Transcript Document 7176505

Electrical Safety
INSY 3020
March 10th, 2005
Adam Piper
Adapted from Region IV - OSHA
What is Electricity?
• Electricity is the movement of electrons.
• Fundamental quantities include:
– Electrical Potential (Volts), V
– Current (Amperes, or Amps), I
– Resistance (Ohms, miliohms, microohms), R
• Main Relationship – OHM’s LAW
V=IR
What kinds of hazards are associated
with Electricity?
•Hazards include:
•Shocks,
•Electrocution,
•Arc Blast,
•Burns,
•Explosions.
Electricity and the Human Body
• ~1ma:
• >3ma:
accidents.
• >10ma:
Sensation on hands.
Painful shock which can cause indirect
Muscle contraction, “no-let-go”
danger.
• >30ma:
Lung paralysis
• >50ma:
Possible ventricular fibrillation.
• 100ma - 4A: Certain ventricular fibrillation
Protective Triangle
Keep Away
Grounding
GFCI
Electrocution Triangle
Electricity
Path
Time
Fatality
•An employee received a fatal electric shock while operating a
high pressure water sprayer which was connected to a portable
light with a receptacle built into the handle.
•The portable light was being used as an extension cord, and
was not approved for wet or damp locations.
•The electrical cord had been spliced and the cord had been
laying in water at the time of the accident.
Fatality
Contact with bare conductors
Live overhead lines
7,200 Volts
Contact with bare conductors
Live overhead lines
Equipment Failure
OSHA Electrical Standard
29CFR 1910 Subpart S
• Based in part
on NFPA 70 E
Standard Includes…
“Premises Wiring”
• Installations of electric conductors
and equipment within or on
buildings or other structures, and
on other premises
– yards,
– parking, and other lots,
– industrial substations;
…Equipment
• A general term including
–
–
–
–
–
–
material,
fittings,
devices,
appliances,
fixtures,
apparatus, and the like,
• used as a part of, or in connection with, an
electrical installation.
1910.332
Training
• Who needs to be trained in Electrical
Safety?
• Employees who face a risk of electric
shock that is not reduced to a safe level
– electrical installation requirements of
1910.303 through 1910.308.
1910.333
Working with Electricity
 Live parts (50 Volts or more) shall
be de-energized before working
on them.
Unless the employer can
demonstrate infeasibility or greater
hazard.
1910.333
Working with Electricity
 Written procedure.
 De-energize equipment & release
stored energy.
 LOTO (will discuss in later lecture)
 Verify de-energization & test.
 Re-energize.
1910.333
Working with Electricity
 No conductive materials or
equipment.
 Nonconductive ladders.
 No conductive apparel.
 Housekeeping – no steel wool or
conductive liquids.
Tools
Non-Rated tool
with cushioned
grip.
Rated insulated tool .
Tool should be
marked with rating.
Insulated Tools
1910.334
Use of Portable Equipment
 Includes cordsets (extension
cords).
 Cord & Plug connected
equipment.
1910.334
Use of Portable Equipment
 Don’t abuse, damage, or use for a
rope.
 Visually inspect before use.
 If damaged …
Shall be removed from service &
not used until repaired.
1910.334
Use of Portable Equipment
 Extension cords shall be grounded
unless used with double insulated
tools.
 Don’t mess with the grounding pin.
One of the most common violations
 No 3-wire grounding adapters, unless
the ground continuity is maintained.
1910.334
Use of Portable Equipment
 Damp/Wet locations require approved
equipment
 Don’t plug in or unplug stuff with wet
hands.
1910.334
Test Equipment
 Test instruments used only by
qualified employees.
 Visually inspected before use,
including leads and probes.
 Rating of equipment (voltage):
Test leads rated for full voltage.
Designed for environment.
1910.335
Protective Equipment
 Employees working in areas where there
are potential electrical hazards shall use
electrical PPE.
