35 Electrical Safety Saman

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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 ?