GB2474374A

GB2474374A - Vessel with a motion-compensated platform for transferring personnel or equipment

Info

Publication number: GB2474374A
Application number: GB1019757A
Authority: GB
Inventors: Brynmor Winston Phillips
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-11-22
Filing date: 2010-11-22
Publication date: 2011-04-13
Also published as: GB201019757D0

Abstract

A vessel 10 comprises a motion-compensated platform 2 for transferring personnel and/or equipment between the vessel and an adjacent body 12. The platform 2 comprises at least one surface 4 for bearing, transporting and transferring a load. The vessel is characterised by the motion-compensated platform being positioned on the vessel in sufficient proximity to the edge of the vessel 16 such that personnel and/or equipment may be transferred directly between the surface and the adjacent body. The platform may include actuators 6, for moving the at least one surface in six degrees of freedom, a control system and motion sensors. A method for transferring equipment and personnel from such a vessel to an adjacent body is also disclosed.

Description

Self Stabilising Platform

Field of Invention

The present invention relates to a vessel with a motion compensation platform.

Background

There is a continuing and long-felt need for safe, stable and reliable means of embarking and disembarking from sea-going vessels. As welt as embarkation and disembarkation from land, persons may also be called to board other vessels and stationary artificial structures such as oil rigs and, more recently, offshore wind turbines.

The problem is particularly acute in respect of installations located in deep waters far from shore. With oil drilling processes taking place in ever-deeper waters, and offshore "wind farms" of turbines being established further away from land to take advantage of greater wind speeds, the process of embarking onto and disembarking from such installations from sea-going vessels becomes more problematic, due to more turbulent and demanding wave conditions. This can be particularly problematic with regards to wind turbines; if a turbine develops a fault which requires a maintenance action to correct, it will remain unavailable for electricity generation until maintenance personnel are able to successfully board the turbine installation and bring on any equipment they require to effect a repair. If boarding attempts have to be postponed due to high waves, repair will be delayed and downtime losses will increase correspondingly.

One solution used widely in the industry is to move a vessel into position such that frictional contact is established between the vessel's bow and features incorporated into the turbine's foundation for the purposes of landing boats, but this method cannot be used if waves of greater than a moderate height are encountered.

To this end various mounting systems have been developed based on principles of motion compensation, whereby the motion of the vessel is compensated for by some means, such that at least part of the mounting system remains effectively stationary relative to fixed, immobile features of the surroundings, such as a turbine installation. This provides a stable surface to allow personnel to embark and disembark with ease. Motion compensations that have been previously used in the art for this purpose have included Stewart platforms, which utilise hydraulic cylinders and motion sensors to maintain a stable position.

A problem with prior art motion compensation solutions has been that they have involved the use of a gangplank to allow personnel to pass between the motion-compensated surface on their vessel and the installation or vessel they are embarking onto or disembarking from. The art of PCT Application No. PCT/NL2007/050080 presents a system in which a Stewart platform is used onboard a vessel in conjunction with just such a gangplank. The use of a gangplank raises problems both in terms of safety and of practicality.

As far as safety is concerned, traversing the gangplank entails a risk to personnel, since even a minor failure of the motion compensation platform -caused, for example, by an especially violent wave or a sudden failure of one of the hydraulic cylinders of a Stewart platform -can result in correspondingly amplified movements at the end of the gangplank to an extent that additional safety measures are needed to accommodate such fluctuations of the gangplank in the form of a passive pressure element' to passively compensate for any remaining motions, such as inaccuracies, drift, wave induced ship motions that are too large to be compensated by the motion compensation actuators or in case one of the drive actuators fail. When traversing the gangplank personnel often have to pass over a drop either to the surface of their vessel, or the installation or vessel they are boarding or disembarking from, or the ocean, and therefore a fall from the gangplank caused by a failure of the motion compensation platform could have fatal consequences.

