Fighting fires on ships

Malcolm Latarche
Malcolm Latarche

14 March 2017

All basic training for seafarers includes some element of firefighting and those with special responsibilities will need to take advanced courses in order to progress their careers. A basic course will last around three days and covers the different types of fires, how fires can start, how to prevent and fight fires, search & rescue, confined spaces and emergency procedures and the equipment used. Once at sea, regular drills and exercises should reinforce the basic training.

Fighting fire on ships is done in several ways and can involve automatic systems releasing water or fire suppressant gases or by manual means using fire hoses and hand-held extinguishers, buckets and sand. Part of the basic training will cover which type of extinguisher to use in different situations. There are six different types of hand-held extinguishers with each type intended for dealing with one or more of the different types of fires and completely unsuited for others:-

  • Powder fire extinguishers are ideal for use in mixed risk environments. They are the only effective solution for fires involving flammable gases.
  • Foam fire extinguishers are ideal for use on fire involving solid combustible materials and are highly effective on flammable liquid fires. The layer of foam applied by these extinguishers helps to prevent re-ignition after the fire has been extinguished.
  • CO2 fire extinguishers are suitable for use on flammable liquid fires and are extremely effective at extinguishing fire involving electrical equipment.
  • Water fire extinguishers are suitable for use in environments containing solid combustible materials such as wood, paper and textiles. They should not be used around electrical equipment (unless water extinguishers with additive are used).
  • Wet chemical fire extinguishers are usually supplied with a special application lance. They are intended for tackling large burning oil fires and are ideally suited to the kitchen/galley environment. * Water mist works on the basis of cooling fire, suffocating it and then cooling the burning media to prevent re-ignition using microscopic particles of water. Water mists extinguishers are ideal for covering areas where multiple fire risks can be found.

Manual fire-fighting when not involving fire extinguishers will be by means of pumps and hoses. A sufficient supply of water for fighting fires is not normally a problem for ships unless the pumps and hoses are damaged or inoperable or if the vessel is at a berth where it either lays aground or where the water depth is very shallow. In the latter cases it is always a wise precaution for the ship’s officers and crew to ensure that a shore hydrant is available nearby.

Unlike fighting fires ashore where the volume of water used is not an issue, at sea an excess of water is highly dangerous and cause the ship to capsize. Water can also react with some cargoes releasing hazardous gasses or even further fires and explosions. The new requirement for container ships to carry a water lance capable to penetrate a container may well help extinguish some fires but some believe that it will be a matter of time before the use of such equipment will actually cause a fire to become much fiercer.

The FSS Code and SOLAS contain regulations that cover all aspects of the fire pumps, hydrants and hoses from capacity, placement and numbers, the exact details will be ship specific and will also be dependent on ship type. The regulations also cover ventilation, dampers and fire doors.

It is a sad fact that deficiencies in fire-fighting equipment and procedures are one of the most common causes of port state control non-compliances and detentions. In a concentrated inspection campaign carried out by various port state control regional organisations in 2012, fire drills and fire pumps and hoses were the cause of 13.6% and 13% of recorded deficiencies respectively. These two causes accounted for the vast majority of detentions recorded during the campaign. Issues with fire plans and
fire extinguishers were at the bottom of the list of subjects resulting in deficiencies being recorded with both registering just 1%.
Another area of concern that is also found regularly during PSC inspections and safety audits is ventilators and dampers being seized in the open position. Where the space served by the ventilator is protected by a fixed fire-fighting system especially one using suppressant gas, the inability to close the ventilator can render the system useless. Until there is a repeat of the 2012 inspection campaign it will be difficult to assess if matters have improved significantly.

Water Water Everywhere

A modern ship is required by SOLAS, national and classification society rules to be built with an integral fire-fighting system. Throughout human history, water has been the main means of extinguishing fire and this is also true on board ships. In most instances ships are surrounded by a ready source of water that only need be transported to the source of the fire.

A ship’s main emergency fire system consists of a specific number of hydrants located strategically throughout the ship. A series of dedicated pumps are provided to supply water from the sea chest to these fire hydrants. The number and capacity of pumps required for a particular ship type is decided by the regulations covering its size, type and purpose.

A system will inevitably contain numerous valves to isolate parts of the system when maintenance or repair work is needed. The valves connecting the pumps to the sea chest should only be closed when work is being done so that at all other times there will be a ready supply of water to the system. Checking the status of valves is an essential part of regular inspections.

