U.S. patent application number 10/399759 was filed with the patent office on 2004-02-12 for disconnectable buoy.
Invention is credited to Montabrun, Bernard, Perratone, Rene, Pollack, Jack.
Application Number | 20040029464 10/399759 |
Document ID | / |
Family ID | 8172170 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040029464 |
Kind Code |
A1 |
Pollack, Jack ; et
al. |
February 12, 2004 |
Disconnectable buoy
Abstract
The invention relates to floating mooring construction (1)
comprising a vessel (2) having a hull (35) with a cavity (9) for
receiving a mooring buoy (8) carrying at least one flowline (13),
and a pulling device (22, 24) connected to the mooring buoy for
pulling the buoy towards the vessel. A flexible element (27) is
comprised between a wall of the recess (9) and the buoy. The
invention is characterised in that the vessel comprises a turret
(5) around which the vessel can weathervane, the recess (9) being
provided in the lower part of the turret (5), wherein the buoy (8)
comprises near its lower end an annular groove (26) in which the
flexible element (27) is seated, the outer surface of the flexible
element including a sharp angle (.alpha.) with a center line (21)
of the buoy. The buoy is attachable to the turret by the pulling
device (22, 24) pulling the buoy into the cavity (9) and
compressing the flexible element (27) against the wall of the
cavity (9). The present invention provides a semi-permanent system,
which is able to transmit relatively large mooring forces to the
turret.
Inventors: |
Pollack, Jack; (Monaco,
MO) ; Perratone, Rene; (Menton, FR) ;
Montabrun, Bernard; (Levens, FR) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Family ID: |
8172170 |
Appl. No.: |
10/399759 |
Filed: |
September 3, 2003 |
PCT Filed: |
October 23, 2001 |
PCT NO: |
PCT/EP01/12386 |
Current U.S.
Class: |
441/4 |
Current CPC
Class: |
B63B 22/026 20130101;
B63B 22/023 20130101; B63B 21/507 20130101 |
Class at
Publication: |
441/4 |
International
Class: |
B63B 022/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2000 |
EP |
00203683.8 |
Claims
1. Floating mooring construction (1) comprising a vessel (2) having
a hull (35) and having a cavity (9) for receiving a mooring buoy
(8), the mooring buoy (8) carrying at least one flowline (13) and
anchor lines (4, 4', connected to the buoy via chain guides (10),
and a pulling device (22, 24) connected to the mooring buoy for
pulling the buoy towards the vessel, a flexible element (27) being
comprised between a wall of the recess (9) and the buoy,
characterised in that, the vessel comprises a turret (5) around
which the vessel can weathervane, the recess (9) being provided in
the lower part of the turret (5), wherein the buoy (8) or the
recess (9) comprises near its lower end the flexible element (27),
the outer surface of which includes a sharp angle (.alpha.) with a
centre line (21) of the buoy, the buoy being attachable to the
turret by the pulling device (22, 24) pulling the buoy into the
cavity (9) and compressing the flexible element (27) against the
wall of the recess (9), the lower end of the buoy being located at
or in the proximity of the lower end of the recess (9) and the
anchor lines (4, 4') being with their upper ends fixed to the buoy
(8).
2. Floating mooring constructive (1) according to claim 1, wherein
the flexible element (27) is seated in a an annular groove (26) on
the recess (9) or on the buoy (8).
3. Floating mooring construction according to any of the preceding
clams, wherein the diameter of the recess (9) and of the buoy (8)
near their lower ends is larger than the diameter of a upper part
(43) of the turret.
4. Floating mooring construction (1) according to claim 1, 2 or 3,
characterised in that, the turret wall comprises a receiving
surface (29) for engaging the flexible element (27), the receiving
surface (29) making a sharp angle with the centre line (21) of the
turret, a first radial bearing surface (32) being connected to the
receiving surface for engaging with a second radial bearing surface
(33) on the hull (35) of the vessel.
5. Floating mooring construction (1) according to claim 1, 2, 3 or
4, wherein the buoy (8) comprises at least one passage (14), the
flowline (13) extending trough the passage (14) and having a fluid
connector (15) at its end which is connectable to a fluid connector
on the vessel.
6. Floating mooring device according to claim 5, wherein the buoy
(18) or the recess (9) comprises near its upper end a seal (40)
which can sealingly close the upper perimeter of the buoy against
the wall of the recess (9) to seal off a chamber (41) around the
fluid connectors (15) which can be drained to form a dry space.
7. Floating mooring construction (1) according to any of the
preceding claims, characterised in that, the buoy (8) comprises a
ballastable buoyant body (36) located below a lower draft level
(17) of the vessel when the buoy is coupled to the vessel.
8. Floating mooring construction (1) according to any of the
preceding claims, characterised in that, the flowline (13), at
least at the position of the buoy (8), is flexible.
Description
[0001] The invention relates to a floating mooring construction
comprising a vessel having a hull and having a cavity for receiving
a mooring buoy, the mooring buoy carrying at least one flowline and
anchor lines connected to the buoy via chain guides, and a pulling
device connected to the mooring buoy for pulling the buoy towards
the vessel, a flexible element being comprised between a wall of
the recess and the buoy.
