PROTECTION, PREVENTION, & EXTINCTION
O Agni, help us to gain prosperity by leading us
on the righteous, redeem us from all our sins
and actions. We bow before you with gratitude.
-Rig Veda
RPL - JAMNAGAR
Fire accident ( 26.10.2006 )
Property Damage of Rs.25 Cr
ONGC – BOMBAY HIGH
ON SHORE RIG
Fire accident ( 21.04.2004 )
Claimed 6 lives with pre mature closure of the
Country’s prestigious On shore oil platform
HPCL VIZAG
Fire accident (Sep‘15 1997 )
Claimed 51 lives & incurred a loss of about Rs 600 cr
And now a construction Site
Can u Access the Lives lost ????
TOPICS
•
CHEMISTRY OF FIRE
•
HOW TO PREVENT FIRES.
•
EXOTHERMIC & ENDOTHERMIC REACTIONS.
•
HOW FIRES ARE INITIATED.
•
KINDS OF FIRES AND ITS CLASSIFICATION.
•
MECHANISM OF EXTINGUISHING FIRES.
•
FIRE EXTINGUISHING MEDIUMS.
CHEMISTRY OF FIRE
COMBUSTION
Fire is combustion, a chemical reaction in which heat and light are produced. The
rate it precedes is fast, because more energy is generated than can escape into the
surrounding medium. This results in rapid acceleration of the reaction because of
the build up of heat energy.
OXIDATION
When the rate of reaction is very slow only heat is produced and slow oxidation
occurs, such as rusting. Combustion is rapid oxidation.
FLAME
Most combustion processes produce flame, which has the ability to spread through an
atmosphere with the emission of heat and light. The flame front is a transition region
separating burnt from un burnt gases, and light is given out from this region.
A fuel oxidation mixture, which liberates enough energy on combustion to allow flame
to spread through the unignited region of the mixture, is called “flammable”.
EXPLOSION
The transmission from combustion to explosion is due to an acceleration of the
reaction, caused either by the rise in temperature (thermal explosion). Generally
explosions are of a chain/thermal nature that is a combination of the two causes
where both heat accumulation and chain auto-acceleration contribute to the
explosion.
THE FIRE TRIANGLE
Combustion will continue as long as these three factors are present in the correct proportions. Removal of any
one leads to the collapse of the triangle, combustion stops and it is the basic principle of fire prevention.
Fuel
-
Oxygen-
SOLIDS, LIQUIDS AND GASES. The common solid
and liquid fuels must emit vapor or gas before they can
burn to produce a flame.
Generally in the form of air. Air comprises
approximately
79%
Nitrogen.
20.7% Oxygen.
0.3% Carbon dioxide.
Heat
-
Causing vaporization of the fuel providing a source of
ignition from, sparks, arcs, naked flames, static
electricity, sun, lighting a hot surface or a sufficient
high temperature for spontaneous ignition.
DIFFERENT STAGES OF FIRE
INCIPIENT STAGE
No visible smoke, flame, no significant heat
SMOULDERING STAGE
Combustion increases develops smoke still
no flame - heat also
FLAME STAGE
Fire develops further ignition occurs and flame
starts
HEAT STAGE
Large amount of Heat, Flame smoke & toxic
gases produced
Please Refer the Chain Reaction, which is the fourth factor in the tetrahedron
THE FIRE TETRAHEDRON
FUEL
EXOTHERMIC AND ENDOTHERMIC REACTIONS
OF FIRE
Exothermic Reaction
A Chemical reaction, which gives out heat in the process, is called exothermic
reaction. Ex. When carbon is glowing a red heat, the combination of reaction of
carbon with O2 is taking place.
The process is depicted by the chemical reaction.
C + O2 = CO2 + 10,890 British thermal unit for 12 oz of carbon.
That is one atom of carbon and one molecule containing two atoms of O2
combines or reacts to form the molecule of CO2.The process is accompanied by
liberation of a large quantity of heat.
Endothermic reaction.
