Provide explanation of the occurrence of fire and explosion by using props (with demonstrations).
CHEMICAL FIRE:
Definition
Fire is a chemical reaction followed by evolution (the expulsion of light and heat). Chemical reactions contain the sense of a chemical process.
Fire Triangle:
Those involved in the reaction are referred to as elements of a fire triangle consisting of:
Heat Sources
Fuel
Oxygen
Flash Point and Flash Point (Fire Point)
Flash Point is the lowest temperature at which a substance (fuel) simply emits steam and flashes (burns out instantly) when provided with an adequate heat source.
Fuel Point (Fire Point) is the lowest temperature at which a substance (fuel) simply emits steam and burns (burns continuously) when fed with a heat source.
The flash point between a substance with another substance is different.
Example:
Gasoline: - 43 ° C
Kerosine: 38 ° C to 74 ° C
Paraffin: 38 ° C
Self Ignition Temperature (Auto Ignition Temperature).
The self-ignition temperature is the temperature at which a substance can ignite by itself in the absence of an external source of heat.
Example:
Gasoline: 253 ° C Acetilin: 229 ° C
Karosine: 228.9 ° C Propace: 467.8 ° C
Paraffin: 316 ° C Butan: 405 ° C
Flammable Range / Combustible Range.
The flammable area is the concentration limit of the mixture between fuel vapor and combustible air when subjected or given a heat source.
Concentration: The volume ratio between the vapor of the fuel and the air.
The burning area is limited by:
Limit can burn up (Upper Flammable Limit / UFL).
Lower Flammable Limit (LFL) limits.
Example:
Crude oil = 1% to 10%
Gasoline = 1.4% to 7.6%
Kerosine = 0.7% to 5.0%
Butan = 1.9% s / d 8.5%
Profan = 2.3% to 9.5%
Acetone = 2.15% to 13%
Benzene = 1.40% to 8%
Toluene = 1.20% to 7%
Acetillin = 2.50% to 83%
BLASTING BY COMBUSTION
Blasting by combustion occurs because of a combustion in a relatively closed space (blasting area).
The result is heat, flame and pressure (mechanical shock).
In general the blasting pressure of the air mixture and the sensitivity of the fuel vapor depends on:
• Composition of the mixture / ingredients.
• Initial pressure.
• Initial temperature.
As an illustration, blasting at sea level pressure and ambient temperature (Ambient Temperature), will have an initial propagation speed of 10 to 30 feet per second.
WEIGHT STEAM
Vapor weight is the ratio between the vapor weight of a substance and the weight of air.
When the vapor weight is more than one, then the steam will always descend to the lower surface.
Example of vapor weight:
Kerosine + 4.5 Gasoline = 3 - 4
Acetillin = 0.9 Propan = 1.56
Ammonia = 0.6 Hydrogen = 0.069
Butan = 2.5 H2S = 1.189
CO = 0.967
MIXING DAMAGE (MISCIBILITY)
Mixing power is the ease of mixing between two substances or more.
Example:
Gasoline with kerosene mixing power is good.
Gasoline with poor mixing power water.
HEAT SOURCES (SOURCES OF HEAT)
Open flame.
Friction (friction).
Electric spark & electric arc (electric spark & arc).
Electric current (electric current).
Spontaneous combustion (spontaneous combustion).
Static electricity.
Lightning (lighting).
Compaction.
Sunlight (sun light).
Nuclear (nuclear).
BASIC PRINCIPLE OF EXAMPLE API
The basic principle of fire extinguishability is: to damage the balance of the mixture between 3 (three) triangles of fire (heat, oxygen and fuel) or to stop the combustion process (chemical reaction of fire).
Reduce heat to below the flash point, this is called cooling.
Separating the air with fuel, called smothering or reducing the ratio of air and fuel to below the limit concentration can burn down, called a diluting.
Close the flow of fuel or take / reduce the amount of material burned (starvation).
Breaks the chain reaction (process) of combustion either chemically or physically.
MATERIAL PROPERTIES THAT EASY TO BE BURNED
Very influenced by 3 factors:
Flash point.
Self ignition temperature (auto ignition temperature).
Flammable range