The practical consideration is that the narrowness of the gangplank limits the equipment that can be safely and efficiently transferred between a vessel and an installation (or other vessel) via the gangplank; equipment transfer is effectively limited to those items which can be carried by those personnel using the gangplank without compromising their safety. Thus, despite the establishment of a stable link between the vessel and the installation or other vessel, equipment still needs to be transferred via crane, helicopter or other means, impacting the efficiency of the operation.

There is therefore a long-felt need for a motion-compensated system for transport of personnel and equipment between vessels and installations/other vessels which does not require personnel to traverse a narrow gangplank. The object of the present invention is to meet this need.

Summary of the Invention

In accordance with the present invention, there is provided a vessel comprising a motion-compensated platform for transferring personnel and/or equipment between the vessel and an adjacent body, said platform comprising at least one surface for bearing, transporting and transferring a load, characterised in that the motion-compensated platform is positioned on the vessel in sufficient proximity to an edge of the vessel that the load in question may be transferred directly between the surface and the adjacent body when the vessel is in position.

The edge of the vessel is preferably the bow or stem.

In some embodiments the motion-compensated platform is positioned such that at least one edge of the at least one surface is either directly above or at least partially overhanging the edge of the vessel. In such embodiments direct transfer of personnel and/or equipment from the surface to the adjacent body would simply require the personnel to need to mount the motion compensation platform and step from the surface directly to the adjacent body, carrying such equipment as they are able to. This eliminates the use of a gangplank as used in the prior art, which requires personnel to spend a longer time traversing across the length of the gangplank and therefore would subject said personnel to a greater safety risk if there is a sudden motion of the compensation platform. The present invention present has advantages in improving the safety to personal embarking or disembarking from other vessels or stationaiy structures without the need and expense for providing additional safety measures.

Any sudden movement of the motion compensation platform can be accommodated by the act of stepping onto or off the platform.

In other embodiments of the invention transfer of personnel and equipment from the motion-compensated platform to the adjacent body is achieved through the use of a crane mounted on the adjacent body. Since the motion-compensated platform provides at least one surface held essentially stationary relative to the adjacent body, this makes effecting such an operation with a crane significantly easier and safer than attempting to perform crane-based operations fromlto a heavily rolling and pitching deck of a vessel. The positioning of the motion-compensated platform in proximity to the edge of the vessel both ensures that the at least one surface is within easy reach of the crane, and minimises the distance that the crane has to transport personnel and/or equipment, improving both efficiency and safety.

Preferably, the motion-compensated platform comprises actuators capable of moving the at least one surface relative to the vessel (preferably in six degrees of freedom), a control system for the actuators, and motion sensors for measuring motions of the vessel relative to at least one element in the surrounding area. These measurements are used as input for the control system, and the motion sensors and control system are calibrated to hold the at least one surface in a stationary position relatively to at least one element in the surrounding area.

A Stewart platform is just such a platform.

As specified, transfer is effected when the vessel is in position against an adjacent body.

Examples of suitable bodies include, but are not limited to, other vessels, land-based installations or offshore installations. Offshore installations could include, but are not limited to, wind turbines or oil rigs.

Preferably, the vessel additionally comprises mating features intended to engage with corresponding features of a an adjacent body. Examples of possible mating features or corresponding features include, but are not limited to, points of frictional contact, bolts, interlocking teeth, locks, screws, and magnets. Mating features may be found on, but are not necessarily limited to, the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel, or the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging. Tn embodiments where mating features are present on both edges, said mating features may be capable of simultaneously engaging with their corresponding features on the adjacent body.

Also in accordance with the present invention, there is provided a method of transferring personnel or equipment from a vessel to an adjacent body through the use of a vessel bearing a motion-compensated platform as described above. This method entails moving the vessel into the proximity of the adjacent body, such that the edge of the vessel which the motion-compensated platform is placed in proximity to is facing the adjacent body, utilising the motion sensors and control system to hold the at least one surface in a stationary position relative to the adjacent body, and then transferring the personnel or equipment from the at least one surface to the adjacent body directly.

