US 7,882,794 B2Granted

Buoyancy device and method for stabilizing and controlling lowering or raising of a structure between the surface and the sea floor

AssigneeSaipem S.P.A.

InventorsMichel Baylot, Marc Bonnissel, Xavier Rocher

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Abstract

A method of using a buoyancy fluid presenting density that is less than that of sea water, and that is confined in a rigid or flexible leaktight casing, so as to constitute an immersed buoyancy element, wherein the buoyancy fluid is a compound that is naturally in the gaseous state at ambient atmospheric temperature and pressure, and in the liquid state at the underwater depth to which the buoyancy element is immersed. The present invention also relates to a method of putting a buoyancy element into place between the surface and the bed of the sea, wherein the fluid is stored in a tank on a surface ship as a liquid in the cooled or compressed liquid state, and it is injected in the liquid state into a pipe from the surface where it is stored to an said immersed casing at an underwater depth at which the underwater pressure is not greater than the vapor pressure of the gas corresponding to the compound at the temperature at the depth.

Claims26

Dependent claims

A device for stabilizing or controlling the lowering or raising of a structure between the surface and the bed of the sea, said structure including or being connected to a buoyancy element having:

a casing;
and
a buoyancy fluid having a density that is less than that of sea water, the buoyancy fluid confined in and entirely filling said casing,
wherein said buoyancy fluid is a quasi incompressible fluid and naturally in a gaseous state at ambient atmospheric temperature and pressure, and naturally in an entirely liquid state at an underwater depth to which said buoyancy element is immersed;
and
wherein said buoyancy element imparts buoyancy to an immersed structure to which it is one of connected, secured, or in which it is integrated;
said device comprising:
at least one connection element of the cable or chain type, comprising:
a first end that is connected to a winch on board a floating support or ship on the surface of the sea, and on which the connection element is wound;
and
a second end that is connected to a fastener element on said structure, or on the buoyancy element that is connected to said structure;
and
wherein the length of said connection element is such that said winch is capable of winding or unwinding said first end of said connection element, so that a bottom portion of said connection element can hang beneath said fastener element.

10 more elements

A method of lowering, raising, or stabilizing a structure between a surface and a bed of a sea by means of a device, the structure having at least one leak-tight compartment, and the device including at least one connection element of a cable or chain type, the connection element having:

a first end that is connected to a winch on board a floating support or ship on the surface of the sea, and on which the connection element is wound;
and
a second end that is connected to at least one of a fastener element on said structure, and a buoyancy element that is connected to the structure;
wherein a length of the connection element is such that the winch is capable of winding or unwinding the first end of the connection element, so that a bottom portion of the connection element can hang beneath the fastener element,
the method comprising the steps of:
unwinding or winding the at least one connection element at its first end by means of the winch;
controlling a speed at which the at least one connection element is lowered or raised by regulating the speed at which the at least one connection element is respectively wound off or on the winch, so as to adjust the length of the bottom portion of the at least one connection element hanging beneath the fastener element;
wherein a lowering, raising, or stabilizing of said structure is obtained when a sum of a weight of a fraction of the bottom portion of the at least one connection element between a fastener point for fastening to the fastener element and a lowest point of the bottom portion, plus the weight of the structure as a whole and of a buoyancy element, is respectively greater than, less than, or equal to a buoyancy thrust that is exerted on the structure and on the buoyancy element;
filling at least one leak-tight compartment at least partially with a buoyancy fluid that is lighter than the sea water that is recovered at the surface of the sea in a vicinity of the device, to produce buoyancy elements, at least one leak-tight compartment being adjusted to cause the structure to occupy an equilibrium position when immersed close to the surface of the sea;
lowering the structure to a desired position by means of the device, so as to regulate the speed at which the structure is lowered, and so as to provide equilibrium to a base of a substantially horizontal structure while it is being lowered;
and
once the structure is immersed to the desired depth, emptying the at least one leak-tight compartment filled with the buoyancy fluid, and simultaneously filling the at least one leak-tight compartment with sea water.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/550,818Filed 25 Mar 2004
Priority: FR 03 0396926 Mar 2003
Published: US 2006/0225810 A112 Oct 2006
Granted: 8 Feb 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

E02B 15/08
Devices for cleaning or keeping clear the surface of open water from oil or like floating materials by separating or removing these materials:…
B63B 27/08
Arrangement of ship-based loading or unloading equipment for cargo or passengers: of winches
B63C 7/006
Salvaging of disabled, stranded, or sunken vessels; Salvaging of vessel parts or furnishings, e.g. of safes; Salvaging of other underwater…
E21B 43/0122
Specially adapted for obtaining from underwater installations: collecting oil or the like from a submerged leakage