1. controlling electrical hazards
TRANSCRIPT
-
8/8/2019 1. Controlling Electrical Hazards.
1/92
Presentation byPresentation byEr. C.P.GeorgeEr. C.P.George
CONTROLLINGCONTROLLING
ELECTRICAL HAZARDS.ELECTRICAL HAZARDS.
-
8/8/2019 1. Controlling Electrical Hazards.
2/92
10/2/2010 cpgeorge 2
CONTROLLINGCONTROLLING
ELECTRICAL HAZARDS.ELECTRICAL HAZARDS.
-
8/8/2019 1. Controlling Electrical Hazards.
3/92
10/2/2010 cpgeorge 3
--BODYBODY
How Electricity Acts?How Electricity Acts?Electric Hazards.Electric Hazards.
How Shock Occurs?How Shock Occurs?The Severity of ShockThe Severity of ShockEffect of Electric Current inEffect of Electric Current in
Human Body.Human Body.InjuriesInjuries
-
8/8/2019 1. Controlling Electrical Hazards.
4/92
10/2/2010 cpgeorge 4
ELECTRIC HAZARDSELECTRIC HAZARDS
InsulationInsulationGuardingGuarding
GroundingGroundingProtective DevicesProtective DevicesSafe Work PracticesSafe Work Practices
TrainingTrainingGood Judgments.Good Judgments.
-
8/8/2019 1. Controlling Electrical Hazards.
5/92
10/2/2010 cpgeorge 5
HOW TO PRACTICEHOW TO PRACTICE
Assess the RiskAssess the RiskRisk assessment methodsRisk assessment methodsHarsh conditionsHarsh conditionsRisky itemsRisky itemsReducing the Risk:Reducing the Risk:a. In under ground power cablesa. In under ground power cablesb. Over head power linesb. Over head power linesc.Electrified railways and tramways.c.Electrified railways and tramways.
-
8/8/2019 1. Controlling Electrical Hazards.
6/92
10/2/2010 cpgeorge 6
HOW ELECTRICITYHOW ELECTRICITY
ACTSACTSOperating an electricOperating an electric
switch may beswitch may be
considered analogous toconsidered analogous to
turning on a water faucet.turning on a water faucet.
-
8/8/2019 1. Controlling Electrical Hazards.
7/92
10/2/2010 cpgeorge 7
ACTS ..ACTS ..
In the case of water, theIn the case of water, thesource is a reservoir or source is a reservoir or
pumping station; thepumping station; thetransportation is throughtransportation is throughpipes; and the force to makepipes; and the force to make
it flow is pressure, providedit flow is pressure, providedby a pump.by a pump.
-
8/8/2019 1. Controlling Electrical Hazards.
8/92
10/2/2010 cpgeorge 8
For electricity, the source isFor electricity, the source isthe power generatingthe power generating
station; current travelsstation; current travelsthrough electric conductorsthrough electric conductorsin the form of wires; andin the form of wires; and
pressure, measured in volts,pressure, measured in volts,is provided by a generator.is provided by a generator.
HOW ELECTRICITYHOW ELECTRICITY
ACTSACTS - - -- --
-
8/8/2019 1. Controlling Electrical Hazards.
9/92
10/2/2010 cpgeorge 9
HOW ELECTRICITYHOW ELECTRICITY
ACTS.ACTS.Resistance to the flow of electricityResistance to the flow of electricity
is measured in ohms and variesis measured in ohms and varies
widely. It is determined by threewidely. It is determined by threefactors: the nature of the substancefactors: the nature of the substance
itself, the length and crossitself, the length and cross- -sectionalsectional
area (size) of the substance, and thearea (size) of the substance, and the
temperature of the substance.temperature of the substance.
-
8/8/2019 1. Controlling Electrical Hazards.
10/92
10/2/2010 cpgeorge 10
Some substances, such as metals,Some substances, such as metals,offer very little resistance to the flowoffer very little resistance to the flowof electric current and are calledof electric current and are calledconductors. Other substances, suchconductors. Other substances, suchas bakelite, porcelain, pottery, andas bakelite, porcelain, pottery, anddry wood, offer such a highdry wood, offer such a high
resistance that they can be used toresistance that they can be used toprevent the flow of electric currentprevent the flow of electric currentand are called insulators.and are called insulators.
HOW ELECTRICITYHOW ELECTRICITY
ACTSACTS
-
8/8/2019 1. Controlling Electrical Hazards.
11/92
10/2/2010 cpgeorge 11
HOW ELECTRICITYHOW ELECTRICITYACTSACTS
Dry wood has a highDry wood has a highresistance, but whenresistance, but whensaturated with water, itssaturated with water, itsresistance drops to theresistance drops to thepoint where it will readilypoint where it will readilyconduct electricity.conduct electricity.The same thing is true of The same thing is true of human skin.human skin.
-
8/8/2019 1. Controlling Electrical Hazards.
12/92
10/2/2010 cpgeorge 12
When it is dry, skin has a fairly highWhen it is dry, skin has a fairly highresistance to electric current; butresistance to electric current; butwhen it is moist, there is a radicalwhen it is moist, there is a radicaldrop in resistancedrop in resistance ..Pure water is a poor conductor, butPure water is a poor conductor, butsmall amounts of impurities, such assmall amounts of impurities, such assalt and acid (salt and acid ( both of which areboth of which are
contained in perspiration),contained in perspiration), make it amake it aready conductor.ready conductor.
ACTSACTS
-
8/8/2019 1. Controlling Electrical Hazards.
13/92
10/2/2010 cpgeorge 13
HOW ELECTRICITY ACTSHOW ELECTRICITY ACTS
When water is present either When water is present either in the environment or on thein the environment or on theskin, anyone working withskin, anyone working withelectricity should exerciseelectricity should exercise
even more caution than theyeven more caution than theynormally would.normally would.
