Transcript Arc Flash Safety

ARC FLASH SAFETY
Bureau of Workers’ Comp
PA Training for Health & Safety
(PATHS)
29 CFR 1910.303
29 CFR 1910.305
29 CFR 1926.400-449,Subpart K
NFPA 70E
PPT- 054-01
1
OSHA Cited Violations: FY 2010
OSHA has long understood the importance of safety
in this area and tracks electrical violations
OSHA Most Cited Violations (2010)
• Electrical-General Requirements (1910.303): 2,770
• Lock-out/Tag-out (1910.147): 3,531
PPT- 054-01
2
OSHA Violations FY 2010
1926.400-449, Subpart K
• 404(f)(6)
• 404(b)(1)(i)
• 405(g)(2)(iv)
• 416(e)(1)
• 403(b)(2)
Grounding path
Ground fault protection
Flexible cords-strain
relief
Worn/frayed cords
or Cables
Equipment installation
and use
PPT- 054-01
473
338
277
256
241
3
OSHA Violations FY 2011
• 1910.147 Lock-out/Tag-out
• 1910.305 Electrical-wiring
Methods
• 1910.303 Electrical-General
Requirements
PPT- 054-01
3,639
3,584
2,863
4
Electrical Hazards
• Shock
• Electrocution: 4th
leading cause of
industrial fatalities
• Fires
• Burns
• Arc Flash
• Arc Blast
PPT- 054-01
5
Arc Flash Defined
• Electrical work may cause injury or death
• One severe occurrence is the Arc Flash event
“Arc Flash: an electrical discharge that uses the air
as a conductor, exploding from a high voltage
source to another conductor or ground nearby. The
release can be 5,000oF or hotter, melting nearby
metals and damaging the electric circuits involved.
The brightness, heat and force of the arc flash can
cause damage to the human body.”
Tyler Lacoma, eHow Contributor, http://www.ehow.com/about_5110071_definition-arc-flash.html
PPT- 054-01
6
Arc Flash
Hazards resulting
from arch flash:
•
•
•
•
•
Heat
Shrapnel
Pressure
Sound
Intense light
 UV
 IR
PPT- 054-01
7
Arc Flash Hazards
Statistics:*
5 to 10 such serious arc flashes a day occur in
the United States
Result: 1 to 2 fatalities
Although protective clothing exists, there is no
guarantee against such severe energy releases
*Dr. Mary Capelli-Schellpfeffer, “Arc Flash Presentation,” as quoted in eHow.com facts, May 30, 2012
PPT- 054-01
8
Causes of Arc Flash
• Overloading/overheating
of circuits
• Damaged circuit breakers
• Over-fusing
• Wiring in a non workman
-like manner
• Faulty electrical panels
PPT- 054-01
9
Causes of Arc Flash
• System overload
• Incorrect wire gauge for
system requirements
PPT- 054-01
10
Causes of Arc Flash
Faulty panels or
overloading panels
PPT- 054-01
11
Arc Blast
• Accompanies the flash
• Intense radiant heat
released
• Nearby surfaces
(persons and objects)
absorb and are
instantly heated to
vaporizing temperatures
PPT- 054-01
12
Arc Blast Hazards
Serious situations!!
PPT- 054-01
13
Electrical System Susceptibility
System
Hazard
Less then 120V
Arc flash highly improbable
480V electrical
services
Sufficient capacity to cause
Above 600V
Medium-voltage with higher
energy/potential for an arc
flash event
http://en.wikipedia.org/wiki/Arc_flash
PPT- 054-01
14
Arc Flash Energy Released
Per Wikipedia
Example: single phase-to-phase fault on 480V
system with 20,000 amps of fault current
Resulting power is 9.6 MW
If fault lasts 10 cycles at 60Hz, resulting energy
would be 1.6 megajoules
Comparison: TNT releases 2,175 J/g or more when
detonated. This fault is equal to 380 grams (about
0.8 pounds) of TNT !!!
http://en.wikipedia.org/wiki/Arc_flash
PPT- 054-01
15
Possible “Traps”
Beware of a “profusion
of electrical confusion”
PPT- 054-01
16
Current/Reaction Chart
Current
Below 1 milliampere
1 milliampere
5 milliampere
6-25 milliamperes
(women)
9-30 milliamperes
50-150 milliamperes
1,000-4,300
milliamperes
10,000 milliamperes
Reaction
Generally not perceptible.
Faint tingle.
Slight shock. Not painful-disturbing. Average
person can let go. Strong involuntary reactions
can lead to other injuries.
Painful shock. Loss of muscular control.
Freezing current (“let-go” range). Person can not
let go but can be thrown from the current if
extensor muscles are stimulated.