Piping is an often neglected part of the fire system but its condition as important as any other part. A damaged or leaking pipe can render the whole system useless. Pipes for the fire system are generally of steel construction and therefore subject to corrosion. This is especially true of pipes on deck exposed to the open air. Corrosion on these pipes often goes undetected especially if paint is concealing areas of wastage.

A suitable fire hose should be stored close to each hydrant together with appropriate connectors and nozzles. As with the pipes, hoses should be checked regularly for damage. All ships are required to carry an international fire hose connector so that in the event of failure of its own fire-fighting system, a ship in port can have its piping and hosing system connected to a shore water supply. The connector can also be used to connect the system to the pumps of another vessel when in port or at sea.

Power for the pumps will be supplied by the ship’s main power system but an emergency fire pump is also required. The rules governing emergency pumps require them to have their own fuel supply and starting arrangements. Usually the emergency pump is diesel powered and has an electric starting system. An alternative means of starting such as a hand crank is also required. The fuel and starting arrangements need to be checked regularly to ensure that the pump can be started in an emergency.

Little if any of the pumps, hoses and other equipment used on board ships is specifically designed for use solely on ships. However, to ensure compliance with SOLAS, flag and class rules, the equipment must be approved for use on board. Virtually every pump manufacturer that targets the marine sector has equipment that is suited for use in fire systems. Most of the suitable pump models are also used in other ship systems. Hoses, nozzles and connectors are also standard and can be obtained from specialist safety equipment providers.

Less is more where water is concerned

Most modern ships are now equipped with a sprinkler or water mist/fog extinguishing system. In such systems, the sprinkler heads are usually a combined detector unit. Sprinkler systems can also be activated manually if a fire is seen before the system activates. When heat or smoke activates, the head water is released to extinguish the fire.

The types of systems are basically similar in that they use water released from overhead points when activated but the mist systems use less water and have other claimed advantages.

The water for the systems is supplied through the sea chest but there is also a tank of fresh water that is used in the first instance for priming the system so that the standing water in the pipes is not corrosive. Sprinkler and water mist systems can be brought into action faster than gas systems since it is not necessary to close openings, shut down ventilation or evacuate the space before release. The time needed to extinguish fires with water mist can be longer than for gas, but water mist also cools the space and controls smoke in the process. An unlimited water supply is also usually available.

In a water mist system, the water is under pressure and released through a spray head. The small water droplets allow the water mist to control, suppress or extinguish fires by cooling both flame and atmosphere and displacing oxygen by evaporation. The mist is also more penetrative than water from sprinklers and also acts as a smoke suppressant thus preventing other heads from being activated by smoke and so reducing water demand. In short the properties of a water mist system can be summarised as:

  • Cooling effect (quick cooling by evaporation latent heat)
  • Oxygen replacement effect (replacement of air with water vapour generated in a large quantity, and absorption of radiation heat)
  • Shut-off effect (the floating fog forming walls of water)
  • Smoke eliminating effect (the floating smoke particles being adsorbed and settled by the fog)

From the safety point of view, the ship’s stability is far less likely to be compromised by the free surface effect of the amount of water used and, for those systems using fresh water, carrying less of it means more cargo capacity is available or less fuel is needed.

Water mist has been shown to be highly effective at extinguishing fires in both demonstrations and actual operational circumstances. Water mist systems come in both high pressure and low pressure variants. Over the years, the pressure needed to produce the fine droplets has reduced from around 100bar to much lower levels – the Tyco AquaMist system, for example, operates at just 7bar. Another low-pressure system is Autronica’s FlexiFOG. As well as operating at low pressure, the FlexiFOG system makes use of push-fit piping, which is claimed to reduce installation costs by around 25%.

There are, however, still plenty of manufacturers that continue to produce high-pressure systems. Proponents of high-pressure systems argue that the higher pressure produces smaller droplets that aid in rapid extinguishing. The water droplets can expand to almost 2,000 times in size as they vaporise, depriving the fire of essential oxygen. The more droplets there are and the greater the area they occupy the more effective will be the suppression.

Although considered an improvement over sprinkler systems, water mist installations are not without problems. After several vessels were detained in US ports as a result of inoperable systems, a number of flag states and P&I clubs considered it necessary to offer advice on maintenance and checking of systems. It appears that the majority of the detentions are due to systems being secured either by closed supply valves or otherwise by placing the system in a manual mode of operation.

