Creating and Implementing the Absorb-Type Activity:“Electrical Hazards”

Robert L. CzewskiAshford University – Online

EDU652 Instructional Design and Delivery Online

Professor: Dr. Kris Jamsa11/7/2010

This Electrical Hazards presentation is part of the (OSHA , 2010) 10-hour General Industry Outreach-Training Course.

The course will be taught to high school juniors and seniors.

The (OSHA , 2010) 10-hour General Industry Outreach

Training Courseis focused on making learners aware of workplace hazards, how to identify, avoid, and/or

control them.

This Electrical Hazards Module will cover common

electrical hazards by: focusing on making workers aware of electrical hazards,

how to identify, avoid, and/or control them

Electrical HazardsElectrical Hazards

Why should workers be aware of Why should workers be aware of electrical hazards?electrical hazards?

One reason is that (Westfall, 2008) One reason is that (Westfall, 2008) electricution is the fourth leading electricution is the fourth leading cause of death among construction cause of death among construction workers.”workers.”

Electrical InjuriesElectrical Injuries

Four types of electrical injuries Four types of electrical injuries include:include:

Electrical shockElectrical shock BurnsBurns Falls caused by electrical shocksFalls caused by electrical shocks DeathDeath

Electrical ShockElectrical ShockAn electrical shock occurs when An electrical shock occurs when electrical current passes through electrical current passes through your body.your body.This can happen if you touch a live This can happen if you touch a live electrical wire.electrical wire.A shock can also occur if you touch A shock can also occur if you touch two live electrical wires.two live electrical wires.Another way to get shocked is to Another way to get shocked is to touch an electrical appliance that is touch an electrical appliance that is internally shorted.internally shorted.

Electrical Shock InjuriesElectrical Shock Injuries

The damage caused by an The damage caused by an electrical shock depends on:electrical shock depends on:

The The PathPath that the current takes that the current takes when it flows through the bodywhen it flows through the body

The The Amount of currentAmount of current flowing flowing through the bodythrough the body

The The Length of timeLength of time the body is the body is in the circuitin the circuit

Electrical Shock InjuriesElectrical Shock Injuries

The The PathPath that the current takes that the current takes when it flows through the body does when it flows through the body does make a difference on the severity of make a difference on the severity of the injury.the injury.If the current flows through the If the current flows through the heart or lungs it can cause death heart or lungs it can cause death (electrocution).(electrocution).Current flowing through other parts Current flowing through other parts of the body can cause burns and/or of the body can cause burns and/or nerve damage.nerve damage.

Electrical Shock InjuriesElectrical Shock InjuriesThe The Amount of currentAmount of current that flows that flows through the body affects the severity through the body affects the severity of the injury.of the injury.

How the Amount of Current Effects the Human Body (Westfall, 2008)

Current Value Typical Effects on the Human Body

1mA Slight tingling sensation

5mA Slight shock. Involuntary reactions. Can cause a person to fall from a ladder.

6-30mA Painful shock, loss of muscular control.

Electrical Shock InjuriesElectrical Shock InjuriesThe The Amount of currentAmount of current that flows that flows through the body affects the severity of through the body affects the severity of the injury.the injury.

How the Amount of Current Effects the Human Body(Continued)

Current Value Typical Effects on the Human Body

50-150mA Extreme pain, respiratory arrest, sever muscular contractions. Death possible.

1000mA to 4300mA

Ventricular fibrillation, severe muscular contractions, nerve damage. Typically causes death.

Source: Occupational Safety and Health Administration

Electrical Shock InjuriesElectrical Shock Injuries Currents greater than 75 Currents greater than 75

mA* can cause ventricular mA* can cause ventricular fibrillation.fibrillation.

Ventricular fibrillation will Ventricular fibrillation will cause death in a few cause death in a few minutes unless a minutes unless a defibrillator is used. defibrillator is used.

