hazard area class.doc

8/10/2019 Hazard Area class.DOC

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Hazardous Area Classification

And The Selection of Equipment

Introduction:

For the classification of hazardous areas the notable standards that are mostfrequently used are IEC60079 Part 10 for U and Euro!e" #$%&'% Part ( for

U only" )PI %00 ) for U$)* $tartin+ from ,uly 1" (00& all the Euro!ean

Countries -ill follo- the Euro!ean .irecti/e 9'9EC" also no-n as the

)E2 .irecti/e*

ATEX Directive 9!9!EC:

.irecti/e 9'9EC" commonly called the )E2 34)toms!heres

E5!losibles .irecti/e is one of a number of ne- a!!roach directi/es

de/elo!ed by the Euro!ean Union and co/ers all equi!ment and !rotecti/e

systems intended for use in !otentially e5!losi/e atmos!heres* he .irecti/e

is no- in effect and become mandatory startin+ from ,uly 1" (00&" and

su!ersedin+ all !re/ious le+islation related to !roducts used in e5!losi/e

atmos!heres*

he )E2 .irecti/e co/ers the follo-in+ ma8or elements

he a!!lication of the CE mar:

Essential health and safety requirements

Products included;equi!ment" !rotecti/e systems" com!onents"

safety" controllin+ or re+ulatin+ de/ices*

EC y!e E5amination Certificate

Conformity assessment !rocedures for

; Product e/aluation

;


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Is in conformity -ith all a!!licable technical !ro/isions and

requirements of )E2 and other directi/es that a!!ly to the

equi!ment" and

>as been the sub8ect of the a!!ro!riate conformity assessment

!rocedures of the )E2 directi/e*

Elements of Hazardous Area Classification:

) hazardous area is one in -hich a flammable mi5ture of +ases or /a!ors

may e5ist* U!on i+nition the flammable mi5ture -ill burn or e5!lode* he

i+nition can be caused by one of t-o methods* he usually attributed method

is by a s!ar:* he second is by a hi+h surface tem!erature bein+ attained"

usually by o!eratin+ equi!ment*

$!ar:s can occur by electrical or mechanical acti/ity* Electrically the s!ar:s

are usually made by s-itchin+ contacts" loose contacts in a circuit carryin+

current" !oorly matin+ metallic faces that are carryin+ current and staticdischar+es*

); ?i5tures of @ases" Aa!ors and )ir

I+nition can only lead to a fire or e5!losion if three com!onents occur

simultaneously" they are

1* ) flammable +as or /a!or is !resent in sufficient quantity 3this occurs

due to lea:a+e or accidental dischar+e from an enclosed /essel" !um!"

com!ressor" /al/e" flan+e or the li:e*

(* $ufficient air is !resent 3it can be assumed that there -ill be al-ays besufficient air in the area* he o5y+en in the air is required for the

combustion*

&* he source of i+nition occurs 3his -ill be a s!ar: ha/in+ sufficient

ener+y" or a hot surface that -ill cause s!ontaneous or auto;i+nition

e*+* a hot e5haust manifold and !i!in+ of a diesel en+ine*


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@ases and Aa!ors

=hen +ases and /a!ors are !resent in air the resultin+ mi5ture may be

flammable* Bot all +ases and /a!ors !roduce flammable mi5tures* Ima+ine a

flammable +as or /a!or slo-ly lea:in+ into a confined /olume of air that is

not re!lenished* Initially the concentration of the +as or /a!or in the mi5ture

-ill be too lo- to su!!ort combustion* )s the concentration increase a

critical !oint -ill be reached -hen combustion -ill be !ossible* his is

called the o-er E5!losi/e imit 3E* If the concentration is increased

beyond this !oint by a si+nificant amount then a second critical !oint -ill be

reached* )t this !oint the mi5ture -ill not contain sufficient o5y+en to

enable combustion to occur* his is called the U!!er E5!losi/e imit 3UE

abo/e -hich no combustion or e5!losion is !ossible*

In terms of hazardous area analysis the UE is not normally of !ractical

si+nificance* Aarious institutions ha/e determined the E for most of the

re+ularly encountered +ases and /a!ors* #oth the E and UE aree5!ressed in !ercenta+e of /olume*

em!erature Class

In order to classify a +as or /a!or by its ability to be i+nited by a hot surface"

the definition em!erature Class is used* I+nition by this classification is

s!ontaneous or automatic* he classification is sim!le to a!!ly and consists

of a t-o;di+it code" the first di+it is the letter 4 and second a number

bet-een 1 and 6* he lo-er the number the hi+her the ma5imum allo-able

surface tem!erature* >ence a 6 +as or /a!or is relati/ely more hazardous

than one -ith a 1 code*

he belo- table com!lies -ith the same classification used in the U$)"e5ce!t that the BEC sub;di/ide the classes in some case to further )" # and

