Fighting a fire on board ship may amount to a life or death struggle; to enter into such a conflict unprepared and unarmed is to invite failure. The 'armaments' or equipment available have been described. Now comes the matter of being prepared. A basic strategy should be followed in all fire fighting situations.
This will involve four distinct aspects, which are locating, informing, containing and finally extinguishing a fire. A fire may be located by detection devices fitted in the various spaces in a ship or simply by smelling or seeing smoke. Alert personnel, whether on watch or not, should always be conscious of the danger of fire and the signs which indicate it.
Certain areas are more liable to outbreaks of fire and these should be regularly visited or checked upon. Once detected the presence of a fire must be made known quickly to as many people as possible. It is essential therefore that the bridge is informed of the location and extent of the fire.
A small fire might reasonably be immediately tackled by the finder but attempts should be made whilst fighting the fire to attract attention. Shouting 'Fire', banging on bulkheads, deliberately setting off equipment alarms in the vicinity, all are possible means of attracting attention.
Anyone finding a fire must decide whether to fight it immediately or whether to leave it and inform others first. The more people who know of a fire the greater the efforts that can be brought to bear upon it. If in doubt—inform! Ships are built to contain fires in the space where they begin.
Fire resisting bulkheads and decks are positioned at appropriate distances in order to limit the spread of fire, and it remains for fire fighting personnel to ensure that these barriers are secure whilst attempting to fight the fire.
All doors and openings should be closed, all ventilation and exhaust fans stopped, and flammable material isolated from the space. It should be remembered that a fire exists in three dimensions and therefore has six sides, so it must be contained on six sides.
A small fire can usually be easily extinguished but it can also quickly become a big fire, so the fire extinguishing must be rapid if it is to be effective. Fire fighting strategy will vary according to the location of the fire. The various areas and their particular problems will now be examined.
Must read ➤ Fire Fighting Equipment
Accommodation
The accommodation areas will be made up almost exclusively of Class A material requiring the use of water or soda-acid type extinguishers. Electrical circuits however should be isolated before directing quantities of water into an accommodation area. AH ventilation and exhaust fans must be stopped and fire flaps closed.
If hoses are employed a water spray should be used in order to achieve the maximum cooling effect. The accommodation will no doubt fill with smoke and therefore breathing apparatus should be available. The galley area presents a somewhat different fire hazard.
Here Class B materials, such as cooking oil, fat or grease, will be present requiring the use of foam, dry powder or carbon dioxide extinguishers. A fire blanket quickly spread over burning cooking utensils could extinguish a potentially dangerous fire.
Machinery spaces
Machinery space fires will involve mainly Class B material requiring the use of foam type extinguishers. Only the smallest of fires should be tackled with hand extinguishers. The alarm should be quickly given and the bridge informed. The ventilation fans should be stopped and fire flaps closed.
Any oil tanks close to the fire should be closed off and kept cool by hosing with water. Foam-making equipment should be used on the fire and foam spread over the tank tops and bilges. Water spray can also be used to cool the surroundings of the fire, but a water jet should not be used in the machinery space since it will move any burning oil around and subsequently spread the fire.
Only if the situation becomes hopeless should the space be evacuated and gas flooding used. The machinery space contains most of the fire fighting equipment as well as the propulsion machinery. If it is vacated then control of the situation is lost to a 'one-shot' attempt at gas flooding.
If evacuation is decided upon all personnel must be made aware of the decision. The space must then be completely sealed against the entry or exit of air and all oil supplies isolated at the tank valves.
When all these matters have been attended to, the flooding gas can be admitted and, if the surrounding bulkheads hold to contain the fire, it will quickly go out. Cooling of the boundary bulkheads should continue from outside the space whilst flooding is taking place.
When the extinguished fire has been left long enough to cool down the space can be re-entered. This should be done from the tunnel, if there is one, or the lowest point remote from the seat of the fire. Engineers wearing breathing apparatus may now enter, taking water spray hoses with them to cool down any hot surfaces.
Cooling and smoke dispersal are the first priorities to provide an atmosphere in which others can operate and gradually bring the machinery back into service. Where a machinery space fire involves electrical equipment then only dry powder or carbon dioxide extinguishers can be used until the equipment is isolated.
Cargo spaces
Flammable limits
Where a fire occurs in a cargo hold with a smoke detection and carbon dioxide flooding system fitted, the procedure is straightforward and has already been described. It is essential to ensure before flooding that all air entry and exit points are closed by fire dampers and all fans are stopped. Oil tankers with their cargo tanks full or empty present a potentially serious fire hazard, A fire occurring in a cargo tank will doubtless lead to an explosion or an explosion will lead to fire.
The rapid use of foam making equipment, the cooling of surrounding areas and the isolation of the fire should immediately take place. The prevention of fire and explosion conditions is the main prerequisite with oil tankers. With reference to hydrocarbon vapours, such as those present in oil tanks, the diagram shown in Figure 13.15 should be considered.
The relative proportions of hydrocarbon vapour and oxygen necessary for a fire or explosion are shown. By keeping the tank atmosphere outside of the flammable limits, no fire or explosion can occur. It is usual practice to inert the tank atmosphere by displacing the oxygen with an inert gas and thus effectively prevent a fire or explosion. The inert gas producing systems have already been described.
Training and awareness
Where is the nearest fire extinguisher? What type is it? How is it operated? At any position in the ship these questions should be asked and answered. Knowing how to operate any extinguisher just by looking at it will indicate some degree of training and an awareness of the fire defences.
Fire drills are often referred to as 'Board of Trade Sports', but they merit a more sober attitude than they receive. Practices are useful and should be seriously undertaken. Equipment should be tried and tested to ensure that it works and is ready when needed. Regular maintenance should take place on extinguishers, fire pumps, hydrants, hoses, etc.
All engineers should be familiar with recharging and overhauling extinguishers and those in charge should make sure it is regularly done. The statutory surveys do much to ensure that equipment is ready for use but the one year period between leaves a lot of time for neglect.
Breathing apparatus
Self-contained breathing apparatus
Many fire fighting situations may require the use of some form of breathing apparatus. The use of such equipment will ensure a supply of oxygen to the wearer so that he can perform his particular tasks in safety. Two basic types are in use—the smoke helmet and the self-contained unit using air cylinders. The smoke helmet arrangement uses a helmet which covers the head and is connected to an air hose. A hand operated pump or bellows supplies the air.
A system of signals between user and supplier must be arranged to ensure safe, correct operation. The self-contained unit consists of one or two cylinders of compressed air kept in a harness which is carried on the back . The high pressure air is fed through a reducing valve and then to a demand valve.
The demand valve is fitted into a face mask and supplies air to meet the breathing requirements of the wearer. A non-return valve permits breathing out to atmosphere. A warning whisde sounds when the air pressure falls to a low value. A standard cylinder will allow for about 20 to 30 minutes' operation.
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