Propulsion unit - for dynamic location of semi-submersible drilling platform, floats in a low draught transit position to facilitate inspection and repair

摘要

A propulsion unit for the dynamic location of a semi-submersible drilling platform with floats capable of submersion in a deep draught drilling position and of floating in a low draught transit position, comprises (a) a body designed to be fixed in and to close off an aperture cut in the upper part of one of the floats and thereby, to isolate a sealed compartment in the float (b) a support mounted on the body having an upper part designed to be extended above the float in such a way that is submerged in the drilling position and out of the water in the transit position (c) a propulsion element mounted in the upper part of the support member for exerting a thrust in a horizontal direction and (d) a transmission connected to the propulsion element and traversing the support members to extend into the sealed compartment. Advantageously, the transmission is connected to the output shaft of a motor so suspended from the body as to be situated in the compartment, which also contains a brake assembly associated with the output shaft. Since the propulsion element is out off the water in the transit position, the screw is readily inspected and in calm weather maintenance or repairs can be carried out without divers. Screw noise causes much less disturbance to acoustic detectors fixed under the floats for detecting the relative position of platform and well head so that vertical drilling is possible.