Basic Electrical Safety
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Basic
Electrical Safety
- Course not designed
to teach you to work on electrical equipment.
- You will not be
qualified to work on electrical equipment.
- If you spot problems
with electrical equipment you should report it to your supervisor.
Objectives
- Be familiar with
the fundamental concepts of electricity.
- Be familiar with
the effects of electricity on the human body.
- Be able to recognize
common electrical hazards.
- Be familiar with
electrical protective devices.
Fundamentals of
Electrical Hazards
- To flow electricity
must have a complete path.
- Electricity flows
through conductors
- water, metal,
the human body
- Insulators are
non-conductors
- The human body
is a conductor
Have
You Ever Been Shocked?
THE
BASICS
- More than 3 ma
- More than 10 ma
- muscle contraction
"no-let-go" danger
- More than 30 ma
- lung paralysis-
usually temporary
- More than 50 ma
- possible ventricular
fob. (heart dysfunction, usually fatal)
- 100 ma to 4 amps
- certain ventricular
fibrillation, fatal
- Over 4 amps
- heart paralysis;
severe burns. Usually caused by >600 volts
- Hazards of Electricity
- Electrocution/Shock/Burns/Death
- Minimum distance
from overhead lines 10 ft.
- Inspect all electrical
tools and equipment
Frayed, cut, broken
wires
grounding prong missing
Improper use of cube taps
improperly applied or missing strain relief
Electrical Protection
- Circuit Breakers
- Provided to
protect EQUIPMENT not people
- Do not reset
breakers with a line voltage higher than 120V and only reset if
you know why it tripped
- GFCI's
- Provided to
protect people
- Trip range
4-6ma
- Monthly test
- Distance
- If you sense
the presence of an electrical hazard or exposed conductors that
may be energized, keep you distance and STAY AWAY
Terminology
Electrical Grounding
Figure 12 : Current flow in a properly grounded circuit
Figure 14: Shock from improperly grounded tool
Figure 15: Fault conditions sensed by a GFCI
Figure 16: Correctly wired duplex receptacle
Fundamentals of
Electrical Hazards
- Voltage
- electrical
pressure (water pressure)
- Amperage
- electrical
flow rate (gallons/min)
- Impedance
- restriction
to electrical flow (pipe friction)
- Circuit
- path of flow
of electricity
- Circuit Element
- objects which
are part of a circuit and though which current flows.
- Fault
- current flow
through an unintended path.
- What is Grounding?
- Protection
from electric shock
- normally
a secondary protection measure
- A ground is a
conductive connection
- between electrical
circuit or equipment and earth or ground plane
- creates a
low resistance to the earth.
Basic Rules of
Electrical Action
- Electricity isnt
live until current flows
- Electrical current
wont flow until there is a complete loop, out from and back to
the power source.
Preventing Accidental
Electrical Contact
Do's and Don'ts
- Do plug
power equipment into wall receptacles with power switches in the Off
position.
- Do unplug
electrical equipment by grasping the plug and pulling. Do not pull or
jerk the cord to unplug the equipment.
- Do not
drape power cords over hot pipes, radiators or sharp objects.
- Do check
the receptacle for missing or damaged parts.
- Do not
plug equipment into defective receptacles.
- Do check
for frayed, cracked, or exposed wiring on equipment cords
- Do check
for defective cords clamps at locations where the power cord enters
the equipment or the attachment plug.
- Extension cords
should not be used in office areas. Generally, extension cords should
be limited to use by maintenance personnel
- Cheater
plugs, extension cords with junction box receptacle ends or other
jury-rigged equipment should not be used.
- Consumer electrical
equipment or appliances should not be used if not properly grounded.
(Look for the UL Label)
- Employees should
know the location of electrical circuit breaker panels that control
equipment and lighting in their respective areas. Circuits and equipment
disconnects must be identified
- Temporary or permanent
storage of any materials must not be allowed within 3 feet of
any electrical panel or electrical equipment.
- Any electrical
equipment causing shocks or with high leakage potential must be tagged
with a Danger tag or equivalent.
Myths and Misconceptions
- Electricity takes
the path of least resistance.
- Electricity wants
to go to ground.
- If an electric
tools falls into a sink or tub of water, the item will short out.
- AC reverse polarity
is not hazardous.
- It takes high
voltage to kill; 120 volts is not dangerous.
- Double insulated
power tools are doubly safe and can be used in wet and damp locations.
This paper appears in the eLCOSH website with the permission of the
author and/or copyright holder and may not be reproduced without their
consent. eLCOSH is an information clearinghouse. eLCOSH and its sponsors
are not responsible for the accuracy of information provided on this web
site, nor for its use or misuse.
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