C classes*


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@rou!in+ of @ases and Aa!ors

In order to classify a +as or /a!or by its ability to be i+nited by a s!ar:" the

definition @as @rou! is used* )+ain the classification is sim!le to a!!ly* It

consists of a three;di+it code* he first and second di+its are I or II 3he IEC

may add @rou! III in future for dust hazards* he third di+it is letter )" #"

or C*

For the oil industry the @rou! I is of little concern because it !ertains only to

under+round minin+* >ence @rou! II)" II# and IIC are of concern in this

subsection* ) @rou! II) +as or /a!or is the hardest of the three sub;+rou!s

to i+nite by a s!ar:* Con/ersely a @rou! IIC +as or /a!or is the easiest to

i+nite*

Hazardous Area Divisions!%ones: Bon;>azardous )rea

Done ( >azardous )rea

Done 1 >azardous )rea

Done 0 >azardous )rea

)d8acent >azardous Dones


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T&pes 'f (rotection )or Hazardous Areas:

?ost electrical equi!ment consists of li/e or acti/e static !arts" and in some

cases such as motors" solenoid /al/es and relays mo/in+ mechanical !arts"

enclosed in an enclosure* he electrically li/e conductors are :e!t out of

touch to !re/ent electric shoc: hazards* he detrimental effects of the

atmos!here e*+* rain" s!rayed -ater" fine dust and !articles are :e!t out of

contact -ith the conductors" insulation" bearin+s and the li:e* For equi!ment

that is to be used in hazardous areas there is the additional requirement that

+ases and /a!ors should be restricted from enterin+ into the enclosure* here

are /arious basic methods that attem!t to ensure that this requirement is

achie/ed at a more or less de+ree" -hich +enerally is de!endent u!on the

Done of the intended area of installation*

he desi+n of the enclosure -ith re+ard to hazardous area a!!lications is

defined by se/eral lo-er case letter codes" mostly sin+le di+its for electrical!o-er equi!ment but occasionally t-o di+its for /ery lo- ener+y electronic

equi!ment*

he most frequently encountered codes are d" e" n" !" and i* he lesser used

codes are o" m" s" and q*

T&pe of (rotection *d+:

y!e of !rotection" for -hich the !arts -hich can i+nite an e5!losi/e

atmos!here are inside an enclosure -hich -ill -ithstand the !ressure of the

E5!losion -ithin the enclosure*


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Pre/ent the transmission of the e5!losion to an e5!losi/e atmos!here

surroundin+ the enclosure*

his ty!e of !rotection is also referred to as 4flame!roof in some literature*

)n enclosure that is desi+ned as ty!e 4d -ill be able to -ithstand an

internal e5!losion of the +as;air mi5ture -ithout bein+ dama+ed beyond

re!air* Furthermore the matin+ surfaces of 8oints e*+* terminal bo5es" bearin+

seals on shafts" -ill be so desi+ned that the flame inside the enclosure -illnot !ass to the outside -ith sufficient ener+y to i+nite the en/ironmental +as;

air mi5ture* In effect the desi+n of the surfaces is such as to act as a /ery

slo- !ressure relief system for the internal e5!losion*

#y the form of the desi+n these enclosures are usually robust" 4hea/y duty

and often made of thic: cast iron" steel or bronze -ith many bolts to fasten

the fabricated sections and lids*

This t&pe of protection is mainl& intended for %one , areas * =hen an

internal e5!losion occurs or under normal runnin+ conditions" the outside

surface of the enclosure must not e5ceed the +as;air auto;i+nitiontem!erature i*e* em!erature Class*


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T&pe of (rotection *I+:

y!e of !rotection" for -hich the ener+y in the electrical circuit is held

so lo- that s!ar:s" arcs or tem!eratures ca!able of causin+ i+nitioncannot occur*

Includes sub;di/ision into the cate+ories ia ib

Ia must not !roduce any i+nition -hen any combination of t-o faults

is !resent*

Ib must not !roduce any i+nition" in normal o!eration" -hen one fault

is !resent*

he circuit and its de/ices do not ha/e sufficient o!eratin+ ener+y or

stored ener+y to cause a s!ar: that -ill i+nite the +as;air mi5ture*

Ia is allo-ed to be used in a Done 0 areas*

Ib can not be used in Done 0 areas* Intrinsically safe ty!e 4i !rotection is not a!!licable to electrical