When a system requiring an automatic operation capability is placed in manual mode, the sensors and alarms are not engaged and the system’s quick response capability is disabled. The chances of a fire spreading increase when the protected space is unmanned and the overall effectiveness of the water mist system could be reduced, particularly in terms of time needed to extinguish the fire.

The advice applies to all ships fitted with water mist systems in machinery spaces which will include vessels with engine rooms above 500m3 where a water-based system is mandatory under SOLAS Reg. II-2/10.5.6, and those with smaller engine rooms where a water mist system has been installed by choice. Where the engine room is periodically unattended, local application water mist systems must be fitted with both automatic and manual release capabilities. The following is an example of the advice issued by the Norwegian P&I Club Gard;

  • Make sure that adequate measures are in place to ensure that fixed waterbased local application fire-fighting systems in engine rooms are fully operative and placed in automatic mode whenever the engine room is unattended. These measures should be included in the vessel’s Safety Management System.
  • Make frequent rounds and inspections of the fixed water-based local application fire-fighting systems, paying close attention to valve alignment as well as ensuring that there is adequate labelling to ensure that existing and new crew members will know that any critical fire-fighting equipment must be made available for immediate use.
  • Pay close attention to IMO’s revised guidelines for maintenance and inspection of fire protection systems and appliances (MSC.1/Circ.1432). For example, weekly check of the pump unit valve positions and monthly verification that control, pump unit and section valves are in the proper open or closed position, are recommended for water mist systems.

Gas protection

In addition to water, there are other means that are used to fight fire on ships. Until its use was banned or restricted under the Montreal Convention, many ships used Halon (a CFC) as a fire suppressant because of its effectiveness in extinguishing fires while at the same time posing no risk to persons in the vicinity. Unlike CO2 systems that work by reducing oxygen levels to starve a fire, Halon extinguishes through a combination of heat absorption and some chemical interference with the flame.

In 2003, 3M developed a Halon alternative called Novec 1230 that now forms the basis for fire extinguishing systems produced under brand names such as Unitor and Tyco. Novec 1230 is used as a total flooding agent and its main advantage is that it does not significantly deplete the oxygen content in the area and tests have shown it to be less toxic than Halon 1301. From the environmental point of view, it contains no bromine or chlorine and has an ozone depleting potential of 0 and a global warming potential of 1, making it effectively the same as CO2.

The systems are individually designed and appropriate sized storage cylinders chosen according to the hydraulics and quantity of agent required. The components are designed and tested to operate in the temperature range 0°C to 50°C. The cylinders are generally stored outside of the area being protected although under certain circumstances they can be kept in the same space. Novec 1230 systems are designed to hold both the Novec 1230 in the form of a liquid and Nitrogen which is used to super-pressurise the container to 24.8 bar (360 psi) at 20°C. When the system is activated the contents flow into the distribution pipework to the discharge nozzle(s) where in less than 10 second it is dispersed as a vapour. During the discharge the enclosure will be fogged which may reduce visibility. This normally clears rapidly and should not obstruct the ability of personnel to safely exit the protected area.

Under normal conditions Novec 1230 is a colourless and low-odour fluid with a density around 11 times that of air. It decomposes at temperatures above 500°C and it is therefore important to avoid applications involving hazards where continuously hot surfaces are involved. Upon exposure to the flame, Novec 1230 will decompose to form halogen acids. Their presence will be readily detected by a sharp, pungent odour before maximum hazardous exposure levels are reached. Fire toxicity studies show that decomposition products from the fire itself especially carbon monoxide, smoke, oxygen depletion and heat may create a greater hazard.

The successful performance of a gaseous total flooding system is largely dependent on the integrity of the protected enclosure. It is essential that a room integrity test is performed on any protected enclosure to establish the total equivalent leakage area and enable a prediction to be made of the enclosure’s ability to retain Novec. The required retention time will depend on the particulars of the hazard, but MSC/Circ.848 states that this should not be less than 15 minutes. Longer retention times may sometimes be necessary if enclosures contain hazards that may readily become deep seated.

CO2 systems – A double edged sword

Considering that Halon systems were banned because of their supposed ozone depleting properties it seems a little ironic that the more common replacement other than Novec 1230 is carbon dioxide (CO2) which is also highly criticised as a modern ‘pollutant’ and greenhouse gas. It can be used either as a hand-held extinguisher or as a flooding system.

