EP2500256A1

EP2500256A1 - Mooring device and method for mooring a vessel to a wind power plant

Info

Publication number: EP2500256A1
Application number: EP12159152A
Authority: EP
Inventors: Pauli Immonen
Original assignee: Mobimar Oy
Current assignee: Mobimar Oy
Priority date: 2011-03-14
Filing date: 2012-03-13
Publication date: 2012-09-19
Anticipated expiration: 2032-03-13
Also published as: FI20115257A0; EP2500256B1

Abstract

The invention relates to a mooring device (100) for mooring a vessel (300) to a wind power plant (200), which mooring device (100) comprises a first (130) and a second (130') gripping means for gripping impact shield pipes (210, 210') of the wind power plant (200), which gripping means (130, 130') comprises a frame part (131, 131'), a first gripping arm (132, 132') and a second gripping arm (133, 133'), which gripping arms (132, 132', 133, 133') are attached in a turnable manner to the frame part (131, 131') and which gripping arms (132, 132', 133, 133') can be turned against the impact shield pipe (210, 210') so that the impact shield pipe (210, 210') is pressed between the first (132, 132') and the second (133, 133') gripping arm. The gripping means (130, 130') comprises at least one roller means (136, 136'), which can be placed against the impact shield pipe (210, 210'). The invention also relates to a method for mooring a vessel (300) to a wind power plant (200).

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a mooring device for a vessel and a method for mooring a vessel to a wind power plant according to the preambles of the independent claims presented below.

BACKGROUND OF THE INVENTION

Electric energy is produced both by using renewable and non-renewable natural resources. With the Kyoto protocol approved in 1997, the interest in limiting greenhouse emissions and thus controlling climate change has increased. Thus the share of electricity produced with renewable natural resources out of the total electricity production has grown during the last few years. Especially the utilisation of wind power has increased significantly.
Wind power plants are usually placed in groups of a few units in coast and sea areas and in elevated and open inland areas. The power of a single wind power plant is typically 1-3 MW and the height can even be over 100 m. For the operating efficiency of the wind power plant to be sufficient, the mean wind speed must be at least 6 m/s at the location of the wind power plant.
Even though wind power plants are generally considered to be operationally reliable, it is clear that wind power plants need to be serviced regularly in order to ensure a flawless operation. Especially the service of a wind power plant at sea is however challenging, because the transition of service personnel and the transfer of the equipment they need between the vessel and the wind power plant is difficult, especially during rough seas.
Typically the transition of people and transfer of equipment is carried out so that the prow of the service vessel is driven against impact shields attached to the body of the wind power plant and the vessel is kept moored to the impact shields with the aid of control devices of the vessel and a propulsion force obtained with a propulsion device. A problem with the method is that keeping the vessel moored to the impact shields is difficult. Additionally, because the vessel moves along with the waves in the height direction, the transition of personnel from the vessel to the wind power plant and back is difficult. In rough seas the transition of the personnel may even be life-threatening. Because a propulsion device is used in the method for keeping the vessel moored to the wind power plant, the method is only applicable for short-term mooring. Rope or another corresponding mooring means may be used for long-term mooring. Mooring of the rope to the wind power plant and detaching thereof from the wind power plant is however difficult and dangerous, especially in rough seas.
The vessel may be moored to the wind power plant also so that the prow of the vessel is driven against the impact shields and the impact shields are gripped with a gripping means suitable for the purpose. The impact shields are gripped for a sufficient time, whereafter the gripping means let go of the impact shields. A problem is that the forces generated by the waves may grow to be so great that the grip of the gripping means detaches prematurely. The problem is especially highlighted in situations, where the mooring occurs in strong waves or where the conditions change significantly during the time when the vessel is moored to the wind power plant.

