basic electrical safety usc ee320

8/16/2019 Basic Electrical Safety USC ee320

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Electrical Hazards AwarenessElectrical Hazards Awareness

andand

SafetySafety


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Electrical ShockElectrical Shock

• Received when current passes

through the body

• Severity of the shock depends on:

Path of current through the body

Amount of current flowing

through the body

ength of time the body is in the

circuit


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!he danger of electrical shock is mainly determined by

" value of current

" type of power supply" duration of exposure

" passage/path of current

" human condition!he minimum current at which the human being feels an electric

shock is about 1 mA at #$ %&' !he limit current at which the human

being can endure the pain of an electric shock is about 7 to mA'

!he ma(imum current at which the human being can still move is

about 1! to 1" mA' )hen the current increases further* the heart

shivers and death results in a few minutes' A man may e(perience

shivering ventricles resulting in death when a current of about 1!! mA passes through the body for about # seconds'


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January 2008 Ver 1.1 +

Electricity in the $odyElectricity in the $ody• Muscles

,uscles control all the body movements

-ncluding . importantly those that keep us alive "

%reathing and Heart

!he brain controls voluntary muscles using &urrentpulses along nerves


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January 2008 Ver 1.1 /

Electricity in the $odyElectricity in the $ody

• External current through the body causes

oss of muscle control

Spasms . -nvoluntary movement

-nability to let go

0urns " e(ternal . internal


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#

'angers of Electrical Shock'angers of Electrical Shock

• urrents greater than / mA3can cause ventricular fibrillation4rapid* ineffective heartbeat5

• )ill cause death in a few

minutes unless a defibrillator isused

• / mA is not much current 6 asmall power drill uses 7$ times

as much

3 mA 8 milliampere 8 191*$$$ of an ampere

Defibrillator in use


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(ow )oltage 'oes *ot +ean (ow(ow )oltage 'oes *ot +ean (ow

HazardHazard• A small amount of electrical current can cause inury*

even death

!he current from a '/"watt* 12$"volt lamp* passing

across the chest* is enough to cause fatal

electrocution

• ;eaths from 1,! volts represent about 12 percent of

all electrocutions


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<


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Electrical %urnsElectrical %urns

• ,ost common shock"related*

nonfatal inury

• >ccurs when you touch

electrical wiring or e?uipmentthat is improperly used or

maintained

• !ypically occurs on the hands

• @ery serious inury that needs

immediate attention


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Caused by 24 volt DCCaused by 24 volt DC

batterybattery

Notice where watch band &

screwdriver were in contact

with skin

Caused by kneeling on aCaused by kneeling on a

defective 110 volt acdefective 110 volt ac

extension cordextension cord

Notice the path in & the path

out

http://www.emedicine.com/cgi-bin/foxweb.exe/makezoom@/em/makezoom?picture=%5Cwebsites%5Cemedicine%5Cemerg%5Cimages%5CLarge%5C169elect3.gif&template=izoom2


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http-//www.osha.gov/S(&/etools/construction/electrical0incidents/$urn0examples.htmlelectrical0$urns


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2n response to an electrical accident3 follow these2n response to an electrical accident3 follow these

procedures immediately-procedures immediately-

• all for help 4cant be handled by one person5 and

follow the emergency response system as set forth in

the safety procedures of each organi&ation'

• Bet the approved first"aid supplies 4these should be

easily accessible when re?uired5'

• ;eenergi&e the circuit'

• Separate the person from the energy source'


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• Make sure you and the victim are in a safe zone -not in contact with any electrical source, away from

downed or broken wires.

• Never grab the person or pull the person o the

current with your hands; you might become part ofthe circuit and become inured as well.

• !se a dry wood broom, leather belt, plastic rope

or something similar that is non-conductive such aswood or plastic cane with hook on the end to freethe person from the energy source.


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• "dminister #rst aid. "pply mouth-to-mouthresuscitation and$or %&' if you know what to do.

• (eep the victim lying down, warm and comfortableto maintain body heat until help arrives. )o not

move the person in case of inury to neck or back.

• *f the victim is unconscious, put him$her on side tolet +uids drain.

•Make sure the victim receives professional medicalattention person shocked could have heart failurehours later.


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Electrical Hazards and How toElectrical Hazards and How to

&ontrol hem&ontrol hem

Clectrical accidents arecaused by a combination ofthree factors:

Dnsafe e?uipment and9orinstallation*

)orkplaces made unsafeby the environment* and

Dnsafe work practices'

1/


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1#

4ecognize the Hazards4ecognize the HazardsHave you seen areas like these?

