EP1113957B1

EP1113957B1 - Mooring device

Info

Publication number: EP1113957B1
Application number: EP99951326A
Authority: EP
Inventors: Staffan ENGSTRÖM
Original assignee: Agir Konsult AB
Current assignee: Agir Konsult AB
Priority date: 1998-09-17
Filing date: 1999-09-16
Publication date: 2004-05-06
Anticipated expiration: 2019-09-16
Also published as: JP2002524354A; WO2000015489A1; DK1113957T3; EP1113957A1; DE69917050D1; DE69917050T2; SE9803166D0; SE9803166L; SE517178C2; ATE265958T1

Abstract

The present invention relates to a mooring arrangement, which allows safe and economical mooring, primarily of smaller vessels to ground-anchored or floating structures at sea, such as sea based wind-power stations, lighthouses and constructions for extracting and loading oil. It may also be used for mooring two vessels against each other, for example a pilot boat to a larger vessel. THe invention solves the problem by means of a mooring arrangement, comprising a connecting means (4), a manoeuvring member (5) arranged at one end of the connecting means, a locking device (6) arranged at the other end of the connecting means and a control means (8).

Description

Technical Field

The present invention relates to a mooring arrangement for mooring a marine vessel to a structure. The invention also relates to marine vessels and structures equipped with such a mooring arrangement.

Background

The mooring up of small vessels and boats to small structures at sea creates special problems, since no protection is provided against heavy sea and wind. The structures may be ground anchored or afloat, such as sea-based wind-power stations, lighthouses or constructions for extracting and loading oil. Due to the fact that waves and wind have a tendency to sweep around structures at sea, such structures must have a considerable horizontal extension, if they not shall be regarded as small. Except for just a short period of the year, transportation of personnel and goods is difficult, and can result in unacceptable risks. In the Baltic Sea just off the coast of Gotland, for example, the maximum wave height exceeds one meter for 80% of the hours in a year. This also is the approximate limit for the wave height at which a smaller boat can lie moored against a quay or dock. The difference in the water level further increases the difficulties of using fixed devices. This is true especially where tide water is significant.
As a rule vessels at sea do not moor against each other, since suitable mooring devices, functioning not just only in very favourable conditions, have not been available. Therefore, pilots normally jump from the pilot boat and piloted vessel without a fixed connection and despite relative movements, which can be considerable. Thus, dangerous situations and accidents occur.
The mooring devices available today consist as a rule of some form of ramp, which may be lowered either from the vessel or from the construction against which the vessel is to be moored. U.S. patent No. 4, 133, 283 describes, for example, a hydraulic power arrangement to counteract the mooring forces between a vessel and a fixed structure when the vessel is moored. This invention is aimed at how to counteract the mooring forces after a vessel is moored. How the mooring arrangement shall be constructed so as to make mooring possible when there is a heavy sea is, however, not disclosed.
U.S. patent No. 4, 083 072 describes a mooring arrangement comprising an attachment assembly, a swivel connection and a locking device. When mooring, a person on the deck of the vessel must take hold of a line hanging down from the attachment assembly. The line is then guided through a loop so as to be drawn in by a winch, which is arranged on the vessel. This procedure when mooring a vessel can be hazardous, especially in heavy seas, since a person must walk forward on deck when mooring.
U.S. patent No. 4,011,615, relates to a gangway for transferring personnel between a ship and a fixed structure. Even this document is aimed at how the mooring forces may be counteracted after a vessel has been moored i.e. how the actual mooring assembly shall be constructed so as to carry out safe mooring is not described.
U.S. patent No. 3,426,719 relates also to a ramp for transferring personnel between a ship and a fixed structure. Exactly as in the previous document, the ramp first and foremost is constructed to counteract mooring forces when the vessel is actually moored. The ramp, also in this case, is provided with a line as in U.S. patent No. 4,083,072 and the actual mooring functions in a corresponding manner.
All the above mentioned mooring arrangements are thus, first and foremost, constructed to counteract the mooring forces when the vessel is secured.
Thus, there is a need for a mooring arrangement which allows simple and safe mooring, even when there is a high sea, and which subsequently allows a dependable fixed connection for transferring personnel and goods between a vessel and a smaller construction in the sea, or between two vessels.

