Electrical Safety - Construction OSHA Office of Training & - - PowerPoint PPT Presentation

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Electrical Safety - Construction OSHA Office of Training & - - PowerPoint PPT Presentation

Nov 27, 2023 113 likes •576 views

Electrical Safety - Construction OSHA Office of Training & Education 1 Electricity - The Dangers About 5 workers are electrocuted every week Causes 12% of young worker workplace deaths Takes very little electricity to cause

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OSHA Office of Training & Education 1

Electrical Safety - Construction

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OSHA Office of Training & Education 2

Electricity - The Dangers

  • About 5 workers are

electrocuted every week

  • Causes 12% of young

worker workplace deaths

  • Takes very little electricity

to cause harm

  • Significant risk of causing

fires

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OSHA Office of Training & Education 3

Electricity – How it Works

  • Electricity is the flow of

energy from one place to another

  • Requires a source of power:

usually a generating station

  • A flow of electrons (current)

travels through a conductor

  • Travels in a closed circuit
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OSHA Office of Training & Education 4

Electrical Terms

  • Current -- electrical movement (measured in amps)
  • Circuit -- complete path of the current.

Includes electricity source, a conductor, and the output device or load (such as a lamp, tool, or heater)

  • Resistance -- restriction to electrical flow
  • Conductors – substances, like metals, with little

resistance to electricity that allow electricity to flow

  • Grounding – a conductive connection to the earth

which acts as a protective measure

  • Insulators -- substances with high resistance to

electricity like glass, porcelain, plastic, and dry wood that prevent electricity from getting to unwanted areas

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OSHA Office of Training & Education 5

Electrical Injuries

There are four main types of electrical injuries:

  • Direct:
  • Electrocution or death due to electrical shock
  • Electrical shock
  • Burns
  • Indirect - Falls
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OSHA Office of Training & Education 6

Electrical Shock

An electrical shock is received when electrical current passes through the body. You will get an electrical shock if a part of your body completes an electrical circuit by…

  • Touching a live wire and an electrical ground, or
  • Touching a live wire and another wire at a

different voltage.

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OSHA Office of Training & Education 7

Shock Severity

  • Severity of the shock depends on:
  • Path of current through the

body

  • Amount of current flowing

through the body (amps)

  • Duration of the shocking

current through the body,

  • LOW VOLTAGE DOES NOT

MEAN LOW HAZARD

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OSHA Office of Training & Education 8

Dangers of Electrical Shock

  • Currents above 10 mA* can

paralyze or “freeze” muscles.

  • Currents more than 75 mA can

cause a rapid, ineffective heartbeat -- death will occur in a few minutes unless a defibrillator is used

  • 75 mA is not much current – a

small power drill uses 30 times as much

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

Defibrillator in use

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OSHA Office of Training & Education 9

Burns

  • Most common shock-related

injury

  • Occurs when you touch

electrical wiring or equipment that is improperly used or maintained

  • Typically occurs on hands
  • Very serious injury that

needs immediate attention

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OSHA Office of Training & Education 10

Falls

  • Electric shock can also

cause indirect injuries

  • Workers in elevated

locations who experience a shock may fall, resulting in serious injury

  • r death
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OSHA Office of Training & Education 11

Electrical Hazards and How to Control Them

Electrical accidents are caused by a combination

  • f three factors:
  • Unsafe equipment

and/or installation,

  • Workplaces made

unsafe by the environment, and

  • Unsafe work practices.
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OSHA Office of Training & Education 12

Hazard – Exposed Electrical Parts

Cover removed from wiring or breaker box

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OSHA Office of Training & Education 13

Control – Isolate Electrical Parts

  • Use guards or

barriers

  • Replace covers

Guard live parts of electric equipment operating at 50 volts or more against accidental contact

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OSHA Office of Training & Education 14

Control – Isolate Electrical Parts - Cabinets, Boxes & Fittings

Conductors going into them must be protected, and unused openings must be closed

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OSHA Office of Training & Education 15

Control – Close Openings

  • Junction boxes, pull

boxes and fittings must have approved covers

  • Unused openings in

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

Photo shows violations

  • f these two requirements
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OSHA Office of Training & Education 16

Hazard - Overhead Power Lines

  • Usually not insulated
  • Examples of equipment that

can contact power lines:

  • Crane
  • Ladder
  • Scaffold
  • Backhoe
  • Scissors lift
  • Raised dump truck bed
  • Aluminum paint roller
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OSHA Office of Training & Education 17