-
8/8/2019 1. Controlling Electrical Hazards.
14/92
10/2/2010 cpgeorge 14
HAZARDSHAZARDS
ELECTROCUTIONELECTROCUTION
ELECTRIC SHOCKELECTRIC SHOCK
BURNSBURNS
FIRESFIRES
EXPLOSIONEXPLOSION
-
8/8/2019 1. Controlling Electrical Hazards.
15/92
10/2/2010 cpgeorge 15
HOW SHOCK OCCURS?HOW SHOCK OCCURS?
Electric shock occurs whenElectric shock occurs whenthe body becomes a part of the body becomes a part of the electric circuit. Thethe electric circuit. Thecurrent must enter the bodycurrent must enter the body
at one point and leave atat one point and leave atanother.another.
-
8/8/2019 1. Controlling Electrical Hazards.
16/92
10/2/2010 cpgeorge 16
Electric shock normally occurs inElectric shock normally occurs inone of three ways. Individualsone of three ways. Individuals whilewhilein contact with the groundin contact with the ground
1. must come in contact with both1. must come in contact with bothwires of the electric circuitwires of the electric circuit
2. one wire of an energized circuit or 2. one wire of an energized circuit or
3. a metallic part that has become3. a metallic part that has becomehot by contact with an energizedhot by contact with an energizedconductor.conductor.
HOW SHOCK OCCURS?HOW SHOCK OCCURS?
-
8/8/2019 1. Controlling Electrical Hazards.
17/92
10/2/2010 cpgeorge 17
GROUNDING PROTECTIONGROUNDING PROTECTION
In case 3 the worker using theseIn case 3 the worker using these
tools and machines is made lesstools and machines is made less
vulnerable to electric shock whenvulnerable to electric shock when
there is a low resistance path fromthere is a low resistance path from
the metallic case of the tool or the metallic case of the tool or machine to the ground.machine to the ground.
-
8/8/2019 1. Controlling Electrical Hazards.
18/92
10/2/2010 cpgeorge 18
This is done through the use of anThis is done through the use of anequipment grounding conductor equipment grounding conductor a a
lowlow- -resistance wire that causes theresistance wire that causes theunwanted current to pass directly tounwanted current to pass directly tothe ground, thereby greatly reducingthe ground, thereby greatly reducingthe amount of current passingthe amount of current passingthrough the body of the person inthrough the body of the person incontact with the tool or machine.contact with the tool or machine.
GROUNDING PROTECTIONGROUNDING PROTECTION
-
8/8/2019 1. Controlling Electrical Hazards.
19/92
10/2/2010 cpgeorge 19
If the equipmentIf the equipmentgrounding conductor hasgrounding conductor hasbeen properly installed, itbeen properly installed, ithas a low resistance tohas a low resistance to
ground, and the worker isground, and the worker isprotected.protected.
GROUNDING PROTECTIONGROUNDING PROTECTION
-
8/8/2019 1. Controlling Electrical Hazards.
20/92
10/2/2010 cpgeorge 20
SHOCKSHOCK
The severity of the shock receivedThe severity of the shock receivedwhen a person becomes a part of anwhen a person becomes a part of an
electric circuit is affected byelectric circuit is affected by1. the amount of current flowing1. the amount of current flowingthrough the body (measured inthrough the body (measured inamperes)amperes)
2. the path of the current through the2. the path of the current through thebodybody3. the length of time the body is in3. the length of time the body is inthe circuitthe circuit
-
8/8/2019 1. Controlling Electrical Hazards.
21/92
10/2/2010 cpgeorge 21
THE SEVERITY OFTHE SEVERITY OFSHOCK..SHOCK..
Other factors that may affect theOther factors that may affect theseverity of shock are the frequencyseverity of shock are the frequency
of the current, the phase of the heartof the current, the phase of the heartcycle when shock occurs, and thecycle when shock occurs, and thegeneral health of the person.general health of the person.
The effects of electric shock dependThe effects of electric shock dependupon the type of circuit, its voltage,upon the type of circuit, its voltage,resistance, current, pathway throughresistance, current, pathway throughthe body, and duration of thethe body, and duration of thecontact.contact.
-
8/8/2019 1. Controlling Electrical Hazards.
22/92
10/2/2010 cpgeorge 22
THE SEVERITY OFTHE SEVERITY OFSHOCK..SHOCK..
Effects can range from a barelyEffects can range from a barelyperceptible tingle to immediateperceptible tingle to immediate
cardiac arrest.cardiac arrest.There are no absolute limits or There are no absolute limits or even known values that showeven known values that show
the exact injury from anythe exact injury from anygiven currentgiven current
-
8/8/2019 1. Controlling Electrical Hazards.
23/92
10/2/2010 cpgeorge 23
EFFECT OF CURRENT IN HUMAN BODY.EFFECT OF CURRENT IN HUMAN BODY. [Hand to foot[Hand to footpath and one second duration for 60Hz]path and one second duration for 60Hz]
1 Milliamps1 Milliamps Perception level. Just a faint tingle.Perception level. Just a faint tingle.
5 Milliamps5 MilliampsSlight shock felt: not painful but disturbing. AverageSlight shock felt: not painful but disturbing. Average
individual can let go.individual can let go.
66--25 Milliamps25 Milliamps[women][women]
Painful Shock, muscular control is lost.Painful Shock, muscular control is lost.
99--30 Milliamps30 Milliamps[men][men]
This is called the freezing current or letThis is called the freezing current or let- -go range.go range.
