MARIN (Maritime Research Institute Netherlands) lashing@sea project

MARIN (Maritime Research Institute Netherlands) lashing@sea project.

A monitoring campaign of five ships in operation, model tests of secured cargo and an extensive survey asking crew for their input was conducted in the container, ro-ro and heavy lift sectors. A consortium of 24 participants representing flag states, classification societies, shipowners and lashing equipment manufacturers, as well as crew from nearly 160 vessels, took part in the project that was sponsored by the Dutch government.

The Dutch government, together with British and Swedish maritime administrations, is set to make several recommendations to the International Maritime Organisation (IMO) and the International Association of Classification Societies (IACS) to improve safety levels and operational efficiency. The industry-wide project was led by the Maritime Research Institute of the Netherlands (MARIN) and the project was named lashing@sea project.

Although the report is from 2010 most conditions and data are still valid, except for the present day mega container ships.

Monitoring Campaign on Five Vessels

To examine cargo-lashing security in more depth, the group instrumented five vessels; two containerships, two ro-ro vessels and a heavylift ship. Results from the ro-ro and heavylift ships correlated with the design assumptions, but the containership data revealed effects that called for attention.

Container Vessels

MARIN measured accelerations along the entire hull of two container vessels, one operating in the North Pacific and one between North Europe and the Far East, for 18 months and three years respectively. Containers in the bottom and higher in the stack were also instrumented. In addition, a model test campaign was performed examining containers stacked in three rows next to each other.

Findings Monitoring Campaign

The project found that accelerations on a ship can be amplified by 50% because of the ship’s hull flexing. Both the encountered weather and the measured values were still inside design limits, however, the impact of unexpected, impulsive loads by wave slamming was clear.

Container stack dynamics were also examined by model testing with multiple rows of containers. Initially, all of the rows moved from port to starboard within expectations. However, there was a severe change when one or two of the rows were destabilised by adding weight and loosening lashing. The effect on the properly secured row was dramatic, with loads increasing up to 200%.

Although the tested configuration was “out of design”, this illustrates how loads in properly secured rows are sensitive to factors such as weight and lashing integrity and the consequential impact this has on neighbouring rows. Extra loads, in combination with other unfavourable factors, could potentially trigger a collapse of containers or securing. The probability of such events could not be evaluated within the scope of the project.

Feedback from crew:

Interviews with crew found that some 50% of those that responded said it was difficult to judge the force of developing wave and cargo loads on the very large container vessels from the bridge. This makes it impossible to evaluate whether loads remain in safe limits and when preventative action to avoid damage needs to take place.

Onboard guidance:

Onboard guidance should be provided to assist crew to identify potential problems such as recognising developing hazardous situations, how to avoid extreme rolling and slamming and how to handle extreme GM in partial load condition.

Page 36 of the report:

The effect of a wave slam is experienced in the aft ship as well. The impact passes through the hull as a travelling wave and when reaching the light and flexible aft structure results in a peak acceleration of similar amplitude as the original slam in the bow.


These big ships apparently don’t always behave in a sea as expected. Reminds me of the MOL Comfort:

The difference of course is in the case of the Comfort it was the hull that failed instead of the cargo lashing system.

From that post about the MOL Comfort:

For Post-Panamax-type vessels such at the MOL Comfort, ClassNK notes this is a particularly tricky situation as the hull form has greater beam and thus higher hydrostatic pressure acting on the hull than Panamax vessels. In addition, with an engine room located mostly aft, the ship is in a perpetual hogging condition its entire life.

There are lashing issues particularly relevant to large container ships. The sheer scale of the lashing arrangements on larger ships makes it difficult for a crew to check them against the CSM and a feeling may prevail that there is little danger to the ship if some containers are lost and that it is charterer’s problem. The larger the ship, the more lashing equipment there is to maintain. Maintenance is not an easy task to keep on top of and incidents do occur because of defective equipment.

The increasing number of containers on board has an obvious effect on the time taken to lash and unlash them, much to the concern of charterers. The use of fully automatic locks, such as those designed to disengage when there is a slight slew of the container around its vertical axis, has raised questions as to whether this sort of movement may be reproduced at sea in heavy weather.

