0000 p - Arc-Flash Hazard White Paper

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FLIR Systems: Bob HillArc-Flash Hazard White Paper

Arc-Flash Hazard Environments

Reqire Strin!ent Sa"ety #easres

Regulations, infrared windows, FLIR training

help protect thermographers and other workers at risk

Realizin! the dan!ers and ta$in! the precations

Over the past two decades, the dangers of arc-flash events and the devastation they

can cause have become fairly well understood. As the leader in infrared (IR) camera

technology, !IR "ystems believes that perhaps less well understood are the

precautions that should be ta#en to prevent such occurrences, or at least minimi$e their

impact.

!IR infrared cameras are often used to uncover potential arc-flash trouble spots, such

as deteriorating electrical connections, that may not be visible to the na#ed eye.

%hermographers, electricians, and other wor#ers at ris# need to be familiar with all

aspects of the arc-flash phenomenon& what it is, how and why it occurs'and how they

can #eep themselves out of harms way anywhere this ha$ard is may be present.

Short circit% deadly "orce

An arc-flash ha$ard is a dangerous condition associated with the release of energy

caused by an electric arc. %he arc consists of energi$ed, ioni$ed plasma that can, within

a fraction of a second, reach some of the highest temperatures that occur on arth'up

to *+,, a temperature at which all #nown materials are vapori$ed. utting those

figures into perspective, the surface temperature of the sun is appro/imately 0,0.

Arc-flash incidents can be triggered anywhere electrical systems are present and

electrical e1uipment is being serviced or repaired. or e/ample, a short circuit can result

when a metal tool is dropped, momentarily reducing or bridging the electrical distance

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between energi$ed components. Other causes include the careless removal of a metal

cover plate3 the failure of a circuit brea#er as it is switched on3 residual moisture in

components3 and voltmeter failure or a probe simultaneously touching phase and

ground. 4ust and impurities on insulating surfaces can provide a path for current, as

can corrosion of e1uipment parts.

As with a bolt of lightning, the power of an arc flash is almost beyond comprehension.

5hen it occurs, a massive 1uantity of concentrated, radiated energy e/plodes outward

and simultaneously unleashes (2) e/panding pressure waves of gas (an arc blast) that

can damage hearing and turn loose metal ob6ects into shrapnel hurtling through the air

at velocities greater than 7 893 (:) a high-intensity flash that can damage eyesightor even cause blindness3 and (*) a superheated gas ball capable of vapori$ing metal

and severely burning anyone in the vicinity.

Real-&orld conseqences

As the founder and principal engineer of an electrical power system consulting firm in

;olorado, !IR customer %hree men were wor#ing on a deadline over a three-day wee#end,? he says. >%hey

were hurrying to repair a transfer switch that had malfunctioned. One man had his

hands up in the e1uipment, the second man was #neeling down ne/t to him with

blueprints, and the third man was the supervisor standing behind him and watching.

>%he first man caused an arc, and he was pretty much incinerated,? 5oods continues.

>%he man on his #nees was engulfed in the fireball and badly burned. %he supervisor'

even though he was about @+? and at least * pounds, the shoc# wave was so

powerful that it pic#ed him up and #noc#ed him bac# about ten feet.?

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One master electrician sadly recalls losing a colleague to arc flash when both were 6ust

starting out as 6ourneymen many years ago. >It was in one of the local mills,? he says.

>9e was standing 2+ feet away, but that wasnt far enough. =ou can still see the imprint

of his shadow on a gla$ed tile wall over at that mill.?

So'erin! statistics

Arc-flash events are not at all infre1uent3 in the ."., between five and ten occur every

day that send their victims to a burn center and, according to one study, result in

medical costs of B2.+ million for each episode. %hose statistics do not include victims

sent to regular hospitals and clinics, cases that go unreported, or cases in which no one

was seriously in6ured. It is estimated that C percent of electrical in6uries are caused by

burns resulting from arc flash and igniting of inflammable clothing. %reatment can

re1uire years of s#in grafting and rehabilitation, with no assurance that the victim will

ever be able to return to wor# or a normal life.

%he arc-flash phenomenon isnt new3 it has been around as long as electricity has been

distributed. Only since the late 20Cs, however, has it been given the attention it

deserves, spearheaded in large measure by the petrochemical industry. %oday anumber of organi$ations'both government and private-sector'provide regulations,

policies, recommendations, and monitoring in order to minimi$e the possibility of arc-

flash incidents and protect those who wor# in environments where arc flash is li#ely to

occur.

