Transcript Electrical Safety - Risk Control Services

Electrical Safety Training
Electrical Hazards
 Every year, between 300 and 500 people in
the U.S. are killed by electrocutions at work.
 Many of those killed
are people who work
with electricity indirectly,
including office workers
and operators.
This course will cover
 How electricity acts
 How shocks occur
 The severity of shocks
 The effects of an electric current in the body
 Burns and other injuries from electricity
 How to correct electrical hazards
 Safe work practices
How Electricity Works
 Many of us take electricity
and how it works for
granted. We simply flip a
switch and it is there.
 However, in order to know
how to deal with the
hazards of electricity, we
must know something
about how it works.
Rules of Electricity
 Electricity travels in a completed circuit
 Electricity will flow through a variety of
materials, shapes and forms
 Electricity always travels in the path of least
resistance
 Electricity always
tries to travel
to ground
Conductors & Insulators
 Some substances, such as metals, offer very
little resistance to the flow of electric current.
They are called conductors.
 Other substances, like porcelain, glass and
dry wood offer such a high resistance that
they can be used to prevent the flow of
electric current. They are called insulators.
Conductors & Insulators
 Water is a good conductor when it contains
impurities, such as salt and acid (both are
present in perspiration).
 When water is present or the skin is wet with
sweat, you should exercise even more
caution than usual when using electrical
devices.
SHOCK
 Electricity travels in closed circuits, and its
normal route is through a conductor. Shock
occurs when the body becomes a part of the
electrical circuit (the person forms a
completed circuit when touching the ground).
 A person usually offers a lesser resistance for
the electricity.
 The current must enter the body at one point
and leave at another.
SHOCK
 Shock occurs in one of three ways – when a
person comes in contact with:
– Both wires of the circuit
– One wire of an energized circuit and the
ground
– A metallic part that has become ‘hot’ by being
in contact with an energized wire, while the
person is also in contact with the ground
Severity of SHOCK
 The severity of the shock received when a
person becomes part of an electrical circuit
depends on three primary factors:
– The amount of current measured in Amps
– The path through the body
– The length of time the body is in the circuit
Effects on the Human Body
 1 mA: Can be felt by the body
 2-10 mA: Minor shock, might result in a fall
 10-25 mA: Loss of muscle control, may not be
able to let go of the current
 25-75 mA: Painful, may lead to collapse or
death
 75-300 mA: Last for ¼ second, almost always
immediately fatal
Voltages and Amperes
 Voltage = Amps X Ohms
(resistance)
 Converting voltage to
amps
 Typical Industrial Voltages
– 110/120 Volts = 60
milliAmps (mA)
– 220/240 Volts = 120 mA
– 440/480 Volts = 240 mA
Shock-Related Injuries
 The most common shock-related injury is a
burn.
 There are three types of burns:
– Electrical burns
– Arc burns
– Thermal burns
Shock-Related Injuries
 Electric shock can also cause injuries of an
indirect or secondary nature in which
involuntary muscle reaction from the electric
shock can cause bruises, bone factures, and
even death resulting from collisions or falls.
 In some cases, injuries caused by electric
shock can be a contributory cause of
delayed fatalities.
Types of Burns
 Electrical burns are the result of electric current
flowing through tissues or bone. Tissue damage is
caused by the heat generated by the current flow
through the body.
 Electrical burns are one of the most serious injuries
you can receive and should be given immediate
attention.
 Arc and flash burns are the result of high
temperatures near the body and are produced by an
electric arc or explosion. They should also be
attended to promptly.
Arcs
 In addition to shock and burn hazards, electricity
poses other dangers.
– For example, when a short circuit occurs, hazards
are created from the resulting arcs. If high current
is involved, the arcs can cause injury or start a fire.
 Extremely high arcs can damage equipment,
causing fragmented metal to fly in all directions.
 Even low-energy arcs can cause violent
explosions in atmospheres that contain
flammable gases, vapors, or combustible dusts.
Electrical Accidents

Electrical accidents appear to be caused by
a combination of three possible factors:
1. Unsafe equipment and/or installation
2. Workplaces made unsafe by the
environment
3. Unsafe work practices
Preventing Electrical Accidents
Insulation
 Electricity uses all of the conductor; if the conductor
is left exposed, any person touching it would be
shocked. That is why conductors have insulation.
