WO2012108769A1

WO2012108769A1 - Transfer system

Info

Publication number: WO2012108769A1
Application number: PCT/NL2012/050071
Authority: WO
Inventors: Klaas Zoet; Maarten Paul Maria VAN MEERWIJK; Markus Van Der Laan
Original assignee: Ridderinkhof B.V.
Priority date: 2011-02-11
Filing date: 2012-02-09
Publication date: 2012-08-16
Also published as: EP2673188A1; NL2006183C2

Abstract

Transfer system for transferring people/goods from a vessel to a maritime structure, for example another vessel or a structure which is anchored to the seafloor. It is proposed to provide the vessel with two spaced-apart masts with a length-adjustable cable extending from each of said masts, the free ends of which are connected to a transfer holder which can contain the people/goods. A third cable is provided between the transfer holder and the maritime structure. Subsequently, it is possible to achieve displacement by pulling in the third cable and easing the first and second cable during displacement of the transfer holder from the vessel to the maritime structure. For the return movement, the cables are operated in reverse manner. In this way, it is possible to achieve transfer of people and goods even at heavy sea.

Description

Transfer system.

The present invention relates to a transfer system comprising a transfer holder. According to the present invention, such a transfer system is used at sea where people and/or goods have to be moved from a vessel to a maritime structure using a transfer holder.

In the prior art, various kinds of structures are known in order to permit displacement between two vessels or between a vessel and terra firma, even when the sea is rough. In particular if the wave action is comprised of two components which are at an angle to one another, e.g. as caused by a turning of the wind, such a displacement is particularly difficult to achieve.

In one system, a telescopic gangway is used which is mounted on a structure which compensates for the waves, as a result of which the free end thereof should, in theory, be stationary with respect to the seafloor. Such a system is particularly complicated and, in addition, can only compensate for limited wave action, as a result of which it cannot be used with relatively high waves. In another known system, a cable is provided between the vessel and the maritime object and the transfer holder is moved along the cable using a guide. In principle, this can be carried out at relatively high waves, but it is very uncomfortable when people have to be transferred.

Since an increasing number of structures are positioned at sea and anchored to the seafloor, and other structures, such as vessels, also remain in the same position for a prolonged period of time, the supply of provisions and transfer of people to and from such maritime structures is becoming increasingly important. In addition to the abovementioned systems, helicopters are used, but the costs associated with the latter are extremely high. Examples of maritime structures which have to be visited regularly are drilling and offshore platforms as well as wind turbine platforms.

It is an object of the present invention to provide a transfer system which can operate with relatively high waves of 5 metres and more, while having a relatively low price and ensuring comfortable transfer of people and goods between the maritime structure and the vessel. In addition, it has to be configured in such a manner that the most essential components of such a transfer system are present on a vessel in any case. In addition, it has to be possible to transfer significant weights, such as, for example, weights of 1 ton and more. This object is achieved with an above-described transfer system by the fact that it comprises first, second and third cables connected thereto, wherein said third cable makes an angle of more than 30° with said first and second cable.

A transfer system of this type is preferably used in combination with a vessel and preferably forms part of an assembly consisting of vessel, maritime structure and the transfer system.

According to the present invention, the vessel has two masts which can be folded down according to a preferred embodiment of the invention and can be positioned

(substantially) vertically by means of guy ropes. These masts are preferably situated on opposite longitudinal sides of the vessel. By suspending the transfer holder between these masts with the aid of the first and second cable, the transfer holder in principle moves concomitantly with the movement of the vessel, as long as the third cable is inoperative. Lateral swinging of the transfer holder is prevented. In this case, the ship's hull is assumed to be elongate and lateral swinging is understood to mean the rolling about the longitudinal axis thereof. If a vessel, for example a platform, catamaran or the like, with different length and/or width dimensions is used, the positioning of the masts will be adjusted accordingly.

If the transfer holder is situated close to the maritime structure, that is to say if the third cable is kept as short as possible and the first and second cables are kept as long as possible, the transfer holder will follow the movement of the maritime structure or, in the case of a maritime structure which is fixed with respect to the seafloor, will not move with respect to the seafloor. During the displacement of the transfer holder from the vessel to the maritime structure, a gradual transition will occur from the movement of the vessel which is conveyed to the transfer holder to the movement (or lack of movement) of the maritime structure. This occurs without any lateral swinging of the transfer holder taking place.

