Buoys – rafts – and aquatic devices – Buoy – For mooring a vessel
Patent
1994-08-08
1996-10-15
Avila, Stephen
Buoys, rafts, and aquatic devices
Buoy
For mooring a vessel
114230, B63B 2202
Patent
active
055649572
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a system for transferring a flowable medium to or from a floating vessel, comprising a buoyancy unit in the form of a buoy which is anchored to the sea bed by means of catenary mooring lines keeping the buoy submerged at a desired depth when it is not in use, at least one transfer line which is connected to the buoy, for the transfer of medium, a downwardly open receiving means provided on the vessel below the water surface and arranged for receipt and connection of the buoy, a hoisting means provided on the vessel for raising of the buoy for introduction thereof into the receiving space, and a means enabling the vessel to turn about an essentially vertical axis through the buoy when this is connected in the receiving means.
A system of the above-mentioned type is known from e.g. U.S. Pat. No. 4,604,961 (corresponds to Norwegian patent specification No. 167 906). This known system is based on a vessel having a through-going deck opening in a central region of the vessel, the lower part of the through opening forming the receiving space for a mooring element in the form of a submerged buoy. In the receiving space there is arranged a rotating body (turret) which is rotatably mounted in the hull of the vessel and is designed for receipt and attachment of the mooring element, the latter to this end being provided with a hydraulically actuated locking mechanism for attachment to the rotating body. Further, the vessel is provided with a derrick for the lowering of a retrieval string having a retrieval connector at its lower end for interconnection with the mooring element, so that this may be pulled up and into the receiving space. The interconnection is obtained in that the mooring element is provided with a conical centering receptacle having a socket arranged at the bottom wherein the retrieval connector may be received and secured, e.g. by means of a bayonet lock. The lower end of the retrieval string preferably is provided with sonar and TV equipment to ensure position in of the retrieval connector in the centering receptacle.
The known system is encumbered with some drawbacks which will be discussed below.
As mentioned, the vessel of the known system is based on a through-going deck opening, which reduces the strength of the vessel and poses demands for additional reinforcements in the bottom and the deck of the vessel. Experience has also shown that ships having a through-going deck opening are subject to fatigue in the hull.
Since the rotating body is attached to the vessel under water, this requires divers for inspection and minor maintenance. Major maintenance requires docking of the vessel. Because of the fact that the rotating body is mounted to the vessel, there arise large frictional forces which are to be overcome by torques from the mooring element. Theses 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 inertia 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.
The hydraulically actuated locking mechanism which is arranged on the mooring element requires divers for connection of the control hydraulics. Diver operations in connection with connection and disconnection render the use of the system as a transport system impossible, when using shuttle tankers. Further, there is a big risk for faulty operation and damages in case of uncontrolled disconnection. In case of breakage of the hydraulic system there is no possibility for the connection of a back-up or auxiliary device.
As mentioned, connection/disconnection takes place by mea
REFERENCES:
patent: 1233489 (1917-07-01), McDougall
patent: 4490121 (1986-02-01), Coppens et al.
patent: 4604961 (1986-08-01), Ortloff et al.
patent: 4701143 (1987-10-01), Key et al.
patent: 4892495 (1990-01-01), Svensen
Breivik Kare
Smedal Arne
Syvertsen Kare
Avila Stephen
Den Norske Stats Oljeselskap A.S.
LandOfFree
System for offshore loading/unloading of a flowable medium, espe does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for offshore loading/unloading of a flowable medium, espe, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for offshore loading/unloading of a flowable medium, espe will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1242209