Control - Overhead Power Lines

  • Stay at least 10 feet away
  • Post warning signs
  • Assume that lines are

energized

  • Use wood or fiberglass

ladders, not metal

  • Power line workers need

special training & PPE

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OSHA Office of Training & Education 18

Hazard - Inadequate Wiring

  • Hazard - wire too small for the current
  • Example - portable tool with an

extension cord that has a wire too small for the tool

  • The tool will draw more current than

the cord can handle, causing

  • verheating and a possible fire

without tripping the circuit breaker

  • The circuit breaker could be the right

size for the circuit but not for the smaller-wire extension cord

Wire Gauge WIRE

Wire gauge measures wires ranging in size from number 36 to 0 American wire gauge (AWG)

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OSHA Office of Training & Education 19

Control – Use the Correct Wire

  • Wire used depends on operation, building materials,

electrical load, and environmental factors

  • Use fixed cords rather than flexible cords
  • Use the correct extension cord

Must be 3-wire type and designed for hard or extra-hard use

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OSHA Office of Training & Education 20

Hazard – Defective Cords & Wires

  • Plastic or rubber

covering is missing

  • Damaged

extension cords & tools

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OSHA Office of Training & Education 21

Hazard – Damaged Cords

  • Cords can be damaged by:
  • Aging
  • Door or window edges
  • Staples or fastenings
  • Abrasion from adjacent

materials

  • Activity in the area
  • Improper use can cause

shocks, burns or fire

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OSHA Office of Training & Education 22

Control – Cords & Wires

  • Insulate live wires
  • Check before use
  • Use only cords that are 3-wire type
  • Use only cords marked for hard or

extra-hard usage

  • Use only cords, connection devices,

and fittings equipped with strain relief

  • Remove cords by pulling on the

plugs, not the cords

  • Cords not marked for hard or extra-

hard use, or which have been modified, must be taken out of service immediately

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OSHA Office of Training & Education 23

Permissible Use of Flexible Cords

Stationary equipment-to facilitate interchange

DO NOT use flexible wiring where frequent inspection would be difficult

  • r where damage would be likely.

Flexible cords must not be . . .

  • run through holes in walls, ceilings,
  • r floors;
  • run through doorways, windows, or

similar openings (unless physically protected);

  • hidden in walls, ceilings, floors,

conduit or other raceways.

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OSHA Office of Training & Education 24

Grounding

Grounding creates a low- resistance path from a tool to the earth to disperse unwanted current. When a short or lightning

  • ccurs, energy flows to the

ground, protecting you from electrical shock, injury and death.

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OSHA Office of Training & Education 25

Hazard – Improper Grounding

  • Tools plugged into

improperly grounded circuits may become energized

  • Broken wire or plug on

extension cord

  • Some of the most

frequently violated OSHA standards

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OSHA Office of Training & Education 26

Control – Ground Tools & Equipment

  • Ground power supply systems,

electrical circuits, and electrical equipment

  • Frequently inspect electrical

systems to insure path to ground is continuous

  • Inspect electrical equipment before

use

  • Don’t remove ground prongs from

tools or extension cords

  • Ground exposed metal parts of

equipment

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OSHA Office of Training & Education 27

Control – Use GFCI (ground-fault circuit interrupter)

  • Protects you from shock
  • Detects difference in current

between the black and white wires

  • If ground fault detected, GFCI

shuts off electricity in 1/40th of a second

  • Use GFCI’s on all 120-volt, single-

phase, 15- and 20-ampere receptacles, or have an assured equipment grounding conductor program.

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OSHA Office of Training & Education 28

Control - Assured Equipment Grounding Conductor Program

Program must cover:

  • All cord sets
  • Receptacles not part of a building or structure
  • Equipment connected by plug and cord

Program requirements include:

  • Specific procedures adopted by the employer
  • Competent person to implement the program
  • Visual inspection for damage of equipment

connected by cord and plug

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OSHA Office of Training & Education 29

Hazard – Overloaded Circuits

Hazards may result from:

  • Too many devices plugged

into a circuit, causing heated wires and possibly a fire

  • Damaged tools overheating
  • Lack of overcurrent

protection

  • Wire insulation melting, which

may cause arcing and a fire in the area where the overload exists, even inside a wall

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OSHA Office of Training & Education 30

Control - Electrical Protective Devices

  • Automatically opens circuit if

excess current from overload

  • r ground-fault is detected –

shutting off electricity

  • Includes GFCI’s, fuses, and

circuit breakers

  • Fuses and circuit breakers

are overcurrent devices. When too much current:

  • Fuses melt
  • Circuit breakers trip
  • pen
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OSHA Office of Training & Education 31