Extreme pain, respiratory arrest, severe muscular
contractions. Death is possible
Rhythmic pumping action of heart ceases. Muscular
contraction and nerve damage occur; death likely.
Cardiac arrest, severe burns; death probable.
OSHA Training Institute, “Construction Focus Four: Electrocution Hazards,” April, 2011
PPT- 054-01
17
Need for an Arc Flash Study
• Numerous inherent
dangers when working
around electrical
systems
• Safety from arc flash
should include an Arc
Flash Study
• Done prior to
conducting work on
hazardous locations
PPT- 054-01
18
Arc Flash Study
Study components per IEEE 1584:
Data Collection (steps 1 & 2)
System diagrams
Modes of operation scenarios
Analysis (steps 3-7)
Determination of bolted fault currents
Protective devices recommended
Document system voltages & classes of equipment
Determine working distance from arc flash source
PPT- 054-01
19
Arc Flash Study
Arc Flash Hazard Analysis (Steps 8 & 9)
Incident energy determination
(Energy needed for an arc flash to cause
second-degree burns)
Flash protection boundaries
(Distance where the second-degree burns
are caused, or where the incident energy is
1.2 calories per centimeter squared or 1.2
cal/cm2)
Both may be calculated using NFPA or IEEE equations
Diane Bonder, eHow Contributor
PPT- 054-01
20
Aids to Safe Operations
• NFPA 70E-2004 Standard
for Electrical Safety
Requirements for
Employee Workplaces
• IEEE 1584 Guide for Arc
Flash Hazard Calculations
PPT- 054-01
21
Arc Flash Hazard Analysis
Results aid in determining:
Proper PPE, distancedependent from possible
threat:
- Shirts
- Pants
- Underwear
- Goggles
- Gloves
PPT- 054-01
-
Hard hats
Shields, face and neck
Heating protection
Shoes
22
Safe Distance Calculations
Used to determine safe distances and PPE
Variables taken into account:
• Voltage
• Working distance
• Clearing time
• Grounding
• Gap between conductors
• Bolted fault current
PPT- 054-01
23
Arc Flash Boundaries
“Distance from an arc
flash within which an
unprotected person has
a 50% chance of
receiving a second
degree burn”
PPT- 054-01
24
Flash Protection Boundary
Arc flash hazard is based
on:
• Fault current
• Arcing time
• Distance
Preplanning your facility
will enhance the safety
of your staff
PPT- 054-01
25
PPE Based on Incident Energy Preplan
PPT- 054-01
26
PPE by Hazard Risk Category
Findings compared to
table which indicates arc
thermal performance of
clothing
Dangers above a 4 is
prohibited
“No Safe PPE Exists
Energized Work
Prohibited”
PPT- 054-01
27
Definitions
• Voltage (E): electromotive force (emf) that
forces electrons to flow through a circuit
measured in Volts (V)
• Current (I): the number of electrons that flow
past a point in a circuit in one second measured
in Amperes or Amps (A)
• Resistance (R): the opposition to current flow
in a circuit that contains only resistance and is
measured in ohms
PPT- 054-01
28
Ohm’s Law
• Relationship between E, I, R
• “One volt of electromotive force will force one
ampere of current to flow through one ohm of
resistance”
E
I
PPT- 054-01
R
By knowing
2 of these
variables, the
other can be
calculated!
29
Power Formula
• Power: the rate at which
work is done and is
measured in Watts (W)
(E x I)=Watts
• So Power is equal to
P= E x I
• Power can be measured in
the thousands of watts per
hour and reads as KWH or
kilowatthours
PPT- 054-01
30
Horsepower and Watts
• Horsepower is the unit of
measure for mechanical
energy
• 746 Watts = 1 Horsepower
(hp) or P = E x I
• Flow of Amps= E/R
• Additional information
PPT- 054-01
31
Qualified Person
• Qualified Person: One who has received training
in and has demonstrated skills and knowledge in
the construction and operation of electric
equipment and installations and the hazards
involved
• OSHA defines these as specially trained to work
on live electrical equipment
• Unqualified Person: per 1910.332(b)(2) must still
be trained in safe electrical practices for their
support jobs (painters, cleaners as examples)
PPT- 054-01
32
Types of Damage
Fully understand the
hazards related to
these activities
If possible, review
case histories of your
industry to devise
safe operations
PPT- 054-01
33
Caution!!
Abide by distances
determined by
NFPA or IEEE
NO SHORT CUTS!!!
