Electrical Safety DIPOSH

7/30/2019 Electrical Safety DIPOSH

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Electrical Safety (Oil & Gas)


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Electrical SafetyTable of Content

Part I:Introduction

Part II: Electricity is Dangerous

Part III: The Danger of Electrical Shock

Part IV: Electrical Hazards

Part V: Electrical Safety Measures


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Objectives of the courseAfter completing this course, you will:

Be familiar with the basic concepts of electricity.

Understand the potential effects of electricity onthe human body.

Be able to recognize common electrical hazardsand control measures


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Part I : Introduction Fundamentals of Electricity

Like Water In A Garden Hose

Resistance = Diameter of HoseExample Larger hose (less resistance),more water flows

Voltage = Water PressureExample 45 PSI


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What is electricity ?

A source of Energy

Essential to Modern Life

Extremely Dangerous

Cannot be seen Cannot be smelt


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Part II

Electricity is Dangerous


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Take Electricity Seriously Electricity is the second leading cause of deathin

construction.

Electrocutions make up 12% of construction fatalitiesannually.

Over 30,000 non-fatal shocks occur each year.

Over 600 deaths occur annually due to electrocution.


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Part IV:

Electrical Hazards Shock Most common and can cause electrocution or

muscle contraction leading to secondary injury whichincludes falls

Fires Enough heat or sparks can ignite combustiblematerials

Explosions Electrical spark can ignite vapors in the air

Arc Flash- can cause burns ranging from 14,000 degrees

f. to 35,000 degrees f Arc Blast In a short circuit event copper can expand

67,000 times. The expansion causes a pressure wave. Airalso expands adding to the pressure wave


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Electrical Fires / Arcs / Explosions Fires

Overheating, arcing & sparking

Arcs Generated during faults / flashover (Lightning)

Very high temperatures / causing burns

Explosions Flammable substances give off vapours

Electrical sparks can ignite (ie. domestic light switch)


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Arc Flash and Arc Blast Arc Flash:

80%-Burns due to

ignition of clothing Temperature-35,000

F

Fatal Burns-10 ft.

2000 peoplehospitalized withburns

Molten metal

Arc Blast:

Pressure Wave

Heat Molten metal

Destruction ofstructures and lif


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Arc Blast Cause

Short Circuit caused by working on energized

equipment Dropped Tool

Occurs in milliseconds

Temp: 30,000 degrees

Air expands very violently 15 tons of pressure


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Arc Blast

ARC-BLAST. The three primary hazards

associated with an arc-blast are: Thermal radiation.

Pressure Wave.

Projectiles.


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Explosions. Explosions occur when electricity

provides a source of ignition for an

explosive mixture in the atmosphere.


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Fires Electricity is one of the most common

causes of fires both in the home and in

the workplace. Defective or misusedelectrical equipment is a major cause.


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Part II:

1: Terminology VOLTAGE unit of measurement of

electromotive force (EMF)

CURRENT - Continuous movement of electronspast a given point. (measured in amperes)

RESISTANCE Opposition to movement ofelectrons. Makes it possible to generate heat,control current flow, & supply correct voltageto devices


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Direct Current vs Alternate Current Always flows in one

direction

Used to charge batteries,run some motors, operatemagnetic lifting devicesand welding equipment.

More common in electricalwork

Changes rapidly in bothdirection and value

Power companies producepower cheaper withalternating current


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Electric CurrentA flow of electrons !

Certain materials conduct better than

others


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Electric current Conductors

Metals such as copper, silver, gold and

aluminium. Loose electrons in abundance so charge

can be transferred easily

Copper very common on cost basis


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Electric current Summary

Movement of electrons

Best in soft metals

Measured in Amperes or Amps

Symbolised by A

i.e. a 13A fuse


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Potential Difference Charge on an object

Measured with respect to earth

Also known as Pressure

Water Analogy

Horizontal pipe water does not flow

Raise one end water flows out

A pressure difference exists


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Potential Difference Raising pipe created a pressure

difference

Raising electric charge has same effectonly electric current will flow

Amount of current that flows dependanton conductor (more water could flowin a bigger pipe)


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Potential Difference Summary

Difference of charge between two objects

Causes a current to flow (water analogy)

Measured in Volts

Symbol V i.e. 230V


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Conductors and Insulators Conductors conduct electricity

Insulators dont

Metals conduct

Wood, plastic, air, oil and rigid glass donot conduct electricity (most of thetime)


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Resistance Back to the water pipe again!