Fully automatic locks were reportedly in use throughout the deck on the Svendborg Maersk. The Danish Maritime Accident Investigation Report comments that these locks reach their minimum breaking load at lower forces than semi-automatic locks and allow stacks to swing considerably due to higher vertical tolerance. The report does not conclude on the causative effect of these locks. This is obviously a complex issue and it appears further investigations are being made. In at least two of the significant container loss cases, fully automatic locks were in use and it was surprising that in both cases it was the owners providing fully automatic locks, albeit with the charterer’s approval. The concern surrounding the use of the locks, or at least the suitability of certain designs, continues.

MacGregor C8A fully automatic twistlock.

The Accident Investigation Report ended with this phrase:

The ship’s robustness to withstand adverse weather conditions without compromising the safety of the cargo had been reduced following the optimization of the cargo capacity.


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Bottle screws are a piece of equipment that requires most oversight. They are susceptible to being bent and crushed and need to be kept in good working order. Has anybody done the sums to see if it is possible to conduct any meaningful inspection of the lashing equipment by the crew available on these mega container ships.

The quest for increasing the number of containers per salaried crewman has consequences.

24,000 containers / 24 crew = 1000 containers per crewman. Perhaps half the crew is available to check lashings, so it becomes 2000 containers per available crewman. Therefore in a 4 hour watch the crewman needs to check 500 containers an hour.

Are we seeing diseconomies of scale?

The solution is obvious: larger autonomous ships. No pesky, error prone crewmen to get in the way. No one to notice when a few containers go missing. What containers? Where you say? 99% of World container volume still manages to arrive at destination. Nothing to see here. Move along. No problem.

The advantages of using 100,000 TEU autonomous ships are obvious. We won’t need very many of them, so traffic will be greatly reduced. Fewer fishermen rundown. Less whale song disrupted by propellor wash!


The only thing the deck crew typically checks are the hatch cover securing devices and the lashing rod turnbuckles which only so up so far. They do not check all the containers. The ones below deck are stacked in cell guides. On deck the containers stacked above the lashing gear are inaccessible. The deck crew, when checking, would typically walk across the deck grabbing the lashing rods. The turnbuckles on the ones found loose would get tightened.


Yes, of course.

Barge lashings are all chain. They usually go up to the top of the fourth or fifth tier with just one container above them on twist-locks. There are usually extra diagonals leading inboard. Sometimes there will be a few bridging chains across the top.

Barge lashing cannot be checked or tightened without going alongside the barge and putting crew aboard. This is routinely done before departing protected waters for long exposed legs of the voyage.

In the Alaska trade, containers are usually stacked athwart ships to reduce the likelihood of containers rolling off.

Perhaps loading the containers athwartships would be part of the answer to reduce container losses on large container ships.


The normal excuses of going too fast and too close to shore with badly stowed/secured and lashed deck cargo.

Wouldn’t this be a simple tech opportunity? The study used a grid of accelerometers on the hull. This seems a simple thing for a developer to integrate into a hull/cargo stress early warning system for the bridge. If unsafe accelerations are known/calculable for a vessel class, with real-time accelerometer feedback the watchstander should be able to be warned to take corrective heading/speed action before it gets untenable.


It is somewhat disappointing that Marin does not come further then naming four possible phenomena that might have caused the loss of all these containers.

I mentioned earlier the dangers of hitting the sea floor causing a very destructive jolt, same applies for slamming. Marin mentions this as the second phenomenon as a possibility for the loss.

What I think could be a serious problem is lateral jolting by wave impacts. As far as I know lateral jolt has not been studied yet anywhere. The acceleration caused by a jolt (not m/s^2 but m/s^3) is much more serious then by a roll. Steel bars and deck fittings could easily snap under these circumstances.

In general the design limits of lateral accelerations assume prudent seamanship.

I wrote this before and as you said it is a serious possibility. Hitting the sea bottom will produce a jolt or jerk which is the rate of change of the acceleration with a short duration with a magnitude of m/sÂł. This can also be expressed in standard gravity per second (g/s).

Marin continues the investigation with three container ships with different lengths. It will be pretty hard or even impossible to arrive at a definite and proven cause of this accident. We will wait and see…

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