Preferably, to permit additional stability mating features of the vessel are engaged with corresponding features of the adjacent body prior to transferring the personnel or equipment.

As mentioned previously, these mating features may be provided on the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel, or on the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging, or both.

Brief Description of the Drawings

Figure 1 depicts a motion-compensated platform along the lines of a Stewart platform; Figures 2 and 3 show two different views of a vessel that has established frictional contact with a wind turbine foundation, in accordance with the prior art; Figures 4 and 5 show two different views of a vessel in frictional contact with a wind turbine foundation, this time utilising a motion-compensated platform in the middle of the boat and a gangway to establish a stable surface for embarkation and disembarkation, in accordance

with the prior art, and

Figures 6 and 7 show two different views of a vessel with a motion-compensated platform at the bow of the boat, in accordance with an embodiment of the present invention.

Detailed Description

A schematic view of one type of motion-compensated platform 2 suitable for use in the present invention is presented in Figure 1. This is a Stewart platform, but it will be readily apparent to persons skilled in the art that any motion-compensated platform can be utilised in the invention. The motion-compensated platform 2 comprises a surface 4 linked to a base 8 by actuators 6. It will be obvious to the person skilled in the art that the surface 4 is not limited in its shape except by the necessity that it must be capable of attachment to the actuators 6. The base 8 may be the ground, a floor, a vessel, or any other suitable place for the actuators 6 to be fixed to. The actuators 6 are capable of extending and contracting in a controlled manner -for example, through the use of active pressure elements such as hydraulic cylinders.

When utilised on a vessel the motion-compensated platform 2 is capable of maintaining the surface 4 at a constant position relative to the fixed world or an object in the fixed world.

This is achieved through the use of motion sensors and a control system. A suitable arrangement of motion sensors and control system is provided in the PCT Application No. PCT/NL2007/050080, but other methods of arranging and calibrating motion sensors and a control system will be evident to persons skilled in the art. In response to data received from the motion sensors, the control system expands and contracts the actuators 6 (for example, through utilisation of active pressure elements such as hydraulic cylinders) in order to maintain the position and orientation of the surface 4 relative to the fixed world or an object in the fixed world.

In a Stewart platform the use of six actuators 6 to move the surface 4 in six degrees of freedom allows for the compensation of both linear motions of a sea-going vessel such as surge (motion from the front to the back), heave (up and down motions) and sway (sideways motions), and also allows for the compensation of rotating motions such as roll (bow from left to right), yaw (vessel rolls from left to right), and pitch (bow up and down).

Combinations of these motions can also be compensated for.

Figures 2 and 3 show two different views of a vessel 10 that has established frictional contact with a wind turbine foundation 12, in accordance with a commonly-used prior art method of embarking from a vessel 10 to a wind turbine foundation 12. Tt will be evident that the present invention and the prior art is not simply limited to wind turbine foundations, but can also encompass other sea-based installations such as oil rigs and tidal power installations, and land-based installations such as ports, and other vessels.

Figure 2 presents a bird's eye view of the vessel 10 in frictional contact, and Figure 3 presents a side view. As can be seen from these Figures, the turbine foundation 12 incorporates a pair of boat landing pillars 14 provided for this purpose. The vessel 10 is brought into contact with these pillars 14 with the bow 16 facing them; the bow 16 possesses mating features 18 permitting frictional contact to be made. Tn particular, the bow 16 is shaped such that at least a part of it may pass between the pillars 14 to make frictional contact with the foundation 12 itself, whilst other parts of the bow 16 make frictional contact with the pillars 14. The portions of the bow 16 which establish frictional contact with the foundation 12 and the pillars 14 may be provided with buffers or cushioning features.

The effect of the frictional contact technique is to dampen, and preferably eliminate, vessel translations at the point of contact. Once this is achieved, assuming that the sea 20 is sufficiently calm to permit this, personnel may then transfer themselves from the vessel 10 to the foundation 12 by ascending a ladder (not shown) located between the pillars 14.

