Buoys – rafts – and aquatic devices – Buoy – For mooring a vessel
Patent
1993-10-26
1996-01-09
Swinehart, Edwin L.
Buoys, rafts, and aquatic devices
Buoy
For mooring a vessel
B63B 2202
Patent
active
054824842
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A swivel is a rotatable pipe joint typically used on production ships extracting oil and gas from submerged wells. It is mounted on a turret transferring the oil and gas from one or more risers to pipelines being connected to storage tanks, processing equipment or the like on the ship. Stacks of swivels can be assembled within a turret structure. Conventional lifting equipment can mount and demount them.
Small scale swivels are conventionally used in existing production ship installations. Many ships using these swivels are located in less turbulent waters or working in fields with fewer demands on ship availability. Because of their size, the swivels are easily handled at sea by conventional equipment, provided there is good weather.
Small scale swivels cannot, however, efficiently handle production from planned large capacity installations. Prospective swivels, with a characteristic weight of 50 to 100 tons, and correspondingly cumbersome dimensions, are being designed for these installations. Conventional equipment will not be able to quickly and efficiently replace heavy swivels at sea.
Many operators replace swivels at a shipyard, often during overhauling. The assumption is that swivel replacement is very dependent on external conditions. But onshore replacement stops production, or at least eliminates ship availability. Because of these inherent delays, some operators are now requiring production ships to carry suitable lifting equipment to replace the swivels.
The best solution for heavy swivels is onboard disassembly and replacement, sending onshore only the parts that are not reparable onboard. Further, disassembly should be performed at a distance from the turret so that production is not impeded.
SUMMARY OF THE INVENTION
This invention is concerned with how large-scale swivels can be mounted and demounted with minimum production stoppage and with minimum impediment. A very high degree of availability is required from production ships. Therefore, a swivel has to be regularly, quickly and often promptly replaceable with minimal weather-dependence. To avoid production delay, the replacement has to occur at sea. Strong and versatile equipment is needed to lift and center large-scale swivels on a turret foundation. Conventional cranes, like trolley winches, give little or no lateral support during lifting. Normal manual steering with ropes is unsatisfactory in view of the pitching and rolling at sea. Swing, especially due to the ship's rolling and pitching, must be strictly controlled or avoided due to small clearances between sensitive parts in the swivel and the turret.
An object of the present invention is therefore to provide a lifting system making swivel positioning less weather-dependent and manpower intensive. Another object of the present invention is to provide an apparatus that laterally supports a swivel during lifting and positioning. Still another object of the present invention is to provide an apparatus laterally supporting a swivel with lightweight lateral supporting frames during the entire lifting operation. A further object of the invention is to provide equipment with a capacity for replacing a swivel on a turret in one operation.
The inventive apparatus comprises a combination of three main components: on a first, operating foundation on the turret, and a second storing foundation spaced from the turret, spare swivel in connection without the second storing foundation, and accurately positioning the swivel onto one of the desired foundations.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated in the drawings, in which:
FIG. 1 is a longitudinal view of part of a ship with a swivel-equipped turret, with lifting and skid-equipped storage systems, and a downwardly extending frame providing lateral support.
FIG. 2 is a plan view showing the relationship of trolley's movement to a sled pathway.
FIG. 3 is a side view of a preferred embodiment, showing a lifting and guiding means in operation.
FIG. 3A is a close-up view taken at A--A of FIG
REFERENCES:
patent: 3812987 (1974-05-01), Watatani
patent: 4305341 (1981-12-01), Stafford
patent: 4708563 (1987-11-01), Van Den Berg et al.
patent: 4841895 (1989-06-01), Brewerton
patent: 5316509 (1994-05-01), Boatman et al.
Norsk Hydro a.s.
Swinehart Edwin L.
LandOfFree
Apparatus for offshore swivel replacement does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for offshore swivel replacement, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for offshore swivel replacement will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1299542