OBJECTS OF THE INVENTION

It is an object of the present invention to reduce or even completely eliminate the above-mentioned problems and flaws, which appear in the prior art.
It is an object of the present invention to provide a mooring device and a method, with the aid of which a vessel can easily be moored to a wind power plant. It is also an object of the invention to provide a mooring device and a method, with which the movements of the vessel moored to a wind power plant can be kept small even in rough seas.
It is an object of the invention to provide a mooring device, which may be used to moor to a wind power plant also in rough seas and stay moored to the wind power plant, even if the conditions would change significantly during the mooring. It is an object of the invention to provide a method, with which the forces directed at the vessel may be kept small also in rough and varying seas.
It is also an object of the present invention to provide a mooring device, which is applicable both for short-term and long-term mooring.
The above-mentioned disadvantages can be reduced or even completely eliminated, and the above-mentioned objects are attained with the present invention, which is characterised in what is defined in the characterising parts of the independent claims presented further below.
Some preferred embodiments according to the invention are disclosed in the dependent claims presented further below.

DESCRIPTION OF THE INVENTION

A typical mooring device according to the invention for mooring a vessel to a wind power plant comprises a first and a second gripping means for gripping impact shield pipes of the wind power plant, which gripping means comprises a frame part and a first and a second gripping arm. The gripping arms of the first and second gripping means are attached in a turnable manner to the frame part, and the gripping arms can be turned against the impact shield pipe so that the impact shield pipe is pressed between the first and second gripping arm. A typical mooring device according to the invention is characterised in that the gripping means comprises at least one roller means, which can be placed against the impact shield pipe.
The gripping of the gripping means of the mooring device according to the invention takes place in two steps. In the first step the gripping arms are turned around the impact shield pipe so that the gripping means is in contact with the impact shield pipe via the roller means, whereby the gripping means can move (roll) in the direction of the longitudinal axis of the impact shield pipe. The gripping arms are turned around the impact shield pipe so that the gripping means cannot substantially or at all move in other directions. Preferably in this first step the gripping means is in contact with the impact shield pipe only via the roller means. In the second step the gripping arms of the gripping means are turned against the impact shield pipe so that the impact shield pipe is pressed between the gripping arms, whereby the gripping means is locked onto the impact shield pipe. The impact shield pipe is then preferably also pressed against the frame part of the gripping means. Because the gripping means is in the second step locked onto the impact shield pipe, the gripping means and impact shield pipe are immobile in relation to each other.
The gripping means comprises at least one roller means, which is arranged to be placed against the impact shield pipe. The roller means are attached to the gripping means so that when the first and second gripping arm of the gripping means is turned toward the impact shield pipe, the roller means come into contact with the impact shield pipe before the impact shield pipe is pressed between the gripping arms. The roller means are preferably attached to the gripping means with a flexible mechanism, due to which the roller means are flexible, and thus do not break, when the gripping arms are pressed against the impact shield pipe. The function of the flexible mechanism may for example be such that it becomes flexible only when the pressing force of the gripping arms exceeds a set limit value. The roller means itself may also be flexible.
The roller means may comprise one or more rollers. The roller means may for example comprise two rollers, which are connected to each other with an axle. The roller means is preferably attached to the gripping means so that when in the above-described first step the impact shield pipe is gripped, the rotation direction of the rollers of the roller means corresponds to the direction of the longitudinal axis of the impact shield pipe. The roller means is preferably attached to the frame part or the gripping arm of the gripping means, for example to the end of the gripping arm.
The mooring device according to the invention makes possible the mooring of a vessel, such as for example a boat or a ship, to a wind power plant at sea. The mooring is achieved with gripping means, with which the impact shield pipes of the wind power plant are gripped. Preferably the gripping means are used to grip two vertical impact shield pipes, which are situated at a distance from each other. The pressing force of the gripping means is preferably dimensioned so that the grip of the gripping means holds even in rough seas. The mooring device according to the invention is also applicable for mooring to impact shield pipes of other structures at sea, such as oil rigs and production platforms.