5050--150 Milliamps150 MilliampsExtreme pain, respiratory arrest, severe muscularExtreme pain, respiratory arrest, severe muscular
contractions. Individual cannot let go. Death iscontractions. Individual cannot let go. Death ispossible.possible.
10001000- -43004300MilliampsMilliamps
Ventricular fibrillation. [The rhythmic pumping actionVentricular fibrillation. [The rhythmic pumping actionof the heart ceases.] Muscular contraction andof the heart ceases.] Muscular contraction and
nerve damage occur. Death is most likely.nerve damage occur. Death is most likely.
10000 Milliamps10000 Milliamps Cardiac arrest, severe burns and probable death.Cardiac arrest, severe burns and probable death.
-
8/8/2019 1. Controlling Electrical Hazards.
24/92
10/2/2010 cpgeorge 24
THE SEVERITY OF SHOCKTHE SEVERITY OF SHOCK[[TABLETABLE- - ANALYSIS]ANALYSIS]
The table also illustrates thatThe table also illustrates that aadifference of less than 100 milliampsdifference of less than 100 milliamps
exists between a current that isexists between a current that isbarely perceptible and one that canbarely perceptible and one that cankillkillMuscular contraction caused byMuscular contraction caused bystimulation may not allow the victimstimulation may not allow the victimto free himself or herself from theto free himself or herself from thecircuit, andcircuit, and the increased duration of the increased duration of exposure increases the dangers toexposure increases the dangers tothe shock victim.the shock victim.
-
8/8/2019 1. Controlling Electrical Hazards.
25/92
10/2/2010 cpgeorge 25
a current of 100 milliampsa current of 100 milliampsfor 3 seconds is equivalentfor 3 seconds is equivalentto a current of 900 milliampsto a current of 900 milliampsapplied for .03 seconds inapplied for .03 seconds in
causing ventricular causing ventricular fibrillationfibrillation
THE SEVERITY OFTHE SEVERITY OFSHOCK..SHOCK..
-
8/8/2019 1. Controlling Electrical Hazards.
26/92
10/2/2010 cpgeorge 26
THE SEVERITY OF SHOCKTHE SEVERITY OF SHOCK
LOW VOLTAGE DOES NOT IMPLYLOW VOLTAGE DOES NOT IMPLYLOW HAZARD!LOW HAZARD!A severe shock can causeA severe shock can causeconsiderably more damage to theconsiderably more damage to thebody than is visible. For example,body than is visible. For example,
a person may suffer internala person may suffer internalhemorrhages and destruction of hemorrhages and destruction of tissues, nerves, and muscles.tissues, nerves, and muscles.
-
8/8/2019 1. Controlling Electrical Hazards.
27/92
10/2/2010 cpgeorge 27
Shock is often only theShock is often only thebeginning in a chain of beginning in a chain of events. The final injuryevents. The final injurymay well be from a fall,may well be from a fall,
cuts, burns, or brokencuts, burns, or brokenbones.bones.
SHOCKSHOCK
-
8/8/2019 1. Controlling Electrical Hazards.
28/92
10/2/2010 cpgeorge 28
BURNS AND OTHER INJURIESBURNS AND OTHER INJURIES
The most common shockThe most common shock- -relatedrelatedinjury is a burn.injury is a burn.
Burns suffered in electricalBurns suffered in electricalaccidents may be of three types:accidents may be of three types:1. electrical burns1. electrical burns
2. arc burns, and2. arc burns, and3.thermal contact burns.3.thermal contact burns.
-
8/8/2019 1. Controlling Electrical Hazards.
29/92
10/2/2010 cpgeorge 29
ELECTRIC BURNSELECTRIC BURNS
Electrical burns are the result of Electrical burns are the result of the electric current flowingthe electric current flowing
through tissues or bone.through tissues or bone.Tissue damage is caused by theTissue damage is caused by theheat generated by the currentheat generated by the currentflow through the body.flow through the body.Electrical burns are one of theElectrical burns are one of themost serious injuries you canmost serious injuries you canreceive and should be givenreceive and should be given
immediate attention.immediate attention.
-
8/8/2019 1. Controlling Electrical Hazards.
30/92
10/2/2010 cpgeorge 30
THERMAL CONTACT BURNSTHERMAL CONTACT BURNS
The thermal contact burns are thoseThe thermal contact burns are thosenormally experienced when the skinnormally experienced when the skin
comes in contact with hot surfacescomes in contact with hot surfacesof overheated electric conductors,of overheated electric conductors,conduits, or other energizedconduits, or other energizedequipment.equipment.
Additionally, clothing may be ignitedAdditionally, clothing may be ignitedin an electrical accident and ain an electrical accident and athermal burn will resultthermal burn will result
-
8/8/2019 1. Controlling Electrical Hazards.
31/92
10/2/2010 cpgeorge 31
ARC OR FLASH BURNSARC OR FLASH BURNS
Arc or flash burns, on the other Arc or flash burns, on the other hand, are the result of highhand, are the result of high
temperatures near the body andtemperatures near the body andare produced by an electric arcare produced by an electric arcor explosion.or explosion.
They should also be attended toThey should also be attended topromptly.promptly.
-
8/8/2019 1. Controlling Electrical Hazards.
32/92
-
8/8/2019 1. Controlling Electrical Hazards.
33/92
10/2/2010 cpgeorge 33
SECONDARY INJURIES..SECONDARY INJURIES..
In addition to shock and burnIn addition to shock and burnhazards, electricity poses other hazards, electricity poses other dangers. For example, when adangers. For example, when ashort circuit occurs, hazards areshort circuit occurs, hazards arecreated from the resulting arcs. If created from the resulting arcs. If high current is involved, these arcshigh current is involved, these arcscan cause injury or start a fire.can cause injury or start a fire.
