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ELECTRICAL
SAFETY
Part 2: Working Safely
ELECTRICITY - THE DANGERS
SHOCK
BURNS
ARC FLASH
FALLS
ELECTRICAL SHOCK
An electrical shock is a current flow through
the body.
The shock occurs when any part of your
body completes a circuit by being:
• In contact with two wires
• In contact with a wire and ground
• In contact with a metal part that is in
contact with a wire in a circuit
and
ground.
ELECTRICAL SHOCK
The response could range
from a faint tingling
sensation to death.
You can perceive a current
as low as 1 milliamp.
At 5 mA you will feel a slight shock. Most
people can let go.
ELECTRICAL SHOCK
“Can’t Let Go” Current
10 mA to 30 mA
Painful shock
and sustained
muscle contraction.
ELECTRICAL SHOCK
50 mA to 150 mA
Extreme pain, respiratory arrest, severe
muscle contractions, possible death
1,000 mA to 4,300 mA
Ventricular fibrillation,
muscle contractions,
nerve damage, death
likely.
ELECTRICAL SHOCK
ELECTRICAL SHOCK
The duration and the amount of current
affect the severity of an electrical shock
injury.
Death can occur in 2 seconds with a
current of 0.1 amps (100 milliamps).
100 mA for 3 seconds is as dangerous as
900 mA for 0.03 seconds.
ELECTRICAL SHOCK
Other factors that may affect the
severity of the shock are:
• The voltage of the current.
• The presence of moisture.
• The phase of the heart cycle when
the shock occurs.
• The general health of the person
prior to the shock.
ELECTRICAL SHOCK
High voltages increase shock injuries
because a higher voltage produces a
greater current.
I = E/R
Resistance - the lower the resistance, the
greater the current will be.
R = E/I
ELECTRICAL SHOCK
Resistance between major extremities of an
average human body is 1,500 ohms hand to
hand or hand to foot.
If you grabbed a wire carrying 120 volts
alternating current how much current would
flow through your body?
I = E/R
ELECTRICAL SHOCK PATHWAYS
1. Right hand
left hand
2. Right
foot left
foot path
3. Right hand
right foot path
4. Left
hand left
foot path
ELECTRICAL BURNS
Electrical burns are the
result of heat generated
by the flow of electric
current through the body.
The dark spot is where the
current entered the body.
ELECTRICAL BURNS
Electricity arced through
the air as a result of a
power box explosion.
The arc was drawn to this
man’s arm pits because
of perspiration.
ELECTRICAL BURNS
Current exited this man
at his knees, catching his
clothing on fire and
burning his upper leg.
ELECTRICAL BURNS
The current exited the
foot of this man. Because
of severe internal
injuries, the foot had to
be amputated a few days
later.
ELECTRICAL BURNS
This worker was
shocked by a tool he
was holding.
A few days later.
ARC FLASH
An arc flash is a short
circuit through the air.
It can occur if a
conductive
object gets too close to a
high-amp current source
or by equipment failure
such as opening or
closing disconnects.
FALLS
Workers who get
shocked while on a
ladder or other elevated
location can fall,
resulting in serious
injury or death.
ELECTRICAL HAZARDS
Electrical shocks, fires or falls can result from:
• Exposed electrical
parts
• Overhead power lines
• Inadequate wiring
• Defective insulation
• Wet conditions
• Improper grounding
• Improper PPE
• Improper tools
• Overloaded circuits
ELECTRICAL HAZARDS
Exposed Electrical Parts
ELECTRICAL HAZARDS
Overhead Power Lines
NIOSH Case Study
Untrained worker raising a
21 foot fence rail under a
7,200 volt power line.
Worker was electrocuted.
ELECTRICAL HAZARDS
Inadequate Wiring
Wire Gauge - wire size
or diameter
Ampacity - the
maximum amount of
current a wire can
carry safely without
overheating
Incorrect wiring practices can cause fires! If
you touch live electrical parts, you will be
shocked. Overloaded wires get hot!
ELECTRICAL HAZARDS
Copper Wire Ampacity Table
Wire Gauge
14
12
10
8
6
4
2
0
2/0
4/0
Maximum Ampacity
15
20
30
45
65
85
115
150
175
250
ELECTRICAL HAZARDS
Defective Insulation
ELECTRICAL HAZARDS
Defective Insulation
Screw penetrated insulation creating a
small arc flash.
ELECTRICAL HAZARDS
Wet Conditions
Wet clothing, high humidity, and perspiration
also increase your chances of being electrocuted
ELECTRICAL HAZARDS
Improper grounding
ELECTRICAL HAZARDS
Improper grounding
ELECTRICAL HAZARDS
Overloaded Circuits
Too much current in a circuit can
lead to a fire or electrical shock.
