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Basic fire & electricalsafety
Saman Rajapakse
Assistant Manager-Technical
Training
Rotax Ltd
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Chemistry of fire
For fire to exist, the following four elements must be present:
Enough oxygen to sustain combustion Enough heat to raise the material to its ignition temperature
Some sort offuelor combustible material, and
The chemical reactionthat is fire.
Take away any of these and the fire will be extinguished
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How fire spreads
1. Direct burning chemical reaction
2. Convection
3. Radiation
4. Conduction
Fire Creep
Burning material falling onto other combustible materials
Flashover
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Ways of fighting fire:
1.Leave it to the experts!
2. Cooling
3. Suffocating
4. Removing the fuel (Starving)
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Classes of fireFires are classified according to the type of fuel that is burning.
Using the wrong type of fire extinguisher on a fire may make matters worse.
The five different fire (fuel) classes
Solids class A fire paper, wood, textiles etc
Liquids or liquefiable solids class B fire - petrol, diesel, hydrocarbons
Gases class C fire flammable gases
Metals class D fire Magnesium, Titanium
Cooking oil fires class F deep fat fryers, commercial kitchens etc
What about f i res in electr ical equ ipment?
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How an extinguisher worksPortable fire extinguishers apply anextinguishing agent that will either:
cool burning fuel
displace or remove oxygen, or
stop the chemical reaction so a fire
cannot continue to burn.
When the handle of an extinguisher
is compressed, it opens an inner
canister of high-pressure gas that
forces the extinguishing agent from
the main cylinder through a siphon
tube and out the nozzle. A fireextinguisher works much like a can
of hair spray.
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How an extinguisher worksPortable fire extinguishers apply anextinguishing agent that will either:
cool burning fuel
displace or remove oxygen, or
stop the chemical reaction so a fire
cannot continue to burn.
When the handle of an extinguisher
is compressed, it opens an inner
canister of high-pressure gas that
forces the extinguishing agent from
the main cylinder through a siphon
tube and out the nozzle. A fireextinguisher works much like a can
of hair spray.
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How to use an extinguisher
1
Always raise the alarm first
1. Pull the safety tag and pin
2. Aim at the base of the fire3. Squeeze the handle levers
4. Sweep the jet from side to side
If you have the slightest doubt about yourability to fight a fire....
EVACUATE IMMEDIATELY!
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How to use an extinguisher 2
Samples of
Instructions
1. Use the right type of extinguisher
2. Keep your escape route clear
and your back to it
3. Get within effective range but
stay safe
4. Always be prepared to abandon
the fight - if you dont think its
safe, escape!
5. Speed is important
6. Beware - Noise, visibility, steam!
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Ways of fighting fire:
1.Leave it to the experts!
2. Cooling
3. Suffocating
4. Removing the fuel (Starving)
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Carbon dioxide [CO2]extinguishers
Black body (Old type) or red body with black label (New type).Best on Class B and C fires but safe to use on any type of fire;
Safe to use on fires involving electricity; Extinguishes by reducing
oxygen levels and cooling.
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Powder extinguishers
Blue body (Old type) or Red body with blue label.Best on Class B fires but safe to use on any type of fire.
Works by chemically interfering with the combustion reaction
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Foam extinguishers
Cream body (Old type) or Red Body with Cream label.Suitable for Class A and B Fires. Not suitable for use on fires
involving electricity; Extinguishes by cooling and sealing the
surface of a burning liquid.
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Water extinguishers
Red body
Suitable for use on Class A Fires, wood and paper etc.Not suitable for combustible liquids, cooking fats etc. Not
safe to use on fires involving electricity; Extinguishes by
cooling
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electric shock
Indirect contact
Direct contact
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Severity of the electric shock
Severity of the electric shock depends on
three factors
Current path taken through the body
Amount of current flowing through the body
Duration of current flowing through the body
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Bodys Resistance
Skin offers most of the bodys
electrical resistance
Increased resistance
Thick and callused skin (foot or hand)
Dry skin
Decreased resistance
Thin skin (inner forearm) Wet or sweaty skin
Broken or abraded skin (scratches)
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Effect of electricity on human
body
Burns
Surface (due to arc flash)
Deep tissue (due to arc blast )
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Effect of electricity on human
body
Electric Shock
Muscular Contraction
Asphyxia
(difficulty to breath ) Respiratory Arrest
Ventricular Fibrillation
(heart failure )
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Ventricular Fibrillation
Factors are Current / Time & Physiological
Structure of body
Can occur at 30mA (0.03 A)
Causes heart to flutter
Muscle cannot open / close properly
Does not pump Lack of oxygen to brain - DEATH
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Electric Shock - Treatment
Isolate supply
immediately
If you cannot isolate
DO NOT attempt totouch casualty
Physically remove
victim using non-
conducting implements
Check for pulse /
breathing, give artificial
respiration/CPR if
necessary
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Residual current circuit
breakers
For human protection maximum designed
tripping current is 30 mille amperes
When 30 mille amp leakage current is
flowing it should trip within 300 mille seconds
When 150 mille amp leakage current is
flowing it should trip within 40 mille seconds
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Work on Electrical Equipment
Always ISOLATE supply Switch off using a device that will create an air gap
that should not fail
Lock off where possible to prevent inadvertentswitching ON whilst work taking place
Always test conductors in a reliable way beforetouching (ie. test the test device before and after use!)
Use appropriate safety equipment
Permit to work may be required for highervoltage or complex installations
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Electrical safety equipment
Insulated boots Insulated
combination plier Insulated sticks
Insulated ladders Insulate gloves
Insulatedmats Arc flash wear
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Double Insulation
Lots of portable equipment is DoubleInsulated
Extra layer of insulating material over liveconductors to prevent exposure ofconductors
Can mean that an earth conductor is notrequired risk reduced by additionalinsulation.(two pin plug top connected )
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Maintenance of Portable Electrical
Equipment
Many accidents result from 230 volt portableequipment
All exposed metal parts of equipment shallbe properly earthed
Proper colour code for wiring shall be
followed Proper plug tops (two pin type only for
double insulated appliances ) shall be used
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Step potential
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Step potential
Just 500 mm between the feet = high voltage
between the feet
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Step potential
Severity of electric shock will be more for the
cow with comparison to the man
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The Law
Factory ordinance
Electricity act
Requirements for electrical installations -17 thedition (Iee regulations )
Require Safe construction, maintenance & work systems
Capability,Environments,Insulation, Earthing, Connections,Fusing, Isolation, Making dead, Live working, Working
Space, Competence.
Covers ALL aspects at ALL voltages.
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Any Clarifications or Questions ?
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