Hazards and Risks when working with Electricity

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Transcript Hazards and Risks when working with Electricity

Hazards and Risks
when working with
Electricity
What is the best way to
prevent the hazards of
electricity?
Avoid energized circuits is
the safest way!
STOP
Think before taking
Action
THINK
About the
Risks and Hazards
OPTIONS
Do you have options like:
LOTO (Lockout/Tagout)
PROTECTION
Are you wearing PPE?
(Personal Protective Equipment)
What are the
Hazards and Risks
1. Shock
2. Arc Flash & Arc Blast
3. Fire Ignition
SHOCK
Shock and its Effects
1.
2.
3.
4.
5.
6.
7.
8.
Immediate:
Muscle contraction
Vital organs damaged
Tingling
Pain
Breathing
Disorientation
Dizziness
Possible death
Shock and its Effects
1.
2.
3.
4.
5.
Long Term:
Memory Loss
Nervous disorders
Chemical imbalances
Damage to vital organs
Sometimes fatal
Effect of Current on the Body
MEN
• Perception Threshold
0.001 Amps (1 mA)
• Painful Shock
0.009 Amps (9 mA)
• Cannot Let-Go Level
0.010 Amps (10 mA)
• Ventricular Fibrillation
.100 Amps (100 mA)
• Heart Failure
0.5 Amps (500 mA)
• Organ Burn
1.5 Amps (1500 mA)
WOMEN
• Perception Threshold
0.0007 Amps (0.7 mA)
• Painful Shock
0.006 Amps (6 mA)
• Cannot Let-Go Level
0.010 Amps (10 mA)
• Ventricular Fibrillation
.100 Amps (100 mA)
• Heart Failure
0.5 Amps (500 mA)
• Organ Burn
1.5 Amps (1500 mA)
Two Types of burns from Shock
Surface Burns:
 Caused by entrance and exit of
electrical currents through the body
 Can be caused by a very small
amount of current
 1st degree to 3rd degree
Two Types of burns from Shock
Internal Tissue Burns:
 Caused by current flowing through
organs of the body
 Caused by currents in excess of 1.5
amps
 4th degree (internal)
 Internal organs
 Typically Fatal
How to prevent Shock
1. Place circuits in an Electrically Safe
Working Condition by Locking Out and
Tagging Out all sources.
2. Verifying that no electrical energy is
present.
NFPA 70 - NEC
1. The original and primary mission of the
NFPA 70 – NEC covered installation of
electrical systems.
2. The NFPA 70 – NEC does not address the
other hazards of electricity.
Exposure to Danger
1. The NEC protects individuals from shock
hazards under normal conditions.
2. It is not designed to protect us from
abnormal conditions.
3. We need additional policies to protect from
abnormal conditions.
Normal Conditions
1. Panel covers in place.
2. Equipment plugged in normally.
3. Normal designed protection in place.
Abnormal Conditions
1. Panel covers removed.
2. Equipment temporarily wired.
3. Normal
designed
protection
such
guards, limits switches, etc. not in place.
as
Protection from
Abnormal Conditions
The Company
 NFPA 70E
 OSHA
 Electrical Safety Procedures manual
 Electrical Safety Training
Protection from
Abnormal Conditions
YOU
 The first line of defense
 Only you can truly keep you safe
 Implement Safety Procedures Outlined in
the Safety Manual
 Only you can ensure that you go home at
night
Arc Flash
&
Arc Blast
Arc Flash
is a high intensity flash which
will also create a very loud
noise (blast)
The Arc Flash produces:
 Electric arc that produces the highest
temperatures on earth – up to 35,000oF (4 x
temp. of the sun)
 The
intense
heat
causes
the
sudden
expansion of air that results in a blast.
 All known materials are vaporized at this
temperature (copper expands 67,000 times,
water 1,670 times)
Arc Flash & Blast
Relative to the human body:
 A second degree burn threshold, or a ‘just
curable burn threshold,’ is skin temperature
raised to 175oF for 0.1 second.
 A third degree burn threshold, or ‘incurable
burn threshold,’ is skin temperature raised to
200oF for 0.1 second.
 Eardrum damage > 720 psf
 Lung damage > 1728 psf
Arc Flash & Blast
Relative to the human body:
 The hazard may be small for systems of
less than 300 volts with limited fault current.
 Any system over 300 volts probably has the
capability to have significant arc flash
event.
