Unit III fire fighting and safety in machinery spaces

1. What is fire?

Fire is one of the greatest hazards at sea. It threatens the safety of the vessel and the lives of everyone aboard. Even a very small fire can quickly turn into a major disaster so it is vital that everyone on board is aware of the risks and plays their part in fire prevention.

Fire is a chemical reaction between a flammable material and air which results in the production of heat and light. A fire cannot occur unless three elements are present. To make them easy to remember, they are often shown as the Fire Triangle.

The three elements needed to produce a fire are:

• A Source of ignition - HEAT.

• Something that will burn - FUEL.

• Support for combustion - AIR.

A fire can only sustain itself if all three components are present. Remove one, and you extinguish the fire. This is the simple basic principle of fire prevention.

Therefore extinguishing a fire is achieved as follows:

1) Removal of the combustible material.

2) Reducing or cutting off the supply of oxygen or air.

3) Using a cooling medium to reduce the temperature of the substance to a level at which combustion ceases. Fire fighting techniques use one or a combination of the above methods to extinguish a fire.

Fires are classified according to the types of material which are acting as fuel. Broadly speaking most fires can be divided into four classes:

1) Solid fires

2) Liquid fires

3) Electrical fires

4) Chemical fires

Each class of fire is handled in a different way regarding both equipment and method. For the first three classes of fire, the three factors providing combustion can be liked to a triangle, which as a mechanical structure is extremely rigid. The removal of any one side will cause the immediate collapse of the triangle. Therefore, if the three supporters of combustion, air, fuel, and heat, are taken as forming the three sides, a fire will exist and remain burning until any one side is removed; whereupon the triangle will collapse, the fire is under control and can be extinguished.

2. Machinery space fires

Any fire on board poses a threat to the safety of the ship and its crew. But by far the most dangerous is a machinery space fire. It can cripple a vessel, deprive it of power and leave the ship at the mercy of the elements.

Machinery space fires are the biggest, single, reason for the total loss of vessels and their cargo. Engine room fires alone account for about half of all on-board fires. It is vital to tackle them quickly and effectively.

The Dangers of Machinery Spaces

• Machinery spaces contain all the elements to start and sustain a fire - heat, air, and fuel.

• In particular, there is usually an abundance of fuel, particularly in the engine room - for example, fuel oil, lubricating oil and hydraulic oil.

• Because the engine room is at the heart of a vessel, a fire will spread rapidly to other parts of the ship.

• Fire fighting conditions are difficult. Access is confined and temperatures can be very high. Using water in these conditions creates a great deal of steam and high levels of humidity. BA activity in these conditions must be strictly controlled to avoid the effects of heat and humidity.

• If a fire occurs in the engine room, temperatures can quickly rise to more than 600° Celsius - enough to melt aluminium, cause plastic switches to burst into flame, and ignite paint. Within minutes, the fire may turn into a raging inferno.

• From the sounding of the alarm, you may have only a few minutes before the fire is burning perilously out of control.