This means that a stable position of the transfer holder is produced by means of the first and second cable, with the position in the "longitudinal direction" of the transfer holder being secured by the third cable.

The easing of the first and second cable and the return movement thereof preferably takes place by means of winches fitted to the vessel. A common winch can be used to control the first and second cable, but it is also possible to use two separate winches for in each case each first and second cable. The third cable may be controlled either by means of a winch on the maritime structure or a winch on the transfer holder. If the transfer system is configured to be as autonomous as possible, that is to say if as many of the components as possible are positioned on the vessel which delivers the goods and ferries people across, the third winch will be present in the transfer holder so that it is only necessary to attach a third or fourth cable to the transfer holder and/or to the maritime structure, respectively. In this case, power has to be provided to this winch on the transfer holder which may be supplied by either a power source (battery) in the transfer holder, preferably on the bottom side, or by providing power via the first and/or second cable. In this case, it is for example possible to provide the core of the cable with a copper guide via which electricity can be transferred from the vessel to the transfer holder. It is also possible to use a combination of the two, which has the advantage of improving reliability and enabling the battery to be used as an additional booster during high loads, when the winch pulls the transfer holder vertically upwards towards the maritime structure.

Although the path of the transfer holder between preferably the rear side of the vessel and the maritime structure may be any conceivable path, according to a particular embodiment of the invention, this path is brought about in such a manner, by controlling the length of the first, second and third cables, that the transfer holder, during a first phase, moves from the vessel according to a substantially horizontal path at a height which is substantially equal to the height of the afterdeck of the vessel in the direction of the maritime structure. Only in the final stage of the path is the transfer holder moved upwards in the direction of the landing site on the maritime structure. This minimizes lateral swinging.

In this case, the landing site on the maritime structure is assumed to be situated in a higher position than the (point of departure of the) ship.

By means of the present invention, it is possible to realize a particularly efficient transfer system in a very inexpensive manner.

According to a particular embodiment of the present invention, the angle between the various cables is such that maximum stability is achieved. In this case, the angle between the first and second cables is preferably greater than 30°. Said angle is measured if the transfer holder is situated on the vessel and the masts are in the upright position. It will be understood that if the transfer holder is moved to a maritime structure across a significant distance, this angle becomes smaller, which, on the one hand, reduces the stabilizing effect, but, on the other hand, also reduces the need for such stabilization due to the larger distance from the vessel, thus still making optimum transfer of the transfer holder possible. The angle between the first cable and the third cable or the second cable and third cable, respectively, is greater and is preferably more than 60°.

According to a particular embodiment of the present invention, the masts can be positioned (rotated) in various positions, i.e. horizontal to the deck (0°), obliquely upwards directed inwards (90° with respect to the deck's longitudinal axis), perpendicularly upwards (90° with respect to the deck's longitudinal axis) and obliquely upwards directed outwards (120° with respect to the deck's longitudinal axis). In the outwardly directed position, the guy ropes are taut and carry in the length direction of the vessel. Thus, starting from the inwardly directed position, the masts can be positioned to lift/move the transfer holder from the deck from a controlled boarding/disembarking position and subsequently, the masts can move to the outwardly directed position, following which the third cable is pulled. In this embodiment, it is possible to position this outwardly directed position in such a way that the two mast ends protrude behind the ship. As a result thereof, it is also possible to lift cargo out of and into the water, as is often the case with maritime applications (generally referred to as A frame). As a result, it is possible to combine the functions of the transfer system and lifting cargo out of and into the water.

