Arc flash incidents can be costly in terms of personnel injury and equipment repair/replacement. This presentation provides an overview of the NFPA 70E 2012 Standard for Electrical Safety in the Workplace and the requirements of the standards, which are intended to better protect electrical workers from injury when they work on energized electrical equipment. This includes all aspects of facility and employer responsibilities for compliance to the NFPA 70E standards, as well as the current status of OSHA enforcement of these standards. Copyright AIST Reprinted with Permission.
1. Arc Flash Protection and Mitigation
Tim Cotter, P.E.
Staff Engineer
Schneider Electric Engineering Services
2. A Quick Look Back…
“I introduced into my ears two metal rods with rounded
ends and joined them to the terminals of the
apparatus.
At the moment the circuit was completed, I received
a shock in the head – and began to hear a noise – a
crackling and boiling.
This disagreeable sensation, which I feared might be
dangerous, has deterred me so that I have not
repeated the experiment.”
3. We’ve come a long way…
“I introduced into my ears two metal rods with
rounded ends and joined them to the terminals of
the apparatus.
At the moment the circuit was completed, I
received a shock in the head – and began to hear a
noise – a crackling and boiling.
This disagreeable sensation, which I feared might
be dangerous, has deterred me so that I have not
repeated the experiment.”
-Alessandro Volta, inventor of the first electric
battery, 1745-1827
4. even from … more recent times.
154. Electricians often test circuits for the presence
of voltage by touching the conductors with the
fingers. This method is safe where the voltage does
not exceed 250 and is often very convenient for
locating a blown-out fuse or for ascertaining whether
or not a circuit is alive. Some men can endure the
electric shock that results without discomfort
whereas others cannot. Therefore, the method is not
feasible in some cases.
AMERICAN ELECTRICIANS’ HANDBOOK
7th Edition 1953 McGraw-Hill
5. But where are we now?
NIOSH Study covering 1980-1995:
93,338 total work-related fatalities in the US
Approximately 1 in 15 were related to electrical hazards (> 1 fatality/
day in the US)
#5 hazard overall
Auto accidents were #1
More recent data – # of deaths down, but proportion
that is related to electrical work is about the same!
Lots of work still to do!
6. Electric Arcs & Arc Flash
Passage of substantial electric current through air
“Short-circuit in air”
May simply flow through ionized air
May flow through vapor of arc-terminal material
Copper, Carbon, etc.
Not necessarily harmful
Arc welding, “static electricity”
Arc Flash Hazard: A dangerous condition associated with the
possible release of energy caused by an electric arc. (NPFA
70E definition)
7. Severity of Arc Flash
Depends on several factors, including:
Magnitude of fault current
System voltage
Duration of arcing fault
Proximity of worker to arc source
Complex issue!
Typical power distribution system – levels may
be severe enough to cause serious injury or
death
13. Relevant Codes & Standards
National Electrical Code NFPA 70 (2011 ed.)
OSHA
NFPA 70E (2012 ed.), Standard for Electrical
Safety In the Workplace
IEEE 1584-2002
14. National Electrical Code – NFPA 70
Best known of all electrical standards?
Dates back to 1897
In general, does not address work practices
Still, starting in 2002, some reference to Arc Flash
NEC 110.16. Flash Protection. Electrical equipment, such as
switchboards, panelboards, industrial control panels, meter socket
enclosures, and motor control centers, that are in other than dwelling
occupancies, and are likely to require examination, adjustment, servicing,
or maintenance while energized shall be field marked to warn qualified
persons of potential electric arc flash hazards. The marking shall be
located so as to be clearly visible to qualified persons before
examination, adjustment, servicing, or maintenance of the equipment.
15. NEC & Arc Flash
Requires equipment to be labeled, but does not
specify a label format
We’ll discuss labeling in more detail later
An NEC-compliant system does not necessarily do a
thing to reduce, eliminate, or manage arc flash
hazards
16. OSHA
Occupational Safety and Health Administration
Created by Occupational Safety and Health Act of
1970
Mission: “To save lives, prevent injuries, and protect
the health of America’s workers.”
