.8 minimum/madmum forward and aft draughts;
.9 wave-induced hull vibration;
.10 documented records of ballasting and/or de-ballasting;
.11 contingency proced:res for situations which may afea the ballast water exchange at sa,including deteriorating weather condhions, pump failure, loss of power, etc.;
.12 time to complete the ballas waer exchange or an appropriate sequence thereof, taking intoaccount that the ballast water may represent 50 % of the total cargo capacity for someships; and
.13 monitoring and controlling the amount of ballast water.
2.2 lf the flow through method is useed, 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 capacitycould be needed to be efeaive when filling clean water fom the bottom and overflowingfom the top; and
.3 cerain watertight and weathertight closures (e.g. manholes) which may be opened duringballast exchange, should be re-secured.
2.3 Ballast waler exchange at sea.should be avoided in feezing weather conditions. However, when it is deemed absolutely necessary, particular anendon should be paid to the hazards associated with the feezing of overboard discharge arrangements, air pipes, ballast system valves together with their mears of control, and the accretion of ice on deck.
2.4 Some ships may need the fitting of a loading instmrnent 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 he safety margins for sability and strngth contained in allowable seagoing conditions specifed in the approved trim and snbility booklet and the loading manual, relevant to individual types of ships and loading conditions. ln this regard partimlar account should be taken of the following requirements:
.1 stabiliqv to be maintained at all times to values not less than those recommended by theorganization (or required by the Adminimadon);
.2 longitudinal stress values not to exeed those permitted by the ship's classification society with regard to prevailing sea conditions; and
.3 cxchange of ballast in tanks or holds where signifcant structural loads may be generatedby sloqhing action in the partially filled tank or hold to be carried out in favourable sea andswell conditions so that the risk of strucmral damage is minimized.
