Ships – Life craft handling device – apparatus – or implement – Moving from storage position to launching position
Patent
1992-02-28
1993-09-21
Sotelo, Jesus D.
Ships
Life craft handling device, apparatus, or implement
Moving from storage position to launching position
B63B 2338
Patent
active
052459420
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION concerns a system for launching a lifeboat from a fixed structure such as an offshore drilling platform.
The system is intended to overcome the problems encountered when launching lifeboats on the weather or windward side of a drilling platform where there is a tendency for the lifeboat to be driven into the legs and pipework of the platform thus preventing rapid escape, for example in the case of fire and when burning debris may fall into the sea from a position directly above the boat.
It is intended that the system should enable the boat to be drawn a safe distance away from the platform once it is afloat.
According to the present invention, a system for launching a lifeboat from a fixed structure such as an off-shore drilling platform, comprising a submerged buoyancy device tethered to the bow of the lifeboat by means of a cable which passes, from the lifeboat to the buoyancy device, and is retained by a release mechanism fixed near the base of the structure, and by a submerged guide member fixed at a similar level but at a distance off the structure, the release mechanism being adapted to release the cable as the lifeboat descends from the structure such that consequent rapid ascent of the buoyancy device draws the cable around the guide member thus drawing the lifeboat bow in a direction away from the structure during descent, and towing the lifeboat rapidly away from the structure, once it is afloat.
The invention will now be described further, by way of example only, with reference to the accompanying drawing which illustrates schematically a fixed drilling platform with a lifeboat launching system embodying the invention.
A drilling platform 10 is supported on legs 11 above the sea bed 12. A number of lifeboats, one of which is illustrated at 13, are suspended around the platform 10 on davits 14. Access to the lifeboats is via the deck 15 forming part of the platform 10.
The launching system for each lifeboat comprises a buoyancy device 16 which is tethered by a cable 17 to the bow of the lifeboat 13.
The cable 17 passes vertically downwards from the lifeboat to a release mechanism in the form of an inverted hook 18 anchored to the sea bed at 19 near the base of the platform, or to one of the legs 11. At this point, the cable carries a fixed ring 26 which locates under hook 18. From there the cable passes horizontally over the sea bed to a second retaining member in the form of a pulley 20 anchored to the sea bed at 21, a distance off the platform. The cable then passes around a second pulley 22 fixed to the base of the buoyancy device 16 and is anchored beyond at 23 to the sea bed.
A marker buoy 24 is attached by a line 25 to the buoyancy device 16.
Hook 18, preferably made of stainless steel, comprises an inclined arm disposed at an angle of 45.degree. or more with respect to a vertical stem, the latter being some 3 meters in height. A snatch weight 27 is suspended from a pulley 28 which rides on cable 17 between ring 26 and pulley 20.
Location of the buoyancy device 16 close to the sea bed, together with the low level horizontal run of cable 17 between hook 18 and pulley 20 ensures that there are no obstructions in the water, for craft approaching the drilling platform, save for the marker buoy 24 which is visible above the surface.
When it is required to launch the lifeboat, it is lowered in the usual manner from the davits 14 towards the surface. As the lifeboat descends, the cable above ring 26 becomes slack so that the ring 26 is released from hook 18 thus releasing the cable 17 which enables the buoyancy device 16 to rise sharply to draw the bow of lifeboat 13 in a direction away from the drilling platform. The arrangement of pulleys 20 and 22 provides a 2:1 ratio of descent of the lifeboat against ascent of the buoyancy device.
When the buoyancy device reaches the surface as indicated at 16' the lifeboat will have assumed a position as indicated at 13' distant from the drilling platform with the cable assuming the configuration as indicated at 17'.
The snatch weight 27 prev
REFERENCES:
patent: 3796281 (1974-03-01), Dowling
patent: 4711196 (1987-12-01), Wilks
E M & I (Safety Systems) Limited
Sotelo Jesus D.
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