Captain Manjit Handa, a bulk carrier master, reflects on the tragic sinking of the Korean ore carrier.
The loss of the VLOC Stellar Daisy at sea has brought home a feeling that as far as bulk carrier safety is concerned, we are back to square one. A series of well-intentioned and very detailed regulations and standards were adopted in the last 20 years to improve bulk carrier safety, yet Stellar Daisy went down in a copy book fashion, suddenly and caused by a catastrophic structural failure. Even though bulk carrier safety is a work in progress, can we, in the absence of any reliable solution on the horizon, take interim measures to prevent another sinking?
I assume the readers are well-versed with the keywords below that are relevant to any discussions on bulk carrier safety.
Age of ship. Annual Surveys. Assessment of ship’s stability. Asymmetrical cargo distribution. Asymmetrical ballast distribution. Bending moments. Close-up survey. Commercial pressure. Condition of Class. Corrosion. Coating breakdown during discharge. Deformation. Enhanced Survey Programme. Fatigue cracking. Flexing. High loading rates. High Density cargo. High Tensile Steel. Hold inspection. Large hatches. Liquefaction. Loading sequence/ Deballasting plan and execution. Local Strength/ Local loading criteria. Max cargo allowed in each hold. Progressive Flooding. Pounding. Panting. Quick capsizing of bulk carriers. Racking. Residual Stress. Shear Force. Side shell flexing. Side frame detachment. Structural damage during discharge. Transverse Bulkhead strength. Torsional stresses. Twisting of hull girder. Unreported repairs. Warping of the hull girder. Wave excited hull vibration. 2 hrly record of SF/BM.
In order to understand the factors affecting bulk carrier safety, a good document to refer is the IACS publication Bulk carriers – Handle with care since it captures quite well the shipping industry’s best understanding of the issue. The publication identifies nine major risks of hull or local structure overstressing and the consequent weakness (when loading high density cargoes.)
- Deviations from the loading manual.
- Shallow draught loading.
- High loading rates.
- Asymmetric cargo and ballast distribution.
- Lack of Effective Ship/shore communication.
- Exceeding load line marks.
- Partially filled ballast tanks or holds.
- Inaccurate cargo weight measurement during loading.
- Structural Damage
The precautions associated with the above are for the understanding and compliance of both the ship’s crew as well as the terminal operators.
Even though the risks listed above are well understood, control measures are not adequately applied by the operators and other stakeholders with sufficiently rigorous application.
· There is a surrender of responsibility usually by the ship’s crew to the terminal because the terminals’ claim that they have been loading ships since the beginning of time, hence they know best. The ship’s crew balk at stopping the loading if the deballasting is unable to keep up with the loading. There could hence be short spells when SF/BM exceed the permissible limits.
- During loading, we must move away from ‘keeping within permissible stress limits’ and move towards ‘keeping to minimum stress limits’.
- It is pretty common to see terminals trying to minimise the number of pours, sometimes even loading a particular hold to its full load in one pour.
- It is not the average loading rate but the max loading rate for a given time that could induce high local stresses.
- The ship’s crew do not usually conduct a thorough assessment of structural damage after any discharge operation, which is mainly because of the small number of crew and other workload of higher priority.
At the structural level, high risk ships are those that have all of the three factors:-
- bigger than panamaxes
- more than 15 years old
- Carry iron ore.
Most vessels generally start their service life as being adequate to the demands of the sea, but may become inadequate at some point later due to deterioration with age. Also our assumptions of the dynamic loads on the hull due to waves and ship’s motions might be drastically erroneous.
In view of the above, it may be necessary to derate big vessels progressively, by adjusting their load lines to reduce their cargo carrying capacity.
It is also important to improve compliance with safe working practices by:
- A tougher regime of cargo hold inspection (for structural damage) between two annual surveys.
- A more comprehensive recording of SF/BM during any loading/discharging operation.
- A better training of officers and crew on bulk carriers regarding the risks associated with high density cargoes.
- Insistence on all structural repairs to be reported to the classification Society.