buoyancy. The support arm 955 ensures that the moving range of the submersible flotation structure 910 is controllable. In one embodiment, the top portion of the support arm 955 is floatable. The lower portion of the support arm 955 may comprise electromagnetic elements that secure the support arm to the hull 900. The support arm 955 may be secured with ropes or cargo straps.

FIG. 1 1 illustrates a sequential view of one example of cable attachment 750. Sequences from a) to d) illustrate the cable 902 having a connector part 903, from where the podded propulsion system may be secured to the vessel once the system is in place. The cable attachment 750 comprises a cradle 751 with a slot that allows the cable 902 to be inserted to the cradle 751 . The cradle slides up the cable 902, tightening by lifting to the lower portion 903 of the connector part 907. The tightening causes a securing arm 752 to approach a sleeve 904 that is configured to secure the connector part. The securing arm 752 lifts the sleeve 904 to detach the lower portion 903 of the connector part 907, allowing the submersible flotation structure 910 to transport the podded propulsion system to the surface 930. The sleeve 904 may be spring-loaded, returning the sleeve 904 to the securing position when the securing arm 752 is not in contact with the sleeve 904.

FIG. 12 illustrates an example of one connector part 907 comprising a lower portion 903 and an upper portion 906, wherein the connection is secured by a latch member 905. The connector part 907 may release itself when a force is applied to the lower portion 903 lifting with the latch member 905 to release position, wherein the latch member 905 may be spring-loaded to assist the release. The upper portion 906 of the connector part 907 is configured to rotate in response to the movement applied to it by the lower portion 903 when reconnecting the connection. When the lower connector portion 903 is connected to the upper portion 906, the first upward movement causes the latch member 905 to secure the connection. The latch mechanism may be automatic or semi-automatic.

FIG. 13 illustrates a detailed view of the connector part 907 having the sleeve 904 configured to secure the latch member 905. In this example, the sleeve 904 is spring-loaded, returning the sleeve to close the gap that allows the latch member 905 to unlock the connector part 907 and allowing the lower portion 903 of the connector part 907 to be moved along with the submersible flotation structure 910.

An example discloses an apparatus for traversing a ferrous surface, comprising: a chassis; at least two wheels; a continuous track configured to be driven by the at least two wheels; and a magnet having poles aligned to attract the apparatus to the ferrous surface. The magnet comprises a first electromagnetic element, wherein an electric current flowing through the first electromagnetic element causes the magnetic field to be generated. The first electromagnetic element is attached to the continuous track. In one embodiment, the apparatus comprises means for driving the electric current to the first electromagnetic element when a portion of the continuous track is in contact with the ferrous surface. In one embodiment, the apparatus comprises means for disconnecting the electric current from the first electromagnetic element when a portion of the continuous track is disconnected from the ferrous surface. In one embodiment, the apparatus comprises a primary inductive element coupled to the chassis and a secondary inductive element coupled to the continuous track, wherein a primary electric current in the primary inductive element causes a secondary electric current in the secondary inductive element and the first electromagnetic element. In one embodiment, the apparatus comprises a suction cup configured to attach the apparatus to the ferrous surface, having a rotation axis transverse to the ferrous surface; an actuator configured to cause a distance between the continuous track and the ferrous surface and configured to rotate the apparatus along the rotation axis, causing a pivoting turn along the ferrous surface. Alternatively, or in addition, in one embodiment, the apparatus is a remotely controlled underwater vehicle comprising: a pivoting arm; a second

electromagnetic element on the end of the pivoting arm, having poles aligned to attract the ferrous surface, wherein the vehicle is configured to floatably approach the ferrous surface and the second electromagnetic element is configured to connect to the ferrous surface; and, after connection, the pivoting arm is configured to move the chassis to the ferrous surface. In one

embodiment, the pivoting arm is configured to move the chassis to the underwater portion of the ferrous surface. In one embodiment, the apparatus comprises a flotation tank configured to control the buoyancy of the apparatus underwater.

Alternatively, or in addition, in one embodiment, the apparatus comprises a first clamping arm configured to clamp onto a leading edge of a propeller blade; a second clamping arm configured to clamp onto a trailing edge of the propeller blade; the first clamping arm and the second clamping arm being coupled to the chassis; the first clamping arm and the second clamping arm comprising means for guiding the apparatus onto the propeller blade surface. In one embodiment, the apparatus comprises a tool arm for manipulating the propeller blade. In one embodiment, the tool arm is configured to carry an instrument for manipulating the propeller blade.

Alternatively, or in addition, a submersible flotation structure is disclosed, comprising at least three flotation tanks, wherein each flotation tank comprises two detachable coupling elements at opposite sides; the flotation tanks being interconnected from opposite sides forming a load-bearing space between the flotation tanks; the flotation tanks comprising means for controlling the buoyancy with the amount of water contained in the flotation tank; a cable attachment connected to at least one flotation tank, configured to be connected to a supporting cable of a podded propulsion system of a vessel at a lowered state, wherein the podded propulsion system is positioned in the load-bearing space. In one embodiment, the structure comprises a spacer element configured to limit the distance between the submersible flotation structure and a hull. In one embodiment, a fourth flotation tank is mountable vertically under a flotation tank. In one embodiment, the cable attachment is connected to the cable at a position above the centre of gravity of the podded propulsion system or a load being moved. In one embodiment, the structure comprises an automatic or semi-automatic latch member for connecting to the supporting cable. Alternatively, or in addition, a method is disclosed, comprising lowering a submersible flotation structure below a podded propulsion system at a lowered state, raising the buoyancy of the submersible flotation structure, causing the submersible flotation structure to position around the podded propulsion system, connecting the submersible flotation structure to a support structure of the podded propulsion system, such as a cable, and transporting the podded propulsion system to the water surface by moving horizontally and controlling the buoyancy of the submersible flotation structure. One embodiment comprises controlling the distance between the submersible flotation structure and the bottom of the ship's hull by a pressure sensor between the submersible flotation structure and the hull, wherein when the pressure level exceeds a

predetermined value it causes a reduction in buoyancy.

