A pontoon structure that can be submerged to receive a vessel then raised to lift it clear of the water for repair work.
In practice
The limitations of a floating dock compared to a graving dock include lower structural strength for very large vessels, susceptibility to weather disruption since the vessel cannot be enclosed, and the inherent risk of sinking if the dock structure is damaged or ballasting is mismanaged. Classification societies and naval architects assess the stability of the floating dock with the vessel aboard, checking that adequate freeboard remains at all stages of the lift. Many ship repair yards in Southeast Asia, the Middle East, and West Africa operate floating docks as their primary drydocking facility.
Regulatory detail & full definition
A floating dock (or floating drydock) is a U-shaped pontoon structure — consisting of a flat deck platform and two hollow vertical wing walls — that can be ballasted down so that its deck platform sinks below the water's surface, allowing a vessel to be manoeuvred over it. The wing walls are then deballasted, raising the pontoon and lifting the vessel clear of the water for inspection and repair. Floating docks offer flexibility in location, as they can be towed to areas lacking permanent graving docks, and they can be mobilised to assist vessels that cannot safely reach a conventional shipyard.
The limitations of a floating dock compared to a graving dock include lower structural strength for very large vessels, susceptibility to weather disruption since the vessel cannot be enclosed, and the inherent risk of sinking if the dock structure is damaged or ballasting is mismanaged. Classification societies and naval architects assess the stability of the floating dock with the vessel aboard, checking that adequate freeboard remains at all stages of the lift. Many ship repair yards in Southeast Asia, the Middle East, and West Africa operate floating docks as their primary drydocking facility.
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