Ships – Mooring device – Having ship-mounted turret
Reexamination Certificate
2000-09-06
2003-05-20
Morano, S. Joseph (Department: 3617)
Ships
Mooring device
Having ship-mounted turret
C114S293000
Reexamination Certificate
active
06564740
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of this Invention
This invention relates to chain tensioning arrangements for use during anchor leg tensioning of a turret moored vessel.
2. Description of the Prior Art
FIG. 1
shows a typical prior art permanently connected turret mooring system in a partial cross-section through the internal turret section of the vessel. Such system includes a vessel V having a well W in which a lower turret
10
is rotatably supported with respect to vessel V at deck D by means of bearings
12
. An upper turret
14
is secured to lower turret
10
. A plurality of anchor legs
16
, (formed at least partially with chains) are secured to the turret in order to substantially secure the lower turret
10
and upper turret
14
to the sea floor. The anchor legs
16
run through chain tubes
18
and via sheave
20
and winch/windlass
22
to a chain locker
24
all located on the upper turret
14
. A separate windlass
22
and sheave
20
is provided for each anchor leg. Such windlass/sheave assemblies are arranged about the upper turret
14
.
Other prior art arrangements have provided a simple winch on the deck of the vessel where the vessel must be rotated with respect to the turret and to a particular anchor chain for tensioning such a chain. Rotation of the vessel requires either a dynamic positioning system or tugboats to orient the vessel against waves, currents and wind or a hydraulic motor and bull gear arrangement for rotating the vessel with respect to the turret. In such arrangements large sheave assembles must be placed at different angular positions on the turret to align with the chain tube and the winch for different angular orientations of the winch with respect to the turret. Large diameter wire rope is required for retrieving anchor leg chains and fluid risers. The possibility of a wire rope breaking poses a great risk to personnel working on the vessel deck where the wire rope passes through several sheave assemblies.
The prior art's placement of an anchor chain winch on the vessel deck requires that a the vessel deck structure be stiffened to accept the large loads of the winch itself and the forces required to tension an anchor leg. Such stiffening requires increased costs associated with increased steel and vessel design work.
The winch on the deck of such prior art arrangements is usually placed several meters from the turret center-line in order to accommodate proper wire rope spooling. Such placement puts the winch operator at a disadvantage during anchor chain tensioning because of the equipment noise and distance between the winch operator and workmen within the turret.
3. Identification of Objects of this Invention
A primary object of this invention is to provide a chain tensioning arrangement for a turret mooring system that reduces the weight and cost of vessel structures associated with the turret mooring.
Another object of the invention is to provide a chain tensioning system which reduces installation time for tensioning an anchor chain of a turret mooring system.
Another object of the invention is to provide a winch and turret arrangement which reduces hazards to personnel during chain tensioning of a permanently connected turret mooring system;
Another object of the invention is to provide a winch and turret arrangement which reduces the number of support vessels required to tension anchor chains of the turret mooring system.
SUMMARY OF THE INVENTION
The objects identified above along with other features and advantages are incorporated in a chain tensioning system for a turret mooring system in which only a single winch is placed on the turret at its center-line and is rotatable with respect to the turret so as to angularly align it with anchor chains spread about the circumference of the turret. Anchor leg tensioning operations can be conducted without regard to vessel heading by rotating the winch with respect to the turret until it is aligned with an anchor chain that is to be tensioned. The invention can be used with external or internal turret mooring systems. A flapper style/ratcheting chain support is provided on the turret for each anchor chain so that mooring leg retrieval operations can continuously be conducted until the desired chain tension is achieved.
REFERENCES:
patent: 4305341 (1981-12-01), Stafford
patent: 4446807 (1984-05-01), Johnson et al.
patent: 5178087 (1993-01-01), O'nion et al.
patent: 5842434 (1998-12-01), Lange et al.
Drawings for 1997 Internal Turret Mooring System.
Hobdy Miles A.
Lindblade Stephen P.
Seaman David M.
Shuhatovich Michael G.
Andrews & Kurth LLP
Bush, Esq. Gary L.
FMC Technologies Inc.
Morano S. Joseph
Vasudeva Ajay
LandOfFree
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