.8 minimum/maximum forward and aft draughts;
.9 wave-induced hull vibration;
.10 documented records of ballasting and/or de-ballasting;
.11 contingency procedures for situations which may affect the ballast water exchange at sea, including deteriorating weather conditions, pump failure, loss of power, etc.;
.12 time to complete the ballast water exchange or an appropriate sequence thereof, taking into account that the ballast water may represent 50 % of the total cargo capacity for some ships; and
.13 monitoring and controlling the amount of ballast water.
2.2 If the flow through method is used, caution should be exercised, since:
.1 air pipes are not designed for continuous ballast water overflow;
.2 current research indicates that pumping of at least three full volumes of the tank capacity could be needed to be effective when filling clean water from the bottom and overflowing from the top; and
.3 certain watertight and weatherright closures (e.g. manholes) which may be opened during ballast exchange, should be re-secured.
2.3 Ballast water exchange at sea should be avoided in freezing weather conditions. However, when it is deemed absolutely necessary, particular attention should be paid to the hazards associated with the freezing of overboard discharge arrangements, air pipes, ballast system valves together with their means of control, and the accretion of ice on deck
2.4 Some ships may need the fitting of a loading instrument to perform calculations of shear forces and bending moments induced by ballast water exchange at sea and to compare with the permissible strength limits.
2.5 An evaluation should be made of the safety margins for stability and strength contained in allowable seagoing conditions specified in the approved trim and stability booklet and the loading manual, relevant to individual types of ships and loading conditions. In this regard particular account should be taken of the following requirements:
.1 stability to be maintained at all times to values not less than those recommended by the Organization (or required by the Administration);
.2 longitudinal stress values not to exceed those permitted by the ship's classification society with regard to prevailing sea conditions; and
.3 exchange of ballast in tanks or holds where significant structural loads may be generated by sloshing action in the partially filled lank or hold to be carried out in favourable sea and swell conditions so that the risk of structural damage is minimized.