THE REGULATIONS
CalOSHA Low voltage (600V) Electrical
Safety Orders
Article 3, § 2320.1
Only qualified persons shall work on
electrical equipment or systems.
A qualified person is defined as a person
designated by the employer, who by reason of
experience or instruction has demonstrated
familiarity with the operation to be performed
and the hazards involved.
THE REGULATIONS
§ 2320.2
Work SHALL NOT be perform on energized
parts of equipment or systems until the
following conditions are met:
1.Responsible supervision has determined
that the work is to be performed while the
equipment or system are energized.
2.Involved personnel have received
instructions
on the work techniques and hazards involved
in working on energized equipment.
THE REGULATIONS
§ 2320.2 (cont’d)
3. Suitable personal protective equipment
and safeguards (approved insulated gloves
or insulated tools) are provided and used.
4. Approved insulated gloves
shall be worn for voltages
in excess of 250 volts to
ground.
THE REGULATIONS
§ 2320.2 (cont’d)
5. Suitable barriers or approved insulating
material shall be provided and used to
prevent
accidental contact with energized parts.
6. Suitable eye protection
has been provided
and used.
THE REGULATIONS
§ 2320.2 (cont’d)
7. Where required for personnel protection,
suitable barricades, tags, or signs are in
place.
THE REGULATIONS
§ 2320.2 (cont’d)
• Each employee who is
exposed to the hazards
of flames or electric arcs
wears apparel that,
when exposed to flames
or electric arcs, does not
increase the extent of injury that would be
sustained by the employee.
THE REGULATIONS
§ 2320.3
All electrical equipment and systems shall be
treated as energized until tested or otherwise
proven to be de-energized.
THE REGULATIONS
General Safety Orders § 3314 (g)
A hazardous energy control
procedure shall be developed
and utilized by the employer
when employees are engaged
in the cleaning, repairing,
servicing, setting-up or
adjusting of prime movers,
machinery and equipment.
LOCKOUT/TAGOUT
LOCKOUT/TAGOUT
Overview of Procedures
Must use own lock and keep key on his/her
person until job is done.
Procedures apply to all
Sources of energy - electrical,
thermal, hydraulic, pneumatic,
mechanical, etc.
LOCKOUT/TAGOUT
Notify all affected employees.
Identify all applicable isolating devices breakers, switches, valves, etc.
LOCKOUT/TAGOUT
Obtain a padlock and tag from lockout
station.
Isolate source of power at the
circuit breaker on MCC panel
and at other sources
of hazardous energy.
LOCKOUT/TAGOUT
On the tag, write name,
date, time and why
equipment is locked
out.
BLOCK
DRAIN
BLEED
TEST
Test to be
sure there is
no release of
hazardous
energy.
LOCKOUT/TAGOUT
Always take precautions to guard against
the possibility of faulty switches or short
circuits when locking out equipment. Test
the equipment with a meter when doing
electrical work.
THE REGULATIONS
Do not use conductive measuring tapes or
ropes when working near energized parts of
equipment.
Legibly mark each motor controller to
indicate the motor it controls and provide a
corresponding marking on each motor.
When a circuit is discontinued, remove the
conductors from the raceway or treat the
circuit as if it is in use.
THE REGULATIONS
Do not use conductive fish tape in raceways
entering enclosures with exposed energized
parts unless the parts are isolated by
barriers.
At least 3 feet of cleared space (no storage)
shall be available in the direction of access
to control panels, circuit breakers,
switchboards, fused switches, and similar
equipment.
THE REGULATIONS
All electrical equipment shall have markings
giving voltage, current, wattage, or other
ratings.
Circuit breakers shall clearly indicate
whether they are in the open “off” or closed
“on” position.
THE REGULATIONS
Flexible cords or cables SHALL NOT be used
• as a substitute for fixed wiring of a
structure,
• where run through holes in walls,
ceilings or floors,
• where run through doorways, windows
or similar openings,
• where attached to building surfaces, or
• where concealed behind building walls,
ceilings or floors
THE REGULATIONS
Flexible cords shall be used only in
continuous lengths without splice or tap.
Hard service flexible cords No. 12 or larger
can be spliced as long as the splice retains
the insulation, outer sheath properties, and
usage characteristics of the cord.
GROUND FAULT CIRCUIT
INTERRUPTER
Use a GFCI when working on
circuits or using electrical
equipment in damp or wet areas.
DOUBLE INSULATED TOOLS
Use double insulated tools
if GFCI is not available.
Always check cord
and plug on all power
tools before use
ELECTRICAL FIRES
NEVER put water on an electrical fire.
Use Class C or ABC fire
extinguishers.
THE REGULATIONS
Wrist watches, rings, or other jewelry
should not be worn while working with or
around machinery with moving parts in
which such objects may be caught, or
around electrically energized equipment.
BE SAFE !
THE
END