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2.0 THE BALLAST VOYAGE
The basis for safe and efficient cargo handling operations begins
during the ballast voyage. For each cargo voyage, the vessel must be
able to demonstrate that it has been maintained in a 'seaworthy' condition
throughout and has done everything necessary for the proper care of
the cargo. To do this, the following should be routine practice:
An approximate guide for the amount of ballast suitable for different weather conditions is:
Wind force Recommended ballast tonnage
up to 4 30% of DWT
4 to 6 37% of DWT
above 6 42% of DWT
Ducted propellers require deeper stern drafts to reduce vibration. The ballast quantity must take account of the draft limitations of the fairway or channel, and the height limitations of overhead bridges and power cables. Required air draft may be achieved by trimming the ship by the stern rather than by adding ballast. If the master believes it safe, he can sail with CBT/SBT ballast only, without taking 'dirty' ballast into the cargo tanks.
If no CBT/SBT capacity has been provided, ballast must be taken into dirty (or crude oil washed), cargo tanks. Such ballast becomes 'dirty ballast' and must be disposed of according to MARPOL regulations. Any oil floating on top of the ballast water may be measured and declared as pumpable cargo by surveyors.