Hydraulic and earth engineering – Marine structure or fabrication thereof – With work deck vertically adjustable relative to floor
Patent
1997-06-09
1999-11-09
Bagnell, David J.
Hydraulic and earth engineering
Marine structure or fabrication thereof
With work deck vertically adjustable relative to floor
405196, B63B 3544
Patent
active
059801590
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a buoyancy assembly suitable for use with marine bodies. It is particularly, but not exclusively applicable to oil exploration platforms and the like.
BACKGROUND TO THE INVENTION
There have been a number of ways that the stability have been provided for in marine structures. stability through changing buoyancy by part of their body coming in or out of water. It is because of this requirement that a large part of their body providing buoyancy and stability is exposed to maximum environmental loading. of pumps to pump water in or out of the vessel as required. foundation or by being attached to large weights known as gravity foundations. or piling, acting against the buoyancy of a floating vessel and keeping the tethers always in tension. The stability of the vessel is either provided by the tension in the tethers or a combination of the tension as well as the buoyancy changes due to the vessel coming in or out of the water.
Providing piled stabilised foundation is expensive, requiring specialised crane vessels, pile driving hammers and the expense of the piles. Gravity stabilised foundation require large, usually concrete, structures and expensive ballast systems. These structures need to be either externally stabilised for transportation and installation offshore or their stability element would need to be water surface piercing attracting environmental loads. Structures sitting on the sea bed fully submerged would need crane vessels to lower them down or raise them up and still require to be stabilised by a foundation.
Floating facilities which are utilised as offshore platforms for mineral production require to keep station whilst being connected to the source of the minerals. However, as they need to be surface piercing for their stability, they are at times subjected to severe environmental loads. In order to minimise their motions and for station keeping a number of facilities have been developed. These include: These are also used to turn a ship around to face the waves. Turrets are required to allow the ships to turn around a moonpool housing pipes connected to the source of the minerals. as the tensioners. operate on a day-to-day basis. No one technology can provide buoyancy and stability when partially and fully submerged as well as providing foundation stability to a structure sitting on the sea bed. No one existing marine stabilising system has the facility to alter its dynamic characteristics to suit changes in the environmental loads. It is the object of the present invention to overcome some or all of these disadvantages.
This invention relates to marine bodies that can provide hydrostatic stability even when fully submerged, have the facility for altering its dynamic characteristics and provide sea bed foundations that minimise or eliminate the vertical loads acting on the sea bed.
SUMMARY OF THE INVENTION
According to the present invention, in its broadest sense, there is provided a buoyancy assembly suitable for supporting, either alone or in combination, a load deck or other marine body said assembly comprising: portion defining a chamber adapted to contain a variable volume of compressed gas, the first portion being open to the water at or near its lowermost-in-use region to allow ingress of water to form a water pool inside the first portion, the surface of the water pool being in contact with the compressed gas above it; portion, said second portion also defining a chamber adapted to contain a variable volume of compressed gas: gas to flow between the first and second portions and vice-versa, the assembly being adapted such that when the assembly is displaced from equilibrium, either up or down, the free surface of the water pool in the first portion will rise or fall with respect to its equilibrium position and the resulting change in gas pressure in the gas above the water pool will cause the first and second portions to move with respect to each other such that a restoring force, upwards or downwards, is generated tending to res
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Bagnell David J.
Lagman Frederick L
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