In an unprecedented period of container stack collapses between November 2020 and February the following year, some 5,762 boxes were lost from five major incidents, mainly in the Pacific.

The tragic events that winter featured comparatively new vessels, including ONE Apus and Maersk Essen. And, using the average value per container of $40,000 per box, that could be more than $230m in cargo losses – without calculating the environmental damage caused by these stack collapses.

The average annual container losses from ships amounted to between 1,000 and 1,500 containers lost in the decade from 2010 to 2019, with the notable exception of 2013, which saw the loss of more than 4,000 boxes with the sinking of MOL Comfort.

Ship designers have moved to mitigate the level of losses through container stack collapses, with Hyundai Heavy Industries announcing on 1 November its development of extended cell guides that will do away with lashing, saving time and money and making container stacks more stable.

Approved in principle by both US class society ABS and the Liberian flag, the system does away with hatch covers and uses a “portable bench” that effectively transfers the container load to the hull, holding the stack without lashings.

HHI’s development may well become the norm, but current vessels still need lashing bridges and lashing work by both crew and dockers, and the risk of container losses from the existing fleet remains.

As a result, lines enlisted the help of maritime experts at Dutch institute Marin to research the causes of stack collapses, in a three-year programme named TopTier, to solve the mystery of the sudden increase in losses.

According to the World Shipping Council’s latest container loss survey, published in June and covering the 2020-2021 period, last year saw a significant reduction in the losses of the previous year, from nearly 4,000 in 2020 to just over 2,000 in 2021.

However, Jos Koning, senior project manager at the TopTier research project, told The Loadstar that while high-profile incidents, such as the ONE Apus, had declined, the number of losses through less-publicised incidents remained a concern.

“Three to four years ago we wanted to reduce the number of container losses, but then the MSC Zoe incident happened and the project was put on hold pending the investigation report,” explained Mr Koning.

MSC Zoe lost 342 containers off the coast of the Netherlands on 1 January 2019. Dutch investigators, led by Dutch Safety Board member Lianne van der Veen, said the investigation into the incident concluded that the high stability of the vessel caused it to rapidly right itself as it rolled, increasing the forces on the container stack.

However, a master mariner and expert in container shipping accidents believes there could have been another force in play. Automatic twistlocks were used on the higher container tiers to expedite loading.

These twistlocks are activated when the weight of the crane spreader pushes down on the box. According to the master mariner, when a ship rolls in heavy weather the motion of the top tiers of cargo is such that it could replicate the downward force of a crane’s spreader, releasing the twistlocks and resulting in a container stack collapse.

Interestingly, stowage co-ordinator Neil Wiggins, also a former seafarer, said the stowage plans for containerships had been modified over the past two years, with changes to load indicators and alarms effectively reducing the loads placed on stacks.

Mr Wiggins added that the use of semi-automatic twistlocks up to the fourth tier of the stack was now more common, with automatic locks only used on the higher tiers.

“Load factors have become more stringent with the tonnes newton forces recalibrated [on loading computers] to a lower level,” he said, and also pointed to the reduction in stack heights, with loading restricted to just seven high, from nine, for a ship that exceeds the 16-degree rolling motion considered to be safe for the lashing equipment on modern container vessels.

TopTier has recognised the role played by lashing equipment and the commercial pressures that captains and crew come under to load as much freight as possible, particularly at times of high demand.

As a result, TopTier’s investigation, as outlined by Mr Koning, has six areas of interest, with the strength of container lashing equipment top of the list, a working group investigating the safe working loads and strengths of lashing equipment, with the expected deterioration of this equipment during the normal working conditions.

A second area of concern is that, with loading plans devised prior to a vessel’s arrival at port, the physical loading should match the load plan. Very often this is not the case, because a container may not match the declared weight, or some containers may have shifted from one location to another for other operational reasons, which could affect the weight distribution and balance of the stacks.

“VGM [verified gross mass] rules have improved the weight declaration problems for load planners, but there can be other reasons why containers end up in an unplanned position,” said Mr Koning.

A third TopTier investigation is into are the effects of a ship’s motion when sailing. In the first instance, there is what Mr Koning describes as the “classical motions”, those the crew and designers can predict and are worst-case design motions. These should not cause box losses because the vessel and its lashing equipment will be designed to meet these types of movements.

“Extreme motions” as described by TopTier are supposed to be avoided by a crew, through good vessel handling.

These include parametric rolling in following seas, identified by the TopTier researchers as a particular threat to containership operations. These conditions were considered so serious by TopTier that the researchers issued a warning to vessel operators describing how to spot these conditions and how to respond.

“Unfavourable combinations of rolling period, vessel speed, heading and wave conditions can trigger sudden and extremely rapid increase of roll motions to hazardous levels, threatening the safety of vessel, crew and cargo. This can happen in relatively mild wave heights,” according to TopTier’s notice to mariners.

Crew are urged to look out for the signs of parametric rolling in following seas, which can occur when the rolling period of the vessel is twice the wave encounter period and the wave lengths are similar to the vessel length.

The TopTier notice warned: “Even a few high waves after each other may trigger unexpected large roll motions, as shown by the measured time traces of roll and pitch motions in the figure below. In this example, the ship is 240m long with a natural roll period of 32s and is sailing in a 5m following sea.”

A fifth element to the research takes in human factors in the operation of the ship, with the focus on avoiding operational actions that will risk the loss of cargo.

However, Mr Koning stresses that none of these issues can be resolved without a regulatory framework that will see compliance made a requirement.

“All five of these suggestions won’t have an impact if ships don’t comply, therefore these changes need to be enshrined in IMO regulations, and that can only occur if they are supported by a wide enough group and put to the attention of the regulator,” stressed Mr Koning.

At the moment the Netherlands has been joined by Germany and Australia in supporting the research. The project began last year with a review of current practices and was completed by spring this year. Now the project is in the technical investigation phase, which will be combined into a series of proposals in May 2024.

Mr Koning has been impressed by the industry’s concern to improve the understanding of how losses occur, while Mr Wiggins has shown that the industry has already modified its operations in a bid to reduce the risk of losses.

That includes the reduction in the height of container stacks on deck. Mr Koning, however, pointed out that this could only be workable if crew were not driven by commercial pressures to again raise cargo stack levels.

Regulation is needed to create a workable framework within which the industry can operate, and prevent the race to the lowest possible standards for the greatest income.

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