Power Tool Requirements

  • Have a three-wire cord with

ground plugged into a grounded receptacle, or

  • Be double insulated, or
  • Be powered by a low-voltage

isolation transformer

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OSHA Office of Training & Education 32

Tool Safety Tips

  • Use gloves and appropriate footwear
  • Store in dry place when not using
  • Don’t use in wet/damp conditions
  • Keep working areas well lit
  • Ensure not a tripping hazard
  • Don’t carry a tool by the cord
  • Don’t yank the cord to disconnect it
  • Keep cords away from heat, oil, & sharp edges
  • Disconnect when not in use and when

changing accessories such as blades & bits

  • Remove damaged tools from use
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OSHA Office of Training & Education 33

Preventing Electrical Hazards - Tools

  • Inspect tools before use
  • Use the right tool

correctly

  • Protect your tools
  • Use double insulated

tools

Double Insulated marking

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OSHA Office of Training & Education 34

Temporary Lights

Protect from contact and damage, and don’t suspend by cords unless designed to do so.

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OSHA Office of Training & Education 35

Clues that Electrical Hazards Exist

  • Tripped circuit breakers or

blown fuses

  • Warm tools, wires, cords,

connections, or junction boxes

  • GFCI that shuts off a circuit
  • Worn or frayed insulation

around wire or connection

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OSHA Office of Training & Education 36

Lockout and Tagging of Circuits

  • Apply locks to power source after de-

energizing

  • Tag deactivated controls
  • Tag de-energized equipment and

circuits at all points where they can be energized

  • Tags must identify equipment or circuits

being worked on

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OSHA Office of Training & Education 37

Safety-Related Work Practices

To protect workers from electrical shock:

  • Use barriers and guards to prevent

passage through areas of exposed energized equipment

  • Pre-plan work, post hazard warnings

and use protective measures

  • Keep working spaces and walkways

clear of cords

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OSHA Office of Training & Education 38

Safety-Related Work Practices

  • Use special insulated tools

when working on fuses with energized terminals

  • Don’t use worn or frayed

cords and cables

  • Don’t fasten extension cords

with staples, hang from nails,

  • r suspend by wire.
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OSHA Office of Training & Education 39

Preventing Electrical Hazards - Planning

  • Plan your work with others
  • Plan to avoid falls
  • Plan to lock-out and tag-
  • ut equipment
  • Remove jewelry
  • Avoid wet conditions and
  • verhead power lines
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OSHA Office of Training & Education 40

Avoid Wet Conditions

  • If you touch a live wire or other

electrical component while standing in even a small puddle of water you’ll get a shock.

  • Damaged insulation, equipment, or

tools can expose you to live electrical parts.

  • Improperly grounded metal switch

plates & ceiling lights are especially hazardous in wet conditions.

  • Wet clothing, high humidity, and

perspiration increase your chances

  • f being electrocuted.
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OSHA Office of Training & Education 41

Preventing Electrical Hazards - PPE

  • Proper foot protection

(not tennis shoes)

  • Rubber insulating

gloves, hoods, sleeves, matting, and blankets

  • Hard hat (insulated -

nonconductive)

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OSHA Office of Training & Education 42

Preventing Electrical Hazards – Proper Wiring and Connectors

  • Use and test GFCI’s
  • Check switches and

insulation

  • Use three prong plugs
  • Use extension cords only

when necessary & assure in proper condition and right type for job

  • Use correct connectors
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OSHA Office of Training & Education 43

Training

  • Deenergize electric equipment before

inspecting or repairing

  • Using cords, cables, and electric tools that

are in good repair

  • Lockout / Tagout recognition and procedures
  • Use appropriate protective equipment

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

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OSHA Office of Training & Education 44

Summary – Hazards & Protections

Hazards

  • Inadequate wiring
  • Exposed electrical parts
  • Wires with bad insulation
  • Ungrounded electrical systems

and tools

  • Overloaded circuits
  • Damaged power tools and

equipment

  • Using the wrong PPE and tools
  • Overhead powerlines
  • All hazards are made worse in

wet conditions Protective Measures

  • Proper grounding
  • Use GFCI’s
  • Use fuses and circuit

breakers

  • Guard live parts
  • Lockout/Tagout
  • Proper use of flexible

cords

  • Close electric panels
  • Training
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OSHA Office of Training & Education 45

Summary

Electrical equipment must be:

  • Listed and labeled
  • Free from hazards
  • Used in the proper manner

If you use electrical tools you must be:

  • Protected from electrical shock
  • Provided necessary safety equipment