Occuaptional Safety and Health Article Review

E H S To d ay I AU G U S T 2 0 1 0 I w w w. E H S To dAy. c o m 33

Implementing Hazard Control Measures for

Arc Hazard Protection

A lthough the electric arc flash

hazard only recently has gar-

nered the attention equal to

that of the long-recognized hazard

of electric shock, the arc hazard is

not new. Until the 1980s, occupa-

tional electrical hazards generally

were described in terms of electric

shock or electrocution, a fatal elec-

tric shock.

Electric shock entails passage

of an electric current through the

body. A shock victim generally must

make contact with an energized

conductor, or otherwise become

part of the electrical circuit. Arc

flash victims do not have to make

physical contact with an energized

conductor or be a part of the elec-

trical circuit. The victim may be

several feet away from energized

conductors or equipment and be

severely injured by the intense

thermal energy transfer produced

by an electric arc. The burn injuries

can be radiant burns to bare ex-

posed skin, large-area body burns

over the past 15 years, the

evolution in regulations,

codes and standards, as well

as basic understanding of

the arc hazard, has elevated

the importance and priority

of managing and mitigating

this hazard in the workplace.

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>> ImplEmEnTIng Hazard ConTrol mEaSurES for arC Hazard proTECTIon

from ignition or melting of clothing or

burns caused by heat transfer through

clothing, including flame-resistant

clothing.

abouT arC flaSH

Arc flash events usually are very short

occurrences – typically less than 0.5

seconds in duration. They can be initi-

ated by a wide range of factors and

complicated by other contributing fac-

tors. There can be human errors, such

as touching an energized conductor

the employee thought was de-ener-

gized, or accidentally dropping a tool

onto an energized conductor.

In addition, there may be environ-

mental causes, such as roof leaks or

dirt accumulation in electrical switch-

gear. There may be management sys-

tem failures in critical aspects of train-

ing, maintenance programs, design

specifications or tool requirements,

such as allowing use of voltage test-

ing devices not rated for industrial and

commercial electrical systems. Switch-

gear or other equipment failures dur-

ing switching or operating interaction

also can expose workers to the hazards

of electric arc flash.

Most arc flash events occur faster

than the unaided human eye can

perceive. High-speed photography of

laboratory simulations of arcing faults

have provided images of how these

events can engulf workers in a ball of

fire. Electric arcs are very hot; next to

the laser, arc flashes create the most

intense heat source on earth. Tempera-

tures in the arc can reach 35,000 de-

grees F. Arc flash events actually are

multiple energy events, with intense

blast, mechanical and acoustic energy

accompanying the intense thermal en-

ergy. People within several feet of an

arc can be severely burned.

A s t h e b o dy o f k n ow l e d g e a n d

understanding of the arc flash phe-

nomena grew, leadership emerged to

change federal regulations; update

building codes; improve the design of

electrical equipment; increase the ap-

plication of circuit protection; create

safe work practices; train personnel in

utility, industrial and commercial work

environments; and develop personal

protective equipment (PPE). Technolo-

gies to further reduce or mitigate arc

flash hazards were brought to market,

including current limitation, metal

cladding, venting to redirect arc blast

forces and “arc resistant” designs.

In 2004, the National Fire Protection

Association (NFPA) and the Institute of

Electrical and Electronics Engineers

Inc. (IEEE) established a collaborative

research project to further study the

phenomena of electric arcs. This col-

laboration helped advance the pro-

tection of workers from heat, pressure,

sound, toxicity and other medical ef-

fects of exposure to electric arcs.

Hazard ConTrol

mEaSurES

Below are a few examples of applying

hazard control measures to the unique

hazard of electric arc flash. The exam-

ples are not all-inclusive, and only serve

to illustrate concepts useful in helping

assure long-term effectiveness and sus-

tainability. The most effective design and

application of an arc flash mitigation

program incorporating these control

measures usually can best be achieved

through a collaboration involving elec-

trical subject matter experts, safety

professionals knowledgeable in safety

management systems and manage-

ment resources that can help assure

financial and other resources are allo-

cated to the program.

Electrical experts may be knowl-

edgeable in all things electrical, but

not in the subtleties of safety manage-

ment systems. Safety professionals,

on the other hand, may be expert in

safety management, but have only a

general or limited knowledge of elec-

trical equipment and work practices.

Bringing experts from different com-

petencies together can produce high

quality results in fleshing out details of

an effective and sustainable electrical

safety program.

Eliminating the hazard – With a

high degree of certainty, the best way

to protect people from an arc flash ex-

posure is to completely eliminate the

arc hazard. It is easier to design new

facilities with the intent to eliminate

arc flash hazards than it is to retrofit

existing electrical installations.

