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Electrical Safety

Online Industrial Training

Tips Engineer Zone

www.tipsengineerzone.in

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Electrical

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Introduction

Lesson objectives:

Identify major electrical hazards
Describe types of electrical hazards
Describe electrical protection methods
Recognize employer requirements to protect workers from electrical hazards

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Introduction

Definitions:

Electricity – movement �of the free electrons between �atoms;

Related terms:

Current – the movement of �electrical charge
Resistance – opposition to current flow
Voltage – a measurement of electrical force

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Introduction

Conductors – substances, such as metals, that have little resistance to electricity
Insulators – substances, such as dry wood, rubber, glass and Bakelite, that have high resistance to electricity
Grounding – a conductive connection to the earth which acts as a protective measure

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Electrical Hazards

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Electrical Hazards

Examples of electrical hazards that could cause workers to be electrocuted.

https://www.osha.gov/video/shipyard_accidents/08_welder_electrocuted.html

https://www.osha.gov/video/shipyard_accidents/15_lockout_tagout_failure.html

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Electrical Hazards

BE SAFE:

Burns
Electrocution
Shock
Arc flash/arc blast
Fire
Explosions

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Electrical Hazards

Burns:

Most common shock-related injury
Three types of electrical burns:

Electrical
Arc flash
Thermal contact

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Electrical Hazards

Electrocution:

Is fatal
Meaning: to kill with electrical shock
Results when a human is exposed to a lethal amount of electrical energy

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Electrical Hazards

Shock:

Body becomes part �of electrical circuit
Reflex response to �passage of electric �current through the body

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Electrical Hazards

Arc Flash/Arc Blast

Arc flash

Sudden release of electrical energy through air when a high-voltage gap exists and there is a breakdown between conductors
Gives off thermal radiation (heat) and bright, intense light that can cause burns
Temperatures as high as 35,000°F

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Electrical Hazards

Arc blast – high-voltage arcs can also produce considerable pressure waves by rapidly heating the air and creating a blast

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Electrical Hazards

Fire:

Most result from problems with "fixed wiring”
Problems with cords, plugs, receptacles, and switches also cause electrical fires

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Electrical Hazards

Explosions:

Occur when electricity ignites explosive mixture of material in the air
Note:

Electricity is source of these hazards
All hazards are of equal importance
Lesson focuses on eliminating electrical hazards

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Electrical Hazards

Examples of fatal accidents:

Case #1: Worker electrocuted when the ladder came in contact with overhead power lines
Case #2: Worker electrocuted when mast came in contact with high voltage overhead lines

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Electrical Hazards

Case #3: Worker changing energized ballast on light fixture was electrocuted and fell to the concrete floor while working from an 8' fiberglass stepladder.

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Electrical Hazards

U.S. Bureau of Labor Statistics:

156 electrocutions for 2014
Up from 141 in 2013

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Types of Electrical Hazards

Contact with overhead power lines:

Overhead and buried �power lines carry �extremely high voltage
Risks

Electrocution (main risk)
Burns and falls

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Types of Electrical Hazards

Cranes are not the only equipment that can reach overhead power lines.
Use of ladders or suspension in a man-basket under or near power lines are risks.

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Types of Electrical Hazards

Important: the covering on an overhead power line is primarily for weather protection; therefore, workers need to know that if they touch a power line, covered or bare, death is probable.
https://www.osha.gov/dts/vtools/construction/ladder_powerline_fnl_eng_web.html

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Types of Electrical Hazards

Contact with energized sources:

Live parts

The major hazards

Electrical shock and burns
Electrical shock occurs �when the body becomes �part of the electric circuit

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Types of Electrical Hazards

Severity and effects of an electrical shock depend on a number of factors

Pathway through the body
Amount of current
Length of time of the exposure
Whether skin is wet or dry

Water

Great conductor
Allows current to flow more easily in wet conditions and through wet skin

