Transcript Electrical Safety

Electrical Safety
Training
• Qualified workers
– Only Qualified workers are allowed to work on or near exposed energized
equipment.
• Unqualified workers
– Unqualified workers are not permitted to work on or near exposed energized
equipment
Concerned About Electricity?
• How many sets of Christmas lights do you plug into
one extension cord?
• Do you still use your hot and sparking electric drill?
• Is your vacuum cleaner’s cord twisted and frayed?
• Have you installed outlet covers to protect your
probing fingers?
Electrical Safety Outline
• Electricity and the human body
• Electrical hazards and safe work practices
• Quiz
Electrical Circuits
A basic completed electrical circuit requires three
things to function correctly:
• Electrical source
• Electrical user
• Wires
Rules of Electricity
• Electricity travels in a completed circuit
• Electricity always travels in the path of
least resistance
• Electricity tries to travel to ground
Electricity and People
• A person usually offers a lessor resistance
for the electricity
• The person forms a completed circuit when
touching the ground
• Electricity always tries to travel to ground
Voltages and Amperes
• Voltage = Amps X Ohms
(resistance)
• Converting voltage to amps
• Typical Industrial Voltages
– 110/120 Volts = 60
milli-amps (mA)
– 220/240 Volts = 120 mA
– 440/480 Volts = 240 mA
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 1/4 second, almost always
immediately fatal
Body’s Resistance
• Skin offers most of the body’s electrical resistance
• Increased resistance
– Thick and callused skin (foot or hand)
– Dry skin
• Decreased resistance
– Thin skin (inner forearm)
– Wet or sweaty skin
– Broken or abraded skin (scratches)
Resistance Varies
• Different levels of electrical resistance
for each person
• Ranges from 500 ohms to many thousands of ohms
• The greater the body’s resistance, the less chance
of harm
• A similar voltage shock can be minor to one person
and deadly to another.
Additional Resistance
• Gloves
• Shoes
• Mats
Hazard Control
• Electrical systems are inherently safe
• Injuries typically occur when:
– Procedures are inappropriate
– Procedures are not followed or ignored
– Safety systems are circumvented
General Electrical Hazards
• High-voltage overhead
power lines
• Damaged insulation on wires
• Digging or trenching near
buried lines
• Broken switches or plugs
• Overloaded circuits
• Overheated appliances or tools
• Static electricity
• Flammable materials
Portable Power Tools
• Inspect portable power tools
• Never use damaged equipment
– Tag it out of service
– Have it repaired or replaced
• Never use portable power equipment in wet or
damp areas
• Stop using power tools if they become hot or
start sparking
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
Electrical Cord Inspection
• Deformed or mission pins
• Damaged outer jacket or insulation
• Evidence of internal damage
• If damaged, take out of service until repaired
Circuit Protection
• Energize or de-energize with appropriate
switches, breakers, etc.
• Do not energize or de-energize with fuses,
terminal lugs, or cable splice connections
• If circuit protection device is tripped—inspect
Grounding Equipment
• Most electrical equipment is designed with a
grounding system
• Do not use equipment with damaged grounding
connectors
• Do not use adapters that interrupt the grounding
connection
Ground Fault Circuit Interrupters
• GFCIs reduce the likelihood of fatal shocks
• Detect small amount of earth current and
automatically switch off the power
• Used with extension cords and portable tools
• Fuses and circuit breakers protect equipment,
not people
Static Electricity
• Created when materials rub together
• Can cause shocks or even minor skin burns
• Reduced or prevented by:
– Proper grounding
– Rubber matting
– Grounding wires, gloves, or shoes
Flammable/Ignitable Materials
• Flammable gases, vapors, or liquids
• Combustible dust
• Can be ignited by static electricity
• Require specially designed electrical equipment
Machine Operators
• Never tamper with electrical interlocks
• Do not repair electrical components of
your machine
• Properly shut off machinery before
working in the point of operation
• Obey warning signs and follow safe
procedures
Summary
• Electricity will try to reach ground even if it
means going through a person
• Even the “small” voltage from your home
can cause serious injury
• Always inspect power tools and cords and
do not use them if damaged
• Do not attempt to repair electrical equipment
unless trained and qualified
Electrical Injuries
Call for emergency help immediately
•
Everyone experiences minor electrical shocks from time to time. In some cases, however, even small amounts of
electricity can be life-threatening because they can produce unconsciousness, cardiac arrest, and cessation of
breathing.
•
Electrical shocks also can produce serious, deep burns and tissue injury, although often even a serious electrical
burn appears as only a minor mark on the skin.
•
If you find a person whom you think has been electrocuted, look first--do not touch. He or she may still be in
contact with the electrical source, and touching him or her may only pass the current through you.
•
If possible, turn off the source of electricity. If this is not possible, move the source away from you and the affected
person using a non-conducting object made of cardboard, plastic, or wood.
