US 4,060,995 AGranted

Immersion of an offshore weight-structure having two compartments

AssigneeSea Tank Co. S.A.

InventorsRoger Lacroix, Claude Lepere

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Abstract

The invention relates to the immersion at a great depth of an offshore weight-structure comprising a concrete base having two multicellular compartments, the one being central and self-resistant and the other being peripheral and subjected to compensating pressures, at least one multitubular pylon fixed to the said base and having a working area installed above it out of the water, and an auxiliary float co-operating with each pylon. The invention is characterized in that ballasting is effected by partial filling of the said self-resistant central compartment to enable the beginning of the immersion to be effected and that the actual immersion is then effected by the action of the said auxiliary float having an elongated cylindrical shape and being partly filled and whose relative position in relation to the said base is varied by mechanical guiding means. The ratio between the number of self-resistant cells and the number of peripheral cells filled with crude oil is determined with a view to immersion of the said structure.

Claims10

Dependent claims

A method of immersing an offshore structure which includes a self-resistant base, a multitubular pylon fixed to the base and having guiding bars extending lengthwise thereof a working area installed on the pylon, an auxiliary hollow float mounted on the pylon and jack means for releasably clamping the float to the guiding bars for varying the relative positions of the base and the float, and wherein the base comprises a central multicellular compartment and a peripheral multicellular compartment the interior of which is adapted to communicte with the surrounding water as well as with a source of pressure fluid compensating for the pressure of the surrounding water, the method comprising:

a. initiating immersion of the base by partially filling the central compartment with liquid;
and
b. thereafter continuing immersion of the base by admitting additional liquid into the central compartment, lowering the base relative to the float by clamping the float to the guiding bars and pumping liquid from the central compartment into the float, the pumping permitting the load on the jack means to be restricted at a substantially constant draft whereby the jack means is usable to great depths.

Dependencies are inferred from the claim text.