Fighting fire

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Prevention cheaper than cure: fire suppression systems are a vital tool for preventing the loss of life and property at sea.

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Hazardous goods: suppression systems can be mounted within containers which discharge when thermically triggered reducing the risks faced by shipping lines from mislabelled goods.

Fire can be devastating on a ship - particularly on a vessel carrying hazardous cargo, with serious risks to crewmembers, ports and harbours. Back in July 2002, a comprehensive set of requirements for fire protection, detection and extinction on board ships entered into force as a new revised chapter of the International Convention for the Safety of Life at Sea (SOLAS).

The regulations were designed to ensure that fires are first of all prevented from occurring - for example by making sure that materials such as carpets and wall coverings are strictly controlled to reduce the fire risk. The regulations were also drawn up to ensure that fires are rapidly detected and that the blaze is contained and extinguished.

However, despite significant attempts made at fire prevention, the challenging aspect of fire suppression has caused some confusion amongst ship owners and operators.

Conflicting advice from classification societies has clouded the issue of what systems are best to deploy, with the complex spectrum of suppression agents and systems now available. The health and safety of crew members is of course paramount, but there has also been significant attention paid to environmental concerns regarding the agents in use.

"The last couple of decades have seen not only numerous changes in materials and choice of fire systems, but also changes in the design and construction materials of commercial vessels," explains Ann Micheli, international sales and marketing co-ordinator, CATEF Marine Fire. "Additionally, the increasing priority given by governing parties to environmental issues, has led to the phasing out of some of the more traditional extinguishing agents." The Montreal Protocol on substances that deplete the ozone layer entered into force in January 1989, and banned the use of Halon, the leading fire suppression agent in the sea freight sector. This ruling was subsequently reinforced by the International Maritime Organisation, which blocked the use of Halon for all new installations. "Over 18 years later, most of the old Halon systems are coming to the end of their working lives, and the question for ship owners of how best to replace them remains," says Micheli.

In the wake of the Halon ban, a myriad of gaseous and other alternatives have come to the fore. While the IMO works hard to consolidate rules and regulations and the many and various methods of evaluating materials, the debate around the safety and effectiveness of fire systems is heating up. In Europe the debate is particularly lively in the comparison of "clean agent" fire systems. There is concern about the safety to personnel who may be exposed to these gases as they discharge, there is confusion as to how protected areas are to be measured, and there remains the question of their environmental impact. For an owner trying to sort the wood from the trees, the conflicting advice from class societies worldwide can be mind boggling.

The burning question remains, what are the extinguishing alternatives for commercial vessels?

"A traditional alternative has been CO2 systems. These benefit from being relatively low cost, and easily replenished worldwide, but because of the high toxicity of the gas, fixed systems can only be used in non-occupied areas of the vessel, with arrangements in place to evacuate the protected area prior to discharge," says Micheli.

Where CO2 is used in garage and engine room spaces, the accommodation areas need to be supplied with other means of extinguishing fire, including portable extinguishers or sprinkler systems.

For larger vessels, where economies of scale can be obtained, high or low pressure sprinkler, or watermist systems can provide effective alternatives to gaseous agents, are completely safe, and can also be extended to use in engine rooms and bilges where oil and fuel based fires are more likely, often by being mixed with foam agents.

Non-corrosive and non-toxic, watermist systems are proving increasingly popular in cruise and passenger ships. In smaller vessels and working boats however, these relatively expensive, high maintenance, systems are also greedy on space, as they require water tanks and pumps with their related weight factor, as well as extensive piping networks.

"Clean Agent" fire systems can be found with a range of gaseous agents, normally HFC's under trademark names such as FM200, and NOVEC 1230. These agents were originally hailed as the perfect replacement to Halon: acting on the heat content of fire rather than taking the oxygen out of the air, these gases are safe for personnel and extremely fast-acting (clean agent systems can extinguish a fire in less than ten seconds after discharge). They leave no residue (so no expensive clean-up as with powder systems), and have a zero-ozone depletion rate.

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