A larger diameter pipe allows more water

to flow than a smaller one If a small diameter section of pipe is

inserted into the large pipe the flow ofwater is restricted

Some materials conduct electricitybetter than others (atomic structuredifferent)


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Resistance Small diameter wires (conductors) allow

less electricity to flow than in similar

bigger diameter wires

The ease by which a material conducts

electricity is known as resistance


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Relationships Electric Current - Amperes

Potential Difference Voltage

Electrical Resistance

All above are related to each other


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Ohms LawFrench physicist Ohm studied

V

I R

the relationship between

Potential difference (V),

Amperes, and Resistance.

His findings became known as Ohms Law

Where V = I * R, I = V / R & R = V / I


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Sources of power Battery DC

Mains Supply

Portable Generators

Solar panels


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UK Electricity Supply System Electricity supplied to factories, offices

and homes at 230 volts

Large factories at 11000 volts or above

Supply has alternating current (a.c.)

Alternates at (frequency) of 50 cyclesper second (50 Hertz or Hz)


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Power When current flows energy is

transmitted and usually consumed by a

load Examples heaters, lights, motion

Such devices must consume electricity

because we have to pay for it!


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Power Power = Volts X Amps (work done)

Measured in Watts (W)

Example 2300 Watt electric kettleAlso referred to as 2.3 kilowatt (kW)


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Electrical circuits Consist of

Power Source

Connecting cables Electrical equipment (energy converter)


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Electrical circuits - EarthingVery important for safety !

Prevents conducting parts of equipment

(ie. metal frames or lids), which do notnormally conduct electricity frombecoming live during faults.


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Part II2. How to Receive Electrical Shock

Leading Causes of Electrical Accidents:

Drilling and cutting through cables

Using defective tools, cables and equipment

Failure to maintain clearance distance of 10 feet Failure to de-energize circuits and follow Lock-out/Tag-outprocedures

Failure to guard live parts from accidental worker contact

Unqualified employees working with electricity

Improper installation/use of temporary electrical systems andequipment

By-passing electrical protective devices

Not using GFCI (ground fault circuit interrupters) devices

Missing ground prongs on extension cords


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Current Flows in a Loop or Circuit

Circuits are AC (alternatingcurrent) or DC (directcurrent).

Current is usually AC. AC current has five parts:(1) Electrical source

(2) HOT wire to the tool.

(3) The tool itself

(4) NEUTRAL wire returns electricityfrom the tool

(5) GROUND


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How Shocks Occur Current travels in closed

circuits throughconductors (water,

metal, the humanbody).

Shock occurs when thebody becomes a part of

the circuit. Current enters at one

point & leaves atanother.


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Shocks Occur in Three Ways Contact with both

conductors

Contact with oneconductor andground

With a tool: contact

with hot metalpart and ground (1),(2) & (3)


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Part IIIThe Danger of Electrical Shock

Severity of Electrical Shock

Severity of the Shock dependson:

Amount of current Determined by voltage

and resistance to flow

Path through the body

Duration of flow through thebody

Other factors such as generalhealth and individual

differences.


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Electric shock 0.5mA 6mA tingling sensationThreshold of perception.

10mA 16mA muscular contractionsets Threshold of danger

30mA 60mA & above prolonged

exposure can be FATAL Death can occur in a fraction of a

second


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Effects of Current Flow More than 3 milliamps (ma): painful shock

More than 10 ma: muscle contraction

More than 20 ma: considered severe shock

More than 30 ma: lung paralysis - usuallytemporary

More than 50 ma: possible ventricular fibrillation(usually fatal)

100 ma to 4 amps: certain ventricular fibrillation(fatal)

Over 4 amps: heart paralysis; severe burns


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Effect of electricity on human

body Burns

Surface

Deep tissue Electric Shock

Muscular Contraction

Asphyxia Respiratory Arrest

Ventricular Fibrillation


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Effect of Current Flow


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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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IEC 479 curves