According to a particular embodiment of the present invention, an arresting cable is provided between the two masts at such a height that this arresting cable touches the first and second cable and/or the transfer holder. In this embodiment, the first and second cable and/or the transfer holder will not touch this arresting cable if the masts are in the outwardly directed position and the longitudinal movement will be determined by the third cable. As soon as the masts are rotated to the perpendicular upward pointing position, the first and second cable and/or the transfer holder will touch this arresting cable and the longitudinal movement will be inhibited by this arresting cable. If the masts are rotated further to the inwardly directed position, the longitudinal movement is determined completely by the arresting cable and the transfer holder will be supported both in the transverse direction, by the first and second cable, and in the longitudinal direction, by the arresting cable. This arresting cable may be provided with means for absorbing energy by means of dampers and/or resilient energy. An additional advantage of the arresting cable installation is that if the third cable were to break at an undesirable point in time during the second movement path 16, (excessive) swinging in the longitudinal direction is prevented and/or absorbed.

According to a particular embodiment of the present invention, the masts are placed in such a manner that, in the perpendicular position with respect to the length direction of the vessel, they are spaced apart in the width direction from the vessel deck upwards. Thus, it is nevertheless possible to achieve the desired relatively great width between the upper ends of the masts on a relatively narrow vessel deck.

The invention will be described below in the claims by means of a transfer system, vessel and assembly. The various particular embodiments thereof as described in the claims dependent therefrom can in each case be used with the other claims.

The present invention also relates to a method for transferring objects from a vessel to a maritime structure and vice versa by displacing a transfer holder between said vessel and said maritime structure, which transfer holder comprises first, second and third cables, wherein the first and second cables are connected to the vessel via a first and second mast and the third cable is connected to the maritime structure, wherein said displacement is achieved by pulling in said third cable when easing said first and second cables and vice versa.

In a variant, it is possible for the maritime structure to comprise a further vessel, such as a ship. In that case, this further vessel may be provided with the same transfer system as described above. This makes it possible to goods or people between two vessels moving on the surface of the sea. In this case, the transfer holder is connected to the first ship in the above-described manner by two cables and is, in addition, connected to the other vessel by two cables. In this case, it is possible to use all of the above-described variants.

The invention will be explained below in more detail by means of an exemplary embodiment which is illustrated in the drawing, in which:

Fig. 1 shows a vessel and a maritime structure; Fig. 2 shows the vessel with a transfer holder which is ready to start and a maritime structure;

Fig. 3a shows the first phase of moving the transfer holder from the vessel to the maritime structure;

Fig. 3b shows how the transfer holder moves away from the vessel;

Fig. 3c shows how the transfer holder is initially pulled in from the maritime structure;

Fig. 3d shows a view onto the afterdeck of a situation according to 3c;

Figs. 4-6 show the subsequent phases of transferring the transfer holder to the maritime structure; and

Fig. 7 shows a rear view of a variant of the invention with an inclined vessel.

Below, the transfer of a transfer holder from a vessel to a maritime structure will be described. It will be understood that the return movement is also covered by the present invention and is carried out substantially in the same way, but obviously adapted to the direction of movement which is being carried out at that point in time. Below, the maritime structure will be described as a part which is fixedly connected to the seafloor, but it will be understood that the maritime structure may comprise any structure, such as another vessel which moves to and fro with the waves in the same or in a different way.

In the figures, reference numeral 1 denotes a vessel on which two folded-down masts, i.e. first mast 4 and second mast 5, are situated near the longitudinal sides thereof, as is illustrated in Fig. I . First winch 15 and second winch 14 are fitted near the masts 4 and 5. In fig. 1, reference numeral 2 denotes a maritime structure, such as an island on which a wind turbine is installed. The latter requires maintenance and to this end, both parts and people have to be transferred from the vessel 1 to the island 2 and vice versa. A buoy 17 is attached to the maritime structure via a cable. Obviously, the vessel will be positioned in an optimum manner with respect to the prevailing sea/wind. That is to say that either the bow or the stern is positioned in the direction of the waves. Fig. 2 diagrammatically shows how this transfer movement takes place. In a first step, the masts 4 and 5 are brought to a more vertical position and, optionally, supported by guy ropes. Subsequently, the transfer holder 7 is placed on the afterdeck of the vessel 1 and first cable 9 is attached to the top side of the transfer holder and extends towards the top end of the first mast 4 and is connected to the first winch 15. The second cable 10 is also connected to the top side of the transfer holder 7 and extends to the top side of the second mast 5 and is connected to the second winch 14. If they are configured as two separate winches, the winches 14 and 15 can be driven by a single synchronized control mechanism. The transfer holder 7 is enclosed by an arresting structure, the shape of which can be seen in Figs. 2 and 3. It is depicted diagrammatically and is denoted by reference numeral 20.