Description of the invention

The purpose of the present invention is to achieve a safe, reliable and cheap mooring arrangement, which eliminates or reduces the problems described above.
This aspect is achieved by an arrangement having the features disclosed in claim 1.
Preferred embodiments of the invention are disclosed in the dependent claims 2 to 10.
The invention may be applied to mooring of smaller vessels primarily to ground-anchored or floating structures in the sea, for example, sea-based wind-power stations, lighthouses or constructions for extracting and loading oil. It can also be used for mooring two vessels against each other, for example, such as a pilot boat from which, during heavy sea, personnel shall be transferred to a larger vessel.

Description of the Drawings

Various embodiments of the invention will now be described more closely here below with reference to the attached drawings, in which
Figure 1 illustrates a system of co-ordinates for a vessel,
Figure 2 illustrates a mooring arrangement when mooring to a structure,
Figure 3 illustrates a mooring arrangement when the vessel is moored against the structure,
Figure 5 illustrates how the gangway is centred to the structure.

Preferred embodiments of the invention

In the description reference is made to the system of co-ordinates, which is defined in Figure 1. The x-axis represents the longitudinal direction of the vessel, y-axis its transverse direction while the z-axis runs vertically. The movements of the vessel have a total of six degrees of freedom (translation in the x-, y- and z-directions and rotation around the x-, y- and z-axes). When the vessel is at rest and not influenced by external forces, it will take up a neutral position in each one of the different degrees of freedom.
Various embodiments will now be described in conjunction with Figures 2 and 3, which show a schematic illustration of the mooring arrangement mounted to a smaller boat 1, during a mooring manoeuvre and when moored to a structure 2, respectively. The structure may comprise of a ground-anchored structure or a floating structure having, within the present field, mainly vertical restricting areas. At the fore of the vessel at 3 there is a connecting means 4 pivotally mounted, comprising a load-bearing girder which also may be used as a gangway for transferring personnel and goods. With the assistance of a manoeuvring member 5 on the vessel, the connecting means 4 is placed at a selected angle and optionally lowered or elevated into a resting position. In the simplest case, the manoeuvring member consists of a fixed support. Preferably, at the forward end of the connecting means there is one part of a locking device 6 and a control means 8, which engages with the hinge 7, which may have resilient or damping properties. The control means 8 may comprise one or several wheels, reels or the like. The control means may also be realised by giving the end of the connecting means a suitable design. The other part 9 of the locking device comprises an attachment means, which in this specific case is provided on the structure 2. As illustrated in Figure 3 and Figure 4, the locking device 6 may for example have the form of a clutch 11, which grips a round rod. The rod runs around and is concentrically fastened at a predetermined distance from the structure 2 and constitutes the corresponding part of the locking device 9. By means of the principle described, mooring may take place from any chosen direction. Furthermore, the vessel will passively follow, when the wind and waves change direction. The illustrated locking device is preferably locked automatically upon contact between the two parts. Unintentional unlocking is prevented, for example, by the clutch 11 being provided with a spring (not shown). Disengagement may be triggered from an optional site, for example, by actuating a hydraulic cylinder (not shown). Thereafter the vessel may leave the site immediately.
In another embodiment, the round rod of the locking device 9 is replaced by a steel cable, mounted between supports, which are fixed to the tower in a similar manner as the round rod. Since the steel cable is flexible, this normally provides an advantageous load condition, which can lead to reduction in material and costs.
Alternatively, the locking device may be provided in connection with the attachment means 3, whereby the gangway 7 provides permanent connection between the connecting means 4 and the structure 2. The remaining parts should then be adapted to this embodiment.
The attachment means, which normally allow certain rotation in three degrees of freedom, may also be arranged so as to manage a limited translation in up to three degrees of freedom. The attachment means may, furthermore, be provided with dampers and springs, to restrain movements even more and to create a return movement. For example, the manoeuvring member 5, whose primary function is to place the connecting means 4 at a selected angle, consists of a hydraulic cylinder, which when combined with restrictions, has a damping function and when combined with hydraulic accumulators, has a spring action. In this fashion forces are achieved that operate to counteract the momentum around the y-axis in this attachment means. Corresponding action is achieved in the other degrees of freedom for both the attachment means. The movement in the attachment means and the damping and spring function may be replaced completely or partly by means of connecting means 4 being arranged non-rigid.
On the structure there is suitably also a platform 10, which has a position and form adapted to the girder 4.
