Double floor (shipbuilding)
The double floor of a ship is formed by the floor construction, the outer skin plating and the double floor or tank ceiling above.
details
The bottom construction of the hull of a seagoing ship consists mainly of bottom walls (cross members), longitudinal members and frames . The outer skin plating forms the outer closure to the lake water. Towards the interior of the ship, the floor construction is closed off at the top by the double floor or tank ceiling, which, for example, in dry freighters in the hold area also forms the hold floor . The double floor is divided into individual tanks by watertight floor walls, which are used to hold water ballast as well as fresh water and bunker or operating oils. Furthermore, the separate tanks protect large parts of the ship from flooding in the event of damage to the outer skin.
The development of the construction of ships with a double bottom was initially not made for safety reasons, but for economic reasons. Initially, the double floor was needed to be able to absorb ballast water ; only in later development steps did the safety gain effect in the event of damage to the outer skin due to ground contact, on the one hand, and use as a bunker tank on the other. In the case of newly built ships with a total bunker capacity of over 600 m³, since August 1, 2010, no bunker tank may touch the outer skin. This means that the use of the raised floor to carry bunkers is no longer permitted in new buildings.
Preservation
The preservation of the double bottom plays an important role in the construction of the ship and in subsequent visits to the shipyard. Because the manholes for the double-bottom tanks are mostly in the hold, it is very difficult to carry out maintenance measures during normal ship operation, because there is often cargo in the hold. The maintenance measures are then usually limited to tank inspections, the replacement of level sensors and the washing of the tanks if too much sediment has accumulated. The necessary conservation measures must therefore be carried out in the shipyard. Therefore, a careful processing of the color is very important. A ship usually only goes to the shipyard every two and a half years and no repairs can be made to the coating for that time.
Basically, tanks can be preserved in two ways: with anodes or with a coating. Depending on the classification society , however, a coating of the water ballast tanks has long been prescribed so that the anode solution is not required.
Individual evidence
literature
- U. Scharnow: Lexicon of seafaring . various years, transpress VEB Verlag für Verkehrwesen Berlin, ISBN 3-344-00190-6 , page 117
- IMO Publication: MARPOL Consolidated Edition 2006 International Maritime Organization, ISBN 978-92-801-4216-7
- IMO Publication: SOLAS Consolidated Edition 2009 International Maritime Organization, ISBN 978-92-801-1505-5