!o-er equi!ment* It is mainly intended for electronic measurin+ and

control circuits i*e* instrumentation and telemetry* he !rinci!le

behind 4i !rotections is that a circuit and its de/ices do not ha/e

sufficient o!eratin+ ener+y or stored ener+y to cause a s!ar: that -ill

i+nite the +as;air mi5ture*


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) s!ar: can occur but it must be inherently too -ee: to i+nite the

mi5ture*

here are t-o sub;di/isions of ty!e 4i" namely 4ia and 4ib * he

ty!e 4ia has a more strin+ent s!ecification than 4ib and therefore

allo-ed to be used in a Done 0 area* y!e 4ib cannot be used in a

Done 0 area*

he system includes the source of !o-er and its %ener -arrier. the

interconnectin+ cables -hich by their nature ha/e inductance and

ca!acitance" and the connected a!!aratus or load*


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11/21

Intrinsicall& Safe S&stems:

Definitions:

)ssociated )!!aratus* )!!aratus in -hich the circuits are not necessarily

intrinsically safe themsel/es but that affect the ener+y in the intrinsically

safe circuits and are relied on to maintain intrinsic safety* )ssociateda!!aratus may be either of the follo-in+

31 Electrical a!!aratus that has an alternati/e;ty!e !rotection for use in the

a!!ro!riate hazardous 3classified location" or

3( Electrical a!!aratus not so !rotected that shall not be used -ithin a

hazardous 3classified location*


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Intrinsically $afe $ystem* )n assembly of interconnected intrinsically safe

a!!aratus" associated a!!aratus" and interconnectin+ cables in that those

!arts of the system that may be used in hazardous 3classified locations are

intrinsically safe circuits*

FPB )n intrinsically safe system may include more than one intrinsically

safe circuit*

Intrinsically $afe Circuit* ) circuit in -hich any s!ar: or thermal effect is

inca!able of causin+ i+nition of a mi5ture of flammable or combustible

material in air under !rescribed test conditions*

$im!le )!!aratus* )n electrical com!onent or combination of com!onents

of sim!le construction -ith -ell;defined electrical !arameters that does not

+enerate more than 1*% /olts" 100 milliam!s" and (% milli-atts" or a !assi/e

com!onent that does not dissi!ate more than 1*& -atts and is com!atible-ith the intrinsic safety of the circuit in -hich it is used*

FPB he follo-in+ a!!aratus are e5am!les of sim!le a!!aratus

3a Passi/e com!onentsG for e5am!le" s-itches" 8unction bo5es" resistance

tem!erature de/ices" and sim!le semiconductor de/ices such as E.s

3b $ources of +enerated ener+y" for e5am!le" thermocou!les and !hotocells"

-hich do not +enerate more than 1*% A" 100 m)" and (% m=*

Equipment Installation:

3) Control .ra-in+* Intrinsically safe a!!aratus" associated a!!aratus" and

other equi!ment shall be installed in accordance -ith the control dra-in+3s*

E5ce!tion ) sim!le a!!aratus that does not interconnect intrinsically safe

circuits*

FPB he control dra-in+ identification is mar:ed on the a!!aratus*

3# ocation* Intrinsically safe a!!aratus shall be !ermitted to be installed in

any hazardous 3classified locations for -hich it has been identified*

@eneral;!ur!ose enclosures shall be !ermitted for intrinsically safe

a!!aratus*

)ssociated a!!aratus shall be !ermitted to be installed in any hazardous3classified location for -hich it has been identified or" if !rotected by other

means" !ermitted by )rticles %01 throu+h %0& and )rticle %0%*


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3# From .ifferent Intrinsically $afe Circuit Conductors* .ifferent

intrinsically safe circuits shall be in se!arate cables or shall be se!arated

from each other by one of the follo-in+ means

31 he conductors of each circuit are -ithin a +rounded metal shield*

3( he conductors of each circuit ha/e insulation -ith a minimum thic:ness

of 0*(% mm 30*01 in**

E5ce!tion Unless other-ise identified*

/roundin$:

3) Intrinsically $afe )!!aratus" )ssociated )!!aratus" and ace-ays*

Intrinsically safe a!!aratus" associated a!!aratus" cable shields" enclosures"

and race-ays" if of metal" shall be +rounded*

FPB $u!!lementary bondin+ to the +roundin+ electrode may be needed for

some associated a!!aratus" for e5am!le" zener diode barriers" if s!ecified in

the control dra-in+* $ee )B$II$) P 1(*6;199%" =irin+ Practices for>azardous 3Classified ocations Instrumentation Part 1 Intrinsic $afety*