H owe ve r, a n o r g a n i z at i o n t h at

asks the question, “Do we have any

exposures that are unnecessary and

could be eliminated?” may discover

some opportunities. One example is

the discovery that a long-established

employee break area, located in an

electrical control room, was within the

calculated arc flash boundary. While

the individuals in the break area may

not have interacted directly with the

electrical equipment, the routine con-

gregation of people within the arc flash

boundary created an unnecessary risk.

Flame-resistant

clothing is one

component

of an arc

flash hazard

mitigation

program, but

do not rely on

PPE as the only

control measure.

d u p o n t

E H S To d ay I AU G U S T 2 0 1 0 I W W W. E H S TO DAY. C O M 35

Relocating the break area to a new location eliminated

the hazard.

Substituting less hazardous equipment or materi-

als – With increased understanding of the need to reduce

worker exposures to arc hazards, equipment manufactur-

ers and system designers are bringing innovative solutions

to market to help employers reduce arc flash exposures to

their workers. The design of new installations and modifi-

cations to existing electrical systems should be analyzed

for arc flash hazards, potential exposures and their severity

identified and options to reduce severity or frequency of

exposures considered.

Design choices that tend to reduce the severity and/or

frequency of exposure to arc hazards include high-resis-

tance grounding for industrial power systems, arc-resistant

switchgear that direct thermal energy from an arc away

from personnel interacting with the gear, current limiting

protective devices that reduce the exposure by shortening

the arc duration and “smart” switchgear and motor con-

trol centers that can reduce exposures by changing how

people interact with the equipment during troubleshoot-

ing and other maintenance tasks.

Implementing engineering controls to reduce ex-

posure or severity – Engineering controls impacting arc

flash exposure span a wide range of consideration. Engi-

neering analysis to identify and quantify potential arc haz-

ard exposures is one very important engineering control

measure in arc hazard mitigation. Remote switching and

remote racking of power circuit breakers are examples of

equipment options that allow personnel to work outside

of the arc flash zone. Other engineering functions very

critical to arc flash mitigation include maintenance and

reliability improvement programs.

It is important that workers responsible for operating

and maintaining the electrical system are familiar with

the effects of their work on the arc flash incident energy.

For example, if there is a process upset and they change

out a fuse to a larger size (no fuse of the existing size was

available quickly), then they need to understand that the

arc flash energy of the equipment has been changed and

may be higher. Protective devices including protective re-

lays, circuit breakers and switchgear must be maintained,

inspected and tested to help assure designed functionality

when operating during an arc fault.

Given that some of the highest frequency and severity of

exposures to arc hazards involve interaction with 600-volt-

class motor control centers, programs to increase mean

time between the failure of motors serve to reduce main-

tenance and operations personnel interaction with motor

control centers. Consider these tasks that occur every time

a motor fails mechanically or electrically: the motor starter

disconnect switch is operated at least twice (to disconnect CIRCLE 138 ON READER CARD OR LINK TO THE VENDOR

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Arc fl ash temperatures can reach

35,000 degrees F.

3 6 W W W. E H S TO DAY. C O M I AU G U S T 2 0 1 0 I E H S To d ay

>> IMPLEMENTING HAZARD CONTROL MEASURES FOR ARC HAZARD PROTECTION and eventually to re-energize), voltage testing is performed

to verify electrical isolation, motor leads are disconnected

and then reconnected and fuses may be removed and rein-

stalled. Each one of these interactions has some risk for an

arc flash incident. Electrical equipment and systems reliabil-

ity improvement is an important component of an arc flash

hazards mitigation program.

Warnings, signs and other communications – Labels

and signage ensure personnel understand their proximity

to potential hazards. Signs and labels may be temporary or

permanent in nature, depending on the work activity or du-

ration of the potential hazard. The warning could be a sign

on switchgear, or a boundary marked on the floor. It could

be a temporary barricade during certain work activity.

Because signage and labeling practices may not be con-

sistent industry-wide, contractors working in multiple fa-

cilities need to be aware of each facility’s standards. One

important consideration is consistency and uniformity, at

least within the site operations, to help assure common un-

derstanding by the people potentially at risk.

Administrative controls, including safe work prac-

tices – Administrative controls include training and quali-

fication requirements, job procedures, planning tools, lock

out practices and auditing systems. These administrative

controls are well addressed in NFPA 70E. However, some

circumstances may call for additional procedures not spe-

cifically described in the standard.

Personal protective equipment – The use of PPE,

including flame-resistant clothing, face shields and other

accessories, is a critical-control measure of any arc flash

hazards mitigation program. However, it should not be the

only control measure.

