Last reviewed 13 February 2013

Almost all goods to be shipped are containerised. Although the containers may appear indestructable, when things go wrong, the consequences are far-reaching. Richard Masters discusses the importance of safe stowage for dangerous goods.


Imagine being in charge of 225,000 tonnes of goods in a warehouse of well over 2.25 million sq ft with a cubic capacity of over 18 million sq ft. Included in those goods are every kind of commodity known to man, from low value scrap metal to top value computer chips and art works. Mixed in with these is every kind of hazardous substance used in manufacturing and processing: flammable liquids and self-reacting substances, corrosives, toxics, gases, peroxides and oxidisers.

That may seem reasonable so far, but imagine that it is not possible to see any of these goods; all the packages are packed into identical steel boxes stacked in tiers in inter-linked cellars 75 ft deep beneath ground level and stacked 50 ft high above ground level. Also, the whole mass is afloat — pitching, rolling, swaying and twisting — subject to extreme wind and wave action, only then can some idea of the responsibility of a container ship’s captain be conveyed.

Containerisation so dominates world trade that the only goods not routinely packed into containers are crude oil and oil-derived fuels — iron ore, coal and grain. Even shippers of higher value raw metal ores and grain are beginning to find that ease of final delivery and stock control make containerisation a viable alternative to shipping in bulk.

Returning to our container ship, the largest container ship working today has the TEU capacity of 16,000, ie there is space for 16,000 20 ft containers. At about 145 sq ft per container, that gives a theoretical floor space of 2,340,000 sq ft on which to load goods, and a cargo capacity of over 18 million cubic feet. Such ships are about 1300 ft long and 175 ft wide, far exceeding the size of the QE2 liner.

What drives this need for ever-increasing vessel size is simple economics. Crew size is one factor: the number of personnel required to operate a ship does not increase exponentially with the size of the ship, so a similar sized crew can operate a medium-sized or very large container ship equally well. But the chief driver is the ever-increasing price of oil, and fuel now accounts for over 50% of a vessel’s operating cost.

These much larger ships carrying a huge number of containers have made the smaller workhorses of the shipping fleets (6000–9000 TEU containerships) uneconomical on the major east-west trade routes in the comparatively short time span since the economic crash of 2008. Ships now being built for delivery in 2013 are expected to have a TEU capacity of 18,000.

Impact on dangerous goods

Having this many containers on our “floating warehouse” sharpens the issues for shippers and carriers when considering how to carry dangerous goods by sea.

When dangerous goods are loaded into containers they look inviolable, secure and fire resistant. It seems counter-intuitive but when viewing film of container ships in distress (see m/v Hanjin Pennsylvania, m/v Hyundai Fortune, m/v Charlotte Maersk and most recently the m/v MSC Flaminia) we see that cargo in containers burns very well, for days and sometimes weeks.

If chemical reaction or fire breaks out among containers stowed in their tiers and rows on ships, the container, instead of protecting the cargo from direct and radiant heat, allows internal temperatures to rise to combustion point while preventing water from reaching the seat of fire and cooling it, even if the seat can in fact be located and accessed.

Once dangerous goods are stowed on ships they cannot be accessed, so they have to be placed in a safe stowage location from the outset.

The result is that any risk of chemical reaction amidst the cargo that can result in emission of heat or destruction of protective packing must be minimised. For this reason we are seeing a gradual tightening of the rules for the carriage of dangerous goods by sea, reflecting concern at the enormous economic consequences of a major dangerous goods incident occurring on these huge vessels.

The carriage rules are tightened through revisions of the International Maritime Dangerous Goods Code (IMDG Code), the rule book for carriage of dangerous goods by sea. The constriction is effected by introducing into the Code additional controls on individual substances that have been noted for causing difficulties. Substance carriage restrictions are applied across the board to all types of vessel, equally to cross-Channel ro-ro ferries and the new giant container ships.

Segregation rules — why ADR and IMDG Codes differ

Leaving aside the extremely challenging requirements for transporting explosives and radioactive particles, a quick glance at the segregation charts in Chapter 7.5.1 of ADR 2013 and Chapter 7.2.4 of the 2012 IMDG Code tells the reader that the segregation restrictions in the IMDG Code chart are more stringent than those in ADR/RID.

This means that, in general, a greater physical distance is required between different types of dangerous substance when they are carried by sea than is tolerated for road and rail carriage.

Example 1

For transport under ADR/RID rules, the table in ADR Chapter 7.5.2 informs us that there is no restriction when packing a Class 4.1 flammable substance with a 2.1 flammable gas, a 5.1 oxidising substance, or a Class 8 corrosive substance, whereas the table in Chapter 7.2.4 of the IMDG Code prohibits all these combinations.

Example 2

Organic peroxides of Class 5.2 may be carried by road or rail in a cargo transport unit along with goods of Class 2, Class 3, Classes 4.1, 4.2 and 4.3, Class 5.1 and 5.2, Class 6.1 and 6.2, Class 7, Class 8 and Class 9. However, under IMDG Code rules, the table in Chapter 7.2.4 informs us that only goods of Class 5.2 and Class 9 may be considered for joint carriage in the same cargo transport unit with Class 5.2.

At sea there is the potential for serious consequences arising from a simple chemical reaction, or even a simple mis-stowage of a self-heating substance that does not exist in the road or rail modes. A chemical reaction can rapidly escalate, communicating from container to container, leading to the types of major incident mentioned above.

Many shippers are puzzled by the differences in the segregation rules between the modes. They are led to offer mixed hazard consignments that do not comply with IMDG Code segregation rules because they base their cargo transport unit packing decisions on principles of segregation they have learned from preparing consignments for transport under ADR/RID rules.

If this error is not picked up at an early stage before placing the booking with the shipping line, and certainly before the container is packed, delays, cost over-runs and frustration will result for the shipper.