 An insulator is a material with high resistance to
electric current. Insulators such as glass, mica,
rubber and plastic are put on conductors to prevent
shock, fires, and short circuits.
 Before connecting a device to a power source, check
the insulation to ensure there are no exposed wires.
Preventing Electrical Accidents
Guarding
 Live parts of electrical equipment operating
at 50 volts or more must be guarded against
accidental contact.
 Installations that are over 600 volts must be
controlled by a lock and must be marked
with appropriate caution signs.
Preventing Electrical Accidents
Grounding
 Grounding is another method of protecting workers
from electric shock. By grounding a tool or device, a
low-resistance path to the earth is intentionally
created.
 When a short occurs in the tool or wiring, the
grounding is accomplished through the intentional
ground (usually a ground wire), and not through the
worker.
 The ground does not guarantee that there will be no
shock, injuries, or fatalities, but it does reduce the
possibilities.
Preventing Electrical Accidents
Circuit Protection Devices
 Circuit protection devices are designed to automatically
limit or shut off the flow of electricity in the event of a
ground-fault, overload, or short circuit in the wiring system.
Fuses and circuit breakers are examples of circuit
protection devices.
– Fuses are designed to melt when too much current flows
through them.
– When too much current flows through a circuit breaker, it
opens (shuts off).
 Fuses and circuit breakers are intended primarily for the
protection of conductors and equipment, but they do also
protect workers from overheated electrical components.
Preventing Electrical Accidents
Ground Fault Circuit Interrupter (GFCI)
 A GFCI is designed to cut
off electrical power within
as little as 1/40 of a second.
 It works by comparing the
amount of current returning
from the device along the
circuit conductors. It is used
in high risk areas such as wet
locations and construction sites.
Preventing Electrical Accidents
Switches
 Generally speaking, it is not advisable to break a circuit once it
has been established. If the circuit is broken with the appliance
on, an arc is usually the result. Switches (circuit breakers) are
designed to contain the arc in a safe way.
 Shutting down an electric appliance by pulling the plug will result
in an arc by breaking the circuit at the plug. The plug is not
designed to be a circuit breaker. The result could be damage to
the wiring at the outlet or damage to the appliance itself.
 Pulling the cord could cause damage to the appliance plug and
cord, setting up a short in the cord and causing the appliance to
either function improperly or not to function at all.
 Always shut down appliances with the switch.
Safe Work Practices
De-Energize Electrical Equipment
 The accidental or unexpected sudden
starting of electrical equipment can cause
severe injury or death.
 Before any inspections or repairs are made,
even on low voltage circuits, the current
should be turned off and the system locked
out.
Safe Work Practices
Portable Power Tools
 Employees should always use
tools that work properly.
 Tools should be inspected
frequently, and those found
questionable should be
removed from service and tagged.
 Never use portable power equipment in wet or damp
areas.
 Stop using power tools if they become hot or start
sparking.
Safe Work Practices
Extension Cords
 Inspect and check for capacity
 For temporary work only
 Do not use as a rope to pull or
lift objects
 Should not be fastened with
staples or hung over hooks
Safe Work Practices
GOOD JUDGEMENT
 Perhaps the single most successful defense against
electrical accidents is the continuous exercising of
good judgment or common sense.
 When working around energized lines, for example,
some basic procedures are to:
– Have the line de-energized
– Ensure that the line remains de-energized by using
lockout/tagout
– Use insulated protective equipment
– Keep a safe distance from energized lines
Safe Work Practices
Protective Equipment
 Workers whose occupations require them to work
constantly and directly with electricity must use the
personal protective equipment required for the jobs they
perform.
 This equipment may consist of
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Rubber insulating gloves
Hoods
Sleeves
Matting
Blankets
Line hose
Industrial protective helmets
Summary
 The control of electrical hazards is an
important part of every safety and health
program.
 Everyone has the right to work in a safe
environment. Through cooperative efforts,
employers and employees can learn to
identify and eliminate or control electrical
hazards.