Ships – Mooring device – Boom type
Patent
1997-08-20
1998-12-01
Avila, Stephen
Ships
Mooring device
Boom type
114293, B63B 2100
Patent
active
058424342
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a mooring assembly for an offshore floater, said assembly comprising a vertical shaft in the floater, a rotating part rotatably mounted about a vertical axis in the vertical shaft, a number of mooring cables extending from the rotating part down to the seabed, and means aboard the floater for tightening/slackening the mooring cables.
BACKGROUND OF THE INVENTION
If a floater is moored offshore by means of a rotating part rotatably mounted in a vertical shaft, said rotating part will, when the floater moves, be pulled along with it as a result of inertia and frictional forces in the bearings of the rotating part in the shaft. The mooring cables, which are brought up into the rotating part, will be exposed to wear and tear, and every endeavor is therefore made to use good rotational bearing components which enable the rotating part to rotate easily in relation to the floater.
The use of "inferior" bearing would be simpler and less expensive but would give an undesired large cable divergence, with correspondingly greater wear of the mooring cables.
SUMMARY OF THE INVENTION
An object of the invention is to make possible the use of simpler and less expensive bearings for said rotating part without thereby exposing the mooring cables to greater hazard of wear.
According to the invention, a mooring assembly, as mentioned by way of introduction, is therefore proposed, said mooring assembly being characterized in that each mooring cable right below the rotating part is secured to a rigid body having two ends, one end being connected by a universal swivel joint to said rotating part and the other end comprising a locking device for locking the mooring line to the rigid body.
When the floater revolves about the rotating part under the influence of wind and current, said rotating part will, as noted, have a tendency to be pulled along during a part of the revolving movement, as a result of inertia and frictional forces. Since the mooring line is brought into the rotating part by means of the swivel-mounted rigid body, moments will arise from the pointing movement, said moments resulting in the rotating part being held back with greater force. This means that the rotational bearings of the rotating part can be made simpler and less expensive since there is decreased dependency upon smoothly operating bearings for the rotating part in the vertical shaft of the floater.
The angle of divergence between the rigid body and the mooring cable will decrease corresponding to the increase in length of the rigid body.
The rotational bearings of the rotating part of the floater may advantageously comprise slide bearings.
The locking device for locking the mooring cable to the rigid body may advantageously be an activable chain stopper. This presupposes that the mooring cable comprises a length of chain for engagement with the chain stopper in the rigid body.
It is particularly advantageous according to the invention that it is possible, from each location on the rotating part to which a rigid body is connected, to form a vertical guide track, in the rotating part, for an elongated flexible element extending from a tightening/slackening device mounted on the floater, such as a winch, said tightening/slackening device being rotatable about an axis, at least approximately vertical, coinciding with the flexible element extending toward the device, for the removal of possible twists in the flexible elongated element, which is connected to the mooring cable or constitutes the mooring cable.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention shall now be further explained by reference to the drawings, wherein
FIG. 1 is a schematic cross section of a floater comprising a mooring assembly according to the invention,
FIG. 2 is a schematic plan view of the mooring assembly of FIG. 1, and
FIG. 3 shows a modified mooring assembly according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a floater which has a deck 2 and a bottom 3. Between the bottom 3 and the deck 2
REFERENCES:
patent: 3414918 (1968-12-01), Petrie et al.
patent: 3774562 (1973-11-01), Dean, III
patent: 4305341 (1981-12-01), Stafford
patent: 4892495 (1990-01-01), Svensen
patent: 5170737 (1992-12-01), Poldervaart
Aavitsland Dag
Lange Espen
Avila Stephen
Kvaerner Engineering AS
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