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Basics of Explosion Protection  INTRODUCTION

HAZARDOUS LOCATIONS

TEMPERATURE CLASSES

Ign i t i on temperature or auto- ign i t i on temperature (AT I ) is the min im um temperature o f a sur face at wh ich an exp los ive a tmosph ere ign i tes . F lamm able vapors and

gases can be c lass i fi ed in to temperature c lasses accord ing to the i r i gn i t i on temperature . The max im um temperature o f a p iece o f equ ipm ent m us t a lways be lower than

the ign i t i on temperature o f the gas - a i r mix ture or vapor - a i r mix ture in wh ich i t is p laced. Equ ipm ent sha l l be marked to show the operat ing temperature or tempera

ture c lass re ferenced to a +40° C (+104° F ) am bient . The temperature c lass (T code) i s i nd ica ted on the man ufac turers namepla te and i s based on the tab le be low.

 AMBIENT TEMPERA TURE

The ambient temperature i s the sur round ing

temperature o f the env i ronment in wh ich a p iece o f  

equ ipment i s i ns ta l l ed , whether i t i s i ndoors or out

doors . The s tandard temperature range for equ ip

me n t d e s ig n i s - 2 0 ° C t o +4 0 ° C ; f o r th i s r a n ge n o

ambient temperature mark ing i s requ i red on the

produc t . E lec t r i ca l equ ipment that i s des igned for  

use in a range o f ambient temperature o ther than

- 2 0 ° C t o +4 0 ° C t h e a c tu a l a mb i e n t te mp e r a t u re

range sha l l be marked on the equ ipment namepla te .

The R. STAHL product l ines, in most cases, exceedthe -20 ° C to +40°C requ i rement . Refer to the

appropr ia te cata log pages for the produc t -spec i f i c

“ A m b i e n t T e m p e r a t u r e R a n g e ” . A n y ra ng es

o u t s i d e - 2 0 ° C t o +4 0 ° C a r e ma r k e d o n t h e p r o d u c t

namepla te .

 A p p li c a ti o n s re q u ir in g p ro d u c t w it h ex tr em e a m b ie n t

t e mp e r a tu r e ra n g e s o u t s id e th o s e s t a n d a rd r a n g es st a te d u n d e r t h e h e a d i n g “ A m b i e n t T e m p e r a t u r e R a n g e ” a r e s p e c i fi e d u n d e r t h e h e a d i n g o f “ S p e c i a l

 A m b ie n t T e m p e r a t u r e R a n g e ” . O n ly p ro d u ct s w it h th is a d d it io n a l c at a lo g in fo rm a ti o n ca n be cu st o m iz e d fo r e xt re m e te m p e ra tu re a p p lic a ti o n s . Pl ea se c o n s u lt

fac tory for your spec ia l needs .

North American  Temperature Code

IEC/CENELEC/NEC 505 Temperature Classes

Maximum Temperature°C °F

T1 T1 450 ° C 842° F

T2 T2 300 ° C 5 72° F

T2 A - 2 80 ° C 5 36° F

T2 B - 2 60 ° C 5 00° F

T2 C - 2 30 ° C 4 46° F

T2 D - 2 15 ° C 4 19° F

T3 T3 200 ° C 3 92° F

T3 A - 1 80 ° C 3 56° F

T3 B - 1 65° C 3 29° F

T3 C - 1 60° C 3 20° F

T4 T4 1 35 ° C 2 7 5 ° F

T4 A - 1 20° C 2 48° F

T5 T5 1 00° C 2 12° F

T6 T6 8 5° C 185° F

EQUIPMENT DESIGN AND CONSTRUCTION

There are a number o f methods o f pro tec t ing e lec t r i ca l equ ipment , wh ich prevent an exp los ion when used in a f l ammable gas a tmosphere, i n the presence o f  combus t ib le dus t or eas i l y i gn i ted f i bers .

