Regulation of container weighing



Aron Sorensen, chief marine technical officer, BIMCO


Shipping is a global industry and with more than 90 percent of international trade being carried by sea, it is the most important element in the world’s supply chain of goods. Shipping cannot fulfil its role without clearly defined rules of play eg. through internationally agreed regulatory instruments with focus on safety of ships, seafarers and environmental protection. BIMCO works to facilitate harmonisation and standardisation of commercial shipping practices while promoting fair business transactions and free access to markets.

When it comes to weighing of containers, the shipping industry already has an international regulation scheme in place. The present regulation two in chapter VI of the International Convention for the Safety of Life at Sea (SOLAS Convention) requires the shipper of containerised goods to provide the ship's master or his representative with the gross mass of the container, prior to loading on the ship, confirmed in writing and with the appropriate shipping documents. Furthermore, the regulation requires that the shipper shall ensure that the gross mass of the loaded (or ‘stuffed’) container is in accordance with the gross mass declared on the shipping documents. The SOLAS Convention does not however require that a container loaded with cargo shall be weighed to verify the documents.

Safety issues

So what is the problem? Unfortunately it frequently occurs that the shipper's declared weight is incorrect. Ships, trucks and port facilities using incorrect weights in the handling and stowage of the container have been the cause or a contributing cause to numerous operational and safety incidents and accidents. For feeder and medium sized container vessels with loading capacity of less than 5,000 twenty-foot equivalent units (TEUs), inaccuracy of container mass could lead to loss of lives and loss of vessels. If a heavy container is declared as light, this container will be stowed in the upper tiers. This is done to ensure that the centre of gravity of the container stack and the overall centre of gravity is kept as low as possible. If the centre of gravity of the ship becomes erratic due to the wrongly declared container masses, this may cause instability or even a negative stability and could cause the vessel to capsize. Furthermore as the ship uses up bunkers from the bottom tanks, the centre of gravity and thereby also the stability will be influenced during its voyage. In June 2011 the DENEB capsized in Algeciras due to a significant stability problem which caused her to capsize. A review after the incident found that out of the 168 containers on the load list, 16 – or roughly one out of 10 – containers had actual weights far in excess of the declared weights. The actual weights exceeded the declared weight in a range from between 1.9 times as much as the declared weight to as much as 6.7 times the declared weight. The total actual weight of these 16 containers was more than 278 tonnes above their total declared weight of about 93 tonnes, making it four times higher than their declared weight.

For larger ships with a capacity of more than 5,000 TEUs, the impact of wrongly declared weights is predominantly restricted to stack weight and lashing violations. As container vessels grow in capacity, more containers are stowed on deck and the strength tolerances are reduced while the breadth of the ship normally ensures sufficient stability.

In January 2007 MSC NAPOLI was seriously damaged in a severe storm. The hull cracked and this caused a flood in the engine room. The ship was later beached off the Devon coast in the UK. The accident was found to be the result of structural failure of the vessel hull skin and girders at the interface between the transverse stiffening of the engine room and the longitudinal stiffening of the cargo area. This was due to the loading on the structure, the containers and the rare sea state exceeding the capacity of the hull girders in this area. During the salvage operation, 660 containers stowed on deck, which had remained dry, were weighed. According to the ‘Report on the investigation of the structural failure of MSC Napoli’, by the UK Marine Accident Investigation Branch, 137 (20 per cent) of these containers were more than three tonnes different to their declared weights. The largest difference was 20 tonnes, and the total weight of the 137 containers was 312 tonnes heavier than on the cargo manifest.

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