Fire Control: Practicalities by Andrew Bray

PRACTICALITIES BY ANDREW BRAY

Where fire is concerned, prevention is certainly better than cure, and common sense precautions lessen the main risks. But if a fire does break out we may have only seconds to save our boat and perhaps our lives, so we must also be prepared to fight.

PREVENTION

Fires have been started by just a pair of spectacles left lying on a cockpit cushion, but the main risks are electrical faults, engines (particularly exhaust systems), devices involving flames (cooking, heating, lighting and cigarettes) and worst of all – explosions caused by ignition of flammable vapours. In each area, there are known practices that reduce the risk.

Electrics
Imagine, for example, a live wire chafes or breaks, or pulls out of a terminal and swings against anything that is connected to the negative side of the battery (eg. the external surface of most engines). The short circuit draws as much current as the copper inside the wire can conduct. This immediately generates enough heat for the wire’s plastic insulation to erupt in flames. Fuses within devices don’t protect against shorts in their supply wiring, so all circuits should be protected at the switchboard by a fuse or breaker of lower current rating than the smallest wire connected to it. Also, intermittent connections can produce sparks that may ignite vapours or nearby materials. Correctly rated fuses and breakers are your main defence against this ever-present source of fire. Engine wiring in particular should be given proper mechanical support so that vibration does not chafe through insulation or fracture wires. Battery terminals and other un-fused connectors should be covered to prevent accidental shorting by dropped tools, for example.  Battery master switches and engine isolators should be easily accessible, outside the engine space.

Smoking
Ignoring any longer term health implications, cigarettes, pipes, matches, and lighters may ignite volatile vapours such as petrol, paint thinners or LPG that happen to be around. And, of course, forgotten cigarettes may also ignite fabrics or painted wood. If a total ban isn’t acceptable then one on smoking below at least reduces the risk.

Cooking systems
It’s true that liquid fuel stoves burning alcohol or paraffin (kerosene) are far less likely to lead to explosions than LPG, but they are slower and less convenient as a cooking medium, and are prone to flare ups, which really do start serious fires.

If possible, stove areas including the deck head above should be lined with sheet metal. All stove fuel supplies should have a remote shut-off in case of a flare up, and those in LPG systems should be closed whenever the stove is not in use. All LPG systems must be installed and inspected to comply with approved standards, but additional features are worth considering, such as Bowden cables or solenoid valves to facilitate routine shut-off, and a “gas fuse” to shut off a major leak automatically. The system should be regularly inspected, paying close attention to flexible hoses connecting to cylinders and gimballed stoves, and potential leak points such as joints and valve stems.

Burners and ovens should have flame failure cut-outs, oven thermostats must work, and saucepans should have lids available for smothering.

Cockpit barbecue units should have close fitting lids and air dampers to permit rapid smothering and be mounted outboard of the rails where a flare-up or dropped embers are not immediately dangerous. LPG barbecues have advantages compared with solid fuel units because they don’t produce sparks in a sudden wind gust, can be shut down immediately and there is no need to carry flammable fire lighting compounds.

LPG fuelled absorption fridges and water heaters depending on pilot flames are accidents waiting to happen, because apart from their own risks, they may ignite vapours originating elsewhere, such as from a leaking paint tin, or a petrol outboard or generator on deck near a hatch.

Heaters
As well as flame failure cut-offs, diesel cabin or water heaters should over-temperature fuel cut-offs too. Heaters and flues should be distanced or insulated from combustible materials and not be left unattended if clothing is being dried. Portable gas and kerosene heaters are particularly dangerous because they can be overturned by a passing wake, as can non-gimballed or unsecured candles and kerosene cabin lamps.

Engines
The combination of high temperatures, fuel, electricity and external belt drives mean that even diesels are a fire threat, especially when out of sight inside a sound proofed box. Fuel systems should use approved (non plastic) hoses, leaks should never be tolerated and the engine and bilges kept free of oil and fuel. Bilge extraction fans may reduce vapours below explosive concentrations but if liquid is present concentrations will rise again once the fan is switched off. Fire retarded insulation and tumescent paints may slow the spread of a fire.
 
Exhaust system
Exhaust gas temperatures are high enough to melt or char components in the typical yachting water lift muffler arrangement within minutes of a cooling water failure, so a loud high temperature alarm sensor in the exhaust/water mixer does more than protect the engine from overheating.