Three e lements are requ i red for an exp los ion to occur - fue l , oxygen and a heat or i gn i t i on source mus t be present . The fue l and

oxygen must be in the cor rec t mix ture . Too l i t t l e fue l , o r a lean mix ture , or too much fue l , a r i ch mix ture cannot i gn i te . These

exp los ive l im i ts are def ined as the “Lower Exp los ive L im i t ” (LEL) and the “Upp er Exp los ive L im i t ” (UEL) .

Each method o f pro tec t ion addresses the F i re T r iang le in some manner . E i ther by conta in ing an in terna l exp los ion or  

e l iminat ing one or more o f the components necessary for an exp los ion to occur .

The mos t common Nor th Amer ican methods o f pro tec t ion are exp los ionproof equ ipment fo r C lass I l ocat ions , and

dus t - ign i t i on proof equ ipment fo r C lass I I l ocat ions . R . STAHL produces a w ide range o f equ ipment fo r use in

hazardous locat ions us ing var ious methods o f pro tec t ion .

Flameproof Type of Protection “d”- or Explosionproof Equipment  A lt h o u g h th e N or th A m e ri ca n te rm “e x p lo s io n p ro o f” an d IEC te rm “ fl a m e p ro o f” ar e id e n tic a l co n c e p ts , th e / O x y g e n

requ i remen ts in the produ c t s tandards are d i f fe rent . Exp los ionpro of is a D iv 1 techno logy which can beused in a NEC or CEC def ined Zone 1 env i ronm ent . F lam eproof i s a Zone 1 techn o logy and can not be used in a D iv . 1 env i ronm ent .

S ince f l ammable gases and vapors are expec ted ins ide an enc losure , the equ ipment mus t be capable o f w i ths tand ing an exp los ion caused by spark ing contac ts o f  

dev ices , h igh temperatures , or an e lec t r i ca l fau l t . The enc losure i s des igned so that hot gases generated dur ing an in terna l exp los ion are coo led be low the ign i t i on

temperature o f the sur round ing f l ammable a tmosphere as they escape through the jo in ts o f the un i t .

In add i t i on , the ex terna l sur faces o f the enc losure mus t not become hot enough to ign i te the sur round ing a tmosphere due to heat energy w i th in the un i t . Th is heat

energy may be the resu l t o f normal opera t ion o f heat -produc ing equ ipment , o r the resu l t o f an e lec t r i ca l a rc to the enc losure f rom an arc ing ground fau l t . Safe ty

fac tors are app l ied to a l l tes t ing o f th is t ype o f enc losure to ensure the un i t w i l l no t rup ture as a resu l t o f an in terna l exp los ion.

INNOVATIVE EXPLOSION PROTECTION by R. STAHL 1-800-782-4357  A

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Basics of Explosion Protection  INTRODUCTION

HAZARDOUS LOCATIONS

Typical European ATEX/CENELEC Marking 

II 2 G E E x d e I IC T6

 Approved mark for apparatus certified by EU test authority

Equipment group I (mining)

Category M1 and M2

L Equipment group II (on surface)

|-Category 1G, Zone 0

-Category 2G, Zone 1

-Category 3G, Zone 2

(G for Gas) 

Category 1D, Zone 20

-Category 2D, Zone 21

 Areas where explosive gas atmosph

is continuously present or present f

long periods of time

 Areas where explosive gas atmosph

is l ikely to occur  in normal operatioor can be expected to be present

frequently

 Area where explosive gas atmosphe

is not likely to occur and if it does,

will only exist for a short period of t

 Area where combustible dust is

continuously or frequently present

 Area where combustible dust clouds

are l ikely to occur during normal

operation

 Area where combustible dust cloudsmay occur infrequently during norm

operation

Category 3D, Zone 22

(D for Dust)

Explosion protected according to CENELEC standards EN 50

Methods of protection, d, e, p, i, o, q, m, n

 Apparatus Group

I Mining - Underground (methane)

II Surface Industries

 A (propane)

B (ethylene)C (hydrogen)

Temperature Class

T1 450° C

T2 300° C

T3 200° C

T4 135° C

T5 100° C

T6 85° C

(STAHL)

INNOVATIVE EXPLOSION PROTECTION by R. STAHL 1-800-782-4357  A