-
8/8/2019 1. Controlling Electrical Hazards.
34/92
10/2/2010 cpgeorge 34
SECONDARY INJURIESSECONDARY INJURIES
Extremely high energy arcs canExtremely high energy arcs candamage equipment, causingdamage equipment, causingfragmented metal to fly in allfragmented metal to fly in alldirections. Even lowdirections. Even low- -energy arcsenergy arcscan cause violent explosions incan cause violent explosions inatmospheres that containatmospheres that contain
flammable gases, vapors, or flammable gases, vapors, or combustible dusts.combustible dusts.
-
8/8/2019 1. Controlling Electrical Hazards.
35/92
10/2/2010 cpgeorge 35
PREVENTINGPREVENTINGELECTRICAL HAZARDSELECTRICAL HAZARDS
These include:These include:1. insulation,1. insulation,
2. guarding,2. guarding,3. grounding,3. grounding,4. electrical protective4. electrical protectivedevices, anddevices, and5. safe work practices5. safe work practices
-
8/8/2019 1. Controlling Electrical Hazards.
36/92
10/2/2010 cpgeorge 36
INSULATIONINSULATION
. Before employees prepare to work. Before employees prepare to workwith electric equipment, it iswith electric equipment, it is
always a good idea for them toalways a good idea for them tocheck the insulation before makingcheck the insulation before makinga connection to a power source toa connection to a power source tobe sure there are no exposed wiresbe sure there are no exposed wiresThe insulation of flexible cords,The insulation of flexible cords,such as extension cords, issuch as extension cords, isparticularly vulnerable to damage.particularly vulnerable to damage.
-
8/8/2019 1. Controlling Electrical Hazards.
37/92
10/2/2010 cpgeorge 37
INSULATIONINSULATION
Also, the insulation should beAlso, the insulation should besuitable for the voltage andsuitable for the voltage andexisting conditions, such asexisting conditions, such astemperature, moisture, oil,temperature, moisture, oil,gasoline, or corrosive fumes.gasoline, or corrosive fumes.The ungrounded conductors, or The ungrounded conductors, or hot wires, may be any color hot wires, may be any color other than green, white, or gray.other than green, white, or gray.
-
8/8/2019 1. Controlling Electrical Hazards.
38/92
10/2/2010 cpgeorge 38
GUARDINGGUARDING
Live parts of electricLive parts of electricequipment operating at 50equipment operating at 50volts or more must bevolts or more must beguarded against accidentalguarded against accidentalcontactcontact
location in a room, vault, or location in a room, vault, or similar enclosure accessiblesimilar enclosure accessibleonly to qualified persons;only to qualified persons;
-
8/8/2019 1. Controlling Electrical Hazards.
39/92
10/2/2010 cpgeorge 39
GUARDING ..GUARDING ..
use of permanent, substantialuse of permanent, substantialpartitions or screens to excludepartitions or screens to excludeunqualified persons;unqualified persons;location on a suitable balcony,location on a suitable balcony,
gallery, or platform elevated andgallery, or platform elevated andarranged to exclude unqualifiedarranged to exclude unqualifiedpersons; or persons; or elevation of 8 feet (2.44 meters)elevation of 8 feet (2.44 meters)or more above the floor.or more above the floor.
-
8/8/2019 1. Controlling Electrical Hazards.
40/92
10/2/2010 cpgeorge 40
GUARDING ..GUARDING ..
Entrances to rooms and other Entrances to rooms and other
guarded locations containingguarded locations containingexposed live parts must beexposed live parts must be
marked with conspicuousmarked with conspicuous
warning signs forbiddingwarning signs forbidding
unqualified persons to enter.unqualified persons to enter.
-
8/8/2019 1. Controlling Electrical Hazards.
41/92
10/2/2010 cpgeorge 41
GUARDING GUARDING
Indoor electric wiring more than 600Indoor electric wiring more than 600volts and that is open to unqualifiedvolts and that is open to unqualifiedpersons must be made with metalpersons must be made with metal- -enclosed equipment or enclosed in aenclosed equipment or enclosed in avault or area controlled by a lock.vault or area controlled by a lock.
In addition, equipment must beIn addition, equipment must bemarked with appropriate cautionmarked with appropriate cautionsigns.signs.
-
8/8/2019 1. Controlling Electrical Hazards.
42/92
10/2/2010 cpgeorge 42
GROUNDINGGROUNDING
It is normally a secondaryIt is normally a secondary
protective measure.protective measure.By grounding a tool or By grounding a tool or
electrical system, a lowelectrical system, a low- -
resistance path to the earth isresistance path to the earth isintentionally created.intentionally created.
-
8/8/2019 1. Controlling Electrical Hazards.
43/92
10/2/2010 cpgeorge 43
GROUNDING ..GROUNDING ..
The term ground refers to aThe term ground refers to aconductive body, usually theconductive body, usually theearth, and means a conductiveearth, and means a conductiveconnection, whether intentionalconnection, whether intentionalor accidental, by which anor accidental, by which anelectric circuit or equipment iselectric circuit or equipment is
connected to earth or theconnected to earth or theground plane.ground plane.
-
8/8/2019 1. Controlling Electrical Hazards.
44/92
10/2/2010 cpgeorge 44
GROUNDING GROUNDING
. When properly done, this path. When properly done, this path
offers sufficiently low resistance andoffers sufficiently low resistance andhas sufficient current carryinghas sufficient current carrying
capacity to prevent the buildup of capacity to prevent the buildup of
voltages that may result in avoltages that may result in apersonnel hazardpersonnel hazard
-
8/8/2019 1. Controlling Electrical Hazards.
