Transcript Electrical Safety Related Work Practices

Employees must be trained concerning Electrical
Safety as required under 1910.331-1910-335 that
pertain to their respective job assignments.
The OSHA e-tool electrical safety presentation was used to
create this presentation
•
•
•
•
•
•
•
•
Maintenance Supervision
Mechanics and Maintenance Workers
Engineers
Equipment Operators
Crane Operators
Riggers
Material Handlers
IT Technicians
•
•
•
•
•
Describe how electricity works
Describe how shocks occur
Describe how electrical current effects the
body
Describe the most common ways
individuals are injured using electricity
Provide solutions to avoid being injured
while using electricity
Operating an electrical switch can be likened to turning on a
water faucet. Behind both a faucet and an electrical switch
there is a source of water/electricity, a way to transport it,
and pressure to make it flow. A faucet's water source is a
reservoir or pumping station. A switch's electrical source is
a power generating station, which provides pressure for
electrical current to travel through conductors.
Three factors determine the
resistance of a substance to the
flow of electricity.
1. What it is made of
2. Its size
3. Its temperature
Substances with very little resistance to the flow of
electrical current are called conductors. Examples are
metals and tap water.
Substances with such a high resistance that they can
be used to prevent the flow of electrical current are
called insulators. Examples are glass, porcelain,
plastic, and dry wood.
Note: Although dry wood is a poor conductor, when
saturated with water it becomes a ready conductor.
Use extreme caution when working with electricity
where there is water in the environment or on the skin.
Wet conditions are common during low-voltage
electrocutions. Under dry conditions, human skin is very
resistant. Wet skin dramatically drops the body's resistance.
Dry Conditions: Current = Volts/Ohms = 120/100,000 =
1mAa barely perceptible level of current
Wet conditions: Current = Volts/Ohms = 120/1,000 =
120mA sufficient current to cause ventricular fibrillation
High voltage electrical energy greatly reduces the body's
resistance by quickly breaking down human skin. Once the
skin is punctured, the lowered resistance results in massive
current flow. Ohm's law in use:
At 1,000 volts, Current = Volts/Ohms = 1,000/500 = 2
Amps which can cause cardiac standstill and serious
damage to internal organs.
Electricity travels in closed circuits, normally through a
conductor. Shock results when the body becomes part of
the electrical circuit; current enters the body at one point
and leaves at another.
Note: Ground circuits provide a path for stray current to pass
directly to the ground, and greatly reduce the amount of
current passing through the body of a person in contact
with a tool or machine that has an electrical short. Properly
installed, the grounding conductor provides protection from
electric shock.
Did you know? ~350 Electrical-Related
Fatalities Occur Each Year
Current
Human Reaction
(Amps)
0.001
Perception level. Just a faint tingle.
0.005
Slight shock felt; not painful but disturbing.
Average individual can let go.
0.006-0.025
(Women)
Painful shock, muscular control is lost.
0.009-0.030
(Men)
This is called the freezing current or
"let-go" range.
0.050-0.150
Extreme pain, Respiratory Arrest, severe muscular
1 - 4.3
Ventricular fibrillation.
10
contractions.
Cardiac arrest, severe burns and likely death.
When muscular contraction caused by stimulation does
not allow the victim to free himself from the circuit,
even relatively low voltages can be extremely
dangerous, because the degree of injury increases with
the length of time the body is in the circuit.
LOW VOLTAGE DOES NOT IMPLY LOW HAZARD!
An exposure of 100mA for 3 seconds can cause the same
amount of damage as an exposure of 900mA for .03
seconds
The most common shock-related injury is a burn. Burns suffered in
electrical incidents may be one or more of the following three
types:



Electrical Burns cause tissue damage, and are the result of heat
generated by the flow of electric current through the body.
Electrical burns are one of the most serious injuries you can
receive and need to receive immediate medical attention.
High temperatures near the body produced by an electric arc or
explosion cause Arc or Flash Burns (also need prompt medical
attention)
Thermal Contact Burns occur when skin comes in contact with
overheated electric equipment, or when clothing is ignited in an
electrical incident.
Note: the graphic pictures were not included. But if you would still like to view
them click http://www.osha.gov/SLTC/etools/construction/electrical_incidents/burns.html
Our bodies use small electrical currents to transmit
signals through the nervous system and contract
muscles, but extra electrical current flowing
through the body can cause serious damage.
Medical problems can include internal bleeding,
tissue destruction, and nerve or muscle damage.
Internal injuries may not be immediately apparent to
the victim or observers; however, left untreated,
they can result in death.
Muscles violently contract when stimulated by excessive
amounts of electricity. These involuntary contractions
can damage muscles, tendons, and ligaments, and may
even cause broken bones. If the victim is holding an
electrocuting object, hand muscles may contract,
making it impossible to drop the object.
Note: injury or death may result from a fall due to muscle
contractions.
Fatalities occur when equipment, such as that listed below,
contacts energized power lines:
•
•
•
•
•
•
•
•
•
Aluminum paint rollers
Excavation equipment
Concrete pumpers
Cranes
Long-handled cement finishing floats
Building materials
Ladders
Tent Poles
Scaffolding
•
•
•
•
•
Locate power lines in your work area
before you begin working
Prior to digging, call 811 to have utilities
identify and mark any buried lines.
Keep yourself and all objects at least 10feet away from all energized power lines.
Have power lines de-energized and
grounded prior to beginning your work.
Use non-conductive ladders (fiberglass)
and other tools.
A ground-fault occurs when current flowing to the
load (drill, saw, etc.) does not return by the
prescribed route.
In a simple 120 volt circuit, current travels
through the black (ungrounded) wire to the load
and returns to the source through the white
(grounded) wire. If some or all of the current
does not travel back through the white wire then
it has gone somewhere else, usually to ground.