29.CFR 1910, Subpart S—deals with electrical
systems
“Law of the Land”!
www.osha.gov
17. OSHA & Arc Flash
OSHA requires use of Personal Protective
Equipment (PPE)
Does not prescribe nature of PPE required for
various tasks
NFPA 70E is referenced in an appendix of OSHA
1910 Subpart S, but is not “incorporated by
reference”
Most serious injuries involve ignition of clothing
Proper clothing must be selected based on
industry standards or practices
NFPA 70E: an industry consensus standard
18. OSHA General Duty Clause
Each employer shall furnish to each of his employees
employment and a place of employment which are free
from recognized hazards that are causing or are likely to
cause death or serious physical harm to his employees.
[OSHA’s PPE requirements] are written in general terms, requiring, for example, that personal protective
equipment be provided "where necessary by reason of hazards..." (§1910.132(a)), and requiring the employer to
select equipment "that will protect the affected employee from the hazards...." (§1910.132(d)(1)). Also,
§1910.132(c) requires the equipment to "be of safe design and construction for the work performed."
Similarly, §1910.335 contains requirements such as the provision and use of "electrical protective equipment that
is appropriate for the specific parts of the body to be protected and the work to be performed (§1910.335(a)(i)).
Industry consensus standards, such as NFPA 70E, can be used by employers as guides to making the
assessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions,
they can be used as evidence of whether the employer acted reasonably.
From OSHA interpretation of the General Duty Clause, 7/25/2003
19. NFPA 70E
“Standard for Electrical Safety In the
Workplace”
Current edition published in September, 2011
Approx. 3-year revision cycle
Revision process underway!
Latest edition: 2012
20. NFPA 70E: Key Provisions
Article 90: Scope
Facilities covered include public and private buildings,
parking lots, carnivals, industrial substations, service-
entrance equipment, and electric utility equipment that is
NOT a generating station, substation, or control center
Facilities NOT covered include ships or automobiles/trucks,
underground installations in mines, “3rd rail”, communications
equipment under the control of communications utilities, and
remaining electric utility installations
Basically the same as the NEC
21. NFPA 70E: Key Provisions
Qualified Employees – ones allowed to do work
Knowledgeable about a piece of equipment or specific work
method
70E defines specific items that should be known
Can recognize and avoid electrical hazards (including arc
flash)
Is familiar with proper use of PPE, insulated tools, and
insulating/shielding materials
Not necessarily synonymous with:
Master Electrician
Professional Engineer
CEO
22. NFPA 70E: Key Provisions
“Live parts to which an employee might be exposed shall be
put into an electrically safe work condition before an
employee works on or near them, unless work on energized
components can be justified according to 130.1”—110.8(A)(1)
Basic protection strategy: de-energize the equipment!
Excerpt from typical Square
D instruction bulletin.
23. NFPA 70E: Key Provisions
Exceptions to the previous rule include the
following: (130.1)
When de-energizing introduces additional or
increased hazards
Deactivation of emergency alarm systems
Life support system
Ventilation in hazardous area
When de-energizing is infeasible
Performing diagnostics or testing that requires
energized circuit
24. NFPA 70E: Key Provisions
If parts not placed in an electrically safe condition, then work
to be performed shall be considered energized electrical work
and shall be performed by written permit only
Decision-making taken out of workers’ hands and shifted to
management
Why a permit?
Make you think twice before doing energized work
Create a “Paper trail”
This applies to the “exemptions”
Management can’t just sign a permit and OK any
energized work
25. Flash Hazard Analysis
The analysis shall determine the flash protection
boundary and the PPE that workers within this
boundary should use
Intended to protect personnel from the possibility of
being injured by an arc flash
How does one perform a flash hazard analysis?
PPE Tables
Calculations
More on this later
26. Flash Protection Boundary
Arc Flash Boundary (100):
An approach limit at a distance
from a prospective arc source
within which a person could
receive a second degree burn if
an electric arc flash were to
occur.
28. How Much Energy is Too Much?
It is generally accepted that an incident energy of 1.2 cal/cm2
is sufficient to cause 2nd-degree burns on unprotected skin
Tolerance may be higher for very short exposures
Why cal/cm2?
Just how hot is 1.2 cal/cm2???
Typical incident energy ranges:
0-200+ cal/cm2
Equipment that has been placed in an electrically safe work
condition: energy level = zero!!