@roundin+ Electrodes*

3) Electrodes Permitted for @roundin+*

31 ?etal Under+round =ater Pi!e* ) metal under+round -ater !i!e in direct

contact -ith the earth for &*0 m 310 ft or more 3includin+ any metal -ellcasin+ effecti/ely bonded to the !i!e and electrically continuous 3or made

electrically continuous by bondin+ around insulatin+ 8oints or insulatin+

!i!e to the !oints of connection of the +roundin+ electrode conductor and

the bondin+ conductors* Interior metal -ater !i!in+ located more than 1*%(

m 3% ft from the !oint of entrance to the buildin+ shall not be used as a !art


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of the +roundin+ electrode system or as a conductor to interconnect

electrodes that are !art of the +roundin+ electrode system*

E5ce!tion In industrial and commercial buildin+s or structures -here

conditions of maintenance and su!er/ision ensure that only qualified

!ersons ser/ice the installation" interior metal -ater !i!in+ located more

than 1*%( m 3% ft from the !oint of entrance to the buildin+ shall be

!ermitted as a !art of the +roundin+ electrode system or as a conductor to

interconnect electrodes that are !art of the +roundin+ electrode system"

!ro/ided that the entire len+th" other than short sections !assin+

!er!endicular throu+h -alls" floors" or ceilin+s" of the interior metal -ater

!i!e that is bein+ used for the conductor is e5!osed*

3( ?etal Frame of the #uildin+ or $tructure* he metal frame of the

buildin+ or structure" -here effecti/ely +rounded*

3& Concrete;Encased Electrode* )n electrode encased by at least %0 mm 3(

in* of concrete" located -ithin and near the bottom of a concrete foundationor footin+ that is in direct contact -ith the earth" consistin+ of at least 6*0 m

3(0 ft of one or more bare or zinc +al/anized or other electrically

conducti/e coated steel reinforcin+ bars or rods of not less than 1& mm 3K

in* in diameter" or consistin+ of at least 6*0 m 3(0 ft of bare co!!er

conductor not smaller than ' )=@* einforcin+ bars shall be !ermitted to be

bonded to+ether by the usual steel tie -ires or other effecti/e means*

3' @round in+* ) +round rin+ encirclin+ the buildin+ or structure" in direct

contact -ith the earth" consistin+ of at least 6*0 m 3(0 ft of bare co!!er

conductor not smaller than ( )=@*

Sealin$:

Conduits and cables that are required to be sealed by %01*% and %0(*% shall

be sealed to minimize the !assa+e of +ases" /a!ors" or dusts* $uch seals shall

not be required to be e5!losion !roof or flame!roof*

Identification:

abels required by this section shall be suitable for the en/ironment -here

they are installed -ith consideration +i/en to e5!osure to chemicals and

sunli+ht*3) erminals* Intrinsically safe circuits shall be identified at terminal and

8unction locations in a manner that -ill !re/ent unintentional interference

-ith the circuits durin+ testin+ and ser/icin+*

3# =irin+* ace-ays" cable trays" and other -irin+ methods for

intrinsically safe system -irin+ shall be identified -ith !ermanently affi5ed

labels -ith the -ordin+ 4Intrinsic $afety =irin+ or equi/alent* he labels


16/21

shall be located so as to be /isible after installation and !laced so that they

may be readily traced throu+h the entire len+th of the installation* Intrinsic

safety circuit labels shall a!!ear in e/ery section of the -irin+ system that is

se!arated by enclosures" -alls" !artitions" or floors* $!acin+ bet-een labels

shall not be more than 7*% m 3(% ft*

Color Codin$*

Color codin+ shall be !ermitted to identify intrinsically safe conductors

-here they are colored li+ht blue and -here no other conductors colored

li+ht blue are used* i:e-ise" color codin+ shall be !ermitted to identify

race-ays" cable trays" and 8unction bo5es -here they are colored li+ht blue

and contain only intrinsically safe -irin+*

T&pe of (rotection *e+:

y!e 4e is also called 4increased safety and intended for a!!aratusthat is to be installed in a Done 1 area*

he !ractical as!ect is the remo/al of a source of i+nition i*e* a s!ar:

or a hot surface*

In many ty!es of equi!ment e*+* luminaries" terminal bo5es" 8unction

bo5es" some desi+ns of motor control stations" tele!hones and !ublic

address s!ea:ers" the elimination of these t-o sources of i+nition is

not a difficult !roblem*

T&pe of (rotection *p+:

his is also :no-n as !ressurization or continuous dilution*

It is mainly a!!lied to lar+e motors" control !anels" dis!lay !anels"

