American Hoist & Derrick Company

Charles A Johnson

Laurence H Lucker, Jr

A mooring apparatus for a semi-submersible oil exploration and drilling rig includes eight drum anchor hoists and winches on which are carried eight wire rope mooring lines. Each of these lines extends up over one of eight head sheaves and vertically down the outside face of the oil rig through a fairleader rotatably mounted with respect to the rig at a bottom submerged portion thereof. A linear line pull machine is mounted to the rig in encompassing relation to each of the vertical runs of mooring line between the head sheave and the fairleader. These eight mooring line assemblies are distributed around the periphery of the rig. Two mooring lines extend at 90.degree. from each other at each corner of the rig. At least one hydraulic power unit is provided for each two of these mooring line assemblies, and air and hydraulic control means are provided utilizing power from this power unit selectively to: (1) reel out and reel in on the mooring lines when low line forces are involved using the anchor hoist; (2) to exert extremely high forces at slow speeds when necessary to set anchors attached to outer ends of the mooring lines and to positively hold the rig against the upward buoyant effect of the rig's pontoons; or (3) to operatively disassociate the linear pull machines from the mooring lines so that the mooring lines can be reeled outwardly at very high speeds.

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Lakeville, MN, United States of America

Charles A Johnson