But when CO2 is passed over glowing carbon a chemical reaction takes place
whereby, two atoms of CO2 are shared between two atoms of carbon to give a
new gas Carbon monoxide (2CO), which is poisonous and flammable. This is
represented by the chemical equation.
C + CO2 = 2CO + 4,360 British thermal unit ABSORBED for 12 oz of carbon
Further enormous quantity of heat is also absorbed in the process to an
extent of 4360 British thermal unit for 12 oz carbon.
This is called Endothermic reaction.
C + CO2 = 2CO + 4,360 British thermal unit absorbed for 12 oz of carbon.
PYROLYSIS
Decomposition brought about by heat. Common fuels must vaporize to burn,
when heated they decompose to smaller molecules with greater volatility and
flammability, and to carbon. It is vapor given off in the heating and
decomposition process that burns.
Because a certain amount of heat is necessary to vaporize a fuel, individual
fuels have critical temperature relative to the ignition processes.
IGNITION TEMPERATURES
Flash Point -
The lowest temperature at which a hydrocarbon liquid
vaporizes and on application of ignition will ignite but
not necessarily support combustion.
Fire Point
The lowest temperature for a fuel at which sufficient
Vapor is given off which on application of ignition
will ignite and support combustion.
-
Spontaneous
-
The temperature at which a fuel will automatically
Combustion ignites without an independent source
of ignition.
Automatic
-
The temperature at which a hydrocarbon liquid is
Ignition heated and will automatically ignite without
applying a source of ignition.
EXPLOSIVE LIMITS
The explosive limits are the proportions of fuel vapor and oxygen coming
together, necessary for a fire or explosion to occur. The Lower Explosive
Limit (LEL), and Upper Explosive Limit (UEL), are expressed as percentages
by volumes of flammable vapors in air.
TRANSMISSION OF FIRE
CONTACT
CONDUCTION
CONVECTION
RADIATION
FIRE SPREAD
Fire can spread by:
Conduction -
Heat traveling along or through conductive material eg.
Unprotected steel girders.
Convection -
Fire spread by rising hot gases and smoke eg. Stair and
lift wells.
Radiation
Materials ignited when placed too close to a source of
radiated heat eg. Electric fires.
-
Direct burning-
Combustible materials giving off sufficient vapor to
encourage combustion and continue burning when
coming into contact with a naked flame, eg.Chair or
mattress being exposed to lighted cigarette.
CLASSIFICATIONS OF FIRES
CLASS A
Solid Combustible Materials such as
WOOD, PAPER,
FABRICS-CARD BOARDS
(QUENCHING-COOLING)
CLASS
CLASS
B
Flammable oil such as
COAL, OIL, GAS, GREASE, CHEMICALS
LNG, LPG
(BLANKETING-SMOTHERING)
C
ELECTRICAL
(NON-CONDUCTING)
PRINCIPLES OF EXTINGUISHMENT
Removal of one or more of the factors of the Triangle of Fire is the basic
principles of fire prevention:
Starvation
-
Removal of the fuel from the fire.
Smothering
-
Limitation of oxygen from the fire.
Cooling
-
Limitation of the heat below the ignition
temperature.
FIRE EXTINGUISHERS
Most fires are relatively small and can be easily extinguished.
It is important that all employees are familiar with fire extinguisher distributed
about the premises and the principles underlying their design, maintenance and
use.
Hand fire extinguishers are designed for small fires and therefore are used
close to the burning material.
Dry Chemical Powders
The basis of most chemical powders is sodium bicarbonate, with the addition of a
metal striate as water proofing agent, is widely used, not only in portable
/wheeled extinguishers but also for general application in large quantities in DCP
Fire Tenders.
Properties:
Principle base chemical
:
Sodium bicarbonate
Additive mixed with the powder
:
Metallic striates Tricalcium
to prevent caking Phosphate
hydrofobic Silicones.
Particle size of the powder
:
20 to 25 microns.
