TT Talk – Fire and explosions in containers
Sources suggest that container fires may occur on a weekly basis and statistics indicate there is a major container cargo fire at sea roughly every 60 days. Tackling fires and subsequent investigations are complex activities.
There have been several well publicised ship-board explosion and fire incidents involving laden containers over the past few years. As the size of container ships increases, so does the potential risk and consequence of a large explosion or fire incident. Despite certain regulatory and technical advances, there is little doubt that the capability to respond to a cargo-related fire at sea has not progressed in proportion to ship capacities and the variety of commodities being carried.
“There is little doubt that the capability to respond to a cargo-related fire at sea has not progressed in proportion to ship capacities and the variety of commodities being carried”
Dealing with an incident at sea
The crew will do all that they can to control a container fire incident at sea, be it in the hold or on deck. To help deal with a fire in a hold, a carbon dioxide (CO2) system will normally be installed if the ship is carrying dangerous goods. The gas released from a CO2 system can displace the oxygen in the hold and smother the fire. However, for CO2 to be effective, the hold must be sealed to retain the gas and prevent oxygen ingress. Following an explosion in a hold, the structure may have been damaged or hatch cover pontoons displaced, making the retention of CO2 impossible. Even so, hatch cover pontoons are not designed to be gas-tight, only weathertight, and thus it is likely that the CO2 will escape over time.
Furthermore, CO2 has virtually no cooling effect on combustion; if oxygen re-enters the hold after the CO2 has been deployed, the fire may redevelop. In addition, a CO2 system will not be effective in controlling fire incidents involving hazardous substances that produce oxygen during decomposition.
If an incident has occurred in a container stowed on deck, then inevitably a CO2 system is not viable for firefighting. In this case, water will be the only option available to the crew as a first line of defence. Although water may be beneficial as boundary cooling, and assist in minimising fire spread, it is unlikely to extinguish a fire inside a container in the short term – and the risk of cargo misdeclaration means that water firefighting carries risk and generally may not be appropriate.
“Seeking expert advice will be essential early in the incident”
So what else can the crew do? Seeking expert advice will be essential early in the incident. The expert will need to be provided with as much information as possible, including the location of the fire, the extent and description of the incident and, as a minimum, a copy of the cargo manifest – particularly the location of containers declared as carrying dangerous cargoes.
If the fire is in a hold, flooding of the hold with water may be considered. This will require flooding to above the level of the containers involved and brings many additional problems. There is potential that more damage results from the water than may have occurred from the fire. As the packaging of various cargoes becomes compromised by water or explosion or fire, it is likely that flooding the hold will produce a ‘chemical soup’ with contaminants from a multitude of cargoes. This can result in toxic substances or gases produced by mixing or decomposition (rotting) of the various cargoes.
In addition to the potential for toxic substances and gases to be produced by the ‘chemical soup’, other cargoes are quite likely to be affected by heating or burning, also changing their properties and hazards.
Once an explosion or fire has occurred, an investigation into the cause will normally be required. This can be a very complex and protracted operation in the larger incidents. Most investigations though will follow a basic format. The starting point is often witness or electronic evidence. This will involve gathering accounts of the events from the crew, including ‘where, when and what’. As a lot of crew members now own mobile phones, photographs or videos of the early stages of an event are sometimes available.
Detection systems can also provide valuable information, such as where the smoke or fire was first detected. If the detection system is a gas extraction system (with monitoring/detection carried out remotely) samples or residues can be obtained from the inside of the extraction pipe work. Engine room alarm logs can provide indications of other system failures, such as the electricity supply to hold lighting. All this information may assist in pinpointing or narrowing down the area where the fire event started or explosion initiated.
Once the available witness evidence is collected, an examination of the physical evidence will be carried out, including damage to the ship structure and containers. This may provide directional indicators of blast and or fire movement and intensity. During the physical examination, samples will be taken for laboratory analysis, the results of which may assist in identifying the cause of the event. This, however, can be very complex, often involving a mix of substances, including both the original cargoes and the decomposition substances created in the incident.
Given the potential complexity and the extent of a large explosion on a container ship followed by a prolonged fire, a multi discipline team may be required. This may include:
• Fire investigators
• Cargo scientists
• Marine engineers
• Naval architects
“Much effort is underway internationally between the different stakeholders to prevent such incidents”
Inevitably, due to the implications to the safety of the crew, the ship and the environment, prevention is much better than cure. Much effort is underway internationally between the different stakeholders to prevent such incidents. This ranges from looking more closely at all elements of the cargo shipping process as well as seeking strengthening of ship-board processes.
Source: TT Club