Consideration at the design phase of new ships
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Statutory Documents - IMO Publications and Documents - Resolutions - Marine Environment Protection Committee - Resolution MEPC.149(55) - Guidelines for Ballast Water Exchange Design and Construction Standards (G11) - (Adopted on 13 October 2006) - Annex - Guidelines for Ballast Water Exchange Design and Construction Standards (G11) - 3 Ballast Water Exchange - Design and Construction Considerations - Consideration at the design phase of new ships

Consideration at the design phase of new ships

  3.2 When designing new ships the following aspects related to ballast water management equipment should be considered:

  • .1 ballast water management and the processes chosen to achieve it, should be considered as a component of the ship's design;

  • .2 design and installation of the ballast water pumping and piping system should ensure that ease of operation and maintenance is maximized;

  • .3 ballast tank design should facilitate all aspects of ballast water management;

  • .4 installation of monitoring and/or recording equipment for all ballast water operations and treatment processes. If any records are automatically recorded by the equipment they should be in a format that can easily be retained and be made readily available to appropriate authorities;

  • .5 remote data management;

  • .6 the design of the ballast water exchange system should be such that it facilitates future compliance of the standards set in Regulation D-2 of the Convention, minimizing the need to install new equipment/retrofitting and to carry out dry-docking and/or hot work. It should reduce, as far as possible, the costs of any adaptation for this purpose. Special consideration should be given to the feasibility of combining ballast water exchange methods with ballast water treatment technologies, aiming at meeting, in the future, the standards of Regulation D-2. Adequate spaces for new complementary equipment and pipelines, which may be necessary to meet future standards D-2, should also be considered and planned.

  3.3 Where designing new ships ballast water systems designs should take special account of the need for sampling the ballast water by port State control or other authorized organizations. The arrangements should be such that samples as required by the Guidelines for ballast water sampling (G2) can be taken. The sampling arrangements should enhance the quality and ease of sampling of ballast water or sediments, without the need to enter potentially dangerous spaces or partially filled ballast tanks.

  3.4 Where ballast water exchange at sea is the chosen method, when designing new ships the following aspects should be considered:

  • .1 design of ship structures to enable ballast water exchange to be conducted at various sea states/swell conditions and provide to the ship information on the maximum sea state that ballast water exchange can be conducted;

  • .2 minimize the burden on ships crew (e.g. minimize the number of operational steps, the number of partially loaded tanks and the time taken);

  • .3 minimize the risk of tank over/under pressurization;

  • .4 minimize the flow of ballast water on deck;

  • .5 maintaining bridge visibility standards (SOLAS V/22), propeller immersion and minimum draft forward at any stage of a designed ballast water exchange operation;

  • .6 the consequences of ballast water exchange at sea, including stability, hull girder strength, shear forces, torsional stresses, resonance, sloshing, slamming and propeller immersion.

  3.5 The ballast water exchange methods currently in use are the sequential, flow-through (tank overflow) and dilution methods:

  • .1 where the sequential method is to be used, particular attention should be given to the ballast tank layout, total ballast capacity, individual tank configuration and hull girder strength. If the plan requires simultaneously empting and refilling closely matched diagonal tanks then consequential torsional stresses should be considered. Still water bending moments, shear forces and stability should remain at or within safe limits;

  • .2 where the flow through method is to be used adequate provision should be made to avoid the risk of over pressurization of ballast tanks or ballast piping. The installation of additional air pipes, access hatches (as an alternative to deck manholes), internal overflow pipes (to avoid flowing over the deck) and interconnecting ballast trunks between tanks where applicable and possible may be considered. Water on decks and/or direct contact posses a safety and occupational health hazard to personnel. The design should, where possible, be such that it avoids water overflowing directly on to decks to avoid the direct contact by personnel with the ballast water;

  • .3 where the dilution method is to be used adequate provision should be made for appropriate piping arrangements to facilitate the ballast water pumping into the previously ballasted tanks through the top of the ballast tank and, simultaneously, discharging the ballast water through the bottom of the tank at the same flow rate while maintaining a constant ballast water level in the tank throughout the exchange operation. Adequate provision should also be made to avoid the risk of over pressurization of ballast tanks or ballast piping. The hydrodynamic performance of the ballast tank is crucial to ensure full water exchange and sediment scouring.

Parent topic: 3 Ballast Water Exchange - Design and Construction Considerations
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