PARAMETRIC ROLLING RESPONSIBLE FOR MAERSK ESSEN LOSS OF CONTAINERS SAYS DMAIB REPORT
The Danish Maritime Accident Investigation Board (DMAIB) has published its report on Maersk Essen, the ship that lost approximately 250 containers on 16 January 2021 while the ship was en route from China to Los Angeles. The number of lost containers was later adjusted to 750.
Analysis 1 Loss of cargo: DMAIB has found that the cargo stowage and securing operations on Maersk Essen were open to uncertainties and variabilities which could influence both the forces acting on the container stacks and the holding capacity of the cargo securing equipment. By themselves, these uncertainties and variabilities did not have the potential to cause the container stack collapses seen on Maersk Essen.
Parametric rolling is the suspected cause of the loss of containers from Maersk Essen. Photo credit: DMAIB
2 Heavy rolling: The investigation of the heavy rolling on the day of the accident concluded that Maersk Essen most likely experienced parametric resonance, possibly in combination with pure loss of stability on a wave crest. This resulted in large roll angles building up during a six-minute period.
3 Weather routing: DMAIB has examined the tools for predicting risk of parametric resonance made available to the company’s fleet. Common to them was that they were dependent on forecast data. Forecasts are encumbered by uncertainty and will vary depending on the weather suppliers’ data sources and calculation models. The parametric risk calculators were found to be prone to this type of uncertainty, which can result in misleading indications of risk.
Conclusion [1] Probable cause: The investigation determined that the heavy rolling was most likely a result of parametric resonance. The acceleration forces acting on the container stacks during the heavy rolling exposed the cargo securing equipment to stress loads which they were neither designed nor able to withstand. Maersk Essen’s loading condition required the ship to avoid roll angles exceeding 19.18° in order to stay within the stress load limits defined in the ship’s loading and stability computer. This limit was exceeded at the time of the container loss.
[2] Lessons learned: Detecting the risk of parametric resonance rolling based on forecast sea conditions can be problematic as they are encumbered by uncertainty. No matter how automatised and detailed the onboard tools for monitoring parametric resonance are, they are prone to the uncertainty of the forecasts which makes them unreliable as tools, unless a broad risk margin is applied. Download the full report at
https://bit.ly/3JdjmeN.
USCG SAFETY ALERT ISSUES ABOUT DANGEROUS GAS BUILD-UP IN FISH HOLDS
This story, alarmingly, is not the first of its kind to reach IIMS. A similar lifejacket clinic at Eastbourne a couple of years ago also revealed a high level of defective flotation devices, some with serious flaws. But is seems the public is not listening and learning.
A recent lifejacket clinic organised by Fowey RNLI found an astonishing 50% were faulty or condemned. The lifejacket clinic invited a team from Ocean Safety Ltd in Plymouth to carry out vital safety checks on a total of 169 lifejackets.
The Report • June 2022 • Issue 100 | 25
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