The safe operation of bulk carriers is dependant on not exceeding allowable stresses in the cycle of loading, discharging, ballasting and de-ballasting. Exceeding the permissible limits specified in the ship's approved loading manual will lead to over-stressing of the ship's structure and may result in catastrophic failure of the hull structure.
To prepare the vessel for safe cargo stowage and planning, the loading and unloading sequences and other operational matters should be informed well in advance.
High loading rates may cause significant overloading within a very short space of time. The officer in charge should be prepared to STOP cargo operations if the loading operation deviates from the agreed loading plan.
There are three main problems associated with high loading rates which may result in over-stressing the ship's structure, namely:
i) The sensitivity of the global hull girder shearing force and bending moments .
ii) Overloading the local structure.
iii) Synchronisation of the ballasting operations.
High cargo loading rates may create problems with the ballasting operation as the pumping capacity of the ship may be relatively low compared to the cargo loading rate. In such cases the cargo operation must be stopped to ensure synchronisation with the ballasting operation is maintained.When necessary, the loading rate must be adjusted to synchronise with the ship's pumping capacity.
Handling of deballasting- ship duties
The ships officer should advise the terminal representative of any deviation from the deballasting plan or any other matter which may affect cargo loading.
If the ship cannot deballast at the rate agreed in the loading plan, or if deballasting is causing the ship to list or trim incorrectly, the terminal representative should be informed in good time and arrangements made for the suspension of loading until the ship has resolved the problem.
The ship should be kept upright or, if a list is required for operational reasons, it should be kept as small as possible.
The master should ensure close supervision of the loading operation and of the ship during final stages of loading. The master should advise the terminal representative when final trimming of the ship has to commence in order to allow for the conveyor system run-off.
It is prudent that a draught survey is carried out with about 90% of the cargo loaded.