Download General Electrical Safety

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Describe how electricity works
Describe how shocks occur
Describe how electrical current affects
the body
Describe the most common ways
individuals are injured using electricity
Provide solutions to avoid being injured
while using electricity
Lockout/Tagout
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Employees
◦ When operating electrical equipment employees
will be familiar with the manufacturer
instructions.
◦ Employees must tag defective equipment out and
report it to their supervisor.
◦ Employees will check electrical cords prior to use.
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Supervisor
◦ Supervisor will make a determination on the
appropriate avenue for replacement or repair of
defective equipment.
Example: A Garden Hose
To Low Pressure
Water Moves from
High Pressure
The same thing occurs in an Electrical Wire
Flow of Current
Current Moves from
High Voltage
To Low Voltage
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.
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The effects of shock can depend upon
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The type of circuit
Voltage resistance
Current
Pathway through the body
Duration of the contact
Effects can range from a tingle to cardiac
arrest.
Current
(Amps)
Human Reaction
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
contractions.
1 - 4.3
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Ventricular fibrillation.
Cardiac arrest, severe burns and probable death.
Note: some smaller microwave ovens use 10.0 Amps (10,000 milliamps) and common
florescent lights use 1 Amp (1,000 milliamps)
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.
Our bodies use small electrical currents to transmit signals through
the nervous system and contract muscles,
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.
Conductors- Substances with relatively little resistance to the
flow of electrical current (e.g., metals).
Water- influences the conductive properties of some materials
Dry wood is a poor conductor
Wood saturated with water becomes a ready conductor
Use extreme caution when working with electricity where there
is water in the environment or on the skin.
Dry Conditions
Human Skin is Resistant
Current = Volts/Ohms = 120/100,000 = 1mA (0.001A)
-Barely perceptible level of current
Wet Conditions
Skin’s Resistance drops dramatically
Current = Volts/Ohms = 120/1,000 = 120mA (0.12A)
-Sufficient current to cause ventricular fibrillation
A low voltage electrocution becomes much more
hazardous in a wet condition
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.
Muscular contraction caused by stimulation does not allow a
victim to free himself from a circuit
The degree of injury increases with the length of time the bdy
is in the circuit.
Thus even relatively low voltages can be extremely dangerous.
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 Form of Electrical Shock)
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 person’s body can act as the path to ground when a fault occurs.
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 providedFollow manufacturers'
recommended testing
procedure to insure
GFCIs are working
correctly.
Important - Plug this
end directly into the
electrical source, not
another flexible cord.
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Ground all power supply
systems, electrical circuits, and
electrical equipment
Do not remove ground
pins/prongs from cord- and
plug-connected equipment or
extension cords
Use double-insulated tools
Ground all exposed metal parts
of equipment
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When mechanical equipment is being operated
near over-head lines, employees standing on the
ground may not contact the equipment unless it is
located so that the required clearance cannot be
violated even at the maximum reach of the
equipment.
These employees and their mechanical equipment
must stay at least 10 feet ( 3.05 meters) away from
the overhead power lines.
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Employees, whose occupations require them to
work directly with electricity, must use the personal
protective equipment required for the jobs they
perform.
This equipment may consist of rubber insulating
gloves, hoods, sleeves, matting, blankets, line
hose, and industrial protective helmets.
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Perhaps the single most successful defense against
electrical accidents is the continuous exercising of
good judgment or common sense.
All employees should be thoroughly familiar with
the safety procedures for their particular jobs.
When work is performed on electrical equipment,
for example, some basic procedure are:
◦ Have the equipment deenergized.
◦ Ensure that the equipment remains deenergized
by using a lockout/tagout procedure.
◦ Use insulating protective equipment.
◦ Keep a safe distance from energized sources.
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Boom type units shall be grounded and the following
clearances shall be maintained or the line de-energized:
Power Line Voltage Phase Minimum Safe Clearance (
to Phase (KV)
Feet)
50 or below
10
Above 50 to 200
15
Above 200 to 350
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Above 350 to 500
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Above 500 to 1,000
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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: Junction boxes such as this
one must be mounted properly.
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Using multi-receptacle boxes designed to be mounted by
fitting them with a power cord and placing them on the
floor.
Using equipment outdoors that is labeled for use only in
dry, indoor locations.
Using circuit breakers or fuses with the wrong rating for
over-current 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
wires.
REMEMBER - ONLY USE EQUIPMENT IN A MANNER PRESCRIBED BY THE MANUFACTURER
The following cords are improperly
wired directly to the electrical
circuit, are not protected by a
GFCI, and are two-wire cords that
are not grounded and not rated for
hard- or extra-hard service.
