Field of the Invention
The present invention relates to a method and a system for handling components, preferably wind turbine components, during transferring of the components from a vessel,
preferably a floating barge, being situated on a sea surface and influenced by wave
10 movements to a fixed structure, wherein the fixed structure preferably is a jack-up ship
or the like structure fixed to a seabed or is a second vessel, preferably a floating installation vessel, wherein a crane comprising a bearing wire is provided at the fixed structure and which crane is arranged for effecting the transferring of the components.
Background of the Invention
15 An increased need of quick and safe transfer of component for offshore wind turbines
from a transport barge to jack-up ship is experienced. Especially there is a need to optimize the use of costly installation vessels like jack-up ships.
When transferring component from one vessel to another vessel or to a fixed structure
20 it is known to use heave compensation.
In the off shore industry heave compensation is known. Both passive heave compensation (PHC) and active heave compensation (AHC) are known.
25 Passive heave compensation is a technique used to reduce the influence of waves upon
lifting and drilling operations. A simple passive heave compensator (PHC) is a soft
spring which utilizes spring isolation to reduce transmissibility to less than 1. PHC differs from Active heave compensation (AHC) by not consuming external power.
The main principle in PHC is to store the energy from the external forces (waves) in30 fluencing the system and dissipate them or reapply them later. Shock absorbers or drill
string compensators are simple forms of PHC, so simple that they are normally named
3
heave compensators, while "passive" is used about more sophisticated hydraulic or mechanical systems.
A typical PHC device consists of a hydraulic cylinder and a gas accumulator. When the
piston rod extends it will reduce the total gas volume and hence compress the gas that
5 in turn increases the pressure acting upon the piston. The compensation ration is low to
ensure low stiffness. A well designed PHC device can achieve efficiencies above 80
percent.

WE CLAIM:
1. Method for handling components (44), preferably wind turbine components
(20,21,22,44), during transferring of the components from a vessel (10), preferably a
floating barge, being situated on a sea surface (16) and influenced by wave movements
5 to a fixed structure (11), wherein the fixed structure (11) preferably is a jack-up ship or
the like structure fixed to a seabed or is a second vessel, preferably a floating installation vessel, wherein a crane (12) comprising a bearing wire (13) is provided at the fixed
structure (11) and which crane (12) is arranged for effecting the transferring of the components (20.21.22,44), characterised in that the method comprising the step of:
10 A- providing a heave compensator (1) being arranged with connection means (7,9) for
connection between the bearing wire (13) and the component (20,21,22,44), wherein
said heave compensator (1) comprises at least two hydraulic piston-cylinder units (2)
and at least one accumulator (8,41) for compressed air, which accumulators (8,41) are
connected with the piston-cylinder units (2),
15 B-I providing at least one active clamp (46) being arranged with connection means for
connection between the vessel (10) and the component (20,21,22,44), wherein said active clamp (46) is arranged for being controlled by a controller (25) being able to release
the clamp (46) and thereby free the component (44) from its connection to the vessel
(10),,
20 C- providing means (26) for monitoring wave movements,
D- arranging the vessel (10) on site of the fixed structure (11),
E- connecting the heave compensator (1) to the bearing wire (13),
F- connecting the active clamps (46) to the vessel (10) and the component (20,21,22,44)
to be transferred, in the situation where step B-I is used,
25 G- pre-setting the heave compensator (1) for the load of the component (20,21,22,44)
to be transferred, e.g. the weight of the load + 10%,
H- bringing the heave compensator (1) in position for attachment to the component
(20,21,22,44),
I- connecting the heave compensator (1) to the component (20,21,22,44) to be trans30 ferred and tightening the bearing wire (13) to a pull where the heave compensator (1) is
operated in a middle area where a constant over-pull is established in the component
(20,21,22,44) to be transferred,
J- monitoring the wave movement and sending information of the wave movement to
the controller (25),
23
K- calculating in the controller (25) the wave movement to determine at least when
crests (17) are expected at the vessel (10),
L- releasing the active clamp (46), in the situation where step B-I is used, when the
vessel (10) is near a wave crest (17), which releasing is controlled by a control signal
5 from the controller (25) being submitted as a result of information from the monitoring
of the wave movement,
M- hoisting the component (20,21,22,44) from the vessel (10) and transferring it to the
fixed structure (11),
N- detaching the component (20,21,22,44) from the heave compensator (1),
10 O- repeating the steps E to N until all necessary components (20,21,22,44) are unloaded
from the vessel (10),
P- removing the vessel (10) from the site of the fixed structure (11), and
Q- arranging a new vessel (10) on site of the fixed structure (11) if more components
(44) are needed and repeating steps E to P.
15
2. Method according to claim 1, wherein Step A includes providing a heave compensator (1) which is a passive heave compensator.
3. Method according to claim 2, wherein Step A includes providing a heave compensa20 tor (1) comprising at least two accumulators (8,41) for compressed air.
4. Method according to claim 3, wherein Step A includes providing the at least two
hydraulic piston-cylinder units (2) with same or different lifting capacities.
25 5. Method according to claim 3, wherein Step A includes combining a selected number
of the hydraulic piston-cylinder units (2) by connecting these by opening/closing hydraulic valves arranged in pipe connections between the hydraulic piston-cylinder units
(2) and activating the selected number of hydraulic piston-cylinder units (2) in order to
obtain a desired lifting capacity for the load of the component (20,21,22,44) to be trans30 ferred.