The vessel was en route from Yantian in China to the US port of Long Beach when it was hit by severe weather in the Pacific ocean and suffered multiple stack collapses. In total, 1,816 containers were lost overboard, including 64 Dangerous Goods containers, 54 loaded with fireworks, eight with batteries and two with liquid ethanol.

The vessel proceeded to the Port of Kobe, where the work of removing containers from the collapsed stacks has begun. Marine claims consultant W K Webster & Co flew a drone over the vessel and ascertained that only six of 22 bays on deck remained intact, from which it estimated that some 2,250 containers will need to be removed.This is slow, difficult work. Shipping line Ocean Network Express has estimated it will take a month or more to clear the collapsed stacks, but W K Webster, which has surveyors in Kobe, said this “may be optimistic”.

Investigations into the cause of the incident are under way, but it is already being speculated that the vessel experienced parametric rolling.This is a problem the industry has been aware of for a very long time.The loss of containers from the APL CHINA in 1998 was attributed to parametric rolling, and the susceptibility of large container ships to parametric rolling in certain sea conditions was talked about even before vessels crossed the 10,000 TEU mark in 2006-07.

Since then more work has been undertaken to understand how dynamic ship stability affects parametric rolling. The IMO included parametric rolling as one of the five dynamic stability failure modes for which it is developing performance-based criteria in the forthcoming ‘Second Generation of the Intact Stability Criteria’ (ISC) it first introduced in 2010.

In a paper published in April this year in the Journal of Ocean Engineering and Technology*, four experts outlined this work, which has been ongoing for 10 years.They noted that investigating stability incidents is difficult and “because these accidents do not occur frequently, it seems impossible to find their causes and develop countermeasures based on experience. Thus, it seems reasonable to think about more quantitative and systematic countermeasures”.

Referring to the pending Second Generation ISC, the authors gave a warning to the Korean shipbuilding industry. “When new stability criteria are implemented, new ships are more likely to have reduced onboard cargo volumes in comparison to existing ships. In the case of existing ships, there is a great possibility that they will be forced to decrease their onboard cargo volume or operating speed, which is expected to have a large impact on future ship operations.” In particular, more restrictive loading conditions “mean that more ships will need to be built than at present”.This would have enormous implications for the industry.

The issue of parametric rolling will, no doubt, receive more attention if the one APUS investigation finds it was a factor in the incident, but the view that the cargo intake of larger vessels needs to be reduced does not seem to be widely shared across the industry.

*‘Current Status of the Second Generation of Intact Stability: Investigation of the Pure Loss of Stability and Parametric Roll Mode’ by Jaeho Chung, Dong Min Shin, Won-Don Kim and Byung Young Moon