and occasionally s!ecial !ur!ose +enerators*

Pre/entin+ the entry of surroundin+ atmos!here into the enclosure by

holdin+ an i+nition;!rotection +as 3air" inert +as under o/er;!ressure

in relation to the surroundin+ atmos!here


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$uitable for Done 1 and Done ( areas*

he !ressurization !rocess is carried out in t-o !arts" the first !art

-hen the equi!ment is ready to be ener+ized and the second !art to

cater for the runnin+ and shutdo-n of the equi!ment*

he first !art is called 4!ur+in+* )ir or inert +as is !assed into and/ented from the enclosure" to !ur+e out any +as;air mi5ture that may

be !resent* he equi!ment is !re/ented from bein+ ener+ized until the

!ur+in+ cycle is com!lete*

he !ur+in+ cycle -ill need to !ass a !rescribed /olume of air or inert

+as throu+h the equi!ment*

?easurin+ de/ices -ill be incor!orated into the !ur+in+ equi!ment to

ensure that the necessary /olume of air or +as has been !assed*

If the !ur+in+ equi!ment fails then the enclosure cannot be ener+ized* he !ur+in+ air must be dra-n from a non;hazardous area source e*+*

throu+h suitable ductin+ or from a !lant air com!ressor*

he !ur+in+ +as for a small enclosure may be ta:en from hi+h

!ressure stora+e cylinders usin+ a suitable !ressure reduction

re+ulator*


18/21

T&pe of (rotection *q+:

he electrical a!!aratus enclosure is filled -ith !o-der or sand*

)n arc occurrin+ in the enclosure does not i+nite an e5!losi/e

atmos!heres surroundin+ the enclosure*

It is mainly intended for electronic equi!ment as it has /ery little

a!!lication in the oil industry*

T&pe of (rotection *o+:

=ith this ty!e of !rotection the acti/e and s!ar:in+ !arts of the

equi!ment are immersed in mineral oil*

he conce!t is similar to that used in the manufacture of bul: oil

immersed and small /olume oil immersed s-itch+ear 3both of -hich

are seldom encountered no-adays* Hil immersion finds a!!lication -ith electronic and telemeterin+

equi!ment*

y!e 4o !rotection is only !ermitted in Done ( and non;hazardous

areas*

Hil immersed s-itch+ear is not normally s!ecified in the oil industry

because there are far better insulatin+ media a/ailable in modern

desi+ns*


19/21

T&pe of (rotection *m+:

y!e 4m enclosures are enca!sulations" for e5am!le and electronic

circuit enca!sulated in solid e!o5y resin or fire;resistance solid

material* here are /ery fe- e5am!les in electrical !o-er equi!ment used in

the oil industry*

T&pe of (rotection *n+:

y!e of Protection 4n* y!e of !rotection -here electrical equi!ment"

in normal o!eration" is not ca!able of i+nitin+ a surroundin+ e5!losi/e

+as atmos!here and a fault ca!able of causin+ i+nition is not li:ely to

occur*

he basic conce!t of ty!e 4n !rotection -as to ha/e an enclosure

desi+n that -ould be suitable for Done ( areas*

T&pe of (rotection *s+:

y!e 4s !rotection is also called 4s!ecial !rotection and enables

unusual desi+ns to be desi+ned" tested and certified*

It is a little used method and the a!!lications are mainly suited to

electronic and lo- !o-er equi!ment*

T&pes of (rotection for In$ress of 0ater and Solid (articles

European (ractice:

IEC60%(9 is the most commonly used standard for definin+ the

4de+ree of in+ress !rotection for both liquids and !articles*


20/21

=hen hazardous area equi!ment is bein+ installed" it -ill need to be

+i/en a minimum de+ree of in+ress !rotection*

he de+ree -ill de!end u!on -hether the equi!ment is to be installed

outdoors and e5!osed to the e5tremes of the -eather" or indoors ande5!osed 3or not to dust or liquid in+ress*

The American (ractice: The 1ational Electrical "anufacturin$

Association 21E"A3:

In the U$) the Bational Electrical ?anufacturin+ )ssociation

3BE?) !laces certain standards on electrical !roducts*

his or+anization has established a 4BE?) ty!e codin+ system for

enclosures*

Each ty!e" numbered from 1 to 1&" describes a s!ecific ty!e of!rotection*

he BE?) codin+ system s!ecifically includes three cate+ories for

equi!ment that is to be installed in oil industry hazardous areas"

namely y!e 7" L and 9" but only for indoor locations*


21/21

"ar#in$ of Equipment 1ameplates:

>azardous area equi!ment that has been tested and a!!ro/ed by a

reco+nized laboratory should ha/e a mar:in+ !late attached to its

surface" in a !lace easily seen by the user*

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