Leaking exhaust into the boat through cracked metalwork or burned tubing is doubly dangerous because the fumes contain poisonous gasses. Exhaust systems should be maintained in good condition, and

Flammables stowage
LPG cylinders and portable tanks or equipment containing petrol should never be stored below decks, nor where their heavier than air vapours could flow below. Regulations regarding the stowage of LPG cylinders should be scrupulously followed. Significant quantities of flammable liquids such as kerosene or diesel fuel should only be stored below in specially constructed tanks with shut-off valves and external vents.

Pressure packs with flammable propellants should be stowed with caps in place to avoid accidental activation but rust may eventually cause leaks from spray cans and tins and abrasion or sharp objects may rupture plastic containers. So, even small quantities of liquid fuels, paints, thinners and lubricating oils etc., should be stowed away from known ignition sources such as batteries, engine, galley, and the exhaust. This isn’t always easy to arrange, but a sealed lazarette or cockpit locker with a downward drain line to the transom or duct from the bottom to an extraction vent, are possibilities. Chemical or fuel smells should be promptly investigated and if a leak has occurred the boat should be deliberately ventilated. Electronic gas and vapour detectors are very sensitive, continue their vigilance while the crew are asleep, and some will automatically turn on extraction fans (eg. EvrSafe)
     
PREPARATIONS
Precautions reduce but can’t eliminate the chance of a fire starting, so they must be backed up by preparations to deal with an outbreak. It can be instructive to inspect the fire fighting systems compulsorily installed on commercial vessels.  

Fire alarms
The quicker a fire is detected and attacked, the less damage it does and the less chance it has of getting out of hand. But one cannot assume that a fire will always be “noticed” immediately. Even a small single cabin yacht should be equipped with at least one battery powered ionisation smoke detector and larger yachts should fit them in each cabin and probably also in lazarettes if these contain wiring or exhaust systems. Smoke detectors above heaters (or remote furnaces in ducted systems) are a wise precaution.

Engine enclosures should have a photo-electric or infra-red sensing fire detector triggering a loud external alarm. Domestic smoke detectors are not suitable in this situation because the engine’s aspiration sucks smoke out of the compartment.

Whether an alarm rudely awakes you or the fire breaks out before your very eyes, in many situations a fire extinguisher is probably your first line of defence and most boats are required by law to carry at least one.

Extinguishers
There are various types of portable (and fixed) extinguishers. Colour coding and classifications vary from country to country. All are reasonably effective against accessible solid fuel fires but vary in their suitability in other situations.

Gaseous agents such as CO2 (Halons are now illegal) are effective at knocking down a fire and can reach inaccessible places but re-ignition may occur if the gas drifts away before the embers have cooled. Dry powders tend to overcome this problem by physically excluding oxygen and are reasonably effective against both liquid and solid fuel fire. But they may prove impossible to deliver to inaccessible places such as the deck head lining or within an engine boxand are very messy to clean up. So there is a good argument for carrying CO2 as well.

Foam is particularly effective against open liquid fires, doesn’t disperse and may be used to flood confined spaces, but is similarly difficult to spray into remote crevices and because it contains water may be dangerous around live 240Volt equipment.

Water is generally very effective against solid fuel fires and a fine mist or spray cools a fire and creates steam which helps to dilute the oxygen levels too. Extinguishers containing water stored under gas pressure are available and are used in some automated engine room fire suppression systems. Small trigger pumped sprayers are sometimes used to extinguish “routine” flare-ups from liquid fuel stoves but too much water risks spreading the fuel.

Extinguisher types and other important points (such as fighting the source, not the flames) are best learned at a training course where one can gain some hands on experience with quelling small fires in controlled situations.

With luck, the relatively small extinguishers typically carried on yachts will put out a fire before it gets out of hand but are less likely to extinguish one that is well established or cannot be reached at source. Carrying more and larger extinguishers is a good idea. There are also two fall-back possibilities – water and smothering – but their effectiveness will depend on circumstances and preparations made in advance.

Fire Hose
When it comes to ordinary combustible materials like wood, GRP, plastics and furnishing fabrics, water is a very effective extinguisher provided it can be delivered in adequate quantities. If the extinguishers don’t kill the fire a bucket is worth trying if it’s all you’ve got but a hose spraying sea or tank water allows you to keep your distance from the heat and flames and to direct the water stream accurately.

Many yachts have saltwater deck wash pumps and with a bit of forethought these can be installed with quick fire fighting reaction in mind. Ideally, the system should have enough pressure and capacity to project a blanketing spray at least half the length of the boat. The hose should be a boat in length, always connected and stored in the cockpit, where it should also be controlled from.