A persons body can act as the path to ground
when a fault occurs.
1. Using a double
insulated drill (no
ground pin) in a wet
location. Water enters
the drill housing and
current flows through
the water and user, and
then back to its source.
2. An individual with
moist hands is
electrocuted while
winding up a damaged
extension cord when
their skin contacts
exposed wiring in the
extension cord.
Use GFCI’s for protection
against ground-faults
(see following slides)
The ground-fault circuit interrupter (GFCI) works by comparing the
amount of current going to and returning from equipment along
the circuit conductors. When the amount going differs from the
amount returning by approximately 5 milliamperes, the GFCI
interrupts the current within as little as 1/40 of a second.
Note: A GFCI will not protect you from line contact hazards (i.e. a
person holding two "hot" wires, a hot and a neutral wire in each
hand, or contacting an overhead power line). However, it protects
against the most common form of electrical shock hazard, the
ground-fault. It also protects against fires, overheating, and
destruction of wire insulation.
Use ground-fault circuit interrupters (GFCIs) on all
120-volt, single-phase, 15- and 20-ampere
receptacles that will be used to supply temporary
power (i.e. hand tools and other portable
equipment).
-Portable GFCIs like this one are available
for situations where GFCI protection is
not otherwise provided-
Important - Plug this end directly into the electrical source, not
another flexible cord.
Follow manufactures recommended testing procedure to
insure GFCI’s are working correctly
If the power supply to the electrical equipment at your site
is not grounded or the path has been broken, fault current
may travel through a worker's body.
Do not remove the ground pin from a plug (even to fit an
ungrounded outlet). Doing so not only means your work
area is unsafe, but makes the cord unfit for future work
where grounding is needed.
Do Not Use Plug Adaptors
To Bypass Grounded Circuits
•
•
•
•
•
Ground all power supply systems, electrical circuits, and
electrical equipment.
Do not remove ground pins/prongs from cord- and plugconnected equipment or extension cords.
Use double-insulated tools.
Ground all exposed metal parts of equipment.
Ground metal parts of the following non-electrical equipment, as
specified by OSHA standard [1926.404(f)(7)(v)]:
 Frames and tracks of electrically operated cranes and hoist.
 Frames of non-electrically driven elevator cars to which
electric conductors are attached.
 Hand-operated metal shifting ropes or cables of electric
elevators.
 Metal partitions, grill work, and similar metal enclosures
around equipment of over 1kV between conductors.
If electrical
equipment is used in
ways for which it is
not designed, you
can no longer
depend on safety
features built in by
the manufacturer.
This may damage
property and cause
employee injuries or
worse
Shock, fire, loss of life and property?
Note: These type
junction boxes must
be properly
mounted.
X
X
X
X
X
X
Using multi-receptacle boxes designed to be mounted by
fitting them with a power cord and placing them on the
floor.
Fabricating extension cords with ROMEX® wire.
Using equipment outdoors that is labeled for use only in dry,
indoor locations.
Using circuit breakers or fuses with the wrong rating for overcurrent protection, e.g. using a 30-amp breaker in a system with
15- or 20-amp receptacles (protection is lost because it will not trip
when the system's load has been exceeded).
Using modified cords or tools, e.g., removing face plates,
insulation, etc.
Using cords or tools with worn insulation or exposed wire.
REMEMBER - ONLY USE EQUIPMENT IN A MANNER PRESCRIBED
BY THE MANUFACTURER
In the first picture flexible cords are being used in lieu of
permanent wiring. They have been there so long they have
been painted over. Also has an adapter in-line.
Note: A common OSHA Violation
Temporary wiring must not be
used in lieu of permanent
wiring
Multi-outlet surge protection
such as this can be used to
supply power to equipment
that needs surge protection,
but not used to provide more
outlets due to the lack of
permanent wiring.
Extension type cords that are not 3-wire type, not designed for hard-usage,
or that have been modified, increase your risk of contacting electrical
current, and must not be used at COB.
•
•
•
•
•
•
•
Only use factory-assembled cord sets (Molded Plug).
Use only extension cords that have a ground wire (3wire type).
Use only extension cords that are marked with a
designation code S, ST, SO, and STO for hard service,
and SJ, SJO, SJT, and SJTO for junior hard service.
Use only cords, connection devices, and fittings that
are equipped with strain relief.
Remove cords from receptacles by pulling on the
plugs, not the cords.
Remove from service flexible cords that have been
modified or damaged.
Never run cords through walls or door frames.
Visually inspect all electrical equipment before use.
Remove any equipment with frayed cords,
missing ground prongs, cracked tool casings,
etc. from service.
Apply a warning tag to any defective tool and
do not use it until it has been properly repaired.
•
•
•
•
•
•
•
Ground all power supply systems, electrical
circuits, and electrical equipment.
Frequently inspect electrical systems to insure
that the path to ground is continuous.
Visually inspect all electrical equipment before
use. Take & Tag any defective equipment out of
service and report it.
Do not remove ground prongs from cord and plug
connected equipment or extension cords.
Use double-insulated tools.
Ground all exposed metal parts of equipment.
Never open electrical panels or equipment unless
you are trained and authorized to do so.
Should a portion of your job require you to actually work on
and test electrical systems and components, then you will
also need to be trained in the following course:
NFPA 70E Standard for Electrical Safety Requirements for
Employee Workplaces -- A Operational Guide for Protection
Against Shock and Arc Flash
If you are certified as a Crane Operator or Signalperson, you
will also need the course:
Powerline Safety for Crane Operators
Old Reddy says:
“Always respect
electricity and never use
damaged equipment”
If you have questions please contact the City of
Burlington, Director of Safety (336) 513-5463
Please sign the training roster upon completion.