Transcript Introduction to Electrical Safety Module 1 1-1

Module 1
Introduction to
Electrical Safety
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Module Objectives
Recognize key statistics
relating to electrical injuries.
Recognize OSHA regulations
and other standards relating
to electrical safety.
Understand basic electrical
terminology.
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Module Objectives
Identify the four types of injury
relating to electrical incidents.
Understand key facts relating to
electric shock.
Understand the basic facts of
electricity.
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Module Objectives
Understand Ohm’s Law and
describe how the terms
current, voltage and resistance
relate to Ohm’s Law.
Recognize the effects of
electricity on the human body.
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Electrifying Statistics
From 1992-2002, there were 3,378
deaths from on-the-job electrical
injuries.
That’s 4.7% of all occupational deaths.
That’s almost one death per day!
Electricity is the 4th leading cause of
injury-related occupational death
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Electrifying Statistics
Contact with overhead power
lines was the leading cause of
electrocutions, causing 42% of
the deaths.
The second leading cause of
electrocutions was failure to
properly de-energize equipment.
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Electrifying Statistics
The third most common cause
was contact with electrical
components mistakenly thought
to be de-energized.
Contact with buried, underground
power lines caused 1% of the
fatalities.
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Electrifying Statistics
Non-fatal injuries were also high, with
46,598 from 1992 through 2002 .
36% were caused by contact with the
electric current of a machine or tool.
34% were caused by contact with wiring
or transformers.
2% were caused by contact with buried,
underground power lines.
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OSHA 29 CFR 1910, Subpart I
OSHA 29 CFR 1910, Subpart P
OSHA 29 CFR 1910, Subpart S
OSHA 29 CFR 1910.147
OSHA 29 CFR 1910.333
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NFPA 70E
Safety related work practices
Safety related maintenance
requirements
Safety requirements for special
equipment
Installation safety requirements
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NFPA 70E Handbook
A supplement to the
NFPA 70E standard
Gives step-by-step
instructions for how to
implement the standard
Provides the thought
process and rationale
for the standard
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What they all Do
OSHA is the SHALL
NFPA 70E standard is the HOW
NFPA 70E handbook is the
STEP-BY-STEP
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Qualified Person
One who has received training in
and has demonstrated skills and
knowledge in the construction and
operation of electric equipment and
installations and the hazards
involved.
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Important Note
This program does not meet the
requirements for a qualified person.
It is intended to raise your
awareness of electrical safety.
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Arc Flash
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Types of Electrical Injury
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Rules of Electrical Action
Electric current won’t flow until
there is a complete loop.
Electric current always tries to
return to its source.
When current flows, work can be
accomplished.
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How Shock Occurs
The body comes into contact with wires
in an energized circuit.
The body comes into contact with one
wire of an energized circuit and a path
to the ground.
The body comes into contact with a
“hot” metallic part that is touching an
energized conductor.
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Severity of Shock
Three factors
The path of the current through the
body.
The amount of current flowing
through the body.
The length of time the body is in the
circuit.
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Basic Facts of Electricity
ELECTRICITY
=
ELECTRONS IN MOTION
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Basic Facts of Electricity
Flow of Electricity
Flow of Water
CURRENT
Flow of electrons
Flow of liquid
Measured in amps
Measured in gallons
per minute (gpm)
I = amps
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Basic Facts of Electricity
Flow of Electricity
Flow of Water
FORCE
Measured in
voltage
Measured in pounds
per square inch (psi)
V or E = volts
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Basic Facts of Electricity
Flow of Electricity
Flow of Water
RESISTANCE
Electrical resistance
to flow is measured
in ohms
Water resistance to
flow is measured as
friction or baffles
R = resistance
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Ohm’s Law
A mathematical formula that
enables the measurement of
electric current moving
through a conductive body
George Simon Ohm
1789-1854
German Physicist
Volts (V) = Amps (I) X Resistance (R)
V = IR
1 volt = 1 amp X 1 ohm of resistance
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A Visual Way to Remember
V
I
R
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Solution
1. Since we know voltage (V) and
resistance (R), which version of the
formula should we use?
I = V/R
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Solution
2. Now which numbers do we plug in?
I = 120/1,000
3. How many amps?
I = .12 amps
4. How many milliamps (mA)?
I = 120 milliamps
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The Human Body Resistance Model
Body Part
Resistance
Dry, intact skin
100,000-600,000 ohms
Wet skin
1,000 ohms
Within the body
400 ohms
Ear to ear
100 ohms
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Effects of Electricity Depend On:
Strength of current.
Duration of contact.
Body mass.
Gender of person.
Moisture on the body.
Path of the current.
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Photo courtesy of Schneider Electric
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Photo courtesy of Schneider Electric
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Photo courtesy of Schneider Electric
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What the Project Manager Felt
1. The drill had 120 volts.
2. The project manager’s dry skin
had a resistance of 100,000 ohms.
3. The flow into the project
manager’s hand was
120 volts/100,000 ohms, 0.0012
amps, or 1.2 milliamps.
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What the Apprentice Felt
1. The drill had 120 volts.
2. The apprentice’s wet skin had a
resistance of 1,000 ohms.
3. The flow into the apprentice’s
hand was 120 volts/1,000 ohms,
0.12 amps, or 120 milliamps.
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Facts About Lower Amperage
A small circuit in your home
carries 12-16 amps of current.
That equals 12,000 to 16,000
milliamps.
As we’ve learned, as little as 120
milliamps can cause death.
Low amperage/voltage circuits
are dangerous!
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NIOSH Low Voltage Study
600 v
440-480 v
8%
22%
110-120 v
1
34%
2
3
4
270-277 v
220-240 v
16%
20%
5
That’s over 1 in 3 deaths at 120 v or less!
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Action Plan
Action
Potential Barriers Overcoming the
Barriers
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