Semi-submersible drilling unit or buoy with floats

摘要

There is described a vessel such as a semi-submersible drilling unit having a drilling deck structure with a plurality of columns depending from the deck. Pontoons are provided at the ends of the columns and a buoyant configuration modifying sleeve-like element is mounted around the columns. The sleeves are annular in cross-section and of generally cylindrical form and terminate at their lower ends in cuffs of reducing outer diameter. This provides an inwardly tapered or curved end to the sleeve. A cable and pulley arrangement is provided for vertically moving the sleeves along the columns and for locating them on the columns close to the unit transit waterplane and at a survival waterplane position.