Why are containers lost overboard? Part 1
“I don’t believe it is possible for a crew of 20 or so on a +20K VLCS to inspect the lashing of every container while loading, nor to make sure that the lashings are kept tight during the voyage.
Anybody here who can come up with an idea for how to avoid stack collapse on VLCSs?”
From the Maritime Safety Innovation Lab :
The majority of stack collapses are associated with heavy weather or the aftereffects (swell) from heavy weather (see Maersk Essen report). Avoiding these areas and being aware of possible parametric or synchronous rolling would go a long way towards avoiding stack collapse.
Most commercial weather programs have a method of displaying IMO resonances that indicate if the vessel is approaching or in areas where these are possible.
As can be seen in the above polar diagram displaying the IMO resonances, the vessel is very close to/in an area where synchronous rolling is possible. The wind waves and swell are close to the starboard beam and care should be taken. This care could include a speed or course change to ensure the vessel’s vector doesn’t get into the area of synchronous rolling.
However, the mariner needs to be aware that these tools are available and are trained in the use of the commercial weather program. Like so many pieces of software/technology on a vessel, they are frequently introduced with no training. This can lead to recriminations after a casualty, where systemic issues (lack of training throughout a fleet) are causal in nature, yet the responsibility and accountability for the loss fall on the operator’s shoulders.
Additional Reading and Links
Gard P&I : Why do containership stacks collapse and who is liable?