[0002] Such a mooring construction for buoy loading of hydrocarbons
at sea is known from U.S. Pat. No. 5,651,708. In the known
construction the buoy comprises an outer body which is attached to
the recess of the vessel by means of horizontally movable locking
wedges. The outer body of the buoy is at its bottom provided with a
combined fender and watertight packing which abuts the lower
circumferential portion of the recess, forming a sealing force
transmitting area between the outer body and the hull of the
vessel. The inner part of the buoy is rotatably seated in the fixed
outer body. Upon severe weather conditions or emergency situations,
the buoy can be released from the vessel by the detaching of the
pull in hawser and by attaching a float to the pull in hawser of
the buoy. The buoy may be reattached by taking in the pull hawser
by a winch on the vessel. In the known system, relatively large
forces are transferred to the bearings between the outer buoy body
and the rotatable inner part. Therefore, the buoy will need to be
released from the vessel at predetermined wave bights. This may
reduce useful operating time of the vessel after disconnecting of
the buoy.
[0003] The known mooring buoy is only suitable for the relatively
small mooring forces and is relatively small as it is intended to
be used with a light mooring system and is not suitable for deep
water. The known mooring system can only carry a limited number of
risers. The bearing system is relatively light, watertight and
hence complex and not easily accessible for repair and change out
purposes.
[0004] It is an object of the present invention to provide a
mooring system which is semi-permanent and which provides a
reliable connection between the buoy and the vessel, also during
extreme weather conditions. It is further object of the present
invention to provide a semi-permanent mooring system, which can
during specific severe weather conditions, or emergencies be
decoupled from the vessel, and relatively easily reattached.
[0005] It is a further object of the present invention to provide a
system which is able to transfer relatively large forces from the
mooring buoy to the vessel and around which the vessel can freely
weathervane.
[0006] It is again an object of the invention to provide a mooring
system which is suitable for use in deep water and which can carry
a large number of risers. The buoy should be easily accessible for
repair or change-out.
[0007] Thereto, the mooring construction according to the present
invention is characterised in that the vessel comprises a turret
around which the vessel can weathervane, the recess being provided
in the lower part of the turret, wherein the buoy or the recess
comprises near its lower end the flexible element, the outer
surface of which includes a sharp angle with a centre line of the
buoy, the buoy being attachable to the turret by the pulling device
pulling the buoy into the cavity and compressing the flexible
element against the wall of the recess, the lower end of the buoy
being located at or in the proximity of the lower end of the
recess, the anchor lines being with their upper ends fixed to the
buoy.
[0008] By providing the recess in the turret around which the
vessel can weathervane, the buoy need not be provided with
rotatable parts. Hence, larger forces can be taken up by the
buoy.
[0009] By compression of the flexible element when the buoy is
wedged into the recess by the pulling device, such as a pull in
hawser or chain, a firm connection is possible. According to the
present invention, a pretension is applied to the buoy by wedging
it into the recess such that the flexible element is deformed and
any play is removed, whereafter the buoy can be locked in place for
instance by a hydraulic locking mechanism which is known per se.
Large radial mooring forces are transmitted from the buoy to the
hull via the flexible elements.
[0010] In the mooring arrangement according to the present
invention, the anchor lines are connected directly to the buoy and
are not tensioned from the vessel itself as is the case in prior
art mooring devices. Hereby a tensioned mooring line configuration
is obtained that is able to absorb relatively large forces, using
only a single pull in hawser for the buoy.
[0011] Preferably the flexible element is seated in an annular
groove on the recess or on the buoy. By adjusting the angle of the
flexible element with respect to the vertical centre line of the
buoy, the stroke of the pulling device for wedging the buoy into
the recess can be easily adjusted and the stiffness of the
connection of the buoy to the turret can be varied.
[0012] In an embodiment of the present invention, the diameter of
the recess and of the buoy near their lower ends is larger than the
diameter of the upper part of the turret. By providing a large
diameter buoy which is substantially completely seated within the
recess, large forces can be taken up and a large number of
relatively long risers and mooring lines may be supported. By
placing the buoy substantially completely within the recess, it can
be protected during use in artic conditions against ice floes and
allows the very large radial mooring forces to be transferred
directly to the lower radial bearing of the turret at the same
level without a moment being created between the connection point
of the mooring lines and the flexible elements.
[0013] It is noted that a mooring construction is known from U.S.
Pat. No. 5,339,760, in which the mooring lines are connected to a
lower end of a mooring buoy which projects for a larger part from
the receiving recess. Near the upper part a flexible element is
provided between the mooring buoy and recess. Due to the large
distance between the connection point of the anchor lines and the
flexible elements, a moment is created on the buoy by the radial
forces and shear forces are acting on the flexible compressible
elements. Hereby the known to design is not capable of withstanding
large radial forces.