In a flooding system CO2 is one of the most commonly used fire-extinguishing agents in ships’ engine rooms. CO2 gas has excellent fire-extinguishing capabilities and is relatively inexpensive, but can pose a serious risk to personnel because it works by reducing the oxygen content in the atmosphere.

With CO2 systems, the period between detecting a fire and releasing the gas often seems quite long because crew must evacuate the area to avoid the lethal effects of the gas. As a consequence, minor fires have sometimes been allowed to escalate causing loss of life and even total loss of ships.

Issues with CO2 systems feature in many official accident investigations and advice to the industry is regularly promulgated by insurers, P&I clubs, class societies and other bodies. The concentration of CO2 above certain levels in fire-fighting applications is a major concern amongst fire safety regulators.

Some safety regulators even prohibit the use of CO2 as a fire-extinguishing agent in spaces where personnel has access during normal operation; one such example can be found in the safety regulations applicable to the offshore oil and gas industries in Norway. SOLAS does not prohibit the use of CO2 in systems protecting a ship’s engine room, or other spaces where crew has access during normal operation. But the risks to personnel are clearly recognised and SOLAS calls for various safeguards, such as two separate and interlocked controls, pre-discharge alarms and time-delays, to protect personnel in the engine room. SOLAS does not, however, allow portable CO2 extinguishers to be placed in the accommodation spaces on board ships, due to the associated risk to personnel.

For the typical engine room fire involving flammable liquids, it is important to introduce the required quantities of CO2 quickly to limit the escalation of the fire. Investigations reveal that evacuation, muster and head counts during engine room fires often take longer than expected because crew are not disciplined in mustering. Because of limited storage capacity very few ships can carry enough gas for more than a single discharge. Therefore, if the release of CO2 is ineffective, other methods must be used to extinguish the fire. The re-entry into the engine room following a fire where gas has been used involves perhaps one of the most dangerous aspects of fire-fighting.

CO2 has a limited cooling effect and the temperature of equipment and structures in the engine room may be very high, in particular if the time taken to release the fixed fire- extinguishing system was long. There is a further risk in fire fighters or crew entering the space too soon, thus allowing entry of oxygen-rich air, can cause the fire to reignite. Most advice issued with regard to CO2 systems recommends fostering awareness of the hazards related to their use through detailed and unambiguous procedures, proper training and prescribed maintenance.

Even on ships where safety is given the high priority it deserves, accident investigations do sometimes reveal deficiencies on instructions for using CO2 systems. From a circular on the matter issued by the Norwegian P&I insurer, Gard, the following advice is recommended:

  • Regular fire drills should be as realistic as possible.
  • Emergency response procedures should contain sufficient detail to assist the crew in dealing with all stages of the emergency and should cover: - actions to be initiated prior to release of CO2, instructions for holding/cool down times before re-entering and ventilating the space, lines of communication, both on board and with relevant shore organisations.
  • Evacuation and mustering procedures should include a simple but reliable system for head-counts in order to avoid any misunderstanding concerning the whereabouts of crew.
  • Manuals, piping schematics, instruction placards and labelling of the CO2 system must be in accordance with the actual installation.
  • The person tasked to release the system must be a person designated in the muster list.
  • Maintenance procedures for the CO2 system should include manufacturers’ recommendations and should be based on the IMO guidelines contained in MSC.1/Circ.1318.
  • Periodic servicing of the CO2 system should be carried out by authorised service suppliers. Regular inspections should ensure that evacuation routes and exits in the engine room are clearly marked and kept free from obstructions at all times.

The dangers of CO2 must be continuously stressed and training and experience transfer between crew should create a common understanding of the functionality, limitations and hazards associated with the ship’s specific CO2 installation.

The design of a CO2 system is covered in the FSS Code and will need to be approved by the flag state or the classification society but there are aspects which should be considered as common sense. For example, at least one engine room ventilation fan should be powered by an emergency generator so as to aid in making the engine room safe for entry after use of the system.

In addition, the dangers of a CO2 system are not confined to the spaces they are designed to protect but extend to the CO2 storage area itself. It is not unknown for the cylinders to leak thus creating a suffocation hazard in the CO2 store room. As a consequence, there should be adequate ventilation and the area should be considered as an enclosed space with appropriate procedures in place for testing prior to entry.