Arrangement in a loading/unloading buoy for use in shallow water

Details Arrangement in a loading/unloading buoy for use in shallow water Arrangement in a loading/unloading buoy for use in shallow water

1997-07-14

1998-10-13

Basinger, Sherman

Buoys, rafts, and aquatic devices

Buoy

For mooring a vessel

114230, B63B 2202

Patent

active

058204296

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to an arrangement in a loading/-unloading buoy for use in shallow waters, wherein the buoy is arranged for introduction and releasable securement in a downwardly open receiving space in a floating vessel, the buoy comprising a centre member arranged for anchoring to the sea bed and having a passage for transfer of flowable medium from or to a transfer line coupled to the underside of the centre member, and an outer member rotatably mounted on the centre member to allow turning of the vessel about the centre member when the outer member is secured in the receiving space.
A loading/unloading buoy of the above-mentioned type e.g. is known from Norwegian laying-open print No. 175 421. This known buoy especially is intended for offshore loading or unloading of hydrocarbons (oil and gas). The outer member of the buoy constitutes a buoyancy member, and when the buoy is not in use, the buoy floats submerged at a chosen distance beneath the sea level, the buoyancy of the buoy corresponding to the weight of the anchoring system of the buoy. In use, the buoy is hoisted up by means of a pick-line attached to the buoy, and the outer member of the buoy is secured in a submerged receiving space at the bottom of the topical vessel, for instance a so-called shuttle tanker. The buoy structure allows the vessel, during loading/unloading operations, to turn about the bottom-anchored centre member of the buoy, under the influence of wind, waves and water currents. Thus, the buoy constitutes a submerged rotating body or turret, and the technique of buoy loading with the use of a buoy of this special type today therefore goes under the designation STL technique (STL=Submerged Turret Loading). This technique has turned out to have very substantial advantages in practice, as both connection and disconnection between vessel and buoy can be carried out in a simple and quick manner, even in bad weather with relatively high waves. Further, the buoy can remain connected to the vessel in all weathers, a quick disconnection being able to be carried out if a weather limitation should be exceeded.
In practice it is often of interest to carry out loading and unloading of hydrocarbons in shallow waters, for example close to an oil refinery. Also in such situations it would be desirable to be able to use the STL technique, partly because of the practical advantages mentioned above, for example in regions having relatively large tide differences and/or strong water currents, and partly for economical reasons, for example in order to be able to save larger investments in connection with the building of quay facilities or the like. The need for such a utilization also exists because of the fact that today ships are built wherein this is the only loading/unloading system which is used when the ship is not alongside a quay.


SUMMARY OF THE INVENTION

Thus, the object of the invention is to further develop a buoy of the mentioned type, so that it is suitable for use in shallow waters.
According to the invention the above-mentioned object is achieved in that the buoy is provided with a bottom support structure which is connected to the centre member of the buoy and arranged for support of the buoy on the sea bed when it is not in use, a number of mooring lines being connected to the first member of the buoy and extending outwards from the buoy a substantial distance along the sea bed and having an inherent elasticity allowing raising of the buoy from the sea bed.
With the expression "shallow waters" in this context is meant places at which the depth normally may be in the range of 25-60 meters. The mooring line then advantageously may have a length in the range of 0.5-2 km, the inherent elasticity of the anchor line system then being utilized. The mooring lines then may consist of wires or common anchor chain, the chain links over the long line length then giving the necessary elasticity which is required to allow raising of the buoy from the bottom up to the topical vessel. Alternatively, there ma

REFERENCES:
patent: 3236266 (1966-02-01), Bily
patent: 3236267 (1966-02-01), Bily
patent: 3694837 (1972-10-01), Von Norring
patent: 3999498 (1976-12-01), Flory
patent: 5431589 (1995-07-01), Corona

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