In this text a wind power plant means a device, with which the motion energy of the wind, i.e. the flowing air, is via rotating blades transformed into rotation energy of a turbine axis. The axis further rotates a generator, which produces electricity. The wind power plant typically further comprises a transmission, with the aid of which the rotating motion is adapted to suit the generator, and a mast, to the top end of which the mechanism of the wind power plant is installed.
The impact shield pipe of the wind power plant means a structure attached at the bottom end of the mast of the wind power plant, near the sea surface, the purpose of which structure is to prevent the vessel from hitting the mast of the wind power plant and thereto attached other structures, such as ladders, and to thereby protect the wind power plant from damage. Traditionally the prow of the vessel is driven against the impact shield pipes of the wind power plant and the vessel is kept moored to the impact shield pipes with the aid of the propulsion force achieved with the propulsion device of the vessel. Typically the impact shield pipes are in the mast direction and the distance between them is 1-3 m and their diameter is 200-350 mm. The wind power plant usually has at least two impact shield pipes.
An advantage of the mooring device according to the invention is that the vessel can easily be moored to the impact shield pipes at a suitable height. When the mooring device has been used to grip so that the mooring device can move in the direction of the longitudinal axis of the impact shield pipes, the mooring device is allowed to move along the impact shield pipes to a height, where the forces directed at the vessel and generated by the waves are as small as possible. When the mooring device has moved to the desired height, the gripping means are locked onto the impact shield pipes. An advantage of the mooring device according to the invention is also that the mooring point can easily be changed, if the conditions in the sea area change. An advantage of the invention is further that the mooring device is suitable for use even in a significant wave height of three meters.
According to a preferred embodiment of the invention the gripping means comprises at least three roller means and at least one roller means is attached to the frame part, the first gripping arm and the second gripping arm. When there are at least three roller means, the gripping means may freely move (roll) in a stable manner in the direction of the longitudinal axis of the impact shield pipe.
According to an embodiment of the invention the gripping means comprises a first hydraulic cylinder for turning the first gripping arm, which first hydraulic cylinder is attached by its first end to the frame part and by its second end to the first gripping arm, and a second hydraulic cylinder for turning the second gripping arm, which second hydraulic cylinder is attached by its first end to the frame part and by its second end to the second gripping arm.
The gripping arms are attached to the frame part so that they form a grab, which can be used to grip the impact shield pipe. In other words the gripping arms function as jaws, between which the impact shield pipe is pressed. The gripping arms are preferably arranged to be moveable, so that they move in the same plane.
According to an embodiment of the invention the mooring device comprises a joint arranged between the first and the second gripping means, via which joint the mooring device can be attached to the vessel. A vessel moored to a wind power plant, to which vessel the mooring device according to the invention is arranged via a joint, can move only so that it turns around a pivot defined by the joint connecting the vessel and the mooring device.
The joint is preferably of a three axis type. The joint is typically formed of two parts, of which the first joint part attaches to the mooring device and the second joint part to the vessel. The joint may for example be a ball joint, the ball-shaped joint surface of which allows movement directed in all spatial directions. An advantage of pivoting is that forces directed to the gripping means via the vessel are significantly decreased compared to a situation, where the mooring device is attached to the vessel in an immobile manner. The movements of a vessel moored to a wind power plant can be kept small even in rough seas, because the vessel can only turn around one pivot. Therefore the transition of people to the vessel and from the vessel is safe.
According to a preferred embodiment of the invention the mooring device comprises a flexible member, which is connected to the joint. The purpose of the flexible member is to reduce forces directed at the vessel and the mooring device, when the vessel is moored to a wind power plant. The flexible member functions as a damper in the situation where the gripping means grip the impact shield pipes. The flexibility of the flexible member is 50-400 mm, preferably 100-200 mm.
According to an embodiment of the invention the gripping means are arranged in the ends of the mooring device. The mooring device may also comprise several gripping means, for example three, four, five or six gripping means.