Figures 4 and 5 show two different views of a vessel 10 that has likewise established frictional contact with a wind turbine foundation 12, and has utilised a motion-compensated platform 2 in accordance with prior art to provide a motion-compensated means of accessing the wind turbine foundation 12 via a surface 4 maintained at a constant position and orientation with respect to the wind turbine foundation 12 and a gangplank 22 between the surface 4 and the wind turbine foundation 12. In some of the prior art, vessels do not establish any sort of physical contact with fixed structures, but maintain their position utilising a Dynamic Positioning system (see "General Technical Information", Inform apm. Tn other prior art methods, vessels establish frictional contact with a fixed structure before personnel are transferred via a motion-compensated platform and gangplank (see "Turbine Access System", h As depicted in the bird's eye view of Figure 4, the gangplank 22 may be lowered between the pillars 14 to permit access to the turbine foundation 12 for any personnel mounted on the surface 4. It will be readily apparent that stairs or ladder arrangements on the vessel 10 may permit personnel to mount the surface 4 once it is raised, or the personnel and equipment to be transferred to the turbine foundation 12 may be positioned on the surface 4 before it is raised and the gangplank lowered.

II will also be readily apparent that a slight movement of the motion-compensated platform 2 could be amplified to lead to an extreme movement at the end of the gangplank 22. Though railings 24 may be provided on both the surface 4 and gangplank 22 to enhance safety, as depicted in the side-on view of Figure 5, this cannot eliminate the possibility of a sudden violent movement of the gangplank 22 in response to a failure of the platform 2.

A preferred embodiment of the present invention is depicted in Figures 6 and 7. As can be seen from the bird's eye view in Figure 6, the motion-compensated platform 2 is now located in a position on the deck of the vessel 10 in proximity to the edge of the vessel 10. In the depicted embodiment an edge of the surface 4 is either directly above or at least partially extends beyond the edge of the vessel; in this case, the edge of the vessel in question is the bow 16 but it will be evident that other edges can also suffice for this purpose. In other embodiments, the motion-compensated platform 2 is merely positioned sufficiently close to the edge of the vessel 10 such that when the vessel 10 is in position adjacent to the wind turbine foundation 12 direct transfer of personnel and/or equipment between the at least one surface 4 and the wind turbine foundation 12 is possible.

Optionally, the positioning of the vessel 10 adjacent to the wind turbine foundation 12 can be accompanied by the engagement of mating features 18 with the wind turbine foundation 12 and the pillars 14, as depicted in the side-on view of Figure 7.

Although the mating features are depicted as being located on the vessel 10 in Figure 7, it will be readily appreciated that mating features could alternately be located on the surface 4.

It will also be readily apparent that whilst the mating features may entail features adapted to enable frictional contact between the vessel 10 and the turbine foundation 12 and/or pillars 14, they may also include other means of maintaining the vessel in a fixed position, such as bolts, interlocking teeth, locks, screws, and magnets plus non-mechanical means like electronic sensors. It will also be readily apparent that wherever the mating features are located, the surface 4 may be shaped so that at least a portion of it follows the outline of the pillars 14 and turbine foundation 12, to minimise any gap between the surface 4 and the turbine foundation 12.

In the embodiment depicted the location of the motion-controlled platform 2 such that at least one edge of the surface 4 is directly above or at least partially projects beyond the edge of the vessel 10 allows the surface 4 to be placed immediately adjacent to the wind turbine foundation 12. This permits the gangplank 22 to be dispensed with entirely, a convenience which not only means that the gangplank 22 does not take up valuable space on the vessel 10 when it is not in use but also eliminates the safety issues concerning the gangplank 22 discussed above, and makes the transfer by hand of bulkier equipment easier. The arrangement is particularly advantageous if the motion-controlled platform 2 is placed at the bow 16 of a vessel 10 and the mating elements 18 on the vessel 10 (or the surface 4) are used to establish frictional contact or some other form of secure contact with the turbine foundation 12 and/or the pillars 14, since the frictional contact or other form of secure contact requires the motion-compensated platform 2 to respond only to the motions of pitch, heave and roll. Furthermore, placement of the motion-compensated platform 2 at the location where frictional contact or some other form of secure contact is made with the turbine foundation 12 and/or the pillars 14 means that any motion which the platform 2 must compensate for will be minimised since any motion of the vessel 10 will be minimised at the point of contact and will increase in amplitude with increasing distance from the point of contact.