Arc flash PPE serves to minimize the injury severity in the

event of an arc flash incident. In order for the PPE to per-

form effectively, its arc thermal performance rating (ATPV)

must meet or exceed the thermal energy transfer during

the arc flash incident. The best way to predict the thermal

energy transfer, or incident energy, is to have performed an

arc flash hazard analysis. PPE clothing and accessories then

can be selected on performance rating (i.e Hazard Risk

Category 1-4 from NFPA70E) and matched to the predicted

energy exposure.

There are many flame-resistant clothing products de-

signed for arc flash application on the market today, but

all are based on two technologies: fabric made from (a)

inherently or (b) chemically treated, flame-resistant fibers.

“Inherent,” as it relates to flame-resistant garments, means

that the flame-resistant properties always have been a part of

the fibers used in the fabric. The protection is intrinsic, per-

manent and cannot be washed out or worn away, no matter

how the garment is used or laundered. The terms “treated” or

“topically treated” refer to a manufacturing process whereby

a mixture of chemicals is added to a naturally flammable

fabric, such as cotton or cotton/nylon blends. Unlike inher-

ent FR fibers, treated fibers may have their flame-resistant

properties diminished or removed, depending on how the

garment is laundered or the chemicals to which it may be

exposed to in the work environment.

In selecting protective garments, the most important

criteria are that it is from a reputable manufacturer and

is labeled with the Hazard Risk Categor y that meets or CIRCLE 140 ON READER CARD OR LINK TO THE VENDOR

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E H S To d ay I AU G U S T 2 0 1 0 I w w w. E H S To dAy. c o m 37

exceeds the potential incident energy exposure. The se-

lection of fabric technology may depend on frequency

of use, environmental conditions, worker feedback from

wear trials, garment durability and an evaluation of total

costs that takes the initial purchase price, garment life

expectancy and laundering and maintenance costs into

consideration.

At-risk workers need to be educated on when, where

and how to properly use PPE garments and accessories.

PPE garments and accessories need to cleaned, inspected

and maintained in accordance with manufactures’ rec-

ommendations in order to preserve the designed protec-

tion performance.

CrEaTE a Program

An effective arc flash hazards mitigation and protection

program is more than buying flame-resistant garments and

making them available for potentially exposed personnel

to wear. An effective program involves management com-

mitment to designing and implementing a comprehensive

set of proven control measures consistent with occupa-

tional safety and health management systems standards,

such as ANSI Z10. An effective program should include, but

is not limited to:

➤ Project engineering practices that include analysis

for opportunities to eliminate or reduce arc flash expo-

sure through wise evaluation of engineering operations in

equipment and systems design.

➤ Maintenance programs that help assure electrical

equipment is kept in proper condition to ensure the safety

features and functionality critical to prevention and/or

mitigation of arc flash hazards maintains or exceeds de-

sign intent.

➤ Warnings, labels, signs and other means to help assure

personnel are informed of identified hazards.

➤ Administrative/management controls to help ensure

personnel are trained and qualified fro their roles and

responsibilities, and that proper tools and resources are

available to perform work safely and that all elements of

the program periodically are audited to monitor and con-

trol drift from designed expectations.

➤ Flame-resistant personal protective garments and

accessories that are engineered and manufactured to

recognized industry standards, selection of PPE based on

engineering analysis to determine predicted thermal inci-

dent energy, PPE rated performance meets or exceeds the

exposure potential and that personnel at risk know when,

where, what and how to wear PPE appropriate for the task

and exposure.

Plant engineers can manage arc flash hazards through

understanding and application of appropriate regulations

and standards, implementing hazard assessments, evaluat-

ing mitigation options, reducing risks and designing and

implementing control measures to help assure an effective

and sustainable program.

H. Landis Floyd II, PE, is a principal consultant – Electri-

cal Safety & Technology – for DuPont in Wilmington, Del.

He holds a B.S. in electrical engineering from Virginia

Polytechnic Institute & State University. He is a profes-

sional member of ASSE, a member of the National Fire

Protection Association (NFPA), a member of the board of

directors of Electrical Safety Foundation International,

and a Fellow of the Institute of Electrical and Electronics

Engineers Inc. (IEEE).

Daniel R. Doan, PE, is a principal consultant – Electrical

Safety & Technology – for DuPont. He holds B.S. and M.S.

degrees in electrical engineering from the Massachusetts

Institute of Technology. He is a senior member of the

Institute of Electrical and Electronics Engineers Inc., a

member of the IEEE 1584 Guide for Arc Flash Calculations

standards committee and member of the IEEE/NFPA Arc

Flash Hazards Research and Testing Planning Committee.

Jennifer Slivka, PE, is a consultant for DuPont. Slivka

received the BSEE degree from the Ohio State University.

She was certified as a Six Sigma Black Belt in 2003. Slivka

is an IEEE member and an ISA member.

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Most arc flash events occur

faster than the human eye

can perceive.

EHS

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