29. Working Inside the FPB
Employer shall determine and document the incident energy
exposure of the worker (cal/cm2)
Based on a working distance from source of arc to
employee’s face and chest
Use FR clothing and PPE appropriate for hazard level
Use additional PPE for parts of the body closer than the
distance at which the incident energy was determined
(Alt.) Select PPE from tables
30. Equipment Labeling
Now required in the 2012 edition of NFPA 70E
130.5 (C) – Several options listed for identifying the arc
flash hazard along with nominal voltage and arc flash
boundary.
Field marked – can’t determine at factory
Minimal information actually required
Most labels contain significantly more information
31. IEEE Standard 1584
“IEEE Guide for Performing Arc-Flash Hazard
Calculations”
Incorporates results of extensive testing performed
by several parties
Provides method for calculating incident arc-flash
energy
Does not replace NEC or NFPA 70E—instead, it
works with and alongside of them
More on this when we talk about calculations
32. NFPA 70E PPE Requirements
PPE should:
Cover all ignitable clothing (130.7(C)(2))
Allow for movement and visibility (130.7(C)(2))
Include head, face, neck, and chin protection
(130.7(C)(3))
Include eye protection (safety glasses)
(130.7(C)(4))
Include FR clothing for body (130.7(C)(6)) for
all exposures over 1.2 cal/cm2
Include hand and arm protection (130.7(C)(7))
Include foot protection (130.7(C)(8))
Conform to relevant ANSI and/or ASTM
standards (130.7(C)(14))
33. Additional PPE Requirements
Outer layers over FR clothing also must be FR
Avoid tight-fitting clothes
Choose PPE that poses minimal interference while
still providing adequate protection
Wear safety glasses under face shields/hoods
Visor in flash suit should protect as well as the rest of
the suit
Non-FR synthetic fabrics not permitted*
34. Selection of PPE
Based on Hazard/Risk Analysis
NFPA 70E Tables
List common work tasks for several types of equipment
Each task assigned a HRC
PPE defined for these HRCs
Calculations
Calculations define AFIE for a given location
Select protective clothing that will protect against that AFIE
Technically, HRCs don’t apply to calculated results, but in
practice, most still correlate calculated AFIE levels to
clothing systems listed in NFPA 70E Table 130.7.C.15
35. Protective Clothing Classes
Min Arc
Rating
Class Description (cal/cm2)
0 Nonmelting, flammable materials N/A
1 FR shirt + FR pants or FR coverall 4
2 FR shirt + FR pants or FR coverall 8
3 (2) + additional PPE to reach 25 cal/cm2 25
4 (2) + additional PPE to reach 40 cal/cm2 40
Category 0 Clothing OK for up to 1.2 cal/cm2
36. H/R Category 0 (Non-FR)
Untreated, long-sleeve shirt
Untreated, long pants
Hearing protection
Safety Glasses
Good for up to 1.2 cal/cm2
Photos courtesy of Oberon
37. H/R Category 1 (one FR layer)
FR pants with ATPV of at least 4 cal/cm2
No more untreated denim!
FR long-sleeve shirt
Optional FR coverall in lieu of FR shirt/pants
FR jacket/parka/rainwear (as needed)
Hard hat
Safety Glasses
Hearing protection
Arc Rated Face Shield
Leather gloves & leather work shoes (as needed)
Good for up to 4.0 cal/cm2
38. H/R Category 2 (one FR layer + cotton)
FR long-sleeve shirt (minimum arc rating
of 8)
Pants: FR with min arc rating of 8
FR Coverall (Arc Rating 8 or more)
permissible in lieu of other FR clothing
FR jacket/parka/rainwear (as needed)
Hard Hat
Safety glasses or Safety Goggles
Leather gloves & leather work shoes
Hearing protection
Face Shield & Arc Rated Balaclava or Arc
Rated Hood
Photos courtesy of Oberon
Good for up to 8.0 cal/cm2
39. H/R Category 3 (two FR layers)
Option 1:
FR shirt/pants
FR coverall
Option 2:
FR clothing system w/arc rating of 25
FR jacket/parka/rainwear (as needed)
Hard hat
Safety glasses or safety goggles
Double-layer switching hood Photos courtesy of Oberon
Hearing protection
Arc rated gloves or rubber gloves w/leather
protectors
Good for up to 25 cal/cm2
Leather work shoes
40. H/R Category 4
FR clothing with arc rating of 40
Flash suit
Shirt/pants/coverall combination providing
equivalent protection
FR jacket/parka/rainwear (as needed)
Hard hat w/FR liner
Safety glasses or safety goggles
Double-layer switching hood
Hearing protection
Arc rated gloves or rubber insulating gloves
w/leather protectors
Leather work shoes
Photos courtesy of Oberon
Good for up to 40 cal/cm2
41. Beyond 40 cal/cm2…
PPE vendors: 100 calorie suits
NFPA 70E: defines no clothing class higher than 40 cal/cm2
Does not explicitly prohibit work at such locations
70E Handbook: appears to have backed off a
statement in the earlier editions that allowing work
at such locations was never the intent of 70E
Other issues to consider
Blast effects
Equipment integrity
Is PPE rated against shrapnel?