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Chart

(1,000 mill amperes = 1 amp; therefore, 15,000 mill amperes = 15 amp circuit)
Current	Reaction
Below 1 milliampere	Generally not perceptible
1 milliampere	Faint tingle
5 milliampere	Slight shock felt; not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries
6-25 milliamperes (women)	Painful shock, loss of muscular control
9-30 milliamperes (men)	The freezing current or “let-go” range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.
50-150 milliampres	Extreme pain, respiratory arrest, severe muscular contractions. Death is possible.
1,000-4,300 milliamperes	Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely
10,000 milliamperes	Cardiac arrest, severe burns; death probable

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Types of Electrical Hazards

Damaged or bare wires

Fault current may travel through a body, causing electrical burns or death, if

Power supply is not grounded
Path has been broken
There are live parts or bare wires

Extreme conditions and rough treatment can change electrical equipment from safe to hazardous

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Types of Electrical Hazards

Defective equipment or tools

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Types of Electrical Hazards

Improper repairs

Examples of incidents

Ballast strap not replaced after repair = Electrocution of 11 year old boy
Cutting off bleed resistor on capacitor= causes 370-volt shock
Removing and leaving off terminal insulator on capacitor = causes 440-volt shock

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Types of Electrical Hazards

Improper use:

Extension and flexible cords

Care
Connection
Capacity

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Types of Electrical Hazards

Capacity affected by

Size of wire

14 gauge = 15 amps
12 gauge = 20 amps

Length of the cord

UL tag capacity
In general any cord over 100 ft. requires one size larger cord �(14 gauge to 12 gauge)

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Types of Electrical Hazards

Power strips:

Can be over loaded �because of multiple �plug arrangement
Most have overload protection �but often malfunction causing fire
Use fixed wiring when possible

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Types of Electrical Hazards

Portable heaters and appliances:

Manufacturer recommendations �not followed
Do not plug into a power strip! �This causes overloads and fires.

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Electrical Protection Methods

Maintain safe distance from �overhead power lines:

Staying away
Following table shows the safe power line clearance distance for various line voltages.
https://youtu.be/Y2MwX738e1Y

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Electrical Protection Methods

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 transmission and distribution)

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Electrical Protection Methods

Use ground-fault circuit interrupters (GFCI):

Designed to protect people from electrical shock
Detects ground faults and interrupts electric current
Limits duration of electrical shock

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Electrical Protection Methods

Three types of GFCI:

Receptacle GFCI
Temporary/portable GFCI
Circuit Breaker GFCI

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1. Receptacle GFCI: Often found on construction work sites, outdoor areas and other locations where damp conditions do or could exist.

2. Temporary/portable GFCI: AP portable GFCI is an extension cord combined with a GFCI. It adds flexibility in using receptacles that are not protected by GFCls. Extension cords with GFCI protection incorporated should be used when

permanent protection is unavailable.

3. Circuit Breaker GFCI: The GFCI circuit breaker controls an entire circuit, and is installed as a replacement for a circuit breaker on the main circuit board. Rather than install multiple GFCI outlets, one GFCI circuit breaker can protect the

entire circuit. At sites equipped with circuit breakers, this type of GFCI might be installed in a panel box to give protection to selected circuits. Circuit breaker GFCIs should be tested monthly. Keep in mind that the test will disconnect power to

everything on the circuit.

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Electrical Protection Methods

Inspect portable tools and extension cords:

Workers need to inspect extension cords prior to their use for any cuts or abrasion.
Electric hand tools that are old, damaged, or misused may have damaged insulation inside.

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Electrical Protection Methods

Use power tools and equipment as designed:

Follow tool safety tips to avoid misusing equipment
Follow manufacturer’s instructions

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Electrical Protection Methods

Common examples of misused equipment

These photos show examples of equipment misuse.

Source: TEEX SH 46F1-HT06

Source of photos: OSHA

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Electrical Protection Methods

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.