Circuit Breaker Trips
 When a circuit has been de-energized by a
protective device, DO NOT manually reenergize
the
circuit
investigating the cause.
without
first
Do not perform
repetitive manual re-closing of breakers or
replacing of fuses.
Circuit Breaker Operation With Covers
on and voltages less than 600V ac rms
 Safety Glasses
 Natural
Fiber
Long
Sleeve Shirt
 Natural
Fiber
Long
Pants
Stand to the side
Fused Switch Operation With Covers
on and voltages less than 600V ac rms
 Safety Glasses
 Natural
Fiber
Long
Sleeve Shirt
 Natural
Fiber
Long
Pants
Stand to the side
FIRE IGNITION
 Clothing can be ignited several feet away
unless flame-resistant (FR) clothing is used.
 Note: Synthetics burn ‘into’ the skin when
ignited.
Now that you are aware of:
shock, arc flash and arc blast,
and fire ignition, what do you do
about it?
Protect Yourself
Protect Yourself Against
1. Shock Hazard
2. Arc Flash and Arc Blast Hazard
3. Fire Ignition
SHOCK Hazard
What is required?
1. Determine the Operating Voltage of the
System.
2. Determine Shock Protection Boundaries.
3. Determine the Personal Protective
Equipment.
SHOCK Hazard
1. Determine the Operating Voltage of the
System.
The voltage in the HAC program,
according to 70E, that is of concern is
50 to 300 volts.
SHOCK Hazard
2. Determine Shock Protection Boundaries.
a. Limited Approach Boundary –
3 ft. 6 in.
b. Restricted Approach Boundary –
Avoid Contact
c. Prohibited Approach Boundary –
Avoid Contact
Approach Boundaries
Limited Approach Boundary –
entered only by qualified persons or
unqualified persons that have been
advised and are escorted by a qualified
person
Approach Boundaries
Restricted Approach Boundary –
entered only by qualified persons and
require use of shock protection
techniques and PPE
Approach Boundaries
Prohibited Approach Boundary –
entered only by qualified persons
requiring same protection as if direct
contact with live part
Qualified Person
One who has skills and knowledge related
to the construction and operation of the
electrical equipment and installations and
has received safety training to recognize
and avoid the hazards involved.
SHOCK Hazard
3. Determine the Personal Protective Equipment.
a. Use Voltage Rated (VR) Gloves rated
greater or equal to the voltage of the
system.
b. Use Voltage Rated (VR) Tools rated greater
or equal to the voltage of the system.
How does this apply to
your training here at
CCAC?
OSHA and NFPA 70E both state that
qualified electrical workers shall not be
asked to work on equipment that is ‘hot’
or ‘live’ except for two demonstrable
reasons:
1. De-energizing introduces additional
or
increased
emergency
hazards,
alarm
ventilation system.
like
system
or
an
a
2. Infeasible due to equipment design
or operational limitations, like voltage
testing for diagnostics or start up
testing.
trade.
Note:
This is the HVACR
Conclusion
When you work on ‘live’ circuits, you are
open to the hazards and risks of electricity.
Therefore, you need to take on the
responsibility of protecting yourself. So,
how can this be done?
NFPA 70E Hazard/Risk Categories
NFPA 70E classifies electrical hazards and risks
from 0 to 4. According to 70E, when working on
‘live’ circuits between 50 and 300 volts, within the
prohibited approach boundary, the classification
is number 1.
NFPA 70E Hazard/Risk Categories
The classification number 1 can be reduced by
one, in this case, to 0, if:
1.
the maximum short circuit current
available is less than 10,000 Amps.
and
2.
if the upstream current limiting fuses
with arcing fault current in their
current limiting range (1/2 cycle fault
clearing time or less).
NFPA 70E Hazard/Risk Category 0
Therefore, classification 0 means that you must
be wearing rubber insulating gloves with leather
protectors, long sleeve natural fiber (cotton) shirt,
long natural fiber (cotton) pants, and using VR
hand tools and meters, and eye protection.
Response
to an
Electrical Accident
Response to an Electrical Accident
1. The first step must be to ‘TURN THE
POWER OFF’
2. Remember that Speed is Essential
3. Extinguish flames
4. Call for Help (911)
5. Begin CPR & First Aid
Response to an Electrical Accident
First Aid
a. Cool the burn with water.
b. Do not attempt to remove burned clothing.
c. Elevate burned limbs.
d. Handle the victim with care.
e. Treat for shock.
Conclusion
When you work on ‘live’ circuits, you are
open to the hazards and risks of electricity.
Therefore, you need to take on the
responsibility of protecting yourself.