Re!lations and recommendations

our separate industry standards have been established that deal with the prevention ofarc-flash incidents&

Occupational "afety and 9ealth Administration (O"9A), 29 Code of Federal

Regulations (CFR) Part 1910, Subpart S

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Dational ire rotection Association (DA) Standard 70, ational !le"tri"al Code

DA 70!, Standard for !le"tri"al Safet# in t$e %or&pla"e

Institute of lectrical and lectronics ngineers (I),Standard 1', *uide for

Perfor+ing r" Flas$ Ha-ard Cal"ulations

OSHA

5hile not specifically addressing arc-flash ha$ards, O"9As :0 ;R art 202, "ubpart

", does set design safety standards for electrical systems. Included are standards for

electric utili$ation systems, including all electric e1uipment and installations used to

provide electric power and light for employee wor#places. "afety-related wor# practices

and maintenance re1uirements, as well as safety re1uirements for special e1uipment,

are also covered.

aul ris#, who covers all of ;anada as a roving instructor for !IR "ystems Infrared

%raining center (I%;), comments that O"9A mandates wor#ing in deenergi$ed

conditions e/cept under special circumstances, such as when a problem cant beuncovered by troubleshooting the e1uipment in a deenergi$ed state. >%hey want you to

wor# on e1uipment that isnt energi$ed,? he says. >And yes, that would be ideal.


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grown to almost C pages. Invariably referred to in the trade as >%he ;ode,? the D;

is the standard reference wor# for electricians and is mostly concerned with installation

practices.

Over the years, the D; has dealt with protection from fire, electrocution, and shoc#

ha$ard. Recently, arc-flash safety has been moving into the picture as well. Of particular

relevance is the D; re1uirement that ha$ard warning labels be posted on

switchboards, panel boards, industrial control centers, and motor control centers to

warn wor#ers of ha$ards that might cause serious in6ury or death due to arcing faults.

%hese labels must be located where they will be visible to 1ualified personnel before

any e/amination, ad6ustment, servicing, or maintenance of the e1uipment is underta#en.

FP 70!

Although O"9A sets forth the legal re1uirements, it does not spell out how they are to

be implemented. DA originally developed DA 7, Standard for !le"tri"al Safet#

in t$e %or&pla"e, as a national consensus safety standard primarily to assist O"9A in

preparing electrical safety standards. In effect, O"9A says what to do and DA 7

e/plains how to do it.

DA 7 guidelines provides re1uirements for lash rotection


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e/ists. In fact, they need to be thoroughly familiar with all DA 7 guidelines

because, in certain situations, covers must be removed to permit access so that an

inspection can be completed.

ven though, strictly spea#ing, companies are not legally re1uired to comply with DA

7, theyll be e/pected to offer a compelling alternative if they choose not to do so. As

5oods puts it, >=ou still have to follow the intent. =ou better be doing so+et$ingthat

protects your wor#ers.? In short, compliance with DA 7 will ensure compliance with

O"9A regulations.

5oods also notes that utility companies are currently e/empt from many provisions of

both DA 7 and the Dational lectrical ;ode. >%his seems #ind of strange,? he says,

>but apparently the idea is that if your 6ob is to produce electricity, you ought to #now

something about it.? 9e adds that O"9A is now proposing changes that may re1uire

utilities to comply with parts of DA 7.

I

Is ma6or contribution to arc-flash ha$ard safety is its "tandard 2+CF, *uide for

Perfor+ing r" Flas$ Ha-ard Cal"ulations. As the title suggests, this publication helps

facilities personnel calculate the ha$ards of arc flash in different types of e1uipment in

various power systems. It provides definitive calculation steps in support of DA 7

and outlines a method for calculating the e/pected incident energy level.

5ith this information, a facility owner can ma#e an informed decision about the level of

that those who wor# on the e1uipment must wear. rom the results of the analysis,

9a$ardGRis# ;ategories are established, and lash rotection


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(he importance o" PPE

ersonal protective e1uipment'such as clothing, gloves, tools, face protection, and

glasses'is intended to protect wor#ers from the most destructive arc-flash events,

mainly those that might cause potentially fatal burns to the head and chest.

DA 7 provides a table of ratings, which are based either on voltage rating

(gloves) or thermal rating (cotton and fire retardant clothing). Also included are

ratings for various #inds of apparel, chiefly shirts, pants, and underwear. is

improving at a rapid pace as new technology is developed and introduced.

Redcin! hazard cate!ories and pro'a'ilities

A fundamental principle of reducing arc-flash ha$ard categories is to #eep fault currents

low. nfortunately, this may be difficult to accomplish in e/isting plants owing to

outmoded design practices of the past. %hese include installing oversi$ed transformers

to accommodate future growth that might never materiali$e3 using transformers with the

secondary side protected by a primary fuse3 using bolted fault currents (currents with no

impedance) for setting brea#er trip points3 and selectively coordinating overcurrent

protection, which involves slowing down the circuit-brea#er tripping time.

ngineering techni1ues e/ist that can address such problems. Once an Arc lash

9a$ard Analysis has been completed, it is relatively easy to perform a study of

overcurrent protective device coordination to ensure that all devices clear a fault as

1uic#ly as possible. And slow-acting protective devices can be replaced with faster

ones.

