Günter Wichmann

Spectacular container losses on the high seas

Even the largest and most modern container ships lose containers. And when the cargo comprises cigarettes, perfume, or electronic equipment, it is not rare for a single container to contain values amounting to US$ 1–2m. The values can be substantially higher in the case of works of art, antiques, or precision machines.

Containers are a symbol of modern and efficient global trade, more than 95% of which is handled via sea routes. Container traffic has undergone particularly intense development. In recent years it has increased by an average of 10% a year. Even now, container ships are sailing the seas with a capacity of more than 10,000 TEUs (Twenty Foot Equivalent Unit).

Studies suggest that ships capable of holding up to 15,000 TEUs may soon be built. Such mega-container ships represent accumulations that would have been inconceivable just a few years ago. In contrast to the horizontal hold distribution of conventional dry-cargo ships with tween decks, container ships are characterised by the vertical separation of the holds.

Containers below deck are safer

All containers below deck are stacked in cell guides. To open the holds, the hatch covers — usually so-called pontoon covers — must be lifted ashore by cranes.

The containers stowed on deck (deck containers) stand on the hatch covers or stowage devices and are held in place by various lashing systems. In the case of open-top container ships, the cell guides extend from the bottom of the ship in the hold to the uppermost row of containers, meaning that containers do not need to be lashed in place on these types of ship.

The number of deck containers has constantly increased in recent years. Depending on the size of the ship, up to ten tiers of containers can be stowed on top of each other below deck, with up to eight tiers above deck running across the entire width of the ship. For reasons of stability, it is common for only light or empty containers to be stowed in the uppermost tier. Thus, up to 60% of containers today are transported on deck with no additional protection against the elements.

Ship rocking leads to damage and container losses

In addition to the ship's poor stability — often resulting from uncertainty regarding the actual weight of the stowed containers — parametric rolling (unstable roll motion suddenly occurring in head seas) commonly lead to damage and container losses. The economic pressure of adhering to tight schedules also frequently results in the ship's command misjudging the weather and the sea state and the forces to which the ship and the containers are exposed.

All deck containers together sometimes result in a gigantic wall and thus represent a huge surface that is exposed to the wind. In connection with the rolling motion of the vessel, caused by the sea state and swell, the containers in the upper tiers on deck, in particular, are sometimes exposed to intense transverse acceleration forces.

These acceleration forces, the pitching of the vessel, and the spillage of sea water on deck in rough seas (green water) exert a severe load on the deck containers and all elements of the lashing system. The outer container rows have no protection against green water, with the result that the container walls can easily be smashed in rough seas and the cargo inside the containers destroyed. Cargo that has been inadequately secured or not secured at all can slip and often contributes to a complete stack of containers being lost.

Total loss of a fully laden container ship remains exception

While the total loss of a fully laden container ship remains the exception, between 2,500 and 10,000 deck containers are estimated to be lost overboard each year, replete with their cargo.

Containers that are lost overboard often drift in the sea for several days, representing a hazard to shipping. As they are difficult to salvage outside of ports, they are usually lost together with their cargo. The impact on the environment is another aspect that should not be forgotten because deck containers are often loaded with dangerous goods. It cost several hundred thousand euros, for example, to locate and salvage three containers containing drums of wood preservative that fell overboard off the Dutch coast in December 2003.

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