Leg elevation modification system - for sea-going rigs, uses deck equipment to modify and stow leg sections

摘要

A method for the shortening of the legs of sea-going jack-up rigs comprises a sectional design of leg and a deck-mounted handling system enabling leg sections to be stored on the deck. In order to meet centre of gravity requirements for ocean-going movement of the rig when its legs are lifted, the elevation of legs above the deck level is kept to a minimum. To shorten the legs, the rig is anchored in shallow water, the deck is jacked up for access to the highest leg joint and the top leg section removed. The rig is then jacked down to the next joint and so forth until the caisson reaches water level. The legs are lengthened by the reverse process. Used for improving the manoeuvrability of sea-going jack-up structures, for improving the speed with which they can be modified before and after ocean voyages without the use of a large crane.