%he main circuit brea#er should trip instantaneously when any fault current is detected.

%his can be accomplished in several ways& %he brea#er can be set to instantaneous

when wor# is to be performed. A maintenance switch, or a pro/imity or motion detector,

can be installed on the brea#er. An optical detection relaying system can be installed.

inally, fuses andGor the transformer can be replaced.

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As important as reducing arc-flash ris# categories is reducing the probability that an arc-

flash event will occur. A corporatewide arc-flash ha$ard program should be

implemented, one that includes ha$ard assessment, documentation, a plan,

development of procedures to minimi$e ha$ard, training for wor#ers, and periodic safety

audits.

reventive measures that can be ta#en include #eepting energi$ed parts from being

e/posed, retrofitting e/posed bus bars with insulated ones, and retrofitting terminal

bloc#s with >finger-safe? components. Arc-resistant electrical e1uipment now on the

mar#et can redirect the forces associated with an arcing fault to a direction away from

where an employee is wor#ing.

It should be emphasi$ed that arc-flash ha$ard analysis and safety program

development are still in the relatively early stages. A great deal more study and testing

remain to be done. One electrician emphasi$es that the best safety procedure is still the

simplest and most obvious& >If youre not 1ualified, and you dont feel safe, and you

dont have to be there'leaveH?

Addin! sa"ety &ith in"rared &indo&s

As was stated earlier, O"9A regulations state that personnel should wor# on

deenergi$ed electrical circuits whenever possible. %he operation of infrared cameras,

however, re1uires that circuitry be energi$ed so that thermographers can perform IR

surveys of high- or low-voltage electrical e1uipment cabinets.

>!IR infrared cameras can be fitted with telescopic lenses,? comments 5oods, >but

someone still has to open up the cabinet. And we dont want the thermographer

unprotected doing that.?

An increasingly popular solution is to install infrared windows, such as 9aw# IR

sightglasses, so that inspection can be performed with doors and cabinets closed. 9aw#

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IR sightglasses provide thermographers with a direct line of sight for IR inspections and

are also transparent to visible light. In addition, they eliminate the need for having a

licensed electrician remove and replace doors and panels for inspections. %he results

are significant increases in inspection speed and area coverage, and greater safety for

wor#ers.

9aw# IR sightglasses are available with either crystalline or mesh barriers. %he >; >

(crystalline) range sightglass can be used indoors or outdoors in either high- or low-

voltage applications, while the >8? (mesh) range sightglass is suitable for indoor, low-

voltage applications. !-approved and easily retrofitted or installed in new e1uipment,

both types provide an all-important physical safety barrier between the inspectors IRcamera and the target. 9aw# IR sightglasses are distributed in the "A by !IR

"ystems.

Sa"ety trainin! "or thermo!raphers

!IR "ystems is e/tremely concerned about arc-flash ha$ards and the dangers they

pose to thermographers. Accordingly, in-depth information about arc-flash ha$ards is an

integral part of the curriculum at the companys Infrared %raining ;enter, where trainingis conducted by highly 1ualified international thermography instructors.

I%; instructor aul ris# advocates the >buddy system? to his students. >=ou have two

thermographers on hand,? he e/plains. >One is dressed in bul#y that almost ma#es

him loo# li#e one of those robots from the @s. %heres no way he can possibly operate

an IR camera. "o instead he functions as the door opener, and the other does the

thermography at a safe distance. One can #eep an eye out for the other. After a certain

length of time, they switch off.?

ris# offers another suggestion in his classes&

>5hether you have a sightglass or not, if youre planning to open the door, do the

fireman tric#. %he fireman will always ta#e his gloves off and put the bac# of his hand on

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the closed door to determine whether theres a high-heat source on the other side. 5e

can accomplish the same thing with our IR cameras. "o as a safety precaution, always

measure the temperature of that door.?

%he I%; offers training, certification, and recertification in all aspects of infrared

thermography use, with facilities featuring e/tensive hands-on laboratories for learning

IR applications. It is the only IR training resource to be I"O 02 certified.

A lon! &ay to !o

5hile it is encouraging that arc-flash ha$ard has come under increased scrutiny in

recent years, there is still a long way to go before this menace can be permanently

eliminated. ntil then, more arc-flash e/plosions will occur every day'and,

unfortunately, more wor#ers will be in6ured or #illed, and more astronomical medical

bills, litigation fees, and production losses will be the conse1uences.

!IR "ystems urges thermographers, electricians, and plant managers to thoroughly

ac1uaint themselves with all of the various precautions that should be ta#en when

wor#ing in a potential arc-flash environment. 5hatever the 6ob, safety comes first.

J J J

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0000 p - Arc-Flash Hazard White Paper