Alternatively, or in addition, the controlling functionality described herein can be performed, at least in part, by one or more hardware components or hardware logic components. An example of the control system described hereinbefore is a computing-based device comprising one or more processors which may be microprocessors, controllers or any other suitable type of processors for processing computer-executable instructions to control the operation of the device in order to control one or more sensors, receive sensor data and use the sensor data. The control system may be positioned on the host system and connected to the apparatus or to the submersible flotation device via the umbilical cord. The computer-executable instructions may be provided using any computer-readable media that is accessible by a computing-based device. Computer-readable media may include, for example, computer storage media, such as memory and communications media. Computer storage media, such as memory, includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EPROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. In contrast, communication media may embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanism. As defined herein, computer storage media does not include communication media. Therefore, a computer storage medium should not be interpreted to be a propagating signal per se. Propagated signals may be present in a computer storage media, but propagated signals per se are not examples of computer storage media. Although the computer storage media is shown within the computing-based device, it will be appreciated that the storage may be distributed or located remotely and accessed via a network or other communication link, for example, by using a communication interface.

The apparatus or the device may comprise an input/output controller arranged to output display information to a display device which may be separate from or integral to the apparatus or device. The input/output controller is also arranged to receive and process input from one or more devices, such as a user input device (e.g. a mouse, keyboard, camera, microphone or other sensor). The remote control of the ROV may use various input or output information or metrics received from sensors of the underwater portions.

The methods described herein may be performed by software in machine- readable form on a tangible storage medium e.g. in the form of a computer program comprising computer program code means adapted to perform all the steps of any of the methods described herein when the program is run on a computer and where the computer program may be embodied on a computer- readable medium. Examples of tangible storage media include computer storage devices comprising computer-readable media, such as disks, thumb drives, memory etc. and do not only include propagated signals. Propagated signals may be present in a tangible storage media, but propagated signals per se are not examples of tangible storage media. The software can be suitable for execution on a parallel processor or a serial processor such that the method steps may be carried out in any suitable order, or simultaneously.

Any range or device value given herein may be extended or altered without losing the effect sought. Although at least a portion of the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. An apparatus for traversing a ferrous surface (100), comprising:

a chassis (110);

at least two wheels (120);

a continuous track (130) configured to be driven by the at least two wheels (120); and

a magnet having poles aligned to attract the apparatus to the ferrous surface (100), ch a ra cte rized by:

the magnet comprising a first electromagnetic element (141), wherein an electric current flowing through the first electromagnetic element (141) causes the magnetic field to be generated;

the first electromagnetic element (141) being attached to the continuous track (130);

the apparatus further comprising a primary inductive element (161, 163,

165) coupled to the chassis (110) and a secondary inductive element (162, 164, 166) coupled to the continuous track (130), wherein a primary electric current in the primary inductive element (161, 163, 165) causes a secondary electric current in the secondary inductive element (162, 164,

166) and the first electromagnetic element (141).

2. An apparatus according to claim 1, characterized by comprising means (150) for driving the electric current to the first electromagnetic element (141) when a portion of the continuous track (130) is in contact with the ferrous surface (100).

3. An apparatus according to claim 1, characterized by comprising means (152) for disconnecting the electric current from the first electromagnetic element (141) when a portion of the continuous track (130) is disconnected from the ferrous surface (100).

4. An apparatus according to any of the claims 1 to 3, characterized by comprising an ultraviolet light configured to kill a portion of the living substance within a fouling.

5. An apparatus according to any of the claims 1 to 4, characterized by comprising:

a suction cup (190) configured to attach the apparatus to the ferrous surface (100), having a rotation axis transverse to the ferrous surface (100);

an actuator (191) configured to cause a distance between the continuous track (130) and the ferrous surface (100) and configured to rotate the apparatus along the rotation axis, causing a pivoting turn along the ferrous surface (100).

6. An apparatus according to any of the claims 1 to 5, characterized in that the apparatus is a remotely controlled underwater vehicle comprising:

a pivoting arm (193);

a second electromagnetic element (194) on the end of the pivoting arm (193), having poles aligned to attract the ferrous surface (100), wherein the vehicle is configured to floatably approach the ferrous surface (100) and the second electromagnetic element (194) is configured to connect to the ferrous surface (100); and

after connection, the pivoting arm (193) is configured to move the chassis (110) to the ferrous surface (100).

An apparatus according to claim 6, characterized in that the pivoting arm (193) is configured to move the chassis (110) to the underwater portion of the ferrous surface (100).

An apparatus according to any of the claims 1 to 7, characterized by comprising a flotation tank (199) configured to control the buoyancy of the apparatus underwater.

9. An apparatus according to any of the claims 1 to 8, characterized by comprising:

a first clamping arm (401 ) configured to clamp onto a leading edge of a propeller blade;

a second clamping arm (402) configured to clamp onto a trailing edge of the propeller blade;

the first clamping arm (401) and the second clamping arm (402) being coupled to the chassis (110);

the first clamping arm (401) and the second clamping arm (402) comprising means for guiding the apparatus onto the propeller blade surface.

10. An apparatus according to claim 9, characterized by comprising a tool arm (403) for manipulating the propeller blade.

11.An apparatus according to claim 10, c h a r a c t e r i z e d by the tool arm (403) being configured to carry an instrument for manipulating the propeller blade.