Buoys – rafts – and aquatic devices – Buoy – For mooring a vessel
Patent
1994-08-08
1995-11-21
Swinehart, Edwin L.
Buoys, rafts, and aquatic devices
Buoy
For mooring a vessel
114230, B63B 2202
Patent
active
054681669
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PICT/N092/00058, filed Mar. 30, 1992.
The invention relates to a system for rotatable mounting of a floating vessel to a submerged loading/unloading buoy which is anchored to the sea bed, the buoy being of the type which is adapted to be introduced into and fastened in a releasable manner in a submerged downwardly open receiving space in the vessel, the buoy during operation being connected to at least one transfer line and forming a transfer connection between this line and a tube system on the vessel.
There are previously known different types of loading/unloading systems for the transfer of hydrocarbons by means of a submerged buoy which, during operation, is received and secured in a submerged receiving space at the underside of a vessel. As examples of prior art, reference can be made to NO patent specification No. 160 914 and NO patent specification No. 167 960 (corresponds to U.S. Pat. No. 4,604,961).
In such buoy loading systems the underwater buoy is anchored to the sea bed, and there will then have to be provided a means making it possible for the vessel, during the influence of wind, current and waves, to turn about the anchored buoy. For this purpose, in the known system according to NO 167 906, there is provided a rotating body (turret) which is rotatably mounted in the receiving space in the hull of the vessel. Because of the fact that the rotating body is mounted to the hull, there arise large frictional forces which are to be overcome by torques from the buoy. These torques are relatively large due to the large outer diameter of the rotating body, and this results in correspondingly large loads. Further, it may result in uncontrolled rotation of the system because of large inertial forces, so that it becomes necessary to use a braking system for retaining the rotating body. In case of desired rotation the braking system is then released, and the rotating body is rotated in a controlled manner by means of active drive.
Further, the known system has a small ability to absorb moments caused by the horizontal mooring forces, something which results in a substantial risk for jamming actions in the mounting arrangement.
In practice, there may also occur large load forces at the place where the transfer line of the buoy enters into the buoy at the underside thereof. At this place there may arise large bending moments and torsional forces, and correspondingly large stresses on the transfer line, partly because of the pitching and rolling of the vessel under the influence of wind and waves, and partly because of the turning of the vessel and the occurring frictional forces between the rotating body and the hull of the vessel.
Thus, it is a general object of the invention to provide a system of the type in question which eliminates the above-mentioned drawbacks.
A more particular object of the invention is to provide a system enabling the buoy to be connected to the tube system of the vessel in a quick and safe manner, the connecting arrangement being able to absorb relatively large tolerances.
A further object of the invention is to provide a system making it possible to eliminate clamping moments between the buoy and the transfer line at the underside of the buoy.
The above-mentioned objects are achieved with a system of the introductorily stated type which, according to the invention, is characterized in that the buoy comprises an outer member which is arranged to be rigidly fastened in the receiving space, and a central inner member which is rotatably mounted in the outer member, so that the vessel is able to turn about the central member when the buoy is fastened in the receiving space, the upper end of the central member being connected to the tube system of the vessel through a swivel means and through at least one flexible Joint means.
In addition to the advantages originating from the achievement of the above stated objects, the system according to the invention among other things has the advantage that the rotary system is a part of the buoy itself, so that an e
REFERENCES:
patent: 4100752 (1978-07-01), Tucker
patent: 4490121 (1984-12-01), Coopens et al.
patent: 4604961 (1986-08-01), Ortloff et al.
patent: 4892495 (1990-01-01), Svensen
Breivik Kare
Smedal Arne
Syvertsen Kare
Den Norske Stats Oleselskap A.S.
Gealow Jon Carl
Swinehart Edwin L.
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