In other embodiments of the invention personnel and/or equipment may be transferred between the surface 4 and the wind turbine foundation 12 through the use of a crane (not shown) mounted on the wind turbine foundation 12. The motion compensation features of the motion-compensated platform 2 ensures that the surface 4 remains in an essentially fixed position relative to the wind turbine foundation 12, allowing transfer by crane to be performed with ease. The position of the platform 2 at the bow 16 of the vessel 10 minimises the distance that personnel and/or equipment would need to be transferred by crane, increasing safety.

It will be understood by the skilled person that the Stewart platform is not the only form of motion-compensated platform 2 suitable for use in this invention, and that platforms 2 adapted for embarkation onto and disembarkation from a wide range of installations and vessels may be produced using the above teaching, and that the platform 2 does not necessarily have to be positioned at the bow 16 to put the invention into effect.

Claims

Claims 1: A vessel comprising a motion-compensated platform for transferring personnel and/or equipment between the vessel and an adjacent body, said platform comprising at least one surface for bearing, transporting and transferring a load, characterised in that the motion-compensated platform is positioned on the vessel in sufficient proximity to the edge of the vessel that personnel and/or equipment may be transferred directly between the surface and the adjacent body.

2: A vessel according to claim 1, wherein the motion-compensated platform is positioned on the vessel such that at least one edge of the at least one surface is either directly above or at least partially overhanging the edge of the vessel.

3: A vessel according to claim any preceding claim, wherein the motion-compensated platform further comprises: actuators capable of moving the at least one surface relative to the vessel; a control system for the actuators; and motion sensors for measuring motions of the vessel relative to at least one element in the surrounding area, which measurements are used as input for the control system; wherein the motion sensors and control system are calibrated to hold the at least one surface in a stationary position relatively to at least one element in the surrounding area.

4: A vessel according to claim 3, wherein the actuators are capable of moving the at least one surface in six degrees of freedom.

5: A vessel according to any preceding claim, additionally comprising mating features intended to engage with corresponding features of an adjacent body.

6: A vessel according to claim 5, wherein the mating features are adapted to engage with at least part of another vessel, at least part of a land-based installation, or at least part of an offshore installation.

7: A vessel according to claim 6, wherein the mating features are adapted to engage with a wind turbine or oil rig.

8: A vessel according to any of claims 5-7, wherein the mating features comprise at least one of the following: points of frictional contact, bolts, interlocking teeth, locks, screws, magnets, and non-mechanical means such as electronic sensors.

9: A vessel according to claim 8, wherein the mating features are adapted to engage with similar mating features on an adjacent body.

10: A vessel according to any of claims 5-9, wherein mating features are present on the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel.

11: A vessel according to any of claims 5-9, wherein mating features are present on the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging.

12: A vessel as in any preceding claim, wherein the edge of the vessel which the at least one edge of at least one surface is either directly above or at least partially overhanging is the bow or stem of the vessel.

13: A method of transferring personnel or equipment between a vessel according to any preceding claim and an adjacent body, comprising the steps of: moving the vessel into the proximity of the adjacent body, such that the edge of the vessel which the motion-compensated platform is placed in proximity to is facing the adjacent body; utilising the motion sensors and control system to hold the at least one surface in a stationary position relative to the adjacent body; transferring the personnel or equipment between the at least one surface and the adjacent body directly.