The distance between the gripping means is typically essentially the same as the distance between the impact shield pipes, whereby more than one impact shield pipe can be held on to at the same time. The distance between the gripping means can be for example in the range of 1-2 m or 2-3 m. The distance between the gripping means can also be adjustable, whereby said distance is adjustable to the distance between the impact shield pipes of different wind power plants.
According to an embodiment of the invention the mooring device comprises at least one third hydraulic cylinder for adjusting the position between the mooring device and the vessel, the second end of which hydraulic cylinder can be attached to the vessel. Typically both ends of the hydraulic cylinder are attached in a pivoted manner. A hydraulic cylinder is preferably arranged in both ends of the mooring device, in connection with the gripping means. There may also be more than two, for example three, four, five or six hydraulic cylinders. In addition to hydraulic cylinders, the propulsion device and/or control devices of the vessel may also be used for adjusting the position between the mooring device and the vessel.
A typical vessel according to the invention comprises a mooring device for mooring the vessel to a wind power plant, which mooring device comprises a first and a second gripping means for gripping impact shield pipes of the wind power plant, which gripping means comprises a frame part and a first and a second gripping arm. The gripping arms of the first and second gripping means are attached in a turnable manner to the frame part, and the gripping arms can be turned against the impact shield pipe so that the impact shield pipe is pressed between the first and second gripping arm. The gripping means additionally comprises at least one roller means, which can be placed against the impact shield pipe.
According to a preferred embodiment of the invention the mooring device is attached to the prow of the vessel. When the mooring device is situated in the prow of the vessel, the vessel can be driven straight toward the wind power plant, so that the gripping means of the mooring device hit the impact shield pipes of the wind power plant. The vessel may for example be a trimaran, which comprises a middle hull and side hulls on both sides of it.
The invention further relates to a method for mooring a vessel to a wind power plant, in which method the vessel is driven close to the wind power plant. The method according to the invention is characterised in that the first and second gripping means are used to grip the impact shield pipes of the wind power plant so that the gripping means are in contact with the impact shield pipes via roller means, whereby the mooring device can move in the direction of the longitudinal axis of the impact shield pipes. Thereafter the gripping arms of the first and second gripping means are turned against the impact shield pipes so that the impact shield pipe is pressed between the first and second gripping arm.
In the method according to the invention the vessel is driven into connection with the wind power plant so that the gripping means can grip the impact shield pipes of the wind power plant. The mooring point is striven to select so that the forces directed at the vessel and generated by the waves are as small as possible. Mostly the gripping means cannot immediately be locked onto the impact shield pipes, but the gripping means are allowed to move (roll) along the impact shield pipes to a suitable point and only then the gripping means are locked onto them. It has through testing been discovered that it is advantageous to moor the vessel above the mean water level, whereby the buoyancy of the hull of the vessel on average has a smaller impact.
According to a preferred embodiment of the invention the gripping arms of the first and second gripping means are turned away from the impact shield pipes to such an extent that the mooring device can move in the direction of the longitudinal axis of the impact shield pipes, whereafter the gripping arms of the first and second gripping means are again turned against the impact shield pipes, so that the impact shield pipe is pressed between the first and second gripping arm.
It may be necessary to change the mooring point for example if the conditions change significantly. If the mooring to the wind power plant has originally been done in calm weather, the mooring point must probably be changed as the waves grow.
The need for changing the mooring point may be evaluated by measuring the magnitude of the forces directed at the mooring device. The mooring device may comprise one or more force sensors, data collecting means for collecting measurement data obtainable from the force sensor and data processing means for processing the collected measurement data. The safety of the mooring is evaluated based on the forces directed at the mooring device. The vessel may for example comprise a system, which gives an alarm, when the forces directed at the mooring device exceed a certain limit.
The embodiments and advantages mentioned in this text relate, where applicable, to each of the mooring device, vessel as well as method according to the invention, even if this is not always specifically mentioned.

