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Titanic Thompson Dock's CAISSON GATE

For more check out Link http://www.titanicmemorials.co.uk/pos... The enormous caisson that held back the sea waters from the titanic dock as she was being built is worth a viewing. the gate obviously lies at the seaward end of the Thompson dock. there are sea vents at it's base to allow sea water to be pumped in and out of the dock. I believe that this could be filled or empied in around 3 hours. Graving Dock What is a graving dock and what is it used for? The word ‘graving’ is an obsolete nautical term for the scraping, cleaning, painting, or tarring of an underwater body. Combined with the word ‘dock’ a graving dock refers to an enclosed basin into which a ship is taken for underwater cleaning or repair. Older graving docks were fitted with watertight entrance gates when closed permitted the dock to be pumped dry. However these gates, hinged on either side, restricted the size of vessels entering and the gates were also difficult to seal and to repair. Later designs of graving docks incorporated the use of a caisson or pontoon (sometimes called a camel by shipbuilders) that fitted closely into the entrance. The caisson is flooded and sunk in place and the water pumped out of the dock. Reversing the process the dock is flooded, the caisson pumped dry, floated and is warped away from the entrance to permit passage of vessels. A graving dock is sometimes called a graving dry dock or just dry dock. It is, however, not a dock. A dock is an artificial basin provided with suitable installations for loading and unloading, close to the sea, where vessels can lie afloat. The dock area may communicate freely with the stream or harbour, or the entrance to it may be closed by a lock or gates. Caisson The primary function of a caisson is a device used for repairing outside damage to the hull at, or below, the waterline while a vessel is afloat. In the case of a graving dock a caisson is an iron or steel structure used for closing the entrance. It is constructed with buoyancy chambers and ballast tanks so that by means of valves and a pump or ejector the weight of the contained water ballast can be varied at will for floating or sinking the caisson into position.