| 摘要 |
A jacking assembly for a leg of a jackup offshore platform includes driving assembly and a movable carriage. The driving assembly includes a pair of counterrotating pinions spaced to receive a double-toothed gear rack of the carriage. The driving assembly is attached to the platform so that it can be entirely removed for reuse, if desired. The double-toothed gear rack is pivotally connected to a movable yoke at the upper end which yoke surrounds the leg. Surfaces of the double-edged gear rack are provided with stiffening members that cooperate with the driving assemblies to guide the gear rack during relative movement between the leg and the offshore platform. To selectively connect the carriage with the leg, the movable yoke is provided with a plurality of actuators having pins received by openings at preselected distances along the leg. A locking device is provided on the platform to engage other openings on the leg to fix the relative location of the platform and the leg while the carriage is repositioned. The driving assembly operates at a first speed while setting the leg and raising the offshore platform and moves at a second, higher speed when the carriage is being repositioned. The stroke length of the jacking mechanism is selected such that, with the leg firmly footed in the ocean floor, the platform can be lifted entirely out of the water and above the wave action in a single stroke. The carriage may also include a sleeve surrounding the leg and being slidable relative to the platform.
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