BRIEF DESCRIPTION OF THE DRAWING

In the following the invention will be described in more detail with reference to the embodiments presented as examples and the enclosed figures, in which

Figure 1: shows from above a situation, where a mooring device according to an embodiment of the invention has been used to grip impact shield pipes of a wind power plant, so that the mooring device may move along the impact shield pipes,
Figure 2: shows from above a situation, where a mooring device according to an embodiment of the invention has been used to grip impact shield pipes of a wind power plant, so that the mooring device is locked onto the impact shield pipes, and
Figure 3: shows the situation according to Figure 2 seen from the side.

DETAILED DESCRIPTION OF THE DRAWING

Figure 1 shows from above a situation, where a mooring device 100 according to an embodiment of the invention has been used to grip impact shield pipes 210, 210' of a wind power plant 200, so that the mooring device 100 may move in the direction of the longitudinal axis of the impact shield pipes 210, 210'.
The mooring device 100 is attached to the prow of the vessel 300 via a joint 110. The joint 110 is of a three axis type and thus allows the vessel 300 to move freely in relation to the pivot point. A flexible member 120 is connected to the joint 110, the purpose of which flexible member is to reduce forces directed at the vessel 300 and mooring device 100, when the vessel 300 is moored to the wind power plant 200.
The mooring device 100 comprises two gripping means 130, 130', the distance between which corresponds to the distance between the impact shield pipes 210, 210' of the wind power plant 200. Both gripping means 130, 130' comprise a frame part 131, 131' and a first gripping arm 132, 132' and a second gripping arm 133, 133', which gripping arms 132, 132', 133, 133' are attached to the frame parts 131, 131' in a turnable manner. The gripping arms 132, 132', 133, 133' are turned with the aid of hydraulic cylinders 134, 134', 135, 135', the first end of which hydraulic cylinders 134, 134', 135, 135' is attached to the frame part 131, 131' and the second end to the gripping arm 132, 132', 133, 133'. The gripping means 130, 130' additionally comprise roller means 136, 136' attached to the frame parts 131, 131', the first gripping arms 132, 132' and the second gripping arms 133, 133'.
The position between the mooring device 100 and the vessel 300 is adjusted with the aid of hydraulic cylinders 140, 140'. The hydraulic cylinder 140 is attached between the first gripping means 130 and the vessel 300. The hydraulic cylinder 140' is on the other hand attached between the second gripping means 130' and the vessel 300. In addition to hydraulic cylinders 140, 140', the position between the mooring device 100 and the vessel 300 can also be adjusted with the vessel's 300 own propulsion device and/or control devices (not shown in Figures 1-3).
In the situation according to Figure 1 the gripping arms 132, 132', 133, 133' of the gripping means 130, 130' are turned around the impact shield pipes 210, 210', so that the gripping means 130, 130' is in contact with the impact shield pipe 210, 210' only via the roller means 136, 136'. Thus the gripping means 130, 130' can move (roll) in the direction of the longitudinal axis of the impact shield pipe 210, 210'. Because the roller means 136, 136' are arranged evenly on the circumference of the impact shield pipe 210, 210', the mooring device 100 rolls steadily in the direction of the longitudinal axis of the impact shield pipes 210, 210'.
The situation shown in Figure 1 is most easily reached so that only one impact shield pipe 210 is gripped at first. Thereafter the mooring device 100 is turned so that also the second impact shield pipe 210' can be gripped.
Figure 2 shows from above a situation, where a mooring device 100 according to an embodiment of the invention has been used to grip impact shield pipes 210, 210' of a wind power plant 200, so that the mooring device 100 is locked onto the impact shield pipes 210, 210'. Figure 3 shows the situation according to Figure 2 seen from the side.
A difference to the situation shown in Figure 1 is that the gripping arms 132, 132', 133, 133' of the gripping means 130, 130' are turned against the impact shield pipes 210, 210'. The gripping means 130, 130' are thus locked onto the impact shield pipes 210, 210', whereby also movement in the direction of the longitudinal axis of the impact shield pipes 210, 210' is prevented. The impact shield pipes 210, 210' are pressed between the frame parts 131, 131' and the gripping arms 132, 132', 133, 133'.
The roller means 136, 136' are attached to the gripping means 130, 130' with a flexible mechanism, due to which the roller means 136, 136' are flexible, and thus do not break, when the gripping arms 132, 132', 133, 133' are pressed against the impact shield pipes 210, 210'.
The mooring point is selected so that the forces directed at the vessel 300 and generated by the waves are as small as possible. If the conditions at sea change significantly, the grip of the gripping means 130, 130' may be loosened to such an extent that the mooring device 100 can roll in the direction of the longitudinal axis of the impact shield pipes 210, 210'. When the mooring device 100 is at a suitable height, the gripping means 130, 130' again lock onto the impact shield pipes 210, 210'.
It is obvious to a person skilled in the art that the invention is not limited merely to the above-described examples, but the invention may vary within the scope of the claims presented below. The dependent claims present some possible embodiments of the invention, and they are as such not to be considered to restrict the scope of protection of the invention.

