Buoyancy device

Details Buoyancy device Buoyancy device

1998-11-16

2001-08-07

Basinger, Sherman (Department: 3617)

Ships

Ballasting

Floats

C114S054000, C405S203000

Reexamination Certificate

active

06269761

ABSTRACT:

The present invention relates to a buoyancy device particularly, but not exclusively, for attachment to large structures requiring to be lifted, lowered, positioned and transported via the ocean.
Conventionally, when an offshore drilling structure comes to the end of its working life, it is decommissioned. In the past, it was thought that decommissioning could entail sinking the drilling structure at the point where it once stood.
However, amongst other factors, environmental factors have recently increased the need for offshore drilling structures to be moved to shallower and calmer waters, or back on land so that the drilling structures can be dismantled safely.
Previously, moving the drilling structures has involved the use of flat back barges, onto which the drilling structures are hauled. However, these barges are expensive and costly in terms of man power requirements.
According to the present invention there is provided a buoyancy device comprising a plurality of buoyancy members substantially equi-spaced around the circumference of a coupling member, the buoyancy members being coupled to the coupling member, wherein at least two of the buoyancy members are inflatable members, the inflatable members being formed from a substantially flexible material, such that the inflatable member substantially collapses when deflated.
Preferably, the coupling member is coupled to a structure required to be moved in water, in use.
Typically the coupling member is a tubular member and the inflatable members may be coupled along the length of the tubular member.
Typically, the tubular member is substantially horizontal in use, when coupled to the structure required to be lifted, and after the inflatable members have been inflated.
Typically, the tubular member is coupled to the structure when the inflatable members are deflated.
Preferably, the tubular member is coupled to the structure in an initially horizontal plane.
Alternatively, the tubular member is initially coupled to the structure such that longitudinal axis of the tubular member is approximately 45° to the horizontal plane.
Preferably, the inflatable member comprises an outer skin of substantially flexible material, the outer skin defining an inner space, the outer skin comprising a body section, and an end section being sealably coupled to both ends of the body section. Preferably, the body and end sections comprise base edges by means of which the inflatable member is coupled to the tubular member. The base edges of the inflatable member may be spaced apart, and preferably, an inflation means inlet and a deflation means outlet are located between the spaced apart base edges.
Preferably, coupling devices are provided to couple the base edges of the inflatable members to the tubular member, and more preferably, a coupling device couples one side member of the body section of a first inflatable member in a back to back relationship with a side member of the body section of a second inflatable member. An inflatable member may have a cross-section which is substantially U-shaped, in use, when inflated.
This provides the invention with the advantage that the spaced apart base edges couple the inflatable member to the tubular member, and also provide access to the inner space from the tubular member to inflate or deflate the inflatable member. Thus, the outer skin of the inflatable member does not require to be pierced in order to provide access to the inner space.
Alternatively, the base edges of the inflatable member may be conjoined, and the inflatable members may be substantially wedge-shaped, in use, when inflated. The inflatable members may be movably coupled in a circumferential direction to the tubular member.
Preferably, the buoyancy device further comprises a pressure sensor to sense the pressure in the surrounding water, and may further comprise a displacement sensor to measure the displacement of the buoyancy device, and may further comprise an acceleration sensor to measure the acceleration of the buoyancy device.
Preferably, there is provided a pressure sensor to sense the pressure within each inflatable member.
Typically, there is provided at least one valve to allow regulation of the pressure within an inflatable member. Preferably, there is at least one inflation valve to allow the pressure of air within each inflatable member to be increased and preferably, there is at least one deflation valve to allow the pressure of air within each inflatable member to be decreased.
Preferably, should one or more of the inflatable members deflate, the pressure within the remaining inflatable members may be increased to compensate for the deflated members. Preferably, the inflatable members are restrained from over-inflation by a restraining device.
Preferably, the buoyancy device further comprises a control system to allow variation of its buoyancy. More preferably, a number of inflatable members are provided with a control system to allow variation of the buoyancy of the inflatable members.
Preferably, the control system is connected to, and reads signals from, the surrounding water pressure sensor, the inflatable member pressure sensor, the displacement sensor and the acceleration sensor. More preferably, the control system varies the buoyancy of the inflatable member in response to the signals read.
Typically, when the pressure within the remaining inflatable members is increased, the remaining inflatable members increase in size to occupy the space left by the deflated member(s).
One or more of the inflatable members may be inflated by air. Alternatively, one or more of the inflatable members are inflated with an incompressible material having a density less than that of the surrounding water. Typically, the inflatable members are inflatable bags.
According to a further aspect of the present invention there is provided a buoyancy device comprising at least one buoyancy member optionally connected to a coupling member for attachment of the coupling member to a structure to be floated, wherein the buoyancy member is inflatable and comprises a substantially flexible portion and one or more end portions, the or each end portion being releasably attached to the flexible portion.
The end portions may be dome-shaped, and the flexible portion may be tubular and may extend between two end portions. The dome-shaped end portions may be arranged in a first configuration in which their convex portions face one another, or may be arranged in a second configuration in which their concave portions are facing one another. The end portions may be connected together by any suitable connector, eg by straps or chains etc. The connectors may have tensioning devices incorporated in order to alter the tension and this can in some embodiments be carried out when the end portions are connected in situ. The end portions can have ports to allow access to the interior of the device.
The end portions can be connected to the flexible portions, for instance, at a section of overlap between the two portions. The flexible portion preferably overlies a respective end portion at said overlap, but this may be reversed. The flexible portion can be hooked onto the end portion, or in a preferred embodiment has bands extending around the flexible portion at the overlap, so as to tighten the band around the flexible portion and compress it against the end portion. One or more bands can be provided, preferably of steel or plastics material, and preferably of an inextensible material.
The invention also provides a buoyancy device comprising an array of buoyancy members connected to a coupling member for attachment to a structure to be floated, wherein the coupling member is disposed at one or more ends of the buoyancy members.
In this embodiment the coupling member can be a plate extending between at least two buoyancy members at an end thereof. The plate can be a simple bar extending between two members which can be adjacent, or can be a lattice which connects a number of adjacent or nonadjacent members in the array.
The invention also provides a buoyancy device c

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