Characteristics
:
a) Free Flowing
b) Non-toxic and unlikely
to give any environmental
Problem
c) Water repellent
d) Non-conductor of Electricity
Extinguishes Fire By
:
1) Smothering
2) Cooling
3) Shielding Radiation of heat.
Dry Chemical Powder Extinguishers:
This Consists of two types:
1) Gas Cartridge type:
The Powder is expelled by pressure released into the body of the
extinguisher from a CO2 gas cartridge
2) Stored Pressure type:
The powder is expelled by pressure maintained in the body of the
extinguisher by nitrogen or air.
DRY CHEMICAL POWDER EXTINGUISHER
SAFETY CLIP
Co2 CATRIDGE
(INNER CONTAINER)
RUBBER HOSE
DRY CHEMICAL POWDER
OUTER CONTAINER
NOZZEL
TO OPERATEE:
KEEP EXTINGUISHER UPRIGHT.
REMOVE SAFETY CLIP STRIKE KNOB.
DIRECT THE POWDER AT THE BASE OF FIRE
RECHARGE:
IMMEDIATELY
DRY CHEMICAL
HAND TYPES
CO2 CARTRIDGE
NOZZLE
PIN
VALVE
VALVE
BICARB. SODA
POWDER TREATED
TOMAKE
WATERPROOF
NOZZLE VALVE
WHEEL TYPES
CARBON DIOXIDE FIRE EXTINGUISHERS
CO2 LIQUID UNDER PRESSURE
HOSE
VALVE
PIN
HANDLE
2.5 LBS
CYLINDER
20 LBS
HORN
CO2 Extinguishers
In this type of extinguisher, the liquid CO2 is contained in a pressure cylinder and
is released by a squeeze trigger mechanism through a horn type applicator.
CARBON DI-OXIDE (CO2) AS EXTINGUISHING MEDIA
Properties
Appearance
Molecular Weight
:
:
Colourless / Odorless Gas (White
Cloudy – smoky appearance)
44
Density
:
1.52
Vapour Pressure at 25OC
:
58.24 bar
Critical Temperature
31.0OC
:
Critical Pressure
:
72.85 atm
Boiling Point (Sublimes)
:
-78OC
Latent Heat of Vaporization
:
0.121 KJ/Kg
Foam Extinguishers
In this type of extinguisher, foam is produced from a foam solution. The foam
concentrate is stored either as a solution or in water within the body of the
extinguisher, or separately in a sealed inner container.
When the extinguisher is activated foam solution is expelled. Foam is produced in
a miniature, self-aspirating foam branch at the end of the discharge hose. The
types of concentrate which may be used are :
•
•
•
Protein
Fluoroprotein
Fluorochemical (AFFF)
a) The foam solution is expelled by pressure released into the body of the
extinguisher from a CO2 cartridge (gas cartridge).
The foam solution is expelled by pressure maintained in the body of the
extinguisher by air or nitrogen (stored pressure).
FOAM TYPE EXTINGUISHER
PLUNGER
NOZZLE
ALLUMINIUM SULPHATE SOLUTION
( INSIDE CONTAINER )
LEVEL INDICATOR
SODIUM BICARBONATE SOLUTION
( OUTSIDE CONTAINER )
TO OPERATE 1. TAKE IT NEAR FIRE.
2. PULL THE KNOB AND TURN IT RIGHT AND LET IT REST ON THE CAP.
3. INVERT AND DIRECT STREAM TO FALL GENTLY ON FIRE.
TO CHARGE 1. RECHARGE IMMEDIATELY AFTER USE.
2. AFTER DISCHARGE THIS EXTINGUISHER MUST BE WASHED OUT WITH FRESH WATER
USING ATLEAST TWO CHANGES.
3. RECHARGE AT LEAST EVERY TWO YEARS.
FOAM AND ITS LIMITATIONS FOR USE ON LIQUID FIRES
1. Foam are not suitable for fires involving gases and light ends.
2. Foam should not be used on materials, which are susceptible to water
damage, and also materials like Sodium and Potassium reacts violently
with water.
