Tuesday, April 4, 2017

Mystery of Sinking Ore Carriers Raises Concerns on Freight Vessel Design and Cargoes

Is Size of Vessels to Blame, or Anomalies in Cargo?
Shipping News Feature
SOUTH ATLANTIC – WORLDWIDE – The sinking of the 266,000 tonne Very Large Ore Carrier (VLOC) Stellar Daisy on Friday has once again raised the issue of the safety of such huge vessels and of the nature of their cargoes. The ship apparently went down rapidly with the crew able to send out only one brief text to alert the owners, Polaris Shipping, that the vessel as going down. Of the 24 crew on board two have been recovered and hope is fading of finding any more survivors.

The ship was sailing from Brazil to China with a load of iron ore when it broke in two some 2,300 miles off the South American coast, according to the Uruguayan navy. By all accounts the weather was not severe, though conditions in the South Atlantic are notoriously changeable, and now speculation has begun on the cause of the sinking.

After the sinking of the containership MOL Comfort in June of 2013 and the subsequent investigation made ship owners and builder aware of how the increasing size of ocean going vessels was affecting safety as the stresses put upon such ships and the steel they were made from hadn’t been properly appreciated. A number of modern vessels required strengthening refits before being returned to service.

With VLOCs being true monsters of the seas it is possible that again the safety margins in their construction have been under anticipated for the life service of the ship. The Stellar Daisy was launched in 1993 and perhaps such ships fatigue life is lower than anticipated due to their very size.

Another theory had resurfaced as well concerning the stability of the sort of cargoes VLOCs carry. A number of ore carriers have sunk suddenly in the last twenty years with little explanation which in 2011 led to some safety experts theorising on the nature of large loads of ore, especially those from clay bearing ores. Though these may appear to be in effect solid they in fact can contain large quantities of water and have shown the ability to liquefy under certain circumstances. This mechanism is little understood but in a vessel carrying tens of thousands of tonnes of material to suddenly have a load start sloshing around in its hold, something that they were never designed for, it is feasible that such as event could cause a catastrophic failure in a vessel’s structure.

Until more details come to light on this latest sinking it is hard to draw a conclusion, but the number of modern super-massive vessels sinking is perhaps cause for enough alarm for more thorough scientific investigation into both ship design and material and in the nature of their loads, especially as the growth of vessels is now seen as an imperative in vessel owners under pressure to keep rates low.