75 mA is not much current 75 mA is not much current – a small power drill uses – a small power drill uses 30 times as much30 times as much

* mA = milliampere = 1/1,000 of an ampere

Defibrillator in use

Electrical Shock InjuriesElectrical Shock Injuries

The severity of an injury also The severity of an injury also depends on the depends on the durationduration of the of the current flow through the body.current flow through the body.If the current flows for a very short period of If the current flows for a very short period of time the injury will be less severe.time the injury will be less severe.Current flowing for a long period of time can Current flowing for a long period of time can cause nerve damage, burns, and death.cause nerve damage, burns, and death.

Getting ShockedGetting Shocked When two wires have different potential When two wires have different potential

differences (voltages), current will flow if they are differences (voltages), current will flow if they are connected togetherconnected together In most household wiring, the black wires are at In most household wiring, the black wires are at

110 volts relative to ground110 volts relative to ground The white wires are at zero volts because they The white wires are at zero volts because they

are connected to groundare connected to ground If you come into contact with an energized (live) If you come into contact with an energized (live)

black wire, and you are also in contact with the black wire, and you are also in contact with the white grounded wire, current will pass through white grounded wire, current will pass through your body andyour body and YOU WILL RECEIVE A YOU WILL RECEIVE A SHOCKSHOCK

Getting ShockedGetting Shocked

If you are in contact with an energized If you are in contact with an energized wire or any energized electrical wire or any energized electrical component, and also with any grounded component, and also with any grounded object, YOU WILL RECEIVE A SHOCKobject, YOU WILL RECEIVE A SHOCK

You can even receive a shock when You can even receive a shock when you are not in contact with a groundyou are not in contact with a ground If you contact both wires of a 240-volt cable, If you contact both wires of a 240-volt cable,

YOU WILL RECEIVE A SHOCK and YOU WILL RECEIVE A SHOCK and possibly be electrocutedpossibly be electrocuted

Electrical Burns Electrical Burns Most common shock-related, Most common shock-related,

nonfatal injurynonfatal injury Occurs when you touch Occurs when you touch

electrical wiring or equipment electrical wiring or equipment that is improperly used or that is improperly used or maintainedmaintained

Typically occurs on the Typically occurs on the handshands

Very serious injury that Very serious injury that needs immediate attentionneeds immediate attention

FallsFalls Electric shock can Electric shock can

also cause indirect or also cause indirect or secondary injuries secondary injuries

Workers in elevated Workers in elevated locations who locations who experience a shock experience a shock can fall, resulting in can fall, resulting in serious injury or serious injury or deathdeath

Inadequate Wiring HazardsInadequate Wiring Hazards A hazard exists when a conductor is too small to A hazard exists when a conductor is too small to

safely carry the current safely carry the current Example:Example: using a portable tool with an extension using a portable tool with an extension

cord that has a wire too small for the toolcord that has a wire too small for the tool The tool will draw more current than the cord can The tool will draw more current than the cord can

handle, causing overheating and a possible fire without handle, causing overheating and a possible fire without tripping the circuit breakertripping the circuit breaker

The circuit breaker could be the right size for the circuit The circuit breaker could be the right size for the circuit but not for the smaller-wire extension cordbut not for the smaller-wire extension cord

Overload HazardsOverload Hazards If too many devices are If too many devices are

plugged into a circuit, the plugged into a circuit, the current will heat the wires to a current will heat the wires to a very high temperature, which very high temperature, which may cause a firemay cause a fire

If the wire insulation melts, If the wire insulation melts, arcing may occur and cause a arcing may occur and cause a fire in the area where the fire in the area where the overload exists, even inside a overload exists, even inside a wallwall

Electrical Protective Electrical Protective DevicesDevices These devices shut off electricity flow in These devices shut off electricity flow in

the event of an overload or ground-fault the event of an overload or ground-fault in the circuitin the circuit

Include fuses, circuit breakers, and Include fuses, circuit breakers, and ground-fault circuit-interrupters (GFCI’s)ground-fault circuit-interrupters (GFCI’s)