PPT- 054-01
34
Signage
Ensure signage fits
hazard and conforms
to regulatory
requirements
PPT- 054-01
35
Hazard Preplan
• Use checklists to
preplan equipment
needs when
performing service or
maintenance
• Label systems for
future maintenance
and arc flash studies
PPT- 054-01
36
Safety Precautions: PPE
• PPE should fit the
requirements of
the job
• Specific level of
PPE is required
PPT- 054-01
37
PPE
Tests for arc rating of PPE
Found in ASTM F1506
“Standard Performance
Specifications for Flame
Resistant Textile
Materials for Wearing
Apparel for Use by
Electrical Workers
Exposed to Momentary
Electric Arc and Related
Thermal Hazards”
PPT- 054-01
38
Match PPE to Task
Level 2 Protective
Coverall
PPT- 054-01
39
Match PPE to Task
PPT- 054-01
40
Match PPE to Task
Prepare for the possible!
PPT- 054-01
41
Tools
• Support equipment
rated for the task
• Tools properly
insulated
• Correct support
equipment for the
job
PPT- 054-01
42
Safety
Robotic removal or
disengagement devices can
do much to maximize
personnel safety
Also:
• Draw-out circuit
breakers on a life bus
• Remote racking
PPT- 054-01
43
Safe Work Practices
Lock-out/Tag-out:
Make sure you’re
wearing the proper
PPE for this job also
PPT- 054-01
44
Avoiding Arc Flash
Assign qualified person
• Conduct system analysis to
determine arc flash hazard
• When working, secure all
power and enact Lockout/Tag-out
• Proper tools and PPE rated
for the job
• Assign electrical safety
program manager familiar
with codes
• Properly maintain system
and components
• Apply warning labels
PPT- 054-01
45
Some Questions OSHA will Ask
From EHSToday, March 13, 2008 (and still timely),
Kenneth Cybart:
OSHA’s goal: for employers to identify all electrical
hazards, potential and actual
Analyze workplace for shock and arc flash hazards, set
safe protection boundaries and define required PPE
Circuit or equipment description at job location?
Written description, drawing
Detailed job description of work?
PPT- 054-01
46
Some Questions OSHA will Ask
Can the fact that the equipment cannot be deenergized or job be deferred be justified?
1910.333(a)(1) Live parts must be de-energized
before employee works on/near them
Less than 50 volts to ground need not be deenergized if there will be no increased exposure to
electrical burns or to explosion due to electric arcs
However, never work on live circuits unless
absolutely necessary
PPT- 054-01
47
Some Questions OSHA will Ask
Live circuit work necessary?
OSHA 1910.33(a)(2): Safety-related work
practices required
NFPA 70E Article 110.8(B)(1): Electrical Hazard
Analysis required before work performed on live
equipment operating at 50 volts and higher
Other questions to ask:
- Safe work procedures?
Detailed work procedure established? Will it be
used?
Job briefing checklist performed?
PPT- 054-01
48
Some Questions OSHA will Ask
Was job briefing given to those doing the job?
Proper management approval obtained?
NFPA 70E annexes to assist your program:
Annex
E
F
I
J
Topic
Electrical Safety Programs
Hazard Risk Evaluation Procedures
Job Briefing Checklists
Energized Work Permits
PPT- 054-01
49
Some Questions OSHA will Ask
Electrical safety analyses performed?
Arc flash hazard analysis performed?
Flash protection boundaries established?
Other potential electrical hazards identified?
Proper insulated tools and equipment used?
Necessary PPE determined?
Insulated blankets/sheeting used to cover all live
parts?
PPT- 054-01
50
Some Questions OSHA will Ask
OSHA: Every employer shall furnish a place of
employment free from recognized hazards…causing
or likely to cause death or serious physical harm…
NFPA 70E: Employers to conduct an electrical
hazard assessment to include a hazard analysis for
shock and arc flash before performing work on live
equipment operating at 50 volts and higher
Review the following when creating your program:
OSHA 1910.132 and 1910.333(a)(1)(i) as well as
1910.269(a)(2)(iii)
PPT- 054-01
51
Summary
• Appreciate the severe consequences which are
possible when working with electrical systems
• Fully plan the job; know and enact safeguards
• Match the required PPE and equipment
to the task
• Consider possible emergency response needs for
yourself and your team and include in your plan
• Conduct the job safely
• Restore safely
• GET HOME SAFELY!!!
PPT- 054-01
52
Bibliography
http://en.wikipedia.org/wiki/Arc_flash
Tyler Lacoma, eHow Contributor,
http://www.ehow.com/about_5110071_definition-arcflash.html
Dr. Mary Capelli-Schellpfeffer, “Arc Flash
Presentation,” as quoted in eHow.com facts, May
30, 2012
Diane Bonder, eHow Contributor
OSHA Training Institute, “Construction Focus Four:
Electrocution Hazards,” April, 2011
http://ehstoday.com/construction/ehs_imp_79112
PPT- 054-01
53
Questions
PPT- 054-01
54