While not anything like the capacity of an engine driven pump, larger DC electrically driven positive displacement diaphragm or rubber impeller pumps can reach high enough pressures to allow a stream of water or a fine mist to be projected via a nozzle. A nozzle adjustable from fine fogging to dense jet is a good option. A trigger nozzle may have advantages but requires either a pressure switch or pump bypass valve.

Smothering
Smothering quells a fire by starving it of oxygen, as when snuffing out a pan fire with the lid. Heat and smoke damage is likely to be very extensive but simply closing hatches and being patient until things have cooled (a matter of many hours) has proved successful in many instances and deserves to be remembered and planned for. The weatherproof design of yachts means that most openings are already provided with well-sealing hatches, but hatches for dorade vents and hawse pipes should probably be stowed in a cockpit locker, not down below. Less obvious air entry points are bilge blower ducts or engine combustion air inlets. As a general safety feature, hatches should be able to be both closed and opened from on deck, except when deliberately locked.  As well as needing to be closed for smothering, they might require to be opened to allow a hose to be directed at a fire below. We hear a lot about dangerous chemicals released in plastics fires but even wood smoke contains immediately dangerous levels of carbon monoxide. In the confines of a yacht, smoke and heat will build up very quickly so fighting the fire from on deck might become necessary even if  the situation does not progress to a dependence on smothering. Forehatches, in particular, should be large enough to allow trapped crew to escape – in a sinking or burning emergency. Apart from preparations for fighting fires in general, there are also some specific precautions that can be taken in relation to particular hazards.

Galley fires
Contained oil fires in saucepans and so on are best dealt with in-situ by smothering with a lid or fire blanket since extinguishers discharged at close quarters tend to splash oil. Spilt oil can be tackled with extinguishers. The fire blanket, extinguisher and fuel cut-off valve should be quickly accessible, but not where a stove fire could prevent them being reached. 

Engine fires
An engine enclosure suits two very positive methods of putting a fire out and should be built with both in mind. It should be as airtight as practical and no larger than needed (many engine spaces effectively extend all the way to the transom). Also, particular attention should be given to sealing around hoses and pipes exiting the space. Combustion air inlet and extraction fan ducting should have dampers of some kind and these, plus fuel shut-off valve and engine isolation switch, should be outside the enclosure.

Shutting down the engine and closing dampers and cutting off fuel and electrical power should eventually cause the fire to smother and also creates a favourable situation for using aerosol or gaseous suppressants. A hole with a pivoting cover can allow a water hose or portable extinguisher to be discharged into an enclosure. Achieving the necessary suppressant concentration in larger spaces will require appropriately large, fixed cylinders with remote activation and should be sized and installed by

Automatic systems
Automatic extinguishers generally discharge gas, foam or water fog, and are typically only fitted within engine spaces. Automatic discharge is not technically difficult, but a practical unattended system must first stop the engine and close air inlets. If this is not done the engine will rapidly suck out the extinguishing gas. Sudden loss of engine power or discharge of an extinguisher into an occupied space may itself be dangerous, so such systems are usually switched to alarm with manual operation when the crew are on board. If the engine runs in the crew’s absence (not uncommon on larger yachts with diesel generators), it makes sense to consider the installation of an automatic extinguishing system.

Simultaneous action
As well as fighting the fire, the crew must also take steps to safeguard their lives. Fire on board may prevent a Mayday being issued even a few minutes later, and is a legitimate reason to issue one immediately. With two or more crew it makes sense for one to fight the fire while the other issues a Mayday and prepares for abandoning ship. In terms of health and safety, it should be remembered that even a successfully fought fire or even a galley accident with a saucepan of hot soup can result in serious burns. Travellers to more remote areas, where medical aid could be days away, should learn about burns treatment and carry appropriate medicines and pain relief.

A personal note
I’ve witnessed several liquid fuel stove flare ups that were big enough to need an extinguisher but, fortunately, like the vast majority of sailors, have never been confronted with a severe fire on my own boat. I’ve had one potentially serious incident though, due to a faulty starter motor solenoid that almost instantaneously produced flaming droplets of burning plastic insulation along two metres of wire. I switched off the power, squirted it once with an extinguisher and the emergency was all over –  bar the cleaning up and the trembling.

I have, however, inspected the aftermath of two severe fires extinguished by smothering (one caused by a loose connection in a paraffin stove), witnessed a 50 ft power cruiser burn to the waterline, picked through the smouldering ruin of half a dozen yachts after a marina conflagration and, perhaps most sobering of all, been too far away to aid a burning yacht that exploded on our horizon only minutes after putting out a Mayday. It can happen. 

M.O.S.S Australia
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Multihull Group
Pantaenius Sailing
Nav at Home
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West Systems 2