45/92
10/2/2010 cpgeorge 45
This does not guarantee that noThis does not guarantee that noone will receive a shock, beone will receive a shock, beinjured, or be killed. It will,injured, or be killed. It will,however, substantially reducehowever, substantially reducethe possibility of suchthe possibility of suchaccidentsaccidents especially whenespecially whenused in combination with proper used in combination with proper safety measures.safety measures.
GROUNDING GROUNDING
-
8/8/2019 1. Controlling Electrical Hazards.
46/92
10/2/2010 cpgeorge 46
GROUNDINGGROUNDING- - TYPESTYPES
There are two kinds of There are two kinds of
grounds.grounds.
One of these is called theOne of these is called the
service or system ground.service or system ground.
-
8/8/2019 1. Controlling Electrical Hazards.
47/92
10/2/2010 cpgeorge 47
--System GroundSystem Ground
In this instance, one wireIn this instance, one wire called the neutral conductorcalled the neutral conductoror grounded conductoror grounded conductor is isgrounded.grounded.This type of ground is primarilyThis type of ground is primarilydesigned to protect machines,designed to protect machines,tools, and insulation againsttools, and insulation againstdamagedamage
-
8/8/2019 1. Controlling Electrical Hazards.
48/92
10/2/2010 cpgeorge 48
GROUNDING FORGROUNDING FOR
ENHANCED PROTECTIONENHANCED PROTECTIONTo offer enhanced protection toTo offer enhanced protection tothe workers themselves, anthe workers themselves, anadditional ground, called theadditional ground, called theequipment ground, must beequipment ground, must befurnished by providing another furnished by providing another
path from the tool or machinepath from the tool or machinethrough which the current canthrough which the current canflow to the ground.flow to the ground.
-
8/8/2019 1. Controlling Electrical Hazards.
49/92
10/2/2010 cpgeorge 49
GROUNDING & SAFETYGROUNDING & SAFETY
This additional groundThis additional groundsafeguards the electricsafeguards the electric
equipment operator in the eventequipment operator in the eventthat a malfunction causes thethat a malfunction causes themetal frame of the tool tometal frame of the tool tobecome accidentally energized.become accidentally energized.
The resulting heavy surgeThe resulting heavy surgeof current will then activate theof current will then activate thecircuit protection devices andcircuit protection devices andopen the circuitopen the circuit ..
-
8/8/2019 1. Controlling Electrical Hazards.
50/92
10/2/2010 cpgeorge 50
CIRCUIT PROTECTIONCIRCUIT PROTECTIONDEVICESDEVICES
Circuit protection devices areCircuit protection devices are
designed to automatically limitdesigned to automatically limitor shut off the flow of or shut off the flow of
electricity in the event of aelectricity in the event of agroundground- -fault, overload, or shortfault, overload, or short
circuit in the wiring system.circuit in the wiring system.
-
8/8/2019 1. Controlling Electrical Hazards.
51/92
10/2/2010 cpgeorge 51
PROTECTIVE DEVICESPROTECTIVE DEVICES
Fuses, circuit breakers, andFuses, circuit breakers, and
groundground- -fault circuitfault circuitinterrupters are three wellinterrupters are three wellknown examples of suchknown examples of suchdevices.devices.
-
8/8/2019 1. Controlling Electrical Hazards.
52/92
10/2/2010 cpgeorge 52
Fuses and circuitFuses and circuit- -breakers arebreakers areover over- -current devices that arecurrent devices that areplaced in circuits to monitor theplaced in circuits to monitor theamount of current that theamount of current that thecircuit will carry.circuit will carry.
They automatically openThey automatically openor break the circuit when theor break the circuit when theamount of current flow becomesamount of current flow becomesexcessive and therefore unsafe.excessive and therefore unsafe.
PROTECTIVE DEVICESPROTECTIVE DEVICES
-
8/8/2019 1. Controlling Electrical Hazards.
53/92
10/2/2010 cpgeorge 53
FUSES & CIRCUITFUSES & CIRCUITBRAKERSBRAKERS
Fuses are designed to meltFuses are designed to meltwhen too much current flowswhen too much current flowsthrough them.through them.
Circuit breakers, onCircuit breakers, onthe other hand, are designedthe other hand, are designedto trip open the circuit byto trip open the circuit byelectroelectro- -mechanical means.mechanical means.
-
8/8/2019 1. Controlling Electrical Hazards.
54/92
10/2/2010 cpgeorge 54
BRAKERSBRAKERS
Fuses and circuit breakers areFuses and circuit breakers areintended primarily for theintended primarily for theprotection of conductors andprotection of conductors andequipment.equipment.They prevent overheating of They prevent overheating of wires and components thatwires and components that
might otherwise create hazardsmight otherwise create hazardsfor operators.for operators.
-
8/8/2019 1. Controlling Electrical Hazards.
55/92
10/2/2010 cpgeorge 55
GROUND FAULTGROUND FAULT
CIRCUIT INTERRUPTERCIRCUIT INTERRUPTERThe groundThe ground- -fault circuit interrupter, or fault circuit interrupter, or
GFCI, is designed to shutoff electricGFCI, is designed to shutoff electric
power within as little as 1/40 of apower within as little as 1/40 of asecond.second.It works by comparing the amount of It works by comparing the amount of
current going to electric equipmentcurrent going to electric equipmentagainst the amount of current returningagainst the amount of current returningfrom the equipment along the circuitfrom the equipment along the circuitconductors.conductors.
-
8/8/2019 1. Controlling Electrical Hazards.
56/92
10/2/2010 cpgeorge 56
INTERUPTERINTERUPTER
If the current difference exceeds 6If the current difference exceeds 6
milliamps, the GFCI interrupts themilliamps, the GFCI interrupts the
current quickly enough to preventcurrent quickly enough to preventelectrocution.electrocution.