IEC 479 Curves

For info only


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IEC 479 curves Zone 1 - No danger

Zone 2 - Usually No effects

Zone 3 Reversible damage, nofibrillation, breathing difficulties

Zone 4 5% chance of fibrillation C1- C2

50% chance of fibrillation after C3

For info only


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Electric Shock - Treatment Isolate supply immediately Dial 999

If you cannot isolate DO NOT attempt

to touch casualty

Physically remove victim using non-conducting implements

Check for pulse / breathing, giveartificial respiration if necessary


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Part V:

Electrical Safety and Control Measures Employers must follow the Electrical

Standards

Electrical installation The Four Proactive Methods:

Electrical Isolation

Equipment Grounding

Circuit Interruption

Safe Work Practices


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Electrical IsolationWe can be safe by keeping electricityaway from us. We can:

Insulatethe conductors. Example: The insulation on extension cords.

Elevatethe conductors. Example: Overhead power lines.

Guard the conductors by enclosing them. Example: Receptacle covers, boxes, & conduit.


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Insulating the Conductors The first way to safeguard workers

from electrically energized wires isthrough insulation.

Rubber and plastic is put on wiresto prevent shock, fires, shortcircuits and for strain relief.

It is always necessary to check theinsulation on equipment and cords

before plugging them in. Remember, even the smallest

defect will allow leakage!


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Double Insulation Lots of portable equipment is Double

Insulated

Extra layer of insulating material overlive conductors to prevent exposure ofconductors

Can mean that an earth conductor isnot required risk reduced byadditional insulation.


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Defective Extension Cords


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Defective Cord Incident Worker attempted to

climb scaffold with

electric drill. Drills cord was damaged

with bare wires showing.

The bare wire contacted

the scaffolding.

The worker died!


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Elevating the Conductors The second way to safeguard workers

from electrically energized wires is byelevating them.

Wires are often elevated by the power

company.

It is always necessary to check thelocation of overhead lines before youbegin work each day.

Remember, never allow yourself, your

tools, or the materials you are workingwith to be within 10 feetofenergizedlines!


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Working Near Overhead Lines

Clearance of worker and

any equipment, tools,materials, or scaffoldnear uninsulated lines is10 feet!


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Overhead Line Incident

A worker wasattempting to movemobile scaffold.

Scaffold madecontact with 7200

volt line. The worker died.


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Guarding the Conductors The third way to safeguard

workers from electricallyenergized wires is by guardingthem.

Covers, boxes, and enclosuresare often put around conductorsto prevent worker contact.

It is always necessary to checkthat electrical boxes and panelsare covered and free frommissing knock-outs.

Remember, electric equipmentoperating at 50 volts or moremust be guarded!


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Guarding the Conductors


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Guarding the Conductors


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Equipment Grounding

We can be safe by providinga separate, low resistance

pathway for electricity whenit does not follow normalflow (grounding).

Grounding gives the stray

current somewhere to goand keeps you frombecoming part of the circuit


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No earthing of equipment

No bonding

Person can receivean electric shock ifequipment becomesfaulty


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Can You Rely on Grounding?

Grounding will not workifthe electricity can flowthrough you more easilythan the ground. This canhappen when:

Your tool doesnt havea ground pin.

Youre working in wetlocations.

Youre touching ametal object


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Equipment bonded together

All equipmentbonded together

No potential(voltage) differencebetween live casingand handrail

If case becomes livefuse should blow

Equipotential Bonding


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What Must be Grounded?

All circuits and extensioncords.

All noncurrent carryingmetal parts.

Portable & semi-portable tools and

equipment unlessdouble insulated.


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Do Not Eliminate the Ground!


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Do Not Reverse Polarity

The prongs are different sizedso you cant turn the plug

around. If you do, theelectrical fields within themotor are always energized. Ifthere is moisture present, the

case is likely to be hot. Evenwith double-insulated tools,you still could get a shock.


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Circuit Interruption

We can be safer by automaticallyshutting off the flow of electricity inthe event of leakage, overload, or

short circuit. Ground Fault Circuit Interrupters

(GFCI) are circuit protection (orovercurrent) devices that protectyou, the worker.

