Fundamentals of Fire Engineering
FIRE TRIANGLE
Based on the fire triangle, the basic 3 elements required to produce fire are namely heat, fuel and oxygen. Absence of any one of the 3 components will prevent fire from being created.
FIRE TETRAHEDRON
Besides the 3 elements shown on the fire triangle, there is a forth element which is essential for the fire to burn continuously once it is ignited. This forth element is known as “CHAIN REACTION”. Once the fire is ignited, the burnt substance produces a lot of heat which in turn burns the remaining fuel substance, causing an avalanche of chain reaction.
TYPES OF FUEL
Fuels are any materials that store potential energy in forms that can be practicably released and used for work or as heat energy. Fuels can be classified into 3 categories, namely solid fuel (e.g. wood, paper & cotton), liquid fuel (e.g. petrol, diesel & kerosene) and gaseous fuel (e.g. LPG, CNG & Hydrogen).
AIR
Air is mainly composed of two gases, oxygen and nitrogen. Air contains 21 % oxygen which supports the combustion process. The minimum percentage of oxygen required in air to support combustion is 16%.
HEAT
A form of energy associated with the motion of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation. Heat can be measured in units of calories and BTU.
1. Conduction
Thermal conduction is the transfer of internal energy by microscopic diffusion and collisions of particles or quasi-particles within a body. The microscopically diffusing and colliding objects include molecules, atoms, and electrons.
2. Convection
Convection is the concerted, collective movement of groups or aggregates of molecules within fluids (e.g., liquids, gases) and rheids, either through advection or through diffusion or as a combination of both of them.
3. Radiation
Radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes electro-magnetic radiation such as radio waves, visible light, and x-rays, particle radiation such as α, β, and neutron radiation and acoustic radiation such as ultrasound, sound, and seismic waves.
SOURCE OF IGNITION
a) Spark: caused by friction, static charge, loose electric connection, welding
b) Flame: match stick, gas cutting torch
c) Chemical Reaction
d) Heat of Compression
e) Nuclear Reaction