In addition, an arresting cable 21 is fitted between the masts 4 and 5 and provides support.

Starting from the position illustrated in Fig. 2, a third cable 1 1 is connected to the island 2. Island 2 is provided with an opening 12 and a trestle 22 which is arranged above the latter and to which the third cable 11 is attached. The third cable can be controlled by a third winch which is situated either near this trestle 22, but is preferably arranged near the transfer holder 7 in the embodiment illustrated here. The third cable can be picked up easily by the vessel by means of a messenger line or a buoy 17 which is situated at the bottom of the island.

Starting from the position in Fig. 2, the masts 4 and 5 are raised further, as a result of which the transfer holder 7 moves out of the arresting device 20 and moves across the deck between the masts 4 and 5 at a small distance above it and is supported by the arresting cable 21. In this case, cable 11 is not yet operational, as is shown in Fig. 3a. Subsequently, the masts 4 and 5 are moved further to a position in which the transfer holder 7 is situated beyond the afterdeck of the vessel, as is shown in Fig. 3b. This is a more or less safe situation which can be achieved without having to tension the third cable 1 1 , which means that the position of the vessel 1 with respect to the island 2 is not yet critical at that point in time. Should the transfer holder fall as a result of cable failure, this would not have any major consequences since it only plunges into the sea from a low height. The third winch 13 for the third cable which is preferably present in the transfer holder may be operated either by means of a battery which is present therein or (in combination with) by a power supply. This power supply may be achieved, for example, by means of the first and second cable. From this point in time, cable 11 is tensioned, resulting in the situation as illustrated in Fig. 3c. Fig. 3d is a top view in which a is the angle between the first and second cable, β is the angle between the first cable 9 and the fourth cable 12 and angle β is the angle between the second cable 10 and the third cable 11. Said angle β is preferably greater than 60° and more particularly greater than 120°.

Fig. 3d shows a top view of this situation.

Starting from the position illustrated in Fig. 3c, by pulling in the third cable and by easing the first and second cables, the transfer holder 7 describes a path which is designated by reference numeral 16 and which comprises a first horizontal part, followed by a vertical part, as is illustrated in Fig. 4.

As a result of the presence of a first and second cable, the transfer holder 7 is prevented from carrying out a swinging to-and-fro movement which is greater than the swinging movement of the amplitude of the vessel when people and goods are being transferred and the vessel is rolling. By ensuring that the transfer holder 7 is kept at as low a level as possible, that is to say as close as possible to the rolling axis of the vessel, movement of the transfer holder will be relatively limited or will even be zero. As a result of the presence of the third and fourth cable, a to-and-fro swinging is prevented between the vessel and the maritime structure.

This is then followed by the situation illustrated in Fig. 5 in which the transfer holder 7 is only moved in the vertical direction. Due to the fact that the transfer holder is then situated at a great distance from the vessel, a rolling movement will hardly have an effect anymore on the transfer holder which is substantially carried by the maritime structure. Eventually, the position illustrated in Fig. 6, the landing position, is arrived at, in which goods and people can pass from the transfer holder onto the island 2. In this case, transfer holder 7 has moved through opening 12. As a result of the tapered shape of the transfer holder and the likewise tapered shape of the opening, the rotationally symmetrical transfer holder is received in the opening in a locating manner and clearly fixed in its end position by means of gantry 22. The users can then leave the transfer holder. In this case, it is possible to take specific measures to optimize the "landing" of the transfer holder as much as possible, for example by the use of damping material and the like. The return movement is carried out in the same manner, with the transfer holder then being received in the arresting device 20 on the deck of the vessel.

Fig. 7 shows a rear view of a variant of the way in which the transfer holder is attached to the first cable 9 and second cable 10 in the situation in which the vessel is tilted significantly about its longitudinal axis. It can be seen that the transfer holder hardly changes position as a result of this tilting movement. This is supported by the fact that a branch cable 23 providing further stabilization is fitted near the attachment of cable 9 and cable 10, respectively, on the transfer holder.