•
Once the person is free of the source of electricity, check the person's breathing and pulse. If either has stopped or
seems dangerously slow or shallow, initiate resuscitation immediately .
•
If the person is faint or pale or shows other signs of shock, lay the person down with the head slightly lower than the
trunk of his or her body and the legs elevated.
•
Treat any major burns and wait for emergency medical assistance to arrive.
Question 1
Where does electricity always want to go, even if it
means traveling through a person?
Question 1
Where does electricity always want to go, even if
it means traveling through a person?
Electricity always wants to
travel to ground, which will
complete the circuit.
Question 2
A shock from an outlet at home may be
painful, lead to collapse, or even death. (True or
False)
Question 2
A shock from an outlet at home may be
painful, lead to collapse, or even death. (True or
False)
True. A 120-volt outlet at home
can give the average person a
shock of 60 mA.
Question 3
Which part of the human body offers the most
electrical resistance?
Question 3
Which part of the human body offers the most
electrical resistance?
The skin offers the most
electrical resistance.
Question 4
Flammable materials can easily be ignited by
___________ electricity.
Question 4
Flammable materials can easily be ignited by
___________ electricity.
Static electricity can easily
ignite a flammable material.
Question 5
Only ___________________ workers are
permitted to work on or near exposed electrical
components.
Question 5
Only ___________________ workers are
permitted to work on or near exposed electrical
components.
Only qualified and trained
workers can repair or
troubleshoot electrical
equipment.
Question 6
When should power tools and extension
cords be inspected?
Question 6
When should power tools and extension
cords be inspected?
Inspect power tools and
extension cords before each
use.
Question 7
Fuses and circuit breaker are designed to protect
people from shocks. (True or False)
Question 7
Fuses and circuit breaker are designed to protect
people from shocks. (True or False)
False. Fuses and circuit
breaker protect machinery
and electrical systems
Question 8
When a circuit breaker trips, you should
immediately reset it. (True or False)
Question 8
When a circuit breaker trips, you should
immediately reset it. (True or False)
False. A tripped breaker
could indicate a problem,
so it should be checked by
a qualified worker.
Question 9
Extension cords should never be used as a
permanent power source. (True or False)
Question 9
Extension cords should never be used as a
permanent power source. (True or False)
True. Extension cords are
designed as a temporary
power source.
Question 10
What should be done with a damaged power tool or
extension cord?
Question 10
What should be done with a damaged power tool
or extension cord?
Tag it as “out of service” and
have it replaced or repaired
by a qualified electrician.
Power Line Safety
• http://www2.worksafebc.com/Publications/Multim
edia/Videos.asp?ReportID=34818
The hazards of power lines
•
You cannot tell if a downed power line is energized
just by looking at it.
•
The electricity in a power line always seeks a path to
the ground. This path might include a tree, a vehicle,
or a fence. These objects then become energized. If
you touch the energized line or object, the electricity
can flow through your body. Keep away from any
object that is in contact with a power line.
•
Once electricity reaches the ground, the ground
itself becomes energized. This can happen if a
broken power line falls to the ground or onto a
vehicle or tree. The electricity then flows through the
ground over a wide area, spreading out like ripples
in a pool of water.
Safe work practices for first responders
•
Treat downed power lines and anything in contact with them as energized.
•
Park away from the power lines. When you arrive at the scene, park your vehicle
well away from any downed lines. Before you exit your vehicle at night, shine a
flashlight through the window to make sure you are not near a downed power line.
•
Stop traffic and keep people away. Pedestrians or motorists may not see power
lines that are on the ground. The surrounding area will be energized. Secure the area
and keep everyone back at least 10 metres (33 feet) - more if the voltage is over 60
kilovolts.
•
Don't become a victim yourself. You cannot help anyone if you are injured or
electrocuted. Never touch anything that is in contact with a downed power line,
including injured or trapped victims, puddles, vehicles, or trees. Do not use a dry stick
or piece of hose as they will not protect you.
•
Call the power company immediately. The power company can ensure that
automatic switching equipment will not restore power to the line. A crew with proper
training and equipment will arrive as soon as possible.
•
Wait for the power company representative to confirm that it is safe to
approach the scene. Only the power company can confirm that the system has
been de-energized and that power will not automatically be restored.
Staying safe inside a vehicle that is in
contact with power lines
•
If possible, move the vehicle away to break
contact with the power line.
•
If the vehicle cannot be moved, stay inside
until emergency crews can safely approach.
If anyone approaches the vehicle, open the
window and call out. Tell them to keep away
and to call 9-1-1 for help.
•
If there is a fire and you must leave the
vehicle, jump out with your feet together.
Never touch the ground and the vehicle at
the same time. Move away slowly by
shuffling and keeping both feet close
together.
Questions?