Circuit breakers & fuses protectequipment, not you, because theytake too much current & too muchtime to trip.


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Receptacle


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Reverse Polarity

Reversed polarityis a condition when

the grounded conductor (neutral) is

incorrectly connected to the ungrounded(hot) terminal of a plug, receptacle, or

other type of conductor


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Reverse Polarity

Hot

Hot

Neutral

Neutral

Reverse PolarityNormal Wiring


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Fuses and RCDs

Fuses essential for safety, will cut off supply at a certain

current level i.e. 13A, 5A, 3A mains supply fuse

Fuse has a fuseable wire element which heats upwhen current flows

Excessive current = excessive heat & wire meltspreventing current flow

RCDs Residual current device

Compares current in Live & Neutral if different andabove a certain value supply switched off


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Circuit Protective Devices

Circuit Breakers and Fuses

Onlyprotect the building,equipment, and toolsfrom

heat build-up! Never depend on circuit

breakers or fuses to preventshocks!

Ground Fault Circuit Interrupter

(GFCI) Is the only device which

willprotect the workerfromshock and electrocution!


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GFCI Protection

All temporary circuits are required tohave GFCI protection or: Equipment & cords must be

included in anAssured EquipmentGrounding Conductor Program

An extension cord isa temporary circuit. Types of GFCIs: receptacle, circuit

breaker and portable Must be wired correctly and tested.


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GFCI Protects People


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How a GFCI Works

The GFCI detects leakage of4-6 milliamps & opens the

circuit in 1/40th of a second.

It will work without the groundplug but not fast enough if

you are the ground .


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Types of GFCI Protection


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Types of GFCI Protection

A GFCI breaker must be installed to protect workersusing 220V masonry saws.


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GFCI Testers

Assured Equipment Grounding


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Assured Equipment GroundingConductor Program

Requires the following:

-Written programand specific procedures

-Program implemented by a Competent Person(onewho is capable of identifying existing and predictable

hazards in the surroundings or working conditionswhich are unsanitary, hazardous, or dangerous toemployees, and who has authorization to takeprompt corrective measures to eliminate them.

-Equipment grounding conductors must be tested(tools, extension cords, and circuits):

At least every three months for cords & tools

At least every six months for receptacles

Results recorded - equipment coded (colored tape)


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Grounding

There are two kinds of grounding:

1. Electrical circuit or system grounding

2. Electrical equipment grounding


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Electrical System Grounding

Circuit

One conductor of the

circuit is intentionally

grounded to earth

Protects circuit from

lightning, or other high

voltage contact

Equipment

All metal frames & enclosures of

equipment are grounded by apermanent connection or bond

The equipment grounding

conductor provides a path for

dangerous fault current to return

to the system ground at the

supply source should a fault

occur


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Without Grounding


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Grounded


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Checking for Ground Continuity


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Temporary Wiring

There must be separatecircuits for electric tools andlighting, each labeled assuch.

Light circuits do not requirea GFCI.

Unless used in a wetlocation.

Test branch circuits beforeuse.

Maintain vertical clearances.

Insulate wires from theirsupports.


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Extension Cords and Cables

Must be in good shape without splices.

Cannot be secured with staples, nailsor bare wire.

Must be protected from damage.

Must have a ground pin.

Should be inspected regularly andpulled from service if defective.

Cannot be repaired with electrical orduct tape. Must repair with heat-

shrink sleeve or bonding/vulcanizingtape to retain original insulationproperties


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Temporary Lighting

All bulbs must beguarded

No broken bulbs orempty sockets

Not suspended by

wiring Low voltage for wet

locations


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Portable Generators The frame of the portable generator

need not be grounded if:

the generator supplies only

cord and plug connectedequipment. The non-current carrying

metal parts of equipmentand the equipmentgrounding conductorterminals of the receptaclesare bonded to the generatorframe.

GFCI is required if >5kV or ifgenerator provides 220V aswell as 110V.


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Safe Work Practices

Before work begins, theemployer must determinewhere exposed andconcealed electrical circuits

are located.

