one-hour introduction to osha · 2019. 6. 20. · focus four: electrocution hazards electrical...

Focus Four: Electrocution Hazards

30-Hour Construction Industry OSHA Outreach Training Program


Topics

• What is an electrocution hazard?

• What are the major types of electrocution hazards in construction?

• How can I protect myself from electrocution hazards?

• What is my employer required to do to protect workers from electrocution?

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What is an electrocution hazard?

Electrocution results when a person is exposed to a lethal amount of electrical energy.


2016 Fatality Statistics

Private industry total: 4,693

Construction industry: 991

Electrocutions:

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Electricity: The Dangers• Causes 12 percent of

workplace deaths among young workers.

• About five workers are electrocuted every week.

• It takes very little electricity to cause harm.

• Electricity poses significant fire risk.


Electricity: How It Works• Electricity:

• is the flow of energy from one place to another;

• requires a source of power, usually a generating station; and

• travels in a closed circuit.

• A flow of electrons (a current) travels through a conductor.

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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).

• Voltage – electrical intensity (volts).

• Resistance – restriction to electrical flow.


Electrical Terms (cont.)

• Conductors – substances, such as metals, with little resistance to electricity and that allow electricity to flow.

• Grounding – a conductive connection to the earth that acts as a protective measure.

• Insulators – substances with high resistance to electricity, such as glass, porcelain, plastic, and dry wood that prevent electricity from getting to unwanted areas.

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No employer shall permit a worker to

work in such proximity to any part

of an electric power circuit that the

worker could contact the electric

power circuit in the course of work

Recognize a hazard?

YES!



Crossing electrical line

must be supported,

protected or removed

to safeguard workers

Recognize a hazard?

YES!

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Spliced electrical

extension cords.

Extension cords

should be marked

DO NOT USE. Also,

bad housekeeping,

trip hazard and

unprotected hole in

photograph

Recognize a hazard?

YES!



1. No GFCI

2. System not grounded

3. Openings where

conductors entered

not closed

4. No cover on boxes

5. Panel boards were

not dead front

Recognize a hazard?

YES!

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Electric drill flexible cord

was spliced to a non-

flexible conductor with

damaged insulation

Recognize a hazard?

YES!



Scaffold was erected

4 ½ feet from 7.2 kV

power lines

Recognize a hazard? YES!

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Continuous path to

ground not maintained;

multiple cords used for

fixed equipment

Recognize a hazard?

YES!



Employer was operating

a stand fan without

grounding protection

Recognize a hazard?

YES!

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Conductors entering boxes,

cabinets, or fittings shall be

protected from abrasion.

Openings through which

conductors enter shall be

effectively closed

Recognize a hazard?

YES!



Flexible cords and cables

may pass through doorways

or other pinch points, if

protection is provided to

avoid damage

Recognize a hazard?

YES!

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An electrical hazard can be defined as a serious workplace hazard that exposes workers to the following:

• Burns

• Electrocution

• Shock

• Arc Flash/Arc Blast

• Fire

• Explosions



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Electrical Injuries There are four main types of electrical injuries:

Direct

• Electrocution

• Electrical shock

• Burns

Indirect

• Falls


Burns• Most common shock-related injury

• Occur when you touch electrical wiring or improperly used or maintained equipment

• Typically occur on hands

• Very serious injury that needs immediate attention

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Electrical Shock• You will get an electrical shock when an electrical

current passes through your body.

• You will get an electrical shock if a part of your body:

◦ completes an electrical circuit;

◦ touches a live wire and an electrical ground; or

◦ touches a live wire and another wire at a different voltage.


Shock SeveritySeverity of the shock depends on:

• path of current through the body

• amount of current flowing through the body (amps)

• duration of the current through the body.

Low voltage does not mean low hazard.

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Electrical Damage to the Body

• When electricity travels through the body, it heats up and burns body tissue internally.

• Electricity leaves the body violently, causing burns or even blowing an exit hole.


Dangers of Electrical Shock• Currents of about 10 mA* can paralyze muscles.

• Currents of 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.