Both are NEC violations and present a safety hazard, based on inaccessible circuit control devices

;o not block the working space around electrical e?uipment 4#$$ volts* nominal* or less5' !his space provides

and maintains sufficient access and working space to permit ready and safe operation and maintenance of such

e?uipment


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Hazard 5 Exposed Electrical 6artsHazard 5 Exposed Electrical 6arts

over removed from wiring or breaker bo(

1


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4ecognize the Hazards4ecognize the HazardsWhat do you do if you see these situations?

Call a timeout and inform your supervisor

;o not remove or open receptacle covers* switch plates* or covers of electrical e?uipment

unless ?ualified and authori&ed


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1=

4ecognize the Hazard4ecognize the Hazard

• Assume all e(posed wiring

is energi&ed until proven

otherwise' S!>P* protectthe area and contact

supervision if you

encounter this situation

Potentially

enerized

e!posed "ire

"ith status

unkno"n


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Hazard 5 'amaged &ordsHazard 5 'amaged &ords

&ords can $e damaged $y-

Aging

'oor or window edges

Staples or fasteningsA$rasion from adacent

materials

Activity in the area

2mproper use can causeshocks3 $urns or fire

2$


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ripping and A$rasion Hazardsripping and A$rasion Hazards• ;onEt cause tripping

ha&ards or create

pinch points for

cords

• -f you must run a

cord temporarily

across the floor*

protect your co"workers by

covering the cord

appropriately

Not #$ #$


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Hazard 5 2mproper 8roundingHazard 5 2mproper 8rounding

• ools plugged intoimproperly groundedcircuits may $ecome

energized

• %roken wire or plug onextension cord

• Some of the mostfre9uently violated :SHAstandards

22


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Hazard 5 'efective &ords ;


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2+

4ecognize the Hazards4ecognize the Hazards%emove from service damaed or frayed cords

%eport electrical e&uipment damae to your supervisor

'tay clear ofbare, e!posed

"irin and

%EP#%( )(*

• @isually inspect electrical e?uipment

before each use for damage and9or

e(ternal defects such as loose*

missing or deformed parts* pinchedor crushed outer ackets or

insulation' !his type of e(ternal

damage may indicate internal

damage to the e?uipment'

• Clectrical cords that are worn or

damaged must be replaced without

delay'• 0efore cleaning electrical e?uipment*

turn it off and unplug it'


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&a$inets3 %oxes3 and =ittings&a$inets3 %oxes3 and =ittings

• Function bo(es* pull bo(esand fittings must haveapproved covers in place

• Dnused openings in cabinets*bo(es and fittings must beclosed 4no missing knockouts5

• Photo shows violations of

these two re?uirements• Report this situation tomanagement


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Hazard 5 :verloaded &ircuitsHazard 5 :verloaded &ircuits

Hazards may result from- oo many devices plugged

into a circuit3 causing heatedwires and possi$ly a fire

'amaged tools overheating (ack of overcurrent

protection S%AG'org " !he Dnofficial Buide !o the >S%A 2#


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2

4ecognize the Hazards4ecognize the Hazards

Never daisy chain multi+outlet strips pluin into each other-


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8rounding 6ath8rounding 6ath• !he path to ground from

circuits* e?uipment* andenclosures must be permanentand continuous

• @iolation shown here is ane(tension cord with a missinggrounding prong

• ;o not make alterations topolari&ed blades or ground pinto make plug fit into non"polari&ed or non"groundedoutlet


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Hazard > :verhead 6ower (inesHazard > :verhead 6ower (ines

?sually not insulated

Examples of e9uipment thatcan contact power lines-

&rane

(adder

Scaffold

%ackhoe

Scissors lift

4aised dump truck $ed

Aluminum paint roller

2=


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7$

4ecognize the Hazards4ecognize the Hazards• Clectrical ha&ards may e(ist

overhead indoors

rane power rails are an

e(ample

•Clectrical ha&ards may alsoe(ist overhead outdoors

,ost lines are bare and

higher voltage than the

HnormalI insulated wiring

ontact is not re?uired to

initiate an arc or cause shock

and burn inuries

,aintain safe approach

distances when working near

energi&ed overhead lines

'tay at least ./ feet a"ay from overhead lines


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&ontrol > :verhead 6ower (ines&ontrol > :verhead 6ower (ines

• Stay at least 1! feet away

• 6ost warning signs

• Assume that lines are

energized• ?se wood or fi$erglass

ladders3 not metal

• 6ower line workers need

special training ; 66E

71


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Electricity is always trying to get

to the ground.

