A watertight basin into which a vessel is floated, then dewatered, allowing access to the entire underwater hull for inspection and repair.
In practice
Once the vessel is undocked and sitting on its blocks, the full scope of a special survey or drydock maintenance programme can be executed: hull blasting and painting, sea valve renewal, rudder overhaul, propeller inspection, tailshaft withdrawal, and structural repairs. The dock floor and walls provide scaffolding attachment points for access to all areas of the hull. Management of the undocking and re-floating process requires careful planning of keel block placement and assessment of the vessel's transverse stability, since a vessel sitting on dry blocks with no buoyancy is subject to toppling risk if poorly supported. Graving docks are classified by their length, width, and maximum vessel draught capacity.
Regulatory detail & full definition
A graving dock is a fixed, watertight basin excavated or constructed ashore into which a vessel is floated at high water, positioned over keel blocks and bilge blocks, and then dewatered by pumping until the vessel rests on its supports and the entire underwater hull is exposed and accessible. The dock is then sealed by a caisson or gate. Graving docks are the traditional form of dry dock and are found at major commercial shipyards and naval dockyards worldwide.
Once the vessel is undocked and sitting on its blocks, the full scope of a special survey or drydock maintenance programme can be executed: hull blasting and painting, sea valve renewal, rudder overhaul, propeller inspection, tailshaft withdrawal, and structural repairs. The dock floor and walls provide scaffolding attachment points for access to all areas of the hull. Management of the undocking and re-floating process requires careful planning of keel block placement and assessment of the vessel's transverse stability, since a vessel sitting on dry blocks with no buoyancy is subject to toppling risk if poorly supported. Graving docks are classified by their length, width, and maximum vessel draught capacity.