Temporary (flexible wiring) must not be
used in place of permanent wiring.
Multioutlet 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.
Note: a common OSHA violation.
•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.
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Electrical panel boxes must be secured and
problems reported immediately.
Junction boxes, outlets, receptacles, and
switches must be closed and problems reported.
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Electric panels must be kept clear of any
obstructions at all times.
Storage is not allowed in electrical vault or
service panel rooms. Find another place for
storage of materials, products, etc.
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Electrical within two (2) feet of any water source
must have GFCI protection. Covers must be in
place at all times.
No flammable chemicals or liquids can be
stored near electrical or in electrical service
rooms.
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What is hazardous energy?
Energy sources including electrical,
mechanical, hydraulic, pneumatic, chemical,
thermal or other sources in machines and
equipment can be hazardous to workers.
During the servicing and maintenance of
machines and equipment, the unexpected
startup or release of stored energy could
cause injury to employees.
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What are the harmful effects of hazardous energy?
Workers servicing or maintaining machines or equipment may be
seriously injured or killed if hazardous energy is not properly controlled.
Injuries resulting from the failure to control hazardous energy during
maintenance activities can be serious or fatal! Injuries may include
electrocution, burns, crushing, cutting, lacerating, amputating, or
fracturing body parts, and others.
A steam valve is automatically turned on burning workers who are
repairing a downstream connection in the piping.
A jammed conveyor system suddenly releases crushing a worker who is
trying to clear the jam.
Internal wiring on a piece of factory equipment electrically shorts
shocking employee who is repairing the equipment.
Craft workers, electricians, machine operators, and laborers are among
the 3 million workers who service equipment routinely and face the
greatest risk of injury. Workers injured on the job from exposure to
hazardous energy lose an average of 24 workdays for recuperation.
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What can be done to control hazardous energy?
Failure to control hazardous energy accounts for nearly 10
percent of the serious accidents in many industries. Proper
lockout/tagout (LOTO) practices and procedures safeguard
workers from the release of hazardous energy. OSHA's
Lockout/Tagout fact sheet (PDF*) describes the practices
and procedures necessary to disable machinery or
equipment to prevent the release of hazardous energy.
The OSHA standard for The Control of Hazardous Energy
(Lockout/Tagout) (29 CFR 1910.147) for general industry
outlines measures for controlling different types of
hazardous energy. The LOTO standard establishes the
employer's responsibility to protect workers from
hazardous energy. Employers are also required to train
each worker to ensure that they know, understand, and are
able to follow the applicable provisions of the hazardous
energy control procedures:
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Proper lockout/tagout (LOTO) practices and procedures safeguard workers from
the release of hazardous energy. The OSHA standard for The Control of Hazardous
Energy (Lockout/Tagout) (29 CFR 1910.147) for general industry, outlines specific
action and procedures for addressing and controlling hazardous energy during
servicing and maintenance of machines and equipment. Employers are also
required to train each worker to ensure that they know, understand, and are able
to follow the applicable provisions of the hazardous energy control procedures.
Workers must be trained in the purpose and function of the energy control
program and have the knowledge and skills required for the safe application,
usage and removal of the energy control devices.
All employees who work in the area where the energy control procedure(s) are
utilized need to be instructed in the purpose and use of the energy control
procedure(s) and about the prohibition against attempting to restart or reenergize
machines or equipment that is locked or tagged out.
All employees who are authorized to lockout machines or equipment and perform
the service and maintenance operations need to be trained in recognition of
applicable hazardous energy sources in the workplace, the type and magnitude of
energy found in the workplace, and the means and methods of isolating and/or
controlling the energy.
Specific procedures and limitations relating to tagout systems where they are
allowed.
Retraining of all employees to maintain proficiency or introduce new or changed
control methods.
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Employees operating electrical equipment
shall be thoroughly familiar with the
operating instructions furnished by the
manufacturer. If the equipment does not
function properly after instructions have
been followed, defective equipment must
be tagged out of service and the condition
of the equipment reported to the
supervisor. The supervisor will make a
determination on the appropriate avenue of
replacement or repair. Employees shall
inspect the condition of the equipment and
electrical cords prior to use.
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OSHA Electrical Standards
https://www.osha.gov/pls/oshaweb/owadisp
.show_document?p_table=STANDARDS&p_id
=9880
OSHA Lockout/Tagout Fact Sheet
https://www.osha.gov/SLTC/controlhazardou
senergy/