- Back in 80-90-ies of the previous century, the rate of bulkers’ loading was already over 10,000-15,000 tonnes per hour. In 1989, I used to load iron ore onto the 127,000 DWT ship of Novorossiysk Shipping Company at the port of Tubarao. The key problem for a cargo officer was neither tilting or stability loss nor the risk of late pumping out of ballast but possible overloading of a ship or a hold with such a fast process (just 9-10 hours) – that is the hull strength.
It was not a special situation and bulkers of that time could cope with it pretty well as well as the crews.
Let’s take it in order.
Total weight of water ballast onboard a bulk cargo carrier is 2-3 times less than cargo weight. So, there is no need to pump out 1,000 tonnes of ballast water when taking onboard 1,000 tonnes of cargo.
When bulk cargo ships start being loaded they do not usually have a sea passage ballast. Their minimal port ballast does not usually exceed 10-15% of cargo weight which lets a ship remain in control.
There are absolutely no problems with stability of tilting.
So, the rate of bulk cargo loading can be increased to 6,000 tonnes per hour, which is a usual practice.
But some problems are possible. The difference between the expected and actual weight can be quite significant. For example, with coal loading rate of 6,000 tonnes per hour a 5-minute delay of the process supervisor can result in a hold overloading with 500 tonnes (plus cargo on the conveyor which should be discharged before the equipment is stopped as required by the operation rules).
So, it is really important to keep a close eye on cargo distribution in the holds. Yet, iron ore which is heavier can cause more problems as compared with coal.
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