At the start of the mooring procedure the vessel moves forward in the water at a certain speed, i.e. in the x-direction according to the system of co-ordinates in Figure 1. Thus, the connecting means 4 normally is placed at such a positive angle that its forward end will meet the structure well below the locking device 9. It may be positioned at angles against the horizontal plane (xy-plane) at between 0 and 90 degrees; a typical value when mooring is 45 degrees. When the end of the connecting means comes into contact with the structure, as a consequence of the remaining movement of the vessel in the x-direction, this then will move upwards in the z-direction. If the manoeuvring member 5 has a damping function, the vessel's movement will thereby be slowed down. This process continues until both the parts 6 and 9 of the locking device are joined together, whereby engagement takes place automatically. Manual engagement is also possible. To facilitate the process, wheels or the like are arranged on the control means 8. Any subsequent energy movement will then, due to the geometry of the participating parts, primarily be absorbed because the fore of the vessel is pressed downwards and thus alters the trim (rotation around y-axis). In Figure 2 this trim-alteration is marked as a degree α between the original, continuously drawn vessel-contour and the new, dashed line vessel-contour. When the forward movement has stopped the trim returns because the vessel moves a little in the negative x-direction. By means of these changes in the degrees of freedom of movement, energy will be successively absorbed by wave accumulation and friction, which results in a dampening of the movements without large forces being created in the construction.
It is also possible to design the construction by starting out from the supposition that the connecting means 4 is positioned at a corresponding negative angle to the horizontal plane. Then the forward end of the connecting means will move downward during the mooring and locking procedure. The round rod or the steel cable of the locking device will instead then be arranged at the lower area of the structure 2.
Figure 5 illustrates how, by arranging the wheels 8 at a suitable angle (β) outwardly in relation to the movement of the connecting means when mooring (toe-out) the connecting means 4 may be centred on the structure 2, provided that the structure within the actual area has a convex cross section. On incorrect centring only one of the wheels of a wheel pair will come into contact with the structure. The toe-out angle means that the forward end of the connecting means may be guided to the corresponding side of the structure, until also the other wheel of the wheel pair makes contact, whereby the side conveyance of both wheels compensate each other and the connecting means continues to move to centre. So as to compensate for great side miscalculations it may be suitable to arrange several pairs of wheels. At a large toe-out angle the passive direction of wind may be eased in this manner. If the wheels are fixed in a resilient manner it can occur that both wheels come into contact with the structure despite incorrect centring. Since the pressure applied by the two wheels to the structure is different, the centring will work also in this case.
When a vessel is moored, the movement of the sea and wind means that it will move in several degrees of freedom. Then the forward movement and the backward movement (translation movement in positive and negative x-direction) will be absorbed by the trim changes around the y-axis. Pitching/trim changes are converted in an analogue manner from a part of the rotation round the y-axis to translation the in x-direction. Heaving, (movement in the z-direction) is converted also to movements in the x-direction. Movements in the y-direction cause translation in the x-direction and rotation round the z-axis. The mobility of the construction also allows rolling (rotation round the x-axis) which does not interfere with the mooring function.
To allow mooring against another vessel, it can be arranged thereon a vertical plane having an attachment means 9 crosswise to the direction of movement and at a suitably height. Mooring preferably takes place by a smaller vessel moving up to be parallel with the larger vessel. This will proceed until the forward part of the connecting means 4 makes contact with the vertical plane and attachment means 9, in an analogue manner as the foregoing description of mooring to a fixed or floating structure.
It is pointed out that one of the advantages that the invention provides, is that movements in the degrees of freedom, which for the mooring function should not continue without control, are to a large extent converted into movements in other degrees of freedom and thereby can be dealt with in a controlled and well defined manner. By such means it is possible to carry out mooring manoeuvres also at sea during high seas and wind. It is especially emphasised that the invention allows forces to be absorbed by the dampening movements rather than by non-resilient twitches. Because the movements are well defined the forces may also be calculated easily, which is of great practical advantage in the development, among other things, when a construction is to be inspected by an authority or a classifying body.
The invention allows a mooring vessel to approach near to the structure and moor in one direction against the prevalent wave and wind direction, which means that one does not have to risk that the vessel shall be thrown against the structure by a breaker. When the mooring has taken place the longitudinal direction is adapted passively after the prevailing direction of wind and waves.
At high sea the moored vessel moves unevenly and it is difficult to steer with precision into a locking device. The present invention allows for considerable miscalculations in height due to adjustment errors, wave movement and water height. Finally, the invention allows that one may unmoor and move away from the site in a simple and safe manner.
By means of the preferred construction, practically the entire means may be placed on the vessel, which can then serve many set ups. This means the system is economical. Another advantage is that maintenance and repair work may take place under protected conditions at a port.