Defibrillator in Use

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

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Falls

• Electric shock can also cause indirect injuries.

• Workers in elevated locations who experience a shock may fall, resulting in serious injury or death.


What are the major types of electrocution hazards in construction?

• Contact with overhead power lines

• Contact with energized sources (e.g., live parts, damaged or bare wires, defective equipment or tools)

• Improper use of extension and flexible cords

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Contact with Overhead Power Lines


Contact with Energized Sources

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Improper use of extension and flexible cords


How can I protect myself from electrocution hazards?

• Maintain a safe distance from overhead power lines

• Use ground-fault circuit interrupters (GFCI)

• Inspect portable tools and extension cords

• Use power tools and equipment as designed

• Follow lockout/tagout procedures

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Maintain a safe distance from overhead power lines

Voltage (nominal, kV, alternating current) Minimum clearance distance (feet)

Up to 50 10

Over 50 to 200 15

Over 200 to 350 20

Over 350 to 500 25

Over 500 to 750 35

Over 750 to 1000 45

Over 1000 (As established by the power line owner/operator or registered professional

engineer who is a qualified person with respect to electrical power transmission

and distribution)


Hazard: Overhead Power Lines• Usually not insulated

• Examples of equipment that can contact power lines:• Crane

• Ladder

• Scaffold

• Backhoe

• Scissor lift

• Raised dump truck bed

• Aluminum paint roller

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Control: Overhead Power Lines• Stay at least 10 feet away.

• Cranes and derricks –20 feet away.

• Post warning signs.

• Assume that lines are energized.

• Use wood or fiberglass ladders, not metal ones.

• Power line workers need special training and PPE.


Overhead Power Lines: The Sad Reality

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Ensure Adequate Clearance• Install flag warnings at

proper distances.

• If it is difficult for an operator to see the power lines, designate a spotter.

• If you cannot maintain adequate clearances, you must have the power company insulate, move, or de-energize the line.


Power Line Facts

• More than 90 percent of the contacts occur on overhead distribution lines.

• Operators are usually safe if they stay on the equipment.

• Ground personnel are more than eight times more likely to be killed.

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The Ground Might Be Hot!

• Electricity dissipateswith the resistance ofthe ground.

• As potential drops, fields develop around the electrified machine.

• If you step across a lineof unequal potential, you could be electrocuted.


If Contact Occurs

• Stay on the machine if possible.

• Warn all others to stay away.

• Notify the power company immediately.

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Bail-Out Procedures

• If you must get out,jump with your feettogether.

• Do not touch themachine.

• Hop or shuffle outof the area.


Maintain a safe distance from overhead power lines

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Use ground-fault circuit interrupters (GFCI)

Types of GFCI’s

• Receptacle GFCI

• Temporary/portable GFCI

• Circuit Breaker


Grounding

• Grounding creates a low-resistance path from a tool to the earth to disperse unwanted current.

• When a short occurs, energy flows to the ground, protecting you from electrical shock, injury, and death.

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Improper Grounding

• Tools plugged into improperly grounded circuits may become energized.

• Broken wire or plug on extension cord.

• The most frequently violated OSHA electrical regulation is improper grounding of equipment and circuitry.


Control: Ground Tools and Equipment • Ground power supply

systems, electrical circuits, and electrical equipment.

• Frequently inspect electrical systems to ensure that 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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Control: GFCIs• Ground fault circuit interrupters (GFCI)s:

• protect from shock,

• detect difference in current between the black and white wires, and• shut off electricity

in 1/40 of a second if ground fault is detected.

• Use GFCIs on all 120-volt, single phase, and 15-and 20-ampere receptacles, or have an assured equipment grounding conductor program.