 PPE – Separate Section (Subpart I)
Personal Protective Equipment = PPE
Will discuss in later lecture
Electrical PPE– ASTM F Standards.
 Will use signage AND barriers where
necessary to prevent contact with current
1910.335
Protective Equipment
 Maintain & periodically test
according to 1910.137.
 Protect the insulating capability
against damage.
 Nonconductive head protection.
 Face & Eye Protection for arc blast.
Electric Arc Hazards
 Electric Arcs can reach temperatures of
34,000oF
 The arcs can vaporize metal, burn skin,
and ignite clothing.
 Vaporized copper expands 67,000 times
in volume.
 High pressures can develop in enclosures,
causing covers and molten metal to fly.
Arc Hazards
 When clothing ignites, it can greatly
increase the amount of skin area
burned, and the chance of a fatality.
 Heat levels of 1.2 cal/cm2 per second
for one second can cause second degree
burns to exposed skin.
 Most arc exposure times are less than 1
second.
Arc Hazards
 Regular cotton work
clothing will
typically not ignite at
heat levels up to 1-2
cal/cm2.
 Heavy denim might
work for about 5-10
cal/cm2.
Arc Heat Example
 480 Volt arc in a box. 6 cycles, at a 12
inch distance.
16,000A
8 - 11
cal/cm2
24,000A
9 – 14
cal/cm2
38,000A
17 – 24 cal/cm2
50,000A
32 – 38 cal/cm2
Commonly Cited Violations
•
•
•
•
•
1910.305(b)(1):
1910.303(g)(2):
1910.305(b)(2):
1910.304(f):
1910.305(g)(1)(iii):
Unused openings
Exposed live parts
Missing covers
Defective Ground
Prohibited
uses of flexible
cords.
Commonly Cited Violations
•
•
•
•
•
1910.303(f): Unlabeled disconnects
1910.305(g)(2)(iii): Strain relief
1910.303(b)(2):
Listed & labeled
1910.303(b)(1):
General Duty Clause
1910.303(g)(1):
Access & working
space.
Blocked Electrical Panels
Strain on Conductors
Inadequate Strain Relief on Cord
Exposed Live Parts
Employee’s
cap is hung on
power strip
energized to
120VAC
Exposed Live Parts
Exposed live parts
Missing
breakers inside
of circuit
breaker panel
Ungrounded Cords
Ground pin
missing on
extension
cord
Damaged Faceplate
Utility Boxes
Utility boxes
are not
approved for
usage as
extension
cords.
Receptacles in Wet Locations
Receptacles in
wet or damp
locations need
covers.
Receptacles in Wet Locations
Receptacles in wet or damp locations need
covers.
Damaged Faceplate
Portable Electric Tools
• Inspect before usage.
• Remove from service tools
with damaged cords.
• Use grounded or double
insulated tools.
• Check continuity of tool.
Rubber Gloves
• Must be air tested daily
before usage.
• Must be electrically tested
every 6 months or replaced.
• Before issuance gloves may
be stored for up to 1 year
without being tested.
Hazard Assessment
• Employers are required to assess the
workplace to determine the hazards present
– Must also determine whether hazards exist that
require the use of personal protective
equipment
• Must look for hazards that are present or are
likely to be present.
ELECTRICAL RELATED
FATALITIES FY-02
OSHA – REGION IV
Alabama | Florida | Georgia
Kentucky | Mississippi | North Carolina
South Carolina | Tennessee
46 workers killed
by
electrocution
19 workers killed
Working on
Power transmission lines
11 workers killed
installing
equipment
4 workers killed
installing
ductwork
2 workers killed
when ladders
contacted power
lines
2 workers killed by
defective electrical
equipment
2 workers killed
during maintenance/
removal of equipment
2 workers killed
during maintenance/
removal of equipment
2 workers
killed working
on electric
signs
1 worker killed by
underground power
1 worker killed
standing in water
adjacent to
disconnect
Would You Risk Your
Life for a job like
this?
Questions & Comments????