Fuses and circuit breakers are Fuses and circuit breakers are overcurrentovercurrent devices devices When there is too much current:When there is too much current:

Fuses meltFuses melt Circuit breakers trip openCircuit breakers trip open

Ground-Fault Circuit Ground-Fault Circuit InterrupterInterrupter

This device protects you from This device protects you from dangerous shockdangerous shock

The GFCI detects a difference in The GFCI detects a difference in current between the black and white current between the black and white circuit wires circuit wires (This could happen when electrical (This could happen when electrical equipment is not working correctly, equipment is not working correctly, causing current “leakage” – known as causing current “leakage” – known as a a ground fault.ground fault.))

If a ground fault is detected, the GFCI If a ground fault is detected, the GFCI can shut off electricity flow in as little can shut off electricity flow in as little as as 1/40 of a second1/40 of a second, protecting you , protecting you from a dangerous shockfrom a dangerous shock

Grounding HazardsGrounding Hazards Some of the most frequently violated OSHA Some of the most frequently violated OSHA

standardsstandards Metal parts of an electrical wiring system that Metal parts of an electrical wiring system that

we touch (switch plates, ceiling light fixtures, we touch (switch plates, ceiling light fixtures, conduit, etc.) should be at zero volts relative to conduit, etc.) should be at zero volts relative to groundground

Housings of motors, appliances or tools that are Housings of motors, appliances or tools that are plugged into improperly grounded circuits may plugged into improperly grounded circuits may become energizedbecome energized

If you come into contact with an improperly If you come into contact with an improperly grounded electrical device, YOU WILL BE grounded electrical device, YOU WILL BE SHOCKEDSHOCKED

Overhead Powerline Overhead Powerline HazardsHazards

Most people don’t realize that Most people don’t realize that overhead powerlines are usually not overhead powerlines are usually not insulatedinsulated

Powerline workers need special Powerline workers need special training and personal protective training and personal protective equipment (PPE) to work safelyequipment (PPE) to work safely

Do not use metal ladders – instead, Do not use metal ladders – instead, use fiberglass laddersuse fiberglass ladders

Beware of powerlines when you Beware of powerlines when you work with ladders andwork with ladders and scaffoldingscaffolding

Some Examples of OSHA Some Examples of OSHA Electrical Requirements . . . .Electrical Requirements . . . .

Grounding PathGrounding Path

The path to ground from The path to ground from circuits, equipment, and circuits, equipment, and enclosures must be enclosures must be permanent and permanent and continuouscontinuous

Violation shown here is an Violation shown here is an extension cord with a extension cord with a missing grounding prongmissing grounding prong

Hand-Held Electric Hand-Held Electric ToolsTools

Hand-held electric tools pose a Hand-held electric tools pose a potential danger because they make potential danger because they make continuous good contact with the handcontinuous good contact with the hand

To protect you from shock, burns, and To protect you from shock, burns, and electrocution, tools must:electrocution, tools must: Have a three-wire cord with ground and Have a three-wire cord with ground and

be plugged into a grounded receptacle, be plugged into a grounded receptacle, oror

Be double insulated, orBe double insulated, or Be powered by a low-voltage isolation Be powered by a low-voltage isolation

transformertransformer

Guarding of Live PartsGuarding of Live Parts Must guard live parts of electric Must guard live parts of electric

equipment operating at 50 volts or more equipment operating at 50 volts or more against accidental contact by: against accidental contact by: Approved cabinets/enclosures, orApproved cabinets/enclosures, or Location or permanent partitions Location or permanent partitions

making them accessible only to making them accessible only to qualified persons, orqualified persons, or

Elevation of 8 ft. or more above the Elevation of 8 ft. or more above the floor or working surfacefloor or working surface

Mark entrances to guarded Mark entrances to guarded locations with conspicuous warning locations with conspicuous warning signssigns

Guarding of Live PartsGuarding of Live Parts

Must enclose or guard Must enclose or guard electric equipment in electric equipment in locations where it locations where it would be exposed to would be exposed to physical damagephysical damage