[0014] Preferably, the sharp angle of the flexible element
according to the present invention is between 1.degree. and
45.degree., more preferably between 5.degree. and 15.degree. with
respect to the vertical. By this substantially vertical orientation
of the flexible element, large radial forces can be handled without
the forces becoming problematic in the flexible element.
[0015] Preferably, the turret wall comprises a receiving surface
which is attached to a radial bearing surface, such as a slide
plate, that can be engaged with a second radial bearing surface on
the hull of the vessel. In this way forces are directly transmitted
from the turret to the vessel via the slide bearing thus reducing
deformations of the lower part of the turret.
[0016] The buoy may comprise a ballastable body located below the
lower draft level of the vessel when the buoy is coupled to the
vessel. After coupling to the vessel, the buoy can be ballasted
such that it exerts little or no upwards force and variation in
draft level of the vessel will not result in changes of the upward
force exerted by the buoy on the turret.
[0017] An embodiment of a floating mooring construction according
to the present invention will be explained in detail with reference
to the accompanying drawings in which:
[0018] FIG. 1 shows a vessel comprising a mooring construction
according to the present invention, and
[0019] FIG. 2 shows a cross-sectional view of a floating production
storage and offloading (FPSO) vessel connected to a subsea
hydrocarbon structure via the mooring construction of the present
invention.
[0020] FIG. 1 shows a mooring construction 1 according to the
present invention comprising a vessel 2, such as FPSO, which is
anchored to the seabed 3 via anchor chains or cables 4, 4'. The
chains 4, 4' are attached to mooring buoy 8 that is coupled to a
turret 5 which is rotatably supported in the hull of the vessel via
upper axial-radial bearings 6 that are connected to a stiff bearing
box construction 7. The bearing box construction 7 isolates the
deformations of the hull of the vessel from the axial-radial
bearings 6. The mooring buoy 8 is seated in a recess or cavity 9,
formed by the lower part of the turret 5. The anchor chains 4, 4'
extend through a chain hawse and tubes 10 and end at a chain
stopper 11. The flow lines 13 are connected to a subsea hydrocarbon
source on the seabed 3 and extend through passageways 14 in the
buoy 8. At the upper end, the flow line 13 comprises valves and a
fluid connector 15 for attaching to product piping on the vessel.
The fluid connector 15 is located above the lower draft level 17 of
the vessel.
[0021] Along its center line 21, the buoy 8 is connected to a pull
in hawser in the form of chain 22 that is attached to a winch 24
that may for instance exert a force on the buoy 8 of 2000 tons.
[0022] The buoy 8 is at his upper end provided with a sealing
element 40 along its perimeter, which may be an inflatable sealing
element for closing off the space between the wall of the recess 9
and the outer surface of the buoy 8. Thereby, water may be drained
from space 41 such that the fluid connectors 15 are located in a
dry area, without water ingressing into the dry area 41 from the
space between the buoy 8 and the wall of the recess 9 below the
seal 40, which during use will be filled with water.
[0023] At its lower part the buoy 8 is provided with a
circumferential groove 26 in which a flexible compression element
27 is seated. The flexible compression element 27 may for instance
be any elastomeric pad made of rubber combined with stainless steel
reinforcing plates. The flexible pad 27 makes an angle a of between
5.degree. and 15.degree. with respect to the vertical such that
upon pulling in of the buoy 8 by the pull in chain 22, the flexible
pad 27 is compressed against a receiving surface 29 extending at
substantially the same angle .alpha. to the vertical as the
flexible pad 27.
[0024] The receiving surface 29 is part of a box construction 30 on
the lower part of the turret 5 comprising a first radial bearing
surface 32 and a second radial bearing surface 33 connected to
radial bearing element 34 that is connected to the hull 35 of the
vessel. Large radial mooring forces are transmitted via the
flexible pads 27 and the slide pads 32, 33 from the relatively
large diameter buoy 8 to the hull of the vessel thus limiting
deformations of the lower part of the turret 5.
[0025] The diameter of the buoy 8 and the cavity 9 near their lower
ends may for instance be 15 m and is larger than the diameter of
the upper part 42 of the turret 5, which diameter may for instance
be 5-6 m.
[0026] The relatively large buoy 8 comprises a ballastable
compartment 36 which may after connection be flooded such that the
buoy 8 does not contribute to an upwards force on the vessel during
loading.
[0027] Upon connection of the buoy 8, the chain 22 is tensioned by
the winch 24 until the lower part of the buoy is wedged into the
recess 9 by compression of the flexible pads 27. Thereafter, a
locking mechanism comprising a hydraulic ram 37 and clamping
fingers 38 may be actuated to lock the upper buoy part in place.
The chain 22 maintains its tensioning force until the locking
mechanism is in place.
[0028] Even though the invention has been described with reference
to an internal turret 5 located within the hull 35 of the vessel,
the mooring construction can also be used in an external turret,
mounted for instance in a yoke at the bow of the vessel.
Furthermore, the compression element 27 may be placed directly on
the outer wall of the buoy 8 or on the wall of the recess 9 or at
on both walls, and may cover a larger length along said walls.
* * * * *