@ite string and you are one of the$est conductors for electricity.

Hazards in Electricity


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+etal (adder and you are

one of the $est conductorsfor electricity.



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Have you ever wondered why the birds that

sit on power lines don't get electric shocks

!t's because the electricity is always lookingfor a way to get to the ground" but the birds

are not touching the ground or anything in

contact with the ground#



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• !reat it as it is

designed to be

treated• Pull the plug* not the

cord

%andle portable electrical e?uipment carefully* in accordance with manufacturers

instructions* and in a manner that will not cause damage


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Hazard > 2nade9uate 2nade9uate S%A 7#

)ire Bauge

)-RC

Wire gauge measureswires ranging in size from

number 36 to 0 American

wire gauge (AWG)


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• 4+5 he path to ground from circuits3

e9uipment3 and enclosures shall $e

permanent and continuous

11!. #!B CfD 8rounding11!. #!B CfD 8rounding


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8rounding8rounding

• !here are two kinds of grounding:

1' Clectrical circuit or system grounding

2' Clectrical e?uipment grounding


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Electrical System 8roundingElectrical System 8rounding

• :ne conductor of the circuit is intentionally

grounded to earth

• 6rotects circuit from lightning3 or other highvoltage contact

8


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E9uipment 8roundingE9uipment 8rounding• All metal frames ; enclosures of e9uipment are grounded

$y a permanent connection or $ond

• he e9uipment 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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8rounding E9uipment &onnected8rounding E9uipment &onnected

$y &ord and 6lug$y &ord and 6lug

• Exposed non>current carrying metal parts of cord and

plug connected e9uipment which may $ecome

energized shall $e grounded

• 2f in a hazardous location

• 2f operated at over 1"! volts


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Note that properly bonded conduit and associated

metal enclosures can also serve as a grounding

conductor.


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CJ>B Clectrical -mprovement Proect +/

Safe 6racticesSafe 6ractices

&ord &ontrol&ord &ontrol• ;o not fasten electrical cords to surfaces with staples* nails*

wire* or any other method that might damage the cord

• C(tension cords

Place them in appropriate locations Dnderstand they are for temporary use only

• !ool cords

Keep track of them* to assure they do not become

damaged

• ;o not plug or unplug electrical cords with wet hands or

while standing in water


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CJ>B Clectrical -mprovement Proect +#


&ord &ontrol &ont.&ord &ontrol &ont.• ;o not use portable electrical e?uipment or e(tension

cords in wet or damp locations without a ground fault

circuit interrupter 4BJ-5 ahead of the plug connection

• BJ-s are also re?uired for temporary power applications

in wet or damp locations* including e(tension cords

• Remove loads from an appliance or e(tension cord before

unplugging it

• -f a plug wonEt stay placed snugly or fits loosely in a

receptacle* donEt use itL call local C.- to replace it


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CJ>B Clectrical -mprovement Proect +


4esetting %reakers4esetting %reakers• )hen circuit breakers and fuses trip* donEt reset or

replace themM

• >nly ?ualified and authori&ed personnel are allowed

to reset breakers and replace fuses

• ontact ?ualified personnel to determine the cause oftrips


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CJ>B Clectrical -mprovement Proect +<


&onductive Apparel&onductive Apparel• ;onEt wear loose

conductive apparel*

4such as rings*

watch bands*bracelets*

necklaces* etc'5

when plugging in

electrical cords

Burn

from arc

Charm

contacted

plu

Charm

contacted pluhere


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CJ>B Clectrical -mprovement Proect +=



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CJ>B Clectrical -mprovement Proect /$


E9uipment ApplicationsE9uipment Applications• onsumer electrical e?uipment or

appliances should be tested andlabeled by a recogni&ed testinglaboratory' 4ook for the D* SA*C! or ,C! abel5

• Always read and follow themanufacturers instructions carefully'0e sure that the e?uipment or tool israted for the environment 4wet* damp*etc'5

• Plug portable space heaters directlyinto outlet: ;o not use e(tension cord'Dse a circuit with as little else on it as

possible since space heaters take alot of power'


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CJ>B Clectrical -mprovement Proect /1


ualificationsualifications• ;o not remove9replace receptacle covers* switch

plates* or covers of electrical e?uipment that may

contain energi&ed conductors without electrical

?ualifications and authori&ation• >nly ?ualified electrical workers may perform

activities such as electrical probing* measuring and

testing electrical energi&ed components 4such as

performing an Habsence of voltageI test5


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CJ>B Clectrical -mprovement Proect /2


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basic electrical safety usc ee320

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