The GFCI is used in highThe GFCI is used in high- -risk areasrisk areas
such as wet locations andsuch as wet locations andconstruction sites.construction sites.
-
8/8/2019 1. Controlling Electrical Hazards.
57/92
10/2/2010 cpgeorge 57
SAFE WORK PRACTICESSAFE WORK PRACTICES
DeDe--energizing electric equipmentenergizing electric equipmentbefore inspecting or making repairsbefore inspecting or making repairs
Using electric tools that are in goodUsing electric tools that are in goodrepair repair
Using good judgment when workingUsing good judgment when working
near energized lines, andnear energized lines, andUsing appropriate protectiveUsing appropriate protectiveequipment.equipment.
-
8/8/2019 1. Controlling Electrical Hazards.
58/92
10/2/2010 cpgeorge 58
SAFE WORK PRACTICESSAFE WORK PRACTICES
Electrical safetyElectrical safety- -relatedrelated
work practice requirementswork practice requirements
are to be strictly adopted asare to be strictly adopted as
per the issued manuals.per the issued manuals.
DEDE ENERGISINGENERGISING
-
8/8/2019 1. Controlling Electrical Hazards.
59/92
10/2/2010 cpgeorge 59
DEDE--ENERGISINGENERGISINGELECTRICAL EQUIPMENTELECTRICAL EQUIPMENT
The accidental or The accidental or
unexpected suddenunexpected sudden
starting of electricalstarting of electrical
equipment can causeequipment can cause
severe injury or death.severe injury or death.
DEDE ENERGISINGENERGISING
-
8/8/2019 1. Controlling Electrical Hazards.
60/92
10/2/2010 cpgeorge 60
Before ANY inspections or Before ANY inspections or
repairs are maderepairs are made even on theeven on the
soso- -called lowcalled low- -voltage circuitsvoltage circuits the current must be turned off atthe current must be turned off at
the switch box and the switchthe switch box and the switch
padlocked in the OFF position.padlocked in the OFF position.
DEDE--ENERGISINGENERGISINGELECTRICAL EQUIPMENTELECTRICAL EQUIPMENT
-
8/8/2019 1. Controlling Electrical Hazards.
61/92
10/2/2010 cpgeorge 61
DEDE--ENERGISINGENERGISING
At the same time, the switch or At the same time, the switch or
controls of the machine or other controls of the machine or other
equipment being locked out of equipment being locked out of service must be securely taggedservice must be securely tagged
to show which equipment or to show which equipment or
circuits are being worked on.circuits are being worked on.
-
8/8/2019 1. Controlling Electrical Hazards.
62/92
10/2/2010 cpgeorge 62
MAINTENANCE WORKSMAINTENANCE WORKS
Maintenance employees shouldMaintenance employees shouldbe qualified for the work whobe qualified for the work who
have been well instructed inhave been well instructed inlockout procedures.lockout procedures.No two locks should be alike;No two locks should be alike;each key should fit only oneeach key should fit only one
lock, and only one key should belock, and only one key should beissued to each maintenanceissued to each maintenanceemployee.employee.
-
8/8/2019 1. Controlling Electrical Hazards.
63/92
10/2/2010 cpgeorge 63
MAINTENANCE WORKMAINTENANCE WORK
If more than one employee isIf more than one employee isrepairing a piece of equipment, eachrepairing a piece of equipment, eachshould lock out the switch with his or should lock out the switch with his or
her own lock and never permither own lock and never permitanyone else to remove it.anyone else to remove it.The maintenance worker should atThe maintenance worker should atall times be certain that he or she isall times be certain that he or she isnot exposing other employees tonot exposing other employees todanger.danger.
-
8/8/2019 1. Controlling Electrical Hazards.
64/92
10/2/2010 cpgeorge 64
OVERHEAD LINESOVERHEAD LINES
If work is to be performed near If work is to be performed near overhead power lines, the lines must beoverhead power lines, the lines must be
dede- -energized and grounded by theenergized and grounded by theowner or operator of the lines, or other owner or operator of the lines, or other protective measures must be providedprotective measures must be providedbefore work is started.before work is started.
Protective measures (such as guardingProtective measures (such as guardingor insulating the lines) must beor insulating the lines) must bedesigned to prevent employees fromdesigned to prevent employees fromcontacting the lines.contacting the lines.
-
8/8/2019 1. Controlling Electrical Hazards.
65/92
10/2/2010 cpgeorge 65
OVERHEAD LINES ..OVERHEAD LINES ..
Unqualified employees andUnqualified employees andmechanical equipment mustmechanical equipment must
stay at least 10 feet (3.05stay at least 10 feet (3.05meters) away from overheadmeters) away from overheadpower lines. If the voltage ispower lines. If the voltage ismore than 50,000 volts, themore than 50,000 volts, the
clearance must be increased byclearance must be increased by4 inches (10 centimeters) for 4 inches (10 centimeters) for each additional 10,000 volts.each additional 10,000 volts.
-
8/8/2019 1. Controlling Electrical Hazards.
66/92
10/2/2010 cpgeorge 66
OH LINESOH LINES
When mechanical equipment isWhen mechanical equipment isbeing operated near overheadbeing operated near overheadlines, employees standing on thelines, employees standing on theground may not contact theground may not contact theequipment unless it is locatedequipment unless it is locatedso that the required clearanceso that the required clearance
cannot be violated even at thecannot be violated even at themaximum reach of themaximum reach of theequipment.equipment.
-
8/8/2019 1. Controlling Electrical Hazards.