No “ballistics rated” flash suit or face shield
Hearing damage
42. Why is PPE Important?
Has major impact on burn survival
rates
Major factor: total % of body burned
Burn of 75% of body (easily
possible if clothing ignites) results
in:
< 50% survival rate for males aged
30-39
< 20% survival rate for males aged
50-59
Rule of thumb: one day in hospital
for each 1% of body burned Photos courtesy of Oberon
43. Clothing Performance Benchmarks
Ease of ignition
Tendency to continue burning after heat
source removed
Degree/ease of flame spread
Amount of heat transmitted
Tendency to melt
Strength—does arc flash tear it apart, or does
it hold together?
44. Relative Performance – non-FR
Clothing
Natural fibers are fairly good, at least if they don’t ignite
Cotton may continue to burn after heat removed
Wool does not normally sustain a fire
Non-FR Synthetics particularly bad either when alone or when
blended w/cotton
Easily ignited
Melt
Increase chance of infection
Exception?
45. PPE Selection Principles
Heavier fabrics provide more protection
Multiple layers more effective than single layer of equivalent
weight
No non-FR synthetics next to skin
“Performance underwear” may contain polyester or
nylon/spandex blend—good for a ski trip, but bad for
electrical work!!
46.
47. Head and Face Protection
Face shields provide some protection against molten splatter
Non-FR face shields provide little or no protection against
burns
Tinted face shield with ATPV rating—better
Protective shield inside FR hood—best
Beware old FR hoods with non-FR shields!
If visibility is a concern, provide lighting!
Safety glasses always required
48. Arc Rating Values
Based on testing
Shown on equipment label
Some PPE—no tests performed, so no official arc rating
assigned
Leather work gloves (unofficially 12 cal/cm2)
Leather glove protectors
Rubber insulating gloves
Class 0 yellow gloves: limited testing indicated ignition
10% of the time at 25 cal/cm2; 50% of the time at 31 cal/
cm2
Shoes (limited testing indicates resistance of 50-60
cal/cm2)
50. PPE Innovations – Improved Visibility
Warning: older clear faceshields may not be FR. In the
presence of a high energy arc, they can melt. The pressure
wave will tend to push the molten plastic into your face.
51. PPE “Gotchas”
Not all FR rainwear is “arc resistant” – i.e., may have
elements that can melt
EVERYTHING needs to be arc resistant (or at least made out
of something that won’t melt or burst into flame) during
energized work
Underwear
Safety vests
Hair nets
Employee ID cards
Logos / names sewn on to FR clothing
Paper towels stuffed in hard hat to catch sweat
Maintain the PPE
Carefully observe laundering instructions
52. Use Your Head
Use PPE correctly…no rolled-up sleeves or unzipped
coveralls
Body positioning when operating devices
But: don’t make face shield an “arc scoop”
No more workers than necessary in vicinity of
energized work
Remove yourself from the source when possible
Hot stick
Remote operations
53. Disclaimers
NFPA 70E, 130.7.C.16, Informational Note #2:
The PPE requirements of this section are intended to protect a person
from arc flash and shock hazards. While some situations could result
in burns to the skin, even with the protection described in Table
130.7.C.16, burn injury should be reduced and survivable. Due to the
explosive effect of some arc events, physical trauma injuries could
occur. The PPE requirements of this section do not address protection
against physical trauma other an exposure to the thermal effects of an
arc flash.
PPE is supposed to be your last line of defense.
How do you feel about sustaining a “survivable”
injury?
54. Thank You
Tim Cotter, P.E.
Staff Engineer
Schneider Electric Engineering Services, LLC