When identifying the ballast water exchange method(s) for the first time for a particular ship, an evaluation should be made which should include:
1) the safety margins for stability and srength contained in allowable sea going conditions, as specified in the approved trim and stability booklet and the loading manual relevant to individual types of ships.
2) Account should also be taken of the loading conditions and the envisaged ballast water exchange method or methods to be used
3) the ballast pumping and piping system taking account of the number of ballast pumps and their capacities. size and arrangements of ballast water tanks.
4) the availability and capacity of tank vents and overflow arrangements, for the flow-through method. the availability and capacity of tank overflow points. prevention of under and over pressurization of the ballast tanks.
Particular account should be taken of the following:
1) stability which is to be maintained at all times and not less than those value srecommended by the Organization or required by the Administration
2) longitudinal stress and where applicable torsional stress values, not to exceed permitted values with regard to prevailing sea conditions
3) exchange of ballast in tanks where significant structural loads may be generated by sloshing action in the partially filed tank to be carried out in favourable sea and swell conditions such that the risk of structural damage is minimised.
5) wave-induced hull vibrations when cairying out ballast water exchange.
6) limitations of the available methods of ballast water exchange in respect of sea and weather conditions.
7) forward and aft draughts and trim, with particular reference to bridge visibility,slamming. propeller immersion and minimum forward draft.
8) additional work loads on the master and crew.
Ref : Ballast Water Exchange Guidelines by IMO