3. Foam is a conductor and should not be used on energized electrical
equipment fires.
4. Foam is not effective on flowing liquid fires.
On hot oil/burning asphalt (which are above the boiling point of water) applying
foam may cause violent frothing and foaming over.
water as extinguishing media
Water
Water is still the most efficient, cheapest and most readily available medium for
extinguishing fires of general nature. Techno-logical developments have produced
additives to increase the efficiency of water as a fire extinguishing for specialized
applications.
Water is a Colorless Liquid
Source
: Easily available, cheap, relatively stable
and heavy liquid can be transported easily from
one place to another place.
Specific Heat
: 180 btu/lb
Latent heat of Vaporization
of Water
: 970 btu/lb
At ordinary pressure – water expands – 1700 times
Water extinguishes fire by
:
1) Cooling
3) Emulsification
2) Smothering
4) Dilution
Aquamist and MicroDrop uses a range of droplet sizes to maximize penetration
of the fire plume, and hence extinguishing performance.
Large Droplets have the momentum to penetrate the fire plume, and will drag the
smallest droplets into the combustion zone.
Smaller Droplets surround the fire, and are pulled into the base of the fire as it
draws in oxygen.
The Smallest droplets cool the gases in the room, strip smoke from the air, and
block the transfer of radiant heat.
The end result is extinguishments, using considerably less water than a
traditional water spray system.
ANNEXURE-1
SOURCES OF IGNITION
S.No.
1
SOURCES OF
IGNITION
(Descending order
of frequency)
Electrical Equipment
EXAMPLES
PREVENTIVE MEASURES
Electrical Defects due to poor
maintenance mostly in wiring, motors,
switches, lamps and hot elements.
Use and approved equipment. Follow
relevant code and establish regular
maintenance.
2
Friction
Hot bearings
Broken machine parts
Choking or jamming of material
Poor adjustment
Follow a regular schedule of
inspection, maintenance and
lubrication
3
Foreign substances
Tramp metal that produces sparks
when struck by rapidly revolving
machinery
Keep foreign material from stock.
Use magnetic or other separators to
remove tramp metal.
4
Open Flames
Cutting and Welding torches (chief
offenders)
Gas and Oil burners
Misuse of gasoline torches
Follow established welding
precautions. Keep burners clean and
properly adjusted. Do not use open
flames near combustibles.
5
Smoking and
matches
Dangerous near flammable liquids and
in areas where combustibles are used
or stored.
Smoke only in permitted areas. Use
prescribed receptacles. Make sure
matches are out.
6
Spontaneous
ignition
Deposits in ducts and flues
Low-grade storage
Industrial wastes
Oily waste and rubbish
Clean ducts and flues frequently.
Remove waste daily. Isolate stored
materials likely to heat spontaneously.
7
Hot Surfaces
Exposure of combustibles to furnaces
Hot ducts of flues
Electrical lamps or irons
Hot metal being processed.
Provide ample clearances, insulation,
air circulation. Check heating
apparatus before leaving it
unattended.
8
Combustion sparks
Rubbish burning
Foundry Copulas
Furnaces and Fire boxes
Process equipment
Use incinerators of approved design.
Provide spark arresters on stacks.
Operate equipment carefully.
9
Overheated
materials
Abnormal process temperatures
Materials in driers
Over heating of flammable liquids
Have careful supervision and
competent operators, supplemented
by well maintained automatic
temperature control.
10
Static Electricity
Dangerous in presence of flammable
vapor
Occurs at spreading and coating rolls
where liquid flows from pipes.
Ground equipment. Use static
Eliminators. Humidify the atmosphere.
HOW TO USE A PORTABLE FIRE EXTINGUISHER
Remember the acronym, "P.A.S.S."
P
-
Pull the Pin.
A
-
Aim extinguisher nozzle at the base of the flames.
S
-
Squeeze trigger while holding the extinguisher upright.
S
-
Sweep the extinguisher from side to side, covering the
area of the fire with the extinguishing agent.