14: A method as in claim 13, wherein personnel or equipment is transferred directly between the at least one surface and the adjacent body via personnel stepping directly from the surface to the adjacent body or vice versa.

15: A method as in claim 13, wherein personnel or equipment is transferred directly between the at least one surface and the adjacent body through the use of a crane mounted on the adjacent body.

16: A method as in any of claims 13 to 15, comprising the additional step of engaging mating features of the vessel with corresponding features of the adjacent body prior to transferring the personnel or equipment.

17: A method as in claim 16, wherein the mating features are present on the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel.

18: A method as in claim 16, wherein the mating features are present on the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging.

19: Apparatus as described in the description and shown in the accompanying drawings.Amendments to the Claims have been filed as foflows: Claims 1: A vessel comprising a motion-compensated platform for transferring personnel and/or equipment between the vessel and an adjacent body, said platform comprising at least one surface for bearing, transporting and transferring a load, characterised in that the motion-compensated platform is positioned on the vessel in sufficient proximity to the edge of the vessel that personnel and/or equipment may be transferred directly between the surface and the adjacent body and that the vessel additionally comprises mating features intended to engage with corresponding features of an adjacent body.2: A vessel according to claim 1, wherein the motion-compensated platform is positioned on the vessel such that at least one edge of the at least one surface is either directly above or at least partially overhanging the edge of the vessel.3: A vessel according to any preceding claim, wherein the motion-compensated platform further comprises: actuators capable of moving the at least one surface relative to the vessel; a control system for the actuators; and motion sensors for measuring motions of the vessel relative to at least one element in the surrounding area, which measurements are used as input for the control system; wherein the motion sensors and control system are calibrated to hold the at least one surface in a stationary position relative to at least one element in the surrounding area.4: A vessel according to claim 3, wherein the actuators are capable of moving the at least one surface in six degrees of freedom.5: A vessel according to any preceding claim, wherein the mating features are adapted to engage with at least part of another vessel, at least part of a land-based installation, or at least part of an offshore installation.6: A vessel according to claim 5, wherein the mating features are adapted to engage with a wind turbine or oil rig.7: A vessel according to any preceding claim, wherein the mating features comprise at least one of the following: points of frictional contact, bolts, interlocking teeth, locks, screws, magnets, and non-mechanical means.8: A vessel according to claim 7, wherein the non-mechanical means comprise electronic sensors.9: A vessel according to claim 7 or 8, wherein the mating features are adapted to engage with similar mating features on an adjacent body.10: A vessel according to any preceding claim, wherein mating features are present on the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel.11: A vessel according to any preceding claim, wherein mating features are present on the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging.12: A vessel as in claim 2, wherein the edge of the vessel which the at least one edge of at least one surface is either directly above or at least partially overhanging is the how or stern of the vessel.13: A method of transferring personnel or equipment between a vessel according to any preceding claim and an adjacent body, comprising the steps of: moving the vessel into the proximity of the adjacent body, such that the edge of the vessel which the motion-compensated platform is placed in proximity to is facing the adjacent body; engaging mating features of the vessel with corresponding features of the adjacent body; utilising the motion sensors and control system to hold the at least one surface in a stationary position relative to the adjacent body; transferring the personnel or equipment between the at least one surface and the adjacent body directly.14: A method as in claim 13, wherein personnel or equipment is transferred directly between the at least one surface and the adjacent body via personnel stepping directly from the surface to the adjacent body or vice versa.15: A method as in claim 13, wherein personnel or equipment is transferred directly between the at least one surface and the adjacent body through the use of a crane mounted on the adjacent body.16: A method as in any of claims 13-15, wherein the mating features are present on the at least one edge of the at least one surface which is either directly above or at least partially overhanging an edge of the vessel.17: A method as in any of claims 13-15, wherein the mating features are present on the edge of the vessel which the at least one edge of the at least one surface is at either directly above or at least partially overhanging.18: Apparatus as described in the description and shown in the accompanying drawings.