Claims

A mooring device for mooring a vessel to a wind power plant, which mooring device comprises:
- a first and a second gripping means for gripping impact shield pipes of the wind power plant, which gripping means comprises a frame part, a first gripping arm and a second gripping arm, which gripping arms are attached in a turnable manner to the frame part and which gripping arms are turnable against the impact shield pipe so that the impact shield pipe is pressed between the first and second gripping arm;
characterised in that the gripping means comprises at least one roller means, which can be placed against the impact shield pipe.
The mooring device according to claim 1, characterised in that the roller means is attached to the frame part.
The mooring device according to claim 1, characterised in that the roller means is attached to the gripping arm.
The mooring device according to claim 1, characterised in that the gripping means comprises at least three roller means and that at least one roller means is attached to the frame part, the first gripping arm and the second gripping arm.
The mooring device according to claim 3 or 4, characterised in that the roller means is attached to the end of the gripping arm.
The mooring device according to any of the preceding claims, characterised in that the gripping means comprises a first hydraulic cylinder for turning the first gripping arm, which first hydraulic cylinder is attached by its first end to the frame part and by its second end to the first gripping arm, and a second hydraulic cylinder for turning the second gripping arm, which second hydraulic cylinder is attached by its first end to the frame part and by its second end to the second gripping arm.
The mooring device according to any of the preceding claims, characterised in that the mooring device comprises a joint arranged between the first and second gripping means, by means of which joint the mooring device can be attached to the vessel.
The mooring device according to claim 7, characterised in that the mooring device comprises a flexible member, which is connected to the joint.
The mooring device according to any of the preceding claims, characterised in that the gripping means are arranged in the ends of the mooring device.
The mooring device according to any of the preceding claims, characterised in that the mooring device comprises at least one third hydraulic cylinder for adjusting the position between the mooring device and the vessel, the second end of which hydraulic cylinder can be attached to the vessel.
A vessel, characterised in that it comprises a mooring device according to claim 1.
The vessel according to claim 11, characterised in that the mooring device is attached to the prow of the vessel.
A method for mooring a vessel, which comprises a mooring device according to claim 1, to a wind power plant, which method comprises:
- driving a vessel close to a wind power plant;
characterised in that the method comprises:
- gripping with the first and second gripping means the impact shield pipes of the wind power plant so that the gripping means are in contact with the impact shield pipes via roller means, whereby the mooring device can move in the direction of the longitudinal axis of the impact shield pipes, and

- turning the gripping arms of the first and second gripping means against the impact shield pipes so that the impact shield pipe is pressed between the first and second gripping arm.
The method according to claim 13, characterised in that the method comprises:
- turning the gripping arms of the first and second gripping means away from the impact shield pipes to such an extent that the mooring device can move in the direction of the longitudinal axis of the impact shield pipes, and

- turning the gripping arms of the first and second gripping means against the impact shield pipes so that the impact shield pipe is pressed between the first and second gripping arm.