Once found, warningsigns/labels must be posted.

Workers need to know thelocation, hazards, and

protective measures.


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Safe Work Practices

Competent Person determines ifperformance of work could bringcontact with energy.

Distance of the worker to theenergy source should beconsidered first.

Tools, materials, and processesshould also be considered tosee if they could potentiallyshorten the safe separation

distance. Examples: Metal Ladders,

Re-bar, Forklift, ScaffoldFrames, etc.


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Safe Work Practices

Must not permit work near

electric circuits unless the

worker is protected by:

De-energizing the circuit

and grounding it.

Guarding it effectively by

insulation.

Other means (maintaining

safe separation)

De-energized circuits andequipment must be

locked/tagged ou t.


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Safe Work Practices

No metal ladders for ornear electrical work.

No wet hands when

plugging or unpluggingcords/equipment.

No raising or loweringtools by the cord.

Unless equipment is

designed for it, cannotbe used in damp andwet locations.

Safe Work Practices:


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Safe Work Practices: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!) Permit to work may be required for

higher voltage or complex installations



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Safe Work Practices:Safe values of Voltage

55 VAC systems have not causedanybody to be electrocuted

Often referred to as a 110VAC centretapped earth supply (CTE) yellowcoloured equipment

Less than 120 VDC considered to besafe



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Safe Work Practices:Electrical equipment selection

Must be suitable for environment Wet, dusty, flammable gases, mechanical

strength, corrosive atmospheres (maggotfarms)

Must be maintained in good condition

Failure to select suitable equipment andmaintain it often results in incidents at a laterdate

M i t f P t bl El t i l


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Maintenance of Portable ElectricalEquipment

Many accidents result from 230 voltportable equipment

Pressure Washers / Vacuum Cleaners Resulting from

Incorrect selection

Inadequate maintenance / poor repairs

Most important checks are easy to do !

Safe Work Practices:M i t f P t bl El t i l


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Visual Inspection Check flexible mains cable for damage to

insulation

If insulation is damaged REPLACE

DO NOT wrap conductors together and tape up

So called Electrical Insulation Tape will not

provide a sufficient barrier between you and apotentially fatal electric shock as has beenproven on many occasions

Safe Work Practices:Maintenance of Po table Elect ical


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Plug Check that only the outer insulation has been

clamped / gripped. Clamping inner conductorinsulation will potentially lead to exposure oflive terminals.

Is fuse correct rating (Instructions shouldadvise correct current value DO NOT use a

nail)

Check that all 3 pins are present and in goodcondition

Safe Work Practices:Maintenance of Portable Electrical


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Testing Only by a competent person

Earth bond test Insulation test

On-load test

Guidance HSE HS(G) 107 (5)Maintaining portable and transportable electrical equipment


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Summary Hazards & Protections

Protective Measures

Proper grounding

Use GFCIs

Use fuses and circuit breakers

Guard live parts Lock-out/ Tag-out

Proper use of flexible cords

Close electrical panels byCompetent Person

Employee training

Ensure Competent Person on site Use proper approved electrical

equipment

Qualified person install electricaldevices

Protective Measures

Proper grounding

Use GFCIs

Use fuses and circuit breakers

Guard live parts Lock-out/Tag-out

Proper use of flexible cords

Close electrical panels byCompetent Person

Employee training

Ensure Competent Person on site Use proper approved electrical

equipment

Qualified person install electricaldevices

Safeguards for personnel


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Safeguards for personnelprotection

Barricades shall be usedin conjunction withsafety signs where it is

necessary to prevent orlimit employee accessto work areas exposingemployees touninsulated energizedconductors or circuitparts

If signs and barricadesdo not provide sufficientwarning and protection

from electrical hazards,an attendant shall bestationed to warn andprotect employees


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Safeguards for personnel


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Safeguards for personnelprotection


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The Law

Electricity at Work Regulations

Require

Safe construction, maintenance & work systems Capability, Environment, Insulation, Grounding,

Connections, Fusing, Isolation, Making dead, Liveworking, Working Space, Competence.

Covers ALL aspects at ALL voltages.

Documents

Electrical Safety DIPOSH