One of the most important knowledge that a Marine Engineer has to know is how to prevent and put off fires. Should a big fire occur in a ship, there is almost no other place to go except the surrounding seas.
Tankers carry flammable oils. Engines use fuel oils. Boilers use fuel oils or gas. Gas welding or cutting repair work uses flammable gases. There is a strong possibility of fire if they are not careful or vigilant.
To understand how a fire can start, we have to know the concept of the Fire Triangle. A fire can only start when there is fuel, heat and oxygen. The 3 sides of a triangle represent this fact. If one of these is absent or removed, the fire does not exist anymore.
So to prevent fires, the best thing to do is to isolate either one of them or better still, all of them. For example, if a place is hot, it is essential not to keep combustible items there. Designers of diesel engines should make sure that their high-pressure fuel pipes are located away from the exhaust pipes.
Fuel can be solid or liquid that gives off flammable vapors when heated. It can also be a gas that starts to burn when its ignition temperature is reached. Examples are paper, wood, cloth, paint, acetylene, and propane gas.
Heat can be transferred by:
- Radiation from any heating appliance, flames, or explosion
- Conduction through any suitable material such as steel or aluminum
- Convection via gases or hot air circulated in ventilation ducts
Oxygen in the air supports combustion. A supply of this gas is essential for a fire to take place. Sometimes chemical reactions in the fire can give out oxygen that sustains the fire. Oxygen gas used in gas welding will quicken the spread of the fire.
Fire fighting is therefore the removal of one or two of the ingredients of the fire triangle. When we use a water hose to shoot at a fire, we are cooling the fire so as to remove the heat. When we turn off the gas cylinder valve, we are cutting off the supply of fuel. When we cover up a fire with sand, we are removing oxygen from the fire.
The fire triangle forms the basis of all the fire protection, fire fighting and training of the staffs on board ship. Once we understand the fire triangle, prevention and control of the fire situation can be achieved readily.
Posted by Thomas Yoon on 11th July 2003