Inspect portable tools and extension cords

Wire Size and Ampicity

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Use power tools and equipment as designed

Tool safety tips

• Never carry a tool by the cord

• Never yank the cord to disconnect it

• Keep cords away from heat, oil, and sharp edges

• Disconnect when not in use and when changing accessories such as blades and bits

• Avoid accidental starting. Do not hold fingers on the switch button while carrying a plugged-in tool


Tool safety tips

• Use gloves and appropriate footwear

• Store in dry a place when not using

• Don’t use in wet/damp environments

• Keep working areas well lit

• Ensure that cords do not cause a tripping hazard

• Remove damaged tools from use

• Use double-insulated tools

Use power tools and equipment as designed

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Follow lockout/tagout procedures

Electrocution Hazards

Follow lockout/tagout procedures

1. Identify

2. Locate

3. Notify

4. De-energize

5. Isolate

6. Lockout

7. Test

8. Return to Off

9. Perform

10. Remove and Notify

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What is my employer required to do to protect workers from electrocution?

• Ensure overhead power line safety

• Isolate electrical parts

• Supply ground-fault circuit Interrupters (GFCI)

• Ensure proper grounding

• Ensure power tools are maintained in a safe condition



• Ensure proper guarding

• Provide training

• Enforce a LOTO safety-related work practices

• Ensure Proper Use of Flexible Cords

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Control: Safety ProgramAssured Equipment Grounding Conductor Program

• Program must cover:

• all cord sets,

• receptacles not part of a building or structure, and• equipment connected by plug and cord.

• Program requirements include:

• specific procedures adopted by the employer,

• competent person to implement the program, and

• visual inspection for damage of equipment connected by cord and plug.


Safety-Related Work PracticesTo 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; and

• keep working spaces and walkways clear of cords.

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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, or suspend by wire.


Preventing Electrical Hazards

Planning

• Plan your work with others.

• Plan to avoid falls.

• Plan to lock out and tag out equipment.

• Remove jewelry.

• Avoid wet conditions and overhead power lines.

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The Best Way to Work on Energized Electrical Equipment

DON’T allow the employee to do the work unless:

• electrical equipment is shut down and locked out, and

• this is verified using a voltmeter to determine electrically safe working condition.



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Summary

During this lesson, participants have been given an overview of major electrocution hazards, ways to protect themselves, and what employers must do to protect workers from electrocution hazards.


Electrocution Hazards Review

1. “BE SAFE” reminds workers that burns, electrocution, shock, arc flash/arc blast, fire and explosions are all:

a. Electrical hazards workers are exposed to when working around cranes and power lines.

b. Serious workplace hazards that workers are exposed to when working in and/or around electrical power sources.

c. Electrical hazards workers are exposed to when working with flammables.

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2. A ground fault circuit interrupter (GFCI):

a. Detects ground faults and interrupts the flow of electric current, and is designed to protect the worker by limiting the duration of an electrical shock.

b. Detects ground faults and interrupts the electric source thus, it disables the equipment that is attached; however, the worker is still exposed to electrocution.

c. A tool used to determine if a power system is properly grounded.



3. To protect yourself from being electrocuted by contact with overhead power lines, you should always assume overhead lines are energized and keep yourself and equipment at least ____ away from power lines up to 50kV.

a. 5 feet

b. 8 feet

c. 10 feet

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4. Which of the following is a safe work practice to protect you from electrocution hazards?

a. Use GFCI only when using double insulated power tools

b. Do not operate electrical equipment when working in wet conditions

c. Attach ungrounded, two-prong adapter plugs to three-prong cords and tools


5. Some requirements employers must do to protect workers from electrocution hazards are: ensure overhead power lines safety; supply GFCIs; isolate electrical parts; ensure proper grounding, and:

1. Provide training2. Ensure power tools are maintained in a safe condition3. Ensure proper use of flexible cords4. Report worker jobsite complaints to OSHA

a. 1, 2, and 3

b. 2, 3, and 4

c. 1, 3, and 4


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Electrocution Hazards Review6. When a power system is properly grounded

workers need to be aware that:

a. It is a safe system and can not change from safe to hazardous; therefore working with electrical equipment is always safe.

b. Electrical equipment can instantly change from safe to hazardous because of extreme conditions and rough treatment.

c. The system will remain safe and will not be impacted by changing worksite conditions or electrical equipment.

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one-hour introduction to osha · 2019. 6. 20. · focus four: electrocution hazards electrical...

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