By Daniel Canty
Few hazards onboard a freight vessel are as dangerous to a crew and cargo as fire. Conflicting advice relating to the safety and longevity of the latest generation of suppression systems has caused confusion for ship owners. SFME clarifies the clean agent question.
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 CO
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 CO
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.
With the benefits offered by clean agent systems extolled by the fire suppression professionals, it seems odd that some controversy surrounds their implementation. "Some class societies have latched onto the idea that clean agents quickly become toxic if too much gas is discharged into the compartment," explains Micheli. This is true of many gases, not just clean agents, and this is the reasoning behind the strict design concentration rules that have been introduced for extinguishing agents both for land and marine application. The LOEAL (Lowest Observed Adverse Effect Level) and NOAEL (No Observed Adverse Effect Level) score of HFC's such as FM200, is very close to the upper permitted limit. "This means that there is little margin for error in determining the correct design concentration of these gases for the size of compartment to be protected."
This remains one of the principal reasons why European class societies are so adamant that compartments should be measured to net volume, rather than gross. "The reality however, is that all approved clean agent systems on the marine market today have been tested thoroughly and will normally have a 20 - 30 % safety factor in-built into the system, so one can have the confidence that there is enough gas in the system to extinguish the fire," she adds. Some class societies such as RINA and MCA require that the systems be manual only release (as opposed to automatic) and that they be equipped with a pre-discharge alarm system, providing sufficient warning for personnel to evacuate.
A further controversy surrounding clean agents is just how long they are going to remain available on the market. An engineered fire system on board a commercial vessel is a considerable investment, and it would be a shame to find your system became obsolete before the end of its forecast working life. "Dupont who manufacture FE-227 accept that eventually HFC-227 will be phased out, just as new improved agents are coming onto the market, but insist that this is not something which will happen within this decade," says Micheli. Certainly not within the lifetime of a fire system bought today, and probably, if and when it is phased out, as with the Halon systems, a certain amount of leeway will be accorded to systems already installed.
All in all, clean agent systems offer a flexible, lightweight alternative. Cost-wise they fall somewhere between CO
engineered systems and watermist, and occupy a fraction of the space on-board. "With the expiry of the Dupont patent on HFC-227 in a couple of years time, the price of this agent is bound to drop," explains Micheli.
For those vessels requiring Halon replacements, Kidde-Fenwal have developed an FM200 system which can, in 90% of cases, use the original Halon pipelines, with consequent saving of costs and installation time.
Clean Agent systems, to date are approved for unoccupied or not normally occupied spaces such as engine rooms, generator spaces, and ro-ro areas, (similar to where CO
systems would be deployed). "Normally in accommodation areas or areas where there are likely to be lots of people, we would supply a watermist or water based sprinkler system, along with a mixture of hand-held extinguishers, including both powder and foam. While these systems may take longer to extinguish a fire, they are innocuous and therefore will not endanger life," explains Micheli.
Recent commercial fire casualties such as the Hyundai Fortune were thought to originate in containers on board carrying mislabelled hazardous goods. As these fires began outside the realm of a traditional fire suppression system it is comforting to know that there are systems available which can be deployed in containers carrying hazardous goods. "These could be clean agent, such as our Marine Fire Suppression systems which are bracket mounted to the side or ceiling of the container and are automatically activated by way of a thermally sensitive glass bulb which is housed in the centre of the cylinder valve. This is designed to burst at 79°C (or whatever temperature limit one requires) thus discharging the system." Clean agent systems are again advantageous in cargo containers, as they do not leave a residue, so are completely safe for goods and equipment inside the container.
Consequences of an onboard fire range from downtime whilst repairs are carried out in drydock, to the catastrophic loss of life to crew. Either spells a disaster for an owner, and ensuring the very best, most suitable system is installed and correctly maintained is an essential responsibility that cannot be allowed to take a backseat.