Bethlehem Steel Corporation's Floating Dry Dock No. 1 in their Sabine Yard, Port Arthur, Texas, is the world's first floating dry dock that can easily convert from a dry dock of normal configuration (829 feet long by 122 feet wide) for docking ships to an extra-wide dry dock (413 feet long by 364 feet wide) to accommodate drill rigs. (See Tables 1 and 2.) This paper describes how the dock was modified from the former U.S. Navy dry dock AFDB-S, built in 1944, to the present computer controlled, state of the art, convertible dock.

Particular emphasis is given to the design of the huge "quick-disconnect" pin connections between sections, and operational procedures for connecting/disconnecting the sections by ballasting/deballasting using computer control of list, trim, deflection and internal ballast water level.


The dock, as originally designed, consisted of seven ship shaped pontoon sections with the two side walls on each section. The side walls of adjacent sections were bolted together with steel plates to form one continuous dock capable of docking battleships. The dock was designed such that the sections could be separated, and their side walls folded down, for ocean tow.

The dry dock now consists of eight pontoon sections (an eighth section was obtained from a sister dry dock) with the side walls of adjacent sections permanently welded together with stiffened steel plates to form two units of four sections each. The units can be pinned together either longitudinally to form the ship dock mode or side by side to form the drill rig dock mode (See Figure 1).


Conversion from the ship mode to the drill rig mode begins by the removal of two 6-inch diameter connecting pins at the longitudinal centerline of the dock and one 8-inch diameter pin in the offshore mooring arm. This allows the outshore half of the dock to float free. The inshore half of the dock is then deballasted until it is floating approximately 4 feet higher than the outshore half. The outshore portion is then pivoted into position using tug boats (See Figure 2).

Final alignment is achieved by fitting vertical protruding "V" shaped members (male) on the outshore dock unit into corresponding "V" shaped guides (female) on the inshore unit, with the sections mated in these "V" guides, eight 24-inch diameter vertical pins, located at the base of the deballasted unit, are automatically aligned directly over their mating holes located at the base of the other unit. The units are then brought to an equal elevation by ballasting, automatically engaging the 24-inch diameter pins in their mating holes and aligning the upper connection's 9-inch diameter horizontal holes (See Figure 3). Hydraulic jacks then insert the horizontal 9-inch diameter pins through these holes completing the connection between the two dock sections.

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