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Electrical Protection Methods

Avoid accidental starting. Do not hold fingers on the switch button while carrying a plugged-in tool.
Use gloves and appropriate footwear.
Store in dry a place when not using.

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Electrical Protection Methods

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.

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Electrical Protection Methods

Follow lockout/tagout (LOTO) procedures:

Lockout/tagout

Essential safety procedure
Protects workers from injury while working on or near electrical circuits and equipment
Prevents contact with operating equipment parts such as, blades, gears, shafts, etc.

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Electrical Protection Methods

LOTO prevents the unexpected release of hazardous gases, fluids, or solid matter in areas where workers are present.

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To protect against being electrocuted, workers need to follow lockout/tagout procedures. When performing lockout/tagout on circuits and equipment, the following checklist can be used:

• Identify all sources of electrical energy for the equipment or circuits in question

• Disable backup energy sources such as generators and batteries

• Identify all shut-offs for each energy source

• Notify all personnel that equipment and circuitry must be shut off, locked out, and tagged out (Simply turning a switch off is not enough)

• Shut off energy sources and lock switch gear in the OFF position. Each worker should apply his/her individual lock and keys kept with the worker

• Test equipment and circuitry to ensure they are de-energized. This must be done by a qualified person

• Deplete stored energy (for example, in capacitors) by bleeding, blocking, grounding, etc.

• Apply a lock or tag to alert other workers that an energy source or piece of equipment has been locked or tagged out

• Make sure all workers are safe and accounted for before equipment and circuits are unlocked and turned back on. Only a qualified person may determine when it is safe to re-energize circuits.

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Electrical Protection Methods

Power source identification:

Mark all breakers accordingly for the circuits they protect
Mark all disconnect means accordingly for the equipment they service
Identify all voltages with proper labeling

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Employer Requirements

Employer requirements to protect workers:

Ensure overhead power line safety
Isolate electrical parts
Supply ground-fault circuit interrupters (GFCI) protection
Establish and implement an AEGCP
Ensure power tools are maintained in a safe condition

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Employer Requirements

Ensure proper guarding
Provide training
Enforce LOTO safety related work practices
Ensure proper use of flexible cords and power strips
Ensure proper identification of power sources

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What’s Wrong?

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What’s Wrong?

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Knowledge Check

What is electricity?

The movement of atoms within an object
The movement of free electrons between atoms
Solid mass
Movement within the nucleus of an atom

Answer: b. The movement of free � electrons between atoms

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Knowledge Check

“Electrocution” means ___.

received a mild electrical shock
killed by electrical shock
exposed to electrical current
any accident involving electricity

Answer: b. killed by electrical shock

R.I.P.

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Knowledge Check

Arc flash/arc blast can reach maximum temperatures up to 350˚F?

True
False

Answer: b. False - temperatures � can reach up to 3,500˚F

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Knowledge Check

Which gauge of wire will carry the most current?

14 gauge
12 gauge
10 gauge
00 gauge

Answer: d. 00 gauge – the lower the � wire gauge number, the � more current it can carry

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Knowledge Check

What does GFCI stand for?

Ground Flexible Conduit Insulator
Ground Flow Current Interceptor
Ground Fault Circuit Interrupter
Ground Floor Connection Intersector

Answer: c. Ground Fault Circuit � Interrupter

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Knowledge Check

Which of the following is a safe practice?

Carrying power tool by the cord
Holding fingers on switch button while carrying a plugged-in tool
Keeping cords away from heat, oil, and sharp edges
Yanking cord to disconnect plug from outlet

Answer: c. Keeping cords away from � heat, oil, and sharp edges

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Knowledge Check

Who is responsible for ensuring that overhead power lines are de-energized?

Power company
Employer
Employee
Municipality

Answer: b. Employer

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Electrical Safety

Training General Industry

Tips Engineer Zone

www.tipsengineerzone.in

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