Claims

A mooring arrangement for mooring a vessel (1) against a structure (2), comprising a connecting means (4) arranged at the vessel (1), a manoeuvring member (5) arranged at a first end of the connecting means (4) for adjusting the angle between the connecting means (4) and the horizontal plane, and a locking device (6) arranged at a second end of the connecting means (4) for fastening the vessel to the structure (2) when mooring, characterized in that a control means (8) is provided at the second end of the connecting means (4), which during mooring, with the aid of the vessel movement, is moveable along the surface of the structure to guide the locking device (6) into engagement with an attachment means (9) arranged at the structure (2).
Mooring arrangement according to claim 1, characterized in that an attachment means (3) is provided on the vessel, to which the connecting means (4) is pivotally mounted.
Mooring arrangement according to any of the foregoing claims, characterized in that the connecting means (4) is adjustable within an angle range of 0 to 90 degrees in relation to the horizontal plane.
Mooring arrangement according to any of the foregoing claims, characterized in that the attachment means (9) is arranged and positioned in such a way at the structure (2) that the vessel (1), during mooring, can have a selected radial position in relation to the structure (2).
Mooring arrangement according to any of the foregoing claims, characterized in that the control means (8) comprises at least one pair of wheels, said wheels being arranged in pairs at a distance from each other and placed in an oblique outward position away from the intended direction of movement.
Mooring arrangement according to any of the foregoing claims, characterized in that the connecting means (4) or at least one of the attachment means (3, 9) have a spring function (5), which operate to return the connecting means (4) to a neutral position for at least one degree of the vessel's freedom of movement.
Mooring arrangement according to any of the foregoing claims, characterized in that the connecting means (4) or at least one of the attachment means (3, 9) have a dampening function (5), which counteract the movements of the connecting means (4) for at least one degree of the vessel's freedom of movement.
Mooring arrangement according to any of the foregoing claims, characterized in that the locking device (6) comprises a gripping device (11) to enclose the attachment means (9).
Mooring arrangement according to any of the foregoing claims, characterized in that the locking device (6) on contact with the attachment means (9) is automatically locked to the attachment means (9).
A ship characterized in that it comprises a mooring arrangement according to any of the preceding claims.