drydock is a type of pontoon for dry docking ships, possessing floodable buoyancy
chambers and a "U"-shaped cross-section. The walls are used to give
the dry dock stability when the floor or deck is below the surface of the water.
When valves are opened, the chambers fill with water, causing the dry dock to
float lower in the water. The deck becomes submerged and this allows a ship to
be moved into position inside. When the water is pumped out of the chambers, the
dry dock rises and the ship is lifted out of the water on the rising deck, allowing
work to proceed on the ship's hull.
A large floating dry dock involves multiple
rectangular sections. These sections can be combined to handle ships of various
lengths, and the sections themselves can come in different dimensions. Each section
contains its own equipment for emptying the ballast and to provide the required
services, and the addition of a bow section can facilitate the towing of the dry
dock once assembled.
Floating Drydock PD-30 laid down at Trogir Shipyard,
Yugoslavia (yard No.176), commissioned on 21 September 1979.
Now in service.
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