Violation shown here is Violation shown here is physical damage to physical damage to conduitconduit

Cabinets, Boxes, and Cabinets, Boxes, and FittingsFittings

Junction boxes, pull boxes Junction boxes, pull boxes and fittings must have and fittings must have approved coversapproved covers

Unused openings in Unused openings in cabinets, boxes and fittings cabinets, boxes and fittings must be closed (no missing must be closed (no missing knockouts)knockouts)

Photo shows violations of Photo shows violations of these two requirementsthese two requirements

Use of Flexible CordsUse of Flexible Cords More vulnerable than fixed wiringMore vulnerable than fixed wiring Do not use if one of the recognized Do not use if one of the recognized

wiring methods can be used insteadwiring methods can be used instead Flexible cords can be damaged by:Flexible cords can be damaged by:

AgingAging Door or window edgesDoor or window edges Staples or fasteningsStaples or fastenings Abrasion from adjacent materialsAbrasion from adjacent materials Activities in the areaActivities in the area

Improper use of flexible cords can Improper use of flexible cords can cause shocks, burns or firecause shocks, burns or fire

Permissible Uses of Permissible Uses of Flexible CordsFlexible CordsExamplesExamples

Pendant, orFixture Wiring

Portable lamps,tools or appliances

Stationary equipment-to facilitate interchange

Prohibited Uses of Prohibited Uses of Flexible CordsFlexible CordsExamplesExamples

Substitute for fixed wiring

Run through walls, ceilings, floors, doors, or windows

Concealed behind or attached to building surfaces

Clues that Electrical Hazards Exist

Tripped circuit breakers or blown fusesTripped circuit breakers or blown fuses Warm tools, wires, cords, connections, or Warm tools, wires, cords, connections, or

junction boxesjunction boxes GFCI that shuts off a circuitGFCI that shuts off a circuit Worn or frayed insulation around wire or Worn or frayed insulation around wire or

connectionconnection

TrainingTraining

Deenergizing electric equipment before Deenergizing electric equipment before inspecting or making repairsinspecting or making repairs

Using electric tools that are in good Using electric tools that are in good repairrepair

Using good judgment when working near Using good judgment when working near energized linesenergized lines

Using appropriate protective equipmentUsing appropriate protective equipment

Train employees working with electric equipment in safe work practices, including:

SummarySummaryElectrical HazardsElectrical Hazards

Inadequate wiringInadequate wiring Exposed electrical partsExposed electrical parts Wires with bad insulationWires with bad insulation Ungrounded electrical systems and toolsUngrounded electrical systems and tools Overloaded circuitsOverloaded circuits Damaged power tools and equipmentDamaged power tools and equipment Using the wrong PPE and toolsUsing the wrong PPE and tools Overhead powerlinesOverhead powerlines All hazards are made worse in wet conditionsAll hazards are made worse in wet conditions

SummarySummaryProtective MeasuresProtective Measures

Proper groundingProper grounding Using GFCI’sUsing GFCI’s Using fuses and circuit breakersUsing fuses and circuit breakers Guarding live partsGuarding live parts Proper use of flexible cordsProper use of flexible cords TrainingTraining

ReferencesReferences

OSHA, 2010, www.OSHA.com, Outreach-Trainer Presentation: Electrical. Retrieved on 11/7/2010 from website: http://www.osha.gov/dte/outreach/construction_generalindustry/gi_outreach_tp.htm

NoteNote: The OSHA Electrical PowerPoint : The OSHA Electrical PowerPoint presentation was modified to presentation was modified to accommodate K-12 Juniors and Seniorsaccommodate K-12 Juniors and Seniors

ReferencesReferences

Westfall, Veronica, Lead Writer, 2008, Electrical Level One, 2008 NEC® Revision, Annotated Instructor’s Guide, Module 26102-08 Electrical Safety, ISBN-10: 0-13-604463-8