By means of the present invention, it is possible to transfer the transfer holder from the vessel to the maritime structure using parts which are known in the prior art and without technical complications. In this case, it is possible to control the various winches from the vessel, from the transfer holder or from the island 2. It is also possible to control the third and fourth cable from the island and the transfer holder, respectively, while the first and second cable are being controlled from a different position, for example from the rear of the vessel.

As has been indicated above, it is possible for a maritime structure to be another vessel. The present invention is particularly useful if the other vessel is much larger than the first above-described vessel (and exhibits relatively small movement behaviour due to its larger size).

By means of the present invention, it is possible to move people and goods across great distances and great heights. By way of example, a distance of 50 metres in rough seas is mentioned, while a difference in height which can be overcome is 50 metres or more. There is therefore little risk that the vessel will hit the maritime structure, so that it is possible to transfer goods and people even at heavy sea.

Upon reading the above, those skilled in the art will immediately be able to think of variants which are covered by the scope of the attached claims. In addition, rights are expressly requested for the embodiments described in the subclaims separate from the associated independent claims.

Claims

1 3 10 CLAIMS

Transfer system comprising a transfer holder (7) and first (9), second (10) and third (1 1) cables connected thereto, wherein said third cable (1 1) makes an angle (β) of more than 30° with said first and second cable.

Transfer system according to Claim 1, wherein said transfer holder is provided with a third winch (13) for moving said third cable (1 1) with respect to said transfer holder (7).

Transfer system according to one of the preceding claims, wherein said angle (a) between said first and second cable is at least 30°.

Transfer system according to one of the preceding claims, configured to be accommodated in a 20-foot container.

Vessel provided with a transfer system according to one of the preceding claims, wherein said vessel is provided with first and second spaced-apart masts (4, 5) which are situated on either side of the longitudinal axis of the vessel and extend vertically, wherein said first cable extends from the first mast and said second cable extends from the second mast, wherein each of said first and second cables is displaceable in order to move said transfer holder (7) with respect to said vessel.

Vessel according to Claim 5, wherein said transfer holder is provided with a third cable and a third winch which influences the length of said cable.

Assembly comprising a vessel and a maritime structure and a transfer system according to one of the preceding Claims 1-4 with a transfer holder, which transfer system operates in between the former, wherein said vessel (1) is provided with first and second spaced-apart masts (4, 5) which extend vertically, wherein a first cable (9) which is attached to the transfer holder (7) extends from the first mast (4) and a second cable (10) which is attached to the transfer holder extends from the second mast (5) and a third cable (1 1) is provided between the transfer holder (7) and the maritime structure (2), wherein each of said cables (9- 1 1) is displaceable in order to move said transfer holder (7) with respect to said vessel and maritime structure.

8. Assembly according to Claim 7, wherein said transfer holder (7) is provided with a third winch (13) for displacing said third cable (1 1).

9. Assembly according to Claim 7 or 8, wherein said vessel (1 ) is provided with a first winch (15) for said first cable (9) and a second winch (14) for said second cable (10).

10. Assembly according to one of the preceding claims, wherein the first and/or second cable is provided with an electrically conductive material via which electricity can be passed from the vessel to the transfer holder.

1 1. Assembly according to one of Claims 7-9, wherein said maritime structure comprises a vessel.

12. Assembly according to one of Claims 7-10, wherein said maritime structure comprises a platform.

13. Assembly according to one of Claims 7-1 1 , wherein said maritime structure comprises a wind turbine.

14. Method for transferring objects from a vessel to a maritime structure and vice versa by displacing a transfer holder (7) between said vessel and said maritime structure, which transfer holder comprises first (9), second (10) and third (1 1) cables, wherein the first and second cable are connected to the vessel via a first

(4) and second (5) mast and the third cable is connected to the maritime structure, wherein said displacement is achieved by pulling in said third cable (11) while easing said first (9) and second (10) cables and vice versa.

Method according to Claim 14, wherein the location of arrival of said transfer holder (7) on said maritime structure (2) is situated higher than the location of departure on said vessel, and wherein the path of said transfer holder is substantially horizontal during a first part until it comes close to said maritime structure and is substantially vertical during a second part.