67/92
10/2/2010 cpgeorge 67
EQUIPMENTSEQUIPMENTS
Employees whose occupationsEmployees whose occupationsrequire them to work directly withrequire them to work directly withelectricity must use the personalelectricity must use the personal
protective equipment required for theprotective equipment required for the jobs they perform. jobs they perform.This equipment may consist of This equipment may consist of rubber insulating gloves, hoods,rubber insulating gloves, hoods,
sleeves, matting, blankets, line hose,sleeves, matting, blankets, line hose,and industrial protective helmets.and industrial protective helmets.
-
8/8/2019 1. Controlling Electrical Hazards.
68/92
10/2/2010 cpgeorge 68
TOOLSTOOLS
To maximize his or her ownTo maximize his or her ownsafety, an employee shouldsafety, an employee shouldalways use tools that workalways use tools that workproperly.properly.Tools must be inspectedTools must be inspected
before use, and those foundbefore use, and those foundquestionable, removed fromquestionable, removed fromservice and properly taggedservice and properly tagged ..
-
8/8/2019 1. Controlling Electrical Hazards.
69/92
10/2/2010 cpgeorge 69
TOOLS ..TOOLS ..
Tools and other equipment shouldTools and other equipment should
be regularly maintained.be regularly maintained.Inadequate maintenance canInadequate maintenance can
cause equipment to deteriorate,cause equipment to deteriorate,
resulting in an unsafe condition.resulting in an unsafe condition.
-
8/8/2019 1. Controlling Electrical Hazards.
70/92
10/2/2010 cpgeorge 70
Tools that are used byTools that are used by
employees to handle energizedemployees to handle energized
conductors must be designedconductors must be designedand constructed to withstandand constructed to withstand
the voltages and stresses tothe voltages and stresses to
which they are exposed.which they are exposed.
TOOLS ..TOOLS ..
-
8/8/2019 1. Controlling Electrical Hazards.
71/92
10/2/2010 cpgeorge 71
TRAININGTRAINING
To ensure that they use safeTo ensure that they use safe
work practices, employeeswork practices, employeesmust be aware of the electricalmust be aware of the electrical
hazards to which they will behazards to which they will be
exposed.exposed.
-
8/8/2019 1. Controlling Electrical Hazards.
72/92
10/2/2010 cpgeorge 72
Employees must be trained inEmployees must be trained in
safetysafety- -related work practices asrelated work practices as
well as any other procedureswell as any other proceduresnecessary for safety fromnecessary for safety from
electrical hazards.electrical hazards.
TRAININGTRAINING
-
8/8/2019 1. Controlling Electrical Hazards.
73/92
10/2/2010 cpgeorge 73
GOOD JUDGEMENTGOOD JUDGEMENT
Perhaps the single mostPerhaps the single most
successful defense againstsuccessful defense againstelectrical accidents is theelectrical accidents is thecontinuous exercising of continuous exercising of
good judgment or commongood judgment or commonsense.sense.
-
8/8/2019 1. Controlling Electrical Hazards.
74/92
10/2/2010 cpgeorge 74
GOOD JUDGEMENTGOOD JUDGEMENT
All employees should beAll employees should bethoroughly familiar with thethoroughly familiar with thesafety procedures for their safety procedures for their particular jobs. When a work isparticular jobs. When a work isperformed on an electricalperformed on an electricalequipment, the safety procedureequipment, the safety procedureshould be strictly followed.should be strictly followed.
-
8/8/2019 1. Controlling Electrical Hazards.
75/92
10/2/2010 cpgeorge 75
1. Have the equipment de1. Have the equipment de- -energized.energized.
2. Ensure that the equipment2. Ensure that the equipmentremains deremains de- -energized by usingenergized by usingsome type of lockout and tagsome type of lockout and tagprocedure.procedure.3. Use insulating protective3. Use insulating protectiveequipment.equipment.4. Keep a safe distance from4. Keep a safe distance from
energized parts.energized parts.
SAFETY PROCEDURESAFETY PROCEDURE
-
8/8/2019 1. Controlling Electrical Hazards.
76/92
10/2/2010 cpgeorge 76
ASSESSING THE RISKASSESSING THE RISK
HazardHazard means anythingmeans anythingwhich can cause harm.which can cause harm.
RiskRisk is the chance, great or is the chance, great or small, that someone willsmall, that someone willactually be harmed by theactually be harmed by thehazard.hazard.
-
8/8/2019 1. Controlling Electrical Hazards.
77/92
10/2/2010 cpgeorge 77
The first stage in controlling riskThe first stage in controlling riskis to carry out a risk assessmentis to carry out a risk assessment
in order to identify what needsin order to identify what needsto be done. (This is a legalto be done. (This is a legalrequirement for all risks atrequirement for all risks at
work.)work.)
ASSESSING THE RISKASSESSING THE RISK
RISK ASSESSMENTRISK ASSESSMENT
-
8/8/2019 1. Controlling Electrical Hazards.
78/92
10/2/2010 cpgeorge 78
RISK ASSESSMENTRISK ASSESSMENT- -METHODMETHOD
identify the hazards;identify the hazards;decide who might be harmed,decide who might be harmed,
and how;and how;evaluate the risks arising fromevaluate the risks arising fromthe hazards and decidethe hazards and decide
whether existing precautionswhether existing precautionsare adequate or more shouldare adequate or more shouldbe taken;be taken;
-
8/8/2019 1. Controlling Electrical Hazards.
79/92
10/2/2010 cpgeorge 79
RISK ASSESSMENTSRISK ASSESSMENTS
if you have five or moreif you have five or moreemployees, record anyemployees, record anysignificant findings;significant findings;
review your assessment fromreview your assessment fromtime to time and revise it if time to time and revise it if necessary.necessary.The risk of injury from electricityThe risk of injury from electricityis strongly linked to where andis strongly linked to where andhow it is used.how it is used.
