Source: http://www.google.com/patents/US5305703?dq=5893120
Timestamp: 2014-03-17 16:02:16
Document Index: 246486290

Matched Legal Cases: ['art 14', 'art 17', 'art 14', 'art 77', 'art 77', 'art 79']

Patent US5305703 - Vessel mooring system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA vessel with a mooring recess on the bottom of the hull moors to a submerged buoyant mooring element anchored to the ocean bottom by hoisting the mooring element from a stowed position at a depth of net neutral buoyancy of the mooring element and its anchoring system into contact with the mooring recess....http://www.google.com/patents/US5305703?utm_source=gb-gplus-sharePatent US5305703 - Vessel mooring systemAdvanced Patent SearchPublication numberUS5305703 APublication typeGrantApplication numberUS 08/019,401Publication dateApr 26, 1994Filing dateFeb 18, 1993Priority dateDec 31, 1992Fee statusPaidAlso published asCA2153055A1, CA2153055C, CN1043207C, CN1097390A, DE69322409D1, EP0677008A1, EP0677008A4, EP0677008B1, US5380229, WO1994015828A1Publication number019401, 08019401, US 5305703 A, US 5305703A, US-A-5305703, US5305703 A, US5305703AInventorsJens KorsgaardOriginal AssigneeJens KorsgaardExport CitationBiBTeX, EndNote, RefManPatent Citations (16), Referenced by (27), Classifications (10), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetVessel mooring systemUS 5305703 AAbstract A vessel with a mooring recess on the bottom of the hull moors to a submerged buoyant mooring element anchored to the ocean bottom by hoisting the mooring element from a stowed position at a depth of net neutral buoyancy of the mooring element and its anchoring system into contact with the mooring recess. The mooring operation is completed safely, quickly, and positively by rapidly withdrawing seawater into the hull through an opening in the mooring recess so as to reduce the hydrostatic pressure acting on the top of the mooring element as the element comes into contact with the hull of the vessel. The pressure reduction is sufficient to shift the mooring element and its anchoring system from a net negative to a net positive buoyancy condition at the keel depth of the vessel. The seawater may be withdrawn by a high capacity pump that is either specifically installed for this purpose or is part of a bow thruster system of a type commonly found on large vessels. Alternative, or additional, seawater suction apparatus includes an evacuated hermetic chamber having a valve opening into the mooring recess. The mooring recess may be coaxial with a vertical well in the hull, in which case water in the well may be drained into an empty hold through a valve opening into the well near the bottom of the hull. The mooring element has an upper part that makes sealing contact with the hull of the vessel and a lower part that is connected to the anchor lines. At least one bearing mounted between the parts permit the upper part to rotate relative to the lower part, so that the vessel may weathervane in response to wind, wave, and current forces.
I claim: 1. An ocean mooring system includinga vessel having a hull with an annular mooring recess in the bottom of the hull; a buoyant mooring element having an upper part that is engageable with the mooring recess in the bottom of the hull; a plurality of lines connecting the mooring element to the ocean floor, the weight of the lines relative to the buoyancy of the mooring element being such that the mooring element assumes an equilibrium position at a preselected depth below the bottom of the hull; and means for hoisting the mooring element from the preselected depth to engagement with the mooring recess in the bottom of the hull, wherein the system further comprises: means for rapidly drawing seawater into the hull through an intake opening located within the mooring recess so as to reduce the downward hydrostatic pressure acting on the upper part of the mooring element as it comes into engagement with the mooring recess. 2. An ocean mooring system according to claim 1 wherein the means for rapidly drawing seawater into the hull provides a flow rate sufficient to produce a substantial net positive buoyancy condition of the combined lines and mooring element as the mooring element engages the submerged bottom portion of the hull.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the invention is shown in FIGS. 1-5. In FIG. 1, a vessel, such as a tanker 11, is moored to a buoyant mooring element 12 that is submerged below the ocean surface 13. The mooring element 12 has an upper part 14 that is engaged with a mooring recess 15 in the bottom of the hull 16 of the vessel. A lower part 17 of the mooring element is connected by catenary anchor lines 18 to stake piles 19 driven into the ocean bottom 20. The stake piles, only two of which are shown, are typically spaced in a circular array around a wellhead 21 that is also connected, by a flexible hose or pipe 22, to the lower part of the buoyant mooring element to deliver oil or gas produced by the well to a conventional onboard piping system 23 through a fluid swivel 24 located in a vertical well 25 extending through the hull.
The Buoyant Mooring Element FIG. 4 shows, on an enlarged scale the construction details of the mooring element 12 in engagement with the mooring recess 15 in the bottom of the hull and the associated parts of the mooring system that are contained in the vessel. FIG. 5 shows, on an even more enlarged scale, the construction of the first embodiment of the mooring element. With reference to these figures, the upper part 14 of the first embodiment of the buoyant mooring element is essentially a disk-shaped hollow tank having a flat annular upper deck 26 surrounding a raised frusto-conical center section 27.
Shipboard Components of the Mooring System The mooring system of the present invention includes several novel components on board the vessel. These will now be described, with particular reference to FIG. 4, which is a side elevation view in cross section of part of the vessel 11 near the bow 51, showing the region of the mooring recess 15 with attached mooring element 12.
Operation of the Mooring System The operation of the mooring system of the invention will now be described with particular reference to FIGS. 2 and 3.
Alternative embodiments FIG. 6 shows a second embodiment of a mooring element 76 in which the upper part 77 is furnished with an exterior downward projecting skirt 78 which permits the trapping of air. This embodiment of the mooring element also is equipped with two bearings between the upper part 77 and the lower part 79: a radial bearing 80 which is capable of transmitting only forces perpendicular to the vertical axis 81 of the mooring element 76 and a thrust bearing 82 capable of transmitting only forces parallel to the axis of rotation 81. This arrangement with separate radial and thrust bearings 80 and 82 is not limited to the mooring element embodiment shown in FIG. 6 but may be substituted for the combined radial and thrust bearing 35 in the other illustrated embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a vessel partially cut away to show a mooring element engaged with a mooring recess in the hull of the vessel in a mooring system according to the
BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to the mooring of oil tankers or other vessels in unprotected waters. More particularly the invention relates to a mooring system which combines a submerged buoyant mooring element anchored to the sea bed by catenary lines and a vessel provided with hoisting apparatus for raising the mooring element into engagement with a mooring recess in the bottom of the vessel hull.
Background Art In recent years, numbers of undersea oil and gas fields have been developed in offshore areas that are subject to extreme weather conditions. Oil or gas is typically delivered from a wellhead on the sea floor to a semi-permanently moored converted tanker or to a special purpose vessel known as a floating storage and off-loading (FSO) vessel or a floating production storage and off-loading (FPSO) vessel. These vessels are designed to remain on station permanently, unless oncoming severe storm or ice floe conditions threaten damage to or loss of the vessel. In such an event, the vessel is unmoored and sails or is towed away. Upon passing of the storm or ice floe condition, the vessel returns and is again moored above the wellhead.
SUMMARY OF THE INVENTION An object of the present invention is to provide an improved mooring system of the above-described type that provides rapid and secure engagement of a buoyant mooring element with a mooring recess in the bottom of a vessel.
CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of U.S. Patent application Ser. No. 07/998,986 filed on Dec. 31, 1992, now abandoned.
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