Ships – Floating platform
Reexamination Certificate
1999-02-08
2001-07-17
Avila, Stephen (Department: 3617)
Ships
Floating platform
C114S265000
Reexamination Certificate
active
06260502
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to a semi-submersible vessel used in connection with offshore operations, services and resource exploration. More particularly, this invention relates to (1) a hybrid of a column stabilized semi-submersible vessel which expands the useful operations and life thereof and (2) improved methods of performing offshore operations, services and resource exploration therewith.
Increased energy demands and decreased energy resources have created a need to explore and produce resources from deeper offshore areas. The demands of deep water exploration and installation present many technical problems for vessel designers. Existing technology used in offshore operations, services and resource exploration fails to adequately address the many challenges associated with deep water.
Placement of equipment in deep waters necessitates new methods of installation, maintenance, repair and removal. For example, rapid transit speed combined with installation and removal capabilities are desired features which are inadequate in existing designs. Service and maintenance needs related to equipment placed in extreme depths, e.g., flow lines, jumpers, tie-ins and service umbilicles, presents significant issues which known technology fails to adequately address. The time frames associated with installation, maintenance, repair and removal services precludes the use of mooring systems in deep water. Thus, efficient station keeping techniques are required. In addition, improved methods for loading, unloading and provision of installation, maintenance, repair and removal services are required.
One type of vessel used in deep waters is known as a semi-submersible vessel. A semi-submersible vessel comprises a deck section which is typically supported by four or more vertical columns which rest on two or more pontoons. The pontoons and portions of the columns are submerged below the operational water line during normal operation. In order to provide adequate structural integrity, cross brace support members are typically used between the columns. Cross brace support members, while essential to the structural integrity of traditional designs for semi-submersible vessels, create undesirable characteristics. For example, cross brace support members create hydrodynamic drag and create problems related to underslung loads. In addition, cross brace support members preclude easy and efficient loading and reloading of vessels.
U.S. Pat. No. 4,436,050 illustrates a hybrid of a traditional cross braced semi-submersible vessel. In the disclosed vessel, a pair of support members run generally parallel between the pontoons. Such an alternative design fails to fully address performance and operational issues.
Canadian Patent No. 1,279,531 discloses a semi-submersible vessel without any cross bracing, but fails to disclose means which would adequately support such a structure.
Thus, a need remains for an improved semi-submersible vessel design with expanded capabilities, and alternative structural supports which do not unnecessarily interfere with advantageous operations of such vessels and methods for maximizing the efficiency and operation of the same.
SUMMARY OF INVENTION
It is therefore an object of the present invention to provide an improved semi-submersible vessel which does not require cross-bracing.
A further object of the present invention is to provide an improved column design which can be incorporated into a semi-submersible vessel.
Another object of the present inventions is to provide an improved method and apparatus for loading a semi-submersible vessel.
A further object of the present invention is to provide an improved and cassette mechanism which improves vessel capabilities.
Another object of the present invention is to provide a reel cassette mechanism with improved failure characteristics.
Yet another object of the present invention is to provide an improved method for loading underslung loads onto a semi-submersible vessel.
Thus to achieve these objects, there is provided in one embodiment of the present invention an improved design for a semi-submersible vessel which includes a deck supported by columns and a haunch means. More particularly, in one embodiment of the present invention, there is provided a vessel comprising two pairs of columns, the first pair being connected to a first pontoon and the second pair being connected to a second pontoon and haunch means which connects the first and second pair of columns to a deck.
In a preferred embodiment, the haunch means comprises a diagonal structure which flares inboard and connects the column to an upper box structure. More particularly, there is provided elliptically shaped columns which more evenly distribute forces. Further preferred, the columns comprise internal bulkheads, which preferably expand in way of the haunch and connect to the upper box structure. In a most preferred embodiment, the columns are elliptically shaped, and include two or more internal bulkheads.
In another aspect of the present invention, there is provided improved elliptical columns for use in a semi-submersible vessel. In a preferred embodiment, the columns include a flared skirt. Most preferred, the skirt flares at an angle from about thirty to about sixty degrees.
In another aspect of the present invention there is provided an improved structural design which further incorporates multiple decks as support members in a unitized structure. More particularly, there is provided a double bottom structure, which includes a first deck, a second deck and a wet deck. Preferably, the wet deck and the second deck are connected by a plurality of support members. Further preferred, the wet deck and the second deck are connected to the columns by a haunch means. The integration of structural components creates a continuous unitized structure.
In another aspect of the present invention, there is provided an improved method for loading or carrying an underslung load. More particularly, there is provided an improved method which includes the steps of placing a barge or similar load carrying vessel under a semi-submersible vessel, lowering a line or lines from said semi-submersible vessel, connecting the lowered line or lines to a load and raising the load. In a particularly preferred embodiment the method include the steps of positioning a transport vessel underneath a semi-submersible vessel, aligning product with a lifting means, raising the loaded product to the undersided of the semi-submersible vessel, and securing the product to the underside with a fastening means. A preferred method for aligning the product is by use of lasers positioning devices. A preferred lifting device is a vehicle hydraulic cylinder. A preferred fastening device is a male/female hydraulic engagement.
In another aspect of the present invention, there is provided a method for installing product comprising the steps of securing a loaded reel to the underside of a semi-submersible vessel, attached a lead line to the product of the reel, unspooling the product with the lead line, associating the product with a dead weight and lowering the dead weight to an installation site. In a preferred embodiment, two or more reels may be secured to the underside of a semi-submersible vessel, whereby either product may be continuously installed from a first and a second reel or two different products may be simultaneously installed. Preferably, the moon pool of the semi-submersible is enlarged to a size which allows for materials and other apparatus to be directly loaded from the underside of the vessel from a transport vessel or other feed source.
In yet another aspect of the present invention there is provided a reel and cassette mechanism with improved failure characteristics. More particularly, there is provided a reel which holds product and includes a horizontal surface and a cylinder, a cassette including a bottom, and an air inlet, and an air compressor. Preferably, the horizontal surface of the reel is positioned adjacent to the bottom of the cassette and the air compr
Kellogg Stanley Groedecke
Ketting Hank
Kratz Owen
Avila Stephen
Fulbright & Jaworski L.L.P.
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