-
8/8/2019 1. Controlling Electrical Hazards.
80/92
10/2/2010 cpgeorge 80
HARSH CONDTIONSHARSH CONDTIONS
The risks are greatest inThe risks are greatest inharsh conditionsharsh conditions- -
for example: in wetfor example: in wetsurroundingssurroundings - - unsuitableunsuitable
equipment can easilyequipment can easilybecome live and can makebecome live and can makeits surroundings liveits surroundings live
-
8/8/2019 1. Controlling Electrical Hazards.
81/92
10/2/2010 cpgeorge 81
HARSH CONDITIONSHARSH CONDITIONS
out of doorsout of doors - - equipment mayequipment maynot only become wet but may benot only become wet but may be
at greater risk of damage.at greater risk of damage.in cramped spaces with a lot of in cramped spaces with a lot of earthed metalwork, such asearthed metalwork, such asinside a tank or bininside a tank or bin - - if anif anelectrical fault developed itelectrical fault developed itcould be very difficult to avoid acould be very difficult to avoid ashock.shock.
RISKY ITEMSRISKY ITEMS
-
8/8/2019 1. Controlling Electrical Hazards.
82/92
10/2/2010 cpgeorge 82
RISKY ITEMSRISKY ITEMS
Some items of equipment canSome items of equipment canalso involve greater risk thanalso involve greater risk than
others.others.Extension leads areExtension leads areparticularly liable to damageparticularly liable to damage - -
to their plugs and sockets, toto their plugs and sockets, totheir electrical connections,their electrical connections,and to the cable itself.and to the cable itself.
-
8/8/2019 1. Controlling Electrical Hazards.
83/92
10/2/2010 cpgeorge 83
RISKY ITEMSRISKY ITEMS
Other flexible leads, particularlyOther flexible leads, particularly
those connected to equipmentthose connected to equipment
which is moved a great deal,which is moved a great deal,
can suffer from similar can suffer from similar
problems.problems.
-
8/8/2019 1. Controlling Electrical Hazards.
84/92
10/2/2010 cpgeorge 84
REDUCING THE RISKREDUCING THE RISK
Ensure that the electricalEnsure that the electricalinstallation is safeinstallation is safe
Provide safe and suitableProvide safe and suitableequipmentequipmentProvide a safety deviceProvide a safety deviceCarry out preventativeCarry out preventativemaintenancemaintenanceWork safelyWork safely
Underground powerUnderground power
-
8/8/2019 1. Controlling Electrical Hazards.
85/92
10/2/2010 cpgeorge 85
Underground power Underground power cablescables
Always assume cables will beAlways assume cables will bepresent when digging in thepresent when digging in the
street, pavement or near street, pavement or near buildings.buildings.Use upUse up- -toto--date service plans,date service plans,
cable avoidance tools andcable avoidance tools andsafe digging practice to avoidsafe digging practice to avoiddanger.danger.
-
8/8/2019 1. Controlling Electrical Hazards.
86/92
10/2/2010 cpgeorge 86
Overhead power linesOverhead power lines
When working near overheadWhen working near overheadlines, it may be possible tolines, it may be possible to
have them switched off if thehave them switched off if theowners are given enoughowners are given enoughnotice.notice.
If this cannot be done,If this cannot be done,consult the owners about theconsult the owners about thesafe working distance fromsafe working distance fromthe cables.the cables.
-
8/8/2019 1. Controlling Electrical Hazards.
87/92
10/2/2010 cpgeorge 87
OHOH-- POWER LINEPOWER LINE
Remember that electricity canRemember that electricity canflash over from overhead linesflash over from overhead lineseven though plant andeven though plant andequipment do not touch them.equipment do not touch them.Most of the fatal electricalMost of the fatal electrical
accidents each year are causedaccidents each year are caused
by contact with overhead lines.by contact with overhead lines.
Electrified railways andElectrified railways and
-
8/8/2019 1. Controlling Electrical Hazards.
88/92
10/2/2010 cpgeorge 88
yytramwaystramways
If working near electrifiedIf working near electrifiedrailways or tramways, consultrailways or tramways, consultthe line or track operatingthe line or track operatingcompany.company.Remember that some railwaysRemember that some railwaysand tramways use electrifiedand tramways use electrified
rails rather than overheadrails rather than overheadcables.cables.
-
8/8/2019 1. Controlling Electrical Hazards.
89/92
10/2/2010 cpgeorge 89
ConclusionConclusion. .
The control of electrical hazards isThe control of electrical hazards is
an important part of every safetyan important part of every safety
and health program.and health program.
The measures suggested hereThe measures suggested here
should be of help in establishingshould be of help in establishingsuch a program of control.such a program of control.
-
8/8/2019 1. Controlling Electrical Hazards.
90/92
10/2/2010 cpgeorge 90
The responsibility for this programThe responsibility for this program
should be delegated to individualsshould be delegated to individuals
who have a complete knowledge of who have a complete knowledge of electricity, electrical work practices,electricity, electrical work practices,
and the appropriate standards for and the appropriate standards for
installation and performanceinstallation and performance
ConclusionConclusion. .
-
8/8/2019 1. Controlling Electrical Hazards.
91/92
10/2/2010 cpgeorge 91
Everyone has the right to workEveryone has the right to workin a safe environment.in a safe environment.
Through cooperative efforts,Through cooperative efforts,employers and employees canemployers and employees canlearn to identify and eliminate or learn to identify and eliminate or
control electrical hazards.control electrical hazards.
ConclusionConclusion. .
-
8/8/2019 1. Controlling Electrical Hazards.
92/92
THANK YOUTHANK YOU